WorldWideScience

Sample records for cyclic thermal loading

  1. Viscoelastoplastic bodies under cyclic loading in thermal-radiation fields

    OpenAIRE

    Atwa D. Zeyad

    2017-01-01

    Deformation of viscoelastoplastic bodies in the neutron and thermal fluxes under a one-time loading has been studied previously in [1–3]. A mathematical model has been set forth in [4] for a cyclic deformation of elastoplastic bodies in a neutron flux. In the paper [5,6] ferrofluid flow and heat transfer in a semi annulus enclosure is investigated considering thermal radiation. This article [7] explores the effect of thermal radiation on Al2O3–water nanofluid flow and heat transfer in an encl...

  2. Thermal to Electric Energy Conversion for Cyclic Heat Loads

    Science.gov (United States)

    Whitehead, Benjamin E.

    Today, we find cyclic heat loads almost everywhere. When we drive our cars, the engines heat up while we are driving and cool while parked. Processors heat while the computer is in use at the office and cool when idle at night. The sun heats the earth during the day and the earth radiates that heat into space at night. With modern technology, we have access to a number of methods to take that heat and convert it into electricity, but, before selecting one, we need to identify the parameters that inform decision making. The majority of the parameters for most systems include duty cycle, total cost, weight, size, thermal efficiency, and electrical efficiency. However, the importance of each of these will depend on the application. Size and weight take priority in a handheld device, while efficiency dominates in a power plant, and duty cycle is likely to dominate in highly demanding heat pump applications. Over the past decade, developments in semiconductor technology has led to the creation of the thermoelectric generator. With no moving parts and a nearly endlessly scalable nature, these generators present interesting opportunities for taking advantage of any source of waste heat. However, these generators are typically only capable of 5-8% efficiency from conversion of thermal to electric energy. [1]. Similarly, advancements in photovoltaic cells has led to the development of thermophotovoltaics. By heating an emitter to a temperature so it radiates light, a thermophotovoltaic cell then converts that light into electricity. By selecting materials that emit light in the optimal ranges of the appropriate photovoltaic cells, thermophotovoltaic systems can potentially exceed the current maximum of 10% efficiency. [2]. By pressurizing certain metal powders with hydrogen, hydrogen can be bound to the metal, creating a metal hydride, from which hydrogen can be later re-extracted under the correct pressure and temperature conditions. Since this hydriding reaction is

  3. Thermal and mechanical cyclic loading of thick spherical vessels made of transversely isotropic materials

    International Nuclear Information System (INIS)

    Komijani, M.; Mahbadi, H.; Eslami, M.R.

    2013-01-01

    The aim of this paper is to obtain the dependency of the ratcheting, reversed plasticity, or shakedown behavior of spherical vessels made of some anisotropic materials to the stress category of imposed cyclic loading. The Hill anisotropic yield criterion with the kinematic hardening theories of plasticity based on the Prager and Armstrong–Frederick models are used to predict the yield of the vessel and obtain the plastic strains. An iterative numerical method is used to simulate the cyclic loading behavior of the structure. The effect of mean and amplitude of the mechanical and thermal loads on cyclic behavior and ratcheting rate of the vessel is investigated respectively. The ratcheting rate for the vessels made of transversely isotropic material is evaluated for the various ratios of anisotropy. -- Highlights: ► Cyclic loading analysis of anisotropic spheres is assessed. ► Using the Prager model results in ratcheting. ► Armstrong-Frederick model predicts ratcheting for load controlled cyclic loadings. ► The A-F model predicts ratcheting to a stabilized cycle for thermal loadings

  4. The effect of infrequent thermal overloads on the behavior of plates subjected to mechanical and cyclic thermal loading

    International Nuclear Information System (INIS)

    Phillips, J.

    1982-01-01

    Many components in high temperature plants experience steady mechanical loads combined with cyclic thermal loads due to routine shutdowns. Less frequent but more severe thermal loads due to unplanned shutdowns may interrupt this routine loading pattern. This report presents the results of computer calculations on the effect of such thermal overloads on the behaviour of a 'Bree plate'. Particular attention is given to the creep and plastic ratcheting deformation properties of the system. It is shown that the plate material properties are an important factor in the problem. With an elastic-perfectly plastic material, behaviour can be predicted from an appropriate linear combination of the results for each type of thermal cycle, multiplied by an enhancement factor in certain cases. With a bilinear kinematic hardening material behaviour is generally determined by the properties of the overload thermal cycle. These results are relevant to many high temperature design problems

  5. Study of the initiation and the propagation of cracks under 3D thermal cyclic loading

    International Nuclear Information System (INIS)

    Ancelet, O.

    2005-01-01

    The incident which has occurred on the Civaux power plant has shown the noxiousness of thermal loading and the difficulty to take it into account at design level. The objective of this report is to study the initiation and the propagation of crack under thermal loading. In this aim the CEA has developed a new experiment named FAT3D. The various experiments carried out showed the harmfulness of a thermal loading, which makes it possible to rapidly initiate a network of cracks and to propagate one (or some) cracks through the totally thickness of the component under certain conditions. These experimental results associated with a mechanical analysis put at fault the usual criteria of damage based on the variations of the equivalent strain. In addition, the study of the propagation stage shows the importance of the plasticity which, in the case of a thermal loading, slows down the propagation of the crack. (author)

  6. Comparative thermal cyclic test of different beryllium grades previously subjected to simulated disruption loads

    International Nuclear Information System (INIS)

    Gervash, A.; Giniyatulin, R.; Mazul, I.

    1999-01-01

    Considering beryllium as plasma facing armour this paper presents recent results obtained in Russia. A special process of joining beryllium to a Cu-alloy material structure is described and recent results of thermal cycling tests of such joints are presented. Summarizing the results, the authors show that a Cu-alloy heat sink structure armoured with beryllium can survive high heat fluxes (≥10 MW/m 2 ) during 1000 heating/cooling cycles without serious damage to the armour material and its joint. The principal feasibility of thermal cycling of beryllium grades and their joints directly in the core of a nuclear reactor is demonstrated and the main results of this test are presented. The paper also describes the thermal cycling of different beryllium grades having cracks initiated by previously applied high heat loads simulating plasma disruptions. (orig.)

  7. Performance study of Ke factors in simplified elastic plastic fatigue analyses with emphasis on thermal cyclic loading

    International Nuclear Information System (INIS)

    Lang, Hermann; Rudolph, Juergen; Ziegler, Rainer

    2011-01-01

    As code-based fully elastic plastic code conforming fatigue analyses are still time consuming, simplified elastic plastic analysis is often applied. This procedure is known to be overly conservative for some conditions due to the applied plastification (penalty) factor K e . As a consequence, less conservative fully elastic plastic fatigue analyses based on non-linear finite element analyses (FEA) or simplified elastic plastic analysis based on more realistic K e factors have to be used for fatigue design. The demand for more realistic K e factors is covered as a requirement of practical fatigue analysis. Different code-based K e procedures are reviewed in this paper with special regard to performance under thermal cyclic loading conditions. Other approximation formulae such as those by Neuber, Seeger/Beste or Kuehnapfel are not evaluated in this context because of their applicability to mechanical loading excluding thermal cyclic loading conditions typical for power plant operation. Besides the current code-based K e corrections, the ASME Code Case N-779 (e.g. Adam's proposal) and its modification in ASME Section VIII is considered. Comparison of elastic plastic results and results from the Rules for Nuclear Facility Components and Rules for Pressure Vessels reveals a considerable overestimation of usage factor in the case of ASME III and KTA 3201.2 for the examined examples. Usage factors according to RCC-M, Adams (ASME Code Case N-779), ASME VIII (alternative) and EN 13445-3 are essentially comparable and less conservative for these examples. The K v correction as well as the applied yield criterion (Tresca or von Mises) essentially influence the quality of the more advanced plasticity corrections (e.g. ASME Code Case N-779 and RCC-M). Hence, new proposals are based on a refined K v correction.

  8. Experiments on thermal characteristics of a natural circulation loop with latent heat energy storage under cyclic pulsed heat load

    Science.gov (United States)

    Tan, G. H.; Ho, C. J.

    An experimental investigation has been made of thermal characteristics of a rectangular, annular single-phase natural circulation loop with the inner tube filled with a solid-liquid phase change material (PCM) under cyclic pulsating heat load. A rectangular, annular loop of 150 cm in height and 75 cm in width was constructed with an annular gap of 0.6 cm, within which water was filled. The inner tube of the annular loop was filled with a PCM (n-Eicosene) or air. Under the cyclic pulsating heat load, temperature field within the water-filled annular loop with PCM- or air-filled inner tube was found to evolve into a steady periodic variation for the range of parameters considered. The water temperature and/or its fluctuating amplitude along the heated or cooled sections of the loop with the PCM-filled inner tube were found to be markedly lower than those measured in the loop with the air-filled inner tube under the identical conditions. On the other hand, along the insulated sections of the loop a somewhat minute difference in temporal variations of the water temperatures exists between the loops with PCM- and air-filled inner tube. In addition, at the outer wall along the cooled section, a time-periodic variation of temperature was detected in synchronizing with the pulsating heat load. Parametric effects of varying amplitude and time-period of the pulsating heat input, as well as of varying the inlet coolant temperature of the cooling jacket were investigated.

  9. Monopod bucket foundations under cyclic lateral loading

    DEFF Research Database (Denmark)

    Foglia, Aligi; Ibsen, Lars Bo

    on bucket foundations under lateral cyclic loading. The test setup is described in detail and a comprehensive experimental campaign is presented. The foundation is subjected to cyclic overturning moment, cyclic horizontal loading and constant vertical loading, acting on the same plane for thousands...

  10. Microstructure Evolution and Protrusion of Electroplated Cu-Filled Through-Silicon Vias Subjected to Thermal Cyclic Loading

    Science.gov (United States)

    Chen, Si; An, Tong; Qin, Fei; Chen, Pei

    2017-10-01

    Through-silicon vias (TSVs) have become an important technology for three-dimensional integrated circuit (3D IC) packaging. Protrusion of electroplated Cu-filled vias is a critical reliability issue for TSV technology. In this work, thermal cycling tests were carried out to identify how the microstructure affects protrusion during thermal cycling. Cu protrusion occurs when the loading temperature is higher than 149°C. During the first five thermal cycles, the grain size of Cu plays a dominant role in the protrusion behavior. Larger Cu grain size before thermal cycling results in greater Cu protrusion. With increasing thermal cycle number, the effect of the Cu grain size reduces and the microstrain begins to dominate the Cu protrusion behavior. Higher magnitude of microstrain within Cu results in greater protrusion increment during subsequent thermal cycles. When the thermal cycle number reaches 25, the protrusion rate of Cu slows down due to strain hardening. After 30 thermal cycles, the Cu protrusion stabilizes within the range of 1.92 μm to 2.09 μm.

  11. Behaviour of Cohesionless Soils During Cyclic Loading

    DEFF Research Database (Denmark)

    Shajarati, Amir; Sørensen, Kris Wessel; Nielsen, Søren Kjær

    Offshore wind turbine foundations are typically subjected to cyclic loading from both wind and waves, which can lead to unacceptable deformations in the soil. However, no generally accepted standardised method is currently available, when accounting for cyclic loading during the design of offshore...... wind turbine foundations. Therefore a literature study is performed in order to investigate existing research treating the behaviour of cohesionless soils, when subjected to cyclic loading. The behaviour of a soil subjected to cyclic loading is found to be dependent on; the relative density, mean...

  12. Progressive buckling under both constant axial load and cyclic distortion

    International Nuclear Information System (INIS)

    Clement, G.; Acker, D.; Lebey, J.

    1988-09-01

    Thin structures submitted to compressive loads must be carefully designed to avoid any risk of ruin by buckling. The aim of this paper is, first, to evidence that the critical buckling load may be notably lowered when cyclic strains are added to the compressive load and, secondly, to propose a practical rule of prevention against the ruin due to the progressive buckling phenomenon. This rule is validated by the results of numerous tests related to the entire range of modes of buckling (i.e. from fully plastic to fully elastic). Practical cases of interest for its use could mainly be those where cyclic thermal stresses are involved

  13. The durability of waveguide fibers at cyclic change of loading, temperature and humidity

    International Nuclear Information System (INIS)

    Karimov, S.N.; Sultonov, U.; Shamsidinov, M.I.

    1992-01-01

    Present article is devoted to durability of waveguide fibers at cyclic change of loading, temperature and humidity. The mounting scheme and loading of sample is presented. The dependence of glass fiber durability on number of thermal cycles at various humidity rates was considered. The dependence of number of cycles on maximal loading at cyclic temperature change was studied.

  14. Magnetoelastic Demagnetization of Steel under Cyclic Loading

    Science.gov (United States)

    Muratov, K. R.; Novikov, V. F.; Neradovskii, D. F.; Kazakov, R. Kh.

    2018-01-01

    Magnetoelastic demagnetization of steel samples under cyclic tensile loads has been analyzed. It has been established that values of residual magnetization that correspond to peak loads are characterized by the power-law dependence on the number of loading cycles. In some cases, in the region of high loads, the qualitative transition to exponential dependence has been observed. Coefficients of the power-law approximation of peak magnetization depend on the value of amplitude load and have specific characteristics in the vicinity of characteristic loads. The ratios of approximated slide load coefficients depending on the load are common for the three considered samples, and there is an outburst in the vicinity of the fatigue limit, which can be used as the basis for developing the rapid nondestructive method for determination of this limit.

  15. A study of plasma facing tungsten components with electrical discharge machined surface exposed to cyclic thermal loads

    International Nuclear Information System (INIS)

    Seki, Yohji; Ezato, Koichiro; Suzuki, Satoshi; Yokoyama, Kenji; Yamada, Hirokazu; Hirayama, Tomoyuki

    2016-01-01

    Through R&D for a plasma facing units (PFUs) in an outer vertical target of an ITER full-tungsten (W) divertor, Japan Atomic Energy Agency succeeded in demonstrating the durability of the W divertor shaped by an electrical discharge machining (EDM). To prevent melting of W armors in the PFUs, an adequate technology to meet requirements of a geometrical shape and a tolerance is one of the most important key issues in a manufacturing process. From the necessity, the EDM has been evaluated to control the final shape of the W armor. Though the EDM was known to be advantages such as an easy workability, a potential disadvantage of presence of micro-cracks on the W surface appeared. In order to examine a potential effect of the micro-crack on a heat removal durability, a high heat flux testing was carried out for the W divertor mock-up with the polish and the EDM. As the result, all of the W armors endured the repetitive heat load of 1000 cycles at an absorbed heat flux of more than 20 MW/m 2 , which strongly encourages the realization of the PFUs of the ITER full-W divertor with the various geometrical shape and the high accuracy tolerance.

  16. Effects of Cyclic Loading on Gravel

    Science.gov (United States)

    Modoni, Giuseppe; Dan, Le Quang; Koseki, Junichi; Maqbool, Sajjad

    The effects of a large number of load repetitions on gravel are discussed based on experimental evidences. To this purpose the results of several triaxial tests carried out on a coarse grained soil, artificially reconstituted at different prescribed levels of density, are reported and compared. The tests reproduce a broad variety of possible field conditions, being performed at different mean effective stresses, by applying sequences of load-unload repetitions, different by number of repetitions and amplitudes of cycles. The analysis of the experimental results has been conducted by focusing the attention on the plastic components of strain, calculated by scaling the non negligible elastic components from the measured ones. A theory for the interpretation of monotonic test results is first briefly presented to form the basis of the analysis of the cyclic test results. This last is referred to the evolution of the stress-strain relationships along with load repetitions, and particularly to the accumulation of distortional and volumetric strains and to the effects of previous cyclic loading on subsequent soil response.

  17. Infrared thermographic analysis of shape memory polymer during cyclic loading

    International Nuclear Information System (INIS)

    Staszczak, Maria; Pieczyska, Elżbieta A; Maj, Michał; Kukla, Dominik; Tobushi, Hisaaki

    2016-01-01

    In this paper we present the effects of thermomechanical couplings occurring in polyurethane shape memory polymer subjected to cyclic tensile loadings conducted at various strain rates. Stress–strain characteristics were elaborated using a quasistatic testing machine, whereas the specimen temperature changes accompanying the deformation process were obtained with an infrared camera. We demonstrate a tight correlation between the mechanical and thermal results within the initial loading stage. The polymer thermomechanical behaviour in four subsequent loading-unloading cycles and the influence of the strain rate on the stress and the related temperature changes were also examined. In the range of elastic deformation the specimen temperature drops below the initial level due to thermoelastic effect whereas at the higher strains the temperature always increased, due to the dissipative deformation mechanisms. The difference in the characteristics of the specimen temperature has been applied to determine a limit of the polymer reversible deformation and analyzed for various strain rates. It was shown that at the higher strain rates higher values of the stress and temperature changes are obtained, which are related to higher values of the polymer yield points. During the cyclic loading a significant difference between the first and the second cycle was observed. The subsequent loading-unloading cycles demonstrated similar sharply shaped stress and temperature profiles and gradually decrease in values. (paper)

  18. Bucket foundations under lateral cyclic loading

    DEFF Research Database (Denmark)

    Foglia, Aligi

    To enable a prosperous development of offshore wind energy, economically feasible technologies must be developed. The monopod bucket foundation is likely to become a cost-effective sub-structure for offshore wind turbines and has the potential to make offshore wind more cost-competitive in the en......To enable a prosperous development of offshore wind energy, economically feasible technologies must be developed. The monopod bucket foundation is likely to become a cost-effective sub-structure for offshore wind turbines and has the potential to make offshore wind more cost......-competitive in the energy market. This thesis addresses issues concerning monopod bucket foundations in the hope of providing tools and ideas that could be used to optimize the design of this sub-structure. The work is focussed on the behaviour of bucket foundations under lateral cyclic loading. Other related...... and propaedeutic topics, such as bucket foundations under transient lateral loading and under monotonic lateral loading, are also investigated. All the scientific work is fundamentally based on small-scale experimental tests of bucket foundations in dense water-saturated sand. The most important scientific...

  19. Laterally cyclic loading of monopile in dense sand

    DEFF Research Database (Denmark)

    Klinkvort, Rasmus Tofte; Hededal, Ole; Svensson, M.

    2011-01-01

    In order to investigate the response from laterally cyclic loading of monopiles a large centrifuge tests series is ongoing at the Technical University of Denmark (DTU). This paper will present some of the tests carried out with a focus on the influence of accumulation of rotation when changing...... the loading conditions. In these tests the load conditions are controlled by two load characteristics, one controlling the level of the cyclic loading and one controlling the characteristic of the cyclic loading. The centrifuge tests were performed in dense dry sand on a pile with prototype dimensions...

  20. Design of mild steel structures under unequal cyclic loads

    International Nuclear Information System (INIS)

    In this paper a method is proposed to investigate the behavior and life of structural components under unequal cyclic loading conditions. Appropriate cyclic moment-curvature relations and life information, in the form of life versus extreme fiber strain, are developed from tests on beams under pure bending conditions. Theoretical predictions of behavior are based on structural geometry and the cyclic moment-curvature relations used in association with the simple curvature-area method. Structural life is also predicted using the life information developed and the theoretical strain history at the critical section in conjunction with a linear damage summation criterion. Theoretical predictions of behavior and life compare reasonably well with the experiments. Based on this study, a design procedure is proposed for mild steel components subjected to unequal cyclic loading conditions. The loads on the tested components were such that they failed due to low cyclic fatigue (i.e., at less than 10 5 cycles)

  1. Development of Pore Pressure and Material Damping during Cyclic Loading

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo

    1994-01-01

    The behaviour of sand during cyclic loading can be characterized as "stabilization", "instant stabilization". "pore pressure buildup" and "liquefaction". The terminologies can be defined exactly by a simple mathematical formulation based on the existence of a cyclic stable state. By introducing...

  2. Behaviour of Dense Frederikshavn Sand During Cyclic Loading

    DEFF Research Database (Denmark)

    Nielsen, Søren Kjær; Shajarati, Amir; Sørensen, Kris Wessel

    of Frederikshavn Sand for an arbitrary stress level and cyclic loading condition. It is discovered that the governing parameters regarding the response is dependent on the stress path and insitu conditions; initial pore pressure, stress state and the combination of average and cyclic shear stresses....

  3. Centrifuge modelling of a laterally cyclic loaded pile

    DEFF Research Database (Denmark)

    Klinkvort, Rasmus Tofte; Leth, Caspar Thrane; Hededal, Ole

    2010-01-01

    A total number of 9 static and 6 cyclic centrifuge tests on laterally loaded piles in very dense, dry sand was erformed. The prototype dimensions of the piles were 1 meter in diameter and penetration depths varying from 6 to 10 meters. The static tests were used to investigate the initial subgrade...... reaction modulus and as a reference for cyclic tests. For the cyclic tests the accumulation of deflections and the change in secant stiffness of the soil from repetitive loading were investigated. From all the tests carried out accumulations of deflections were seen. rom the centrifuge tests it was seen...

  4. INFLUENCE OF INTERMITTENT CYCLIC LOADING ON REINFORCED CONCRETE RESISTANCE MODEL

    Directory of Open Access Journals (Sweden)

    Vasyl Karpiuk

    2017-01-01

    Full Text Available This article describes the study of reinforced concrete span bending structures under conditions of high-level cyclic loading. Previous studies on the development of physical models of bending reinforced concrete element fatigue resistance, cyclic effect of lateral forces, and methods of calculation, are important and appropriate owing to certain features and the essential specificity of the mentioned loading type. These primarily include the nonlinearity of deformation, damage accumulation in the form of fatigue micro- and macro-cracks, and exhausting destruction of construction materials. In this paper, key expressions determining the endurance limits of concrete, longitudinal reinforcement, and anchoring longitudinal reinforcement, which contribute to endurance throughout the entire construction, are considered. Establishing a link between stresses in the elements and deformations in the element under conditions of cyclic loading action is of equal importance because of the presence of cyclic stress-induced creep deformation.

  5. Fatigue durability under random cyclic loading

    Science.gov (United States)

    Volkov, S. S.; Struzhanov, V. V.

    2017-12-01

    Methods for predicting the durability of metals have been developed while taking into account the effect of random loads acting during the service life of structures. Methods of the theory of functions of random variables are applied. Normal distribution and the Rayleigh distribution are used to estimate the random loads from the experimental histogram. A numerical example illustrates the influence of the statistical parameters of the load distribution on the predicted number of cycles before failure.

  6. High thermal load component

    International Nuclear Information System (INIS)

    Fuse, Toshiaki; Tachikawa, Nobuo.

    1996-01-01

    A cooling tube made of a pure copper is connected to the inner portion of an armour (heat resistant member) made of an anisotropic carbon/carbon composite (CFC) material. The CFC material has a high heat conductivity in longitudinal direction of fibers and has low conductivity in perpendicular thereto. Fibers extending in the armour from a heat receiving surface just above the cooling tube are directly connected to the cooling tube. A portion of the fibers extending from a heat receiving surface other than portions not just above the cooling tube is directly bonded to the cooling tube. Remaining fibers are disposed so as to surround the cooling tube. The armour and the cooling tube are soldered using an active metal flux. With such procedures, high thermal load components for use in a thermonuclear reactor are formed, which are excellent in a heat removing characteristic and hardly causes defects such as crackings and peeling. (I.N.)

  7. Degradation forecast for PEMFC cathode-catalysts under cyclic loads

    Science.gov (United States)

    Moein-Jahromi, M.; Kermani, M. J.; Movahed, S.

    2017-08-01

    Degradation of Fuel Cell (FC) components under cyclic loads is one of the biggest bottlenecks in FC commercialization. In this paper, a novel experimental based algorithm is presented to predict the Catalyst Layer (CL) performance loss during cyclic load. The algorithm consists of two models namely Models 1 and 2. The Model 1 calculates the Electro-Chemical Surface Area (ECSA) and agglomerate size (e.g. agglomerate radius, rt,agg) for the catalyst layer under cyclic load. The Model 2 is the already-existing model from our earlier studies that computes catalyst performance with fixed structural parameters. Combinations of these two Models predict the CL performance under an arbitrary cyclic load. A set of parametric/sensitivity studies is performed to investigate the effects of operating parameters on the percentage of Voltage Degradation Rate (VDR%) with rank 1 for the most influential one. Amongst the considered parameters (such as: temperature, relative humidity, pressure, minimum and maximum voltage of the cyclic load), the results show that temperature and pressure have the most and the least influences on the VDR%, respectively. So that, increase of temperature from 60 °C to 80 °C leads to over 20% VDR intensification, the VDR will also reduce 1.41% by increasing pressure from 2 atm to 4 atm.

  8. Multiaxial elastoplastic cyclic loading of austenitic 316L steel

    Czech Academy of Sciences Publication Activity Database

    Mazánová, Veronika; Polák, Jaroslav; Škorík, Viktor; Kruml, Tomáš

    2017-01-01

    Roč. 11, č. 40 (2017), s. 162-169 ISSN 1971-8993 R&D Projects: GA ČR(CZ) GA13-23652S; GA MŠk LM2015069; GA MŠk(CZ) LQ1601; GA ČR GA15-08826S Institutional support: RVO:68081723 Keywords : 316L steel * Crack initiation * Cyclic stress-strain curve * Multiaxial cyclic loading Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis

  9. Durability of Modified Expanded Polystyrene Concrete after Dynamic Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Wenbo Shi

    2016-01-01

    Full Text Available EPS concrete was produced by mixing the expanded polystyrene spheres (EPS and polymer emulsion and thickener to the matrix concrete, and this concrete had good vibration energy absorption characteristics. Based on the experimental data obtained on EPS volume ratio of 0%, 20%, 30%, and 40% by replacing matrix or coarse aggregate, the two design styles had nearly the same compressive strength. By applying frequency of 5 Hz, 50000 or 100000 times, 40 KN, 50 KN, and 60 KN cyclic loading, it is shown that the higher the inclusion size was, the lower the compressive strength of the EPS concrete would be; the larger the applying dynamic cyclic load was, the more obvious the compressive strength changing would be. Meanwhile, the strength of EPS concrete had no evident change after durability test. The results of this research had practical significance on using EPS concrete in some long-term cyclic dynamic load engineering.

  10. Testing and modeling of cyclically loaded rock anchors

    Directory of Open Access Journals (Sweden)

    Joar Tistel

    2017-12-01

    Full Text Available The Norwegian Public Roads Administration (NPRA is planning for an upgrade of the E39 highway route at the westcoast of Norway. Fixed links shall replace ferries at seven fjord crossings. Wide spans and large depths at the crossings combined with challenging subsea topography and environmental loads call for an extension of existing practice. A variety of bridge concepts are evaluated in the feasibility study. The structures will experience significant loads from deadweight, traffic and environment. Anchoring of these forces is thus one of the challenges met in the project. Large-size subsea rock anchors are considered a viable alternative. These can be used for anchoring of floating structures but also with the purpose of increasing capacity of fixed structures. This paper presents first a thorough study of factors affecting rock anchor bond capacity. Laboratory testing of rock anchors subjected to cyclic loading is thereafter presented. Finally, the paper presents a model predicting the capacity of a rock anchor segment, in terms of a ribbed bar, subjected to a cyclic load history. The research assumes a failure mode occurring in the interface between the rock anchor and the surrounding grout. The constitutive behavior of the bonding interface is investigated for anchors subjected to cyclic one-way tensile loads. The model utilizes the static bond capacity curve as a basis, defining the ultimate bond τbu and the slip s1 at τbu. A limited number of input parameters are required to apply the model. The model defines the bond-slip behavior with the belonging rock anchor capacity depending on the cyclic load level (τmax cy/τbu, the cyclic load ratio (R = τmin cy/τmax cy, and the number of load cycles (N. The constitutive model is intended to model short anchor lengths representing an incremental length of a complete rock anchor.

  11. Response of monopiles under cyclic lateral loading in sand

    DEFF Research Database (Denmark)

    Nicolai, Giulio; Ibsen, Lars Bo

    2015-01-01

    Currently the main design guidelines propose to reduce the lateral resistance of offshore piles when accounting for cyclic loading. The present work provides results from laboratory tests in which such reduction has not occurred. The experimental investigation is based on testing a small-scale mo......Currently the main design guidelines propose to reduce the lateral resistance of offshore piles when accounting for cyclic loading. The present work provides results from laboratory tests in which such reduction has not occurred. The experimental investigation is based on testing a small...

  12. Thermomechanical behavior of actively cooled, brazed divertor components under cyclic high heat flux loads

    International Nuclear Information System (INIS)

    You, J.H.; Bolt, H.; Duwe, R.; Linke, J.; Nickel, H.

    1997-01-01

    Actively cooled divertor mock-ups consisting of various low-Z armor tiles brazed to refractory metal heat sinks were tested in the electron beam test facility at Juelich. Screening and thermal cycling tests were perfomed on the mock-ups to estimate the overall thermal performance under cyclic high heat flux (HHF) loadings. By detecting the temperature of the armor surface and the braze layer, it was possible to assess the heat removal capability and the accumulation of interfacial damage. Microstructures were investigated to elucidate the degradation of the joints. Finite element analyses are carried out for the simulated HHF test conditions. Temperature fields and thermal stresses are calculated for a typical divertor module. The nature of thermomechanical behavior of the divertor mock-ups under cyclic HHF loadings is discussed. (orig.)

  13. Thermomechanical behavior of actively cooled, brazed divertor components under cyclic high heat flux loads

    Science.gov (United States)

    You, J. H.; Bolt, H.; Duwe, R.; Linke, J.; Nickel, H.

    1997-12-01

    Actively cooled divertor mock-ups consisting of various low- Z armor tiles brazed to refractory metal heat sinks were tested in the electron beam test facility at Jülich. Screening and thermal cycling tests were perfomed on the mock-ups to estimate the overall thermal performance under cyclic high heat flux (HHF) loadings. By detecting the temperature of the armor surface and the braze layer, it was possible to assess the heat removal capability and the accumulation of interfacial damage. Microstructures were investigated to elucidate the degradation of the joints. Finite element analyses are carried out for the simulated HHF test conditions. Temperature fields and thermal stresses are calculated for a typical divertor module. The nature of thermomechanical behavior of the divertor mock-ups under cyclic HHF loadings is discussed.

  14. Mechanical properties of concrete to cyclic uniaxial tensile loading ...

    Indian Academy of Sciences (India)

    The mechanical properties of concrete under cyclic tensile loading using square waveform, sine waveform and ramp waveform are studied. ... College of Civil and Transportation Engineering, Hobai University, Nanjing 210098, China; College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing ...

  15. Laboratory experiments of bucket foundations under cyclic loading

    DEFF Research Database (Denmark)

    Foglia, Aligi; Ibsen, Lars Bo

    This report collects information on the experimental campaign concerning bucket foundations under lateral cyclic loading conducted by the authors between 2011 and 2014. The report includes a step by step manual on the test procedures and a number of information and graphs for each experiment...

  16. Effect of Color Shading Procedures and Cyclic Loading on the ...

    African Journals Online (AJOL)

    2018-02-07

    Feb 7, 2018 ... How to cite this article: Tuncel I, Turp I, Usumez A. Effect of color shading procedures and cyclic loading on the biaxial flexural strength of zirconia. Niger J Clin Pract 2018;21:7-12. This is an open access article distributed under the terms of the Creative Commons. Attribution-NonCommercial-ShareAlike 3.0 ...

  17. Effect of Color Shading Procedures and Cyclic Loading on the ...

    African Journals Online (AJOL)

    Purpose: Zirconia is the most preferred ceramic restoration in posterior areas because of its flexural strength. The aim of the study is the evaluation of biaxial flexural strength of different colored zirconium oxide core materials after cyclic loading. Material and Methods: Zirconia discs (12 mm diameter and 1.2 mm thickness) ...

  18. Undrained behaviour of volcanic soils under monotonic and cyclic loading

    Science.gov (United States)

    de Cristofaro, Martina; Brunzo, Antonia; Mottola, Luciano; Netti, Nadia; Olivares, Lucio; Orense, Rolando; Asadi, Sadeq

    2017-04-01

    Undrained behaviour of volcanic soils under monotonic and cyclic loading. In this study, we focus on the undrained behaviour of volcanic deposits under monotonic and cyclic loading in order to define the susceptibility to liquefaction of granular volcanic deposits. We assume that, in the case of saturated granular volcanic deposits susceptible to liquefaction, an undrained unstable behaviour can be responsible for both, the evolution of flowslide due to rainfall and liquefaction under seismic loading. Starting from these considerations we define a complex experimental program to analyze their undrained behaviour through laboratory testing on reconstituted specimens of cohesionless volcanic soils. The first part of the experimental program is devoted to the use of the steady state concept to evaluate the influence of void ratio and effective confining pressure on the undrained behaviour of Cervinara pyroclastic soils (Italy) under monotonic and cyclic loading. The second part of the experimental program is devoted to the analysis of the influence of particles crushing of pumice soils from Rangiriri (New Zeland) in both monotonic and cyclic undrained triaxial tests.

  19. Resistance to cyclic loading of teeth restored with posts

    DEFF Research Database (Denmark)

    Sahafi, A; Peutzfeldt, A; Ravnholt, G

    2005-01-01

    This in vitro study evaluated the effect of presence of post, presence of core, and of shape, type, and surface treatment of posts on resistance to cyclic loading of crowned human teeth. For all teeth, crowns designed without ferrule were cast in sterling silver and luted with resin cement (Panavia...

  20. Assessment of burned coal shale properties based on cyclic load

    Science.gov (United States)

    Grygierek, Marcin; Kalisz, Piotr; Pacześniowski, Krzysztof; Pytlik, Andrzej; Zięba, Magdalena

    2018-04-01

    Road surfaces that are subjected to cyclic loads generated by vehicle wheels must meet the requirements concerning the durability in the assumed period of use. The durability of the layered pavement construction systems depends on the value and frequency of the load as well as on the mechanical features of its individual layers. Layers of unbound, mechanically stabilized mixtures are a significant aspect of surfaces that are susceptible. Mixtures of this type can be applied both to the subgrade layers as well as to the bottom pavement layers, including the improved course. Considering the cyclic nature of the load on the surface of the entire system, mechanically stabilized layers are subject to continuous, but slow, densification during the period of use, which results in the formation of permanent deformations and so-called structural ruts. Post-mining waste is frequently used in road construction. which is the so-called burned shale that can be used for the bottom layers of the surface and layers of the improved subgrade (soil replacement). This material was the subject of the analysis. The evaluation was based mainly on the results of pilot studies covering cyclic loads of the layer/course made of the so-called red shale. The applied research method was aimed at preliminary assessment of its suitability for the assessment of the behaviour of the disintegrated medium under the conditions of test loads simulating the movement of vehicles.

  1. Thermal conductivity of evacuated perlite at low temperatures as a function of load and load history

    Science.gov (United States)

    Dube, W. P.; Sparks, L. L.; Slifka, A. J.

    1991-01-01

    Perlite, a powdered insulation, is commonly used in large cryogenic storage dewars. When these dewars are thermally cycled, the perlite in the evacuated space between the inner and outer vessels of the dewar experiences a changing mechanical load due to thermal expansion and contraction of the inner vessel. Thermal conductivity data were obtained using a boil-off calorimeter. The apparent thermal conductivity of evacuated perlite increases strongly with applied load. Hysteretic behavior of the conductivity was observed when perlite was subjected to cyclic mechanical loading.

  2. Investigation of Cyclic Deformation and Fatigue of Polycrystalline Cu under Pure Compression Cyclic Loading Conditions

    Science.gov (United States)

    Hsu, Tzu-Yin Jean

    It is commonly accepted that fatigue crack is initiated under tensile fatigue stresses. However, practical examples demonstrate that cracks may also initiate under pure compressive fluctuating loads such as the failures observed in aircraft landing gear frames. However, the mechanism of such failures is rarely investigated. Furthermore, knowledge on cyclic deformation response under pure compressive fatigue condition is also very limited or non-existent. Our recent work already verified that fatigue cracks may nucleate from stress concentration sites under pure compression fatigue, but whether or not a form of stress concentration is always needed to initiate a crack under pure compression fatigue remains uncertain. In this study, compression fatigue tests under different peak stresses were carried out on smooth bars of fully annealed OFHC Copper. The purpose of these tests is to investigate not only the cyclic deformation response but also the possibility of crack nucleation without the stress concentrator. Results showed that overall the cyclic stress-strain response and microstructural evolution of OFHC Copper under pure compression fatigue exhibits rather dissimilar behaviour compared to those under symmetrical fatigue. The specimens hardened rapidly within 10 cycles under pure compression fatigue unlike the gradual cyclic hardening behaviour in symmetrical fatigue with the same peak stress amplitude. Compressive cyclic creep behaviour was also observed under the same testing conditions. Moreover, unlike conventional tension-compression fatigue, only moderate slip activity was detectable on the surface instead of typical PSB features detected from TEM observations. The surface observations has revealed that surface slip bands did not increase in number nor did they become more pronounced in height with increasing number of cycles. In addition, surface roughening by grain boundary extrusion was detected to become more severe as the cycling progressed. Therefore

  3. Inelastic behavior of materials and structures under monotonic and cyclic loading

    CERN Document Server

    Brünig, Michael

    2015-01-01

    This book presents studies on the inelastic behavior of materials and structures under monotonic and cyclic loads. It focuses on the description of new effects like purely thermal cycles or cases of non-trivial damages. The various models are based on different approaches and methods and scaling aspects are taken into account. In addition to purely phenomenological models, the book also presents mechanisms-based approaches. It includes contributions written by leading authors from a host of different countries.

  4. Effect of loading history on cyclic stress-strain response

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr; Weiss, B.; Melisova, D.

    2001-01-01

    Roč. 314, 1/2 (2001), s. 1-6 ISSN 0921-5093. [TMS Annual Meeting. Nashville, 12.03.2000-16.03.2000] R&D Projects: GA AV ČR IBS2041001 Institutional research plan: CEZ:AV0Z2041904 Keywords : cyclic plasticity * loading history * mean stress Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.978, year: 2001

  5. Empirical approach based on centrifuge testing for cyclic deformations of laterally loaded piles in sand

    DEFF Research Database (Denmark)

    Truong, P.; Lehane, B. M.; Zania, Varvara

    2018-01-01

    A systematic study into the response of monopiles to lateral cyclic loading in medium dense and dense sand was performed in beam and drum centrifuge tests. The centrifuge tests were carried out at different cyclic load and magnitude ratios, while the cyclic load sequence was also varied...

  6. Study of the initiation and the propagation of cracks under 3D thermal cyclic loading; Etude de l'amorcage et de la propagation des fissures sous chargement thermique cyclique 3D

    Energy Technology Data Exchange (ETDEWEB)

    Ancelet, O

    2005-07-01

    The incident which has occurred on the Civaux power plant has shown the noxiousness of thermal loading and the difficulty to take it into account at design level. The objective of this report is to study the initiation and the propagation of crack under thermal loading. In this aim the CEA has developed a new experiment named FAT3D. The various experiments carried out showed the harmfulness of a thermal loading, which makes it possible to rapidly initiate a network of cracks and to propagate one (or some) cracks through the totally thickness of the component under certain conditions. These experimental results associated with a mechanical analysis put at fault the usual criteria of damage based on the variations of the equivalent strain. In addition, the study of the propagation stage shows the importance of the plasticity which, in the case of a thermal loading, slows down the propagation of the crack. (author)

  7. Investigation on effectiveness of a prefabricated vertical drain during cyclic loading

    International Nuclear Information System (INIS)

    Indraratna, B; Ni, J; Rujikiatkamjorn, C

    2010-01-01

    The effectiveness of prefabricated vertical drains (PVDs) in enhancing the stability of soft soils during cyclic loading was investigated using triaxial cyclic loading tests. Both undrained and with PVD tests were employed to study the associated excess pore pressure and accumulated strain under the repeated loading condition. The loading frequency and cyclic stress ratio have been chosen to be the variables which influence the performance of soft clays. The experimental results illustrate that with PVDs, the excess pore water pressure generation during cyclic loading decreases significantly. It is found that the excess pore water pressure build up depends on both loading frequency and cyclic stress ratio. The excess pore water pressure will increase when each of them is increased. Furthermore, when the loading frequency is 0.1 Hz, the ratio of coefficient of consolidation under cyclic loading to that under static loading is almost one. With the increasing loading frequency, this ratio increases accordingly.

  8. Thin circular cylinder under axisymmetrical thermal and mechanical loading

    International Nuclear Information System (INIS)

    Arnaudeau, F.; Zarka, J.; Gerij, J.

    1977-01-01

    To assess structural integrity of components subjected to cyclic thermal loadings one must look at thermal ratchetting as a possible failure mode. Considering a thin circular cylinder subjected to constant internal pressure and cyclically varying thermal gradient through the thickness Bree, J. Strain Analysis 2 (1967) No.3, obtained a diagram that serves as a foundation for many design rules (e.g.: ASME code). The upper part of the french LMFBR main vessel is subjected to an axisymmetrical axial thermal loading and an axial load (own weight). Operation of the reactor leads to cyclic variations of the axial thermal loading. The question that arises is whether or not the Bree diagram is realistic for such loading conditions. A special purpose computer code (Ratch) was developed to analyse a thin circular cylinder subjected to axisymmetrical mechanical and thermal loadings. The Mendelson's approach of this problem is followed. Classical Kirchoff-Love hypothesis of thin shells is used and a state of plane stress is assumed. Space integrations are performed by Gaussian quadrature in the axial direction and by Simpson's one third rule throughout the thickness. Thermoelastic-plastic constitutive equations are solved with an implicit scheme (Nguyen). Thermovisco-plastic constitutive equations are solved with an explicit time integration scheme (Treanor's algorithm especially fitted). A Bree type diagram is obtained for an axial step of temperature which varies cyclically and a sustained constant axial load. The material behavior is assumed perfectly plastic and creep effect is not considered. Results show that the domain where no ratchetting occurs is reduced when compared with the domain predicted by the Bree diagram

  9. Volume Changes in Filled Rubber Under Uniaxial Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Elina KAZINA

    2011-09-01

    Full Text Available Styrene-butadiene rubber, neat and filled with different silica content was investigated under uniaxial cyclic loading under a constant crosshead speed, with increasing deformation amplitude in subsequent loading cycles. Rubber was investigated in order to evaluate the reversibility of structure rearrangements, occurring in rubber when subjected to cyclic loading. Volume uniformly increases with growing strain and shows hysteresis at unloading. After complete unloading, no residual strain changes are observed. These data are in good conformity with the data of density measurements, which were made on specimens before and after the tests. By correlating data, obtained from volume changes and kinetics of hysteresis losses there were made assumptions on deformation mechanisms at different elongations. Deformational mechanisms, responsible for volume changes in rubber are reversible. Volume changes in specimen occur due to voids formation caused by filler microstructure breakage, rubber chains disentanglement, spaces between rubber macromolecular chains shrinkage, and chain slippage under higher elongations. Voids formation and deformation of rubber macromolecular chain reaches equilibrium state after certain elongation.http://dx.doi.org/10.5755/j01.ms.17.3.592

  10. Effect of intergranular stress on yielding of 316H during room temperature cyclic loading

    International Nuclear Information System (INIS)

    Assessment of cyclic deformation is an integral part of nuclear power plant life assessment code, as many of the components in plant go through scheduled and unscheduled cyclic deformation owing to varying thermal and mechanical stresses. In polycrystalline material like 316H, a type of micro stress known as intergranular stress is generated due to elastic and plastic anisotropies during such cyclic loading. In tension-compression loading cycles, these stresses remain in the material as a residual stress upon unloading to zero stress from the tensile/compressive peak or intermediates stresses. The magnitude of these stresses vary depending on the point in the cycle from which it was unloaded from. When the material is re-loaded either in the same or reverse loading direction these residual stresses increase or decrease the effective stress acting in the material and as such the macroscopic yield stress of the material in subsequent cycle is changed significantly. The magnitude of intergranular stresses in many differently oriented grain families can be measured simultaneously using time of flight (ToF) neutron diffraction technique. In this paper, we have used this technique to experimentally study, how these intergranular stresses affect the yield (proof) stress of 316H at room temperature. (author)

  11. Mercury embrittlement of Cu-Al alloys under cyclic loading

    Science.gov (United States)

    Regan, T. M.; Stoloff, N. S.

    1977-01-01

    The effect of mercury on the room temperature, high cycle fatigue properties of three alloys: Cu-5.5 pct Al, Cu-7.3 pct Al, and Cu-6.3 pct Al-2.5 pct Fe has been determined. Severe embrittlement under cyclic loading in mercury is associated with rapid crack propagation in the presence of the liquid metal. A pronounced grain size effect is noted under mercury, while fatigue properties in air are insensitive to grain size. The fatigue results are discussed in relation to theories of adsorption-induced liquid metal embrittlement.

  12. Phase Transformation Evolution in NiTi Shape Memory Alloy under Cyclic Nanoindentation Loadings at Dissimilar Rates

    Science.gov (United States)

    Amini, Abbas; Cheng, Chun; Kan, Qianhua; Naebe, Minoo; Song, Haisheng

    2013-01-01

    Hysteresis energy decreased significantly as nanocrystalline NiTi shape memory alloy was under triangular cyclic nanoindentation loadings at high rate. Jagged curves evidenced discrete stress relaxations. With a large recovery state of maximum deformation in each cycle, this behavior concluded in several nucleation sites of phase transformation in stressed bulk. Additionally, the higher initial propagation velocity of interface and thermal activation volume, and higher levels of phase transition stress in subsequent cycles explained the monotonic decreasing trend of dissipated energy. In contrast, the dissipated energy showed an opposite increasing trend during triangular cyclic loadings at a low rate and 60 sec holding time after each unloading stage. Due to the isothermal loading rate and the holding time, a major part of the released latent heat was transferred during the cyclic loading resulting in an unchanged phase transition stress. This fact with the reorientation phenomenon explained the monotonic increasing trend of hysteresis energy. PMID:24336228

  13. Small-Scale Testing Rig for Long-Term Cyclically Loaded Monopiles in Cohesionless Soil

    DEFF Research Database (Denmark)

    Roesen, Hanne Ravn; Ibsen, Lars Bo; Andersen, Lars Vabbersgaard

    2012-01-01

    , and the period of the cyclic loading. However, the design guidance on these issues is limited. Thus, in order to investigate the pile behaviour for cyclically long-term loaded monopiles, a test setup for small-scale tests in saturated dense cohesionless soil is constructed and presented in here. The cyclic...... length = 600 mm proves that the test setup is capable of applying the cyclic long-term loading. The plastic deformations during loading depend not only on the loading applied but also of the relative density of the soil and, thus, the tests are carried out with relative densities of 77-88%, i.e. similar...

  14. Effects of Cyclic Loading on the Uniaxial Behavior of Nitinol

    Science.gov (United States)

    Schlun, M.; Zipse, A.; Dreher, G.; Rebelo, N.

    2011-07-01

    The widespread development and use of implants made from NiTi is accompanied by the publication of many NiTi material characterization studies. These publications have increased significantly the knowledge about the mechanical properties of NiTi. However, this knowledge also increased the complexity of the numerical simulation of NiTi implants or devices. This study is focused on the uniaxial behavior of NiTi tubing due to cyclic loading and had the goal to deliver both precise and application-oriented results. Single aspects of this study have already been published (Wagner in Ein Beitrag zur strukturellen und funktionalen Ermüdung von Drähten und Federn aus NiTi-Formgedaechtnislegierungen, Ph.D. Thesis, 2005; Eucken and Duerig in Acta Metall 37:2245-2252, 1989; Yawny et al. in Z Metallkd 96:608-618, 2005); however, there is no publication known that shows all the single effects combined in a "duty cycle case." It was of particular importance to summarize the main effects of pre-strain and subsequent small or large strain amplitudes on the material properties. The phenomena observed were captured in an extended Abaqus® Nitinol material model, presented by Rebelo et al. (A Material Model for the Cyclic Behavior of Nitinol, SMST Extended Abstracts 2010). The cyclic tensile tests were performed using a video extensometer to obtain accurate strain measurement on small electro-polished dog-bone specimen that were incorporated into a stent framework so that standard manufacturing methods could be used for the fabrication. This study indicates that a prestrain beyond 6% strain alters the transformation plateaus and if the cyclic displacement amplitude is large enough, additional permanent deformations are observed, the lower plateau and most notably the upper plateau change. The changes to the upper plateau are very interesting in the sense that an additional stress plateau develops: its "start stress" is lowered thereby creating a new plateau up to the highest level

  15. Damage assessment of low-cycle fatigue by crack growth prediction. Fatigue life under cyclic thermal stress

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2013-01-01

    The number of cycles to failure of specimens in fatigue tests can be estimated by predicting crack growth. Under a cyclic thermal stress caused by fluctuation of fluid temperature, due to the stress gradient in the thickness direction, the estimated fatigue life differs from that estimated for mechanical fatigue tests. In this paper, the influence of crack growth under cyclic thermal loading on the fatigue life was investigated. First, the thermal stress was derived by superposing analytical solutions, and then, the stress intensity factor was obtained by the weight function method. It was shown that the thermal stress depended not on the rate of the fluid temperature change but on the rise time, and the magnitude of the stress was increased as the rise time was decreased. The stress intensity factor under the cyclic thermal stress was smaller than that under the uniform stress distribution. The change in the stress intensity factor with the crack depth was almost the same regardless of the rise time. The estimated fatigue life under the cyclic thermal loading could be 1.6 times longer than that under the uniform stress distribution. The critical size for the fatigue life determination was assumed to be 3 mm for fatigue test specimens of 10 mm diameter. By evaluating the critical size by structural integrity analyses, the fatigue life was increased and the effect of the critical size on the fatigue life was more pronounced for the cyclic thermal stress. (author)

  16. Damage assessment of low-cycle fatigue by crack growth prediction. Fatigue life under cyclic thermal stress

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2013-01-01

    The number of cycles to failure of specimens in fatigue tests can be estimated by predicting crack growth. Under a cyclic thermal stress caused by fluctuation of fluid temperature, due to the stress gradient in the thickness direction, the estimated fatigue life differs from that estimated for mechanical fatigue tests. In this paper, the influence of crack growth under cyclic thermal loading on the fatigue life was investigated. First, the thermal stress was derived by superposing analytical solutions, and then, the stress intensity factor was obtained by the weight function method. It was shown that the thermal stress depended not on the rate of the fluid temperature change but on the rise time, and the magnitude of the stress was increased as the rise time was decreased. The stress intensity factor under the cyclic thermal stress was smaller than that under the uniform stress distribution. The change in the stress intensity factor with the crack depth did not depend on the heat transfer coefficient and only slightly depended on the rise time. The estimated fatigue life under the cyclic thermal loading could be 1.6 times longer than that under the uniform stress distribution. The critical size for the fatigue life determination was assumed to be 3 mm for fatigue test specimens of 10 mm diameter. By evaluating the critical size by structural integrity analyses, the fatigue life was increased and the effect of the critical size on the fatigue life was more pronounced for the cyclic thermal stress. (author)

  17. Methods of evaluation of thermal tolerance of cyclic sports athletes

    Directory of Open Access Journals (Sweden)

    Kish А.А.

    2017-12-01

    Full Text Available The purpose of the study is investigation of thermal stability in athletes of cyclic sports and assessment of its influence on physical working capacity under hyperthermia. Material and methods. 15 male athletes of cyclic sports who had the senior degree as minimum were included in the study Middle age 24,2±1,1 years. Work was performed in the climatic camera of the Center of sports medicine and rehabilitation in several stages, on each of which assessment of physical working capacity and a thermal condition of athletes was carried out. Results. In the real work the burdening action of the heating climate on indicators of physical working capacity and a thermal condition of athletes of cyclic sports is shown; the operating ranges of high temperatures are determined. Conclusion. The data obtained by means of the offered technique, confirm importance of definition of individual thresholds of shipping of a thermal state at athletes and the burdening action of a heat on their physical working capacity.

  18. In-situ investigations of structural changes during cyclic loading by high resolution reciprocal space mapping

    DEFF Research Database (Denmark)

    Diederichs, Annika M.; Thiel, Felix; Lienert, Ulrich

    2017-01-01

    Abstract A major failure reason for structural materials is fatigue-related damage due to repeatedly changing mechanical loads. During cyclic loading dislocations self-organize into characteristic ordered structures, which play a decisive role for the materials lifetime. These heterogeneous...... the materials behavior during cyclic deformation and to improve the material design. While monitoring macroscopic stress and strain during cyclic loading, reciprocal space maps of diffraction peaks from single grains are obtained with high resolution. High Resolution Reciprocal Space Mapping was applied...

  19. Quantifying the increase in lateral capacity of monopiles in sand due to cyclic loading

    DEFF Research Database (Denmark)

    Nicolai, Giulio; Ibsen, Lars Bo; O'Loughlin, Conleth

    2017-01-01

    The contribution of this paper is a simple method to predict the higher moment capacity of a monopile in dense silica sand after drained cyclic loading. The method accounts for the effect of cyclic load magnitude, symmetry and number of cycles, and is calibrated against a series of single gravity...... be predicted using the existing industry standard p–y approach for cyclic loading in sand....

  20. Comparison of the thermoelastic phenomenon expressions in stainless steels during cyclic loading

    Directory of Open Access Journals (Sweden)

    M. Sapieta

    2017-01-01

    Full Text Available The main purpose of this paper is to compare the thermoelastic stress in specimens of stainless steel. As material specimens we chose stainless steel of AISI 304, AISI 316Ti and AISI 316L types. The specimens were cyclically loaded with three-point bending. The whole process was recorded using an infrared camera. The thermal differences that occurred during the test were evaluated based on the thermoelastic stress equations. Subsequently, stress distributions in the specimens were compared for different types of stainless steel.

  1. Assessment of Composite Delamination Self-Healing Under Cyclic Loading

    Science.gov (United States)

    O'Brien, T. Kevin

    2009-01-01

    Recently, the promise of self-healing materials for enhanced autonomous durability has been introduced using a micro-encapsulation technique where a polymer based healing agent is encapsulated in thin walled spheres and embedded into a base polymer along with a catalyst phase. For this study, composite skin-stiffener flange debonding specimens were manufactured from composite prepreg containing interleaf layers with a polymer based healing agent encapsulated in thin-walled spheres. Constant amplitude fatigue tests in three-point bending showed the effect of self-healing on the fatigue response of the skin-stiffener flange coupons. After the cycling that created debonding, fatigue tests were held at the mean load for 24 hours. For roughly half the specimens tested, when the cyclic loading was resumed a decrease in compliance (increase in stiffness) was observed, indicating that some healing had occurred. However, with continued cycling, the specimen compliance eventually increased to the original level before the hold, indicating that the damage had returned to its original state. As was noted in a prevoius study conducted with specimens tested under monotonically increasing loads to failure, healing achieved via the micro-encapsulation technique may be limited to the volume of healing agent available relative to the crack volume.

  2. Macro-residual strains due to cyclic loading of composites

    CERN Document Server

    Hashin, Z

    1999-01-01

    Macro-residual strains produced by load cycles on elastic-brittle composites are analytically expressed in terms of the effective thermal expansion coefficients of the composite as affected by the damage states developing during the $9 cycling. Limiting values of residual strain are evaluated for unidirectional fiber composites and cross-ply laminates. Frictional losses due to internal sliding are not considered. (17 refs).

  3. Martensitic Transformation in Ultrafine-Grained Stainless Steel AISI 304L Under Monotonic and Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Heinz Werner Höppel

    2012-02-01

    Full Text Available The monotonic and cyclic deformation behavior of ultrafine-grained metastable austenitic steel AISI 304L, produced by severe plastic deformation, was investigated. Under monotonic loading, the martensitic phase transformation in the ultrafine-grained state is strongly favored. Under cyclic loading, the martensitic transformation behavior is similar to the coarse-grained condition, but the cyclic stress response is three times larger for the ultrafine-grained condition.

  4. Observations on bucket foundations under cyclic loading in dense saturated sand

    DEFF Research Database (Denmark)

    Foglia, Aligi; Ibsen, Lars Bo; Nicolai, Giulio

    2014-01-01

    for each test. The discus¬sion of the results focuses on three aspects: a critical cyclic loading configuration isfound and compared with a previous study, a limit value of cyclic moment for which no degenerative rotation occurs is obtained and the effect of the loading frequency on the plastic...

  5. Thermal Cyclic Resistance Polyester Resin Composites Reinforce Fiber Nut Shell

    Science.gov (United States)

    Fahmi, Hendriwan

    2017-12-01

    The purpose of study is to determine the effect of fiber length and thermal cyclic of the bending strength of polyester resin composite reinforced by fibers nut shell. The materials used in this study is a nut shell fibers with fiber length of 1 cm, 2 cm and 3 cm and polyester resin with composition 70-30%wt. Fiber nut shell treated soaking in NaOH 30% for 30 minutes, then rinse with clean water so that the fiber free of alkali and then dried. Furthermore, the composite is heated in an oven to a temperature of 100°C for 1 hour and then cooled in the open with a variety of thermal cyclic 30, 40, and 50 times. Bending properties of composites known through the testing process using a three-point bending test equipment universal testing machine. The test results show that the bending strength bending highest in fiber length of 3 cm with 30 treatment cycles of thermal to the value of 53.325 MPa, while the lowest occurred in bending strength fiber length of 1 cm with no cycles of thermal treatment to the value of 30.675 MPa.

  6. Stress recovery and cyclic behaviour of an Fe-Mn-Si shape memory alloy after multiple thermal activation

    Science.gov (United States)

    Hosseini, E.; Ghafoori, E.; Leinenbach, C.; Motavalli, M.; Holdsworth, S. R.

    2018-02-01

    The stress recovery and cyclic deformation behaviour of Fe-17Mn-5Si-10Cr-4Ni-1(V,C) shape memory alloy (Fe-SMA) strips, which are often used for pre-stressed strengthening of structural members, were studied. The evolution of recovery stress under different constraint conditions was studied. The results showed that the magnitude of the tensile stress in the Fe-SMA member during thermal activation can have a signification effect on the final recovery stress. The higher the tensile load in the Fe-SMA (e.g., caused by dead load or thermal expansion of parent structure during heating phase), the lower the final recovery stress. Furthermore, this study investigated the cyclic behaviour of the activated SMA followed by a second thermal activation. Although the magnitude of the recovery stress decreased during the cyclic loading, the second thermal activation could retrieve a significant part of the relaxed recovery stress. This observation suggests that the relaxation of recovery stress during cyclic loading is due to a reversible phase transformation-induced deformation (i.e., forward austenite-to-martensite transformation) rather than an irreversible dislocation-induced plasticity. Retrieval of the relaxed recovery stress by the reactivation process has important practical implications as the prestressing loss in pre-stressed civil structures can be simply recovered by reheating of the Fe-SMA elements.

  7. Multiaxial elastoplastic cyclic loading of austenitic 316L steel

    Directory of Open Access Journals (Sweden)

    V. Mazánová

    2017-04-01

    Full Text Available Cyclic stress-strain response and fatigue damage character has been investigated in austenitic stainless steel 316L. Hollow cylindrical specimens have been cyclically deformed in combined tension-compression and torsion under constant strain rate condition and different constant strain and shear strain amplitudes. In-phase and 90° out-of-phase cyclic straining was applied and the stress response has been monitored. Cyclic hardening/softening curves were assessed in both channels. Cyclic softening followed for higher strain amplitudes by long-term cyclic hardening was observed. Cyclic stress-strain curves were determined. Study of the surface damage in fractured specimens revealed the types and directions of principal cracks and the sources of fatigue crack initiation in slip bands.

  8. A Fatigue Life Prediction Model of Welded Joints under Combined Cyclic Loading

    Science.gov (United States)

    Goes, Keurrie C.; Camarao, Arnaldo F.; Pereira, Marcos Venicius S.; Ferreira Batalha, Gilmar

    2011-01-01

    A practical and robust methodology is developed to evaluate the fatigue life in seam welded joints when subjected to combined cyclic loading. The fatigue analysis was conducted in virtual environment. The FE stress results from each loading were imported to fatigue code FE-Fatigue and combined to perform the fatigue life prediction using the S x N (stress x life) method. The measurement or modelling of the residual stresses resulting from the welded process is not part of this work. However, the thermal and metallurgical effects, such as distortions and residual stresses, were considered indirectly through fatigue curves corrections in the samples investigated. A tube-plate specimen was submitted to combined cyclic loading (bending and torsion) with constant amplitude. The virtual durability analysis result was calibrated based on these laboratory tests and design codes such as BS7608 and Eurocode 3. The feasibility and application of the proposed numerical-experimental methodology and contributions for the technical development are discussed. Major challenges associated with this modelling and improvement proposals are finally presented.

  9. On the design of thermally loaded fiber optics feedthroughs

    Directory of Open Access Journals (Sweden)

    Marinković Dragan Z.

    2016-01-01

    Full Text Available Thermo-mechanical design aspects of various structures exposed to cyclic thermal loading have a crucial impact on their lifetime. This is particularly valid for fiber optics feedthroughs that involve several materials with significantly different thermal expansion ratios. Thermal loading in such structures may give rise to non-trivial thermally induced deformations and therewith stresses, which can be adequately predicted and assessed only by a detailed 3-D numerical simulation. This paper considers a couple of design solutions of fiber optics feedthroughs, which have exhibited certain weaknesses in their application. Numerical simulation by means of the finite element method has been conducted to reveal the weak points of the design.

  10. Studies on resilient modulus value from cyclic loading tests for cohesive soil

    Directory of Open Access Journals (Sweden)

    Sas Wojciech

    2017-06-01

    Full Text Available In this article the cyclic CBR test as a reference method in determination of resilient modulus (Mr is confronted with results of cyclic triaxial and unconfined uniaxial cyclic test. The main idea of conducted experiments is establish relationship between cyclic loading tests in testing of natural subsoil and road materials. The article shows results of investigation on cohesive soil, namely sandy silty clay, commonly problematic soil in Poland. The results of repeated loading triaxial test resilient modulus were displayed in order to compare them with cyclic CBR test results by using the Mr–Ө model. Some empirical correlation between factors obtained from triaxial test or uniaxial unconfined cyclic test and cyclic CBR test was introduced here. The behavior of resilient modulus was also examined in this paper.

  11. Reliability prediction for structures under cyclic loads and recurring inspections

    Directory of Open Access Journals (Sweden)

    Alberto W. S. Mello Jr

    2009-06-01

    Full Text Available This work presents a methodology for determining the reliability of fracture control plans for structures subjected to cyclic loads. It considers the variability of the parameters involved in the problem, such as initial flaw and crack growth curve. The probability of detection (POD curve of the field non-destructive inspection method and the condition/environment are used as important factors for structural confidence. According to classical damage tolerance analysis (DTA, inspection intervals are based on detectable crack size and crack growth rate. However, all variables have uncertainties, which makes the final result totally stochastic. The material properties, flight loads, engineering tools and even the reliability of inspection methods are subject to uncertainties which can affect significantly the final maintenance schedule. The present methodology incorporates all the uncertainties in a simulation process, such as Monte Carlo, and establishes a relationship between the reliability of the overall maintenance program and the proposed inspection interval, forming a “cascade” chart. Due to the scatter, it also defines the confidence level of the “acceptable” risk. As an example, the damage tolerance analysis (DTA results are presented for the upper cockpit longeron splice bolt of the BAF upgraded F-5EM. In this case, two possibilities of inspection intervals were found: one that can be characterized as remote risk, with a probability of failure (integrity nonsuccess of 1 in 10 million, per flight hour; and other as extremely improbable, with a probability of nonsuccess of 1 in 1 billion, per flight hour, according to aviation standards. These two results are compared with the classical military airplane damage tolerance requirements.

  12. Thermal-Mechanical Stress Analysis of PWR Pressure Vessel and Nozzles under Grid Load-Following Mode: Interim Report on the Effect of Cyclic Hardening Material Properties and Pre-existing Cracks on Stress Analysis Results

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, Subhasish [Argonne National Lab. (ANL), Argonne, IL (United States); Soppet, William [Argonne National Lab. (ANL), Argonne, IL (United States); Majumdar, Saurin [Argonne National Lab. (ANL), Argonne, IL (United States); Natesan, Ken [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-03-15

    This report provides an update on an assessment of environmentally assisted fatigue for light water reactor components under extended service conditions. This report is a deliverable under the work package for environmentally assisted fatigue as part of DOE’s Light Water Reactor Sustainability Program. In a previous report (September 2015), we presented tensile and fatigue test data and related hardening material properties for 508 low-alloys steel base metal and other reactor metals. In this report, we present thermal-mechanical stress analysis of the reactor pressure vessel and its hot-leg and cold-leg nozzles based on estimated material properties. We also present results from thermal and thermal-mechanical stress analysis under reactor heat-up, cool-down, and grid load-following conditions. Analysis results are given with and without the presence of preexisting cracks in the reactor nozzles (axial or circumferential crack). In addition, results from validation stress analysis based on tensile and fatigue experiments are reported.

  13. Creep and damage in shells of revolution under cyclic loading and heating

    OpenAIRE

    Breslavsky, D.; Morachkovsky, O.; Tatarinova, O.

    2014-01-01

    Creep of cyclically loaded thin shells of revolution and their fracture due to creep and fatigue mechanisms are studied. Creep-damage equations for steels and nickel-based alloys are built by the use of scalar damage parameter. Constitutive equations were derived using the method of asymptotic expansions and averaging over a period of cyclic loading. The cases of fast and slow varying of temperature and loading are regarded. General problem statement and method for solution of creep problems ...

  14. Planning of physical load of annual cycle of students’, practicing cyclic kinds of sports, training

    Directory of Open Access Journals (Sweden)

    R.S. Nagovitsyn

    2017-06-01

    Full Text Available Purpose: to offer the variant of physical load’s distribution in annual cycle of students’, practicing cyclic kinds of sports training. Material: in the research pedagogic HEE students, specializing in skiing and light athletic participated (n=18 - boys, n=8 -girls, age - 18-23 years. The students were divided into two groups: experimental and control. Results: by comparison we determined the following: volume and intensity of physical load in micro-cycle and macro-cycle; indicators of cyclic load’s distribution in year plan of students’ training. In cyclic group of skiers we used the method of standard-interval and alternative exercises. I.e. exercises of one load are fulfilled repeatedly. Other method implies variable, increasing or decreasing physical load. Cyclic load, fulfilled at heart beats rate of 160-190 bpm, accented on intensity, prevails. The main requirement is: fulfillment of movements with maximal quickness. In group of light athletic sportsmen the method of standard - continuous exercises, implying moderate intensity, was used. For example: standard current exercises - passing distance of 3 km, 5 km or 10 km. Cyclic load, fulfilled at heart beats rate of 140-160 bpm, accented on volume. Conclusions: In cyclic load of light athletic group aerobic character of work prevails. In cyclic load of skiers’ group mixed and anaerobic character of work prevails.

  15. The behavior of welded joint in steel pipe members under monotonic and cyclic loading

    International Nuclear Information System (INIS)

    Chang, Kyong-Ho; Jang, Gab-Chul; Shin, Young-Eui; Han, Jung-Guen; Kim, Jong-Min

    2006-01-01

    Most steel pipe members are joined by welding. The residual stress and weld metal in a welded joint have the influence on the behavior of steel pipes. Therefore, to accurately predict the behavior of steel pipes with a welded joint, the influence of welding residual stress and weld metal on the behavior of steel pipe must be investigated. In this paper, the residual stress of steel pipes with a welded joint was investigated by using a three-dimensional non-steady heat conduction analysis and a three-dimensional thermal elastic-plastic analysis. Based on the results of monotonic and cyclic loading tests, a hysteresis model for weld metal was formulated. The hysteresis model was proposed by the authors and applied to a three-dimensional finite elements analysis. To investigate the influence of a welded joint in steel pipes under monotonic and cyclic loading, three-dimensional finite elements analysis considering the proposed model and residual stress was carried out. The influence of a welded joint on the behavior of steel pipe members was investigated by comparing the analytical result both steel pipe with a welded joint and that without a welded joint

  16. Rockfall triggering by cyclic thermal stressing of exfoliation fractures

    Science.gov (United States)

    Collins, Brian D.; Stock, Greg M.

    2016-01-01

    Exfoliation of rock deteriorates cliffs through the formation and subsequent opening of fractures, which in turn can lead to potentially hazardous rockfalls. Although a number of mechanisms are known to trigger rockfalls, many rockfalls occur during periods when likely triggers such as precipitation, seismic activity and freezing conditions are absent. It has been suggested that these enigmatic rockfalls may occur due to solar heating of rock surfaces, which can cause outward expansion. Here we use data from 3.5 years of field monitoring of an exfoliating granite cliff in Yosemite National Park in California, USA, to assess the magnitude and temporal pattern of thermally induced rock deformation. From a thermodynamic analysis, we find that daily, seasonal and annual temperature variations are sufficient to drive cyclic and cumulative opening of fractures. Application of fracture theory suggests that these changes can lead to further fracture propagation and the consequent detachment of rock. Our data indicate that the warmest times of the day and year are particularly conducive to triggering rockfalls, and that cyclic thermal forcing may enhance the efficacy of other, more typical rockfall triggers.

  17. Experimental Comparison of Non-Slender Piles under Static Loading and under Cyclic Loading in Sand

    DEFF Research Database (Denmark)

    Sørensen, Søren Peder Hyldal; Ibsen, Lars Bo

    2012-01-01

    An experimental evaluation of the pile behavior of non-slender piles exposed to static and cyclic lateral loading is presented. The tests were conducted in a pressure tank at Aalborg University. This enabled the possibility of applying an overburden pressure to the soil. When conducting small......-scale tests at 1-g the determination of the friction angle and the Young’s modulus of elasticity of the soil are difficult and further these soil parameters varies greatly with depth. These uncertainties were avoided by application of an overburden pressure....

  18. Effects of loading frequency on cyclic parameters of unsaturated Zenoz kaolin

    Directory of Open Access Journals (Sweden)

    Mojezi Mohsen

    2016-01-01

    Full Text Available According to the considerable effects of the loading frequency on the cyclic behaviour of the soils and lack of the sufficient and precise data in this field for the unsaturated soils, more attention needs to be paid to the experimental investigations in various loading paths and frequencies. Meanwhile the unsaturated cyclic tests require advanced equipment and need more precision and time. In this paper, the results of two groups of tests which were performed on an unsaturated fine grained soil in the same initial condition are presented and compared during specific stress paths (pre-cycles of loading and during cycles. The tests are performed using the same suction-controlled cyclic triaxial apparatus in the same stress path before loading cycles, but two conditions of the cyclic loading frequencies (slow cyclic tests with the constant suction condition during the cycles and rapid cyclic tests with the unsteady suction condition during the cyclic path. The results show that increase in the loading frequency leads to the considerable increase in the shear modulus of the samples in the same strain levels.

  19. Stress release during cyclic loading of 20 nm palladium films

    Energy Technology Data Exchange (ETDEWEB)

    Lukáč, František, E-mail: frantisek.lukac@mff.cuni.cz [Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, CZ-18000 Praha 8 (Czech Republic); Vlček, Marián; Vlach, Martin [Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, CZ-18000 Praha 8 (Czech Republic); Wagner, Stefan; Uchida, Helmut; Pundt, Astrid [Institute for Materials Physics, University of Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Bell, Anthony [Deutsche Elektronen-Synchrotron (DESY), HASYLAB, Notkestrasse 85, D-2260 Hamburg (Germany); Čížek, Jakub [Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, CZ-18000 Praha 8 (Czech Republic)

    2015-10-05

    Highlights: • Repeated hydrogenation of 20 nm Pd films was investigated by in situ X-ray diffraction. • Hydride precipitates form coherent interfaces with matrix in nanocrystalline and epitaxial thin films. • Grain boundaries affect precipitation of the hydride phase in the nanocrystalline film. • Stress in epitaxial film is tensile due to different thermal expansion of Pd and sapphire. • After hydrogen absorption/desorption cycle the stress in both films becomes tensile. - Abstract: Gas phase loading of nanocrystalline and epitaxial 20 nm Pd films deposited on single crystalline sapphire substrates was studied in this work. The nanocrystalline film was deposited at room temperature and the epitaxial film deposited at 800 °C. The nanocrystalline film suffers from in-plane compressive stress imposed by atomic peening processes. The epitaxial film exhibits tensile stress caused by the different thermal expansion coefficients of Pd and sapphire substrate. Coherent phase transition into the hydride phase was observed both for the nanocrystalline and for the epitaxial film. For both films, the lattice parameters continuously increase during the phase transition to the hydride phase. Both films exhibit enhanced hydride formation pressure compared to bulk Pd. Misfit dislocations are formed at interface between Pd film and substrate during hydrogenation. This leads to irreversible change of stress state of the films subjected to sorption and desorption cycle with hydrogen.

  20. Small-Scale Testing of Cyclic Laterally Loaded Monopiles in Dense Saturated Sand

    DEFF Research Database (Denmark)

    Nicolai, Giulio; Ibsen, Lars Bo

    2014-01-01

    Monopiles are currently the most common foundations for offshore wind turbines, which are subjected to millions of cyclic loads that are still not well interpreted in the design guidelines. The accumulated rotation of the turbine and the change of foundation stiffness due to the long-term cyclic ...

  1. Analysis of creep curves produced by the linear viscoelasticity theory under cyclic stepwise loadings

    Directory of Open Access Journals (Sweden)

    Andrew V. Khokhlov

    2017-07-01

    Full Text Available Basic qualitative properties of the creep curves generated by the linear integral constitutive relation of viscoelasticity (with an arbitrary creep compliance under cyclic piecewise-constant uni-axial loadings (with an arbitrary asymmetry stress ratio are studied analytically. General formulas and a number of exact two-sided bounds are obtained for maximal, minimal and ratcheting strain values during each cycle, for their sequences limits, for the rate of plastic (non-recoverable strain accumulation and for cyclic creep curve deviation from the creep curve at constant stress which is equal to the cycle mean stress. Their dependence on loading cycle parameters and creep compliance properties are analyzed. Monotonicity and convexity intervals of cyclic creep curves, sequences of maximal and minimal strain values and ratcheting strain sequence, their evolution with cycle number growth and conditions for their boundedness, monotonicity and convergence are examined. The linear viscoelasticity theory abilities for simulation of ratcheting, creep acceleration, cyclic hardening or softening and cyclic stability under symmetric cyclic loadings are considered. The analysis carried out revealed the importance of convexity restriction imposed on a creep compliance and the governing role of its derivative limit value at infinity. It is proved that the limit value equality to zero is the criterion for non-accumulation of plastic strain, for memory fading and for asymptotic symmetrization of cyclic creep curve deviation from the creep curve at the mean stress. The qualitative features of theoretic cyclic creep curves are compared to basic properties of typical test creep curves of viscoelastoplastic materials under cyclic multi-step uni-axial loadings in order to elucidate the linear theory applicability scope, to reveal its abilities to provide an adequate description of basic rheological phenomena related to cyclic creep and to develop techniques of

  2. Bond-Slip Relationship for CFRP Sheets Externally Bonded to Concrete under Cyclic Loading.

    Science.gov (United States)

    Li, Ke; Cao, Shuangyin; Yang, Yue; Zhu, Juntao

    2018-02-26

    The objective of this paper was to explore the bond-slip relationship between carbon fiber-reinforced polymer (CFRP) sheets and concrete under cyclic loading through experimental and analytical approaches. Modified beam tests were performed in order to gain insight into the bond-slip relationship under static and cyclic loading. The test variables are the CFRP-to-concrete width ratio, and the bond length of the CFRP sheets. An analysis of the test results in this paper and existing test results indicated that the slope of the ascending segment of the bond-slip curve decreased with an increase in the number of load cycles, but the slip corresponding to the maximum shear stress was almost invariable as the number of load cycles increased. In addition, the rate of reduction in the slope of the ascending range of the bond-slip curve during cyclic loading decreased as the concrete strength increased, and increased as the load level or CFRP-to-concrete width ratio enhanced. However, these were not affected by variations in bond length if the residual bond length was longer than the effective bond length. A bilinear bond-slip model for CFRP sheets that are externally bonded to concrete under cyclic loading, which considered the effects of the cyclic load level, concrete strength, and CFRP-to-concrete ratio, was developed based on the existing static bond-slip model. The accuracy of this proposed model was verified by a comparison between this proposed model and test results.

  3. Experimental and numerical studies of various thermal sleeves subjected to severe cyclic thermal shocks

    International Nuclear Information System (INIS)

    Masson, J.C.; Moinereau, D.

    1990-01-01

    During the first operating years of nuclear power plants of different countries, damage was encountered on thermal sleeves used as nozzle protection. Following this discovery studies were initiated to determine the causes and to find solutions. At first a problem of vibration was found and easily solved by reducing gaps and reinforcing the welding of the sleeves. But preliminary tests with cyclic thermal shocks showed a risk of fatigue crack initiation and propagation both in the sleeve fixation and in the nozzle. Therefore a large research and development program was led principally by EDF laboratories of Les Renardieres, to demonstrate the absence of nocivity of thermal shocks during the plants life time [fr

  4. Mechanical performance of a screw-type veterinary suture anchor subjected to single load to failure and cyclic loads.

    Science.gov (United States)

    Balara, Jason M; McCarthy, Robert J; Boudrieau, Randy J; Kraus, Karl H

    2004-01-01

    To characterize the mechanical performance of a veterinary bone anchor under static and cyclic loads. Mechanical testing study. Cadaveric canine humeri. Humeri (6 pairs) were collected from skeletally mature dogs (mean [+/-SD] age, 17.2+/-2.1 months; weight, 20.8+/-1.5 kg). Bone anchors were inserted in the proximal metaphysis using nylon, and were longitudinally extracted. For the opposite humerus, anchors were subjected to longitudinal cyclic load (50% of the load at failure of their pair) for 1200 cycles then longitudinally loaded to failure. Anchors were then installed in a similar and adjacent area of these 2(nd) humeri with nylon and cyclically tested perpendicular to the axis of anchor insertion (100% of the longitudinal holding power of their pair) for 1200 cycles, then perpendicularly loaded to failure. Paired t-tests were used to compare holding power before and after longitudinal cyclic testing. Longitudinal holding power of the screw-type anchor in the proximal humerus was 385+/-30 N. Anchor pullout was the only mode of failure. Anchors in the paired humeri did not fail after 1200 cycles of 50% longitudinal loading, and post-cycle holding strength was not different (335+/-87 N; P=.32). Perpendicularly loaded anchors did not fail after 1200 cycles of 100% of opposite longitudinal holding strength, and had post-cycle perpendicular holding strengths of 514+/-72 N. Suture breakage was the mode of failure. Bone anchor holding strength is dependent on orientation of suture load. Screw-type bone anchor holding strength was not affected by longitudinal cyclic loading, and holding strengths of approximately 385 N can be expected in metaphyseal bone of large-breed mature dogs. Perpendicularly loaded anchors have higher failure loads, and holding strength of approximately 514 N can be expected in metaphyseal bone of the proximal humerus.

  5. Creep crack growth by grain boundary cavitation under monotonic and cyclic loading

    Science.gov (United States)

    Wen, Jian-Feng; Srivastava, Ankit; Benzerga, Amine; Tu, Shan-Tung; Needleman, Alan

    2017-11-01

    Plane strain finite deformation finite element calculations of mode I crack growth under small scale creep conditions are carried out. Attention is confined to isothermal conditions and two time histories of the applied stress intensity factor: (i) a monononic increase to a plateau value subsequently held fixed; and (ii) a cyclic time variation. The crack growth calculations are based on a micromechanics constitutive relation that couples creep deformation and damage due to grain boundary cavitation. Grain boundary cavitation, with cavity growth due to both creep and diffusion, is taken as the sole failure mechanism contributing to crack growth. The influence on the crack growth rate of loading history parameters, such as the magnitude of the applied stress intensity factor, the ratio of the applied minimum to maximum stress intensity factors, the loading rate, the hold time and the cyclic loading frequency, are explored. The crack growth rate under cyclic loading conditions is found to be greater than under monotonic creep loading with the plateau applied stress intensity factor equal to its maximum value under cyclic loading conditions. Several features of the crack growth behavior observed in creep-fatigue tests naturally emerge, for example, a Paris law type relation is obtained for cyclic loading.

  6. Drained Response of Bucket Foundations under Cyclic Lateral Load

    DEFF Research Database (Denmark)

    Foglia, Aligi; Ibsen, Lars Bo

    2013-01-01

    Introduction The monopod bucket foundation is an innovative support structure for offshore wind turbines. It consists of a shallow embedded foundation which penetrates the seabed by means of a suction created within the caisson. The behaviour of bucket foundations against long-term lateral cyclic...

  7. Cyclic Elastoplastic Performance of Aluminum 7075-T6 Under Strain- and Stress-Controlled Loading

    Science.gov (United States)

    Agius, Dylan; Wallbrink, Chris; Kourousis, Kyriakos I.

    2017-12-01

    Elastoplastic investigations of aerospace aluminum are important in the development of an understanding of the possible cyclic transient effects and their contribution to the material performance under cyclic loading. Cyclic plasticity can occur in an aerospace aluminum component or structure depending on the loading conditions and the presence of external and internal discontinuities. Therefore, it is vital that the cyclic transient effects of aerospace aluminum are recognized and understood. This study investigates experimentally the cyclic elastoplastic performance of aluminum 7075-T6 loaded in symmetric strain control, and asymmetric stress and strain control. A combination of cyclic hardening and softening was noticed from high strain amplitude symmetric strain-controlled tests and at low stress amplitude asymmetric stress-controlled tests. From asymmetric strain control results, the extent of mean stress relaxation depended on the size of the strain amplitude. Additionally, saturation of the ratcheting strain (plastic shakedown) was also found to occur during asymmetric stress control tests. The experimental results were further analyzed using published microstructure research from the past two decades to provide added explanation of the micro-mechanism contribution to the cyclic transient behavior.

  8. The influence of gas–solid reaction kinetics in models of thermochemical heat storage under monotonic and cyclic loading

    International Nuclear Information System (INIS)

    Nagel, T.; Shao, H.; Roßkopf, C.; Linder, M.; Wörner, A.; Kolditz, O.

    2014-01-01

    Highlights: • Detailed analysis of cyclic and monotonic loading of thermochemical heat stores. • Fully coupled reactive heat and mass transport. • Reaction kinetics can be simplified in systems limited by heat transport. • Operating lines valid during monotonic and cyclic loading. • Local integral degree of conversion to capture heterogeneous material usage. - Abstract: Thermochemical reactions can be employed in heat storage devices. The choice of suitable reactive material pairs involves a thorough kinetic characterisation by, e.g., extensive thermogravimetric measurements. Before testing a material on a reactor level, simulations with models based on the Theory of Porous Media can be used to establish its suitability. The extent to which the accuracy of the kinetic model influences the results of such simulations is unknown yet fundamental to the validity of simulations based on chemical models of differing complexity. In this article we therefore compared simulation results on the reactor level based on an advanced kinetic characterisation of a calcium oxide/hydroxide system to those obtained by a simplified kinetic model. Since energy storage is often used for short term load buffering, the internal reactor behaviour is analysed under cyclic partial loading and unloading in addition to full monotonic charge/discharge operation. It was found that the predictions by both models were very similar qualitatively and quantitatively in terms of thermal power characteristics, conversion profiles, temperature output, reaction duration and pumping powers. Major differences were, however, observed for the reaction rate profiles themselves. We conclude that for systems not limited by kinetics the simplified model seems sufficient to estimate the reactor behaviour. The degree of material usage within the reactor was further shown to strongly vary under cyclic loading conditions and should be considered when designing systems for certain operating regimes

  9. Molecular Simulations of Cyclic Loading Behavior of Carbon Nanotubes Using the Atomistic Finite Element Method

    Directory of Open Access Journals (Sweden)

    Jianfeng Wang

    2009-01-01

    Full Text Available The potential applications of carbon nanotubes (CNT in many engineered bionanomaterials and electromechanical devices have imposed an urgent need on the understanding of the fatigue behavior and mechanism of CNT under cyclic loading conditions. To date, however, very little work has been done in this field. This paper presents the results of a theoretical study on the behavior of CNT subject to cyclic tensile and compressive loads using quasi-static molecular simulations. The Atomistic Finite Element Method (AFEM has been applied in the study. It is shown that CNT exhibited extreme cyclic loading resistance with yielding strain and strength becoming constant within limited number of loading cycles. Viscoelastic behavior including nonlinear elasticity, hysteresis, preconditioning (stress softening, and large strain have been observed. Chiral symmetry was found to have appreciable effects on the cyclic loading behavior of CNT. Mechanisms of the observed behavior have been revealed by close examination of the intrinsic geometric and mechanical features of tube structure. It was shown that the accumulated residual defect-free morphological deformation was the primary mechanism responsible for the cyclic failure of CNT, while the bond rotating and stretching experienced during loading/unloading played a dominant role on the strength, strain and modulus behavior of CNT.

  10. Effectiveness of screw surface coating on the stability of zirconia abutments after cyclic loading.

    Science.gov (United States)

    Basílio, Mariana de Almeida; Butignon, Luis Eduardo; Arioli Filho, João Neudenir

    2012-01-01

    Different surface treatments have been developed in attempts to prevent the loosening of abutment screws. The aim of the current study was to compare the effectiveness of titanium alloy screws with tungsten-doped diamond-like carbon (W-DLC) coating and uncoated screws in providing stability to zirconia (ZrO2) ceramic abutments after cyclic loading. Twenty prefabricated ZrO2 ceramic abutments on their respective external-hex implants were divided into two groups of equal size according to the type of screw used: uncoated titanium alloy screw (Ti) or titanium alloy screw with W-DLC coating (W-DLC/Ti). The removal torque value (preload) of the abutment screw was measured before and after loading. Cyclic loading between 11 and 211 N was applied at an angle of 30 degrees to the long axis of the implants at a frequency of 15 Hz. A target of 0.5 X 106 cycles was defined. Group means were calculated and compared using analysis of variance and the F test (α = .05). Before cyclic loading, the preload for Ti screws was significantly higher than that for W-DLC/Ti screws (P = .021). After cyclic loading, there was no significant difference between them (P = .499). Under the studied conditions, it can be concluded that, after cyclic loading, both abutment screws presented a significant reduction in the mean retained preload and similar effectiveness in maintaining preload.

  11. Mechanical behaviour and microstructural evolution of alloy 800H under biaxial cyclic loading

    International Nuclear Information System (INIS)

    Dolabella Portella, P.; Feng Jiao; Oesterle, W.; Ziebs, J.

    1999-01-01

    The mechanical behaviour of alloy 800H under biaxial cyclic loading was investigated at room temperature and at 800 C. The low-cycle fatigue experiments were carried out using tubular specimens under axial and torsional loading with constant total equivalent strain amplitude following either proportional or nonproportional loading paths. The cyclic hardening observed under nonproportional loading was clearly higher than that under proportional loading. The extra hardening due to the nonproportional loading path was more pronounced at room temperature. The evolution of the dislocation structure was characterized by transmission electron microscopy of specimens after interrupted fatigue tests. The changes in the dislocation structure and the precipitation phenomena are in accordance with the observed mechanical behaviour of the specimens. Twinning was observed in very few grains of some specimens and does not influence the extra hardening under nonproportional loading, martensite was not detected in any specimen. (orig.)

  12. Micromechanics of intergranular creep failure under cyclic loading

    DEFF Research Database (Denmark)

    van der Giessen, Erik; Tvergaard, Viggo

    1996-01-01

    boundaries are modelled individually. The model incorporates power-law creep of the grains, viscous grain boundary sliding between grains as well as the nucleation and growth of grain boundary cavities until they coalesce and form microcracks. Study of a limiting case with a facet-size microcrack reveals....... The analyses provide some new understanding that helps to explain the sometimes peculiar behaviour under balanced cyclic creep. Copyright (C) 1996 Acta Metallurgica Inc....

  13. Prediction of fatigue crack growth rate under biaxial low-cyclic loading

    International Nuclear Information System (INIS)

    Braude, N.Z.; Shkanov, I.N.; Galeeva, F.G.

    1991-01-01

    A new criterion of the crack growth prediction under biaxial loading based on the local stress-strained state in the crack apex, the plastic zone size and the cyclic fracture margin of safety is proposed. Predicted data are compared with experimental data presented by the authors. A satisfactory result concerning stress level effect, material behaviour and biaxial loading parameter is obtained

  14. Physical Modelling of Bucket Foundation Under Long-Term Cyclic Lateral Loading

    DEFF Research Database (Denmark)

    Foglia, Aligi; Ibsen, Lars Bo; Andersen, Lars Vabbersgaard

    2012-01-01

    functioning. In this article a 1g physical model of bucket foundation under horizontal and moment cyclic loading is described. A testing program including four tests was carried out. Every test was conducted for at least 30000 cycles, each with different loading features. The capability of the model...

  15. INFLUENCE OF CYCLIC LOADING ON THE DEFLECTION DEVELOPMENT OF CONCRETE SPECIMENS

    Directory of Open Access Journals (Sweden)

    Marek Foglar

    2015-12-01

    Full Text Available Durability of the structures is one of the most discussed issues of last decades. It is one of the most easily measured properties for analysis during the structural lifetime. Concrete deflections increase over time due to rheological effects (creep and shrinkage in addition cyclic creep can be observed on the cyclically loaded structures. The deflection increase due to the cyclic creep is not properly quantified. The fatigue damage function presented in this paper provides an analytical solution for the deflection development due to cyclic loading. The evaluation of the deflection is based on the reduction of the initial modulus of elasticity. Main principles of the function are discussed and compared with the standardized approaches for the fatigue assessment. Experimental verification of the fatigue damage function was carried out on reinforced concrete specimens and on prestressed concrete slab. To improve the standardized approaches, the real stress distribution was considered with the use of newly- developed method of partial integration over the height of the specimen compressive zone. The deflection increase due to cyclic loading was measured regularly with inductive displacement transducer. Comparison of the measured values and the values calculated using the presented function shows good agreement. The fatigue damage function can be used easily in “in- hand” calculations, or can be inserted into FEM-based software and used in practical applications for assessing the increase in the deformations of concrete structural elements caused by cyclic loading.

  16. Experimental Investigation and FE Analysis on Constitutive Relationship of High Strength Aluminum Alloy under Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Yuanqing Wang

    2016-01-01

    Full Text Available Experiments of 17 high strength aluminum alloy (7A04 specimens were conducted to investigate the constitutive relationship under cyclic loading. The monotonic behavior and hysteretic behavior were focused on and the fracture surface was observed by scanning electron microscope (SEM to investigate the microfailure modes. Based on Ramberg-Osgood model, stress-strain skeleton curves under cyclic loading were fitted. Parameters of combined hardening model including isotropic hardening and kinematic hardening were calibrated from test data according to Chaboche model. The cyclic tests were simulated in finite element software ABAQUS. The test results show that 7A04 aluminum alloy has obvious nonlinearity and ultra-high strength which is over 600 MPa, however, with relatively poor ductility. In the cyclic loading tests, 7A04 aluminum alloy showed cyclic hardening behavior and when the compressive strain was larger than 1%, the stiffness degradation and strength degradation occurred. The simulated curves derived by FE model fitted well with experimental curves which indicates that the parameters of this combined model can be used in accurate calculation of 7A04 high strength aluminum structures under cyclic loading.

  17. Evaluation of the AZ31 cyclic elastic-plastic behaviour under multiaxial loading conditions

    Directory of Open Access Journals (Sweden)

    V. Anes

    2014-10-01

    Full Text Available Components and structures are designed based in their material’s mechanical properties such as Young's modulus or yield stress among others. Often those properties are obtained under monotonic mechanical tests but rarely under cyclic ones. It is assumed that those properties are maintained during the material fatigue life. However, under cyclic loadings, materials tend to change their mechanical properties, which can improve their strength (material hardening or degrade their mechanical capabilities (material softening or even a mix of both. This type of material behaviour is the so-called cyclic plasticity that is dependent of several factors such as the load type, load level, and microstructure. This subject is of most importance in design of structures and components against fatigue failures in particular in the case of magnesium alloys. Magnesium alloys due to their hexagonal compact microstructure have only 3 slip planes plus 1 twining plane which results in a peculiar mechanical behaviour under cyclic loading conditions especially under multiaxial loadings. Therefore, it is necessary to have a cyclic elastic-plastic model that allows estimating the material mechanical properties for a certain stress level and loading type. In this paper it is discussed several aspects of the magnesium alloys cyclic properties under uniaxial and multiaxial loading conditions at several stress levels taking into account experimental data. A series of fatigue tests under strain control were performed in hour glass specimens test made of a magnesium alloy, AZ31BF. The strain/stress relation for uniaxial loadings, axial and shear was experimentally obtained and compared with the estimations obtained from the theoretical elastic-plastic models found in the state-of-the-art. Results show that the AZ31BF magnesium alloy has a peculiar mechanical behaviour, which is quite different from the steel one. Moreover, the state of the art cyclic models do not capture in

  18. Effects of cyclic shear loads on strength, stiffness and dilation of rock fractures

    Directory of Open Access Journals (Sweden)

    Thanakorn Kamonphet

    2015-12-01

    Full Text Available Direct shear tests have been performed to determine the peak and residual shear strengths of fractures in sandstone, granite and limestone under cyclic shear loading. The fractures are artificially made in the laboratory by tension inducing and saw-cut methods. Results indicate that the cyclic shear load can significantly reduce the fracture shear strengths and stiffness. The peak shear strengths rapidly decrease after the first cycle and tend to remain unchanged close to the residual strengths through the tenth cycle. Degradation of the first order asperities largely occurs after the first cycle. The fracture dilation rates gradually decrease from the first through the tenth cycles suggesting that the second order asperities continuously degrade after the first load cycle. The residual shear strengths are lower than the peak shear strengths and higher than those of the smooth fractures. The strength of smooth fracture tends to be independent of cyclic shear loading.

  19. A constitutive model for AS4/PEEK thermoplastic composites under cyclic loading

    Science.gov (United States)

    Rui, Yuting; Sun, C. T.

    1990-01-01

    Based on the basic and essential features of the elastic-plastic response of the AS4/PEEK thermoplastic composite subjected to off-axis cyclic loadings, a simple rate-independent constitutive model is proposed to describe the orthotropic material behavior for cyclic loadings. A one-parameter memory surface is introduced to distinguish the virgin deformation and the subsequent deformation process and to characterize the loading range effect. Cyclic softening is characterized by the change of generalized plastic modulus. By the vanishing yield surface assumption, a yield criterion is not needed and it is not necessary to consider loading and unloading separately. The model is compared with experimental results and good agreement is obtained.

  20. Fatigue lifetime investigations on aluminium 2024 under two stage cyclic loading by means of experiments and three microstructural models

    International Nuclear Information System (INIS)

    Burkart, K.; Schleicher, M.; Jansen, C.; Bomas, H.; Mayr, P.

    2000-01-01

    The aim of this work is to achieve information about the development of fatigue failure in the aluminium alloy 2024. The attention was focused on short fatigue cracks under cyclic loading and the occurring load sequence effects on lifetime under two-level cyclic loading. Following the experiments, a revision of three different microstructural crack growth models, which were found in the literature, was made. Based on the data of constant-level cyclic loading, predictions of two-level cyclic loading behaviour were made and compared with the experimentally measured crack propagation rates and reached lifetimes. (orig.) [de

  1. Experimental investigation of steel fiber-reinforced concrete beams under cyclic loading

    Science.gov (United States)

    Ranjbaran, Fariman; Rezayfar, Omid; Mirzababai, Rahmatollah

    2018-01-01

    An experimental study has been conducted to study the cyclic behavior of reinforced concrete beams in which steel fibers were added to the concrete mix. Seven similar geometrically specimens in full scale were studied under four- point bending test in the form of slow cyclic loading. One sample as a control specimen was made without steel fibers or 0% volume fraction (vf) and six other samples with 1, 2 and 4% vf of steel fibers in twin models. The maximum and ultimate resistance, ductility, degradation of loading and unloading stiffness, absorption and dissipation of energy and equivalent viscous damping were studied in this investigation and the effect of steel fibers on the cyclic behavior was compared with each other. Generally, the addition of steel fibers up to a certain limit value (vf = 2%) improves the cyclic behavior of reinforced concrete beams and results in the increase of maximum strength and ultimate displacement.

  2. Cyclic response and early damage evolution in multiaxial cyclic loading of 316L austenitic steel

    Czech Academy of Sciences Publication Activity Database

    Mazánová, Veronika; Škorík, Viktor; Kruml, Tomáš; Polák, Jaroslav

    2017-01-01

    Roč. 100, JUL (2017), s. 466-476 ISSN 0142-1123 R&D Projects: GA MŠk LM2015069; GA MŠk(CZ) LQ1601; GA ČR(CZ) GA13-23652S; GA ČR GA15-08826S Institutional support: RVO:68081723 Keywords : 316L steel * Crack initiation * Cyclic plasticity * Damage mechanism * Multiaxial straining Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis Impact factor: 2.899, year: 2016

  3. Experimental Setup for Cyclic Lateral Loading of Monopiles in Sand

    DEFF Research Database (Denmark)

    Roesen, Hanne Ravn; Andersen, Lars Vabbersgaard; Ibsen, Lars Bo

    2012-01-01

    The majority of all offshore wind turbines are installed on monopiles, i.e. large diameter stiff piles. During the environmental loading of the wind turbine the monopile is subjected to millions of load cycles which might cause an accumulated rotation of the wind turbine. In this paper the influe...

  4. Transient Monotonic and Cyclic Load Effects on Mono Bucket Foundations

    DEFF Research Database (Denmark)

    Nielsen, Søren Dam

    Today, 80 % of all European offshore wind turbines are installed on monopiles. A cost-effective alternative to the monopile is the mono bucket foundation. For an offshore wind turbine foundation in open seas, the dominant load is often coming from waves. During storms, large waves are formed...... and when hitting the foundation they induce high impact loads with a short duration. It is important that the foundation is able to resists these huge loads. Fortunately, the conducted research showed that the capacity of the mono bucket foundation is high to impact loads. When exposed to a huge wave load...... accumulating for each wave impact. The presented research has shown indications that only the first waves contribute to the permanent rotation. These indications are seen in small-scale laboratory tests and on a full-scale mono bucket foundation....

  5. Effects of laboratory heating, cyclic pore pressure, and cyclic loading on fracture properties of asphalt mixture.

    Science.gov (United States)

    2012-04-01

    This study involved the identification and evaluation of laboratory conditioning methods and testing protocols considering heat oxidation, moisture, and load that more effectively simulate asphalt mixture aging in the field, and thereby help to prope...

  6. Experimental Testing of Monopiles in Sand Subjected to One-Way Long-Term Cyclic Lateral Loading

    DEFF Research Database (Denmark)

    Roesen, Hanne Ravn; Ibsen, Lars Bo; Andersen, Lars Vabbersgaard

    2013-01-01

    cycles. The tests are conducted in dense saturated sand. The maximum moment applied in the cyclic tests is varied from 18% to 36% of the ultimate lateral resistance found in a static loading test. The tests reveal that the accumulated rotation can be expressed by use of a power function. Further, static...... tests conducted post cyclic loading indicate that the static ultimate capacity increases with the magnitude of cyclic loading....

  7. Fatigue Performance of SFPSC under Hot-Wet Environments and Cyclic Bending Loads

    Directory of Open Access Journals (Sweden)

    Shanshan Luo

    2018-01-01

    Full Text Available A new structural material named “steel fiber polymer structural concrete (SFPSC” with features of both high strength and high toughness was developed by this research group and applied to the bridge superstructures in the hot-wet environments. In order to investigate the fatigue performance and durability of SFPSC under hot-wet environments, the environment and fatigue load uncoupling method and the coupling action of environment and fatigue load were used or developed. Three-point bending fatigue experiments with uncoupling action of environments and cyclic loads were carried out for SFPSC specimens which were pretreated under hot-wet environments, and the experiments with the coupling action of environments and cyclic loads for SFPSC specimens were carried out under hot-wet environments. Then, the effects of hot-wet environments and the experimental methods on the fatigue mechanism of SFPSC material were discussed, and the environmental fatigue equations of SFPSC material under coupling and uncoupling action of hot-wet environments and cyclic bending loads were established. The research results show that the fatigue limits of SFPSC under the coupling action of the environments and cyclic loads were lower about 15%. The proposed fatigue equations could be used to estimate the fatigue lives and fatigue limits of SFPSC material.

  8. Instantaneous angular speed monitoring of gearboxes under non-cyclic stationary load conditions

    Science.gov (United States)

    Stander, C. J.; Heyns, P. S.

    2005-07-01

    Recent developments in the condition monitoring and asset management market have led to the commercialisation of online vibration-monitoring systems. These systems are primarily utilised to monitor large mineral mining equipment such as draglines, continuous miners and hydraulic shovels. Online monitoring systems make diagnostic information continuously available for asset management, production outsourcing and maintenance alliances with equipment manufacturers. However, most online vibration-monitoring systems are based on conventional vibration-monitoring technologies, which are prone to giving false equipment deterioration warnings on gears that operate under fluctuating load conditions. A simplified mathematical model of a gear system was developed to illustrate the feasibility of monitoring the instantaneous angular speed (IAS) as a means of monitoring the condition of gears that are subjected to fluctuating load conditions. A distinction is made between cyclic stationary load modulation and non-cyclic stationary load modulation. It is shown that rotation domain averaging will suppress the modulation caused by non-cyclic stationary load conditions but will not suppress the modulation caused by cyclic stationary load conditions. An experimental investigation on a test rig indicated that the IAS of a gear shaft could be monitored with a conventional shaft encoder to indicate a deteriorating gear fault condition.

  9. Bond–Slip Relationship for CFRP Sheets Externally Bonded to Concrete under Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Ke Li

    2018-02-01

    Full Text Available The objective of this paper was to explore the bond–slip relationship between carbon fiber-reinforced polymer (CFRP sheets and concrete under cyclic loading through experimental and analytical approaches. Modified beam tests were performed in order to gain insight into the bond–slip relationship under static and cyclic loading. The test variables are the CFRP-to-concrete width ratio, and the bond length of the CFRP sheets. An analysis of the test results in this paper and existing test results indicated that the slope of the ascending segment of the bond–slip curve decreased with an increase in the number of load cycles, but the slip corresponding to the maximum shear stress was almost invariable as the number of load cycles increased. In addition, the rate of reduction in the slope of the ascending range of the bond–slip curve during cyclic loading decreased as the concrete strength increased, and increased as the load level or CFRP-to-concrete width ratio enhanced. However, these were not affected by variations in bond length if the residual bond length was longer than the effective bond length. A bilinear bond–slip model for CFRP sheets that are externally bonded to concrete under cyclic loading, which considered the effects of the cyclic load level, concrete strength, and CFRP-to-concrete ratio, was developed based on the existing static bond–slip model. The accuracy of this proposed model was verified by a comparison between this proposed model and test results.

  10. Bond–Slip Relationship for CFRP Sheets Externally Bonded to Concrete under Cyclic Loading

    Science.gov (United States)

    Li, Ke; Cao, Shuangyin; Yang, Yue; Zhu, Juntao

    2018-01-01

    The objective of this paper was to explore the bond–slip relationship between carbon fiber-reinforced polymer (CFRP) sheets and concrete under cyclic loading through experimental and analytical approaches. Modified beam tests were performed in order to gain insight into the bond–slip relationship under static and cyclic loading. The test variables are the CFRP-to-concrete width ratio, and the bond length of the CFRP sheets. An analysis of the test results in this paper and existing test results indicated that the slope of the ascending segment of the bond–slip curve decreased with an increase in the number of load cycles, but the slip corresponding to the maximum shear stress was almost invariable as the number of load cycles increased. In addition, the rate of reduction in the slope of the ascending range of the bond–slip curve during cyclic loading decreased as the concrete strength increased, and increased as the load level or CFRP-to-concrete width ratio enhanced. However, these were not affected by variations in bond length if the residual bond length was longer than the effective bond length. A bilinear bond–slip model for CFRP sheets that are externally bonded to concrete under cyclic loading, which considered the effects of the cyclic load level, concrete strength, and CFRP-to-concrete ratio, was developed based on the existing static bond–slip model. The accuracy of this proposed model was verified by a comparison between this proposed model and test results. PMID:29495383

  11. Cyclic mechanical loading promotes bacterial penetration along composite restoration marginal gaps.

    Science.gov (United States)

    Khvostenko, D; Salehi, S; Naleway, S E; Hilton, T J; Ferracane, J L; Mitchell, J C; Kruzic, J J

    2015-06-01

    Secondary caries is the most common reason for composite restoration replacement and usually forms between dentin and the filling. The objective of this study was to investigate the combined effect of cyclic loading and bacterial exposure on bacterial penetration into gaps at the interface between dentin and resin composite restorative material using a novel bioreactor system and test specimen design. Human molars were machined into 3mm thick disks with 2mm deep × 5 mm diameter cavity preparations into which composite restorations were placed. A ∼ 15-30 μm (small) or ∼ 300 μm wide (large) marginal gap was introduced along half of the interface between the dentin and restoration. Streptococcus mutans UA 159 biofilms were grown on each sample prior to testing each in a bioreactor both with and without cyclic loading. Both groups of samples were tested for 2 weeks and post-test biofilm viability was confirmed with a live-dead assay. Samples were fixed, mounted and cross-sectioned to reveal the gaps and observe the depth of bacterial penetration. It was shown that for large gap samples the bacteria easily penetrated to the full depth of the gap independent of loading or non-loading conditions. The results for all cyclically loaded small gap samples show a consistently deep bacterial penetration down 100% of the gap while the average penetration depth was only 67% for the non-loaded samples with only two of six samples reaching 100%. A new bioreactor was developed that allows combining cyclic mechanical loading and bacterial exposure of restored teeth for bacterial biofilm and demineralization studies. Cyclic loading was shown to aid bacterial penetration into narrow marginal gaps, which could ultimately promote secondary caries formation. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  12. Performance of Geosynthetic-Reinforced Soils Under Static and Cyclic Loading

    Directory of Open Access Journals (Sweden)

    M. Touahmia

    2017-04-01

    Full Text Available This paper investigates and discusses the composite behavior of geosynthetic reinforced soil mass. It presents the results of a series of large-scale laboratory tests supported by analytical methods to examine the performance of geogrid reinforcement subjected to static and cyclic pullout loading. The testing equipment and procedures used for this investigation are outlined. The results show that geosynthetic reinforcement can mobilize great resistance to static pulling load under high confining pressures. The reinforcement exhibits gradual deformation under cyclic loading showing no sign of imminent pullout failure for all levels of applied loads. In general, the results demonstrate that geosynthetic can be used in situations where loads are non-static, although care will be required in ensuring that appropriate factors of safety are applied to control the resulting deformation. A simplified analytical model for calculating the pulling capacity of geosynthetic reinforcement is proposed.

  13. CISM course on mechanical behaviour of soils under environmentally induced cyclic loads

    CERN Document Server

    Wood, David; Mechanical Behaviour of Soils Under Environmentally Induced Cyclic Loads

    2012-01-01

    The book gives a comprehensive description of the mechanical response of soils (granular and cohesive materials) under cyclic loading. It provides the geotechnical engineer with the theoretical and analytical tools necessary for the evaluation of settlements developng with time under cyclic, einvironmentally idncued loads (such as wave motion, wind actions, water table level variation) and their consequences for the serviceability and durability of structures such as the shallow or deep foundations used in offshore engineering, caisson beakwaters, ballast and airport pavements and also to interpret monitoring data, obtained from both natural and artificial slopes and earth embankments, for the purposes of risk assessment and mitigation.

  14. Behavior of precast ferrocement thin walls under cyclic loading: an experimental and analytical study

    Directory of Open Access Journals (Sweden)

    Daniel Alveiro Bedoya Ruiz

    2014-01-01

    Full Text Available Thin ferrocement walls are the structural elements that comprise the earthquake resistant system of housing built with this material. This article presents the results drawn from an experimental campaign carried out over full-scale precast ferrocement thin walls, which were assessed under cyclic loading conditions. The tests assessed the strength of the walls, their hysteretic behavior, ductility, energy dissipation, equivalent damping, their coefficient of energy dissipation and their characteristic failure mode when subjected to cyclic loading conditions. Finally, an analytical model that modeled the nonlinear dynamic behavior exhibited by ferrocement walls was implemented; its feasibility and potential use in earthquake resistant design of ferrocement walls was evaluated.

  15. Impact of Cyclic Loading on Chloride Diffusivity and Mechanical Performance of RC Beams under Seawater Corrosion

    Directory of Open Access Journals (Sweden)

    Sen Pang

    2017-01-01

    Full Text Available An experimental study was conducted to investigate the impact of cyclic loading on the mechanical performance and chloride diffusivity of RC beams exposed to seawater wet-dry cycles. To induce initial damage to RC beam specimen, cyclic loading controlled by max load and cycles was applied. Then beam specimens underwent 240 wet-dry cycles of seawater. Results show that the chloride content increased as max load and cycle increased. The chloride content at steel surface increased approximatively linearly as average crack width increased. Moreover, the max load had more influence on chloride content at steel surface than cycle. The difference of average chloride diffusion coefficient between tension and compression concrete was little at uncracked position. Average chloride diffusion coefficient increased as crack width increased when crack width was less than 0.11 mm whereas the increasing tendency was weak when crack width exceeded 0.11 mm. The residual yield load and ultimate load of RC beams decreased as max load and cycle increased. Based on univariate analysis of variance, the max load had more adverse effect on yield load and ultimate load than cycle.

  16. Laboratory Test Setup for Cyclic Axially Loaded Piles in Sand

    DEFF Research Database (Denmark)

    Thomassen, Kristina; Ibsen, Lars Bo; Andersen, Lars Vabbersgaard

    2017-01-01

    conditions for all tests. For verifications purposes six static tension tests conducted at three different vertical effective stress levels of 0, 35 and 70 kPa. The load-displacement curves showed that the test setup provides repeatable test results. A preliminary comparison between the unit shaft friction...

  17. Thermal ratchetting in pipes subjected to cyclic thermal downshocks and primary traction charge

    International Nuclear Information System (INIS)

    Corsi, F.; Fabi, A.; Di Giamberardino, P.; Di Ianni, A.; Cesari, F.; Ghia, S.

    1983-01-01

    The paper presents the study about the structural behaviour in ratchetting regime at elevated temperature of an AISI 316 pipe (nominal dimensions are: diameter D=71 mm, thickness s=4.26 mm). The work is part of the research program of collaboration between ENEA and CEA and takes place in the ENEA CRE Casaccia. The experimental-theoretical comparison is showen. The numeric calculations are performed by codes of the finite elements system CASTEM developed at the CEA in Saclay using different constitutive laws for the material. Testing is carried out in a special sodium test facility, built for the purpose. It's given a brief description of the plant and of the used instrumentation on the test section. The specimen is subjected to the combination of cyclic primary and secondary loads. The primary load, a uniform traction stress, is applied by hydraulic jacks whereas the secondary load is a cold radial shock obtained with a sodium flow at lower temperature (300 0 C) in the test section initially at uniform temperature (500 0 C). Ten cycles are excuted. The principal aim of this effort was to analyze in detail the 'Ratchetting' phenomena but on the same time the study allowed to compare different strain measurement technics (the test section was instrumented with capacitive and resistive gages) and to validate the used finite element system in cyclic non-linear field. (orig.)

  18. THE STRENGTH OF REINFORCED CONCRETE BEAM ELEMENTS UNDER CYCLIC ALTERNATING LOADING AND LOW CYCLE LOAD OF CONSTANT SIGN

    Directory of Open Access Journals (Sweden)

    Semina Yuliya Anatol'evna

    2015-09-01

    Full Text Available The behavior of reinforced concrete elements under some types of cyclic loads is described in the paper. The main aim of the investigations is research of the stress-strain state and strength of the inclined sections of reinforced concrete beam elements in conditions of systemic impact of constructive factors and the factor of external influence. To spotlight the problem of cyclic loadings three series of tests were conducted by the author. Firstly, the analysis of the tests showed that especially cyclic alternating loading reduces the bearing capacity of reinforced concrete beams and their crack resistance by 20 % due to the fatigue of concrete and reinforcement. Thus the change of load sign creates serious changes of stress-strain state of reinforced concrete beam elements. Low cycle loads of constant sign effect the behavior of the constructions not so adversely. Secondly, based on the experimental data mathematical models of elements’ strength were obtained. These models allow evaluating the impact of each factor on the output parameter not only separately, but also in interaction with each other. Furthermore, the material spotlighted by the author describes stress-strain state of the investigated elements, cracking mechanism, changes of deflection values, the influence of mode cyclic loading during the tests. Since the data on the subject are useful and important to building practice, the ultimate aim of the tests will be working out for improvement of nonlinear calculation models of span reinforced concrete constructions taking into account the impact of these loads, and also there will be the development of engineering calculation techniques of their strength, crack resistance and deformability.

  19. Experimental study of bond-slip performance of corroded reinforced concrete under cyclic loading

    Directory of Open Access Journals (Sweden)

    Haijun Zhou

    2015-03-01

    Full Text Available Reinforced concrete structures exposed to marine environment often sustain high levels of chloride-induced reinforcement corrosion, which causes reinforcement corrosion and resulting in degraded performance under cyclic service loading. This article studied the dynamic bond performance between corroded reinforcing and concrete under force controlled loading. Tests were carried out to evaluate the cyclic bond-slip degradation with different reinforcement corrosion levels. A series of 30 specimens with various corrosion levels of rebar and stirrup were made. The specimen was cast as concrete cube with the dimension of 200 mm, and a steel rebar was centrally embedded with two stirrups around. The embedded steel rebar and stirrups were corroded using an electrochemical accelerated corrosion technique. The corrosion crack opening width and length were recorded after completion of artificial corrosion. Then, cyclic loading test was carried out; three different force levels of 24, 36, and 48 kN were adopted. The effects of reinforcement corrosion rate on crack opening, maximum slip, energy dissipation, and unloading stiffness were discussed in detail. It was found that both reinforcement corrosion rate and crack opening would have significant effects on cyclic bond performance. Further studies are urgently needed to quantify these effects to the cyclic bond performance.

  20. Chloride Ingress in Concrete Cracks under Cyclic Loading

    DEFF Research Database (Denmark)

    Küter, André; Geiker, Mette Rica; Olesen, John Forbes

    2005-01-01

    was similar for both sets and the maximum crack width was kept constant throughout the exposure period by means of precracking and an external prestressed reinforcement. Chloride profiles after 40 days revealed a considerable increase in ingress towards the crack tip in contrast to data from the literature....... Preliminary investigations have been undertaken to quantify the effect of dynamic load application on the chloride ingress into concrete cracks. Specimens were designed allowing ingress of a chloride solution into a single crack of a saturated unreinforced mortar beam. One set of specimens was subjected...... to a load frequency of ten applications per minute and a second set to one application per hour simulating static cracks, however limiting the ingress hampering effects of autogenous healing and a possible dense precipitation on the crack faces. The averaged chloride exposure interval of the crack faces...

  1. Plastic strain accumulation during asymmetric cyclic loading of Zircaloy-2 at room temperature

    International Nuclear Information System (INIS)

    Rajpurohit, R.S.; Santhi Srinivas, N.C.; Singh, Vakil

    2016-01-01

    Asymmetric cyclic loading leads to accumulation of cyclic plastic strain and reduces the fatigue life of components. This phenomenon is known as ratcheting fatigue. Zircaloy-2 is a important structural material in nuclear reactors and used as pressure tubes and fuel cladding in pressurized light and heavy water nuclear reactors. Due to power fluctuations, these components experience plastic strain cycles in the reactor and their life is reduced due to strain cycles. Power fluctuations also cause asymmetric straining of the material and leads to accumulation of plastic strain. The present investigation deals with the effect of the magnitude of mean stress, stress amplitude and stress rate on hardening/softening behavior of Zircaloy-2 under asymmetric cyclic loading, at room temperature. It was observed that plastic strain accumulation increased with mean stress and stress amplitude; however, it decreased with stress rate. (author)

  2. Cyclic Loading of Growing Tissue in a Bioreactor: Mathematical Model and Asymptotic Analysis

    KAUST Repository

    Pohlmeyer, J. V.

    2013-10-24

    A simplified 2D mathematical model for tissue growth within a cyclically-loaded tissue engineering scaffold is presented and analyzed. Such cyclic loading has the potential to improve yield and functionality of tissue such as bone and cartilage when grown on a scaffold within a perfusion bioreactor. The cyclic compression affects the flow of the perfused nutrient, leading to flow properties that are inherently unsteady, though periodic, on a timescale short compared with that of tissue proliferation. A two-timescale analysis based on these well-separated timescales is exploited to derive a closed model for the tissue growth on the long timescale of proliferation. Some sample numerical results are given for the final model, and discussed. © 2013 Society for Mathematical Biology.

  3. Durability evaluation method for contact component interconnections in printed circuit boards under thermal loads

    Science.gov (United States)

    Azin, Anton; Zhukov, Andrey A.; Ponomarev, Sergey A.; Ponomarev, Sergey V.

    2017-11-01

    In designing sophisticated printed circuit boards, required evaluation of the product life cycle is relevant in terms of presumably applied load conditions during operation. The paper describes the durability evaluation method of printed circuit board components with contact output such as ball grid array (BGA) and pitch grid array (PGA) under thermal loads. Experiment data and numerical simulation results of soldered connections have been obtained. This method is demonstrated by a practical application example-evaluating of printed circuit board durability under cyclic thermal loads. The application of proposed method for printed circuit boards would make it possible to predict the service life of these designed products.

  4. Edge-cracks in single crystals under monotonic and cyclic loads

    DEFF Research Database (Denmark)

    Hutchinson, J.W.; Tvergaard, Viggo

    1999-01-01

    . Plasticity is assumed to occur as slip along planes inclined at 45 degrees to the surface. Problems where slip is limited to persistent slip bands are considered side-by-side with the problem where slip is not confined. Results for both monotonic and cyclic loadings are presented, with emphasis on the crack...

  5. Response of stiff piles in sand to long-term cyclic lateral loading

    DEFF Research Database (Denmark)

    Bakmar, Christian LeBlanc; Houlsby, Guy T.; Byrne, Byron W.

    2010-01-01

    The monopile is currently the preferred foundation type for most offshore wind farms. Whilst static capacity of the monopile is important, a safe design must also address issues of accumulated rotation and stiffness after long-term cyclic loading. Design guidance on this issue is limited. To addr...

  6. Evaluation of torque loss in Co-Cr castable abutments after cyclic loading

    Directory of Open Access Journals (Sweden)

    Somayeh Zeighami

    2018-03-01

    Conclusion: Misfit between the castable implant components can cause torque loss before and after cyclic loading. However, it is more appropriate to relate the results of this study to the screw loosening of the above mentioned abutments than judging their clinical performance.

  7. Simulation of pore pressure accumulation under cyclic loading using Finite Volume Method

    DEFF Research Database (Denmark)

    Tang, Tian; Hededal, Ole

    2014-01-01

    This paper presents a finite volume implementation of a porous, nonlinear soil model capable of simulating pore pressure accumulation under cyclic loading. The mathematical formulations are based on modified Biot’s coupled theory by substituting the original elastic constitutive model...

  8. Thermal loading study for FY 1995

    International Nuclear Information System (INIS)

    1996-01-01

    This report provides the results of sensitivity analyses designed to assist the test planners in focusing their in-situ measurements on parameters that appear to be important to waste isolation. Additionally, the study provides a preliminary assessment of the feasibility of certain thermal management options. A decision on thermal loading is a critical part of the scientific and engineering basis for evaluating regulatory compliance of the potential repository for waste isolation. To show, with reasonable assurance, that the natural and engineered barriers will perform adequately under expected repository conditions (thermally perturbed) will require an integrated approach based on thermal testing (laboratory, and in-situ), natural analog observations, and analytic modeling. The Office of Civilian Radioactive Waste Management needed input to assist in the planning of the thermal testing program. Additionally, designers required information on the viability of various thermal management concepts. An approximately 18-month Thermal Loading Study was conducted from March, 1994 until September 30, 1995 to address these issues. This report documents the findings of that study. 89 refs., 71 figs., 33 tabs

  9. Thermal loading study for FY 1995

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-01-31

    This report provides the results of sensitivity analyses designed to assist the test planners in focusing their in-situ measurements on parameters that appear to be important to waste isolation. Additionally, the study provides a preliminary assessment of the feasibility of certain thermal management options. A decision on thermal loading is a critical part of the scientific and engineering basis for evaluating regulatory compliance of the potential repository for waste isolation. To show, with reasonable assurance, that the natural and engineered barriers will perform adequately under expected repository conditions (thermally perturbed) will require an integrated approach based on thermal testing (laboratory, and in-situ), natural analog observations, and analytic modeling. The Office of Civilian Radioactive Waste Management needed input to assist in the planning of the thermal testing program. Additionally, designers required information on the viability of various thermal management concepts. An approximately 18-month Thermal Loading Study was conducted from March, 1994 until September 30, 1995 to address these issues. This report documents the findings of that study. 89 refs., 71 figs., 33 tabs.

  10. Cyclic loading of thick vessels based on the Prager and Armstrong-Frederick kinematic hardening models

    International Nuclear Information System (INIS)

    Mahbadi, H.; Eslami, M.R.

    2006-01-01

    The aim of this paper is to relate the type of stress category in cyclic loading to ratcheting or shakedown behaviour of the structure. The kinematic hardening theory of plasticity based on the Prager and Armstrong-Frederick models is used to evaluate the cyclic loading behaviour of thick spherical and cylindrical vessels under load and deformation controlled stresses. It is concluded that kinematic hardening based on the Prager model under load and deformation controlled conditions, excluding creep, results in shakedown or reversed plasticity for spherical and cylindrical vessels with the isotropy assumption of the tension/compression curve. Under an anisotropy assumption of the tension/compression curve, this model predicts ratcheting. On the other hand, the Armstrong-Frederick model predicts ratcheting under load controlled cyclic loading and reversed plasticity for deformation controlled stress. The interesting conclusion is that the Armstrong-Frederick model is well capable to predict the experimental data under the assumed type of stresses, wherever experimental data are available

  11. Evaluation of the base/subgrade soil under repeated loading : phase II, in-box and ALF cyclic plate load tests.

    Science.gov (United States)

    2012-03-01

    This research study aims at evaluating the performance of base and subgrade soil in flexible pavements under repeated loading test conditions. For this purpose, an indoor cyclic plate load testing equipment was developed and used to conduct a series ...

  12. Cyclic loading effect on the flexural properties of commercial mdf and particleboard panels

    Directory of Open Access Journals (Sweden)

    Cláudio Henrique Soares Del Menezzi

    2011-09-01

    Full Text Available This paper aimed at evaluating the effect of fatigue through different loading cycles (20,0000; 40,000 and 80,000 cycles on deflection and flexural properties of commercial MDF and particleboard panels. A 2.2 seconds (0.45 Hz cyclic loading was employed and the applied load about 25% of modulus of rupture was used. After the tests, final deflection (with load, residual deflection (without load and flexural properties of the panels were evaluated. According to the results, the flexural properties for both kinds of panels were not affected by the loading cycles tested. However, it was identified that the MDF residual deflection was affected between 20,000 and 80,000 loading cycles.

  13. Effects of three luting agents and cyclic impact loading on shear bond strengths to zirconia with tribochemical treatment

    Directory of Open Access Journals (Sweden)

    Naoko Kawai

    2012-06-01

    Conclusions: After 106 compressive cyclic impact loading, the highest bond to zirconia was obtained with 10-methacryloxydecyl-dihydrogenphosphate containing a luting system (Panavia Fluoro Cement. After applying tribochemical treatment to zirconia, all cements used in this study survived more than 106 shear or compressive cyclic impact loading at 10 kg.

  14. Modelling the drained response of bucket foundations for offshore wind turbines under general monotonic and cyclic loading

    DEFF Research Database (Denmark)

    Foglia, Aligi; Gottardi, Guido; Govoni, Laura

    2015-01-01

    the typical conditions of offshore wind turbines: very large cyclic overturning moment, large cyclic horizontal load and comparatively little, self-weight induced, vertical load. The experimental soil-foundation response is interpreted within the macro-element approach, using an existing analytical model...

  15. Lifetime prediction of structures submitted to thermal fatigue loadings

    International Nuclear Information System (INIS)

    Amiable, S.

    2006-01-01

    The aim of this work is to predict the lifetime of structures submitted to thermal fatigue loadings. This work lies within the studies undertaken by the CEA on the thermal fatigue problems from the french reactor of Civaux. In particular we study the SPLASH test: a specimen is heated continuously and cyclically cooled down by a water spray. This loading generates important temperature gradients in space and time and leads to the initiation and the propagation of a crack network. We propose a new thermo-mechanical model to simulate the SPLASH experiment and we propose a new fatigue criterion to predict the lifetime of the SPLASH specimen. We propose and compare several numerical models with various complexity to estimate the mechanical response of the SPLASH specimen. The practical implications of this work are the reevaluation of the hypothesis used in the French code RCC, which are used to simulate thermal shock and to interpret the results in terms of fatigue. This work leads to new perspectives on the mechanical interpretation of the fatigue criterion. (author)

  16. Effect of Cyclic Loading on Surface Instability of Silicone Rubber under Compression

    Directory of Open Access Journals (Sweden)

    Zhonglin Li

    2017-04-01

    Full Text Available This work combines experiments and finite element simulations to study the effect of pre-imposed cyclic loading on surface instability of silicon rubber under compression. We first fabricate cuboid blocks of silicon rubber and pinch them cyclicly a few times. Then, an in-house apparatus is set to apply uniaxial compression on the silicon rubber under exact plane strain conditions. Surprisingly, we find multiple creases on the surface of silicone rubber, significantly different from what have been observed on the samples without the cyclic pinching. To reveal the underlying physics for these experimentally observed multiple creases, we perform detailed nanoindentation experiments to measure the material properties at different locations of the silicon rubber. The modulus is found to be nonuniform and varies along the thickness direction after the cyclic pinching. According to these experimental results, three-layer and multilayer finite element models are built with different materials properties informed by experiments. The three-layer finite element model can excellently explain the nucleation and pattern of multiple surface creases on the surface of compressed silicone rubber, in good agreement with experiments. Counterintuitively, the multilayer model with gradient modulus cannot be used to explain the multiple creases observed in our experiments. According to these simulations, the experimentally observed multiple creases should be attributed to a thin and stiff layer formed on the surface of silicon rubber after the pre-imposed cyclic loading.

  17. Influence of bondcoat composition and manufacturing parameters on the lifetime of thermal barrier coatings under cyclic temperature loading; Einfluss der Bondcoatzusammensetzung und Herstellungsparameter auf die Lebensdauer von Waermedaemmschichten bei zyklischer Temperaturbelastung

    Energy Technology Data Exchange (ETDEWEB)

    Subanovic, Marko

    2008-08-21

    In the present study the influence of the bond coat composition on the lifetime of thermal barrier coatings during thermal cycling was investigated. The knowledge, that the reactive elements (RE), which are essential for the improvement of the oxide scale adhesion, are ''lost'', during the bond coat processing, made it necessary to investigate systematically the influence of the different manufacturing stages on the RE distribution. After VPS (vacuum plasma spraying) with a high oxygen partial pressure in the spraying chamber, the reactive elements in the NiCoCrAl-coating were tied up in oxide precipitates, and thus their beneficial effect on the scale adhesion was inhibited. Another important observation is that the RE's are depleted during the bondcoat vacuum heat-treatment. The degree of Y-depletion depends not only on the Y-reservoir in the coating (Y-content and thickness) but also on the heat-treatment parameters, such as vacuum quality and temperature. A thin, dense alumina oxide scale with a smooth interface between bond coat and TGO doesn't necessary lead to a lifetime extension of the EB-PVD TBC's. TBC's with such oxide morphology typically failed due to crack formation and propagation along the interface between the TGO and the bondcoat. By addition of zirconium it was possible to shift the failure initiation from the interface TGO/bondcoat to the interface TBC/TGO, which can apparently accommodate more thermal strain energy before failure. The shift of the failure location was achieved by a change of the oxide morphology, which mainly relies on adjusting a non-even wavy interface between the TGO and the bond coat and formation of defected oxide layers. In contrast, a defected oxide scale with a high growth rate shortened the life time of APSTBC's. Porosity and spinel formation weakened the mechanical integrity of the oxide scale, and facilitated the crack formation and propagation of the already existing

  18. Deformation Behavior of Recycled Concrete Aggregate during Cyclic and Dynamic Loading Laboratory Tests

    Directory of Open Access Journals (Sweden)

    Wojciech Sas

    2016-09-01

    Full Text Available Recycled concrete aggregate (RCA is a relatively new construction material, whose applications can replace natural aggregates. To do so, extensive studies on its mechanical behavior and deformation characteristics are still necessary. RCA is currently used as a subbase material in the construction of roads, which are subject to high settlements due to traffic loading. The deformation characteristics of RCA must, therefore, be established to find the possible fatigue and damage behavior for this new material. In this article, a series of triaxial cyclic loading and resonant column tests is used to characterize fatigue in RCA as a function of applied deviator stress after long-term cyclic loading. A description of the shakedown phenomenon occurring in the RCA and calculations of its resilient modulus (Mr as a function of fatigue are also presented. Test result analysis with the stress-life method on the Wohler S-N diagram shows the RCA behavior in accordance with the Basquin law.

  19. Test method research on weakening interface strength of steel - concrete under cyclic loading

    Science.gov (United States)

    Liu, Ming-wei; Zhang, Fang-hua; Su, Guang-quan

    2018-02-01

    The mechanical properties of steel - concrete interface under cyclic loading are the key factors affecting the rule of horizontal load transfer, the calculation of bearing capacity and cumulative horizontal deformation. Cyclic shear test is an effective method to study the strength reduction of steel - concrete interface. A test system composed of large repeated direct shear test instrument, hydraulic servo system, data acquisition system, test control software system and so on is independently designed, and a set of test method, including the specimen preparation, the instrument preparation, the loading method and so on, is put forward. By listing a set of test results, the validity of the test method is verified. The test system and the test method based on it provide a reference for the experimental study on mechanical properties of steel - concrete interface.

  20. The influence of veneering porcelain thickness of all-ceramic and metal ceramic crowns on failure resistance after cyclic loading.

    Science.gov (United States)

    Shirakura, Akihiko; Lee, Heeje; Geminiani, Alessandro; Ercoli, Carlo; Feng, Changyong

    2009-02-01

    In some clinical situations, the length of either a prepared tooth or an implant abutment is shorter than ideal, and the thickness of a porcelain crown must be increased. Thickness of the coping and the veneering porcelain should be considered to prevent mechanical failure of the crown. The purpose of this study was to investigate the influence of veneering porcelain thickness for all-ceramic and metal ceramic crowns on failure resistance after cyclic loading. All-ceramic and metal ceramic crowns (n=20) were fabricated on an implant abutment (RN Solid Abutment) for the study. Two different framework designs with 2 different incisal thicknesses of veneering porcelain (2 mm and 4 mm) were used for each all-ceramic and metal ceramic crown system, resulting in 4 experimental groups (n=10) with identically shaped crowns. The all-ceramic crown consisted of alumina (Procera AllCeram) frameworks and veneering porcelain (Cerabien), while metal ceramic crowns were made of high noble metal (Leo) frameworks and veneering porcelain (IPS Classic). All crowns were cemented on the corresponding abutments using a resin cement (Panavia 21). They were subjected to 1000 cycles of thermal cycling (5 degrees C and 55 degrees C; 5-second dwell time). The crowns were tested with a custom-designed cyclic loading apparatus which delivered simultaneous unidirectional cyclic loading at 135 degrees, vertically, at an rpm of 250, with a load of 49 N. Each specimen was loaded for 1.2 x 106 cycles or until it failed. The specimens were thoroughly evaluated for cracks and/or bulk fracture with an optical stereomicroscope (x10) and assigned a score of success, survival, or failure. The specimens without bulk fracture after cyclic loading were loaded along the long axis of the tooth, on the incisal edge, in a universal testing machine at a crosshead speed of 1.5 mm/min, until fracture. Fisher's exact test was used to compare the success and survival rate between the 2 different materials (alpha=.05

  1. Failure modes of vacuum plasma spray tungsten coating created on carbon fibre composites under thermal loads

    Energy Technology Data Exchange (ETDEWEB)

    Hirai, T., E-mail: takeshi.hirai@iter.or [JET-EFDA, Culham Science Centre, OX14 3DB, Abingdon (United Kingdom); Forschungszentrum Juelich EURATOM-Association, FZJ, D-52425 Juelich (Germany); Bekris, N. [JET-EFDA, Culham Science Centre, OX14 3DB, Abingdon (United Kingdom); EFDA CSU, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB (United Kingdom); Coad, J.P. [JET-EFDA, Culham Science Centre, OX14 3DB, Abingdon (United Kingdom); Culham Science Centre, EURATOM-UKAEA Fusion Association, Abingdon, Oxfordshire, OX14 3DB (United Kingdom); Grisolia, C. [JET-EFDA, Culham Science Centre, OX14 3DB, Abingdon (United Kingdom); Association Euratom-CEA, Cadarache DSM/DRFC, F-13108, St-Paul-lez-Durance (France); Linke, J. [JET-EFDA, Culham Science Centre, OX14 3DB, Abingdon (United Kingdom); Forschungszentrum Juelich EURATOM-Association, FZJ, D-52425 Juelich (Germany); Maier, H. [JET-EFDA, Culham Science Centre, OX14 3DB, Abingdon (United Kingdom); Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, D-85748 Garching bei Muenchen (Germany); Matthews, G.F. [JET-EFDA, Culham Science Centre, OX14 3DB, Abingdon (United Kingdom); Culham Science Centre, EURATOM-UKAEA Fusion Association, Abingdon, Oxfordshire, OX14 3DB (United Kingdom); Philipps, V.; Wessel, E. [JET-EFDA, Culham Science Centre, OX14 3DB, Abingdon (United Kingdom); Forschungszentrum Juelich EURATOM-Association, FZJ, D-52425 Juelich (Germany)

    2009-07-01

    Vacuum plasma spray tungsten (VPS-W) coating created on a carbon fibre reinforced composite (CFC) was tested under two thermal load schemes in the electron beam facility to examine the operation limits and failure modes. In cyclic ELM-like short transient thermal loads, the VPS-W coating was destroyed sub-layer by sub-layer at 0.33 GW/m{sup 2} for 1 ms pulse duration. At longer single pulses, simulating steady-state thermal loads, the coating was destroyed at surface temperatures above 2700 deg. C by melting of the rhenium containing multilayer at the interface between VPS-W and CFC. The operation limits and failure modes of the VPS-W coating in the thermal load schemes are discussed in detail.

  2. Fatigue Properties of Plain Concrete under Triaxial Tension-Compression-Compression Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Dongfu Zhao

    2017-01-01

    Full Text Available Fatigue tests were performed on plain concrete under triaxial tension-compression-compression (T-C-C cyclic loading with constant and variable amplitude using a large multiaxial machine. Experimental results show that, under constant amplitude fatigue loads, the development of residual strain in the fatigue loading direction depends mostly on the lateral compressive stress ratio and is nearly independent of stress level. Under variable amplitude fatigue loads, the fatigue residual strain is related to the relative fatigue cycle and lateral compressive stress ratio but has little relationship with the loading process. To model this system, the relative residual strain was defined as the damage variant. Damage evolutions for plain concrete were established. In addition, fatigue damage analysis and predictions of fatigue remaining life were conducted. This work provides a reference for multistage fatigue testing and fatigue damage evaluation of plain concrete under multiaxial loads.

  3. Cyclic plastic material behavior leading to crack initiation in stainless steel under complex fatigue loading conditions

    International Nuclear Information System (INIS)

    Facheris, G.

    2014-01-01

    The improvement of the reliability and of the safety in the design of components belonging to the primary cooling circuit of a light water nuclear reactor is nowadays one of the most important research topics in nuclear industry. One of the most important damage mechanisms leading the crack initiation in this class of components is the low cycle fatigue (LCF) driven by thermal strain fluctuations caused by the complex thermo-mechanical loading conditions typical for the primary circuit (e.g. operating thermal transients, thermal stratification, turbulent mixing of cold and hot water flows, etc.). The cyclic application of the resulting plastic deformation to the steel grades commonly used for the fabrication of piping parts (e.g. austenitic stainless steels) is associated with a continuous evolution of the mechanical response of the material. As an additional complication, the cyclic behavior of stainless steels is influenced by temperature, strain amplitude and cyclic accumulation of inelastic strain (i.e. ratcheting). The accurate prediction of the structural response of components belonging to the primary cooling circuit requires the development of a reliable constitutive model that must be characterized by a reduced complexity to allow its application in an industrial context. In this framework, the main goal of the current dissertation is to formulate, calibrate and implement in a commercial Finite Element code, a constitutive model that is suitable for the stainless stain grade 316L subjected to complex loading conditions. As a first task, a characterization of the mechanical behavior of 316L subjected to uniaxial and multiaxial strain-controlled conditions (including LCF and ratcheting) is carried out performing several tests in the laboratories of the Paul Scherrer Institute (PSI, Villigen, Switzerland) and of Politecnico di Milano (Italy). The uniaxial experiments demonstrate that, prescribing a strain-controlled ratcheting path, a harder material response

  4. Effect of Cyclic Loading on Micromotion at the Implant-Abutment Interface.

    Science.gov (United States)

    Karl, Matthias; Taylor, Thomas D

    2016-01-01

    Cyclic loading may cause settling of abutments mounted on dental implants, potentially affecting screw joint stability and implant-abutment micromotion. It was the goal of this in vitro study to compare micromotion of implant-abutment assemblies before and after masticatory simulation. Six groups of abutments (n = 5) for a specific tissue-level implant system with an internal octagon were subject to micromotion measurements. The implant-abutment assemblies were loaded in a universal testing machine, and an apparatus and extensometers were used to record displacement. This was done twice, in the condition in which they were received from the abutment manufacturer and after simulated loading (100,000 cycles; 100 N). Statistical analysis was based on analysis of variance, two-sample t tests (Welch tests), and Pearson product moment correlation (α = .05). The mean values for micromotion ranged from 33.15 to 63.41 μm and from 30.03 to 42.40 μm before and after load cycling. The general trend toward reduced micromotion following load cycling was statistically significant only for CAD/CAM zirconia abutments (P = .036) and for one type of clone abutment (P = .012), with no significant correlation between values measured before and after cyclic loading (Pearson product moment correlation; P = .104). While significant differences in micromotion were found prior to load cycling, no significant difference among any of the abutment types tested could be observed afterward (P > .05 in all cases). A quantifiable settling effect at the implant-abutment interface seems to result from cyclic loading, leading to a decrease in micromotion. This effect seems to be more pronounced in low-quality abutments. For the implant system tested in this study, retightening of abutment screws is recommended after an initial period of clinical use.

  5. The Effect of Cyclic Loading on the Mechanical Performance of Surgical Mesh

    Directory of Open Access Journals (Sweden)

    Ho Y.C.

    2010-06-01

    Full Text Available Polymeric meshes in the form of knitted nets are commonly used in the surgical repair of pelvic organ prolapses. Although a number of these prosthetic meshes are commercially available, there is little published data on their mechanical performance, in particular on the change in stiffness under the repeated loading experienced in vivo. In this in vitro study, cyclic tensile loading was applied to rectangular strips of four different commercially available meshes. The applied force and resultant displacement was monitored throughout the tests in order to evaluate the change in stiffness. In addition, each mesh was randomly marked using indelible ink in order to permit the use of threedimensional digital image correlation to evaluate local displacements during the tests. However, the scale and form of the deformation experienced by some of the meshes made correlation difficult so that confirmation of the values of stiffness were only obtained for two meshes. The results demonstrate that all the meshes experience an increase in stiffness during cyclic loading, that in most cases cyclic creep occurs and in some cases large-scale, irreversible reorganisation of the mesh structure occurs after as few as 200 cycles at loads of the order of 10N.

  6. Cyclic Loading Effect on Color Stability of Unshaded versus Shaded Zirconia.

    Science.gov (United States)

    Spyropoulou, Panagiota-Eirini; Kamposiora, Phophi; Eliades, George; Papavasiliou, George; Razzoog, Michael E; Bayne, Stephen C

    2016-01-01

    Shaded versions of dental zirconia may improve initial color matching to teeth, but might change color with cyclic mechanical loading. The purpose of this study was to measure the color of unshaded and shaded zirconia dental ceramic before and after cyclic mechanical loading and calculate color differences (ΔE). Disk-shaped specimens (N = 30, Nobel Procera, 0.8 mm thick, 12 mm diameter) of unshaded or shaded zirconia (intrinsically shaded by small oxide modifications) were fabricated by the Nobel Biocare using standard CAD-CAM processing. Milled surfaces were polished. CIE L*a*b* values were measured (Konica Minolta spectrophotometer) before and after mechanical cycling (custom modified Leinfelder test machine, biaxial flexure loading, load = 80 N × 500,000 cycles, dry), and L*a*b* individual differences and ΔE color differences were calculated and compared (ANOVA, p zirconia specimens was influenced by cyclic loading (p zirconia restorations, especially in the esthetic zone. Minor color changes that are individually imperceptible to the human eye within different restorative components may be compounded to produce clinically significant color change that is not aesthetically acceptable. © 2015 Wiley Periodicals, Inc.

  7. Influence of zirconia surface treatment on veneering porcelain shear bond strength after cyclic loading.

    Science.gov (United States)

    Nishigori, Atsushi; Yoshida, Takamitsu; Bottino, Marco C; Platt, Jeffrey A

    2014-12-01

    The influence of yttria-stabilized tetragonal zirconia polycrystal surface treatment on veneering porcelain shear bond strength after cyclic loading is not fully understood. The purpose of this study was to investigate the influence of yttria-stabilized tetragonal zirconia polycrystal surface treatment on veneering porcelain shear bond strength and cyclic loading on the shear bond strength between the 2 materials. A total of 48 cylinder-shaped yttria-stabilized tetragonal zirconia polycrystal specimens were fabricated with computer-aided design and computer-aided manufacturing (CAD/CAM), sintered for 8 hours at 1500°C, ground with 320-grit diamond paper, and divided into 4 groups (n = 12) according to surface treatment as follows: no treatment/control; heat treatment of 650°C to 1000°C at 55°C/min; airborne-particle abrasion with 50-μm alumina at 0.4 MPa pressure for 10 seconds; or heat treatment after abrasion. A veneering porcelain cylinder was built and fired on the prepared yttria-stabilized tetragonal zirconia polycrystal specimens. The shear bond strength was tested with a universal testing machine. Six specimens from each group were subjected to cyclic loading (10000 cycles, 1.5 Hz, 10 N load) before testing. The mean ± SD ranged from 10.7 ± 15.4 to 34.1 ± 10.0. Three-way ANOVA found no statistically significant (P > .05) effect of surface treatment and cyclic loading on shear bond strength. The Sidak multiple comparisons procedure found that cyclic loading specimens had significantly lower shear bond strength than noncyclic loading specimens after airborne-particle abrasion without heat treatment (P = .013). Within the limitations of this study, the shear bond strength between yttria-stabilized tetragonal zirconia polycrystal and veneering porcelain was not significantly affected by surface treatment. Airborne-particle abrasion without subsequent heat treatment should be avoided as a surface treatment in fabrication methods. Copyright © 2014

  8. Experimental Comparison of Statically and Cyclically Loaded Non-Slender Piles in Sand

    DEFF Research Database (Denmark)

    Sørensen, Søren Peder Hyldal; Ibsen, Lars Bo

    and hence the effective stresses in the soil have been increased homogeneously. The tests have been conducted in a pressure tank at Aalborg University. A total of 29 quasi-static tests and 14 cyclic tests have been conducted on laterally loaded piles situated in sand. Aluminium pipe piles instrumented...... used as foundation for modern offshore wind energy converters. The aim of the present work is to investigate the pile behaviour for non-slender piles by means of small-scale testing. The pile behaviour is investigated and compared for both static and cyclic loading. When conducting small-scale tests...... the effective stresses in the soil will be low and vary linearly with depth. As a consequence of this the soil parameters will vary greatly with depth and the determination of soil parameters is subject to great uncertainties. To overcome these uncertainties an overburden pressure, P0, has been applied...

  9. Damage propagation in a masonry arch subjected to slow cyclic and dynamic loadings

    Directory of Open Access Journals (Sweden)

    J. Toti

    2014-07-01

    Full Text Available In the present work, the damage propagation of a masonry arch induced by slow cyclic and dynamic loadings is studied. A two-dimensional model of the arch is proposed. A nonlocal damage-plastic constitutive law is adopted to reproduce the hysteretic characteristics of the masonry material, subjected to cyclic static loadings or to harmonic dynamic excitations. In particular, the adopted cohesive model is able to take into account different softening laws in tension and in compression, plastic strains, stiffness recovery and loss due to crack closure and reopening. The latter effect is an unavoidable feature for realistically reproducing hysteretic cycles. In the studied case, an inverse procedure is used to calibrate the model parameters. Then, nonlinear static and dynamic responses of the masonry arch are described together with damage propagation paths.

  10. Crack density and electrical resistance in indium-tin-oxide/polymer thin films under cyclic loading

    KAUST Repository

    Mora Cordova, Angel

    2014-11-01

    Here, we propose a damage model that describes the degradation of the material properties of indium-tin-oxide (ITO) thin films deposited on polymer substrates under cyclic loading. We base this model on our earlier tensile test model and show that the new model is suitable for cyclic loading. After calibration with experimental data, we are able to capture the stress-strain behavior and changes in electrical resistance of ITO thin films. We are also able to predict the crack density using calibrations from our previous model. Finally, we demonstrate the capabilities of our model based on simulations using material properties reported in the literature. Our model is implemented in the commercially available finite element software ABAQUS using a user subroutine UMAT.[Figure not available: see fulltext.].

  11. Mechanical stability of the diamond-like carbon film on nitinol vascular stents under cyclic loading

    International Nuclear Information System (INIS)

    Kim, Hyun-Jong; Moon, Myoung-Woon; Lee, Kwang-Ryeol; Seok, Hyun-Kwang; Han, Seung-Hee; Ryu, Jae-Woo; Shin, Kyong-Min; Oh, Kyu Hwan

    2008-01-01

    The mechanical stability of diamond-like carbon (DLC) films coated on nitinol vascular stents was investigated under cyclic loading condition by employing a stent crimping system. DLC films were coated on the vascular stent of a three dimensional structure by using a hybrid ion beam system with rotating jig. The cracking or delamination of the DLC coating occurred dominantly near the hinge connecting the V-shaped segments of the stent where the maximum strain was induced by a cyclic loading of contraction and extension. However the failures were significantly suppressed as the amorphous Si (a-Si) buffer layer thickness increased. Interfacial adhesion strength was estimated from the spalled crack size in the DLC coating for various values of the a-Si buffer layer thickness

  12. CYCLIC PLASTIC BEHAVIOUR OF UFG COPPER UNDER CONTROLLED STRESS AND STRAIN LOADING

    Directory of Open Access Journals (Sweden)

    Lucie Navrátilová

    2012-01-01

    Full Text Available The influence of stress- and strain-controlled loading on microstructure and cyclic plastic behaviour of ultrafine-grained copper prepared by equal channel angular pressing was examined. The stability of microstructure is a characteristic feature for stress-controlled test whereas grain coarsening and development of bimodal structure was observed after plastic strain-controlled tests. An attempt to explain the observed behaviour was made.

  13. Does Abutment Collar Length Affect Abutment Screw Loosening After Cyclic Loading?

    Science.gov (United States)

    Siadat, Hakimeh; Pirmoazen, Salma; Beyabanaki, Elaheh; Alikhasi, Marzieh

    2015-07-01

    A significant vertical space that is corrected with vertical ridge augmentation may necessitate selection of longer abutments, which would lead to an increased vertical cantilever. This study investigated the influence of different abutment collar heights on single-unit dental implant screw-loosening after cyclic loading. Fifteen implant-abutment assemblies each consisted of an internal hexagonal implant were randomly assigned to 3 groups: Group1, consisting of 5 abutments with 1.5 mm gingival height (GH); Group2, 5 abutments with 3.5 mm GH; and Group3, 5 abutments with 5.5 mm GH. Each specimen was mounted in transparent auto-polymerizing acrylic resin block, and the abutment screw was tightened to 35 Ncm with an electric torque wrench. After 5 minutes, initial torque loss (ITL) was recorded for all specimens. Metal crowns were fabricated with 45° occlusal surface and were placed on the abutments. A cyclic load of 75 N and frequency of 1 Hz were applied perpendicular to the long axis of each specimen. After 500 000 cycles, secondary torque loss (STL) was recorded. One-way ANOVA analysis was used to evaluate the effects of abutment collar height before and after cyclic loading. One-way ANOVA showed that ITL among the groups was not significantly different (P = .52), while STL was significantly different among the groups (P = .008). Post-hoc Tukey HSD tests showed that STL values were significantly different between the abutments with 1.5 mm GH (Group1) and with 5.5 mm GH (Group3) (P = .007). A paired comparison t-test showed that cyclic loading significantly influenced the STL in comparison with the ITL in each group. Within the limitations of this study, it can be concluded that increase in height of the abutment collar could adversely affect the torque loss of the abutment screw.

  14. The Effect of Cyclic Loading on the Compressive Strength of Core Build-Up Materials.

    Science.gov (United States)

    Zankuli, Muayed A; Silikas, Nick; Devlin, Hugh

    2015-01-15

    To evaluate the effect of cyclic loading on compressive strength of core build-up materials. Four dual-cured composites (Core.X Flow, Grandio Core, Bright Flow Core, Spee-Dee) and one light-cured reinforced resin-modified glass ionomer (Fuji II LC) were tested. One hundred cylindrical specimens (4 mm × 6 mm) were prepared. Each material had two groups (ten specimens to be tested under static loading and ten specimens to be tested after cyclic loading). The specimens were stored wet, and after 30 days, one group of each material was cyclically loaded (for 250,000 cycles with a frequency of 1.6 Hz under stress load of 68.6 N) in a chewing simulator CS-4.2. Then specimens were subjected to static compressive loading until failure in a universal testing machine. Mean compressive strength values before cycling ranged from 144 MPa (15.8) for Fuji II LC to 277 MPa (23.2) for Grandio Core. Independent t-test showed no statistically significant difference (p > 0.05) in the compressive strength of each material before and after cycling (p = 0.7 Grandio Core, p = 0.3 Core.X Flow, p = 0.6 Bright Flow Core, p = 0.2 Spee-Dee, p = 0.6 Fuji II LC); however, there was a statistically significant difference between the materials when comparing before and after cycling. All tested materials showed no reduction in the compressive strength after cycling. Therefore, the tested materials can survive 1 year in service without a reduction in compressive strength. © 2015 by the American College of Prosthodontists.

  15. Influence of surface treatment and cyclic loading on the durability of repaired all-ceramic crowns

    Directory of Open Access Journals (Sweden)

    Ahmed Attia

    2010-04-01

    Full Text Available OBJECTIVE: This study investigated the durability of repaired all-ceramic crowns after cyclic loading. MATERIAL AND METHODS: Eighty In-ceram zirconia crowns were fabricated to restore prepared maxillary premolars. Resin cement was used for cementation of crowns. Palatal cusps were removed to simulate fracture of veneering porcelain and divided into 4 groups (n = 20. Fracture site was treated before repair as follows: roughening with diamond bur, (DB; air abrasion using 50 µm Al2O3, (AA and silica coating using Cojet system followed by silane application, (SC. Control group (CG 20 specimens were left without fracture. Palatal cusps were repaired using composite resin. Specimens were stored in water bath at 37ºC for one week. Ten specimens of each group were subjected to cyclic loading. Fracture load (N was recorded for each specimen using a universal testing machine. Two-way analysis of variance (ANOVA and Tukey honestly significant difference (HSD test (a=.05 were used for statistical analysis. RESULTS: There was statistically significant difference between control and tested groups, (p<0.001. Post Hoc analysis with the Tukey HSD test showed that cyclic loading fatigue significantly decreased means fracture load of control and test groups as follows (CG, 950.4±62.6 / 872.3±87.4, P = 0.0004, (DB, 624.2 ±38 / 425.5± 31.7, P <.001, (AA, 711.5 ±15.5 / 490 ± 25.2, p <0.001 and (SC, 788.7 ± 18.1 / 610.2 ± 25.2, P <.001, while silica coating and silane application significantly increased fracture load of repaired crowns (p<0.05. CONCLUSION: Repair of fractured In-ceram zirconia crowns after chairside treatment of the fracture site by silica coating and silane application could improve longevity of repaired In-ceram zirconia crowns.

  16. Thermal Conductivity and Thermal Gradient Cyclic Behavior of Refractory Silicate Coatings on SiC/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

    2001-01-01

    Plasma-sprayed mullite and BSAS coatings have been developed to protect SiC/SiC ceramic matrix composites from high temperature environmental attack. In this study, thermal conductivity and thermal barrier functions of these coating systems are evaluated using a laser high-heat-flux test rig. The effects of water vapor on coating thermal conductivity and durability are studied by using alternating furnace and laser thermal gradient cyclic tests. The influence of laser high thermal-gradient cycling on coating failure modes is also investigated.

  17. [Structural and functional changes of the foot after cyclic centrifugal physical loads in sports runners].

    Science.gov (United States)

    Lagutin, M P; Samusev, R P

    2009-01-01

    Foot structural and functional peculiarities after cyclic centrifugal physical loads in sports runners were studied. The work demonstrates the results of computer morphometry of 120 athlete runners (50 boys and 70 girls) aged 15-17 years--the students of Volgograd School of Olympic Reserve and Volgograd State Academy of Physical Education. Cyclic centrifugal loads of shock-type (long run on an inclined plane) resulted in significant reduction of the foot arch hight. In female runners, the reduction was found mainly in the longitudinal foot arch, while in male runners it was detected in transverse foot arch. Two basic types of foot arch reaction to prolonged cyclic loads were detected. This allowed us, for the first time, to divide the static flat-footedness into two major categpries: compensated, or dynamic, and true. In compensated static flat-footedness, the structural and functional foot parameters returned to their initial levels after the rehabilitation, while in true flat-footedness the complex rehabilitation measures could not restore the initial morpho-functional parameters: foot arches remained reduced.

  18. Bond strength evaluation of ceramic and stainless steel bracket bases subjected to cyclic tensile loading.

    Science.gov (United States)

    Soderquist, Scott A; Drummond, James L; Evans, Carla A

    2006-02-01

    The aim of this study was to evaluate the effects of loading, static and cyclic, on 1 stainless steel and 3 ceramic bracket bonding bases. The brackets were chosen because of the different characteristics of their bonding bases. The brackets in each group were bonded to bovine teeth by using the same adhesive and subjected to both static and cyclic tensile loading; the results were analyzed (ANOVA and Scheffé) for statistical differences among the groups. The analysis showed that ceramic brackets have unique characteristics compared with stainless steel; the most significant is higher bond strengths. The effects of cyclic loading were shown to be significant, in that fatigue testing caused a decrease in mean tensile bond strength for most groups. An additional factor on the bond strength might be the composition and design of the bracket base. Simulations of occlusal forces (a combination of tensile, shear, and compressive forces) to orthodontic materials during in-vitro studies in accordance with clinical use might adequately describe actual clinical performance.

  19. Creep of MDF panels under constant load and cyclic environmental conditions. Influence of surface coating

    OpenAIRE

    Fernández-Golfín Seco, J. I.; Díez Barra, M. Rafael

    1997-01-01

    Four different strategies of surface coating (based on 80 g m2 melamin impregnated papers) were used on 19 mm thick commercial MDF panels to assess its reological behaviour under cyclic humidity conditions (20ºC 30 % rh-20ºC 90 % rh). Three different levels of stress (20 %, 30 % and 40 %), based on the ultimate load in bending, were used. Tests were conducted by means of the three points load system. For the same stress level, the relative creep of MDF panels was higher than that in par...

  20. Study on Performance of Steel Fiber Concrete Bridge Pier Specimens under Horizontal Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Baiben Chen

    2017-01-01

    Full Text Available Because of that steel fiber can effectively prevent the extension and development of small cracks in the concrete, steel fiber reinforced concrete has good toughness and tensile strength. In the application of building materials, steel fiber reinforced concrete is an ideal elastic-plastic material. For the seismic performance, it has advantages. In order to analyze the seismic performance of steel fiber reinforced concrete, 4 piers of the scale model test under horizontal cyclic loading were done. The results showed that failure mode of steel fiber reinforced concrete is better than that of ordinary concrete, and has a large yield moment under the external loads.

  1. The Characterization of Mechanical Properties of a Rabbit Femur-Anterior Cruciate Ligament-Tibia Complex During Cyclic Loading

    Science.gov (United States)

    Sekiguchi, Hidetaka; Han, Jungsoo; Ryu, Jaiyoung; Han, Changsoo

    The purpose of this study was to investigate the effect of cyclic loading, which produced the condition of ACLs during sports activities, on tensile properties of femur-ACL-tibia complexes (FATCs). Paired FATCs of 40 New Zealand white rabbits were tested on a materials testing machine. One specimen of each pair was designated as a control and loaded until failure. The contralateral specimen was loaded cyclically (1.4 Hz, 1 hr.) with 20%, 30%, 40%, or 50% of ultimate tensile strength (UTS) of the control and then loaded until failure. The UTS and mode of failure were recorded after each test. Five specimens ruptured during cyclic loading in the 50% group. In the 40% group, the mean value of UTS of cycled specimens was significantly lower than that of controls. There was no statistically significant difference in UTS values between control and cycled specimens in the 20% and 30% groups. Cycled specimens had a significantly higher incidence of substance failure than controls. Our results demonstrated that FATCs have the strength to withstand cyclic loading within normal sports activity levels. However, FACTs can be damaged by cyclic loading under strenuous sports activity levels. We speculate that cyclic loading makes the ACL substance weaker than the insertion site.

  2. Compressive residual stress relaxation in hardened steel during cyclic and static load

    Science.gov (United States)

    Cseh, D.; Mertinger, V.

    2017-05-01

    The benefits of applied compressive residual stress on fatigue properties of materials is a well-known phenomenon, but not well described in all respects. The fatigue life and the fatigue limit could be improved by targeted created compressive residual stress in the surface layers therefore, diversified surface compressing methods are developed and used in the engineering industry. The relaxation of the compressive residual stress state during a cyclic and static load is determinative for the life time of a componenet. Compressive stress relaxation was experimentally determined during the cyclic and static load. The compressive residual stress was induced by shot penning on the surface of stainless steel, micro alloyed high strength steel and hardened steel specimens. The residual stress state was investigated nondestructively by X-ray diffraction method then these specimens were load. After a certain number of cycles the fatigue load was stopped and the residual stress state was recorded again and again until fracture. To investigate the relaxation process during static load a four-point bending bench was used. The compressive residual stress relaxation was correlated to the applied fatigue stress level, the cycle number the quality of alloys.

  3. Transient hydrogen diffusion analyses coupled with crack-tip plasticity under cyclic loading

    International Nuclear Information System (INIS)

    Kotake, Hirokazu; Matsumoto, Ryosuke; Taketomi, Shinya; Miyazaki, Noriyuki

    2008-01-01

    The effect of hydrogen on the material strengths of metals is known as the hydrogen embrittlement, which affects the structural integrity of a hydrogen energy system. In the present paper, we developed a computer program for a transient hydrogen diffusion-elastoplastic coupling analysis by combining an in-house finite element program with a general purpose finite element computer program to analyze hydrogen diffusion. In this program, we use a hypothesis that the hydrogen absorbed in the metal affects the yield stress of the metal. In the present paper, we discuss the effects of the cyclic loading on the hydrogen concentration near the crack tip. An important finding we obtained here is the fact that the hydrogen concentration near the crack tip greatly depends on the loading frequency. This result indicates that the fatigue lives of the components in a hydrogen system depend not only on the number of loading cycles but also on the loading frequency

  4. Quasi-brittle material behavior under cyclic loading: from virtual testing to structural computation

    International Nuclear Information System (INIS)

    Vassaux, Maxime

    2015-01-01

    Macroscopic constitutive laws are developed not only because they allow for large-scale computations but also because refine dissipative mechanisms observed at lower scales. Within the framework of this study, the development of such models is carried out in the context of seismic loading, that is to say reverse cyclic loading, applied to the quasi-brittle materials and more precisely, concrete-like materials. Nowadays, robust and predictive macroscopic constitutive laws are still rare because of the complexity of cracking related phenomena. Among the challenges to face, the material parameters identification is far from being the easiest due to the lack of experimental data. Indeed, the difficulties to carry out cyclic tests on concrete-like materials are numerous. To overcome these difficulties, a virtual testing approach based on a refine model is proposed in this study in order to feed continuum models with the missing material parameters. Adopting a microscopic point of view, a representative volume element is seen as a structure. The microscopic model has been developed with the aim to require a minimal number of material parameters which only need basic mechanical tests to be identified. From an existing lattice model developed to deal with monotonic loading, several enhancements have been realized in order to extend its range of applicability, making it capable of dealing with complex multi-axial cyclic loadings. The microscopic model has been validated as a virtual testing machine that is able to help the identification procedure of continuous constitutive laws. This identification approach has been applied on a new constitutive law developed within the framework of isotropic continuum damage mechanics accounting for cyclic related effects. In particular, the concept of regularized unilateral effect has been introduced to describe the progressive crack closure. The macroscopic model has been calibrated with the help from the aforementioned virtual testing

  5. Effect of cyclic load on vertical misfit of prefabricated and cast implant single abutment

    Directory of Open Access Journals (Sweden)

    Rudys Rodolfo de Jesus Tavarez

    2011-02-01

    Full Text Available OBJECTIVES: The purpose of this in vitro study was to evaluate misfit alterations at the implant/abutment interface of external and internal connection implant systems when subjected to cyclic loading. MATERIAL AND METHODS: Standard metal crowns were fabricated for 5 groups (n=10 of implant/abutment assemblies: Group 1, external hexagon implant and UCLA cast-on premachined abutment; Group 2, internal hexagon implant and premachined abutment; Group 3, internal octagon implant and prefabricated abutment; Group 4, external hexagon implant and UCLA cast-on premachined abutment; and Group 5, external hexagon implant and Ceraone abutment. For groups 1, 2, 3 and 5, the crowns were cemented on the abutments and in group 4 crowns were screwed directly on the implant. The specimens were subjected to 500,000 cycles at 19.1 Hz of frequency and non-axial load of 133 N in a MTS 810 machine. The vertical misfit (μm at the implant/abutment interface was evaluated before (B and after (A application of the cyclic loading. Data were analyzed statistically by using two-away ANOVA and Tukey's post-hoc test (p<0.05. RESULTS: Before loading values showed no difference among groups 2 (4.33±3.13, 3 (4.79±3.43 and 5 (3.86±4.60; between groups 1 (12.88±6.43 and 4 (9.67±3.08, and among groups 2, 3 and 4. However, groups 1 and 4 were significantly different from groups 2, 3 and 5. After loading values of groups 1 (17.28±8.77 and 4 (17.78±10.99 were significantly different from those of groups 2 (4.83±4.50, 3 (8.07±4.31 and 5 (3.81±4.84. There was a significant increase in misfit values of groups 1, 3 and 4 after cyclic loading, but not for groups 2 and 5. CONCLUSIONS: The cyclic loading and type of implant/abutment connection may develop a role on the vertical misfit at the implant/abutment interface.

  6. Effect of dynamic monotonic and cyclic loading on fracture behavior for Japanese carbon steel pipe STS410

    Energy Technology Data Exchange (ETDEWEB)

    Kinoshita, Kanji; Murayama, Kouichi; Ogata, Hiroyuki [and others

    1997-04-01

    The fracture behavior for Japanese carbon steel pipe STS410 was examined under dynamic monotonic and cyclic loading through a research program of International Piping Integrity Research Group (EPIRG-2), in order to evaluate the strength of pipe during the seismic event The tensile test and the fracture toughness test were conducted for base metal and TIG weld metal. Three base metal pipe specimens, 1,500mm in length and 6-inch diameter sch.120, were employed for a quasi-static monotonic, a dynamic monotonic and a dynamic cyclic loading pipe fracture tests. One weld joint pipe specimen was also employed for a dynamic cyclic loading test In the dynamic cyclic loading test, the displacement was controlled as applying the fully reversed load (R=-1). The pipe specimens with a circumferential through-wall crack were subjected four point bending load at 300C in air. Japanese STS410 carbon steel pipe material was found to have high toughness under dynamic loading condition through the CT fracture toughness test. As the results of pipe fracture tests, the maximum moment to pipe fracture under dynamic monotonic and cyclic loading condition, could be estimated by plastic collapse criterion and the effect of dynamic monotonic loading and cyclic loading was a little on the maximum moment to pipe fracture of the STS410 carbon steel pipe. The STS410 carbon steel pipe seemed to be less sensitive to dynamic and cyclic loading effects than the A106Gr.B carbon steel pipe evaluated in IPIRG-1 program.

  7. Study the Cyclic Plasticity Behavior of 508 LAS under Constant, Variable and Grid-Load-Following Loading Cycles for Fatigue Evaluation of PWR Components

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, Subhasish [Argonne National Lab. (ANL), Argonne, IL (United States); Barua, Bipul [Argonne National Lab. (ANL), Argonne, IL (United States); Soppet, William K. [Argonne National Lab. (ANL), Argonne, IL (United States); Majumdar, Saurin [Argonne National Lab. (ANL), Argonne, IL (United States); Natesan, Ken [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-09-01

    This report provides an update of an earlier assessment of environmentally assisted fatigue for components in light water reactors. This report is a deliverable in September 2016 under the work package for environmentally assisted fatigue under DOE’s Light Water Reactor Sustainability program. In an April 2016 report, we presented a detailed thermal-mechanical stress analysis model for simulating the stress-strain state of a reactor pressure vessel and its nozzles under grid-load-following conditions. In this report, we provide stress-controlled fatigue test data for 508 LAS base metal alloy under different loading amplitudes (constant, variable, and random grid-load-following) and environmental conditions (in air or pressurized water reactor coolant water at 300°C). Also presented is a cyclic plasticity-based analytical model that can simultaneously capture the amplitude and time dependency of the component behavior under fatigue loading. Results related to both amplitude-dependent and amplitude-independent parameters are presented. The validation results for the analytical/mechanistic model are discussed. This report provides guidance for estimating time-dependent, amplitude-independent parameters related to material behavior under different service conditions. The developed mechanistic models and the reported material parameters can be used to conduct more accurate fatigue and ratcheting evaluation of reactor components.

  8. Effect of cyclic loading on microleakage of silorane based composite compared with low shrinkage methacrylate-based composites

    Directory of Open Access Journals (Sweden)

    Hamid Kermanshah

    2016-01-01

    Conclusion: Silorane did not provide better marginal seal than the low shrinkage methacrylate-based composites (except Aelite. In addition, cyclic loading did not affect the marginal microleakage of evaluated composite restorations .

  9. Mechanism of crack initiation and crack growth under thermal and mechanical fatigue loading

    International Nuclear Information System (INIS)

    Utz, S.; Soppa, E.; Silcher, H.; Kohler, C.

    2013-01-01

    The present contribution is focused on the experimental investigations and numerical simulations of the deformation behaviour and crack development in the austenitic stainless steel X6CrNiNb18-10 under thermal and mechanical cyclic loading in HCF and LCF regimes. The main objective of this research is the understanding of the basic mechanisms of fatigue damage and the development of simulation methods, which can be applied further in safety evaluations of nuclear power plant components. In this context the modelling of crack initiation and crack growth inside the material structure induced by varying thermal or mechanical loads are of particular interest. The mechanisms of crack initiation depend among other things on the type of loading, microstructure, material properties and temperature. The Nb-stabilized austenitic stainless steel in the solution-annealed condition was chosen for the investigations. Experiments with two kinds of cyclic loading - pure thermal and pure mechanical - were carried out and simulated. The fatigue behaviour of the steel X6CrNiNb18-10 under thermal loading was studied within the framework of the joint research project [4]. Interrupted thermal cyclic tests in the temperature range of 150 C to 300 C combined with non-destructive residual stress measurements (XRD) and various microscopic investigations, e.g. in SEM (Scanning Electron Microscope), were used to study the effects of thermal cyclic loading on the material. This thermal cyclic loading leads to thermal induced stresses and strains. As a result intrusions and extrusions appear inside the grains (at the surface), at which microcracks arise and evolve to a dominant crack. Finally, these microcracks cause a continuous and significant decrease of residual stresses. The fatigue behaviour of the steel X6CrNiNb18-10 under mechanical loading at room temperature was studied within the framework of the research project [5], [8]. With a combination of interrupted LCF tests and EBSD

  10. Mechanism of crack initiation and crack growth under thermal and mechanical fatigue loading

    Energy Technology Data Exchange (ETDEWEB)

    Utz, S.; Soppa, E.; Silcher, H.; Kohler, C. [Stuttgart Univ. (Germany). Materials Testing Inst.

    2013-07-01

    The present contribution is focused on the experimental investigations and numerical simulations of the deformation behaviour and crack development in the austenitic stainless steel X6CrNiNb18-10 under thermal and mechanical cyclic loading in HCF and LCF regimes. The main objective of this research is the understanding of the basic mechanisms of fatigue damage and the development of simulation methods, which can be applied further in safety evaluations of nuclear power plant components. In this context the modelling of crack initiation and crack growth inside the material structure induced by varying thermal or mechanical loads are of particular interest. The mechanisms of crack initiation depend among other things on the type of loading, microstructure, material properties and temperature. The Nb-stabilized austenitic stainless steel in the solution-annealed condition was chosen for the investigations. Experiments with two kinds of cyclic loading - pure thermal and pure mechanical - were carried out and simulated. The fatigue behaviour of the steel X6CrNiNb18-10 under thermal loading was studied within the framework of the joint research project [4]. Interrupted thermal cyclic tests in the temperature range of 150 C to 300 C combined with non-destructive residual stress measurements (XRD) and various microscopic investigations, e.g. in SEM (Scanning Electron Microscope), were used to study the effects of thermal cyclic loading on the material. This thermal cyclic loading leads to thermal induced stresses and strains. As a result intrusions and extrusions appear inside the grains (at the surface), at which microcracks arise and evolve to a dominant crack. Finally, these microcracks cause a continuous and significant decrease of residual stresses. The fatigue behaviour of the steel X6CrNiNb18-10 under mechanical loading at room temperature was studied within the framework of the research project [5], [8]. With a combination of interrupted LCF tests and EBSD

  11. Interactive evolution concept for analyzing a rock salt cavern under cyclic thermo-mechanical loading

    Science.gov (United States)

    König, Diethard; Mahmoudi, Elham; Khaledi, Kavan; von Blumenthal, Achim; Schanz, Tom

    2016-04-01

    The excess electricity produced by renewable energy sources available during off-peak periods of consumption can be used e.g. to produce and compress hydrogen or to compress air. Afterwards the pressurized gas is stored in the rock salt cavities. During this process, thermo-mechanical cyclic loading is applied to the rock salt surrounding the cavern. Compared to the operation of conventional storage caverns in rock salt the frequencies of filling and discharging cycles and therefore the thermo-mechanical loading cycles are much higher, e.g. daily or weekly compared to seasonally or yearly. The stress strain behavior of rock salt as well as the deformation behavior and the stability of caverns in rock salt under such loading conditions are unknown. To overcome this, existing experimental studies have to be supplemented by exploring the behavior of rock salt under combined thermo-mechanical cyclic loading. Existing constitutive relations have to be extended to cover degradation of rock salt under thermo-mechanical cyclic loading. At least the complex system of a cavern in rock salt under these loading conditions has to be analyzed by numerical modeling taking into account the uncertainties due to limited access in large depth to investigate material composition and properties. An interactive evolution concept is presented to link the different components of such a study - experimental modeling, constitutive modeling and numerical modeling. A triaxial experimental setup is designed to characterize the cyclic thermo-mechanical behavior of rock salt. The imposed boundary conditions in the experimental setup are assumed to be similar to the stress state obtained from a full-scale numerical simulation. The computational model relies primarily on the governing constitutive model for predicting the behavior of rock salt cavity. Hence, a sophisticated elasto-viscoplastic creep constitutive model is developed to take into account the dilatancy and damage progress, as well as

  12. Acoustic Emission Characteristics of Red Sandstone Specimens Under Uniaxial Cyclic Loading and Unloading Compression

    Science.gov (United States)

    Meng, Qingbin; Zhang, Mingwei; Han, Lijun; Pu, Hai; Chen, Yanlong

    2018-04-01

    To explore the acoustic emission (AE) characteristics of rock materials during the deformation and failure process under periodic loads, a uniaxial cyclic loading and unloading compression experiment was conducted based on an MTS 815 rock mechanics test system and an AE21C acoustic emissions test system. The relationships among stress, strain, AE activity, accumulated AE activity and duration for 180 rock specimens under 36 loading and unloading rates were established. The cyclic AE evolutionary laws with rock stress-strain variation at loading and unloading stages were analyzed. The Kaiser and Felicity effects of rock AE activity were disclosed, and the impact of the significant increase in the scale of AE events on the Felicity effect was discussed. It was observed that the AE characteristics are closely related to the stress-strain properties of rock materials and that they are affected by the developmental state and degree of internal microcracks. AE events occur in either the loading or unloading stages if the strain is greater than zero. Evolutionary laws of AE activity agree with changes in rock strain. Strain deformation is accompanied by AE activity, and the density and intensity of AE events directly reflect the damage degree of the rock mass. The Kaiser effect exists in the linear elastic stage of rock material, and the Felicity effect is effective in the plastic yield and post-peak failure stages, which are divided by the elastic yield strength. This study suggests that the stress level needed to determine a significant increase in AE activity was 70% of the i + 1 peak stress. The Felicity ratio of rock specimens decreases with the growth of loading-unloading cycles. The cycle magnitude and variation of the Felicity effect, in which loading and unloading rates play a weak role, are almost consistent.

  13. An anisotropic damage model for concrete structures under cyclic loading-uniaxial modeling

    Science.gov (United States)

    Long, Yuchuan; He, Yuming

    2017-05-01

    An anisotropic damage model is developed based on conventional rotating crack approach. It uses nonlinear unloading/linear reloading branches to model the hysteretic behavior of concrete. Two damage variables, determined by the ratio of accumulated dissipating energy to fracture energy, are introduced to represent the stiffness degradation in tension and compression. Three cyclic tests are simulated by this model and sensitivity analyses are conducted as well. The numerical responses calculated by the damage model are consistent with those obtained from the experiments. The numerical results reflect the nonlinear behavior observed in those tests, such as the damage-induced stiffness degradation, accumulation of residual deformation, energy dissipation caused by hysteretic behavior and stiffness recovery effect due to crack closure. Sensitivity analyses show that the damage exponents have significant influence on the computational accuracy. It is concluded that the anisotropic damage model is applicable to the nonlinear analyses of concrete structures subjected to cyclic loading.

  14. Estimation of fatigue strength under multiaxial cyclic loading by varying the critical plane orientation

    Directory of Open Access Journals (Sweden)

    Marta Kurek

    2016-07-01

    Full Text Available The main purpose of this paper is to examine the influence of the critical plane orientation on the estimated fatigue strength of metals under multiaxial loading. The algorithm employed to evaluate fatigue strength implements the criterion of maximum normal and shear stress on a suitable damage plane (critical plane. The angle  defining the critical plane orientation is measured with respect to the direction that maximises the applied normal stress. Eleven (11 structural materials under combined bending and torsion cyclic loading are examined. For each analysed material, the value of  angle is selected so that the value of the scatter, defined by a root-mean-square value, is minimum. On the basis of such a calculation, an empirical expression for  is proposed, that takes into account the values of bending and torsion fatigue strengths at a reference number of loading cycles. According to such an expression,  is constant for a given material.

  15. Thermal loading effects on geological disposal

    International Nuclear Information System (INIS)

    Come, B.; Venet, P.

    1984-01-01

    A joint study on the thermal loading effects on geological disposal was carried out within the European Community Programme on Management and Storage of Radioactive Waste by several laboratories in Belgium, France and the Federal Republic of Germany. The purpose of the work was to review the thermal effects induced by the geological disposal of high-level wastes and to assess their consequences on the 'admissible thermal loading' and on waste management in general. Three parallel studies dealt separately with the three geological media being considered for HLW disposal within the CEC programme: granite (leadership: Commissariat a l'energie atomique (CEA), France), salt (leadership: Gesellschaft fuer Strahlen- und Umweltforschung (GSF), Federal Republic of Germany), and clay (leadership: Centre d'etude de l'energie nucleaire (CEN/SCK), Belgium). The studies were based on the following items: only vitrified high-level radioactive waste was considered; the multi-barrier confinement concept was assumed (waste glass, container (with or without overpack), buffer material, rock formation); the disposal was foreseen in a deep mined repository, in an 'in-land' geological formation; only normal situations and processes were covered, no 'accident' scenario being taken into account. Although reasonably representative of a wide variety of situations, the data collected and the results obtained are generic for granite, formation-specific for salt (i.e. related to the north German Zechstein salt formation), and site-specific for clay (i.e. concentrated on the Boom clay layer at the Mol site, Belgium). For each rock type, realistic temperature limits were set, taking into account heat propagation, thermo-mechanical effects inside the rock formations, induced or modified groundwater or brine movement, effects on the buffer material as well as effects on the waste glass and canister, and finally, nuclide transport

  16. Seismic and Power Generation Performance of U-Shaped Steel Connected PV-Shear Wall under Lateral Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Hongmei Zhang

    2014-01-01

    Full Text Available BIPV is now widely used in office and residential buildings, but its seismic performance still remained vague especially when the photovoltaic (PV modules are installed on high-rise building facades. A new form of reinforced concrete shear wall integrated with photovoltaic module is proposed in this paper, aiming to apply PV module to the facades of high-rise buildings. In this new form, the PV module is integrated with the reinforced concrete wall by U-shaped steel connectors through embedded steel plates. The lateral cyclic loading test is executed to investigate the seismic behavior and the electric and thermal performance with different drift angles. The seismic behavior, including failure pattern, lateral force-top displacement relationship, and deformation capacity, was investigated. The power generation and temperature variation on the back of the PV module and both sides of the shear wall were also tested. Two main results are demonstrated through the experiment: (1 the U-shaped steel connectors provide enough deformation capacity for the compatibility of the PV module to the shear wall during the whole cyclic test; (2 the electricity generation capacity is effective and stable during this seismic simulation test.

  17. Sulfur loaded in micropore-rich carbon aerogel as cathode of lithium-sulfur battery with improved cyclic stability

    Science.gov (United States)

    Li, Zihao; Li, Xiaogang; Liao, Youhao; Li, Xiaoping; Li, Weishan

    2016-12-01

    We report a novel composite of sulfur loaded in micropore-rich carbon aerogel (CA-S), as cathode of lithium-sulfur battery. Carbon aerogel (CA) is synthesized through phenol-formaldehyde reaction with a low catalyst concentration and carbonization under high temperature, and loaded with sulfur via chemical deposition and heat treatment. The physical properties of the resulting CA and the electrochemical performances of the resulting CA-S are investigated by scanning electron microscopy, thermal gravimetric analysis, Brunauer-Emmett-Teller characterization, electrochemical impedance spectroscopy, and galvanostatic discharge/charge test, with a comparison of a common carbon material, acetylene black (AB), and sulfur loaded in AB (AB-S). It is found that the CA is micropore-rich with micropore volume over 66% of total pore volume, and the CA-S exhibits significantly improved cyclic stability compared with AB-S. The improved performance of CA-S is attributed to the confinement of the micropores in CA to small sulfur allotropes and corresponding lithium sulfides.

  18. Ratcheting study in pressurized piping components under cyclic loading at room temperature

    International Nuclear Information System (INIS)

    Ravi Kiran, A.; Agrawal, M.K.; Reddy, G.R.; Vaze, K.K.; Ghosh, A.K.; Kushwaha, H.S.

    2006-07-01

    The nuclear power plant piping components and systems are often subjected to reversing cyclic loading conditions due to various process transients, seismic and other events. Earlier the design of piping subjected to seismic excitation was based on the principle of plastic collapse. It is believed that during such events, fatigue-ratcheting is likely mode of failure of piping components. The 1995 ASME Boiler and Pressure Vessel code, Section-III, has incorporated the reverse dynamic loading and ratcheting into the code. Experimental and analytical studies are carried out to understand this failure mechanism. The biaxial ratcheting characteristics of SA 333, Gr. 6 steel and SS 304 stainless steel at room temperature are investigated in the present work. Experiments are carried out on straight pipes subjected to internal pressure and cyclic bending load applied in a three point and four point bend test configurations. A shake table test is also carried out on a pressurized elbow by applying sinusoidal base excitation. Analytical simulation of ratcheting in the piping elements is carried out. Chaboche nonlinear kinematic hardening model is used for ratcheting simulation. (author)

  19. Influence of surface treatment and cyclic loading on the durability of repaired all-ceramic crowns

    Science.gov (United States)

    ATTIA, Ahmed

    2010-01-01

    Objective This study investigated the durability of repaired all-ceramic crowns after cyclic loading. Material and methods Eighty In-ceram zirconia crowns were fabricated to restore prepared maxillary premolars. Resin cement was used for cementation of crowns. Palatal cusps were removed to simulate fracture of veneering porcelain and divided into 4 groups (n = 20). Fracture site was treated before repair as follows: roughening with diamond bur, (DB); air abrasion using 50 µm Al2O3, (AA) and silica coating using Cojet system followed by silane application, (SC). Control group (CG) 20 specimens were left without fracture. Palatal cusps were repaired using composite resin. Specimens were stored in water bath at 37°C for one week. Ten specimens of each group were subjected to cyclic loading. Fracture load (N) was recorded for each specimen using a universal testing machine. Two-way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) test (α=.05) were used for statistical analysis. Results There was statistically significant difference between control and tested groups, (pcrowns (pzirconia crowns after chairside treatment of the fracture site by silica coating and silane application could improve longevity of repaired In-ceram zirconia crowns. PMID:20485932

  20. Proper Generalized Decomposition (PGD) for the numerical simulation of polycrystalline aggregates under cyclic loading

    Science.gov (United States)

    Nasri, Mohamed Aziz; Robert, Camille; Ammar, Amine; El Arem, Saber; Morel, Franck

    2018-02-01

    The numerical modelling of the behaviour of materials at the microstructural scale has been greatly developed over the last two decades. Unfortunately, conventional resolution methods cannot simulate polycrystalline aggregates beyond tens of loading cycles, and they do not remain quantitative due to the plasticity behaviour. This work presents the development of a numerical solver for the resolution of the Finite Element modelling of polycrystalline aggregates subjected to cyclic mechanical loading. The method is based on two concepts. The first one consists in maintaining a constant stiffness matrix. The second uses a time/space model reduction method. In order to analyse the applicability and the performance of the use of a space-time separated representation, the simulations are carried out on a three-dimensional polycrystalline aggregate under cyclic loading. Different numbers of elements per grain and two time increments per cycle are investigated. The results show a significant CPU time saving while maintaining good precision. Moreover, increasing the number of elements and the number of time increments per cycle, the model reduction method is faster than the standard solver.

  1. Mechanical Behavior of Red Sandstone under Incremental Uniaxial Cyclical Compressive and Tensile Loading

    Directory of Open Access Journals (Sweden)

    Baoyun Zhao

    2017-01-01

    Full Text Available Uniaxial experiments were carried out on red sandstone specimens to investigate their short-term and creep mechanical behavior under incremental cyclic compressive and tensile loading. First, based on the results of short-term uniaxial incremental cyclic compressive and tensile loading experiments, deformation characteristics and energy dissipation were analyzed. The results show that the stress-strain curve of red sandstone has an obvious memory effect in the compressive and tensile loading stages. The strains at peak stresses and residual strains increase with the cycle number. Energy dissipation, defined as the area of the hysteresis loop in the stress-strain curves, increases nearly in a power function with the cycle number. Creep test of the red sandstone was also conducted. Results show that the creep curve under each compressive or tensile stress level can be divided into decay and steady stages, which cannot be described by the conventional Burgers model. Therefore, an improved Burgers creep model of rock material is constructed through viscoplastic mechanics, which agrees very well with the experimental results and can describe the creep behavior of red sandstone better than the Burgers creep model.

  2. Damage & fracture of high-explosive mock subject to cyclic loading

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Cheng [Los Alamos National Laboratory; Rae, Philip J [Los Alamos National Laboratory; Cady, Carl M [Los Alamos National Laboratory; Lovato, Manuel L [Los Alamos National Laboratory

    2011-01-11

    We use four-point bend specimen with a single shallow edge notch to study the fracture process in Mock 900-21, a PBX 9501 high explosive simulant mock. Subject to monotonic loading we determine quantitatively the threshold load for macroscopic crack initiation from the notch tip. The four-point bend specimen is then subject to cyclic loading in such a way that during the first cycle, the applied force approaches but does not exceed the threshold load determined from the monotonic loading test and in the subsequent cycles, the overall maximum deformation is maintained to be equal to that of the first cycle. It is expected and is also confirmed that no macroscopic damage and cracking occur during the first cycle. However, we observe that sizable macroscopic crack is generated and enlarged during the subsequent cycles, even though the applied force never exceeds the threshold load. Details of the process of damage fonnation, accumulation, and crack extension are presented and the mechanical mechanism responsible for such failure process is postulated and discussed.

  3. Upregulation of matrix synthesis in chondrocyte-seeded agarose following sustained bi-axial cyclic loading

    Directory of Open Access Journals (Sweden)

    Belinda Pingguan-Murphy

    2012-08-01

    Full Text Available OBJECTIVES: The promotion of extracellular matrix synthesis by chondrocytes is a requisite part of an effective cartilage tissue engineering strategy. The aim of this in vitro study was to determine the effect of bi-axial cyclic mechanical loading on cell proliferation and the synthesis of glycosaminoglycans by chondrocytes in threedimensional cultures. METHOD: A strain comprising 10% direct compression and 1% compressive shear was applied to bovine chondrocytes seeded in an agarose gel during two 12-hour conditioning periods separated by a 12-hour resting period. RESULTS: The bi-axial-loaded chondrocytes demonstrated a significant increase in glycosaminoglycan synthesis compared with samples exposed to uni-axial or no loading over the same period (p<0.05. The use of a free-swelling recovery period prior to the loading regime resulted in additional glycosaminoglycan production and a significant increase in DNA content (p<0.05, indicating cell proliferation. CONCLUSIONS: These results demonstrate that the use of a bi-axial loading regime results in increased matrix production compared with uni-axial loading.

  4. Simulation of reinforced concrete short shear wall subjected to cyclic loading

    International Nuclear Information System (INIS)

    Parulekar, Y.M.; Reddy, G.R.; Vaze, K.K.; Pegon, P.; Wenzel, H.

    2014-01-01

    Highlights: • Prediction of the capacity of squat shear wall using tests and analysis. • Modification of model of concrete in the softening part. • Pushover analysis using softened truss theory and FE analysis is performed. • Modified concrete model gives reasonable accurate peak load and displacement. • The ductility, ultimate load and also crack pattern can be accurately predicted. - Abstract: This paper addresses the strength and deformation capacity of stiff squat shear wall subjected to monotonic and pseudo-static cyclic loading using experiments and analysis. Reinforced concrete squat shear walls offer great potential for lateral load resistance and the failure mode of these shear walls is brittle shear mode. Shear strength of these shear walls depend strongly on softening of concrete struts in principal compression direction due to principal tension in other direction. In this work simulation of the behavior of a squat shear wall is accurately predicted by finite element modeling by incorporating the appropriate softening model in the program. Modification of model of concrete in the softening part is suggested and reduction factor given by Vecchio et al. (1994) is used in the model. The accuracy of modeling is confirmed by comparing the simulated response with experimental one. The crack pattern generated from the 3D model is compared with that obtained from experiments. The load deflection for monotonic loads is also obtained using softened truss theory and compared with experimental one

  5. Theoretical analysis, infrared and structural investigations of energy dissipation in metals under cyclic loading

    International Nuclear Information System (INIS)

    Plekhov, O.A.; Saintier, N.; Palin-Luc, T.; Uvarov, S.V.; Naimark, O.B.

    2007-01-01

    The infrared and structural investigations of energy dissipation processes in metals subjected to cyclic loading have given impetus to the development of a new thermodynamic model with the capability of describing the energy balance under plastic deformation. The model is based on the statistical description of the mesodefect ensemble evolution and its influence on the dissipation ability of the material. Constitutive equations have been formulated for plastic and structural strains, which allow us to describe the stored and dissipated parts of energy under plastic flow. Numerical results indicate that theoretical predictions are in good agreement with the experimentally observed temperature data

  6. Fracture mode during cyclic loading of implant-supported single-tooth restorations

    DEFF Research Database (Denmark)

    Hosseini, Mandana; Kleven, Erik; Gotfredsen, Klaus

    2012-01-01

    restorations of zirconia abutment-retained crowns with zirconia copings veneered with glass-ceramics (n=8) and feldspathic ceramics (n=8). The control group was composed of 16 metal ceramic restorations of titanium abutment-retained crowns with gold alloy copings veneered with glass (n=8) and feldspathic......STATEMENT OF PROBLEM: Fracture of veneering ceramics in zirconia-based restorations has frequently been reported. Investigation of the fracture mode of implant-supported ceramic restorations by using clinically relevant laboratory protocols is needed. PURPOSE: This study compared the mode...... and resisted more cyclic loads than the ceramic restorations, particularly when the metal ceramic crowns were veneered with glass-ceramics....

  7. Damage Accumulation in Cyclically-Loaded Glass-Ceramic Matrix Composites Monitored by Acoustic Emission

    Directory of Open Access Journals (Sweden)

    D. G. Aggelis

    2013-01-01

    Full Text Available Barium osumilite (BMAS ceramic matrix composites reinforced with SiC-Tyranno fibers are tested in a cyclic loading protocol. Broadband acoustic emission (AE sensors are used for monitoring the occurrence of different possible damage mechanisms. Improved use of AE indices is proposed by excluding low-severity signals based on waveform parameters, rather than only threshold criteria. The application of such improvements enhances the accuracy of the indices as accumulated damage descriptors. RA-value, duration, and signal energy follow the extension cycles indicating moments of maximum or minimum strain, while the frequency content of the AE signals proves very sensitive to the pull-out mechanism.

  8. Effect of surfaces similarity on contact resistance of fractal rough surfaces under cyclic loading

    Science.gov (United States)

    Gao, Yuanwen; Liu, Limei; Ta, Wurui; Song, Jihua

    2018-03-01

    Although numerous studies have shown that contact resistance depends significantly on roughness and fractal dimension, it remains elusive how they affect contact resistance between rough surfaces. The interface similarity index is first proposed to describe the similarity of the contact surfaces, which gives a good indication of the actual contact area between surfaces. We reveal that the surfaces' similarity be an origin of contact resistance variation. The cyclic loading can increase the contact stiffness, and the contact stiffness increases with the increase of the interface similarity index. These findings explain the mechanism of surface roughness and fractal dimension on contact resistance, and also provide reference for the reliability design of the electrical connection.

  9. Interface debond crack growth in tension–tension cyclic loading of single fiber polymer composites

    DEFF Research Database (Denmark)

    Pupurs, Andrejs; Goutianos, Stergios; Brøndsted, Povl

    2013-01-01

    Fiber/matrix interface debond crack growth from a fiber break is defined as one of the key mechanisms of fatigue damage in unidirectional composites. Considering debond as an interface crack its growth in cyclic loading is analyzed utilizing a power law, where the debond growth rate is a power...... for glass fiber/epoxy single fiber composites. Analytical method in the steady-state growth region and FEM for short debonds are combined for calculating the strain energy release rate of the growing debond crack. Interface failure parameters in fatigue are determined by fitting the modeling...

  10. Variation in Stiffness of Monopiles in Dense Sand Under Cyclic Lateral Loads

    DEFF Research Database (Denmark)

    Nicolai, Giulio; Ibsen, Lars Bo

    2016-01-01

    The stiffness of the soil-foundation system is an important parameter that is taken into account in design. Recent studies of offshore wind turbines have shown that long-term cyclic lateral loading, induced by waves and wind, may lead to an increase in the foundation stiffness during the lifetime...... of the foundation. This is in contrast to design methods proposed by current guidelines. The present paper represents a further step towards improving the general knowledge regarding such stiffness change issues. Test results from an experimental investigation are presented and discussed. The interpretation focuses...

  11. Cyclic elastic analysis of a PWR nozzle subjected to a repeated thermal shock

    International Nuclear Information System (INIS)

    Locci, J.M.; Prost, J.P.

    1979-01-01

    In the primary piping system of a PWR nuclear power plant, some nozzles are subjected to strong thermal shocks due to sudden thermal variations in the internal water flow. The thermal gradients are sufficiently high to induce general elastic plastic behaviour. The design of these nozzles using the simplified elastic plastic analysis given in the ASME III Code NB-3200 generally leads to a very high usage factor. The aim of this work is to show by giving an example that a complete cyclic elastic plastic analysis makes it possible to considerably reduce the usage factor. (orig.)

  12. Experimental Investigation on the Fatigue Mechanical Properties of Intermittently Jointed Rock Models Under Cyclic Uniaxial Compression with Different Loading Parameters

    Science.gov (United States)

    Liu, Yi; Dai, Feng; Dong, Lu; Xu, Nuwen; Feng, Peng

    2018-01-01

    Intermittently jointed rocks, widely existing in many mining and civil engineering structures, are quite susceptible to cyclic loading. Understanding the fatigue mechanism of jointed rocks is vital to the rational design and the long-term stability analysis of rock structures. In this study, the fatigue mechanical properties of synthetic jointed rock models under different cyclic conditions are systematically investigated in the laboratory, including four loading frequencies, four maximum stresses, and four amplitudes. Our experimental results reveal the influence of the three cyclic loading parameters on the mechanical properties of jointed rock models, regarding the fatigue deformation characteristics, the fatigue energy and damage evolution, and the fatigue failure and progressive failure behavior. Under lower loading frequency or higher maximum stress and amplitude, the jointed specimen is characterized by higher fatigue deformation moduli and higher dissipated hysteresis energy, resulting in higher cumulative damage and lower fatigue life. However, the fatigue failure modes of jointed specimens are independent of cyclic loading parameters; all tested jointed specimens exhibit a prominent tensile splitting failure mode. Three different crack coalescence patterns are classified between two adjacent joints. Furthermore, different from the progressive failure under static monotonic loading, the jointed rock specimens under cyclic compression fail more abruptly without evident preceding signs. The tensile cracks on the front surface of jointed specimens always initiate from the joint tips and then propagate at a certain angle with the joints toward the direction of maximum compression.

  13. Simplified Probabilistic Analysis of Settlement of Cyclically Loaded Soil Stratum by Point Estimate Method

    Science.gov (United States)

    Przewłócki, Jarosław; Górski, Jarosław; Świdziński, Waldemar

    2016-12-01

    The paper deals with the probabilistic analysis of the settlement of a non-cohesive soil layer subjected to cyclic loading. Originally, the settlement assessment is based on a deterministic compaction model, which requires integration of a set of differential equations. However, with the use of the Bessel functions, the settlement of a soil stratum can be calculated by a simplified algorithm. The compaction model parameters were determined for soil samples taken from subsoil near the Izmit Bay, Turkey. The computations were performed for various sets of random variables. The point estimate method was applied, and the results were verified by the Monte Carlo method. The outcome leads to a conclusion that can be useful in the prediction of soil settlement under seismic loading.

  14. Numerical Calculation of Damping for Monopile Foundations under Cyclic Load During Steady-State Vibration

    DEFF Research Database (Denmark)

    Bayat, Mehdi; Andersen, Lars Vabbersgaard; Andersen, Søren

    2013-01-01

    Dynamic loading and fatigue has significant effects on offshore wind turbine foundations. To obtain a proper design of a turbine and its foundation it is therefore important to understand how the structure and soil interact regarding damping. Especially, this paper demonstrates the damping...... and stiffness of the saturated soil within the seabed due to pore water flow generated by the cyclic motion of a monopile. The concept of a Kelvin-Voigt model is employed and combined with a Finite Element Method (FEM) model of the pile. The two-dimensional analysis of each individual soil layer is performed...... in ABAQUS by coding input files, utilizing Python and MATLAB. A parametric study is performed to illustrate the effects of model size, soil properties such as permeability, void ratio, Young’s modulus, bulk modulus, and load parameters such as amplitude and frequency. It is found that by increasing the bulk...

  15. Cyclic loading biomechanical analysis of the pullout strengths of rotator cuff and glenoid anchors: 2013 update.

    Science.gov (United States)

    Barber, F Alan; Herbert, Morley A

    2013-05-01

    The purpose of this study was to evaluate the biomechanical and design characteristics of newer suture anchors under cyclic loading. Suture anchors were tested in fresh porcine cortical and cancellous bone by cyclic loading (10 to 100 N for 200 cycles) followed by destructive testing parallel to the insertion axis at 12.5 mm per second. End points included ultimate failure load, displacement at 100 and 200 cycles, failure mode, and stiffness. Anchors tested included ReelX (Stryker Endoscopy, San Jose, CA); Footprint Ultra PK (4.5 and 5.5 mm) (Smith & Nephew, Andover, MA); TwinFix (4.5, 5.5, and 6.5 mm made from polyether ether ketone [PEEK], hydroxyapatite [HA], and titanium [Ti]) (Smith & Nephew Endoscopy, Andover, MA); Morphix (2.5 and 5.5 mm) (MedShape Solutions, Atlanta, GA); CrossFT BC (ConMed-Linvatec, Largo, FL); JuggerKnot (1.5 and 2.8 mm) (Biomet Sports Medicine, Warsaw, IN); Healicoil (Smith & Nephew Endoscopy, Andover, MA); Quattro (X, Link, and GL) (Cayenne Medical, Scottsdale, AZ); Healix (Biocryl Rapide [BR], PEEK, and Ti) (DePuy Mitek, Raynham, MA); Twin Loop (3.5 mm, PEEK) (Stryker Endoscopy, San Jose, CA); PressFT (2.1 and 2.6 mm) (ConMed Linvatec, Largo FL); Y-Knot (ConMed Linvatec, Largo FL); Gryphon (BR and PEEK) (DePuy Mitek, Raynham, MA); and Iconix (1, 2, and 3) (Stryker Endoscopy, San Jose, CA). Rotator cuff anchors showed greater failure loads than did glenoid anchors in metaphyseal bone (rotator cuff anchors 448 N v glenoid anchors 296 N) (P = .001) and cancellous bone (rotator cuff anchors 435 N v glenoid anchors 225 N) (P strengths than did glenoid anchors, regardless of bone type. TwinFix anchors showed more cyclic displacement than did other rotator cuff anchors (except the ReelX and Morphix anchors) and the glenoid anchors tested. The failure mode was dependent on the specific anchor. Suture anchor constructs tested showed that failure load is dependent on anchor type (rotator cuff anchor or glenoid anchor) but not on anchor location

  16. Partial alpha-colony fractures and their protrusions during cyclic loading of a titanium alloy

    International Nuclear Information System (INIS)

    Cameron, D.W.; Hoeppner, D.W.

    1984-01-01

    In the course of an extended study of the cyclic load response of several gas turbine alloys, a very interesting phenomenon was observed in some specimens of IMI 829. The response documented shows the emergence of loosely-bound sections of material into the notch root of test specimens. The authors have not seen this effect reported by other investigators. The experimental apparatus consists of a scanning electron microscope coupled with a load frame to view the real-time surface response of cyclically loaded specimens. For reference, the specimen geometry is shown, the cross section (A-A) is rectangular, measuring approximately 1mm X 4mm. Normal preparation is to notch one side of the specimen using a jeweller's saw and metallurgically polish and etch one of the flat surfaces for observation. IMI 829 (Ti-5.5Al-3.5Sn-3.0Zr-0.25Mo-1Nb-0.3Si) is a near-alpha titanium alloy, examined here in the beta-annealed condition which displays plate-like alpha colonies with some primary alpha on the prior beta grain boundaries. It can also manifest a Widmanstaetten-type microstructure. Having a nominal grain size of approximately 1mm, the microstructure-specimen size combination allows for an interesting study in pseudo-continua. Although the experiments were predominantly designed to investigate crack-microstructure interactions, the features of interest here were generated within the saw-cut notch root of the specimen. In the process of nucleating a crack in the notch root, three of six specimens developed discontinuities which were not perpendicular to either the loading axis or the observed specimen surface. In two of these three cases, while the crack was progressing across the ligament and downward through the specimen, some sections broke away

  17. Behaviour of hybrid fibre reinforced concrete beam–column joints under reverse cyclic loads

    International Nuclear Information System (INIS)

    Ganesan, N.; Indira, P.V.; Sabeena, M.V.

    2014-01-01

    Highlights: • Developed a high performance hybrid fibre reinforced cementitious composite. • Exterior beam-column joints have been tested under reversed cyclic loading. • Ductility factor, energy dissipation and stiffness degradation have been evaluated. • Contribution to reduce congestion of reinforcement in beam column joints. - Abstract: An experimental investigation was carried out to study the effect of hybrid fibres on the strength and behaviour of High performance concrete beam column joints subjected to reverse cyclic loads. A total of 12 reinforced concrete beams column joints were cast and tested in the present investigation. High performance concrete of M60 grade was designed using the modified ACI method suggested by Aïtcin. Crimped steel fibres and polypropylene fibres were used in hybrid form. The main variables considered were the volume fraction of (i) crimped steel fibres viz. 0.5% (39.25 kg/m 3 ) and 1.0% (78.5 kg/m 3 ) and (ii) polypropylene fibres viz. 0.1% (0.9 kg/m 3 ), 0.15% (1.35 kg/m 3 ), and 0.2% (1.8 kg/m 3 ). Addition of fibres in hybrid form improved many of the engineering properties such as the first crack load, ultimate load and ductility factor of the composite. The combination of 1% (78.5 kg/m 3 ) volume fraction of steel fibres and 0.15% (1.35 kg/m 3 ) volume fraction of polypropylene fibres gave better performance with respect to energy dissipation capacity and stiffness degradation than the other combinations

  18. Effect of framework design on fracture load after thermal cycling and mechanical loading of implant-supported zirconia-based prostheses.

    Science.gov (United States)

    Komine, Futoshi; Kamio, Shingo; Takata, Hiroki; Yagawa, Shogo; Taguchi, Serina; Taguchi, Kohei; Hashiguchi, Akiko; Matsumura, Hideo

    2018-01-30

    This study evaluated the effect of zirconia framework design on fracture load of implant-supported zirconia-based prostheses after thermal cycling and mechanical loading. Three different zirconia framework designs were investigated: uniform-thickness (UNI), anatomic (ANA), and supported anatomic (SUP) designs. Each framework was layered with feldspathic porcelain (ZAC group) or indirect composite material (ZIC group). The specimens then underwent fracture load testing after thermal cycling and cyclic loading. In the ZAC group, mean fracture load was significantly lower for UNI design specimens than for the other framework designs. In the ZIC group, there was no significant difference in mean fracture load between ANA design specimens and either UNI or SUP design specimens. To improve fracture resistance of implant-supported zirconia-based prostheses after artificial aging, uniformly thick layering material and appropriate lingual support with zirconia frameworks should be provided.

  19. Experimental and Numerical Study of Mild Steel Behaviour under Cyclic Loading with Variable Strain Ranges

    Directory of Open Access Journals (Sweden)

    Paulina Krolo

    2016-01-01

    Full Text Available To simulate the effect of variable strains on steel grades S275 and S355, an experimental displacement control test of plate specimens was performed. Specimens were tested under monotonic and cyclic loading according to the standard loading protocol of SAC 2000. During experimental testing, strain values were measured with an extensometer at the tapered part of the specimen. Strains obtained by the experimental tests are disproportional to the applied displacements at the ends of the specimens. This phenomenon occurs due to the imperfections of the specimen, hardening of the material, and the buckling behaviour that appears in real structures due to the high deformation experienced during earthquakes. Due to the relative simplicity and wide applicability of the Chaboche hardening model of steel, the calibration of hardening parameters based on experimental test results was conducted. For the first time, calibration of steel hardening parameters was performed following the Chaboche procedure to define the cyclic behaviour with variable strain ranges. The accuracy of the hardening model with variable strain ranges, which were simulated using ABAQUS software, was verified using the experimental results.

  20. Loosening torque of Universal Abutment screws after cyclic loading: influence of tightening technique and screw coating.

    Science.gov (United States)

    Bacchi, Atais; Regalin, Alexandre; Bhering, Claudia Lopes Brilhante; Alessandretti, Rodrigo; Spazzin, Aloisio Oro

    2015-10-01

    The purpose of this study was to evaluate the influence of tightening technique and the screw coating on the loosening torque of screws used for Universal Abutment fixation after cyclic loading. Forty implants (Titamax Ti Cortical, HE, Neodent) (n=10) were submerged in acrylic resin and four tightening techniques for Universal Abutment fixation were evaluated: A - torque with 32 Ncm (control); B - torque with 32 Ncm holding the torque meter for 20 seconds; C - torque with 32 Ncm and retorque after 10 minutes; D - torque (32 Ncm) holding the torque meter for 20 seconds and retorque after 10 minutes as initially. Samples were divided into subgroups according to the screw used: conventional titanium screw or diamond like carbon-coated (DLC) screw. Metallic crowns were fabricated for each abutment. Samples were submitted to cyclic loading at 10(6) cycles and 130 N of force. Data were analyzed by two-way ANOVA and Tukey's test (5%). The tightening technique did not show significant influence on the loosening torque of screws (P=.509). Conventional titanium screws showed significant higher loosening torque values than DLC (P=.000). The use of conventional titanium screw is more important than the tightening techniques employed in this study to provide long-term stability to Universal Abutment screws.

  1. Crack initiation life analysis in notched pipe under cyclic bending loads

    International Nuclear Information System (INIS)

    Lee, Joon Seong; Kwak, Sang Log; Kim, Young Jin; Park, Youn Won

    2001-01-01

    In order to improve leak-before-break methodology, more precisely the crack growth evaluation, a round robin analysis was proposed by the CEA Saclay. The aim of this analysis was to evaluate the crack initiation life, penetration life and shape of through wall crack under cyclic bending loads. The proposed round robin analysis is composed of three main topic; fatigue crack initiation, crack propagation and crack penetration. This paper deals with the first topic, crack initiation in a notched pipe under four point bending. Both elastic-plastic finite element analysis and Neuber's rule were used to estimate the crack initiation life and the finite element models were verified by mesh-refinement, stress distribution and global deflection. In elastic-plastic finite element analysis, crack initiation life was determined by strain amplitude at the notch tip and strain-life curve of the material. In the analytical method, Neuber's rule with the consideration of load history and mean stress effect, was used for the life estimation. The effect of notch tip radius, strain range, cyclic hardening rule were examined in this study. When these results were compared with the experimental ones, the global deformation was a good agreement but crack initiation cycle was higher than the experimental result

  2. The Role of Overloading on the Reduction of Residual Stress by Cyclic Loading in Cold-Drawn Prestressing Steel Wires

    Directory of Open Access Journals (Sweden)

    Jesús Toribio

    2017-01-01

    Full Text Available Prestressing steel wires are commonly used as reinforcement elements in structures bearing fatigue loads. These wires are obtained by a conforming process called cold drawing, where a progressive reduction of the wire diameter is produced, causing residual stress in the commercial wire. The aim of this paper is to analyze the effect of diverse in-service cyclic loading conditions (cyclic loading and cyclic loading with overload on such a residual stress field. To achieve this goal, firstly, a numerical simulation of the wire drawing process of a commercial prestressing steel wire was carried out to reveal the residual stress state induced by the manufacture technique. Afterwards, a numerical simulation was performed of the in-service loading conditions of a prestressing steel wire in which the previously calculated residual stress state is included. The analysis of the obtained results shows a significant reduction of the residual stress state of about 50% for common in-service loadings and as high as 90% for certain cases undergoing overloads during cyclic loading. Therefore, an improvement of the mechanical performance of these structural components during their life in-service can be achieved.

  3. A new elasto-plastic spring element for cyclic loading of piles using the p-y curve concept

    DEFF Research Database (Denmark)

    Hededal, Ole; Klinkvort, Rasmus Tofte

    2010-01-01

    in terms of monotonic loading (until failure) as e.g. prescribed byAPI (2000). However, the cyclic and dynamic performance is only to a limited degree accounted for. Here the elasto-plastic framework is applied allowing definition of unloading-reloading branches, hence enabling modeling of cyclic response......” as e.g. seen from centrifuge tests carried out. This article presents the theoretical formulations, discusses numerical implementation and finally presents simulations....

  4. High temperature fatigue behaviour of TZM molybdenum alloy under mechanical and thermomechanical cyclic loads

    Science.gov (United States)

    Shi, H. J.; Niu, L. S.; Korn, C.; Pluvinage, G.

    2000-02-01

    High temperature isothermal mechanical fatigue and in-phase thermomechanical fatigue (TMF) tests in load control were carried out on a molybdenum-based alloy, one of the best known of the refractory alloys, TZM. The stress-strain response and the cyclic life of the material were measured during the tests. The fatigue lives obtained in the in-phase TMF tests are lower than those obtained in the isothermal mechanical tests at the same load amplitude. It appears that an additional damage is produced by the reaction of mechanical stress cycles and temperature cycles in TMF situation. Ratcheting phenomenon occurred during the tests with an increasing creep rate and it was dependent on temperature and load amplitude. A model of lifetime prediction, based on the Woehler-Miner law, was discussed. Damage coefficients that are functions of the maximum temperature and the variation of temperature are introduced in the model so as to evaluate TMF lives in load control. With this method the lifetime prediction gives results corresponding well to experimental data.

  5. High temperature fatigue behaviour of TZM molybdenum alloy under mechanical and thermomechanical cyclic loads

    International Nuclear Information System (INIS)

    Shi, H.J.; Niu, L.S.; Korn, C.; Pluvinage, G.

    2000-01-01

    High temperature isothermal mechanical fatigue and in-phase thermomechanical fatigue (TMF) tests in load control were carried out on a molybdenum-based alloy, one of the best known of the refractory alloys, TZM. The stress-strain response and the cyclic life of the material were measured during the tests. The fatigue lives obtained in the in-phase TMF tests are lower than those obtained in the isothermal mechanical tests at the same load amplitude. It appears that an additional damage is produced by the reaction of mechanical stress cycles and temperature cycles in TMF situation. Ratcheting phenomenon occurred during the tests with an increasing creep rate and it was dependent on temperature and load amplitude. A model of lifetime prediction, based on the Woehler-Miner law, was discussed. Damage coefficients that are functions of the maximum temperature and the variation of temperature are introduced in the model so as to evaluate TMF lives in load control. With this method the lifetime prediction gives results corresponding well to experimental data

  6. Retention Strength after Compressive Cyclic Loading of Five Luting Agents Used in Implant-Supported Prostheses

    Directory of Open Access Journals (Sweden)

    Angel Alvarez-Arenal

    2016-01-01

    Full Text Available The purpose of this study was to evaluate and compare the retention strength of five cement types commonly used in implant-retained fixed partial dentures, before and after compressive cyclic loading. In five solid abutments screwed to 5 implant analogs, 50 metal Cr-Ni alloy copings were cemented with five luting agents: resin-modified glass ionomer (RmGI, resin composite (RC, glass ionomer (GI, resin urethane-based (RUB, and compomer cement (CC. Two tensile tests were conducted with a universal testing machine, one after the first luting of the copings and the other after 100,000 cycles of 100 N loading at 0.72 Hz. The one way ANOVA test was applied for the statistical analysis using the post hoc Tukey test when required. Before and after applying the compressive load, RmGI and RC cement types showed the greatest retention strength. After compressive loading, RUB cement showed the highest percentage loss of retention (64.45%. GI cement recorded the lowest retention strength (50.35 N and the resin composite cement recorded the highest (352.02 N. The type of cement influences the retention loss. The clinician should give preference to lower retention strength cement (RUB, CC, and GI if he envisages any complications and a high retention strength one (RmGI, RC for a specific clinical situation.

  7. On the evolution and modelling of lattice strains during the cyclic loading of TWIP steel

    International Nuclear Information System (INIS)

    Saleh, Ahmed A.; Pereloma, Elena V.; Clausen, Bjørn; Brown, Donald W.; Tomé, Carlos N.; Gazder, Azdiar A.

    2013-01-01

    The evolution of lattice strains in fully annealed Fe–24Mn–3Al–2Si–1Ni–0.06C twinning-induced plasticity (TWIP) steel is investigated via in situ neutron diffraction during cyclic (tension–compression) loading between strain limits of ±1%. The pronounced Bauschinger effect observed upon load reversal is accounted for by a combination of the intergranular residual stresses and the intragranular sources of back stress, such as dislocation pile-ups at the intersection of stacking faults. The recently modified elasto-plastic self-consistent (EPSC) model which empirically accounts for both intergranular and intragranular back stresses has been successfully used to simulate the macroscopic stress–strain response and the evolution of the lattice strains. The EPSC model captures the experimentally observed tension–compression asymmetry as it accounts for the directionality of twinning as well as Schmid factor considerations. For the strain limits used in this study, the EPSC model also predicts that the lower flow stress on reverse shear loading reported in earlier Bauschinger-type experiments on TWIP steel is a geometrical or loading path effect

  8. In vivo cyclic loading as a potent stimulatory signal for bone formation inside tissue engineering scaffold

    Directory of Open Access Journals (Sweden)

    A Roshan-Ghias

    2010-02-01

    Full Text Available In clinical situations, bone defects are often located at load bearing sites. Tissue engineering scaffolds are future bone substitutes and hence they will be subjected to mechanical stimulation. The goal of this study was to test if cyclic loading can be used as stimulatory signal for bone formation in a bone scaffold. Poly(L-lactic acid (PLA/ 5% beta-tricalcium phosphate (beta-TCP scaffolds were implanted in both distal femoral epiphyses of eight rats. Right knees were stimulated (10N, 4Hz, 5 min five times, every two days, starting from the third day after surgery while left knees served as control. Finite element study of the in vivo model showed that the strain applied to the scaffold is similar to physiological strains. Using micro-computed tomography (CT, all knees were scanned five times after the surgery and the related bone parameters of the newly formed bone were quantified. Statistical modeling was used to estimate the evolution of these parameters as a function of time and loading. The results showed that mechanical stimulation had two effects on bone volume (BV: an initial decrease in BV at week 2, and a long-term increase in the rate of bone formation by 28%. At week 13, the BV was then significantly higher in the loaded scaffolds.

  9. Non-destructive natural frequency tests of cyclic fatigue-loaded nickel-titanium rotary instruments.

    Science.gov (United States)

    Hsieh, Sung-Chih; Lee, Sheng-Yang; Ciou, Chun-Yu; Huang, Haw-Ming

    2010-06-01

    Nickel-titanium (NiTi) instruments are extensively used in endodontic treatment because of their outstanding mechanical properties. However, unexpected fracture of NiTi rotary instruments occurs during endodontic procedures. Therefore, a reliable method to detect the structural status of a used NiTi instrument is needed. The aim of this study is to use natural frequency for monitoring structural changes of a NiTi instrument during and after the instrumentation process. In this study, laboratory modal testing experiments were performed on cyclic fatigue-loaded NiTi rotary instruments with a natural frequency detecting device. In addition, three-dimensional finite element (FE) models were established for assessing the structural changes that take place in repeatedly loaded NiTi instruments. Repeated rotational loading resulted in a significant decrease (p tested instruments reached 77-85% of their total life limit. In FE analysis, a strong correlation between natural frequency and change in elastic modulus of the NiTi instrument was found. These findings indicated that natural frequency may represent an effective parameter for evaluating the micro-structural status of NiTi rotary instruments subjected to fatigue loadings.

  10. Fatigue behaviour of core-spun yarns containing filament by means of cyclic dynamic loading

    Science.gov (United States)

    Esin, S.; Osman, B.

    2017-10-01

    The behaviour of yarns under dynamic loading is important that leads to understand the growth characteristics which is exposed to repetitive loadings during usage of fabric made from these yarns. Fabric growth is undesirable property that originated from low resilience characteristics of fabric. In this study, the effects of the filament fineness and yarn linear density on fatigue behaviour of rigid-core spun yarns were determined. Cotton covered yarns containing different filament fineness of polyester (PET) draw textured yarns (DTY) (100d/36f, 100d/96f, 100d/144f, 100d/192f and 100d/333f) and yarn linear densities (37 tex, 30 tex, 25 tex and 21 tex) were manufactured by using a modified ring spinning system at the same spinning parameters. Repetitive loads were applied for 25 cycles at levels between 0.1 and 3 N. Dynamic modulus and dynamic strain of yarn samples were analyzed statistically. Results showed that filament fineness and yarn linear density have significance effect on dynamic modulus and dynamic strain after cyclic loading.

  11. The Effect of the Aminic Substituent on the Thermal Decomposition of Cyclic Dithiocarbamates

    Directory of Open Access Journals (Sweden)

    Cavalheiro Éder T.G.

    1999-01-01

    Full Text Available Thermogravimetric and Differential Scanning Calorimetric investigation of the thermal behaviour of NH4+, Na+, Zn2+, Cd2+ e Pb2+ dithiocarbamates obtained from cyclic amines, is described under nitrogen and air atmospheres in order to investigate the effect of a cyclic ring on the mechanism of decomposition. Intermediates were identified by X-ray Diffraction analysis. Zn2+, Cd2+ e Pb2+ oxysulphates were detected under air atmosphere suggesting the thermal decomposition under these conditions as an alternating synthetic route to prepare those compounds. The final decomposition products were the metallic sulphides under N2 atmosphere while transition metal oxides and sodium sulphate were obtained under air. Melting enthalpies are also reported from DSC data.

  12. Abutment screw loosening of endosseous dental implant body/abutment joint by cyclic torsional loading test at the initial stage.

    Science.gov (United States)

    Katsuta, Yasuhiro; Watanabe, Fumihiko

    2015-01-01

    Cyclic torsional loading tests were carried out in the laboratory using various implant systems, in order to clarify differences between the systems in loosening of abutment screws. Six samples from six commercially available abutment systems were used, giving a total of 36 samples. Four of the systems used internal connections, and two used external connections. The abutment screw for each system was tightened to a torque value specified by the manufacturer, and after 5 min, the loosening torque was measured using a digital torque meter. Measurements were taken twice, and a second measurement was taken as a reference value. A cyclic torsional loading test with 100,000 cycles was performed on the sample, and the loosening torque was again measured after the test. In conclusion, loosening of the abutment screw occurred as a result of cyclic torsional loading, and the degree of loosening varied with each implant system.

  13. Influence of eccentric cyclic loading on implant components: Comparison between external joint system and internal joint system.

    Science.gov (United States)

    Sakamoto, Kei; Homma, Shinya; Takanashi, Takuya; Takemoto, Shinji; Furuya, Yoshitaka; Yoshinari, Masao; Yajima, Yasutomo

    2016-12-01

    The purpose of this in vitro study was to investigate the influence of eccentric loading on implant components by measuring screw loosening and observing these components under several load positions and magnitudes. The external and internal joint system implants with butt joint connection were subjected to cyclic loading tests according to the specifications of ISO 14801. Load position was set at 0, 4, or 8 mm, and load was set at 100 or 300 N. On the external joint system, the reverse torque values decreased with distal shift in the loading position and an increase in magnitude of load, and abrasion and deformation on the anti-rotation device were observed. On the internal joint system, no large decrease in reverse torque was observed even though increasing the load position and load, however, abrasion and deformation on the anti-rotation device as well as fracture at implant/abutment connection were observed.

  14. Damage mechanisms in PBT-GF30 under thermo-mechanical cyclic loading

    International Nuclear Information System (INIS)

    Schaaf, A.; De Monte, M.; Hoffmann, C.; Vormwald, M.; Quaresimin, M.

    2014-01-01

    The scope of this paper is the investigation of damage mechanisms at microscopic scale on a short glass fiber reinforced polybutylene terephthalate (PBT-GF30) under thermo-mechanical cyclic loading. In addition the principal mechanisms are verified through micro mechanical FE models. In order to investigate the fatigue behavior of the material both isothermal strain controlled fatigue (ISCF) tests at three different temperatures and thermo-mechanical fatigue (TMF) tests were conducted on plain and notched specimens, manufactured by injection molding. The goal of the work is to determine the damage mechanisms occurring under TMF conditions and to compare them with the mechanisms occurring under ISCF. For this reason fracture surfaces of TMF and ISCF samples loaded at different temperature levels were analyzed using scanning electron microscopy. Furthermore, specimens that failed under TMF were examined on microsections revealing insight into both crack initiation and crack propagation. The findings of this investigation give valuable information about the main damage mechanisms of PBT-GF30 under TMF loading and serve as basis for the development of a TMF life estimation methodology

  15. Acoustic Emission Assessment of Impending Fracture in a Cyclically Loading Structural Steel

    Directory of Open Access Journals (Sweden)

    Igor Rastegaev

    2016-11-01

    Full Text Available Using the advanced acoustic emission (AE technique, we address the problem of early identification of crack initiation and growth in ductile structural steels under cyclic loading. The notched 9MnSi5 steel specimens with weld joints were fatigue tested at room and lower temperatures with concurrent AE measurements. Detection of AE in ductile materials where fatigue crack initiation and propagation is mediated by local dislocation behavior ahead of the notch or crack tip is challenging because of an extremely low amplitude of the AE signal. With account of this issue, two new practically oriented criteria for recognition of different stages of fatigue are proposed on the basis of AE data: (1 a power spectrum-based criterion and (2 a pattern recognition-based criterion utilizing modern clustering algorithms. The applicability of both criteria is verified using obtained AE data. A good correspondence between AE outcomes and experimental observations of the fatigue behavior was obtained and is discussed.

  16. Self-sensing of carbon nanofiber concrete columns subjected to reversed cyclic loading

    Science.gov (United States)

    Howser, R. N.; Dhonde, H. B.; Mo, Y. L.

    2011-08-01

    Civil infrastructures are generally a country's most expensive investment, and concrete is the most widely used material in the construction of civil infrastructures. During a structure's service life, concrete ages and deteriorates, leading to substantial loss of structural integrity and potentially resulting in catastrophic disasters such as highway bridge collapses. A solution for preventing such occurrences is the use of structural health monitoring (SHM) technology for concrete structures containing carbon nanofibers (CNF). CNF concrete has many structural benefits. CNF restricts the growth of nanocracks in addition to yielding higher strength and ductility. Additionally, test results indicate a relationship between electrical resistance and concrete strain, which can be well utilized for SHM. A series of reinforced concrete (RC) columns were built and tested under a reversed cyclic loading using CNF as a SHM device. The SHM device detected and assessed the level of damage in the RC columns, providing a real-time health monitoring system for the structure's overall integrity.

  17. Self-sensing of carbon nanofiber concrete columns subjected to reversed cyclic loading

    International Nuclear Information System (INIS)

    Howser, R N; Dhonde, H B; Mo, Y L

    2011-01-01

    Civil infrastructures are generally a country's most expensive investment, and concrete is the most widely used material in the construction of civil infrastructures. During a structure's service life, concrete ages and deteriorates, leading to substantial loss of structural integrity and potentially resulting in catastrophic disasters such as highway bridge collapses. A solution for preventing such occurrences is the use of structural health monitoring (SHM) technology for concrete structures containing carbon nanofibers (CNF). CNF concrete has many structural benefits. CNF restricts the growth of nanocracks in addition to yielding higher strength and ductility. Additionally, test results indicate a relationship between electrical resistance and concrete strain, which can be well utilized for SHM. A series of reinforced concrete (RC) columns were built and tested under a reversed cyclic loading using CNF as a SHM device. The SHM device detected and assessed the level of damage in the RC columns, providing a real-time health monitoring system for the structure's overall integrity

  18. Fatigue life assessment of a non-load carrying fillet joint considering the effects of a cyclic plasticity and weld bead shape

    Directory of Open Access Journals (Sweden)

    S. Tsutsumi

    2016-10-01

    Full Text Available Fatigue life depends strongly on irreversible contributions that accumulate during cyclic loading and unloading of structures. However, the correct identification of the loading path in terms of uniaxial or multi-axial stress states, proportional or non-proportional loading is essential because these factors can significantly alter the material response. In this study, finite element analysis was conducted to assess the fatigue crack initiation life of a non-load carrying fillet joint by considering weld bead shape and a cyclic plasticity accumulation during fatigue loading, which is a main cause of crack initiation. Cyclic plasticity behaviour including cyclic hardening and softening together was investigated with an unconventional plasticity model called the subloading surface model and extended to include both elastic boundary and cyclic damage concepts. The cyclic plasticity model can capture realistic plastic strain accumulation during high cycle fatigue under macroscopically elastic stressing conditions

  19. Calcium-Magnesium-Aluminosilicate (CMAS) Infiltration and Cyclic Degradations of Thermal and Environmental Barrier Coatings in Thermal Gradients

    Science.gov (United States)

    Zhu, Dongming; Harder, Bryan; Smialek, Jim; Miller, Robert A.

    2014-01-01

    In a continuing effort to develop higher temperature capable turbine thermal barrier and environmental barrier coating systems, Calcium-Magnesium-Aluminosilicate (CMAS) resistance of the advanced coating systems needs to be evaluated and improved. This paper highlights some of NASA past high heat flux testing approaches for turbine thermal and environmental barrier coatings assessments in CMAS environments. One of our current emphases has been focused on the thermal barrier - environmental barrier coating composition and testing developments. The effort has included the CMAS infiltrations in high temperature and high heat flux turbine engine like conditions using advanced laser high heat flux rigs, and subsequently degradation studies in laser heat flux thermal gradient cyclic and isothermal furnace cyclic testing conditions. These heat flux CMAS infiltration and related coating durability testing are essential where appropriate CMAS melting, infiltration and coating-substrate temperature exposure temperature controls can be achieved, thus helping quantify the CMAS-coating interaction and degradation mechanisms. The CMAS work is also playing a critical role in advanced coating developments, by developing laboratory coating durability assessment methodologies in simulated turbine engine conditions and helping establish CMAS test standards in laboratory environments.

  20. Comparative thermal cyclic testing and strength investigation of different Be/Cu joints

    International Nuclear Information System (INIS)

    Gervash, A.; Giniyatulin, R.; Komarov, V.; Mazul, I.; Litunovsky, N.; Ganenko, A.; Vainerman, A.; Fedotov, V.; Davydov, D.; Zalavutdinov, R.

    1998-01-01

    One of the main problems for ITER divertor target technology is to provide a reliable joint between Be as armour material and copper alloy heat-sink structure. Such joints are to satisfy numerous requirements. In particular these joints should successfully withstand cyclic hear fluxes and should have good properties after neutron irradiation. To study such a complex problem, several investigation stages were planed in Russia. This paper presents the results of comparative thermal cyclic testing of different Be/Cu candidates. Summarising the thermal cyclic test results and analysing the metallography of those joints it was found that the life-time of all tested joints is limited by rather thick brittle intermetallic layers in the bonding zone caused by relatively long brazing time using heating and cooling down in traditional ohmic furnace. This paper thus presents attempts of using a unique brazing technique with fast e-beam heating. Metallographic investigation as well as X-ray spectrometric analysis of joints produced using the new technique were done. The recent results of testing of Be/Cu joints produced by fast e-beam brazing are discussed and some ideas for the nearest future investigations are presented. (orig.)

  1. Experimental study on lateral strength of wall-slab joint subjected to lateral cyclic load

    Science.gov (United States)

    Masrom, Mohd Asha'ari; Mohamad, Mohd Elfie; Hamid, Nor Hayati Abdul; Yusuff, Amer

    2017-10-01

    Tunnel form building has been utilised in building construction since 1960 in Malaysia. This method of construction has been applied extensively in the construction of high rise residential house (multistory building) such as condominium and apartment. Most of the tunnel form buildings have been designed according to British standard (BS) whereby there is no provision for seismic loading. The high-rise tunnel form buildings are vulnerable to seismic loading. The connections between slab and shear walls in the tunnel-form building constitute an essential link in the lateral load resisting mechanism. Malaysia is undergoing a shifting process from BS code to Eurocode (EC) for building construction since the country has realised the safety threats of earthquake. Hence, this study is intended to compare the performance of the interior wall slab joint for a tunnel form structure designed based on Euro and British codes. The experiment included a full scale test of the wall slab joint sub-assemblages under reversible lateral cyclic loading. Two sub-assemblage specimens of the wall slab joint were designed and constructed based on both codes. Each specimen was tested using lateral displacement control (drift control). The specimen designed by using Eurocode was found could survive up to 3.0% drift while BS specimen could last to 1.5% drift. The analysis results indicated that the BS specimen was governed by brittle failure modes with Ductility Class Low (DCL) while the EC specimen behaved in a ductile manner with Ductility Class Medium (DCM). The low ductility recorded in BS specimen was resulted from insufficient reinforcement provided in the BS code specimen. Consequently, the BS specimen could not absorb energy efficiently (low energy dissipation) and further sustain under inelastic deformation.

  2. Effect of cyclic loadings on the stress corrosion crack growth rate in Alloy 600 in PWR primary water

    Energy Technology Data Exchange (ETDEWEB)

    Guerre, Catherine; Raquet, Olivier [CEA, DEN/DPC/SCCME/LECA, bat.458, 91191 Gif-sur-Yvette Cedex (France); Duisabeau, Laure [CEA, DEN/DMN/SEMI/LCMI, bat.625, 91191 Gif-sur-Yvette Cedex (France); Turluer, G. [IRSN, DSR/SAMS, BP17, 92262 Fontenay-aux-roses Cedex (France)

    2004-07-01

    Fatigue air pre-cracked Compact Tensile (CT) specimens in Alloy 600 were tested in primary water (325 deg. C) of Pressurized Water Reactors (PWR). In order to assess the effect of cyclic loading on crack growth, CT specimens are tested under constant loadings and low frequencies cyclic loadings: triangular and saw-tooth. Two Alloy 600 materials, with different intrinsic susceptibility to Stress Corrosion Cracking (SCC), are studied. Crack growth rates are monitored in-situ by the direct current potential drop method and are validated by postmortem observations. Fracture surfaces are characterized by macroscopic and microscopic observations. Comparison of the crack growth rate and of the fracture features demonstrated that they depend on the characteristics of the mechanical loading (constant, triangular or sawtooth) and on the material intrinsic sensibility to SCC. (authors)

  3. Portevin-Le Chatelier effect under cyclic loading: experimental and numerical investigations

    Science.gov (United States)

    Mazière, M.; Pujol d'Andrebo, Q.

    2015-10-01

    The Portevin-Le Chatelier (PLC) effect is generally evidenced by the apparition of serrated yielding under monotonic tensile loading conditions. It appears at room temperature in some aluminium alloys, around ? in some steels and in many other metallic materials. This effect is associated with the propagation of bands of plastic deformation in tensile specimens and can in some cases lead to unexpected failures. The PLC effect has been widely simulated under monotonic conditions using finite elements and an appropriate mechanical model able to reproduce serrations and strain localization. The occurrence of serrations can be predicted using an analytical stability analysis. Recently, this serrated yielding has also been observed in specimens made of Cobalt-based superalloy under cyclic loading, after a large number of cycles. The mechanical model has been identified in this case to accurately reproduce this critical number of cycle where serrations appear. The associated apparition of localized bands of deformation in specimens and their influence on its failure has also been investigated using finite element simulations.

  4. A coupled damage-plasticity model for the cyclic behavior of shear-loaded interfaces

    Science.gov (United States)

    Carrara, P.; De Lorenzis, L.

    2015-12-01

    The present work proposes a novel thermodynamically consistent model for the behavior of interfaces under shear (i.e. mode-II) cyclic loading conditions. The interface behavior is defined coupling damage and plasticity. The admissible states' domain is formulated restricting the tangential interface stress to non-negative values, which makes the model suitable e.g. for interfaces with thin adherends. Linear softening is assumed so as to reproduce, under monotonic conditions, a bilinear mode-II interface law. Two damage variables govern respectively the loss of strength and of stiffness of the interface. The proposed model needs the evaluation of only four independent parameters, i.e. three defining the monotonic mode-II interface law, and one ruling the fatigue behavior. This limited number of parameters and their clear physical meaning facilitate experimental calibration. Model predictions are compared with experimental results on fiber reinforced polymer sheets externally bonded to concrete involving different load histories, and an excellent agreement is obtained.

  5. Detecting thermally driven cyclic deformation of an exfoliation sheet with lidar and radar

    Science.gov (United States)

    Collins, Brian D.; Stock, Greg M.

    2014-01-01

    Rock falls from steep, exfoliating cliffs are common in many landscapes. Of the many mechanisms known to trigger rock falls, thermally driven deformation is among the least quantified, despite potentially being a prevalent trigger due to its occurrence at all times of year. Here we present the results of a field-based monitoring program using instrumentation, ground-based lidar, and ground-based radar to investigate the process of thermally driven deformation of an exfoliation sheet, and the ability of remote sensing tools to capture cyclic expansion and contraction patterns. Our results indicate that thermally driven exfoliation occurs on diurnal cycles and can be measured at the submillimeter to centimeter scale using high-resolution strain gauges, short-range (2 km) radar interfer-ometry.

  6. Quasi-static characterisation of trained pseudoelastic shape memory alloy wire subjected to cyclic loading: transformation kinetics

    DEFF Research Database (Denmark)

    Enemark, Søren; Santos, Ilmar

    2016-01-01

    -loop model are implemented in a state-of-the-art constitutive model based on the framework by Lagoudas and coworkers. The original and modified models are fitted to consistent experimental results from mechanical cyclic loading under isothermal conditions (0–800 MPa, 30–70 °C) of a trained pseudoelastic...

  7. Effect of Static and Cyclic Loading on Ceramic Laminate Veneers Adhered to Teeth with and Without Aged Composite Restorations

    NARCIS (Netherlands)

    Gresnigt, Marco M. M.; Ozcan, Mutlu; Kalk, Warner; Galhano, Graziela

    2011-01-01

    Purpose: Existing composite restorations on teeth are often remade prior to the cementation of fixed dental prostheses. The aim of this study was to evaluate the effect of static and cyclic loading on ceramic laminate veneers adhered to aged resin composite restorations. Materials and Methods:

  8. Failure of thermal barrier coatings under thermal and mechanical fatigue loading. Microstructural observations and modelling aspects

    Energy Technology Data Exchange (ETDEWEB)

    Brodin, Haakan

    2004-09-01

    Industrial and air-borne gas turbine hot components suffer from creep, oxidation, corrosion and microstructural degradation if not shielded from the hot and aggressive combustion gases. Two major strategies commercially available are adopted; film cooling by pressurised air and application of protective coatings. Protective coatings form a slow-growing oxide that protects from oxidation and corrosion. By application of a thermal insulator, a thermal barrier coating, the material will be protected from high temperature through good insulation properties of the coating system. If thermal barrier coatings are to be used in situations where capabilities and possibilities for inspections are limited, better knowledge of the fatigue properties of the coatings is also needed. Therefore development of a reliable fatigue life model is needed. The present work aims at serving as a basis from which a general physically founded thermal barrier coating life model can be formulated. The effects of exposure to high temperatures and mechanical loads on thermal barrier coatings under service like conditions have been investigated in the present thesis. Emphasis is put on the coupling between materials science and solid mechanics approaches in order to establish a better knowledge concerning degradation mechanisms and fatigue life issues than what is common if only one discipline is explored. Investigations of material exposed to isothermal oxidation and thermal cyclic fatigue were performed on plasma-sprayed systems with NiCoCrAlY or NiCrAlY bond coats and yttria partially stabilised zirconia top coats. It has been shown that the thermally grown oxide that will form upon high temperature exposure influences the failure behaviour. If the oxide is composed mainly of alumina, the fatigue properties are good since the adhesion between the ceramic top coat and the metallic bond coat is good. This is also shown in a comparison between different plasma sprayed thermal barrier coating

  9. Quantifying Cyclic Thermal Stresses Due to Solar Exposure in Rock Fragments in Gale Crater, Mars

    Science.gov (United States)

    Hallet, B.; Mackenzie-Helnwein, P.; Sletten, R. S.

    2017-12-01

    Curiosity and earlier rovers on Mars have revealed in detail rocky landscapes with decaying outcrops, rubble, stone-littered regolith, and bedrock exposures that reflect the weathering processes operating on rock exposed to Mars' cold and hyperarid environment. Evidence from diverse sources points to the importance of thermal stresses driven by cyclic solar exposure in contributing to the mechanical weathering of exposed rock and generation of regolith in various settings on Earth [1,2,3], and even more so on extraterrestrial bodies where large, rapid cyclic temperature variations are frequent (e.g. Mars [4], as well as comets [5], asteroids [6] and other airless bodies [7]). To study these thermal stresses, we use a 3d finite element (FE) model constrained by ground-based surface temperature measurements from Curiosity's Environmental Monitoring Station (REMS). The numerical model couples radiation and conduction with elastic response to determine the temperature and stress fields in individual rocks on the surface of Mars based on rock size and thermo-mechanical properties. We provide specific quantitative results for boulder-size basalt rocks resting on the ground using a realistic thermal forcing that closely matches the REMS temperature observations, and related thermal inertia data. Moreover, we introduce analytical studies showing that these numerical results can readily be generalized. They are quite universal, informing us about thermal stresses due to cyclic solar exposure in general, for rock fragments of different sizes, lithologies, and fracture- thermal- and mechanical-properties. Using Earth-analogue studies to gain insight, we also consider how the shapes, fractures, and surface details of rock fragments imaged by Curiosity likely reflect the importance of rock breakdown due to thermal stresses relative to wind-driven rock erosion and other surface processes on Mars. References:[1] McFadden L et al. (2005) Geol. Soc.Am. Bull. 117(1-2): 161-173 [2

  10. Effect of coating thickness on microstructure and low temperature cyclic thermal fatigue behavior of thermal barrier coating (Al2O3)

    Science.gov (United States)

    Verma, Vijay; Patel, Sachin; Swarnkar, Vikas; K, Rajput S.

    2018-03-01

    Effect of coating thickness on low temperature cyclic thermal fatigue behaviour of Al2O3 thermal barrier coating (TBC) was concluded through the cyclic furnace thermal fatigue test (CFTF). Detonation gun (Thermal Spray) process was used for bond coating of NiCr and top coating of Al2O3 on Aluminium Alloy 6061 substrate. Top coating was done at two level of thickness to investigate the effect of coating thickness on low temperature cyclic thermal fatigue. The top coat of thickness 100μm-150μm was considered as thin TBC while the top coat of thickness 250μm-300μm was considered as thick TBC. The thickness of bond coat was taken as 120μm constant for both level of Al2O3 top coating. During CFTF test appearance of any crack on coated surface was adapted as main criterion of coating failure. Crack initiation was observed at edges and corner of thin thermal barrier coating after 60 number of thermal fatigue cycles while in case of thick thermal barrier coating these crack initiation was observed after 72 cycles of cyclic thermal fatigue test. During the study, it was observed that thick thermal barrier coating survived for long duration in comparison of thin TBC. Hence it can be concluded that application of thick TBC is more favourable to improve thermal durability of any component.

  11. Study of Perylenetetracarboxylic Acid Dimethylimide Films by Cyclic Thermal Desorption and Scanning Probe Microscopy

    Science.gov (United States)

    Pochtennyi, A. E.; Lappo, A. N.; Il'yushonok, I. P.

    2018-02-01

    Some results of studying the direct-current (DC) conductivity of perylenetetracarboxylic acid dimethylimide films by cyclic oxygen thermal desorption are presented. The microscopic parameters of hopping electron transport over localized impurity and intrinsic states were determined. The bandgap width and the sign of major current carriers were determined by scanning probe microscopy methods (atomic force microscopy, scanning probe spectroscopy, and photoassisted Kelvin probe force microscopy). The possibility of the application of photoassisted scanning tunneling microscopy for the nanoscale phase analysis of photoconductive films is discussed.

  12. Load-bearing capacity of screw-retained CAD/CAM-produced titanium implant frameworks (I-Bridge®2) before and after cyclic mechanical loading.

    Science.gov (United States)

    Dittmer, Marc Philipp; Nensa, Moritz; Stiesch, Meike; Kohorst, Philipp

    2013-01-01

    Implant-supported screw-retained fixed dental prostheses (FDPs) produced by CAD/ CAM have been introduced in recent years for the rehabilitation of partial or total endentulous jaws. However, there is a lack of data about the long-term mechanical characteristics. The aim of this study was to investigate the failure mode and the influence of extended cyclic mechanical loading on the load-bearing capacity of these frameworks. Ten five-unit FDP frameworks simulating a free-end situation in the mandibular jaw were manufactured according to the I-Bridge®2-concept (I-Bridge®2, Biomain AB, Helsingborg, Sweden) and each was screw-retained on three differently angulated Astra Tech implants (30º buccal angulation/0º angulation/30º lingual angulation). One half of the specimens was tested for static load-bearing capacity without any further treatment (control), whereas the other half underwent five million cycles of mechanical loading with 100 N as the upper load limit (test). All specimens were loaded until failure in a universal testing machine with an occlusal force applied at the pontics. Load-displacement curves were recorded and the failure mode was macro- and microscopically analyzed. The statistical analysis was performed using a t-test (p=0.05). All the specimens survived cyclic mechanical loading and no obvious failure could be observed. Due to the cyclic mechanical loading, the load-bearing capacity decreased from 8,496 N±196 N (control) to 7,592 N±901 N (test). The cyclic mechanical loading did not significantly influence the load-bearing capacity (p=0.060). The failure mode was almost identical in all specimens: large deformations of the framework at the implant connection area were obvious. The load-bearing capacity of the I-Bridge®2 frameworks is much higher than the clinically relevant occlusal forces, even with considerably angulated implants. However, the performance under functional loading in vivo depends on additional aspects. Further studies are

  13. The Effect of Compressive Cyclic Loading on the Retention of Cast Single Crowns Cemented to Implant Abutments.

    Science.gov (United States)

    Alvarez-Arenal, Angel; Gonzalez-Gonzalez, Ignacio; Pinés-Hueso, Javier; deLlanos-Lanchares, Hector; del Rio Highsmith, Jaime

    2016-01-01

    The aim of this study was to evaluate and compare the retention strength of three cements commonly used in implant-supported prostheses before and after compressive cyclic loading. The working model consisted of five solid abutments, 7 mm in height and with a 6-degree taper, screw retained to five implant analogs secured in a rectangular block of self-curing acrylic. On the abutments, 30 metal Cr-Ni alloy copings were cemented using three luting agents: glass ionomer, resin urethane-based, and compomer cement (n = 10). Two tensile tests were conducted with a universal testing machine, before and after 100,000 cycles of 100 N and 0.72 Hz compressive cyclic loading in a humid environment. Before applying the compressive load, the retention strength of the resin urethane-based cement was slightly higher than that of the compomer cement and 75% greater than the glass-ionomer cement. After compressive loading, the resin urethane-based cement showed the highest percentage of loss of retention (64.45%, compared with 50% for glass-ionomer and compomer cement). However, the glass-ionomer cement showed the lowest mean retentive strength with 50.35 N as opposed to 75.12 N for the compomer cement and 71.25 N for the resin urethane-based. Compressive cyclic loading significantly influences the retention strength of the luting agents tested. All three cements may favor the retrievability of the crowns.

  14. Pedicle screw anchorage of carbon fiber-reinforced PEEK screws under cyclic loading.

    Science.gov (United States)

    Lindtner, Richard A; Schmid, Rene; Nydegger, Thomas; Konschake, Marko; Schmoelz, Werner

    2018-03-01

    Pedicle screw loosening is a common and significant complication after posterior spinal instrumentation, particularly in osteoporosis. Radiolucent carbon fiber-reinforced polyetheretherketone (CF/PEEK) pedicle screws have been developed recently to overcome drawbacks of conventional metallic screws, such as metal-induced imaging artifacts and interference with postoperative radiotherapy. Beyond radiolucency, CF/PEEK may also be advantageous over standard titanium in terms of pedicle screw loosening due to its unique material properties. However, screw anchorage and loosening of CF/PEEK pedicle screws have not been evaluated yet. The aim of this biomechanical study therefore was to evaluate whether the use of this alternative nonmetallic pedicle screw material affects screw loosening. The hypotheses tested were that (1) nonmetallic CF/PEEK pedicle screws resist an equal or higher number of load cycles until loosening than standard titanium screws and that (2) PMMA cement augmentation further increases the number of load cycles until loosening of CF/PEEK screws. In the first part of the study, left and right pedicles of ten cadaveric lumbar vertebrae (BMD 70.8 mg/cm 3  ± 14.5) were randomly instrumented with either CF/PEEK or standard titanium pedicle screws. In the second part, left and right pedicles of ten vertebrae (BMD 56.3 mg/cm 3  ± 15.8) were randomly instrumented with either PMMA-augmented or nonaugmented CF/PEEK pedicle screws. Each pedicle screw was subjected to cyclic cranio-caudal loading (initial load ranging from - 50 N to + 50 N) with stepwise increasing compressive loads (5 N every 100 cycles) until loosening or a maximum of 10,000 cycles. Angular screw motion ("screw toggling") within the vertebra was measured with a 3D motion analysis system every 100 cycles and by stress fluoroscopy every 500 cycles. The nonmetallic CF/PEEK pedicle screws resisted a similar number of load cycles until loosening as the contralateral standard

  15. Microscale experimental investigation of deformation and damage of argillaceous rocks under cyclic hydric and mechanical loads

    International Nuclear Information System (INIS)

    Wang, Linlin; Yang, Diansen; Heripre, Eva; Chanchole, Serge; Bornert, Michel; Pouya, Ahmad; Halphen, Bernard

    2012-01-01

    Document available in abstract form only. Argillaceous rocks are possible host rocks for underground nuclear waste repositories. They exhibit complex coupled thermo-hydro-chemo-mechanical behavior, the description of which would strongly benefit from an improved experimental insight on their deformation and damage mechanisms at microscale. We present some recent observations of the evolution of these rocks at the scale of their composite microstructure, essentially made of a clay matrix with embedded carbonates and quartz particles with sizes ranging from a few to several tens of micrometers, when they are subjected to cyclic variations of relative humidity and mechanical loading. They are based on the combination of high definition and high resolution imaging in an environmental scanning electron microscope (ESEM), in situ hydro-mechanical loading of the samples, and digital image correlation techniques. Samples, several millimeters in diameter, are held at a constant temperature of 2 deg. Celsius while the vapor pressure in the ESEM chamber is varied from a few to several hundreds of Pascals, generating a relative humidity ranging from about 10% up to 90%. Results show a strongly heterogeneous deformation field at microscale, which is the result of complex hydro-mechanical interactions. In particular, it can be shown that local swelling incompatibilities can generate irreversible deformations in the clay matrix, even if the overall hydric deformations seem reversible. In addition, local damage can be generated, in the form of a network of microcracks, located in the bulk of the clay matrix and/or at the interface between clay and other mineral particles. The morphology of this network, described in terms of crack length, orientation and preferred location, has been observed to be dependent on the speed of the variation of the relative humidity, and is different in a saturation or desaturation process. Besides studying the deformation and damage under hydric

  16. Effect of cyclic loading on microleakage of silorane based composite compared with low shrinkage methacrylate-based composites

    Science.gov (United States)

    Kermanshah, Hamid; Yasini, Esmail; Hoseinifar, Razieh

    2016-01-01

    Background: There are many concerns regarding the marginal seal of composite restorations, especially when composite restorations are subjected to cyclic loading. The aim of this study was to evaluate the effect of cyclic loading on the microleakage of silorane based composite compared with low shrinkage methacrylate-based composites in class V cavities. Materials and Methods: In this in vitro study, class V cavities were prepared on the facial and lingual surfaces of 48 human premolars (96 cavities). The teeth were randomly divided into four groups of 12 teeth (24 cavities) each and restored as follows: Group 1 (Siloran System Adhesive + Filtek P90), Group 2 (All Bond SE + Aelite LS Posterior), Group 3 (Futurabond NR + Grandio), and Group 4 (G-Bond + Kalore-GC). All the specimens were thermocycled for 2000 cycles (5-55°C) and then half of the specimens from each group, were Load cycled. All teeth were immersed in 0.5% basic fuchsine dye, sectioned, and observed under a stereomicroscope. Data were analyzed using Wilcoxon test, Kruskal–Wallis, and Mann–Whitney U-tests. P < 0.05 was considered as significant. Results: In both unloaded and loaded groups, no statistically significant differences were observed among four composites at the occlusal margin, but a significant difference in gingival microleakage was found between Aelite and silorane. Occlusal and gingival microleakage was not affected by cyclic loading in none of the four restorative materials. Conclusion: Silorane did not provide better marginal seal than the low shrinkage methacrylate-based composites (except Aelite). In addition, cyclic loading did not affect the marginal microleakage of evaluated composite restorations. PMID:27274348

  17. Effect of cyclic loading on microleakage of silorane based composite compared with low shrinkage methacrylate-based composites.

    Science.gov (United States)

    Kermanshah, Hamid; Yasini, Esmail; Hoseinifar, Razieh

    2016-01-01

    There are many concerns regarding the marginal seal of composite restorations, especially when composite restorations are subjected to cyclic loading. The aim of this study was to evaluate the effect of cyclic loading on the microleakage of silorane based composite compared with low shrinkage methacrylate-based composites in class V cavities. In this in vitro study, class V cavities were prepared on the facial and lingual surfaces of 48 human premolars (96 cavities). The teeth were randomly divided into four groups of 12 teeth (24 cavities) each and restored as follows: Group 1 (Siloran System Adhesive + Filtek P90), Group 2 (All Bond SE + Aelite LS Posterior), Group 3 (Futurabond NR + Grandio), and Group 4 (G-Bond + Kalore-GC). All the specimens were thermocycled for 2000 cycles (5-55°C) and then half of the specimens from each group, were Load cycled. All teeth were immersed in 0.5% basic fuchsine dye, sectioned, and observed under a stereomicroscope. Data were analyzed using Wilcoxon test, Kruskal-Wallis, and Mann-Whitney U-tests. P < 0.05 was considered as significant. In both unloaded and loaded groups, no statistically significant differences were observed among four composites at the occlusal margin, but a significant difference in gingival microleakage was found between Aelite and silorane. Occlusal and gingival microleakage was not affected by cyclic loading in none of the four restorative materials. Silorane did not provide better marginal seal than the low shrinkage methacrylate-based composites (except Aelite). In addition, cyclic loading did not affect the marginal microleakage of evaluated composite restorations.

  18. Creep-fatigue of High Temperature Materials for VHTR: Effect of Cyclic Loading and Environment

    Energy Technology Data Exchange (ETDEWEB)

    Celine Cabet; L. Carroll; R. Wright; R. Madland

    2011-05-01

    Alloy 617 is the one of the leading candidate materials for Intermediate Heat eXchangers (IHX) of a Very High Temperature Reactor (VHTR). System start-ups and shut-downs as well as power transients will produce low cycle fatigue (LCF) loadings of components. Furthermore, the anticipated IHX operating temperature, up to 950°C, is in the range of creep so that creep-fatigue interaction, which can significantly increase the fatigue crack growth, may be one of the primary IHX damage modes. To address the needs for Alloy 617 codification and licensing, a significant creep-fatigue testing program is underway at Idaho National Laboratory. Strain controlled LCF tests including hold times up to 1800s at maximum tensile strain were conducted at total strain range of 0.3% and 0.6% in air at 950°C. Creep-fatigue testing was also performed in a simulated VHTR impure helium coolant for selected experimental conditions. The creep-fatigue tests resulted in failure times up to 1000 hrs. Fatigue resistance was significantly decreased when a hold time was added at peak stress and when the total strain was increased. The fracture mode also changed from transgranular to intergranular with introduction of a tensile hold. Changes in the microstructure were methodically characterized. A combined effect of temperature, cyclic and static loading and environment was evidenced in the targeted operating conditions of the IHX. This paper This paper reviews the data previously published by Carroll and co-workers in references 10 and 11 focusing on the role of inelastic strain accumulation and of oxidation in the initiation and propagation of surface fatigue cracks.

  19. Structural analysis of reinforced concrete structures under monotonous and cyclic loadings: numerical aspects

    International Nuclear Information System (INIS)

    Lepretre, C.; Millard, A.; Nahas, G.

    1989-01-01

    The structural analysis of reinforced concrete structures is usually performed either by means of simplified methods of strength of materials type i.e. global methods, or by means of detailed methods of continuum mechanics type, i.e. local methods. For this second type, some constitutive models are available for concrete and rebars in a certain number of finite element systems. These models are often validated on simple homogeneous tests. Therefore, it is important to appraise the validity of the results when applying them to the analysis of a reinforced concrete structure, in order to be able to make correct predictions of the actual behaviour, under normal and faulty conditions. For this purpose, some tests have been performed at I.N.S.A. de Lyon on reinforced concrete beams, subjected to monotonous and cyclic loadings, in order to generate reference solutions to be compared with the numerical predictions given by two finite element systems: - CASTEM, developed by C.E.A./.D.E.M.T. - ELEFINI, developed by I.N.S.A. de Lyon

  20. A Failure Estimation Method of Steel Pipe Elbows under In-plane Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Bub-Gyu Jeon

    2017-02-01

    Full Text Available The relative displacement of a piping system installed between isolated and nonisolated structures in a severe earthquake might be larger when without a seismic isolation system. As a result of the relative displacement, the seismic risks of some components in the building could increase. The possibility of an increase in seismic risks is especially high in the crossover piping system in the buildings. Previous studies found that an elbow which could be ruptured by low-cycle ratcheting fatigue is one of the weakest elements. Fatigue curves for elbows were suggested based on component tests. However, it is hard to find a quantitative evaluation of the ultimate state of piping elbows. Generally, the energy dissipation of a solid structure can be calculated from the relation between displacement and force. Therefore, in this study, the ultimate state of the pipe elbow, normally considered as failure of the pipe elbow, is defined as leakage under in-plane cyclic loading tests, and a failure estimation method is proposed using a damage index based on energy dissipation.

  1. A failure estimation method of steel pipe elbows under in-plane cyclic loading

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Bub Gyu; Kim, Sung Wan; Choi, Hyoung Suk; Park, Dong Uk [Seismic Simulation Tester Center, Pusan National University, Yangsan (Korea, Republic of); Kim, Nam Sik [Dept. of Civil and Environmental Engineering, Pusan National University, Busan (Korea, Republic of)

    2017-02-15

    The relative displacement of a piping system installed between isolated and nonisolated structures in a severe earthquake might be larger when without a seismic isolation system. As a result of the relative displacement, the seismic risks of some components in the building could increase. The possibility of an increase in seismic risks is especially high in the crossover piping system in the buildings. Previous studies found that an elbow which could be ruptured by low-cycle ratcheting fatigue is one of the weakest elements. Fatigue curves for elbows were suggested based on component tests. However, it is hard to find a quantitative evaluation of the ultimate state of piping elbows. Generally, the energy dissipation of a solid structure can be calculated from the relation between displacement and force. Therefore, in this study, the ultimate state of the pipe elbow, normally considered as failure of the pipe elbow, is defined as leakage under in-plane cyclic loading tests, and a failure estimation method is proposed using a damage index based on energy dissipation.

  2. Fatigue Modeling for Superelastic NiTi Considering Cyclic Deformation and Load Ratio Effects

    Science.gov (United States)

    Mahtabi, Mohammad J.; Shamsaei, Nima

    2017-09-01

    A cumulative energy-based damage model, called total fatigue toughness, is proposed for fatigue life prediction of superelastic NiTi alloys with various deformation responses (i.e., transformation stresses), which also accounts for the effects of mean strain and stress. Mechanical response of superelastic NiTi is highly sensitive to chemical composition, material processing, as well as operating temperature; therefore, significantly different deformation responses may be obtained for seemingly identical NiTi specimens. In this paper, a fatigue damage parameter is proposed that can be used for fatigue life prediction of superelastic NiTi alloys with different mechanical properties such as loading and unloading transformation stresses, modulus of elasticity, and austenite-to-martensite start and finish strains. Moreover, the model is capable of capturing the effects of tensile mean strain and stress on the fatigue behavior. Fatigue life predictions using the proposed damage parameter for specimens with different cyclic stress responses, tested at various strain ratios ( R ɛ = ɛ min /ɛ max) are shown to be in very good agreement with the experimentally observed fatigue lives.

  3. Numerical analyses of caisson breakwaters on soft foundations under wave cyclic loading

    Science.gov (United States)

    Wang, Yuan-zhan; Yan, Zhen; Wang, Yu-chi

    2016-03-01

    A caisson breakwater is built on soft foundations after replacing the upper soft layer with sand. This paper presents a dynamic finite element method to investigate the strength degradation and associated pore pressure development of the intercalated soft layer under wave cyclic loading. By combining the undrained shear strength with the empirical formula of overconsolidation clay produced by unloading and the development model of pore pressure, the dynamic degradation law that describes the undrained shear strength as a function of cycle number and stress level is derived. Based on the proposed dynamic degradation law and M-C yield criterion, a dynamic finite element method is numerically implemented to predict changes in undrained shear strength of the intercalated soft layer by using the general-purpose FEM software ABAQUS, and the accuracy of the method is verified. The effects of cycle number and amplitude of the wave force on the degradation of the undrained shear strength of the intercalated soft layer and the associated excess pore pressure response are investigated by analyzing an overall distribution and three typical sections underneath the breakwater. By comparing the undrained shear strength distributions obtained by the static method and the quasi-static method with the undrained shear strength distributions obtained by the dynamic finite element method in the three typical sections, the superiority of the dynamic finite element method in predicting changes in undrained shear strength is demonstrated.

  4. Capacity fade modelling of lithium-ion battery under cyclic loading conditions

    Science.gov (United States)

    Ashwin, T. R.; Chung, Yongmann M.; Wang, Jihong

    2016-10-01

    A pseudo two-dimensional (P2D) electro-chemical lithium-ion battery model is presented in this paper to study the capacity fade under cyclic charge-discharge conditions. The Newman model [1,2] has been modified to include a continuous solvent reduction reaction responsible for the capacity fade and power fade. The temperature variation inside the cell is accurately predicted using a distributed thermal model coupled with the internal chemical heat generation. The model is further improved by linking the porosity variation with the electrolyte partial molar concentration, thereby proving a stronger coupling between the battery performance and the chemical properties of electrolyte. The solid electrolyte interface (SEI) layer growth is estimated for different cut-off voltages and charging current rates. The results show that the convective heat transfer coefficient as well as the porosity variation influences the SEI layer growth and the battery life significantly. The choice of an electrolyte decides the conductivity and partial molar concentration, which is found to have a strong influence on the capacity fade of the battery. The present battery model integrates all essential electro-chemical processes inside a lithium-ion battery under a strong implicit algorithm, proving a useful tool for computationally fast battery monitoring system.

  5. Determining operational thermal loads and their influence on component quality

    International Nuclear Information System (INIS)

    Metzner, K.J.; Wilke, U.; Bartonicek, J.; Herter, K.H.

    2004-01-01

    This contribution discusses thermal loads on safety-relevant nuclear power plant components in three steps: 1. Assessment of thermal loads in transient reports (specified loads) and on the basis of temperature measurements; 2. Assessment of the thermohydraulic boundary conditions for stress-strain analysis (temperature distribution across pipe systems in lateral and longitudinal direction, measurement of heat transfer coefficients); 3. Stress and fatigue analyses. Practical experience has shown that all three elements must be linked in order to provide realistic fatigue data as a basis for further measures (e.g. selective non-destructive testing). The primary loop of a PWR reactor is used as an example to illustrate the relevant parameters of fatigue assessment for thermal loads. (orig.) [de

  6. Cyclic loading behaviour and crack monitoring potential of graphene nanoplatelet (GNP) based strain sensors in simple structures

    Science.gov (United States)

    Sai, M.; Sethy, D.; Varghese, F. V.; Balasubramaniam, K.

    2018-03-01

    Graphene Nanoplatelet (GNP)/poly methylmethacrylate (PMMA) based strain sensors were prepared via solution casting process at different initial resistances. The real time strain monitoring capability under various loading conditions (ramp, step and cyclic) and stability of the sensor was explored. The effectiveness of the sensor for crack monitoring in a simple structure was also studied and compared with a standard strain gauge. Experimental results showed a linear change in resistance with the strain in all loading conditions. In cyclic loading at a frequency of 5 Hz, high sensitivity sensors exhibited a considerable amount of time lag for steady response with the strain which was observed to be absent at 0.1 Hz. A significant amount of unrecoverable change in the resistance was observed in the sensors even after unloading, because of which the effective gauge factor of the sensor was reduced. The magnitude of this unrecoverable change in resistance was found to decrease with decrease in the gauge factor and frequency of cyclic loading. However, the GNP/PMMA sensor had shown a greater sensitivity in monitoring a crack in a cantilever beam over a conventional strain gauge.

  7. Thermal load resistance of erosion-monitoring beryllium maker tile for JET ITER like wall project

    International Nuclear Information System (INIS)

    Hirai, T.; Linke, J.; Sundelin, P.; Rubel, M.; Coad, J.P.; Matthews, G.F.; Lungu, C.P.

    2007-01-01

    The ITER reference materials, beryllium (Be), carbon fibre composite (CFC) and tungsten (W), have been tested separately in tokamaks. An integrated test demonstrating both compatibility of metal plasma facing components with high-power operation and acceptable tritium retention has not yet been carried out. At JET, the size, magnetic field strength and high plasma current allow to conducting tests with the combination of the materials. Thus, the ITER-like Wall (ILW) project has been launched. In the project, Be will be the plasmafacing material on the main chamber wall of JET. To assess the erosion of the Be tiles, a Be marker tile was proposed and designed. The test samples which simulate the JET Be marker tile have been produced in MEdC, Romania in order to study the thermal load resistance of the JET Be marker (20 x 20 mm 2 size with 30 mm height). The marker tile sample consists of bulk Be, high-Z interlayer (2-3 μm Ni coating) and 8-9 μm Be coating. Thermionic Vacuum Arc (TVA) techniques based on the electron-induced evaporation have been selected for this purpose. In the present work, the global characterization of the maker tile samples and thermal load tests were performed. After the pre-characterization (microstructure observation by scanning electron microscope and elemental analysis by means of Wavelength Dispersive X-ray Spectroscopy and Energy Dispersive X-ray Spectroscopy), the thermal loading tests were performed in the electron beam facility JUDITH. The coating consisted of tiny platelets of ∝0.1 um in diameter and localized larger platelets of 1 um in diameter. The surface and bulk temperature were observed during the tests. In the screening thermal load test, the samples were loaded to 6 MW/m 2 for 10 s. The layers did not show any macroscopic damages at up to 4.5 MW/m 2 for 10 s (45 MJ/m 2 ). However, the coating delaminated and the maker was damaged when the thermal loading reached at 5 MW/m 2 (∝50 MJ/m 2 ). Cyclic heat load tests were

  8. Experimental investigation and analysis of damage evolution in concrete under high-cyclic fatigue loadings

    International Nuclear Information System (INIS)

    Thiele, Marc

    2016-01-01

    structure. The results of the investigation indicated that rather the fatigue related changes in material behavior are mainly a result of viscous processes in cement stone especially in phase I and II of the fatigue process. Furthermore, it was observed that creep in concrete leads to similar but lesser changes in material behavior of concrete. Beside this, tests with different scales of specimens have shown an appreciable effect of size on the resulting material behavior under static and cyclic loadings respectively. From these experimental findings a detailed description was derived about the processes which take place within the material structure during the fatigue loading and also leads to the observed macroscopic changes in material behavior. In this context, the tests have shown that relating to stiffness reduction a scalar value could not capture the damage effect on the stressstrain- relationship caused by fatigue. A following consideration gives an overview about applicability of the different measured parameters for the detection of the degree of fatigue damage with regard to a reliable damage indicator. Finally an approach is presented which is able to describe the investigated developments of significant values within the observed fatigue process.

  9. Creep of MDF panels under constant load and cyclic environmental conditions. Influence of surface coating

    Directory of Open Access Journals (Sweden)

    Fernández-Golfín, J. I.

    1997-06-01

    Full Text Available Four different strategies of surface coating (based on 80 g m2 melamin impregnated papers were used on 19 mm thick commercial MDF panels to assess its reological behaviour under cyclic humidity conditions (20ºC 30 % rh-20ºC 90 % rh. Three different levels of stress (20 %, 30 % and 40 %, based on the ultimate load in bending, were used. Tests were conducted by means of the three points load system. For the same stress level, the relative creep of MDF panels was higher than that in particle boards with similar characteristics. This behaviour was just the opposite than the one exhibited by the panels when the comparison is made based on the same level of load (kg Melamin coating seems to strongly influence the creep behaviour of the raw material, especially when surface and edge coating were combined.

    Cuatro tipos de acabados superficiales distintos, aplicados sobre tableros MDF comerciales de 19 mm de espesor, son empleados en el estudio del comportamiento reológico de los tableros MDF ante condiciones alternantes de humedad relativa (20ºC/30 % hr-20ºC/90 % hr. Para el análisis del comportamiento reológico de los tableros se consideran tres niveles de tensión distintos (20 %, 30 %y 40 %, calculados en función de la carga última de rotura a flexión. Los ensayos son efectuados aplicando la carga en punto medio. La fluencia relativa de los tableros MDF resulta ser superior a la exhibida por los tableros de partículas de similares características, observándose que los revestimientos melamínicos aplicados superficialmente influyen eficazmente en la mejora de su comportamiento reológico. Cuando la comparación entre tableros MDF y de partículas se efectúa considerando idénticos niveles de carga aplicada en vez de tensión, el resultado de la comparación resulta ser, justamente, el contrario.

  10. Influence of Hold Time and Stress Ratio on Cyclic Creep Properties Under Controlled Tension Loading Cycles of Grade 91 Steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woo Gon; Park, Jae Young; Jang, Jin Sung [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Ekaputra, I Made Wicaksana; Kim, Seon Jin [Pukyong National University, Busan (Korea, Republic of)

    2017-04-15

    Influences of hold time and stress ratio on cyclic creep properties of Grade 91 steel were systemically investigated using a wide range of cyclic creep tests, which were performed with hold times (HTs) of 1 minute, 3 minutes, 5 minutes, 10 minutes, 20 minutes, and 30 minutes and stress ratios (R) of 0.5, 0.8, 0.85, 0.90, and 0.95 under tension loading cycles at 600°C. Under the influence of HT, the rupture time increased to HT = 5 minutes at R = 0.90 and R = 0.95, but there was no influence at R = 0.50, 0.80, and 0.85. The creep rate was constant regardless of an increase in the HT, except for the case of HT = 5 minutes at R = 0.90 and R = 0.95. Under the influence of stress ratio, the rupture time increased with an increase in the stress ratio, but the creep rate decreased. The cyclic creep led to a reduction in the rupture time and an acceleration in the creep rate compared with the case of monotonic creep. Cyclic creep was found to depend dominantly on the stress ratio rather than on the HT. Fracture surfaces displayed transgranular fractures resulting from microvoid coalescence, and the amount of microvoids increased with an increase in the stress ratio. Enhanced coarsening of the precipitates in the cyclic creep test specimens was found under all conditions.

  11. The influence of low-temperature degradation and cyclic loading on the fracture resistance of monolithic zirconia molar crowns.

    Science.gov (United States)

    Nakamura, K; Harada, A; Kanno, T; Inagaki, R; Niwano, Y; Milleding, P; Örtengren, U

    2015-07-01

    The present study analyzed the kinetics of low-temperature degradation (LTD) in zirconia, and evaluated the influence of LTD and cyclic loading on the fracture resistance of monolithic zirconia molar crowns. Bar-shaped zirconia specimens were divided into nine groups and autoclaved at 134°C for 0-200h to induce LTD. The surface fraction and penetration depth of the monoclinic phase were examined using X-ray diffraction and scanning electron microscopy. Monolithic zirconia molar crowns were prepared for crown fracture testing. The crowns were autoclaved for 0-100h (n=6) and cemented to dies. Six crown-die samples that were not autoclaved and six samples that were autoclaved for 100h were subjected to cyclic loading with a load of 300N for 240,000 cycles. All samples were tested in a load-to-failure test. The monoclinic fraction on the surface increased with autoclaving time and reached a plateau after 50h. The depth of the monoclinic phase increased without reaching a plateau. The fracture load of the crowns significantly decreased from 5683N (SD: 342) to 3975N (SD: 194) after 100h of autoclaving. Cyclic loading did not significantly affect the fracture resistance of the crowns in all cases. Kinetic analysis showed no linear correlation between the surface fraction and depth of the monoclinic phase after 50h of autoclaving. Even though LTD increased the monoclinic phase, resulting in lower strength, the fracture resistance of the monolithic zirconia crowns was still sufficient to withstand the loading conditions in the molar regions. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Effect of heat treatment on cyclic fatigue resistance, thermal behavior and microstructures of K3 NiTi rotary instruments.

    Science.gov (United States)

    Chang, Seok Woo; Kim, Yu-Chan; Chang, Hyejung; Jee, Kwang-Koo; Zhu, Qiang; Safavi, Kamran; Shon, Won-Jun; Bae, Kwang-Shik; Spangberg, Larz Sw; Kum, Kee-Yeon

    2013-11-01

    The aim of this study was to investigate the effect of heat treatment on the cyclic fatigue resistance, thermal behavior and microstructural changes of K3 NiTi rotary instruments. Twelve control (as-received) and 12 experimental (heat-treated) K3 NiTi rotary instruments were compared in this study. Those experimental K3 instruments were heated in a furnace for 30 min at 450°C and then quenched in water. The cyclic fatigue resistance was measured with a fatigue tester. The thermal characteristic and the microstructures of both instruments were investigated by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM), respectively. There was a significant increase in the cyclic fatigue resistance between the heat-treated instruments and the as-received instruments (T-test, p NiTi files and changed the thermal behavior of the instruments without marked changes in the constituting phases of NiTi alloy.

  13. Study of cyclic thermal aging of tube type receivers as a function of the duration of the cycle

    Science.gov (United States)

    Setien, Eneko; Fernández-Reche, Jesús; Ariza, María Jesús; Álvarez-de-Lara, Mónica

    2017-06-01

    The tube type receivers are exposed to variable duration cyclic operating conditions, which can jeopardize its reliability, and make it hard to estimate its long term performance. The designers have to deal with this problem and estimate the receiver long term performance based on the poor available litterature and the data sheets of the material. In order to help the designer better estimate the performance of the receivers, in this paper the cyclic thermal aging is analyzed as a function of the cycle duration. For this purpose, coated and uncoated Inconel alloy 625 tubular samples, similar to those used in the commercial receivers, are cyclically aged with different thermal cycle duration. The aging of these samples has been analyzed by means of oxidation kinetics, microstructure examination and mechanical and optical properties. The effect of the thermal cycle duration is studied and discussed by comparison of the results.

  14. Thermal loading study for FY 1996. Volume 1

    International Nuclear Information System (INIS)

    1996-01-01

    The primary objective of this study was to provide recommendations for Mined Geologic Disposal System requirements affected by thermal loading that will provide sufficient definition to facilitate development of design concepts and support life cycle cost determinations. The study reevaluated and/or redefined selected thermal goals used for design and are currently contained in the requirements documents or the Controlled Design Assumption Document. The study provided recommendations as to what, if any, actions (such as edge loading and limiting of the heat variability between waste packages) are needed and must be accommodated in the design. Additionally, the study provided recommendations as to what alternative thermal loads should be maintained for continued flexibility. Section 1 provides the study objective, background, scope, and organization of the report. Section 2 documents the requirements and standards to include quality assurance (QA) requirements, any requirements used or evaluated, and the inputs and assumptions considered. Section 3 provides the analysis and recommendations for the thermal goals reevaluation. Section 4 discusses the evaluation of edge loading and provides conclusions. Section 5 provides the analyses done to establish recommendations as to what requirements need to be implemented to either limit or manage the amount of heat output variability that may occur. Section 6 discusses alternate thermal loadings; Section 7 provides the study conclusions and recommendations; Section 8 provides the references, standards, and regulations; and Section 9 contains the acronym list

  15. Squeeze-Film Lubrication of the Human Ankle Joint Subjected to the Cyclic Loading Encountered in Walking

    Czech Academy of Sciences Publication Activity Database

    Hlaváček, Miroslav

    2005-01-01

    Roč. 127, č. 1 (2005), s. 141-147 ISSN 0742-4787 R&D Projects: GA ČR(CZ) GA103/04/0150 Institutional research plan: CEZ:AV0Z20710524 Keywords : cyclic loading * human ankle joint * squeeze-film lubrication * synovial fluid filtration * synovial gel formation Subject RIV: JJ - Other Materials Impact factor: 0.682, year: 2005

  16. Thermal cyclic oxidation behavior of the developed compositionally gradient graphite material of SiC/C in air environment

    International Nuclear Information System (INIS)

    Nakano, Junichi; Fujii, Kimio; Shindo, Masami

    1993-08-01

    For the developed compositionally gradient graphite material composed of surface SiC coating layer, middle SiC/C layer and graphite matrix, the thermal cyclic oxidation test was performed together with two kinds of the SiC coated graphite materials in air environment. It was made clear that the developed material exhibited high performance under severe thermal cyclic condition independent of the morphology of middle SiC/C layers and had the longer time or the more cycle margins from crack initiation to failure for surface SiC coating layer compared with the SiC coated graphite materials. (author)

  17. Experimental primers containing synthetic and natural compounds reduce enzymatic activity at the dentin–adhesive interface under cyclic loading

    Science.gov (United States)

    Sousa, Ana Beatriz Silva; de Mattos Pimenta Vidal, Cristina; Leme-Kraus, Ariene Arcas; de Carvalho Panzeri Pires-de-Souza, Fernanda; Bedran-Russo, Ana K.

    2016-01-01

    Objective To evaluate the effect of experimental primers (chlorhexidine, enriched mixture of proanthocyanidins and doxycycline) on the adhesive properties and gelatinolytic activity at dentin-resin interfaces of occlusal Class I restorations. Methods The inactivation of enzymes by the experimental primers was assessed by fluorescence assay and gelatin zymography. To assess the adhesive properties, occlusal Class I cavities were prepared in sound human molars, etched with phosphoric acid and restored with one of the primers and an etch-and-rinse adhesive system (Adper Single Bond Plus - 3M ESPE). After the restorative procedures, the specimens were divided into two subgroups (n = 6) consisting of storage in incubation buffer or axial cyclic loading at 50 N and 1,000,000 cycles. Then, the sectioned and sliced specimens were assigned to in situ zymography assay and microtensile bond strength (TBS) test. Results Fluorescence assay and gelatin zymography revealed that the experimental primers inactivated rMMPs. In situ zymography (2-way ANOVA, Tukey, p 0.05). Significance The use of experimental primers impaired the enzymatic activity at the dentin-adhesive interface after cyclic loading and the activity of rMMPs. Cyclic loading did not have a significant effect on the bond strength. PMID:27524231

  18. Cyclic thermal behavior associated to the degassing process at El Hierro submarine volcano, Canary Islands.

    Science.gov (United States)

    Fraile-Nuez, E.; Santana-Casiano, J. M.; González-Dávila, M.

    2016-12-01

    One year after the ceasing of magmatic activity in the shallow submarine volcano of the island of El Hierro, significant physical-chemical anomalies produced by the degassing process as: (i) thermal anomalies increase of +0.44 °C, (ii) pH decrease of -0.034 units, (iii) total dissolved inorganic carbon, CT increase by +43.5 µmol kg-1 and (iv) total alkalinity, AT by +12.81 µmol kg-1 were still present in the area. These evidences highlight the potential role of the shallow degassing processes as a natural ecosystem-scale experiments for the study of significant effects of global change stressors on marine environments. Additionally, thermal time series obtained from a temporal yo-yo CTD study, in isopycnal components, over one of the most active points of the submarine volcano have been analyzed in order to investigate the behavior of the system. Signal processing of the thermal time series highlights a strong cyclic temperature period of 125-150 min at 99.9% confidence, due to characteristic time-scales revealed in the periodogram. These long cycles might reflect dynamics occurring within the shallow magma supply system below the island of El Hierro.

  19. Thermal Gradient Cyclic Behavior of a Thermal/Environmental Barrier Coating System on SiC/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

    2002-01-01

    Thermal barrier and environmental barrier coatings (TBCs and EBCs) will play a crucial role in future advanced gas turbine engines because of their ability to significantly extend the temperature capability of the ceramic matrix composite (CMC) engine components in harsh combustion environments. In order to develop high performance, robust coating systems for effective thermal and environmental protection of the engine components, appropriate test approaches for evaluating the critical coating properties must be established. In this paper, a laser high-heat-flux, thermal gradient approach for testing the coatings will be described. Thermal cyclic behavior of plasma-sprayed coating systems, consisting of ZrO2-8wt%Y2O3 thermal barrier and NASA Enabling Propulsion Materials (EPM) Program developed mullite+BSAS/Si type environmental barrier coatings on SiC/SiC ceramic matrix composites, was investigated under thermal gradients using the laser heat-flux rig in conjunction with the furnace thermal cyclic tests in water-vapor environments. The coating sintering and interface damage were assessed by monitoring the real-time thermal conductivity changes during the laser heat-flux tests and by examining the microstructural changes after the tests. The coating failure mechanisms are discussed based on the cyclic test results and are correlated to the sintering, creep, and thermal stress behavior under simulated engine temperature and heat flux conditions.

  20. Multiaxial creep of tubes from Incoloy 800H and Inconel 617 under static and cyclic loading conditions

    International Nuclear Information System (INIS)

    Penkalla, H.J.; Nickel, H.; Schubert, F.

    1987-01-01

    This paper is concerned with the description of creep under triaxial loading with the aid of Norton's law and v. Mises' theory. The load combination of internal pressure, tension and torsion is more closely scrutinized. The superposition of cyclic stresses in the tensile threshold range is discussed as well as the instances of partial relaxation. In accordance with the discussed loading modes, experimental results are presented which, until now, have delivered a satisfactory agreement between theory and practice. A more explicit analysis of the creep-induced damage is given regarding the assessment of the expected life until failure under triaxial loading. This delivers information concerning a suitable test stress for the long-term stress assessment. (orig./DG) [de

  1. Thermal loading study for FY 1996. Volume 2

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-11-08

    The primary objective of this study was to provide recommendations for Mined Geologic Disposal System requirements affected by thermal loading that will provide sufficient definition to facilitate development of design concepts and support life cycle cost determinations. The study reevaluated and/or redefined selected thermal goals used for design and are currently contained in the requirements documents or the Controlled Design Assumption Document. The study provided recommendations as to what, if any, actions (such as edge loading and limiting of the heat variability between waste packages) are needed and must be accommodated in the design. Additionally, the study provided recommendations as to what alternative thermal loads should be maintained for continued flexibility. This report contains seven appendices: Technical basis for evaluation of thermal goals below the potential nuclear was repository at Yucca Mountain; Thermal-mechanical evaluation of the 200 C drift-wall temperature goal; Evaluation of ground stability and support; Coupled ventilation and hydrothermal evaluations; Heat flow and temperature calculations for continuously ventilated emplacement drifts; Thermal management using aging and/or waste package selection; and Waste stream evaluations.

  2. Thermal loading study for FY 1996. Volume 2

    International Nuclear Information System (INIS)

    1996-01-01

    The primary objective of this study was to provide recommendations for Mined Geologic Disposal System requirements affected by thermal loading that will provide sufficient definition to facilitate development of design concepts and support life cycle cost determinations. The study reevaluated and/or redefined selected thermal goals used for design and are currently contained in the requirements documents or the Controlled Design Assumption Document. The study provided recommendations as to what, if any, actions (such as edge loading and limiting of the heat variability between waste packages) are needed and must be accommodated in the design. Additionally, the study provided recommendations as to what alternative thermal loads should be maintained for continued flexibility. This report contains seven appendices: Technical basis for evaluation of thermal goals below the potential nuclear was repository at Yucca Mountain; Thermal-mechanical evaluation of the 200 C drift-wall temperature goal; Evaluation of ground stability and support; Coupled ventilation and hydrothermal evaluations; Heat flow and temperature calculations for continuously ventilated emplacement drifts; Thermal management using aging and/or waste package selection; and Waste stream evaluations

  3. MODELING OF NONLINEAR CYCLIC LOAD BEHAVIOR OF I-SHAPED COMPOSITE STEEL-CONCRETE SHEAR WALLS OF NUCLEAR POWER PLANTS

    Directory of Open Access Journals (Sweden)

    AHMER ALI

    2013-02-01

    Full Text Available In recent years steel-concrete composite shear walls have been widely used in enormous high-rise buildings. Due to high strength and ductility, enhanced stiffness, stable cycle characteristics and large energy absorption, such walls can be adopted in the auxiliary building; surrounding the reactor containment structure of nuclear power plants to resist lateral forces induced by heavy winds and severe earthquakes. This paper demonstrates a set of nonlinear numerical studies on I-shaped composite steel-concrete shear walls of the nuclear power plants subjected to reverse cyclic loading. A three-dimensional finite element model is developed using ABAQUS by emphasizing on constitutive material modeling and element type to represent the real physical behavior of complex shear wall structures. The analysis escalates with parametric variation in steel thickness sandwiching the stipulated amount of concrete panels. Modeling details of structural components, contact conditions between steel and concrete, associated boundary conditions and constitutive relationships for the cyclic loading are explained. Later, the load versus displacement curves, peak load and ultimate strength values, hysteretic characteristics and deflection profiles are verified with experimental data. The convergence of the numerical outcomes has been discussed to conclude the remarks.

  4. In-Plane Anisotropy in Mechanical Behavior and Microstructural Evolution of Commercially Pure Titanium in Tensile and Cyclic Loading

    Science.gov (United States)

    Sinha, Subhasis; Gurao, N. P.

    2017-12-01

    Tensile and cyclic deformation behavior of three samples oriented at 0, 45, and 90 deg to the rolling direction in the rolling direction-transverse direction (RD-TD) plane of cold-rolled and annealed plate of commercially pure titanium is studied in the present investigation. The sample along the RD (R0) shows the highest strength but lowest ductility in monotonic tension. Although ultimate tensile strength (UTS) and elongation of samples along 45 and 90 deg to the RD (R45 and R90, respectively) are similar, the former has significantly higher yield strength than the latter, indicating different strain-hardening behavior. It is found that the R90 sample exhibits the highest monotonic ductility as well as fatigue life. This is attributed to a higher propensity for twinning in this sample with the presence of multiple variants and twin intersections. Cyclic life is also influenced by the high tendency for detwinning of contraction twins in this orientation. Elastoplastic self-consistent (EPSC) simulations of one-cycle tension-compression load reversal indicate that the activity of pyramidal 〈 c + a〉 slip and extension twinning oscillates during cyclic loading that builds up damage in a cumulative manner, leading to failure in fatigue.

  5. Thermal Load Reduction System Development in a Hyundai Sonata PHEV

    Energy Technology Data Exchange (ETDEWEB)

    Kreutzer, Cory J.; Rugh, John; Tomerlin, Jeff

    2017-03-28

    Increased market penetration of electric drive vehicles (EDVs) requires overcoming a number of hurdles, including limited vehicle range and the elevated cost in comparison to conventional vehicles. Climate control loads have a significant impact on range, cutting it by over 50% in both cooling and heating conditions. To minimize the impact of climate control on EDV range, the National Renewable Energy Laboratory has partnered with Hyundai America and key industry partners to quantify the performance of thermal load reduction technologies on a Hyundai Sonata plug-in hybrid electric vehicle. Technologies that impact vehicle cabin heating in cold weather conditions and cabin cooling in warm weather conditions were evaluated. Tests included thermal transient and steady-state periods for all technologies, including the development of a new test methodology to evaluate the performance of occupant thermal conditioning. Heated surfaces demonstrated significant reductions in energy use from steady-state heating, including a 29%-59% reduction from heated surfaces. Solar control glass packages demonstrated significant reductions in energy use for both transient and steady-state cooling, with up to a 42% reduction in transient and 12.8% reduction in steady-state energy use for the packages evaluated. Technologies that demonstrated significant climate control load reduction were selected for incorporation into a complete thermal load reduction package. The complete package is set to be evaluated in the second phase of the ongoing project.

  6. Cyclic Crack Monitoring of a Reinforced Concrete Column under Simulated Pseudo-Dynamic Loading Using Piezoceramic-Based Smart Aggregates

    Directory of Open Access Journals (Sweden)

    Qingzhao Kong

    2016-11-01

    Full Text Available Structural health monitoring is an important aspect of maintenance for bridge columns in areas of high seismic activity. In this project, recently developed piezoceramic-based transducers, known as smart aggregates (SA, were utilized to perform structural health monitoring of a reinforced concrete (RC bridge column subjected to pseudo-dynamic loading. The SA-based approach has been previously verified for static and dynamic loading but never for pseudo-dynamic loading. Based on the developed SAs, an active-sensing approach was developed to perform real-time health status evaluation of the RC column during the loading procedure. The existence of cracks attenuated the stress wave transmission energy during the loading procedure and reduced the amplitudes of the signal received by SA sensors. To detect the crack evolution and evaluate the damage severity, a wavelet packet-based structural damage index was developed. Experimental results verified the effectiveness of the SAs in structural health monitoring of the RC column under pseudo-dynamic loading. In addition to monitoring the general severity of the damage, the local structural damage indices show potential to report the cyclic crack open-close phenomenon subjected to the pseudo-dynamic loading.

  7. Residual stress evolution regularity in thermal barrier coatings under thermal shock loading

    Directory of Open Access Journals (Sweden)

    Ximin Chen

    2014-01-01

    Full Text Available Residual stress evolution regularity in thermal barrier ceramic coatings (TBCs under different cycles of thermal shock loading of 1100°C was investigated by the microscopic digital image correlation (DIC and micro-Raman spectroscopy, respectively. The obtained results showed that, as the cycle number of the thermal shock loading increases, the evolution of the residual stress undergoes three distinct stages: a sharp increase, a gradual change, and a reduction. The extension stress near the TBC surface is fast transformed to compressive one through just one thermal cycle. After different thermal shock cycles with peak temperature of 1100°C, phase transformation in TBC does not happen, whereas the generation, development, evolution of the thermally grown oxide (TGO layer and micro-cracks are the main reasons causing the evolution regularity of the residual stress.

  8. Thermal Loading of a Direct Drive Target Rarefied Gas

    International Nuclear Information System (INIS)

    Christensen, B.R.; Raffray, A.R.; Tillack, M.S.

    2005-01-01

    In an inertial fusion energy (IFE) power plant, each fusion micro-explosion (∼10 Hz) causes thermal and structural loads on the IFE reactor wall and driver optics. The loading on the wall must remain sufficiently low to ensure that economic and safety constraints are met.One proposed method for decreasing the intensity of the wall loading is to fill the reaction chamber with a gas, such as Xe, at low density. The gas will absorb much of the radiation and ion energy from the fusion event, and then slowly release it to the chamber wall. Unfortunately the protective gas introduces major heat loads on the direct drive target. The thermal loading of a target, during injection, largely determines the viability of that target upon reaching chamber center. Thus, the density of the gas must be carefully selected to ensure that a target will survive injection.The objective of this work is to quantify and characterize the heat flux resulting from the interaction of the target and the protective gas. The loading of the target is modeled using DS2V, a commercial DSMC (Direct Simulation Monte Carlo) program. Using DS2V, this work explores the effect of the protective gas density, temperature, sticking (condensation) and accommodation coefficients on the heat flux to the target

  9. Triangular osteosynthesis and iliosacral screw fixation for unstable sacral fractures: a cadaveric and biomechanical evaluation under cyclic loads.

    Science.gov (United States)

    Schildhauer, Thomas A; Ledoux, William R; Chapman, Jens R; Henley, M Bradford; Tencer, Allan F; Routt, M L Chip

    2003-01-01

    To conduct a biomechanical comparison of a new triangular osteosynthesis and the standard iliosacral screw osteosynthesis for unstable transforaminal sacral fractures in the immediate postoperative situation as well as in the early postoperative weight-bearing period. Twelve preserved human cadaveric lumbopelvic specimens were cyclicly tested in a single-limb-stance model. A transforaminal sacral fracture combined with ipsilateral superior and inferior pubic rami fractures were created and stabilized. Loads simulating muscle forces and body weight were applied. Fracture site displacement in three dimensions was evaluated using an electromagnetic motion sensor system. Specimens were randomly assigned to either an iliosacral and superior pubic ramus screw fixation or to a triangular osteosynthesis consisting of lumbopelvic stabilization (between L5 pedicle and posterior ilium) combined with iliosacral and superior pubic ramus screw fixation. Peak loaded displacement at the fracture site was measured for assessment of initial stability. Macroscopic fracture behavior through 10,000 cycles of loading, simulating the early postoperative weight-bearing period, was classified into type 1 with minimal motion at the fracture site, type 2 with complete displacement of the inferior pubic ramus, or type 3 with catastrophic failure. The triangular osteosynthesis had a statistically significantly smaller displacement under initial peak loads (mean +/- standard deviation [SD], 0.163 +/- 0.073 cm) and therefore greater initial stability than specimens with the standard iliosacral screw fixation (mean +/- SD, 0.611 +/- 0.453 cm) ( = 0.0104), independent of specimen age or sex. All specimens with the triangular osteosynthesis demonstrated type 1 fracture behavior, whereas iliosacral screw fixation resulted in one type 1, two type 2, and three type 3 fracture behaviors before or at 10,000 cycles of loading. Triangular osteosynthesis for unstable transforaminal sacral fractures

  10. Cyclic deformation and precipitation behaviour of NiCr22Co12Mo9 during thermal fatigue

    International Nuclear Information System (INIS)

    Pan, Y.; Lang, K.H.; Loehe, D.; Macherauch, E.

    1993-01-01

    Specimens of the nickel-base superalloy NiCr22C12Mo9 (corresponding to Inconel 617) are thermally fatigued with a constant minimum temperature T min =473 K and maximum temperatures T max =873, 1123, 1323, and 1473 K. Cryclic hardening is observed in test with T max ≤1323 K, whereas cyclic softening occurs in tests with T max =1473 K. Coherent and incoherent γ'-precipitates develop during cycling with T max =873 K. In experiments with T max ≤1323 K the major secondary precipitates are found to be M 23 C 6 carbides. In tests with T max =1323 K, carbide bands are produced in former twin areas. Almost no carbides are observed after thermal cycling with T max =1473 K. The thermal cyclic deformation behaviour of the material is discussed taking into account the occurring precipitation features and other microstructural changes. A model to explain the development of carbide bands is suggested. (orig.)

  11. Resistance to impact of cross-linked denture base biopolymer materials: effect of relining, glass flakes reinforcement and cyclic loading.

    Science.gov (United States)

    da Cruz Perez, Luciano Elias; Lucia Machado, Ana; Eduardo Vergani, Carlos; Andrade Zamperini, Camila; Cláudia Pavarina, Ana; Vicente Canevarolo, Sebastião

    2014-09-01

    The effect of reinforcement and cyclic loading on the resistance to impact (RI) of denture base biopolymer materials was evaluated using Charpy (C) and falling-weight (FW) impact tests. Bar-shaped (60×6×2mm(3)) and denture-shaped specimens (2mm) for the C and FD tests, respectively, were prepared with Lucitone 550 (L) and Vipi Wave (V) and relined (2mm) using the same material or the autopolymerizing relining resins Tokuyama Rebase II (T) and Ufi Gel Hard (U). Bulk specimens (60×6×4mm(3)) of all materials (L, V, T and U) were also prepared and tested. To evaluate the effect of reinforcement, glass flakes were added to the powder of the relining resins T and U (5% by weight). Half of bar-shaped (n=320) and half of the denture-shaped specimens (n=480) were subjected to cyclic loading (10,000 cycles) before the impact tests. Data were analyzed by one-way ANOVAs (α=0.05) and revealed that the RI of L and V were comparable and higher than those of U and T. Compared to L and V, the RI was increased by relining with T and decreased by relining with U. When relining was made using the same material (L and V) the RI was maintained. Flexural cyclic loading and the incorporation of glass flakes into the resins T and U did not cause any significant alteration in the RI. A high correlation between results from C and FW tests was observed (r=0.8854). Relining may exert effects on the RI of L and V denture base resins, which vary according to the relining material used. The high correlation between C and FW, suggests that the Charpy test, using bar-shaped specimens, can be a simple and reliable method for evaluating factors that may influence the RI of denture base polymers. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Anisotropic TGO rumpling in EB-PVD thermal barrier coatings under in-phase thermomechanical loading

    Energy Technology Data Exchange (ETDEWEB)

    Balint, D.S., E-mail: d.balint@imperial.ac.uk [Department of Mechanical Engineering, Imperial College London, London SW7 2AZ (United Kingdom); Kim, S.-S.; Liu Yufu; Kitazawa, R.; Kagawa, Y. [Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8409 (Japan); Evans, A.G. [College of Engineering, University of California, Santa Barbara, CA 93106 (United States)

    2011-04-15

    An electron beam physical vapor deposited (EB-PVD) Y{sub 2}O{sub 3}-ZrO{sub 2} thermal barrier system has been tested under in-phase thermomechanical fatigue (TMF) conditions with thermal gradient in the through-thickness direction. Undulations in the thermally grown oxide (TGO) were observed to have clear anisotropic behavior with respect to the directions parallel and perpendicular to the loading axis. It was found that undulation wavelengths were nearly the same in both directions but the amplitude in the perpendicular direction was much larger than in the parallel direction. A recent model of TGO rumpling was adapted and used to analyze and explain the origins of the observed rumpling behavior under TMF conditions. Methods for deducing variation in the coefficient of thermal expansion with temperature and in the creep properties of the substrate from the experimental strain data are also presented in the course of the derivations. Model results show that tensile stress applied in the loading direction can overcome the compression occurring from lateral expansion during oxide formation, causing undulations to flatten; undulations perpendicular to the loading axis are unaffected. However, ratcheting in the strain cycle experienced by the substrate, which occurs naturally by substrate creep, is necessary for anisotropic rumpling under cyclic stress conditions. Model predictions for constant applied stress are also presented, demonstrating a reversal in the direction of undulation alignment under compression. A threshold stress is identified, in both tension and compression, sufficient to produce appreciable anisotropic rumpling. The model predictions provide a clear mechanism for the anisotropy and further evidence that the lateral expansion strain in the oxide is the driving force for oxide rumpling.

  13. Drift scale thermomechanical analysis for thermal loading and retrievability studies

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, F.C.

    1995-12-31

    Currently, the repository portion of the Mined Geologic Disposal System for the disposal of spent nuclear fuel and high level radioactive waste is in the advanced conceptual design (ACD) stage. As a part of the Thermal Loading Systems Study and the Retrievability Period Systems Study, a numerical method was used to estimate the stability of emplacement drifts. Drift stability is an important performance issue, particularly for the concept of a waste package (WP) in an open drift. Drift stability is both a preclosure and postclosure issue. Specifically, preclosure worker safety and WP retrievability can be affected by drift stability. Important postclosure drift stability issues are the potential for rockfall which might damage a WP or the potential formation of cracks and upheaval of rock masses which may alter the hydrologic performance of the repository. In the current study, thermomechanical analyses, using the Discontinuous Deformation Analysis (DDA) numerical code, were performed to support the thermal loading study and the retrievability study. The coupled effects between thermal and mechanical behavior induced by the excavation, thermal loading and rapid cooling were analyzed using rock-mass models. Input data for the jointed-rock pattern, in situ stress condition, and the material properties of intact rock and rock joints were adopted from the Yucca Mountain Site Characterization Project.

  14. Shear Performance of Horizontal Joints in Short Precast Concrete Columns with Sleeve Grouted Connections under Cyclic Loading

    OpenAIRE

    Feng, Bo; Xiong, Feng; Liu, Bingyu; Chen, Jiang; Zhang, Yiping

    2016-01-01

    In this study, two short precast concrete columns and two cast-in-situ concrete columns were tested under cyclic loads. It was shown that the sleeve grouted connection was equivalent to the cast-in-situ connections for short columns when the axial compression ratio was 0.6. In order to determine the influence of the axial compression ratio and the shear-span ratio on the shear capacity of the horizontal joint, a FE model was established and verified. The analysis showed that the axial compres...

  15. Ratchetting behavior of primary heat transport (PHT) piping material SA-333 carbon steel subjected to cyclic loads at room temperature

    International Nuclear Information System (INIS)

    Kulkarni, S.; Desai, Y.M.; Kant, T.; Reddy, G.R.; Gupta, C.; Chakravarthy, J.K.

    2004-01-01

    Ratchetting behavior of SA-333 Gr. 6 carbon steel used as primary heat transport (PHT) piping material has been investigated with three constitutive models proposed by Armstrong-Frederick, Chaboche and Ohno-Wang involving different hardening rules. Performance of the above mentioned models have been evaluated for a broad set of uniaxial and biaxial loading histories. The uniaxial ratchetting simulations have been performed for a range of stress ratios (R) by imposing different stress amplitudes and mean stress conditions. Numerical simulations indicated significant ratchetting and opening of hysteresis loop for negative stress ratio with constant mean stress. Application of cyclic stress without mean stress (R = -1.0) has been observed to produce negligible ratchet-strain accumulation in the material. Simulation under the biaxial stress condition was based on modeling of an internally pressurized thin walled pipe subjected to cyclic bending load. Numerical results have been validated with the experiments as per simulation conditions. All three models have been found to predict the observed accumulation of circumferential strain with increasing number of cycles. However, the Armstrong Frederick (A-F) model was found to be inadequate in simulating the ratchetting response for both uniaxial as well as biaxial loading cases. The A-F model actually over-predicted the ratchetting strain in comparison with the experimental strain values. On the other hand, results obtained with the Chaboche and the Ohno-Wang models for both the uniaxial as well as biaxial loading histories have been observed to closely simulate the experimental results. The Ohno-Wang model resulted in better simulation for the presents sets of experimental results in comparison with the Chaboche model. It can be concluded that the Ohno-Wang model suited well compared to the Chaboche model for above sets of uniaxial and biaxial loading histories. (authors)

  16. Can human mesenchymal stem cells survive on a NiTi implant material subjected to cyclic loading?

    Science.gov (United States)

    Habijan, T; Glogowski, T; Kühn, S; Pohl, M; Wittsiepe, J; Greulich, C; Eggeler, G; Schildhauer, T A; Köller, M

    2011-06-01

    Nickel-titanium shape memory alloys (NiTi-SMAs) exhibit mechanical and chemical properties which make them attractive candidate materials for various types of biomedical applications. However, the high nickel content of NiTi-SMAs may result in adverse tissue reactions, especially when they are considered for load-bearing implants. It is generally assumed that a protective titanium oxide layer separates the metallic alloy from its environment and that this explains the good biocompatibility of NiTi. Cyclic loading may result in failure of the protective oxide layer. The scientific objective of this work was to find out whether cyclic dynamic strain, in a range relevant for orthopedic implants, diminishes the biocompatibility of NiTi-SMAs. In order to analyze the biocompatibility of NiTi-SMA surfaces subjected to cyclic loading, NiTi-SMA tensile specimens were preloaded with mesenchymal stem cells, transferred to a sterile cell culture system and fixed to the pull rods of a tensile testing machine. Eighty-six thousand and four hundred strain cycles at 2% pseudoelastic strain were performed for a period of 24 h or 7 days. Cytokines (IL-6, IL-8 and VEGF) and nickel ion release were determined within the cell culture medium. Adherent cells on the tensile specimens were stained with calcein-AM and propidium iodide to determine cell viability. Dynamic loading of the tensile specimens did not influence the viability of adherent human mesenchymal stem cells (hMSCs) after 24 h or 7 days compared with the non-strained control. Dynamic cycles of loading and unloading did not affect nickel ion release from the tensile specimens. The release of IL-6 from hMSCs cultured under dynamic conditions was significantly higher after mechanical load (873 pg ml(-1)) compared with static conditions (323 pg ml(-1)). The present work demonstrates that a new type of mechanical in vitro cell culture experiment can provide information which previously could only be obtained in large animal

  17. Thermal Vacuum Test Correlation of a Zero Propellant Load Case Thermal Capacitance Propellant Gauging Analytical Model

    Science.gov (United States)

    Mckim, Stephen A.

    2016-01-01

    This thesis describes the development and correlation of a thermal model that forms the foundation of a thermal capacitance spacecraft propellant load estimator. Specific details of creating the thermal model for the diaphragm propellant tank used on NASA's Magnetospheric Multiscale spacecraft using ANSYS and the correlation process implemented are presented. The thermal model was correlated to within plus or minus 3 degrees Celsius of the thermal vacuum test data, and was determined sufficient to make future propellant predictions on MMS. The model was also found to be relatively sensitive to uncertainties in applied heat flux and mass knowledge of the tank. More work is needed to improve temperature predictions in the upper hemisphere of the propellant tank where predictions were found to be 2 to 2.5 C lower than the test data. A road map for applying the model to predict propellant loads on the actual MMS spacecraft toward its end of life in 2017-2018 is also presented.

  18. Transient Dynamic Response and Failure of Composite Structure Under Cyclic Loading with Fluid Structure Interaction

    Science.gov (United States)

    2014-09-01

    19  2.  Loading Jig ............................................................................. 21  3.  Water Tank...20  Figure 16.  Loading jig ...exported to word processing software. *Capabilities can be performed only if the required add-on equipment/loading jig is purchased. Figure 15

  19. Influence of three types of abutments on preload values before and after cyclic loading with structural analysis by scanning electron microscopy.

    Science.gov (United States)

    Butignon, Luis Eduardo; Basilio, Mariana de Almeida; Pereira, Rodrigo de Paula; Arioli Filho, Joao Neudenir

    2013-01-01

    To evaluate the effectiveness of three types of abutments in the maintenance of screw joint preload before and after cyclic loading as well as to observe possible microdamage in the structure of the components using a scanning electron microscope (SEM). Forty-five external-hex implants were embedded in epoxy resin, received their respective abutments, and were randomly divided into three experimental groups (n = 15): (1) machined titanium (Ti) abutments; (2) pre-machined gold (Au) abutments; and (3) machined zirconia (ZrO(2)) abutments. The abutment screws were tightened according to the manufacturer's recommended torque. Initially, a static bending test was performed using five specimens of each group to determine the load applied in the cyclic loading test. Thus, 10 specimens of each group were used to measure the reverse torque value (preload) of the abutment screw before and after loading. A cyclic loading (0.5 × 10(6) cycles; 15 Hz) between 11 and 211 N was applied at an angle of 30 degrees to the long axis of the implants. The group means were compared using analysis of variance and the Tukey test (α = .05). The reverse torque analysis before cyclic loading showed no significant difference among the groups (P > .05). After cyclic loading, all preload means decreased significantly. The lowest decrease in preload was observed in the Ti group, whereas the highest decrease was observed in the ZrO(2) group, with a significant difference noted between them (P = .010). The Au group presented an intermediate decrease, with no significant difference compared to the other groups (P > .05). SEM images showed structural changes in the mating surfaces of the abutments after cyclic loading. The load application reduced the preload means significantly in all groups, and more significantly in the ZrO(2) group.

  20. The effect of cyclic and dynamic loads on carbon steel pipe

    International Nuclear Information System (INIS)

    Rudland, D.L.; Scott, P.M.; Wilkowski, G.M.

    1996-02-01

    This report presents the results of four 152-mm (6-inch) diameter, unpressurized, circumferential through-wall-cracked, dynamic pipe experiments fabricated from STS410 carbon steel pipe manufactured in Japan. For three of these experiments, the through-wall crack was in the base metal. The displacement histories applied to these experiments were a quasi-static monotonic, dynamic monotonic, and dynamic, cyclic (R = -1) history. The through-wall crack for the third experiment was in a tungsten-inert-gas weld, fabricated in Japan, joining two lengths of STS410 pipe. The displacement history for this experiment was the same history applied to the dynamic, cyclic base metal experiment. The test temperature for each experiment was 300 C (572 F). The objective of these experiments was to compare a Japanese carbon steel pipe material with US pipe material, to ascertain whether this Japanese steel was as sensitive to dynamic and cyclic effects as US carbon steel pipe. In support of these pipe experiments, quasi-static and dynamic, tensile and fracture toughness tests were conducted. An analysis effort was performed that involved comparing experimental crack initiation and maximum moments with predictions based on available fracture prediction models, and calculating J-R curves for the pipe experiments using the η-factor method

  1. Smart-aggregate-based damage detection of fiber-reinforced-polymer-strengthened columns under reversed cyclic loading

    Science.gov (United States)

    Howser, Rachel; Moslehy, Yashar; Gu, Haichang; Dhonde, Hemant; Mo, Y. L.; Ayoub, Ashraf; Song, Gangbing

    2011-07-01

    Structural health monitoring is an important aspect of the maintenance of large civil infrastructures, especially for bridge columns in areas of high seismic activity. In this project, recently developed innovative piezoceramic-based sensors were utilized to perform the health monitoring of a shear-critical reinforced concrete (RC) bridge column subjected to reversed cyclic loading. After the column failed, it was wrapped with fiber reinforced polymer (FRP) sheets, commonly used to retrofit seismically damaged structures. The FRP-strengthened column was retested under the same reversed cyclic loading pattern. Innovative piezoceramic-based sensors, called 'smart aggregates', were utilized as transducers for health monitoring purposes. On the basis of the smart aggregates developed, an active-sensing approach and an impact-hammer-based approach were used to evaluate the health status of the RC column during the loading procedure. Wave transmission energy is attenuated by the existence of cracks during the loading procedure, and this attenuation phenomenon alters the curve of the transfer function between the actuator and sensor. To detect the damage occurrence and evaluate the damage severity, transfer function curves were compared with those obtained during the period of healthy status. A transfer-function-based damage index matrix was developed to demonstrate the damage severity at different locations. Experimental results verified the effectiveness of the smart aggregates in health monitoring of the FRP-strengthened column as well as the unstrengthened column. The experimental results show that the proposed smart-aggregate-based approach can successfully detect damage occurrence and evaluate its severity.

  2. Mechanical Behavior of AZ31B Mg Alloy Sheets under Monotonic and Cyclic Loadings at Room and Moderately Elevated Temperatures

    Science.gov (United States)

    Nguyen, Ngoc-Trung; Seo, Oh Suk; Lee, Chung An; Lee, Myoung-Gyu; Kim, Ji-hoon; Kim, Heon Young

    2014-01-01

    Large-strain monotonic and cyclic loading tests of AZ31B magnesium alloy sheets were performed with a newly developed testing system, at different temperatures, ranging from room temperature to 250 °C. Behaviors showing significant twinning during initial in-plane compression and untwinning in subsequent tension at and slightly above room temperature were recorded. Strong yielding asymmetry and nonlinear hardening behavior were also revealed. Considerable Bauschinger effects, transient behavior, and variable permanent softening responses were observed near room temperature, but these were reduced and almost disappeared as the temperature increased. Different stress–strain responses were inherent to the activation of twinning at lower temperatures and non-basal slip systems at elevated temperatures. A critical temperature was identified to account for the transition between the twinning-dominant and slip-dominant deformation mechanisms. Accordingly, below the transition point, stress–strain curves of cyclic loading tests exhibited concave-up shapes for compression or compression following tension, and an unusual S-shape for tension following compression. This unusual shape disappeared when the temperature was above the transition point. Shrinkage of the elastic range and variation in Young’s modulus due to plastic strain deformation during stress reversals were also observed. The texture-induced anisotropy of both the elastic and plastic behaviors was characterized experimentally. PMID:28788514

  3. Mechanical Behavior of AZ31B Mg Alloy Sheets under Monotonic and Cyclic Loadings at Room and Moderately Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Ngoc-Trung Nguyen

    2014-02-01

    Full Text Available Large-strain monotonic and cyclic loading tests of AZ31B magnesium alloy sheets were performed with a newly developed testing system, at different temperatures, ranging from room temperature to 250 °C. Behaviors showing significant twinning during initial in-plane compression and untwinning in subsequent tension at and slightly above room temperature were recorded. Strong yielding asymmetry and nonlinear hardening behavior were also revealed. Considerable Bauschinger effects, transient behavior, and variable permanent softening responses were observed near room temperature, but these were reduced and almost disappeared as the temperature increased. Different stress–strain responses were inherent to the activation of twinning at lower temperatures and non-basal slip systems at elevated temperatures. A critical temperature was identified to account for the transition between the twinning-dominant and slip-dominant deformation mechanisms. Accordingly, below the transition point, stress–strain curves of cyclic loading tests exhibited concave-up shapes for compression or compression following tension, and an unusual S-shape for tension following compression. This unusual shape disappeared when the temperature was above the transition point. Shrinkage of the elastic range and variation in Young’s modulus due to plastic strain deformation during stress reversals were also observed. The texture-induced anisotropy of both the elastic and plastic behaviors was characterized experimentally.

  4. Fatigue data for polyether ether ketone (PEEK under fully-reversed cyclic loading

    Directory of Open Access Journals (Sweden)

    Rakish Shrestha

    2016-03-01

    Full Text Available In this article, the data obtained from the uniaxial fully-reversed fatigue experiments conducted on polyether ether ketone (PEEK, a semi-crystalline thermoplastic, are presented. The tests were performed in either strain-controlled or load-controlled mode under various levels of loading. The data are categorized into four subsets according to the type of tests, including (1 strain-controlled fatigue tests with adjusted frequency to obtain the nominal temperature rise of the specimen surface, (2 strain-controlled fatigue tests with various frequencies, (3 load-controlled fatigue tests without step loadings, and (4 load-controlled fatigue tests with step loadings. Accompanied data for each test include the fatigue life, the maximum (peak and minimum (valley stress–strain responses for each cycle, and the hysteresis stress–strain responses for each collected cycle in a logarithmic increment. A brief description of the experimental method is also given.

  5. New glyme-cyclic imide lithium salt complexes as thermally stable electrolytes for lithium batteries

    Science.gov (United States)

    Tamura, Takashi; Hachida, Takeshi; Yoshida, Kazuki; Tachikawa, Naoki; Dokko, Kaoru; Watanabe, Masayoshi

    New glyme-Li salt complexes were prepared by mixing equimolar amounts of a novel cyclic imide lithium salt LiN(C 2F 4S 2O 4) (LiCTFSI) and a glyme (triglyme (G3) or tetraglyme (G4)). The glyme-Li salt complexes, [Li(G3)][CTFSI] and [Li(G4)][CTFSI], are solid and liquid, respectively, at room temperature. The thermal stability of [Li(G4)][CTFSI] is much higher than that of pure G4, and the vapor pressure of [Li(G4)][CTFSI] is negligible at temperatures lower than 100 °C. Although the viscosity of [Li(G4)][CTFSI] is high (132.0 mPa s at 30 °C), because of its high molar concentration (ca. 3 mol dm -3), its ionic conductivity at 30 °C is relatively high, i.e., 0.8 mS cm -1, which is slightly lower than that of a conventional organic electrolyte solution (1 mol dm -3 LiTFSI dissolved in propylene carbonate). The self-diffusion coefficients of a Li + cation, a CTFSI - anion, and a glyme molecule were measured by the pulsed gradient spin-echo NMR method (PGSE-NMR). The ionicity (dissociativity) of [Li(G4)][CTFSI] at 30 °C is ca. 0.5, as estimated from the PGSE-NMR diffusivity measurements and the ionic conductivity measurements. Results of linear sweep voltammetry revealed that [Li(G4)][CTFSI] is electrochemically stable in an electrode potential range of 0-4.5 V vs. Li/Li +. The reversible deposition-stripping behavior of lithium was observed by cyclic voltammetry. The [LiCoO 2|[Li(G4)][CTFSI]|Li metal] cell showed a stable charge-discharge cycling behavior during 50 cycles, indicating that the [Li(G4)][CTFSI] complex is applicable to a 4 V class lithium secondary battery.

  6. Microcracking in composite laminates under thermal and mechanical loading. Thesis

    Science.gov (United States)

    Maddocks, Jason R.

    1995-01-01

    Composites used in space structures are exposed to both extremes in temperature and applied mechanical loads. Cracks in the matrix form, changing the laminate thermoelastic properties. The goal of the present investigation is to develop a predictive methodology to quantify microcracking in general composite laminates under both thermal and mechanical loading. This objective is successfully met through a combination of analytical modeling and experimental investigation. In the analysis, the stress and displacement distributions in the vicinity of a crack are determined using a shear lag model. These are incorporated into an energy based cracking criterion to determine the favorability of crack formation. A progressive damage algorithm allows the inclusion of material softening effects and temperature-dependent material properties. The analysis is implemented by a computer code which gives predicted crack density and degraded laminate properties as functions of any thermomechanical load history. Extensive experimentation provides verification of the analysis. AS4/3501-6 graphite/epoxy laminates are manufactured with three different layups to investigate ply thickness and orientation effects. Thermal specimens are cooled to progressively lower temperatures down to -184 C. After conditioning the specimens to each temperature, cracks are counted on their edges using optical microscopy and in their interiors by sanding to incremental depths. Tensile coupons are loaded monotonically to progressively higher loads until failure. Cracks are counted on the coupon edges after each loading. A data fit to all available results provides input parameters for the analysis and shows them to be material properties, independent of geometry and loading. Correlation between experiment and analysis is generally very good under both thermal and mechanical loading, showing the methodology to be a powerful, unified tool. Delayed crack initiation observed in a few cases is attributed to a

  7. Effect of torsional loading of nickel-titanium instruments on cyclic fatigue resistance.

    Science.gov (United States)

    Cheung, Gary Shun-Pan; Oh, Seung-Hei; Ha, Jung-Hong; Kim, Sung Kyo; Park, Se-Hee; Kim, Hyeon-Cheol

    2013-12-01

    The aim of this study was to evaluate the effect of torsional preload on the cyclic fatigue life of nickel-titanium rotary instruments. ProFile (#25/0.06) (Dentsply Maillefer, Ballaigues, Switzerland) and ProTaper (F1; Dentsply Maillefer) were used. Each file was preloaded at 4 conditions (ie, no preloading and 25%, 50%, and 75% of mean ultimate torsional strength) of torsional prestress before the fatigue test. The torsional preloads were applied by securing 5 mm of the file tip while keeping the file straight, rotating it clockwise until the preset torque, and then returning to the original position. This motion was repeated until a preset number (10, 30, or 50) of repetitions were reached (n = 12). After torsional preloading, the number of cycles to failure was evaluated in a simulated canal. Data were analyzed using 2-way analysis of variance and the Duncan post hoc comparison. The fractured fragment surfaces were examined under a scanning electron microscope for the topographic features of fractured instruments. For both instruments, there was a significant effect because of the extent of torsional preloads. The 50% and 75% torsionally preloaded ProFile and all ProTaper preloading groups had a higher number of cycles to failure than the other group(s). There was little difference in the lateral view appearance between new and torsionally preloaded files. After cyclic fatigue testing, all preloaded instruments showed numerous microcracks adjacent to the fracture site on lateral view examination. The microcracks did not seem to follow the machining grooves on the instrument surface but rather ran irregularly. The torsional preloads within the superelastic limit of the material may improve the cyclic fatigue resistance of nickel-titanium rotary instruments. Copyright © 2013 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  8. The Investigation of Knitted Materials Bonded Seams Behaviour upon Cyclical Fatigue Loading

    Directory of Open Access Journals (Sweden)

    Gita BUSILIENĖ

    2017-08-01

    Full Text Available In this research uniaxial tension behaviour of PES knitted materials with bonded seams is analysed. The objects of the investigation were two types of knitted materials, having the same fibre composition (93 % PES, 7 % EL, but different in knitting pattern, i. e. plain single jersey and rib 1 × 1. Bonded overlap seams were formed by changing the orientation of knitted materials strips, i. e. parallel/parallel, parallel/bias, parallel/perpendicular, bias/bias and bias/perpendicular. The strips of each knitted material were joined by two types of thermoplastic polyurethane (PU films different in thickness (75 mm and 150 mm. Mechanical characteristics of bonded seams were defined in longitudinal direction. During uniaxial tension such parameters as maximal force Fmax (N and maximal elongation ɛmax (% were recorded from typical tension diagrams. The changes of tested specimens strength and deformation were compared before and after cyclical fatigue tension the conditions of which were 50 cycles up to tension force F equal 24.5 N. The results have shown that changes before and after cyclical fatigue tension are mostly determined by the structure of knitted materials, the orientation of knitted materials strips in bonded seam, but not effected by thermoplastic polyurethane film. These results are opposite compared to the results of biaxial tension of the same type of specimens, which have shown that changes before and after cyclical fatigue punching are mostly determined by the type of thermoplastic film, but not effected by the orientation of knitted materials strips in bonded seams. DOI: http://dx.doi.org/10.5755/j01.ms.23.2.16065

  9. Numerical Analysis of Carbon Fiber Reinforced Plastic (CFRP Shear Walls and Steel Strips under Cyclic Loads Using Finite Element Method

    Directory of Open Access Journals (Sweden)

    N. Askarizadeh

    2017-12-01

    Full Text Available Reinforced concrete shear walls are the main elements of resistance against lateral loads in reinforced concrete structures. These walls should not only provide sufficient resistance but also provide sufficient ductility in order to avoid brittle fracture, particularly under strong seismic loads. However, many reinforced concrete shear walls need to be stabilized and reinforced due to various reasons such as changes in requirements of seismic regulations, weaknesses in design and execution, passage of time, damaging environmental factors, patch of rebar in plastic hinges and in some cases failures and weaknesses caused by previous earthquakes or explosion loads. Recently, Fiber Reinforced Polymer (FRP components have been extensively and successfully used in seismic improvement. This study reinforces FRP reinforced concrete shear walls and steel strips. CFRP and steel strips are evaluated by different yield and ultimate strength. Numerical and experimental studies are done on walls with scale 1/2. These walls are exposed to cyclic loading. Hysteresis curves of force, drift and strain of FRP strips are reviewed in order to compare results of numerical work and laboratory results. Both numerical and laboratory results show that CFRP and steel strips increase resistance, capacity and ductility of the structure.

  10. Mechanical Degradation of Porous NiTi Alloys Under Static and Cyclic Loading

    Science.gov (United States)

    Hosseini, Seyyed Alireza

    2017-12-01

    Pore characteristics and morphology have significant effect on mechanical behavior of porous NiTi specimens. In this research, porous NiTi with different pore sizes, shapes and morphology were produced by powder metallurgy methods using space-holder materials. The effect of the pore characteristics on the mechanical properties was investigated by static and cyclic compression tests at body temperature. The results show that specimens with low porosity and isolated pores exhibit more mechanical strength and recoverable strain. The specimen with 36% porosity produced without space holder could preserve its properties up to 10% strain and its strain recovery was complete after cyclic compression tests. On the other hand, the specimens produced by a urea space holder with more than 60% interconnected porosity show rapid degradation of their scaffolds. The highly porous specimens degraded even below 5% strain due to crack formation and propagation in the thin pore walls. For highly porous specimens produced by a NaCl space holder, the pores are partially interconnected with a cubic shape; nevertheless, their mechanical behavior is close to low-porosity specimens.

  11. Deformation-strength Characteristics of Unsaturated Granular Subbase Course Material under Monotonic and Cyclic Loading

    OpenAIRE

    張, 媛

    2014-01-01

    Throughout a year, climatic changes highly influence the degree of saturation of subbase course layer inside pavement structures in cold snowy regions, such as Hokkaido, Japan. Besides, pavements have to transfer traffic loads from the asphalt-mixture layer to the subbase course layer. Accordingly, it is necessary to understand the mechanical behaviors of the subbase course layer effected by seasonal variations of degree of saturation and traffic loads. In this study, a series of monotonic an...

  12. Observations during static and cyclic undrained loading of dense Aalborg University sand no. 1

    DEFF Research Database (Denmark)

    Sabaliauskas, Tomas; Diaz, Alberto Troya; Ibsen, Lars Bo

    . Soil strength and stiffness are found to change depending on the type of loading applied. Effective friction angle is found to be changing during various phases of loading. Linear Mohr Coulomb model could potentially be sufficient for modeling the full spectrum of dense sand behavior if extended...... with a changing friction angle following the examined patterns of response. A total stress path based material model is presented in this paper....

  13. HANFORD DOUBLE SHELL TANK (DST) THERMAL & SEISMIC PROJECT SUMMARY OF COMBINED THERMAL & OPERATING LOADS

    Energy Technology Data Exchange (ETDEWEB)

    MACKEY, T.C.

    2006-03-17

    This report summarizes the results of the Double-Shell Tank Thermal and Operating Loads Analysis (TOLA) combined with the Seismic Analysis. This combined analysis provides a thorough, defensible, and documented analysis that will become a part of the overall analysis of record for the Hanford double-shell tanks (DSTs).

  14. Fatigue strength in polymer-reinforced concrete beams under cyclic loading

    International Nuclear Information System (INIS)

    Kwak, K.H.; Kim, J.J.

    1995-01-01

    This research focuses on producing an inexpensive polymer, and also on experiments for producing various colors of the high strength polymer concrete in concrete structures. At present, only a few tests on the shear behavior of polymer-reinforced concrete (PRC) beams have been reported. Even fewer experiments on fatigue loading have been carried out to date. In the current experiments, reinforced concrete beams with a polymer fraction are investigated. The beams in this study are reinforced with conventional stirrups at appropriate intervals, and are designed to take static and fatigue loads. The strength of the beams is measured and the behavior of the beams under each loading are observed to determine the advantages of adding a polymer to reinforced concrete beams. Since the shear-fatigue behavior of PRC beams is not well understood, the appropriate limit state model of PRC beams subjected to shear-fatigue loading is developed in this research by incorporating the uncertainties which are assessed based on fatigue test results. Using specimens of reinforced concrete or PRC beams with and without stirrups, compression and split cylinder tests, as well as fatigue tests, were performed. The static test data consist of load, displacement and strain measurements at specified reinforcement locations. In this study, mean regression S-N curves are obtained to investigate the shear-fatigue characteristics that the test results are distributed over a wide fatigue life range at the same fatigue load level but, in general, the mean shear-fatigue strength of PRC beams with stirrups is higher than for PRC beams without stirrups. In the static tests, it has been observed that the beams have the same fracture modes as those of reinforced concrete. In the fatigue tests, the PRC beams were observed to perform rather poorly with regard to impact load, but it can be said that the increase in strength and excellent repair performance of the beams were verified. (orig.)

  15. Study of the behavior of welded assemblies subjected to cyclic loads of variable amplitudes

    International Nuclear Information System (INIS)

    Plumier, A.

    1977-01-01

    The optimum design of structures subjected to variable loads requires the fatigue loading to be defined not only by the extreme stresses which can occur in the structure, but also by the distribution of the amplitudes of loadings. This emphasizes the importance of relations allowing the definition of permissible stresses under variable amplitude loading on the basis of permissible stresses under constant amplitude loading: such relations lead to a thorough use of the very numerous results acquired in classical fatigue testings. The statistical analysis of our tests results confirms, for four as welded joints, the good fit of theoretical values calculated on the basis of BIERETT's theory, so that this theory seems precise enough for calculations rules. However, the differences between theory and experiments, as well as regards the passage from classical fatigue to programmed fatigue, as for the definition of resistance of a welded joint on the basis of classes in classial fatigue, can reach as much as 30%. This lack of precision can be reduced by precise definition of joints classes, also defining permissible sizes of welds defects, on the one hand, and by the precise definition of a curve taking account of an influence of the severity of the notch effect of joints on the passage from classical fatigue to programmed fatigue, on the other hand. Our tests results, which were obtained on joints with very weak or very strong notches led to suggest such a curve

  16. Crack propagation behaviour in stainless steel AISI 316L at elevated temperatures under static and cyclic loading

    International Nuclear Information System (INIS)

    Lange, H.

    1991-01-01

    Experimental investigations of crack growth under creep and creep-fatigue conditions are presented. The experiments were performed with the austenitic steel AISI 316L, that will be used in fast breeder reactors. A comparison of crack propagation behaviour at temperatures of T = 550deg C and T = 700deg C in common through-thickness cracked specimens and in plates containing surface cracks is carried out by application of several fracture mechanics parameters. The quantitative description of crack initiation times and crack velocities is persued particularly. The propagation rate of one-dimensional cracks under cyclic loading conditions at T = 550deg C is also treated with fracture mechanical methods. The influence of the hold periods on crack speed is discussed. (orig.) [de

  17. Experimental and Analytical Study of Slender Reinforced Concrete Shear Wall under Cyclic In-Plane Lateral Load

    Directory of Open Access Journals (Sweden)

    Diego Sosa

    2017-01-01

    Full Text Available This study describes a slender reinforced concrete shear wall experimental test under in-plane cyclic lateral load, and the development of an analytical model which uses the fiber method approach to consider hysteretic nonlinear constitutive material models behavior. The shear wall tested had bending behavior, since the amount of longitudinal reinforcing bars produced weak bending capacity compared to the shear strength. The analytical model tries to represent global and local behavior of the wall, and its calibration is based on reaching experimental parameters like area enclosed and secant stiffness on every loop. After the analytical model was calibrated, the relation between some performance points and damage states observed during the test is studied.

  18. Three-dimensional boron particle loaded thermal neutron detector

    Science.gov (United States)

    Nikolic, Rebecca J.; Conway, Adam M.; Graff, Robert T.; Kuntz, Joshua D.; Reinhardt, Catherine; Voss, Lars F.; Cheung, Chin Li; Heineck, Daniel

    2014-09-09

    Three-dimensional boron particle loaded thermal neutron detectors utilize neutron sensitive conversion materials in the form of nano-powders and micro-sized particles, as opposed to thin films, suspensions, paraffin, etc. More specifically, methods to infiltrate, intersperse and embed the neutron nano-powders to form two-dimensional and/or three-dimensional charge sensitive platforms are specified. The use of nano-powders enables conformal contact with the entire charge-collecting structure regardless of its shape or configuration.

  19. Load Frequency Control of AC Microgrid Interconnected Thermal Power System

    Science.gov (United States)

    Lal, Deepak Kumar; Barisal, Ajit Kumar

    2017-08-01

    In this paper, a microgrid (MG) power generation system is interconnected with a single area reheat thermal power system for load frequency control study. A new meta-heuristic optimization algorithm i.e. Moth-Flame Optimization (MFO) algorithm is applied to evaluate optimal gains of the fuzzy based proportional, integral and derivative (PID) controllers. The system dynamic performance is studied by comparing the results with MFO optimized classical PI/PID controllers. Also the system performance is investigated with fuzzy PID controller optimized by recently developed grey wolf optimizer (GWO) algorithm, which has proven its superiority over other previously developed algorithm in many interconnected power systems.

  20. Estimation of crack growth in the creep range during plastic cyclic loading

    International Nuclear Information System (INIS)

    Kullik, M.; Maile, K.

    1988-01-01

    The effect of creep stress on the crack growth at high temperatures was examined using the heat-resistant steel 13 CrMo 44 (St. 1.7335). The material was loaded with a static load at 560deg C, which led to a permanent strain of 2%. The tensile test values remained unchanged, but the notch impact work was considerably reduced. The fatigue crack growth in CT samples was not affected by the creep prestress. However, due to higher stress in the remaining ligament there was an acceleration in cracking compared to the initial state in the CCT samples. Stopping times at the load reversal points led to additional creep damage and therefore to a further rise in the crack growth rate. The dependence of the crack growth rate on frequency at high temperatures can be approximately described in the creep range by a linear superimposition of fatigue crack growth and creep crack growth. (orig./DG) [de

  1. Thermal Vacuum Test Correlation of A Zero Propellant Load Case Thermal Capacitance Propellant Gauging Analytics Model

    Science.gov (United States)

    McKim, Stephen A.

    2016-01-01

    This thesis describes the development and test data validation of the thermal model that is the foundation of a thermal capacitance spacecraft propellant load estimator. Specific details of creating the thermal model for the diaphragm propellant tank used on NASA's Magnetospheric Multiscale spacecraft using ANSYS and the correlation process implemented to validate the model are presented. The thermal model was correlated to within plus or minus 3 degrees Centigrade of the thermal vacuum test data, and was found to be relatively insensitive to uncertainties in applied heat flux and mass knowledge of the tank. More work is needed, however, to refine the thermal model to further improve temperature predictions in the upper hemisphere of the propellant tank. Temperatures predictions in this portion were found to be 2-2.5 degrees Centigrade lower than the test data. A road map to apply the model to predict propellant loads on the actual MMS spacecraft toward its end of life in 2017-2018 is also presented.

  2. Particle loading time and humidity effects on the efficiency of an N95 filtering facepiece respirator model under constant and inhalation cyclic flows.

    Science.gov (United States)

    Mahdavi, Alireza; Haghighat, Fariborz; Bahloul, Ali; Brochot, Clothilde; Ostiguy, Claude

    2015-06-01

    It is necessary to investigate the efficiencies of filtering facepiece respirators (FFRs) exposed to ultrafine particles (UFPs) for long periods of time, since the particle loading time may potentially affect the efficiency of FFRs. This article aims to investigate the filtration efficiency for a model of electrostatic N95 FFRs with constant and 'inhalation-only' cyclic flows, in terms of particle loading time effect, using different humidity conditions. Filters were exposed to generated polydisperse NaCl particles. Experiments were performed mimicking an 'inhalation-only' scenario with a cyclic flow of 85 l min(-1) as the minute volume [or 170 l min(-1) as mean inhalation flow (MIF)] and for two constant flows of 85 and 170 l min(-1), under three relative humidity (RH) levels of 10, 50, and 80%. Each test was performed for loading time periods of 6h and the particle penetration (10-205.4nm in electrical mobility diameter) was measured once every 2h. For a 10% RH, the penetration of smaller size particles (penetrating particle size (MPPS), decreased over time for both constant and cyclic flows. For 50 and 80% RH levels, the changes in penetration were typically observed in an opposite direction with less magnitude. The penetrations at MPPS increased with respect to loading time under constant flow conditions (85 and 170 l min(-1)): it did not substantially increase under cyclic flows. The comparison of the cyclic flow (85 l min(-1) as minute volume) and constant flow equal to the cyclic flow minute volume indicated that, for all conditions the penetration was significantly less for the constant flow than that of cyclic flow. The comparison between the cyclic (170 l min(-1) as MIF) and constant flow equal to cyclic flow MIF indicated that, for the initial stage of loading, the penetrations were almost equal, but they were different for the final stages of the loading time. For a 10% RH, the penetration of a wide range of sizes was observed to be higher with the

  3. Literature review on cyclic lateral loading effects of mono-bucket foundations

    DEFF Research Database (Denmark)

    Kapitanov, Lachezar Rosenov; Duroska, Peter; Quirante, Cesar Antonio Garcia

    2016-01-01

    are of interest for its simplicity, however, they cannot normally consider the load frequency as well as soil real response due to pore-pressure development. On the other hand, numerical analyses including sophisticated constitutive soil models which account for the more realistic response are available...

  4. Development of Pore Pressure in Cohesionless Soils with Initial Shear Stresses during Cyclic Loading

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo; Jacobsen, H. Moust

    1989-01-01

    A number of triaxial tests with the loading harmonically oscillating around an initial and anisotropic stress state have been performed. Hereby the influence of the initial shear stress on the development of pore pressure in a cohesionless  sand specimen have been clarified. A simple theory...

  5. Analysis of carbon based materials under fusion relevant thermal loads

    International Nuclear Information System (INIS)

    Compan, Jeremie Saint-Helene

    2008-01-01

    Carbon based materials (CBMs) are used in fusion devices as plasma facing materials for decades. They have been selected due to the inherent advantages of carbon for fusion applications. The main ones are its low atomic number and the fact that it does not melt but sublimate (above 3000 C) under the planned working conditions. In addition, graphitic materials retain their mechanical properties at elevated temperatures and their thermal shock resistance is one of the highest, making them suitable for thermal management purpose during long or extremely short heat pulses. Nuclear grade fine grain graphite was the prime form of CBM which was set as a standard but when it comes to large fusion devices created nowadays, thermo-mechanical constraints created during transient heat loads (few GW.m-2 can be deposited in few ms) are so high that carbon/carbon composites (so-called Carbon Fiber Composites (CFCs)) have to be utilized. CFCs can achieve superior thermal conductivity as well as mechanical properties than fine grain graphite. However, all the thermo-mechanical properties of CFCs are highly dependent on the loading direction as a consequence of the graphite structure. In this work, the background on the anisotropy of the graphitic structures but also on the production of fine grain graphite and CFCs is highlighted, showing the major principles which are relevant for the further understanding of the study. Nine advanced CBMs were then compared in terms of microstructure and thermo-mechanical properties. Among them, two fine grain graphites were considered as useful reference materials to allow comparing advantages reached by the developed CFCs. The presented microstructural investigation methods permitted to make statements which can be applied for CFCs presenting similarities in terms of fiber architecture. Determination of the volumetric percentage of the major sub-units of CFCs, i.e. laminates, felt layers or needled fiber groups, lead to a better understanding on

  6. Identification of error sources in fatigue analyses for thermal loadings

    International Nuclear Information System (INIS)

    Binder, Franz; Gantz, Dieter

    2006-09-01

    To identify thermal loadings (thermal shocks and thermal stratification), in German NPPs, special fatigue monitoring systems have been installed. The detailed temperature measurement uses sheathed thermocouples, which are located on the external component surface. Tightening straps are used for the widespread method of locking the thermocouples into position. The calculation of material fatigue for a loading sequence has to be carried out based on the measured temperature profile of the outer component surface. Should the analysis comply with the ASME III code, Section NB, alternatively the Articles NB-3200 or NB-3600 can be applied. In fatigue analyses based on the outer-surface temperature, the thermal situation at the inner-surface has to be determined (inverse temperature-field calculation). This leading analysis step is not regulated in the ASME III code. Using general purpose finite element programs, this problem cannot be explicitly solved, because it requires knowledge of the thermal situation at all boundaries (temperature or heat transfer). In the frequently practiced method in a finite element calculation, the inner surface temperature profile is varied until a satisfactory compliance of the calculated outer surface temperature with the measured profile is obtained. Since the input parameters are derived from a variable field, the variation process is large-scale and non-explicit (another input-configuration may cause a similar outer surface temperature). Furthermore, the remaining deviation cannot be quantified regarding the resulting error in the calculated material fatigue. Five typical thermocouple installation methods existing in German LWRs were compared and evaluated regarding the quality of outer surface temperature acquisition. With the evaluation of the experimental data, the essential finding is that for the test transients the maximum of the true outer surface temperature change rate is registered incorrectly with all thermocouple

  7. Performance of tungsten-based materials and components under ITER and DEMO relevant steady-state thermal loads

    Energy Technology Data Exchange (ETDEWEB)

    Ritz, Guillaume Henri

    2011-07-01

    In nuclear fusion devices the surfaces directly facing the plasma are irradiated with high energy fluxes. The most intense loads are deposited on the divertor located at the bottom of the plasma chamber, which has to withstand continuous heat loads with a power density of several MW . m{sup -2} as well as transient events. These are much shorter (in the millisecond and sub-millisecond regime) but deposit a higher power densities of a few GW . m{sup -2}. The search for materials that can survive to those severe loading conditions led to the choice of tungsten which possesses advantageous attributes such as a high melting point, high thermal conductivity, low thermal expansion and an acceptable activation rate. These properties made it an attractive and promising candidate as armor material for divertors of future fusion devices such as ITER and DEMO. For the DEMO divertor, conceptual studies on helium-cooled tungsten plasma-facing components were performed. The concept was realized and tested under DEMO specific cyclic thermal loads. The examination of the plasma-facing components by microstructural analyses before and after thermal loading enabled to determine the mechanisms for components failure. Among others, it clearly showed the impact of the tungsten grade and the thermal stress induced crack formation on the performance of the armor material and in general of the plasma-facing component under high heat loads. A tungsten qualification program was launched to study the behaviour of various tungsten grades, in particular the crack formation, under fusion relevant steady-state thermal loads. In total, seven commercially available materials from two industrial suppliers were investigated. As the material's thermal response is strongly related to its microstructure, this program comprised different material geometries and manufacturing technologies. It also included the utilization of an actively cooled specimen holder which has been designed to perform

  8. Performance of tungsten-based materials and components under ITER and DEMO relevant steady-state thermal loads

    International Nuclear Information System (INIS)

    Ritz, Guillaume Henri

    2011-01-01

    In nuclear fusion devices the surfaces directly facing the plasma are irradiated with high energy fluxes. The most intense loads are deposited on the divertor located at the bottom of the plasma chamber, which has to withstand continuous heat loads with a power density of several MW . m -2 as well as transient events. These are much shorter (in the millisecond and sub-millisecond regime) but deposit a higher power densities of a few GW . m -2 . The search for materials that can survive to those severe loading conditions led to the choice of tungsten which possesses advantageous attributes such as a high melting point, high thermal conductivity, low thermal expansion and an acceptable activation rate. These properties made it an attractive and promising candidate as armor material for divertors of future fusion devices such as ITER and DEMO. For the DEMO divertor, conceptual studies on helium-cooled tungsten plasma-facing components were performed. The concept was realized and tested under DEMO specific cyclic thermal loads. The examination of the plasma-facing components by microstructural analyses before and after thermal loading enabled to determine the mechanisms for components failure. Among others, it clearly showed the impact of the tungsten grade and the thermal stress induced crack formation on the performance of the armor material and in general of the plasma-facing component under high heat loads. A tungsten qualification program was launched to study the behaviour of various tungsten grades, in particular the crack formation, under fusion relevant steady-state thermal loads. In total, seven commercially available materials from two industrial suppliers were investigated. As the material's thermal response is strongly related to its microstructure, this program comprised different material geometries and manufacturing technologies. It also included the utilization of an actively cooled specimen holder which has been designed to perform sophisticated

  9. Dynamic Creep Buckling: Analysis of Shell Structures Subjected to Time-dependent Mechanical and Thermal Loading

    Science.gov (United States)

    Simitses, G. J.; Carlson, R. L.; Riff, R.

    1985-01-01

    The objective of the present research is to develop a general mathematical model and solution methodologies for analyzing the structural response of thin, metallic shell structures under large transient, cyclic, or static thermomechanical loads. Among the system responses associated with these loads and conditions are thermal buckling, creep buckling, and ratcheting. Thus geometric and material nonlinearities (of high order) can be anticipated and must be considered in developing the mathematical model. A complete, true ab-initio rate theory of kinematics and kinetics for continuum and curved thin structures, without any restriction on the magnitude of the strains or the deformations, was formulated. The time dependence and large strain behavior are incorporated through the introduction of the time rates of metric and curvature in two coordinate systems: fixed (spatial) and convected (material). The relations between the time derivative and the covariant derivative (gradient) were developed for curved space and motion, so the velocity components supply the connection between the equations of motion and the time rates of change of the metric and curvature tensors.

  10. Rammed earth walls strengthened with polyester fabric strips: Experimental analysis under in-plane cyclic loading

    Czech Academy of Sciences Publication Activity Database

    Miccoli, L.; Müller, U.; Pospíšil, Stanislav

    2017-01-01

    Roč. 149, September (2017), s. 29-36 ISSN 0950-0618 R&D Projects: GA MŠk(CZ) LO1219 Keywords : rammed earth * pseudo-dynamic loads * shear-compression tests * strengthening * polyester fabric strips Subject RIV: JM - Building Engineering OBOR OECD: Construction engineering, Municipal and structural engineering Impact factor: 3.169, year: 2016 http://www.sciencedirect.com/science/article/pii/S0950061817310000

  11. Fracture mechanics analysis of a longitudinally cracked bend under cyclic loading

    International Nuclear Information System (INIS)

    Kussmaul, K.; Uhlmann, D.; Koski, K.; Hunger, H.

    1993-01-01

    Where information is available about the actual crack configuration, the boundary conditions of the load case, the geometry, and the material characteristics, extensive numerical calculations by means of the finite element method allow crack growth to be calculated for pipe bends carrying longitudinal cracks. If the influence of multiple-crack fields is taken into account in the crack growth calculations, good agreement is obtained with experimental findings. Less sophisticated assessments of individual cracks furnish results which are on the safe side. (author)

  12. Performance of HESCO Bastion Units Under Combined Normal and Cyclic Lateral Loading

    Science.gov (United States)

    2017-02-01

    13 Figure 13. Drawing of steel plate for applying normal loading to top of test specimen, showing attachment point for...Laboratory photograph showing the connection between the reaction wall and the steel plate atop the HESCO bastion...kilonewtons pounds (mass) 0.45359237 kilograms pounds (mass) per square foot 4.882428 kilograms per square meter square feet 0.09290304 square meters

  13. MEMS measurements of single cell stiffness decay due to cyclic mechanical loading.

    Science.gov (United States)

    Barazani, Bruno; Warnat, Stephan; MacIntosh, Andrew J; Hubbard, Ted

    2017-08-25

    The goal of this study was to measure the mechanical stiffness of individual cells and to observe changes due to the application of repeated cell mechanical loads. 28 single baker's yeast cells (Saccharomyces cerevisiae) were fatigue tested and had their stiffness measured during repetitive loading cycles performed by a MEMS squeezer in aqueous media. Electrothermal micro-actuators compressed individual cells against a reference back spring; cell and spring motions were measured using a FFT image analysis technique with ~10 nm resolution. Cell stiffness was calculated based on measurements of cell elongation vs. applied force which resulted in stiffness values in the 2-10 N/m range. The effect of increased force was studied for cells mechanically cycled 37 times. Cell stiffness decreased as the force and the cycle number increased. After 37 loading cycles (~4 min), forces of 0.24, 0.29, 0.31, and 0.33 μN caused stiffness drops of 5%, 13%, 31% and 41% respectively. Cells force was then set to 0.29 μN and cells were tested over longer runs of 118 and 268 cycles. After 118 cycles (~12 min) cells experienced an average stiffness drop of 68%. After 268 cycles (~25 min) cells had a stiffness drop of 77%, and appeared to reach a stiffness plateau of 20-25% of the initial stiffness after approximately 200 cycles.

  14. Synergistic Effects of Stress-Rupture and Cyclic Loading on Strain Response of Fiber-Reinforced Ceramic-Matrix Composites at Elevated Temperature in Oxidizing Atmosphere

    Directory of Open Access Journals (Sweden)

    Longbiao Li

    2017-02-01

    Full Text Available In this paper, the synergistic effects of stress rupture and cyclic loading on the strain response of fiber-reinforced ceramic-matrix composites (CMCs at elevated temperature in air have been investigated. The stress-strain relationships considering interface wear and interface oxidation in the interface debonded region under stress rupture and cyclic loading have been developed to establish the relationship between the peak strain, the interface debonded length, the interface oxidation length and the interface slip lengths. The effects of the stress rupture time, stress levels, matrix crack spacing, fiber volume fraction and oxidation temperature on the peak strain and the interface slip lengths have been investigated. The experimental fatigue hysteresis loops, interface slip lengths, peak strain and interface oxidation length of cross-ply SiC/MAS (magnesium alumino-silicate, MAS composite under cyclic fatigue and stress rupture at 566 and 1093 °C in air have been predicted.

  15. Maximum thermal loading test of BWR fuel assembly

    International Nuclear Information System (INIS)

    Nakajima, Yoshitaka; Yoshimura, Kunihiro; Nakamura, Satoshi; Ishizuka, Takao.

    1987-01-01

    Various proving tests on the reliability of nuclear power plants have been conducted at the Nuclear Power Engineering Test Center and at the Japan Power Plant Engineering and Inspection Corporation. The tests were initiated at the request of the Ministry of International Trade and Industry (MITI). Toshiba undertook one of the proving tests on the reliability of nuclear fuel assembly; the maximum thermal loading test of BWR fuel assembly from the Nuclear Power Engineering Test Center. These tests are part of the proving tests mentioned above, and their purpose is to confirm the reliability of the thermal hydraulic engineering techniques. Toshiba has been engaged for the past nine years in the design, fabrication and testing of the equipment. For the project, a test model fuel assembly was used to measure the critical power of the BWR fuel assembly and the void and fluidity of the coolant. From the test results, it has been confirmed that the heat is transferred safely from the fuel assembly to the coolant in the BWR nuclear power plant. In addition, the propriety and reliability of the thermal hydraulic engineering techniques for the fuel assembly have been proved. (author)

  16. Relationship between thermal loading and parasitism in the mosquitofish

    International Nuclear Information System (INIS)

    Aho, J.M.; Gibbons, J.W.; Esch, G.W.

    1976-01-01

    The relationship between thermal loading and parasitism was examined in 980 mosquitofish, Gambusia affinis, taken from areas of varying thermal conditions at the Savannah River Plant (SRP) near Aiken, S. C. Collections were made at 2-week intervals from May to August 1974 and again from January to February 1975. The metacercaria of two strigeid trematodes, Ornithodiplostomum ptychocheilus and Diplostomum scheuringi were the only species of parasites recovered. Ornithodiplostomum ptychocheilus was always found encysted in the brain and eyes, whereas D. scheuringi was restricted exclusively to the body cavity. The density of the body-cavity parasite was highest in fish from areas of ambient temperatures and declined in fish from areas with higher water temperatures. The density of the brain parasite, on the other hand, was higher in fish from areas directly receiving thermal effluent than in fish from ambient-temperature areas. The body-cavity parasite was absent from mosquitofish from Pond C, but the infection percentages were relatively consistent in fish from other areas in the Par Pond system regardless of water temperature. The brain metacercaria were recovered from 95 percent of fish from Pond C

  17. A Splitting Scheme for Solving Reaction-Diffusion Equations Modeling Dislocation Dynamics in Materials Subjected to Cyclic Loading

    Science.gov (United States)

    Pontes, J.; Walgraef, D.; Christov, C. I.

    2010-11-01

    Strain localization and dislocation pattern formation are typical features of plastic deformation in metals and alloys. Glide and climb dislocation motion along with accompanying production/annihilation processes of dislocations lead to the occurrence of instabilities of initially uniform dislocation distributions. These instabilities result into the development of various types of dislocation micro-structures, such as dislocation cells, slip and kink bands, persistent slip bands, labyrinth structures, etc., depending on the externally applied loading and the intrinsic lattice constraints. The Walgraef-Aifantis (WA) (Walgraef and Aifanits, J. Appl. Phys., 58, 668, 1985) model is an example of a reaction-diffusion model of coupled nonlinear equations which describe 0 formation of forest (immobile) and gliding (mobile) dislocation densities in the presence of cyclic loading. This paper discuss two versions of the WA model and focus on a finite difference, second order in time 1-Nicolson semi-implicit scheme, with internal iterations at each time step and a spatial splitting using the Stabilizing, Correction (Christov and Pontes, Mathematical and Computer Modelling, 35, 87, 2002) for solving the model evolution equations in two dimensions. The results of two simulations are presented. More complete results will appear in a forthcoming paper.

  18. The mechanical properties of nanofilled resin-based composites: the impact of dry and wet cyclic pre-loading on bi-axial flexure strength.

    Science.gov (United States)

    Curtis, Andrew R; Palin, William M; Fleming, Garry J P; Shortall, Adrian C C; Marquis, Peter M

    2009-02-01

    To determine the influence of nano-sized filler particles and agglomerates of nanoparticles ('nanoclusters') in resin-based composite (RBC) materials on the bi-axial flexure strength (BFS) following cyclic pre-loading and storage in a 'dry' or 'wet' environment. Seven commercially available RBC restoratives, Heliomolar (Ivoclar Vivadent, Schaan, Liechtenstein), Z100 MP Restorative, Filtek Z250, Filtek Supreme (3M ESPE, St. Paul, MN, USA) in Body (FSB) and Translucent (FST) shades, Grandio and Grandio Flow (VOCO, Cuxhaven, Germany), containing differing filler particle types and morphologies were investigated. Specimens were pre-loaded at 20, 50 or 100 N for 2000 cycles and stored in a 'dry' or 'wet' environment prior to BFS testing. A general linear model analysis of variance highlighted a reduction in the BFS following pre-loading, however, individual RBC materials responded differently. The RBCs containing agglomerated nano-sized particles or 'nanoclusters' (Filtek Supreme) demonstrated distinctive and unique patterns of response to pre-loading. Cyclic pre-loading at 20 and 50 N significantly increased the Weibull modulus of both FSB (8.53+/-1.91 and 10.23+/-2.29) and FST (16.89+/-3.78 and 10.91+/-2.45) compared with FSB and FST control (no pre-cyclic load) specimens (5.98+/-1.34 and 7.99+/-1.78, respectively). BFS of FSB and FST was maintained or significantly increased compared with the other materials following 20 and 50 N cyclic pre-load (P<0.05). The 'nanoclusters' provided a distinct reinforcing mechanism compared with the microhybrid, microfill or nanohybrid RBC systems resulting in significant improvements to the strength and reliability, irrespective of the environmental storage and testing conditions. Silane infiltration within interstices of the nanoclusters may modify the response to pre-loading induced stress, thereby enhancing damage tolerance and providing the potential for improved clinical performance.

  19. Effects of constant and cyclical thermal regimes on growth and feeding of juvenile cutthroat trout of variable sizes

    Science.gov (United States)

    M. H. Meeuwig; J. B. Dunham; J. P. Hayes; G. L. Vinyard

    2004-01-01

    The effects of constant (12, 18, and 24°C) and cyclical (daily variation of 15–21 and 12–24 °C) thermal regimes on the growth and feeding of Lahontan cutthroat trout (Oncorhynchus clarki henshawi) of variable sizes were examined. Higher constant temperatures (i.e., 24°C) and more variable daily temperatures (i.e., 12–24°C daily cycle) negatively...

  20. Effect of autoclave sterilization on the cyclic fatigue resistance of thermally treated Nickel-Titanium instruments.

    Science.gov (United States)

    Zhao, D; Shen, Y; Peng, B; Haapasalo, M

    2016-10-01

    To compare the cyclic fatigue resistance of HyFlex CM, Twisted Files (TF), K3XF, Race, and K3, and evaluate the effect of autoclave sterilization on the cyclic fatigue resistance of these instruments both before and after the files were cycled. Five types of NiTi instruments with similar size 30, .06 taper were selected: HyFlex CM, TF, K3XF, Race and K3. Files were tested in a simulated canal with a curvature of 60° and a radius of 3 mm. The number of cycles to failure of each instrument was determined to evaluate cyclic fatigue resistance. Each type of instruments was randomly divided into four experimental groups: group 1 (n = 20), unsterilized instruments; group 2 (n = 20), pre-sterilized instruments subjected to 10 cycles of autoclave sterilization; group 3 (n = 20), instruments tested were sterilized at 25%, 50% and 75% of the mean cycles to failure as determined in group 1, and then cycled to failure; group 4 (n = 20), instruments cycled in the same manner as group 3 but without sterilization. The fracture surfaces of instruments were examined by scanning electron microscopy (SEM). HyFlex CM, TF and K3XF had significantly higher cyclic fatigue resistance than Race and K3 in the unsterilized group 1 (P Autoclave sterilization significantly increased the MCF of HyFlex CM and K3XF (P Autoclaving extended the cyclic fatigue life of HyFlex CM and K3XF. © 2015 International Endodontic Journal. Published by John Wiley & Sons Ltd.

  1. Comparison effect of artificial tooth type and cyclic loading on the bond strength to auto-polymerized acrylic denture base resins

    Directory of Open Access Journals (Sweden)

    Fateme Nematollahi

    2013-05-01

    Full Text Available   Background and Aims: Failure of bonding between artificial teeth and denture base material is a considerable problem for patients who wear dentures. According to the different impact of artificial teeth and different information about resistance force of mastication and also with deficiency in researchs, this study was designed to compare the bond strength of composite and acrylic artificial teeth to auto-polymerized denture base resins with and without cyclic loading.   Materials and Methods: In this experimental and in vitro study, an acrylic resin auto-polymerized (Rapid Repair, Dentsply and four artificial teeth (Acrylic Marjan new, Composite Glamour teeth and Ivoclar acrylic and composite teeth were used. Therefore, 8 groups of 10 specimens each were evaluated. All specimens were thermocycled for 5000 cycles, in water baths between 5 and 55 ◦ C. Half the specimens in each group were treated with cyclic loading at 50N for 14, 400 cycles at 1.2 Hz. The shear bond strengths were measured using a Universal Testing Machine. Data were analyzed using Two-way ANOVA test.   Results: Statistical analysis demonstrated no significant effect of cyclic loading on the shear bond strength, but the type of artificial tooth affected the shear bond strength (P=0.006. Also, the interaction between Cyclic loading and the type of artificial tooth showed no significant difference (P=0.98. Tukey test showed that acrylic teeth (Ivoclar had statistically higher bond strength values than that of other teeth (PGlamour=0.02, (PComposite ivoclar=0.01 and (PMarjan new=0.02.   Conclusion: Within the limitation of this study, the predominant type of fracture in all groups was cohesive, therefore the bond strength was adequate in all teeth and the type of artificial tooth may influence the bond strength of denture teeth to denture base resin. Cyclic loading had no significant effect on the bond strength of denture teeth to the auto-polymerized acrylic resin.

  2. THE RESPONSE OF TUNNEL LINING ON THERMAL LOADING

    Directory of Open Access Journals (Sweden)

    Markéta Levorová

    2012-07-01

    Full Text Available The long-term functionality, i.e. stability of the lining of disposal tunnels is a precondition for the safe removal and reprocessing of spent nuclear waste from deep underground repositories in the near or more distant future. The reason for removing containers with radioactive waste from such repositories lies in the potential development of presently unavailable “perfect” technology for its reprocessing. The stability problems of the tunnel lining exposed to the long-term thermal load generated by the waste in the disposal container was the subject of one task of the European TIMODAZ project (Thermal Impact on the Damaged Zone around a Radioactive Waste Disposal in Clay Host Rocks. Research was carried out by means of physical modeling. Although the project was terminated in September 2010, recorded data is being further analyzed. This paper describes the design, construction and results of an in-situ model which has been built at the Underground Research Centre Josef in the Czech Republic.

  3. Effect of Surface Impulsive Thermal Loads on Fatigue Behavior of Constant Volume Propulsion Engine Combustor Materials

    National Research Council Canada - National Science Library

    Zhu, Dongming

    2004-01-01

    .... In this study, a simulated engine test rig has been established to evaluate thermal fatigue behavior of a candidate engine combustor material, Haynes 188, under superimposed CO2 laser surface impulsive thermal loads (30 to 100 Hz...

  4. Dynamic deformation and failure characteristic of rock foundation by means of effect of cyclic shear loading

    International Nuclear Information System (INIS)

    Fujiwara, Yoshikazu; Hibino, Satoshi; Kanagawa, Tadashi; Komada, Hiroya; Nakagawa, Kameichiro

    1984-01-01

    The main structures of nuclear power plants are built on hard and soft rocks. The rock-dynamic properties used for investigating the stability of the structures have been determined so far by laboratory tests for soft rocks. In hard rocks, however, joints and cracks exist, and the test including these effects is not able to be performed in laboratories at present. Therefore, a dynamic repeating shearing test equipment to be used under the condition including the joints and cracks of actual ground has been made for a base rock of tuff breccia. In this paper, the test results are reported as follows. The geological features of the testing site and the arrangement of tested rocks, the preparation for tests, test equipment, loading method, measuring method, analysis, and the result and the examination. The results of dynamic deformation and failure characteristics were as follows: (1) the dynamic shear-elasticity-modulus Gd of the base rock showed greater values as the normal stress increased, while Gd decreased and showed the strain dependence as the dynamic shear strain amplitude γ increased; (2) the relationship between Gd and γ was well represented with the equation proposed by Hardin-Drnevich; (3) damping ratio increased as γ increased, and decreased as normal stress increased; (4) When a specimen was about to break, γ suddenly increased, and the dynamic shear strain amplitude at yield point was in the range of approximately (3.4 to 4.1) x 10 -3 . (Wakatsuki, Y.)

  5. Estimation of crack growth in the creep range during plastic cyclic loading

    International Nuclear Information System (INIS)

    Kullik, M.; Maile, K.

    1990-01-01

    Crack growth investigations were performed on the creep-resistant steel 13 CrMo 4 4 in the fatigue and the creep fatigue regime, especially regarding the influence of creep damage on crack growth. To this effect, 2% creep strain was applied to the material at a temperature of 560deg C. The crack propagation rate was determined as a functionof the specimen shape, temperature, test frequency and hold times. In the case of compact tension (CT-)specimens, creep pretreatment does not affect crack growth. For center-cracked tension (CCT-)specimens, however, the creep pretreatment results in a considerable increase in the crack propagation rate. Hold times of 90 minutes at maximum loading cause an increase in da/dN due to further cavity nucleation. The hold time at which cavity nucleation might occur is evaluated. The dependency on frequency of crack growth may be evaluated by means of a linear superposition of creep and fatigue crack growth. The transition frequency above which pure fatigue crack growth occurs is calculated and the regimes of fatigue, creep and creep-fatigue interaction with environmental influences are characterized. (orig.)

  6. Effect of highly reflective roofing sheet on building thermal loads for a school in Osaka

    Directory of Open Access Journals (Sweden)

    Yuan Jihui

    2017-01-01

    Full Text Available Currently, urban heat island (UHI phenomenon and building energy consumptions are becoming serious. Strategies to mitigate UHI and reduce building energy consumptions are implemented worldwide. In Japan, as an effective means of mitigating UHI and saving energy of buildings, highly reflective (HR and green roofs are increasingly used. In order to evaluate the effect of roofs with high reflection and thermal insulation on the energy conservation of buildings, we investigated the roof solar reflectivity of the subject school in Osaka, in which the HR roofing sheet was installed on the roof from 2010. Thermal loads, including cooling and heating loads of the top floor of school, were calculated using the thermal load calculation software, New HASP/ACLD-β. Comparing the thermal loads after HR roofing sheet installation to previous, the annual thermal load decreased about 25 MJ/m2-year and the cooling load decreased about 112 MJ/m2-year. However, the heating load increased about 87 MJ/m2-year in winter. To minimize the annual thermal load, thermal insulation of the roof was also considered be used together with HR roofing sheet in this study. The results showed that the combination of HR roofing sheet and high thermal insulation is more effective to reduce the annual thermal load.

  7. Thermal ice loads on dams and ancillary structures: A brief review

    International Nuclear Information System (INIS)

    Gerard, R.

    1989-01-01

    A major consideration in the design of low to medium head dams in cold regions is the thrust exerted by thermal expansion of a solid ice sheet. Such loads are also of concern in the design of gates, intakes and other ancillary structures. Such loads can be greater than 300-400 kilo Newtons per meter, and are of greatest concern when ice is unshielded by snow from temperature fluctuations. Details are presented of calculation of thermal ice loads, and field measurements of thermal ice forces. Past structural failures, field and laboratory investigations, and analyses, all confirm that thermal ice loads on wide structures such as dams, and isolated structures such as bridge piers and water intakes, can be much more significant than is suggested by the loads currently specified in various North American design guidelines for hydraulic structures. While some guidelines for thermal ice loads are excessively conservative, particularly for protected situations such as gates set between piers, in other more common situations they are dangerously low. Three useful approaches that would yield information for improving thermal ice load specification are: hindcast upper bounds on thermal ice loads by assessing the ice regime and load bearing capacity of existing structures; field measurement of thermal ice loads and stresses using modern instrumentation; and measurement and analysis of the formation and movement of lake and reservoir ice covers. 23 refs., 4 figs

  8. Furnace Cyclic Behavior of Plasma-Sprayed Zirconia-Yttria and Multi-Component Rare Earth Oxide Doped Thermal Barrier Coatings

    Science.gov (United States)

    Zhu, Dongming; Nesbitt, James A.; McCue, Terry R.; Barrett, Charles A.; Miller, Robert A.

    2002-01-01

    Ceramic thermal barrier coatings will play an increasingly important role in advanced gas turbine engines because of their ability to enable further increases in engine temperatures. However, the coating performance and durability become a major concern under the increasingly harsh thermal cycling conditions. Advanced zirconia- and hafnia-based cluster oxide thermal barrier coatings with lower thermal conductivity and improved thermal stability are being developed using a high-heat-flux laser-rig based test approach. Although the new composition coatings were not yet optimized for cyclic durability, an initial durability screening of numerous candidate coating materials was carried out using conventional furnace cyclic tests. In this paper, furnace thermal cyclic behavior of the advanced plasma-sprayed zirconia-yttria-based thermal barrier coatings that were co-doped with multi-component rare earth oxides was investigated at 1163 C using 45 min hot cycles. The ceramic coating failure mechanisms were studied by using scanning electron microscopy combined with X-ray diffraction phase analysis after the furnace tests. The coating cyclic lifetime will be discussed in relation to coating phase structures, total dopant concentrations, and other properties.

  9. Abutments with reduced diameter for both cement and screw retentions: analysis of failure modes and misfit of abutment-crown-connections after cyclic loading.

    Science.gov (United States)

    Moris, Izabela Cristina Maurício; Faria, Adriana Cláudia Lapria; Ribeiro, Ricardo Faria; Rodrigues, Renata Cristina Silveira

    2017-04-01

    The aim of this study was to analyze failure modes and misfit of abutments with reduced diameter for both cement and screw retentions after cyclic loading. Forty morse-taper abutment/implant sets of titanium were divided into four groups (N = 10): G4.8S-4.8 abutment with screw-retained crown; G4.8C-4.8 abutment with cemented crown; G3.8S-3.8 abutment with screw-retained crown; and G3.8C-3.8 abutment with cemented crown. Copings were waxed on castable cylinders and cast by oxygen gas flame and injected by centrifugation. After, esthetic veneering ceramic was pressed on these copings for obtaining metalloceramic crowns of upper canine. Cemented crowns were cemented on abutments with provisional cement (Temp Bond NE), and screw-retained crowns were tightened to their abutments with torque recommended by manufacturer (10 N cm). The misfit was measured using a stereomicroscope in a 10× magnification before and after cyclic loading (300,000 cycles). Tests were visually monitored, and failures (decementation, screw loosening and fractures) were registered. Misfit was analyzed by mixed linear model while failure modes by chi-square test (α = 0.05). Cyclic loading affected misfit of 3.8C (P ≤ 0.0001), 3.8S (P = 0.0055) and 4.8C (P = 0.0318), but not of 4.8S (P = 0.1243). No differences were noted between 3.8S with 4.8S before (P = 0.1550) and after (P = 0.9861) cyclic loading, but 3.8C was different from 4.8C only after (P = 0.0015) loading. Comparing different types of retentions at the same diameter abutment, significant difference was noted before and after cyclic loading for 3.8 and 4.8 abutments. Analyzing failure modes, retrievable failures were present at 3.8S and 3.8C groups, while irretrievable were only present at 3.8S. The cyclic loading decreased misfit of cemented and screw-retained crowns on reduced diameter abutments, and misfit of cemented crowns is greater than screw-retained ones. Abutments of reduced diameter failed more than

  10. Effects of Static Tensile Load on the Thermal Expansion of Gr/PI Composite Material.

    Science.gov (United States)

    1981-06-01

    is the effect of load on the thermal expansion. The effects of static tensile load on the coefficient of thermal expansion of mild steel and Invar ...thermally calibrated material ( Invar ) was used to com- pensate for apparent thermal strain. In all tests the specimens were reported to reach a... alloy (Ti-6A1-4V) specimen was performed to establish the general validity of the test method. This test was performed between room temperature and

  11. Comportamiento de viviendas de ferrocemento bajo cargas cíclic Behavior of ferrocement housing under cyclical loads

    Directory of Open Access Journals (Sweden)

    Daniel Bedoya Ruiz

    2009-07-01

    Full Text Available La escasez de vivienda en el mundo ha llevado desde hace varios años a la búsqueda de nuevos materiales y sistemas alternativos para su construcción. El ferrocemento desde hace más de 25 décadas viene siendo estudiado y aplicado como solución de vivienda en varios países; Colombia, uno de ellos. En este trabajo se presenta parte de los resultados de una investigación acerca del comportamiento de las viviendas de ferrocemento bajo cargas cíclicas. Se probaron dos módulos de vivienda a escala real construidos con paneles prefabricados de pared delgada de ferrocemento. Sobre cada módulo de ferrocemento se realizaron ensayos de carga cíclica y se evaluó su comportamiento. Los resultados obtenidos muestran la sensibilidad de este sistema estructural ante varios ciclos de carga, con pérdidas de rigidez cercanas al 20% para los primeros ciclos y hasta un 85% al final de los mismos.The shortage of dwelling in the world has taken for several years to the search of new materials and alternative systems for its construction. For more than 25 decades, ferrocement has been studied and applied as a dwelling solution in several countries, among them Colombia.. This article refers to the results of a research about seismic behavior of ferrocement dwellings. Two modules built on real scale with prefabricated panels of ferrocement thin wall were used. On each module of ferrocement, tests of cyclical load were carried out, and its behavior was evaluated. The obtained results showed the sensitivity of this structural system under several cycles of load, with losses of rigidity near to 20% for the first cycles and up to 85% at the end of the same.

  12. Design rules of mechanical structure of reactors. Damage due to cyclic loading. Progressive distortion. Practical analysis of ratcheting

    International Nuclear Information System (INIS)

    Clement, Gerard; Cousseran, Pierre; Lebey, Jacques; Moulin, Didier; Roche, Roland; Tremblais, Andre.

    1982-08-01

    At first is given a definition of what is ratcheting. A short discussion shows that computation results do not agree with experimental results. This is attributed to the complexity of the real material behavior. These considerations lead to try to build a design rule mainly based on the results of experimental tests. A large experimental program is in progress at CEN-Saclay. Using these results and the results available in open litterature, it was possible to propose a rule based on the concept of effective primary stress Psub(eff). The effective primary stress is a fictitious primary stress giving the same effects that the real loading (it is to say the same effect that the combination of an applied primary stress P and a cyclic straining). Determination of an upper bound value of Psub(eff) is made with the help of an efficiency diagram. More precisely the efficiency diagram include a curve giving a conservative value of an efficiency index V=P/Psub(eff) as a function of the secondary quotient SQ=ΔQ/P. Finally limitation of Psub(eff) intensity is discussed in regard with the current practice [fr

  13. Shear Performance of Horizontal Joints in Short Precast Concrete Columns with Sleeve Grouted Connections under Cyclic Loading.

    Science.gov (United States)

    Feng, Bo; Xiong, Feng; Liu, Bingyu; Chen, Jiang; Zhang, Yiping

    2016-01-01

    In this study, two short precast concrete columns and two cast-in-situ concrete columns were tested under cyclic loads. It was shown that the sleeve grouted connection was equivalent to the cast-in-situ connections for short columns when the axial compression ratio was 0.6. In order to determine the influence of the axial compression ratio and the shear-span ratio on the shear capacity of the horizontal joint, a FE model was established and verified. The analysis showed that the axial compression ratio is advantageous to the joint and the shear capacity of the horizontal joint increases with increase of the shear-span ratio. Based on the results, the methods used to estimate the shear capacity of horizontal joints in the Chinese Specification and the Japanese Guidelines are discussed and it was found that both overestimated the shear capacity of the horizontal joint. In addition, the Chinese Specification failed to consider the influence of the shear-span ratio.

  14. Fatigue Damage and Lifetime of SiC/SiC Ceramic-Matrix Composite under Cyclic Loading at Elevated Temperatures.

    Science.gov (United States)

    Li, Longbiao

    2017-03-31

    In this paper, the fatigue damage and lifetime of 2D SiC/SiC ceramic-matrix composites (CMCs) under cyclic fatigue loading at 750, 1000, 1100, 1200 and 1300 °C in air and in steam atmosphere have been investigated. The damage evolution versus applied cycles of 2D SiC/SiC composites were analyzed using fatigue hysteresis dissipated energy, fatigue hysteresis modulus, fatigue peak strain and interface shear stress. The presence of steam accelerated the damage development inside of SiC/SiC composites, which increased the increasing rate of the fatigue hysteresis dissipated energy and the fatigue peak strain, and the decreasing rate of the fatigue hysteresis modulus and the interface shear stress. The fatigue life stress-cycle (S-N) curves and fatigue limit stresses of 2D SiC/SiC composites at different temperatures in air and in steam condition have been predicted. The fatigue limit stresses approach 67%, 28%, 39% 17% and 28% tensile strength at 750, 1000, 1100, 1200 and 1300 °C in air, and 49%, 10%, 9% and 19% tensile strength at 750, 1000, 1200 and 1300 °C in steam conditions, respectively.

  15. Improved structural strength and lifetime of monoblock divertor targets by using doped tungsten alloys under cyclic high heat flux loading

    Science.gov (United States)

    Nogami, S.; Guan, W. H.; Hattori, T.; James, K.; Hasegawa, A.

    2017-12-01

    The divertor is one of the most important components of a fusion reactor, which performs the function of the removal of waste material from fusion plasma. Because the divertor is subjected to cyclic high heat flux loading up to about 20 MW m-2 induced by the plasma, the plasma facing material of the divertor should exhibit good thermo-mechanical properties. In this work, the possibility of improving the structural strength and the lifetime of fusion reactor divertors by using K-doped W and K-doped W-3%Re as plasma facing material instead of ordinary pure W was evaluated by thermo-mechanical finite element analysis (FEA). These materials have been developed for divertor applications in Japan and show higher recrystallization temperature and strength than pure W. The results of the present study indicated that K-doped W and K-doped W-3%Re render lower applied strain to the divertor and longer fatigue life of the plasma facing material. The evaluation results regarding the macro-crack formation life based on the FEA analyses indicated the possibility of an extension of the fatigue life by using K-doped W and K-doped W-3%Re.

  16. Bond Capability of Universal Adhesive Systems to Dentin in Self-etch Mode after Short-term Storage and Cyclic Loading

    Science.gov (United States)

    Costa, Daniele Morosini; Somacal, Deise Caren; Borges, Gilberto Antonio; Spohr, Ana Maria

    2017-01-01

    Objective: The aim was to evaluate, in vitro, the tensile bond strength to dentin of Scotchbond Universal (SU), All-Bond Universal (AU) and One Coat 7 Universal (OC7) adhesives applied in self-etch mode, after 24 h of storage and after 500,000 loading cycles, using Clearfil SE Bond (SE) as a control. Materials and Methods: The adhesives were applied on the dentin of bovine teeth, followed by the application of a composite resin. Thirty specimens were obtained for each adhesive. Half of the specimens were submitted to cyclic loading for 500,000 cycles. All specimens were submitted to a tensile bond strength test in a universal testing machine at a crosshead speed of 0.5 mm/minute. Results: According to two-way ANOVA and Tukey’s test (α=5%), the interaction between the adhesive and cyclic loading factors was significant (p=0.001). The means followed by the same letter represent no significant difference in the bond strength (MPa) after 24 h: OC7=7.86A (±2.90), SU=6.78AB (±2.03), AU=5.61BC (±2.32), and SE=3.53C (±1.89). After cyclic loading, SE, SU and AU maintained bond strength comparable to 24 h period. There was a significant decrease only for OC7. Conclusion: SU, AU and OC7 had bond strength to dentin comparable to that of SE. Only OC7 had decreased bond strength to dentin after cyclic loading. PMID:28839476

  17. Influence of cyclic fatigue in water on the load-bearing capacity of dental bridges made of zirconia.

    Science.gov (United States)

    Kohorst, Philipp; Dittmer, Marc Philipp; Borchers, Lothar; Stiesch-Scholz, Meike

    2008-09-01

    The humid atmosphere and permanent occurrence of chewing forces in the oral environment lead to degradation of ceramics used for prosthetic restorations. The aim of this in vitro study was to evaluate the influence of artificial aging on the load-bearing capacity of four-unit bridges, with both undamaged and predamaged zirconia frameworks. Additionally, different parameters for chewing simulation have been investigated and a finite element analysis was made to predict the location of highest tensile stresses within the bridges. A total of 60 frameworks were milled from presintered zirconia and divided into six homogeneous groups. Prior to veneering, frameworks of two groups were "damaged" by a defined saw cut similar to an accidental flaw generated during shape cutting. After veneering, FPDs were subjected to thermal and mechanical cycling - with the exception of control groups. The load-bearing capacity of tested FPDs was significantly reduced by artificial aging. In comparison to unaged specimens, fracture resistance decreased by about 40%, whereas preliminary damage did not have a significant effect. Increasing number of cycles and increasing upper load limit failed to show any additional effect on fracture force. To predict the progression of degradation under the terms of in vitro simulation for even longer periods, further aging experiments are required.

  18. Probabilistic Simulation of Combined Thermo-Mechanical Cyclic Fatigue in Composites

    Science.gov (United States)

    Chamis, Christos C.

    2011-01-01

    A methodology to compute probabilistically-combined thermo-mechanical fatigue life of polymer matrix laminated composites has been developed and is demonstrated. Matrix degradation effects caused by long-term environmental exposure and mechanical/thermal cyclic loads are accounted for in the simulation process. A unified time-temperature-stress-dependent multifactor-interaction relationship developed at NASA Glenn Research Center has been used to model the degradation/aging of material properties due to cyclic loads. The fast probability-integration method is used to compute probabilistic distribution of response. Sensitivities of fatigue life reliability to uncertainties in the primitive random variables (e.g., constituent properties, fiber volume ratio, void volume ratio, ply thickness, etc.) computed and their significance in the reliability-based design for maximum life is discussed. The effect of variation in the thermal cyclic loads on the fatigue reliability for a (0/+/-45/90)s graphite/epoxy laminate with a ply thickness of 0.127 mm, with respect to impending failure modes has been studied. The results show that, at low mechanical-cyclic loads and low thermal-cyclic amplitudes, fatigue life for 0.999 reliability is most sensitive to matrix compressive strength, matrix modulus, thermal expansion coefficient, and ply thickness. Whereas at high mechanical-cyclic loads and high thermal-cyclic amplitudes, fatigue life at 0.999 reliability is more sensitive to the shear strength of matrix, longitudinal fiber modulus, matrix modulus, and ply thickness.

  19. Influence of buildings geometrical and physical parameters on thermal cooling load

    International Nuclear Information System (INIS)

    Melo, C.

    1980-09-01

    A more accurate method to evaluate the thermal cooling load in buildings and to analyze the influence of geometrical and physical parameters on air conditioning calculations is presented. The sensitivity of the cooling load, considering the thermal capacity of the materials, was simulated in a computer for several different situations. (Author) [pt

  20. Modeling Strength Degradation of Fiber-Reinforced Ceramic-Matrix Composites Subjected to Cyclic Loading at Elevated Temperatures in Oxidative Environments

    Science.gov (United States)

    Longbiao, Li

    2018-02-01

    In this paper, the strength degradation of non-oxide and oxide/oxide fiber-reinforced ceramic-matrix composites (CMCs) subjected to cyclic loading at elevated temperatures in oxidative environments has been investigated. Considering damage mechanisms of matrix cracking, interface debonding, interface wear, interface oxidation and fibers fracture, the composite residual strength model has been established by combining the micro stress field of the damaged composites, the damage models, and the fracture criterion. The relationships between the composite residual strength, fatigue peak stress, interface debonding, fibers failure and cycle number have been established. The effects of peak stress level, initial and steady-state interface shear stress, fiber Weibull modulus and fiber strength, and testing temperature on the degradation of composite strength and fibers failure have been investigated. The evolution of residual strength versus cycle number curves of non-oxide and oxide/oxide CMCs under cyclic loading at elevated temperatures in oxidative environments have been predicted.

  1. The importance of thermal loading conditions to waste package performance at Yucca Mountain

    International Nuclear Information System (INIS)

    Buscheck, T.A.; Nitao, J.J.

    1994-10-01

    Temperature and relative humidity are primary environmental factors affecting waste package corrosion rates for the potential repository in the unsaturated zone at Yucca Mountain, Nevada. Under ambient conditions, the repository environment is quite humid. If relative humidity is low enough (<70%), corrosion will be minimal. Under humid conditions, corrosion is reduced if the temperature is low (<60 C). Using the V-TOUGH code, the authors model thermo-hydrological flow to investigate the effect of repository heat on temperature and relative humidity in the repository for a wide range of thermal loads. These calculations indicate that repository heat may substantially reduce relative humidity on the waste package, over hundreds of years for low thermal loads and over tens of thousands of year for high thermal loads. Temperatures associated with a given relative humidity decrease with increasing thermal load. Thermal load distributions can be optimized to yield a more uniform reduction in relative humidity during the boiling period

  2. Cyclic process of simazine removal from waters by adsorption on zeolite H-Y and its regeneration by thermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Sannino, Filomena, E-mail: fsannino@unina.it [Dipartimento di Scienze del Suolo, della Pianta, dell' Ambiente e delle Produzioni Animali, Universita di Napoli ' Federico II' , Via Universita 100, 80055 Portici (Italy); Ruocco, Silvia [Dipartimento di Scienze del Suolo, della Pianta, dell' Ambiente e delle Produzioni Animali, Universita di Napoli ' Federico II' , Via Universita 100, 80055 Portici (Italy); Marocco, Antonello; Esposito, Serena; Pansini, Michele [Laboratorio Materiali - Dipartimento di Meccanica, Strutture, Ambiente e Territorio - Universita di Cassino - Via Di Biasio 43 - 03043 Cassino (Italy)

    2012-08-30

    Highlights: Black-Right-Pointing-Pointer Bringing agrochemical concentration below the law limit allowed in wastewaters. Black-Right-Pointing-Pointer Regenerating the adsorbent which can be used again in the cyclic process. Black-Right-Pointing-Pointer Destroying the agrochemical molecules by combustion. - Abstract: Removal of the agrochemical simazine from polluted waters through adsorption by zeolite Y in its protonic form was studied. The investigated parameters were: pH, time, initial simazine concentration and solid/liquid ratio. An iterative process of simazine removal from waters is proposed, featuring: (i) final agrochemical concentration well below 0.05 mg/dm{sup 3}, the maximum concentration allowed by Italian laws in wastewaters; (ii) regeneration of the adsorbent by a few minutes thermal treatment in air at about 500 Degree-Sign C, which results in the combustion of simazine without damage of the adsorbent; (iii) destruction of the agrochemical compound by combustion.

  3. Cyclic process of simazine removal from waters by adsorption on zeolite H-Y and its regeneration by thermal treatment

    International Nuclear Information System (INIS)

    Sannino, Filomena; Ruocco, Silvia; Marocco, Antonello; Esposito, Serena; Pansini, Michele

    2012-01-01

    Highlights: ► Bringing agrochemical concentration below the law limit allowed in wastewaters. ► Regenerating the adsorbent which can be used again in the cyclic process. ► Destroying the agrochemical molecules by combustion. - Abstract: Removal of the agrochemical simazine from polluted waters through adsorption by zeolite Y in its protonic form was studied. The investigated parameters were: pH, time, initial simazine concentration and solid/liquid ratio. An iterative process of simazine removal from waters is proposed, featuring: (i) final agrochemical concentration well below 0.05 mg/dm 3 , the maximum concentration allowed by Italian laws in wastewaters; (ii) regeneration of the adsorbent by a few minutes thermal treatment in air at about 500 °C, which results in the combustion of simazine without damage of the adsorbent; (iii) destruction of the agrochemical compound by combustion.

  4. Development of Viscoelastic Multi-Body Simulation and Impact Response Analysis of a Ballasted Railway Track under Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Daisuke Nishiura

    2017-06-01

    Full Text Available Simulation of a large number of deformable bodies is often difficult because complex high-level modeling is required to address both multi-body contact and viscoelastic deformation. This necessitates the combined use of a discrete element method (DEM and a finite element method (FEM. In this study, a quadruple discrete element method (QDEM was developed for dynamic analysis of viscoelastic materials using a simpler algorithm compared to the standard FEM. QDEM easily incorporates the contact algorithm used in DEM. As the first step toward multi-body simulation, the fundamental performance of QDEM was investigated for viscoelastic analysis. The amplitude and frequency of cantilever elastic vibration were nearly equal to those obtained by the standard FEM. A comparison of creep recovery tests with an analytical solution showed good agreement between them. In addition, good correlation between the attenuation degree and the real physical viscosity was confirmed for viscoelastic vibration analysis. Therefore, the high accuracy of QDEM in the fundamental analysis of infinitesimal viscoelastic deformations was verified. Finally, the impact response of a ballast and sleeper under cyclic loading on a railway track was analyzed using QDEM as an application of deformable multi-body dynamics. The results showed that the vibration of the ballasted track was qualitatively in good agreement with the actual measurements. Moreover, the ballast layer with high friction reduced the ballasted track deterioration. This study suggests that QDEM, as an alternative to DEM and FEM, can provide deeper insights into the contact dynamics of a large number of deformable bodies.

  5. FY 93 thermal loading systems study final report: Volume 1. Revision 1

    International Nuclear Information System (INIS)

    Saterlie, S.F.; Thomson, B.H.

    1994-01-01

    The ability to meet the overall performance requirements for the proposed Mined Geology Disposal System at Yucca Mountain, Nevada requires the two major subsystem (natural barriers and engineered barriers) to positively contribute to containment and radionuclide isolation. In addition to the postclosure performance the proposed repository must meet preclosure requirements of safety, retrievability, and operability. Cost and schedule were also considered. The thermal loading strategy chosen may significantly affect both the postclosure and preclosure performance of the proposed repository. Although the current Site Characterization Plan reference case is 57 kilowatts (kW)/acre, other thermal loading strategies (different areal mass loadings) have been proposed which possess both advantages and disadvantages. The objectives of the FY 1993 Thermal Loading Study were to (1) place bounds on the thermal loading which would establish the loading regime that is ''too hot'' and the loading regime that is ''too cold'', to (2) ''grade'' or evaluate the performance, as a function of thermal loading, of the repository to contain high level wastes against performance criteria and to (3) evaluate the performance of the various options with respect to cost, safety, and operability. Additionally, the effort was to (4) identify important uncertainties that need to be resolved by tests and/or analyses in order to complete a performance assessment on the effects of thermal loading. The FY 1993 Thermal Loading Study was conducted from December 1, 1992 to December 30, 1993 and this final report provides the findings of the study. Volume 1 contains the Introduction; Performance requirements; Input and assumptions; Near-field thermal analysis; Far-field thermal analysis; Cost analysis; Other considerations; System analysis; Additional thermal analysis; and Conclusions and recommendations. 71 refs., 54 figs

  6. Characterization of Ternary NiTiPd High-Temperature Shape-Memory Alloys under Load-Biased Thermal Cycling

    Science.gov (United States)

    Bigelow, Glen S.; Padula, Santo A.; Noebe, Ronald D.; Garg, Anita; Gaydosh, Darrell

    2010-01-01

    While NiTiPd alloys have been extensively studied for proposed use in high-temperature shape-memory applications, little is known about the shape-memory response of these materials under stress. Consequently, the isobaric thermal cyclic responses of five (Ni,Pd)49.5Ti50.5 alloys with constant stoichiometry and Pd contents ranging from 15 to 46 at. pct were investigated. From these tests, transformation temperatures, transformation strain (which is proportional to work output), and unrecovered strain per cycle (a measure of dimensional instability) were determined as a function of stress for each alloy. It was found that increasing the Pd content over this range resulted in a linear increase in transformation temperature, as expected. At a given stress level, work output decreased while the amount of unrecovered strain produced during each load-biased thermal cycle increased with increasing Pd content, during the initial thermal cycles. However, continued thermal cycling at constant stress resulted in a saturation of the work output and nearly eliminated further unrecovered strain under certain conditions, resulting in stable behavior amenable to many actuator applications.

  7. Fiber amplifiers under thermal loads leading to transverse mode instability

    DEFF Research Database (Denmark)

    Johansen, Mette Marie; Hansen, Kristian Rymann; Alkeskjold, Thomas Tanggaard

    2014-01-01

    Transverse mode instability (TMI) in rare-earth doped fiber amplifiers operating above an average power threshold is caused by intermodal stimulated thermal Rayleigh scattering due to quantum defect heating. We investigate thermally induced longitudinal waveguide perturbations causing power trans...

  8. Effects of Brass (Cu3Zn2) as High Thermal Expansion Material on Shrink Disc Performance During High Thermal Loading

    Science.gov (United States)

    Mazlan, MIS; Mohd, SA; Bahar, ND; Aziz, SAA

    2018-03-01

    This research work is focused on shrink disc operation at high temperature. Geometrical and material design selections have been done by taking into consideration the existing shrink disc operating at high temperature condition. The existing shrink disc confronted slip between shaft and shaft sleeve during thermal loading condition. The assessment has been obtained through virtual experiment by using Finite Element Analysis (FEA) -Thermal Transient Stress for 900 seconds with 300 °C of thermal loading. This investigation consists of the current and improved version of shrink disc, where identical geometries and material properties were utilized. High Thermal Expansion (HTE) material has been introduced to overcome the current design of the shrink disc. Brass (Cu3Zn2) has been selected as the HTE material in the improved shrink disc design due to its high thermal expansion properties. The HTE has shown a significant improvement on the total contact area and contact pressure on the shaft and the shaft sleeve. The improved shrink disc embedded with HTE during thermal loading exhibit a minimum of 1244.1 mm2 of the total area on shaft and shaft sleeve which uninfluenced the total contact area at normal condition which is 1254.3 mm2. Meanwhile, the total pressure of improved shrink disc had an increment of 108.1 MPa while existing shrink disc total pressure has lost 17.2 MPa during thermal loading.

  9. A Novel Repair Method for Radial Tears of the Medial Meniscus: Biomechanical Comparison of Transtibial 2-Tunnel and Double Horizontal Mattress Suture Techniques Under Cyclic Loading.

    Science.gov (United States)

    Bhatia, Sanjeev; Civitarese, David M; Turnbull, Travis Lee; LaPrade, Christopher M; Nitri, Marco; Wijdicks, Coen A; LaPrade, Robert F

    2016-03-01

    Complete radial tears of the medial meniscus have been reported to be functionally similar to a total meniscectomy. At present, there is no consensus on an ideal technique for repair of radial midbody tears of the medial meniscus. Prior attempts at repair with double horizontal mattress suture techniques have led to a reportedly high rate of incomplete healing or healing in a nonanatomic (gapped) position, which compromises the ability of the meniscus to withstand hoop stresses. A newly proposed 2-tunnel radial meniscal repair method will result in decreased gapping and increased ultimate failure loads compared with the double horizontal mattress suture repair technique under cyclic loading. Controlled laboratory study. Ten matched pairs of male human cadaveric knees (average age, 58.6 years; range, 48-66 years) were used. A complete radial medial meniscal tear was made at the junction of the posterior one-third and middle third of the meniscus. One knee underwent a horizontal mattress inside-out repair, while the contralateral knee underwent a radial meniscal repair entailing the same technique with a concurrent novel 2-tunnel repair. Specimens were potted and mounted on a universal testing machine. Each specimen was cyclically loaded 1000 times with loads between 5 and 20 N before experiencing a load to failure. Gap distances at the tear site and failure load were measured. The 2-tunnel repairs exhibited a significantly stronger ultimate failure load (median, 196 N; range, 163-212 N) than did the double horizontal mattress suture repairs (median, 106 N; range, 63-229 N) (P = .004). In addition, the 2-tunnel repairs demonstrated decreased gapping at all testing states (P meniscus significantly decrease the ability of the meniscus to dissipate tibiofemoral loads, predisposing patients to early osteoarthritis. Improving the ability to repair medial meniscal radial tears in a way that withstands cyclic loads and heals in an anatomic position could significantly

  10. A novel approach to generate random surface thermal loads in piping

    Energy Technology Data Exchange (ETDEWEB)

    Costa Garrido, Oriol, E-mail: oriol.costa@ijs.si; El Shawish, Samir; Cizelj, Leon

    2014-07-01

    Highlights: • Approach for generating continuous and time-dependent random thermal fields. • Temperature fields simulate fluid mixing thermal loads at fluid–wall interface. • Through plane-wave decomposition, experimental temperature statistics are reproduced. • Validation of the approach with a case study from literature. • Random surface thermal loads generation for future thermal fatigue analyses of piping. - Abstract: There is a need to perform three-dimensional mechanical analyses of pipes, subjected to complex thermo-mechanical loadings such as the ones evolving from turbulent fluid mixing in a T-junction. A novel approach is proposed in this paper for fast and reliable generation of random thermal loads at the pipe surface. The resultant continuous and time-dependent temperature fields simulate the fluid mixing thermal loads at the fluid–wall interface. The approach is based on reproducing discrete fluid temperature statistics, from experimental readings or computational fluid dynamic simulation's results, at interface locations through plane-wave decomposition of temperature fluctuations. The obtained random thermal fields contain large scale instabilities such as cold and hot spots traveling at flow velocities. These low frequency instabilities are believed to be among the major causes of the thermal fatigue in T-junction configurations. The case study found in the literature has been used to demonstrate the generation of random surface thermal loads. The thermal fields generated with the proposed approach are statistically equivalent (within the first two moments) to those from CFD simulations results of similar characteristics. The fields maintain the input data at field locations for a large set of parameters used to generate the thermal loads. This feature will be of great advantage in future sensitivity fatigue analyses of three-dimensional pipe structures.

  11. Thermal loading of wind power converter considering dynamics of wind speed

    DEFF Research Database (Denmark)

    Baygildina, Elvira; Peltoniemi, Pasi; Pyrhönen, Olli

    2013-01-01

    ), and the thermal stress of power devices is investigated from the frequency spectrum point of view of wind speed. It is concluded that because of the strong inertia effects by the aerodynamic behavior of wind turbines, thermal stress of the semiconductors is relatively more stable and only influenced by the low......The thermal loading of power semiconductors is a crucial performance related to the reliability and cost of the wind power converter. However, the thermal loading impacts by the variation of wind speeds have not yet been clarified, especially when considering the aerodynamic behavior of the wind...

  12. [Wear intensity and surface roughness of microhybrid composite and ceramic occlusal veneers on premolars after the thermocycling and cyclic mechanical loading tests].

    Science.gov (United States)

    Zhang, H Y; Jiang, T; Cheng, M X; Zhang, Y W

    2018-02-18

    To evaluate the wear intensity and surface roughness of occlusal veneers on premolars made of microhybrid composite resin or two kinds of ceramics in vitro after the thermocycling and cyclic mechanical loading tests. In the study,24 fresh extracted human premolars without root canal treatment were prepared (cusps reduction of 1.5 mm in thickness to simulate middle to severe tooth wear, the inclinations of cusps were 20°). The prepared teeth were restored with occlusal veneers made of three different materials: microhybrid composite, heat-pressed lithium disilicate ceramic and computer-aided design/computer-aided manufacturing (CAD/CAM) lithium disilicate ceramic in the thickness of 1.5 mm. The occlusal veneers were cemented with resin cement. The specimens were fatigued using the thermocycling and cyclic mechanical loading tests after being stored in water for 72 h. The wear of specimens was measured using gypsum replicas and 3D laser scanner before and after the thermocycling and cyclic mechanical loading tests and the mean lost distance (mm) was used to indicate the level of wear. The surfaces of occlusal contact area were observed and the surface roughness was recorded using 3D laser scanning confocal microscope before and after the fatigue test. Differences between the groups were compared using ONE-way ANOVA(Pmechanical loading tests. The mean wear of microhybrid composite group, heat-pressed lithium disilicate ceramic group, and CAD/CAM lithium disilicate ceramic group was (-0.13±0.03) mm, (-0.05±0.01) mm and (-0.05±0.01) mm, the wear of microhybrid composite was significantly higher than the two ceramic groups(PCAD/CAM lithium disilicate ceramic (P=0.010). From the view of wear speed, microhybrid composite was significantly higher than the two kinds of ceramics, but it was similar to enamel when the opposing tooth was natural. The surface roughness before the themocycling and cyclic mechanical loading test of microhybrid composite was significantly

  13. Thermal simulation of different construction types in six climatic regions on heating and cooling loads

    CSIR Research Space (South Africa)

    Kumirai, T

    2012-10-01

    Full Text Available A thermal simulation model was prepared for a “typical” suburban building of 120 square meters and nine different passive designs were simulated to evaluate their impact on the heating and cooling load....

  14. Research and application of thermal power unit’s load dynamic adjustment based on extraction steam

    Science.gov (United States)

    Li, Jun; Li, Huicong; Li, Weiwei

    2018-02-01

    The rapid development of heat and power generation in large power plant has caused tremendous constraints on the load adjustment of power grids and power plants. By introducing the thermodynamic system of thermal power unit, the relationship between thermal power extraction steam and unit’s load has analyzed and calculated. The practical application results show that power capability of the unit affected by extraction and it is not conducive to adjust the grid frequency. By monitoring the load adjustment capacity of thermal power units, especially the combined heat and power generating units, the upper and lower limits of the unit load can be dynamically adjusted by the operator on the grid side. The grid regulation and control departments can effectively control the load adjustable intervals of the operating units and provide reliable for the cooperative action of the power grid and power plants, to ensure the safety and stability of the power grid.

  15. Influence of pores on crack initiation in monotonic tensile and cyclic loadings in lost foam casting A319 alloy by using 3D in-situ analysis

    International Nuclear Information System (INIS)

    Wang, Long; Limodin, Nathalie; El Bartali, Ahmed; Witz, Jean-François; Seghir, Rian; Buffiere, Jean-Yves; Charkaluk, Eric

    2016-01-01

    Lost Foam Casting (LFC) process is replacing the conventional gravity Die Casting (DC) process in automotive industry for the purpose of geometry optimization, cost reduction and consumption control. However, due to lower cooling rate, LFC produces in a coarser microstructure that reduces fatigue life. In order to study the influence of the casting microstructure of LFC Al-Si alloy on damage micromechanisms under monotonic tensile loading and Low Cycle Fatigue (LCF) at room temperature, an experimental protocol based on the three dimensional (3D) in-situ analysis has been set up and validated. This paper focuses on the influence of pores on crack initiation in monotonic and cyclic tensile loadings. X-ray Computed Tomography (CT) allowed the microstructure of material being characterized in 3D and damage evolution being followed in-situ also in 3D. Experimental and numerical mechanical fields were obtained by using Digital Volume Correlation (DVC) technique and Finite Element Method (FEM) simulation respectively. Pores were shown to have an important influence on strain localization as large pores generate enough strain localization zones for crack initiation both in monotonic tensile and cyclic loadings.

  16. Evaluation of FRP Confinement Models for Substandard Rectangular RC Columns Based on Full-Scale Reversed Cyclic Lateral Loading Tests in Strong and Weak Directions

    Directory of Open Access Journals (Sweden)

    Hamid Farrokh Ghatte

    2016-09-01

    Full Text Available Although many theoretical and experimental studies are available on external confinement of columns using fiber-reinforced polymer (FRP jackets, as well as numerous models proposed for the axial stress-axial strain relation of concrete confined with FRP jackets, they have not been validated with a sufficient amount and variety of experimental data obtained through full-scale tests of reinforced concrete (RC columns with different geometrical and mechanical characteristics. Particularly, no systematical experimental data have been presented on full-scale rectangular substandard RC columns subjected to reversed cyclic lateral loads along either their strong or weak axes. In this study, firstly, test results of five full-scale rectangular substandard RC columns with a cross-sectional aspect ratio of two (300 mm × 600 mm are briefly summarized. The columns were tested under constant axial load and reversed cyclic lateral loads along their strong or weak axes before and after retrofitting with external FRP jackets. In the second stage, inelastic lateral force-displacement relationships of the columns are obtained analytically, making use of the plastic hinge assumption and different FRP confinement models available in the literature. Finally, the analytical findings are compared with the test results for both strong and weak directions of the columns. Comparisons showed that use of different models for the stress-strain relationship of FRP-confined concrete can yield significantly non-conservative or too conservative retrofit designs, particularly in terms of deformation capacity.

  17. Loadings in thermal barrier coatings of jet engine turbine blades an experimental research and numerical modeling

    CERN Document Server

    Sadowski, Tomasz

    2016-01-01

    This book discusses complex loadings of turbine blades and protective layer Thermal Barrier Coating (TBC), under real working airplane jet conditions. They obey both multi-axial mechanical loading and sudden temperature variation during starting and landing of the airplanes. In particular, two types of blades are analyzed: stationary and rotating, which are widely applied in turbine engines produced by airplane factories.

  18. Experimental and numerical thermal buckling studies on cylinders

    International Nuclear Information System (INIS)

    Brochard, J.; Combescure, A.; Locatelli, T.; Tomassian, R.

    1989-01-01

    An important program of buckling experiments is carried out by C.E.A./D.E.M.T on thin cylinders subjected to a very strong axial gradient of temperature, an axial tension stress, and an external pressure, in order to evaluate: - damage due to thermal buckling, - influence of a thermal load on reduction of buckling pressure, - progressive buckling under a cyclic thermal load

  19. Effect of cyclical thermal to mechanical properties of Hybrid Laminate Composites (HLC) with skin recycle polypropylene/natural fiber/halloysite and core PP/KF composites

    Science.gov (United States)

    Sri Suharty, Neng; Ismail, Hanafi; Suci Handayani, Desi; Diharjo, Kuncoro; Rachman Wibowo, Fajar; Arnita Wuri, Margaretha

    2016-02-01

    This research has successfully synthesized six hybrid laminate composites (HLC). These HLC consist of two layers skin composites and one layer of core PP/KF composites. There are sticked with epoxy adhesive by using cold press method. In this research 6 types of skin are used, namely the rPP (recycled polypropylene, HC1); rPP/DVB/PP-g-AA/KF (HC2); rPP/DVB/PP-g-AA/Hall (HC3); rPP/DVB/PP-g-AA/Hall+ZB (HC4); rPP/DVB/PP-g-AA/KF/Hall (HC5) and rPP/DVB/PP-g-AA/KF/Hall+ZB (HC6) composites. The mechanical properties assessment tensile strength (TS) of various HLC before and after cyclical thermal (CT) was done by ASTM D638. While testing the flame retardant: such as time to ignition (TTI) and burning rate (BR) was done by ASTM D635. Heat stability of HLC can be recognized by conducting the CT treatment. It is to determine the effect of fluctuating heat loads on mechanical properties of HLC materials. The TS result of five HLCs (HC2, HC3, HC4, HC5 and HC6) before CT treatment were higher than HC1 (blank HLC). Those five HLC are also able to increase the TTI and reduce the BR compared to HC1. The CT treatment conditions performed at 45 oC as much as 125 times. After CT treatment, the TS values only slightly decline compared to before CT treatment.

  20. Crack growth resistance under thermal shock loading of alumina

    Energy Technology Data Exchange (ETDEWEB)

    Saadaoui, M. [Ecole Mohammadia d`Ingenieurs (EMIL), Rabat (Morocco); Fantozzi, G. [GEMPPM-UMR CNRS 5510, INSA Lyon, Villeurbanne (France)

    1998-06-01

    Thermal shock experiments, conducted in an apparatus in which all the parameters can be controlled, are modelled by a two dimensional cooling model, allowing a precise determination of the induced stress intensity factors (SIF). Fracture mechanics analysis in terms of stress intensity factors is applied to determine R-curve behaviour of indentation cracks in alumina materials subjected to thermal shock. The instant of unstable crack growth was obtained by acoustic emission (AE). As in bending tests, the coarse grained material showed a more pronounced R-curve behaviour than the fine grained material. The results are discussed considering the influence of the R-curve behaviour on the retained strength after thermal shock. (orig.) 25 refs.

  1. Eficiencia de los motores de inducción con carga cíclica; Efficiency of Induction Motors with Cyclic Load

    Directory of Open Access Journals (Sweden)

    Elías de la Rosa Masdueño

    2011-02-01

    Full Text Available Se propone un nuevo método para determinar la eficiencia de trabajo de los motores de inducción queaccionan cargas cíclicas tales como bombas reciprocantes, martinetes, etc. El método se basa en lasegregación de pérdidas, y la determinación del gráfico de corriente y la energía total del ciclo. Se muestrauna comprobación experimental basada en un método de Monte Carlo.  A new method for finding the working efficiency of the induction motors moving cyclic loads is proposed.This type of loading is frequent in mechanism like piston pumps, hammers, etc. The method is based inthe losses segregation and the determination of the current graphic and the total energy in the cycle. Anexperimental proof based on Monte Carlo method is shown.

  2. An in-situ neutron diffraction study of a multi-phase transformation and twinning-induced plasticity steel during cyclic loading

    Science.gov (United States)

    Saleh, Ahmed A.; Brown, Donald W.; Pereloma, Elena V.; Clausen, Bjørn; Davies, Christopher H. J.; Tomé, Carlos N.; Gazder, Azdiar A.

    2015-04-01

    In-situ neutron diffraction during cyclic tension-compression loading (˜+3.5% to -2.8%) of a 17Mn-3Al-2Si-1Ni-0.06C steel that exhibits concurrent transformation and twinning -induced plasticity effects indicated a significant contribution of intragranular back stresses to the observed Bauschinger effect. Rietveld analysis revealed a higher rate of martensitic transformation during tension compared to compression. Throughout cycling, α'-martensite exhibited the highest phase strains such that it bears an increasing portion of the macroscopic load as its weight fraction evolves. On the other hand, the ɛ-martensite strain remained compressive as it accommodated most of the internal strains caused by the shape misfit associated with the γ→ɛ and/or ɛ→α' transformations.

  3. An in-situ neutron diffraction study of a multi-phase transformation and twinning-induced plasticity steel during cyclic loading

    Energy Technology Data Exchange (ETDEWEB)

    Saleh, Ahmed A., E-mail: asaleh@uow.edu.au [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, New South Wales 2522 (Australia); Brown, Donald W.; Clausen, Bjørn; Tomé, Carlos N. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Pereloma, Elena V. [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, New South Wales 2522 (Australia); Electron Microscopy Centre, University of Wollongong, Wollongong, New South Wales 2500 (Australia); Davies, Christopher H. J. [Department of Mechanical and Aerospace Engineering, Monash University, Clayton, Victoria 3800 (Australia); Gazder, Azdiar A. [Electron Microscopy Centre, University of Wollongong, Wollongong, New South Wales 2500 (Australia)

    2015-04-27

    In-situ neutron diffraction during cyclic tension-compression loading (∼+3.5% to −2.8%) of a 17Mn-3Al-2Si-1Ni-0.06C steel that exhibits concurrent transformation and twinning -induced plasticity effects indicated a significant contribution of intragranular back stresses to the observed Bauschinger effect. Rietveld analysis revealed a higher rate of martensitic transformation during tension compared to compression. Throughout cycling, α′-martensite exhibited the highest phase strains such that it bears an increasing portion of the macroscopic load as its weight fraction evolves. On the other hand, the ε-martensite strain remained compressive as it accommodated most of the internal strains caused by the shape misfit associated with the γ→ε and/or ε→α′ transformations.

  4. Load frequency control of three area interconnected hydro-thermal ...

    African Journals Online (AJOL)

    user

    Sam Higginbottom Institute of Agriculture, Technology & Sciences- Deemed University, Allahabad, INDIA ... This paper present analysis on dynamic performance of Load Frequency Control (LFC) of three area interconnected ..... Higher values of Kp give better steady-state performance, but worse transient response.

  5. Load frequency control of three area interconnected hydro-thermal ...

    African Journals Online (AJOL)

    This paper present analysis on dynamic performance of Load Frequency Control (LFC) of three area interconnected hydrothermal reheat power system by the use of Artificial Intelligent and PI Controller. In the proposed scheme, control methodology developed using conventional PI controller, Artificial Neural Network ...

  6. Thermal buckling analysis of annular FGM plate having variable thickness under thermal load of arbitrary distribution by finite element method

    Energy Technology Data Exchange (ETDEWEB)

    Ghomshei, Mansour Mohieddin; Abbasi, Vahid [Islamic Azad University, Alborz (Iran, Islamic Republic of)

    2013-04-15

    In this paper, a finite element formulation is developed for analyzing the axisymmetric thermal buckling of FGM annular plates of variable thickness subjected to thermal loads generally distributed nonuniformly along the plate radial coordinate. The FGM assumed to be isotropic with material properties graded in the thickness direction according to a simple power-law in terms of the plate thickness coordinate, and has symmetry with respect to the plate midplane. At first, the pre-buckling plane elasticity problem is developed and solved using the finite element method, to determine the distribution of the pre-buckling in-plane forces in terms of the temperature rise distribution. Subsequently, based on Kierchhoff plate theory and using the principle of minimum total potential energy, the weak form of the differential equation governing the plate thermal stability is derived, then by employing the finite element method, the stability equations are solved numerically to evaluate the thermal buckling load factor. Convergence and validation of the presented finite element model are investigated by comparing the numerical results with those available in the literature. Parametric studies are carried out to cover the effects of parameters including thickness-to-radius ratio, taper parameter and boundary conditions on the thermal buckling load factor of the plates.

  7. Above and below boiling thermal loading strategies for large waste packages

    International Nuclear Information System (INIS)

    Smith, M.L.

    1994-01-01

    A simplified repository thermal model was developed with the Mathcad computer code which indicates that large waste packages may be compatible with both above and below boiling repository thermal loading strategies. Minimum spent fuel decay time of at least 20 to 30 years was shown to be important for both thermal loading strategies. Constant isothermal boundary conditions are assumed at the ground surface (296 K) and 305 meters below the water table (309.7 K) with a uniform temperature change of 1.55 10 -2 K/meter. Homogeneous tuff properties are assumed: conductivity (2.1 watt/m-k); density (2.22 gm/cm 3 ); and thermal capacitance (2.17 joule/cm 3 K). Based on these properties, the tuff thermal diffusion coefficient is 9.68 x 10 -7 m 2 /sec

  8. Optimized load sharing control by means of thermal reliability management

    DEFF Research Database (Denmark)

    Nesgaard, Carsten; Andersen, Michael Andreas E.

    2004-01-01

    time and system cost. However, due to non-ideal parts each converter unit deviates from the ideal case, which makes a power system comprised of parallel-connected converters a rather poor performing system. To account for the non-ideal parts some form of load sharing is needed, whereby it is ensured...... of the system’s potential load sharing control is a must.......With new applications for high-current low-output voltage power systems emerging nearly every day the need for new and cost-efficient power system designs is a matter of course. As output voltage levels continue to decrease an approach that seems more and more attractive is the implementation...

  9. Investigation into Fretting Fatigue Under Cyclic Contact Load and in Conjunction with Plain Fatigue of Titanium Alloy

    National Research Council Canada - National Science Library

    Al-Noaimi, Abdulla

    2008-01-01

    ... difference between the axial and the contact load. The primary goal of this study is to investigate the effect of phase difference between axial and contact loads on fretting fatigue behavior of Ti-6Al-4V alloy and to determine...

  10. Influence of a cyclic load on the embrittlement kinetics of alloys by the example of the 475 C embrittlement of duplex steel and the dynamic embrittlement of a nickel base alloy

    International Nuclear Information System (INIS)

    Wackermann, Ken

    2015-01-01

    The objective of this study was to investigate the dependence of high temperature embrittlement mechanisms on high temperature fatigue and vice versa. As model embrittlement mechanisms the 475 C Embrittlement of ferritic austenitic duplex stainless steel (1.4462) and the Dynamic Embrittlement of nickel-based superalloys (IN718) were selected. The 475 C Embrittlement is a thermally activated decomposition of the ferritic phase which hardens the material. In contrast to this a cyclic plastic deformation weakens the steel by a deformation-induced dissolution of the decomposition. Fatigue tests with different frequencies, loading amplitudes at room temperature and at 475 C with Duplex Stainless Steel in different states of embrittlement show that the ongoing 475 C Embrittlement and the deformation-induced dissolution are competing mechanisms. It depends on the frequency, the loading amplitude and the temperature which mechanism is dominant. Applying the model of the yield stress distribution function to the hysteresis branches of the fatigue tests allows an analysis of the fatigue behaviour of each phase individually. This analysis shows that the global fatigue behaviour for the test conditions applied in this study is mainly controlled by the ferritic phase. According to the existing understanding of Dynamic Embrittlement it is an oxygen grain boundary diffusion arising by tensile stress at elevated temperatures with the result of a fast intercrystalline crack propagation. In reference tests under vacuum conditions without oxygen grain boundary diffusion, a slow transcrystalline fracture appears. To analyse the Dynamic Embrittlement, the crack propagation was tested at 650 C with different frequencies and superimposed hold times in the fatigue cycle at maximum stress. The results shows that the existing model of Dynamic Embrittlement needs to be adapted to the effects of cyclic plastic deformation. In hold times, the oxygen grain boundary diffusion in front of the

  11. Understanding and modelling of the aniso-thermal cyclic mechanical behaviour of the AISI 316LN austenitic stainless steel

    International Nuclear Information System (INIS)

    Gentet, D.

    2009-11-01

    The main subject of this report consists in proposing a mechanical model of the viscoplastic behaviour of an austenitic stainless steel under isothermal and aniso-thermal low cycle fatigue loadings at high temperatures (550-900 K). In this domain, numerous phenomena linked to dynamic strain ageing (DSA) and to dipolar dislocation structure formation may appear. Isothermal and aniso-thermal low cycle fatigue tension-compression tests were performed in order to verify some aspects about the effect of temperature on the mechanical behaviour. The study of the hysteresis loops and the observation of dislocation structures carried on transmission electron microscopy establish two different DSA mechanisms during isothermal tests. The effect of temperature history is shown for for particular temperature sequences. It is demonstrated that the stress amplitude increase when the sample is submitted to cycles at 'high temperature' is linked to the second mechanism of DSA. It comes from the increase of short range interaction between dislocations (chromium segregation), but it is also the consequence of the lack of dipolar structure annihilation at low temperature. From the experimental analysis of DSA mechanisms and dipolar restoration, a macroscopic aniso-thermal model is developed using physical internal variables (densities of dislocations). The equations of a polycrystalline model are rewritten with the aim of getting a simple multi-scale approach which can be used on finite elements analysis software. Between 550 and 873 K, the simulation results are in good accordance with the macroscopic and microscopic observations of low cycle fatigue, relaxation, and 2D-ratchetting tests. (author)

  12. The Feasibility Study on Thermal Loading Control of Wind Power Converters with a Flexible Switching Frequency

    DEFF Research Database (Denmark)

    Qin, Zian; Wang, Huai; Blaabjerg, Frede

    2015-01-01

    of the IGBT modules, the power losses and thereby the thermal stresses can be controlled by varying the PWM switching frequency according to power loading conditions. This paper investigates the feasibility to apply this flexible modulation strategy in a 3 MW wind power converter application to reduce......Thermal loading of wind power converters is critical to their reliability performance. Especially for IGBT modules applied in a converter, both of the mean value and variation of the junction temperature have significant impact on the lifetime. Besides other strategies to reduce the thermal loading...... the temperature fluctuations due to wind speed variations. The trade-off between the reduced amplitude of temperature fluctuations and the additional power losses that may be introduced is quantitatively studied....

  13. Modelling and simulation of randomly oriented carbon fibre-reinforced composites under thermal load

    Science.gov (United States)

    Treffler, R.; Fröschl, J.; Drechsler, K.; Ladstätter, E.

    2016-03-01

    Carbon fibre-reinforced sheet moulding compounds (CF-SMC) already exhibit a complex material behaviour under uniaxial loads due to the random orientation of the fibres in the matrix resin. Mature material models for metallic materials are generally not transferable. This paper proposes an approach for modelling the fatigue behaviour of CF-SMC based on extensive static and cyclic tests using low cost secondary carbon fibres (SCF). The main focus is on describing the stiffness degradation considering the dynamic modulus of the material. Influence factors such as temperature, orientation, rate dependence and specimen thickness were additionally considered.

  14. Influence of thermal loading on the ecology of intertidal algae

    International Nuclear Information System (INIS)

    Vadas, R.L.; Keser, M.; Rusanowski, P.c.

    1976-01-01

    Thermal effluents from the Maine Yankee Atomic Power Company (operating intermittently from October 1972 to December 1974) increased water temperatures in the discharge area by 7 to 15 0 C. Plant operation and the removal of a causeway increased mixing and salinities in Montsweag Bay. Four small red algae immigrated into the area, but no species were lost from the system. Distribution and abundance patterns of the dominant algae, Ascophyllum nodosum and Fucus vesiculosus, were altered by the thermal discharge. The cover of F. vesiculosus decreased, whereas that of A. nodosum increased in 1973 but declined significantly in 1974. Reductions in biomass and percent cover were accompanied by changes in the growth dynamics of A. nodosum. Growth and survival in the discharge area were enhanced in 1973 but reduced in 1974. Growth was initiated earlier at all sites affected by the warm water. Plants at experimental sites not directly in the discharge channel grew at accelerated rates during the two years, but stressed plants in the discharge produced few or no viable apexes in 1974. The net effect has been a compression and reduction of intertidal algae into a narrower and less dense band

  15. Nonlinear response analysis and experimental verification for thin-walled plates to thermal-acoustic loads

    Directory of Open Access Journals (Sweden)

    Yundong SHA

    2017-12-01

    Full Text Available For large deflection strongly nonlinear response problem of thin-walled structure to thermal-acoustic load, thermal-acoustic excitation test and corresponding simulation analysis for clamped metallic thin-walled plate have been implemented. Comparing calculated values with experimental values shows the consistency and verifies the effectiveness of calculation method and model for thin-walled plate subjected to thermal-acoustic load. Then this paper further completes dynamic response calculation for the cross reinforcement plate under different thermal-acoustic load combinations. Based on the obtained time-domain displacement response, analyses about structure vibration forms are mainly focused on three typical motions of post-buckled plate, indicating that the relative strength between thermal load and acoustic load determines jump forms of plate. The Probability spectrum Density Functions (PDF of displacement response were drawn and analyzed by employing statistical analysis method, and it clearly shows that the PDF of post-buckled plate exhibits bimodal phenomena. Then the Power Spectral Density (PSD functions were used to analyze variations of response frequencies and corresponding peaks with the increase of temperatures, as well as how softening and hardening areas of the plate are determined. In the last section, this paper discusses the change laws of tensile stress and compressive stress in pre/post buckling areas, and gives the reasons for N glyph trend of the stress Root Mean Square (RMS. Keywords: Buckling, Experimental verification, Nonlinear response, Power spectral density, Probability spectrum density, Snap-through, Thermal-acoustic load, Thin-walled structure

  16. The Effect of Thermal Mass on Annual Heat Load and Thermal Comfort in Cold Climate Construction

    DEFF Research Database (Denmark)

    Stevens, Vanessa; Kotol, Martin; Grunau, Bruno

    2016-01-01

    been shown to reduce the annual heating demand. However, few studies exist regarding the effects of thermal mass in cold climates. The purpose of this research is to determine the effect of high thermal mass on the annual heat demand and thermal comfort in a typical Alaskan residence using energy...... that while increased thermal mass does have advantages in all climates, such as a decrease in summer overheating, it is not an effective strategy for decreasing annual heat demand in typical residential buildings in Alaska. (C) 2015 American Society of Civil Engineers.......Thermal mass in building construction refers to a building material's ability to absorb and release heat based on changing environmental conditions. In building design, materials with high thermal mass used in climates with a diurnal temperature swing around the interior set-point temperature have...

  17. Modal frequency degeneracy in thermally loaded optical resonators.

    Science.gov (United States)

    Bullington, Amber L; Lantz, Brian T; Fejer, Martin M; Byer, Robert L

    2008-05-20

    We observe power coupling from the fundamental mode to frequency-degenerate higher-order spatial modes in optical resonators illuminated with a 30 W laser. Thermally-induced modal frequency degeneracy facilitates power transfer from the fundamental mode to higher-order modes, reduces power coupling into the cavity, and triggers power fluctuations. Modeling thermoelastic deformation of a mirror's surface shows predicted modal frequency degeneracy to be in reasonable agreement with experimental observations. Predictions for the Laser Interferometer Gravitational-wave Observatory (LIGO) show that the circulating fundamental-mode power necessary for gravitational-wave detection is compromised at coating absorptions of 3.8 and 0.44 ppm for Enhanced and Advanced LIGO Fabry-Pérot cavities, respectively.

  18. Admissible thermal loading in geological formations. Consequences on radioactive waste disposal methods

    International Nuclear Information System (INIS)

    1982-01-01

    The thermal loading in salt formation is studied for the disposal of high-level radioactive waste embedded in glass. Temperature effect on glass leaching, stability of gel layer on glass surface, quantity of leaching solution available in the borehole and corrosion resistance of materials used for containers are examined. The geological storage medium must satisfy particularly complex requirements: stratigraphy, brine migration, permeability, fissuring, mechanical strength, creep, thermal expansion, cavity structure ..

  19. Influence of the average stress in a unidirectional glass-epoxi composite material subjected to off-axis cyclic loads

    Directory of Open Access Journals (Sweden)

    Revuelta, D.

    2006-06-01

    Full Text Available A fatigue theoretical model for continuous glass-fibrereinforced epoxy composite material under general loadconditions was developed in previous works based onthe principal fatigue failure modes and on local failurecriteria. It was demonstrated that fatigue life dependedon the cyclic shear stress and the maximum stress transverseto the crack growth direction. Following the previousmodel, this work analyzes the influence of the averageapplied stress on the fatigue life of the material.En trabajos anteriores del autor desarrollo un modeloteorico de vida a fatiga para materiales compuestos unidireccionalesde matriz epoxi reforzados con fibra devidrio bajo condiciones generales de carga basado en losmodos fundamentales de rotura por fatiga y en criteriosde rotura local. Se comprobo que la vida de fatigadependia de la tension ciclica de cortadura y de la maximatension transversal a la direccion de crecimiento delas grietas. Siguiendo el modelo previo, este trabajo analizala influencia que tiene la tension media aplicada enla vida a fatiga de estos materiales.

  20. In vitro evaluation of the fracture resistance and microleakage of porcelain laminate veneers bonded to teeth with composite fillings after cyclic loading.

    Science.gov (United States)

    Sadighpour, Leyla; Geramipanah, Farideh; Allahyari, Somayeh; Fallahi Sichani, Babak; Kharazi Fard, Mohamd Javad

    2014-08-01

    There is insufficient data regarding the durability of porcelain laminate veneers bonded to existing composite fillings. The aim of the present study was to evaluate the fracture resistance and microleakage of porcelain laminate veneers bonded to teeth with existing composite fillings. Thirty maxillary central incisors were divided into three groups (for each group, n=10): intact teeth (NP), teeth with class III composite fillings (C3) and teeth with class IV cavities (C4). Porcelain laminate veneers were made using IPS-Empress ceramic and bonded with Panavia F2 resin cement. The microleakage of all of the specimens was tested before and after cyclic loading (1 × 10(6) cycles, 1.2 Hz). The fracture resistance values (N) were measured using a universal testing machine, and the mode of failure was also examined. The statistical analyses were performed using one-way ANOVA and Tukey post hoc tests (α=.05). There was a significant difference in the mean microleakage of group C4 compared with group NT (P=.013). There was no significant difference in the fracture loads among the groups. The microleakage and failure loads of porcelain laminate veneers bonded to intact teeth and teeth with standard class III composite fillings were not significantly different.

  1. Dynamic Strength and Accumulated Plastic Strain Development Laws and Models of the Remolded Red Clay under Long-Term Cyclic Loads: Laboratory Test Results

    Directory of Open Access Journals (Sweden)

    Li Jian

    2015-09-01

    Full Text Available The dynamic strength and accumulated plastic strain are two important parameters for evaluating the dynamic response of soil. As a special clay, the remolded red clay is often used as the high speed railway subgrade filling, but studies on its dynamic characteristics are few. For a thorough analysis of the suitability of the remolded red clay as the subgrade filling, a series of long-term cyclic load triaxial test under different load histories are carried out. Considering the influence of compactness, confining pressure, consolidation ratio, vibration frequency and dynamic load to the remolded red clay dynamic property, the tests obtain the development curves of the dynamic strength and accumulated plastic strain under different test conditions. Then, through curve fitting method, two different hyperbolic models respectively for the dynamic strength and accumulated plastic strain are built, which can match the test datum well. By applying the dynamic strength model, the critical dynamic strength of the remolded red clay are gained. Meanwhile, for providing basic datum and reference for relevant projects, all key parameters for the dynamic strength and accumulated plastic strain of the remolded red clay are given in the paper.

  2. Dynamic strain distribution measurement and crack detection of an adhesive-bonded single-lap joint under cyclic loading using embedded FBG

    International Nuclear Information System (INIS)

    Ning, Xiaoguang; Murayama, Hideaki; Kageyama, Kazuro; Wada, Daichi; Kanai, Makoto; Ohsawa, Isamu; Igawa, Hirotaka

    2014-01-01

    In this study, the dynamic strain distribution measurement of an adhesive-bonded single-lap joint was carried out in a cyclic load test using a fiber Bragg grating (FBG) sensor embedded into the adhesive/adherend interface along the overlap length direction. Unidirectional carbon fiber reinforced plastic (CFRP) substrates were bonded by epoxy resin to form the joint, and the FBG sensor was embedded into the surface of one substrate during its curing. The measurement was carried out with a sampling rate of 5 Hz by the sensing system, based on the optical frequency domain reflectometry (OFDR) throughout the test. A finite element analysis (FEA) was performed for the measurement evaluation using a three-dimensional model, which included the embedded FBG sensor. The crack detection method, based on the longitudinal strain distribution measurement, was introduced and performed to estimate the cracks that occurred at the adhesive/adherend interface in the test. (paper)

  3. Internal stress relaxation and load redistribution during the twinning-detwinning-dominated cyclic deformation of a wrought magnesium alloy, ZK60A

    International Nuclear Information System (INIS)

    Wu, L.; Agnew, S.R.; Brown, D.W.; Stoica, G.M.; Clausen, B.; Jain, A.; Fielden, D.E.; Liaw, P.K.

    2008-01-01

    A study of the internal strain (stress) evolution during cyclic deformation dominated by {101-bar2} twinning and detwinning mechanisms within a magnesium alloy, ZK60A, was conducted using in situ neutron diffraction. It is shown that once the matrix grains twin, the (00.2) matrix and twin grains are relaxed relative to the neighbors. This load redistribution between the soft- and hard-grain orientations is a result of plastic anisotropy. The twins which formed during the initial compression sustain a tensile stress along the c-axis, when the applied compressive stress is less than ∼80 MPa upon unloading. This local (intergranular) tensile stress is hypothesized to be effective for driving the detwinning event under a macroscopic compressive field along the c-axis. The activation stresses, 15 and 6 MPa, respectively, for the {101-bar2} extension twinning and detwinning, are approximated, based on the relaxation of the internal stresses in the matrix and twin grains

  4. Effects of Cyclic Loading on Mechanical Behavior of 24S-T4 and 75S-T6 Aluminum Alloys and SAE 4130 Steel

    Science.gov (United States)

    Macgregor, C W; Grossman, N

    1952-01-01

    An investigation was conducted to determine the effects of cyclic loading on the mechanical behavior of 24S-T4 and 75S-T6 aluminum alloys and SAE 4130 steel. Specimens of the three materials were subjected to various numbers of prior fatigue cycles both below and above the fatigue limits. Special slow-bend tests were employed to show the effects of prior cycles of fatigue stressing on the transition temperature to brittle fracture for SAE 4130 steel and on the energy-absorption capacity of the aluminum alloys. Micrographic studies were made to observe and measure crack formation and propagation and additional special tests were conducted to supplement the results of the slow-bend tests. These included Charpy impact tests, mirohardness surveys, tension tests, and fretting-corrosion studies.

  5. Experimental study of the cyclic behaviour of a 316 L stainless steel under complex multiaxial loadings in tension-torsion-internal and external pressures

    International Nuclear Information System (INIS)

    Bocher, L.; Delobelle, P.

    1997-01-01

    This paper is concerned with the experimental determination of the behaviour of a 316 L austenitic stainless steel at room temperature and under non proportional cyclic strainings in tension-torsion-internal and external pressures. The two or three sinusoidal strains were applied both in and out-of-phase and the main investigations deal with the additional hardening due to multiaxiality of the loadings. Typical stabilized hysteresis loops are presented. With respect to the maximum additional hardening the different tests can be classified as follows: in phase tests, out-of-phase internal-external pressures tests, out-of-phase tension-torsion tests and finally tension-torsion-pressure with significant phase angles. (orig.)

  6. Crack growth in Fe-2.7 wt% Si single crystals under cyclic loading and 3D atomistic results in bcc iron

    Czech Academy of Sciences Publication Activity Database

    Landa, Michal; Machová, Anna; Uhnáková, Alena; Pokluda, J.; Lejček, Pavel

    2016-01-01

    Roč. 87, June (2016), s. 63-70 ISSN 0142-1123 R&D Projects: GA ČR(CZ) GAP108/10/0698; GA ČR GAP108/12/0144; GA ČR(CZ) GA15-20666S; GA ČR GA13-13616S Institutional support: RVO:61388998 ; RVO:68378271 Keywords : grack growth * cyclic loading * Bcc iron Subject RIV: JL - Materials Fatigue, Friction Mechanics; BM - Solid Matter Physics ; Magnetism (FZU-D) Impact factor: 2.899, year: 2016 http://ac.els-cdn.com/S014211231500448X/1-s2.0-S014211231500448X-main.pdf?_tid=96e3e5a0-fb08-11e5-92cb-00000aab0f02&acdnat=1459845181_19fcdd93d31b1f140714e52b835b33d8

  7. Structural Technology Evaluation and Analysis Program (STEAP). Delivery Order 0046: Multiscale Modeling of Composite Structures Subjected to Cyclic Loading

    Science.gov (United States)

    2012-09-01

    was also used to evaluate the state of damage accumulation for the fatigue loadings at 1500, 25000 , 50000, and 100000 loading cycles. Once the chosen...Dimensions Fiber Orientation Number of Plies Length [mm] Width [mm] Thickness [mm] 0 8 250 13 1 90 16 177 25 2 Quasi- iso . 16 250 25 2...Failure Strength, f [MPa] 0 158 (13) 2,841 (296) 90 8.644 (0.712) 63 (14) Quasi- iso . 60.7 (2.2) 872 (30) The next set of experiments

  8. Effects of air-abrasion pressure on the resin bond strength to zirconia: a combined cyclic loading and thermocycling aging study

    Directory of Open Access Journals (Sweden)

    Eman Z. Al-Shehri,

    2017-06-01

    Full Text Available Objectives To determine the combined effect of fatigue cyclic loading and thermocycling (CLTC on the shear bond strength (SBS of a resin cement to zirconia surfaces that were previously air-abraded with aluminum oxide (Al2O3 particles at different pressures. Materials and Methods Seventy-two cuboid zirconia specimens were prepared and randomly assigned to 3 groups according to the air-abrasion pressures (1, 2, and 2.8 bar, and each group was further divided into 2 groups depending on aging parameters (n = 12. Panavia F 2.0 was placed on pre-conditioned zirconia surfaces, and SBS testing was performed either after 24 hours or 10,000 fatigue cycles (cyclic loading and 5,000 thermocycles. Non-contact profilometry was used to measure surface roughness. Failure modes were evaluated under optical and scanning electron microscopy. The data were analyzed using 2-way analysis of variance and χ2 tests (α = 0.05. Results The 2.8 bar group showed significantly higher surface roughness compared to the 1 bar group (p < 0.05. The interaction between pressure and time/cycling was not significant on SBS, and pressure did not have a significant effect either. SBS was significantly higher (p = 0.006 for 24 hours storage compared to CLTC. The 2 bar-CLTC group presented significantly higher percentage of pre-test failure during fatigue compared to the other groups. Mixed-failure mode was more frequent than adhesive failure. Conclusions CLTC significantly decreased the SBS values regardless of the air-abrasion pressure used.

  9. Thermal-vacuum facility with in-situ mechanical loading. [for testing space construction materials

    Science.gov (United States)

    Tennyson, R. C.; Hansen, J. S.; Holzer, R. P.; Uffen, B.; Mabson, G.

    1978-01-01

    The paper describes a thermal-vacuum space simulator used to assess property changes of fiber-reinforced polymer composite systems. The facility can achieve a vacuum of approximately .0000001 torr with temperatures ranging from -200 to +300 F. Some preliminary experimental results are presented for materials subjected to thermal loading up to 200 F. The tests conducted include the evaluation of matrix modulus and strength, coefficients of thermal expansion, and fracture toughness. Though the experimental program is at an early stage, the data appear to indicate that these parameters are influenced by hard vacuum.

  10. Physical and JIT Model Based Hybrid Modeling Approach for Building Thermal Load Prediction

    Science.gov (United States)

    Iino, Yutaka; Murai, Masahiko; Murayama, Dai; Motoyama, Ichiro

    Energy conservation in building fields is one of the key issues in environmental point of view as well as that of industrial, transportation and residential fields. The half of the total energy consumption in a building is occupied by HVAC (Heating, Ventilating and Air Conditioning) systems. In order to realize energy conservation of HVAC system, a thermal load prediction model for building is required. This paper propose a hybrid modeling approach with physical and Just-in-Time (JIT) model for building thermal load prediction. The proposed method has features and benefits such as, (1) it is applicable to the case in which past operation data for load prediction model learning is poor, (2) it has a self checking function, which always supervises if the data driven load prediction and the physical based one are consistent or not, so it can find if something is wrong in load prediction procedure, (3) it has ability to adjust load prediction in real-time against sudden change of model parameters and environmental conditions. The proposed method is evaluated with real operation data of an existing building, and the improvement of load prediction performance is illustrated.

  11. Electromagnetic and mechanical characteristion of ITER CS-MC conductors affected by transverse cyclic loading, part 2: Interstrand contact resistance

    NARCIS (Netherlands)

    Nijhuis, Arend; Noordman, Niels H.W.; ten Kate, Herman H.J.; Mitchell, Neil; Bruzzone, Pierluigi

    1999-01-01

    A special cryogenic press has been built to study the mechanical and electrical properties of full-size ITER multistrand Nb3Sn cable-in-conduit conductor samples under transverse, mechanical loading. This simulates the transverse magnetic force that occurs when the conductors are used in a coil. The

  12. Temperature and press load stimulation on thermal transport in fibrous and porous composite insulators

    International Nuclear Information System (INIS)

    Rehman, M.A.; Maqsood, A.

    2006-01-01

    Thermal transport properties of synthetic pliable insulators are measured as a function of applied pressure at constant temperatures. Advantageous Transient Plane Source (ATPS) method is used for the simultaneous measurement of thermal conductivity and thermal diffusivity of these materials and heat capacity per unit volume is then calculated. Three samples namely foam, closed cell foam and fiber glass are subjected to press load, taking into account the flexibility and sustainability of the samples and the requirements of the technique used. The thermal data of the samples were determined within the temperature range (300-414K) and pressure range (Normal -15kPa). These materials are used for thermal insulation and temperature control of air-conditioned space, acoustic and sound insulation, agriculture and fishery, sports and leisure goods, building and civil engineering, industrial packaging cold storage ware house, boiler work and other electric appliances, so they are helpful in reducing energy losses. (author)

  13. A Hybrid Power Control Concept for PV Inverters with Reduced Thermal Loading

    DEFF Research Database (Denmark)

    Yang, Yongheng; Wang, Huai; Blaabjerg, Frede

    2014-01-01

    on a single-phase PV inverter under yearly operation is presented with analyses of the thermal loading, lifetime, and annual energy yield. It has revealed the trade-off factors to select the power limit and also verified the feasibility and the effectiveness of the proposed control concept....

  14. Thermal loading and reliability of 10 MW multilevel wind power converter at different wind roughness classes

    DEFF Research Database (Denmark)

    Isidori, Andrea; Rossi, Fabio Mario; Blaabjerg, Frede

    2012-01-01

    This paper focuses on the design, thermal loading and reliability of a three-level Neutral Point Clamped (3-L NPC) back-to-back full scale converter for a 10 MW direct-drive wind turbine equipped with a Permanent Magnet Synchronous Generator (PMSG). The reliability performance of the three...

  15. Design and Implementation of a Thermal Load Reduction System in a Hyundai PHEV

    Energy Technology Data Exchange (ETDEWEB)

    Kreutzer, Cory J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rugh, John P [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-08-08

    Increased market penetration of electric drive vehicles (EDVs) requires overcoming a number of hurdles including limited vehicle range and the elevated cost of EDVs as compared to conventional vehicles. Climate control loads have a significant impact on range, cutting it by over 50% in both cooling and heating conditions. In order to minimize the impact of climate control on EDV range, the National Renewable Energy Laboratory has partnered with Hyundai America and key industry partners to quantify the performance of thermal load reduction technologies on a Hyundai Sonata PHEV. Technologies that impact vehicle cabin heating in cold weather conditions and cabin cooling in warm weather conditions were evaluated. Tests included thermal transient and steady-state periods for all technologies, including the development of a new test methodology to evaluate the performance of occupant thermal conditioning. Heated surfaces and increased insulation demonstrated significant reductions in energy use from steady-state heating, including a 29% - 59% reduction from heated surfaces. Solar control glass packages demonstrated significant reductions in energy use for both transient and steady-state cooling, with up to a 42% reduction in transient and 12.8% reduction in steady-state energy use for the packages evaluated. Technologies that demonstrated significant climate control load reduction were selected for incorporation into a complete thermal load reduction package. The complete package is set to be evaluated in the second phase of the ongoing project.

  16. Thermal shock behaviour of tungsten after high flux H-plasma loading

    NARCIS (Netherlands)

    Wirtz, M.; Linke, J.; Pintsuk, G.; De Temmerman, G.; Wright, G. M.

    2013-01-01

    Previous studies have shown that transient thermal shock loads induce crack networks on tungsten samples especially at low base temperatures. To achieve test conditions which are more relevant for the performance of tungsten-armoured plasma facing components in next step thermonuclear fusion devices

  17. Ice thermal storage air conditioning system for electric load leveling; Denryoku heijunka to hyochikunetsu system

    Energy Technology Data Exchange (ETDEWEB)

    Shigenaga, Y. [Daikin Industries Ltd., Osaka (Japan)

    1998-08-15

    Thermal storage air conditioning system is the one to use energy stored into thermal storing materials by using night electric power and to operate effective air conditioning. Therefore, as load can be treated by the stored energy, volume of the apparatus can be reduced. And, by reduction of the consumed power at day time, it can contribute to leveling of electric power demand. In general, there are two types in the thermal storage method: one is a method to store as thermal energy, and the other is that to store as chemical energy. For conditions required for the storing materials, important elements on their actual uses are not only physical properties such as large thermal storage per unit and easy thermal in- and out-puts, but also safety, long-term reliability, and easy receiving and economics containing future. The ice thermal storage air conditioning system is classified at the viewpoint of type of ice, kind of thermal storing medium, melting method on using cooling and heating, kinds of thermal medium on cooling and heating. 3 refs., 5 figs., 2 tabs.

  18. Numerical simulation of thermal loading produced by shaped high power laser onto engine parts

    International Nuclear Information System (INIS)

    Song Hongwei; Li Shaoxia; Zhang Ling; Yu Gang; Zhou Liang; Tan Jiansong

    2010-01-01

    Recently a new method for simulating the thermal loading on pistons of diesel engines was reported. The spatially shaped high power laser is employed as the heat source, and some preliminary experimental and numerical work was carried out. In this paper, a further effort was made to extend this simulation method to some other important engine parts such as cylinder heads. The incident Gaussian beam was transformed into concentric multi-circular patterns of specific intensity distributions, with the aid of diffractive optical elements (DOEs). By incorporating the appropriate repetitive laser pulses, the designed transient temperature fields and thermal loadings in the engine parts could be simulated. Thermal-structural numerical models for pistons and cylinder heads were built to predict the transient temperature and thermal stress. The models were also employed to find the optimal intensity distributions of the transformed laser beam that could produce the target transient temperature fields. Comparison of experimental and numerical results demonstrated that this systematic approach is effective in simulating the thermal loading on the engine parts.

  19. Cyclic plasticity of an austenitic-ferritic stainless steel under biaxial non proportional loading; Plasticite cyclique d'un acier inoxydable austeno-ferritique sous chargement biaxial non-proportionnel

    Energy Technology Data Exchange (ETDEWEB)

    Aubin, V

    2001-11-15

    Austenitic-ferritic stainless steels are supplied since about 30 years only, so they are yet not well-known. Their behaviour in cyclic plasticity was studied under uniaxial loading but not under multiaxial loading, whereas only a thorough knowledge of the phenomena influencing the mechanical behaviour of a material enables to simulate and predict accurately its behaviour in a structure. This work aims to study and model the behaviour of a duplex stainless steel under cyclic biaxial loading. A three step method was adopted. A set of tension-torsion tests on tubular specimen was first defined. We studied the equivalence between loading directions, and then the influence of loading path and loading history on the stress response of the material. Results showed that duplex stainless steel shows an extra-hardening under non proportional loading and that its behaviour depends on previous loading. Then, in order to analyse the results obtained during this first experimental stage, the yield surface was measured at different times during cyclic loading of the same kind. A very small plastic strain offset (2*10{sup -5}) was used in order not to disturb the yield surface measured. The alteration of isotropic and kinematic hardening variables were deduced from these measures. Finally, three phenomenological constitutive laws were identified with the experimental set. We focused our interest on the simulation of stabilized stress levels and on the simulation of the cyclic hardening/softening behaviour. The comparison between experimental and numerical results enabled the testing of the relevance of these models. (authors)

  20. Temporal evolution of a granitic rock under thermal loads generated by fission products

    International Nuclear Information System (INIS)

    Ventura, M.A.; Ferreri, J.C.

    1985-01-01

    The thermal time history of a granitic mass under thermal loads, generated by the terminal subproducts arising from the Argentine nuclear programme is analyzed. This rock will be the final repository of those subproducts. The analysis is based on the consideration of a representative unit cell of the rock's centre using the Heating 5 programme. A preliminary analysis is made in order to obtain criteria with respect to the accuracy of the problem. Temporal evolution curves of the temperature on zones of interest of the unit cell considered are shown. Under the thermal loads considered, 500W by container, a maximum temperature of 55 deg C at the wall of the orifice subproducts' deposit is obtained. (Author) [es

  1. Graphene oxide-loaded shortening as an environmentally friendly heat transfer fluid with high thermal conductivity

    Directory of Open Access Journals (Sweden)

    Vongsetskul Thammasit

    2017-01-01

    Full Text Available Graphene oxide-loaded shortening (GOS, an environmentally friendly heat transfer fluid with high thermal conductivity, was successfully prepared by mixing graphene oxide (GO with a shortening. Scanning electron microscopy revealed that GO particles, prepared by the modified Hummer’s method, dispersed well in the shortening. In addition, the latent heat of GOS decreased while their viscosity and thermal conductivity increased with increasing the amount of loaded GO. The thermal conductivity of the GOS with 4% GO was higher than that of pure shortening of ca. three times, from 0.1751 to 0.6022 W/mK, and increased with increasing temperature. The GOS started to be degraded at ca. 360°C. After being heated and cooled at 100°C for 100 cycles, its viscosity slightly decreased and no chemical degradation was observed. Therefore, the prepared GOS is potentially used as environmentally friendly heat transfer fluid at high temperature.

  2. Lifetime prediction of structures submitted to thermal fatigue loadings; Prediction de duree de vie de structures sous chargement de fatigue thermique

    Energy Technology Data Exchange (ETDEWEB)

    Amiable, S

    2006-01-15

    The aim of this work is to predict the lifetime of structures submitted to thermal fatigue loadings. This work lies within the studies undertaken by the CEA on the thermal fatigue problems from the french reactor of Civaux. In particular we study the SPLASH test: a specimen is heated continuously and cyclically cooled down by a water spray. This loading generates important temperature gradients in space and time and leads to the initiation and the propagation of a crack network. We propose a new thermo-mechanical model to simulate the SPLASH experiment and we propose a new fatigue criterion to predict the lifetime of the SPLASH specimen. We propose and compare several numerical models with various complexity to estimate the mechanical response of the SPLASH specimen. The practical implications of this work are the reevaluation of the hypothesis used in the French code RCC, which are used to simulate thermal shock and to interpret the results in terms of fatigue. This work leads to new perspectives on the mechanical interpretation of the fatigue criterion. (author)

  3. Effects of load and thermal histories on mechanical behavior of materials; Proceedings of the Symposium, Denver, CO, Feb. 25, 26, 1987

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, P.K.; Nicholas, T.

    1987-01-01

    This volume includes topics on fatigue crack propagation; isothermal and thermal-mechanical fatigue; and microstructure, fracture, and damage. Papers are presented on transients in fatigue crack growth, elevated-temperature fatigue crack propagation, the role of crack closure in crack retardation in P/M and I/M aluminum alloys, the acoustic interrogation of fatigue overload effects, and the effects of frequency and environment on crack growth in Inconel 718. Special attention is given to isothermal fatigue failure mechanisms in low-tin lead-based solder, the stress and strain controlled low-cycle fatigue of Pb-Sn solder for electronic packaging applications, load sequence effects on the deformation of isolated microplastic grains, and thermal fatigue of stainless steel. Other papers are on the influence of thermal aging on the creep crack growth behavior of a Cr-Mo steel, the effect of cyclic loading on the fracture toughness of a modified 4340 steel, and the effects of hot rolling condition and boron microalloying on phase transformation and microstructure in niobium-bearing interstitial free steel.

  4. Monotonic and cyclic deformation behaviour of ultrafine-grained aluminium

    International Nuclear Information System (INIS)

    May, J.; Amberger, D.; Dinkel, M.; Hoeppel, H.W.; Goeken, M.

    2008-01-01

    The effect of the enhanced strain-rate sensitivity (SRS) of ultrafine-grained commercially pure aluminium Al 99.5 on the mechanical properties under monotonic as well as under cyclic loading was investigated. Compared with the conventional grain-sized counterpart, for the monotonic tests, a strongly enhanced strength combined with a high ductility was obtained, depending on the strain rate. The enhanced SRS also affects the cyclic deformation behaviour and the fatigue lives. At a lower strain rate shorter fatigue lives and a different cyclic hardening behaviour are observed. Microstructural changes during cyclic deformation are investigated by X-ray diffraction profile analysis. Based on the fatigue behaviour and the X-ray diffraction profile analysis, thermally activated annihilation processes of dislocations are regarded to be the relevant deformation mechanism leading to enhanced SRS and ductility

  5. Thermal analysis of large diameter container (LDC) with alternate loadings of KE Basin sludge

    International Nuclear Information System (INIS)

    MILDON, D.T.

    2003-01-01

    A thermal analysis was performed to determine temperature distribution and hydrogen generation for a Large Diameter Container (LDC) having a two layer load configuration made up of a lower layer, consisting of sludge from the weasel pit, and an upper layer, consisting of the KE Basin canister sludge. For each alternate loading, the response of the LDC during shipping and storage in a T Plant cell was determined. Results for various alternate loadings were compared to the base case previously reported in SNF--9955 [Crea, 2002], 4 identical batches each with 60% floor, 40% canister sludge. Results for various cases are summarized in Table 5 and transient histories for each case are contained in figures as noted in the table. The thermal response and hydrogen generation rate of the base case bounds all alternate loadings except the third alternate loading, where 0.8 m 3 of canister sludge is loaded on the top of 1.2 m 3 of weasel pit sludge. For this case, the peak sludge temperature exceeded 100 C during shipping after 6.8 days (Note: sludge boiling does not occur in any case because the LDC pressurizes during transport and interstitial water is never saturated)

  6. Optimization of ITER Nb3Sn CICCs for coupling loss, transverse electromagnetic load and axial thermal contraction

    Science.gov (United States)

    Nijhuis, A.; van Lanen, E. P. A.; Rolando, G.

    2012-01-01

    the distinct difference in mechanical response of the cable during axial contraction for short and long pitches. For short pitches periodic bending in different directions with relatively short wavelength is imposed because of a lack of sufficient lateral restraint of radial pressure. This can lead to high bending strain and eventually buckling. Whereas for cables with long twist pitches, the strands are only able to react as coherent bundles, being tightly supported by the surrounding strands, providing sufficient lateral restraint of radial pressure in combination with enough slippage to avoid single strand bending along detrimental short wavelengths. Experimental evidence of good performance was already provided with the test of the long pitch TFPRO2-OST2, which is still until today, the best ITER-type cable to strand performance ever without any cyclic load (electromagnetic and thermal contraction) degradation. For reduction of the coupling loss, specific choices of the cabling twist sequence are needed to minimize the area of linked strands and bundles that are coupled and form loops with the applied changing magnetic field, instead of simply avoiding longer pitches. In addition we recommend increasing the wrap coverage of the CS conductor from 50% to at least 70%. A larger wrap coverage fraction enhances the overall strand bundle lateral restraint. The long pitch design seems the best solution to optimize the ITER CS conductor within the given restrictions of the present coil design envelope, only allowing marginal changes. The models predict significant improvement against strain sensitivity and substantial decrease of the AC coupling loss in Nb3Sn CICCs, but also for NbTi CICCs minimization of the coupling loss can obviously be achieved. Although the success of long pitches to transverse load degradation was already demonstrated, the prediction of the elegant innovative combination with low coupling loss needs to be validated by a short sample test.

  7. Thermal load histories for North American roof assembles using various cladding materials including wood-thermoplastic composite shingles

    Science.gov (United States)

    J. E. Winandy

    2006-01-01

    Since 1991, thermal load histories for various roof cladding types have been monitored in outdoor attic structures that simulate classic North American light-framed construction. In this paper, the 2005 thermal loads for wood-based composite roof sheathing, wood rafters, and attics under wood-plastic composite shingles are compared to common North American roof...

  8. Total System Performance Assessment- License Application Design Selection (LADS) Phase 1 Analysis for Higher Thermal Load (Feature 26)

    International Nuclear Information System (INIS)

    N. Erb

    1999-01-01

    The objective of this report is to evaluate the effect of potential changes to the TSPA-VA base case design on long-term repository performance. The design feature that is evaluated in this report is a higher thermal load (Feature 26 or F26). The following paragraph briefly describes the motivation for evaluating higher thermal loading. Higher thermal load has been identified as a design feature that might have a beneficial effect on long-term repository performance. A higher thermal load will increase temperatures and decrease relative humidity on the waste package surface. The decrease in relative humidity may delay the onset of corrosion, thus delaying the failure of waste packages and the release of radionuclides from the engineered barrier system (EBS). For the current calculation a thermal load of 109 MTU/acre (metric tons of uranium per acre) is considered. Two cases are evaluated, one with the base case inventory and a higher thermal load and a second with an increased inventory that would cover the current repository footprint at the higher thermal load. This report documents the modeling assumptions and calculations conducted to evaluate the long-term performance of higher thermal loading. The performance measure for this evaluation is dose-rate. Results are presented that compare the dose-rate time histories with the new design feature to that for the TSPA-VA base case calculation (CRWMS M and O, 1998a)

  9. Entropy Generation in Thermal Radiative Loading of Structures with Distinct Heaters

    Directory of Open Access Journals (Sweden)

    Mohammad Yaghoub Abdollahzadeh Jamalabadi

    2017-09-01

    Full Text Available Thermal loading by radiant heaters is used in building heating and hot structure design applications. In this research, characteristics of the thermal radiative heating of an enclosure by a distinct heater are investigated from the second law of thermodynamics point of view. The governing equations of conservation of mass, momentum, and energy (fluid and solid are solved by the finite volume method and the semi-implicit method for pressure linked equations (SIMPLE algorithm. Radiant heaters are modeled by constant heat flux elements, and the lower wall is held at a constant temperature while the other boundaries are adiabatic. The thermal conductivity and viscosity of the fluid are temperature-dependent, which leads to complex partial differential equations with nonlinear coefficients. The parameter study is done based on the amount of thermal load (presented by heating number as well as geometrical configuration parameters, such as the aspect ratio of the enclosure and the radiant heater number. The results present the effect of thermal and geometrical parameters on entropy generation and the distribution field. Furthermore, the effect of thermal radiative heating on both of the components of entropy generation (viscous dissipation and heat dissipation is investigated.

  10. Environmental effect on cracking of an 304L austenitic stainless steels in PWR primary environment under cyclic loading

    International Nuclear Information System (INIS)

    Huin, N.

    2013-01-01

    The present study was undertaken in order to get further insights on cracking mechanisms in a 304L stainless steel. More precisely, a first objective of this study was to evaluate the effect of various cold working conditions on the cyclic stress-strain behavior and the fatigue life in air and in PWR primary environment. In air a prior hardening was found to reduce the fatigue life in the LCF regime but not in primary environment. In both environments, the fatigue limit of the hardened materials was increased after cold working.The second objective addresses the effect of the air and the PWR primary environments on the cracking mechanisms (initiation and propagation) in the annealed material in the LCF regime. More precisely, the kinetics of crack initiation and micro crack propagation were evaluated with a multi scale microscopic approach in air and in primary environment. In PWR primary environment, during the first cycles, preferential oxidation occurs along emerging dissociated dislocation and each cycle generates a new C-rich/Fe-rich oxide layer. Then, during cycling, the microstructure evolves from stacking fault into micro twinning and preferential oxidation occurs by continuous shearing and dissolution of the passive film. Beyond a certain crack depth (≤3 μm), the crack starts to propagate with a direction close to a 90 degrees angle from the surface. The crack continues its propagation by successive generation of shear bands and fatigue striations at each cycle up to failure. The role of corrosion hydrogen on these processes is finally discussed. (author)

  11. Experimental Research on Longitudinal Steel Bar Bond Properties in Modified Recycled Aggregate Concrete Beam-Column Interior Joint under Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Jia-Li Fu

    2017-01-01

    Full Text Available Three recycled aggregate concrete (RAC beam-column interior-joint specimens (including two modified recycled aggregate concrete interior joints with replacement of fly ash ratio of 15% were tested under cyclic loading in order to study the bond behavior of the longitudinal steel bar at RAC joint. The tests obtained load-strain hysteresis curves of longitudinal bars. The relative bond strength of longitudinal bar in characteristic stages was calculated. The test results indicated that the longitudinal steel bar in RAC joint is able to supply a stable bond stress both in the full crack stage and in the ultimate stage, meaning that the requirements of stress transferring and displacement coordinating between RAC and reinforcements can be satisfied. The larger the diameter of steel bar, the more serious the bond strength degradation. The RAC with fly ash can improve the interface compactness and bond strength of recycled aggregate in full crack stage. When beam-column interface of concrete compression zone reaches ultimate strain, the compressive stress of the longitudinal reinforcement cannot be exerted. The bond stress of the steel bar cannot realize the pull and compressive stress conversion in the length of the core area of the joint owing to the stress hysteresis of the compression rebars.

  12. Experimental study on 1/30 scale model of reinforced concrete reactor building under cyclic lateral loading

    International Nuclear Information System (INIS)

    Fukada, Yasuo; Hirashima, Shinichi; Shohara, Ryoichi

    1980-01-01

    At the time of carrying out the aseismatic design of BWR type reactor buildings, in particular the design to the limit earthquake for design (S2 earthquake), it is necessary to grasp the load-deformation relationship of the buildings not only in elastic region but also extending to plastic region. The BWR type reactor buildings are the complex structures composed of the thick walls of box type and cylindrical-conical type. As the first stage of the experimental approach for grasping various properties of such structures to earthquake force, three kinds of the main elements of the buildings resisting earthquakes were taken out individually, and three 1/30 scale models were subjected to horizontal loading experiment. In this paper, the concept of this experiment, tested models, experimental method and a part of the experimental results are reported. The experiment took about 14 months from the design of the tested models to the completion of experiment. At present, the data analysis is continued. The stress intensity corresponding to the limit earthquake for design was lower than 1/2.5 as compared with the ultimate end, and sufficient margin remained. The deformation at that time was sufficiently small, and the number and the width of cracks were also small. The buildings seemed to accomplish the functions sufficiently. (Kako, I.)

  13. Crack propagation under thermal cycling loading inducing a thermal gradient in the specimen thickness

    International Nuclear Information System (INIS)

    Le, H.N.

    2009-05-01

    This study aims to figure out the crack growth phenomenon by thermal fatigue induced by thermal gradient through thickness of specimen. Firstly, an experimental facility has been developed: a rectangular parallelepiped specimen is subjected to thermal cycling between 350 C and 100 C; the specimen is freed to expand and contract. Two semi-circular notches (0,1 mm depth and 4 mm length) have been machined on the surface of the specimen. A series of interrupted tests has been carried out to characterize and quantify the crack growth in depth and surface of the pre-existing crack. Next, a three-dimensional crack growth simulation has been implemented in ABAQUS. Automation using Python was used to simulate the propagation of a crack under thermal cycling, with re-meshing at crack front after each calculation step. No assumption has been taken on the crack front during the crack propagation. A comparison with test results showed very good agreement on the evolution of crack front shape and on the kinetics of propagation on the edge and the heart of pre-existing crack. An analytical approach was also developed based on the calculation of stress intensity factors (SIC). A two-dimensional approach was first introduced enabling us to better understand the influence of various thermal and geometric parameters. Finally, a three dimensional approach, with an elliptical assumption crack shape during the propagation, leading to a prediction of crack growth on the surface and in depth which is very similar to that obtained numerically, but with computational time much lower. (author)

  14. The impact of transient thermal loads on beryllium as plasma facing material

    International Nuclear Information System (INIS)

    Spilker, Benjamin Christof

    2017-01-01

    The rising global energy consumption requires a broad research and development approach in the field of energy technology. Besides renewables, nuclear fusion promises an efficient, CO 2 free, no long-term radioactive waste producing, and safe energy source using only deuterium and lithium as primary resources, which are widely abundant. However, several technical challenges have to be overcome before a nuclear fusion power plant can be built. For this purpose, the experimental reactor ITER is currently under construction in France. ITER is intended to demonstrate the scientific and technological feasibility of net energy generation via nuclear fusion. The most heavily loaded components inside a fusion reactor, which are directly facing the fusion plasma, have to be armoured with well suited materials, which need to be able to withstand the high thermal and particle loads for an economically reasonable lifetime. For ITER, beryllium is chosen as plasma facing material for the largest fraction of the inner vacuum vessel, the so called first wall. Tungsten will be applied in the bottom region of the vacuum vessel, the so called divertor, which acts as the exhaust system of the machine. The choice of beryllium as plasma facing material was driven by its outstanding advantages, e.g. the low atomic number assures that eroded wall material does not strongly decrease the fusion plasma performance, while it combines a high thermal conductivity with low chemical sputtering characteristics. However, the relatively low melting temperature of beryllium of 1287 C comprises the risk of amour damage by melting during transient plasma events, such as edge localized modes or plasma disruptions. Even when mitigated, these events put tremendous power densities in the GW m -2 range with durations in the ms scale onto the plasma facing materials. Hence, the performance of the ITER reference beryllium grade S-65 under transient thermal loads was studied within this work. Thereby, the

  15. The impact of transient thermal loads on beryllium as plasma facing material

    Energy Technology Data Exchange (ETDEWEB)

    Spilker, Benjamin Christof

    2017-01-24

    The rising global energy consumption requires a broad research and development approach in the field of energy technology. Besides renewables, nuclear fusion promises an efficient, CO{sub 2} free, no long-term radioactive waste producing, and safe energy source using only deuterium and lithium as primary resources, which are widely abundant. However, several technical challenges have to be overcome before a nuclear fusion power plant can be built. For this purpose, the experimental reactor ITER is currently under construction in France. ITER is intended to demonstrate the scientific and technological feasibility of net energy generation via nuclear fusion. The most heavily loaded components inside a fusion reactor, which are directly facing the fusion plasma, have to be armoured with well suited materials, which need to be able to withstand the high thermal and particle loads for an economically reasonable lifetime. For ITER, beryllium is chosen as plasma facing material for the largest fraction of the inner vacuum vessel, the so called first wall. Tungsten will be applied in the bottom region of the vacuum vessel, the so called divertor, which acts as the exhaust system of the machine. The choice of beryllium as plasma facing material was driven by its outstanding advantages, e.g. the low atomic number assures that eroded wall material does not strongly decrease the fusion plasma performance, while it combines a high thermal conductivity with low chemical sputtering characteristics. However, the relatively low melting temperature of beryllium of 1287 C comprises the risk of amour damage by melting during transient plasma events, such as edge localized modes or plasma disruptions. Even when mitigated, these events put tremendous power densities in the GW m{sup -2} range with durations in the ms scale onto the plasma facing materials. Hence, the performance of the ITER reference beryllium grade S-65 under transient thermal loads was studied within this work. Thereby

  16. Composite Reliability Evaluation of Load Demand Side Management and Dynamic Thermal Rating Systems

    Directory of Open Access Journals (Sweden)

    Jiashen Teh

    2018-02-01

    Full Text Available Electric power utilities across the globe are facing higher demand for electricity than ever before, while juggling to balance environmental conservation with transmission corridor expansions. Demand side management (DSM and dynamic thermal rating systems (DTR play an important role in alleviating some of the challenges faced by electric power utilities. In this paper, various DSM measures are explored and their interactions with the application of the DTR system in the transmission network are examined. The proposed modelling of DSM in this paper implements load shifting on load demand curves from the system, bus and load sector levels. The correlation effects of line ratings are considered in the DTR system modelling as the weather that influences line ratings is also correlated. The modelling of the line ratings was performed using the time series method, the auto regressive moving average (ARMA model. Both the DSM and the DTR systems were implemented on the modified IEEE reliability test network. The modification was achieved by developing a load model starting from the perspective of the load sectors at each bus and a new collective hourly load curve for the system was obtained by combining the loads at all buses. Finally, the results in this paper elucidate the interaction of DSM and DTR systems.

  17. Thermal load effects on fatigue life of a cracked railway wheel

    Directory of Open Access Journals (Sweden)

    Azadeh Haidari

    Full Text Available AbstractIn this paper, fatigue life of a cracked railway wheel under thermo-mechanical loads is studied. For this purpose a FE model of a wheel, with two brake shoes and a portion of rail is created and suitable loads and boundary conditions are applied to the model. It is assumed that the wheel has contained an elliptical crack in the definite depth of the tread surface and thermalloads are determined by modeling the contact of the rail-wheel and two brake blocks. In order to investigate the thermalloads effect on the fatigue life of the cracked wheel, analyses areperformed in two cases: mechanical analysis and thermo-mechanical analysis; while difference between them, shows thermal load effects and its importance. In this work the wheel rotation on rail is modeled and a 3D FE model for determination of rail-wheel contact pressure is used while in many of the previous investigations, either rolling wasn't modeled or its effect was simplified as a translating pressure distribution along the rail-wheel contact region and also the Hertz contact theory had used for determination of contact pressure in wheel- rail interface. Finally, effects of angular velocity on fatigue life of a cracked wheel under -mechanical and mechanical loads are shown. The obtained results confirm the important influences of thermal loads on the wheel fatigue life in all mentioned cases that are studied in this article.

  18. Assessment of the Dynamic Behaviour of Saturated Soil Subjected to Cyclic Loading from Offshore Monopile Wind Turbine Foundations

    DEFF Research Database (Denmark)

    Damgaard, Mads; Bayat, Mehdi; Andersen, Lars Vabbersgaard

    2014-01-01

    The fatigue life of offshore wind turbines strongly depends on the dynamic behaviour of the structures including the underlying soil. To diminish dynamic amplification and avoid resonance, the eigenfrequency related to the lowest eigenmode of the wind turbine should not coalesce with excitation...... frequencies related to strong wind, wave and ice loading. Typically, lateral response of monopile foundations is analysed using a beam on a nonlinear Winkler foundation model with soil-pile interaction recommended by the design regulations. However, as it will be shown in this paper, the guideline approaches...... consequently underestimate the eigenfrequency compared to full-scale measurements. This discrepancy leads the authors to investigate the influence of pore water pressure by utilising a numerical approach and consider the soil medium as a two-phase system consisting of a solid skeleton and a single pore fluid...

  19. Gas chromatographic-mass spectrometric separation, identification and determination of C6-C12 cyclic imides in thermally treated epoxy and alkyd resins to locate hot spots inside large electricity generators.

    Science.gov (United States)

    Husain, S; Alvi, S N; Rao, R N

    1999-11-05

    A simple and rapid GC-MS method for separation, identification and quantitative determination of long-chain cyclic imides in the 300 degrees C thermally treated epoxy and alkyd resins has been developed. The method provides a positive means of identifying C6-C12 cyclic imide derivatives by GC-MS and enables the specific area of overheating to be identified, thereby averting catastrophic failures of power generators in service.

  20. Study of surfaces and surface layers on high temperature materials after short-time thermal loads

    International Nuclear Information System (INIS)

    Bolt, H.; Hoven, H.; Koizlik, K.; Linke, J.; Nickel, H.; Wallura, E.

    1985-11-01

    Being part of the plasma-wall interaction during TOKAMAK operation, erosion- and redeposition processes of First Wall materials substantially influence plasma parameters as well as the properties of the First Wall. An important redeposition process of eroded material is the formation of thin films by atomic condensation. Examinations of First Wall components after TOKAMAK operation lead to the assumption that these thin metallic films tend to agglomerate to small particles under subsequent heat load. In laboratory experiments it is shown that thin metallic films on various substrates can agglomerate under short time high heat fluxes and also under longer lasting lower thermal loads, thus verifying the ''agglomeration hypothesis''. (orig.) [de

  1. Temporal evolution of a granitic rock under thermal loads generated by fission products

    International Nuclear Information System (INIS)

    Ventura, M.A.; Ferreri, J.C.

    1985-01-01

    A parametric study of the thermal history of a granitic mass under thermal loads originating in terminal subproducts of the fuel cycle is performed. Variations of the conductivity and density of the rock and the unit cell dimensions are considered. In this way it was tried to delimit (for short time intervals of the order of 100 years) the influence of possible uncertainties in the rock's knowledge on the results of interest for the engineering design. In the reasonable situations considered, the maximum temperature in the rock did not rise over 80 deg C. (Author) [es

  2. A biomechanical comparison of tendon-bone interface motion and cyclic loading between single-row, triple-loaded cuff repairs and double-row, suture-tape cuff repairs using biocomposite anchors.

    Science.gov (United States)

    Barber, F Alan; Drew, Otis R

    2012-09-01

    To compare tendon-bone interface motion and cyclic loading in a single-row, triple-loaded anchor repair with a suture-tape, rip-stop, double-row rotator cuff repair. Using 18 human shoulders from 9 matched cadaveric pairs, we created 2 groups of rotator cuff repairs. Group 1 was a double-row, rip-stop, suture-tape construct. Group 2 was a single-row, triple-loaded construct. Before mechanical testing, the supraspinatus footprint was measured with calipers. A superiorly positioned digital camera optically measured the tendon footprint motion during 60° of humeral internal and external rotation. Specimens were secured at a fixed angle not exceeding 45° in reference to the load. After preloading, each sample was cycled between 10 N and 100 N for 200 cycles at 1 Hz, followed by destructive testing at 33 mm/s. A digital camera with tracking software measured the repair displacement at 100 and 200 cycles. Ultimate load and failure mode for each sample were recorded. The exposed anterior footprint border (6.5% ± 6%) and posterior footprint border (0.9% ± 1.7%) in group 1 were statistically less than the exposed anterior footprint border (30.3% ± 17%) and posterior footprint border (29.8% ± 14%) in group 2 (P = .003 and P footprint displacements in group 1 (1.6 mm and 1.4 mm, respectively) were less than those in group 2 (both 3.6 mm) (P = .007 and P = .004, respectively). Mean displacement after 100 cycles for group 1 and group 2 was 2.0 mm and 3.2 mm, respectively, and at 200 cycles, mean displacement was 2.5 mm and 4.2 mm, respectively (P = .02). The mean ultimate failure load in group 1 (586 N) was greater than that in group 2 (393 N) (P = .02). The suture-tendon interface was the site of most construct failures. The suture-tape, rip-stop, double-row rotator cuff repair had greater footprint coverage, less rotational footprint displacement, and a greater mean ultimate failure load than the triple-loaded, single-row repair on mechanical testing. No double-row or

  3. Alternative Filament Loading Solution for Accurate Analysis of Boron Isotopes by Negative Thermal Ionization Mass Spectrometry

    Science.gov (United States)

    Dwyer, G. S.; Vengosh, A.

    2008-12-01

    The negative thermal ionization mass spectrometry technique has become the major tool for investigating boron isotopes in the environment. The high sensitivity of BO2- ionization enables measurements of ng levels of boron. However, B isotope measurement by this technique suffers from two fundamental problems (1) fractionation induced by selective ionization of B isotopes in the mass spectrometer; and (2) CNO- interference on mass 42 that is often present in some load solutions (such as B-free seawater processed through ion-exchange resin). Here we report a potentially improved methodology using an alternative filament loading solution with a recently-installed Thermo Scientific TRITON thermal ionization mass spectrometer. Our initial results suggest that this solution -- prepared by combining high-purity single- element standard solutions of Ca, Mg, Na, and K in proportions similar to those in seawater in a 5% HCl matrix -- may offer significant improvement over some other commonly used load solutions. Total loading blank is around 15pg as determined by isotope dilution (NIST952). Replicate analyses of NIST SRM951 and modern seawater thus far have yielded 11B/10B ratios of 4.0057 (±0.0008, n=14) and 4.1645 (±0.0017, n=7; δ11B=39.6 permil), respectively. Replicate analyses of samples and SRM951 yield an average standard deviation (1 σ) of approximately 0.001 (0.25 permil). Fractionation during analysis (60-90 minutes) has thus far typically been less than 0.002 (0.5 permil). The load solution delivers ionization efficiency similar to directly-loaded seawater and has negligible signal at mass 26 (CN-), a proxy for the common interfering molecular ion (CNO-) on mass 42. Standards and samples loaded with the solution behave fairly predictably during filament heating and analysis, thus allowing for the possibility of fully automated data collection.

  4. Assessment of the behavior of reinforced concrete beams retrofitted with pre-stressed CFPR subjected to cyclic loading

    Science.gov (United States)

    Hojatkashani, Ata; Zanjani, Sara

    2018-02-01

    Rehabilitation of weak and damaged structures has been considered widely during recent years. A relatively modern way of strengthening concrete components is to confine parts under tension and shear by means of carbon fiber reinforce polymer (CFRP). This way of strengthening due to the conditions of composite materials such as light weight, linear elastic behavior until failure point, high tensile strength, high elastic modulus, resistance against corrosion, and high fatigue resistance has become so common. During structural strengthening by means of not pre-stressed FRP materials, usually, it is not possible to benefit from the maximum capacity of FRP materials. In addition, sometimes, the expensive cost of such materials will not make a suitable balance between rates of strengthening and consuming spending. Thus, pre-stressing CFRP materials has an undeniable role in the effective use of materials. In the current research, general procedure of simulation using finite-element method (FEM) by means of the numerical package ABAQUS has been presented. In this article, 12 reinforced concrete (RC) models in two states (strengthened with simple and pre-stressed CFRP) under cycling loading have been considered. A parametric study has been carried out in this research on the effects of parameters such as CFRP surface area, percentage of tensile steel rebar and pre-stressing stress on ultimate load carrying capacity (ULCC), stiffness, and the ability of depreciation energy for the samples. In the current article also, for design parameters, percentages of tensile steel rebars, surface area of CFPR sheets, and the effective pre-stressing stress in RC beams retrofitted with pre-stressed CFPR sheets have investigated. In this paper, it was investigated that using different amount of parameters such as steel rebar percentage, CFRP surface area percentage, and CFRP pre-stressing, the resulted ULCC and energy depreciation of the specimens was observed to be increasing and

  5. Assessment of the behavior of reinforced concrete beams retrofitted with pre-stressed CFPR subjected to cyclic loading

    Science.gov (United States)

    Hojatkashani, Ata; Zanjani, Sara

    2018-03-01

    Rehabilitation of weak and damaged structures has been considered widely during recent years. A relatively modern way of strengthening concrete components is to confine parts under tension and shear by means of carbon fiber reinforce polymer (CFRP). This way of strengthening due to the conditions of composite materials such as light weight, linear elastic behavior until failure point, high tensile strength, high elastic modulus, resistance against corrosion, and high fatigue resistance has become so common. During structural strengthening by means of not pre-stressed FRP materials, usually, it is not possible to benefit from the maximum capacity of FRP materials. In addition, sometimes, the expensive cost of such materials will not make a suitable balance between rates of strengthening and consuming spending. Thus, pre-stressing CFRP materials has an undeniable role in the effective use of materials. In the current research, general procedure of simulation using finite-element method (FEM) by means of the numerical package ABAQUS has been presented. In this article, 12 reinforced concrete (RC) models in two states (strengthened with simple and pre-stressed CFRP) under cycling loading have been considered. A parametric study has been carried out in this research on the effects of parameters such as CFRP surface area, percentage of tensile steel rebar and pre-stressing stress on ultimate load carrying capacity (ULCC), stiffness, and the ability of depreciation energy for the samples. In the current article also, for design parameters, percentages of tensile steel rebars, surface area of CFPR sheets, and the effective pre-stressing stress in RC beams retrofitted with pre-stressed CFPR sheets have investigated. In this paper, it was investigated that using different amount of parameters such as steel rebar percentage, CFRP surface area percentage, and CFRP pre-stressing, the resulted ULCC and energy depreciation of the specimens was observed to be increasing and

  6. Thermal loads on tokamak plasma-facing components during normal operation and disruptions

    International Nuclear Information System (INIS)

    McGrath, R.T.

    1990-01-01

    Power loadings experienced by tokamak plasma-facing components during normal operation and during off-normal events are discussed. A model for power and particle flow in the tokamak boundary layer is presented and model predictions are compared to infrared measurements of component heating. The inclusion of the full three-dimensional geometry of the components and of the magnetic flux surface is very important in the modeling. Experimental measurements show that misalignment of component armour tile surfaces by only a millimeter can lead to significant localized heating. An application to the design of plasma-facing components for future machines is presented. Finally, thermal loads expected during tokamak disruptions are discussed. The primary problems are surface melting and vaporization due to localized intense heating during the disruption thermal quench and volumetric heating of the component armour and structure due to localised impact of runaway electrons. (author)

  7. Fatigue life prediction in a unidirectional glass-epoxy composite material subjected to off-axis cyclic loads

    Directory of Open Access Journals (Sweden)

    Revuelta, D.

    2005-03-01

    Full Text Available Most of today s fatigue analysis and design methods for composite laminates were developed primarily on the basis of experience with homogeneous metals. Such methods are subject to serious drawbacks, however, because the failure the modes of failure observed in metals. A theoretical model for predicting the fatigue life of continuous glass-fibre/epoxy composite materials under general loading conditions has been developed on the basis of fundamental fatigue failure modes and local failure criteria.

    La mayoría de los actuales métodos de cálculo y diseño a fatiga de estructuras de materiales compuestos se han desarrollado principalmente a partir de la experiencia previa en materiales metálicos homogéneos. Sin embargo, estos métodos presentan serios inconvenientes debido a que la heterogeneidad y micro estructura orientada características de los materiales compuestos laminados provocan modos de fallo diferentes a los de los metales. Basándose en los modos fundamentales de rotura por fatiga y en criterios de rotura local, se desarrolla un modelo teórico de vida a fatiga para materiales compuestos de matriz epoxi reforzados con fibra de vidrio bajo condiciones generales de carga

  8. RIP INPUT TABLES FROM WAPDEG FOR LA DESIGN SELECTION: HIGHER THERMAL LOADING

    International Nuclear Information System (INIS)

    K. Mon

    1999-01-01

    The purpose of this calculation is to document (1) the Waste Package Degradation (WAPDEG) version 3.09 (CRWMS M and O 1998b. Software Routine Report for WAPDEG (Version 3.09)) simulations used to analyze waste package degradation and failure under the repository exposure conditions characterized by the higher thermal loading repository design feature and, (2) post-processing of these results into tables of waste package degradation time histories suitable for use as input into the Integrated Probabilistic Simulator for Environmental Systems version 5.19.01 (RIP) computer program (Golder Associates 1998). Specifically, the WAPDEG simulations discussed in this calculation correspond to waste package emplacement conditions (repository environment and design) defined in the Total System Performance Assessment-Viability Assessment (TSPA-VA), with the exception that the higher thermal loading Design Feature (Design Feature 26) of the License Application Design Selection (LADS) analysis was analyzed. Higher thermal loading would keep the drift temperature above the boiling point of water for a longer period of time, thereby minimizing moisture around the waste packages during a longer post-closure period. The higher thermal loading would also affect the surrounding rock, which may have adverse effects. The only failure mechanism of this feature would be if the effects on the surrounding rock were determined to be unacceptable. As a result of the change in waste package placement relative to the TSPA-VA base-case design, different temperature and relative humidity time histories at the waste package surface are calculated (input to the WAPDEG simulations), and consequently different waste package failure histories (as calculated by WAPDEG) result

  9. STATIC AND DYNAMIC ANALYSIS UNDER MECHANICAL AND THERMAL LOADS OF THE DOUBLE SCARA ROBOT

    Directory of Open Access Journals (Sweden)

    Iosif TEMPEA

    2016-05-01

    Full Text Available The paper presents a synthesis of the Double SCARA Robot modelling, leading to an optimal solution, from workspace point of view, as well as precision and stability of the endeffector in performing the planned trajectory. For the design of the final mechanism CATIA software has been used, as well as NASTRAN/PATRAN software, for the mechanism analysis under mechanical and thermal loads.

  10. Building thermal loads: A case study for David Hellen Petta public secondary school

    CSIR Research Space (South Africa)

    Kumirai, T

    2013-03-01

    Full Text Available Building Handbook South Africa Volume 5: The Essential Guide Building Thermal Loads: A case study for David Hellen Petta public secondary school T Kumirai Built Environment, Council for Scientific and Industrial Research PO Box 395, Pretoria..., 0001 South Africa tkumirai@csir.co.za Abstract Statistics published by the Department of Basic Education in November 2010 reveal the following: a) There are 11 834 516 learners that attend public schools, b) there are 387 837 educators...

  11. Determination of thermal reactivity coefficients for the first fuel loading of MO34

    International Nuclear Information System (INIS)

    Lueley, J.; Vrban, B.; Farkas, G.; Hascik, J.; Hinca, R.; Petriska, M.; Slugen, V.

    2012-01-01

    The article introduces determination of thermal reactivity coefficients, especially summarized (isothermal) and moderator (density) reactivity coefficients between 200 grad C and 260 grad C with 2 grad C step, - in compliance with the assignment - for the first fuel loading into the RC of NP Mochovce units using 2 nd generation fuel during the start-up using calculation code MCNP5 1.60. (authors)

  12. Performance of Nb3Sn quadrupole magnets under localized thermal load

    Energy Technology Data Exchange (ETDEWEB)

    Kashikhin, V.V.; Bossert, r.; Chlachidze, G.; Lamm, M.; Mokhov, N.V.; Novitski, I.; Zlobin, A.V.; /Fermilab

    2009-06-01

    This paper describes the results of design and analyses performed on 120-mm Nb{sub 3}Sn and NbTi quadrupole magnets with parameters relevant for the LHC IR upgrade. A realistic radiation heat load is evaluated in a wide luminosity range and translated into the magnet quench performance. The simulation results are supported by thermal measurements on a 90-mm Nb{sub 3}Sn quadrupole coil.

  13. High temperature thermal creep under variable stress and temperature loading conditions

    International Nuclear Information System (INIS)

    Bocek, M.

    1985-01-01

    The present paper is concerned with thermal creep of cavitating materials subjected to time variable stresses and/or temperatures. Creep cavitation damage, because reducing the load bearing capability will influence the creep behavior of structures loaded by tension. The calculations are based on a phenomenological cavitation damage model, from which the life fraction rule (LFR) is deduced. For complex stress/temperature loading conditions by means of the LFR analytical expressions for the corresponding lifetimes are derived. Only stationary stress rupture data together with the loading conditions enter the computations. In the present procedure the damage function A(t), as a variable structure parameter, enters a constitutive strain rate/stress equation through an effective (true) stress. The latter, for given loading conditions, is derived from the solution of the general tensile test equation. Solving the strain rate/stress equation in terms of strain or time, the constitutive creep equation for ideally plastic cavitating materials exposed to non-stationary loading conditions are derived

  14. Deformation mechanisms in cyclic creep and fatigue

    International Nuclear Information System (INIS)

    Laird, C.

    1979-01-01

    Service conditions in which static and cyclic loading occur in conjunction are numerous. It is argued that an understanding of cyclic creep and cyclic deformation are necessary both for design and for understanding creep-fatigue fracture. Accordingly a brief, and selective, review of cyclic creep and cyclic deformation at both low and high strain amplitudes is provided. Cyclic loading in conjunction with static loading can lead to creep retardation if cyclic hardening occurs, or creep acceleration if softening occurs. Low strain amplitude cyclic deformation is understood in terms of dislocation loop patch and persistent slip band behavior, high strain deformation in terms of dislocation cell-shuttling models. While interesting advances in these fields have been made in the last few years, the deformation mechanisms are generally poorly understood

  15. A coupled nuclear reactor thermal energy storage system for enhanced load following operation

    International Nuclear Information System (INIS)

    Alameri, Saeed A.; King, Jeffrey C.

    2013-01-01

    Nuclear power plants operate most economically at a constant power level, providing base load electric power. In an energy grid containing a high fraction of renewable power sources, nuclear reactors may be subject to significantly variable power demands. These variable power demands can negatively impact the effective capacity factor of the reactor and result in severe economic penalties. Coupling a nuclear reactor to a large thermal energy storage block will allow the reactor to better respond to variable power demands. In the system described in this paper, a Prismatic core Advanced High Temperature Reactor supplies constant power to a lithium chloride molten salt thermal energy storage block that provides thermal power as needed to a closed Brayton cycle energy conversion system. During normal operation, the thermal energy storage block stores thermal energy during the night for use in the times of peak demand during the day. In this case, the nuclear reactor stays at a constant thermal power level. After a loss of forced circulation, the reactor reaches a shut down state in less than half an hour and the average fuel, graphite and coolant temperatures remain well within the design limits over the duration of the transient, demonstrating the inherent safety of the coupled system. (author)

  16. Thermal Loading and Lifetime Estimation for Power Device Considering Mission Profiles in Wind Power Converter

    DEFF Research Database (Denmark)

    Ma, Ke; Liserre, Marco; Blaabjerg, Frede

    2015-01-01

    As a key component in the wind turbine system, the power electronic converter and its power semiconductors suffer from complicated power loadings related to environment, and are proven to have high failure rates. Therefore, correct lifetime estimation of wind power converter is crucial for the re......As a key component in the wind turbine system, the power electronic converter and its power semiconductors suffer from complicated power loadings related to environment, and are proven to have high failure rates. Therefore, correct lifetime estimation of wind power converter is crucial....... Consequently, a relative more advanced approach is proposed in this paper, which is based on the loading and strength analysis of devices and takes into account different time constants of the thermal behaviors in power converter. With the established methods for loading and lifetime estimation for power...... devices, more detailed information of the lifetime-related performance in wind power converter can be obtained. Some experimental results are also included to validate the thermal behavior of power device under different mission profiles....

  17. Thermal Energy Storage for Building Load Management: Application to Electrically Heated Floor

    Directory of Open Access Journals (Sweden)

    Hélène Thieblemont

    2016-07-01

    Full Text Available In cold climates, electrical power demand for space conditioning becomes a critical issue for utility companies during certain periods of the day. Shifting a portion or all of it to off-peak periods can help reduce peak demand and reduce stress on the electrical grid. Sensible thermal energy storage (TES systems, and particularly electrically heated floors (EHF, can store thermal energy in buildings during the off-peak periods and release it during the peak periods while maintaining occupants’ thermal comfort. However, choosing the type of storage system and/or its configuration may be difficult. In this paper, the performance of an EHF for load management is studied. First, a methodology is developed to integrate EHF in TRNSYS program in order to investigate the impact of floor assembly on the EHF performance. Then, the thermal comfort (TC of the night-running EHF is studied. Finally, indicators are defined, allowing the comparison of different EHF. Results show that an EHF is able to shift 84% of building loads to the night while maintaining acceptable TC in cold climate. Moreover, this system is able to provide savings for the customer and supplier if there is a significant difference between off-peak and peak period electricity prices.

  18. Comparison of Energy Dissipation, Stiffness, and Damage of Structural Oriented Strand Board (OSB, Conventional Gypsum, and Viscoelastic Gypsum Shearwalls Subjected to Cyclic Loads

    Directory of Open Access Journals (Sweden)

    Andrew S. Blasetti

    2012-06-01

    Full Text Available A key element in the seismic load resisting system of a wood framed structure is the shear wall which is typically sheathed on one side with plywood or oriented strand board (OSB and gypsum on the other. The shear capacity of gypsum sheathed shear walls is typically neglected in high seismic areas due to the susceptibility of conventional drywall screw connections to damage caused by earthquakes. The earthquake resistance of an innovative viscoelastic (VE gypsum shearwall is evaluated and compared to conventional structural and non-structural walls. Ten 8 ft × 8 ft wood framed wall specimens of three configurations [nailed-OSB, screw-gypsum, and VE polymer-gypsum] were subjected to a cyclic test protocol. The energy dissipation, stiffness, and damage characteristics of all shearwalls are reported herein. Testing results indicate the VE-gypsum walls can dissipate more energy than the OSB structural panels and 500% more energy that the conventional gypsum sheathed walls and contains a constant source of energy dissipation not seen in the structural and non-structural walls. The wall stiffness of the OSB wall degrades at a far greater rate that the VE gypsum wall and at continued cycling degrades below the VE wall stiffness. Unlike both of the conventional wall types, the VE wall showed no visible or audible signs of damage when subjected to shear displacements up to 1.

  19. Magnetic field induced tunability on the thermal conductivity of ferrofluids loaded with carbon nanofibers

    Science.gov (United States)

    Ortiz-Salazar, M.; Pech-May, N. W.; Vales-Pinzon, C.; Medina-Esquivel, R.; Alvarado-Gil, J. J.

    2018-02-01

    In this paper, it is shown that the thermal conductivity of magnetic fluids, formed by a ferrofluid loaded with carbon nanofibers, can be tuned by applying a moderate intensity magnetic field. The tuning is generated by orienting the nanoparticles in the ferrofluid, which in turn partially align the carbon nanofibers, favoring or hindering heat flow along a given direction. Thermal diffusivity at several volume concentrations of nanofibers (0, 0.25, 0.50, 1, 2 and 5%) was measured using the thermal wave resonant cavity technique, located inside a uniform moderate intensity magnetic field. Measurements were performed for random and aligned carbon nanofibers, oriented in the parallel and perpendicular directions with respect to the heat flux. The experimental results show that for 5% volume concentration of carbon nanofibers in the ferrofluid, in random configuration, i.e. without external magnetic field applied, the effective thermal conductivity increased 3 times compared to that of the ferrofluid matrix. Moreover, for parallel alignment of the carbon nanofibers with respect to the heat flux direction, the effective thermal conductivity increased 5 times. However, for perpendicular alignment of the carbon nanofibers with respect to the heat flux direction only a 2 times increment in the effective thermal conductivity is obtained. A 750 G intensity magnetic field is used for both alignment configurations. Additionally, the effect of the concentration of carbon nanofibers on the thermal time-response of the magnetic fluids was studied by switching on/off the magnetic field. The Lewis–Nielsen model was used to interpret the dependence of the thermal conductivity results as a function the concentration and orientation of the carbon nanofibers.

  20. Modeling thermal-hydrological response of the unsaturated zone at Yucca Mountain, Nevada, to thermal load at a potential repository.

    Science.gov (United States)

    Haukwa, C B; Wu, Yu-Shu; Bodvarsson, G S

    2003-01-01

    This paper presents a numerical study on the response of the unsaturated zone (UZ) system of Yucca Mountain to heat generated from decaying radioactive wastes emplaced at the proposed repository. The modeling study is based on the current thermal-hydrological (TH) mountain-scale model, which uses a locally refined 2D north-south cross-section and dual-permeability numerical approach. The model provides a prediction of the mountain-scale TH response under the thermal-load scenario of 1.45 kW/m, while accounting for future climatic changes and the effects of drift ventilation. The TH simulation results show that ventilation of the repository drifts has a large impact on thermal-hydrologic regimes and moisture-flow conditions at the repository. In both cases, with and without ventilation, the TH model predicts dry or reduced liquid saturation near the drifts for over 1000 years, during which liquid flux through the drifts is reduced to either zero or less than the ambient flux. Without ventilation, the model predicts higher temperatures at the repository, but no major moisture redistribution in the UZ except in the areas very near the heated drifts.

  1. Detailed partial load investigation of a thermal energy storage concept for solar thermal power plants with direct steam generation

    Science.gov (United States)

    Seitz, M.; Hübner, S.; Johnson, M.

    2016-05-01

    Direct steam generation enables the implementation of a higher steam temperature for parabolic trough concentrated solar power plants. This leads to much better cycle efficiencies and lower electricity generating costs. For a flexible and more economic operation of such a power plant, it is necessary to develop thermal energy storage systems for the extension of the production time of the power plant. In the case of steam as the heat transfer fluid, it is important to use a storage material that uses latent heat for the storage process. This leads to a minimum of exergy losses during the storage process. In the case of a concentrating solar power plant, superheated steam is needed during the discharging process. This steam cannot be superheated by the latent heat storage system. Therefore, a sensible molten salt storage system is used for this task. In contrast to the state-of-the-art thermal energy storages within the concentrating solar power area of application, a storage system for a direct steam generation plant consists of a latent and a sensible storage part. Thus far, no partial load behaviors of sensible and latent heat storage systems have been analyzed in detail. In this work, an optimized fin structure was developed in order to minimize the costs of the latent heat storage. A complete system simulation of the power plant process, including the solar field, power block and sensible and latent heat energy storage calculates the interaction between the solar field, the power block and the thermal energy storage system.

  2. Modeling of creep-fatigue interaction of zirconium {alpha} under cyclic loading at 200 C; Modelisation du comportement et de l`endommagement en fatigue-fluage du zirconium {alpha} a 200C

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, C.

    1996-04-01

    The present work deals with mechanical behaviour of zirconium alpha at 200 deg. C and crack initiation prediction methods, particularly when loading conditions lead to interaction of fatigue and creep phenomena. A classical approach used to study interaction between cyclic effects and constant loading effects does not give easy understanding of experimental results. Therefore, a new approach has been developed, which allow to determine a number of cycles for crack initiation for complex structures under large loading conditions. To study influence of fatigue and creep interaction on crack initiation, a model was chosen, using a scalar variable, giving representation of the material deterioration state. The model uses a non linear cumulating effect between the damage corresponding to cyclic loads and the damage correlated to time influence. The model belongs to uncoupled approaches between damage and behaviour, which is described here by a two inelastic deformations model. This mechanical behaviour model is chosen because it allows distinction between a plastic and a viscous part in inelastic flow. Cyclic damage is function of stress amplitude and mean stress. For the peculiar sensitivity of the material to creep, a special parameter bas been defined to be critical toward creep damage. It is the kinematic term associated to state variables describing this type of hardening in the viscous mechanism. (author).

  3. Antimicrobial, Mechanical and Thermal Studies of Silver Particle-Loaded Polyurethane

    Directory of Open Access Journals (Sweden)

    Deepen Paul

    2013-12-01

    Full Text Available Silver-particle-incorporated polyurethane films were evaluated for antimicrobial activity towards two different bacteria: Escherichia coli (E. coli and Staphylococcus aureus (S. aureus. Distributed silver particles sourced from silver nitrate, silver lactate and preformed silver nanoparticles were mixed with polyurethane (PU and variously characterized by field emission scanning electron microscopy (FESEM, fourier transform infra-red (FTIR spectroscopy, X-ray diffraction (XRD and contact angle measurement. Antibacterial activity against E.coli was confirmed for films loaded with 10% (w/w AgNO3, 1% and 10% (w/w Ag lactate and preformed Ag nanoparticles. All were active against S. aureus, but Ag nanoparticles loaded with PU had a minor effect. The apparent antibacterial performance of Ag lactate-loaded PU is better than other Ag ion-loaded films, revealed from the zone of inhibition study. The better performance of silver lactate-loaded PU was the likely result of a porous PU structure. FESEM and FTIR indicated direct interaction of silver with the PU backbone, and XRD patterns confirmed that face-centred cubic-type silver, representative of Ag metal, was present. Young’s modulus, tensile strength and the hardness of silver containing PU films were not adversely affected and possibly marginally increased with silver incorporation. Dynamic mechanical analysis (DMA indicated greater thermal stability.

  4. Antimicrobial, mechanical and thermal studies of silver particle-loaded polyurethane.

    Science.gov (United States)

    Paul, Deepen; Paul, Sharmistha; Roohpour, Nima; Wilks, Mark; Vadgama, Pankaj

    2013-12-09

    Silver-particle-incorporated polyurethane films were evaluated for antimicrobial activity towards two different bacteria: Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Distributed silver particles sourced from silver nitrate, silver lactate and preformed silver nanoparticles were mixed with polyurethane (PU) and variously characterized by field emission scanning electron microscopy (FESEM), fourier transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD) and contact angle measurement. Antibacterial activity against E.coli was confirmed for films loaded with 10% (w/w) AgNO3, 1% and 10% (w/w) Ag lactate and preformed Ag nanoparticles. All were active against S. aureus, but Ag nanoparticles loaded with PU had a minor effect. The apparent antibacterial performance of Ag lactate-loaded PU is better than other Ag ion-loaded films, revealed from the zone of inhibition study. The better performance of silver lactate-loaded PU was the likely result of a porous PU structure. FESEM and FTIR indicated direct interaction of silver with the PU backbone, and XRD patterns confirmed that face-centred cubic-type silver, representative of Ag metal, was present. Young's modulus, tensile strength and the hardness of silver containing PU films were not adversely affected and possibly marginally increased with silver incorporation. Dynamic mechanical analysis (DMA) indicated greater thermal stability.

  5. Macrophyte Community Response to Nitrogen Loading and Thermal Stressors in Rapidly Flushed Mesocosm Systems.

    Science.gov (United States)

    Kaldy, James E; Brown, Cheryl A; Nelson, Walter G; Frazier, Melanie

    2017-12-01

    A mesocosm system was developed to simulate estuarine conditions characteristic of short water-residence time ecosystems of the Pacific Coast of North America, and used to evaluate the response of multiple macrophyte metrics to gradients of NO 3 loading and temperature. Replicated experiments found that few responses could be directly attributed to NO 3 loading up to 6 x ambient. Some response metrics exhibited weak relationships with nutrient loading but could not be resolved with available statistical power. While direct nutrient responses were found for some species-specific metrics (e.g. green macroalgal growth and biomass, tissue N%, etc.), many patterns were confounded with temperature. Temperature generally had a larger effect on response metrics than did nutrient load. Experimental macrophyte communities exhibited community shifts consistent with the predicted effects of nutrient loading at 20 °C, but there was no evidence of other eutrophication symptoms (phytoplankton blooms or hypoxia) due to the short system-residence time. The Z. marina Nutrient Pollution Index (NPI) tracked the NO 3 gradient at 10 °C, but exhibited no response at 20 °C, which may limit the utility of this metric in areas with marked thermal seasonality. Results suggest that teasing apart the influence of temperature and nutrients on the expression of eutrophication symptoms will require complex multi-stressor experiments and the use of indicators that are sensitive across a broad range of conditions.

  6. A 3D Lumped Thermal Network Model for Long-term Load Profiles Analysis in High Power IGBT Modules

    DEFF Research Database (Denmark)

    Bahman, Amir Sajjad; Ma, Ke; Ghimire, Pramod

    2016-01-01

    The conventional RC lumped thermal networks are widely used to estimate the temperature of power devices, but they are lack of accuracy in addressing detailed thermal behaviors/couplings in different locations and layers of the high power IGBT modules. On the other hand, Finite Element (FE......)-based simulation is another method which is often used to analyze the steady-state thermal distribution of IGBT modules, but it is not possible to be used for long-term analysis of load profiles of power converter, which is needed for reliability assessments and better thermal design. This paper proposes a novel...... enables both accurate and fast temperature estimation of high power IGBT modules in the real loading conditions of the converter; meanwhile the critical details of the thermal dynamics and thermal distribution are also maintained. The proposed thermal model is verified by both FEM simulation...

  7. Heating treatments affect the thermal behaviour of doxorubicin loaded in PEGylated liposomes.

    Science.gov (United States)

    Perinelli, Diego R; Cespi, Marco; Bonacucina, Giulia; Rendina, Filippo; Palmieri, Giovanni Filippo

    2017-12-20

    Doxil ® is a stealth marketed PEGylated liposomal formulation, containing the anticancer drug doxorubicin. After loading via a pH gradient, fibrillar supramolecular structures of doxorubicin sulfate originates inside the core of the liposomes. Recently, the crystallinity of doxorubicin sulfate has been confirmed by high-resolution calorimetry. However, no detailed information are available on the nature of doxorubicin sulfate nanocrystals and on the effect of different thermal treatments. Thus, the aim of this work was to characterize the thermal behaviour of Doxil ® in comparison to the unloaded liposomes using microcalorimetry, dynamic light scattering and high-resolution ultrasound spectroscopy (HR-US). Different thermal programmes were applied with the aim to highlight the effect of the treatments on the formulation. The used techniques confirmed the ordered state of doxorubicin nanocrystals inside PEGylated liposomes. Particularly, microcalorimetry and HR-US highlighted the changes in the thermal behaviour of the drug under different heating programmes. Doxorubicin nanocrystals were found to be stable after heating up to 80°C, but an irreversible thermal behaviour was observed after a prolonged heating at elevated temperature (2h at 80°C). The non-reversibility could be related to the formation of a different ordered structure and enhanced by the slight leakage of the drug occurring after a prolonged heating. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Influence of boehmite nanoparticle loading on the mechanical, thermal, and rheological properties of biodegradable polylactide/ poly(e-caprolactone) blends

    CSIR Research Space (South Africa)

    Agwuncha, SC

    2015-01-01

    Full Text Available -1 Macromolecular Materials and Engineering Vol. 300(1), 31-47 Influence of Boehmite Nanoparticle Loading on the Mechanical, Thermal, and Rheological Properties of Biodegradable Polylactide/Poly(e-caprolactone) Blendsa Stephen C. Agwuncha, Suprakas Sinha...

  9. Load-deflection characteristics of superelastic and thermal nickel-titanium wires.

    Science.gov (United States)

    Gatto, Elda; Matarese, Giovanni; Di Bella, Guido; Nucera, Riccardo; Borsellino, Chiara; Cordasco, Giancarlo

    2013-02-01

    The aim of this study was to investigate the mechanical properties of superelastic and thermal nickel-titanium (NiTi) archwires for correct selection of orthodontic wires. Seven different NiTi wires of two different sizes (0.014 and 0.016 inches), commonly used during the alignment phase, were tested. A three-point bending test was carried out to evaluate the load-deflection characteristics. The archwires were subjected to bending at a constant temperature of 37°C and deflections of 2 and 4 mm. Analysis of variance showed that thermal NiTi wires exerted significantly lower working forces than superelastic wires of the same size in all experimental tests (P Wire size had a significant effect on the forces produced: with an increase in archwire dimension, the released strength increased for both thermal and superelastic wires. Superelastic wires showed, at a deflection of 2 mm, narrow and steep hysteresis curves in comparison with the corresponding thermal wires, which presented a wide interval between loading and unloading forces. During unloading at 4 mm of deflection, all wires showed curves with a wider plateau when compared with 2 mm deflection. Such a difference for the superelastic wires was caused by the martensite stress induced at higher deformation levels. A comprehensive understanding of mechanical characteristics of orthodontic wires is essential and selection should be undertaken in accordance with the behaviour of the different wires. It is also necessary to take into account the biomechanics used. In low-friction mechanics, thermal NiTi wires are to be preferred to superelastic wires, during the alignment phase due to their lower working forces. In conventional straightwire mechanics, a low force archwire would be unable to overcome the resistance to sliding.

  10. Study on simplified estimation of J-integral under thermal loading

    International Nuclear Information System (INIS)

    Takahashi, Y.

    1993-01-01

    For assessing structural integrity or safety of nuclear power plants, strength of structures under the presence of flaws sometimes needs to be evaluated. Because relative large inelastic deformation is anticipated in the liquid metal reactor components even without flaws due to high operating temperature and large temperature gradients, inelastic effects should be properly taken into account in the flaw assessment procedures. It is widely recognized that J-integral and its variations - e.g. fatigue J-integral range and creep J-integral - play substantial roles in the flaw assessment under the presence of large inelastic deformation. Therefore their utilization has been promoted in the recent flaw assessment procedure both for low and high temperature plants. However, it is not very practical to conduct a detailed numerical computation for cracked structures to estimate the values of these parameters for the purpose of trailing crack growth history. Thus development of simplified estimation methods which do not require full numerical calculation for cracked structures is desirable. A method using normalized J-integral solutions tabulated in the handbook is a direct extension of linear fracture mechanics counterpart and it can be used for standard specimen and simple structural configurations subjected to specified loading type. The reference stress method has also been developed but in this case limit load solutions, which are often difficult to obtain for general stress distribution, are necessary instead of nonlinear J-integral solutions. However, both methods have been developed mainly for mechanical loading and thus applying these techniques to thermal stress problem is rather difficult except the cases where the thermal stress can be properly substituted by equivalent mechanical loading as in the case of simple thermal expansion loading. Therefore alternative approach should be pursued for estimating J-integral and their variations in thermal stress problems

  11. Effect of epoxidised soybean oil loading as plasticiser on physical, mechanical and thermal properties of polyvinylchloride

    Science.gov (United States)

    Rahmah, M.; Nurazzi, N. Mohd; Farah Nordyana, A. R.; Syed Anas, S. M.

    2017-07-01

    The aim of this paper is to study the effect of epoxidised soybean oil (ESO) as an alternative plasticizer on physical, mechanical and thermal properties of plasticised polyvinyl chloride (PPVC). Samples were prepared using 10, 20, 30 and 40% by weight percent of ESO. The samples were characterized for density, water absorption, tensile, hardness and thermal properties. The addition of ESO as plasticizer in PVC had caused significant effect on the physical and mechanical properties of PPVC. Increasing of ESO loading had resulted in decreased density, tensile strength, tensile modulus but increased in elongation at break and shore hardness. From water absorption study, it was observed that the all the samples reached the plateau absorption at days 8 to 10 with absorption percentages of between 1.8 to 2%. In general the crystallinity of PPVC maintained between 10 to 13% with increase in ESO loading while the melting point ( Tm) is slightly decreased about 3 to 6°C. In this study, ESO which acts as plasticiser were found to result in lower glass transition temperature (Tg). The enhancements of super cooling with higher ESO loading were found to increase the crystallization temperature, promoting crystallisation and act as nucleating agent.

  12. Compensated gadolinium-loaded plastic scintillators for thermal neutron detection (and counting)

    Energy Technology Data Exchange (ETDEWEB)

    Dumazert, Jonathan; Coulon, Romain; Bertrand, Guillaume H. V.; Hamel, Matthieu; Sguerra, Fabien; Dehe-Pittance, Chrystele; Normand, Stephane [CEA, LIST, Laboratoire Capteurs Architectures Electroniques, 99 Gif-sur-Yvette, (France); Mechin, Laurence [CNRS, UCBN, Groupe de Recherche en Informatique, Image, Automatique et Instrumentation de Caen, 4050 Caen, (France)

    2015-07-01

    Plastic scintillator loading with gadolinium-rich organometallic complexes shows a high potential for the deployment of efficient and cost-effective neutron detectors. Due to the low-energy photon and electron signature of thermal neutron capture by gadolinium-155 and gadolinium-157, alternative treatment to Pulse Shape Discrimination has to be proposed in order to display a trustable count rate. This paper discloses the principle of a compensation method applied to a two-scintillator system: a detection scintillator interacts with photon radiation and is loaded with gadolinium organometallic compound to become a thermal neutron absorber, while a non-gadolinium loaded compensation scintillator solely interacts with the photon part of the incident radiation. Posterior to the nonlinear smoothing of the counting signals, a hypothesis test determines whether the resulting count rate after photon response compensation falls into statistical fluctuations or provides a robust image of a neutron activity. A laboratory prototype is tested under both photon and neutron irradiations, allowing us to investigate the performance of the overall compensation system in terms of neutron detection, especially with regards to a commercial helium-3 counter. The study reveals satisfactory results in terms of sensitivity and orientates future investigation toward promising axes. (authors)

  13. Performance Evaluation of a Thermal Load Reduction System in a Hyundai Sonata PHEV

    Energy Technology Data Exchange (ETDEWEB)

    Kreutzer, Cory J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rugh, John P [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Titov, Eugene V [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Gallagher, James [Gentherm, Inc.; Scott, Matthew [Hyundai America Technical Center, Inc.

    2017-11-28

    Increased adoption of electric-drive vehicles (EDVs) requires overcoming hurdles including limited vehicle range. Vehicle cabin heating and cooling demand for occupant climate control requires energy from the main battery and has been shown to significantly degrade vehicle range. During peak cooling and heating conditions, climate control can require as much or more energy as propulsion. As part of an ongoing project, NREL and project partners Hyundai America Technical Center, Inc. (HATCI), Gentherm , Pittsburgh Glass Works (PGW), PPG Industries, Sekisui, 3M, and Hanon Systems developed a thermal load reduction system in order to reduce the range penalty associated with electric vehicle climate control. Solar reflective paint, solar control glass, heated and cooled/ventilated seats, heated surfaces, and heated windshield with door demisters were integrated into a Hyundai Sonata plug-in hybrid electric vehicle (PHEV). Cold weather field-testing was conducted in Fairbanks, Alaska while warm weather testing was conducted in Death Valley, California to assess the system performance in comparison to the baseline production vehicle. In addition, environmental chamber testing at peak heating and cooling conditions was performed to assess the performance of the system in standardized conditions compared to the baseline. Experimental results are presented in this paper providing quantitative data to automobile manufacturers on the impact of climate control thermal load reduction technologies to increase the advanced thermal technology adoption and market penetration of electric drive vehicles.

  14. Automatic mesh generation for finite element calculations in the case of thermal loads

    International Nuclear Information System (INIS)

    Cords, H.; Zimmermann, R.

    1975-01-01

    The presentation describes a method to generate finite element nodal point networks on the basis of isothermals and flux lines. Such a mesh provides a relatively fine partitioning at regions where pronounced temperature variations exist. In case of entirely thermal loads a net of this kind is advantageous since the refinement is provided at exactly those locations where high stress levels are expected. In the present contribution the method was employed to analyze the structural behavior of a nuclear fuel element under operating conditions. The graphite block fuel elements for high temperature reactors are of prismatic shape with a large number of parallel bores in the axial direction. Some of these bores are open at both ends and cooling is effected by helium flowing through. Blind holes contain the fuel as compacts or cartridges. The basic temperature distribution in a horizontal section of the block was obtained by the boundary point least squares method which yields analytical expressions for both temperature and thermal flux. The corresponding computer code was presented at an earlier SMiRT conference. The method is particularly useful for regular arrays of heat sources and sinks as encountered in heat exchanger problems. The generated mesh matches the requirements of a subsequent structural analysis with finite elements provided there are no other than thermal loads

  15. Thermal management analysis of a Li-ion battery cell using phase change material loaded with carbon fibers

    International Nuclear Information System (INIS)

    Samimi, Fereshteh; Babapoor, Aziz; Azizi, Mohammadmehdi; Karimi, Gholamreza

    2016-01-01

    High latent heat of PCMs (phase change materials) has made them as one of the most important materials for thermal management purposes. However, PCMs’ low thermal diffusivities could limit their use in applications which require fast thermal response. The goal of this study is to simulate thermal performance of a lithium ion battery cell in the presence of carbon fiber-PCM composites. The effect of carbon fiber loading within the PCM on thermal performance is studied and the results are compared with the experimental data. The results showed that the presence of carbon fibers increases the effective thermal conductivity of PCM and hence influences temperature distribution within the cell. PCM composites containing higher percentages of carbon fibers present a more uniform temperature distribution. The results showed that the minimum and maximum thermal conductivity enhancement of 85% and 155% respectively (105% on average). A reasonable agreement is obtained between the simulation results and the experimental data. - Highlights: • Phase change materials (PCMs) are used for thermal management purposes. • Effective thermal conductivity of PCMs can be enhanced by loading carbon fibers. • Thermal performance of a battery is studied in presence of carbon fiber loaded PCM. • The presence of carbon fibers in the PCM can improve Li-ion battery performance.

  16. Optimal control of a fuel cell/wind/PV/grid hybrid system with thermal heat pump load

    CSIR Research Space (South Africa)

    Sichilalu, S

    2016-10-01

    Full Text Available This paper presents an optimal energy management strategy for a grid-tied photovoltaic–wind-fuel cell hybrid power supply system. The hybrid system meets the load demand consisting of an electrical load and a heat pump water heater supplying thermal...

  17. Numerical analysis of energy piles under different boundary conditions and thermal loading cycles

    Directory of Open Access Journals (Sweden)

    Khosravi Ali

    2016-01-01

    Full Text Available The thermo- mechanical behavior of energy piles has been studied extensively in recent years. In the present study, a numerical model was adapted to study the effect of various parameters (e.g. heating/cooling temperature, head loading condition and soil stiffness on the thermo-mechanical behavior of an energy pile installed in unsaturated sandstone. The results from the simulations were compared with measurements from a thermal response test on a prototype energy pile installed beneath a 1-story building at the US Air Force Academy (USAFA in Colorado Springs, CO. A good agreement was achieved between the results obtained from the prototype and the numerical models. A parametric evaluation were also carried out which indicated the significance of the stiffness of the unsaturated sandstone and pile’s head loading condition on stress-strain response of the energy pile during heating/cooling cycles.

  18. Thermal loss of life and load-carrying capacity of marine induction motors

    International Nuclear Information System (INIS)

    Gnacinski, P.

    2014-01-01

    Highlights: • The effect of voltage quality on induction motors is investigated. • Power quality significantly affects machine lifetime and load-carrying capacity. • Permissible load levels for induction motors are proposed. - Abstract: This work deals with the effect of a lowered voltage quality on the thermal loss of life and load-carrying capacity of marine induction cage machines. Results of experimental investigations and computer calculations are presented for two low power induction motors with different properties. One of them has a comparatively strongly-saturated magnetic circuit and is especially exposed to the risk of overheating under overvoltage. The other machine has a comparatively weakly-saturated magnetic circuit, and is especially sensitive to undervoltage. The induction motor lifetime expectancy is also estimated on the basis of the temperature coefficient of power quality, whose value is proportional to the windings temperature rise in induction motors especially sensitive to various power quality disturbances. The dependence of the temperature coefficient of power quality and permissible loads for induction motors supplied with voltages of lowered quality is proposed

  19. Thermal decomposition behavior of nano/micro bimodal feedstock with different solids loading

    Science.gov (United States)

    Oh, Joo Won; Lee, Won Sik; Park, Seong Jin

    2018-01-01

    Debinding is one of the most critical processes for powder injection molding. The parts in debinding process are vulnerable to defect formation, and long processing time of debinding decreases production rate of whole process. In order to determine the optimal condition for debinding process, decomposition behavior of feedstock should be understood. Since nano powder affects the decomposition behavior of feedstock, nano powder effect needs to be investigated for nano/micro bimodal feedstock. In this research, nano powder effect on decomposition behavior of nano/micro bimodal feedstock has been studied. Bimodal powders were fabricated with different ratios of nano powder, and the critical solids loading of each powder was measured by torque rheometer. Three different feedstocks were fabricated for each powder depending on solids loading condition. Thermogravimetric analysis (TGA) experiment was carried out to analyze the thermal decomposition behavior of the feedstocks, and decomposition activation energy was calculated. The result indicated nano powder showed limited effect on feedstocks in lower solids loading condition than optimal range. Whereas, it highly influenced the decomposition behavior in optimal solids loading condition by causing polymer chain scission with high viscosity.

  20. Admissible thermal loading in geological formations. Consequences on radioactive waste disposal methods

    International Nuclear Information System (INIS)

    1982-01-01

    Every granite formation possesses, the following main characteristics: presence of fissures; physico-chemical alterability; presence of internal or peripheral heterogeneities. From samples at ambient temperature, sound granite is found to have the properties of a hard, elastic rock with a relatively low thermal conductivity. Its natural permeability is low or very low, and most of the percolating water passes through fissures affecting the rock mass. In this report are examined: effects of heat on cavity stability, mechanical interaction between conditioned wastes and the geological environment, effects on the stability of infilling materials, heat effects on the host rock and underground water, assessment of the permissible thermal load and design of the storage facility

  1. Research on Power System Scheduling Improving Wind Power Accommodation Considering Thermal Energy Storage and Flexible Load

    Science.gov (United States)

    Zou, Chenlu; Cui, Xue; Wang, Heng; Zhou, Bin; Liu, Yang

    2018-01-01

    In the case of rapid development of wind power and heavy wind curtailment, the study of wind power accommodation of combined heat and power system has become the focus of attention. A two-stage scheduling model contains of wind power, thermal energy storage, CHP unit and flexible load were constructed. This model with the objective function of minimizing wind curtailment and the operation cost of units while taking into account of the total coal consumption of units, constraint of thermal energy storage and electricity-heat characteristic of CHP. This paper uses MICA to solve the problem of too many constraints and make the solution more feasible. A numerical example showed that the two stage decision scheduling model can consume more wind power, and it could provide a reference for combined heat and power system short-term operation

  2. Thermal buckling behavior of defective CNTs under pre-load: A molecular dynamics study.

    Science.gov (United States)

    Mehralian, Fahimeh; Tadi Beni, Yaghoub; Kiani, Yaser

    2017-05-01

    Current study is concentrated on the extraordinary properties of defective carbon nanotubes (CNTs). The role of vacancy defects in thermal buckling response of precompressed CNTs is explored via molecular dynamics (MD) simulations. Defective CNTs are initially compressed at a certain ratio of their critical buckling strain and then undergo a uniform temperature rise. Comprehensive study is implemented on both armchair and zigzag CNTs with different vacancy defects including monovacancy, symmetric bivacancy and asymmetric bivacancy. The results reveal that defects have a pronounced impact on the buckling behavior of CNTs; interestingly, defective CNTs under compressive pre-load show higher resistance to thermal buckling than pristine ones. In the following, the buckling response of defective CNTs is shown to be dependent on the vacancy defects, location of defects and chirality. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Staff Technical Position on geological repository operations area underground facility design: Thermal loads

    International Nuclear Information System (INIS)

    Nataraja, M.S.

    1992-12-01

    The purpose of this Staff Technical Position (STP) is to provide the US Department of Energy (DOE) with a methodology acceptable to the Nuclear Regulatory Commission staff for demonstrating compliance with 10 CFR 60.133(i). The NRC staff's position is that DOE should develop and use a defensible methodology to demonstrate the acceptability of a geologic repository operations area (GROA) underground facility design. The staff anticipates that this methodology will include evaluation and development of appropriately coupled models, to account for the thermal, mechanical, hydrological, and chemical processes that are induced by repository-generated thermal loads. With respect to 10 CFR 60.133(i), the GROA underground facility design: (1) should satisfy design goals/criteria initially selected, by considering the performance objectives; and (2) must satisfy the performance objectives 10 CFR 60.111, 60.112, and 60.113. The methodology in this STP suggests an iterative approach suitable for the underground facility design

  4. Evolution of mechanical characteristics and permeability of clayey materials under the influence of thermal loadings

    International Nuclear Information System (INIS)

    Boucly-Norotte, V.

    1991-01-01

    This research thesis reports the study of the effects on a long term of temperature variations on the volume and texture of clayey soils, notably with respect to their initial petro-physical and petro-graphical characteristics, and to their consolidation state. From an experimental point of view, this research is based on the monitoring of the volume strain and of the permeability of samples placed in an oedometric cell and submitted to thermal loadings within the 20 C - 110 C range. A thorough texture investigation (mercury-based porosimetry, observation by scanning electronic microscopy, and so on) before and after testing allows the evolution of material texture to be assessed [fr

  5. Thermal and radiation loads on the first wall and divertor plates in the KTM tokamak

    International Nuclear Information System (INIS)

    Azizov, Eh.A.; Buzhinskij, O.I.; Gladush, G.G.; Darmagraj, V.V.; Priyampol'skij, I.R.; Dvorkin, N.Ya.; Lejkin, I.N.; Tazhibaeva, I.L.; Shestakov, V.P.

    2001-01-01

    The constructing of the KTM tokamak is intended for wide scale studies of behavior both inner-chamber element materials and structures (first wall, limiters, divertor, hf-antennas, etc.) under conditions approaching to the ITER-FEAT and a future thermonuclear reactors. The KTM tokamak is designed for maintain of interaction conditions of plasma-wall, plasma flows and divertor field, stimulating conditions of ITER-FEAT; and for examination of a future tokamaks' materials. In the work the thermal loads on the first wall, divertor plates are presented

  6. Thermal models of buildings. Determination of temperatures, heating and cooling loads. Theories, models and computer programs

    Energy Technology Data Exchange (ETDEWEB)

    Kaellblad, K.

    1998-05-01

    The need to estimate indoor temperatures, heating or cooling load and energy requirements for buildings arises in many stages of a buildings life cycle, e.g. at the early layout stage, during the design of a building and for energy retrofitting planning. Other purposes are to meet the authorities requirements given in building codes. All these situations require good calculation methods. The main purpose of this report is to present the authors work with problems related to thermal models and calculation methods for determination of temperatures and heating or cooling loads in buildings. Thus the major part of the report deals with treatment of solar radiation in glazing systems, shading of solar and sky radiation and the computer program JULOTTA used to simulate the thermal behavior of rooms and buildings. Other parts of thermal models of buildings are more briefly discussed and included in order to give an overview of existing problems and available solutions. A brief presentation of how thermal models can be built up is also given and it is a hope that the report can be useful as an introduction to this part of building physics as well as during development of calculation methods and computer programs. The report may also serve as a help for the users of energy related programs. Independent of which method or program a user choose to work with it is his or her own responsibility to understand the limits of the tool, else wrong conclusions may be drawn from the results 52 refs, 22 figs, 4 tabs

  7. Durability of zirconia thermal-barrier ceramic coatings on air-cooled turbine blades in cyclic jet engine operation

    Science.gov (United States)

    Liebert, C. H.; Jacobs, R. E.; Stecura, S.; Morse, C. R.

    1976-01-01

    Thermal barrier ceramic coatings of stabilized zirconia over a bond coat of Ni Cr Al Y were tested for durability on air cooled turbine rotor blades in a research turbojet engine. Zirconia stabilized with either yttria, magnesia, or calcia was investigated. On the basis of durability and processing cost, the yttria stabilized zirconia was considered the best of the three coatings investigated.

  8. Damage and fatigue crack growth of Eurofer steel first wall mock-up under cyclic heat flux loads. Part 2: Finite element analysis of damage evolution

    International Nuclear Information System (INIS)

    You, Jeong-Ha

    2014-01-01

    Highlights: • The surface heat flux load of 3.5 MW/m 2 produced substantial stresses and inelastic strains in the heat-loaded surface region, especially at the notch root. • The notch root exhibited a typical notch effect such as stress concentration and localized inelastic yield leading to a preferred damage development. • The predicted damage evolution feature agrees well with the experimental observation. • The smooth surface also experiences considerable stresses and inelastic strains. However, the stress intensity and the amount of inelastic deformation are not high enough to cause any serious damage. • The level of maximum inelastic strain is higher at the notch root than at the smooth surface. On the other hand, the amplitude of inelastic strain variation is comparable at both positions. • The amount of inelastic deformation is significantly affected by the length of pulse duration time indicating the important role of creep. - Abstract: In the preceding companion article (part 1), the experimental results of the high-heat-flux (3.5 MW/m 2 ) fatigue tests of a Eurofer bare steel first wall mock-up was presented. The aim was to investigate the damage evolution and crack initiation feature. The mock-up used there was a simplified model having only basic and generic structural feature of an actively cooled steel FW component for DEMO reactor. In that study, it was found that microscopic damage was formed at the notch root already in the early stage of the fatigue loading. On the contrary, the heat-loaded smooth surface exhibited no damage up to 800 load cycles. In this paper, the high-heat-flux fatigue behavior is investigated with a finite element analysis to provide a theoretical interpretation. The thermal fatigue test was simulated using the coupled damage-viscoplastic constitutive model developed by Aktaa. The stresses, inelastic deformation and damage evolution at the notch groove and at the smooth surface are compared. The different damage

  9. Cu-Al alloy formation by thermal annealing of Cu/Al multilayer films deposited by cyclic metal organic chemical vapor deposition

    Science.gov (United States)

    Moon, Hock Key; Yoon, Jaehong; Kim, Hyungjun; Lee, Nae-Eung

    2013-05-01

    One of the most important issues in future Cu-based interconnects is to suppress the resistivity increase in the Cu interconnect line while decreasing the line width below 30 nm. For the purpose of mitigating the resistivity increase in the nanoscale Cu line, alloying Cu with traces of other elements is investigated. The formation of a Cu alloy layer using chemical vapor deposition or electroplating has been rarely studied because of the difficulty in forming Cu alloys with elements such as Al. In this work, Cu-Al alloy films were successfully formed after thermal annealing of Cu/Al multilayers deposited by cyclic metal-organic chemical vapor deposition (C-MOCVD). After the C-MOCVD of Cu/Al multilayers without gas phase reaction between the Cu and Al precursors in the reactor, thermal annealing was used to form Cu-Al alloy films with a small Al content fraction. The resistivity of the alloy films was dependent on the Al precursor delivery time and was lower than that of the aluminum-free Cu film. No presence of intermetallic compounds were detected in the alloy films by X-ray diffraction measurements and transmission electron spectroscopy.

  10. Crack initiation and crack growth in high temperature materials under cyclic thermal stresses; Rissinitiierung und Risswachstum in Hochtemperaturwerkstoffen unter zyklisch thermischer Beanspruchung

    Energy Technology Data Exchange (ETDEWEB)

    Gruen, C.

    1996-12-01

    The high temperatures of use in drive units, such as the combustion chamber or the hot gas turbine, for example, usually cause high temperature changes. Great temperature differences occur for short periods in the components, and thermal shock is produced. In this work, theoretical and experimental investigations are introduced on crack initiation and crack growth in high temperature materials under cyclic thermal stresses. The experiments were carried out with the inter-metallic phase Ni{sub 3}Al, the nickel-based alloy Nimonic 80A and the iron-based alloy PM 2000 strengthened by oxide dispersion (ODS). A characteristic crack appearance picture was found for each material, which was examined more closely. The stresses occurring in the sample during one cycle were calculated with the aid of the finite element program ABAQUS, knowing the specific material parameters. Based on the linear-elastic fracture mechanics, stress intensity factors were calculated on the superimposition principle. Using the material data from isothermal crack propagation experiments, the prediction of fatigue crack spread with cyclic thermal stresses is compared with the experimental findings. (orig./AKF) [Deutsch] Die hohen Einsatztemperaturen in Antriebsaggregaten wie z.B. der Brennkammer oder der Heissgasturbine bedingen in der Regel hohe Temperaturwechsel. Dabei treten kurzzeitig grosse Temperaturunterschiede in den Bauteilen auf, ein Thermoschock wird erzeugt. In der vorliegenden Arbeit werden theoretische und experimentelle Untersuchungen zur Rissinitiierung und zum Risswachstum in Hochtemperaturwerkstoffen unter zyklisch thermischer Belastung vorgestellt. Die Experimente wurden mit der intermetallischen Phase Ni{sub 3}Al, der Nickelbasislegierung Nimonic 80A und der oxid-dispersionsverfestigten (ODS) Eisenbasislegierung PM2000 durchgefuehrt. Fuer jeden Werkstoff stellte sich ein charakteristisches Risserscheinungsbild dar, das naeher untersucht wurde. Die in der Probe auftretenden

  11. Development of ion-plated aluminide diffusion coatings for thermal cyclic oxidation and hot corrosion protection of a nickel-based superalloy and a stainless steel

    Science.gov (United States)

    Elsawy, Abdel Raouf

    This project was carried out at the University of Toronto and Cametoid Ltd of Whitby, Ontario. Ohno continuous casting; a novel net shape casting technique, was used to generate, Al-Y, Al-Ce, Al-La, and Al-Si-Y, in form of 1.6 to 1.7 mm diameter alloy wires. These alloy wires exhibited suitable properties for use as feed materials to an Ion Vapor Deposition facility. The deposition parameters were optimized to provide coatings with a compact and cohesive columnar structure with reduced porosity and diffusion barriers that were essential to ensure the success of the diffusion process in the subsequent stage. Solid-state diffusion heat treatment processes were developed in order to form the stable aluminide phases, AlNi and FeAl, on IN738 and S310 substrates, respectively. Experiments simulating the coating service conditions and environments encountered during the prospective aerospace and fuel cell applications were conducted to evaluate the performance of each aluminide coating developed during this study. Thermal cyclic oxidation and molten sulfate corrosion studies were performed on coated IN738 pins at 1050°C and 900°C, respectively, simulating the service environment of turbine engine blades and other hot section components. Molten carbonate corrosion behavior was investigated for coated S310 coupons that were immersed in, or covered with a thin film of molten carbonate, at 650°C, in air plus 30%CO2, to simulate the operating conditions of the cathode-side separator plates of molten carbonate fuel cells. The behavior of the reactive elements, yttrium, cerium, lanthanum, and silicon in enhancing the adhesion of the protective aluminum oxide scale was determined by weight variation experiments, structural examination and compositional analysis. The influence of the base material elements, nickel, chromium, and iron, on the formation of protective oxides was investigated. All coatings were found to provide significant improvement for thermal cyclic oxidation

  12. Effect of Thermal Bridges in Insulated Walls on Air-Conditioning Loads Using Whole Building Energy Analysis

    Directory of Open Access Journals (Sweden)

    Mohamed F. Zedan

    2016-06-01

    Full Text Available Thermal bridges in building walls are usually caused by mortar joints between insulated building blocks and by the presence of concrete columns and beams within the building envelope. These bridges create an easy path for heat transmission and therefore increase air-conditioning loads. In this study, the effects of mortar joints only on cooling and heating loads in a typical two-story villa in Riyadh are investigated using whole building energy analysis. All loads found in the villa, which broadly include ventilation, transmission, solar and internal loads, are considered with schedules based on local lifestyles. The thermal bridging effect of mortar joints is simulated by reducing wall thermal resistance by a percentage that depends on the bridges to wall area ratio (TB area ratio or Amj/Atot and the nominal thermal insulation thickness (Lins. These percentage reductions are obtained from a correlation developed by using a rigorous 2D dynamic model of heat transmission through walls with mortar joints. The reduction in thermal resistance is achieved through minor reductions in insulation thickness, thereby keeping the thermal mass of the wall essentially unchanged. Results indicate that yearly and monthly cooling loads increase almost linearly with the thermal bridge to wall area ratio. The increase in the villa’s yearly loads varies from about 3% for Amj/Atot = 0.02 to about 11% for Amj/Atot = 0.08. The monthly increase is not uniform over the year and reaches a maximum in August, where it ranges from 5% for Amj/Atot = 0.02 to 15% for Amj/Atot = 0.08. In winter, results show that yearly heating loads are generally very small compared to cooling loads and that heating is only needed in December, January and February, starting from late night to late morning. Monthly heating loads increase with the thermal bridge area ratio; however, the variation is not as linear as observed in cooling loads. The present results highlight the importance of

  13. Investigation into the Cyclic Strength of the Bodies of Steam Shutoff Valves from 10Kh9MFB-Sh Steel

    Science.gov (United States)

    Skorobogatykh, V. N.; Kunavin, S. A.; Prudnikov, D. A.; Shchenkova, I. A.; Bazhenov, A. M.; Zadoinyi, V. A.; Starkovskii, G. L.

    2018-02-01

    Steam shutoff valves are operated under complex loading conditions at thermal and nuclear power stations. In addition to exposure to high temperature and stresses resulting in fatigue, these valves are subjected to cyclic loads in heating-up-cooling down, opening-closing, etc. cycles. The number of these cycles to be specified in designing the valves should not exceed the maximum allowable value. Hence, the problem of cyclic failure rate of steam shutoff valve bodies is critical. This paper continues the previous publications about properties of the construction material for steam shutoff valve bodies (grade 10Kh9MFB-Sh steel) produced by electroslag melting and gives the results of investigation into the cyclic strength of this material. Fatigue curves for the steal used for manufacturing steam shutoff valve bodies are presented. The experimental data are compared with the calculated fatigue curves plotted using the procedures outlined in PNAE G-002-986 and RD 10-249-98. It is confirmed that these procedures may be used in designing valve bodies from 10Kh9MFB-Sh steel. The effect of the cyclic damage after preliminary cyclic loading of the specimens according to the prescribed load conditions on the high-temperature strength of the steel is examined. The influence of cyclic failure rate on the long-term strength was investigated using cylindrical specimens with a smooth working section in the as-made conditions and after two regimes of preliminary cyclic loading (training) at a working temperature of 570°C and the number of load cycles exceeding the design value, which was 2 × 103 cycles. The experiments corroborated that the material (10Kh9MFB-Sh steel) of the body manufactured by the method of electroslag melting had high resistance to cyclic failure rate. No effect of cyclic damages in the metal of the investigated specimens on the high-temperature strength has been found.

  14. Mechanical Behaviour of Stainless Steels under Dynamic Loading: An Investigation with Thermal Methods

    Directory of Open Access Journals (Sweden)

    Rosa De Finis

    2016-11-01

    Full Text Available Stainless steels are the most exploited materials due to their high mechanical strength and versatility in producing different alloys. Although there is great interest in these materials, mechanical characterisation, in particular fatigue characterisation, requires the application of several standardised procedures involving expensive and time-consuming experimental campaigns. As a matter of fact, the use of Standard Test Methods does not rely on a physical approach, since they are based on a statistical evaluation of the fatigue limit with a fixed probabilistic confidence. In this regard, Infra-Red thermography, the well-known, non-destructive technique, allows for the development of an approach based on evaluation of dissipative sources. In this work, an approach based on a simple analysis of a single thermographic sequence has been presented, which is capable of providing two indices of the damage processes occurring in material: the phase shift of thermoelastic signal φ and the amplitude of thermal signal at twice the loading frequency, S2. These thermal indices can provide synergetic information about the mechanical (fatigue and fracture behaviour of austenitic AISI 316L and martensitic X4 Cr Ni Mo 16-5-1; since they are related to different thermal effects that produce damage phenomena. In particular, the use of φ and S2 allows for estimation of the fatigue limit of stainless steels at loading ratio R = 0.5 in agreement with the applied Standard methods. Within Fracture Mechanics tests, both indices demonstrate the capacity to localize the plastic zone and determine the position of the crack tip. Finally, it will be shown that the value of the thermoelastic phase signal can be correlated with the mechanical behaviour of the specific material (austenitic or martensitic.

  15. Controlled High Filler Loading of Functionalized Al2O3-Filled Epoxy Composites for LED Thermal Management

    Science.gov (United States)

    Permal, Anithambigai; Devarajan, Mutharasu; Hung, Huong Ling; Zahner, Thomas; Lacey, David; Ibrahim, Kamarulazizi

    2018-03-01

    Thermal management in light-emitting diode (LED) has been extensively researched recently. This study is intended to develop an effective thermally conductive epoxy composite as thermal interface material (TIM) for headlamp LEDs. Silane-functionalized aluminum oxide (Al2O3) powder of different average particle sizes (44 and 10 µm) was studied for its feasibility as filler at its maximum loading. A detailed comparison of three different methods of particle dispersions, hand-mix, speed-mix and calendaring process (3-roll mill), has been reported. The dispersion of Al2O3 particles, the thermal conductivity and thermal degradation characteristics of the composites were investigated and explained in detail. At 75 wt.% filler loading, 10 and 44 µm Al2O3 achieved composite thermal conductivities of 1.13 and 2.08 W/mK, respectively, which is approximately 528 and 1055% of enhancement with respect to neat epoxy. The package-level thermal performance of the LED employing the Al2O3-filled TIMs was carried out using thermal transient analysis. The experimental junction-to-ambient thermal resistances ( R thJ-A) achieved were 6.65, 7.24, and 8.63 K/W for Al2O3_44µm, Al2O3_10µm and neat epoxy, respectively. The results revealed that the Al2O3_44µm fillers-filled composite performed better in both material-level and package-level thermal characteristics.

  16. Controlled High Filler Loading of Functionalized Al2O3-Filled Epoxy Composites for LED Thermal Management

    Science.gov (United States)

    Permal, Anithambigai; Devarajan, Mutharasu; Hung, Huong Ling; Zahner, Thomas; Lacey, David; Ibrahim, Kamarulazizi

    2018-01-01

    Thermal management in light-emitting diode (LED) has been extensively researched recently. This study is intended to develop an effective thermally conductive epoxy composite as thermal interface material (TIM) for headlamp LEDs. Silane-functionalized aluminum oxide (Al2O3) powder of different average particle sizes (44 and 10 µm) was studied for its feasibility as filler at its maximum loading. A detailed comparison of three different methods of particle dispersions, hand-mix, speed-mix and calendaring process (3-roll mill), has been reported. The dispersion of Al2O3 particles, the thermal conductivity and thermal degradation characteristics of the composites were investigated and explained in detail. At 75 wt.% filler loading, 10 and 44 µm Al2O3 achieved composite thermal conductivities of 1.13 and 2.08 W/mK, respectively, which is approximately 528 and 1055% of enhancement with respect to neat epoxy. The package-level thermal performance of the LED employing the Al2O3-filled TIMs was carried out using thermal transient analysis. The experimental junction-to-ambient thermal resistances (R thJ-A) achieved were 6.65, 7.24, and 8.63 K/W for Al2O3_44µm, Al2O3_10µm and neat epoxy, respectively. The results revealed that the Al2O3_44µm fillers-filled composite performed better in both material-level and package-level thermal characteristics.

  17. HANFORD DOUBLE SHELL TANK THERMAL AND SEISMIC PROJECT SUMMARY OF COMBINED THERMAL AND OPERATING LOADS WITH SEISMIC ANALYSIS

    Energy Technology Data Exchange (ETDEWEB)

    MACKEY TC; DEIBLER JE; RINKER MW; JOHNSON KI; ABATT FG; KARRI NK; PILLI SP; STOOPS KL

    2009-01-15

    This report summarizes the results of the Double-Shell Tank Thermal and Operating Loads Analysis (TaLA) combined with the Seismic Analysis. This combined analysis provides a thorough, defensible, and documented analysis that will become a part of the overall analysis of record for the Hanford double-shell tanks (DSTs). The bases of the analytical work presented herein are two ANSYS{reg_sign} finite element models that were developed to represent a bounding-case tank. The TaLA model includes the effects of temperature on material properties, creep, concrete cracking, and various waste and annulus pressure-loading conditions. The seismic model considers the interaction of the tanks with the surrounding soil including a range of soil properties, and the effects of the waste contents during a seismic event. The structural evaluations completed with the representative tank models do not reveal any structural deficiencies with the integrity of the DSTs. The analyses represent 60 years of use, which extends well beyond the current date. In addition, the temperature loads imposed on the model are significantly more severe than any service to date or proposed for the future. Bounding material properties were also selected to provide the most severe combinations. While the focus of the analyses was a bounding-case tank, it was necessary during various evaluations to conduct tank-specific analyses. The primary tank buckling evaluation was carried out on a tank-specific basis because of the sensitivity to waste height, specific gravity, tank wall thickness, and primary tank vapor space vacuum limit. For this analysis, the occurrence of maximum tank vacuum was classified as a service level C, emergency load condition. The only area of potential concern in the analysis was with the buckling evaluation of the AP tank, which showed the current limit on demand of l2-inch water gauge vacuum to exceed the allowable of 10.4 inches. This determination was based on analysis at the

  18. Thermal load testing of erosion-monitoring beryllium marker tile for the ITER-Like Wall Project at JET

    Energy Technology Data Exchange (ETDEWEB)

    Hirai, T. [Forschungszentrum Juelich, Association EURATOM-FZJ, D-52425 Juelich (Germany)], E-mail: t.hirai@fz-juelich.de; Linke, J. [Forschungszentrum Juelich, Association EURATOM-FZJ, D-52425 Juelich (Germany); Rubel, M. [Alfven Laboratory, Association EURATOM-VR, 100 44 Stockholm (Sweden); Coad, J.P. [Culham Science Centre, EURATOM-UKAEA Fusion Association, Abingdon (United Kingdom); Likonen, J. [VTT, Association Euratom-Tekes, 02044 VTT (Finland); Lungu, C.P. [National Institute of Lasers, Plasma and Radiation Physics, Association EURATOM-MEdC, Bucharest (Romania); Matthews, G.F. [Culham Science Centre, EURATOM-UKAEA Fusion Association, Abingdon (United Kingdom); Philipps, V.; Wessel, E. [Forschungszentrum Juelich, Association EURATOM-FZJ, D-52425 Juelich (Germany)

    2008-12-15

    ITER-Like Wall Project has been launched at JET in order to perform a fully integrated test of plasma-facing materials. During the next major shutdown a full metal wall will be installed: tungsten in the divertor and beryllium in the main chamber. Beryllium erosion is one of key issues to be addressed. Special marker tiles have been designed for this purpose. Test coupons of such markers have been manufactured and examined. The performance test under high power deposition was carried in the electron beam facility JUDITH. The results of material characterization before and after high heat flux loads are presented. The samples survived, without macroscopic damage, power loads of up to 4.5 MW/m{sup 2} for 10 s (surface temperature {approx}650 deg. C) and 50 cyclic loads at 3.5 MW/m{sup 2} lasting 10 s each (surface temperature {approx}600 deg. C)

  19. Thermal runaway detection of cylindrical 18650 lithium-ion battery under quasi-static loading conditions

    Science.gov (United States)

    Sheikh, Muhammad; Elmarakbi, Ahmed; Elkady, Mustafa

    2017-12-01

    This paper focuses on state of charge (SOC) dependent mechanical failure analysis of 18650 lithium-ion battery to detect signs of thermal runaway. Quasi-static loading conditions are used with four test protocols (Rod, Circular punch, three-point bend and flat plate) to analyse the propagation of mechanical failures and failure induced temperature changes. Finite element analysis (FEA) is used to model single battery cell with the concentric layered formation which represents a complete cell. The numerical simulation model is designed with solid element formation where stell casing and all layers followed the same formation, and fine mesh is used for all layers. Experimental work is also performed to analyse deformation of 18650 lithium-ion cell. The numerical simulation model is validated with experimental results. Deformation of cell mimics thermal runaway and various thermal runaway detection strategies are employed in this work including, force-displacement, voltage-temperature, stress-strain, SOC dependency and separator failure. Results show that cell can undergo severe conditions even with no fracture or rupture, these conditions may slow to develop but they can lead to catastrophic failures. The numerical simulation technique is proved to be useful in predicting initial battery failures, and results are in good correlation with the experimental results.

  20. Manual for Cyclic Triaxial Test

    DEFF Research Database (Denmark)

    Shajarati, Amir; Sørensen, Kris Wessel; Nielsen, Søren Kjær

    This manual describes the different steps that is included in the procedure for conducting a cyclic triaxial test at the geotechnical Laboratory at Aalborg University. Furthermore it contains a chapter concerning some of the background theory for the static triaxial tests. The cyclic/dynamic tria......This manual describes the different steps that is included in the procedure for conducting a cyclic triaxial test at the geotechnical Laboratory at Aalborg University. Furthermore it contains a chapter concerning some of the background theory for the static triaxial tests. The cyclic....../dynamic triaxial cell is overall constructed in the same way as the static triaxial cell at Aalborg University, but with the ability to apply any kind of load sequence to the test sample. When conducting cyclic triaxial tests, it is recommended that the manual is followed very tediously since there are many steps...

  1. Cyclic Fatigue Durability of Uncoated and EBC Coated 3D SiC/SiC Composites Under Thermal Gradient Conditions at 2700F in Air

    Science.gov (United States)

    Smith, Craig; Harder, Bryan; Zhu, Dongming; Bhatt, Ramakrishna; Kalluri, Sreeramesh

    2017-01-01

    Ceramic matrix composites (CMCs) such as SiCSiC are currently being designed and implemented in high temperature sections of aerospace turbine engines. Such components will be subject to through-thickness thermal gradients, which may affect the durability. In this study, SiCSiC CMCs with a hybrid chemical vapor infiltrated (CVI) and polymer infiltration and pyrolysis (PIP) matrix were loaded in tension while one surface was heated with a laser and the opposite surface was cooled. The samples were each coated with an environmental barrier coating (EBC), which was produced by electron beam physical deposition (EBPVD). Results for CMCs tested with and without the EBC be discussed.

  2. Constant load supports attenuating shocks and vibrations for networks of pipes submitted to large thermal dilatation

    International Nuclear Information System (INIS)

    Prisecaru, Ilie; Panait; Adrian; Serban, Viorel; Ciocan, George; Androne, Marian; Florea, Ioana; State, Elena

    2004-01-01

    Full text: To avoid some drawbacks in the classical supports employed currently in networks of pipes it was conceived, designed, built and experimentally tested a new type of constant load supports which attenuate largely the shocks and vibrations for networks of pipes subjected to large thermal dilatation. These supports are particularly needed for solving the severe problems of the vibrations in networks of pipes in thermoelectric stations, nuclear power plants, or heavy water production plants. These supports allow building networks of new types, more reliable and of lower cost. The new type of support was developed on the basis of a number of patents protected by OSIM. It has a simple structure, ensures a secure functioning without blocking or other kinds of failures and is resistant to a very large variety of stresses. The new type of support of constant load avoids the drawbacks in classical supports i.e. the stress/deformation diagram is practically independent of stress level. The characteristic of the support is geometrically non-linear and presents a plateau with a small slope over a rather large deformation range which results from a serially mounted structure of sandwiches the deformation of which is controlled by a system of deforming central and peripheral pieces. The new supports of constant load, called SERB-PIPE, present a controlled elasticity and a high degree of damping as the package of elastic blades (the sandwich structure) is made of two sub-packages with relative movements what ensure the attenuation of the shocks and vibrations produced by the fluid flow within the pipes and or by seismic motions. By contrast with classical supports, the new supports have a simple structure and a high reliability. Breakdown under stress leading to severe changes in the stress distribution in pipe networks, which could generate overloads in pipes and over-loading in other supports, cannot occur. One can also mention that these supports can be built in a

  3. Auxiliary System Load Schemes in Large Thermal and Nuclear Power Plants

    International Nuclear Information System (INIS)

    Kuzle, I.; Bosnjak, D.; Pandzic, H.

    2010-01-01

    Uninterrupted auxiliary system power supply in large power plants is a key factor for normal operation, transient states, start-ups and shutdowns and particularly during fault conditions. Therefore, there are many challenges in designing the main electrical system as well as the auxiliary systems power supply. Depending upon the type of fuel used and the environmental control system required, a thermal power plant may consume as much as 10% of its total generation for auxiliary power, while a nuclear power plant may require only 4 - 6% auxiliaries. In general, the larger the power generating plant, the higher the voltage selected for the AC auxiliary electric system. Most stations in the 75 to 500 MW range utilize 4,2 kV as the base auxiliary system voltage. Large generating stations 500 - 1000 MW and more use voltage levels of 6,9 kV and more. Some single dedicated loads such as electric driven boiler feed pumps are supplied ba a 13,8 kV bus. While designing the auxiliary electric system, the following areas must be considered: motor starting requirements, voltage regulation requirements, short-circuit duty requirements, economic considerations, reliability and alternate sources. Auxiliary power supply can't be completely generalized and each situation should be studied on its own merits to determine the optimal solution. Naturally, nuclear power plants have more reliability requirements and safety design criteria. Main coolant-pump power supply and continuity of service to other vital loads deserve special attention. This paper presents an overview of some up-to-date power plant auxiliary load system concepts. The main types of auxiliary loads are described and the electric diagrams of the modern auxiliary system supply concepts are given. Various alternative sources of auxiliary electrical supply are considered, the advantages and disadvantages of these are compared and proposals are made for high voltage distribution systems around the thermal and nuclear plant

  4. The effect of unsteadiness on the time-mean thermal loads in a turbine stage

    Science.gov (United States)

    Kirtley, K. R.; Celestina, M. L.; Adamczyk, J. J.

    1993-01-01

    Two steady numerical analysis methods and one unsteady method are used to study the viscous three-dimensional flow in the middle stage of the Pratt & Whitney alternate design Space Shuttle Main Engine fuel turbine. The principal characteristic of this flow is that the secondary flows generated in the rotor blade reconfigure a radial inlet total temperature distortion into one with a pitchwise exit hot streak distortion. Secondary flows in the following vane redistribute the radial variation while unsteadiness causes a segregation of hot and cold flow from the hot streak within the vane. Such redistribution and segregation can lead to unexpected thermal loads and reduced durability. The physical phenomena and the ability of a steady analysis to capture them are investigated by performing a numerical experiment whereby the results of the two steady analysis methods are compared to the time-mean of the unsteady simulation. The flow physics related to the segregation and mixing of total temperature are discussed.

  5. Comparison of Buildings\\' Thermal Loads against Building Orientations for Sustainable Housing in Pakistan

    Directory of Open Access Journals (Sweden)

    Arif Khan

    2012-07-01

    Full Text Available As the sustainable settlements have been included as a vital end product of all planning exercises, the architectural layouts should be well integrated with the sun path charts and the orientations of windows. Appropriate orientations can offer thermally indoor conditions besides physical and psychological comfort in any settlement at lesser energy demand. This investigation uses a vast number of computer simulations to visualize and make better decisions about heating and cooling requirements of a building and facades as a function of window orientation in composite climatic condition of Lahore. This study in particular evaluates the solar load in residential buildings responsive to the objective of sustainable new housing leading to thoughtful integration of architecture. The orientation of the buildings could then be essentially integrated to the current architectural and urban design practices in order to optimize the relationship between the given site ant the orientations for sustainable developments.

  6. Neuro-Fuzzy Computational Technique to Control Load Frequency in Hydro-Thermal Interconnected Power System

    Science.gov (United States)

    Prakash, S.; Sinha, S. K.

    2015-09-01

    In this research work, two areas hydro-thermal power system connected through tie-lines is considered. The perturbation of frequencies at the areas and resulting tie line power flows arise due to unpredictable load variations that cause mismatch between the generated and demanded powers. Due to rising and falling power demand, the real and reactive power balance is harmed; hence frequency and voltage get deviated from nominal value. This necessitates designing of an accurate and fast controller to maintain the system parameters at nominal value. The main purpose of system generation control is to balance the system generation against the load and losses so that the desired frequency and power interchange between neighboring systems are maintained. The intelligent controllers like fuzzy logic, artificial neural network (ANN) and hybrid fuzzy neural network approaches are used for automatic generation control for the two area interconnected power systems. Area 1 consists of thermal reheat power plant whereas area 2 consists of hydro power plant with electric governor. Performance evaluation is carried out by using intelligent (ANFIS, ANN and fuzzy) control and conventional PI and PID control approaches. To enhance the performance of controller sliding surface i.e. variable structure control is included. The model of interconnected power system has been developed with all five types of said controllers and simulated using MATLAB/SIMULINK package. The performance of the intelligent controllers has been compared with the conventional PI and PID controllers for the interconnected power system. A comparison of ANFIS, ANN, Fuzzy and PI, PID based approaches shows the superiority of proposed ANFIS over ANN, fuzzy and PI, PID. Thus the hybrid fuzzy neural network controller has better dynamic response i.e., quick in operation, reduced error magnitude and minimized frequency transients.

  7. Elastic-Plastic Nonlinear Response of a Space Shuttle External Tank Stringer. Part 2; Thermal and Mechanical Loadings

    Science.gov (United States)

    Knight, Norman F., Jr.; Warren, Jerry E.; Elliott, Kenny B.; Song, Kyongchan; Raju, Ivatury S.

    2012-01-01

    Elastic-plastic, large-deflection nonlinear thermo-mechanical stress analyses are performed for the Space Shuttle external tank s intertank stringers. Detailed threedimensional finite element models are developed and used to investigate the stringer s elastic-plastic response for different thermal and mechanical loading events from assembly through flight. Assembly strains caused by initial installation on an intertank panel are accounted for in the analyses. Thermal loading due to tanking was determined to be the bounding loading event. The cryogenic shrinkage caused by tanking resulted in a rotation of the intertank chord flange towards the center of the intertank, which in turn loaded the intertank stringer feet. The analyses suggest that the strain levels near the first three fasteners remain sufficiently high that a failure may occur. The analyses also confirmed that the installation of radius blocks on the stringer feet ends results in an increase in the stringer capability.

  8. [Thermal load at workstations in the underground coal mining: Results of research carried out in 6 coal mines].

    Science.gov (United States)

    Słota, Krzysztof; Słota, Zbigniew; Kułagowska, Ewa

    Statistics shows that almost half of Polish extraction in underground mines takes place at workstations where temperature exceeds 28°C. The number of employees working in such conditions is gradually increasing, therefore, the problem of safety and health protection is still growing. In the present study we assessed the heat load of employees at different workstations in the mining industry, taking into account current thermal conditions and work costs. The evaluation of energy cost of work was carried out in 6 coal mines. A total of 221 miners employed at different workstations were assessed. Individual groups of miners were characterized and thermal safety of the miners was assessed relying on thermal discomfort index. The results of this study indicate considerable differences in the durations of analyzed work processes at individual workstations. The highest average energy cost was noted during the work performed in the forehead. The lowest value was found in the auxiliary staff. The calculated index of discomfort clearly indicated numerous situations in which the admissible range of thermal load exceeded the parameters of thermal load safe for human health. It should be noted that the values of average labor cost fall within the upper, albeit admissible, limits of thermal load. The results of the study indicate that in some cases work in mining is performed in conditions of thermal discomfort. Due to high variability and complexity of work conditions it becomes necessary to verify the workers' load at different workstations, which largely depends on the environmental conditions and work organization, as well as on the performance of workers themselves. Med Pr 2016;67(4):477-498. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

  9. Thermal load at workstations in the underground coal mining: Results of research carried out in 6 coal mines

    Directory of Open Access Journals (Sweden)

    Krzysztof Słota

    2016-08-01

    Full Text Available Background: Statistics shows that almost half of Polish extraction in underground mines takes place at workstations where temperature exceeds 28°C. The number of employees working in such conditions is gradually increasing, therefore, the problem of safety and health protection is still growing. Material and Methods: In the present study we assessed the heat load of employees at different workstations in the mining industry, taking into account current thermal conditions and work costs. The evaluation of energy cost of work was carried out in 6 coal mines. A total of 221 miners employed at different workstations were assessed. Individual groups of miners were characterized and thermal safety of the miners was assessed relying on thermal discomfort index. Results: The results of this study indicate considerable differences in the durations of analyzed work processes at individual workstations. The highest average energy cost was noted during the work performed in the forehead. The lowest value was found in the auxiliary staff. The calculated index of discomfort clearly indicated numerous situations in which the admissible range of thermal load exceeded the parameters of thermal load safe for human health. It should be noted that the values of average labor cost fall within the upper, albeit admissible, limits of thermal load. Conclusions: The results of the study indicate that in some cases work in mining is performed in conditions of thermal discomfort. Due to high variability and complexity of work conditions it becomes necessary to verify the workers’ load at different workstations, which largely depends on the environmental conditions and work organization, as well as on the performance of workers themselves. Med Pr 2016;67(4:477–498

  10. Experimental and Numerical Study of the Interfacial Shear Strength in Carbon Fiber/Epoxy Resin Composite under Thermal Loads

    Directory of Open Access Journals (Sweden)

    Hongxiao Wang

    2018-01-01

    Full Text Available This study examined the influence mechanism of temperature on the interfacial shear strength (IFSS between carbon fiber (CF and epoxy resin (EP matrices under various thermal loads using experimental and numerical simulation methods. To evaluate the change in IFSS as a function of the increase in temperature, a microbond test was performed under controlled temperature environment from 23°C to 150°C. The experimental results showed that IFSS values of CF/EP reduce significantly when the temperature reaches near glass transition temperature. To interpret the effect of thermal loads on IFSS, a thermal-mechanical coupling finite element model was used to simulate the process of fiber pull-out from EP. The results revealed that temperature dependence of IFSS is linked to modulus of the matrix as well as to the coefficients of thermal expansion of the fiber and matrix.

  11. Thermal and dynamic loads on the EPR containment due to hydrogen combustion

    International Nuclear Information System (INIS)

    Eyink, J.; Movahed, M.; Petzold, K.G.; Kotchourko, A.; Royl, P.; Travis, J.R.

    2001-01-01

    A major aspect of the EPR safety concept is to cope with severe accidents including core melt and to maintain the integrity of the containment even for those hypothetical events. One potential threat for the containment is related to the combustion of hydrogen, which may be produced in a large amount during core degradation. The European Pressurized Water Reactor (EPR) hydrogen mitigation concept consists of about 44 recombiners, located mainly in the equipment rooms (only 4 recombiners are located in the dome area). This paper is devoted to two important potential threats on the containment related to hydrogen removal: - Thermal loads resulting from recombiner action and/or combustion are of importance also with respect to the integrity of the local composite liner foreseen at some crucial locations of the containment; - Dynamic loads resulting from fast deflagration may impair containment wall or internal walls even if the AICC (adiabatic isochoric complete combustion) pressure is below the design pressure. Two types of combustion calculations have been performed: a) In cases, where fast deflagration cannot be excluded, combustion has been calculated with COM3D, a special CFD code developed to calculate dynamic pressure loads on walls, and b) 'Standing flame' combustion as well as recombination processes have been calculated with GASFLOW for bounding scenarios in order to evaluate maximum containment wall surface temperatures for cases of long-lasting combustion, mainly with emphasis on the application of a partial liner. Because of the depressurization of the reactor coolant system directly into the containment atmosphere via a relief tank and rupture discs a high concentration of steam is available for nearly all scenarios. For these scenarios no threat to internal walls is expected based on the combustion loads identified by the analyses presented here. In case of fast secondary cool-down a large amount of energy is removed to the secondary side of the SG and

  12. Modelling and analysis of thermal and stress loads in train disc brakes - braking from 250 km/h to standstill

    OpenAIRE

    Reibenschuh, Marko; Oder, Grega; Čuš, Franc; Potrč, Iztok

    2012-01-01

    Thermal and stress analysis of disc brakes under specific loads (driving downhill and braking to a standstill) was calculated. The FEM (Finite Element Method) was used to carry out the analysis. The analysis dealt with centrifugal load for two cases of braking, braking to a standstill on a flat surface and braking downhill, maintaining constant speed and afterwards braking to a standstill. The main boundary condition in both cases was the entered heat flux on the braking surface of the disc a...

  13. Modelling and analysis of thermal and stress loads in train disc brakes - braking from 250 km/h to standstill:

    OpenAIRE

    Čuš, Franc; Oder, Grega; Potrč, Iztok; Reibenschuh, Marko

    2009-01-01

    Thermal and stress analysis of disc brakes under specific loads (driving downhill and braking to a standstill) was calculated. The FEM (Finite Element Method) was used to carry out the analysis. The analysis dealt with centrifugal load for two cases of braking, braking to a standstill on a flat surface and braking downhill, maintaining constant speed and afterwards braking to a standstill. The main boundary condition in both cases was the entered heat flux on the braking surface of the disc a...

  14. Recent results on high thermal energy load testing of beryllium for ITER first wall application

    Science.gov (United States)

    Kupriyanov, I. B.; Roedig, M.; Nikolaev, G. N.; Kurbatova, L. A.; Linke, J.; Gervash, A. A.; Giniyatulin, R. N.; Podkovyrov, V. L.; Muzichenko, A. D.; Khimchenko, L.

    2011-12-01

    In this paper, progress in the high heat flux (HHF) qualification testing of TGP-56FW beryllium grade for ITER first wall applications is presented. Two actively cooled Be/CuCrZr brazing mock-ups were tested under complex thermal loading conditions in the electron beam facility JUDITH-1 (step 1: vertical displacement event test at 40 MJ m-2, 0.3 s, 1 shot; step 2: disruption tests at 3 MJ m-2, 1 shot, Δt=5 ms; step 3: repetitive fatigue test at 80 MW m-2, 1000 shots, Δt=25 ms). After testing, metallographic investigations on the microstructure and crack morphology were carried out. The results of these studies of Be tiles are reported and discussed. The overall results of TGP-56FW grade qualification testing have demonstrated the reliable performance capability of TGP-56FW for application as the armor of the ITER first wall. In addition, the results of first experiments with TGP-56FW and S-65C beryllium grades in the QSPA-Be plasma gun facility are also reported. In these experiments, beryllium tiles (80×80×10 mm3) were tested in a hydrogen plasma stream (5 cm in diameter) with pulse duration 0.5 ms and heat loads of 0.5-2 MJ m-2. Experiments were performed at room temperature. The evolution of the surface microstructure and mass loss of beryllium exposed to up to 100 shots is presented.

  15. Recent results on high thermal energy load testing of beryllium for ITER first wall application

    International Nuclear Information System (INIS)

    Kupriyanov, I B; Nikolaev, G N; Kurbatova, L A; Roedig, M; Linke, J; Gervash, A A; Giniyatulin, R N; Podkovyrov, V L; Muzichenko, A D; Khimchenko, L

    2011-01-01

    In this paper, progress in the high heat flux (HHF) qualification testing of TGP-56FW beryllium grade for ITER first wall applications is presented. Two actively cooled Be/CuCrZr brazing mock-ups were tested under complex thermal loading conditions in the electron beam facility JUDITH-1 (step 1: vertical displacement event test at 40 MJ m - 2, 0.3 s, 1 shot; step 2: disruption tests at 3 MJ m - 2, 1 shot, Δt=5 ms; step 3: repetitive fatigue test at 80 MW m - 2, 1000 shots, Δt=25 ms). After testing, metallographic investigations on the microstructure and crack morphology were carried out. The results of these studies of Be tiles are reported and discussed. The overall results of TGP-56FW grade qualification testing have demonstrated the reliable performance capability of TGP-56FW for application as the armor of the ITER first wall. In addition, the results of first experiments with TGP-56FW and S-65C beryllium grades in the QSPA-Be plasma gun facility are also reported. In these experiments, beryllium tiles (80×80×10 mm 3 ) were tested in a hydrogen plasma stream (5 cm in diameter) with pulse duration 0.5 ms and heat loads of 0.5-2 MJ m - 2. Experiments were performed at room temperature. The evolution of the surface microstructure and mass loss of beryllium exposed to up to 100 shots is presented.

  16. PSA-2, Stress Analysis, Thermal Expansion and Loads in Multi Anchor Piping System

    International Nuclear Information System (INIS)

    Nickols, A.N.

    1975-01-01

    1 - Description of problem or function: PSA2 computes the reactions and stresses caused by thermal expansion and loads in a multi-anchor piping system which may contain loops and may be partially restrained at any point in any direction. 2 - Method of solution: The linear equations for the statically indeterminate pipe system are set up by a generalization of Brock's matrix method. By a systematic use of linear transforms, the matrix of the system of linear equations can be obtained by incidence algebra in the form of a symmetric banded matrix. 2 - Restrictions on the complexity of the problem - Maximum of: 36 sections. 3 - Unusual features of the program - PSA2 takes into account: (a) elasticity of the attachment of the pipe to the foundation, (b) restraints on pipe displacements by anchors and intermediate partial constraints of linear type, (c) given constant forces and moments acting upon the pipe system, (d) thermal expansion, (e) any geometrical structure of the pipe system, (f) several cases of stressing per pipe system, and (g) both metric and English units

  17. A damage model of Zr {alpha} under cyclic loading at 200 degree Celsius; Modelisation de l`endommagement du Zr {alpha} sous chargement cyclique a 200 deg C

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, C.; Drubay, B. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. de Mecanique et de Technologie; Cailletaud, G. [Ecole Nationale Superieure des Mines, 75 - Paris (France); Mottot, M. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Direction des Technologies Avancees

    1994-12-31

    A damage model for anticipating zirconium {alpha} test-piece rupture under cyclic solicitations at 200 degree Celsius is presented. The article is divided into three parts : an experimental approach, the damage model presentation and the application of this model. (O.L.). 10 refs., 7 figs., 4 tabs.

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