WorldWideScience

Sample records for thermal fatigue loading

  1. 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)

  2. 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

  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. 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

  5. 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.

  6. 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

  7. 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

  8. 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)

  9. Thermal Acoustic Fatigue Apparatus

    Data.gov (United States)

    Federal Laboratory Consortium — The Thermal Acoustic Fatigue Apparatus (TAFA) is a progressive wave tube test facility that is used to test structures for dynamic response and sonic fatigue due to...

  10. 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.

  11. The Effect of a Non-Gaussian Random Loading on High-Cycle Fatigue of a Thermally Post-Buckled Structure

    Science.gov (United States)

    Rizzi, Stephen A.; Behnke, marlana N.; Przekop, Adam

    2010-01-01

    High-cycle fatigue of an elastic-plastic beam structure under the combined action of thermal and high-intensity non-Gaussian acoustic loadings is considered. Such loadings can be highly damaging when snap-through motion occurs between thermally post-buckled equilibria. The simulated non-Gaussian loadings investigated have a range of skewness and kurtosis typical of turbulent boundary layer pressure fluctuations in the vicinity of forward facing steps. Further, the duration and steadiness of high excursion peaks is comparable to that found in such turbulent boundary layer data. Response and fatigue life estimates are found to be insensitive to the loading distribution, with the minor exception of cases involving plastic deformation. In contrast, the fatigue life estimate was found to be highly affected by a different type of non-Gaussian loading having bursts of high excursion peaks.

  12. Effect of thermo-mechanical loading histories on fatigue crack growth behavior and the threshold in SUS 316 and SCM 440 steels. For prevention of high cycle thermal fatigue failures

    International Nuclear Information System (INIS)

    Okazaki, Masakazu; Muzvidziwa, Milton; Iwasaki, Akira; Kasahara, Naoto

    2014-01-01

    High cycle thermal fatigue failure of pipes induced by fluid temperature change is one of the interdisciplinary issues to be concerned for long term structural reliability of high temperature components in energy systems. In order to explore advanced life assessment methods to prevent the failure, fatigue crack propagation tests were carried out in a low alloy steel and an austenitic stainless steel under typical thermal and thermo-mechanical histories. Special attention was paid to both the effect of thermo-mechanical loading history on the fatigue crack threshold, as well as to the applicability of continuum fracture mechanics treatment to small or short cracks. It was shown experimentally that the crack-based remaining fatigue life evaluation provided more reasonable assessment than the traditional method based on the semi-empirical law in terms of 'usage factor' for high cycle thermal fatigue failure that is employed in JSME Standard, S017. The crack propagation analysis based on continuum fracture mechanics was almost successfully applied to the small fatigue cracks of which size was comparable to a few times of material grain size. It was also shown the thermo-mechanical histories introduced unique effects to the prior fatigue crack wake, resulting in occasional change in the fatigue crack threshold. (author)

  13. Fatigue Reliability under Random Loads

    DEFF Research Database (Denmark)

    Talreja, R.

    1979-01-01

    We consider the problem of estimating the probability of survival (non-failure) and the probability of safe operation (strength greater than a limiting value) of structures subjected to random loads. These probabilities are formulated in terms of the probability distributions of the loads and the...... propagation stage. The consequences of this behaviour on the fatigue reliability are discussed....

  14. Automatic fatigue monitoring based on real loads. Live demonstration

    International Nuclear Information System (INIS)

    Bergholz, Steffen; Rudolph, Juergen; Bruckmueller, Florian; Heinz, Benedikt; Jouan, Benoit

    2012-01-01

    The fatigue assessment of power plant components based on local fatigue monitoring approaches is an essential part of the integrity concept and modern lifetime management. An integral approach like the AREVA Fatigue Concept (AFC) basically consists of two essential modules: realistic determination of occurring operational thermal loads by means of a high end fatigue monitoring system and related highly qualified fatigue assessment methods and tools. The fatigue monitoring system delivers continuously realistic load data at the fatigue relevant locations. Consequently, realistic operational load sequences are available as input data for all ensuing fatigue analyses. This way, realistic load data are available and qualified fatigue usage factors can be determined. The mode of operation of the fatigue monitoring system will be explained in the framework of a live demonstration by means of the FAMOSi (i = integrated) demonstration wall. The workflow starts with the continuous online measurement of outer wall temperatures transients on a pipe. Visualization is implemented within the FAMOSi viewer software. In a second step, inner wall temperatures are directly calculated. In a third step, the resulting linearly elastic stress history will be calculated as the basis for subsequent code conforming fatigue assessment. Subsequently, the related advanced fatigue assessment methods of the three staged AFC-approach are addressed.

  15. Thermal-Acoustic Fatigue of a Multilayer Thermal Protection System in Combined Extreme Environments

    Directory of Open Access Journals (Sweden)

    Liu Liu

    2014-06-01

    Full Text Available In order to ensure integrity of thermal protection system (TPS structure for hypersonic vehicles exposed to severe operating environments, a study is undertaken to investigate the response and thermal-acoustic fatigue damage of a representative multilayer TPS structure under combined thermal and acoustic loads. An unsteady-state flight of a hypersonic vehicle is composed of a series of steady-state snapshots, and for each snapshot an acoustic load is imposed to a static steady-state TPS structure. A multistep thermal-acoustic fatigue damage intensity analysis procedure is given and consists of a heat transfer analysis, a nonlinear thermoelastic analysis, and a random response analysis under a combined loading environment and the fatigue damage intensity has been evaluated with two fatigue analysis techniques. The effects of thermally induced deterministic stress and nondeterministic dynamic stress due to the acoustic loading have been considered in the damage intensity estimation with a maximum stress fatigue model. The results show that the given thermal-acoustic fatigue intensity estimation procedure is a viable approach for life prediction of TPS structures under a typical mission cycle with combined loadings characterized by largely different time-scales. A discussion of the effects of the thermal load, the acoustic load, and fatigue analysis methodology on the fatigue damage intensity has been provided.

  16. Effect of loading parameter on fretting fatigue

    Science.gov (United States)

    Kowser, Md. Arefin; Chowdhury, Mohammad Asaduzzaman; Shah, Quazi Md. Zobaer

    2017-06-01

    Fretting fatigue has become one of the major concern in the recent few decades since developed designs both structure's and complex engineering are facing with fatigue accompanied by friction. In this study, load factors as normal and bending forces influence on stress distribution along contact surface as well as fatigue life has been experimented by FEM analysis. Fatigue life is influenced prominently by variable fretting loads than variable tensile loadings. Maximum Von mises Stress and strain shows uniform horizontal straight line is found for maximum loading while for both type of bending, minimum loads yield the same character. It has been observed that stress distribution is more uniform for varying bending loads when variable fretting loads yield stress singularity nearer to the tip of contact between fretting pad and beam.

  17. Thermal fatigue evaluation of piping system Tee-connections

    International Nuclear Information System (INIS)

    Metzner, K.J.; Braillard, O.; Faidy, C.; Marcelles, I.; Solin, J.; Stumpfrock, L.

    2004-01-01

    Thermal fatigue is one significant long-term degradation mechanism nuclear power plants (NPP), in particular, as operating plants become older and life time extension activities have been initiated. In general, the common thermal fatigue issues are understood and controlled by plant instrumentation systems. However, incidents in some plants indicate that certain piping system Tees are susceptible to turbulent temperature mixing effects that cannot be adequately monitored by common thermocouple instrumentation. The THERFAT project has been initiated to advance the accuracy and reliability of thermal fatigue load determination in engineering tools and research oriented approaches to outline a science based practical methodology for managing thermal fatigue risks in Tee-connections susceptible to high cyclic thermal fatigue. (orig.)

  18. Fatigue and thermal fatigue of Pb-Sn solder joints

    International Nuclear Information System (INIS)

    Frear, D.; Grivas, D.; McCormack, M.; Tribula, D.; Morris, J.W. Jr.

    1987-01-01

    This paper presents a fundamental investigation of the fatigue and thermal fatigue characteristics, with an emphasis on the microstructural development during fatigue, of Sn-Pb solder joints. Fatigue tests were performed in simple shear on both 60Sn-40Pb and 5Sn-95Pb solder joints. Isothermal fatigue tests show increasing fatigue life of 60Sn-40Pb solder joints with decreasing strain and temperature. In contrast, such behavior was not observed in the isothermal fatigue of 5Sn-95Pb solder joints. Thermal fatigue results on 60Sn-40Pb solder cycled between -55 0 C and 125 0 C show that a coarsened region develops in the center of the joint. Both Pb-rich and Sn-rich phases coarsen, and cracks form within these coarsened regions. The failure mode 60Sn-40Pb solder joints in thermal and isothermal fatigue is similar: cracks form intergranularly through the Sn-rich phase or along Sn/Pb interphase boundaries. Extensive cracking is found throughout the 5Sn-95Pb joint for both thermal and isothermal fatigue. In thermal fatigue the 5Sn-95Pb solder joints failed after fewer cycles than 60Sn-40Pb

  19. Fatigue Reliability under Multiple-Amplitude Loads

    DEFF Research Database (Denmark)

    Talreja, R.

    1979-01-01

    A method to determine the fatigue of structures subjected to multiple-amplitude loads is presented. Unlike the more common cumulative damage methods, which are usually based on fatigue life data, the proposed method is based on tensile strength data. Assuming the Weibull distribution for the init...

  20. Mesoscopic scale thermal fatigue damage

    International Nuclear Information System (INIS)

    Robertson, C.; Fissolo, A.; Fivel, M.

    2001-01-01

    In an attempt to better understand damage accumulation mechanisms in thermal fatigue, dislocation substructures forming in 316L steel during one specific test were examined and simulated. Hence, thin foils taken out of massive, tested specimens were first observed in transmission electron microscopy (TEM). These observations help in determining one initial dislocation configuration to be implemented in a 3-D model combining 3D discrete dislocation dynamics simulation (DDD) and finite element method computations (FEM). It was found that the simulated mechanical behaviour of the DDD microstructure is compatible with FEM and experimental data. The numerically generated dislocation microstructure is similar to ladder-like dislocation arrangements as found in many fatigued f.c.c. materials. Distinct mechanical behaviour for the two active slip systems was shown and deformation mechanisms were proposed. (authors)

  1. Fatigue in Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    1999-01-01

    test results. Both the fracture mechanics analysis and the fatigue test results indicate that Miner's rule, which is normally used in the design against fatigue in steel structures, may give results, which are unconservative, and that the validity of the results obtained from Miner's rule will depend......Fatigue damage accumulation in steel structures under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series have been carried through on various...... types of welded plate test specimens and full-scale offshore tubular joints. The materials that have been used are either conventional structural steel with a yield stress of ~ 360-410 MPa or high-strength steel with a yield stress of ~ 810-1010 MPa. The fatigue tests and the fracture mechanics analyses...

  2. Fatigue Performance under Multiaxial Loading

    Science.gov (United States)

    1990-01-01

    Abramov and H. Nagler. "Investigation of Effect of Welding on the Fatigue Properties of HY-80 Steel," New York Naval Shipyard, Material Laboratory...Project 6160-2, Progress Report 3, July 1961. 4-23.Stern, I., R. Wolfe, H. Nagler and P. Abramov . "Effects of Various Weld Flaws on Fatigue Properties of...V., P. Abramov and E. Lewis. "Investigation of the Effect of Welding on the Fatigue Properties of HY- 80 Steel," New York Naval Shipyard, Material

  3. Comparison of mechanical fatigue with thermal fatigue in ceramics

    International Nuclear Information System (INIS)

    Wilson, B.A.; Case, E.D.

    1993-01-01

    Thermal fatigue studies have shown a saturation of damage accumulation with cycling. Similar damage saturation has been observed for mechanical fatigue. This study compares damage saturation behavior for mechanical fatigue with thermal fatigue in ceramics. Studies of thermal fatigue of ceramics show that the accumulation of thermal shock cycling damage depends on the magnitude of the thermal shock, ΔΤ (where ΔΤ is the temperature change of the specimen from the initial temperature to the temperature of the quenching medium). Three distinct regimes of damage accumulation exist depending on the magnitude of ΔΤ. For the first regime where the thermal shock cycling is below ΔΤ c , a critical thermal shock value, there is no thermal damage detected. In the second regime where ΔΤ is higher than ΔΤ c but lower than ΔΤ 1 , the accumulating microcrack damage initially induces a rapid change in material property P. As the number of cycles increases a steady state value of properties is reached. For the third regime ΔΤ is higher than ΔΤ 1 and rapid crack growth results in fracture of the specimen. Each regime depends on ΔΤ since, for a given specimen and quenching medium, the maximum thermal shock stress is proportional to ΔΤ. So characterization of each regime by ΔΤ is indicative of the maximum stress applied by the thermal shock

  4. Thermal fatigue cracking of austenitic stainless steels

    International Nuclear Information System (INIS)

    Fissolo, A.

    2001-01-01

    This report deals with the thermal fatigue cracking of austenitic stainless steels as AISI 316 LN and 304 L. Such damage has been clearly observed for some components used in Fast Breeder reactors (FBR) and Pressure Water Reactor (PWR). In order to investigate thermal fatigue, quasi-structural specimen have been used. In this frame, facilities enforcing temperature variations similar to those found under the operation conditions have been progressively developed. As for components, loading results from impeded dilatation. In the SPLASH facility, the purpose was to establish accurate crack initiation conditions in order to check the relevance of the usual component design methodology. The tested specimen is continuously heated by the passage of an electrical DC current, and submitted to cyclic thermal down shock (up to 1000 deg C/s) by means of periodical spraying of water on two opposite specimen faces. The number of cycles to crack initiation N i is deduced from periodic examinations of the quenched surfaces, by means of optical microscopy. It is considered that initiation occurs when at least one 50μm to 150□m long crack is observed. Additional SPLASH tests were performed for N >> N i , with a view to investigate the evolution of a surface multiple cracking network with the number of cycles N. The CYTHIA test was mainly developed for the purpose of assessing crack growth dynamics of one isolated crack in thermal fatigue conditions. Specimens consist of thick walled tubes with a 1 mm circular groove is spark-machined at the specimen centre. During the test, the external wall of the tube is periodically heated by using a HF induction coil (1 MHz), while its internal wall is permanently cooled by flowing water. Total crack growth is derived from post-mortem examinations, whereby the thermal fatigue final rupture surface is oxidized at the end of the test. The specimen is broken afterwards under mechanical fatigue at room temperature. All the tests confirm that

  5. Thermal fatigue. Fluid-structure interaction at thermal mixing events

    Energy Technology Data Exchange (ETDEWEB)

    Schuler, X.; Herter, K.H.; Moogk, S. [Stuttgart Univ. (Germany). MPA; Laurien, E.; Kloeren, D.; Kulenovic, R.; Kuschewski, M. [Stuttgart Univ. (Germany). Inst. of Nuclear Technology and Energy Systems

    2012-07-01

    In the framework of the network research project ''Thermal Fatigue - Basics of the system-, outflow- and material-characteristics of piping under thermal fatigue'' funded by the German Federal Ministry of Education and Research (BMBF) fundamental numerical and experimental investigations on the material behaviour under transient thermal-mechanical stress conditions (high cycle fatigue - HCF) are carried out. The project's background and its network of scientific working groups with their individual working tasks are briefly introduced. The main focus is especially on the joint research tasks within the sub-projects of MPA and IKE which are dealing with thermal mixing of flows in a T-junction configuration and the fluidstructure- interactions (FSI). Therefore, experiments were performed with the newly established FSI test facility at MPA which enables single-phase flow experiments of water in typical power plant piping diameters (DN40 and DN80) at high pressure (maximum 75 bar) and temperatures (maximum 280 C). The experimental results serve as validation data base for numerical modelling of thermal flow mixing by means of thermo-fluid dynamics simulations applying CFD techniques and carried out by IKE as well as for modelling of thermal and mechanical loads of the piping structure by structural mechanics simulations with FEM methods which are executed by MPA. The FSI test facility will be described inclusively the applied measurement techniques, e. g. in particular the novel near-wall LED-induced Fluorescence method for non-intrusive flow temperature measurements. First experimental data and numerical results from CFD and FEM simulations of the thermal mixing of flows in the T-junction are presented.

  6. Monitoring for fatigue. Examples of unexpected component loading

    International Nuclear Information System (INIS)

    Golembiewski, H.J.; Kleinoeder, W.

    2000-01-01

    Continuous as well as short term monitoring for material fatigue serves to identify actual component loading. The loading generally comprises temperature transients and inhomogenous temperature distributions. In designing special instrumentation for data acquisition, design engineers typically rely on the experiences made in similar types of plants as well as on existing design specifications and stress analyses. In short, the layout of the data acquisition systems used for fatigue monitoring is a direct reflection of the know-how and experience. Fortunately, the collected data sometimes also reveal previously unknown loading effects. These can then be examined, backed up by more detailed measurements, analyzed for their fatiguing effects and - if required - incorporated into the regular operating procedures. Thus experience is gained, and subsequent instrumentation layouts can be modified in line with the newly acquired know-how. The present paper elaborates on a number of examples for loading effects that have recently come into focus in Western-type PWRs: thermal stratification in primary loop induced by pressurizer outsurge, mixing of varying temperature coolant flows in tee branches, temperature loading caused by leaking check valves during periodic component functional tests. The loading is discussed using P and IDs, temperature readings, calculational results of inner wall temperatures and stresses, and finally in terms of usage factors. Such information provides the impetus for improving operating procedures and thus ultimately helps to secure safe and economic component operation. Monitoring for material fatigue has been demonstrated to provide ample rewards to compensate for the efforts involved. (author)

  7. Simulation of Stochastic Loads for Fatigue Experiments

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Brincker, Rune

    1989-01-01

    A simple direct simulation method for stochastic fatigue-load generation is described in this paper. The simulation method is based on the assumption that only the peaks of the load process significantly affect the fatigue life. The method requires the conditional distribution functions of load...... ranges given the last peak values. Analytical estimates of these distribution functions are presented in the paper and compared with estimates based on a more accurate simulation method. In the more accurate simulation method samples at equidistant times are generated by approximating the stochastic load...... process by a Markov process. Two different spectra from two tubular joints in an offshore structure (one narrow banded and one wide banded) are considered in an example. The results show that the simple direct method is quite efficient and results in a simulation speed of about 3000 load cycles per second...

  8. Simulation of Stochastic Loads for Fatigue Experiments

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Brincker, Rune

    1989-01-01

    process by a Markov process. Two different spectra from two tubular joints in an offshore structure (one narrow banded and one wide banded) are considered in an example. The results show that the simple direct method is quite efficient and results in a simulation speed of about 3000 load cycles per second......A simple direct simulation method for stochastic fatigue-load generation is described in this paper. The simulation method is based on the assumption that only the peaks of the load process significantly affect the fatigue life. The method requires the conditional distribution functions of load...... ranges given the last peak values. Analytical estimates of these distribution functions are presented in the paper and compared with estimates based on a more accurate simulation method. In the more accurate simulation method samples at equidistant times are generated by approximating the stochastic load...

  9. Simulation of Stochastic Loads for Fatigue Experiments

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Brincker, Rune

    process by a Markov process. Two different spectra from two tubular joints in an offshore structure (one narrow banded and one wide banded) are considered in an example. The results show that the simple direct method is quite efficient and is results in a simulation speed at about 3000 load cycles per......A simple direct simulation method for stochastic fatigue load generation is described in this paper. The simulation method is based on the assumption that only the peaks of the load process significantly affect the fatigue life. The method requires the conditional distribution functions of load...... ranges given the last peak values. Analytical estimates of these distribution functions are presented in the paper and compared with estimates based on a more accurate simulation method. In the more accurate simulation method samples at equidistant times are generated by approximating the stochastic load...

  10. 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)

  11. 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)

  12. Thermal fatigue behaviour of controlled surface flaws in alumina

    Energy Technology Data Exchange (ETDEWEB)

    Saadaoui, M. [Maghrebian Information Processing Society (MIPS), Rabat (Morocco); Olagnon, C.; Fantozzi, G. [G.E.M.P.P.M., INSA de Lyon, Villeurbanne (France)

    1997-12-31

    Indented rectangular specimens were thermally cycled at an applied temperature difference {Delta}T, and the plot of the critical cycle number versus the initial crack size allowed the determination of a thermal fatigue domain in the V-K{sub 1} diagram (crack growth rate versus the stress intensity factor). Comparison with subcritical crack growth (SCG) laws obtained under isothermal mechanical loading reveals cyclic fatigue effects and shows that life time prediction cannot be done simply from the mechanical results. (orig.) 5 refs.

  13. Effects of loading sequences and size of repeated stress block of loads on fatigue life calculated using fatigue functions

    International Nuclear Information System (INIS)

    Schott, G.

    1989-01-01

    It is well-known that collective form, stress intensity and loading sequence of individual stresses as well as size of repeated stress blocks can influence fatigue life, significantly. The basic variant of the consecutive Woehler curve concept will permit these effects to be involved into fatigue life computation. The paper presented will demonstrate that fatigue life computations using fatigue functions reflect the loading sequence effect with multilevel loading precisely and provide reliable fatigue life data. Effects of size of repeated stress block and loading sequence on fatigue life as observed with block program tests can be reproduced using the new computation method. (orig.) [de

  14. 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.)

  15. 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

  16. Thermal fatigue appears to be more damaging than uniaxial isothermal fatigue for the austentic stainless steels, and application of multiaxial fatigue criteria

    Energy Technology Data Exchange (ETDEWEB)

    Fissolo, Antoine; Gourdin, Cedric [DM2S/SEMT/LISN, Gif sur Yvette (France); Vincent, Ludovic [DMN/SRMA/LCD, Gif sur Yvette (France)

    2009-07-01

    For nuclear reactor components, uniaxial isothermal fatigue curves are used to estimate the crack initiation under thermal fatigue. However, such approach would be not sufficient in some cases where cracking was observed. To investigate differences between uniaxial and thermal fatigue damage, tests have been carried out at CEA using the thermal fatigue devices SPLASH and FAT3D: a bi-dimensional (2-D) loading status is obtained in SPLASH, whereas a tri-dimensional (3-D) loading status is obtained in FAT3D. All the analysed tests clearly show that crack initiation in thermal fatigue is faster than in uniaxial isothermal fatigue conditions: for identical levels of strain, the number of cycles required to achieve crack initiation is significantly lower. The enhanced damaging effect probably results from a pure mechanical origin: a nearly perfect biaxial state corresponds to an increased hydrostatic stress. Consequently, multiaxial fatigue criteria must be applied. The Zamrik's strain criterion and the energy criterion proposed by Ecole Polytechnique provide the best estimations. In that framework, the proposed new method coupling both RCC-MR strain estimations and Zamrik's criterion appears to be more promising for the designer. (orig.)

  17. Large Area Nondestructive Evaluation of a Fatigue Loaded Composite Structure

    Science.gov (United States)

    Zalameda, Joseph N.; Burke, Eric R.; Horne, Michael R.; Madaras, Eric I.

    2016-01-01

    Large area nondestructive evaluation (NDE) inspections are required for fatigue testing of composite structures to track damage initiation and growth. Of particular interest is the progression of damage leading to ultimate failure to validate damage progression models. In this work, passive thermography and acoustic emission NDE were used to track damage growth up to failure of a composite three-stringer panel. Fourteen acoustic emission sensors were placed on the composite panel. The signals from the array were acquired simultaneously and allowed for acoustic emission location. In addition, real time thermal data of the composite structure were acquired during loading. Details are presented on the mapping of the acoustic emission locations directly onto the thermal imagery to confirm areas of damage growth leading to ultimate failure. This required synchronizing the acoustic emission and thermal data with the applied loading. In addition, processing of the thermal imagery which included contrast enhancement, removal of optical barrel distortion and correction of angular rotation before mapping the acoustic event locations are discussed.

  18. Proof of fatigue strength of nuclear components part II: Numerical fatigue analysis for transient stratification loading considering environmental effects

    International Nuclear Information System (INIS)

    Krätschmer, D.; Roos, E.; Schuler, X.; Herter, K.-H.

    2012-01-01

    For the construction, design and operation of nuclear components and systems the appropriate technical codes and standards provide detailed analysis procedures which guarantee a reliable behaviour of the structural components throughout the specified lifetime. Especially for cyclic stress evaluation the different codes and standards provide different fatigue analyses procedures to be performed considering the various mechanical and thermal loading histories and geometric complexities of the components. To consider effects of light water reactor coolant environments, new design curves included in report NUREG/CR-6909 for austenitic stainless steels and for low alloy steels have been presented. For the usage of these new design curves an environmental fatigue correction factor for incorporating environmental effects has to be calculated and used. The application of this environmental correction factor to a fatigue analysis of a nozzle with transient stratification loads, derived by in-service monitoring, has been performed. The results are used to compare with calculated usage factors, based on design curves without taking environmental effects particularly into account. - Highlights: ► We model an nozzle for fatigue analysis und mechanical and thermal loading conditions. ► A simplified as well as a general elastic–plastic fatigue analysis considering environmental effects is performed. ► The influence of different factors calculating the environmental factor F en are shown. ► The presented numerical evaluation methodology allows the consideration of all relevant parameters to assess lifetime.

  19. Foil system fatigue load environments for commercial hydrofoil operation

    Science.gov (United States)

    Graves, D. L.

    1979-01-01

    The hydrofoil fatigue loads environment in the open sea is examined. The random nature of wave orbital velocities, periods and heights plus boat heading, speed and control system design are considered in the assessment of structural fatigue requirements. Major nonlinear load events such as hull slamming and foil unwetting are included in the fatigue environment. Full scale rough water load tests, field experience plus analytical loads work on the model 929 Jetfoil commercial hydrofoil are discussed. The problem of developing an overall sea environment for design is defined. State of the art analytical approaches are examined.

  20. Study on cylindrical specimen subjected to oligocyclic thermal fatigue

    International Nuclear Information System (INIS)

    Cesari, F.; Battistella, P.; Quaranta, S.; Arduino, M.

    1993-01-01

    During the last years the development in the analysis of the thermal fatigue phenomenon was remarkable in particularly in industry. This improvement was more and more evident on the specific power of the engines, involving a general rise in the working temperature and in the stress level of oligocyclic thermal fatigue due to the start /stop of the engine. As far as this is concerned, the theoretical capabilities of the LIN (Nuclear Engineering Laboratory of Montecuccolino) has been requested in the frame of a collaboration with the IVECO Spa of Turin in view of verifying experimental data. The investigation of the thermal fatigue consequences has been undertaken by analyzing a cylindrical sample; its material was similar to that of the engine's head. Its was axially clamped in the two extremes and subjected to repeated thermal cycles. Beginning from the first experimental results supplied by IVECO, a theoretical - numerical campaign has been started in order to attempt a correct interpretation of the experimental behavior. The computer codes adopted in this study are mainly two typical FE programs (CASTEM and ANSYS) which have been carried out in parallel. First, both the physical and mechanical experimental conditions have been accurately reproduced in the model prepared for structural analysis. Second, several runs of calculations ware worked out to obtain a stress-strain description during some load - unload cycles. The material law is obviously non-linear because the strong variations in the temperature distributions cause high stress levels well above the yielding point

  1. Fatigue in Aluminum Highway Bridges under Random Loading

    DEFF Research Database (Denmark)

    Rom, Søren; Agerskov, Henning

    2014-01-01

    Fatigue damage accumulation in aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series on welded plate test...... is normally used in the design against fatigue in aluminum bridges, may give results which are unconservative. The validity of the results obtained from Miner’s rule will depend on the distribution of the load history in tension and compression....

  2. Equi-biaxial loading effect on austenitic stainless steel fatigue life

    Directory of Open Access Journals (Sweden)

    C. Gourdin

    2016-10-01

    Full Text Available Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures. In some nuclear power plant components, the fatigue loading may be equibiaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a strain tensor in equibiaxial tension. Two calibration tests (with strain gauges and image correlation were used to obtain the relationship between the imposed deflection and the radial strain on the FABIME2 specimen. A numerical study has confirmed this relationship. Biaxial fatigue tests are carried out on two austenitic stainless steels for different values of the maximum deflection, and with a load ratio equal to -1. The interpretation of the experimental results requires the use of an appropriate definition of strain equivalent. In nuclear industry, two kinds of definition are used: von Mises and TRESCA strain equivalent. These results have permitted to estimate the impact of the equibiaxiality on the fatigue life of components

  3. Fatigue in Steel Highway Bridges under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning; Nielsen, J.A.; Vejrum, Tina

    1997-01-01

    on welded plate test specimens have been carried through. The materials that have been used are either conventional structural steel with a yield stress of ~ 400-410 MPa or high-strength steel with a yield stress of ~ 810-840 MPa.The fatigue tests have been carried out using load histories, which correspond...... to one week's traffic loading, determined by means of strain gage measurements on the orthotropic steel deck structure of the Farø Bridges in Denmark.The test series which have been carried through show a significant difference between constant amplitude and variable amplitude fatigue test results. Both...... the fatigue test results and the fracture mechanics analysis indicate that the linear fatigue damage accumulation formula, which is normally used in the design against fatigue in steel bridges, may give results, which are unconservative. The validity of the results obtained from the linear fatigue damage...

  4. Thermography Inspection for Early Detection of Composite Damage in Structures During Fatigue Loading

    Science.gov (United States)

    Zalameda, Joseph N.; Burke, Eric R.; Parker, F. Raymond; Seebo, Jeffrey P.; Wright, Christopher W.; Bly, James B.

    2012-01-01

    Advanced composite structures are commonly tested under controlled loading. Understanding the initiation and progression of composite damage under load is critical for validating design concepts and structural analysis tools. Thermal nondestructive evaluation (NDE) is used to detect and characterize damage in composite structures during fatigue loading. A difference image processing algorithm is demonstrated to enhance damage detection and characterization by removing thermal variations not associated with defects. In addition, a one-dimensional multilayered thermal model is used to characterize damage. Lastly, the thermography results are compared to other inspections such as non-immersion ultrasonic inspections and computed tomography X-ray.

  5. Effects of Icing on Wind Turbine Fatigue Loads

    International Nuclear Information System (INIS)

    Frohboese, Peter; Anders, Andreas

    2007-01-01

    The external conditions occurring at cold climate sites will affect wind turbines in different ways. The effects of ice accretion on wind turbines and the influence on the turbine fatigue loads are examined. The amount of icing prior to turbine installation needs to be estimated by using standard measurement data and considering the geometry of the proposed turbine. A procedure to calculate the expected ice accretion on wind turbines out of standard measurement data is explained and the results are discussed. Different parameters to describe the accreted ice on the turbine are examined separately in a fatigue load calculation. The results of the fatigue load calculation are discussed and selected cases are presented

  6. Detection of thermal fatigue in composites by second harmonic Lamb waves

    International Nuclear Information System (INIS)

    Li, Weibin; Cho, Younho; Achenbach, Jan D

    2012-01-01

    Composite materials which are widely used in the aerospace industry, are usually subjected to frequent variation of temperature. Thermal cyclic loading may induce material degradation. Considering the long-term service of aircraft composites and the importance of safety in the aircraft industry, even a little damage that may be accumulative via thermal fatigue is often of great concern. Therefore, there is a demand to develop non-destructive approaches to evaluate thermal fatigue damage in an early stage. Due to the sensitivity of acoustic nonlinearity to micro-damage, the nonlinear ultrasonic technique has been explored as a promising tool for early detection of micro-damage. This paper investigates an experimental scheme for characterizing thermal fatigue damage in composite laminates using second harmonic Lamb waves. The present results show a monotonic increase of acoustic nonlinearity with respect to thermal fatigue cycles. The experimental observation of the correlation between the acoustic nonlinearity and thermal fatigue cycles in carbon/epoxy laminates verifies that nonlinear Lamb waves can be used to assess thermal fatigue damage rendering improved sensitivity over conventional linear feature based non-destructive evaluation techniques. Velocity and attenuation based ultrasonic studies are carried out for comparison with the nonlinear ultrasonic approach and it is found that nonlinear acoustic parameters are more promising indicators of thermal fatigue damage than linear ones. (paper)

  7. Using lamb waves tomonitor moisture absorption thermally fatigues composite laminates

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae Sun; Cho, Youn Ho [School of Mechanical Engineering, Pusan National University, Busan (Korea, Republic of)

    2016-06-15

    Nondestructive evaluation for material health monitoring is important in aerospace industries. Composite laminates are exposed to heat cyclic loading and humid environment depending on flight conditions. Cyclic heat loading and moisture absorption may lead to material degradation such as matrix breaking, debonding, and delamination. In this paper, the moisture absorption ratio was investigated by measuring the Lamb wave velocity. The composite laminates were manufactured and subjected to different thermal aging cycles and moisture absorption. For various conditions of these cycles, not only changes in weight and also ultrasonic wave velocity were measured, and the Lamb wave velocity at various levels of moisture on a carbon-epoxy plate was investigated. Results from the experiment show a linear correlation between moisture absorption ratio and Lamb wave velocity at different thermal fatigue stages. The presented method can be applied as an alternative solution in the online monitoring of composite laminate moisture levels in commercial flights.

  8. The Fatigue Behavior of Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    2009-01-01

    Fatigue damage accumulation in steel structures under random loading has been studied in a number of investigations at the Technical University of Denmark. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part...

  9. The Fatigue Behavior of Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    2008-01-01

    Fatigue damage accumulation in steel structures under random loading has been studied in a number of investigations at the Technical University of Denmark. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part...

  10. Influence of dental restorations and mastication loadings on dentine fatigue behaviour: Image-based modelling approach.

    Science.gov (United States)

    Vukicevic, Arso M; Zelic, Ksenija; Jovicic, Gordana; Djuric, Marija; Filipovic, Nenad

    2015-05-01

    The aim of this study was to use Finite Element Analysis (FEA) to estimate the influence of various mastication loads and different tooth treatments (composite restoration and endodontic treatment) on dentine fatigue. The analysis of fatigue behaviour of human dentine in intact and composite restored teeth with root-canal-treatment using FEA and fatigue theory was performed. Dentine fatigue behaviour was analysed in three virtual models: intact, composite-restored and endodontically-treated tooth. Volumetric change during the polymerization of composite was modelled by thermal expansion in a heat transfer analysis. Low and high shrinkage stresses were obtained by varying the linear shrinkage of composite. Mastication forces were applied occlusally with the load of 100, 150 and 200N. Assuming one million cycles, Fatigue Failure Index (FFI) was determined using Goodman's criterion while residual fatigue lifetime assessment was performed using Paris-power law. The analysis of the Goodman diagram gave both maximal allowed crack size and maximal number of cycles for the given stress ratio. The size of cracks was measured on virtual models. For the given conditions, fatigue-failure is not likely to happen neither in the intact tooth nor in treated teeth with low shrinkage stress. In the cases of high shrinkage stress, crack length was much larger than the maximal allowed crack and failure occurred with 150 and 200N loads. The maximal allowed crack size was slightly lower in the tooth with root canal treatment which induced somewhat higher FFI than in the case of tooth with only composite restoration. Main factors that lead to dentine fatigue are levels of occlusal load and polymerization stress. However, root canal treatment has small influence on dentine fatigue. The methodology proposed in this study provides a new insight into the fatigue behaviour of teeth after dental treatments. Furthermore, it estimates maximal allowed crack size and maximal number of cycles for a

  11. Thermal stress and creep fatigue limitations in first wall design

    International Nuclear Information System (INIS)

    Majumdar, S.; Misra, B.; Harkness, S.D.

    1977-01-01

    The thermal-hydraulic performance of a lithium cooled cylindrical first wall module has been analyzed as a function of the incident neutron wall loading. Three criteria were established for the purpose of defining the maximum wall loading allowable for modules constructed of Type 316 stainless steel and a vanadium alloy. Of the three, the maximum structural temperature criterion of 750 0 C for vanadium resulted in the limiting wall loading value of 7 MW/m 2 . The second criterion limited thermal stress levels to the yield strength of the alloy. This led to the lowest wall loading value for the Type 316 stainless steel wall (1.7 MW/m 2 ). The third criterion required that the creep-fatigue characteristics of the module allow a lifetime of 10 MW-yr/m 2 . At wall temperatures of 600 0 C, this lifetime could be achieved in a stainless steel module for wall loadings less than 3.2 MW/m 2 , while the same lifetime could be achieved for much higher wall loadings in a vanadium module

  12. Fatigue design of nuclear class 1 piping considering thermal stratification

    International Nuclear Information System (INIS)

    Kweon, Hyeong Do; Kim, Jong Sung; Lee, Kang Yong

    2008-01-01

    In ASME B and PV Code, Section III, Subsection NB-3600, thermal stratification is not taken into account to determine the peak stress intensity range for fatigue design of nuclear class 1 piping. Therefore, the effects of several parameters such as boundary layer thickness, temperature difference, stratification length, wall thickness, inner diameter and material properties on peak temperature and peak stress intensity due to non-linear temperature distribution of thermal stratification in a pipe cross-section are studied through the numerical parametric study. The results of the parametric study are closely examined and consolidated to introduce an additional term into the equation of ASME so that the modified equation can be used to determine the peak stress intensity range due to all loads including thermal stratification

  13. Fatigue life assessment under multiaxial variable amplitude loading

    International Nuclear Information System (INIS)

    Morilhat, P.; Kenmeugne, B.; Vidal-Salle, E.; Robert, J.L.

    1996-06-01

    A variable amplitude multiaxial fatigue life prediction method is presented in this paper. It is based on a stress as input data are the stress tensor histories which may be calculated by FEM analysis or measured directly on the structure during the service loading. The different steps of he method are first presented then its experimental validation is realized for log and finite fatigue lives through biaxial variable amplitude loading tests using cruciform steel samples. (authors). 9 refs., 7 figs

  14. Stochastic modeling of thermal fatigue crack growth

    CERN Document Server

    Radu, Vasile

    2015-01-01

    The book describes a systematic stochastic modeling approach for assessing thermal-fatigue crack-growth in mixing tees, based on the power spectral density of temperature fluctuation at the inner pipe surface. It shows the development of a frequency-temperature response function in the framework of single-input, single-output (SISO) methodology from random noise/signal theory under sinusoidal input. The frequency response of stress intensity factor (SIF) is obtained by a polynomial fitting procedure of thermal stress profiles at various instants of time. The method, which takes into account the variability of material properties, and has been implemented in a real-world application, estimates the probabilities of failure by considering a limit state function and Monte Carlo analysis, which are based on the proposed stochastic model. Written in a comprehensive and accessible style, this book presents a new and effective method for assessing thermal fatigue crack, and it is intended as a concise and practice-or...

  15. Study on Standard Fatigue Vehicle Load Model

    Science.gov (United States)

    Huang, H. Y.; Zhang, J. P.; Li, Y. H.

    2018-02-01

    Based on the measured data of truck from three artery expressways in Guangdong Province, the statistical analysis of truck weight was conducted according to axle number. The standard fatigue vehicle model applied to industrial areas in the middle and late was obtained, which adopted equivalence damage principle, Miner linear accumulation law, water discharge method and damage ratio theory. Compared with the fatigue vehicle model Specified by the current bridge design code, the proposed model has better applicability. It is of certain reference value for the fatigue design of bridge in China.

  16. Thermal fatigue cracking of austenitic stainless steels; Fissuration en fatigue thermique des aciers inoxydables austenitiques

    Energy Technology Data Exchange (ETDEWEB)

    Fissolo, A

    2001-07-01

    This report deals with the thermal fatigue cracking of austenitic stainless steels as AISI 316 LN and 304 L. Such damage has been clearly observed for some components used in Fast Breeder reactors (FBR) and Pressure Water Reactor (PWR). In order to investigate thermal fatigue, quasi-structural specimen have been used. In this frame, facilities enforcing temperature variations similar to those found under the operation conditions have been progressively developed. As for components, loading results from impeded dilatation. In the SPLASH facility, the purpose was to establish accurate crack initiation conditions in order to check the relevance of the usual component design methodology. The tested specimen is continuously heated by the passage of an electrical DC current, and submitted to cyclic thermal down shock (up to 1000 deg C/s) by means of periodical spraying of water on two opposite specimen faces. The number of cycles to crack initiation N{sub i} is deduced from periodic examinations of the quenched surfaces, by means of optical microscopy. It is considered that initiation occurs when at least one 50{mu}m to 150{open_square}m long crack is observed. Additional SPLASH tests were performed for N >> N{sub i}, with a view to investigate the evolution of a surface multiple cracking network with the number of cycles N. The CYTHIA test was mainly developed for the purpose of assessing crack growth dynamics of one isolated crack in thermal fatigue conditions. Specimens consist of thick walled tubes with a 1 mm circular groove is spark-machined at the specimen centre. During the test, the external wall of the tube is periodically heated by using a HF induction coil (1 MHz), while its internal wall is permanently cooled by flowing water. Total crack growth is derived from post-mortem examinations, whereby the thermal fatigue final rupture surface is oxidized at the end of the test. The specimen is broken afterwards under mechanical fatigue at room temperature. All the

  17. Multiaxial low cycle fatigue life under non-proportional loading

    International Nuclear Information System (INIS)

    Itoh, Takamoto; Sakane, Masao; Ohsuga, Kazuki

    2013-01-01

    A simple and clear method of evaluating stress and strain ranges under non-proportional multiaxial loading where principal directions of stress and strain are changed during a cycle is needed for assessing multiaxial fatigue. This paper proposes a simple method of determining the principal stress and strain ranges and the severity of non-proportional loading with defining the rotation angles of the maximum principal stress and strain in a three dimensional stress and strain space. This study also discusses properties of multiaxial low cycle fatigue lives for various materials fatigued under non-proportional loadings and shows an applicability of a parameter proposed by author for multiaxial low cycle fatigue life evaluation

  18. Fatigue in Steel Highway Bridges under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning; Nielsen, Jette Andkjær

    1999-01-01

    have been carried through. The materials that have been used are either conventional structural steel with a yield stress of f(y) similar to 400-410 MPa or high-strength steel with a yield stress of f(y) similar to 810-840 MPa. The fatigue tests have been carried out using load histories, which...... correspond to one week's traffic loading, determined by means of strain gauge measurements on the orthotropic steel deck structure of the Faro Bridges in Denmark. The test series carried through show a significant difference between constant amplitude and variable amplitude fatigue test results. Both...... the fracture mechanics analysis and the fatigue test results indicate that Miner's rule, which is normally used in the design against fatigue in steel bridges, may give results that are unconservative. The validity. of the results obtained from Miner's rule will depend on the distribution of the load history...

  19. Gearbox Fatigue Load Estimation for Condition Monitoring of Wind Turbines

    DEFF Research Database (Denmark)

    Perisic, Nevena; Pedersen, Bo Juul; Kirkegaard, Poul Henning

    2012-01-01

    control and data acquisition (SCADA) system. Estimated loads can be further used for prediction of remaining operating lifetime of turbine components, detection of high stress level or fault detection. An augmented Kalman filter is chosen as the fatigue load estimator because its characteristics well suit...

  20. Wind Climate Parameters for Wind Turbine Fatigue Load Assessment

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Svenningsen, Lasse; Moser, Wolfgang

    2016-01-01

    established from the on-site distribution functions of the horizontal mean wind speeds, the 90% quantile of turbulence along with average values of vertical wind shear and air density and the maximum flow inclination. This paper investigates the accuracy of fatigue loads estimated using this equivalent wind...... climate required by the current design standard by comparing damage equivalent fatigue loads estimated based on wind climate parameters for each 10 min time-series with fatigue loads estimated based on the equivalent wind climate parameters. Wind measurements from Boulder, CO, in the United States...... and Høvsøre in Denmark have been used to estimate the natural variation in the wind conditions between 10 min time periods. The structural wind turbine loads have been simulated using the aero-elastic model FAST. The results show that using a 90% quantile for the turbulence leads to an accurate assessment...

  1. 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.

  2. In situ fatigue loading stage inside scanning electron microscope

    Science.gov (United States)

    Telesman, Jack; Kantzos, Peter; Brewer, David

    1988-01-01

    A fatigue loading stage inside a scanning electron microscopy (SEM) was developed. The stage allows dynamic and static high-magnification and high-resolution viewing of the fatigue crack initiation and crack propagation processes. The loading stage is controlled by a closed-loop servohydraulic system. Maximum load is 1000 lb (4450 N) with test frequencies ranging up to 30 Hz. The stage accommodates specimens up to 2 inches (50 mm) in length and tolerates substantial specimen translation to view the propagating crack. At room temperature, acceptable working resolution is obtainable for magnifications ranging up to 10,000X. The system is equipped with a high-temperature setup designed for temperatures up to 2000 F (1100 C). The signal can be videotaped for further analysis of the pertinent fatigue damage mechanisms. The design allows for quick and easy interchange and conversion of the SEM from a loading stage configuration to its normal operational configuration and vice versa. Tests are performed entirely in the in-situ mode. In contrast to other designs, the NASA design has greatly extended the life of the loading stage by not exposing the bellows to cyclic loading. The loading stage was used to investigate the fatigue crack growth mechanisms in the (100)-oriented PWA 1480 single-crystal, nickel-based supperalloy. The high-magnification observations revealed the details of the crack growth processes.

  3. Fatigue life prediction of mechanical structures under stochastic loading

    Directory of Open Access Journals (Sweden)

    Leitner Bohuš

    2018-01-01

    Full Text Available Problems of fatigue life prediction of materials and structures are discussed in the paper. Service loading is assumed as a continuous loading process with possible discontinuous events, which are caused by various operating conditions. The damage in a material is due to a cumulative degradation process. The damaging process is then represented either by rain-flow matrices or by a fatigue damage function which is derived using some hypothesis of a fatigue failure criterion. Presented theoretical procedure enables a very effective estimation of a service life and/or reliable evaluation of residual life of any structures under various types of loading and environmental conditions. This approach creates a good basis for powerful expert systems in structural and mechanical engineering. The aim of the paper is to present briefly some results of analysis of load-bearing steel structure loads of special railway crane PKP 25/20i which was utilized in some specific ad relatively hard operating conditions. Virtual models of the structure were being used in an analysis of acting working dynamics loads influence to be able to forecast fatigue life of load-bearing of the crane jib.

  4. Thermal fatigue crack growth in mixing tees nuclear piping - An analytical approach

    International Nuclear Information System (INIS)

    Radu, V.

    2009-01-01

    The assessment of fatigue crack growth due to cyclic thermal loads arising from turbulent mixing presents significant challenges, principally due to the difficulty of establishing the actual loading spectrum. So-called sinusoidal methods represent a simplified approach in which the entire spectrum is replaced by a sine-wave variation of the temperature at the inner pipe surface. The need for multiple calculations in this process has lead to the development of analytical solutions for thermal stresses in a pipe subject to sinusoidal thermal loading, described in previous work performed at JRC IE Petten, The Netherlands, during the author's stage as seconded national expert. Based on these stress distributions solutions, the paper presents a methodology for assessment of thermal fatigue crack growth life in mixing tees nuclear piping. (author)

  5. Keep fatigue usage low for LTO. Benefits of load monitoring and related fatigue evaluations for long term operation

    International Nuclear Information System (INIS)

    Rothenhoefer, H.; Koenig, G.

    2012-01-01

    Design fatigue calculations normally cover a service life of 40 years. Based on design transients with a specified number of cycles the evaluations have to prove that the fatigue usage after 40 years will stay below 1. In 40+ years of operation real loads can differ much from design loads so that premature ageing can occur. For long term operation, monitoring of real loads and detailed fatigue analysis for selected locations can be used to optimize operational modes in order to reduce the loads causing fatigue. As a result fatigue usage can be kept below 1 even for 60+ years. (author)

  6. High cycle fatigue of austenitic stainless steels under random loading

    International Nuclear Information System (INIS)

    Gauthier, J.P.; Petrequin, P.

    1987-08-01

    To investigate reactor components, load control random fatigue tests were performed at 300 0 C and 550 0 C, on specimens from austenitic stainless steels plates in the transverse orientation. Random solicitations are produced on closed loop servo-hydraulic machines by a mini computer which generates random load sequence by the use of reduced Markovian matrix. The method has the advantage of taking into account the mean load for each cycle. The solicitations generated are those of a stationary gaussian process. Fatigue tests have been mainly performed in the endurance region of fatigue curve, with scattering determination using stair case method. Experimental results have been analysed aiming at determining design curves for components calculations, depending on irregularity factor and temperature. Analysis in term of mean square root fatigue limit calculation, shows that random loading gives more damage than constant amplitude loading. Damage calculations following Miner rule have been made using the probability density function for the case where the irregularity factor is nearest to 100 %. The Miner rule is too conservative for our results. A method using design curves including random loading effects with irregularity factor as an indexing parameter is proposed

  7. Study of the effect of an equi-biaxial loading on the fatigue lifetime of austenitic stainless steel

    International Nuclear Information System (INIS)

    Bradai, Soumaya

    2014-01-01

    Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures.In some nuclear power plant components, the fatigue loading may be equi-biaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a strain tensor in equi-biaxial tension. The aim of this study is to present the experimental and numerical results obtained with a device 'FABIME2' developed in the LISN in collaboration with EDF and AREVA. The association of the experimental results, obtained on the new experimental fatigue device FABIME2, with the numerical analyses obtained by FEM simulation with Cast3M code, has enabled to define the aggravating effect of the equi-biaxial fatigue loading. However, this effect is covered by the Design fatigue curve defined from the nuclear industry. For the crack propagation, a first simplified approach enables to study the kinetic behavior of crack propagation in equi-biaxial fatigue. (author) [fr

  8. 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.

  9. Diaphragmatic fatigue during inspiratory muscle loading in normoxia and hypoxia.

    Science.gov (United States)

    Walker, David Johannes; Farquharson, Franziska; Klenze, Hannes; Walterspacher, Stephan; Storz, Lucia; Duerschmied, Daniel; Roecker, Kai; Kabitz, Hans-Joachim

    2016-06-15

    Diaphragmatic fatigue (DF) occurs during strenuous loading of respiratory muscles (e.g., heavy-intensity whole-body exercise, normocapnic hyperpnea, inspiratory resistive breathing). DF develops early on during normoxia, without further decline toward task failure; however, its progression during inspiratory muscle loading in during hypoxia remains unclear. Therefore, the present study used volume-corrected transdiaphragmatic pressures during supramaximal magnetic phrenic nerve stimulation (Pdi,twc) to investigate the effect of hypoxia on the progression of diaphragmatic fatigue during inspiratory muscle loading. Seventeen subjects completed two standardized rounds of inspiratory muscle loading (blinded, randomized) under the following conditions: (i) normoxia, and (ii) normobaric hypoxia (SpO2 80%), with Pdi,twc assessment every 45 s. In fatiguers (i.e., Pdi,twc reduction >10%, n=10), biometric approximation during normoxia is best represented by Pdi,twc=4.06+0.83 exp(-0.19 × x), in contrast to Pdi,twc=4.38-(0.05 × x) during hypoxia. Progression of diaphragmatic fatigue during inspiratory muscle loading assessed by Pdi,tw differs between normoxia and normobaric hypoxia: in the former, Pdi,tw follows an exponential decay, whereas during hypoxia, Pdi,tw follows a linear decline. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. 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.

  11. Fatigue Analysis of Load-Carrying Fillet Welds

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Tychsen, Jesper; Andersen, Jens Ulfkjær

    2006-01-01

    The fatigue strength of load-carrying fillet welds is, in most codes of practice, performed neglecting the influence of bending in the weld throat section. However, some commonly applied structural details give rise to significant bending in the weld throat section. An example of such a detail is....... Using the test results, it is shown that the new definition of fatigue stress can be used for a wide range of DOB with a low standard deviation of the resulting SN curve....... is a doubler plate connection, which is often applied in connection with modifications of offshore structures. As a part of the present work, fatigue tests have been performed with test specimens fabricated by the current industry standard for welded offshore steel structures. The fatigue tests show...... that the degree of bending (DOB) has an influence on the fatigue lifetime. The fatigue lifetime decreases significantly when increasing the bending stress. In order to take into account the effect of the bending, a new fatigue stress definition applicable for fillet welds failing through the weld is presented...

  12. The nature of wind turbine fatigue loads in wind farms

    DEFF Research Database (Denmark)

    Larsen, Gunner Chr.; Larsen, Torben J.; Aagaard Madsen, Helge

    2013-01-01

    agreements were found between the extend of wake affected direction regimes. As for the magnitude of the (mean) wake loading, the tower top moments were under-estimated with of the order 15%, whereas the tower bottom moments were found to agree well with the measured results.......The aim of the present paper is to further validate the predictive capability of the DWM/HAWC2 package for simulation of structural loadings in wind farms. The validation in particular focus on tower fatigue loading characteristics (i.e. equivalent moments) as function of turbine relative position...... tower top and bottom bending moments as well as tower the top torsion moment. The numerical predictions are based on a simulation package, where the Dynamic Wake Meandering model is interfaced with the in-house aeroelastic code HAWC2. Comparing simulated and measured tower fatigue loading, good...

  13. Issues related to SPR joints subjected to fatigue loads

    Science.gov (United States)

    De Luca, A.; Senatore, F.; Greco, A.

    2016-05-01

    SPR joints will represent an alternative solution to spot welding in automotive field. However, their fatigue behavior shows several critical issues. After a brief introduction of this new solution, different crack modes are described, emphasizing the parameters that characterize them, i.e. the applied loads, the geometry of the joint and other phenomenon as fretting, vibration and corrosion.

  14. Study on fatigue analysis for operational load histories

    International Nuclear Information System (INIS)

    Wilhelm, Paul; Rudolph, Juergen; Steinmann, Paul

    2013-01-01

    Some laboratories performed fatigue tests in dissolved oxygen water at elevated temperature to better understand the influence of a long hold-time within cyclic loading. Also, the combined effect of complex waveform and surface finish was examined. The data show a less severe influence compared to the prediction model from Argonne National Laboratory; an increase in fatigue life was noticed and attributed to different effects. To evaluate an operational load history with this experimental data an algorithm is developed, which finds hold-times and the examined complex waveform in a stress-time series. All those cycles, which are either geometrically comparable to the complex loading signal or containing a hold period, are evaluated with the test results and not with the formula from Argonne National Laboratory. The reduction of the cumulative usage factor is calculated. Based on this discussion a realistic test condition is derived for further research activities.

  15. Modeling of the mechanical behavior of austenitic stainless steels under pure fatigue and fatigue relaxation loadings

    International Nuclear Information System (INIS)

    Hajjaji-Rachdi, Fatima

    2015-01-01

    Austenitic stainless steels are potential candidates for structural components of sodium-cooled fast neutron reactors. Many of these components will be subjected to cyclic loadings including long hold times (1 month) under creep or relaxation at high temperature. These hold times are unattainable experimentally. The aim of the present study is to propose mechanical models which take into account the involved mechanisms and their interactions during such complex loadings. First, an experimental study of the pure fatigue and fatigue-relaxation behavior of 316L(N) at 500 C has been carried out with very long hold times (10 h and 50 h) compared with the ones studied in literature. Tensile tests at 600 C with different applied strain rates have been undertaken in order to study the dynamic strain ageing phenomenon. Before focusing on more complex loadings, the mean field homogenization approach has been used to predict the mechanical behavior of different FCC metals and alloys under low cycle fatigue at room temperature. Both Hill-Hutchinson and Kroener models have been used. Next, a physically-based model based on dislocation densities has been developed and its parameters measured. The model allows predictions in a qualitative agreement with experimental data for tensile loadings. Finally, this model has been enriched to take into account visco-plasticity, dislocation climb and interaction between dislocations and solute atoms, which are influent during creep-fatigue or fatigue relaxation at high temperature. The proposed model uses three adjustable parameters only and allows rather accurate prediction of the behavior of 316L(N) steel under tensile loading and relaxation. (author) [fr

  16. Thermal Fatigue of Die-Casting Dies: An Overview

    Directory of Open Access Journals (Sweden)

    Abdulhadi Hassan A.

    2016-01-01

    Full Text Available Coupled studies by experimental and numerical simulations are necessary for an increased understanding of the material behaviour as related to the interaction between the thermal and mechanical conditions. This paper focus on the mechanisms of thermal fatigue in the failure of dies and cores used in the die casting of aluminum alloys. The thermal fatigue resistance is expressed by two crack parameters which are the average maximum crack and the average cracked area. Samples of various types of H13 steel were compared with a standard H13 steel by testing under identical thermal fatigue cycles. To determine the thermal constraint developed in the sample during the test, a finite difference technique was used to obtain the temperature distribution, based on temperature measurements at the boundaries. The resulting stresses and strains were computed, and the strain calculated at the edge or weakest point of the sample was used to correlate the number of cycles to crack initiation. As the strain at the edge increased, the number of cycles to failure decreased. The influence of various factors on thermal fatigue behavior was studied including austenitizing temperature, surface condition, stress relieving, casting, vacuum melting, and resulfurization. The thermal fatigue resistance improved as the austenitizing temperature increased from 1750 to 2050ºF.

  17. Load fatigue performance of conical implant-abutment connections.

    Science.gov (United States)

    Seetoh, Y L; Tan, Keson B; Chua, E K; Quek, H C; Nicholls, Jack I

    2011-01-01

    Conical implant-abutment connections for platform switching have been recently introduced in implant systems. This study investigated the load fatigue performance of three conical abutment systems and their corresponding titanium and zirconia abutments. Regular-diameter implants of the Ankylos (AK), PrimaConnex (PC), and Straumann (ST) systems were tested with their corresponding titanium (Ti) and zirconia (Zr) abutments tightened to the recommended torque (n = 5 implant-abutment assemblies per group). A rotational load fatigue machine applied a sinusoidally varying tensile-compressive 21 N load to specimens at a 45-degree angle, producing an effective bending moment of 35 Ncm at a frequency of 10 Hz. The number of cycles to failure was recorded, with the upper limit set at 5 million cycles. Results were evaluated through analyses of variance. Except for the ST Zr group, which showed no failures in four samples and one failure just below the screw head, and the AK Ti group, in which one sample was preserved without fracture, all groups experienced failure of at least one of the components, whether the abutment screw only, the abutment, and/or the implant neck. There were significant differences between systems. There was no difference between systems for the Ti abutments, and the ST group was significantly different from the AK and PC groups for the Zr abutments. Ti conical abutments appear to have poorer load fatigue performance compared with earlier studies of external-hexagon connections. The load fatigue performance of Zr conical abutments varied and seemed to be highly system dependent. Many of the fractures in both the Ti and Zr abutment groups occurred within the implant, and retrieval would pose a significant clinical challenge. The clinician should weigh the mechanical, biologic, and esthetic considerations before selection of any implant system, connection type, or abutment material.

  18. Design optimization of cruciform specimens for biaxial fatigue loading

    Directory of Open Access Journals (Sweden)

    R. Baptista

    2014-10-01

    Full Text Available In order to correctly assess the biaxial fatigue material properties one must experimentally test different load conditions and stress levels. With the rise of new in-plane biaxial fatigue testing machines, using smaller and more efficient electrical motors, instead of the conventional hydraulic machines, it is necessary to reduce the specimen size and to ensure that the specimen geometry is appropriated for the load capacity installed. At the present time there are no standard specimen’s geometries and the indications on literature how to design an efficient test specimen are insufficient. The main goal of this paper is to present the methodology on how to obtain an optimal cruciform specimen geometry, with thickness reduction in the gauge area, appropriated for fatigue crack initiation, as a function of the base material sheet thickness used to build the specimen. The geometry is optimized for maximum stress using several parameters, ensuring that in the gauge area the stress is uniform and maximum with two limit phase shift loading conditions. Therefore the fatigue damage will always initiate on the center of the specimen, avoiding failure outside this region. Using the Renard Series of preferred numbers for the base material sheet thickness as a reference, the reaming geometry parameters are optimized using a derivative-free methodology, called direct multi search (DMS method. The final optimal geometry as a function of the base material sheet thickness is proposed, as a guide line for cruciform specimens design, and as a possible contribution for a future standard on in-plane biaxial fatigue tests.

  19. Optimal fatigue analysis of structures during complex loadings

    Directory of Open Access Journals (Sweden)

    Karaouni Habib

    2016-01-01

    Full Text Available A new framework for high cycle fatigue analysis of metallic structures under complex multi-parameter loadings was here developed. This allows to reduce the analysis on a 2-D window with a characterized one-parameter cyclic loading thanks to an equivalence rule relative to damage between any two loadings. The simplified inelastic analysis introduced by J. Zarka [J. Zarka et al. 1990. A new approach in inelastic analysis of structures. CADLM] was used to find the limit state of the structure. A new design rules for fatigue analysis by utilizing automatic learning systems was successfully performed. A database was built by coupling numerical simulations and experimental results on several welded specimens which are considered as a general structure in the proposed approach. This could be possible by the introduction of an intelligent description of a general fatigue case based on the actual theories and models. A software, FATPRO [M.I. Systems, FatPro, available at http://www.mzintsys.com/our_products_fatpro.html], based on this work has been developed at MZ Intelligent Systems.

  20. Analysis of the consumption of useful life by thermal fatigue in the gas turbine nozzles during the operation at continuous load and transients; Analisis de consumo de vida por fatiga termica en las toberas de turbina de gas durante operacion con carga continua y transitorios

    Energy Technology Data Exchange (ETDEWEB)

    Perez Hernandez, Efrain Betuel

    2007-08-15

    The gas turbines operate at extremely high temperatures, with high thermal and mechanical stresses, causing that the life of the involved components diminishes. In the present thesis the temperature distribution on the nozzle obtained in other investigation as a result of heat transfer and fluid flow analysis applying CDF code Star-CD was used. Next, the program NISA was used to perform the analysis of thermal stresses by means of finite element method. Finally, the results of stress analysis were introduced to the program nCode to accomplish the nozzle remaining useful life assessment due to thermal fatigue in critical location on the nozzle by means of the CLF module (Critical Location Fatigue). The full methodology used to determine the nozzle operational conditions, load history, material properties and the fatigue model used to determine the number of cycles to failure of the nozzle during constant load and transients operation is presented. [Spanish] Las turbinas de gas operan a temperaturas extremadamente altas, a elevados esfuerzos termicos y mecanicos, ocasionando que la vida de los componentes involucrados se reduzca. En la presente tesis se presentan los resultados realizados por otras investigaciones de temperaturas obtenidas a partir de un analisis de transferencia de calor y flujo de fluidos de la tobera mediante el programa Star-CD basado en volumenes finitos. Posteriormente, se utilizo el programa NISA para realizar el analisis de esfuerzos mediante elementos finitos. Finalmente, se llevaron los resultados al programa nCode para realizar la estimacion de vida util por fatiga termica en un punto critico de la tobera mediante el modulo CLF (Critical Location Fatigue). Se muestra la metodologia empleada para determinar las condiciones de operacion, historial de carga, propiedades del material y el modelo de dano por fatiga para determinar el numero de ciclo para falla de la tobera durante operacion con carga continua y transitorios.

  1. Structural investigation of composite wind turbine blade considering various load cases and fatigue life

    International Nuclear Information System (INIS)

    Kong, C.; Bang, J.; Sugiyama, Y.

    2005-01-01

    This study proposes a structural design for developing a medium scale composite wind turbine blade made of E-glass/epoxy for a 750 kW class horizontal axis wind turbine system. The design loads were determined from various load cases specified at the IEC61400-1 international specification and GL regulations for the wind energy conversion system. A specific composite structure configuration, which can effectively endure various loads such as aerodynamic loads and loads due to accumulation of ice, hygro-thermal and mechanical loads, was proposed. To evaluate the proposed composite wind turbine blade, structural analysis was performed by using the finite element method. Parametric studies were carried out to determine an acceptable blade structural design, and the most dominant design parameters were confirmed. In this study, the proposed blade structure was confirmed to be safe and stable under various load conditions, including the extreme load conditions. Moreover, the blade adapted a new blade root joint with insert bolts, and its safety was verified at design loads including fatigue loads. The fatigue life of a blade that has to endure for more than 20 years was estimated by using the well-known S-N linear damage theory, the service load spectrum, and the Spera's empirical equations. With the results obtained from all the structural design and analysis, prototype composite blades were manufactured. A specific construction process including the lay-up molding method was applied to manufacturing blades. Full-scale static structural test was performed with the simulated aerodynamic loads. From the experimental results, it was found that the designed blade had structural integrity. In addition, the measured results of deflections, strains, mass, and radial center of gravity agreed well with the analytical results. The prototype blade was successfully certified by an international certification institute, GL (Germanisher Lloyd) in Germany

  2. Fatigue of bridges with a horizontal rotation axle under random wind load

    NARCIS (Netherlands)

    Maljaars, J.; Steenbergen, R.D.J.M.

    2012-01-01

    The operating mechanisms of movable bridges are subjected to various types of fluctuating loads which may induce fatigue damage. Wind load acting on the bridge deck - when the bridge is open - is one of the important load types. A wind load model is proposed that can be used in the fatigue design

  3. Fracture strength of all-ceramic restorations after fatigue loading

    Science.gov (United States)

    Baladhandayutham, Balasudha

    Fracture strength of monolithic and bilayered LAVA and e. max lower molar crowns after load cycling was measured and compared. The study included three groups (n = 8) from LAVA zirconia and three groups from e. max lithium disilicate to compare influences of different layers, thicknesses and manufacturing techniques. Prefabricated anatomically designed crowns were cemented to dies made from Z 100 composite resin using Rely X Luting Plus resin modified glass ionomer cement. Cemented crowns were stored at 37° C for 24 hours then cyclic loaded to test fatigue properties. The crowns were loaded to 200,000 cycles at 25N at a rate of 40 cycles / minute to simulate oral function. Subsequently, fracture properties for each group were measured using an Instron Universal Testing machine. Microscopic evaluation of the surface of fatigued samples did not reveal micro-cracks at the end of 50,000 cycles but minor wear facets were observed at the site of contact from the steatite ball antagonist. Crowns from LAVA bilayered groups showed step by step fractures while crowns from all other groups fractured as a single event as observed by the high speed camera. Zirconia bilayered crowns showed the highest loads to fracture while lithium disilicate monolithic crowns showed the lowest, within the limitations of the study. The study also showed that monolithic zirconia crowns of 0.6mm thickness resulted in relatively high magnitude for forces at fracture.

  4. In situ SEM thermal fatigue of Al/graphite metal matrix composites

    Science.gov (United States)

    Zong, G. S.; Rabenberg, L.; Marcus, H. L.

    1990-01-01

    Several thermal fatigue-induced failure mechanisms are deduced for unidirectional graphite-reinforced 6061 Al-alloy MMCs subjected to in situ thermal cycling. These thermal cycling conditions are representative of MMC service cycles in aerospace environments, where thermal fatigue is primarily associated with changes in the stress states near the interfaces due to coefficient of thermal expansion mismatch between fiber and matrix. This in situ SEM thermal-cycling study clarified such factors affecting MMCs' thermal fatigue as local fiber content and distribution, void volume, fiber stiffness, thermal excursion magnitude, and number of thermal cycles. MMC microfailure modes in thermal fatigue have been deduced.

  5. A comparison of the fracture resistance of three machinable ceramics after thermal and mechanical fatigue.

    Science.gov (United States)

    Yang, Rui; Arola, Dwayne; Han, Zhihui; Zhang, Xiuyin

    2014-10-01

    Mechanical and thermal fatigue may affect ceramic restorations in the oral environment. The purpose of this study was to determine the influence of thermal and mechanical cycling on the fracture load and fracture patterns of 3 machinable ceramics. Seventy-two human third molar teeth were prepared for bonding ceramic specimens of Sirona CEREC Blocs, IPS e.maxCAD, or inCoris ZI meso blocks. The 24 specimens of each ceramic were divided into 4 groups (n=6), which underwent no preloading (control), thermocycling (5°C-55°C, 2000 cycles), mechanical cycling (10(5) cycles, 100 N), and thermocycling (5°C-55°C, 2000 cycles) plus mechanical cycling (10(5) cycles, 100 N). The specimens were subsequently loaded to failure, and both stereomicroscopy and scanning electron microscopy were used to investigate the fracture patterns. The data were analyzed with 2-way ANOVA and the Fisher exact probability test (α=.05). Mechanical and thermal cycling had a significant influence on the critical load to failure of the 3 ceramics. No significant difference was found between mechanical cycling for 10(5) times and thermocycling for 2000 times within the same ceramic. The specimens of inCoris ZI experienced significantly higher fracture loads for all the groups. The fracture patterns of the 3 machinable ceramics showed that failure mainly occurred at the cement-dentin interface. The effects of combined thermal and mechanical cycling on the fracture load of ceramics were more significant than any individual mode of cyclic fatigue. Overall, the inCoris ZI resisted thermal and mechanical fatigue better than the Sirona CEREC and IPS e.maxCAD. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  6. Characterising Turbulence Intensity for Fatigue Load Analysis of Wind Turbines

    DEFF Research Database (Denmark)

    Hansen, Kurt Schaldemose; Larsen, Gunner Chr.

    2005-01-01

    Turbulence in wind velocity presents a major factor for modern wind turbine design as cost reduction as are sort for the dynamic structures. Therefore this paper contains a parametrisation of the turbulence intensity at given sites, relevant for the calculation of fatigue loading of wind turbines....... The parameterisation is based on wind speed measurements extracted from the “Database on Wind Characteristics” (www.winddata.com). The parameterisation is based on the LogNormal distribution, which has proven to be suitable distribution to describe the turbulence intensity distribution....

  7. Dislocation substructures developed in martensitic steels under thermal fatigue

    Science.gov (United States)

    Alvarez-Armas, I.; Armas, A. F.; Petersen, C.

    1992-09-01

    Thermal fatigue tests were carried out on a martensitic steel, DIN denomination W. Nr. 1.4914, commonly named MANET I. The tests were performed in air by allowing the sample to serve as its own heater and converting any longitudinal thermal deformation of the specimen into elastic or inelastic deformation. The low temperature was held constant and equal to 473 K and variable values, 823, 873, 923, 973 K for the high temperature were selected. The effects of different thermal cycling ranges on the mechanical behavior and the accompanying microstructural changes in the specimen were evaluated. A continous softening preceded by a stability period was observed in all thermal fatigue tests. Higher temperature changes produce an accelerated softening process. The original lath structure evolves to a mixed structure of expanded laths and subgrains or a fully subgrain structure depending on the temperature range.

  8. 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.

  9. Evolution of surface topography in dependence on the grain orientation during surface thermal fatigue of polycrystalline copper

    CERN Document Server

    Aicheler, M; Taborelli, M; Calatroni, S; Neupert, H; Wuensch, W; Sgobba, S

    2011-01-01

    Surface degradation due to cyclic thermal loading plays a major role in the Accelerating Structures (AS) of the future Compact Linear Collider (CLIC) In this article results on surface degradation of thermally cycled polycrystalline copper as a function of the orientation of surface grains are presented Samples with different grain sizes were subjected to thermal fatigue using two different methods and were then characterized using roughness measurements and Orientation Imaging Scanning-Electron-Microscopy (OIM-SEM) Samples fatigued by a pulsed laser show the same trend in the orientation-fatigue damage accumulation as the sample fatigued by pulsed Radio-Frequency-heating (RF) it is clearly shown that 11 1 1] surface grains develop significantly more damage than the surface grains oriented in {[}100] and three reasons for this behaviour are pointed out Based on observations performed near grain boundaries their role in the crack initiation process is discussed The results are in good agreement with previous f...

  10. Hydrogen enhanced thermal fatigue of y-titanium aluminide

    NARCIS (Netherlands)

    Dunfee, William; Gao, Ming; Wei, Robert P.; Wei, W.

    1995-01-01

    A study of hydrogen enhanced thermal fatigue cracking was carried out for a gamma-based Ti-48Al-2Cr alloy by cycling between room temperature and 750 or 900 °C. The results showed that hydrogen can severely attack the gamma alloy, with resulting lifetimes as low as three cycles, while no failures

  11. 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.

  12. Fatigue performance of variable message sign & luminaire support structures : volume I, fatigue related wind loads on highway support structures

    Science.gov (United States)

    1998-04-01

    In Order to determine equivalent static pressures for fatigue loads on cantilevered highway support structures a : cantilevered Variable Message Sign(VMS) located along Interstate westbound at mile marker 48.5 in northern : New Jersey was continuousl...

  13. Fatigue performance of variable message sign & luminaire support structures : volume II, fatigue related wind loads on highway support structures.

    Science.gov (United States)

    1998-05-01

    In Order to determine equivalent static pressures for fatigue loads on cantilevered highway support structures a : cantilevered Variable Message Sign(VMS) located along Interstate westbound at mile marker 48.5 in northern : New Jersey was continuousl...

  14. Fatigue crack threshold relevant to stress ratio, crack wake and loading histories

    International Nuclear Information System (INIS)

    Okazaki, Masakazu; Iwasaki, Akira; Kasahara, Naoto

    2013-01-01

    Fatigue crack propagation behavior was investigated in a low alloy steel which experienced several kind of loading histories. Both the effects of stress ratio, test temperature on the fatigue crack threshold, and the change in the threshold depending on the thermo-mechanical loading histories, were experimentally investigated. It was shown that the thermo-mechanical loading history left its effect along the prior fatigue crack wake resulting in the change of fatigue crack threshold. Some discussions are made on how this type of loading history effect should be treated from engineering point of view. (author)

  15. Monitoring training load to understand fatigue in athletes.

    Science.gov (United States)

    Halson, Shona L

    2014-11-01

    Many athletes, coaches, and support staff are taking an increasingly scientific approach to both designing and monitoring training programs. Appropriate load monitoring can aid in determining whether an athlete is adapting to a training program and in minimizing the risk of developing non-functional overreaching, illness, and/or injury. In order to gain an understanding of the training load and its effect on the athlete, a number of potential markers are available for use. However, very few of these markers have strong scientific evidence supporting their use, and there is yet to be a single, definitive marker described in the literature. Research has investigated a number of external load quantifying and monitoring tools, such as power output measuring devices, time-motion analysis, as well as internal load unit measures, including perception of effort, heart rate, blood lactate, and training impulse. Dissociation between external and internal load units may reveal the state of fatigue of an athlete. Other monitoring tools used by high-performance programs include heart rate recovery, neuromuscular function, biochemical/hormonal/immunological assessments, questionnaires and diaries, psychomotor speed, and sleep quality and quantity. The monitoring approach taken with athletes may depend on whether the athlete is engaging in individual or team sport activity; however, the importance of individualization of load monitoring cannot be over emphasized. Detecting meaningful changes with scientific and statistical approaches can provide confidence and certainty when implementing change. Appropriate monitoring of training load can provide important information to athletes and coaches; however, monitoring systems should be intuitive, provide efficient data analysis and interpretation, and enable efficient reporting of simple, yet scientifically valid, feedback.

  16. Thermal fatigue of austenitic stainless steel: influence of surface conditions through a multi-scale approach

    International Nuclear Information System (INIS)

    Le-Pecheur, Anne

    2008-01-01

    Some cases of cracking of 304L austenitic stainless steel components due to thermal fatigue were encountered in particular on the Residual Heat Removal Circuits (RHR) of the Pressurized Water Reactor (PWR). EDF has initiated a R and D program to understand assess the risks of damage on nuclear plant mixing zones. The INTHERPOL test developed at EDF is designed in order to perform pure thermal fatigue test on tubular specimen under mono-frequency thermal load. These tests are carried out under various loadings, surface finish qualities and welding in order to give an account of these parameters on crack initiation. The main topic of this study is the research of a fatigue criterion using a micro:macro modelling approach. The first part of work deals with material characterization (stainless steel 304L) emphasising the specificities of the surface roughness link with a strong hardening gradient. The first results of the characterization on the surface show a strong work-hardening gradient on a 250 microns layer. This gradient does not evolved after thermal cycling. Micro hardness measurements and TEM observations were intensively used to characterize this gradient. The second part is the macroscopic modelling of INTHERPOL tests in order to determine the components of the stress and strain tensors due to thermal cycling. The third part of work is thus to evaluate the effect of surface roughness and hardening gradient using a calculation on a finer scale. This simulation is based on the variation of dislocation density. A goal for the future is the determination of the fatigue criterion mainly based on polycrystalline modelling. Stocked energy or critical plane being available that allows making a sound choice for the criteria. (author)

  17. 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.

  18. High-temperature thermal fatigue of AISI 316L steel

    International Nuclear Information System (INIS)

    Petersen, C.; Rubiolo, G.H.

    1991-01-01

    A test method for performing uniaxial low-cycle thermal fatigue tests on metals is described. The test facility consists of an ohmic heating system built in a closed loop material testing maschine. The used hollow, hourglass-shaped, tubular specimens are subjected to constant linear heating and cooling rates in a temperature range of a fixed minimum temperature (200deg C) and a variable maximum temperature (550 to 750deg C) in air atmosphere. The specimens are constrained at mean temperature and the test starts tension going towards the minimum temperature. Total mechanical strain amplitudes between 0.4 and 1.4% are evaluated by applying a strain measuring system that allows direct recording of mechanical strain by eliminatingthe thermal component from the measurable net strain. Thermal fatigue life of AISI 316 L steel is found to be shorter than isothermal, strain controlled fatigue life at a temperature equal to the mean temperature of thermal cycling and in some cases even shorter than the maximum temperature of thermal cycling. As scanning electron microscopy of failed specimens shows, crack initiation occurs in most cases on nonmetallic inclusions or impurities and the fracture topology has a typical striation appearance. (orig.)

  19. The effects of loading history on fatigue crack growth threshold

    International Nuclear Information System (INIS)

    Ogawa, Takeshi; Tokaji, Keiro; Ochi, Satoshi; Kobayashi, Hideo.

    1987-01-01

    The effects of loading history on threshold stress intensity range (ΔK th ) were investigated in a low alloy steel SFVQ1A (A508 - 3) and a low carbon steel S10C. A single overload and multiple overloads were chosen as loading history. Crack growth and crack closure following the loading histories were measured at load ratios of 0.05 and 0.70. Threshold values were determined as a fatigue limit of preloaded specimens. The ΔK th values increased with increasing overload stress intensity factor (K h ). For a given K h value, multiple overloads produced much larger increase in ΔK th than a single overload and threshold values expressed by maximum stress intensity factor (K max,th ) were almost constant, independent of stress ratio. The results obtained were discussed in terms of crack closure behaviour, and a method was proposed to evaluate the threshold value based on plasticity-induced crack closure. (author)

  20. 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.

  1. Fatigue in Welded High-Strength Steel Plate Elements under Stochastic Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Martinez, L. Lopez

    1999-01-01

    The present project is a part of an investigation on fatigue in offshore structures in high-strength steel. The fatigue life of plate elements with welded attachments is studied. The material used has a yield stress of ~ 810-840 MPa, and high weldability and toughness properties. Fatigue test...... series with constant amplitude loading and with various types of stochastic loading have been carried through on test specimens in high-strength steel, and - for a comparison - on test specimens in conventional offshore structural steel with a yield stress of ~ 400-410 MPa.A comparison between constant...... amplitude and variable amplitude fatigue test results shows shorter fatigue lives in variable amplitude loading than should be expected from the linear fatigue damage accumulation formula. Furthermore, in general longer fatigue lives were obtained for the test specimens in high-strength steel than those...

  2. A simple approximative procedure for taking into account low cycle fatigue loads

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, G.; Thomsen, K.

    1996-09-01

    In this paper a simple approximative algorithm for taking into account low cycle fatigue loads is presented. Traditionally, the fatigue life consumption of a wind turbine is estimated by considering a number of (independent) load cases and performing a rainflow counting analysis on each of those. These results are then subsequently synthesized into a total load spectrum by performing a weighed sum of the number of individual load case ranges. The fatigue life consumption is thus obtained by applying the Palmgren-Miner rule on the total load spectrum. However, due to the assumption of isolated basic load cases, the above procedure fail to represent the low-frequency contributions related to the transition between those load cases. The procedure to be described in the following aims at taking the fatigue contribution, related to the transitions between the defined load cases, into account in an approximative manner. (au)

  3. Assessment of thermal fatigue crack propagation in safety injection PWR lines

    International Nuclear Information System (INIS)

    Simos, N.; Reich, M.; Costantino, C.J.; Hartzman, M.

    1990-01-01

    Cyclic thermal stratification resulting in alternating thermal stresses in pipe cross sections has been identified as the primary cause of high cycle thermal fatigue failure. A number of piping lines in operating plants around the world, susceptible to thermal stratification, have experienced circumferential cracking as a result of high levels of alternating bending stresses. This paper addresses the mechanisms of crack initiation and crack growth and provides estimates of fatigue cycles to failure for a typical safety injection line with such cyclic load history. Utilizing a 3-D finite element analysis, the temperature profile and the corresponding thermal stress field of a complete thermal cycle in a safety injection line consisting of a horizontal pipe section and an elbow, is obtained. Since the observed cracking occurred in the region of the elbow-to-horizontal pipe weld, the analysis performed assessed (1) the impact of the level of local geometric discontinuities on the initiation of an inside surface flaw is greatest and (2) the number of thermal cycles required to drive a small surface crack through the pipe wall. 12 refs., 14 figs., 2 tabs

  4. Periostin deficiency increases bone damage and impairs injury response to fatigue loading in adult mice.

    Directory of Open Access Journals (Sweden)

    Nicolas Bonnet

    Full Text Available Bone damage removal and callus formation in response to fatigue loading are essential to prevent fractures. Periostin (Postn is a matricellular protein that mediates adaptive response of cortical bone to loading. Whether and how periostin influences damage and the injury response to fatigue remains unknown. We investigated the skeletal response of Postn(-/- and Postn(+/+ mice after fatigue stimulus by axial compression of their tibia. In Postn(+/+ mice, cracks number and surface (CsNb, CsS increased 1h after fatigue, with a decrease in strength compared to non-fatigued tibia. At 15 days, CsNb had started to decline, while CtTV and CtBV increased in fatigued vs non-fatigued tibia, reflecting a woven bone response that was present in 75% of the fatigued bones. Cortical porosity and remodelling also prominently increased in the fatigued tibia of Postn(+/+ mice. At 30 days, paralleling a continuous removal of cortical damage, strength of the fatigued tibia was similar to the non-fatigue tibia. In Postn(-/- mice, cracks were detectable even in the absence of fatigue, while the amount of collagen crosslinks and tissue hardness was decreased compared to Postn(+/+. Fatigue significantly increased CsNb and CsS in Postn(-/-, but was not associated with changes in CtTV and CtBV, as only 16% of the fatigued bones formed some woven bone. Cortical porosity and remodelling did not increase either after fatigue in Postn(-/-, and the level of damage remained high even after 30 days. As a result, strength remained compromised in Postn(-/- mice. Contrary to Postn(+/+, which osteocytic lacunae showed a change in the degree of anisotropy (DA after fatigue, Postn(-/- showed no DA change. Hence periostin appears to influence bone materials properties, damage accumulation and repair, including local modeling/remodeling processes in response to fatigue. These observations suggest that the level of periostin expression could influence the propensity to fatigue fractures.

  5. Fatigue life prediction in composites using progressive damage modelling under block and spectrum loading

    DEFF Research Database (Denmark)

    Passipoularidis, Vaggelis; Philippidis, T.P.; Brøndsted, Povl

    2010-01-01

    series can be simulated. The predictions are validated against fatigue life data both from repeated block tests at a single stress ratio as well as against spectral fatigue using the WISPER, WISPERX and NEW WISPER load sequences on a Glass/Epoxy multidirectional laminate typical of a Wind Turbine Rotor....... In general, FADAS performs well in predicting life under both spectral and block loading fatigue....

  6. Deterministic Processing of Complex Multiaxial Fatigue Load Data on a Tubular Specimen with Hole

    Czech Academy of Sciences Publication Activity Database

    Papuga, J.; Hrubý, Z.; Růžička, M.; Balda, Miroslav; Svoboda, Jaroslav

    2012-01-01

    Roč. 35, č. 6 (2012), s. 523-537 ISSN 8756-758X R&D Projects: GA ČR(CZ) GA101/09/0904 Institutional research plan: CEZ:AV0Z20760514 Keywords : fatigue life prediction * random loading * multiaxial loading * mean stress effects Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.861, year: 2012

  7. The Effects of Load Carriage and Muscle Fatigue on Lower-Extremity Joint Mechanics

    Science.gov (United States)

    Wang, He; Frame, Jeff; Ozimek, Elicia; Leib, Daniel; Dugan, Eric L.

    2013-01-01

    Military personnel are commonly afflicted by lower-extremity overuse injuries. Load carriage and muscular fatigue are major stressors during military basic training. Purpose: To examine effects of load carriage and muscular fatigue on lower-extremity joint mechanics during walking. Method: Eighteen men performed the following tasks: unloaded…

  8. Thermal Cycling on Fatigue Failure of the Plutonium Vitrification Melter

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, Jeffrey; Gorczyca, Jennifer

    2009-02-11

    One method for disposition of excess plutonium is vitrification into cylindrical wasteforms. Due to the hazards of working with plutonium, the vitrification process must be carried out remotely in a shielded environment. Thus, the equipment must be easily maintained. With their simple design, induction melters satisfy this criterion, making them ideal candidates for plutonium vitrification. However, due to repeated heating and cooling cycles and differences in coefficients of thermal expansion of contacting materials fatigue failure of the induction melter is of concern. Due to the cost of the melter, the number of cycles to failure is critical. This paper presents a method for determining the cycles to failure for an induction melter by using the results from thermal and structural analyses as input to a fatigue failure model.

  9. SUSCEPTOBILITY TO THERMAL FATIGUE OF CLOSED DIE HOT FORGING DIES

    Directory of Open Access Journals (Sweden)

    Frederico de Castro Magalhães

    2014-06-01

    Full Text Available Hot forging dies providing high productive performance reduce production costs. The lifetime of the dies is expressed by the number of forgings (production cycle produced before being rejected by the presence of a failure mechanism, associated with unacceptable dimensions and or geometry of the end product or even breakage of the dies. One of the failure mechanisms of hot forging dies is thermal fatigue, caused by cyclic heating and cooling. A subroutine, based on the work of Maim and Norstrom [1], was developed for the DEFORM 2D numerical software, using the finite element method, in order to predict die regions susceptible to thermal fatigue. The use of adequate coefficients for the description of the heat transfer phenomena allowed the validation of the proposed subroutine.

  10. 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...

  11. Fatigue Crack Growth in Bodies with Thermally Sprayed Coating

    Czech Academy of Sciences Publication Activity Database

    Kovářík, O.; Haušild, P.; Medřický, Jan; Tomek, L.; Siegl, J.; Mušálek, Radek; Curry, N.; Björklund, S.

    2016-01-01

    Roč. 25, 1-2 (2016), s. 311-320 ISSN 1059-9630. [ITSC 2015 : International Thermal Spray Conference and Exposition. Long Beach, California, 11.05. 2015 -14.05. 2015 ] R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : Thermal barrier coating * fatigue * crack growth * digital image correlation * digital image correlation Subject RIV: JK - Corrosion ; Surface Treatment of Materials Impact factor: 1.488, year: 2016 http://link.springer.com/article/10.1007%2Fs11666-015-0329-9

  12. Fatigue Crack Growth in Bodies with Thermally Sprayed Coating

    Czech Academy of Sciences Publication Activity Database

    Kovářík, O.; Haušild, P.; Medřický, Jan; Tomek, L.; Siegl, J.; Mušálek, Radek; Curry, N.; Björklund, S.

    2016-01-01

    Roč. 25, 1-2 (2016), s. 311-320 ISSN 1059-9630. [ITSC 2015: International Thermal Spray Conference and Exposition. Long Beach, California, 11.05.2015-14.05.2015] R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : Thermal barrier coating * fatigue * crack growth * digital image correlation * digital image correlation Subject RIV: JK - Corrosion ; Surface Treatment of Materials Impact factor: 1.488, year: 2016 http://link.springer.com/article/10.1007%2Fs11666-015-0329-9

  13. Experimental Study on Fatigue Behaviour of BFRP-Concrete Bond Interfaces under Bending Load

    Directory of Open Access Journals (Sweden)

    Jianhe Xie

    2018-01-01

    Full Text Available Basalt fiber reinforced polymer (BFRP composites are increasingly being used to retrofit concrete structures by external bonding. For such strengthened members, the BFRP-concrete interface plays the crucial role of transferring stresses. This study aims to investigate the fatigue behaviour of the interface under bending load. A series of tests were conducted on BFRP-concrete bonded joint, including static, fatigue, and postfatigue loading. The fatigue failure modes, the development of deflection, the evolution of BFRP strains, and the propagation of interfacial cracks were analysed. In addition, the debonding-induced fatigue life of BFRP-concrete bonded joints was studied. Finally, a new model of fatigue life was proposed by defining the effective fatigue bond stress. The results showed that the fatigue experience has a significant effect on the BFRP strength especially near the root of concrete transverse crack and on the bond performance of the adhesive near the interface crack tip. There are two main fatigue failure modes: BFRP rupture and BFRP debonding. The fatigue damage development of the bond interface has three stages: rapid, stable, and unstable growth. The proposed model for the debonding-induced fatigue life is more conservative for the BFRP-concrete bonded joints under pure shear load than for those under bending load.

  14. Performance of patch repaired composite panels under fatigue loads

    International Nuclear Information System (INIS)

    Darwish, Feras H.; Hamoush, S.; Shivakumar, K.

    2006-01-01

    This paper evaluates the performance of bonded patch-scarf repairs of full scale laminated composite panels under cyclic load conditions. Nondestructive testing to characterize the quality of repairs and destructive testing to evaluate the performance of repaired panels were used in this study. Carbon/Epoxy prepreg material used was used to lay up six-ply (12 in. x 27 in. /305x686mm) (-60/60/0) s quasi-isotropic laminates. 7-ply scarf repair with a gradient of 0.5 inch (12.7mm) per layer was used to perform the repair of a damaged zone. The patch consisted of 7.5 inches (190mm) diameter adhesive film, 1 inch (25.4mm) diameter filler ply at 90fiber orientation, and six plies (2-7 inches (51-178mm) diameter) to match the lay-up of the parent material. The study was extended to include defective repairs. The defect was engineered by inserting a 1 inch (25.4 mm) circular Teflon flaw between the fifth and sixth layers of the patch. A total of 28 panels were prepared and divided into five categories: (1) three pristine panels (undamaged parental materials); (2) three damaged panels (1-inch-centered-hole); (3) two repaired panels with wrong fiber orientation; (4) nine good repaired panels, and (5) eleven defective repair panels (1 inch flaw). A nondestructive evaluation to check the conditions of the repairs was performed on most of the tested panels that include the pulse-echo C-scan and pseudo through transmission air coupled and water coupled C-scan. Based on the results of the experimental evaluation of this study, good repair restored 95% of the tensile strength while defective repair restored 90% of the tensile strength of the pristine panels. Under fatigue loading, panels repaired with a 1 inch delamination flaw within the patch layers showed a major reduction in fatigue life compared to the good repair panels under similar loading conditions. (author)

  15. Effects of loading sequence for notched specimens under high-low two-step fatigue loading

    Science.gov (United States)

    Crews, J. H., Jr.

    1971-01-01

    The effects of loading sequence on crack-initiation period were investigated for notched aluminum-alloy specimens under high-low two-step loading with special emphasis on local cyclic stresses and strains at the notch root. Local stress and strain were determined by a procedure based on an equation proposed by Neuber which relates elastoplastic stress and strain at a notch. Local stress and strain were also measured experimentally to verify the Neuber equation. The effects of initial high load on the crack-initiation periods were demonstrated with notched specimens and were simulated in unnotched specimens fatigue tested with local stress sequences. An analysis of the results indicated that sequence effects were not caused solely by local residual stresses, as is usually assumed; the existence of a damaging effect, resulting from the high local strain cycles, was demonstrated. The sequence effects observed with notched specimens were interpreted as the combined result of residual stresses and high local strain cycles.

  16. A model of rotationally-sampled wind turbulence for predicting fatigue loads in wind turbines

    Science.gov (United States)

    Spera, David A.

    1995-01-01

    Empirical equations are presented with which to model rotationally-sampled (R-S) turbulence for input to structural-dynamic computer codes and the calculation of wind turbine fatigue loads. These equations are derived from R-S turbulence data which were measured at the vertical-plane array in Clayton, New Mexico. For validation, the equations are applied to the calculation of cyclic flapwise blade loads for the NASA/DOE Mod-2 2.5-MW experimental HAWT's (horizontal-axis wind turbines), and the results compared to measured cyclic loads. Good correlation is achieved, indicating that the R-S turbulence model developed in this study contains the characteristics of the wind which produce many of the fatigue loads sustained by wind turbines. Empirical factors are included which permit the prediction of load levels at specified percentiles of occurrence, which is required for the generation of fatigue load spectra and the prediction of the fatigue lifetime of structures.

  17. Load assumption for fatigue design of structures and components counting methods, safety aspects, practical application

    CERN Document Server

    Köhler, Michael; Pötter, Kurt; Zenner, Harald

    2017-01-01

    Understanding the fatigue behaviour of structural components under variable load amplitude is an essential prerequisite for safe and reliable light-weight design. For designing and dimensioning, the expected stress (load) is compared with the capacity to withstand loads (fatigue strength). In this process, the safety necessary for each particular application must be ensured. A prerequisite for ensuring the required fatigue strength is a reliable load assumption. The authors describe the transformation of the stress- and load-time functions which have been measured under operational conditions to spectra or matrices with the application of counting methods. The aspects which must be considered for ensuring a reliable load assumption for designing and dimensioning are discussed in detail. Furthermore, the theoretical background for estimating the fatigue life of structural components is explained, and the procedures are discussed for numerous applications in practice. One of the prime intentions of the authors ...

  18. 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.)

  19. 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

  20. 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.

  1. Time and frequency domain models for multiaxial fatigue life estimation under random loading

    Directory of Open Access Journals (Sweden)

    Andrea Carpinteri

    2015-07-01

    Full Text Available Engineering structures and components are often subjected to random fatigue loading produced, for example, by wind turbulences, marine waves and vibrations. The methods available in the literature for fatigue assessment under random loading are formulated in time domain or, alternatively, in frequency domain. The former methods require the knowledge of the loading time history, and a large number of experimental tests/numerical simulations is needed to obtain statistically reliable results. The latter methods are generally more advantageous with respect to the time domain ones, allowing a rapid fatigue damage evaluation. In the present paper, a multiaxial criterion formulated in the frequency-domain is presented to estimate the fatigue lives of smooth metallic structures subjected to combined bending and torsion random loading. A comparison in terms of fatigue life prediction by employing a time domain methods, previously proposed by the authors, is also performed.

  2. Damage identification of RC bridge decks under fatigue loading

    Directory of Open Access Journals (Sweden)

    Zanuy, C.

    2014-12-01

    Full Text Available The complex nature of structural phenomena still requires the comparison between numerical models and the real structural performance. Accordingly, many civil structures are monitored to detect structural damage and provide updated data for numerical models. Monitoring usually relies on the change of dynamic properties (experimental modal analysis. Regarding concrete structures, existing works have typically focused on the progressive decrease of natural frequencies under gradually increasing loads. In this paper, high-cycle fatigue effects are analyzed. An experimental campaign on specimens reproducing the top slab of concrete girders has been carried out, including fatigue tests and a reference static test. Impact-excitation tests were done at different stages to extract dynamic properties. Output-only models (only based on the structural response to an external excitation that is not measured were used as identification techniques. The evolution of dynamic properties was correlated with damage development, with emphasis on the fatigue process stages: crack formation, cyclic reduction of tension-stiffening and brittle fracture of the reinforcement.La naturaleza compleja de muchos fenómenos estructurales requiere que los modelos numéricos necesiten ser verificados con el comportamiento estructural real. Por ello, muchas estructuras son monitorizadas, tanto para detectar posibles daños estructurales como para proporcionar datos a incluir en los modelos. A menudo, la monitorización se basa en el cambio de las propiedades dinámicas mediante técnicas de análisis modal experimental. Con respecto al hormigón estructural, la mayoría de los trabajos existentes se ha centrado en el cambio de las frecuencias propias con cargas monótonamente crecientes. En este artículo se analizan los efectos de la fatiga. Se ha llevado a cabo una campaña experimental sobre piezas que reproducen la losa superior de tableros de puentes, realizándose ensayos

  3. Experimental Investigation on Fatigue Behavior of Epoxy Resin under Load and Displacement Controls

    Directory of Open Access Journals (Sweden)

    Mahmood Mehrdad Shokrieh

    2014-12-01

    Full Text Available The mechanical properties of epoxy resin including tensile and flexural modulus, tensile and flexural strength for static conditions are currently studied. The frequency effect as significant parameter at room temperature is investigated and fatigue behavior of the epoxy resin in tension-tension loading conditions for different frequencies of 2, 3 and 5 Hz are obtained. The epoxy resin has been taken under flexural bending fatigue loading and fatigue life is investigated. The results of the experiments show the values of 2.5 and 3 GPa of tensile and flexural modules and 59.98 and 110.02 MPa of tensile and flexural strengths for the resin, respectively. To achieve a linear load-deflection relationship in a three-point bending experiment, a maximum allowable deflection of 5 mm is acquired. The relationship between the frequency and fatigue life shows higher frequency results in lower fatigue life. Loading with frequency of 2 Hz has provided 5.8 times more fatigue life compared with 5 Hz loading. For a tension-tension fatigue loading condition, the variation of tensile module of epoxy resin shows no noticeable change during the fatigue loading condition. This module decreases significantly only in the primary and failure cycles close to the fracture point. In further experiments, fatigue behavior of epoxy resin was tested under flexural bending fatigue loadings with controlled deflection at room temperature. Maximum applied normalized stresses versus the number of cycles to failure curve are illustrated and it can be performed in order to predict the number of cycles to failure for the resin in arbitrary applied normal stresses as well.

  4. Evolution of thermal fatigue management of piping in US LWRs

    International Nuclear Information System (INIS)

    McDewitt, M.; Wolfe, K.; McGill, R.

    2015-01-01

    Fatigue usage caused by cyclic changes of thermally stratified reactor coolant in Light Water Reactor (LWR) pressure boundary piping was not an original consideration in US Nuclear Power Plant (NPP) designs. During the mid 1980's, several events involving cracking and leakage due to thermal cycling occurred in reactor coolant system branch piping at both US and International NPPs. In 1988, the US Nuclear Regulatory Commission (US NRC) issued Bulletin 88-08 to alert LWR licensees of the potential for piping failures due to stratified thermal cycling. In response to these events, the US nuclear industry developed initiatives to identify susceptible components and established measures to monitor and prevent future failures. These initiatives have been effective in preventing leakage events, but have also identified fewer defects than expected based on screening model predictions. Improved analytical techniques are being investigated to maintain program effectiveness while minimizing unnecessary non-destructive examinations. This paper discusses the evolution of the US thermal fatigue initiatives, and analytical concepts being evaluated to improve program efficiency. (authors)

  5. Thermally induced high frequency random amplitude fatigue damage at sharp notches

    International Nuclear Information System (INIS)

    Lewis, M.W.J.

    1992-01-01

    Experiments have been performed using the SUPERSOMITE facility to investigate the initiation and growth of fatigue cracks at the tips of sharp surface notches subjected to random thermally-induced stress. The experimental situation is complex involving plasticity, random amplitude loading and heat transfer medium/surface coupling. Crack initiation and growth prediction have been considered using the Creager and Neuber methods to compute the strain ranges in the vicinity of the notch root. Good agreement has been obtained between the experimental results and theoretical predictions. The paper reports the results of the analysis of the notch behavior

  6. Probabilistic framework for the assessment of structures submitted to thermal fatigue

    International Nuclear Information System (INIS)

    Sudret, B.

    2005-01-01

    A probabilistic framework is set up to assess the fatigue life of components of nuclear power plants. It intends to incorporate all kinds of uncertainties such as those appearing in the specimen fatigue strength (number-of-cycles-to-failure of specimens), design margin factors (taking into account the size, surface finish and environmental effects), mechanical model (precisely, the uncertainty on the model input parameters) and the thermal loading. A comprehensive example involving a mechanical model of a pipe submitted to a deterministic inner temperature is analyzed. The use of the First Order Reliability Method (FORM) allows to compute the probability of failure as a function of the foreseen life time and to rank the input random variables according to their importance in response sensitivity. (author)

  7. Out of phase thermal mechanical fatigue investigation of a directionally solidified superalloy DZ125

    Directory of Open Access Journals (Sweden)

    Hu Xiaoan

    2016-02-01

    Full Text Available Out of phase (OP thermal mechanical fatigue (TMF behavior of a directionally solidified (DS superalloy DZ125 was experimentally and numerically studied. Two different temperature conditions, which are 500–1000 °C and 400–900 °C, were considered in the present research. Stress and strain responses as well as fatigue life results were presented and discussed. Scanning electron microscope (SEM and metallographic analysis were used to study the damage mechanism. An oxidation assisted crack initiation and propagation phenomenon were found to explain the shorted life under TMF cycles. In order to characterize the stress and strain deformations under TMF loadings, a modified Chaboche’s constitutive model was applied. Additionally, the TMF life of the material was modeled and predicted by Neu–Sehitoglu damage law with high accuracy.

  8. Thermal fatigue tests with actively cooled divertor mock-ups for ITER

    International Nuclear Information System (INIS)

    Roedig, M.; Duwe, R.; Linke, J.; Schuster, A.; Wiechers, B.; Ibbott, C.; Jacobson, D.; Le Marois, G.; Lind, A.; Lorenzetto, P.; Vieider, G.; Peacock, A.; Ploechl, L.; Severi, Y.; Visca, E.

    1998-01-01

    Mock-ups for high heat flux components with beryllium and CFC armour materials have been tested by means of the electron beam facility JUDITH. The experiments concerned screening tests to evaluate heat removal efficiency and thermal fatigue tests. CFC monoblocks attached to DS-Cu (Glidcop Al25) and CuCrZr tubes by active metal casting and Ti brazing showed the best thermal fatigue behaviour. They survived more than 1000 cycles at heat loads up to 25 MW m -2 without any indication of failure. Operational limits are given only by the surface temperature on the CFC tiles. Most of the beryllium mock-ups were of the flat tile type. Joining techniques were brazing, hot isostatic pressing (HIP) and diffusion bonding. HIPed and diffusion bonded Be/Cu modules have not yet reached the standards for application in high heat flux components. The limit of this production method is reached for heat loads of approximately 5 MW m -2 . Brazing with and without silver seems to be a more robust solution. A flat tile mock-up with CuMnSnCe braze was loaded at 5.4 MW m -2 for 1000 cycles without damage The first test with a beryllium monoblock joined to a CuCrZr tube by means of Incusil brazing shows promising results; it survived 1000 cycles at 4.5 MW m -2 without failure. (orig.)

  9. A method for calculation of finite fatigue life under multiaxial loading in high-cycle domain

    Directory of Open Access Journals (Sweden)

    M. Malnati

    2014-04-01

    Full Text Available A method for fatigue life assessment in high-cycle domain under multiaxial loading is presented in this paper. This approach allows fatigue assessment under any kind of load history, without limitations. The methodology lies on the construction - at a macroscopic level - of an “indicator” in the form of a set of cycles, representing plasticity that can arise at mesoscopic level throughout fatigue process. During the advancement of the loading history new cycles are created and a continuous evaluation of the damage is made.

  10. Lifetime evaluation for thermal fatigue: application at the first wall of a tokamak fusion reactor

    International Nuclear Information System (INIS)

    Merola, M.; Biggio, M.

    1989-01-01

    Thermal fatigue seems to be the most lifetime limiting phenomenon for the first wall of the next generation Tokamak fusion reactors. This work deals with the problem of the thermal fatigue in relation to the lifetime prediction of the fusion reactor first wall. The aim is to compare different lifetime methodologies among them and with experimental results. To fulfil this purpose, it has been necessary to develop a new numerical methodology, called reduced-3D, especially suitable for thermal fatigue problems

  11. Water quench thermal fatigue analysis of grade P22 and grade P91 steels

    Science.gov (United States)

    Appling, William C.

    Power plants and other facilities that utilize high temperature steam flow have been using corrosion-resistant steels with high creep-rupture strengths in their piping systems. Fatigue crack failures have occurred in these piping systems, potentially from the sudden temperature changes from the internal water spray system used to control steam temperature. A new test to investigate the thermal quench fatigue response of metals was developed to aid the study of these failures in P22 and P91 steel pipes. The focus of this thesis was to develop the test and begin development of the quench fatigue response of P22 and P91. Testing involved evaluating the pre and post-test hardness measurements of the quench fatigue specimens and correlating these results with the results of the quench fatigue runs. Specimens were evaluated in quench fatigue for two test conditions: a maximum stress condition and a stress loading similar to what has been measured in existing piping systems. The maximum stress state was used to induce failure in the specimens within a reasonable amount of time and to evaluate any change in material microstructure. The second test condition had a temperature drop of approximately 200 °C and more closely simulated general operating conditions for the piping systems in question. This test condition also included a preload on the specimen in the axial direction to simulate the stress induced from the internal pressure of the piping systems. In addition to experimental analysis, a finite element model was developed and tested to verify the initial material deformation that occurred from quench spraying.

  12. Residual fatigue lifetime estimation of railway axles for various loading spectra

    Czech Academy of Sciences Publication Activity Database

    Pokorný, Pavel; Hutař, Pavel; Náhlík, Luboš

    2016-01-01

    Roč. 82, APR (2016), s. 25-32 ISSN 0167-8442 R&D Projects: GA MŠk(CZ) EE2.3.20.0214; GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : Fatigue failure * Residual fatigue lifetime * Crack propagation * Railway axle * Load spectrum Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.659, year: 2016

  13. Air-coupled guided waves combined with thermography for monitoring fatigue in biaxially loaded composite tubes

    OpenAIRE

    2011-01-01

    Abstract Non-destructive methodologies for remote monitoring of fatigue induced by mechanical load in fibre reinforced plastics are presented. Hollow cylinders (glass fibre winding) were stepwise biaxially fatigued and measured in single-sided access configurations. Based on conversion of air-coupled ultrasound to guided waves, it is shown that accumulated fatigue damage is accompanied by decrease in phase velocity and increase in attenuation. The change in wave velocity caused by ...

  14. Behaviour of Ti-doped CFCs under thermal fatigue tests

    Energy Technology Data Exchange (ETDEWEB)

    Centeno, A. [Instituto Nacional del Carbon (CSIC), Apdo. 73, 33080 Oviedo (Spain); Pintsuk, G.; Linke, J. [Forschungszentrum Juelich GmbH, EURATOM Association, 52425 Juelich (Germany); Gualco, C. [Ansaldo Energia, I-16152 Genoa (Italy); Blanco, C., E-mail: clara@incar.csic.es [Instituto Nacional del Carbon (CSIC), Apdo. 73, 33080 Oviedo (Spain); Santamaria, R.; Granda, M.; Menendez, R. [Instituto Nacional del Carbon (CSIC), Apdo. 73, 33080 Oviedo (Spain)

    2011-01-15

    In spite of the remarkable progress in the design of in-vessel components for the divertor of the first International Thermonuclear Experimental Reactor (ITER), a great effort is still put into the development of manufacturing technologies for carbon armour with improved properties. Newly developed 3D titanium-doped carbon fibre reinforced composites and their corresponding undoped counterparts were brazed to a CuCrZr heat sink to produce actively cooled flat tile mock-ups. By exposing the mock-ups to thermal fatigue tests in an electron beam test facility, the material behaviour and the brazing between the individual constituents in the mock-up was qualified. The mock-ups with titanium-doped CFCs exhibited a significantly improved thermal fatigue resistance compared with those undoped materials. The comparison of these mock-ups with those produced using pristine NB31, one of the reference materials as plasma facing material for ITER, showed almost identical results, indicating the high potential of Ti-doped CFCs due to their improved thermal shock resistance.

  15. Simple Theory of Thermal Fatigue Caused by RF Pulse Heating

    CERN Document Server

    Kuzikov, S

    2004-01-01

    The projects of electron-positron linear colliders imply that accelerating structures and other RF components will undergo action of extremely high RF fields. Except for breakdown threat there is an effect of the damage due to multi-pulse mechanical stress caused by Ohmic heating of the skin layer. A new theory of the thermal fatigue is considered. The theory is based on consideration of the quasi-elastic interaction between neighbor grains of metal due to the expansion of the thermal skin-layer. The developed theory predicts a total number of the RF pulses needed for surface degradation in dependence on temperature rise, pulse duration, and average temperature. The unknown coefficients in the final formula were found, using experimental data obtained at 11.4 GHz for the copper. In order to study the thermal fatigue at higher frequencies and to compare experimental and theoretical results, the experimental investigation of degradation of the copper cavity exposed to 30 GHz radiation is carried out now, basing...

  16. Effect of vibration loading on the fatigue life of part-through notched pipe

    International Nuclear Information System (INIS)

    Mittal, Rahul; Singh, P.K.; Pukazhendi, D.M.; Bhasin, V.; Vaze, K.K.; Ghosh, A.K.

    2011-01-01

    A systematic experimental and analytical study has been carried out to investigate the effect of vibration loading on the fatigue life of the piping components. Three Point bend (TPB) specimens machined from the actual pipe have been used for the evaluation of Paris constants by carrying out the experiments under vibration + cyclic and cyclic loading as per the ASTM Standard E647. These constants have been used for the prediction of the fatigue life of the pipe having part-through notch of a/t = 0.25 and aspect ratio (2c/a) of 10. Predicted results have shown the reduction in fatigue life of the notched pipe subjected to vibration + cyclic loading by 50% compared to that of cyclic loading. Predicted results have been validated by carrying out the full-scale pipe (with part-through notch) tests. Notched pipes were subjected to loading conditions such that the initial stress-intensity factor remains same as that of TPB specimen. Experimental results of the full-scale pipe tests under vibration + cyclic loading has shown the reduction in fatigue life by 70% compared to that of cyclic loading. Fractographic examination of the fracture surface of the tested specimens subjected to vibration + cyclic loading have shown higher presence of brittle phases such as martensite (in the form of isolated planar facets) and secondary micro cracks. This could be the reason for the reduction of fatigue life in pipe subjected to vibration + cyclic loading. - Highlights: → Vibration loading affects fatigue crack growth rate. → Crack initiation life depends on crack tip radius. → Crack initiation life depends on the characteristic distance. → Characteristic distance depends on the loading conditions. → Vibration + cyclic load gives lower fatigue life.

  17. Including load sequence effects in the fatigue damage estimation of an offshore wind turbine substructure

    NARCIS (Netherlands)

    Dragt, R.C.; Maljaars, J.; Tuitman, J.T.; Salman, Y.; Otheguy, M.E.

    2016-01-01

    Retardation is a load sequence effect, which causes a reduced fatigue crack growth rate after an overload is encountered. Retardation can be cancelled when the overload is followed by an underload. The net effect is beneficial to the fatigue lifetime of Offshore Wind Turbines (OWTs). To be able to

  18. Discerning the Fatigue Crack Growth Behavior of API X65 Steels Under Sequence Loading

    Directory of Open Access Journals (Sweden)

    N. I. I. Mansor

    Full Text Available Abstract This paper presents the effect of sequence loading on fatigue crack growth of API X65 steel tested in room temperature. Most of pipeline steels are subjected to wide spectrum of loading during the length of service. Influence of load history effect can cause a trickier assessment to the fatigue behaviour. The objective of this study is to determine the fatigue crack growth behaviour under sequence loading. The material used in this study is X65 steel grade, broadly used in transporting the oil and gas. The constant amplitude loading under mode-I loading and stress ratio of 0.1 and 0.7 are investigate. The effects of sequence load are presents by the two-level block loading. The retardation effect is more intense for block sequence loading. At least about 9.7x104 delayed numbers of cycles was observed which is two times longer compared to constant amplitude loading. The load sequence was suggested affected by retardation consequently delayed the crack growth. It was further observed an increase of overload load ratio consequently resulted a crack grows faster about 18%. It was concluded a lengthy in crack growth was associated with the delay cycles suggesting that the fatigue life depends mainly on size of delay zone and compressive residual stress near the crack tip.

  19. Role of bonding defects in a self-reinforced polypropylene (PURE under fatigue loading

    Directory of Open Access Journals (Sweden)

    Skotarek Christoph

    2014-06-01

    The paper deals with the fatigue behavior of this type of material and the role of the bonding imperfections on the damage accumulation process. For this purpose local deformation fields using DIC determined after quasi- static loading, step-wise increased loading and cyclic loading are compared with each other. These findings are related to the damage pattern observed after final fracture.

  20. The Effects of Fatigue, Load Carriage, and Physical Activity History on Musculoskeletal Injury Mechanisms

    Science.gov (United States)

    2013-09-01

    of load carriage and muscle fatigue. During walking, the knee joint experiences an external adduction moment [4]. Large varus knee loading...leads to cartilage degeneration and medial knee osteoarthritis (OA) [5,6,7]. Thus, the long- term effect of repetitive high varus knee loading could...lead to medial knee OA; in the short term, walking with large varus knee loading could result in knee pain. Load carriage increases vertical

  1. Mean load effect on fatigue of welded joints using structural stress and fracture mechanics approach

    International Nuclear Information System (INIS)

    Kim, Jong Sung; Kim, Cheol; Jin, Tae Eun; Dong, P.

    2006-01-01

    In order to ensure the structural integrity of nuclear welded structures during design life, the fatigue life has to be evaluated by fatigue analysis procedures presented in technical codes such as ASME B and PV Code Section III. However, existing fatigue analysis procedures do not explicitly consider the presence of welded joints. A new fatigue analysis procedure based on a structural stress/fracture mechanics approach has been recently developed in order to reduce conservatism by erasing uncertainty in the analysis procedure. A recent review of fatigue crack growth data under various mean loading conditions using the structural stress/fracture mechanics approach, does not consider the mean loading effect, revealed some significant discrepancies in fatigue crack growth curves according to the mean loading conditions. In this paper, we propose the use of the stress intensity factor range ΔK characterized with loading ratio R effects in terms of the structural stress. We demonstrate the effectiveness in characterizing fatigue crack growth and S-N behavior using the well-known data. It was identified that the S-N data under high mean loading could be consolidated in a master S-N curve for welded joints

  2. DYNAMIC STRAIN MAPPING AND REAL-TIME DAMAGE STATE ESTIMATION UNDER BIAXIAL RANDOM FATIGUE LOADING

    Data.gov (United States)

    National Aeronautics and Space Administration — DYNAMIC STRAIN MAPPING AND REAL-TIME DAMAGE STATE ESTIMATION UNDER BIAXIAL RANDOM FATIGUE LOADING SUBHASISH MOHANTY*, ADITI CHATTOPADHYAY, JOHN N. RAJADAS, AND CLYDE...

  3. 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

  4. Numerical analysis of two experiments related to thermal fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Bieder, Ulrich; Errante, Paolo [DEN-STMF, Commissariat a l' Energie Atomique et aux Energies Alternatives, Universite Paris-Saclay, Gif-sur-Yvette (France)

    2017-06-15

    Jets in cross flow are of fundamental industrial importance and play an important role in validating turbulence models. Two jet configurations related to thermal fatigue phenomena are investigated: • T-junction of circular tubes where a heated jet discharges into a cold main flow and • Rectangular jet marked by a scalar discharging into a main flow in a rectangular channel. The T-junction configuration is a classical test case for thermal fatigue phenomena. The Vattenfall T-junction experiment was already subject of an OECD/NEA benchmark. A LES modelling and calculation strategy is developed and validated on this data. The rectangular-jet configuration is important for basic physical understanding and modelling and has been analyzed experimentally at CEA. The experimental work was focused on turbulent mixing between a slightly heated rectangular jet which is injected perpendicularly into the cold main flow of a rectangular channel. These experiments are analyzed for the first time with LES. The overall results show a good agreement between the experimental data and the CFD calculation. Mean values of velocity and temperature are well captured by both RANS calculation and LES. The range of critical frequencies and their amplitudes, however, are only captured by LES.

  5. The multiaxial fatigue response of cylindrical geometry under proportional loading subject to fluctuating tractions

    Science.gov (United States)

    Martinez, Rudy D.

    A multiaxial fatigue model is proposed, as it would apply to cylindrical geometry in the form of industrial sized pressure vessels. The main focus of the multiaxial fatigue model will be based on using energy methods with the loading states confined to fluctuating tractions under proportional loading. The proposed fatigue model is an effort to support and enhance existing fatigue life predicting methods for pressure vessel design, beyond the ASME Boiler and Pressure Vessel codes, ASME Section VIII Division 2 and 3, which is currently used in industrial engineering practice for pressure vessel design. Both uniaxial and biaxial low alloy pearlittic-ferritic steel cylindrical cyclic test data are utilized to substantiate the proposed fatigue model. Approximate material hardening and softening aspects from applied load cycling states and the Bauschinger effect are accounted for by adjusting strain control generated hysteresis loops and the cyclic stress strain curve. The proposed fatigue energy model and the current ASME fatigue model are then compared with regards to the accuracy of predicting fatigue life cycle consistencies.

  6. Reliability Analysis for Adhesive Bonded Composite Stepped Lap Joints Loaded in Fatigue

    DEFF Research Database (Denmark)

    Kimiaeifar, Amin; Sørensen, John Dalsgaard; Lund, Erik

    2012-01-01

    This paper describes a probabilistic approach to calculate the reliability of adhesive bonded composite stepped lap joints loaded in fatigue using three- dimensional finite element analysis (FEA). A method for progressive damage modelling is used to assess fatigue damage accumulation and residual...... by the wind turbine standard IEC 61400-1. Finally, an approach for the assessment of the reliability of adhesive bonded composite stepped lap joints loaded in fatigue is presented. The introduced methodology can be applied in the same way to calculate the reliability level of wind turbine blade components...

  7. Fretting Fatigue Behaviour of Pin-Loaded Thermoset Carbon-Fibre-Reinforced Polymer (CFRP Straps

    Directory of Open Access Journals (Sweden)

    Fabio Baschnagel

    2016-04-01

    Full Text Available This paper focuses on the fretting fatigue behaviour of pin-loaded carbon-fibre-reinforced polymer (CFRP straps studied as models for rigging systems in sailing yachts, for suspenders of arch bridges and for pendent cables in cranes. Eight straps were subjected to an ultimate tensile strength test. In total, 26 straps were subjected to a fretting fatigue test, of which ten did not fail. An S–N curve was generated for a load ratio R of 0.1 and a frequency f of 10 Hz, showing a fatigue limit stress of the straps around the matrix fatigue limit, corresponding to 46% of the straps’ ultimate tensile strength (σUTS. The fatigue limit was defined as 3 million load cycles (N = 3 × 106, but tests were even conducted up to N = 11.09 × 106. Catastrophic failure of the straps was initiated in their vertex areas. Investigations on the residual strength and stiffness properties of straps tested around the fatigue limit stress (for N ≥ 1 × 106 showed little influence of the fatigue loading on these properties. Quasi-static finite element analyses (FEA were conducted. The results obtained from the FEA are in good agreement with the experiments and demonstrate a fibre parallel stress concentration in the vertex area of factor 1.3, under the realistic assumption of a coefficient of friction (cof between pin and strap of 0.5.

  8. How Thermal Fatigue Cycles Change the Rheological Behavior of Polymer Modified Bitumen?

    NARCIS (Netherlands)

    Glaoui, B.; Merbouh, M.; Van de Ven, M.F.C.; Chailleux, E.; Youcefi, A.

    2013-01-01

    The paper deals with the problem of thermal fatigue cycles phenomenon, which affects the performance of flexible pavement. The purpose of the paper is to extent the knowledge on the rheology of polymer modified bitumen which was affected by cycles of thermal fatigue. The aim of this research is to

  9. Investigation of thermal fatigue of chromium-molybdenum steels, used for calcining and agglomeration constructions

    International Nuclear Information System (INIS)

    Sinyavskij, D.P.; Gorkalo, A.P.

    1979-01-01

    The technique for investigating thermal fatigue of materials is described. The data on sample stress deformed state and current temperature values are taken from the local volume of the material studied. Results of investigating thermal fatigue of the 15KhMl and 20KhMl steels are presented

  10. Fatigue assessment of laserbeam-welded aluminium joints under multiaxial loading

    Energy Technology Data Exchange (ETDEWEB)

    Zemke, M.; Sonsino, C.M.; Kaufmann, H. [Fraunhofer Institute for Structural Durability and System Reliability LBF, Darmstadt (Germany); Wiebesiek, J.

    2011-10-15

    This paper presents the results and evaluation of the multiaxial fatigue behaviour of laserbeam-welded overlapped tubular joints made from the artificially hardened aluminium alloy AlSi1MgMn T6 (EN AW 6082 T6) under multiaxial loadings with constant and variable amplitudes. Several fatigue test series under pure axial and pure torsional loadings as well as combined axial and torsional proportional and non-proportional loadings have been carried out in the range of 2.10{sup 4} to 2.10{sup 7}cycles. The assessment of the investigated thin-walled joints is based on a local notch stress concept. In this concept the fatigue critical area of the weld root is substituted by a fictitious notch radius r{sub ref}= 0.05 mm. The equivalent stresses in the notch, considering especially the fatigue life reducing influence of non-proportional loading in comparison to proportional loading, were calculated by a recently developed hypothesis, which is called the Stress Space Curve Hypothesis (SSCH). This hypothesis is based on the time evolution of the stress state during one load cycle. In addition, the fatigue strength evaluation of multiaxial spectrum loading was carried out using a modified Gough-Pollard algorithm. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Performance Deterioration of Heavy-Haul Railway Bridges under Fatigue Loading Monitored by a Multisensor System

    Directory of Open Access Journals (Sweden)

    Zhiwu Yu

    2018-01-01

    Full Text Available Heavy-haul railway bridges play an increasingly essential role in the transportation in China due to the increasing transport volume. The performance deterioration of the scale models of a typical heavy-haul railway bridge under fatigue loading is monitored in this work, based on a multisensor system including the fiber-reinforced polymer optical fiber Bragg grating and electrical resistance strain gauges, linear variable displacement transducer, and accelerometer. Specifically, by monitoring/observing on the failure mode, fatigue life, load-midspan deflection response, material strain development, and so forth, this work develops an S-N model by comparing the relationship between fatigue life and rebar stress range with that between fatigue life and load level and proposes a damage evolution model considering the coupling of the stiffness degradation and inelastic deformation of specimens. It is found that the fatigue life of specimens is determined by the fatigue life of the rebar at the bottom and it may be lower than 2.0 million cycles with a 30-ton axle weight when environmental factors are taken into account. The predictions of the models agree well with experimental results. Therefore, this work furthers the understanding of the fatigue performance deterioration of the bridges by using a multisensor system.

  12. Positron lifetimes and microhardness in thermal fatigued 4Cr5MoSiV steel

    International Nuclear Information System (INIS)

    Tang, C.Q.; Xia, Z.C.; Li, X.Z.; Yao, B.T.

    2000-01-01

    Positron lifetimes and microhardness have been measured as a function of the thermal fatigue cycle number (N) in 4Cr5MoSiV steel. It is found that with increasing N: (a) the positron lifetime parameters τ 1 , τ 2 , I 1 , I 2 and τ and the microhardness parameter MH all exhibit quasi-periodic up-and-down variation; (b) these parameters have the same period of variation; and (c) the period of up-and-down variation becomes gradually longer. The variation of MH reveals that fatigue hardening and fatigue softening occur alternately in the process of thermal fatigue. The variations of positron lifetime parameters reveal variations of defects in the fatigued materials. These variations are attributed to microdeformation and dynamic recovery dominating alternately in the process of thermal fatigue. Copyright (2000) CSIRO Australia

  13. Experimental simulation of a martensitic stainless steel coating subjected to thermal fatigue

    International Nuclear Information System (INIS)

    Revel, P.; Laboratoire Systemes et Machines de Haute Precision; Necib, K.; Beranger, G.

    1998-01-01

    The purpose of this work was the experimental simulation of the thermal fatigue of mechanical components such as continuous casting rolls. In order to protect the roll against surface degradation due to thermal fatigue, a stainless steel coating was deposited. Initially a temperature map was constructed from experimental measurements. The coating microstructure was then characterized in its initial state and after a few thermal fatigue cycles. Isothermal mechanical tests were performed on the coating and on the base material in the temperature range 20-700 deg C. Residual stresses were shown to decrease rapidly with an increased number of thermal cycles. Decreases in hardness were also correlated with lower yield strengths. (authors)

  14. Relaxation of Shot-Peened Residual Stresses Under Creep Loading (Preprint)

    National Research Council Canada - National Science Library

    Buchanan, Dennis J; John, Reji; Brockman, Robert A

    2008-01-01

    .... Compressive residual stresses retard initiation and growth of fatigue cracks. During the component loading history, loading, or during elevated temperature static loading, such as thermal exposure and creep...

  15. Thermal fatigue behavior of US and Russian grades of beryllium

    International Nuclear Information System (INIS)

    Watson, R.D.; Youchison, D.L.; Dombrowski, D.E.; Guiniatouline, R.N.; Kupriynov, I.B.

    1996-01-01

    A novel technique has been used to test the relative low cycle thermal fatigue resistance of different grades of US and Russian beryllium which is proposed as plasma facing armor for fusion reactor first wall, limiter, and divertor components. The 30 KW electron beam test system at Sandia National Laboratories was used to sweep the beam spot along one direction at 1 Hz. This produces a localized temperature ''spike'' of 750 degrees C for each pass of the beam. Large thermal stress in excess of the yield strength are generated due to very high spot heat flux, 250 MW/m 2 . Cyclic plastic strains on the order of 0.6% produced visible cracking on the heated surface in less than 3000 cycles. An in-vacuo fiber optic borescope was used to visually inspect the beryllium surfaces for crack initiation. Grades of US beryllium tested included: S-65C, S-65H, S-200F, S-300F-H, Sr-200, I-400, extruded high purity. HIP'd sperical powder, porous beryllium (94% and 98% dense), Be/30% BeO, Be/60% BeO, and TiBe 12 . Russian grades included: TGP-56, TShGT, DShG-200, and TShG-56. Both the number of cycles to crack initiation, and the depth of crack propagation, were measured. The most fatigue resistant grades were S-65C, DShG-200, TShGT, and TShG-56. Rolled sheet Be(SR-200) showed excellent crack propagation resistance in the plane of rolling, despite early formation of delamination cracks. Only one sample showed no evidence of surface melting, Extruded (T). Metallographic and chemical analyses are provided. Good agreement was found between the measured depth of cracks and a 2-D elastic-plastic finite element stress analysis

  16. Fatigue Load Sensitivity Based Optimal Active Power Dispatch For Wind Farms

    DEFF Research Database (Denmark)

    Zhao, Haoran; Wu, Qiuwei; Huang, Shaojun

    2017-01-01

    sensitivity are derived, which significantly improves the computation efficiency of the local WT controller. The proposed algorithm can be implemented in different active power control schemes. Case studies were conducted with a wind farm under balance control for both low and high wind conditions......This paper proposes an optimal active power dispatch algorithm for wind farms based on Wind Turbine (WT) load sensitivity. The control objectives include tracking power references from the system operator and minimizing fatigue loads experienced by WTs. The sensitivity of WT fatigue loads to power...... references is defined which simplifies the formulation of the optimal power dispatch problem. Since the sensitivity value is calculated at the local WT controller, the computation burden of the central wind farm controller is largely reduced. Moreover, explicit analytical equations of the fatigue load...

  17. High Cycle Thermal Fatigue Analysis for a Mixing Tee in Safety Injection and Shutdown Cooling System of SKN Unit 3 and 4 Power Plant

    International Nuclear Information System (INIS)

    Yang, Kyeong Jin; Lee, Dong Jae; Kim, Dae Soo; Huh, Man Gil

    2011-01-01

    Safety Injection and Shutdown Cooling system (SISC) in a nuclear power plant has an important role of core cooling during plant shutdown and on emergency conditions. A heat exchanger on the SISC removes the heat energy generated in the reactor core during shutdown cooling event. Mixing tee placed on downstream of the heat exchanger designates a Tshaped branch connection where the hot flow passed through the by-pass line mixes with the flow passed through the heat exchanger, and due to the characteristics of fluid with bad heat conductivity, the flow develops a mixing zone in a distance from the mixing tee. The pipe wall in the mixing zone experiences the thermal oscillation of high cycle, and therefore is in a state of the high cycle thermal fatigue loadings. In this work, performed is the high cycle thermal fatigue analysis for a mixing tee under the prescribed thermal loadings in a mixing zone. Using the evaluation guide established by JSME, JSME S017- 2003 which has evaluation procedure composing of the four steps, we evaluate the fatigue integrity of the mixing tee of which the results show that the mixing tee satisfies the fatigue integrity in the last step (fourth) of four steps of evaluation procedure where the fatigue usage factor, U was calculated and then compared with the well known criterion, U<1. Representative results of the fatigue analysis are also discussed

  18. Monitoring fatigue loads on wind turbines using cycle counting data acquisition systems

    Energy Technology Data Exchange (ETDEWEB)

    Soeker, H.; Seifert, H. [Deutsches Windenergie-Institut (Germany); Fragoulis, A.; Vionis, P.; Foussekis, D. [Center for Renewable Energy Sources (Greece); Dahlberg, J.A.; Poppen, M. [The Aeronautical Research Institue of Sweden (Sweden)

    1996-09-01

    As in any industrial application, the duration of a wind turbine`s life is a key parameter for the evaluation of its economic potential. Assuming a service life of 20 years, components of the turbine have to withstand a number of load cycles of up to 10{sup 8}. Such numbers of load cycles impose high demands on the fatigue characteristics of both, the used materials and the design. Nevertheless, fatigue loading of wind turbine components still remains a parameter of high uncertainty in the design of wind turbines. The specific features of these fatigue loads can be expected to vary with the type of turbine and the site of operation. In order to ensure the reliability of the next generation of larger scale wind turbines improved load assumptions will be of vital importance. Within the scope of the presented research program DEWI, C.R.E.S. and FFA monitored fatigue loads of serial produced wind turbines by means of a monitoring method that uses on-line cycle counting techniques. The blade root bending moments of two pitch controlled, variable speed wind turbines operating in the Hamswehrum wind farm, and also that of a stall controlled, fixed speed wind turbine operating in CRES` complex terrain test site, were measured by DEWI and CRES. In parallel FFA used their database of time series measurements of blade root bending moments on a stall controlled, fixed speed turbine at Alsvik Windfarm in order to derive semi-empirical fatigue load data. The experience gained from application of the on-line measurement technique is discussed with respect to performance, data quality, reliability and cost effectiveness. Investigations on the effects of wind farm and complex terrain operation on the fatigue loads of wind turbine rotor blades are presented. (au)

  19. Towards the prediction of thermal fatigue cracks networks development; Vers la prediction de l'apparition de reseau de fissures en fatigue thermique

    Energy Technology Data Exchange (ETDEWEB)

    Osterstock, St. [CEA Saclay, Dept. des Materiaux pour le Nucleaire (DEN/DANS/DMN/SRMA), 91 - Gif-sur-Yvette (France)

    2008-07-01

    In the framework of the influence of the surface and the structure of materials used in the cooling system of reactor, Depres studied in 2004 at the CEA, the evolution of the microstructure inside the surface grains under a thermal fatigue loading, from dynamic of dislocations calculation. In this context the aim of this study is to bring experimental elements of validation of the numerical results obtained by Depres and to verify if these elements allow the prediction of cracks networks apparition. (A.L.B.)

  20. EFFECTIVNESS OF THE FATIGUE CRITERIA FOR COMBINED BENDING – TORSION LOADING

    Directory of Open Access Journals (Sweden)

    Štěpán Major

    2010-12-01

    Full Text Available Most of mechanical components in the engineering are frequently subjected to combined loading, which can lead to sudden fatigue failure. In present work the fatigue life of plasma-nitrided and virgin specimens is studied. Specimens made of low-alloy high-strength steel. Specimens were subjected to an in-phase combined bending-torsion loading. The plasma-nitrided specimens have significantly improved fatigue resistance. The most relevant goal of this paper is to verify the efficiency of classical and advanced stress based multiaxial criteria. The criterion proposed by McDiarmid was found to be the most precise in the fatigue life prediction for virgin specimens. On the other hand, the Matake criterion was the most successful for nitrided specimens.

  1. Analysis of Powertrain Loading Dynamic Characteristics and the Effects on Fatigue Damage

    Directory of Open Access Journals (Sweden)

    Jinyang Bai

    2017-10-01

    Full Text Available The objective of this study is to investigate the effects of key factors on the powertrain loading dynamic characteristics and fatigue damage. First, the engine and the transmission output shaft torque of a multi-axle vehicle powertrain system were measured by proving grounds (PG testing and analyzed with a conclusion that the powertrain loading changes were mainly related to three key factors: the mean engine torque, the harmonic engine torque, and the vibration properties of the system. Subsequently, a dynamic model considering the three factors was built and validated by the test data. Finally, fatigue damage of shaft parts and gear parts were calculated to investigate the influence degrees of the three factors. The results show that, the harmonic engine torque and the vibration properties of the powertrain system have a great influence on the fatigue damage of shaft parts, and the mean engine torque is the main factor causing the fatigue damage of gear parts.

  2. 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

  3. A Case for Including Atmospheric Thermodynamic Variables in Wind Turbine Fatigue Loading Parameter Identification

    International Nuclear Information System (INIS)

    Kelley, Neil D.

    1999-01-01

    This paper makes the case for establishing efficient predictor variables for atmospheric thermodynamics that can be used to statistically correlate the fatigue accumulation seen on wind turbines. Recently, two approaches to this issue have been reported. One uses multiple linear-regression analysis to establish the relative causality between a number of predictors related to the turbulent inflow and turbine loads. The other approach, using many of the same predictors, applies the technique of principal component analysis. An examination of the ensemble of predictor variables revealed that they were all kinematic in nature; i.e., they were only related to the description of the velocity field. Boundary-layer turbulence dynamics depends upon a description of the thermal field and its interaction with the velocity distribution. We used a series of measurements taken within a multi-row wind farm to demonstrate the need to include atmospheric thermodynamic variables as well as velocity-related ones in the search for efficient turbulence loading predictors in various turbine-operating environments. Our results show that a combination of vertical stability and hub-height mean shearing stress variables meet this need over a period of 10 minutes

  4. Training Load and Fatigue Marker Associations with Injury and Illness: A Systematic Review of Longitudinal Studies.

    Science.gov (United States)

    Jones, Christopher M; Griffiths, Peter C; Mellalieu, Stephen D

    2017-05-01

    Coaches, sport scientists, clinicians and medical personnel face a constant challenge to prescribe sufficient training load to produce training adaption while minimising fatigue, performance inhibition and risk of injury/illness. The aim of this review was to investigate the relationship between injury and illness and longitudinal training load and fatigue markers in sporting populations. Systematic searches of the Web of Science and PubMed online databases to August 2015 were conducted for articles reporting relationships between training load/fatigue measures and injury/illness in athlete populations. From the initial 5943 articles identified, 2863 duplicates were removed, followed by a further 2833 articles from title and abstract selection. Manual searching of the reference lists of the remaining 247 articles, together with use of the Google Scholar 'cited by' tool, yielded 205 extra articles deemed worthy of assessment. Sixty-eight studies were subsequently selected for inclusion in this study, of which 45 investigated injury only, 17 investigated illness only, and 6 investigated both injury and illness. This systematic review highlighted a number of key findings, including disparity within the literature regarding the use of various terminologies such as training load, fatigue, injury and illness. Athletes are at an increased risk of injury/illness at key stages in their training and competition, including periods of training load intensification and periods of accumulated training loads. Further investigation of individual athlete characteristics is required due to their impact on internal training load and, therefore, susceptibility to injury/illness.

  5. Effects of casting defects, matrix structures and loading conditions on the fatigue strength of ductile irons

    Directory of Open Access Journals (Sweden)

    Endo Masahiro

    2014-06-01

    Full Text Available A novel method is presented to estimate the lower bound of the scatter in fatigue limit of ductile iron based upon the information of microstructural in homogeneities and loading conditions. The predictive capability of the method was verified by comparing to the experimental data obtained by the rotating-bending, torsion and combined tension-torsion fatigue tests for ductile irons with ferritic, pearlitic and bulls-eye (ferritic/pearlitic microstructures.

  6. Mean load effects on the fatigue life of offshore wind turbine monopile foundations

    DEFF Research Database (Denmark)

    Blasques, José Pedro Albergaria Amaral; Natarajan, Anand

    2013-01-01

    This paper discusses the importance of mean load effects on the estimation of the fatigue damage in offshore wind turbine monopile foundations. The mud line bending moment time series are generated using a fully coupled aero-hydro-elastic model accounting for non-linear water waves and sea current...... of the fatigue life of offshore wind turbine monopile foundations. Moreover, it is shown that a nonlinear hydrodynamic model is required in order to correctly account for the effect of the current....

  7. Thickness effect in composite laminates in static and fatigue loading

    NARCIS (Netherlands)

    Lahuerta Calahorra, F.

    2017-01-01

    Thick Laminates (above 6mm) are increasingly present in large composites structures such as wind turbine blades. Designs are based on static and fatigue coupon tests performed on 1-4mm thin laminates. However, a thickness effect has been observed in limited available experimental data. For this

  8. High-accuracy CFD prediction methods for fluid and structure temperature fluctuations at T-junction for thermal fatigue evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Shaoxiang, E-mail: qian.shaoxiang@jgc.com [EN Technology Center, Process Technology Division, JGC Corporation, 2-3-1 Minato Mirai, Nishi-ku, Yokohama 220-6001 (Japan); Kanamaru, Shinichiro [EN Technology Center, Process Technology Division, JGC Corporation, 2-3-1 Minato Mirai, Nishi-ku, Yokohama 220-6001 (Japan); Kasahara, Naoto [Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2015-07-15

    Highlights: • Numerical methods for accurate prediction of thermal loading were proposed. • Predicted fluid temperature fluctuation (FTF) intensity is close to the experiment. • Predicted structure temperature fluctuation (STF) range is close to the experiment. • Predicted peak frequencies of FTF and STF also agree well with the experiment. • CFD results show the proposed numerical methods are of sufficiently high accuracy. - Abstract: Temperature fluctuations generated by the mixing of hot and cold fluids at a T-junction, which is widely used in nuclear power and process plants, can cause thermal fatigue failure. The conventional methods for evaluating thermal fatigue tend to provide insufficient accuracy, because they were developed based on limited experimental data and a simplified one-dimensional finite element analysis (FEA). CFD/FEA coupling analysis is expected as a useful tool for the more accurate evaluation of thermal fatigue. The present paper aims to verify the accuracy of proposed numerical methods of simulating fluid and structure temperature fluctuations at a T-junction for thermal fatigue evaluation. The dynamic Smagorinsky model (DSM) is used for large eddy simulation (LES) sub-grid scale (SGS) turbulence model, and a hybrid scheme (HS) is adopted for the calculation of convective terms in the governing equations. Also, heat transfer between fluid and structure is calculated directly through thermal conduction by creating a mesh with near wall resolution (NWR) by allocating grid points within the thermal boundary sub-layer. The simulation results show that the distribution of fluid temperature fluctuation intensity and the range of structure temperature fluctuation are remarkably close to the experimental results. Moreover, the peak frequencies of power spectrum density (PSD) of both fluid and structure temperature fluctuations also agree well with the experimental results. Therefore, the numerical methods used in the present paper are

  9. Fatigue of weld ends under combined in- and out-of-phase multiaxial loading

    Directory of Open Access Journals (Sweden)

    E. Shams

    2016-10-01

    Full Text Available Weld start and end points are fatigue failure sensitive locations. Their fatigue behaviour especially in thin sheet structures under multiaxial load conditions is not sufficiently explored so far. Therefore, a research project was initiated to increase the knowledge concerning this topic, which is of special interest in the automotive industry. In the present study, fatigue tests on welded joints were conducted. In the numerical part of the study, notch stresses were calculated with an idealised weld end model. A numerical method which combines the geometrical and statistical size effect to an integrated approach was used, in order to consider the size effects

  10. Influence of inspiratory resistive loading on expiratory muscle fatigue in healthy humans.

    Science.gov (United States)

    Peters, Carli M; Welch, Joseph F; Dominelli, Paolo B; Molgat-Seon, Yannick; Romer, Lee M; McKenzie, Donald C; Sheel, A William

    2017-09-01

    What is the central question of this study? This study is the first to measure objectively both inspiratory and expiratory muscle fatigue after inspiratory resistive loading to determine whether the expiratory muscles are activated to the point of fatigue when specifically loading the inspiratory muscles. What is the main finding and its importance? The absence of abdominal muscle fatigue suggests that future studies attempting to understand the neural and circulatory consequences of diaphragm fatigue can use inspiratory resistive loading without considering the confounding effects of abdominal muscle fatigue. Expiratory resistive loading elicits inspiratory as well as expiratory muscle fatigue, suggesting parallel coactivation of the inspiratory muscles during expiration. It is unknown whether the expiratory muscles are likewise coactivated to the point of fatigue during inspiratory resistive loading (IRL). The purpose of this study was to determine whether IRL elicits expiratory as well as inspiratory muscle fatigue. Healthy male subjects (n = 9) underwent isocapnic IRL (60% maximal inspiratory pressure, 15 breaths min -1 , 0.7 inspiratory duty cycle) to task failure. Abdominal and diaphragm contractile function was assessed at baseline and at 3, 15 and 30 min post-IRL by measuring gastric twitch pressure (P ga,tw ) and transdiaphragmatic twitch pressure (P di,tw ) in response to potentiated magnetic stimulation of the thoracic and phrenic nerves, respectively. Fatigue was defined as a significant reduction from baseline in P ga,tw or P di,tw . Throughout IRL, there was a time-dependent increase in cardiac frequency and mean arterial blood pressure, suggesting activation of the respiratory muscle metaboreflex. The P di,tw was significantly lower than baseline (34.3 ± 9.6 cmH 2 O) at 3 (23.2 ± 5.7 cmH 2 O, P muscle fatigue. Agonist-antagonist interactions for the respiratory muscles appear to be more important during expiratory versus inspiratory

  11. Characteristics of Metal Magnetic Memory Testing of 35CrMo Steel during Fatigue Loading

    Directory of Open Access Journals (Sweden)

    Zhibin Hu

    2018-02-01

    Full Text Available The fatigue fracture of a drillstring could cause drilling disturbances and some negative impacts (e.g., economic loss will be brought when restoring the drillstring to functionality. In order to evaluate the effects of the fatigue damage of the drillstring during drilling, a new apparatus, which could monitor the load level in real-time, was built to perform the four-point bending fatigue test on 35CrMo steel, a typical material of drillstrings. Such an apparatus is based on metal magnetic memory (MMM technology and can acquire the tangential and normal components of MMM signals. Based on the analysis of the change of surface morphology and MMM signals, it was concluded that the variation of MMM signals could be divided into four stages, which are used to accurately describe the fatigue damage process of the drillstring. Additionally, the MMM signal characteristics are introduced to especially evaluate the fatigue damage of the drillstring, including crack initiation. Furthermore, the scanning electron microscopy (SEM results demonstrated that morphologies of fatigue fracture were related to the variation of MMM signals. Linear fitting results indicated that fatigue crack length had a good linear relationship with the characteristics, so it is feasible to monitor fatigue damage and predict the residual life of a drillstring by using MMM technology.

  12. 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.

  13. Fatigue Behavior of 2A12 Aluminum Alloy Under Multiaxial Loading

    Directory of Open Access Journals (Sweden)

    CHEN Ya-jun

    2017-08-01

    Full Text Available The multiaxial fatigue behavior of 2A12 aluminum alloy was studied with SDN100/1000 electro-hydraulic servo tension-torsion fatigue tester under multiple variables, and the failure mechanism was investigated by scanning electron microscopy (SEM. The results show that under the loading condition of equivalent stress, the fatigue life decreases with the increase of phase angle. For the phase angle 0°, some special features can be observed in the crack initial zone, such as the tire pattern,fishbone pattern and stalactite pattern. There are secondary cracks and vague fatigue striations in the crack propagation zone; the multiaxial fatigue life decreases with the change of mean stress for tension or torsion. Some white flocculent oxides can be found in the crack initiation zone, and secondary crack as well as shear-type elongated dimples in the instantaneous fracture zone; facing different loading waveforms, the multiaxial life of sine wave is the longest, triangle wave in the second place, and the square wave is the shortest, under the loading condition of equivalent stress, square wave leads to the maximum structural energy dissipation. Under the low and high two step loading, 2A12 shows training effect.

  14. Fatigue life of bovine meniscus under longitudinal and transverse tensile loading.

    Science.gov (United States)

    Creechley, Jaremy J; Krentz, Madison E; Lujan, Trevor J

    2017-05-01

    The knee meniscus is composed of a fibrous extracellular matrix that is subjected to large and repeated loads. Consequently, the meniscus is frequently torn, and a potential mechanism for failure is fatigue. The objective of this study was to measure the fatigue life of bovine meniscus when applying cyclic tensile loads either longitudinal or transverse to the principal fiber direction. Fatigue experiments consisted of cyclic loads to 60%, 70%, 80% or 90% of the predicted ultimate tensile strength until failure occurred or 20,000 cycles was reached. The fatigue data in each group was fit with a Weibull distribution to generate plots of stress level vs. cycles to failure (S-N curve). Results showed that loading transverse to the principal fiber direction gave a two-fold increase in failure strain, a three-fold increase in creep, and a nearly four-fold increase in cycles to failure (not significant), compared to loading longitudinal to the principal fiber direction. The S-N curves had strong negative correlations between the stress level and the mean cycles to failure for both loading directions, where the slope of the transverse S-N curve was 11% less than the longitudinal S-N curve (longitudinal: S=108-5.9ln(N); transverse: S=112-5.2ln(N)). Collectively, these results suggest that the non-fibrillar matrix is more resistant to fatigue failure than the collagen fibers. Results from this study are relevant to understanding the etiology of atraumatic radial and horizontal meniscal tears, and can be utilized by research groups that are working to develop meniscus implants with fatigue properties that mimic healthy tissue. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Microstructural response of ultrafine-grained copper to fatigue loading

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr; Buksa, Michal; Wang, Q.; Zheng, M.

    2007-01-01

    Roč. 13, č. 1 (2007), s. 512-518 ISSN 1335-1532. [Metallography 2007. Stará Lesná, 02.05.2007-04.05.2007] R&D Projects: GA MŠk(CZ) 1P05ME804 Institutional research plan: CEZ:AV0Z20410507 Keywords : Ultrafine-grained copper * Fatigue * Softening/hardening Subject RIV: JG - Metallurgy

  16. Use of the WEST-1 wind turbine simulator to predict blade fatigue load distribution

    Science.gov (United States)

    Janetzke, D. C.

    1983-01-01

    To test the ability of WEST-1 to predict blade fatigue load distribution, actual wind signals were fed into the simulator and the response data were recorded and processed in the same manner as actual wind turbine data. The WEST-1 simulator was operated in a stable, unattended mode for six hours. The probability distribution of the cyclic flatwise bending moment for the blade was comparable to that for an actual wind turbine in winds with low turbulence. The input from a stationary anemometer was found to be inadequate for use in the prediction of fatigue load distribution for blade design purposes and modifications are necessary.

  17. Study on crack propagation in tubular joints under compressive fatigue loadings

    OpenAIRE

    Acevedo, Claire; Nussbaumer, Alain

    2009-01-01

    Large scale tubular truss beams, approximately of 9 m long and 2 m high, were tested under constant amplitude fatigue loading. The beams were made out of circular hollow sections of steel S355, welded to form a uni-planar truss with K-joints, in a shape common to bridge construction. The main goal of these tests was to focus on the fatigue behavior of the joints loaded in compression that is with chord in compression, one diagonal in compression and the remaining diagonal in tension. The test...

  18. Fatigue Debond Growth in Sandwich Structures Loaded in Mixed Mode Bending (MMB)

    DEFF Research Database (Denmark)

    Quispitupa, Amilcar; Berggreen, Christian; Carlsson, Leif A.

    2008-01-01

    Static and cyclic debond growth in sandwich specimens loaded in mixed mode bending (MMB) is examined. The MMB sandwich specimens were manufactured using H100 PVC foam core and E-glass/polyester non-crimp quadro-axial [0/45/90/-45]s DBLT-850 face sheets. Static test were performed to determine...... the fracture toughness of the debonded sandwich specimens at different mixed mode loadings. The mixed mode ratio (mode I to mode II) was controlled by changing the lever arm distance of the MMB test rig. Compliance technique and visual inspection was employed to measure the crack length during fatigue. Fatigue...

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

    International Nuclear Information System (INIS)

    Thiele, Marc

    2016-01-01

    The main objective of this thesis is the fatigue behavior of concrete under high-cycle compressive loadings. Current knowledge about fatigue behavior of concrete is still incomplete. This concerns especially the process of fatigue which is preceding the fatigue failure. The leak of knowledge about fatigue behavior is opposed to the steady growing importance of this topic within the practice in civil engineering. Therefore, within this thesis a systematic and comprehensive investigation of the process of fatigue itself was done. This contributes to the better understanding of the progression of damage and the corresponding processes within the material. The experimental investigation consisted mainly of experiments with constant amplitude loadings in compression with cylindrical specimen made of normal strength concrete. Two differed load levels were used which resulted in numbers of cycles to failure of 10 6 and 10 7 as well as 10 3 and 10 4 . The experiments were done in combination with different types of nondestructive and destructive testing methods like strain measuring, deformation of surface, ultrasonic signals, acoustic emissions, optical microscopy and also scattering electron microscopy. To access some parameters of influence in relation to the fatigue behavior additional creep tests and also several tests with different scales of specimen were done. The fatigue process of concrete is determined as an evolution of damage that starts from the beginning of the loading process. This evolution has manifold and different influences on the different material properties of concrete. In this relation a major finding was that fatigue related damage leads to a transformation of the complete stress-strain-relationship. This relationship is also subjected to an evolution process. Due to the authors observations it could not be determined that the investigated changes in macroscopic material behavior are caused by a development of micro cracks within the material

  20. Effect of torsional loading on compressive fatigue behaviour of trabecular bone.

    Science.gov (United States)

    Fatihhi, S J; Rabiatul, A A R; Harun, M N; Kadir, Mohammed Rafiq Abdul; Kamarul, T; Syahrom, Ardiyansyah

    2016-02-01

    The present study reports the effects of combined torsional and compressive cyclic loading on trabecular bone in order to mimic true physiological conditions and thereby provides improved data that represents clinical and real life conditions. However, only compressive behaviour is evaluated in most previous studies of bone mechanics. From the monotonic evaluation, it is observed that lower stress is needed for the onset of microcrack in the sample under torsional loading, compared to the stress needed in compression. Trabecular bone samples were subjected to a combination of torsion and compression fatigue at different stress levels during which they were compared to compressive axial fatigue. The stress levels were determined by considering the monotonic strength at 25-50% for both compressive and shear stresses. Significant decrease in fatigue lifetime is observed in between samples of pure compression fatigue and those with superpositioned torsional loading (ptorsional stress level. In this case, the failure of the sample is said to be 'torsional dominant'. Fatigue behaviour of bovine trabecular bone begins with plastic deformation, followed by strain accumulation and modulus reduction. As the strain rate increases, more energy dissipates and the sample finally failed. Further, the analysis of fractograph revealed something on the trabeculae by bending in sample with superpositioned torsional loading. In conclusion, torsional loading decreases the quality of the trabecular properties in terms of stiffness, life and structural integrity. It is hoped that results from this study will improve the understanding of the behaviour of trabecular bone under combined fatigue and help to develop future assessments of trabecular failure. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Load Identification of Offshore Platform for Fatigue Life Estimation

    DEFF Research Database (Denmark)

    Perisic, Nevena; Kirkegaard, Poul Henning; Tygesen, Ulf T.

    2014-01-01

    of the structure and the discrete Kalman filter which recursively estimates unknown states of the system in real time. As a test-case, the algorithm is designed to estimate the equivalent total loading forces of the structure. The loads are estimated from noised displacement measurements of a single location...

  2. Behavior of sandwich panels subjected to bending fatigue, axial compression loading and in-plane bending

    Science.gov (United States)

    Mathieson, Haley Aaron

    This thesis investigates experimentally and analytically the structural performance of sandwich panels composed of glass fibre reinforced polymer (GFRP) skins and a soft polyurethane foam core, with or without thin GFRP ribs connecting skins. The study includes three main components: (a) out-of-plane bending fatigue, (b) axial compression loading, and (c) in-plane bending of sandwich beams. Fatigue studies included 28 specimens and looked into establishing service life (S-N) curves of sandwich panels without ribs, governed by soft core shear failure and also ribbed panels governed by failure at the rib-skin junction. Additionally, the study compared fatigue life curves of sandwich panels loaded under fully reversed bending conditions (R=-1) with panels cyclically loaded in one direction only (R=0) and established the stiffness degradation characteristics throughout their fatigue life. Mathematical models expressing fatigue life and stiffness degradation curves were calibrated and expanded forms for various loading ratios were developed. Approximate fatigue thresholds of 37% and 23% were determined for non-ribbed panels loaded at R=0 and -1, respectively. Digital imaging techniques showed significant shear contribution significantly (90%) to deflections if no ribs used. Axial loading work included 51 specimens and examined the behavior of panels of various lengths (slenderness ratios), skin thicknesses, and also panels of similar length with various rib configurations. Observed failure modes governing were global buckling, skin wrinkling or skin crushing. In-plane bending involved testing 18 sandwich beams of various shear span-to-depth ratios and skin thicknesses, which failed by skin wrinkling at the compression side. The analytical modeling components of axially loaded panels include; a simple design-oriented analytical failure model and a robust non-linear model capable of predicting the full load-displacement response of axially loaded slender sandwich panels

  3. Investigation on electromagnetic characteristics of modeling thermal fatigue cracks in numerical simulation by eddy current testing

    International Nuclear Information System (INIS)

    Wang, Jing; Yusa, Noritaka; Hashizume, Hidetoshi; Pan Hongliang; Kemppainen, Mika; Virkkuen, Iikka

    2012-01-01

    The present study discusses electromagnetic characteristics of modeling thermal fatigue crack in numerical simulation from view point of eddy current testing. Two thermal fatigue cracks introduced into SUS304 stainless steel plates are investigated. Eddy current signals are gathered by a differential plus point probe with several frequencies, 50 kHz, 100 kHz and 400 kHz. In the numerical simulation thermal fatigue crack is modeled as a region with constant width, true profile revealed by results of destructive testing, and uniform conductivity firstly. Further simulations are carried out to consider the possibility of variation of electromagnetic characteristics around the edge of crack. The results show that thermal fatigue cracks should be modeled as an almost nonconductive region no matter how the frequency is utilized. (author)

  4. Formation of thermal fatigue cracks in periodic rapid quenching of metal

    Energy Technology Data Exchange (ETDEWEB)

    Ots, A. [Tallinn Technical University, Thermal Engineering Department, Tallinn (Estonia)

    1998-12-31

    Water lancing is an effective technique for cleaning boiler heating surfaces from ash deposits by burning low-grade fuels with complicated composition of mineral matter. In water cleaning cycles of boiler`s heat transfer surfaces due to rapid quenching destruction of corrosion protective oxide film and formation of thermal fatigue cracks on the outer surface of the tube`s metal occur. The criterion of the thermal fatigue cracks` formation and their growth intensity depend on the character of temperature field in the tube`s metal outer layer. The solution of non-stationary heat conductivity equation for metal rapid quenching conditions is given. The convective heat transfer coefficients from hot metal surface to water jet were established experimentally. Thermal fatigue crack growth intensity was investigated in real boilers` heat transfer surfaces` tubes as well as in laboratory conditions. The formula for predicting thermal fatigue cracks` depth depending on the number of cleaning cycles. (orig.) 5 refs.

  5. 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.

  6. In situ microradioscopy and microtomography of fatigue-loaded dental two-piece implants.

    Science.gov (United States)

    Wiest, Wolfram; Zabler, Simon; Rack, Alexander; Fella, Christian; Balles, Andreas; Nelson, Katja; Schmelzeisen, Rainer; Hanke, Randolf

    2015-11-01

    Synchrotron real-time radioscopy and in situ microtomography are the only techniques providing direct visible information on a micrometre scale of local deformation in the implant-abutment connection (IAC) during and after cyclic loading. The microgap formation at the IAC has been subject to a number of studies as it has been proposed to be associated with long-term implant success. The next step in this scientific development is to focus on the in situ fatigue procedure of two-component dental implants. Therefore, an apparatus has been developed which is optimized for the in situ fatigue analysis of dental implants. This report demonstrates both the capability of in situ radioscopy and microtomography at the ID19 beamline for the study of cyclic deformation in dental implants. The first results show that it is possible to visualize fatigue loading of dental implants in real-time radioscopy in addition to the in situ fatigue tomography. For the latter, in situ microtomography is applied during the cyclic loading cycles in order to visualize the opening of the IAC microgap. These results concur with previous ex situ studies on similar systems. The setup allows for easily increasing the bending force, to simulate different chewing situations, and is, therefore, a versatile tool for examining the fatigue processes of dental implants and possibly other specimens.

  7. Effect of load, cadence, and fatigue on tibio-femoral joint force during a half squat.

    Science.gov (United States)

    Hattin, H C; Pierrynowski, M R; Ball, K A

    1989-10-01

    Ten male university student volunteers were selected to investigate the 3D articular force at the tibio-femoral joint during a half squat exercise, as affected by cadence, different barbell loads, and fatigue. Each subject was required to perform a half squat exercise with a barbell weight centered across the shoulders at two different cadences (1 and 2 s intervals) and three different loads (15, 22 and 30% of the one repetition maximum). Fifty repetitions at each experimental condition were recorded with an active optoelectronic kinematic data capture system (WATSMART) and a force plate (Kistler). Processing the data involved a photogrammetric technique to obtain subject tailored anthropometric data. The findings of this study were: 1) the maximal antero-posterior shear and compressive force consistently occurred at the lowest position of the weight, and the forces were very symmetrically disposed on either side of this halfway point; 2) the medio-lateral shear forces were small over the squat cycle with few peaks and troughs; 3) cadence increased the antero-posterior shear (50%) and the compressive forces (28%); 4) as a subject fatigues, load had a significant effect on the antero-posterior shear force; 5) fatigue increased all articular force components but it did not manifest itself until about halfway through the 50 repetitions of the exercise; 6) the antero-posterior shear force was most affected by fatigue; 7) cadence had a significant effect on fatigue for the medio-lateral shear and compressive forces.

  8. Modeling the Tensile Strength of Carbon Fiber - Reinforced Ceramic - Matrix Composites Under Multiple Fatigue Loading

    Science.gov (United States)

    Li, Longbiao

    2016-06-01

    An analytical method has been developed to investigate the effect of interface wear on the tensile strength of carbon fiber - reinforced ceramic - matrix composites (CMCs) under multiple fatigue loading. The Budiansky - Hutchinson - Evans shear - lag model was used to describe the micro stress field of the damaged composite considering fibers failure and the difference existed in the new and original interface debonded region. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. The interface shear stress degradation model and fibers strength degradation model have been adopted to analyze the interface wear effect on the tensile strength of the composite subjected to multiple fatigue loading. Under tensile loading, the fibers failure probabilities were determined by combining the interface wear model and fibers failure model based on the assumption that the fiber strength is subjected to two - parameter Weibull distribution and the loads carried by broken and intact fibers satisfy the Global Load Sharing criterion. The composite can no longer support the applied load when the total loads supported by broken and intact fibers approach its maximum value. The conditions of a single matrix crack and matrix multicrackings for tensile strength corresponding to multiple fatigue peak stress levels and different cycle number have been analyzed.

  9. Additional thermal fatigue data on nickel- and cobalt-base superalloys, part 1

    Science.gov (United States)

    Howes, M. A. H.

    1973-01-01

    The fluidized bed technique was used to measure the relative thermal fatigue resistance of twenty-one superalloys. Among the thirty-six variations of composition, solidification method, and surface protection the cycles to cracking differed by two to three orders of magnitude. Some alloys suffered serious weight losses and oxidation. Thermal fatigue data, oxidation, and dimensional changes are reported. The types of superalloys are identified.

  10. 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.

  11. Fatigue behaviour of fiberglass wind turbine blade material under variable amplitude loading

    Energy Technology Data Exchange (ETDEWEB)

    Delft, D.R.V. Van; Winkel, G.D. de [Delft Univ. of Technology, STEVIN Lab., Delft (Netherlands); Joosse, P.A. [Stork Product Engineering b.v., Amsterdam (Netherlands)

    1996-09-01

    In the work presented here fatigue tests with the WISPER and WISPERX load sequence have been carried out and analysed. The test programme includes tests at low stress levels which results in fatigue lives of 50 millions of cycles. The results are compared with constant amplitude tests in the very high cycle range, carried out in a previous programme. The results are also compared with ECN results in the lower cycle range (on identical specimens). It appeared, that the difference between the fatigue life of the specimens tested with the WISPER and the WISPERX load sequence is larger than can be expected from the theoretical damage rates. Moreover, the slope of the S-N data differs from theoretical values obtained by using commonly applied design rules. (au)

  12. The thermal fatigue resistance of H-13 Die Steel for aluminum die casting dies

    Science.gov (United States)

    1982-01-01

    The effects of welding, five selected surface coatings, and stress relieving on the thermal fatigue resistance of H-13 Die Steel for aluminum die casting dies were studied using eleven thermal fatigue specimens. Stress relieving was conducted after each 5,000 cycle interval at 1050 F for three hours. Four thermal fatigue specimens were welded with H-13 or maraging steel welding rods at ambient and elevated temperatures and subsequently, subjected to different post-weld heat treatments. Crack patterns were examined at 5,000, 10,000, and 15,000 cycles. The thermal fatigue resistance is expressed by two crack parameters which are the average maximum crack and the average cracked area. The results indicate that a significant improvement in thermal fatigue resistance over the control was obtained from the stress-relieving treatment. Small improvements were obtained from the H-13 welded specimens and from a salt bath nitrogen and carbon-surface treatment. The other surface treatments and welded specimens either did not affect or had a detrimental influence on the thermal fatigue properties of the H-13 die steel.

  13. On the experimental procedure for fatigue studies of structural materials under asymmetrical loading conditions

    International Nuclear Information System (INIS)

    Kalugin, V.E.; Nemanov, M.S.

    1977-01-01

    The behaviour of hollow and solid specimens of the VT6 alloy during jib-type bending under an asymmetric loading cycle was studied in order to develop a fatigue test procedure. A criterion for the selection of the proportions of specimen dimensions has been suggested. A first-approximation cycle asymmetry factor value for the material involved has been determined. Average cycle stress control during specimen assembly and cyclic loading has been included

  14. Study of the quantitative assessment method for high-cycle thermal fatigue of a T-pipe under turbulent fluid mixing based on the coupled CFD-FEM method and the rainflow counting method

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y.; Lu, T., E-mail: likesurge@sina.com

    2016-12-01

    Highlights: • Two characteristic parameters of the temperature fluctuations are used for qualitative analysis. • A quantitative assessment method for high-cycle thermal fatigue of a T-pipe is proposed. • The time-dependent curves for the temperature and thermal stress are not always “in-phase”. • Large magnitude of thermal stresses may not mean large number of fatigue cycles. • The normalized fatigue damage rate and normalized RMS temperature are positively related. - Abstract: With the development of nuclear power and nuclear power safety, high-cycle thermal fatigue of the pipe structures induced by the flow and heat transfer of the fluid in pipes have aroused more and more attentions. Turbulent mixing of hot and cold flows in a T-pipe is a well-recognized source of thermal fatigue in piping system, and thermal fatigue is a significant long-term degradation mechanism. It is not an easy work to evaluate thermal fatigue of a T-pipe under turbulent flow mixing because of the thermal loads acting at fluid–structure interface of the pipe are so complex and changeful. In this paper, a one-way Computational Fluid Dynamics-Finite Element Method (CFD-FEM method) coupling based on the ANSYS Workbench 15.0 software has been developed to calculate transient thermal stresses with the temperature fields of turbulent flow mixing, and thermal fatigue assessment has been carried out with this obtained fluctuating thermal stresses by programming in the software platform of Matlab based on the rainflow counting method. In the thermal analysis, the normalized mean temperatures and the normalized root mean square (RMS) temperatures are obtained and compared with the experiment of the test case from the Vattenfall benchmark facility to verify the accuracy of the CFD calculation and to determine the position which thermal fatigue is most likely to occur in the T-junction. Besides, more insights have been obtained in the coupled CFD-FEM analysis and the thermal fatigue

  15. Mitigation of Fatigue Loads Using Individual Pitch Control of Wind Turbines Based on FAST

    DEFF Research Database (Denmark)

    Zhang, Yunqian; Chen, Zhe; Cheng, Ming

    2011-01-01

    With the increase of wind turbine dimension and capacity, the wind turbine structures are subjected to prominent loads and fatigue which would reduce the lifetime of wind turbines. Individual pitch control (IPC) is used in this paper to attenuate the blade root bending moment and the tilt and yaw...

  16. A Wind Farm Active Power Dispatch Strategy for Fatigue Load Reduction

    DEFF Research Database (Denmark)

    Zhang, Baohua; N. Soltani, Mohsen; Hu, Weihao

    2016-01-01

    One of the biggest challenges in wind farm management is to cope with requirements from the grid companies and to optimize efficiency and minimize wear on wind turbines. This paper addresses an optimized active power dispatch strategy of a wind farm to reduce the fatigue load of wind turbines, wh...

  17. Fatigue Crack and Delamination Growth in Fibre Metal Laminates under Variable Amplitude Loading

    NARCIS (Netherlands)

    Khan, S.

    2013-01-01

    This thesis presents the investigation into the fatigue propagation and delamination growth of Fibre Metal Laminates under variable amplitude loading. As explained in the first chapter, the motivation of the research is twofold: first, to obtain a clear understanding and detailed characterization of

  18. Recent developments on SMA actuators: predicting the actuation fatigue life for variable loading schemes

    Science.gov (United States)

    Wheeler, Robert W.; Lagoudas, Dimitris C.

    2017-04-01

    Shape memory alloys (SMAs), due to their ability to repeatably recover substantial deformations under applied mechanical loading, have the potential to impact the aerospace, automotive, biomedical, and energy industries as weight and volume saving replacements for conventional actuators. While numerous applications of SMA actuators have been flight tested and can be found in industrial applications, these actuators are generally limited to non-critical components, are not widely implemented and frequently one-off designs, and are generally overdesigned due to a lack of understanding of the effect of the loading path on the fatigue life and the lack of an accurate method for predicting actuator lifetimes. In recent years, multiple research efforts have increased our understanding of the actuation fatigue process of SMAs. These advances can be utilized to predict the fatigue lives and failure loads in SMA actuators. Additionally, these prediction methods can be implemented in order to intelligently design actuators in accordance with their fatigue and failure limits. In the following paper, both simple and complex thermomechanical loading paths have been considered. Experimental data was utilized from two material systems: equiatomic Nickel-Titanium and Nickelrich Nickel-Titanium.

  19. Development of reliable design rules for adhesively bonded joints loaded in fatigue

    NARCIS (Netherlands)

    Straalen, IJ.J. van; Botter, E.

    2005-01-01

    Design rules considering fatigue for practical applications are mostly based on spectra representing the cyclic loading and the so-called SN-curves (Wohler curves). For welded and mechanically fasted joints the reliability of these design ruiles is proved over the years. For adhesive bonded joints

  20. Impact of Higher Fidelity Models on Simulation of Active Aerodynamic Load Control For Fatigue Damage Reduction

    NARCIS (Netherlands)

    Resor, B.; Wilson, D.; Berg, D.; Berg, J.; Barlas, T.; Van Wingerden, J.W.; Van Kuik, G.A.M.

    2010-01-01

    Active aerodynamic load control of wind turbine blades is being investigated by the wind energy research community and shows great promise, especially for reduction of turbine fatigue damage in blades and nearby components. For much of this work, full system aeroelastic codes have been used to

  1. Damage Precursor Investigation of Fiber-Reinforced Composite Materials Under Fatigue Loads

    Science.gov (United States)

    2013-09-01

    capability, needs Maintenance Action Damage Detection by NDE and/or in-situ sensors (Ultrasonic, Thermography , Acoustic Emission, etc.) Incipient... Damage Prognosis for Materials and Structures in Complex Systems, AFOSR Discovery Challenge Thrust (DCT) Workshop on Prognosis of Aircraft and Space... Damage Precursor Investigation of Fiber-Reinforced Composite Materials Under Fatigue Loads by Asha J. Hall, Raymond E. Brennan IV, Anindya

  2. Fatigue life of carburized steel specimens under push-pull loading

    Czech Academy of Sciences Publication Activity Database

    Major, Štěpán; Hubálovský, Š.; Šedivý, J.; Bryscejn, Jan

    2014-01-01

    Roč. 1, č. 1 (2014), s. 99-104 ISSN 2313-0555 Institutional support: RVO:68378297 Keywords : carburizing * fatigue life * sub-surface crack * highstrength steel * push-pull loading Subject RIV: JM - Building Engineering http://www.naun.org/cms.action?id=7631

  3. Investigations on creep fatigue alternating load strength of nickel alloys

    International Nuclear Information System (INIS)

    Raule, G.

    1987-01-01

    On all three nickel based materials examined (IN 713 LC, IN 617 and Nimonic 86), the crack change numbers were considerably reduced by introducing stopping times. The cyclic stresses of the materials IN 713 LC and Nimonic 86 were not affected by the interposed stopping times. The material IN 617 is subject to considerably lower stresses with increasing stopping times than in alternate stressing without stopping times. The determination of equivalent stresses by Berling and Conway's method represents a suitable process for describing the creep fatigue behaviour of the materials examined, using creep results. This material behaviour can be assessed using the linear life proportion rule, if one takes into consideration that the resulting life constants are considerably affected by the method used to determine the time creep proportion. (orig./MM) [de

  4. Numerical and Experimental Analysis of Aircraft Wing Subjected to Fatigue Loading

    Directory of Open Access Journals (Sweden)

    Hatem Rahim Wasmi

    2016-10-01

    Full Text Available This study deals with the aircraft wing analysis (numerical and experimental which subjected to fatigue loading in order to analyze the aircraft wing numerically by using ANSYS 15.0 software and experimentally by using loading programs which effect on fatigue test specimens at laboratory to estimate life of used metal (aluminum alloy 7075-T651 the wing metal and compare between numerical and experimental work, as well as to formulate an experimental mathematical model which may find safe estimate for metals and most common alloys that are used to build aircraft wing at certain conditions. In experimental work, a (34 specimen of (aluminum alloy 7075-T651 were tested using alternating bending fatigue machine rig. The test results are ; (18 Specimen to establish the (S-N curve and endurance limit and the other specimens used for variable amplitude tests were represented by loading programs which represents actual flight conditions. Also it has been obtained the safe fatigue curves which are described by mathematical formulas. ANSYS results show convergence with experimental results about cumulative fatigue damage (D, a mathematical model is proposed to estimate the life; this model gives good results in case of actual loading programs. Also, Miner and Marsh rules are applied to the specimens and compared with the proposal mathematical model in order to estimate the life of the wing material under actual flight loading conditions, comparing results show that it is possible to depend on present mathematical model than Miner and Marsh theories because the proposal mathematical model shows safe and good results compared with experimental work results.

  5. Crack retardation by load reduction during fatigue crack propagation

    International Nuclear Information System (INIS)

    Kim, Hyun Soo; Nam, Ki Woo; Ahn, Seok Hwan; Do, Jae Yoon

    2003-01-01

    Fracture life and crack retardation behavior were examined experimentally using CT specimens of aluminum alloy 5083. Crack retardation life and fracture life were a wide difference between 0.8 and 0.6 in proportion to ratio of load reduction. The wheeler model retardation parameter was used successfully to predict crack growth behavior. By using a crack propagation rule, prediction of fracture life can be evaluated quantitatively. A statistical approach based on Weibull distribution was applied to the test data to evaluate the dispersion in the retardation life and fracture life by the change of load reduction

  6. Modeling Delamination in Postbuckled Composite Structures Under Static and Fatigue Loads

    Science.gov (United States)

    Bisagni, Chiara; Brambilla, Pietro; Bavila, Carlos G.

    2013-01-01

    The ability of the Abaqus progressive Virtual Crack Closure Technique (VCCT) to model delamination in composite structures was investigated for static, postbuckling, and fatigue loads. Preliminary evaluations were performed using simple Double Cantilever Beam (DCB) and Mixed-Mode Bending (MMB) specimens. The nodal release sequences that describe the propagation of the delamination front were investigated. The effect of using a sudden or a gradual nodal release was evaluated by considering meshes aligned with the crack front as well as misaligned meshes. Fatigue simulations were then performed using the Direct Cyclic Fatigue (DCF) algorithm. It was found that in specimens such as the DCB, which are characterized by a nearly linear response and a pure fracture mode, the algorithm correctly predicts the Paris Law rate of propagation. However, the Abaqus DCF algorithm does not consider different fatigue propagation laws in different fracture modes. Finally, skin/stiffener debonding was studied in an aircraft fuselage subcomponent in which debonding occurs deep into post-buckling deformation. VCCT was shown to be a robust tool for estimating the onset propagation. However, difficulties were found with the ability of the current implementation of the Abaqus progressive VCCT to predict delamination propagation within structures subjected to postbuckling deformations or fatigue loads.

  7. Fatigue crack growth rate of API X70 steel pipelines under spectrum loading

    International Nuclear Information System (INIS)

    Beden, S.M.; Abdullah, S.; Ariffin, A.K.

    2012-01-01

    Pipelines offer the most efficient way to transport bulk quantities of gas and oil, either from points of production to storage locations or from storage locations to distributed points of end use. As one of the main materials of west–east gas transmission pipes, X70 pipelines usually serve under variable amplitude loading (VAL). Base on the importance of in-service API X70 pipelines, it is important for the safe operation of this system to know its behaviour under VAL. This paper focuses on the ability of using the NASGRO model to predict the fatigue crack growth (FCG), based on investigation with the modified Wheeler model and experimental data. The results show that the NASGRO model give a fatigue life near by to that published in literatures and also showed the FCG rate response of X70 pipeline steels when exposed to VAL with different overload values. Extra modification to the NASGRO model may lead to better representing of FCG rate. Highlights: ► The assessment of fatigue crack propagation under different load histories are proposed and presented in this paper. ► Due to lack of knowledge in the related area, as yet no universal model exists. ► The output was based on both simulation and experiments. The simulation part was carried out based on the NASGRO model. ► This work focus on fatigue crack growth (FCG) and fatigue life based on the comparison with the previous work.

  8. In situ microradioscopy and microtomography of fatigue-loaded dental two-piece implants

    International Nuclear Information System (INIS)

    Wiest, Wolfram; Zabler, Simon; Rack, Alexander; Fella, Christian; Balles, Andreas; Nelson, Katja; Schmelzeisen, Rainer; Hanke, Randolf

    2015-01-01

    Results of a novel in situ microradiography and microtomography setup for the study of fatigue processes are presented. This setup is optimized for the requirements of dental implants and use at synchrotron imaging beamlines. Synchrotron real-time radioscopy and in situ microtomography are the only techniques providing direct visible information on a micrometre scale of local deformation in the implant–abutment connection (IAC) during and after cyclic loading. The microgap formation at the IAC has been subject to a number of studies as it has been proposed to be associated with long-term implant success. The next step in this scientific development is to focus on the in situ fatigue procedure of two-component dental implants. Therefore, an apparatus has been developed which is optimized for the in situ fatigue analysis of dental implants. This report demonstrates both the capability of in situ radioscopy and microtomography at the ID19 beamline for the study of cyclic deformation in dental implants. The first results show that it is possible to visualize fatigue loading of dental implants in real-time radioscopy in addition to the in situ fatigue tomography. For the latter, in situ microtomography is applied during the cyclic loading cycles in order to visualize the opening of the IAC microgap. These results concur with previous ex situ studies on similar systems. The setup allows for easily increasing the bending force, to simulate different chewing situations, and is, therefore, a versatile tool for examining the fatigue processes of dental implants and possibly other specimens

  9. In situ microradioscopy and microtomography of fatigue-loaded dental two-piece implants

    Energy Technology Data Exchange (ETDEWEB)

    Wiest, Wolfram; Zabler, Simon, E-mail: simon.zabler@physik.uni-wuerzburg.de [University of Würzburg (Germany); Rack, Alexander [European Synchrotron Radiation Facility (France); Fella, Christian; Balles, Andreas [University of Würzburg (Germany); Nelson, Katja; Schmelzeisen, Rainer [Medical Centre – University of Freiburg (Germany); Hanke, Randolf [University of Würzburg (Germany); Fraunhofer EZRT, Fürth (Germany)

    2015-10-09

    Results of a novel in situ microradiography and microtomography setup for the study of fatigue processes are presented. This setup is optimized for the requirements of dental implants and use at synchrotron imaging beamlines. Synchrotron real-time radioscopy and in situ microtomography are the only techniques providing direct visible information on a micrometre scale of local deformation in the implant–abutment connection (IAC) during and after cyclic loading. The microgap formation at the IAC has been subject to a number of studies as it has been proposed to be associated with long-term implant success. The next step in this scientific development is to focus on the in situ fatigue procedure of two-component dental implants. Therefore, an apparatus has been developed which is optimized for the in situ fatigue analysis of dental implants. This report demonstrates both the capability of in situ radioscopy and microtomography at the ID19 beamline for the study of cyclic deformation in dental implants. The first results show that it is possible to visualize fatigue loading of dental implants in real-time radioscopy in addition to the in situ fatigue tomography. For the latter, in situ microtomography is applied during the cyclic loading cycles in order to visualize the opening of the IAC microgap. These results concur with previous ex situ studies on similar systems. The setup allows for easily increasing the bending force, to simulate different chewing situations, and is, therefore, a versatile tool for examining the fatigue processes of dental implants and possibly other specimens.

  10. Effect of Static Load Hold Periods on the Corrosion Fatigue Behavior of Austenitic Stainless Steels in Simulated BWR Environments

    Science.gov (United States)

    Seifert, H. P.; Ritter, S.; Leber, H.

    The effect of static load hold times of 6 to 744 h on corrosion fatigue life of low- and highcarbon and stabilized austenitic stainless steels was investigated with both sharply notched and pre-cracked fracture mechanics specimens in simulated boiling water reactor (BWR) hydrogen (HWC) and normal water chemistry (NWC) at 288 °C. With regard to continuous cyclic saw tooth loading with a load ratio R close to zero in HWC environment, an increase of the genuine corrosion fatigue initiation life was observed with increasing static load hold periods at maximum or mean load of the applied load range, which seemed to saturate for long hold periods above 12 to 24 h. On the other hand, static hold periods at minimum load, where potential microcracks are closed, had no effect on genuine fatigue initiation life. Furthermore, the static load hold times had very little effect on the subsequent stationary short corrosion fatigue crack growth rates. Static hold times of up to 744 h had no effect on the corrosion fatigue crack growth rates in pre-cracked solution annealed stainless steel specimens in NWC and HWC environment. No significant effect of static load hold times on the technical corrosion fatigue initiation life are thus expected based on these preliminary results and the current US NRC regulatory guide 1.207 seems to be adequate from this point of view. A credit for a mitigating effect of long static load hold periods in the field cannot be derived from this work.

  11. Experimental studies on fatigue behavior of macro fiber composite (MFC) under mechanical loading

    Science.gov (United States)

    Pandey, Akash; Arockiarajan, A.

    2016-04-01

    Macro fiber Composite (MFC) finds its application in active control, vibration control and sensing elements. MFC can be laminated to surfaces or embedded in the structures to be used as an actuator and sensors. Due to its attractive properties and applications, it may be subjected to continuous loading, which leads to the deterioration of the properties. This study is focused on the fatigue lifetime of MFC under tensile and compressive loading at room temperature. Experiments were performed using 4 point bending setup, with MFC pasted at the center of the mild steel beam, to maintain constant bending stress along MFC. MFC is pasted using vacuum bagging technique. Sinusoidal loading is given to sample while maintaining R=0.13 (for tensile testing) and R=10 (for compressive testing). For d31 and d33 type of MFC, test was conducted for the strain values of 727 μ strain, 1400 μ strain, 1700 μ strain and 1900 μ strain for fatigue under tensile loading. For fatigue under compressive loading, both d33 and d31, was subjected to minimum strain of -2000 μ strain. Decrease in the slope of dielectric displacement vs. strain is the measure for the degradation. 10 percent decrease in the slope is set as the failure criteria. Experimental results show that MFC is very reliable below 1700 μ strain (R=0.13) at the room temperature.

  12. Influence of residual stresses and loading frequencies on corrosion fatigue crack growth behavior of weldments

    Science.gov (United States)

    Kitsunai, Y.; Tanaka, M.; Yoshihisa, E.

    1998-04-01

    The effect of residual stresses and loading frequencies on corrosion fatigue crack growth behavior under synthetic seawater with a free corrosion potential was examined using center-cracked tension (CCT) and single edge-cracked tension (SECT) specimens machined from mild steel butt-welded joints and the parent material. A series of fatigue crack growth tests were carried out with a sinusoidal loading wave form at a stress ratio of 0.05 with a loading frequency of 0.017 to 6.7 Hz. The results show that the crack growth resistance of a weld metal in the SECT specimen is higher than that in the CCT specimen regardless of testing conditions. The discrepancy is attributed to the differences in residual stress distribution at the crack tip in the two specimen geometries. The crack growth rate of the weld metal in the CCT specimen in seawater increased with decreasing loading frequency. The acceleration of the crack growth rate may be related to the occurrence of brittle striation or cleavage due to hydrogen embrittlement. It was found that the corrosion fatigue crack growth rate of a welded joint with tensile residual stress can be predicted using the effective stress intensity factor range, which takes into account both the residual stress and the loading frequency effects.

  13. 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.

  14. The effect of primary loading on fatigue life of cylindrical roller bearings

    Science.gov (United States)

    Crețu, S. S.

    2016-08-01

    Experimental and theoretical works shown that if a roller-raceway rolling contact is loaded in the elastic-plastic domain then, after the first rolling cycles, the material elastically shakedowns to a slightly modified axial profile and stable compressive residual stresses. Fatigue life tests carried out on four groups of NJ206 cylindrical roller bearings pointed out the superiority of the bearings groups that primary supported a few cycles of rolling loading in the elastic-plastic domain. An elastic-perfect plastic analysis was performed to reveal the role played by the roller's crowning geometry, operating clearance, misalignment angle and operating loads on contact pressures distributions achieved between each roller and the corresponding inner and outer raceways. The modified reference rating lives, evaluated using the lamina technique, exposed a good agreement with the values provided by fatigue life tests.

  15. WISPER and WISPERX: Final definition of two standardised fatigue loading sequences for wind turbine blades

    Science.gov (United States)

    Tenhave, A. A.

    1992-09-01

    Relevant information used to develop WISPER (Wind turbine reference Spectrum) and WISPERX, standardized variable amplitude test loading histories for use in the fatigue design of horizontal axis wind turbine blades, is presented. WISPER and WISPERX are based on flap load service measurements on nine different horizontal axis wind turbines, covering a wide range of materials, rotor diameters and geographical locations. Their backgrounds are reported, basic data and associated data handling procedures are described, and quantitative data analysis results and statistical information on both standards are presented. The information given will enable fatigue specialists to judge whether the standard will suit their test objectives and to check for correct application of the load sequences on their test equipment.

  16. Effect of Load Range on Probabilistic Fatigue Crack Growth Resistance in Flux Cored Arc Welded Api 2w GR. Steel

    Science.gov (United States)

    Kim, Seon-Jin; Sohn, Sang-Hoon; Sohn, Hye-Jeong

    The aim of this paper is to investigate the effects of the load range on the spatial variation of fatigue crack growth resistance in three different zones, WM, HAZ and BM for flux cored arc welded API 2W Gr. 50 steel using the stochastic model based on reliability theory. Experimental fatigue crack growth tests were performed on ASTM standard CT specimens. The results indicates that the load range has strong dependency on probabilistic fatigue crack growth for the three different zones WM, HAZ and BM, and also the spatial variation of fatigue crack growth resistance.

  17. Effects of thermal fatigue on shear punch strength of tooth-colored restoratives.

    Science.gov (United States)

    Melody, Fam Mei Shi; U-Jin, Yap Adrian; Natalie, Tan Wei Min; Elizabeth, Tay Wan Ling; Chien, Jessica Yeo Siu

    2016-01-01

    This study investigated the effect of thermal fatigue on the shear strength of a range of tooth-colored restorative materials including giomers, zirconia-reinforced glass ionomer cement (GIC), nano-particle resin-modified GIC, highly viscous GICs, and composite resin. Twenty specimens of each material were fabricated in standardized washers (17 mm outer diameter, 9 mm internal diameter, 1 mm thick). The specimens were cured, stored in 100% humidity at 37.5°C for 24 h, and randomly divided into two groups of 10. Group A specimens were nonthermocycled (NT) and stored in distilled water at 37°C for 168 h. Group B specimens were thermocycled (TC) for 10,000 cycles (168 h) with baths X, Y, and Z adjusted to 35°C, 15°C, and 45°C, respectively. Each cycle had dwell times of 28 s in X, and 2s in Y/Z in the order XYXZ. Specimens then underwent shear punch testing at a crosshead speed of 0.5 mm/min with a 2 kN load cell. Statistical analysis of shear strength was done using t-test and two-way ANOVA/Scheffe's post hoc test at significance level P IX GP Fast), no significant differences in shear strength were generally observed between the NT and TC groups. For both groups, the composite resin (Filtek Z250XT) had the highest shear strength while the zirconia-reinforced (zirconomer) and a highly viscous GIC (Ketac Molar Quick) had the lowest. The effect of thermocycling on shear strength was material dependent. Thermal fatigue, however, did not significantly influence the shear strength of most materials assessed. The "sculptable" composite and giomer were significantly stronger than the other materials evaluated. Shear strength of the "flowable" injectable hybrid giomer was intermediate between the composite and GICs.

  18. 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.

  19. Measuring footprints of wind turbine fatigue loads using monitoring methods. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Soeker Holger [ed.; Oestman, Anders; Thor, Sven-Erik [Aeronautical Research Inst. of Sweden, Bromma (Sweden)

    2001-03-01

    In the described research project the fatigue monitoring technique is applied on three 500kW wind turbines of the same type operating under different external conditions i.e. stand alone, wind farm and complex terrain conditions. Respective sites have been selected in Germany (stand alone and wind farm) and in Greece (complex terrain). During the measurement campaigns three new data bases have been created holding on-line monitoring data sets and time series data of the wind turbines' key loads. As a fourth data source time series measurements from the wind farm at Alsvik, Sweden, have been used for the project work. The central aspect of the work has been to establish 'footprints' of the measured load quantities for varying external conditions and to develop and accumulate skills and experience in reading the load information stored in such fatigue load 'footprints'. The term 'footprint' refers to the rainflow cycle frequency spectra of the observed load quantity recorded during a representative time interval together with a set of parameters describing the external and operational conditions during that time interval. In fatigue monitoring the rainflow counting data reduction technique is applied to the measured load samples on-line, reducing hardware memory and off-line evaluation demands. It has been attempted to introduce a framework of few statistic parameters that describe the fatigue load footprint and also relate to external physical conditions (s.a. average wind speed, turbulence etc.). In addition to the traditional formulations of statistic parameters in terms of time series statistics, special parameters adapted to on-line rainflow counted data sets have been examined. On-line fatigue footprint monitoring has so far been applied as a diagnostic tool. In the project the development of a scheme has been started that shall enable to normalise the footprinting results and furthermore to extrapolate them to external

  20. Fatigue Crack-Growth Resistance of Aluminum Alloys Under Spectrum Loading. Volume 2. Aluminum Lithium Alloys.

    Science.gov (United States)

    1985-12-01

    Bretz (Alcoa) 13a. TYPE OF REPORT 13b. TIME COVERED 14 DATE OF REPORT IYr . Mo.. Daye IS. PAGE COUNT Technical Report FROM 30Segt82 TO _1 Ma85 DECEMBER...alloy for both constant-amplitude loading and two F-18 load spectrums. One of the spectrums was dominated by tension loads ( TD ) and the other spectrum...indicating contact between the opposing fracture surfaces. Several observations can be made based on the TD and TC spectrum FCP test results: 1. The fatigue

  1. 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.

  2. High-Frequency Axial Fatigue Test Procedures for Spectrum Loading

    Science.gov (United States)

    2016-07-20

    closed-loop digital test frame controller with a command feedback compensation scheme was used to minimize controller error during testing. 15...controller response during variable amplitude loading, and a closed-loop digital test frame controller with a command feedback compensation scheme was...failures beyond 10 7 cycles can be caused by several competing failure mechanisms and may result in a transition from surface dominated crack

  3. Fracture Strength After Fatigue Loading of Lithium Disilicate Pressed Zirconia Crowns.

    Science.gov (United States)

    Kim, So-Yeun; Choi, Jae-Won; Ju, Sung-Won; Ahn, Jin-Soo; Yoon, Mi-Jung; Huh, Jung-Bo

    2016-01-01

    The aim of this study was to evaluate the fracture resistance of fatigued lithium disilicate pressed zirconia crowns versus other ceramic crowns. Lithium disilicate pressed zirconia, fluorapatite pressed zirconia, monolithic lithium disilicate, and monolithic zirconia crowns were fabricated. Cyclic and static loadings were applied to the mesiobuccal cusp tip after thermocycling and fracture strengths were recorded. Fatigued lithium disilicate pressed zirconia crowns were found to have a fracture resistance of 9,117.81 ± 727.04 N, compared with 9,240.61 ± 887.21 N for monolithic zirconia crowns, 3,030.18 ± 1,505.83 N for fluorapatite pressed zirconia crowns, and 4,173.94 ± 877.46 N for monolithic lithium disilicate crowns (P = .001). This in vitro study shows that fatigued lithium disilicate pressed zirconia and monolithic zirconia crowns have better fracture resistance than fluorapatite pressed zirconia and monolithic lithium disilicate crowns.

  4. Characterization of vitamin-cisplatin-loaded chitosan nano-particles for chemoprevention and cancer fatigue.

    Science.gov (United States)

    Othayoth, Rajath; Mathi, Pardhasaradhi; Bheemanapally, Khaggeswar; Kakarla, Lavanya; Botlagunta, Mahendran

    2015-01-01

    Vitamins have been shown to reduce chemotherapy-related fatigue (CRF) by conserving energy loss both during and after cancer treatment. However, it remains unknown whether this reduction of fatigue interferes with the cancer drugs or alters the effectiveness of these agents. The objective was to synthesize vitamin-cisplatin-loaded chitosan nano-particles for chemoprevention and cancer fatigue. Multi-vitamin (C, D3, and B12)-cisplatin composite nano-formulation called NanoCisVital (NCV) to overcome CRF. The interactions between vitamins and NCV were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and a particle size analyser. The chemo-preventive activity was performed by in vitro bio assays. SEM analysis showed spherical shape and the size is particles can be used to reduce CRF without much affecting the anti-cancer properties of cisplatin.

  5. 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.

  6. Effect of electrical pulse treatment on the thermal fatigue resistance of bionic compacted graphite cast iron processed in water

    International Nuclear Information System (INIS)

    Liu, Yan; Zhou, Hong; Su, Hang; Yang, Chunyan; Cheng, Jingyan; Zhang, Peng; Ren, Luquan

    2012-01-01

    Highlights: ► Electrical pulse treatment can reduce cracks on bionic units before thermal fatigue tests. ► Electrical pulse treatment can reduce crack sources during thermal fatigue tests. ► Thermal fatigue resistance of bionic units processed in water is enhanced. ► Thermal fatigue resistance of bionic CGI processed in water is improved. -- Abstract: In order to further enhance the thermal fatigue resistance of bionic compacted graphite cast iron (CGI) which is processed by laser in water, the electrical pulse treatment is applied to improve the thermal fatigue resistance of bionic units. The results show that the electrical pulse treatment causes the supersaturated carbon atoms located in the lattice of austenite to react with the iron atoms to form the Fe 3 C. The microstructures of the bionic units processed in water are refined by the electrical pulse treatment. The cracks on the bionic units are reduced by the electrical pulse treatment before the thermal fatigue tests; and during the tests, the thermal fatigue resistance of bionic units is therefore enhanced by reducing the crack sources. By this way, the thermal fatigue resistance of bionic CGI processed in water is improved.

  7. Fatigue Crack Propagation Under Variable Amplitude Loading Analyses Based on Plastic Energy Approach

    Directory of Open Access Journals (Sweden)

    Sofiane Maachou

    2014-04-01

    Full Text Available Plasticity effects at the crack tip had been recognized as “motor” of crack propagation, the growth of cracks is related to the existence of a crack tip plastic zone, whose formation and intensification is accompanied by energy dissipation. In the actual state of knowledge fatigue crack propagation is modeled using crack closure concept. The fatigue crack growth behavior under constant amplitude and variable amplitude loading of the aluminum alloy 2024 T351 are analyzed using in terms energy parameters. In the case of VAL (variable amplitude loading tests, the evolution of the hysteretic energy dissipated per block is shown similar with that observed under constant amplitude loading. A linear relationship between the crack growth rate and the hysteretic energy dissipated per block is obtained at high growth rates. For lower growth rates values, the relationship between crack growth rate and hysteretic energy dissipated per block can represented by a power law. In this paper, an analysis of fatigue crack propagation under variable amplitude loading based on energetic approach is proposed.

  8. 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.

  9. 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

  10. Effects of pulse current stimulation on the thermal fatigue crack propagation behavior of CHWD steel

    International Nuclear Information System (INIS)

    Lin, H.Q.; Zhao, Y.G.; Gao, Z.M.; Han, L.G.

    2008-01-01

    The fatigue crack propagating behaviors of cast hot working die (CHWD) steel untreated and treated by an electric current in the intermediate stage of thermal fatigue were investigated in the present study. The circle/elliptical heating affected zone (HAZ) was formed ahead of the notch tip on the fatigued specimens after pulse electric current stimulation. Both SEM observation and X-ray diffraction analysis revealed that pulse electric current stimulation refined grains/subgrains in the HAZs. With the prolonging of discharging duration, the grains/subgrains decreased in size and the dislocation density and microhardness increased gradually. The grain refinement and dislocation density increase played an important role in the material strengthening, which inevitably enhanced the propagation resistance and delayed the propagation of thermal fatigue cracks. Therefore, the pulse electric current stimulation was an effective method to improve the service lifetime of die material

  11. Thermal fatigue damage evaluation of a PWR NPP steam generator injection nozzle model subjected to thermal stratification phenomenon

    International Nuclear Information System (INIS)

    Leite da Silva, Luiz; Rodrigues Mansur, Tanius; Cimini Junior, Carlos Alberto

    2011-01-01

    Thermal stratification phenomenon with the same thermodynamic steam generator (SG) injection nozzle parameters was simulated. After 41 experiments, the experimental section was dismantled; cut and specimens were made of its material. Other specimens were made of the preserved pipe material. By comparing their fatigue tests results, the pipe material damage was evaluated. The water temperature layers and also the outside pipe wall temperatures were measured at the same level. Strains outside the pipe in 7 positions were measured. The experimental section develops thermal stratified flows, stresses and strains caused enlargement of material grain size and reduction in fatigue life.

  12. Assessment of Wind Parameter Sensitivity on Ultimate and Fatigue Wind Turbine Loads: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Amy N [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sethuraman, Latha [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Jonkman, Jason [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Quick, Julian [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2018-02-13

    Wind turbines are designed using a set of simulations to ascertain the structural loads that the turbine could encounter. While mean hub-height wind speed is considered to vary, other wind parameters such as turbulence spectra, sheer, veer, spatial coherence, and component correlation are fixed or conditional values that, in reality, could have different characteristics at different sites and have a significant effect on the resulting loads. This paper therefore seeks to assess the sensitivity of different wind parameters on the resulting ultimate and fatigue loads on the turbine during normal operational conditions. Eighteen different wind parameters are screened using an Elementary Effects approach with radial points. As expected, the results show a high sensitivity of the loads to the turbulence standard deviation in the primary wind direction, but the sensitivity to wind shear is often much greater. To a lesser extent, other wind parameters that drive loads include the coherence in the primary wind direction and veer.

  13. Assessment of Wind Parameter Sensitivity on Extreme and Fatigue Wind Turbine Loads

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Amy N [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sethuraman, Latha [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Jonkman, Jason [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Quick, Julian [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2018-01-12

    Wind turbines are designed using a set of simulations to ascertain the structural loads that the turbine could encounter. While mean hub-height wind speed is considered to vary, other wind parameters such as turbulence spectra, sheer, veer, spatial coherence, and component correlation are fixed or conditional values that, in reality, could have different characteristics at different sites and have a significant effect on the resulting loads. This paper therefore seeks to assess the sensitivity of different wind parameters on the resulting ultimate and fatigue loads on the turbine during normal operational conditions. Eighteen different wind parameters are screened using an Elementary Effects approach with radial points. As expected, the results show a high sensitivity of the loads to the turbulence standard deviation in the primary wind direction, but the sensitivity to wind shear is often much greater. To a lesser extent, other wind parameters that drive loads include the coherence in the primary wind direction and veer.

  14. Structural Performance of Polymer Fiber Reinforced Engineered Cementitious Composites Subjected to Static and Fatigue Flexural Loading

    Directory of Open Access Journals (Sweden)

    Mohamed A.A. Sherir

    2015-07-01

    Full Text Available This paper presents the influence of silica sand, local crushed sand and different supplementary cementing materials (SCMs to Portland cement (C ratio (SCM/C on the flexural fatigue performance of engineered cementitious composites (ECCs. ECC is a micromechanically-based designed high-performance polymer fiber reinforced concrete with high ductility which exhibits strain-hardening and micro-cracking behavior in tension and flexure. The relative high cost remains an obstacle for wider commercial use of ECC. The replacement of cement by SCMs, and the use of local sand aggregates can lower cost and enhance greenness of the ECC. The main variables of this study were: type and size of aggregates (local crushed or standard silica sand, type of SCMs (fly ash “FA” or slag, SCM/cement ratio of 1.2 or 2.2, three fatigue stress levels and number of fatigue cycles up to 1 million. The study showed that ECC mixtures produced with crushed sand (with high volume of fly ash and slag exhibited strain hardening behavior (under static loading with deformation capacities comparable with those made with silica sand. Class F-fly ash combined with crushed sand was the best choice (compared to class CI fly ash and slag in order to enhance the ECC ductility with slag–ECC mixtures producing lowest deflection capacity. FA–ECC mixtures with silica sand developed more damage under fatigue loading due to higher deflection evolution than FA–ECC mixtures with crushed sand.

  15. Fatigue behaviour FEM modeling of deep groove ball bearing mounted in automotive alternator submitted to variable loading

    Directory of Open Access Journals (Sweden)

    Azianou Ayao. E.

    2014-06-01

    Full Text Available Ball bearings subsurface materials are subjected to rolling contact fatigue with multiaxial stress state during loading cycle. The complex operating conditions of automotive bearings are different from classic operating conditions their fatigue crack initiation predicted by standards can be seen underestimated. This work presents a numerical approach of ball bearings to evaluate its fatigue behaviour in order to predict the life. A preliminary study has been done to evaluate the load distribution in the bearings. The results are integrated in a numerical dynamic model to study the bearing material rolling fatigue behaviour in constant and variable loading cases. By using fatigue criteria and damage laws, the analysis of stress state in bearing material leads to life prediction or the number of cycles before crack initiations. These results are compared to current standard methods used for ball bearing life prediction.

  16. The Effect of Fatigue Cracks on Fastener Flexibility, Load Distribution and Fatigue Crack Growth

    Science.gov (United States)

    2012-05-01

    Degrees of Freedom (DOF). The models were solved using NX Nastran [333]. The basic model of the joint has 163,729 tetrahedral 10-node elements and is...The model previously described was built using NASTRAN . Other simplified modeling methods of calculating load transfer are explored later using the...for”, MIL-S-8879C, 25 July 1991 332. Siemens, NX 7.5.0.32, Computer Modeling Software, 2009 333. Siemens, NX Nastran 7.0 64-bit ILP, Computer

  17. 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

  18. Simple criterion for predicting fatigue life under combined bending and torsion loading

    Directory of Open Access Journals (Sweden)

    K. Slámečka

    2017-07-01

    Full Text Available Multiaxial fatigue is a challenging problem and, consequently, a number of methods has been developed to aid in design of components and assemblies. Following the complexity of the problem, these approaches are often elaborate and it is difficult to use them for simple loading cases. In this paper, an empirical approach for constant amplitude, proportional axial and torsion loading is introduced to serve as a basic engineering tool for estimating fatigue life of rotational structural parts. The criterion relies on a quadratic equivalent-stress formula and requires one constant parameter to be determined from experiments. The comparison with similar classical stressbased approaches using data on diverse materials (several steels, aluminium alloy, and nickel base superalloy reveals very good agreement with experimental data.

  19. The Use of Spectral Method for Fatigue Life Assessment for Non-Gaussian Random Loads

    Directory of Open Access Journals (Sweden)

    Niesłony Adam

    2016-06-01

    Full Text Available The well-known problem with the fatigue lifetime assessment of non-Gaussian loading signals with the use of spectral method has been presented in the paper. A correction factors that transform the non-Gaussian signal into an equivalent Gaussian signal proposed by Bracessi et al. (2009 has been used for the purpose of lifetime calculations together with Palmgren-Miner Hypothesis. The calculations have been performed for the 10HNAP steel under random non-Gaussian load with four dominating frequencies. The signal has been generated on the test stand SHM250 for random tension-compression tests. The results with zero and non-zero mean stresses have been used to calculate the fatigue life with the frequency domain method based on Dirlik’s model and with a time domain method with the use of the rainflow cycle counting algorithm. The obtained calculation results have been compared with experimental results.

  20. The Fracture of Plasma-Treated Polyurethane Surface under Fatigue Loading

    Directory of Open Access Journals (Sweden)

    Ilya A. Morozov

    2018-02-01

    Full Text Available Plasma treatment of soft polymers is a promising technique to improve biomedical properties of the materials. The response to the deformation of such materials is not yet clear. Soft elastic polyurethane treated with plasma immersion ion implantation is subjected to fatigue uniaxial loading. The influence of the strain amplitude and the plasma treatment regime on damage character is discussed. Surface defects are studied in unloaded and stretched states of the material. As a result of fatigue loading, transverse cracks (with closed overlapping edges as well as with open edges deeply propagating into the polymer and longitudinal folds which are break and bend inward, appear on the surface. Hard edges of cracks cut the soft polymer which is squeezed from the bulk to the surface. The observed damages are related to the high stiffness of the modified surface and its transition to the polymer substrate.

  1. Experimental investigation of high cycle thermal fatigue in a T-junction piping system

    Energy Technology Data Exchange (ETDEWEB)

    Selvam, P. Karthick; Kulenovic, Rudi; Laurien, Eckart [Stuttgart Univ. (Germany). Inst. of Nuclear Technology and Energy Systems (IKE)

    2015-10-15

    High cycle thermal fatigue damage of structure in the vicinity of T-junction piping systems in nuclear power plants is of importance. Mixing of coolant streams at significant temperature differences causes thermal fluctuations near piping wall leading to gradual thermal degradation. Flow mixing in a T-junction is performed. The determined factors result in bending stresses being imposed on the piping system ('Banana effect').

  2. The influence of environment and frequency on near threshold and spectrum loading fatigue behaviour of SA508 RPV steel

    International Nuclear Information System (INIS)

    Achilles, R.D.; Bulloch, J.H.

    1987-01-01

    Since the discovery of an environmentally assisted fatigue crack growth phenomenon in Light Water Reactor (LWR) environments, numerous studies including Bamford (1980) and Kondo et al (1972), have been conducted over the past fifteen years. The present paper describes a series of fatigue tests in pure argon and a Pressurised Water Reactor (PWR) environment which have a number of differing loading sequences. (orig.)

  3. The influence of environment and frequency on near threshold and spectrum loading fatigue behaviour of SA508 RPV steel

    International Nuclear Information System (INIS)

    Achilles, R.D.; Bulloch, J.H.

    1987-01-01

    Since the discovery of an environmentally assisted fatigue crack growth phenomenon in Light Water Reactor (LWR) environments, numerous studies have been conducted over the past fifteen years. The present paper describes a series of fatigue tests in pure argon and a Pressurised Water Reactor (PWR) environment which have a number of differing loading sequences

  4. Acoustic Emission-Based Methodology to Evaluate Delamination Crack Growth Under Quasi-static and Fatigue Loading Conditions

    NARCIS (Netherlands)

    Saeedifar, M.; Ahmadi Najafabadi, Mehdi; Mohammadi, Kaivan; Fotouhi, Mohamad; Hosseini Toudeshky, Hossein; Shah Mohammadi, Mohammad Reza

    2018-01-01

    The aim of this study was to investigate the applicability of acoustic emission (AE) technique to evaluate delamination crack in glass/epoxy composite laminates under quasi-static and fatigue loading. To this aim, double cantilever beam specimens were subjected to mode I quasi-static and fatigue

  5. Experimental investigation on the effect of creep on the damage evolution of CFRP structures during fatigue loading

    NARCIS (Netherlands)

    Zarouchas, D.; Eleftheroglou, N.; Gdoutos, Emmanuel E.

    2016-01-01

    This paper presents an experimental investigation on the effect of creep on the damage evolution of Carbon Fiber Reinforced Polymer structures during fatigue loading. A new experimental campaign is proposed where unidirectional CFRP specimens are tested under the combination of fatigue and constant

  6. Effect of Micro-Structure on Fatigue Behavior of Intact Rocks under Completely Reversed Loading

    Directory of Open Access Journals (Sweden)

    Saeed Jamali Zavareh

    2017-01-01

    Full Text Available Rock formations and structures can be subjected to both static and dynamic loadings. Static loadings resulting from different sources such as gravity and tectonic forces and dynamic forces are intermittently transmitted via vibrations of the earth’s crust, through major earthquakes, rock bursts, rock blasting and drilling and also, traffic. Reaction of rocks to cyclic and repetitive stresses resulting from dynamic loads has been generally neglected with the exception of a few rather limited studies. In this study, , two crystalline quarry stones in Iran; (Natanz gabbro and Green onyx and one non-crystalline rock (Asmari limestone are used to evaluate the effect of micro-structure of intact rock on fatigue behavior. These rocks have different mineral compositions and formation conditions. A new apparatus based on rotating beam fatigue testing machine (R.R.Moore, which is commonly used for laboratory fatigue test in metals, is developed and fatigue behavior and existence of the endurance limit were evaluated for the mentioned rocks based on stress-life method. The obtained results in the variation of applied amplitude stress versus loading cycle number (S-N diagram followed common relationship in other materials. In addition, the endurance limit is perceived for all tested rocks. The results also illustrated that the endurance limits for all types of tested rocks in this study are ranged between 0.4 and 0.6 of their tensile strengths. The endurance limit to tensile strength fraction of green onyx and Natanz gabbro were approximated in a higher value compared to the Asmari limestone with non-crystalline micro-structure.

  7. Computation of Onset and Growth of Delamination in Double Cantilever beam Specimens Subjected to Fatigue Loading

    OpenAIRE

    Krishna Lok Singh; Madhu K.S; Mallikarjun Vaggar

    2014-01-01

    In this article, the delamination onset and growth behavior of double cantilever beam (DCB) specimens has been presented. The modeling of a debonded region using master and slave surface technique for DCB specimens is done in ABAQUS CAE. The analysis of DCB specimens comprising of fatigue cyclic load has been done in ABAQUS. An onset and Paris delamination growth regimes are plotted. The growth regime being linear in log-log scale, the prediction of constants of this regime has been obtained ...

  8. The Influence of Loading Ratio on Fatigue Crack Propagation Through a Bi-material Interface

    Czech Academy of Sciences Publication Activity Database

    Náhlík, Luboš; Hutař, Pavel; Knésl, Zdeněk

    2007-01-01

    Roč. 348-349, - (2007), s. 317-320 ISSN 1013-9826. [International Conference on Fracture and Damage Mechanics /6./. Funchal, Madeira, 17.07.2007-19.07.2007] R&D Projects: GA ČR(CZ) GA101/05/0320 Institutional research plan: CEZ:AV0Z20410507 Keywords : bi-material interface * loading ratio * plasticity-induced crack closure * critical stress Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.224, year: 2005

  9. Fatigue failure load of two resin-bonded zirconia-reinforced lithium silicate glass-ceramics: Effect of ceramic thickness.

    Science.gov (United States)

    Monteiro, Jaiane Bandoli; Riquieri, Hilton; Prochnow, Catina; Guilardi, Luís Felipe; Pereira, Gabriel Kalil Rocha; Borges, Alexandre Luiz Souto; de Melo, Renata Marques; Valandro, Luiz Felipe

    2018-03-24

    To evaluate the effect of ceramic thickness on the fatigue failure load of two zirconia-reinforced lithium silicate (ZLS) glass-ceramics, adhesively cemented to a dentin analogue material. Disc-shaped specimens were allocated into 8 groups (n=25) considering two study factors: ZLS ceramic type (Vita Suprinity - VS; and Celtra Duo - CD), and ceramic thickness (1.0; 1.5; 2.0; and 2.5mm). A trilayer assembly (ϕ=10mm; thickness=3.5mm) was designed to mimic a bonded monolithic restoration. The ceramic discs were etched, silanized and luted (Variolink N) into a dentin analogue material. Fatigue failure load was determined using the Staircase method (100,000 cycles at 20Hz; initial fatigue load ∼60% of the mean monotonic load-to-failure; step size ∼5% of the initial fatigue load). A stainless-steel piston (ϕ=40mm) applied the load into the center of the specimens submerged in water. Fractographic analysis and Finite Element Analysis (FEA) were also performed. The ceramic thickness influenced the fatigue failure load for both ZLS materials: Suprinity (716N up to 1119N); Celtra (404N up to 1126N). FEA showed that decreasing ceramic thickness led to higher stress concentration on the cementing interface. Different ZLS glass-ceramic thicknesses influenced the fatigue failure load of the bonded system (i.e. the thicker the glass ceramic is, the higher the fatigue failure load will be). Different microstructures of the ZLS glass-ceramics might affect the fatigue behavior. FEA showed that the thicker the glass ceramic is, the lower the stress concentration at the tensile surface will be. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

  10. THE FATIGUE DURABILITY OF THE MODIFIED ASPHALT CONCRETE UNDER THE EFFECT OF INTENSIVE TRAFFIC LOADS

    Directory of Open Access Journals (Sweden)

    Yuri KALGIN

    2016-06-01

    Full Text Available The problem of prediction of the service life of asphalt concrete surface constructed with modified asphalt concrete application onto a traffic lane is examined. Asphalt concrete behaviour in road surface under the traffic loads was analysed. There were shown The results of experiments and their mathematical analysis of the assessment of standard and modified cold asphalt concrete fatigue life on road surface were shown. The service life of an asphalt concrete surface covered with standard and modified cold asphalt concrete is examined. The prediction has been received with an account of stress relaxation processes in asphalt concrete pavement and unevenness of traffic load application.

  11. Optimized Power Dispatch in Wind Farms for Power Maximizing Considering Fatigue Loads

    DEFF Research Database (Denmark)

    Zhang, Baohua; N. Soltani, Mohsen; Hu, Weihao

    2018-01-01

    load of the shafts and the towers within a certain range from the values using traditional strategy, which adopts maximum power point tracking (MPPT) control for each WT. A WT derating control strategy is included in the WT controller and the fatigue load for the tower and shaft is evaluated offline...... at a series of turbulence intensity, mean wind speed and active power reference to form a lookup table, which is used for the WF control. The proposed strategy is compared with WT MPPT control strategy and WF MPPT control strategy. The simulation results show the effectiveness of the proposed strategy....

  12. Effects of striated laser tracks on thermal fatigue resistance of cast iron samples with biomimetic non-smooth surface

    International Nuclear Information System (INIS)

    Tong, Xin; Zhou, Hong; Liu, Min; Dai, Ming-jiang

    2011-01-01

    In order to enhance the thermal fatigue resistance of cast iron materials, the samples with biomimetic non-smooth surface were processed by Neodymium:Yttrium Aluminum Garnet (Nd:YAG) laser. With self-controlled thermal fatigue test method, the thermal fatigue resistance of smooth and non-smooth samples was investigated. The effects of striated laser tracks on thermal fatigue resistance were also studied. The results indicated that biomimetic non-smooth surface was benefit for improving thermal fatigue resistance of cast iron sample. The striated non-smooth units formed by laser tracks which were vertical with thermal cracks had the best propagation resistance. The mechanisms behind these influences were discussed, and some schematic drawings were introduced to describe them.

  13. Effects of Variable Contact Load on Fretting Fatigue Behavior of Shot-Peened and Un-Peened Titanium Alloy

    National Research Council Canada - National Science Library

    Lee, Chia-hwa

    2004-01-01

    .... The primary goal of this study was to explore fretting fatigue behavior under constant and variable contact load configurations using both shot-peened and un-peened specimens made up of Ti-6Al-4V alloy...

  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. Accelerated fatigue testing of dentin-composite bond with continuously increasing load.

    Science.gov (United States)

    Li, Kai; Guo, Jiawen; Li, Yuping; Heo, Young Cheul; Chen, Jihua; Xin, Haitao; Fok, Alex

    2017-06-01

    The aim of this study was to evaluate an accelerated fatigue test method that used a continuously increasing load for testing the dentin-composite bond strength. Dentin-composite disks (ϕ5mm×2mm) made from bovine incisor roots were subjected to cyclic diametral compression with a continuously increasingly load amplitude. Two different load profiles, linear and nonlinear with respect to the number of cycles, were considered. The data were then analyzed by using a probabilistic failure model based on the Weakest-Link Theory and the classical stress-life function, before being transformed to simulate clinical data of direct restorations. All the experimental data could be well fitted with a 2-parameter Weibull function. However, a calibration was required for the effective stress amplitude to account for the difference between static and cyclic loading. Good agreement was then obtained between theory and experiments for both load profiles. The in vitro model also successfully simulated the clinical data. The method presented will allow tooth-composite interfacial fatigue parameters to be determined more efficiently. With suitable calibration, the in vitro model can also be used to assess composite systems in a more clinically relevant manner. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  16. Simplified rotor load models and fatigue damage estimates for offshore wind turbines.

    Science.gov (United States)

    Muskulus, M

    2015-02-28

    The aim of rotor load models is to characterize and generate the thrust loads acting on an offshore wind turbine. Ideally, the rotor simulation can be replaced by time series from a model with a few parameters and state variables only. Such models are used extensively in control system design and, as a potentially new application area, structural optimization of support structures. Different rotor load models are here evaluated for a jacket support structure in terms of fatigue lifetimes of relevant structural variables. All models were found to be lacking in accuracy, with differences of more than 20% in fatigue load estimates. The most accurate models were the use of an effective thrust coefficient determined from a regression analysis of dynamic thrust loads, and a novel stochastic model in state-space form. The stochastic model explicitly models the quasi-periodic components obtained from rotational sampling of turbulent fluctuations. Its state variables follow a mean-reverting Ornstein-Uhlenbeck process. Although promising, more work is needed on how to determine the parameters of the stochastic model and before accurate lifetime predictions can be obtained without comprehensive rotor simulations. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  17. Role of Lactobacillus acidophilus loaded floating beads in chronic fatigue syndrome: behavioral and biochemical evidences.

    Science.gov (United States)

    Singh, P K; Chopra, K; Kuhad, A; Kaur, I P

    2012-04-01

      In recent years the interface between neuropsychiatry and gastroenterology has converged in to a new discipline referred to as enteric neuroscience. Implications of brain-gut communication in the pathogenesis of psychiatric disorders indicate a possible role of suitably packaged/delivered probiotics as newer therapeutic options. In the present study probable role of per-oral administration of free Lactobacillus acidophilus (LAB) and LAB loaded alginate beads in attenuation of the symptoms associated with chronic fatigue syndrome (CFS) were evaluated.   Chronic fatigue syndrome following physical fatigue was induced in rats by forcing them to swim (forced swim test; FST) in water till exhaustion, after weighing them down with 10% their body weight, daily for 28 days. Immobility (I) and postswim fatigue time (PSF) were taken as suitable markers. Free LAB and LAB loaded floating beads (FBs) were administered, from 21 to 28 days.   Immobility and PSF were found to increase considerably in FST rats (665 ± 22 s and 196 ± 6 s) as compared with the naïve (32 ± 7 s and 22 ± 2 s) at 20 days, establishing severe fatigue like behavior. FST control group exhibited significant (P < 0.05) hypertrophy of spleen, hypotrophy of thymus, and increased oxido-nitrosative stress in brain and tumor necrosis factor-α (TNF-α) levels in serum. Treatment with LAB and LAB FBs significantly decreased I and PSF and attenuated (P < 0.05) oxido-nitrosative stress and TNF-α levels. Spleen and thymus were also restored to their original size in this group.   The findings suggest a valuable therapeutic role of LAB especially when incorporated into alginate beads for the treatment of CFS. © 2012 Blackwell Publishing Ltd.

  18. Metallurgical investigation of 2 austenitic stainless steel sodium mixers cracked in service by thermal fatigue

    International Nuclear Information System (INIS)

    Donati, J.R.; Keroulas, F.de; Masse, J.

    1979-01-01

    Two sodium mixers in the sodium heated steam generator test circuit at the EDF Renardieres centre developed leaks after approximately 7,000 hours operation under power. In both cases the investigation found cracking due to plastic fatigue caused by stresses of thermal origin. In one case the damage is explained solely by the size of the temperature oscillations; in the other case, unfavourable geometry reduced the duration of the initiation phase. Different types of cracking characteristic of thermal fatigue in sodium are presented. (author)

  19. Testing of thermal fatigue resistance of tools and rolls for hot working

    Science.gov (United States)

    Terčelj, Milan; Fazarinc, Matevž; Kugler, Goran

    2017-09-01

    In the present contribution two tests for thermal fatigue testing, which have been developed in our group, are presented. First test has provided internal cooling system of sample, while second has external cooling. For both tests heating and cooling of samples are computer guided that enables very reliable results of testing. The first test is more appropriate for testing the base material, i.e. roll cast irons, roll steels, tool steels. The second test is more appropriate for experiments that are aimed for selection of appropriate tool surface treatment, i.e. laser cladding, nitriding, coating, etc., and to compare and to achieve improved resistance against thermal fatigue of produced surface layers.

  20. Effects of material and loading variables on fatigue life of carbon and low-alloy steels in LWR environments

    International Nuclear Information System (INIS)

    Chopra, O.K.; Shack, W.J.

    1995-03-01

    The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Section III of the Code specifies fatigue design curves for structural materials. While effects of reactor coolant environments are not explicitly addressed by the design curves, test data suggest that the Code fatigue curves may not always be adequate in coolant environments. This paper reports the results of recent fatigue tests that examine the effects of steel type, strain rate, dissolved oxygen level, strain range, loading waveform, and surface morphology on the fatigue life of A106-Gr B carbon steel and A533-Gr B low-alloy steel in water

  1. Absolute and Relative Training Load and Its Relation to Fatigue in Football

    Directory of Open Access Journals (Sweden)

    Unai Zurutuza

    2017-06-01

    Full Text Available The aim of the study was to assess the relationship of external and internal training load (TL indicators with the objective and subjective fatigue experienced by 15 semi-professional football players, over eight complete weeks of the competition period in the 2015–2016 season, which covered microcycles from 34th to 41st. The maximum heart rate (HRmax and maximum speed (Vmax of all the players were previously measured in specific tests. The TL was monitored via questionnaires on rating of perceived exertion (RPE, pulsometers and GPS devices, registering the variables: total distance (TD, player load 2D (PL2D, TD at >80% of the Vmax (TD80, TD in deceleration at < -2 m⋅sec-2 (TDD <-2, TD in acceleration >2 m⋅sec-2 (TDA >2, Edwards (ED, time spent at between 50 and 80% (50–80% HRmax, 80–90% (80–90% HRmax, and >90% of the HRmax (>90% HRmax, and RPE both respiratory/thoracic (RPEres and leg/muscular (RPEmus. All the variables were analyzed taking into account both the absolute values accumulated over the week and the normalized values in relation to individual mean competition values. Neuromuscular fatigue was measured objectively using the countermovement jump test and subjectively via the Total Quality Recovery (TQR scale questionnaire. Analytical correlation techniques were later applied within the general linear model. There is a correlation between the fatigue experienced by the player, assessed objectively and subjectively, and the load accumulated over the week, this being assessed in absolute and relative terms. Specifically, the load relative to competition correlated with the physical variables TD (-0.279, PL2D (-0.272, TDD < -2 (-0.294, TDA >2 (-0.309, and sRPEmus (-0.287. The variables related to heart rate produced a higher correlation with TQR. There is a correlation between objectively and subjectively assessed fatigue and the accumulated TL of a player over the week, with a higher sensitivity being shown when compared to

  2. Concept of a Maneuvering Load Control System and Effect on the Fatigue Life Extension

    Directory of Open Access Journals (Sweden)

    N. Paletta

    Full Text Available Abstract This paper presents a methodology for the conceptual design of a Maneuver Load Control system taking into account the airframe flexibility. The system, when switched on, is able to minimize the bending moment augmentation at a wing station near the wing root during an unsteady longitudinal maneuver. The reduction of the incremental wing bending moment due to maneuvers can lead to benefits such as improved pay-loads/gross weight capabilities and/or extended structural fatigue life. The maneuver is performed by following a desired vertical load factor law with elevators deflections, starting from the trim equilibrium in level flight. The system observes load factor and structural bending through accelerometers and calibrated strain sensors and then sends signals to a computer that symmetrically actuates ailerons for reducing the structural bending and elevators for compensating the perturbation to the longitudinal equilibrium. The major limit of this kind of systems appears when it has to be installed on commercial transport aircraft for reduced OEW or augmented wing aspect-ratio. In this case extensive RAMS analyses and high redundancy of the MLC related sub-systems are required by the Certification Authority. Otherwise the structural design must be performed at system off. Thus the unique actual benefit to be gained from the adoption of a MLC system on a commercial transport is the fatigue life extension. An application to a business aircraft responding to the EASA Certification Specifications, Part 25, has been performed. The aircraft used for the numerical application is considered only as a test case-study. Most of design and analysis considerations are applicable also to other aircraft, such as unmanned or military ones, although some design requirements can be clearly different. The estimation of the fatigue life extension of a structural joint (wing lower skin-stringer, located close to the wing root, has been estimated by showing

  3. Stress Analysis and Fatigue Behaviour of PTFE-Bronze Layered Journal Bearing under Real-Time Dynamic Loading

    Science.gov (United States)

    Duman, M. S.; Kaplan, E.; Cuvalcı, O.

    2018-01-01

    The present paper is based on experimental studies and numerical simulations on the surface fatigue failure of the PTFE-bronze layered journal bearings under real-time loading. ‘Permaglide Plain Bearings P10’ type journal bearings were experimentally tested under different real time dynamic loadings by using real time journal bearing test system in our laboratory. The journal bearing consists of a PTFE-bronze layer approximately 0.32 mm thick on the steel support layer with 2.18 mm thick. Two different approaches have been considered with in experiments: (i) under real- time constant loading with varying bearing widths, (ii) under different real-time loadings at constant bearing widths. Fatigue regions, micro-crack dispersion and stress distributions occurred at the journal bearing were experimentally and theoretically investigated. The relation between fatigue region and pressure distributions were investigated by determining the circumferential pressure distribution under real-time dynamic loadings for the position of every 10° crank angles. In the theoretical part; stress and deformation distributions at the surface of the journal bearing analysed by using finite element methods to determine the relationship between stress and fatigue behaviour. As a result of this study, the maximum oil pressure and fatigue cracks were observed in the most heavily loaded regions of the bearing surface. Experimental results show that PTFE-Bronze layered journal bearings fatigue behaviour is better than the bearings include white metal alloy.

  4. The origins of Asteroidal rock disaggregation: Interplay of thermal fatigue and microstructure

    Science.gov (United States)

    Hazeli, Kavan; El Mir, Charles; Papanikolaou, Stefanos; Delbo, Marco; Ramesh, K. T.

    2018-04-01

    The distributions of size and chemical composition in regolith on airless bodies provide clues to the evolution of the solar system. Recently, the regolith on asteroid (25143) Itokawa, visited by the JAXA Hayabusa spacecraft, was observed to contain millimeter to centimeter sized particles. Itokawa boulders commonly display well-rounded profiles and surface textures that appear inconsistent with mechanical fragmentation during meteorite impact; the rounded profiles have been hypothesized to arise from rolling and movement on the surface as a consequence of seismic shaking. This investigation provides a possible explanation of these observations by exploring the primary crack propagation mechanism during thermal fatigue of a chondrite. Herein, we present the evolution of the full-field strains on the surface as a function of temperature and microstructure, and examine the crack growth during thermal cycling. Our experimental results demonstrate that thermal-fatigue-driven fracture occurs under these conditions. The results suggest that the primary fatigue crack path preferentially follows the interfaces between monominerals, leaving the minerals themselves intact after fragmentation. These observations are explained through a microstructure-based finite element model that is quantitatively compared with our experimental results. These results on the interactions of thermal fatigue cracking with the microstructure may ultimately allow us to distinguish between thermally induced fragments and impact products.

  5. Effect of additional holes on transient thermal fatigue life of gas turbine casing

    Directory of Open Access Journals (Sweden)

    H. Bazvandi

    2017-10-01

    Full Text Available Gas turbines casings are susceptible to cracking at the edge of eccentric pin hole, which is the most likely position for crack initiation and propagation. This paper describes the improvement of transient thermal fatigue crack propagation life of gas turbines casings through the application of additional holes. The crack position and direction was determined using non-destructive tests. A series of finite element patterns were developed and tested in ASTM-A395 elastic perfectly-plastic ductile cast iron. The effect of arrangement of additional holes on transient thermal fatigue behavior of gas turbines casings containing hole edge cracks was investigated. ABAQUS finite element package and Zencrack fracture mechanics code were used for modeling. The effect of the reduction of transient thermal stress distribution around the eccentric pin hole on the transient thermal fatigue crack propagation life of the gas turbines casings was discussed. The result shows that transient thermal fatigue crack propagation life could be extended by applying additional holes of larger diameter and decreased by increasing the vertical distance, angle, and distance between the eccentric pin hole and the additional holes. The results from the numerical predictions were compared with experimental data.

  6. Thermally Induced Ultra High Cycle Fatigue of Copper Alloys of the High Gradient Accelerating Structures

    CERN Document Server

    Heikkinen, Samuli; Wuensch, Walter

    2010-01-01

    In order to keep the overall length of the compact linear collider (CLIC), currently being studied at the European Organization for Nuclear Research (CERN), within reasonable limits, i.e. less than 50 km, an accelerating gradient above 100 MV/m is required. This imposes considerable demands on the materials of the accelerating structures. The internal surfaces of these core components of a linear accelerator are exposed to pulsed radio frequency (RF) currents resulting in cyclic thermal stresses expected to cause surface damage by fatigue. The designed lifetime of CLIC is 20 years, which results in a number of thermal stress cycles of the order of 2.33•1010. Since no fatigue data existed in the literature for CLIC parameter space, a set of three complementary experiments were initiated: ultra high cycle mechanical fatigue by ultrasound, low cycle fatigue by pulsed laser irradiation and low cycle thermal fatigue by high power microwaves, each test representing a subset of the original problem. High conductiv...

  7. Thermal fatigue behavior of H-13 die steel for aluminum die casting with various ion sputtered coatings

    Science.gov (United States)

    Nieh, C. Y.; Wallace, J. F.

    1981-01-01

    Sputtered coatings of Mo, W, Pt, Ag, Au, Co, Cr, Ni, Ag + Cu, Mo + Pt, Si3N4, A1N, Cr3C2, Ta5Si3, and ZrO2 were applied to a 2-inch-square, 7-inch-long thermal fatigue test specimen which was then internally water cooled and alternately immersed in molten aluminum and cooled in air. After 15,000 cycles the thermal fatigue cracks at the specimen corners were measured. Results indicate that a significant improvement in thermal fatigue resistance was obtained with platinum, molybdenum, and tungsten coatings. Metallographic examination indicates that the improvement in thermal fatigue resistance resulted from protection of the surface of the die steel from oxidation. The high yield strength and ductility of molybdenum and tungsten contributed to the better thermal fatigue resistance.

  8. Physical fatigue and the perception of differences in load: a signal detection approach.

    Science.gov (United States)

    Blitz, P S; Van Moorst, A

    1978-06-01

    Workload is an important factor related to perception of physical fatigue. Because a person engaged in physical activity eventually leading to painful exhaustion is in a pay-off situation, the paradigm of signal detection might be applicable to the perception of differences in load. Two male track and field athletes, aged 22 and 24 yr., participated in two experiments. In Exp. 1 difference threshold were determined with 25%, 50%, 60%, 65% and 70% of VO2 max as basic loads on a bicycle ergometer. Results showed a decreasing k over increasing work loads, contrary to Weber's law. In Exp. 2 a non-parametric signal detection procedure was used, with 25%, 40%, 50% and 60% of VO2 max as noise levels and a signal intensity of 1.5 watt in every condition. A chi 2 test for a 2-factor design showed only an effect of noise level. The converging results of both experiments led to the conclusion of a relative increasing sensitivity across increasing work loads. The main goal for future research will be to develop the signal detection method as a framework for research on fatigue.

  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. Surface modification and fatigue behavior of nitinol for load bearing implants

    Science.gov (United States)

    Bernard, Sheldon A.

    Musculoskeletal disorders are recognized amongst the most significant human health problems that exist today. Even though considerable research and development has gone towards understanding musculoskeletal disorders, there is still lack of bone replacement materials that are appropriate for restoring lost structures and functions, particularly for load-bearing applications. Many materials on the market today, such as titanium and stainless steel, suffer from significantly higher modulus than natural bone and low bioactivity leading to stress shielding and implant loosening over longer time use. Nitinol (NiTi) is an equiatomic intermetallic compound of nickel and titanium whose unique biomechanical and biological properties contributed to its increasing use as a biomaterial. An innovative method for creating dense and porous net shape NiTi alloy parts has been developed to improve biological properties while maintaining comparable or better mechanical properties than commercial materials that are currently in use. Laser engineered net shaping (LENS(TM)) and surface electrochemistry modification was used to create dense/porous samples and micro textured surfaces on NiTi parts, respectively. Porous implants are known to promote cell adhesion and have a low elastic modulus, a combination that can significantly increase the life of an implant. However, porosity can significantly reduce the fatigue life of an implant, and very little work has been reported on the fatigue behavior of bulk porous metals, specifically on porous nitinol alloy. High-cycle rotating bending and compression-compression fatigue behavior of porous NiTi fabricated using LENS(TM) were studied. In cyclic compression loading, plastic strain increased with increasing porosity and it was evident that maximum strain was achieved during the first 50000 cycles and remained constant throughout the remaining loading. No failures were observed due to loading up to 150% of the yield strength. When subjected

  11. Prediction of composite fatigue life under variable amplitude loading using artificial neural network trained by genetic algorithm

    Science.gov (United States)

    Rohman, Muhamad Nur; Hidayat, Mas Irfan P.; Purniawan, Agung

    2018-04-01

    Neural networks (NN) have been widely used in application of fatigue life prediction. In the use of fatigue life prediction for polymeric-base composite, development of NN model is necessary with respect to the limited fatigue data and applicable to be used to predict the fatigue life under varying stress amplitudes in the different stress ratios. In the present paper, Multilayer-Perceptrons (MLP) model of neural network is developed, and Genetic Algorithm was employed to optimize the respective weights of NN for prediction of polymeric-base composite materials under variable amplitude loading. From the simulation result obtained with two different composite systems, named E-glass fabrics/epoxy (layups [(±45)/(0)2]S), and E-glass/polyester (layups [90/0/±45/0]S), NN model were trained with fatigue data from two different stress ratios, which represent limited fatigue data, can be used to predict another four and seven stress ratios respectively, with high accuracy of fatigue life prediction. The accuracy of NN prediction were quantified with the small value of mean square error (MSE). When using 33% from the total fatigue data for training, the NN model able to produce high accuracy for all stress ratios. When using less fatigue data during training (22% from the total fatigue data), the NN model still able to produce high coefficient of determination between the prediction result compared with obtained by experiment.

  12. Effects of Electromigration on the Creep and Thermal Fatigue Behavior of Sn58Bi Solder Joints

    Science.gov (United States)

    Zuo, Yong; Ma, Limin; Guo, Fu; Qiao, Lei; Shu, Yutian; Lee, Andree; Subramanian, K. N.

    2014-12-01

    Electromigration (EM), creep, and thermal fatigue (TF) are the most important aspects of the reliability of electronic solder joints, the failure mechanisms of which used to be investigated separately. However, current, mechanical loading, and temperature fluctuation usually co-exist under real service conditions, especially as the magnitude of current density is increasing with joint miniaturization. The importance of EM can no longer be simply ignored when analyzing the creep and TF behavior of a solder joint. The published literature reports that current density substantially changes creep rate, but the intrinsic mechanism is still unclear. Hence, the purpose of this study was to investigate the effects of EM on the creep and TF behavior of Sn58Bi solder joints by analyzing the evolution of electrical resistance and microstructure. The results indicated that EM shortens the lifetime of creep or TF of Sn58Bi solder joints. During creep, EM delays or suppresses the cracking and deforming process, so fracture occurs at the cathode interface. During TF, EM suppresses the cracking process and changes the interfacial structure.

  13. Damage evaluation under thermal fatigue of a vertical target full scale component for the ITER divertor

    International Nuclear Information System (INIS)

    Missirlian, M.; Escourbiac, F.; Merola, M.; Durocher, A.; Bobin-Vastra, I.; Schedler, B.

    2007-01-01

    An extensive development programme has been carried out in the EU on high heat flux components within the ITER project. In this framework, a Full Scale Vertical Target (VTFS) prototype was manufactured with all the main features of the corresponding ITER divertor design. The fatigue cycling campaign on CFC and W armoured regions, proved the capability of such a component to meet the ITER requirements in terms of heat flux performances for the vertical target. This paper discusses thermographic examination and thermal fatigue testing results obtained on this component. The study includes thermal analysis, with a tentative proposal to evaluate with finite element approach the location/size of defects and the possible propagation during fatigue cycling

  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. 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

  16. A discrete element model for damage and fracture of geomaterials under fatigue loading

    Science.gov (United States)

    Gao, Xiaofeng; Koval, Georg; Chazallon, Cyrille

    2017-06-01

    Failure processes in geomaterials (concrete, asphalt concrete, masonry, etc.) under fatigue loading (repeated moving loads, cycles of temperature, etc.) are responsible for most of the dysfunctions in pavements, brick structures, etc. In the beginning of the lifetime of a structure, the material presents only inner defects (micro cracks, voids, etc.). Due to the effect of the cyclic loading, these small defects tend to grow in size and quantity which damage the material, reducing its stiffness. With a relatively high number of cycles, these growing micro cracks become large cracks, which characterizes the fracture behavior. From a theoretical point of view, both mechanisms are treated differently. Fracture is usually described locally, with the propagation of cracks defined by the energy release rate at the crack tip; damage is usually associated to non-local approaches. In the present work, damage and fracture mechanics are combined in a local discrete element approach.

  17. Anisotropy of thermal fatigue properties of cold-rolled TiNi sheet

    NARCIS (Netherlands)

    Mulder, J.H.; Mulder, J.H.; Thoma, P.E.; Beyer, J.

    1994-01-01

    The texture of cold-rolled and heat-treated TiNi sheet has been measured and designated as {110}(110)p. This material has been used in thermal fatigue tests during and after which the anisotropy and development of several thermomechanical properties, such as transformation temperatures and strains,

  18. In-Pile thermal fatigue of First Wall mock-ups under ITER relevant conditions

    International Nuclear Information System (INIS)

    Blom, F.; Schmalz, F.; Kamer, S.; Ketema, D.J.

    2006-01-01

    The objective of this study is to perform in-pile thermal fatigue testing of three actively cooled First Wall (FW) mock-ups to check the effect of neutron irradiation on the Be/CuCrZr joints under representative FW operation conditions. Three FW mock-ups with Beryllium armor tiles will be neutron irradiated at 1 dpa (in Be) with parallel thermal fatigue testing for 30,000 cycles. The temperatures, stress distributions and stress amplitudes at the Be/CuCrZr interface of the mock-ups will be as close as possible to the values calculated for ITER FW panels. For this objective the PWM mocks-up subjected to thermal fatigue will be integrated with high density (W) plates on the Be-side to provide heat flux by nuclear heating. The assembly will be placed in the pool-side facility of the HFR and thermal cycling is then arranged by mechanical movement towards and from the core box. As the thermal design of the irradiation rig is very critical a pilot-irradiation will be performed to cross check the models used in the thermal design of the rig. The project is currently in the design phase of both the pilot and actual irradiation rig. The irradiation of the actual rig is planned to start at mid 2007 and last for two years. (author)

  19. The effect of elbow flexor fatigue on spine kinematics and muscle activation in response to sudden loading at the hands.

    Science.gov (United States)

    Zwambag, Derek P; Freeman, Nikole E; Brown, Stephen H M

    2015-04-01

    Sudden loads, originating at either the hands or the feet, can cause injury to spine structures. As muscles are primarily responsible for stabilization following a perturbation, the effect of spine muscle fatigue in this context has been well investigated. However, the effect of fatigue of arm muscles, which can help control perturbations originating at the hands, on the spine is unknown. The purpose of this study was to determine if the magnitude of spine flexion or the pre-activation, reflex amplitude, and reflex latency of spine muscles were altered by elbow flexor fatigue during a sudden loading (6.8 kg) perturbation at the hands. Elbow flexor fatigue was induced by an isometric 30% maximal elbow flexion moment until failure. Results demonstrate that spine kinematics were not altered in the presence of elbow flexor fatigue. Small magnitude differences in trunk muscle pre- and peak activation indicate that the presence of elbow flexor fatigue does not necessitate substantially greater spine muscle action under the tested conditions. Despite fatigued elbow flexors, the arm muscles were sufficiently able to control the perturbation. Interestingly, 5/14 participants demonstrated altered reflex latencies in all observed muscles that lasted up to 10 min after the fatiguing task. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Influence of grain orientation on evolution of surface features in fatigued polycrystalline copper: a comparison of thermal and uniaxial mechanical fatigue results

    CERN Document Server

    Aicheler, M

    2010-01-01

    Surface state plays a major role in the crack nucleation process of pure metals in the High-Cycle-Fatigue (HCF) as well as in the Ultra-High-Cycle-Fatigue (UHCF) regime. Therefore, in studies dealing with HCF or UHCF, special attention is paid to the evolution of surface degradation during fatigue life. The accelerating structures of the future Compact Linear Collider (CLIC) under study at CERN will be submitted to a high number of thermal-mechanical fatigue cycles, arising from Radio Frequency (RF) induced eddy currents, causing local superficial cyclic heating. The number of cycles during the foreseen lifetime of CLIC reaches 2x10(11). Fatigue may limit the lifetime of CLIC structures. In order to assess the effects of superficial fatigue, specific tests are defined and performed on polycrystalline Oxygen Free Electronic (OFE) grade Copper, a candidate material for the structures. Surface degradation depends on the orientation of near-surface grains. Copper samples thermally fatigued in two different fatigu...

  1. Evaluation of Fatigue Crack Propagation of Gears Considering Uncertainties in Loading and Material Properties

    Directory of Open Access Journals (Sweden)

    Haileyesus B. Endeshaw

    2017-11-01

    Full Text Available Failure prediction of wind turbine gearboxes (WTGs is especially important since the maintenance of these components is not only costly but also causes the longest downtime. One of the most common causes of the premature fault of WTGs is attributed to the fatigue fracture of gear teeth due to fluctuating and cyclic torque, resulting from stochastic wind loading, transmitted to the gearbox. Moreover, the fluctuation of the torque, as well as the inherent uncertainties of the material properties, results in uncertain life prediction for WTGs. It is therefore essential to quantify these uncertainties in the life estimation of gears. In this paper, a framework, constituted by a dynamic model of a one-stage gearbox, a finite element method, and a degradation model for the estimation of fatigue crack propagation in gear, is presented. Torque time history data of a wind turbine rotor was scaled and used to simulate the stochastic characteristic of the loading and uncertainties in the material constants of the degradation model were also quantified. It was demonstrated that uncertainty quantification of load and material constants provides a reasonable estimation of the distribution of the crack length in the gear tooth at any time step.

  2. Assessment of muscle load and fatigue with the usage of frequency and time-frequency analysis of the EMG signal.

    Science.gov (United States)

    Bartuzi, Paweł; Roman-Liu, Danuta

    2014-01-01

    The aim of the study was to determine the effect of the muscle load and fatigue on the values of the parameters calculated on the basis of the time, frequency (Fourier transform) and time-frequency (wavelet transform) analysis of the EMG signal, for low levels of load. Fifteen young men took part in the study. The EMG signal was registered from right side biceps brachii (BB) and trapezius (TR) muscles in static conditions, at load 10%, 20% and 30% MVC (maximal voluntary contraction). On the basis of the analysis there were selected parameters sensitive to force (RMS) and parameters sensitive to fatigue but simultaneously insensitive to force (MPF--mean power frequency determined on the basis of Fourier transform, CMPFdb5--mean power frequency determined on the basis of the wavelet transform). The results indicate that CMPFdb5 can show similar (muscle BB) or greater (muscle TR) sensitivity to fatigue than MPF. It can suggest that, for low levels of load, the wavelet transform parameters can be more effective in assessing muscle fatigue than the parameters based on the Fourier transform. The obtained results can allow for a more precise analysis of muscle fatigue at low levels of load. Further analysis for a greater number of muscles activated at low levels of load, with the usage of the parameters tested is desirable.

  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. Thermal mixing in T-junction piping system concerned with high-cycle thermal fatigue in structure

    International Nuclear Information System (INIS)

    Tanaka, Masaaki; Ohshima, Hiroyuki; Monji, Hideaki

    2008-01-01

    In Japan Atomic Energy Agency (JAEA), a numerical simulation code 'MUGTHES' has been developed to investigate thermal striping phenomena caused by turbulence mixing of fluids in different temperature and to provide transient data for an evaluation method of high-cycle thermal fatigue. MUGTHES adopts Large Eddy Simulation (LES) approach to predict unsteady phenomena in thermal mixing and employs boundary fitted coordinate system to be applied to complex geometry in a power reactor. Numerical simulation of thermal striping phenomena in a T-junction piping system (T-pipe) is conducted. Boundary condition for the simulation is chosen from an existing water experiment in JAEA, named as WATLON experiment. In the numerical simulation, standard Smagorinsky model is employed as eddy viscosity model with the model coefficient of 0.14 (=Cs). Numerical results of MUGTHES are verified by the comparisons with experimental results of velocity and temperature. Through the numerical simulation in the T-pipe, applicability of MUGTHES to the thermal striping phenomena is confirmed and the characteristic large-scale eddy structure which dominates thermal mixing and may cause high-cycle thermal fatigue is revealed. (author)

  5. Influence of thermomechanical fatigue loading on the fracture resistance of all-ceramic posterior crowns.

    Science.gov (United States)

    Senyilmaz, Dilek Pinar; Canay, Senay; Heydecke, Guido; Strub, Joerg Rudolf

    2010-06-01

    This study evaluated the fracture resistance and the survival rate of different all-ceramic crowns in-vitro after thermomechanical fatigue loading in comparison to porcelain-fused-to-metal posterior crowns. Sixteen crowns for human mandibular first molars were made of each of the following: Cercon, IPS-Empress 2 In-Ceram Zirconia, Procera AllZircon and porcelain-fused-to-metal. Half of the specimens of each group was thermocycled and dynamically loaded using a chewing simulator All samples were thereafter tested for the maximum fracture resistance. The survival rates after 1-2 million cycles in the artificial mouth were 100% in all the tested crown systems. The chewing simulation and thermocycling did not significantly decrease the fracture strength of the ceramic crowns (P>0.005). The median fracture load of Cercon, Procera AllZircon, In-Ceram Zirconia and PFM was significantly higher than IPS-Empress 2 both for loaded and non loaded groups (PZirconia and PFM was not significant (P>0.005). All-ceramic systems showed fracture load values similar to those of porcelain-fused-to-metal molar crowns and therefore may be considered for use in clinical studies.

  6. 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.

  7. Interfacial Crack Arrest in Sandwich Panels with Embedded Crack Stoppers Subjected to Fatigue Loading

    DEFF Research Database (Denmark)

    Martakos, G.; Andreasen, J. H.; Berggreen, Christian

    2017-01-01

    A novel crack arresting device has been implemented in sandwich panels and tested using a special rig to apply out-of-plane loading on the sandwich panel face-sheets. Fatigue crack propagation was induced in the face-core interface of the sandwich panels which met the crack arrester. The effect...... of the embedded crack arresters was evaluated in terms of the achieved enhancement of the damage tolerance of the tested sandwich panels. A finite element (FE) model of the experimental setup was used for predicting propagation rates and direction of the crack growth. The FE simulation was based on the adoption...... as the overall performance of the crack arresters....

  8. Experimental examination for microcrack lifetime calculation under proportionally multiaxial fatigue loading with constant and variable amplitudes

    International Nuclear Information System (INIS)

    Savaidis, G.; Seeger, T.

    1994-01-01

    Basic experimental examinations were performed in the frame of this work, for determining the deformation and failure behaviour of metallic materials at multiaxially proportional fatigue loading with variable amplitudes, using the materials StE 460 and AlMg4.5Mn. With the help of deformation controlled, varying single stage Woehler tests with Hour-glass and thin-walled tube specimens, applying pure normal force, pure torsion and composed normal force and torsion, the cyclic deformation behaviour, incipient cracking and crack opening and crack growth behaviour of the materials was examined. (orig.) [de

  9. Thermal cycling fatigue behavior of hardfacing heat-resistant stainless steel for continuous caster rolls

    International Nuclear Information System (INIS)

    Jung, Jae Young; Sung, Hwan Jin; Ahn, Sang Ho

    1998-01-01

    The variation of tensile properties and hardness as a function of tempering temperature and time has been investigated using a hardfacing 12%Cr stainless steel. The mechanical properties of the hardfacing 12%Cr stainless steel could be generalized by the Larson-Miller parameter, which concurrently considers the effects of tempering temperature and time. Thermal cycling fatigue behavior of a hardfacing 12%Cr stainless steel has been investigated using a special thermal fatigue testing apparatus. The resistance of thermal fatigue was deteriorated mainly by the low ductility and true fracture strength of material. The temperature distribution in the specimen was calculated using finite element program and compared to experimental results. The strain and stress distributions were evaluated taking into account the temperature distribution and the temperature dependence of the material properties. The results showed that maximum values of strain and stress were produced within the induction-heating region. The strain amplitude obtained in this study was much smaller than that of fully constrained case, which corresponds to thermal expansion due to temperature difference. This result arises from the reduction of the temperature gradient due to thermal conduction to the neighboring region. The magnitude of strain raised with the increase in the temperature gradient, which is due to the rapid cooling and heating rates in the induction-heating region

  10. Fatigue Behavior of High Strength Steel S890Q Containing Thermally Cut Straight Edges

    OpenAIRE

    Cicero, S.; García, T.; Álvarez, J.A.; Bannister, A.; Klimpel, A.; Martín-Meizoso, A.; Aldazabal, J.

    2016-01-01

    This paper evaluates the effect of different thermal cutting methods on the fatigue life of high strength steel S890Q. The investigation covers flame, plasma and laser cutting methodologies, and specimens with rectangular sections and cut straight edges. The experimental program is composed of 30 specimens that were conducted to failure by applying fatigue cycles with a stress ratio (R) of 0.1 in a high frequency testing machine. The resultant best-fit S-N curves have been compared, revealing...

  11. A comparison between Japanese and French A16 defect assessment procedures for thermal fatigue crack growth

    International Nuclear Information System (INIS)

    Wakai, T.; Horikiri, M.; Poussard, C.; Drubay, B.

    2005-01-01

    This paper presents the results of a benchmark on thermal fatigue crack growth evaluation for a thick-wall cylinder subjected to cyclic thermal transients. The simplified crack growth evaluation methods of both JNC in JAPAN and A16 procedures proposed by CEA in France are presented. The predictions obtained using both methods are compared with the experimental data. The JNC method, which accounts for the non-linear stress component provides predictions of crack advance in a good agreement with the experimental data. In contrast, significant differences are observed between the A16 predictions and the experimental data. The discrepancies are mainly due to the non-linear stress component which is not accounted for in the A16 method. When using the JNC stress intensity factor solution determined by finite element analysis to account for the non-linear stress component, the A16 method well predicts the thermal fatigue crack growth behavior

  12. Thermal fatigue damage in monofilament reinforced copper for heat sink applications in divertor elements

    Science.gov (United States)

    Schöbel, M.; Jonke, J.; Degischer, H. P.; Paffenholz, V.; Brendel, A.; Wimpory, R. C.; Di Michiel, M.

    2011-02-01

    In fusion reactor systems extreme conditions require materials with high temperature and radiation resistance. The divertor component consists of a plasma facing W plate attached to a Cu heat sink to extract the heat from the nuclear reaction chamber coolant. The Coefficient of Thermal Expansion (CTE) mismatch between the W plate and the Cu heat sink causes interface delamination reducing the long term stability of the divertor. To avert this problem, composites are developed as interlayer materials with a high thermal conducting Cu matrix reinforced with up to 50 vol.% SiC or W monofilaments to increase the mechanical strength and to reduce the CTE mismatch. Thermal stresses are transferred from the macroscopic interface between the components into the bulk of the composite. Oscillating micro stresses may lead to fiber delamination and matrix damage during thermal cycling. Different matrix alloys, fiber materials and interface designs are investigated. In situ neutron diffraction performed during thermal cycling show the effect of bonding strength on the stress amplitudes expected under service conditions. The long term stability is tested by measurements after further ex situ cycling. Thermal fatigue damage and its propagation are visualized by in situ as well as ex situ high resolution synchrotron tomography. The combination of both methods helps to understand the strain induced damage mechanisms. Weak bonding leads to delamination of the fiber-matrix interfaces. Strong bonding causes severe matrix deformation and damage. Fiber cracks originating from sample production cause accumulating thermal fatigue damage during thermal cycling.

  13. Thermal fatigue life prediction based on crack propagation behaviors in high-temperature materials for power plant components

    International Nuclear Information System (INIS)

    Nitta, Akihito; Ogata, Takashi; Kuwabara, Kazuo

    1986-01-01

    For reducing an electric power supply cost, it is desired to extend the life of thermal power plant being still supplying the greater part of electric power in Japan. It is, therefore, becoming more and more important for the remaining life control of long-operated thermal power plants to exactly estimate the thermal fatigue damage accumulating in high temperature components. In this report, a discussion was made on thermal fatigue life laws derived from the crack propagation laws. As a result, the life laws were found to be effective for the evaluation of thermal fatigue life as well as isothermal fatigue life. Based on the concept of the life laws, the thermal and isothermal fatigue lives were also predicted as a propagation period of a crack with initial length equal to grain size from the characteristics of high temperature fatigue crack propagation. In addition to them, the rapid straining method was found to be required for more accurate estimation of creep strain in in-phase thermal fatigue. (author)

  14. 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.

  15. 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

  16. Thermo-Vibro-Acoustic Loads and Fatigue of Hypersonic Flight Vehicle Structure

    Science.gov (United States)

    2009-06-01

    Realistic panel edge fixity . • Thermal isolation of the test articles from structural heat sinks. • Control of the differential thermal expansion between...Concept 1 The finite element model for design concept 1 is shown in Figure 9-1 along with all its fixities and the appropriate boundary conditions...heat exchanger shares some of the outer face sheet load. The manifolds are not stiff enough to provide good edge fixity , so the panel responds as if

  17. Interfacial crack arrest in sandwich beams subjected to fatigue loading using a novel crack arresting device – Numerical modelling

    DEFF Research Database (Denmark)

    Martakos, G.; Andreasen, J.H.; Berggreen, Christian

    2017-01-01

    A novel crack arresting device is implemented in foam-cored composite sandwich beams and tested using the Sandwich Tear Test (STT) configuration. A finite element model of the setup is developed, and the predictions are correlated with observations and results from a recently conducted experimental...... fatigue test study. Based on a linear elastic fracture mechanics approach, the developed FE model is utilised to simulate crack propagation and arrest in foam-cored sandwich beam specimens subjected to fatigue loading conditions. The effect of the crack arresters on the fatigue life is analysed......, and the predictive results are subsequently compared with the observations from the previously conducted fatigue tests. The FE model predicts the energy release rate and the mode mixity based on the derived crack surface displacements, utilising algorithms for the prediction of accelerated fatigue crack growth...

  18. Experimental investigation of interfacial crack arrest in sandwich beams subjected to fatigue loading using a novel crack arresting device

    DEFF Research Database (Denmark)

    Martakos, G.; Andreasen, J.H.; Berggreen, Christian

    2017-01-01

    A recently proposed face-sheet–core interface crack arresting device is implemented in sandwich beams and tested using the Sandwich Tear Test configuration. Fatigue loading conditions are applied to propagate the crack and determine the effect of the crack stopper on the fatigue growth rate...... the energy release rate, mode mixity and to simulate crack propagation and arrest of the crack. Finally, the effectiveness of the crack arresting device is demonstrated on composite sandwich beams subjected to fatigue loading conditions....... and arrest of the crack. Digital image correlation is used through the duration of the fatigue experiment to track the strain evolution as the crack tip advances. The measured strains are related to crack tip propagation, arrest, and re-initiation of the crack. A finite element model is used to calculate...

  19. The analysis of initiation and growth of cracks in diffusion aluminium coatings on ZS6U alloy in conditions of thermal fatigue

    International Nuclear Information System (INIS)

    Ciesla, M.; Swadzba, L.; Supernak, W.

    2002-01-01

    The paper deals with the analysis of thermal fatigue of nickel based ZS6U super alloy with 'Si-Ai' and 'Cr-Al' aluminium diffusion coatings. The processes of initiation and growth of cracks in diffusion coating in the conditions of cyclic changing temperature (500 o C - 950 o C) and simultaneous F o constant axial force loading have been analysed. The results of numerical calculations of stress distribution in the specimen with aluminium coatings have been presented. They enabled to elaborate the models of mechanical behaviour of coatings, which in turn helped to explain different character of cracks in the assumed experimental conditions. Thermal fatigue tests performed at lower static component of F o loading spectrum proved that aluminium coatings obtained in course of 'Si-Al' process show the highest lifetime respectively of their thickness. Moreover, the lifetime of 'Si-Al' aluminium coatings decreases together with the increase of static component of load fatigue spectrum unlike in case of 'Cr-Al' coatings. (author)

  20. Effect of luting agent on the load to failure and accelerated-fatigue resistance of lithium disilicate laminate veneers.

    Science.gov (United States)

    Gresnigt, Marco M M; Özcan, Mutlu; Carvalho, Marco; Lazari, Priscilla; Cune, Marco S; Razavi, Peywand; Magne, Pascal

    2017-12-01

    The aim of this study was to investigate the influence of the luting agent on the application of laminate veneers (LVs) in an accelerated fatigue and load-to-failure test after thermo-cyclic aging. Sound maxillary central incisors (N=40) were randomly divided into four groups to receive LVs (Li 2 Si 2 O 5 ) that were adhesively bonded: Group CEMF: Adhesive cement (Variolink Esthetic LC), fatigue test; Group CEMLF: Adhesive cement, load-to-failure test; Group COMF: Resin composite (Enamel HFO), fatigue test; Group COMLF: Resin composite, load-to-failure test. The specimens were thermo-mechanically aged (1.2×10 6 cycles at 1.7Hz/50N, 8000 cycles 5-55°C) and then subjected to either accelerated fatigue (5Hz, 25N increasing after each 500 cycles) or load to failure (1mm/min). Failure types were classified and data analyzed using chi-square, Kaplan Meier survival, Log Rank (Mantel-Cox) and independent-samples t-test. After thermo-mechanical aging, fracture resistance (pveneer. The delivery of laminate veneers using a direct restorative composite rather than a resin cement resulted in significantly less chipping and fractures, higher fracture strength in both accelerated fatigue and load-to-failure. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  1. Influence of outdoor running fatigue and medial tibial stress syndrome on accelerometer-based loading and stability.

    Science.gov (United States)

    Schütte, Kurt H; Seerden, Stefan; Venter, Rachel; Vanwanseele, Benedicte

    2018-01-01

    Medial tibial stress syndrome (MTSS) is a common overuse running injury with pathomechanics likely to be exaggerated by fatigue. Wearable accelerometry provides a novel alternative to assess biomechanical parameters continuously while running in more ecologically valid settings. The purpose of this study was to determine the influence of outdoor running fatigue and MTSS on both dynamic loading and dynamic stability derived from trunk and tibial accelerometery. Runners with (n=14) and without (n=16) history of MTSS performed an outdoor fatigue run of 3200m. Accelerometer-based measures averaged per lap included dynamic loading of the trunk and tibia (i.e. axial peak positive acceleration, signal power magnitude, and shock attenuation) as well as dynamic trunk stability (i.e. tri-axial root mean square ratio, step and stride regularity, and sample entropy). Regression coefficients from generalised estimating equations were used to evaluate group by fatigue interactions. No evidence could be found for dynamic loading being higher with fatigue in runners with MTSS history (all measures p>0.05). One significant group by running fatigue interaction effect was detected for dynamic stability. Specifically, in MTSS only, decreases mediolateral sample entropy i.e. loss of complexity was associated with running fatigue (p<0.01). The current results indicate that entire acceleration waveform signals reflecting mediolateral trunk control is related to MTSS history, a compensation that went undetected in the non-fatigued running state. We suggest that a practical outdoor running fatigue protocol that concurrently captures trunk accelerometry-based movement complexity warrants further prospective investigation as an in-situ screening tool for MTSS individuals. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. 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...

  3. Analytical assessment for stress corrosion fatigue of CANDU fuel elements under load following conditions

    International Nuclear Information System (INIS)

    Horhoianu, Grigore; Ionescu, Drags; Pauna, Eduard

    2012-01-01

    When nuclear power reactors are operated in a load following (LF) mode, the nuclear fuel may be subjected to step changes in power on weekly, daily, or even hourly basis, depending on the grid's needs. Two load following tests performed in TRIGA Research Reactor of Institute for Nuclear Research (INR) Pitesti were simulated with finite elements computer codes in order to evaluate Stress Corrosion Fatigue (SCF) of the sheath arising from expansion and contraction of the pellets in the corrosive environment. The 3D finite element analyses show that the cyclic strains give highly multiaxial stresses in the sheath at ridge region. This paper summarizes the results of the analytical assessment for SCF and their relation to CANDU fuel performance in LF tests conditions. (orig.)

  4. 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.

  5. Crystallographic Analysis of Fatigue Crack Initiation Behavior in Coarse-Grained Magnesium Alloy Under Tension-Tension Loading Cycles

    Science.gov (United States)

    Tamada, Kazuhiro; Kakiuchi, Toshifumi; Uematsu, Yoshihiko

    2017-07-01

    Plane bending fatigue tests are conducted to investigate fatigue crack initiation mechanisms in coarse-grained magnesium alloy, AZ31, under the stress ratios R = -1 and 0.1. The initial crystallographic structures are analyzed by an electron backscatter diffraction method. The slip or twin operation during fatigue tests is identified from the line angle analyses based on Euler angles of the grains. Under the stress ratio R = -1, relatively thick tension twin bands are formed in coarse grains. Subsequently, compression twin or secondary pyramidal slip operates within the tension twin band, resulting in the fatigue crack initiation. On the other hand, under R = 0.1 with tension-tension loading cycles, twin bands are formed on the specimen surface, but the angles of those bands do not correspond to tension twins. Misorientation analyses of c-axes in the matrix grain and twin band reveal that double twins are activated. Under R = 0.1, fatigue crack initiates along the double twin boundaries. The different manners of fatigue crack initiation at R = -1 and 0.1 are related to the asymmetricity of twining under tension and compression loadings. The fatigue strengths under different stress ratios cannot be estimated by the modified Goodman diagram due to the effect of stress ratio on crack initiation mechanisms.

  6. 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.

  7. Second Harmonic Generation Imaging and Fourier Transform Spectral Analysis Reveal Damage in Fatigue-Loaded Tendons

    Science.gov (United States)

    Fung, David T.; Sereysky, Jedd B.; Basta-Pljakic, Jelena; Laudier, Damien M.; Huq, Rumana; Jepsen, Karl J.; Schaffler, Mitchell B.; Flatow, Evan L.

    2016-01-01

    Conventional histologic methods provide valuable information regarding the physical nature of damage in fatigue-loaded tendons, limited to thin, two-dimensional sections. We introduce an imaging method that characterizes tendon microstructure three-dimensionally and develop quantitative, spatial measures of damage formation within tendons. Rat patellar tendons were fatigue loaded in vivo to low, moderate, and high damage levels. Tendon microstructure was characterized using multiphoton microscopy by capturing second harmonic generation signals. Image stacks were analyzed using Fourier transform-derived computations to assess frequency-based properties of damage. Results showed 3D microstructure with progressively increased density and variety of damage patterns, characterized by kinked deformations at low, fiber dissociation at moderate, and fiber thinning and out-of-plane discontinuities at high damage levels. Image analysis generated radial distributions of power spectral gradients, establishing a “fingerprint” of tendon damage. Additionally, matrix damage was mapped using local, discretized orientation vectors. The frequency distribution of vector angles, a measure of damage content, differed from one damage level to the next. This study established an objective 3D imaging and analysis method for tendon microstructure, which characterizes directionality and anisotropy of the tendon microstructure and quantitative measures of damage that will advance investigations of the microstructural basis of degradation that precedes overuse injuries. PMID:20232150

  8. 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.

  9. Fatigue and perceptual responses of heavier- and lighter-load isolated lumbar extension resistance exercise in males and females

    Directory of Open Access Journals (Sweden)

    Charlotte Stuart

    2018-03-01

    Full Text Available Background There is a lack of research considering acute fatigue responses to high- and low-load resistance training as well as the comparison between male and female responses. Furthermore, limited studies have considered fatigue response testing with the inclusion of perceptions of discomfort and exertion. Methods The present study included males (n = 9; 23.8 ± 6.4 years; 176.7 ± 6.2 cm; 73.9 ± 9.3 kg and females (n = 8; 21.3 ± 0.9 years; 170.5 ± 6.1 cm; 65.5 ± 10.8 kg who were assessed for differences in fatigue (i.e., loss of torque at maximal voluntary contraction (MVC immediately following isolated lumbar extension (ILEX exercise at heavy- (HL and light-(LL loads (80% and 50% MVC, respectively. Participants also reported perceptual measures of effort (RPE-E and discomfort (RPE-D between different resistance training protocols. Results Analysis of variance revealed significantly greater absolute and relative fatigue following LL compared to HL conditions (p < 0.001. Absolute fatigue significantly differed between males and females (p = 0.012, though relative fatigue was not significantly different (p = 0.160. However, effect sizes for absolute fatigue (HL; Males = −1.84, Females = −0.83; LL; Males = −3.11, Females = −2.39 and relative fatigue (HL; Males = −2.17, Females = −0.76; LL; Males = −3.36, Females = −3.08 were larger for males in both HL and LL conditions. RPE-E was maximal for all participants in both conditions, but RPE-D was significantly higher in LL compared to HL (p < 0.001 with no difference between males and females. Discussion Our data suggests that females do not incur the same degree of fatigue as males following similar exercise protocols, and indeed that females might be able to sustain longer exercise duration at the same relative loads. As such females should manipulate training variables accordingly, perhaps performing greater repetitions at a relative load, or using heavier relative

  10. Self-sealing of thermal fatigue and mechanical damage in fiber-reinforced composite materials

    Science.gov (United States)

    Moll, Jericho L.

    Fiber reinforced composite tanks provide a promising method of storage for liquid oxygen and hydrogen for aerospace applications. The inherent thermal fatigue of these vessels leads to the formation of microcracks, which allow gas phase leakage across the tank walls. In this dissertation, self-healing functionality is imparted to a structural composite to effectively seal microcracks induced by both mechanical and thermal loading cycles. Two different microencapsulated healing chemistries are investigated in woven glass fiber/epoxy and uni-weave carbon fiber/epoxy composites. Self-healing of mechanically induced damage was first studied in a room temperature cured plain weave E-glass/epoxy composite with encapsulated dicyclopentadiene (DCPD) monomer and wax protected Grubbs' catalyst healing components. A controlled amount of microcracking was introduced through cyclic indentation of opposing surfaces of the composite. The resulting damage zone was proportional to the indentation load. Healing was assessed through the use of a pressure cell apparatus to detect nitrogen flow through the thickness direction of the damaged composite. Successful healing resulted in a perfect seal, with no measurable gas flow. The effect of DCPD microcapsule size (51 microm and 18 microm) and concentration (0--12.2 wt%) on the self-sealing ability was investigated. Composite specimens with 6.5 wt% 51 microm capsules sealed 67% of the time, compared to 13% for the control panels without healing components. A thermally stable, dual microcapsule healing chemistry comprised of silanol terminated poly(dimethyl siloxane) plus a crosslinking agent and a tin catalyst was employed to allow higher composite processing temperatures. The microcapsules were incorporated into a satin weave E-glass fiber/epoxy composite processed at 120°C to yield a glass transition temperature of 127°C. Self-sealing ability after mechanical damage was assessed for different microcapsule sizees (25 microm and 42

  11. 3D-FE Modeling of 316 SS under Strain-Controlled Fatigue Loading and CFD Simulation of PWR Surge Line

    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); Listwan, Joseph [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)

    2017-03-01

    In financial year 2017, we are focusing on developing a mechanistic fatigue model of surge line pipes for pressurized water reactors (PWRs). To that end, we plan to perform the following tasks: (1) conduct stress- and strain-controlled fatigue testing of surge-line base metal such as 316 stainless steel (SS) under constant, variable, and random fatigue loading, (2) develop cyclic plasticity material models of 316 SS, (3) develop one-dimensional (1D) analytical or closed-form model to validate the material models and to understand the mechanics associated with 316 SS cyclic hardening and/or softening, (4) develop three-dimensional (3D) finite element (FE) models with implementation of evolutionary cyclic plasticity, and (5) develop computational fluid dynamics (CFD) model for thermal stratification, thermal-mechanical stress, and fatigue of example reactor components, such as a PWR surge line under plant heat-up, cool-down, and normal operation with/without grid-load-following. This semi-annual progress report presents the work completed on the above tasks for a 316 SS laboratory-scale specimen subjected to strain-controlled cyclic loading with constant, variable, and random amplitude. This is the first time that the accurate 3D-FE modeling of the specimen for its entire fatigue life, including the hardening and softening behavior, has been achieved. We anticipate that this work will pave the way for the development of a fully mechanistic-computer model that can be used for fatigue evaluation of safety-critical metallic components, which are traditionally evaluated by heavy reliance on time-consuming and costly test-based approaches. This basic research will not only help the nuclear reactor industry for fatigue evaluation of reactor components in a cost effective and less time-consuming way, but will also help other safety-related industries, such as aerospace, which is heavily dependent on test-based approaches, where a single full-scale fatigue test can cost

  12. 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

  13. Impact of Frequency of Load Changes in Fatigue Tests on the Temperature of the Modified Polymer

    Science.gov (United States)

    Komorek, Andrzej; Komorek, Zenon; Krzyzak, Aneta; Przybylek, Pawel; Szczepaniak, Robert

    2017-08-01

    In the article, the authors describe the analysis of the impact of the frequency of fatigue tests on the temperature of the modified polymer. The base material for producing the samples was the epoxy resin Epidian 57 cured with Z1 hardener. The presented study is part of a research program of adhesive joints made with the composition Epidian 57/Z1 aiming to determine the effect of physical modification of the adhesive composition on its properties and on the properties of adhesive joints made with such a modified composition. The tested adhesive compositions were modified by additions of micro- and nanoparticles in an amount of 1.85 % (micro- and nanoparticles) or 10 % (microparticles) in weight, depending on the type of the particles. In the studies, the authors used the particles of tungsten, microspheres and carbon nanotubes. The polymer samples produced by casting were loaded with compressive identical, one-sided loads at two different frequencies of load changes. During the tests, the authors recorded the temperature changes as a function of the number of cycles. The changes in the temperature field on the surface of the samples during the tests were observed by the infrared camera. As a result of the studies, it was possible to observe a significant impact of the composition of the polymer and the frequency of load changes during the test on the temperature of the sample.

  14. 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.

  15. Effect of carbides on thermal fatigue property of K465 cast superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Guan, H.R.; Yang, J.X.; Zheng, Q.; Wang, Y.L.; Sun, X.F.; Hu, Z.Q. [Chinese Academy of Sciences, Shenyang (China). Inst. of Metal Research

    2006-07-01

    Thermal fatigue (TF) tests on nickel-base K465 superalloy in as-cast and solution treated conditions were conducted from 1050 C to 20 C repeatedly. Main experimental results showed that thermal fatigue crack of as-cast K465 alloy propagated faster than that of solution treated K465 alloy, and the rise of holding time at the maximum temperature accelerated TF crack propagation. Metallographic observations depicted that the TF cracks were nucleated at Chinese script MC carbide and propagated along the cracked MC carbide in as-cast condition, whereas most M6C carbide particles obstructed TF crack growth in solution treated condition. Chinese script MC carbide was responsible for the reduction of TF life in as-cast condition. (orig.)

  16. Examination of high heat flux components for the ITER divertor after thermal fatigue testing

    International Nuclear Information System (INIS)

    Missirlian, M.; Escourbiac, F.; Schmidt, A.; Riccardi, B.; Bobin-Vastra, I.

    2011-01-01

    An extensive development programme has been carried out in the EU on high heat flux components within the ITER project. In this framework, a full-scale vertical target (VTFS) prototype was manufactured with all the main features of the corresponding ITER divertor design. The fatigue cycling campaign on CFC and W armoured regions, proved the capability of such a component to meet the ITER requirements in terms of heat flux performances for the vertical target. This paper discusses metallographic observations performed on both CFC and W part after this intensive thermal fatigue testing campaign for a better understanding of thermally induced mechanical stress within the component, especially close to the armour-heat sink interface.

  17. Fatigue load considerations and use of high efficiency materials in the nuclear refurbishment projects: a structural engineering perspective

    Energy Technology Data Exchange (ETDEWEB)

    Mohee, F. M., E-mail: fmm_p@yahoo.com [Univ. of Waterloo, ON (Canada)

    2014-07-01

    For the Darlington refurbishment project in Canada, fatigue load consideration is a very crucial component in the analysis and design of different structures in the nuclear facilities. New and innovative structural materials having much higher ultimate tensile strength and modulus of elasticity, that are free from corrosion, should be considered along with fatigue load during the analysis and design of the nuclear refurbishment projects. The structural analysis should include beam, column and slabs, vibrating, rotating and crane supporting structures, robotic structures, pipe supports, Serapid chain and associated automated gate structures, flask supporting structures, processing unit and lidding unit support structures. (author)

  18. Fatigue load considerations and use of high efficiency materials in the nuclear refurbishment projects: a structural engineering perspective

    International Nuclear Information System (INIS)

    Mohee, F. M.

    2014-01-01

    For the Darlington refurbishment project in Canada, fatigue load consideration is a very crucial component in the analysis and design of different structures in the nuclear facilities. New and innovative structural materials having much higher ultimate tensile strength and modulus of elasticity, that are free from corrosion, should be considered along with fatigue load during the analysis and design of the nuclear refurbishment projects. The structural analysis should include beam, column and slabs, vibrating, rotating and crane supporting structures, robotic structures, pipe supports, Serapid chain and associated automated gate structures, flask supporting structures, processing unit and lidding unit support structures. (author)

  19. 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.

  20. 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.

  1. Influence of Pitting Corrosion on Fatigue and Corrosion Fatigue of Ship and Offshore Structures, Part II: Load - Pit - Crack Interaction

    Directory of Open Access Journals (Sweden)

    Jakubowski Marek

    2015-09-01

    Full Text Available In the paper has been discussed influence of stresses on general corrosion rate and corrosion pit nucleation rate and growth , whose presence has been questioned by some authors but accepted by most of them. Influence of roughness of pit walls on fatigue life of a plate suffering pit corrosion and presence of the so called „ non-damaging” pits which never lead to initiation of fatigue crack, has been presented. Possibility of prediction of pit-to-crack transition moment by two different ways, i.e. considering a pit a stress concentrator or an equivalent crack, has been analyzed. Also, influence of statistical distribution of depth of corrosion pits as well as anticorrosion protection on fatigue and corrosion fatigue has been described.

  2. The effects of state anxiety and thermal comfort on sleep quality and eye fatigue in shift work nurses

    OpenAIRE

    Dehghan, Habibollah; Azmoon, Hiva; Souri, Shiva; Akbari, Jafar

    2014-01-01

    Psychological problems as state anxiety (SA) in the work environment has negative effect on the employees life especially shift work nurses, i.e. negative effect on mental and physical health (sleep quality, eye fatigue and comfort thermal). The purpose of this study was determination of effects of state anxiety and thermal comfort on sleep quality and eye fatigue in shift work nurses. Methods: This cross-sectional research conducted on 82 shift-work personnel of 18 nursing workstations of Is...

  3. 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.

  4. The effects of state anxiety and thermal comfort on sleep quality and eye fatigue in shift work nurses.

    Science.gov (United States)

    Dehghan, Habibollah; Azmoon, Hiva; Souri, Shiva; Akbari, Jafar

    2014-01-01

    Psychological problems as state anxiety (SA) in the work environment has negative effect on the employees life especially shift work nurses, i.e. negative effect on mental and physical health (sleep quality, eye fatigue and comfort thermal). The purpose of this study was determination of effects of state anxiety and thermal comfort on sleep quality and eye fatigue in shift work nurses. This cross-sectional research conducted on 82 shift-work personnel of 18 nursing workstations of Isfahan hospitals in 2012. To measure the SA, sleep quality, visual fatigue and thermal comfort, Spielberger state-trait anxiety inventory, Pittsburg sleep quality index, eye fatigue questionnaire and thermal comfort questionnaire were used respectively. The data were analyzed with descriptive statistics, student test and correlation analysis. Correlation between SA and sleep quality was -0.664(P thermal comfort was -0.276(P = 0.016) and between SA and eye fatigue was 0.57 (P thermal conditions and reduce state anxiety level can be reduce eye fatigue and increase the sleep quality in shift work nurses.

  5. Probabilistic modeling of crack networks in thermal fatigue; Modelisation probabiliste de formation de reseaux de fissures de fatigue thermique

    Energy Technology Data Exchange (ETDEWEB)

    Malesys, N

    2007-11-15

    Thermal superficial crack networks have been detected in mixing zone of cooling system in nuclear power plants. Numerous experimental works have already been led to characterize initiation and propagation of these cracks. The random aspect of initiation led to propose a probabilistic model for the formation and propagation of crack networks in thermal fatigue. In a first part, uniaxial mechanical test were performed on smooth and slightly notched specimens in order to characterize the initiation of multiple cracks, their arrest due to obscuration and the coalescence phenomenon by recovery of amplification stress zones. In a second time, the probabilistic model was established under two assumptions: the continuous cracks initiation on surface, described by a Poisson point process law with threshold, and the shielding phenomenon which prohibits the initiation or the propagation of a crack if this one is in the relaxation stress zone of another existing crack. The crack propagation is assumed to follow a Paris' law based on the computation of stress intensity factors at the top and the bottom of crack. The evolution of multiaxial cracks on the surface can be followed thanks to three quantities: the shielding probability, comparable to a damage variable of the structure, the initiated crack density, representing the total number of cracks per unit surface which can be compared to experimental observations, and the propagating crack density, representing the number per unit surface of active cracks in the network. The crack sizes distribution is also computed by the model allowing an easier comparison with experimental results. (author)

  6. Probabilistic Material Strength Degradation Model for Inconel 718 Components Subjected to High Temperature, High-Cycle and Low-Cycle Mechanical Fatigue, Creep and Thermal Fatigue Effects

    Science.gov (United States)

    Bast, Callie C.; Boyce, Lola

    1995-01-01

    The development of methodology for a probabilistic material strength degradation is described. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing predictions of high-cycle mechanical fatigue and high temperature effects with experiments are presented. Results from this limited verification study strongly supported that material degradation can be represented by randomized multifactor interaction models.

  7. Stress-based fatigue reliability analysis ofthe rail fastening spring clipunder traffic loads

    Directory of Open Access Journals (Sweden)

    Saeed Mohammadzadeh

    Full Text Available Nowadays, the rail fastening systems play an important role for preserving the connection between the rails and sleepers in various conditions. In this paper, stress based concept is used to develop a comprehensive approach for fatigue reliability analysisof fastening spring clip. Axle load, speed and material properties are assumed to be random variables. First, track and train models are analyzed dynamically in order to achieve displacement time history of fas-tening spring clip. Then this displacement time history is applied to the fastening spring clip in FE software to obtain variable ampli-tude of stresses. Crack nucleation life is calculated by rain-flow method and Palmgren-Miner linear damage rule. First Order Relia-bility Method (FORM and Monte-Carlosimulation technique are employed for the reliability index estimations. The influences of various random variables on the probability of failure are investi-gated by sensitivity analysis. The results show that the equivalent stress range and material parameter have significant effect on fa-tigue crack nucleation.

  8. Flaw assessment guide for high-temperature reactor components subject to creep-fatigue loading

    International Nuclear Information System (INIS)

    Ainsworth, R.A.; Takahashi, Y.

    1990-10-01

    A high-temperature flaw assessment procedure is described. This procedure is a result of a collaborative effort between Electric Power Research Institute in the United States, Central Research Institute of Electric Power Industry in Japan, and Nuclear Electric plc in the United Kingdom. The procedure addresses preexisting defects subject to creep-fatigue loading conditions. Laws employed to calculate the crack growth per cycle are defined in terms of fracture mechanics parameters and constants related to the component material. The crack-growth laws can be integrated to calculate the remaining life of a component or to predict the amount of crack extension in a given period. Fatigue and creep crack growth per cycle are calculated separately, and the total crack extension is taken as the simple sum of the two contributions. An interaction between the two propagation modes is accounted for in the material properties in the separate calculations. In producing the procedure, limitations of the approach have been identified. 25 refs., 1 fig

  9. Effect of unit size on thermal fatigue behavior of hot work steel repaired by a biomimetic laser remelting process

    Science.gov (United States)

    Cong, Dalong; Li, Zhongsheng; He, Qingbing; Chen, Dajun; Chen, Hanbin; Yang, Jiuzhou; Zhang, Peng; Zhou, Hong

    2018-01-01

    AISI H13 hot work steel with fatigue cracks was repaired by a biomimetic laser remelting (BLR) process in the form of lattice units with different sizes. Detailed microstructural studies and microhardness tests were carried out on the units. Studies revealed a mixed microstructure containing martensite, retained austenite and carbide particles with ultrafine grain size in units. BLR samples with defect-free units exhibited superior thermal fatigue resistance due to microstructure strengthening, and mechanisms of crack tip blunting and blocking. In addition, effects of unit size on thermal fatigue resistance of BLR samples were discussed.

  10. Turbulence descriptors for scaling fatigue loading spectra of wind turbine structural components

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, N D

    1994-07-01

    The challenge for the designer in developing a new wind turbine is to incorporate sufficient strength in its components to safely achieve a 20- or 30-year service life. To accomplish this, the designer must understand the load and stress distributions (in a statistical sense at least) that the turbine is likely to encounter during its operating life. Sources of loads found in the normal operating environment include start/stop cycles, emergency shutdowns, the turbulence environment associated with the specific site and turbine location, and extreme or ``rare`` events that can challenge the turbine short-term survivability. Extreme events can result from an operational problem (e.g., controller failure) or violent atmospheric phenomena (tornadic circulations, strong gust fronts). For the majority of the operating time, however, the character of the turbulent inflow is the dominant source of the alternating stress distributions experienced by the structural components. Methods of characterizing or scaling the severity of the loading spectra (or the rate of fatigue damage accumulation) must be applicable to a wide range of turbulent inflow environments -- from solitary isolation to the complex flows associated with multi-row wind farms. The metrics chosen must be related to the properties of the turbulent inflow and independent of the nature of local terrain features.

  11. Stress induced martensite at the crack tip in NiTi alloys during fatigue loading

    Directory of Open Access Journals (Sweden)

    E. Sgambitterra

    2014-10-01

    Full Text Available Crack tip stress-induced phase transformation mechanisms in nickel-titanium alloys (NiTi were analyzed by Digital Image Correlation (DIC, under fatigue loads. In particular, Single Edge Crack (SEC specimens, obtained from a commercial pseudoelastic NiTi sheet, and an ad-hoc experimental setup were used, for direct measurements of the near crack tip displacement field by the DIC technique. Furthermore, a fitting procedure was developed to calculate the mode I Stress Intensity Factor (SIF, starting from the measured displacement field. Finally, cyclic tensile tests were performed at different operating temperature, in the range 298-338 K, and the evolution of the SIF was studied, which revealed a marked temperature dependence.

  12. Thermal/mechanical simulation and laboratory fatigue testing of an alternative yttria tetragonal zirconia polycrystal core-veneer all-ceramic layered crown design.

    Science.gov (United States)

    Bonfante, Estevam A; Rafferty, Brian; Zavanelli, Ricardo A; Silva, Nelson R F A; Rekow, Elizabeth D; Thompson, Van P; Coelho, Paulo G

    2010-04-01

    This study evaluated the stress levels at the core layer and the veneer layer of zirconia crowns (comprising an alternative core design vs. a standard core design) under mechanical/thermal simulation, and subjected simulated models to laboratory mouth-motion fatigue. The dimensions of a mandibular first molar were imported into computer-aided design (CAD) software and a tooth preparation was modeled. A crown was designed using the space between the original tooth and the prepared tooth. The alternative core presented an additional lingual shoulder that lowered the veneer bulk of the cusps. Finite element analyses evaluated the residual maximum principal stresses fields at the core and veneer of both designs under loading and when cooled from 900 degrees C to 25 degrees C. Crowns were fabricated and mouth-motion fatigued, generating master Weibull curves and reliability data. Thermal modeling showed low residual stress fields throughout the bulk of the cusps for both groups. Mechanical simulation depicted a shift in stress levels to the core of the alternative design compared with the standard design. Significantly higher reliability was found for the alternative core. Regardless of the alternative configuration, thermal and mechanical computer simulations showed stress in the alternative core design comparable and higher to that of the standard configuration, respectively. Such a mechanical scenario probably led to the higher reliability of the alternative design under fatigue.

  13. 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

  14. 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.

  15. Effect of luting agent on the load to failure and accelerated-fatigue resistance of lithium disilicate laminate veneers

    NARCIS (Netherlands)

    Gresnigt, Marco M. M.; Ozcan, Mutlu; Carualho, Marco; Lazari, Priscilla; Cune, Marco S.; Razavi, Peywand; Magne, Pascal

    2017-01-01

    Objective. The aim of this study was to investigate the influence of the luting agent on the application of laminate veneers (LVs) in an accelerated fatigue and load-to-failure test after thermo-cyclic aging. Methods. Sound maxillary central incisors (N = 40) were randomly divided into four groups

  16. Evaluation of Variation in Residual Strength of Carbon Fiber Reinforced Plastic Plate with a Hole Subjected to Fatigue Load

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Young; Kang, Min Sung; Koo, Jae Mean; Seok, Chang Sung [Sungkyunkwan University, Seoul (Korea, Republic of)

    2010-10-15

    CFRP (Carbon Fiber Reinforced Plastic) has received considerable attention in various fields as a structural material, because of its high specific strength, high specific stiffness, excellent design flexibility, favorable chemical properties, etc. Most products consisting of several parts are generally assembled by mechanical joining methods (using rivets, bolts, pins, etc.). Holes must be drilled in the parts to be joined, and the strength of the components subjected to static and fatigue loads caused by stress concentration must be decreased. In this study, we experimentally evaluated the variation in the residual strength of a holenotched CFRP plate subjected to fatigue load. We repeatedly subjected the hole-notched specimen to fatigue load for a certain number of cycles, and then we investigated the residual strength of the hole-notched specimen by performing the fracture test. From the results of the test, we can observe the initiation of a directional crack caused by the applied fatigue load. Further, we observed that the residual strength increases with a decrease in the notch effect due to this crack. It was evaluated that the residual strength increases to a certain level and subsequently decreases. This variation in the residual strength was represented by a simple equation by using a model of the decrease in residual strength for plain plate, which was developed by Reifsnider and a stress redistribution model for hole-notched plate, which was developed by Yip.

  17. Evaluation of Variation in Residual Strength of Carbon Fiber Reinforced Plastic Plate with a Hole Subjected to Fatigue Load

    International Nuclear Information System (INIS)

    Kim, Sang Young; Kang, Min Sung; Koo, Jae Mean; Seok, Chang Sung

    2010-01-01

    CFRP (Carbon Fiber Reinforced Plastic) has received considerable attention in various fields as a structural material, because of its high specific strength, high specific stiffness, excellent design flexibility, favorable chemical properties, etc. Most products consisting of several parts are generally assembled by mechanical joining methods (using rivets, bolts, pins, etc.). Holes must be drilled in the parts to be joined, and the strength of the components subjected to static and fatigue loads caused by stress concentration must be decreased. In this study, we experimentally evaluated the variation in the residual strength of a holenotched CFRP plate subjected to fatigue load. We repeatedly subjected the hole-notched specimen to fatigue load for a certain number of cycles, and then we investigated the residual strength of the hole-notched specimen by performing the fracture test. From the results of the test, we can observe the initiation of a directional crack caused by the applied fatigue load. Further, we observed that the residual strength increases with a decrease in the notch effect due to this crack. It was evaluated that the residual strength increases to a certain level and subsequently decreases. This variation in the residual strength was represented by a simple equation by using a model of the decrease in residual strength for plain plate, which was developed by Reifsnider and a stress redistribution model for hole-notched plate, which was developed by Yip

  18. Effect of Fillet Rolling Load on the Fatigue Performance of a Micro-Alloy Steel Diesel Engine Crankshaft

    Science.gov (United States)

    Çevik, Gül; Gürbüz, Rıza

    2017-05-01

    Fillet rolling process is an effective method used to improve the fatigue performance of crankshafts by hardening the fillet region and inducing compressive residual stresses. This paper summarizes the work conducted to investigate the effect of rolling load on fatigue behaviour of a micro-alloy steel crankshaft used in diesel engine applications. Based on the staircase test methodology, component-scale resonant bending fatigue tests were conducted to obtain stress versus number of cycles curves and to evaluate the fatigue endurance limits of the crankshaft at un-rolled condition and fillet-rolled conditions at three different loads. Test data was analysed by Dixon-Mood method to calculate the endurance limits. Results showed that the endurance limit increased significantly with fillet rolling process in comparison to un-rolled condition. Endurance limit further increased with the increasing rolling load however with a limited extent above which excessive hardening deteriorates the fillet region; that is the workability limit. The outcomes of this study has shed light on the fillet rolling process to select the optimum rolling load for the used design and material conditions.

  19. Implementation of internal model based control and individual pitch control to reduce fatigue loads and tower vibrations in wind turbines

    Science.gov (United States)

    Mohammadi, Ebrahim; Fadaeinedjad, Roohollah; Moschopoulos, Gerry

    2018-05-01

    Vibration control and fatigue loads reduction are important issues in large-scale wind turbines. Identifying the vibration frequencies and tuning dampers and controllers at these frequencies are major concerns in many control methods. In this paper, an internal model control (IMC) method with an adaptive algorithm is implemented to first identify the vibration frequency of the wind turbine tower and then to cancel the vibration signal. Standard individual pitch control (IPC) is also implemented to compare the performance of the controllers in term of fatigue loads reduction. Finally, the performance of the system when both controllers are implemented together is evaluated. Simulation results demonstrate that using only IMC or IPC alone has advantages and can reduce fatigue loads on specific components. IMC can identify and suppress tower vibrations in both fore-aft and side-to-side directions, whereas, IPC can reduce fatigue loads on blades, shaft and yaw bearings. When both IMC and IPC are implemented together, the advantages of both controllers can be used. The aforementioned analysis and comparisons were not studied in literature and this study fills this gap. FAST, AreoDyn and Simulink are used to simulate the mechanical, aerodynamic and electrical aspects of wind turbine.

  20. Influence of test parameters on the thermal-mechanical fatigue behavior of a superalloy

    Science.gov (United States)

    Malpertu, J. L.; Rémy, L.

    1990-01-01

    The thermal-mechanical fatigue (TMF) behavior of IN-100, a cast nickel-base superalloy, was investigated with a basic mechanical strain-temperature loop applied in a temperature range from 600 °C to 1050 °C (873 to 1323 K). Peak strains were applied at intermediate temperatures, giving a faithful simulation of real component parts. Tests with or without a mean strain were used; other tests involved a longer period or a tensile hold time, and they were compared with conventional “in-phase” TMF cycles. An interrupted test procedure was used with a plastic replication technique to define a conventional TMF life to 0.3-mm crack depth, as well as a life to 50-µm, crack depth, to characterize the crack initiation period. Some stress-strain hysteresis loops were reported. Thermal-mechanical fatigue life was found to be dependent upon test parameters, while the life to crack initiation was not. Oxidation of specimens and micro-cracks was found to be important in all the tests. These results were then discussed and compared with those under low cycle fatigue at high temperature.

  1. 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

  2. Assessment of Pressure Fluctuation Effect for Thermal Fatigue in a T-junction Using Thermo-Hydro Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Pyo, Jaebum; Kim, Jungwoo; Huh, Namsu [Seoul National Univ. of Science and Technology, Seoul (Korea, Republic of); Kim, Sunhye [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2013-10-15

    As a result, when evaluating thermal fatigue for the mixing tee, temperature fluctuation is dominant for this phenomenon, it can be reasonably assumed that the pressure is constant on the pipe inner wall. Recently, thermal fatigue due to mixing of the fluids having different temperatures has been considered as an important issue on the fatigue evaluation of nuclear piping. Mainly, this phenomenon occurs in a T-junction operating with the fluids consisted of different temperatures. Because of the turbulent mixing of hot and cold water, the temperature on the inner wall of the pipe fluctuates rapidly, causing the variation of thermal stresses in the pipe and resulting in high cycle thermal fatigue. In practice, cracking by high cycle thermal fatigue is reported at a T-junction in the residual heat removal system at Civaux unit 1 in France. However, because of irregular flow inside the pipe, the pressure also fluctuates rapidly as well as temperature in the inner wall of the pipe. Therefore, in this paper, three-dimensional thermo-hydro analysis was performed for the mixing tee of the shutdown cooling system of the pressurized water reactor plant, examining the pressure variation at the pipe inner wall. Based on the analysis result, this study aims at assessing the pressure fluctuation effect on the thermal fatigue. In this paper, it is verified that there is pressure fluctuation as well as temperature on the inner wall of mixing tee operating with the fluids having different temperatures. However, since the amplitude of pressure is relatively smaller than design pressure of the shutdown cooling system, the effect wouldn't be important for the thermal fatigue.

  3. Fatigue behavior of an insulation system for the ITER magnets in the load and strain controlled mode

    Energy Technology Data Exchange (ETDEWEB)

    Prokopec, R. [Atomic Institute of the Austrian Universities, Vienna University of Technology, 1020 Vienna (Austria); Humer, K. [Atomic Institute of the Austrian Universities, Vienna University of Technology, 1020 Vienna (Austria)], E-mail: khumer@ati.ac.at; Weber, H.W. [Atomic Institute of the Austrian Universities, Vienna University of Technology, 1020 Vienna (Austria)

    2007-10-15

    The application of glass-fiber reinforced plastics as insulation materials for fusion magnet coils (e.g. of ITER) requires a full mechanical material characterization under ITER relevant conditions. The tension-tension fatigue test is useful to simulate the pulsed tokamak operation of the ITER coils in the relevant range of 10{sup 4}-10{sup 5} cycles. The fatigue process can be run under load or strain control, which may influence the material behavior under cyclic load conditions. Therefore, investigations were performed at 77 K using an industrial glass-fiber reinforced composite impregnated with epoxy resin. For both the load and the strain controlled mode, R-values of 0.3 and 0.5 and a frequency of 10 Hz were chosen. The results are discussed with respect to the lifetime performance of ITER.

  4. Fatigue History and in-situ Loading Studies of the overload Effect Using High Resolution X-ray Strain Profiling

    International Nuclear Information System (INIS)

    Croft, M.; Jisrawi, N.; Zhong, Z.; Holtz, R.; Sadananda, K.; Skaritka, J.; Tsakalakos, T.

    2007-01-01

    High-energy synchrotron X-ray diffraction experiments are used to perform local crack plane strain profiling of 4140 steel compact tension specimens fatigued at constant amplitude, subjected to a single overload cycle, then fatigued some more at constant amplitude. X-ray strain profiling results on a series of samples employing in-situ load cycling are correlated with the crack growth rate (da/dN) providing insight into the da/dN retardation known as the 'overload effect'. Immediately after the overload, the strain under maximum load is greatly reduced but the range of strain, between zero and maximum load, remains unchanged compared to the pre-overload values. At the point of maximum retardation, it is the strain range that is greatly reduced while the maximum-load strain has begun to recover to the pre-overload value. For a sample that has recovered to approximately half of the original da/dN value following the overload, the strain at maximum load is fully recovered while the strain range, though partially recovered, is still substantially reduced. The dominance of the strain range in the overload effect is clearly indicated. Subject to some assumptions, strong quantitative support for a crack growth rate driving force of the suggested form [(K max ) -p (ΔK) p ] γ is found. A dramatic nonlinear load dependence in the spatial distribution of the strain at maximum retardation is also demonstrated: at low load the response is dominantly at the overload position; whereas at high loads it is dominantly at the crack tip position. This transfer of load response away from the crack tip to the overload position appears fundamental to the overload effect for high R-ratio fatigue as studied here

  5. Variation of Extreme and Fatigue Design Loads on the Main Bearing of a Front Mounted Direct Drive System

    DEFF Research Database (Denmark)

    Abrahamsen, Asger Bech; Natarajan, Anand

    2016-01-01

    on the thrust and bending moments at the main bearing, both for ultimate design and in fatigue. It is found that the initial superconductor generator weight of 363 tons must be reduced by 25% in order not to result in higher extreme loads on main and yaw bearing than the reference10 MW geared reference drive...... train. A weight reduction of 50% is needed in order to maintain main bearing fatigue damage equivalent to the reference drive train. Thus a target mass of front mounted superconducting direct drive generators is found to be between 183-272 tons....

  6. 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).

  7. Transient thermal stresses analysis and thermal fatigue damage evaluation for skirt attachment of coke drum

    Science.gov (United States)

    Ambarita, H.; Siahaan, A. S.; Kawai, H.; Daimaruya, M.

    2018-02-01

    In the last decade, the demand for delayed coking capacity has been steadily increasing. The trend in the past 15 to 20 years has been for operators to try to maximize the output of their units by reducing cycle times. This mode of operation can result in very large temperature gradients within the drums during preheating stage and even more so during the quench cycle. This research provide the optimization estimation of fatigue life due to each for the absence of preheating stage and cutting stage. In the absence of preheating stage the decreasing of fatigue life is around 19% and the increasing of maximum stress in point 5 of shell-to-skirt junction is around 97 MPa. However for the absence of cutting stage it was found that is more severe compare to normal cycle. In this adjustment fatigue life reduce around 39% and maximum stress is increased around 154 MPa. It can concluded that for cycle optimization, eliminating preheating stage possibly can become an option due to the increasing demand of delayed coking process.

  8. Coarsening of the Sn-Pb Solder Microstructure in Constitutive Model-Based Predictions of Solder Joint Thermal Mechanical Fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Vianco, P.T.; Burchett, S.N.; Neilsen, M.K.; Rejent, J.A.; Frear, D.R.

    1999-04-12

    Thermal mechanical fatigue (TMF) is an important damage mechanism for solder joints exposed to cyclic temperature environments. Predicting the service reliability of solder joints exposed to such conditions requires two knowledge bases: first, the extent of fatigue damage incurred by the solder microstructure leading up to fatigue crack initiation, must be quantified in both time and space domains. Secondly, fatigue crack initiation and growth must be predicted since this metric determines, explicitly, the loss of solder joint functionality as it pertains to its mechanical fastening as well as electrical continuity roles. This paper will describe recent progress in a research effort to establish a microstructurally-based, constitutive model that predicts TMF deformation to 63Sn-37Pb solder in electronic solder joints up to the crack initiation step. The model is implemented using a finite element setting; therefore, the effects of both global and local thermal expansion mismatch conditions in the joint that would arise from temperature cycling.

  9. Bonding ability of three ethanol-based adhesives after thermal fatigue.

    Science.gov (United States)

    Perdigão, Jorge; Gomes, George; Sezinando, Ana

    2011-06-01

    To study the effect of thermal fatigue on the microTBS and interfacial morphology of three ethanol-based etch-&-rinse 2-bottle adhesives. microTBS - 24 third molars were randomly assigned to one of three adhesive systems: (1) Adper Single Bond Plus (SBP, 3M ESPE); (2) Ambar (AMB, FGM); (3) Excite (EXC, Ivoclar Vivadent), and restored with a hybrid resin composite. For each adhesive, half of the specimens were thermocycled (TC) for 20,000 cycles (5-55 degrees C) while the other half was kept in distilled water for 24 hours at 37 degreesC (control). Specimens were sectioned in X and Y directions and the resulting sticks were tested to failure in tension mode at a crosshead speed of 1 mm/minute. Statistical analysis was computed using ANOVA and Tukey's post hoc for the microTBS; and non-parametric cross-tabulation with Chi-Square for the pre-testing failures at P< 0.05. Interfacial morphology -The occlusal enamel was removed from 12 extracted molars perpendicular to the long axis of the tooth. Teeth were equally assigned to one of the three adhesives and restored with a 1 mm-thick layer of a hybrid composite resin. A 2 mm-thick disk was sectioned from each specimen and cross-sectioned in two identical halves. Half of the each specimen was TC for 20,000 cycles (5-55 degrees C) while the other half was kept in distilled water for 24 hours at 37 degrees C (control). Specimens were chemically challenged and prepared for FESEM observation to observe the integrity of the hybrid layer before and after thermal fatigue. Micrographs were recorded digitally at standard magnifications and measurements were taken with the microscope embedded image software. microTBS - SBP and AMB resulted in statistically similar mean microTBS regardless of thermal fatigue. EXC resulted in statistically lower mean microTBS than SBP and AMB for the control (P< 0.001) and for the TC specimens (P< 0.0001). Interfacial morphology - The hybrid layers of SBP and AMB were densely infiltrated without

  10. Thermal fatigue cracking in T-fittings of feed water systems

    International Nuclear Information System (INIS)

    Oesterberg, J.

    1983-03-01

    The existence of thermal fatigue cracks can be determined by ultrasonic methods. The depth of the cracks will be of importance for evaluation of the seriousness of the situation. Currently, no method is available for determining depth of cracks without cutting and grinding. Methods for gaining information of crack depth have been discussed with leading European materials testing institutes. More elaborate ultrasonic methods have been tested with negative results. On testing signals from crack corners flood possible signals from the crack tips. At present no reliable technique based on ultrasonics exist (in Europe, that will give information of crack depth.(P.Aa.)

  11. Submerged Arc Stainless Steel Strip Cladding—Effect of Post-Weld Heat Treatment on Thermal Fatigue Resistance

    Science.gov (United States)

    Kuo, I. C.; Chou, C. P.; Tseng, C. F.; Lee, I. K.

    2009-03-01

    Two types of martensitic stainless steel strips, PFB-132 and PFB-131S, were deposited on SS41 carbon steel substrate by a three-pass submerged arc cladding process. The effects of post-weld heat treatment (PWHT) on thermal fatigue resistance and hardness were evaluated by thermal fatigue and hardness testing, respectively. The weld metal microstructure was investigated by utilizing optical microscopy, scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). Results showed that, by increasing the PWHT temperature, hardness decreased but there was a simultaneous improvement in weldment thermal fatigue resistance. During tempering, carbide, such as (Fe, Cr)23C6, precipitated in the weld metals and molybdenum appeared to promote (Fe, Cr, Mo)23C6 formation. The precipitates of (Fe, Cr, Mo)23C6 revealed a face-centered cubic (FCC) structure with fine grains distributed in the microstructure, thereby effectively increasing thermal fatigue resistance. However, by adding nickel, the AC1 temperature decreased, causing a negative effect on thermal fatigue resistance.

  12. 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.

  13. 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.

  14. 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.

  15. Thermal Fatigue Evaluation of Pb-Free Solder Joints: Results, Lessons Learned, and Future Trends

    Science.gov (United States)

    Coyle, Richard J.; Sweatman, Keith; Arfaei, Babak

    2015-09-01

    Thermal fatigue is a major source of failure of solder joints in surface mount electronic components and it is critically important in high reliability applications such as telecommunication, military, and aeronautics. The electronic packaging industry has seen an increase in the number of Pb-free solder alloy choices beyond the common near-eutectic Sn-Ag-Cu alloys first established as replacements for eutectic SnPb. This paper discusses the results from Pb-free solder joint reliability programs sponsored by two industry consortia. The characteristic life in accelerated thermal cycling is reported for 12 different Pb-free solder alloys and a SnPb control in 9 different accelerated thermal cycling test profiles in terms of the effects of component type, accelerated thermal cycling profile and dwell time. Microstructural analysis on assembled and failed samples was performed to investigate the effect of initial microstructure and its evolution during accelerated thermal cycling test. A significant finding from the study is that the beneficial effect of Ag on accelerated thermal cycling reliability (measured by characteristic lifetime) diminishes as the severity of the accelerated thermal cycling, defined by greater ΔT, higher peak temperature, and longer dwell time increases. The results also indicate that all the Pb-free solders are more reliable in accelerated thermal cycling than the SnPb alloy they have replaced. Suggestions are made for future work, particularly with respect to the continued evolution of alloy development for emerging application requirements and the value of using advanced analytical methods to provide a better understanding of the effect of microstructure and its evolution on accelerated thermal cycling performance.

  16. Thermally Stimulated Current and Polarization Fatigue in Pb(Zr,Ti)O3 Thin Films

    Science.gov (United States)

    Okino, Hirotake; Toyoda, Yoshiaki; Shimizu, Masaru; Horiuchi, Toshihisa; Shiosaki, Tadashi; Matsushige, Kazumi

    1998-09-01

    In order to clarify the origin of the polarization fatigue phenomena,charge traps in ferroelectric Pb(Zr,Ti)O3 (PZT) thin filmswere measured using the thermally stimulated current (TSC) technique.For polarization fatigued Pt/PZT/Pt/SiO2/Si(100) capacitors,a peak of TSC was observed, andthe trap density estimated from the TSC dataincreased as switching cycles increased.Activation energy and density of the charge trapswere estimated to be 0.7 0.8 eV andon the order of 1018 cm-3,respectively.It was also observed thatdegradation of remanent polarization of PZTwas improved by the TSC measurement process.On the other hand, no TSC peak was observed forfatigue free Ir/PZT/Ir/IrO2/SiO2/Si(100) capacitors.From these results, it was suggested thatthe main origin of the polarization fatigue phenomenawas the domain pinning caused by trapped charge carriersinjected by polarization reversal.

  17. Thermal fatigue of a 304L austenitic stainless steel: simulation of the initiation and of the propagation of the short cracks in isothermal and aniso-thermal fatigue; Fatigue thermique d'un acier inoxydable austenitique 304L: simulation de l'amorcage et de la croissance des fissures courtes en fatigue isotherme et anisotherme

    Energy Technology Data Exchange (ETDEWEB)

    Haddar, N

    2003-04-01

    The elbow pipes of thermal plants cooling systems are submitted to thermal variations of short range and of variable frequency. These variations bound to temperature changes of the fluids present a risk of cracks and leakages. In order to solve this problem, EDF has started the 'CRECO RNE 808' plan: 'thermal fatigue of 304L austenitic stainless steels' to study experimentally on a volume part, the initiation and the beginning of the propagation of cracks in thermal fatigue on austenitic stainless steels. The aim of this study is more particularly to compare the behaviour and the damage of the material in mechanic-thermal fatigue (cycling in temperature and cycling in deformation) and in isothermal fatigue (the utmost conditions have been determined by EDF for the metal: Tmax = 165 degrees C and Tmin = 90 degrees C; the frequency of the thermal variations can reach a Hertz). A lot of experimental results are given. A model of lifetime is introduced and validated. (O.M.)

  18. Fatigue crack growth of aluminium alloy 7075-T651 under non-proportional mixed mode I and II loads

    Directory of Open Access Journals (Sweden)

    Xiaobo Yu

    2016-10-01

    Full Text Available This study aims to investigate fatigue growth behaviour in AA7075-T651 under non-proportional mixed mode I and II loads. Fatigue tests were performed under cyclic tension and torsion using a thin-walled tubular specimen with a key-hole style crack starter. After the generation of a single-side mode I pre-crack, varied forms of mixed mode loads were applied, which in most cases led to a short distance coplanar growth followed by a long and stable crack path deviation. It was found that under most of the non-proportional mixed mode load cases, the direction of the deviated crack path could not be reasonably predicted using the commonly accepted maximum tangential stress criterion. Meanwhile, in some cases, the crack path directions could be approximately predicted using the maximum shear stress criterion. It was also confirmed for the first time that a long, stable and noncoplanar shear mode fatigue crack growth could be produced in AA7075T651 under non-proportional mixed mode I and II loads. ©2016 Commonwealth of Australia

  19. 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

  20. 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

  1. Imposed Thermal Fatigue and Post-Thermal-Cycle Wear Resistance of Biomimetic Gray Cast Iron by Laser Treatment

    Science.gov (United States)

    Sui, Qi; Zhou, Hong; Zhang, Deping; Chen, Zhikai; Zhang, Peng

    2017-08-01

    The present study aims to create coupling biomimetic units on gray cast iron substrate by laser surface treatment (LST). LSTs for single-step (LST1) and two-step (LST2) processes, were carried out on gray cast iron in different media (air and water). Their effects on microstructure, thermal fatigue, and post-thermal-cycle wear (PTW) resistance on the specimens were studied. The tests were carried out to examine the influence of crack-resistance behavior as well as the biomimetic surface on its post-thermal-cycle wear behavior and different units, with different laser treatments for comparison. Results showed that LST2 enhanced the PTW behaviors of gray cast iron, which then led to an increase in its crack resistance. Among the treated cast irons, the one treated by LST2 in air showed the lowest residual stress, due to the positive effect of the lower steepness of the thermal gradient. Moreover, the same specimen showed the best PTW performance, due to its superior crack resistance and higher hardness as a result of it.

  2. 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

  3. Effect of Stress Ratio and Loading Frequency on the Corrosion Fatigue Behavior of Smooth Steel Wire in Different Solutions

    Directory of Open Access Journals (Sweden)

    Songquan Wang

    2016-09-01

    Full Text Available In this work, the effects of loading condition and corrosion solution on the corrosion fatigue behavior of smooth steel wire were discussed. The results of polarization curves and weight loss curves showed that the corrosion of steel wire in acid solution was more severe than that in neutral and alkaline solutions. With the extension of immersion time in acid solution, the cathodic reaction of steel wire gradually changed from the reduction of hydrogen ion to the reduction of oxygen, but was always the reduction of hydrogen ion in neutral and alkaline solutions. The corrosion kinetic parameters and equivalent circuits of steel wires were also obtained by simulating the Nyquist diagrams. In corrosion fatigue test, the effect of stress ratio and loading frequency on the crack initiation mechanism was emphasized. The strong corrosivity of acid solution could accelerate the nucleation of crack tip. The initiation mechanism of crack under different conditions was summarized according to the side and fracture surface morphologies. For the crack initiation mechanism of anodic dissolution, the stronger the corrosivity of solution was, the more easily the fatigue crack source formed, while, for the crack initiation mechanism of deformation activation, the lower stress ratio and higher frequency would accelerate the generation of corrosion fatigue crack source.

  4. Effects of carbon content on high-temperature mechanical and thermal fatigue properties of high-boron austenitic steels

    Directory of Open Access Journals (Sweden)

    Xiang Chen

    2016-01-01

    Full Text Available High-temperature mechanical properties of high-boron austenitic steels (HBASs were studied at 850 °C using a dynamic thermal-mechanical simulation testing machine. In addition, the thermal fatigue properties of the alloys were investigated using the self-restraint Uddeholm thermal fatigue test, during which the alloy specimens were cycled between room temperature and 800°C. Stereomicroscopy and scanning electron microscopy were used to study the surface cracks and cross-sectional microstructure of the alloy specimens after the thermal fatigue tests. The effects of carbon content on the mechanical properties at room temperature and high-temperature as well as thermal fatigue properties of the HBASs were also studied. The experimental results show that increasing carbon content induces changes in the microstructure and mechanical properties of the HBASs. The boride phase within the HBAS matrix exhibits a round and smooth morphology, and they are distributed in a discrete manner. The hardness of the alloys increases from 239 (0.19wt.% C to 302 (0.29wt.% C and 312 HV (0.37wt.% C; the tensile yield strength at 850 °C increases from 165.1 to 190.3 and 197.1 MPa; and the compressive yield strength increases from 166.1 to 167.9 and 184.4 MPa. The results of the thermal fatigue tests (performed for 300 cycles from room temperature to 800 °C indicate that the degree of thermal fatigue of the HBAS with 0.29wt.% C (rating of 2–3 is superior to those of the alloys with 0.19wt.% (rating of 4–5 and 0.37wt.% (rating of 3–4 carbon. The main cause of this difference is the ready precipitation of M23(C,B6-type borocarbides in the alloys with high carbon content during thermal fatigue testing. The precipitation and aggregation of borocarbide particles at the grain boundaries result in the deterioration of the thermal fatigue properties of the alloys.

  5. 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.

  6. 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.

  7. The Influence of PV Module Materials and Design on Solder Joint Thermal Fatigue Durability

    Energy Technology Data Exchange (ETDEWEB)

    Bosco, Nick; Silverman, Timothy J.; Kurtz, Sarah

    2016-11-01

    Finite element model (FEM) simulations have been performed to elucidate the effect of flat plate photovoltaic (PV) module materials and design on PbSn eutectic solder joint thermal fatigue durability. The statistical method of Latin Hypercube sampling was employed to investigate the sensitivity of simulated damage to each input variable. Variables of laminate material properties and their thicknesses were investigated. Using analysis of variance, we determined that the rate of solder fatigue was most sensitive to solder layer thickness, with copper ribbon and silicon thickness being the next two most sensitive variables. By simulating both accelerated thermal cycles (ATCs) and PV cell temperature histories through two characteristic days of service, we determined that the acceleration factor between the ATC and outdoor service was independent of the variables sampled in this study. This result implies that an ATC test will represent a similar time of outdoor exposure for a wide range of module designs. This is an encouraging result for the standard ATC that must be universally applied across all modules.

  8. Thermal-fatigue and oxidation resistance of cobalt-modified Udimet 700 alloy

    International Nuclear Information System (INIS)

    Bizon, P.T.; Barrow, B.J.

    1986-04-01

    Comparative thermal-fatigue and oxidation resistances of cobalt-modified wrought Udimet 700 alloy (obtained by reducing the cobalt level by direct substitution of nickel) were determined from fluidized-bed tests. Bed temperatures were 1010 and 288 C (1850 and 550 C) for the first 5500 symmetrical 6-min cycles. From cycle 5501 to the 14000-cycle limit of testing, the heating bed temperature was increased to 1050 C (1922 F). Cobalt levels between 0 and 17 wt% were studied in both the bare and NiCrAlY overlay coated conditions. A cobalt level of about 8 wt% gave the best thermal-fatigue life. The conventional alloy specification is for 18.5% cobalt, and hence, a factor of 2 in savings of cobalt could be achieved by using the modified alloy. After 13500 cycles, all bare cobalt-modified alloys lost 10 to 13 percent of their initial weight. Application of the NiCrAlY overlay coating resulted in weight losses of 1/20 to 1/100 of that of the corresponding bare alloy

  9. An investigation of wall temperature characteristics to evaluate thermal fatigue at a T-junction pipe

    International Nuclear Information System (INIS)

    Miyoshi, Koji; Nakamura, Akira; Utanohara, Yoichi; Takenaka, Nobuyuki

    2014-01-01

    Thermal fatigue cracking may initiate at a T-junction pipe where high and low temperature fluids mix. In this study, wall temperature characteristics at a T-junction pipe were investigated to improve the evaluation method for thermal fatigue. The stainless steel test section consisted of a horizontal main pipe (diameter, 150 mm) and a T-junction connected to a vertical branch pipe (diameter, 50 mm). The inlet flow velocities in the main and branch pipes were set to 0.99 m/s and 0.66 m/s respectively to produce a wall jet pattern in which the jet from the branch pipe was bent by the main pipe flow and made to flow along the pipe wall. The temperature difference was 34.1 K. A total of 148 thermocouples were installed to measure the wall temperature on the pipe inner surface in the downstream region. The maximum of temperature fluctuation intensity on the pipe inner surface was measured as 5% of the fluid temperature difference at the inlets. The dominant frequency of the large temperature fluctuations in the region downstream from z = 0.5D m was equal to 0.2 of the Strouhal number, which was equal to the frequency caused by the vortex streets generated around the jet flow. The large temperature fluctuation was also observed with the period of about 10 s. The fluctuation was caused by spreading of the heated region in the circumferential direction. (author)

  10. Thermal fatigue testing of a diffusion-bonded beryllium divertor mock-up under ITER relevant conditions

    International Nuclear Information System (INIS)

    Youchison, D.L.; Guiniiatouline, R.; Watson, R.D.

    1994-01-01

    Thermal response and thermal fatigue tests of four 5 mm thick beryllium tiles on a Russian divertor mock-up were completed on the Electron Beam Test System at Sandia National Laboratories. The beryllium tiles were diffusion bonded onto an OFHC copper saddleblock and a DSCu (MAGT) tube containing a porous coating. Thermal response tests were performed on the tiles to an absorbed heat flux of 5 MW/m 2 and surface temperatures near 300 degrees C using 1.4 MPa water at 5.0 m/s flow velocity and an inlet temperature of 8-15 degrees C. One tile was exposed to incrementally increasing heat fluxes up to 9.5 MW/m 2 and surface temperatures up to 690 degrees C before debonding at 10 MW/m 2 . A third tile debonded after 9200 thermal fatigue cycles at 5 MW/m 2 , while another debonded after 6800 cycles. In all cases, fatigue failure occurred in the intermetallic layers between the beryllium and copper. No fatigue cracking of the bulk beryllium was observed. During thermal cycling, a gradual loss of porous coating produced increasing sample temperatures. These experiments indicate that diffusion-bonded beryllium tiles can survive several thousand thermal cycles under ITER relevant conditions without failure. However, the reliability of the diffusion bonded Joint remains a serious issue

  11. A practical approach for predicting fatigue reliability under random cyclic loading

    International Nuclear Information System (INIS)

    Tang Jun; Zhao Jie

    1995-01-01

    The purpose of this paper is to provide a simple approach for reliability analysis based on fatigue or overstress failure modes of mechanical components, and explain how this integrated method carries out spectral fatigue damage and failure reliability analysis. In exploring the ability to predict spectral fatigue life and assess the reliability under a specified dynamics environment, a methodology for reliability assessment and its corresponding fatigue life prediction of mechanical components using a supply-demand interference approach is developed in this paper. Since the methodology couples dynamics analysis and stochastic analysis for fatigue damage and reliability prediction, the conversion of the duty cycle history for the reliability study of an individual component is also presented. Using the proposed methodology, mechanical component reliability can be predicted according to different mission requirements. For an explanation of this methodology, a probabilistic method of deciding the relationship between the allowable stress or fatigue endurance limit and reliability is also presented

  12. Investigation of structure-property relationships of polyisobutylene-based biomaterials: Morphology, thermal, quasi-static tensile and long-term dynamic fatigue behavior.

    Science.gov (United States)

    Götz, C; Lim, G T; Puskas, J E; Altstädt, V

    2012-06-01

    This study examines the morphology, thermal, quasi-static and long-term dynamic creep properties of one linear and three arborescent polyisobutylene-based block copolymers (L_SIBS31, D_IBS16, D_IBS27 and D_IBS33). Silicone rubber, a common biopolymer, was considered as a benchmark material for comparison. A unique hysteretic testing methodology of Stepwise Increasing Load Test (SILT) and Single Load Test (SLT) was used in this study to evaluate the long-term dynamic fatigue performance of these materials. Our experimental findings revealed that the molecular weight of polyisobutylene (PIB) and polystyrene (PS) arms [M(n)(PIB(arm)) and M(n)(PS(arm))], respectively had a profound influence on the nano-scaled phase separation, quasi-static tensile, thermal transition, and dynamic creep resistance behaviors of these PIB-based block copolymers. However, silicone rubber outperformed the PIB-based block copolymers in terms of dynamic creep properties due to its chemically crosslinked structure. This indicates a need for a material strategy to improve the dynamic fatigue and creep of this class of biopolymers to be considered as alternative to silicone rubber for biomedical devices. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. 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)

  14. 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

  15. Influence of microstructural parameters on the deformation and failure behaviour of the ODS alloy PM 2000 under creep and creep-fatigue loading

    International Nuclear Information System (INIS)

    Bothe, K.; Kussmaul, K.; Maile, K.

    1999-01-01

    The influence of grain size, manufacturing type and specimen direction (anisotropy) with respect to deformation and failure behaviour under creep, fatigue and creep-fatigue load was investigated. Thus, a basis for the correlation between microstructure and mechanical behaviour has been established. The specific damage and failure behaviour could be explained by means of the different microstructures observed. (orig.)

  16. The effect of preparation height and luting agent on the resistance form of cemented cast crowns under load fatigue.

    Science.gov (United States)

    Leong, Elvin W J; Choon Tan, Keson Beng; Nicholls, Jack Ivan; Chua, Ee Kiam; Wong, Keng Mun; Neo, Jennifer Chiew Lian

    2009-09-01

    The minimum amount of resistance form required for the success of a clinical crown is unknown.There is little information on the fatigue performance of complete coverage restorations on natural tooth preparations cemented with different luting cements. The purpose of this study was to evaluate the effect of tooth preparation height and luting agent on resistance form using unidirectional load fatigue testing. For a given tooth preparation with a clinically relevant total occlusal convergence (TOC), the adequacy of resistance form was investigated. Sixty-four human maxillary premolars were prepared with occlusal-cervical dimensions of 2, 3,4, or 5 mm and a TOC of 20 degrees. Complete metal crowns were cemented using either zinc phosphate cement (HY Bond;ZP groups) or resin cement (Panavia F; PF groups). Cyclic load fatigue testing was done with an applied load of 6.0 kg at 2.6 Hz. Load cycles to preliminary failure were detected with a strain gauge at the palatal crown-tooth interface. Results were subjected to the Kruskal-Wallis test and the Wilcoxon post-hoc rank sum test (alpha=.05). Groups ZP4, ZP5, PF2, PF3, PF4, and PF5 had the highest mean number of cycles to preliminary failure,while group ZP2 had the lowest mean number of cycles to failure. Group ZP2 was significantly different (Pcement exhibited a poorer fatigue performance compared to Panavia F. There was no significant difference in the number of cycles to failure for groups ZP4,ZP5, PF2, PF3, PF4, and PF5. For both cements, the number of cycles to failure increased with increasing resistance length. (J Prosthet Dent 2009;102:155-164)

  17. 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)

  18. Influence of Mixed Mode I-Mode II Loading on Fatigue Delamination Growth Characteristics of a Graphite Epoxy Tape Laminate

    Science.gov (United States)

    Ratcliffe, James G.; Johnston, William M., Jr.

    2014-01-01

    Mixed mode I-mode II interlaminar tests were conducted on IM7/8552 tape laminates using the mixed-mode bending test. Three mixed mode ratios, G(sub II)/G(sub T) = 0.2, 0.5, and 0.8, were considered. Tests were performed at all three mixed-mode ratios under quasi-static and cyclic loading conditions, where the former static tests were used to determine initial loading levels for the latter fatigue tests. Fatigue tests at each mixed-mode ratio were performed at four loading levels, Gmax, equal to 0.5G(sub c), 0.4G(sub c), 0.3G(sub c), and 0.2G(sub c), where G(sub c) is the interlaminar fracture toughness of the corresponding mixed-mode ratio at which a test was performed. All fatigue tests were performed using constant-amplitude load control and delamination growth was automatically documented using compliance solutions obtained from the corresponding quasi-static tests. Static fracture toughness data yielded a mixed-mode delamination criterion that exhibited monotonic increase in Gc with mixed-mode ratio, G(sub II)/G(sub T). Fatigue delamination onset parameters varied monotonically with G(sub II)/G(sub T), which was expected based on the fracture toughness data. Analysis of non-normalized data yielded a monotonic change in Paris law exponent with mode ratio. This was not the case when normalized data were analyzed. Fatigue data normalized by the static R-curve were most affected in specimens tested at G(sub II)/G(sub T)=0.2 (this process has little influence on the other data). In this case, the normalized data yielded a higher delamination growth rate compared to the raw data for a given loading level. Overall, fiber bridging appeared to be the dominant mechanism, affecting delamination growth rates in specimens tested at different load levels and differing mixed-mode ratios.

  19. Crack Growth Behavior in the Threshold Region for High Cycle Fatigue Loading

    Science.gov (United States)

    Forman, R. G.; Zanganeh, M.

    2014-01-01

    This paper describes the results of a research program conducted to improve the understanding of fatigue crack growth rate behavior in the threshold growth rate region and to answer a question on the validity of threshold region test data. The validity question relates to the view held by some experimentalists that using the ASTM load shedding test method does not produce valid threshold test results and material properties. The question involves the fanning behavior observed in threshold region of da/dN plots for some materials in which the low R-ratio data fans out from the high R-ratio data. This fanning behavior or elevation of threshold values in the low R-ratio tests is generally assumed to be caused by an increase in crack closure in the low R-ratio tests. Also, the increase in crack closure is assumed by some experimentalists to result from using the ASTM load shedding test procedure. The belief is that this procedure induces load history effects which cause remote closure from plasticity and/or roughness changes in the surface morphology. However, experimental studies performed by the authors have shown that the increase in crack closure is a result of extensive crack tip bifurcations that can occur in some materials, particularly in aluminum alloys, when the crack tip cyclic yield zone size becomes less than the grain size of the alloy. This behavior is related to the high stacking fault energy (SFE) property of aluminum alloys which results in easier slip characteristics. Therefore, the fanning behavior which occurs in aluminum alloys is a function of intrinsic dislocation property of the alloy, and therefore, the fanned data does represent the true threshold properties of the material. However, for the corrosion sensitive steel alloys tested in laboratory air, the occurrence of fanning results from fretting corrosion at the crack tips, and these results should not be considered to be representative of valid threshold properties because the fanning is

  20. Refinements and Tests of an Advanced Controller to Mitigate Fatigue Loads in the Controls Advanced Research Turbine: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Wright, A.; Fleming, P.

    2010-12-01

    Wind turbines are complex, nonlinear, dynamic systems forced by aerodynamic, gravitational, centrifugal, and gyroscopic loads. The aerodynamics of wind turbines are nonlinear, unsteady, and complex. Turbine rotors are subjected to a complicated 3-D turbulent wind inflow field, with imbedded coherent vortices that drive fatigue loads and reduce lifetime. Design of control algorithms for wind turbines must account for multiple control objectives. Future large multi-megawatt turbines must be designed with lighter weight structures, using active controls to mitigate fatigue loads, while maximizing energy capture. Active damping should be added to these dynamic structures to maintain stability for operation in a complex environment. At the National Renewable Energy Laboratory (NREL), we have designed, implemented, and tested advanced controls to maximize energy extraction and reduce structural dynamic loads. These control designs are based on linear models of the turbine that are generated by specialized modeling software. In this paper, we present field test results of an advanced control algorithm to mitigate blade, tower, and drivetrain loads in Region 3.

  1. The thermal fatigue resistance of vermicular cast iron coupling with H13 steel units by cast-in process

    International Nuclear Information System (INIS)

    Wang, Chengtao; Zhou, Hong; Lin, Peng Yu; Sun, Na; Guo, Qingchun; Zhang, Peng; Yu, Jiaxiang; Liu, Yan; Wang, Mingxing; Ren, Luquan

    2010-01-01

    This paper focuses on improving the thermal fatigue resistance on the surface of vermicular cast iron coupling with inserted H13 steel blocks that had different cross sections, by cast-in processing. The microstructure of bionic units was examined by scanning electron microscope. Micro-hardness and thermal fatigue resistance of bionic samples with varied cross sections and spacings were investigated, respectively. Results show that a marked metallurgical bonding zone was produced at interface between the inserted H13 steel block and the parent material - a unique feature of the bionic structure in the vermicular cast iron samples. The micro-hardness of the bionic samples has been significantly improved. Thermal resistance of the samples with the circular cross section was the highest and the bionics sample with spacing of 2 mm spacing had a much longer thermal fatigue life, thus resulting in the improvement for the thermal fatigue life of the bionic samples, due to the efficient preclusion for the generation and propagation of crack at the interface of H13 block and the matrix.

  2. Accelerated fatigue testing of LM 19.1 blades

    DEFF Research Database (Denmark)

    Kristensen, Ole Jesper Dahl; Jørgensen, E.

    2003-01-01

    material. In addition to the thermal imaging surveillance the blades were instrumented with strain gauges. This report presents the temperature duringtest, calibration test results, moment range measurements, strain statistics, thermal imaging registrations and a determination of the size and cause......A series of 19.1 metre wind turbine blades manufactured by LM Glasfiber A/S of Lunderskov, Denmark were subjected to a series of flapwise fatigue tests. The object of these fatigue tests is to evaluate the impact of an increased load on the blade in afatigue test and to give information...... if it is possible to increase the load in fatigue test to shorten test time. The tests were carried out as a part of a project financed by the Danish Energy Agency. During the fatigue tests the blades have beensurveyed with thermal imaging equipment to determine how an increase in fatigue load affects the blade...

  3. Stability of ultrafine-grained structure of copper under fatigue loading

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr; Pantělejev, L.; Man, O.

    2011-01-01

    Roč. 10, - (2011), s. 201-206 E-ISSN 1877-7058 R&D Projects: GA ČR GAP108/10/2001 Institutional research plan: CEZ:AV0Z20410507 Keywords : fatigue of ultrafine-grained Cu * stability of ultrafine-grained structure * cyclic slip bands * shear bands Subject RIV: JL - Materials Fatigue, Friction Mechanics

  4. Prediction of thermal fatigue in Tooling for die-casting copper via finite element analysis

    International Nuclear Information System (INIS)

    Sakhuja, Amit; Brevick, Jerald R.

    2004-01-01

    Recent research by the Copper Development Association (CDA) has demonstrated the feasibility of die-casting electric motor rotors using copper. Electric motors using copper rotors are significantly more energy efficient relative to motors using aluminum rotors. However, one of the challenges in copper rotor die-casting is low tool life. Experiments have shown that the higher molten metal temperature of copper (1085 deg. C), as compared to aluminum (660 deg. C) accelerates the onset of thermal fatigue or heat checking in traditional H-13 tool steel. This happens primarily because the mechanical properties of H-13 tool steel decrease significantly above 650 deg. C. Potential approaches to mitigate the heat checking problem include: 1) identification of potential tool materials having better high temperature mechanical properties than H-13, and 2) reduction of the magnitude of cyclic thermal excursions experienced by the tooling by increasing the bulk die temperature. A preliminary assessment of alternative tool materials has led to the selection of nickel-based alloys Haynes 230 and Inconel 617 as potential candidates. These alloys were selected based on their elevated temperature physical and mechanical properties. Therefore, the overall objective of this research work was to predict the number of copper rotor die-casting cycles to the onset of heat checking (tool life) as a function of bulk die temperature (up to 650 deg. C) for Haynes 230 and Inconel 617 alloys. To achieve these goals, a 2D thermo-mechanical FEA was performed to evaluate strain ranges on selected die surfaces. The method of Universal Slopes (Strain Life Method) was then employed for thermal fatigue life predictions

  5. The thermal fatigue behaviour of creep-resistant Ni-Cr cast steel

    Directory of Open Access Journals (Sweden)

    B. Piekarski

    2007-12-01

    Full Text Available The study gives a summary of the results of industrial and laboratory investigations regarding an assessment of the thermal fatigue behaviour of creep-resistant austenitic cast steel. The first part of the study was devoted to the problem of textural stresses forming in castings during service, indicating them as a cause of crack formation and propagation. Stresses are forming in carbides and in matrix surrounding these carbides due to considerable differences in the values of the coefficients of thermal expansion of these phases. The second part of the study shows the results of investigations carried out to assess the effect of carbon, chromium and nickel on crack resistance of austenitic cast steel. As a criterion of assessment the amount and propagation rate of cracks forming in the specimens as a result of rapid heating followed by cooling in running water was adopted. Tests were carried out on specimens made from 11 alloys. The chemical composition of these alloys was comprised in a range of the following values: (wt-%: 18-40 %Ni, 17-30 %Cr, 1.2-1.6%Si and 0.05-0.6 %C. The specimens were subjected to 75 cycles of heating to a temperature of 900oC followed by cooling in running water. After every 15 cycles the number of the cracks was counted and their length was measured. The results of the measurements were mathematically processed. It has been proved that the main factor responsible for an increase in the number of cracks is carbon content in the alloy. In general assessment of the results of investigations, the predominant role of carbon and of chromium in the next place in shaping the crack behaviour of creep-resistant austenitic cast steel should be stressed. Attention was also drawn to the effect of high-temperature corrosion as a factor definitely deteriorating the cast steel resistance to thermal fatigue.

  6. Fatigue crack growth threshold as a design criterion - statistical scatter and load ratio in the Kitagawa-Takahashi diagram

    International Nuclear Information System (INIS)

    Kolitsch, S.; Gänser, H.-P.; Maierhofer, J.; Pippan, R.

    2016-01-01

    Cracks in components reduce the endurable stress so that the endurance limit obtained from common smooth fatigue specimens cannot be used anymore as a design criterion. In such cases, the Kitagawa-Takahashi diagram can be used to predict the admissible stress range for infinite life, at a given crack length and stress range. This diagram is constructed for a single load ratio R. However, in typical mechanical engineering applications, the load ratio R varies widely due to the applied load spectra and residual stresses. In the present work an extended Kitagawa-Takahashi diagram accounting for crack length, crack extension and load ratio is constructed. To describe the threshold behaviour of short cracks, a master resistance curve valid for a wide range of steels is developed using a statistical approach. (paper)

  7. Ex-situ X-ray computed tomography data for a non-crimp fabric based glass fibre composite under fatigue loading

    Directory of Open Access Journals (Sweden)

    Kristine M. Jespersen

    2017-12-01

    Full Text Available The data published with this article are high resolution X-ray computed tomography (CT data obtained during an ex-situ fatigue test of a coupon test specimen made from a non-crimp fabric based glass fibre composite similar to those used for wind turbine blades. The fatigue test was interrupted four times for X-ray CT examination during the fatigue life of the considered specimen. All the X-ray CT experiments were performed in the region where unidirectional fibre fractures first became visible, and thereby include the damage progression in 3D in this specific region during fatigue loading of the specimen.

  8. Load limit of mini-implants with reduced abutment height based on fatigue fracture resistance: experimental and finite element study.

    Science.gov (United States)

    Toyoshima, Yusuke; Wakabayashi, Noriyuki

    2015-01-01

    The primary objective of this study was to investigate the fracture resistance of experimental mini-implants with a reduced abutment height. The secondary objective was to assess the effects of implant diameter and bone level on the load limit, using finite element simulations. Two Ti-6A1-4V 1.8-mm-diameter implants were subjected to monotonic bending testing and fatigue tests incorporating 5 x 10(6) cycles (ISO 14801): a commercially available implant (c18), and an experimental implant with a reduced abutment height (e18). The load limit was estimated using the finite element models based on the maximum stress at failure in the experiments. For simulations, implants with increased diameters of 2.1 and 2.4 mm were also modeled, and the load limit was estimated for all models in a bone model. In the bending test, e18 revealed a higher mean load at yield stress than c18, and this was attributed to the reduced height of the former. An endurance limit of 140 N was detected for both c18 and e18 in the fatigue test, while the load limit of e18 was higher than that of c18. The estimated load limit increased as the implant diameter or the bone level increased, with the highest value of 510 N observed at a diameter of 2.4 mm. A higher load limit was evident in the experimental mini-implant with a reduced abutment height. The simulations indicated that the load limit increased with increased implant diameter and higher bone levels.

  9. Laser High-Cycle Thermal Fatigue of Pulse Detonation Engine Combustor Materials Tested

    Science.gov (United States)

    Zhu, Dong-Ming; Fox, Dennis S.; Miller, Robert A.

    2001-01-01

    Pulse detonation engines (PDE's) have received increasing attention for future aerospace propulsion applications. Because the PDE is designed for a high-frequency, intermittent detonation combustion process, extremely high gas temperatures and pressures can be realized under the nearly constant-volume combustion environment. The PDE's can potentially achieve higher thermodynamic cycle efficiency and thrust density in comparison to traditional constant-pressure combustion gas turbine engines (ref. 1). However, the development of these engines requires robust design of the engine components that must endure harsh detonation environments. In particular, the detonation combustor chamber, which is designed to sustain and confine the detonation combustion process, will experience high pressure and temperature pulses with very short durations (refs. 2 and 3). Therefore, it is of great importance to evaluate PDE combustor materials and components under simulated engine temperatures and stress conditions in the laboratory. In this study, a high-cycle thermal fatigue test rig was established at the NASA Glenn Research Center using a 1.5-kW CO2 laser. The high-power laser, operating in the pulsed mode, can be controlled at various pulse energy levels and waveform distributions. The enhanced laser pulses can be used to mimic the time-dependent temperature and pressure waves encountered in a pulsed detonation engine. Under the enhanced laser pulse condition, a maximum 7.5-kW peak power with a duration of approximately 0.1 to 0.2 msec (a spike) can be achieved, followed by a plateau region that has about one-fifth of the maximum power level with several milliseconds duration. The laser thermal fatigue rig has also been developed to adopt flat and rotating tubular specimen configurations for the simulated engine tests. More sophisticated laser optic systems can be used to simulate the spatial distributions of the temperature and shock waves in the engine. Pulse laser high

  10. An overview of fatigue

    International Nuclear Information System (INIS)

    Mc Evily, A.J.

    1987-01-01

    Four topics are briefly discussed in this paper: fatigue crack initiation and growth in a nickel-base superalloy single crystal, the environment effect on near-threshold fatigue crack growth behaviour, the role of crack closure in load-interaction effects in fatigue crack growth, and the nature of creep-fatigue interactions, if any, during fatigue crack growth. (Author)

  11. Creep-fatigue life property of FBR high-temperature structural materials under tension-torsion loading and life evaluation method

    International Nuclear Information System (INIS)

    Ogata, Takashi; Nitta, Akito

    1994-01-01

    Creep-fatigue damage in high temperature structural components in a FBR progress under multiaxial stress condition depending on their operating conditions and configuration. Therefore, multiaxial stress effects on creep-fatigue damage evolution must be clarified to make precise creep-fatigue damage evaluation of these components. In this study, creep-fatigue tests in FBR high temperature materials such as SUS304, 316FR stainless steels and a modified 9Cr steel were conducted under biaxial stress subjecting tension-compression and torsion loading, in order to examine biaxial stress effects on failure mechanism and life property, and to discuss creep-fatigue life evaluation methods under biaxial stress. Main results obtained in this study are summarized as follows: 1. The main cracks under cyclic torsion loading propagated by shear mode in three materials. But intergranular failure was occurred in SUS304 and 316FR, and transgranular failure was observed in Mod.9Cr steel. 2. Nonlinear damage accumulation model proposed based on uniaxial creep-fatigue test results was extended to apply for creep-fatigue damage evaluation under biaxial stress state by considering the biaxial stress effects on fatigue and creep damage evolution. 3. It was confirmed that creep-fatigue life under biaxial stress could be predicted by the extended evaluation method with higher accuracy than existing methods. (author)

  12. 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.

  13. 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.

  14. 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

  15. Thermal fatigue analysis of vertical annulus with inner rotating cylinder induced by two temperature fluid mixing

    International Nuclear Information System (INIS)

    Miyano, Hiroshi; Narabayashi, Tadashi

    2011-01-01

    Mechanical seal for nuclear reactor coolant recirculation pump must purge the cold water supply from the outside. The cold purge water is flowing into the hot water zone in the pump through a narrow gap between pump shaft and casing over. On the mixing region of the cold purge water and hot water in the narrow gap, the random level temperature fluctuation occurs on the structural metal surface of casing cover and pump shaft. Then it could lead to cyclic thermal stress and fatigue damage. The experiments and analysis have done, made clear the mechanism of generation of temperature fluctuations. Also, it was studied how to measure the structure of the mixing zone temperature control and how to prevent the occurrence of a large temperature fluctuation. In addition, it is proposed the method of evaluating a random temperature fluctuation by using the envelope curve and its fatigue by OOR counting to applying to the evaluation of the similar random fluid temperature fluctuation problems. (author)

  16. 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

  17. Nondestructive characterization of fatigue damage with thermography

    Science.gov (United States)

    Roesner, Henrik; Sathish, Shamachary; Meyendorf, Norbert

    2001-08-01

    A thermal imaging NDE method has been developed for nondestructive characterization of early stages of fatigue damage. The method is based on evaluation of the thermal effects induced in a material by a short-term mechanical loading. The mechanical loading causes in addition to thermoelastic temperature change, an increase due to heat dissipation that depends upon the microstructure of the material in a characteristic manner. The origin of this heat dissipation is the mechanical damping process. Utilizing the initial temperature rise due to a short-term mechanical loading, the dissipated energy per cycle was evaluated as a thermal parameter. This new thermal NDE parameter allows a quantitative characterization of the mechanical hysteresis, without the need for calibration to eliminate influences of thermal boundary conditions. The measurement of the thermal NDE parameters has been performed on Ti-6Al-4V dog-bone specimens, fatigued in low cycle fatigue (LCF) as well as in high cycle fatigue (HCF) experiments. Characteristic dependence of the NDE parameters on the already accumulated fatigue damage has been observed. The advantage of the thermal method is the applicability to components under service conditions because of simplicity, rapid measurements (a few seconds) and the ability of locally resolved evaluations.

  18. Effect of Surface Modifications on the Retention of Cement-retained Implant Crowns under Fatigue Loads: An In vitro Study

    Science.gov (United States)

    Ajay, R.; Suma, K.; Ali, Seyed Asharaf; Kumar Sivakumar, Jambai Sampath; Rakshagan, V.; Devaki, V.; Divya, K.

    2017-01-01

    Background: Masticatory forces cause fatigue to the dental luting agents, adversely affecting the retention of these cement-retained crowns. Sandblasting (SB) and diamond abrading the abutment surface improves the bond strength of luting agents. However, the effect of acid etching (AE) on the implant abutment surface and the effect of other surface modifications under masticatory load are yet to be documented. Purpose: The aim of the study was to evaluate the effect of abutment surface modifications on the retention of cement-retained restorations subjected to cyclic fatigue loads. Materials and Methods: Forty Ni-Cr copings were made on Cp-titanium laboratory analogs. The specimens were divided into two groups as Group I: Uniaxial tensile loading (UTL) and Group II: Offaxial cyclic loading followed by uniaxial tensile loading [CTL]. Further subgrouped as, subgroup I: Control (C), subgroup II: SB, subgroup III: AE, and subgroup IV: SB + AE. The copings were luted with Zn2(PO4)3 and subjected to uniaxial tensile loading. Copings were recemented, and CTL was conducted. Two-way analysis of variance was used as the statistical test of significance. Results: In relation to the subgroups, the bond strength of Zn2(PO4)3 was higher in Group I than in Group II. The bond strength in subgroup IV was superior in both Group I and Group II (547.170 N ± 5.752 and 531.975 N ± 6.221 respectively). Conclusions: For both UTL and CTL, abutment SB + AE elicited maximum coping retention followed by AE. Off-axial cyclic loading adversely affected the retention irrespective of the surface modifications. PMID:29284956

  19. Mechanical characterization of W-armoured plasma-facing components after thermal fatigue

    International Nuclear Information System (INIS)

    Serret, D; Richou, M; Missirlian, M; Loarer, T

    2011-01-01

    The future fusion device ITER is aimed at demonstrating the scientific and technical feasibility of fusion power. Tens of thousands of W-armoured plasma-facing components (PFCs) will be installed in the vertical targets of the ITER divertor and subjected to a high heat flux. The purpose of this paper is to present the results of mechanical and microstructural characterization of tungsten PFCs after thermal fatigue tests. On each component, Vickers hardness measurements are made. In parallel, the mean grain diameter in the corresponding zone of tungsten material is determined. The empirical Hall-Petch relation was adapted to experimental data. However, due to the plateau effect on recrystallization hardness, this relation does not seem to be relevant once recrystallization is complete: a new approach is proposed for predicting the margin to the tungsten melting onset.

  20. Thermal-fatigue properties of coated materials for fusion device applications

    International Nuclear Information System (INIS)

    Mullendore, A.W.; Whitley, J.B.; Mattox, D.M.

    1981-01-01

    The adherence of plasma sprayed coatings of TiC, VC, TiB 2 and B on substrates of Cu, 316 SS, Mo, Ta and Poco AXF-5Q artificial graphite has been evaluated in a pulsed electron beam, thermal fatigue environment. The materials are candidates for application as limiter and armor components of tokamak fusion devices. Up to 500 cycles of heating at power densities of 1.5 kW/cm 2 for 1.5 sec. were used. Materials were tested both in the as-sprayed (19 to 33% porosity) condition and after hot isostatic pressing (HIP) to increase coating density. Some (e.g. TiC on Mo and Ta) showed good survivability in both the as-sprayed and HIP densified conditions. TiB 2 on Mo and Ta and VC on Poco graphite were improved while TiC + V on Mo and Ta were degraded by the HIP treatment

  1. Service Life Of Main Piping Component Due To Low Thermal Stresses.Fatigue

    International Nuclear Information System (INIS)

    Miroshnik, R.; Jeager, A.; Ben Haim, H.

    1998-01-01

    The paper deals with estimating the service life of the power station Main piping component and describing the repair process for extending of its service life. After a long period of service, several circular fatigue cracks have been discovered at the bottom of the Main piping component chamber. Finite element analyses of transient thermal stresses, caused by power station startup, are carried out in the paper. The calculation results show good agreement between the theoretical locations of the maximum stresses and the actual locations of the cracks. There is a good agreement between theoretical evaluation and actual service life, as well. The possibility of machining out the cracks in order to prevent their growing is examined here. The machining enables us to extend the power station component's life service

  2. Large eddy simulation of a T-Junction with upstream elbow: The role of Dean vortices in thermal fatigue

    International Nuclear Information System (INIS)

    Tunstall, R.; Laurence, D.; Prosser, R.; Skillen, A.

    2016-01-01

    Highlights: • A T-Junction with an upstream bend is studied using wall-resolved LES and POD. • The bend generates Dean vortices which remain prominent downstream of the junction. • Dean vortex swirl-switching results in an unsteady secondary flow about the pipe axis. • This provides a further mechanism for near-wall temperature fluctuations. • Upstream bends can have a crucial role in T-Junction thermal fatigue problems. - Abstract: Turbulent mixing of fluids in a T-Junction can generate oscillating thermal stresses in pipe walls, which may lead to high cycle thermal fatigue. This thermal stripping problem is an important safety issue in nuclear plant thermal-hydraulic systems, since it can lead to unexpected failure of the pipe material. Here, we carry out a large eddy simulation (LES) of a T-Junction with an upstream bend and use proper orthogonal decomposition (POD) to identify the dominant structures in the flow. The bend generates an unsteady secondary flow about the pipe axis, known as Dean vortex swirl-switching. This provides an additional mechanism for low-frequency near-wall temperature fluctuations downstream of the T-Junction, over those that would be produced by mixing in the same T-Junction with straight inlets. The paper highlights the important role of neighbouring pipe bends in T-Junction thermal fatigue problems and the need to include them when using CFD as a predictive tool.

  3. Effects of service condition on rolling contact fatigue failure mechanism and lifetime of thermal spray coatings—A review

    Science.gov (United States)

    Cui, Huawei; Cui, Xiufang; Wang, Haidou; Xing, Zhiguo; Jin, Guo

    2015-01-01

    The service condition determines the Rolling Contact Fatigue(RCF) failure mechanism and lifetime under ascertain material structure integrity parameter of thermal spray coating. The available literature on the RCF testing of thermal spray coatings under various condition services is considerable; it is generally difficult to synthesize all of the result to obtain a comprehensive understanding of the parameters which has a great effect on a thermal spray coating's resistance of RCF. The effects of service conditions(lubrication states, contact stresses, revolve speed, and slip ratio) on the changing of thermal spray coatings' contact fatigue lifetime is introduced systematically. The effects of different service condition on RCF failure mechanism of thermal spray coating from the change of material structure integrity are also summarized. Moreover, In order to enhance the RCF performance, the parameter optimal design formula of service condition and material structure integrity is proposed based on the effect of service condition on thermal spray coatings' contact fatigue lifetime and RCF failure mechanism. The shortage of available literature and the forecast focus in future researches are discussed based on available research. The explicit result of RCF lifetime law and parameter optimal design formula in term of lubrication states, contact stresses, revolve speed, and slip ratio, is significant to improve the RCF performance on the engineering application.

  4. Low cycle thermal fatigue testing of beryllium grades for ITER plasma facing components

    Energy Technology Data Exchange (ETDEWEB)

    Watson, R.D.; Youchison, D.L. [Sandia National Labs., Livermore, CA (United States); Dombrowski, D.E. [Brush Wellman, Inc., Cleveland, OH (United States); Guiniatouline, R.N. [Efremov Institute, (Russia); Kupriynov, I.B. [Russian Institute of Inorganic Materials (Russia)

    1996-02-01

    A novel technique has been used to test the relative low cycle thermal fatigue resistance of different grades of US and Russian beryllium, which is proposed as plasma facing armor for fusion reactor first wall, limiter, and divertor components. The 30 kW electron beam test system at Sandia National Laboratories was used to sweep the beam spot along one direction at 1 Hz. This produces a localized temperature ``spike`` of 750{degree}C for each pass of the beam. Large thermal stresses in excess of the yield strength are generated due to very high spot heat flux, 250 MW/m{sup 2}. Cyclic plastic strains on the order of 0.6% produced visible cracking on the heated surface in less than 3000 cycles. An in-vacuo fiber optic borescope was used to visually inspect the beryllium surfaces for crack initiation. Grades of US beryllium tested included: S-65C, S- 65H, S-200F, S-200F-H, SR-200, I-400, extruded high purity, HIP`d spherical powder, porous beryllium (94% and 98% dense), Be/30% BeO, Be/60% BeO, and TiBe{sub 12}. Russian grades included: TGP-56, TShGT, DShG-200, and TShG-56. Both the number of cycles to crack initiation, and the depth of crack propagation, were measured. The most fatigue resistant grades were S-65C, DShG-200, TShGT, and TShG-56. Rolled sheet Be (SR-200) showed excellent crack propagation resistance in the plane of rolling, despite early formation of delamination cracks. Only one sample showed no evidence of surface melting, Extruded (T). Metallographic and chemical analyses are provided. Good agreement was found between the measured depth of cracks and a 2-D elastic-plastic finite element stress analysis.

  5. Low cycle thermal fatigue testing of beryllium grades for ITER plasma facing components

    International Nuclear Information System (INIS)

    Watson, R.D.; Youchison, D.L.; Dombrowski, D.E.; Guiniatouline, R.N.; Kupriynov, I.B.

    1996-01-01

    A novel technique has been used to test the relative low cycle thermal fatigue resistance of different grades of US and Russian beryllium, which is proposed as plasma facing armor for fusion reactor first wall, limiter, and divertor components. The 30 kW electron beam test system at Sandia National Laboratories was used to sweep the beam spot along one direction at 1 Hz. This produces a localized temperature ''spike'' of 750 degree C for each pass of the beam. Large thermal stresses in excess of the yield strength are generated due to very high spot heat flux, 250 MW/m 2 . Cyclic plastic strains on the order of 0.6% produced visible cracking on the heated surface in less than 3000 cycles. An in-vacuo fiber optic borescope was used to visually inspect the beryllium surfaces for crack initiation. Grades of US beryllium tested included: S-65C, S- 65H, S-200F, S-200F-H, SR-200, I-400, extruded high purity, HIP'd spherical powder, porous beryllium (94% and 98% dense), Be/30% BeO, Be/60% BeO, and TiBe 12 . Russian grades included: TGP-56, TShGT, DShG-200, and TShG-56. Both the number of cycles to crack initiation, and the depth of crack propagation, were measured. The most fatigue resistant grades were S-65C, DShG-200, TShGT, and TShG-56. Rolled sheet Be (SR-200) showed excellent crack propagation resistance in the plane of rolling, despite early formation of delamination cracks. Only one sample showed no evidence of surface melting, Extruded (T). Metallographic and chemical analyses are provided. Good agreement was found between the measured depth of cracks and a 2-D elastic-plastic finite element stress analysis

  6. 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

  7. Fatigue crack growth control in pressure vessel using single peak overload and load hold at elevated temperatures

    International Nuclear Information System (INIS)

    Chen, Ling; Nakamura, Haruo; Kobayashi, Hideo

    1995-01-01

    Pressure vessels are periodically subjected to a proof test to assure structural integrity. During that period, it may be possible to control the fatigue crack growth by simultaneous heating globally or locally around a crack tip. From this viewpoint, retardation behavior of a fatigue crack due to a single peak overload at a high temperature (∼300degC) was examined in an A 533 B-1 steel. Parameters investigated were overload ratio, applied temperature, hold time at higher temperature, and unloading temperature of overload. The higher the applied temperature, the greater the effect of retardation especially when unloading of the overload is done at lower temperatures. Also, the hold time at maximum load promotes oxide-film-induced crack closure. To evaluate those effects, a simple model is proposed based on the Dugdale model. (author)

  8. Evaluation of fatigue damage induced by thermal striping in a T junction using the three dimensional coupling method and frequency response method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sun Hye; Choi, Jae boong; Kim, Moon Ki [Sungkyunkwan Univ., Seoul (Korea, Republic of); Huh, Nam Su [Seoul Nat' l Univ., Seoul (Korea, Republic of); Lee, Jin Ho [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2012-10-15

    Thermal fatigue cracking induced by thermal stratification, cycling and striping have been observed in several PWR plants. Especially, thermal striping, the highly fluctuating thermal layer, became one of the significant problems, since it can cause un predicted high cycle thermal fatigue (HCTF) at piping systems. This problem are usually found in T junctions of energy cooling systems, where cold and hot flows with high level of turbulence mix together. Thermal striping can cause the networks of fatigue crack at the vicinity of weld parts and these cracks can propagate to significant depth in a relatively short time. Therefore, thermal striping and fatigue crack initiations should be predicted in advance to prevent the severe failure of piping systems. The final goal of this research is to develop a rational thermal and mechanical model considering thermohydraulic characteristics of thermal striping and an evaluation procedure to predict the initiation of thermal fatigue crack. As a first step, we evaluated the fatigue damage in a T junction using two widely used methods. Then, we analyzed the results of each method and conducted comparisons and verifications.

  9. Effect of Abutment Preparation and Fatigue Loading in a Moist Environment on the Fracture Resistance of the One-Piece Zirconia Dental Implant.

    Science.gov (United States)

    Kamel, Mohamed; Vaidyanathan, Tritala K; Flinton, Robert

    One-piece zirconia dental implants have been widely used in Europe for many years. This in vitro study was done to evaluate the effect of abutment preparation and fatigue (cyclic) loading in a moist environment on the fracture resistance of the one-piece zirconia dental implant. Twenty-four Cera Root zirconium oxide dental implants, divided into three groups of eight, were used in this study: group 1 (control group): implants with no preparation, tested in a dry environment; group 2: implants with no preparation, tested in a moist environment (simulating clinical conditions); and group 3: implants after abutment preparation tested in a moist environment. All implants received IPS e.max porcelain crowns. All samples were subjected to nearly 1 million cycles of sinusoidal fatigue loading (-10 N to -200 N) in a universal testing machine. The postfatigue samples were loaded to fracture. Significant differences (α = .05) in mean fracture loads were statistically analyzed. There was no catastrophic failure of any of the implants during the fatigue tests. The mean (SD) of the fracture loads in postfatigue load-to-failure tests were: group 1: 1,202.9 (62.6); group 2: 1,164.6 (73.8); and group 3: 953.5 (103). Analysis of variance (ANOVA) and post hoc Tukey-Kramer contrast revealed a statistically significant difference (P fracture load of group 3 and those of groups 1 and 2, but no significant difference (P > .05) between groups 1 and 2. While there was a statistically significant adverse effect of abutment preparation and fatigue loading in a moist environment on the postfatigue implant failure load, the load-to-fracture mean of surface-prepared implants after fatigue tests was nevertheless significantly higher than the mean fracture load of the crowns (P < .05) as well as the minimum load-bearing requirement (300 N) for anterior restorations. Abutment preparation in a one-piece zirconia implant is therefore considered clinically safe and acceptable.

  10. Synergistic Effects of Temperature, Oxidation and Multicracking Modes on Damage Evolution and Life Prediction of 2D Woven Ceramic-Matrix Composites under Tension-Tension Fatigue Loading

    Science.gov (United States)

    Longbiao, Li

    2017-08-01

    In this paper, the synergistic effects of temperature, oxidation and multicracking modes on damage evolution and life prediction in 2D woven ceramic-matrix composites (CMCs) have been investigated. The damage parameter of fatigue hysteresis dissipated energy and the interface shear stress were used to monitor the damage evolution inside of CMCs. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface/fiber oxidation model, interface wear model and fibers statistical failure model at elevated temperature, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfy the Global Load Sharing (GLS) criterion. When the broken fibers fraction approaches to the critical value, the composite fatigue fractures. The evolution of fatigue hysteresis dissipated energy, the interface shear stress and broken fibers fraction versus cycle number, and the fatigue life S-N curves of SiC/SiC at 1000, 1200 and 1300 °C in air and steam condition have been predicted. The synergistic effects of temperature, oxidation, fatigue peak stress, and multicracking modes on the evolution of interface shear stress and fatigue hysteresis dissipated energy versus cycle numbers curves have been analyzed.

  11. Recrystallization and thermal shock fatigue resistance of nanoscale ZrC dispersion strengthened W alloys as plasma-facing components in fusion devices

    Science.gov (United States)

    Xie, Z. M.; Miao, S.; Liu, R.; Zeng, L. F.; Zhang, T.; Fang, Q. F.; Liu, C. S.; Wang, X. P.; Lian, Y. Y.; Liu, X.; Cai, L. H.

    2017-12-01

    Recrystallization and thermal shock fatigue resistance behavior of nanoscale ZrC dispersion strengthened bulk tungsten alloys (W-0.5 wt% ZrC, WZrC) as potential candidates for plasma-facing components were investigated. By employing heat treatments with isochronal experiments, the evolution of the tungsten grain size/orientation, second phase particle distribution, thermal conductivity and mechanical properties were systematically studied. The effects of edge-localized mode like transient heat events on the as-rolled and recrystallized WZrC were investigated carefully. Pulses from an electron beam with durations of 1 ms were used to simulate the transient heat loading in fusion devices. The cracking thresholds, cracking mechanisms and recrystallization under repetitive (100 shots) transient heat loads were investigated. Results indicate that the cracking threshold of all the WZrC samples is 220-330 MW/m2 (corresponding to a heat load parameter F = 7.0-10.4 MJ/m2s1/2) at room temperature and the heat bombardment induced recrystallization occurs at a heat parameter of 10.4 MJ/m2s1/2.

  12. 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

  13. A hydro-thermo-mechanics analyze of the thermal fatigue in the mixing tee junction

    Energy Technology Data Exchange (ETDEWEB)

    Gourdin, C.; Chapuliot, S. [CEA Saclay, Dir. de l' Energie Nucleaire, (DEN/DM2S/SEMT/LISN), 91 - Gif sur Yvette (France); Magnaud, J.P. [CEA Saclay, Dir. de l' Energie Nucleaire (DEN/DM2S/SFME/LTMF), 91 - Gif sur Yvette (France); Payen, T. [Institut de Radioprotection et de Surete Nucleaire (IRSN/DES/SAMS), 92 - 92 - Fontenay aux Roses (France)

    2003-07-01

    Work presented here, has been achieved at Cea, and is related to the comprehension of the mechanisms leading to cracking under thermal loading in the zones of mixing. The main objective of this work is to analyze, by computation, the thermal loading induced by the turbulent mixing following a tee junction and to explain how it can create cracking, from the internal skin of the component to a leakage, as it was observed in Civaux Power Plant in 1998. The phenomenon is still today not completely understood. One of the principal reasons to this partial incomprehension undoubtedly resides in the multi-field aspect of the loading and of the associated damage, utilizing three different and complementary scientific disciplines: thermohydraulics, thermomechanics and material science. The presentation proposed here, consists in connecting the analyses resulting from these various fields. The first part concentrates on thermohydraulics simulations. The choice of an adequate modeling is discussed on the basis of observed cracking in order to highlight phenomena of large scale beats, which are supposed one of the major causes leading to the failure of the structures. The second part deals with the use of the temperature fields obtained in the first part in order to carry out thermomechanical simulations. All these simulations are 3-dimensional and represent the complex geometry of Civaux RRA piping line, including a tee junction and elbows, water flow velocity. Mean and temperatures variations, mean and stresses variations are also presented. As final results make it possible to determine a map of the damage associated with these complex thermal loading. (authors)

  14. Monitoring and Failure Analysis of Corroded Bridge Cables under Fatigue Loading Using Acoustic Emission Sensors

    Directory of Open Access Journals (Sweden)

    Hui Li

    2012-03-01

    Full Text Available Cables play an important role in cable-stayed systems, but are vulnerable to corrosion and fatigue damage. There is a dearth of studies on the fatigue damage evolution of corroded cable. In the present study, the acoustic emission (AE technology is adopted to monitor the fatigue damage evolution process. First, the relationship between stress and strain is determined through a tensile test for corroded and non-corroded steel wires. Results show that the mechanical performance of corroded cables is changed considerably. The AE characteristic parameters for fatigue damage are then established. AE energy cumulative parameters can accurately describe the fatigue damage evolution of corroded cables. The failure modes in each phase as well as the type of acoustic emission source are determined based on the results of scanning electron microscopy. The waveform characteristics, damage types, and frequency distribution of the corroded cable at different damage phases are collected. Finally, the number of broken wires and breakage time of the cables are determined according to the variation in the margin index.

  15. The effect of the changing microstructure on the fatigue behaviour during cyclic rolling contact loading

    International Nuclear Information System (INIS)

    Voskamp, A.P.; Mittemeijer, E.J.

    1997-01-01

    During rolling contact fatigue of the inner rings of ball bearings three stages of material response can be distinguished, in terms of the volume that is plastically deformed upon overrolling. After a first stage of material strengthening during which a decrease occurs for the volume that is deformed plastically, an effectively stationary, second stage is entered which is eventually succeeded by a third stage exhibiting a pronounced increase of the volume that is deformed plastically upon overrolling, which leads to failure. It is suggested that carbon diffusion induced by local temperature peaks occurring at the moment of overrolling is the key mechanism leading to fatigue damage. The amount of decomposed retained austenite is a useful, practical parameter to assess fatigue life. It is shown that published ideas about the role of certain components of residual stress in enhancing fatigue life are not correct and that the so-called Palmgren-Miner rule, as applied in practice, and the risk volume defined by Lundberg and Palmgren are inappropriate for assessing fatigue life. (orig.)

  16. Use of ultrasonic back-reflection intensity for predicting the onset of crack growth due to low-cycle fatigue in stainless steel under block loading.

    Science.gov (United States)

    Islam, Md Nurul; Arai, Yoshio; Araki, Wakako

    2015-02-01

    The present study proposes the use of ultrasonic back-reflected waves for evaluating low cycle fatigue crack growth from persistent slip bands (PSBs) of stainless steel under block loading. Fatigue under high-low block loading changes the back-reflected intensity of the ultrasonic wave that emanates from the surface. Measuring the change in ultrasonic intensity can predict the start of crack growth with reasonable accuracy. The present study also proposes a modified constant cumulative plastic strain method and a PSB damage evolution model to predict the onset of crack growth under block loads. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Energy-based fatigue model for shape memory alloys including thermomechanical coupling

    Science.gov (United States)

    Zhang, Yahui; Zhu, Jihong; Moumni, Ziad; Van Herpen, Alain; Zhang, Weihong

    2016-03-01

    This paper is aimed at developing a low cycle fatigue criterion for pseudoelastic shape memory alloys to take into account thermomechanical coupling. To this end, fatigue tests are carried out at different loading rates under strain control at room temperature using NiTi wires. Temperature distribution on the specimen is measured using a high speed thermal camera. Specimens are tested to failure and fatigue lifetimes of specimens are measured. Test results show that the fatigue lifetime is greatly influenced by the loading rate: as the strain rate increases, the fatigue lifetime decreases. Furthermore, it is shown that the fatigue cracks initiate when the stored energy inside the material reaches a critical value. An energy-based fatigue criterion is thus proposed as a function of the irreversible hysteresis energy of the stabilized cycle and the loading rate. Fatigue life is calculated using the proposed model. The experimental and computational results compare well.

  18. 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

  19. 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

  20. 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

  1. Crack initiation and propagation paths in small diameter FSW 6082-T6 aluminium tubes under fatigue loading

    Directory of Open Access Journals (Sweden)

    Roberto Tovo

    2016-03-01

    Full Text Available This paper reports results of fatigue tests of friction stir welded (FSW aluminium tubes. Relatively small 38 mm diameter tubes were used and hence an automated FSW process using a retracting tool was designed for this project, as the wall thickness of the aluminium tube was similar to the diameter of the FSW tool. This is a more complex joint geometry to weld than the more usual larger diameter tube reported in the literature. S-N fatigue testing was performed using load ratios of R = 0.1 and R = -1. Crack path analysis was performed using both low magnification stereo microscopy and scanning electron microscopy, in order to identify crack initiation sites and to determine the direction of crack propagation. Work is still in progress to follow the crack path through the various microstructural zones associated with the weld. A simple statistical analysis was used to characterize the most typical crack initiation site. This work forms part of a wider project directed at determining multiaxial fatigue design rules for small diameter 6082-T6 aluminium tubes that could be of use in the ground vehicle industry.

  2. Short-term fatigue analysis for tower base of a spar-type wind turbine under stochastic wind-wave loads

    Directory of Open Access Journals (Sweden)

    Haoran Li

    2018-01-01

    Full Text Available Due to integrated stochastic wind and wave loads, the supporting platform of a Floating Offshore Wind Turbine (FOWT has to bear six Degrees of Freedom (DOF motion, which makes the random cyclic loads acting on the structural components, for instance the tower base, more complicated than those on bottom-fixed or land-based wind turbines. These cyclic loads may cause unexpected fatigue damages on a FOWT. This paper presents a study on short-term fatigue damage at the tower base of a 5 MW FOWT with a spar-type platform. Fully coupled time-domain simulations code FAST is used and realistic environment conditions are considered to obtain the loads and structural stresses at the tower base. Then the cumulative fatigue damage is calculated based on rainflow counting method and Miner's rule. Moreover, the effects of the simulation length, the wind-wave misalignment, the wind-only condition and the wave-only condition on the fatigue damage are investigated. It is found that the wind and wave induced loads affect the tower base's axial stress separately and in a decoupled way, and the wave-induced fatigue damage is greater than that induced by the wind loads. Under the environment conditions with rated wind speed, the tower base experiences the highest fatigue damage when the joint probability of the wind and wave is included in the calculation. Moreover, it is also found that 1 h simulation length is sufficient to give an appropriate fatigue damage estimated life for FOWT.

  3. Influence of the resin cement thickness on the fatigue failure loads of CAD/CAM feldspathic crowns.

    Science.gov (United States)

    Gressler May, Liliana; Kelly, J Robert; Bottino, Marco Antonio; Hill, Tom

    2015-08-01

    to evaluate the influence of the occlusal resin cement thickness on the cyclic loads-to-failure of feldspathic crowns and to compare the results to data from monotonic tests. A large range of cement thickness (50μm and 500μm) was tested, in order to better measure the influence of this variable. Feldspathic ceramic crowns (Vita Mark II blocks, Vita Zahnfabrik) were bonded to dentin analog dies (G10 (NEMA grade G10, International Paper), with occlusal resin cement thicknesses of 50μm and 500μm (Multilink Automix, Ivoclar). The dies were prepared with microchannels for water transport to the cement layer. After 96-h water storage, the specimens (n=20) were submitted to cyclic loads (500,000 cycles at 20Hz; initial maximum load=40% of monotonic load, from previous data) following a staircase sensitivity design (step size=25N). Failure loads at 500,000 cycles were compared to monotonic failure loads (from a previous study with specimens produced by the same author, using the same materials, specimen configuration and cementation protocol). Crowns with an occlusal cement layer of 50μm were more resistant than those cemented with 500μm (246.4±22.9N vs. 158.9±22.9N), under wet cyclic testing conditions (pcement thickness of 50μm was more favorable for the structural performance of feldspathic crowns than was 500μm. Cyclic fatigue reduced failure loads well below those found under monotonic loading. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  4. Effects of loading variables on fatigue-crack growth in liquid-metal environments

    CSIR Research Space (South Africa)

    Fernandes, PJL

    1995-10-01

    Full Text Available Liquid-metal-induced embrittlement (LMIE) refers to the loss of ductility in normally ductile metals and alloys when stressed while in contact with a liquid metal. In this study, the fatigue crack growth behaviour of brass in molten gallium...

  5. Muscle fatigue and metabolic responses following three different antagonist pre-load resistance exercises

    NARCIS (Netherlands)

    Carregaro, Rodrigo; Cunha, Rafael; Oliveira, Carlos Gomes; Brown, Lee E.; Bottaro, Martim

    2013-01-01

    Purpose: Preload of antagonist muscles can be achieved by reciprocal actions (RAs) or by opposing muscle actions. However, evidence concerning neuromuscular and fatigue responses are scarce. Objective: To compare the effects of different knee flexor (KF) preload methods on knee extension (KE) vastus

  6. Fatigue-related changes in the coordination of lifting and their effect of low back load

    NARCIS (Netherlands)

    Van Dieën, Jaap H.; Toussaint, Huub M.; Maurice, Cora; Mientjes, Martine

    1996-01-01

    In this study, changes in movement coordination caused by fatigue that developed during repetitive lifting were examined. Five men performed 6 times a 5-min bout of lifting an 8-kg barbell at 15 lifts/min, using two lifting techniques; one minimized trunk rotation (squat lift), and the other

  7. Static and Fatigue behavior of Pin-Loaded Metal Matrix Joints

    Science.gov (United States)

    1984-06-01

    NO. NO. NO. NO, 11. TITLE (Include Security Clasification ) Static and Fatigue 62201F 2401 01 79 Rphavinr of Metal Matrix Joints (U) 12. PERSONAL AUTHOR...Specimen Steel Pin I (1/4" Dia.) Steel Plate (1/4" thick) Steel Shims Hydraulic Grip Figure 3 Pin-Bearing Test Assemblage (Note: Not to scale) 26 200 B

  8. Fretting fatigue behavior of high-strength steel monostrands under bending load

    DEFF Research Database (Denmark)

    Winkler, Jan; Georgakis, Christos T.; Fischer, Gregor

    2015-01-01

    In this paper, the fretting fatigue behavior of pretensioned high-strength steel monostrands is investigated. To measure the local deformations on the strands, a novel method based on the digital image correlation (DIC) technique was used to quantify the relative movement between individual wires...

  9. FAMOSi: AREVA's new fatigue monitoring system

    International Nuclear Information System (INIS)

    Abib, E.; Heinz, B.

    2015-01-01

    With its local instrumentation, the Fatigue Monitoring System integrated (FAMOSi) is able to detect real thermal loadings like thermal stratification at the primary and secondary piping system. These thermal loadings are the basis for a reliable stress and fatigue evaluation and an essential part for plant lifetime extension programs. FAMOSi uses a fatigue estimation method for an on-line overview about the fatigue status of the plant's components. Detailed fatigue calculations under consideration of environmental assisted fatigue effects were done with the off-line part of the system. This contributes to optimize the operating modes or, to detect malfunctions of components like leaking valves. FAMOSi is used in several power plants in Europe and across the world to reach a better knowledge of plant behavior during start-up, shut-down, spray events or steam generator charging. In some lifetime extension programs, the exchange of heavy components could be avoided due to realistic stress and fatigue calculation based on real thermal loadings. Fatigue monitoring with FAMOSi contributes to cost savings, introduces condition based maintenance and provides a solid basis for life time extension. (authors)

  10. 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...

  11. Analysis of the effect of curtailment on power and fatigue loads of two aligned wind turbines using an actuator disc approach

    International Nuclear Information System (INIS)

    Martinen, Silke; Nilsson, Karl; Breton, Simon-Philippe; Ivanell, Stefan; Carlén, Ingemar

    2014-01-01

    To study the effects of curtailment on both power production and fatigue loading, actuator disc (ACD) simulations of two turbines aligned in the wind direction are performed with the EllipSys3D code developed at DTU/Risø. A simple non-aeroelastic fatigue load evaluation method for ACD simulations is developed. Blade loads, extracted along a line that rotates in the rotor plane with the rotational velocity of the respective turbine, are used to calculate flapwise bending moments. After applying a rainflow counting algorithm an equivalent moment is calculated. Power curtailment is introduced by increasing the blade pitch angle of the first turbine. Evaluation is made with regards to fatigue load reduction at the second turbine and the change in the total production. Further parameters investigated are the spacing between the two turbines and the level of imposed pre-generated turbulence. The aeroelastic code Vidyn, Ganander [1], is used for validation of the ACD load evaluation method. For this purpose, the EllipSys3D simulations are rerun without the second turbine. Time series of cross sectional velocity fields are extracted at positions corresponding to the former placement of the downstream turbine and used as input for aeroelastic turbine load calculations in Vidyn. The results from Vidyn and the results based on the ACD loads show similar trends. Fatigue loads at the downwind turbine are clearly decreasing as the blade pitch angle of the upstream turbine is increasing. The achievable amount of fatigue load reduction depends on the level of the imposed pre-generated turbulence as well as the spacing between the turbines. The presented method is intended for further development of wind park optimization strategies

  12. 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

  13. Image analysis of microscopic crack patterns applied to thermal fatigue heat-checking of high temperature tool steels.

    Science.gov (United States)

    Le Roux, Sabine; Medjedoub, Farid; Dour, Gilles; Rézaï-Aria, Farhad

    2013-01-01

    Surface cracking or heat-checking is investigated at a microscopic scale on a hot work tool steel (X38CrMoV5) tested under thermal fatigue. Thermal fatigue tests are periodically interrupted to observe the surface of the specimens by scanning electron microscopy (SEM). A non destructive and semi-automatic method is developed to assess and evaluate the two-dimensional crack pattern initiated on the oxide scale layer formed on the specimen surface. The crack pattern is characterized by image analysis in terms of density, morphological and topological features. This technique allows to determine the number of cycles to initiate the microscopic heat-checking and to follow its evolution. Copyright © 2012 Elsevier Ltd. All rights reserved.

  14. Fatigue crack growth rate behaviour of friction-stir aluminium alloy AA2024-T3 welds under transient thermal tensioning

    International Nuclear Information System (INIS)

    Ilman, M.N.; Kusmono,; Iswanto, P.T.

    2013-01-01

    Highlights: • FSW enables unweldable aircraft material AA2024-T3 to be welded without cracking. • FSW applied to aircraft structure is required to have superior fatigue resistance. • Transient thermal tensioning (TTT) is being developed for stress relieving in FSW. • The fatigue crack growth rates of FSW joints under TTT are studied. - Abstract: Friction stir welding (FSW) has become a serious candidate technology to join metallic fuselage panels for the next generation of civil aircrafts. However, residual stress introduced during welding which subsequently affects fatigue performance is still a major problem that needs to be paid attention. The present investigation aims to improve fatigue crack growth resistance of friction stir aluminium alloy AA2024-T3 welds using transient thermal tensioning (TTT) treatment. In this investigation, aluminium alloy AA2024-T3 plates were joined using FSW process with and without TTT. The welding parameters used including tool rotation speed (Rt) and the plate travelling speed (v) were 1450 rpm and 30 mm/min respectively. The TTT treatments were carried out by heating both sides of friction stir weld line using moving electric heaters ahead of, beside and behind the tool at a heating temperature of 200 °C. Subsequently, a sequence of tests was carried out including microstructural examination, hardness measurement, tensile test and fatigue crack growth rate (FCGR) test in combination with fractography using scanning electron microscopy (SEM). The FCGR test was carried out using a constant amplitude fatigue experiment with stress ratio (R) of 0.1 and frequency (f) of 11 Hz whereas specimens used were centre-crack tension (CCT) type with the initial crack located at the weld nugget. Results of this investigation showed that at low ΔK, typically below 9 MPa m 0.5 , the friction stir welds under TTT treatments lowered fatigue crack growth rate (da/dN) and the lowest (da/dN) was achieved as the heaters were located ahead of

  15. Probabilistic thermal-mechanical fatigue criterion for lost foam casting aluminium alloys based on 2D/3D porosities distribution

    Directory of Open Access Journals (Sweden)

    Szmytka F.

    2014-06-01

    Full Text Available A thermal-mechanical fatigue criterion is proposed to assess the lifetime of aluminium alloys produced by a lost foam casting process. It is based on the observed size distribution of pores sizes which are considered as critical zones for cracks initiation and gives reliable results when both pores sizes are identified from X-ray tomography and mean stresses are taken into account. Lifetime probabilities are finally successfully compared with experimental results.

  16. Creep-fatigue damage assessment by subsequent fatigue straining

    International Nuclear Information System (INIS)

    Yaguchi, M.; Nakamura, T.; Ishikawa, A.; Asada, Y.

    1993-01-01

    A series of creep-fatigue tests has been conducted with Modified 9Cr-1Mo steel at 600 deg. C in a high vacuum environment of 0.1mPa to assess an accumulation of creep-fatigue damage. In these tests, each test specimen has been subjected to prior creep-fatigue loading followed by subsequent fatigue loading or prior fatigue loading followed by subsequent creep-fatigue loading. A linear summation of cumulative damage of fatigue and creep life fraction is smaller than unity for the former case, and larger than unity for the latter case. SEM observation was conducted and it was shown that in the case of prior creep-fatigue loading, crack mode transforms from transgranular to intergranular type with the increase of the number of cycles of prior creep-fatigue loading, while crack mode is generally intergranular in the case of prior fatigue loading. (author)

  17. 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.

  18. Subjective sensation on sleep, fatigue, and thermal comfort in winter shelter-analogue settings

    Science.gov (United States)

    Maeda, Kazuki; Mochizuki, Yosuke; Tsuzuki, Kazuyo; Nabeshima, Yuki

    2017-10-01

    We aimed to examine sleep in shelter-analogue settings in winter to determine the subjective sensation and environmental conditions in evacuation shelters. Twelve young healthy students took part in the sleep study of two nights for seven hours from Midnight to 7 AM in the gymnasium. One night the subject used a pair of futons and on the other the subject used the emergency supplies of four blankets and a set of portable partitions. During the night, air temperature, humidity and air velocity were measured in the area around the sleeping subjects. Sleep parameters measured by actigraphy, skin temperature, microclimate temperature, rectal temperature, and the heart rates of the subjects were continuously measured and recorded during the sleeping period. The subjects completed questionnaires regarding their thermal comfort and subjective sleep before and after the sleep. The subjects felt more coldness on their head and peripheral parts of the body using the emergency blankets than the futon during the sleep. Moreover, fatigue was felt more on the lower back and lower extremities from using emergency blankets than the futon after sleep. However, the sleep efficiency index and subjective sleep evaluation by OSA questionnaire did not reveal any good correlationship. The emergency supplies should be examined for their suitability to provide comfortable and healthy sleep in the shelter-analogue settings.

  19. Effects of Contact Load on the Fretting Fatigue Behavior of IN-100 at Elevated Temperature

    Science.gov (United States)

    2009-03-01

    act as crack closure mechanisms in another nickel-based superalloy , IN-718, when fatigued in the high temperature environment. This glaze oxide...100. Inconels are alloys of nickel which contain high concentrations of cobalt , chromium, and molybdenum. They are very well suited for high...Studies on Nickel alloys A study by Wan and Yue [21] investigated both smooth and notched specimens of a single-crystal nickel-based superalloy , DD3

  20. 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.

  1. Effect of load ratio and saltwater corrosive environment on the initiation life of fatigue of 10Ni5CrMoV steel

    Science.gov (United States)

    Xie, Xing; Yi, Hong; Xu, Jian; Gen, Liming; Chen, Luyun

    2017-09-01

    Fatigue initiation life has been studied with 10CrNi5MoV steel for use in ocean engineering at different load ratios and in different environmental media. The microstructure and micro-topography have been observed and analyzed by means of SEM, EDS and EBSD. Our findings indicate that, the initiation life of 10Ni5CrMoV steel in seawater is shorter than that in air, and the difference in longevity is larger with the increasing of load ratio. Corrosion pits had a great influence on initial corrosion fatigue life.

  2. 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...

  3. 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)

  4. 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.

  5. 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....

  6. 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

  7. 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.

  8. Effect of mouth-motion fatigue and thermal cycling on the marginal accuracy of partial coverage restorations made of various dental materials.

    Science.gov (United States)

    Stappert, Christian F J; Chitmongkolsuk, Somsak; Silva, Nelson R F A; Att, Wael; Strub, Joerg R

    2008-09-01

    To investigate the influence of mouth-motion fatigue on marginal-accuracy of partial-coverage-restorations-(PCRs) of various dental materials. Eighty molars were prepared equally and divided into five groups (n=16). PCRs were fabricated of following dental materials: Group-GO=Gold-Pontor-MPF(double dagger), Group-TA=Targis*, Group-EX=IPS-e.max-Press*, Group-EM=IPS-Empress*, Group-PC=ProCAD*/Cerec 3(dagger) ((double dagger)Metalor/*Ivoclar-Vivadent/(dagger)Sirona-Dental-System). Gold-PCRs were cemented conventionally. Residual 64 PCRs were adhesively luted and subjected to masticatory loading (1.2million-cycles, 1.6Hz, 49N) and thermal cycling (5 degrees C/55 degrees C, 60s, dwell-time, 5500cycles). Discrepancies in marginal-accuracy were examined on epoxy replicas (200 x magnification). Statistical analysis was performed by unpaired and paired t-tests (alpha=0.05). After cementing, marginal-accuracy (geometrical mean)[95% confidence limits] was recorded: GO-47[43-51]microm, TA-42[38-45]microm, EX-60[52-67]microm, EM-52[45-60]microm and PC-75[59-94]microm. No significant differences were found between groups GO, TA and EM. Values of Group-EX were significantly higher compared to Group-TA (p=0.04). Group-PC demonstrated significantly decreased marginal-accuracy towards groups GO (p=0.03) and TA (p=0.02). Except for Group-GO (p=0.01), no significant changes in marginal-accuracy were observed after mouth-motion fatigue and thermal cycling (GO-42[38-45]microm, TA-42[38-47]microm, EX-56[49-65]microm, EM-54[46-64]microm and PC-71[59-84]microm). However, Group-GO and Group-EM showed significant deviations in marginal-accuracy after aging (p=0.04). Marginal discrepancies of groups EX and EM were similar (p=1.0). Values of Group-PC were significantly higher when compared to groups GO (p=0.01) and TA (p=0.02). Buccal-lingual marginal discrepancies were significantly higher than mesial-distal in all groups and stages. Cast-gold-PCRs demonstrated superior marginal

  9. 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

  10. Effect of tool profile and fatigue loading on the local hardness around scratches in clad and unclad aluminium alloy 2024

    International Nuclear Information System (INIS)

    Khan, M.K.; Fitzpatrick, M.E.; Hainsworth, S.V.; Edwards, L.

    2009-01-01

    Nanoindentation has been used to study the hardness changes produced by scratching of aluminium alloy AA2024, with and without a clad layer of pure aluminium. The hardness was mapped around scratches made with diamond tools of different profiles. One tool produced significant plastic damage with associated hardening at the scratch root, whilst the other produced a 'cleaner' cut with no hardening. The different behaviours are attributed to whether the tool makes the scratch by a 'cutting' or a 'ploughing' mechanism. The degree of plastic damage around the scratches has been correlated with peak broadening data obtained using synchrotron X-ray diffraction. There was no change observed in the local hardness around the scratch with fatigue loading.

  11. Fatigue-related changes in the coordination of lifting and their effect on low back load.

    Science.gov (United States)

    van Dieën, J H; Toussaint, H M; Maurice, C; Mientjes, M

    1996-12-01

    In this study, changes in movement coordination caused by fatigue that developed during repetitive lifting were examined. Five men performed 6 times a 5-min bout of lifting an 8-kg barbell at 15 lifts/min, using two lifting techniques; one minimized trunk rotation (squat lift), and the other minimized rotation in the knee joint (stoop lift). Kinematics and dynamics were studied by means of movement analysis and inverse dynamics, using a two-dimensional linked segment model. Within-subject variation over repetitive lifts of the time course of joint angles was smaller than between-subjects variation on the first analyzed lift. Relative timing between joint rotations did not change significantly across repetitive lifts, except between knee and hip in the squat lift. No change of the lumbosacral torque over repetitive lifts was found. The adaptability of the neural control appeared to be sufficient to accommodate the strong changes of the input-output characteristics of the muscles caused by fatigue so that an essentially constant performance of the movement act was maintained.

  12. One-handed load carrying--cardiovascular, muscular and subjective indices of endurance and fatigue.

    Science.gov (United States)

    Kilbom, A; Hägg, G M; Käll, C

    1992-01-01

    A group of 5 women and 11 men walked on a treadmill, each carrying a weight in the right hand. In separate experiments, the mass was varied to give total exhaustion within 3 min, 5 min, 9 min, and 13 min. In additional experiments 50% and 25% of the masses leading to exhaustion after 5 min were used, and these were stopped after 16 min. Heart rate (fc) and systolic blood pressure (BPs) were measured noninvasively. There was a consistent increase in fc x BPs during the experiments leading to exhaustion, while steady-states were obtained in the nonexhausting trials. An electromyogram (EMG) was recorded with cutaneous electrodes over the flexor carpi ulnaris and flexor digitorum superficialis muscles and the number of zero crossings (ZC) of the EMG signal per time unit were analysed. As the subjects approached exhaustion, the number of ZC declined exponentially, reaching approximately 50% of their initial values. In the nonexhausting experiments, however, the decline was slower and less marked, and during the second half of the experiment the number of ZC increased again. Subjectively, endurance was underestimated by all the subjects. It was concluded that cardiovascular and muscle criteria of fatigue in carrying coincided. Prolonged carrying in one hand of more than 6 kg or 10 kg for young healthy women and men respectively should not be recommended, since it could lead to cardiovascular non steady-states and EMG signs of fatigue.

  13. Fatigue damage assessment of electric roads based on probabilistic load models

    Science.gov (United States)

    Ceravolo, R.; Miraglia, G.; Surace, C.

    2017-05-01

    The electro-mobility is becoming an increasingly present reality in recent years. The most important drawback of this technology is known to be limited battery autonomy. In an attempt to overcome this problem, for specific studies and testing, a number of roads have been implemented with coil systems in order to transfer power to electric vehicles, as described in this article. While on the one hand this could solve the problem of charging, on the other hand the introduction of a technology within an existing infrastructure could result in further structural issues. Since little or no information on the possible structural effect of the introduction of a charging system in the road is currently available, this study has focused on the long-term fatigue analysis of an electric road infrastructure in which an inductive wireless charging system has been introduced into the road structure. To perform the fatigue analysis, a recursive procedure defined within a probabilistic framework was developed and applied to a benchmark case study. The results obtained from the analysis represent an initial database for the definition of strategies and protocols for the monitoring, maintenance and operations of future electric roads infrastructures.

  14. Fatigue analysis and life prediction of composite highway bridge decks under traffic loading

    Directory of Open Access Journals (Sweden)

    Fernando N. Leitão

    Full Text Available Steel and composite (steel-concrete highway bridges are currently subjected to dynamic actions of variable magnitude due to convoy of vehicles crossing on the deck pavement. These dynamic actions can generate the nucleation of fractures or even their propagation on the bridge deck structure. Proper consideration of all of the aspects mentioned pointed our team to develop an analysis methodology with emphasis to evaluate the stresses through a dynamic analysis of highway bridge decks including the action of vehicles. The design codes recommend the application of the curves S-N associated to the Miner's damage rule to evaluate the fatigue and service life of steel and composite (steel-concrete bridges. In this work, the developed computational model adopted the usual mesh refinement techniques present in finite element method simulations implemented in the ANSYS program. The investigated highway bridge is constituted by four longitudinal composite girders and a concrete deck, spanning 40.0m by 13.5m. The analysis methodology and procedures presented in the design codes were applied to evaluate the fatigue of the bridge determining the service life of the structure. The main conclusions of this investigation focused on alerting structural engineers to the possible distortions, associated to the steel and composite bridge's service life when subjected to vehicle's dynamic actions.

  15. 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.

  16. Understanding the Fatigue Behavior of FML Structures and Materials under Complex Variable Amplitude Loading

    NARCIS (Netherlands)

    Alderdiesten, R.; Benedictus, R.; Khan, S.

    2009-01-01

    This paper presents various failure mechanisms in FMLs, highlights the presence or absence of interaction effects, and describes how the failure mechanisms can be described for predicting damage growth under arbitrary complex load spectra.

  17. Assessment of thermal fatigue damage caused by local fluid temperature fluctuation (part I: characteristics of constraint and stress caused by thermal striation and stratification)

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2014-01-01

    Highlights: • The source of the membrane constraint due to local temperature fluctuation was shown. • Thermal fatigue that occurred at a mixing tee and branched elbow was analyzed. • Cracking occurrence was reasonably explained by the constraint and stress conditions. - Abstract: This study was aimed at identifying the constraint conditions under local temperature fluctuation by thermal striping at a mixing tee and by thermal stratification at an elbow pipe branched from the main pipe. Numerical and analytical approaches were made to derive the thermal stress and its fluctuation. It was shown that an inhomogeneous temperature distribution in a straight pipe caused thermal stress due to a membrane constraint even if an external membrane constraint did not act on the pipe. Although the membrane constraint increased the mean stress at the mixing tee, it did not contribute to fluctuation of the thermal stress. On the other hand, the membrane constraint played an important role in the fatigue damage accumulation near the stratification layer of the branched elbow. Based on the constraint and stress conditions analyzed, the characteristics of the cracking observed in actual nuclear power plants were reasonably explained. Namely, at the mixing tee, where thermal crazing has been found, the lack of contribution of the membrane constraint to stress fluctuation caused a stress gradient in the thickness direction and arrested crack growth. On the other hand, at the branched elbow, where axial through-wall cracks have been found, the relatively large hoop stress fluctuation was brought about by movement of the stratified layer together with the membrane constraint even under a relatively low frequency of stress fluctuation

  18. Crack growth through low-cycle fatigue loading of material ARMOX 500T

    Directory of Open Access Journals (Sweden)

    V. Pepel

    2016-10-01

    Full Text Available This paper presents microstructure analysis of the creation and growth of cracks in uniaxial load. Analyse were done for steel Armox 500T (armour sheet. Results show that cracks are present quit early in steel lifetime. First micro cracks occur before the 200th cycles, whereby crack growth is progressive during further loading. Also it can be seen that after a certain number of cycles there are more longer cracks then shorter ones.

  19. System-Level Heat Transfer Analysis, Thermal- Mechanical Cyclic Stress Analysis, and Environmental Fatigue Modeling of a Two-Loop Pressurized Water Reactor. A Preliminary Study

    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)

    2015-01-03

    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 in April 2015 under the work package for environmentally assisted fatigue under DOE's Light Water Reactor Sustainability program. In this report, updates are discussed related to a system level preliminary finite element model of a two-loop pressurized water reactor (PWR). Based on this model, system-level heat transfer analysis and subsequent thermal-mechanical stress analysis were performed for typical design-basis thermal-mechanical fatigue cycles. The in-air fatigue lives of components, such as the hot and cold legs, were estimated on the basis of stress analysis results, ASME in-air fatigue life estimation criteria, and fatigue design curves. Furthermore, environmental correction factors and associated PWR environment fatigue lives for the hot and cold legs were estimated by using estimated stress and strain histories and the approach described in NUREG-6909. The discussed models and results are very preliminary. Further advancement of the discussed model is required for more accurate life prediction of reactor components. This report only presents the work related to finite element modelling activities. However, in between multiple tensile and fatigue tests were conducted. The related experimental results will be presented in the year-end report.

  20. Effects of Force Load, Muscle Fatigue, and Magnetic Stimulation on Surface Electromyography during Side Arm Lateral Raise Task: A Preliminary Study with Healthy Subjects

    Directory of Open Access Journals (Sweden)

    Liu Cao

    2017-01-01

    Full Text Available The aim of this study was to quantitatively investigate the effects of force load, muscle fatigue, and extremely low-frequency (ELF magnetic stimulation on surface electromyography (SEMG signal features during side arm lateral raise task. SEMG signals were recorded from 18 healthy subjects on the anterior deltoid using a BIOSEMI ActiveTwo system during side lateral raise task (with the right arm 90 degrees away from the body with three different loads on the forearm (0 kg, 1 kg, and 3 kg; their order was randomized between subjects. The arm maintained the loads until the subject felt exhausted. The first 10 s recording for each load was regarded as nonfatigue status and the last 10 s before the subject was exhausted was regarded as fatigue status. The subject was then given a five-minute resting between different loads. Two days later, the same experiment was repeated on every subject, and this time the ELF magnetic stimulation was applied to the subject’s deltoid muscle during the five-minute rest period. Three commonly used SEMG features, root mean square (RMS, median frequency (MDF, and sample entropy (SampEn, were analyzed and compared between different loads, nonfatigue/fatigue status, and ELF stimulation and no stimulation. Variance analysis results showed that the effect of force load on RMS was significant (p0.05. In comparison with nonfatigue status, for all the different force loads with and without ELF stimulation, RMS was significantly larger at fatigue (all p<0.001 and MDF and SampEn were significantly smaller (all p<0.001.

  1. Effects of Force Load, Muscle Fatigue, and Magnetic Stimulation on Surface Electromyography during Side Arm Lateral Raise Task: A Preliminary Study with Healthy Subjects.

    Science.gov (United States)

    Cao, Liu; Wang, Ying; Hao, Dongmei; Rong, Yao; Yang, Lin; Zhang, Song; Zheng, Dingchang

    2017-01-01

    The aim of this study was to quantitatively investigate the effects of force load, muscle fatigue, and extremely low-frequency (ELF) magnetic stimulation on surface electromyography (SEMG) signal features during side arm lateral raise task. SEMG signals were recorded from 18 healthy subjects on the anterior deltoid using a BIOSEMI ActiveTwo system during side lateral raise task (with the right arm 90 degrees away from the body) with three different loads on the forearm (0 kg, 1 kg, and 3 kg; their order was randomized between subjects). The arm maintained the loads until the subject felt exhausted. The first 10 s recording for each load was regarded as nonfatigue status and the last 10 s before the subject was exhausted was regarded as fatigue status. The subject was then given a five-minute resting between different loads. Two days later, the same experiment was repeated on every subject, and this time the ELF magnetic stimulation was applied to the subject's deltoid muscle during the five-minute rest period. Three commonly used SEMG features, root mean square (RMS), median frequency (MDF), and sample entropy (SampEn), were analyzed and compared between different loads, nonfatigue/fatigue status, and ELF stimulation and no stimulation. Variance analysis results showed that the effect of force load on RMS was significant ( p 0.05). In comparison with nonfatigue status, for all the different force loads with and without ELF stimulation, RMS was significantly larger at fatigue (all p < 0.001) and MDF and SampEn were significantly smaller (all p < 0.001).

  2. Evaluation and visualization of multiaxial fatigue behavior under random non-proportional loading condition

    Directory of Open Access Journals (Sweden)

    Takahiro Morishita

    2017-07-01

    Full Text Available In cyclic multiaxial stress/strain condition under nonproportional loading in which principal direction of stress/strain are changed in a cycle, it becomes difficult to analyze stress/strain ranges because of complexity of multiaxial stress/strain states depending on time in cycles. In order to evaluate stress/strain simply and suitably under non-proportional loading, Itoh and Sakane have proposed a method called as IS-method and a strain parameter for life evaluation under non-proportional loading NP. In the method, 6-components of stress/strain are converted to an equivalent stress/strain indicating the amplitude and the direction of principal stress/strain as a function of time as well as an intensity of loading nonproportionality fNP. Based on IS-method, the authors also have developed a tool which enables to analyze multiaxial stress/strain condition with the nonproportionality of loading history and evaluate failure life under nonproportional multiaxial loading. The tool indicates the analyzed results on monitor and users can understand visually not only variation of the stress/strain conditions but also non-proportionality during the cycle, which helps the design of material strength.

  3. Load fatigue of teeth with different ferrule lengths, restored with fiber posts, composite resin cores, and all-ceramic crowns.

    Science.gov (United States)

    Ma, Polly S; Nicholls, Jack I; Junge, Thomas; Phillips, Keith M

    2009-10-01

    There is no evidence to suggest that the ferrule length needed for an all-ceramic crown is different from that needed for a cast metal or metal ceramic crown. The purpose of this study was to relate different ferrule lengths with the number of fatigue cycles needed for failure of the crown cement for an all-ceramic crown cemented with a resin cement. Fifteen maxillary central incisors were divided into 3 groups (n=5), with ferrules of 0.0 mm (no-ferrule group), 0.5 mm (0.5-mm ferrule group), and 1.0 mm (1.0-mm ferrule group), respectively. Each tooth was restored with a 0.050-inch glass-filled composite post (ParaPost FiberWhite) and a composite resin core (ParaCore). The posts were cemented with resin cement (ParaPost Cement), and the composite resin cores were bonded to dentin using a dentin bonding agent (ParaPost Cement, Conditioner A & B). Each specimen was prepared with a 7-mm total preparation height, a 1.5-mm lingual axial wall, and a 1.0-mm shoulder around the tooth. The crowns for all specimens were pressed with a pressable ceramic material (IPS Empress 2) and cemented with resin cement (Variolink II). A 6-kg cyclic test load was applied to each specimen at 135 degrees to the long axis of the tooth. The independent variable measured was the number of load fatigue cycles required for failure of the crown cement. The data were subjected to the Kruskal-Wallis test to detect overall significance and the Mann-Whitney U test for pairwise comparisons with Bonferroni correction (alpha=.017). The mean (SD) number of cycles to failure for each group was: no-ferrule group, 213 (317); 0.5-mm ferrule group, 155,137 (68,991); and 1.0-mm ferrule group, 262,872 (21,432). None of the specimens in the 1.0-mm ferrule group failed. Significant differences were found between the no-ferrule group and the 0.5-mm ferrule group, and the no-ferrule group and the 1.0-mm ferrule group (P.017). Specimens with a 0.0-mm ferrule survived few fatigue cycles despite the fact that both the

  4. Prevention and treatment of the Farley-Tihange phenomenon of nuclear auxiliary pipes based on thermal fatigue

    International Nuclear Information System (INIS)

    Cao Feng; Wang Jianjun; Ding Youyuan

    2012-01-01

    Farley-Tihange Phenomenon due to thermal fatigue frequently appears on the downstream area filled with cool and heat water of the residual heat removal heat-exchange equipment and the base metal and welding joint of the RIS and RRA pipes connected with the primary coolant pipe directly in global Nuclear power plants in operation. Which brings unacceptable defects, even worse, LOCA. During the pre-service inspection, autonomic ultrasonic test and radiographic test were done to relative pipes and welds of Unit 3 of the Qinshan Nuclear Power Phase Ⅱ. This article summarizes the recurrent position and potential risks of the Farley-Tihange phenomenon, establishes the fault tree of its failure causes, analyses failure mechanism and models of heat fatigue, presents systematically prevention and treatment methods including in-operation supervision, shut-down inspections, emergent maintenance program and so on. (authors)

  5. A study of classroom acoustics and school teachers' noise exposure, voice load and speaking time during teaching, and the effects on vocal and mental fatigue development.

    Science.gov (United States)

    Kristiansen, Jesper; Lund, Søren Peter; Persson, Roger; Shibuya, Hitomi; Nielsen, Per Møberg; Scholz, Matthias

    2014-11-01

    The study investigated the noise exposure in a group of Danish school teachers. The aims were to investigate if noise posed a risk of impairment of hearing and to study the association between classroom acoustical conditions, noise exposure, vocal symptoms, and cognitive fatigue. Background noise levels, vocal load and speaking time were measured on 35 teachers during actual classroom teaching. The classrooms were characterized acoustically by measurements of reverberation time. Before and after the workday, the teachers answered a questionnaire on fatigue symptoms and carried out two cognitive test tasks sensitive to mental fatigue. The average noise level during the lessons was 72 dB(A), but during indoor sports activities the average noise level increased 6.6 dB(A). Room reverberation time (range 0.39-0.83 s) had no significant effect on the noise level. The teachers were talking with a raised voice in 61% of the time, and the vocal load increased 0.65 dB(A) per dB(A) increase in the average lesson noise level. An increase in voice symptoms during the workday correlated significantly with individual average noise exposure, and a decrease in performance in the two-back test correlated significantly with individual average vocal load. Noise exposure in general classrooms posed no risk of noise-induced hearing impairment in school teachers. However, the results provide evidence for an association between noise exposure and vocal load and development of vocal symptoms and cognitive fatigue after work.

  6. The Effect of Ankle, Knee and Hip Isokinetic Fatigue on Shock Absorption and Rate of Loading during Pair-leg Landing

    Directory of Open Access Journals (Sweden)

    Hamideh Khodaveisi

    2016-12-01

    Conclusion: Findings of this study indicate that the fatigue protocol using Isokinetic devices with uniform speed, increases muscle strength due to generating stress at all the joints, thereby, compensating the active and passive joints for shock absorption, and load distribution on the lower extremities. 

  7. The Role of Visual Noise in Influencing Mental Load and Fatigue in a Steady-State Motion Visual Evoked Potential-Based Brain-Computer Interface.

    Science.gov (United States)

    Xie, Jun; Xu, Guanghua; Luo, Ailing; Li, Min; Zhang, Sicong; Han, Chengcheng; Yan, Wenqiang

    2017-08-14

    As a spatial selective attention-based brain-computer interface (BCI) paradigm, steady-state visual evoked potential (SSVEP) BCI has the advantages of high information transfer rate, high tolerance to artifacts, and robust performance across users. However, its benefits come at the cost of mental load and fatigue occurring in the concentration on the visual stimuli. Noise, as a ubiquitous random perturbation with the power of randomness, may be exploited by the human visual system to enhance higher-level brain functions. In this study, a novel steady-state motion visual evoked potential (SSMVEP, i.e., one kind of SSVEP)-based BCI paradigm with spatiotemporal visual noise was used to investigate the influence of noise on the compensation of mental load and fatigue deterioration during prolonged attention tasks. Changes in α , θ , θ + α powers, θ / α ratio, and electroencephalography (EEG) properties of amplitude, signal-to-noise ratio (SNR), and online accuracy, were used to evaluate mental load and fatigue. We showed that presenting a moderate visual noise to participants could reliably alleviate the mental load and fatigue during online operation of visual BCI that places demands on the attentional processes. This demonstrated that noise could provide a superior solution to the implementation of visual attention controlling-based BCI applications.

  8. In vitro evaluation of the effect of thermal and mechanical fatigues on the bonding of an autopolymerizing soft denture liner to denture base materials using different primers.

    Science.gov (United States)

    Minami, Hiroyuki; Suzuki, Shiro; Minesaki, Yoshito; Kurashige, Hisanori; Tanaka, Takuo

    2008-07-01

    This in vitro study evaluated the effect of priming procedures on bonding of an autopolymerizing silicone denture liner (Sofreliner) to a denture base material after fatigue processes using cyclic thermal stressing and repetitive mechanical stressing. Denture base specimens were fabricated by use of an autopolymerizing denture base resin and Co-Cr alloy into a cylinder shape 8-mm diameter and 4-mm high. The bonding surfaces of denture base specimens were polished with 600-grit silicon carbide paper. Resin denture base specimens were pretreated with applications of resin primer (Sofreliner Primer or Reline Primer for resin). Metal specimens were pretreated with application of metal primer (Reline Primer for metal) or coated with adhesive resin (C&B Metabond) followed by application of resin primer (Sofreliner Primer). Tensile specimens were fabricated by polymerizing a 2-mm thickness of Sofreliner between a pair of pretreated denture base cylinders. Repetitive mechanical stressing was performed by using a University of Alabama-type wear-testing apparatus as a stress generator. Vertical 75 N load with 15 degrees rotation was applied 66,700, 133,300, 266,700, and 400,000 times, then residual tensile resistance to failure was measured. Seven specimens were fabricated for 16 groups--four cyclic loading groups for four pretreatment groups. Residual tensile resistance to failure of specimens before the fatiguing process and after 5000, 10,000, 20,000, and 30,000 thermocycles were used as reference. The mean values of each group were statistically analyzed by three-way ANOVA and Bonferroni/Dunn test at a 95% confidence level. Failure modes were assessed for all specimens measured. In the denture-bonded groups, residual tensile resistance to failure of Sofreliner Primer-treated group was significantly higher than that of the Reline Primer at each thermocycling interval (p denture liner after cyclic loading. Application of Sofreliner Primer for a resin denture base provided

  9. 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.)

  10. 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.

  11. A User’s Manual for a Computer Program to Generate Fatigue Spectrum Loading Sequences

    Science.gov (United States)

    1978-11-01

    IAJ ~ ~ 0.LJC C - tyo . .. a-w wLj- V1 Z- Z 7, . - CC .4 y r ZV)<<C -4 7r 1:, -. ) CJL.0-- - ŕ- wr Cf- QLj -4Q.- Z 4 rl) 0 "U -~ ~ 7 - I C_ r L/)~~ 2’j... SPEED , (EQUIVALENT AIRSPEED), KNOTS. A VALUE MUST BE ENTERED ONLY FOR THE SEGMENTS WITH M3 8 OR 13. 140 FATIGUE DAMAGE CALCULATION PROGRAM 16PA Page-of...I0_ 37 , ,7,3,1 ,, 1 1 17,1,3 1Z, 101 I I I I 1 38 1 1733 Ve AIRPLANE SPEED , (EQUIVALENT AIRSPEED), KNOTS. A VALUE MUST BE ENTERED ONLY FOR THE

  12. Cerebral blood flow, fatigue, mental effort, and task performance in offices with two different pollution loads

    DEFF Research Database (Denmark)

    Nishihara, Naoe; Wargocki, Pawel; Tanabe, Shin-ichi

    2014-01-01

    pollution levels created by placing or removing a pollution source (i.e. a used carpet) behind a screen. During the exposure, the subjects performed four different office tasks presented on a computer monitor. The tasks were performed at two paces: normal and maximum. When the pollution source was present......The effects of indoor air quality on symptoms, perceptions, task performance, cerebral blood flow, fatigue, and mental effort of individuals working in an office were investigated. Twenty-four right-handed Danish female subjects in an office were exposed in groups of two at a time to two air......, the air quality was perceived to be worse and more errors were made when subjects typed text at the maximum pace. No other changes in subjective responses, performance, or physiological measurements were associated with different exposures. Although cerebral blood flow and voice analysis did not detect...

  13. Thermal fatigue in mixing tees: A step by step simplified procedure

    International Nuclear Information System (INIS)

    Faidy, Claude

    2003-01-01

    Following the CIVAUX 1 incident of a leak on RHR system, EDF has developed a step by step procedure to screen and analyse similar locations: mixing tees with long duration at high ΔT between the 2 fluids. The paper present the procedure, the background of the methodology and few R and D work that support this procedure. The procedure is based on: screening criteria on maximum DT and minimum duration. screening criteria without any duration consideration, only DT and material. a simplified and conservative estimation of a usage factor. a detailed analysis of usage factor and crack growth rate, based on specific data collection of operating transients. Around that procedure EDF launched an R and D program on fatigue curves and fatigue reduction factors for high cycle fatigue. The procedure is compared with field experience and recent R and D fatigue tests. (author)

  14. 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.

  15. Creep fatigue damage of large shells submitted to thermal gradients due to sodium level variations

    International Nuclear Information System (INIS)

    Debaene, J.P.; Blaix, J.C.

    1989-01-01

    The authors present the studies performed on the upper part of the single redan of SPX2 in order to reduce the starts up duration. Main emphasis is put on the creep fatigue aspect. They present the preliminary studies performed in order to improve the behavior of structures either by technological changes, or by the adaptation of the start up procedure. The elastic analysis and inelastic analyses and the creep fatigue damage results are exposed

  16. Fatigue life assessment of thin-walled welded joints under non-proportional load-time histories by the shear stress rate integral approach

    Directory of Open Access Journals (Sweden)

    A. Bolchoun

    2016-10-01

    Full Text Available Fatigue life tests under constant and variable amplitude loadings were performed on the tube-tube thin-walled welded specimens made of magnesium (AZ31 and AZ61 alloys. The tests included pure axial, pure torsional and combined in-phase and out-of-phase loadings with the load ratio  RR " ", " " 1  . For the tests with variable amplitude loads a Gaußdistributed loading spectrum with S L 4 5 10  cycles was used. Since magnesium welds show a fatigue life reduction under out-of-phase loads, a stress-based method, which takes this behavior into account, is proposed. The out-of-phase loading results in rotating shear stress vectors in the section planes, which are not orthogonal to the surface. This fact is used in order to provide an out-of-phase measure of the load. This measure is computed as an area covered by the shear stress vectors in all planes over a certain time interval, its computation involves the shear stress and the shear stress rate vectors in the individual planes. Fatigue life evaluation for the variable amplitudes loadings is performed using the Palmgren-Miner linear damage accumulation, whereas the total damage of every cycle is split up into two components: the amplitude component and the out-of-phase component. In order to compute the two components a modification of the rainflow counting method, which keeps track of the time intervals, where the cycles occur, must be used. The proposed method also takes into account different slopes of the pure axial and the pure torsional Wöhler-line by means of a Wöhler-line interpolation for combined loadings

  17. The multi-axial material fatigue under the combined loading with mean stress in three dimensions

    Directory of Open Access Journals (Sweden)

    Fojtík F.

    2009-12-01

    Full Text Available This contribution describes the application of Fuxa's conjugated strength criterion on the experimental results under combined loading of specimens made from common construction steel 11523.0, melt T31052. The specimens were stepwise loaded by the torque amplitude, combination of torque amplitude and tension pre-stress, further by the amplitude of the torque in combination with inner overpressure and axial tension force. The last set of specimens was loaded by the torque amplitude in combination with inner and external overpressure and with axial tension force. To obtain the data required as the input values for the conjugated criterion the stress/strain analysis of the specimens by the finite element method in software ANSYS was performed. The experiments were performed on modified testing machine equipped by overpressure chamber.

  18. Investigations on the lifetime behaviour of a P23 pipe under fatigue loading

    Energy Technology Data Exchange (ETDEWEB)

    Friedmann, V.; Hartrott, P. von [Fraunhofer IWM, Freiburg (Germany)

    2008-07-01

    The performance of girth welds on new P23 low chromium steel pipes under cyclic loading at 450 C was investigated. The loading conditions were chosen to be representative for bore crack initiation and growth observed in main steam lines fabricated of 0.5Cr0.5Mo0.25V (CrMoV) steel. The microstructure of the base material and weldments was analysed. A lifetime model, initially set up for the prediction of thermo-cyclic loading, is used to predict the isothermal component behaviour. It is based on a Chaboche-type deformation model and the DTMF crack growth model. The failure mechanism of two component tests was compared to the model assumptions and the component lifetimes and failure locations are compared to the model predictions. (orig.)

  19. Influence of Endodontic Treatment and Retreatment on the Fatigue Failure Load, Numbers of Cycles for Failure, and Survival Rates of Human Canine Teeth.

    Science.gov (United States)

    Missau, Taiane; De Carlo Bello, Mariana; Michelon, Carina; Mastella Lang, Pauline; Kalil Pereira, Gabriel; Baldissara, Paolo; Valandro, Luiz Felipe; Souza Bier, Carlos Alexandre; Pivetta Rippe, Marília

    2017-12-01

    This study evaluated the effects of endodontic treatment and retreatment on the fatigue failure load, numbers of cycles for failure, and survival rates of canine teeth. Sixty extracted canine teeth, each with a single root canal, were selected and randomly divided into 4 groups (n = 15): untreated, teeth without endodontic intervention; prepared, teeth subjected only to rotary instrumentation; filled, teeth receiving complete endodontic treatment; and retreated, teeth retreated endodontically. After the different endodontic interventions, the specimens were subjected to fatigue testing by the stepwise method: 200 N (× 5000 load pulses), 300 N, 400 N, 500 N, 600 N, 800 N, and 900 N at a maximum of 30,000 load pulses each or the occurrence of fracture. Data from load to failure and numbers of cycles for fracture were recorded and subjected to Kaplan-Meier and Log Rank tests (P retreated, filled, and untreated groups presented statistically significantly higher fatigue failure loads and numbers of cycles for failure than did the prepared group. Weibull analysis showed no statistically significant difference among the treatments for characteristic load to failure and characteristic number of cycles for failure, although, for number of cycles, a higher Weibull modulus was observed in filled and retreated conditions. The predominant mode of failure was catastrophic. Teeth subjected to complete endodontic treatment and retreatment behaved similarly in terms of fatigue failure load and number of cycles to failure when compared with untreated teeth. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  20. 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.

  1. 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 ...

  2. Assessment of wind turbine drive-train fatigue loads under torsional excitation

    DEFF Research Database (Denmark)

    Gallego Calderon, Juan Felipe; Natarajan, Anand

    2015-01-01

    This paper establishes validated models that can accurately account for the dynamics of the gearbox, along with the external dynamics that excite the system. A drive-train model implementation is presented where the gearbox and generator are coupled to the wind turbine structure in a dynamic...... allows the computation of the bearing and gear-mesh loads. The proposed models are validated by experiments from a 750 kW test-rig. The drive-train model is configured for a 5 MW power capacity and coupled to the corresponding wind turbine and load simulations are carried out under turbulent wind...

  3. Influence of Nonlinear Irregular Waves on the Fatigue Loads of an Offshore Wind Turbine

    NARCIS (Netherlands)

    Van der Meulen, M.B.; Ashuri, T.; Van Bussel, G.J.W.; Molenaar, D.P.

    2012-01-01

    In order to make offshore wind power a cost effective solution that can compete with the traditional fossil energy sources, cost reductions on the expensive offshore support structures are required. One way to achieve this, is to reduce the uncertainty in wave load calculations by using a more

  4. 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.

  5. 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

  6. Numerical simulation of long-period fluid temperature fluctuation at a mixing tee for the thermal fatigue problem

    Energy Technology Data Exchange (ETDEWEB)

    Utanohara, Yoichi, E-mail: utanohara@inss.co.jp [Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Nakamura, Akira, E-mail: a-naka@inss.co.jp [Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Miyoshi, Koji, E-mail: miyoshi.koji@inss.co.jp [Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Kasahara, Naoto, E-mail: kasahara@n.t.u-tokyo.ac.jp [University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2016-08-15

    Highlights: • A large eddy simulation of a mixing tee was carried out. • Fluid temperature fluctuation could be predicted qualitatively. • Grid convergence was almost attained and the simulation continued until 100 s. • A longer-period temperature fluctuation than the well-known St = 0.2 appeared. • Prediction of long-period temperature fluctuations improves the thermal fatigue assessment. - Abstract: Thermal fatigue cracks may be initiated at mixing tees where high and low temperature fluids flow in and mix. According to a previous study, damage by thermal fatigue depends on the frequency of the fluid temperature fluctuation near the wall surface. Structures have the time constant of structural response that depends on physical properties of the structure and the gain of the frequency response tends to become maximum at the frequency lower than the typical frequency of fluid temperature fluctuation. Hence the effect of the lower frequency, that is, long-period temperature fluctuation is important for the thermal fatigue assessment. The typical frequency of fluid temperature fluctuation is about St = 0.2 (nearly 6 Hz), where St is Strouhal number and means non-dimensional frequency. In the experimental study by Miyoshi et al. (2014), a longer-period fluctuation than St = 0.2 was also observed. Results of a fluid–structure coupled analysis by Kamaya et al. (2011) showed this long-period temperature fluctuation causes severer damage to piping. In the present study, a large eddy simulation was carried out to investigate the predictive performance of the long-period fluid temperature fluctuation more quantitatively. Numerical simulation was conducted for the WATLON experiment which was the water experiment of a mixing tee performed at the Japan Atomic Energy Agency. Four computational grids were used to confirm grid convergence. In the short time (9 s) simulations, tendencies of time-averaged and fluctuated velocities could be followed. Time

  7. Experimental investigation of the flow, oxidation, cooling, and thermal-fatigue characteristics of a laminated porous sheet material

    Science.gov (United States)

    Hickel, R. O.; Warren, E. L.; Kaufman, A.

    1972-01-01

    The basic flow and oxidation characteristics of a laminated porous material (Lamilloy) are presented. The oxidation characteristics of Lamilloy are compared to a wireform-type porous material for the case when both materials are made from Hastelloy-X alloy. The cooling performance of an air cooled vane made from Lamilloy, as determined from cascade tests made at gas temperatures ranging from 1388 to 1741 C (2350 to 3165 F) is also discussed, as well as of a cascade-type thermal fatigue test of the Lamilloy vane.

  8. Investigation of in-plane biaxial low cycle fatigued austenitic stainless steel AISI 321. I. Mechanical testing on the planar biaxial load machine

    International Nuclear Information System (INIS)

    Taran, Yu.V.; Balagurov, A.M.; Kuznetsov, A.N.; Schreiber, J.; Bomas, H.; Stoeberl, Ch.; Rathjen, P.; Vorster, W.J.J.; Korsunsky, A.M.

    2007-01-01

    During fatigue loading of structural materials such as stainless steel, changes in the microstructure which affect the mechanical and physical properties occur. Experimental simulation of the loading conditions that induce the changes can be performed by mechanical loading, usually in the form of uniaxial tension-compression cycling. However, real machines and structures are subjected to more complex multiaxial stresses. Fatigue and fracture under multiaxial stresses are one of the most important current topics aimed at ensuring improved reliability of industrial components. The first step towards better understanding of this problem is to subject the materials to biaxial loading. The material examined was low austenitic stainless steel AISI 321 H. A set of the four samples of cruciform geometry was subjected to the biaxial tension-compression fatigue cycling with the frequency of 0.5 Hz at the applied load of 10-17 kN. The samples are intended for the neutron diffraction measurements of the residual stresses and the mechanical characterizations on a dedicated stress-diffractometer

  9. 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...

  10. Hold-time effects on the fatigue life of CuCrZr alloys for fusion applications

    International Nuclear Information System (INIS)

    Wu, Xianglin; Pan, Xiao; Singh, Bachu N.; Li, Meimei; Stubbins, James F.

    2007-01-01

    The fatigue and creep-fatigue response of copper alloys is of interest due to the cyclic thermal-mechanical loading processes a fusion first wall will experience during operation. Creep-fatigue experiments were performed on a CuCrZr alloy with an overaged heat treatment at room temperature to determine the effects on fatigue life of a 10 s hold period applied at the maximum tension and compression points in the fatigue loading cycle. The hold period produced a reduction in the number of cycles to failure. This reduction was largest at the lowest strain amplitudes and the longest fatigue lives, the region of most interest for component design. Stress relaxation was observed during the hold periods even at room temperature where thermally-activated creep processes are not expected. The large reduction in fatigue life is apparently due to a change in the crack initiation mode from transgranular with no hold period to intergranular with a hold period

  11. Fatigue Performance Assessment of Composite Arch Bridge Suspenders Based on Actual Vehicle Loads

    Directory of Open Access Journals (Sweden)

    Bin Chen

    2015-01-01

    Full Text Available In the through arch bridges, the suspenders are the key components connecting the arch rib and the bridge deck in the middle, and their safety is an increasing focus in the field of bridge engineering. In this study, various vehicle traffic flow parameters are investigated based on the actual vehicle data acquired from the long-term structural health monitoring system of a composite arch bridge. The representative vehicle types and the probability density functions of several parameters are determined, including the gross vehicle weight, axle weight, time headway, and speed. A finite element model of the bridge structure is constructed to determine the influence line of the cable force for various suspenders. A simulated vehicle flow, generated using the Monte Carlo method, is applied on the influence lines of the target suspender to determine the stress process, and then the stress amplitude spectrum is obtained based on the statistical analysis of the stress process using the rainflow counting method. The fatigue performance levels of various suspenders are analyzed according to the Palmgren-Miner linear cumulative damage theory, which helps to manage the safety of the suspenders.

  12. A Low Order Model for Analyzing effects of Blade Fatigue Load Control

    DEFF Research Database (Denmark)

    Kallesøe, Bjarne Skovmose

    2006-01-01

    A new low order mathematical model is introduced to analyse blade dynamics and blade load reducing control strategies for wind turbines. The model consists of a typical wing section model combined with a rotor speed model, leading to four structural degrees of freedom (flapwise, edgewise, and tor......A new low order mathematical model is introduced to analyse blade dynamics and blade load reducing control strategies for wind turbines. The model consists of a typical wing section model combined with a rotor speed model, leading to four structural degrees of freedom (flapwise, edgewise......, and torsional blade oscillations, and rotor speed). The aerodynamics is described by a model of unsteady aerodynamic. The equations of motion are derived in nonlinear and linear form. The linear equations of motion are used for stability analysis and control design. The nonlinear equations of motion are used...

  13. Creep-fatigue damage assessment by subsequent fatigue straining

    International Nuclear Information System (INIS)

    Yaguchi, Masatsugu; Nakamura, Toshiya; Ishikawa, Akiyoshi; Asada, Yasuhide

    1993-01-01

    A series of creep-fatigue tests has been conducted with Modified 9Cr-1Mo steel at 600 C in a high vacuum environment of 0.1 mPa to assess an accumulation of creep-fatigue damage. In these tests, each test specimen has been subjected to prior creep-fatigue loading followed by subsequent fatigue loading or prior fatigue loading followed by subsequent creep-fatigue loading. A linear summation of cumulative damage of fatigue and creep life fraction was smaller than unity for the former case, and larger than unity for the latter case. Scanning electron microscopic observation showed that in the case of prior creep-fatigue loading, a crack propagated from inclusions around which cavities were observed and its appearance transformed from transgranular to intergranular type with the increase of the number of cycles of prior creep-fatigue loading, while crack mode was predominantly intergranular in the case of prior fatigue loading. It was suggested that in the case of prior creep-fatigue loading, the fatigue life becomes shorter than that predicted by the linear rule due to early initiation of a crack caused from the cavity creation. In the case of prior fatigue loading, the crack propagates different courses in each loading to lead to the life fraction which is larger than unity

  14. Non-Linear Mechanical Behavior of Plasma Sprayed Alumina Under Mechanical and Thermal Loading

    Czech Academy of Sciences Publication Activity Database

    Mušálek, Radek; Matějíček, Jiří; Vilémová, Monika; Kovářík, O.

    2010-01-01

    Roč. 19, 1-2 (2010), s. 422-428 ISSN 1059-9630. [ International Thermal Spray Conference (ITSC 2009):Expanding Thermal Spray Performance to New Markets and Applications. Las Vegas, NV, 04.05.2009-07.05.2009] R&D Projects: GA ČR GA106/08/1240; GA MŠk ME 901 Institutional research plan: CEZ:AV0Z20430508 Keywords : APS coatings * fatigue and fracture * hardness and (visco-) elastic properties * influence of spray parameters * stiffness * thermal cycling Subject RIV: JK - Corrosion ; Surface Treatment of Materials Impact factor: 1.844, year: 2010 http://www.springerlink.com/content/a8387uk8716x53x1/fulltext.pdf

  15. 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....

  16. 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

  17. 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.

  18. Stress fracture healing: fatigue loading of the rat ulna induces upregulation in expression of osteogenic and angiogenic genes that mimic the intramembranous portion of fracture repair.

    Science.gov (United States)

    Wohl, Gregory R; Towler, Dwight A; Silva, Matthew J

    2009-02-01

    Woven bone is formed in response to fatigue-induced stress fractures and is associated with increased local angiogenesis. The molecular mechanisms that regulate this woven bone formation are unknown. Our objective was to measure the temporal and spatial expression of osteo- and angiogenic genes in woven bone formation in response to increasing levels of fatigue-induced damage. We used the rat forelimb compression model to produce four discrete levels of fatigue damage in the right ulna of 115 male Fischer rats. Rats were killed at 0 (1 h), 1, 3 and 7 days after loading. Using qRT-PCR, we quantified gene expression associated with osteogenesis (BMP2, Msx2, Runx2, Osx, BSP, Osc), cell proliferation (Hist4), and angiogenesis (VEGF, PECAM-1) from the central half of the ulna. The spatial distribution of BMP2, BSP and PCNA was assessed by immunohistochemistry or in situ hybridization in transverse histological sections 1, 4, and 7 mm distal to the ulnar mid-diaphysis. One hour after loading, BMP2 was significantly upregulated in neurovascular structures in the medial ulnar periosteum. Expression of angiogenic markers (VEGF, PECAM-1) increased significantly between Day 0 and 1 and, as with BMP2 expression, remained upregulated through Day 7. While Osx and BSP were upregulated on Day 1, the other osteogenic genes (Msx2, Runx2, Osx, BSP and Osc) were induced on Day 3 in association with the initiation of periosteal woven bone formation and continued through Day 7. The magnitude of osteogenic gene expression, particularly matrix genes (BSP, Osc) was significantly proportional the level of fatigue damage. The woven bone response to fatigue injury is remarkably similar to the "intramembranous" portion of fracture repair - rapid formation of periosteal woven bone characterized by early BMP2 expression, cell proliferation, and upregulation of osteogenic genes. We speculate that woven bone repair of fatigue damage may be an abbreviated fracture response without the requirement

  19. Thermal shock and thermal fatigue resistant ZrO2/Al2O3 ceramics in the eutectic composition range. Pt. 1

    International Nuclear Information System (INIS)

    Liu, T.; Dorfschmidt, K.; Oberacker, R.

    1992-01-01

    Thermal shock and thermal fatigue resistant ZrO 2 /Al 2 O 3 ceramics in the eutectic composition range have been prepared and characterized in this work. The microstructures such as chemical composition (Al 2 O 3 -content), stabilizer (Y 2 O 3 , CeO 2 ), porosity, grain size and crack configuration (duplex, dendrite microstructure) have been varied systematically by different processing techniques. Mechanical properties such as Youngs modulus, bending strength, fracture toughness and R-curve behaviour have been investigated. Interrelations between the above microstructures and the mechanical properties have been established. Optimized combination of high toughness and high strength has been reached in crack free, fine-grained Ce-stabilized ZA-materials. On the other hand pronounced inelastic behaviour has been measured by optimization of the crack configuration in the duplex and dendrite microstructures. 6 refs., 1 tab., 10 figs

  20. 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