WorldWideScience

Sample records for behavioural mechanisms underlying

  1. Neural mechanisms underlying the evolvability of behaviour

    OpenAIRE

    Katz, Paul S.

    2011-01-01

    The complexity of nervous systems alters the evolvability of behaviour. Complex nervous systems are phylogenetically constrained; nevertheless particular species-specific behaviours have repeatedly evolved, suggesting a predisposition towards those behaviours. Independently evolved behaviours in animals that share a common neural architecture are generally produced by homologous neural structures, homologous neural pathways and even in the case of some invertebrates, homologous identified neu...

  2. Coping styles and behavioural flexibility: towards underlying mechanisms

    OpenAIRE

    Coppens, Caroline M.; de Boer, Sietse F.; Koolhaas, Jaap M.

    2010-01-01

    A coping style (also termed behavioural syndrome or personality) is defined as a correlated set of individual behavioural and physiological characteristics that is consistent over time and across situations. This relatively stable trait is a fundamental and adaptively significant phenomenon in the biology of a broad range of species, i.e. it confers differential fitness consequences under divergent environmental conditions. Behavioural flexibility appears to be an important underlying attribu...

  3. Believing versus interacting: Behavioural and neural mechanisms underlying interpersonal coordination

    DEFF Research Database (Denmark)

    Konvalinka, Ivana; Bauer, Markus; Kilner, James;

    in joint action has investigated only one of these mechanisms at a time – low-level processes underlying joint coordination, or high-level cognitive mechanisms that give insight into how people think about another. In real interactions, interplay between these two mechanisms modulates how we interact...... into neural mechanisms underlying belief of interacting with another person as well as engaging in interaction with the responsive other....

  4. Mechanical behaviour of an austenitic stainless steel under repeated impacts

    International Nuclear Information System (INIS)

    Cyclic indentation tests realised with an energy controlled spherical indenter allow a characterisation of the material behaviour under dynamic solicitations. This solicitation is, for example, able to show erosion and matting phenomenon. This test has been performed on AISI 316 stainless steels samples. Results have shown an increase of the hardness and the depth of the affected area versus the cycles number. With a micrographic optical analysis, we have detected a work hardening effect below the contact area. (authors)

  5. Behaviour of bcc technical superconductors under dynamic mechanical stress

    International Nuclear Information System (INIS)

    The behavior of bcc technical superconductors NbTi, NbZr and Nb under dynamic mechanical stress was investigated using two measuring techniques. In shot-sample training experiments the load was measured at which, in wire samples with a transport current applied, normal transitions occured in succesive straining cycles. Complementary, the acoustic emission from superconductors was monitored during strain at 4.2 K. A mechanism based on the formation of a stress induced shear transformation was proposed to account for the training behavior. This partially reversible shearing of the lattice is not sufficient to furnish the required energy for transition in the normal state but it may be detected by means of acoustic emission. On the other hand, a time correlation between acoustic emission and normal transition was found although training behavior and emission responded differently to the same metallurgical treatment. The experiments strongly indicate that the mechanism directly responsible for local energy release is microyielding, induced by the shear transformation. The stress relaxation which accompanies this transformation results in an increased load on the rest of the sample cross-section. Consequently microyielding caused by the transformation could occur in that region of the sample without being detected on the stress-strain curve. This would result in a sufficient release of energy to increase the sample temperature above its critical value. (orig./HP)

  6. Prolonged secretion of cortisol as a possible mechanism underlying stress and depressive behaviour.

    Science.gov (United States)

    Qin, Dong-Dong; Rizak, Joshua; Feng, Xiao-Li; Yang, Shang-Chuan; Lü, Long-Bao; Pan, Lei; Yin, Yong; Hu, Xin-Tian

    2016-01-01

    Stress is associated with the onset of depressive episodes, and cortisol hypersecretion is considered a biological risk factor of depression. However, the possible mechanisms underlying stress, cortisol and depressive behaviours are inconsistent in the literature. This study examined the interrelationships among stress, cortisol and observed depressive behaviours in female rhesus macaques for the first time and explored the possible mechanism underlying stress and depressive behaviour. Female monkeys were video-recorded, and the frequencies of life events and the duration of huddling were analysed to measure stress and depressive behaviour. Hair samples were used to measure chronic cortisol levels, and the interactions between stress and cortisol in the development of depressive behaviour were further evaluated. Significant correlations were found between stress and depressive behaviour measures and between cortisol levels and depressive behaviour. Stress was positively correlated with cortisol levels, and these two factors interacted with each other to predict the monkeys' depressive behaviours. This finding extends the current understanding of stress/cortisol interactions in depression, especially pertaining to females. PMID:27443987

  7. Investigating the time-dependent behaviour of Boom clay under thermo-mechanical loading

    CERN Document Server

    Cui, Yu-Jun; Tang, Anh-Minh; Delage, Pierre; Li, Xiang-Ling; 10.1680/geot.2009.59.4.319

    2009-01-01

    Among the various laboratory studies to investigate the Thermo-Hydro-Mechanical (THM) behaviour of Boom clay, relatively few were devoted to the time dependent behaviour, limiting any relevant analysis of the long-term behaviour of the disposal facility. The present work aims at investigating the time-dependent behaviour of Boom clay under both thermal and mechanical loading. High-pressure triaxial tests at controlled temperatures were carried out for this purpose. The tests started with constant-rate thermal and/or mechanical consolidation and ended with isobar heating and/or isothermal compression at a constant stress rate or by step loading. Significant effects of temperature as well as of compression and heating rates were observed on the volume change behaviour. After being loaded to a stress lower than the pre-consolidation pressure (5 MPa) at a low temperature of 25\\degree C and at a rate lower than 0.2 kPa/min, the sample volume changes seemed to be quite small, suggesting a full dissipation of pore w...

  8. Mechanical behaviour of the T91 martensitic steel under monotonic and cyclic loadings in liquid metals

    International Nuclear Information System (INIS)

    The paper deals with the mechanical properties in liquid metals of the T91 martensitic steel, a candidate material for the window of an accelerating driven system (ADS). Two main questions are examined, the risk of liquid metal embrittlement and the accelerated fatigue damage by a liquid metal. It is found that the transition from ductile to brittle behaviour induced by a liquid metal is possible as a result of a decrease in surface energy caused by the adsorbed liquid metal. The embrittlement can occur only with a hard microstructure and a nucleation of very sharp defects inside the liquid metal. Under cycling straining, the fatigue resistance of the standard T91 steel is decreased by a factor of about 2 in the liquid metal as compared to air. It is proposed that short crack growth is promoted by the liquid metal which weakens the microstructural grain boundary barriers and skip the microcrack coalescence stage

  9. Thermo-mechanical behaviour of coolant channels for heavy water reactors under accident conditions

    International Nuclear Information System (INIS)

    The objective of nuclear safety research programme is to develop and verify computer models to accurately predict the behavior of reactor structural components under operating and off normal conditions. Indian Pressurised Heavy Water Reactors (PHWRs) are tube type of reactors. The coolant channel assemblies, being one of the most important components, need detailed analysis under all operating conditions as well as during postulated conditions of accidents for its thermo-mechanical behaviour. One of the postulated accident scenarios for heavy water moderated pressure tube type of reactors i.e. PHWRs is Loss Of Coolant Accident (LOCA) coincident with Loss Of Emergency Core Cooling System (LOECCS). In this case, even though the reactor is tripped, the decay heat may not be removed adequately due to low or no flow condition and inventory depletion of primary side. Since the emergency core cooling system is presumed to be not available, the cooling of the fuel pins and the coolant channel assembly depends on the moderator cooling system, which is assumed to be available. Moderator cooling system is a separate system in PHWRs. In PHWRs, the fuel assembly is surrounded by pressure tube, an annulus insulating environment and a concentric calandria tube. In this postulated accident scenario, a structural integrity evaluation has been carried out to assess the modes of deformation of pressure tube-calandria tube assembly in a tube type nuclear reactor. The loading of pressure and temperature causes the pressure tube to sag/balloon and come in contact with the outer cooler calandria tube. The resulting heat transfer could cool and thus control the deformation of the pressure tube thus introducing inter-dependency between thermal and mechanical contact behaviour. The amount of heat thus expelled significantly depends on the thermal contact conductance and the nature of contact between the two tubes. Deformation of pressure tube creates a heat removal path to the relatively

  10. Microstructures of UO2 with controlled properties: understanding of elaboration mechanisms and of the mechanical behaviour under temperature

    International Nuclear Information System (INIS)

    The objective of this research work is to develop new UO2 fuel materials, without additive but with microstructure characteristics and mechanical properties controlled at high temperatures. More precisely, it aims at correlating initial powders and their implementation conditions with the microstructures obtained after sintering, and at correlating microstructure characteristics of sintered pellets with their mechanical behaviour at high temperatures. The author described the pellet fabrication process and mentions effects of some powder geometrical characteristics and sintering conditions on granular growth and densification. He gives an overview of knowledge on mechanisms of viscoplastic strain of UO2, on the effect of material parameters and of solicitation conditions on the mechanical behaviour of UO2. He describes and discusses an experimental investigation of industrial UO2 powder sintering which aimed at identifying parameters which influence the final microstructure densification and formation. He reports the development of a 'model' UO2 powder fabrication process with which powder characteristics are better controlled than in the case of industrial powders. These 'model' powders are used to more precisely investigate the effects of powder parameters (quantity of fine particles, specific area and morphology) on densification and grain size after sintering

  11. On the mechanical behaviour of a butt jointed thermoplastic composite under bending

    NARCIS (Netherlands)

    Baran, I.; Warnet, L.; Akkerman, R.; Thomsen, O.T

    2015-01-01

    In the present work, the mechanical behavior of a recently developed novel butt jointed thermoplastic composite was investigated under bending conditions. The laminated skin and the web were made of carbon fiber (AS4) and polyetherketoneketone (PEKK). The butt joint (filler) was injection molded fro

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

    CERN Document Server

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

    2012-01-01

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

  13. Hydro-mechanical behaviour of two reference Belgian clay formations under non-isothermal conditions

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Two deep clay formations are being investigated in Belgium in connection with the design of a repository for 'High-Level Radioactive Waste': Boom clay BC at Mol (located between 160 and 270 m depths), considered the reference host formation, and Ypresian clay YC at Kallo (located between 300 and 450 m depths) as an alternative one. A comprehensive experimental programme has been carried out on these materials to explore water permeability at different temperatures and sample orientations, as well as to analyse volume change behaviour on loading/unloading at different temperatures and sample orientations (including pre and post-yield compressibility, yield properties and volume changes on drained thermal loading). Table 1 summarises some properties of BC and YC. Figure 1 presents the pore size distribution PSD curves of both clays obtained by mercury intrusion porosimetry. They display contrasting features (bi-modal pore network in YP with larger dominant pore sizes). Larger water permeability values are expected on YC as indicated in Table 1 and Figure 2, not only as a consequence of its higher void ratio but also due to these double porosity features. Water retention properties, of particular concern on sample retrieval from large depths, are also affected due to desaturation processes that are associated with the double porosity network of YP and its effects on air-entry value (a lower initial suction is measured on YP, despite being retrieved from larger depths). Figure 2 shows vertical and horizontal water permeability results under constant volume conditions and different temperatures. BC and YC display small anisotropy at sample scale - permeability is slightly larger on horizontal direction-. With regard to temperature effects, the figure shows that water permeability dependency on temperature in YC is slightly higher than the water viscosity prediction for both orientations. Instead BC displayed a thermal

  14. Mechanical Behaviour under Tensile Loading of Textile Reinforced Concrete with Short Fibres

    OpenAIRE

    Barhum, Rabea; Mechtcherine, Viktor

    2011-01-01

    This treatise addresses the influence of the addition of short dispersed and integral fibres made of alkali-resistant glass on the fracture behaviour of textile-reinforced concrete (TRC). A series of uniaxial, deformation-controlled tension tests was performed to study the strength-, deformation-, and fracturebehaviour of thin, narrow plates made of TRC both with and without the addition of short fibres. Furthermore, uniaxial tension tests on specimens reinforced with only short fibres and si...

  15. Characterization of the deformation mechanisms and modelling of the mechanical behaviour under multi-axial loadings of SiC/SiC composite tubes

    International Nuclear Information System (INIS)

    SiC/SiC composites are candidate materials for in-core components of future nuclear reactors. The analysis of these structures using numerical simulations requires material constitutive laws. The present work focuses on understanding the deformation mechanisms of these materials in order to build a constitutive model able to predict their stress-strain response under complex loadings. An extensive characterization of the mechanical behaviour of SiC/SiC multi-layered tubes - similar to fuel cladding concepts - was carried out, using tension internal pressure, tension-torsion and bending tests, that allowed to build an important experimental basis for the understanding of the mechanisms and the identification of constitutive laws. In-situ and post-failure observations have allowed quantifying the orientation of surface matrix cracks as a function of the loading type. Full-field measurements using Digital Image Correlation at the tow scale brought precise information on the composite surface kinematics, such as the crack opening or the deformation of the matrix fragments. These measurements also evidence the importance of the tow reorientation, that could explain specific features of the macroscopic behaviour because of its coupling with matrix cracking. Finally, these experimental data allowed to build a constitutive model, identified on only four uniaxial tests, able to predict satisfactorily the macroscopic behaviour under several biaxial loadings. The correct prediction of local quantities, such as the characteristics of the matrix cracking in tension, has also been verified. (author)

  16. Fatigue behaviour of coke drum materials under thermal-mechanical cyclic loading

    Directory of Open Access Journals (Sweden)

    Jie Chen

    2014-01-01

    Full Text Available Coke drums are vertical pressure vessels used in the delayed coking process in petroleum refineries. Significant temperature variation during the delayed coking process causes damage in coke drums in the form of bulging and cracking. There were some studies on the fatigue life estimation for the coke drums, but most of them were based on strain-fatigue life curves at constant temperatures, which do not consider simultaneous cyclic temperature and mechanical loading conditions. In this study, a fatigue testing system is successfully developed to allow performing thermal-mechanical fatigue (TMF test similar to the coke drum loading condition. Two commonly used base and one clad materials of coke drums are then experimentally investigated. In addition, a comparative study between isothermal and TMF lives of these materials is conducted. The experimental findings lead to better understanding of the damage mechanisms occurring in coke drums and more accurate prediction of fatigue life of coke drum materials.

  17. The behaviour of quantum mechanical systems under continuous measurement: Watchdog effect and master equation

    International Nuclear Information System (INIS)

    In this thesis the influence of continuously repeting measurement by the environment on a quantum mechanical system is studied. The interaction with the environment which is in principle present for each physical object can have an important influence on the considered system as the ''watchdog'' effect has clearly demonstrated. These situations are however quite special. Of much more importance is the effect of the environment on macroscopical objects for which only regarding this interaction a derivation of master equations can be founded. (HSI)

  18. High-temperature behaviour of IN 738 LC under isothermal and thermo-mechanical cyclic loading

    Energy Technology Data Exchange (ETDEWEB)

    Frenz, H. [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin (Germany); Meersmann, J. [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin (Germany); Ziebs, J. [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin (Germany); Kuehn, H.-J. [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin (Germany); Sievert, R. [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin (Germany); Olschewski, J. [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin (Germany)

    1997-07-01

    The temperature dependence of the cyclic behavior of IN 738 LC was studied. Cyclic iso- and non-isothermal tests were performed with proportional and non-proportional tension/torsion strain paths. It was shown that maximum and minimum stress values measured in isothermal strain controlled tests correspond quite well with results of non-isothermal tests. Thermal-mechanical constitutive equations based on the viscoplastic Chaboche model were used to describe the non-isothermal stress-strain behavior. (orig.)

  19. The impact of flavonoids on spatial memory in rodents: from behaviour to underlying hippocampal mechanisms

    OpenAIRE

    Rendeiro, Catarina; Spencer, Jeremy P. E.; Vauzour, David; Butler, Laurie T.; Ellis, Judi A.; Williams, Claire M.

    2009-01-01

    Emerging evidence suggests that a group of dietary-derived phytochemicals known as flavonoids are able to induce improvements in memory, learning and cognition. Flavonoids have been shown to modulate critical neuronal signalling pathways involved in processes of memory, and therefore are likely to affect synaptic plasticity and long-term potentiation mechanisms, widely considered to provide a basis for memory. Animal dietary supplementation studies have further shown that flavonoid-rich foods...

  20. Mechanical behaviour of high level nuclear waste overpacks under repository loading and during welding

    International Nuclear Information System (INIS)

    One of the concepts for final disposal of high level nuclear waste in Switzerland consists of a mined repository approximately 1200 m deep in the crystalline bedrock of Northern Switzerland. In order to delay the return of the radionuclides to the biosphere, and to reduce their concentration there to acceptable levels, reliance is placed in the multiple safety barrier principle. In addition to the natural barriers the following engineered barriers are envisaged: the waste form itself (vitrified high level nuclear waste), an overpack, and a compacted bentonite backfill within which the overpack is placed horizontally in the axis of the repository gallery. The first part of the present work reports on the participation in the COMPAS project (COntainer Mechanical Performance ASsessment). This project was carried out within the framework of the European Atomic Energy Community's cost-sharing programme on 'Radioactive Waste Management and Disposal'. It was concerned with the mechanical performance of overpacks for vitrified high level nuclear waste. The second part of this work deals with the issue of stress corrosion cracking of the high level nuclear waste overpack from NAGRA which is made out of GS-40 cast steel. After a description of the material properties of GS-40 cast steel, the one-dimensional FIBRE model is discussed, which should give an insight into the parameters involved in a thermomechanical calculation of a welding process. The calculations were performed with the commercially available finite element code ADINA. The output from ADINA was used as input to the postprocessor ORVIRT when fracture calculations are considered. (author) figs., tabs., refs

  1. Mechanical behaviour of a friction stir spot welding lap under static loading

    Science.gov (United States)

    Herbelot, C.; Hoang, T. Dang; Imad, A.; Benseddiq, N.

    2011-01-01

    Friction stir spot welding (FSSW) is a recent welding method which takes advantage of being performed in the solid state and presents many benefits such as a lower heat-input, a reduction of residual stresses and an elimination of the solidification defects for example. The present study investigates, for fixed process parameters and tool geometry, the fracture and damage of a single-lap friction stir spot welding joints formed from thin sheets of aluminum alloy 6082 T6. An experimental approach was carried out in order to analyze the sequence of damage mechanisms using acoustic emission (A.E.) and measurement of fields by digital image correlation (D.I.C.) techniques simultaneously. The A.E. technique allows the monitoring of the evolution of acoustic activities by taking into account energy of the events. The D.I.C. technique confirms the damage scenarios after the treatment of strain field at any point near the fastener and especially between the exit hole and the shoulder footprint. The coupling of those two techniques allows to identify characteristic points and a breakdown of the load displacement curve in phases.

  2. Influence of free water content on the compressive mechanical behaviour of cement mortar under high strain rate

    Indian Academy of Sciences (India)

    Jikai Zhou; Xudong Chen; Longqiang Wu; Xiaowei Kan

    2011-06-01

    The effect of free water content upon the compressive mechanical behaviour of cement mortar under high loading rate was studied. The uniaxial rapid compressive loading testing of a total of 30 specimens, nominally 37 mm in diameter and 18.5 mm in height, with five different saturations (0%, 25%, 50%, 75% and 100%, respectively) were executed in this paper. The technique ‘Split Hopkinson pressure bar’ (SHPB) was used. The impact velocity was 10 m/s with the corresponding strain rate as 102/s. Water-cement ratio of 0.5 was used. The compressive behaviour of the materials was measured in terms of the maximum stress, Young’s modulus, critical strain at maximum stress and ultimate strain at failure. The data obtained from test indicates that the similarity exists in the shape of strain–stress curves of cement mortars with different water content, the upward section of the stress–strain curve shows bilinear characteristics, while the descending stage (softening state) is almost linear. The dynamic compressive strength of cement mortar increased with the decreasing of water content, the dynamic compressive strength of the saturated specimens was 23% lower than that of the totally dry specimens. With an increase in water content, the Young’s modulus first increases and then decreases, the Young’s modulus of the saturated specimens was 23% lower than that of the totally dry specimens. No significant changes occurred in the critical and ultimate strain value as the water content is changed.

  3. A mechanical rheological model for the prediction of the creep behaviour of metallic materials under constant loading

    International Nuclear Information System (INIS)

    A mechanical rheological model for the prediction of the creep behaviour of metallic materials is presented. The model is based on the time dependence of the material structure during creep. It consists of a Hooke element with constant spring parameter and of a pseudo-Kelvin element with time dependent characteristic parameters for the spring and for the dashpot. The time dependence of the models characteristic parameters is correlated with the time dependence of the material structure parameters. For the time dependence of the model parameters exponential functions were used. Furthermore, these parameters are considered to be functions of stress and temperature. The derived constitutive equation of the proposed mechanical model related with the time dependence of the material structure describes the creep behaviour up to the tertiary creep stage. For the verification of the proposed model numerical results are discussed in connection with experimental results on oxygen free pure copper. The applicability of the model on technical materials has been demonstrated on the austenitic steel X 8 CrNiMoNb 16.16. (orig.)

  4. Multi-scale modeling of the thermo-hydro- mechanical behaviour of heterogeneous materials. Application to cement-based materials under severe loads

    International Nuclear Information System (INIS)

    The work of modeling presented here relates to the study of the thermo-hydro- mechanical behaviour of porous materials based on hydraulic binder such as concrete, High Performance Concrete or more generally cement-based materials. This work is based on the exploitation of the Digital Concrete model, of the finite element code Symphonie developed in the Scientific and Technical Centre for Building (CSTB), in coupling with the homogenization methods to obtain macroscopic behaviour laws drawn from the Micro-Macro relations. Scales of investigation, macroscopic and microscopic, has been exploited by simulation in order to allow the comprehension fine of the behaviour of cement-based materials according to thermal, hydrous and mechanical loads. It appears necessary to take into account various scales of modeling. In order to study the behaviour of the structure, we are brought to reduce the scale of investigation to study the material more particularly. The research tasks presented suggest a new approach for the identification of the multi-physic behaviour of materials by simulation. In complement of the purely experimental approach, based on observations on the sample with measurements of the apparent parameters on the macroscopic scale, this new approach allows to obtain the fine analysis of elementary mechanisms in acting within the material. These elementary mechanisms are at the origin of the evolution of the macroscopic parameters measured in experimental tests. In this work, coefficients of the thermo-hydro-mechanical behaviour law of porous materials and the equivalent hydraulic conductivity were obtained by a multi-scales approach. Applications has been carried out on the study of the damaged behaviour of cement-based materials, in the objective to determine the elasticity tensor and the permeability tensor of a High Performance Concrete at high temperatures under a mechanical load. Also, the study of the strain evolution of cement-based materials at low

  5. Fuel thermal/mechanical behaviour under loss of coolant accident conditions as predicted by the FACTAR code

    International Nuclear Information System (INIS)

    FACTAR (Fuel And Channel Temperature And Response) is a computer code developed to simulate the transient thennal and mechanical behaviour of 37-element or 28-element fuel bundles within a single CANDU fuel channel for moderate (ie., sheath temperatures less than the melting point of Zircaloy) loss-of-coolant accident (LOCA) conditions including transition and large break LOCAs with emergency coolant injection assumed available. FACTAR's predictions of fuel temperature and sheath failure times are used for subsequent assessment of fission product releases and fuel string expansion. In this paper, model capabilities and calculated quantities of the code are summarised. The results from overly severe test cases are presented in order to clearly demonstrate the effect on calculated fuel channel behaviour of a mechanistic assessment of fuel-to-sheath heat transfer, and the impact of using a diffusion-limited model for Zircaloy/steam reaction (i.e., FROM) as opposed to a reaction rate correlation, coupled with the assumption of unlimited steam supply. (author)

  6. An investigation on thermoelastic behaviour of functionally graded thick spherical vessels under combined thermal and mechanical loads

    Directory of Open Access Journals (Sweden)

    D. Karimi

    2008-12-01

    Full Text Available Purpose: The subject of this paper is to study the thermoelastic behavior of thick functionally graded hollow sphere under thermal and mechanical loads. The mechanical and thermal properties of FG sphere are assumed to be functions of radial position.Design/methodology/approach: In present study, two methods are used to estimate the effective mechanical properties of FG sphere. One of the simplest methods in estimation of the effective mechanical and thermal properties of a mixture of two constituent materials is the Rule of Mixture (R-M scheme. Another scheme for estimating the mechanical properties is due to the work of Mori-Tanaka. When the mechanical properties of FG sphere are estimated by using the Mori-Tanaka scheme, thermal material properties of FG body may be determined utilizing the R-M or the other methods which will be discussed as follows.Findings: Results for the temperature, radial displacement, radial stress and hoop stress fields through the geometry of the sphere are give. The figures reveal that some minor difference may be obtained for two schemes and the difference between the results for displacement distribution is larger than difference of temperature and stress distributions.Practical implications: The thermal material properties are obtained utilizing the Hatta-Taya and Rosen-Hashin relations. Also, the mechanical properties are estimated using the Mori-Tanaka scheme. In addition to the methods of approximation of material properties cited above, the rule of mixture scheme for determination of thermal and mechanical properties is also considered and results of these two schemes are compared for two cases of material composition through the geometry of FG sphere. The FG sphere is assumed to be symmetrically loaded and one-dimensional steady-state analysis of isotropic linear thermoelastic FG sphere under combined thermal and mechanical loads is investigated. Solution of the heat conduction equation and the Navier

  7. Complex associative memory processing and sleep: a systematic review and meta-analysis of behavioural evidence and underlying EEG mechanisms.

    Science.gov (United States)

    Chatburn, Alex; Lushington, Kurt; Kohler, Mark J

    2014-11-01

    The beneficial influence of sleep on memory consolidation is well established; however, the mechanisms by which sleep can dynamically consolidate new memories into existing networks for the continued environmental adaptation of the individual are unclear. The role of sleep in complex associative memory is an emerging field and the literature has not yet been systematically reviewed. Here, we systematically review the published literature on the role of sleep in complex associative memory processing to determine (i) if there is reasonable published evidence to support an active role for sleep facilitating complex associative processes such rule and gist extraction and false memory; (ii) to determine which sleep physiological events and states impact these processes, and to quantify the strength of these relationships through meta-analysis. Twenty-seven studies in healthy adults were identified which combined indicate a moderate effect of sleep in facilitating associative memory as tested behaviourally. Studies which have measured sleep physiology have reported mixed findings. Significant associations between sleep electrophysiology and outcome appear to be based largely on mode of acquisition. We interpret these findings as supporting reactivation based models of associative processing. PMID:25452112

  8. CANDU fuel behaviour under transient conditions

    International Nuclear Information System (INIS)

    The Canadian R and D program to understand CANDU fuel behaviour under transient conditions is described. Fuel sheath behaviour studies have led to the development of a model of transient plastic strain in inert gas, which integrates the deformation due to several mechanisms. Verification tests demonstrated that on average the model overpredicts strain by 20%. From oxidation kinetics studies a sheath failure embrittlement criterion based on oxygen distribution has been developed. We have also established a rate equation for high-temperature stress-dependent crack formation due to embrittlement of the sheath by beryllium. An electric, simulated fuel element is being used in laboratory tests to characterize the behaviour of fuel in the horizontal. In-reactor, post-dryout tests have been done for several years. There is an axially-segmented, axisymmetric fuel element model in place and a fully two-dimensional code is under development. Laboratory testing of bundles, in its early stages, deals with the effects of geometric distortion and sheath-to-sheath interaction. In-reactor, post-dryout tests of CANDU fuel bundles with extensive central UO2 melting did not result in fuel fragmentation nor damage to the pressure tube. (author)

  9. Strategic Behaviour under Regulation Benchmarking

    OpenAIRE

    Jamasb, Tooraj; Nillesen, Paul; Michael G. Pollitt

    2003-01-01

    Liberalisation of generation and supply activities in the electricity sectors is often followed by regulatory reform of distribution networks. In order to improve the efficiency of distribution utilities, some regulators have adopted incentive regulation schemes that rely on performance benchmarking. Although regulation benchmarking can influence the ?regulation game?, the subject has received limited attention. This paper discusses how strategic behaviour can result in inefficient behav...

  10. Intermetallic alloys: Deformation, mechanical and fracture behaviour

    International Nuclear Information System (INIS)

    The state of the art in intermetallic alloys development with particular emphasis on deformation, mechanical and fracture behaviour is documented. This review paper is prepared to lay the ground stones for a future work on mechanical property characterization and fracture behaviour of intermetallic alloys at GKSS. (orig.)

  11. The mechanical behaviour of packed particulates

    International Nuclear Information System (INIS)

    Within the Canadian Nuclear Fuel Waste Management program, the central concept is to package used fuel in containers that would be deposited in an underground vault in a plutonic rock formation. To provide internal mechanical support for the container, the reference design specifies it to be filled with a matrix of compacted particulate material (called 'packed particulate'), such as quartz sand granules. The focus of this report is on the mechanical properties of the packed-particulate material, based on information drawn from the extant literature. We first consider the packing density of particulate matrices to minimize the remnant porosity and maximize mechanical stability under conditions of external pressure. Practical methods, involving vibratory packing, are reviewed and recommendations made to select techniques to achieve optimum packing density. The behaviour of particulates under compressive loading has been of interest to the powder metallurgy industry (i.e., the manufacture of products from pressed/sintered metal and ceramic powders) since the early decades of this century. We review the evidence showing that in short timescales, stress induced compaction occurs by particle shuffling and rearrangement, elastic distortion, plastic yielding and microfracturing. Analytical expressions are available to describe these processes in a semiquantitative fashion. Time-dependent compaction, mainly via creep mechanisms, is more complex. Much of the theoretical and experimental information is confined to higher temperatures (> 500 degrees C), where deformation rates are more rapid. Thus, for the relatively low ambient temperatures of the waste container (∼100 degrees C), we require analytical techniques to extrapolate the collective particulate creep behaviour. This is largely accomplished by employing current theories of creep deformation, particularly in the form of Deformation Mechanism Maps, which allow estimation of creep rates over a wide range of stress

  12. Thermo-mechanical fatigue behaviour of the near-{gamma}-titanium aluminide alloy TNB-V5 under uniaxial and multiaxial loading

    Energy Technology Data Exchange (ETDEWEB)

    Brookes, Stephen Peter

    2009-12-19

    With increasing environmental awareness and the general need to economise on the use of fossil fuels, there is growing pressure for industry to produce lighter, more efficient, gas turbine engines. One such material that will help to achieve these improvements is the intermetallic gamma titanium aluminide ({gamma}-TiAl) alloy. At only half the density of current nickel-based superalloys its weight saving capability is highly desirable, however, its mechanical properties have not yet been fully explored especially, when it is to be considered for structural components in aeronautical gas turbine engines. Critical components in these engines typically experience large variations in temperatures and multiaxial states of stress under non-isothermal conditions. These stress states are known as tri-axial thermo-mechanical fatigue (TMF). The work presented here investigates the effects these multi-axial stresses, have on a {gamma}-TiAl, (Ti-45Al-5Nb-0.2B-0.2C) alloy under TMF conditions. The uniaxial, torsional and axialtorsional TMF behaviour of this {gamma}-TiAl alloy have been examined at 400 - 800 C with strain amplitudes ranging from 0.15% to 0.7%. The tests were conducted at both thermomechanical in-phase (IP) and out-of-phase (OP). Selected tests additionally contained a 180 seconds hold period. Fatigue lifetimes are strongly influenced by the strain amplitude, a small increase in amplitude reduces the lifetime considerably. The uniaxial IP tests showed significantly longer fatigue lifetimes than of all the tests performed. Torsional loading although have shorter fatigue lifetimes than the uniaxial IP loading they have longer fatigue lifetimes than the uniaxial OP loading. The non-proportional axial-torsional 90 degree OP test is most damaging which resulted in a shorter lifetime than the uniaxial OP test with the same Mises equivalent mechanical strain amplitude. A hold period at maximum temperatures reduced the lifetime for all tests regardless of the temperature

  13. Prospective and Pavlovian mechanisms in aversive behaviour.

    Science.gov (United States)

    Rigoli, Francesco; Pezzulo, Giovanni; Dolan, Raymond J

    2016-01-01

    Studying aversive behaviour is critical for understanding negative emotions and associated psychopathologies. However a comprehensive picture of the mechanisms underlying aversion is lacking, with associative learning theories focusing on Pavlovian reactions and decision-making theoretic approaches on prospective functions. We propose a computational model of aversion that combines goal-directed and Pavlovian forms of control into a unifying framework in which their relative importance is regulated by factors such as threat distance and controllability. Using simulations, we test whether the model can reproduce available empirical findings and discuss its relevance to understanding factors underlying negative emotions such as fear and anxiety. Furthermore, the specific method used to construct the model permits a natural mapping from its components to brain structure and function. Our model provides a basis for a unifying account of aversion that can guide empirical and interventional study contexts. PMID:26539969

  14. Modelling of the mechanical behaviour of a material containing spherical cavities under pressure; example of the aging of a metal tritide

    International Nuclear Information System (INIS)

    The study aims at modeling the mechanical behaviour of a material containing spherical cavities under pressure (bubbles) of nano-metric size. This work deals with research on tritium storage in metals. In this way, metal tritides are obtained. During time, helium is generated by tritium decay. Helium appears as a gas, which forms bubbles in the metal tritide. These bubbles subsequently cause damage within the material. The purpose of this work was therefore the following: (i) to determine the overall elastic moduli as a function of the volume fraction of cavities. thus providing an information about material damage, (ii) to analyze the macroscopic inflation of the material in order to solve storage problems, (iii) to determine the local stress fields for predicting the evolutions of the bubbles and the matrix. With the help of the scale change methods (homogenization) the macroscopic mechanical properties of the material can be determined as a function of its morphology on a microscopic scale. Thus the damage of the material can be estimated by experimental measurements of the global elastic moduli. Homogenization also allows the elastic inflation to be evaluated as well as the effects of cavity clusters and local variations of the elastic moduli. The internal stresses are determined on the microscopic scale (cavity scale). Two analytical methods (Eshelby-Mura and Legendre polynomials) and one numerical approach (Abaqus) are used to obtain more information and a best description of the material. It is shown that bubbles should attain the same size and same pressure and the plastic strain zones are determined. (author)

  15. Mechanical behaviour of compacted decomposed granite soil

    OpenAIRE

    Lee, I K

    1991-01-01

    The purpose of this research was to determine the mechanical behaviour of decomposed granite soil, especially when it is used as a construction material. The soil tested was a completely weathered granite soil (grade V) taken from Seoul, Korea and was a well graded silty sand and gravel. Triaxial compression tests have been carried out on compacted samples and special attention has been given to the determination of the effects of the moisture condition on the behaviour. The test results show...

  16. Preventing Toxic Behaviour through Game Mechanics

    OpenAIRE

    Fahlström, Josefine; Matson, Emma

    2014-01-01

    Toxic Behaviour, the phenomena where a person behaves in a way meant to intimidate or belittle another person, is an influential issue spreading across the virtual spaces that is online gaming communities. In this thesis we explore the possible correlations between Toxic Behaviour and game mechanics in online multi-player games by analyzing League of Legends (Riot Games, 2009), one of the most prominent online games currently dominating the market (Statista, 2014). We have analysed the game u...

  17. Investigations on mechanical behaviour of dental composites.

    Science.gov (United States)

    Ilie, Nicoleta; Hickel, Reinhard

    2009-12-01

    Since a direct comparison of composites efficacy in clinical studies is very difficult, our study aimed to analyse in laboratory tests under standardised and simulated clinical conditions a large variety of commercial composite materials belonging to eight different materials categories. Thus, 72 hybrid, nano-hybrid, micro-filled, packable, ormocer-based and flowable composites, compomers and flowable compomers were compared in terms of their mechanical behaviour. Flexural strength (FS), flexural modulus (FM), diametric tensile (DTS) and compressive strength (CS) were measured after the samples had been stored in water for 24 h at 37 degrees C. Results were statistically analysed using one-way ANOVA with Tukey HSD post hoc test (alpha = 0.05) as well as partial eta2 statistics. Large varieties between the tested materials within the same material category were found. The hybrid, nano-hybrid, packable and ormocer-based composites do not differ significantly among each other as a material type, reaching the highest FS values. Nano-hybrid composites are characterised by a good FS, the best DTS but a low FM. The lowest mechanical properties achieved the micro-filled hybrids. The flowable composites and compomers showed for all properties comparable result. Both flowable material categories do not differ significantly from the micro-filled composites for the most mechanical properties, showing only a higher DTS. The filler volume was shown to have the highest influence on the measured properties, inducing a maximum FS and FM at a level of 60%, whereas such dependence was not measured for DTS or CS. The influence of the type of material on the mechanical properties was significant but very low, showing the strongest influence on the CS. PMID:19242739

  18. Poromechanical behaviour of hardened cement paste under isotropic loading

    CERN Document Server

    Ghabezloo, Siavash; Guédon, Sylvine; Martineau, Francçois; Saint-Marc, Jérémie

    2008-01-01

    The poromechanical behaviour of hardened cement paste under isotropic loading is studied on the basis of an experimental testing program of drained, undrained and unjacketed compression tests. The macroscopic behaviour of the material is described in the framework of the mechanics of porous media. The poroelastic parameters of the material are determined and the effect of stress and pore pressure on them is evaluated. Appropriate effective stress laws which control the evolution of total volume, pore volume, solid volume, porosity and drained bulk modulus are discussed. A phenomenon of degradation of elastic properties is observed in the test results. The microscopic observations showed that this degradation is caused by the microcracking of the material under isotropic loading. The good compatibility and the consistency of the obtained poromechanical parameters demonstrate that the behaviour of the hardened cement paste can be indeed described within the framework of the theory of porous media.

  19. Mechanical Behaviour of Materials Volume II Fracture Mechanics and Damage

    CERN Document Server

    François, Dominique; Zaoui, André

    2013-01-01

    Designing new structural materials, extending lifetimes and guarding against fracture in service are among the preoccupations of engineers, and to deal with these they need to have command of the mechanics of material behaviour. This ought to reflect in the training of students. In this respect, the first volume of this work deals with elastic, elastoplastic, elastoviscoplastic and viscoelastic behaviours; this second volume continues with fracture mechanics and damage, and with contact mechanics, friction and wear. As in Volume I, the treatment links the active mechanisms on the microscopic scale and the laws of macroscopic behaviour. Chapter I is an introduction to the various damage phenomena. Chapter II gives the essential of fracture mechanics. Chapter III is devoted to brittle fracture, chapter IV to ductile fracture and chapter V to the brittle-ductile transition. Chapter VI is a survey of fatigue damage. Chapter VII is devoted to hydogen embrittlement and to environment assisted cracking, chapter VIII...

  20. Protective containment behaviour under exceeded design loads

    International Nuclear Information System (INIS)

    The contribution describes the calculation results of the behaviour of containment structure if loaded in excess of its design load. The Temelin NPP comprises two WWER 1000 blocks and containment consists of a pre-stressed reinforced concrete structure with a system of unbonded cables. The objective of the calculations was to determine the level of load caused by the internal pressure and temperature at which the containment protective function would fail. In the first step, the maximum overpressure was determined, which may be transferred by the containment structure. In further steps analyses were made of various combinations of simultaneous pressure and temperature loads. The contribution presents relevant calculation results, including the evaluation of containment structure behaviour including liner under loads that exceed its design parameters. (author)

  1. Impact of nutrition on canine behaviour: current status and possible mechanisms

    OpenAIRE

    bosch, G; Beerda, B.; Hendriks, W.H.; Poel, van der, D.; M.W. A. Verstegen

    2007-01-01

    Each year, millions of dogs worldwide are abandoned by their owners, relinquished to animal shelters, and euthanised because of behaviour problems. Nutrition is rarely considered as one of the possible contributing factors of problem behaviour. This contribution presents an overview of current knowledge on the influence of nutrition on canine behaviour and explores the underlying mechanisms by which diet may affect behaviour in animals. Behaviour is regulated by neurotransmitters and hormones...

  2. Optimal stomatal behaviour under stochastic rainfall.

    Science.gov (United States)

    Lu, Yaojie; Duursma, Remko A; Medlyn, Belinda E

    2016-04-01

    Vegetation CO2 uptake is always accompanied by water loss. The balance in this gas exchange is controlled by the stomata, through which CO2 and water vapour diffuse between the leaf and the atmosphere. The optimal stomatal behaviour theory proposes that vegetation should optimise its stomatal behaviour such that, for given water availability, photosynthesis is maximised. In this paper, we optimise stomatal conductance as a function of soil water content for the maximum expected value of photosynthesis rate. This optimisation process is considered under stochastic rainfall. The optimal solution is largely shaped by two constraints: the risks of soil water exhaustion and surface runoff, which results in an inverse S-shaped curve of stomatal conductance along the soil water gradient. We derive the optimal functional relationship between stomatal conductance and soil water content under varying rainfall frequency, mean annual precipitation and atmospheric CO2 concentration. Comparisons with large-scale observational data show that the model is able to broadly capture responses of photosynthesis, transpiration, and water use efficiency along rainfall gradients, although notable discrepancies suggest additional factors are important in shaping these responses. Our work provides a theoretical framework for analysing the vegetation gas exchange under environmental change. PMID:26796317

  3. FRP-to-concrete bond behaviour under high strain rates

    OpenAIRE

    Li, Xiaoqin

    2012-01-01

    Fibre reinforced polymer (FRP) composites have been used for strengthening concrete structures since early 1990s. More recently, FRP has been used for retrofitting concrete structures for high energy events such as impact and blast. Debonding at the FRP-to-concrete interface is one of the predominant failure modes for both static and dynamic loading. Although extensive research has been conducted on the static bond behaviour, the bond-slip mechanics under high strain rates is n...

  4. Behaviour of concrete filled steel tubular columns under fire

    Institute of Scientific and Technical Information of China (English)

    查晓雄; 钟善桐

    2002-01-01

    A three dimensional nonlinear FE program is used to calculate the fire resistances of concrete filledsteel tubular columns under fire. The temperature distributions in the circular section fire are decided by solvingthe Fourier Transfer Equation , and the mechanical behaviour and failure of concrete filled steel tubular columnsunder fire are thus investigated, and the effects of several parameters on the fire resistance are analysed. Theresults obtained are in good agreement with the Eurocode.

  5. Simulating farmer behaviour under water markets

    Science.gov (United States)

    Padula, SIlvia; Erfani, Tohid; Henriques, Catarina; Maziotis, Alexandros; Garbe, Jennifer; Swinscoe, Thomas; Harou, Julien; Weatherhead, Keith; Beevers, Lindsay; Fleskens, Luuk

    2015-04-01

    Increasing water scarcity may lead water managers to consider alternative approaches to water allocation including water markets. One concern with markets is how will specific sectors interact with a potential water market, when will they gain or loose water and will they benefit economically - why, when and how? The behaviours of different individual abstractors or institutional actors under water markets is of interest to regulators who seek to design effective market policies which satisfy multiple stakeholder groups. In this study we consider two dozen agricultural water users in eastern England (Nar basin). Using partially synthetic but regionally representative cropping and irrigation data we simulate the buying and selling behaviour of farmers on a weekly basis over multiple years. The impact of on-farm water storage is assessed for farmers who own a reservoir. A river-basin-scale hydro-economic multi-agent model is used that represents individual abstractors and can simulate a spot market under various licensing regimes. Weekly varying economic demand curves for water are calibrated based on historical climate and water use data. The model represents the trade-off between current use value and expected gains from trade to reach weekly decisions. Early results are discussed and model limitations and possible extensions are presented.

  6. Effect of water on the mechanical behaviour of shales

    Energy Technology Data Exchange (ETDEWEB)

    Wakim, J.; Hadj-Hassen, F.; Tijani, M. [Ecole des Mines de Paris - CGES, 77 - Fontainebleau (France); Noirel, J.F. [Charbonnage de France - DTN, 57 - Freyming Merlebach (France)

    2005-07-01

    This paper aims to presenting the results of a research conducted in order to study the effect of water on the mechanical behaviour of the Lorraine Basin Colliery shale. The work performed can be divided into four main parts. The first part is dedicated to classical tests and it includes geological and mineralogical analysis as well as mechanical laboratory tests. The second part is devoted to the phenomenon of shale swelling under water effect. New procedures and equipment of testing were set up in order to characterise this swelling behaviour and to determine its model parameters. The tests performed in this second part are allowed to develop a phenomenological model which describes the elasto-visco-plastic behaviour of shales before and after saturation. The last phase of the work is dedicated to implement the new model in the finite element code VIPLEF in order to apply in tunnel excavated in swelling anisotropic rocks. (authors)

  7. Mechanical behaviour of nanoparticles: Elasticity and plastic deformation mechanisms

    Indian Academy of Sciences (India)

    Celine Gerard; Laurent Pizzagalli

    2015-06-01

    Nano-objects often exhibit drastically different properties compared to their bulk counterpart, opening avenues for new applications in many fields, such as in advanced composite materials, nanomanufacturing, nanoelectromechanical systems etc. As such, related research topics have become increasingly prominent in recent years. In this review on the mechanical behaviour of nanoparticles, the main investigation approaches are first briefly presented. The main results in terms of elasticity and plastic deformation mechanisms are then reported and discussed.

  8. Analysis of operator's behaviour under accidental transients

    International Nuclear Information System (INIS)

    Since 1979, EDF has been conducting intensive test campaigns on full-scale PWR simulators in order to study and improve the operators behaviour under incident as well as accident conditions. This paper presents some results obtained during tests carried out in 1986 on the P4 (1300 MWe power plant series) simulators of the Paluel Training Center. These results essentially concern the observed deviations, the diagnosis and the safety engineer's role. They are compared with the results of previous tests on 900 MWe unit simulators. The test organization and methodology, the result analysis methods and the biases introduced by this kind of test are also discussed. (author). 7 refs, 1 fig., 6 figs

  9. Mechanical behaviour of jute cloth/wool felts hybrid laminates

    International Nuclear Information System (INIS)

    Highlights: • New fibre reinforced hybrid composites with wool and jute fibres were manufactured. • Effect of two different stacking sequences on mechanical behaviour was investigated. • The impact performances of wool/jute interply hybrid composites were studied. • Hybridization with jute significantly enhanced mechanical properties of wool composites. - Abstract: This experimental work is aimed at the characterization of new fibre reinforced composites based on epoxy resin with both protein (wool) and lignocellulosic (jute) natural fibres. Wool-based and hybrid (wool/jute) composites with two different stacking sequences (intercalated and sandwich) were developed. Their microstructure has been investigated through optical and scanning electron microscopy, whereas their quasi-static mechanical behaviour has been evaluated in tension and bending. In addition, the impact behaviour under low-velocity impact at three different impact energies, namely 6 J, 8 J and 9 J has been addressed. The tensile and flexural tests have been monitored using acoustic emission (AE) in order to elicit further information about failure mechanisms. AE monitoring showed that development of damage was due to nucleation of matrix microcracks and subsequent debonding and pull-out phenomena in wool fibre composites and that only in hybrid composites a sufficient stress transfer across the jute fibre/matrix interface was achieved. The results confirmed the positive role of hybridization with jute fibres in enhancing both the tensile and flexural behaviour of wool-based composites, though highlighting the need for an improved adhesion between wool fibres and epoxy matrix

  10. Behaviour of Mechanically Laminated CLT Members

    Science.gov (United States)

    Kuklík, P.; Velebil, L.

    2015-11-01

    Cross laminated timber (CLT) is one of the structural building systems based on the lamination of multiple layers, where each layer is oriented perpendicularly to each other. Recent requirements are placed to develop an alternative process based on the mechanical lamination of the layers, which is of particular interest to our research group at the University Centre for Energy Efficient Buildings. The goal is to develop and verify the behaviour of mechanically laminated CLT wall panels exposed to shear stresses in the plane. The shear resistance of mechanically jointed CLT is ensured by connecting the layers by screws. The paper deals with the experimental analysis focused on the determination of the torsional stiffness and the slip modulus of crossing areas for different numbers of orthogonally connected layers. The results of the experiments were compared with the current analytical model.

  11. Effectiveness and underlying mechanisms of a group-based cognitive behavioural therapy-based indicative prevention program for children with elevated anxiety levels

    NARCIS (Netherlands)

    Starrenburg, M.L.A. van; Kuijpers, R.C.W.M.; Hutschemaekers, G.J.M.; Engels, R.C.M.E.

    2013-01-01

    Background Anxiety is a problem for many children, particularly because of its negative consequences not only on the wellbeing of the child, but also on society. Adequate prevention and treatment might be the key in tackling this problem. Cognitive behavioural therapy (CBT) has been found effective

  12. Chemo-mechanical coupling behaviour of leached concrete

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, V.H. [Laboratoire d' Analyse des Materiaux et Identification, Ecole Nationale des Ponts et Chaussees, Institut Navier, 6 et 8, Avenue Blaise Pascal, 77455 Marne la Vallee Cedex 2 (France); Colina, H. [ATILH, 7, Place de la Defense, 92974 Paris-La-Defense Cedex (France); Torrenti, J.M. [LCPC Paris, 58, Boulevard Lefebvre 75732 Paris Cedex 15 (France); LMT, ENS Cachan, 61, Avenue du President Wilson, 94235 Cachan (France)], E-mail: jean-michel.torrenti@ponts.org; Boulay, C. [LCPC Paris, 58, Boulevard Lefebvre 75732 Paris Cedex 15 (France); Nedjar, B. [Laboratoire d' Analyse des Materiaux et Identification, Ecole Nationale des Ponts et Chaussees, Institut Navier, 6 et 8, Avenue Blaise Pascal, 77455 Marne la Vallee Cedex 2 (France)

    2007-11-15

    This paper deals with concrete behaviour under chemical and mechanical degradations. Experimental investigations are described where the effects of the calcium leaching process of concrete on its mechanical properties are highlighted. The calcium leaching and mechanical tests on cement paste, mortar and concrete samples are presented. Because of the slow kinetics of leaching under deionised water, an accelerated method has been chosen by using an ammonium nitrate solution instead. The specimens are immersed into a 6 mol/l ammonium nitrate solution with a controlled pH disposal. To quantify the leaching evolution, the degradation depth is then measured at certain time intervals by means of a phenolphthalein solution. The experimental results show the chemical degradation of the cement-based material and the important role of aggregate in the calcium leaching process of concrete. Compression tests of concrete samples are also performed. We observe that there is a strong coupling between the calcium leaching and the mechanical behaviour; as leaching grows, a loss of stiffness and of strength are observed and a smoother post-peak behaviour is noted.

  13. Effectiveness and underlying mechanisms of a group-based cognitive behavioural therapy-based indicative prevention program for children with elevated anxiety levels

    OpenAIRE

    Starrenburg, M.L.A. van; Kuijpers, R.C.W.M.; Hutschemaekers, G. J. M.; Engels, R. C. M. E.

    2013-01-01

    Background Anxiety is a problem for many children, particularly because of its negative consequences not only on the wellbeing of the child, but also on society. Adequate prevention and treatment might be the key in tackling this problem. Cognitive behavioural therapy (CBT) has been found effective for treating anxiety disorders. “Coping Cat” is one of the few evidence-based CBT programs designed to treat anxiety symptoms in children. The main aim of this project is to conduct a Randomized Co...

  14. Modelling of the Mechanical Behaviour of Ultra-Fine Grained Titanium Alloys at High Strain Rates

    OpenAIRE

    Halle, T.; Herzig, N.; Krüger, L; Meyer, L.W.; Musch, D.; Razorenov, S. V.; Skripnyak, E. G.; Skripnyak, V. A.

    2008-01-01

    Results of numerical simulations of the mechanical behaviour of coarse grained and UFG titanium alloys under quasi-static uniaxial compression and plane shock wave loading are presented in this paper. Constitutive equations predict the strain hardening behaviour, the strain rate sensitivity of the flow stress and the temperature softening of titanium alloys with a range of grain sizes from 20 µm to 100 nm. Characteristics of the mechanical behaviour of UFG a and a+ß titanium alloys in wide ra...

  15. Experimental validation of upgraded designs for PERMCAT reactors considering the mechanical behaviour of a Pd/Ag membrane under H2 atmosphere

    International Nuclear Information System (INIS)

    The PERMCAT process has been chosen in ITER to be the final clean-up stage of the 3-step Tritium Exhaust Processing system. One of the main critical aspects of such a technology is the mechanical stress of the Pd/Ag membrane due to hydrogen uptake during operation. This hydrogen effect is negligible when the component is operated at the nominal temperature of 400 oC. However in case of hydrogen permeation at lower temperatures it can yield to significant expansion of the lattice parameter, inducing a noticeable macroscopic elongation of the membrane. A dedicated experimental device has been built to study in more details the technical consequences of such off-normal operational conditions. The apparatus comprises a finger-type Pd/Ag membrane (fixed only at one end) enclosed in a quartz tube allowing in-situ observations during operation with hydrogen. By varying the operational conditions (temperature and hydrogen pressure at the feed and permeate sides) some critical aspects are pointed out: membrane elongations of more than 2 % are measured for a temperature of 50 oC and some bending of the membrane takes place once the temperature is below 150 oC. Accordingly the first generation of PERMCAT reactors comprises finger-type membranes fixed only at one end. This can ensure reliability of the component in case of nominal operational conditions. However the design is not considered sufficiently robust for reactor applications. Thus new mechanical designs are proposed so as to improve the robustness of the unit and ensure its integrity even under off-normal operation conditions. Two different upgraded components have been produced using either an additional stainless steel edge welded bellows or a special and dedicated convoluted (corrugated) Pd/Ag membrane. The experimental validation of these new concepts is carried out with gas processing tests using water vapour as the '' contaminated '' species and deuterium as the swamping gas. Results of experiments on the both

  16. Development of a New Experimental Apparatus for the Study of the Mechanical Behaviour of a Rock Discontinuity Under Monotonic and Cyclic Loads

    Science.gov (United States)

    Ferrero, A. M.; Migliazza, M.; Tebaldi, G.

    2010-11-01

    The shear behaviour of rock discontinuities in seismic condition is still not fully understood although earthquakes can be an important triggering cause of instability phenomena of rock blocks. For this purpose, a special apparatus was designed and developed at the University of Parma (Italy), which is to be placed inside the MTS press available in the Laboratory of Materials Testing. The press allows the application of monotonic and cyclic loads, in load or in deformation control. Quantitative evaluation of the rock-joint damage is realized by a photogrammetric survey of the discontinuity before and after the tests. The surface comparison enables the identification of the damaged areas. Finally, theoretical and experimental results are interpreted in the light of the damage model developed by Belem et al. (Rock Mech Rock Eng 33(4):217-242, 2001) for a quantitative evaluation of joint roughness and resistance.

  17. Mechanical and frictional behaviour of nano-porous anodised aluminium

    Energy Technology Data Exchange (ETDEWEB)

    Tsyntsaru, N., E-mail: tintaru@phys.asm.md [Institute of Applied Physics of ASM, 5 Academy str., Chisinau, MD 2028 (Moldova, Republic of); Kavas, B., E-mail: bkavas@ford.com.tr [Istanbul Technical University, Department of Metallurgical and Materials Engineering, 34469 Maslak (Turkey); Ford Otomotiv San A.S., Istanbul (Turkey); Sort, J., E-mail: jordi.sort@uab.cat [Institució Catalana de Recerca i Estudis Avançats (ICREA) and Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Spain); Urgen, M., E-mail: urgen@itu.edu.tr [Istanbul Technical University, Department of Metallurgical and Materials Engineering, 34469 Maslak (Turkey); Celis, J.-P., E-mail: jean-pierre.celis@mtm.kuleuven.be [KU Leuven, Dept. MTM, Kasteelpark Arenberg 44, B-3001 (Belgium)

    2014-12-15

    The porous structure of anodic aluminium oxide (AAO) can be used in versatile applications such as a lubricant reservoir in self-lubricating systems. Such systems are subjected to biaxial loading, which can induce crack formation and propagation, ultimately leading to catastrophic mechanical failure. In this study, the mechanical and tribological behaviour of AAO, prepared from two different types of electrolytes (sulphuric and oxalic acids), are studied in detail. The electrolytic conditions are adjusted to render highly tuneable average pore diameters (between 16 and 75 nm), with porosity levels ranging from 9% to 65%. Well-ordered porous AAO are produced by two-step anodization at rather low temperatures. Mechanical properties, mainly hardness and Young's modulus, are investigated using nanoindentation. Both the porosity degree and the composition of the electrolytic baths used to prepare the AAO have an influence on the mechanical properties. Ball-on-flat configuration was used to estimate the tribological behaviour under dry conditions. No major cracks were observed by scanning electron microscopy, neither after indentation or fretting tests. In the running-in period of tribology experiments the pores were filled with debris. This was followed by the formation of a highly adherent tribolayer – a third body consisting of fine worn particles originated from both the sample and the counterbody. Pore diameter and porosity percentage are found to strongly affect hardness and Young's modulus, but they do not have a major effect on the frictional behaviour. - Highlights: • Well-ordered porous AAO with pore diameters between 16 and 75 nm were produced. • Porosity and composition of electrolytic baths influence the mechanical properties. • Ball-on-flat configuration was used in tribological testing under dry conditions. • Adherent tribolayer consisting of fine worn particles prevents AAO from cracking. • Testing parameters are moreover essential

  18. Composite fuel behaviour under and after irradiation

    International Nuclear Information System (INIS)

    Two kinds of composite fuels have been irradiated in the SILOE reactor. They are made of UO2 particles dispersed in a molybdenum metallic (CERMET) or a MgAl2O4 ceramic (CERCER) matrix. The irradiation conditions have allowed to reach a 50000 MWd/t U burn-up in these composite fuels after a hundred equivalent full power days long irradiation. The irradiation is controlled by a continuous measure of the pellet centre line temperature. It allows to have information about the TANOX rods thermal behaviour and the fuels thermal conductivities in comparing the centre line temperature versus linear power curves among themselves. Our results show that the CERMET centre line temperature is much lower than the CERCER and UO2 ones: 520 deg. C against 980 deg. C at a 300W/cm linear power. After pin puncturing tests the rods are dismantled to recover each fuel pellet. In the CERCER case, the cladding peeling off has revealed that the fuel came into contact with the cladding and that some of the pellets were linked together. Optical microscopy observations show a changing of the MgAl2O4 matrix state around the UO2 particles at the pellets periphery. This transformation may have caused a swelling and would be at the origin of the pellet-cladding and the pellet-pellet interactions. No specific damage is seen after irradiation. The CERMET pellets are not cracked and remain as they were before irradiation. The CERCER crack network is slightly different from that observed in UO2. Kr retention was evaluated by annealing tests under vacuum at 1580 deg. C or 1700 deg. C for 30 minutes. The CERMET fission gas release is lower than the CERCER one. Inter- and intragranular fission gas bubbles are observed in the UO2 particles after heat treatments. The CERCER pellet periphery has also cracked and the matrix has transformed again around UO2 particles to present a granular and porous aspect. (author). 4 refs, 6 figs, 2 tabs

  19. Modelling Traveller Behaviour under Emergency Evacuation Conditions

    NARCIS (Netherlands)

    Pel, A.J.; Bliemer, M.C.J.; Hoogendoorn, S.P.

    2011-01-01

    Dynamic traffic simulation models are frequently used to support decisions when planning an evacuation. This paper focuses on limitations in the modelling of travellers’ behaviour with respect to traffic information and compliance to evacuation instructions. More specifically, we propose a model fra

  20. Biochemical mechanisms underlying atherogenesis

    Directory of Open Access Journals (Sweden)

    Dr.P.V.L.N. Srinivasa Rao

    2012-02-01

    Full Text Available Atherosclerosis remains one of the major causes of death and premature disability in developed countries. Though atherosclerosis was formerly considered a bland lipid storage disease, substantial advances in basic and experimental sciences have illuminated the role of endothelium, inflammation and immune mechanisms in its pathogenesis. Current concept of atherosclerosis is that of a dynamic and progressive disease arising from in- jury to endothelium, also known as endothelial dysfunction and an inflammatory response to that injury. The lesions of atherosclerosis occur principally in large and medium sized arteries. Atherosclerosis affects various regions of the circulation preferentially and can lead to ischemia of heart, brain or extremities resulting in in- farction.This produces distinct clinical manifestations depending on the vessel involved. Several predisposing factors to cardiovascular diseases such as diabetes mellitus, hypertension, obesity, infections act as triggers to the devel- opment of atherosclerosis by causing endothelial dysfunction and/or promoting inflammatory response. The evolution of pathogenetic mechanisms has passed through various directions such as oxidative stress, inflam- mation and immune responses. It is now known that all these are not acting independently but are interrelated and getting unified in the current concept of atherogenesis. The following discussion aims at providing an in- sight into these developments which can help in a better comprehension of the disease and management of its clinical complications

  1. Behaviour of high performance concrete under high temperature (60-450 deg C) for surface long-term storage: thermo-hydro-mechanical residual properties

    International Nuclear Information System (INIS)

    After various thermal treatments (up to 450 deg C), residual thermo-hydro-mechanical (T-H-M) properties of two OPC high performance concretes (HPC) were analyzed in the context of surface long-term storage. Materials were prepared with silico-calcareous aggregates (standard HPC) and hematite aggregates (heavy HPC). The initial micro structural (porosity =10%) and transport (gas permeability ∼ 10-19 m2) properties are similar for both concretes. As far as the mechanical aspect is concerned, heavy HPC shows a higher compressive strength and elastic modulus than standard HPC (78 and 63 MPa, 81 and 49 GPa, respectively). Heavy HPC is also characterized by a higher thermal conductivity (7.3 W m-1 K-1 compared to 2.7 W m-1 K-1 for standard concrete). Results analysis show that thermo-hydro-mechanical damages are smaller for heavy HPC. Between 60 and 250 deg C, the elastic modulus and the compressive strength of standard HPC decrease by 40% and 16%, respectively. For heavy HPC, these parameters respectively decrease by 10% and 4% A similar trend was observed for thermal conductivity evolution. Gas permeability and porosity data confirm the good behavior of heavy HPC. As a conclusion, hematite HPC seems to provide more interesting T-H-M residual properties than standard HPC. Limited thermal expansion and thermal gradients induced by hematite are probably responsible of this behavior. Copyright (2001) Material Research Society

  2. Mechanical Behaviour of the Wood Masonry

    Directory of Open Access Journals (Sweden)

    Fazia FOUCHAL

    2011-09-01

    Full Text Available In this paper we study the walls wood masonry behaviour. First, we propose a regulatory validation of the walls wood masonry behaviour subjected to vertical and horizontal loads according to Eurocode 5. Then we present the numerical application on the wall wood supported two floors level.

  3. Behaviour of biofilms formed by Pseudomonas fluorescens under different flow regimes when exposed to surfactants : role of the biofilm mechanical stability

    OpenAIRE

    Simões, M; Pereira, M. O.; Vieira, M. J.

    2005-01-01

    The effectiveness of cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) to control biofilms formed by Pseudomonas fluorescens on stainless steel slides under laminar and turbulent conditions, using a flow cell reactor, is compared in this study. The antimicrobial action of the surfactants was evaluated in terms of the activity of the biofilm, the biofilm mass that remained on the surface after treatment and the biofilm morphological characteristics. The mec...

  4. Experimental study of aluminium honeycomb behaviour under dynamic multiaxial loading

    Directory of Open Access Journals (Sweden)

    Markiewicz E.

    2012-08-01

    Full Text Available Split Hopkinson Pressure Bar system (SHPB with large-diameter and Nylon bars introducing a shear-compression loading device is used in order to investigate the dynamic behaviour of aluminium honeycomb under multiaxial loadings conditions. All shear-compression configurations including the loading angle variation from 0∘ to 60∘ are performed with an impact velocity of about 15m/s. The adapted SHPB system with the device are validated numerically and a phenomenon of separation between the input bar and the input beveled bar is observed. Numerical results suggest that this phenomenon provides a cutting of the reflected wave. An electro optical extensometer is employed in experiments. A good agreement between the numerical elastic waves and the experimental ones is obtained. Experimental results show a significant effect of the loading angle on the apparent stress-strain curves. The initial peak value and the plateau stress decrease with the increase of the loading angle. The combined shear-compression device with an enhancement at the alignment set-up provides efficient results for samples dynamically loaded. This device will be used to investigate the influence of the in-plane orientation angle on the deformation mechanisms and multiaxial behaviour of aluminium honeycomb under dynamic and quasi-static loading conditions.

  5. Mechanical behaviour of diamond reinforced metals

    International Nuclear Information System (INIS)

    Diamond reinforced metals with a diamond content of 55-60 vol.% were made by gas driven liquid metal infiltration. They were characterized with regard to their stiffness, strength and fracture toughness as a function of diamond particle size and matrix alloy by means of tensile and Chevron notch tests, respectively. The choice of the metal matrix, i.e. pure Al, Al-Cu, Cu-B and Ag-Si alloys was made in view of their application in thermal management where high thermal conductivity is important. For undamaged material Young's moduli, measured in unloading-reloading cycles necessary to measure static Young's modulus, of 250 GPa for Al-based and 300 GPa for Ag-based composites were obtained. The copper-based composites exhibited much lower values indicating that the small deformation necessary to measure Young's modulus induced already considerable damage. Strain to fracture of the composites was found to be a few tenth of a percent. An ultimate tensile strength of approximately 300 MPa was reached for the silver-based composites compared with roughly 150 MPa for the Al-based and below 50 MPa for the Cu-based composites. The size of the diamond particles had little influence on stiffness and strength of the composites but fracture toughness increased with increasing particle size. The differences in the mechanical behaviour of the configurations investigated can be rationalized by observations made during fractographic investigations by scanning electron microscopy. Additionally, the damage evolution in the composites was observed by the repeated determination of the specimen's stiffness during the tensile tests.

  6. Mechanisms of change in human behaviour

    OpenAIRE

    Marchal, Paul; Bartelings, Heleen; Bastardie, François; Batsleer, Jurgen; Delaney, Alyne; Girardin, Raphael; Gloaguen, Pierre; Hamon, Katell; Hoefnagel, Ellen; Jouanneau, Charlène; Mahevas, Stephanie; Nielsen, Rasmus; Piwowarczyk, Joanna; Poos, Jan-Jaap; SCHULZE Torsten

    2014-01-01

    The scope of this report is to present the science developed within the VECTORS project to improve the understanding of the key processes driving the behaviour of human agents utilising a variety of EU maritime domains. While particular attention has been paid to the spatial interactions between fishing activities and other human uses (e.g., maritime traffic, offshore wind parks, aggregate extractions), the behaviour of non-fishing sectors of activity has also been considered. Various quantit...

  7. The behaviour of fibrous composite materials under nuclear radiations exposure

    International Nuclear Information System (INIS)

    The main feature of fibrous composite materials are briefly described, which are constitued by a netwoek of ceramic high performance fiber embebed in a ductile matrix material. These composite materials show such a kind of anisotropic strength that their uses has been widely spreaded in the last times. This philosophy of strengthening was used by the Nature, where are abundant examples of fibrous composites like horn, bamboo tissues, etc. In this paper are collected the published results about behaviour of reinforced dibers and fibrous composites under nuclear radiation exposure. The results show a very wide sort of fenomenae depending on many factors. Are fibers, like the boron one, which shows an inconvenient behaviour and another like graphite fibers which appears to improve its features. Is is concluded that was not achieved enough information about the behaviour of the interface under irradiation in order to build up a theory about the behaviour of the full composite under irradiation exposure. (author)

  8. Numerical modelling investigation of rock mass behaviour under gravity dams

    OpenAIRE

    Alshkane, Younis Mustafa Ali

    2015-01-01

    The study of rock mass behaviour is a broad subject in the rock mechanics field which still needs more research and investigation, especially for geotechnical issues associated with dam construction. Since it is difficult to study rock mass behaviour at a large scale in the laboratory, the numerical modelling technique is an alternative method which can be used efficiently in this field. In this thesis two codes have been selected for this purpose. The first code was a continuum code FLAC (Fa...

  9. Mechanical Behaviour of Materials Volume 1 Micro- and Macroscopic Constitutive Behaviour

    CERN Document Server

    François, Dominique; Zaoui, André

    2012-01-01

    Advances in technology are demanding ever-increasing mastery over the materials being used: the challenge is to gain a better understanding of their behaviour, and more particularly of the relations between their microstructure and their macroscopic properties.   This work, of which this is the first volume, aims to provide the means by which this challenge may be met. Starting from the mechanics of deformation, it develops the laws governing macroscopic behaviour – expressed as the constitutive equations – always taking account of the physical phenomena which underlie rheological behaviour. The most recent developments are presented, in particular those concerning heterogeneous materials such as metallic alloys, polymers and composites. Each chapter is devoted to one of the major classes of material behaviour.   As the subtitles indicate, Volume 1 deals with micro- and macroscopic constitutive behaviour and Volume 2 with damage and fracture mechanics. A third volume will be devoted to exercises and the...

  10. Behaviour of fiber reinforced concrete slabs under impact loading

    International Nuclear Information System (INIS)

    The behaviour of steel fiber reinforced concrete slabs under impact loads has been investigated. The results obtained show that fracturing and spallation effects are reduced to a large extend due to the high energy absorption and the increased yield strength of this material. Crater depths are comparable to those obtained using normal concrete targets. Systematic tests using different fiber types and dimensions show that the terminal ballistic behaviour is strongly dependent on these parameters. (orig.)

  11. Mechanical behaviour of reactor pressure vessel in severe accident

    International Nuclear Information System (INIS)

    The article describes the main achievements in developing methodology for analysing mechanical behaviour of pressure vessels with and without penetrations at high temperatures related to accident scenarios. Validation and applications of the methodology are presented. (orig.)

  12. BEHAVIOURAL DESIGN APPROACH FOR IMPROVING MECHANICAL PRODUCT PERFORMANCE FORM DESIGN

    OpenAIRE

    Sun, Huichao; Houssin, Remy; Gardoni, Mickael; Jean, Renaud

    2014-01-01

    The mechanical engineering problems today become more and more complex particularly in the area of new product development. Mechanical product design is usually performed simply taking into consideration system functions and structures, while users’ behaviours in terms of using the system are generally not fully considered enough early in the design phase. This paper covers the multi-trade engineering design, and deals with the development of a behavioural design approach to help designers to...

  13. Analysis of operator's behaviour under accidental transients

    International Nuclear Information System (INIS)

    Since 1979, EDF has been conducting intensive test campaigns on full-scale PWR simulators in order to study and improve the operators behavior under incident as well as accident conditions. This paper presents some results obtained during tests carried out in 1986 on the P4 (1300 MWe power plant series) simulators of the Paluel Training Center. These results essentially concern the observed deviations, the diagnosis and the safety engineer's role. They are compared with the results of previous test ou 900 MWe unit simulators. The test organization and methodology, the result analysis methods and the biases introduced by this kind of test are also discussed

  14. Modelling the hydro-mechanical behaviour of swelling unsaturated soils

    International Nuclear Information System (INIS)

    The use of compacted swelling soils in engineering practice is very widely spread, especially in geotechnical and environmental engineering. After their setup, these materials are likely to be subject to complex suction/stress paths involving significant variations of their hydro-mechanical properties which can affect their initial behaviour. It is important to be able to predict the hydro-mechanical behaviour of these materials taking into account the significant applications for which they are intended. Barcelona team developed a finite-element code (Code-Bright) for the thermo-hydro-mechanical coupling (THM) integrating the BBM elastoplastic model for unsaturated soils based on the independent variables approach. This model is recognized to correctly describe the hydro-mechanical behaviour of unsaturated soils but fails to take into account some particular observed aspects on swelling soils. A second model BExM was then proposed to address these aspects. The objective of this study is: (i) to implement the elastoplastic model BExM for the unsaturated swelling soils in the finite-element code (Code-Bright); (ii) to check the numerical model validity through the numerical simulation of laboratory tests made on swelling soils; and (iii) to apply this model to some practical problems. For this purpose, a new family of numerical procedures adapted to the BExM model was introduced into the code. The equation of the yield surface of this model for a given deviatoric stress states was given in a manner to facilitate calculations of its derivatives. The model was checked by the numerical simulation of suction-controlled odometric tests made on three different swelling soils. The simulation results showed that the numerical model is able to correctly reproduce the experimental data. Lastly, the model was applied to two practical problems: radioactive waste repository in deep geological layers and a shallow footing under the action of a swelling soil. The results obtained

  15. Undrained Behaviour of Silt under Static and Cyclic Loading

    Institute of Scientific and Technical Information of China (English)

    YANG Shaoli; ROLF Sandven; LARS Grande

    2002-01-01

    In this study, the undrained behaviour of silt under low stress level is studied. An effective preparation methodfor built in silt samples in the triaxial test was firstly developed. By triaxial testing of samples at low confining pressures itwas found that silt easily loses stability and liquefies. Loose silt may show temporary liquefaction under static loading, anddevelop full liquefaction under cyclic loading. The most important factors influencing the silt behaviour are porosity, confin-ing pressure, consolidation state, cyclic loading level and number of cycles. The maximum obtainable shear stress is primarilya function of the confining pressure and the internal frictional angle. The actual structure of the silt material is the key factorin controlling its behaviour.

  16. Mechanical Behaviour of Phyllosilicate-Rich Faults

    Science.gov (United States)

    Collettini, Cristiano; Niemeijer, André; Viti, Cecilia; Marone, Chris

    2010-05-01

    A number of observations indicate that phyllosilicate-rich faults are widespread within the brittle crust. Here, we report on laboratory experiments designed to investigate the frictional behavior of 1) intact foliated solid rocks sheared in their in-situ geometry and 2) powders obtained from crushing and sieving the samples used in the solid experiments; 3) powders obtained from non foliated samples. The samples were collected from the Zuccale low-angle normal fault (Italy) and are characterised by different amounts of phyllosilicates (from 60 to 10 % of talc, smectite biotite and chlorite) plus calcite, hornblende and tremolite. Friction of powders, at room humidity and temperature, is in the range 0.27-0.62 and it is controlled by the abundance of weak phyllosilicates (talc and smectite). Over a range of normal stresses from 10 to 150 MPa and sliding velocities from 1 to 300 μm/s, the powdered material with a) 60% of phyllosilicates exhibits velocity strengthening behaviour associated to calcite grain rotation and translation in a phyllosilicate-rich groundmass; b) powders with identical mineralogical composition. In addition, the solid samples become more and more velocity strengthening with increasing sliding velocity. Field observations along exhumed and phyllosilicate-rich faults worldwide suggest that phyllosilicates-rich strands bound lenses of stronger and non foliated lithologies. Within this fault structure fault creep and aseismic slip along weak and phyllosilicate-rich foliated surfaces (velocity strengthening behaviour) might increase stress on lenses of stronger materials (velocity weakening behaviour) from which a rupture can nucleate. In this view, some crustal faults can behave as weak structures over long timescales (millions of years) and be intermittently seismogenic on shorter timescales.

  17. Behaviourism and the mechanization of the mind.

    Science.gov (United States)

    Lecas, Jean-Claude

    2006-01-01

    The significance of Behaviourism is examined in relation to its far conceptual roots, i.e. comparative animal studies initiated by Darwin, mechanistic physiological thinking initiated by Descartes and empiricist associationism. The Behaviourist anti-mentalist position induced neuromechanistic interpretations based on Pavlovian reflexes, stimulus-response connectionism and the very first hypotheses on synaptic plasticity. As a result, the evolutionary tradition was dropped and the two other trends were combined into a new adaptive version of Cartesian automaton, with persisting influences in modern reductionist thinking, from robotics and cognitive science to the neuroscience of learning and memory. PMID:16731496

  18. Modelling the thermo-mechanical volume change behaviour of compacted expansive clays

    CERN Document Server

    Tang, Anh-Minh; 10.1680/geot.2009.59.3.185

    2009-01-01

    Compacted expansive clays are often considered as a possible buffer material in high-level deep radioactive waste disposals. After the installation of waste canisters, the engineered clay barriers are subjected to thermo-hydro-mechanical actions in the form of water infiltration from the geological barrier, heat dissipation from the radioactive waste canisters, and stresses generated by clay swelling under almost confined conditions. The aim of the present work is to develop a constitutive model that is able to describe the behaviour of compacted expansive clays under these coupled thermo-hydro-mechanical actions. The proposed model is based on two existing models: one for the hydro-mechanical behaviour of compacted expansive clays and another for the thermo-mechanical behaviour of saturated clays. The elaborated model has been validated using the thermo-hydro-mechanical test results on the compacted MX80 bentonite. Comparison between the model prediction and the experimental data show that this model is able...

  19. Creep of uranium dioxide: bending test and mechanical behaviour

    International Nuclear Information System (INIS)

    These PhD work in the frame of Pellet-Cladding Interactions studies, in the fuel assemblies of nuclear plants. Electricite de France (EDF) must well demonstrate and insure the integrity of the cladding. For that purpose, the viscoplastic behaviour of the nuclear fuel has to be known and, if possible, controlled. This PhD work aimed to characterize the creep of uranium dioxide, in conditions of transient power regime. First, a literature survey on mechanical behaviour of UO2 revealed that the ceramic was essentially studied with compressive tests, and that its creep behaviour is characterized by two domains, depending on the stress level. To estimate the loadings in a fuel pellet, EDF and CEA developed specific global codes. A simulation during a power ramp allowed the order of magnitude of the loadings in the pellet to be determined (temperature, thermal gradients, strains, strain rate...). The stress calculation using a finite element simulation requires the identification of behaviour laws, able to describe the behaviour under small strains, low strain rates, and under tensile stresses. Starting from this observation, three point bending method has been chosen to test the uranium dioxide. As, for representativeness reasons, testing specimens cut in actual fuel pads was required in our study; a ten millimeters span has been used. For this study, a specific three-point testing device has been developed, that can tests specimens up to 2 000 C in a controlled atmosphere (Ar + 5% H2). A special care has been taken for the measurement of the deflexion of the sample, which is measured using a laser beam, that allow an accuracy of ±2μm to be reached at high temperature. Specimens with 0,5 to 1 mm thickness have been tested using this jig. A Norton's law describe, with respective stress exponent and activation energy values of 1.73 and 540 kJ.mole-1, provided a good description of the stationary creep rate. Then, the mechanical behaviour of the fuel has been modeled

  20. Chemo-mechanical coupling behaviour of leached concrete. Part I : Experimental results

    OpenAIRE

    NGUYEN,VH; COLINA, H; Torrenti, Jean Michel; Boulay, Claude; Nedjar, Boumediene

    2007-01-01

    This paper deals with concrete behaviour under chemical and mechanical degradations. Experimental investigations are described where the effects of the calcium leaching process of concrete on its mechanical properties are highlighted. The calcium leaching and mechanical tests on cement paste, mortar and concrete samples are presented. Because of the slow kinetics of leaching under deionised water, an accelerated method has been chosen by using an ammonium nitrate solution instead. The specime...

  1. Brain mechanisms underlying sensation-seeking in humans

    OpenAIRE

    Norbury, A. E.

    2015-01-01

    Sensation-seeking is a personality trait concerned with motivation for intense and unusual sensory experiences, that has been identified as risk factor for a variety of psychopathologies with high social cost; in particular gambling and substance addictions. It has previously proved difficult to tease out neural mechanisms underlying sensation-seeking in humans, due to a lack of cognitive-behavioural paradigms probing sensation-seeking-like behaviour in the lab. The first aim of this thesis w...

  2. Mechanical behaviour of dissimilar metal welds

    International Nuclear Information System (INIS)

    This report addresses the problems of dissimilar metal welds connecting an austenitic stainless steel component to a ferritic steel component. In LMFBRs such welds appear at the junction of the austenitic stainless steel vessel with the ferritic steel roof and in sodium and water or steam pipes. The latter are exposed to high temperatures in the creep range. A wide range of austenitic stainless steels and ferritic steels (carbon steels, low allow steels and alloy steels) are covered; the study encompasses more than 20 different weld metals (austenitic stainless steels and nickel base alloys). The report begins with a presentation of the materials, geometries and welding procedures treated in the study, followed by a review of service experience from examinations of dissimilar metal welds after elevated temperature service, in particular failed welds. Results of laboratory tests performed for reproducing service failures are then discussed. A further section is devoted to a review of test results on fatigue behaviour and impact toughness for dissimilar metal welded joints when creep is not significant. Finally, the problem of residual life assessment is addressed. A set of recommendations concludes the report. They concern the material selection, welding procedure, life prediction and testing of dissimilar metal welds. 84 refs

  3. Mechanisms and functions of brain and behavioural asymmetries

    OpenAIRE

    Tommasi, Luca

    2008-01-01

    For almost a century the field of brain and behavioural asymmetries has been dominated by studies on humans, resting on the evidence that the anatomical structures underlying language functions are asymmetrical, and that human handedness is lateralized at the population level. Today, there is not only evidence of population-level lateralization of brain and behaviour across a variety of vertebrate and invertebrate species, but also a growing consensus that the comparative analysis of the envi...

  4. Multiscale approach of mechanical behaviour of SiC/SiC composites: elastic behaviour at the scale of the tow

    OpenAIRE

    CHATEAU, Camille; Gelebart, Lionel; Bornert, Michel; CREPIN, Jérome; Caldemaison, Daniel

    2010-01-01

    SiC/SiC composites are candidates for structural applications at elevated temperatures in the context of the development of the 4th generation of nuclear reactors. A multiscale approach is under development to construct a predictive modelling of their complex mechanical behaviour due to their heterogeneous microstructure. This approach is based on two scale transitions: from the fibres/matrix microstructure to the tow and from the tow to the woven composite, each scale presenting a significan...

  5. A strong genetic correlation underlying a behavioural syndrome disappears during development because of genotype-age interactions.

    Science.gov (United States)

    Class, Barbara; Brommer, Jon E

    2015-06-22

    In animal populations, as in humans, behavioural differences between individuals that are consistent over time and across contexts are considered to reflect personality, and suites of correlated behaviours expressed by individuals are known as behavioural syndromes. Lifelong stability of behavioural syndromes is often assumed, either implicitly or explicitly. Here, we use a quantitative genetic approach to study the developmental stability of a behavioural syndrome in a wild population of blue tits. We find that a behavioural syndrome formed by a strong genetic correlation of two personality traits in nestlings disappears in adults, and we demonstrate that genotype-age interaction is the likely mechanism underlying this change during development. A behavioural syndrome may hence change during organismal development, even when personality traits seem to be strongly physiologically or functionally linked in one age group. We outline how such developmental plasticity has important ramifications for understanding the mechanistic basis as well as the evolutionary consequences of behavioural syndromes. PMID:26041348

  6. Mechanical behaviour characterizing and simulation of polyacrylate rubber

    Directory of Open Access Journals (Sweden)

    D. dos Santos

    2010-01-01

    Full Text Available Purpose: of this paper is to investigate the influence of EB radiation on the mechanical behaviour of UV curing polyacrylate rubber (ACM and to simulate its behaviour.Design/methodology/approach: The material was irradiated by two different EB doses, 100 kGy and 250 kGy, its mechanical behaviour was investigated with the help of uniaxial, equibiaxial and planar shear experiments. The results were applied to the Ogden’s Model (1972 in order to obtain the parameters to simulate the material behaviour by finite element method (FEM and to compare experimental and FEM curves. The structure molecular changes caused by EB were investigated with the help of infrared spectroscopy.Findings: In most cases the experimental results showed an increase in the strength at rupture and a decrease in the elongation at the rupture with increasing of radiation dose. Equibiaxial and planar shear tests presented similar behaviour like uniaxial results, in terms of elongation decrease and strength increase, with some deviations. Ogden’s Model third order provided simulated curves with similar behaviour in comparison to experimental curves. The infrared spectroscopy showed different chemical group contents in the analyzed regions, surface and middle region.Research limitations/implications: Two doses of EB radiation were applied; higher or lower doses were not investigated.Practical implications: Improved behaviour of UV curing ACM can extend the range of industrial applications, or improve its performance in known applications.Originality/value: Usually EB radiation has been used to modify polymeric structure and to improve thermal and mechanical polymers behaviour. Regarding like rubber materials EB is usually applied as an alternative form of vulcanization. UV is a new type of curing for polyacrylate rubbers, which are usually cured by thermal processes.

  7. Failure behaviour of carbon/carbon composite under compression

    Energy Technology Data Exchange (ETDEWEB)

    Tushtev, K.; Grathwohl, G. [Universitaet Bremen, Advanced Ceramics, Bremen (Germany); Koch, D. [Deutsches Zentrum fuer Luft- und Raumfahrt, Institut fuer Bauweisen- und Konstruktionsforschung, Keramische Verbundstrukturen, Stuttgart (Germany); Horvath, J.

    2012-11-15

    In this work the properties of Carbon/Carbon-material are investigated under quasi-static compression and model-like characterized. The investigated material was produced by pyrolysis of a Carbon/Carbon - composite of bidirectionally reinforced fabric layers. For the compression tests, a device to prevent additional bending stress was made. The stress-strain behaviour of this material has been reproduced in various publications. This will be discussed on the fracture behaviour and compared the experimental results from the compression tests with the characteristics of tensile and shear tests. The different compression and tensile properties of stiffness, poisson and strength were assessed. Differences between the tensile and compression behaviour resulting from on-axis tests by micro buckling and crack closure and off-axis experiments by superimposed pressure normal stresses that lead to increased shear friction. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Mechanical behaviour of aluminium-lithium alloys

    Indian Academy of Sciences (India)

    N Eswara Prasad; A A Gokhale; P Rama Rao

    2003-02-01

    Aluminium-lithium alloys hold promise of providing a breakthrough response to the crying need for lightweight alloys for use as structurals in aerospace applications. Considerable worldwide research has gone into developing a range of these alloys over the last three decades. As a result, substantial understanding has been developed of the microstructure-based micromechanisms of strengthening, of fatigue and fracture as well as of anisotropy in mechanical properties. However, these alloys have not yet greatly displaced the conventionally used denser Al alloys on account of their poorer ductility, fracture toughness and low cycle fatigue resistance. This review aims to summarise the work pertaining to study of structure and mechanical properties with a view to indicate the directions that have been and can be pursued to overcome property limitations.

  9. Prediction of PEC core mechanical behaviour

    International Nuclear Information System (INIS)

    A brief description of the original PEC core restraint system is presented. Recent advanced seismic analysis studies have necessitated the introduction of anti-seismic design modifications which have increased the difficulties of fuel handling. Computer codes and numerical methods, used by ENEA to resolve core restraint and fuel handling problems are given together with an outline of mechanical tests and handling experiments in support of the anti-seismic core design. (author)

  10. Morphology and mechanical behaviour of concretes reinforced by amorphous cast fibres

    International Nuclear Information System (INIS)

    This research thesis addresses the characterization of the morphology and mechanical behaviour of concretes reinforced by amorphous cast fibres. It first gathers some general characteristics and observations related to the amorphous cast fibre: roughness, failure mode, amorphous structure, X-ray analysis, fire resistance. Experimental methods and techniques developed for morphological analysis and mechanical tests are presented (sample preparation, tensile test, and compression sample) and the use of image automatic analysis techniques is then addressed (void morphology and granulometry analysis, inter-void distance measurement, fibre spatial distribution). The next part reports the study of the mechanical behaviour under axial compression

  11. Post Irradiation Mechanical Behaviour of Three EUROFER Joints

    Energy Technology Data Exchange (ETDEWEB)

    Lucon, E.; Leenaers, A.; Vandermeulen, W.

    2006-08-15

    The post-irradiation mechanical properties of three EUROFER joints (two diffusion joints and one TIG weld) have been characterized after irradiation to 1.8 dpa at 300 degrees Celsius in the BR-2 reactor. Tensile, KLST impact and fracture toughness tests have been performed. Based on the results obtained and on the comparison with data from EUROFER base material irradiated under similar conditions, the post-irradiation mechanical behaviour of both diffusion joints (laboratory and mock-up) appears similar to that of the base material. The properties of the TIG joint are affected by the lack of a post-weld heat treatment, which causes the material from the upper part of the weld to be significantly worse than that of the lower region. Thus, specimens from the upper layer exhibit extremely pronounced hardening and embrittlement caused by irradiation. The samples extracted from the lower layer show much better resistance to neutron exposure, although their measured properties do not match those of the diffusion joints. The results presented demonstrate that diffusion joining can be a very promising technique.

  12. Kinesin's backsteps under mechanical load

    CERN Document Server

    Hyeon, Changbong; Onuchic, Jose' N

    2009-01-01

    Kinesins move processively toward the plus end of microtubules by hydrolyzing ATP for each step. From an enzymatic perspective, the mechanism of mechanical motion coupled to the nucleotide chemistry is often well explained using a single-loop cyclic reaction. However, several difficulties arise in interpreting kinesin's backstepping within this framework, especially when external forces oppose the motion of kinesin. We review evidence, such as an ATP-independent stall force and a slower cycle time for backsteps, that has emerged to challenge the idea that kinesin backstepping is due to ATP synthesis, i.e., the reverse cycle of kinesin's forward-stepping chemomechanics. Supplementing the conventional single-loop chemomechanics with routes for ATP-hydrolyzing backward steps and nucleotide-free steps, especially under load, gives a better physical interpretation of the experimental data on backsteps.

  13. Molecular Mechanisms Underlying Bacterial Persisters

    DEFF Research Database (Denmark)

    Maisonneuve, Etienne; Gerdes, Kenn

    2014-01-01

    All bacteria form persisters, cells that are multidrug tolerant and therefore able to survive antibiotic treatment. Due to the low frequencies of persisters in growing bacterial cultures and the complex underlying molecular mechanisms, the phenomenon has been challenging to study. However, recent...... technological advances in microfluidics and reporter genes have improved this scenario. Here, we summarize recent progress in the field, revealing the ubiquitous bacterial stress alarmone ppGpp as an emerging central regulator of multidrug tolerance and persistence, both in stochastically and environmentally...

  14. Behaviour of fission-product iodine under severe accident conditions

    International Nuclear Information System (INIS)

    On account of the radiological properties of I-131 the behaviour of fission-product iodine is of great importance under severe reactor accident conditions. The chemical properties of iodine: Its easy conversion into several oxidation compounds, its capability of forming not only volatile (organo-iodide, elemental iodine), hardly volatile, readily soluble (cesium iodide/iodate) but also insoluble (silver iodide) compounds, and its susceptibility to ionizing radiation, are further aspects of significance. Intensive investigations on iodine behaviour under reactor accident conditions carried out worldwide over the last ten years have shown - even though a number of details have yet to be elucidated - that physicochemical processes form a natural, i.e. passive, barrier against the possible release of iodine. (orig.)

  15. Experimental study of aluminium honeycomb behaviour under dynamic multiaxial loading

    OpenAIRE

    Markiewicz E.; Haugou G.; Chaari F.; Zouari B.; Tounsi R.; Dammak F.

    2012-01-01

    Split Hopkinson Pressure Bar system (SHPB) with large-diameter and Nylon bars introducing a shear-compression loading device is used in order to investigate the dynamic behaviour of aluminium honeycomb under multiaxial loadings conditions. All shear-compression configurations including the loading angle variation from 0∘ to 60∘ are performed with an impact velocity of about 15m/s. The adapted SHPB system with the device are validated numerically and a phenomenon of separation between the inpu...

  16. Computation of the mechanical behaviour of nuclear reactor components

    International Nuclear Information System (INIS)

    A possible limiting factor of the service life of a reactor is the mechanical load carrying margin, i.e. the excess of the load carrying capacity over the actual loading, of the central, heavy section components. This margin decreases during service but, for safety reasons, may not fall below a critical value. Therefore, it is essential to check and to control continuously the factors which cause the decrease. The reasons for the decrease are shown at length and in detail in an example relating to the test which almost achieved failure of a pipe emanating from a reactor pressure vessel, weakened by an artificial crack and undergoing a water-hammer loading. The latter was caused by a sudden valve closure supposed to follow upon a break far downstream. The computational and experimental difficulties associated with the simultaneous occurrence of an extreme weakening and an extreme loading in an already rather complicated geometry are explained. It is concluded that available computational tools and present know-how are sufficient to simulate the behaviour under such conditions as would prevail in normal service, and even to analyse departures from them, as long as not all difficulties arise simultaneously. (author) figs., tabs., refs

  17. Behaviour of gas cooled reactor fuel under accident conditions

    International Nuclear Information System (INIS)

    The Specialists Meeting on Behaviour of Gas Cooled Reactor Fuel under Accident Conditions was convened by the International Atomic Energy Agency on the recommendation of the International Working Group on Gas Cooled Reactors. The purpose of the meeting was to provide an international forum for the review of the development status and for the discussion on the behaviour of gas cooled reactor fuel under accident conditions and to identify areas in which additional research and development are still needed and where international co-operation would be beneficial for all involved parties. The meeting was attended by 45 participants from France, Germany, Japan, Switzerland, the Union of Soviet Socialists Republics, the United Kingdom, the United States of America, CEC and the IAEA. The meeting was subdivided into five technical sessions: Summary of Current Research and Development Programmes for Fuel; Fuel Manufacture and Quality Control; Safety Requirements; Modelling of Fission Product Release - Part I and Part II; Irradiation Testing/Operational Experience with Fuel Elements; Behaviour at Depressurization, Core Heat-up, Power Transients; Water/Steam Ingress - Part I and Part II. 22 papers were presented. A separate abstract was prepared for each of these papers. At the end of the meeting a round table discussion was held on Directions for Future R and D Work and International Co-operation. Refs, figs and tabs

  18. Behaviour of organic iodides under pwr accident conditions

    International Nuclear Information System (INIS)

    Laboratory experiments were performed to study the behaviour of radioactive methyl iodide under PWR loss-of-coolant conditions. The pressure relief equipment consisted of an autoclave for simulating the primary circuit and of an expansion vessel for simulating the conditions after a rupture in the reactor coolant system. After pressure relief, the composition of the CH3sup(127/131)I-containing steam-air mixture within the expansion vessel was analysed at 80 0C over a period of 42 days. On the basis of the values measured and of data taken from the literature, both qualitative and quantitative assessments have been made as to the behaviour of radioactive methyl iodide in the event of loss-of-coolant accidents. (author)

  19. The behaviour of radioactive waste packages under fire accident conditions

    International Nuclear Information System (INIS)

    An experimental study has been made of the behaviour of packaged Intermediate Level Wastes (ILW) subjected to heat. The conditions used represented fire accidents in the transport of the ILW to the repository in shielded transport containers and in the handling of the packages at the repository. The behaviour of four waste materials immobilised in cement and organic resin were studied. Each waste used had features which allowed the results to be applied to a wide range of other waste streams. Samples of these materials have been heated under controlled and well instrumented conditions in furnaces and pool fires. Inactive simulant wastes were used in small and full scale experiments. Fully active waste materials were used in small scale experiments only. Data are presented on the temperature profiles through the packaged ILW and on the release of volatile and particulate materials as a function of time and temperature. (orig.)

  20. Thermal shock behaviour of different tungsten grades under varying conditions

    International Nuclear Information System (INIS)

    Thermonuclear fusion power plants are a promising option to ensure the energy supply for future generations, but in many fields of research enormous challenges have to be faced. A major step on the way to the prototype fusion reactor DEMO will be ITER which is build in Cadarache, southern France. One of the most critical issues is the field of in-vessel materials and components, in particular the plasma facing materials (PFM). PFMs that will be used in a device like ITER have to withstand severe environmental conditions in terms of steady state and transient thermal loads as well as high particle fluxes such as hydrogen, helium and neutrons. Candidate wall materials are beryllium, tungsten and carbon based materials like CFC (carbon fibre composite). Tungsten is the most promising material for an application in the divertor region with very severe loading conditions and it will most probably also be used as PFM for DEMO. Hence, this work focuses on the investigation of the thermal shock response of different tungsten grades in order to understand the damage mechanisms and to identify material parameters which influence this behaviour under ITER and DEMO relevant operation conditions. Therefore the microstructure and the mechanical and thermal properties of five industrially manufactured tungsten grades were characterised. All five tungsten grades were exposed to transient thermal events with very high power densities of up to 1.27 GWm-2 at varying base temperatures between RT and 600 C in the electron beam device JUDITH 1. The pulse numbers were limited to a maximum of 1000 in order to avoid immoderate workload on the test facility and to have enough time to cover a wide range of loading conditions. The results of this damage mapping enable to define different damage and cracking thresholds for the investigated tungsten grades and to identify certain material parameters which influence the location of these thresholds and the distinction of the induced damages

  1. Thermal shock behaviour of different tungsten grades under varying conditions

    Energy Technology Data Exchange (ETDEWEB)

    Wirtz, Oliver Marius

    2012-07-19

    Thermonuclear fusion power plants are a promising option to ensure the energy supply for future generations, but in many fields of research enormous challenges have to be faced. A major step on the way to the prototype fusion reactor DEMO will be ITER which is build in Cadarache, southern France. One of the most critical issues is the field of in-vessel materials and components, in particular the plasma facing materials (PFM). PFMs that will be used in a device like ITER have to withstand severe environmental conditions in terms of steady state and transient thermal loads as well as high particle fluxes such as hydrogen, helium and neutrons. Candidate wall materials are beryllium, tungsten and carbon based materials like CFC (carbon fibre composite). Tungsten is the most promising material for an application in the divertor region with very severe loading conditions and it will most probably also be used as PFM for DEMO. Hence, this work focuses on the investigation of the thermal shock response of different tungsten grades in order to understand the damage mechanisms and to identify material parameters which influence this behaviour under ITER and DEMO relevant operation conditions. Therefore the microstructure and the mechanical and thermal properties of five industrially manufactured tungsten grades were characterised. All five tungsten grades were exposed to transient thermal events with very high power densities of up to 1.27 GWm{sup -2} at varying base temperatures between RT and 600 C in the electron beam device JUDITH 1. The pulse numbers were limited to a maximum of 1000 in order to avoid immoderate workload on the test facility and to have enough time to cover a wide range of loading conditions. The results of this damage mapping enable to define different damage and cracking thresholds for the investigated tungsten grades and to identify certain material parameters which influence the location of these thresholds and the distinction of the induced

  2. Modelling the mechanical behaviour of heterogeneous Ta/TA6V welded joints: behaviour and failure criteria

    International Nuclear Information System (INIS)

    As laser welding of two different materials (heterogeneous welding) leads to a joint having a characteristic size close to the millimetre, i.e. much smaller than that of a structure, and as such a junction displays completely different mechanical properties because of the metallurgical transformations induced by intense thermal loading, the aim of this research thesis is to develop a behaviour model, flexible and robust enough, to represent all together the mechanical behaviours of the Ta, the TA6V and the melted zone. This model must be able to take plasticity and visco-plasticity into account, and also to provide a failure criterion through damage mechanics and its coupling with the behaviour. The author first reports the experimental characterization of the base materials (Ta and TA6V) by using tensile tests under different strain rates and different directions, relaxation tests and fatigue shear tests. He also characterizes the melted zone by describing the influence of a thermal treatment (induced by welding) on the formation of the melted zone, and by using different tests: four point bending on notched specimens, nano-indentation test, and longitudinal tensile test. In a second part, the author develops the model within the framework of continuum thermodynamics, and explores the numerical issues. The last part deals with the validation of the model for the concerned materials (Ta and TA6V) and melted zone

  3. Excavation effect on thermo hydro- mechanical behaviour of geological barrier

    International Nuclear Information System (INIS)

    Heat emitted by nuclear waste has great influences on mechanical and hydraulic properties of the surrounded media and also on the movement of water, vapour and air. Due to the complexity of the phenomena that might take place in a waste repository, an adequate understanding of the behaviour of the barriers is not an easy task. The difficulty of the task is increased by the fact that many effect s are coupled. In order to study these effects, series of coupled thermo-hydro-mechanical formulations are used. The first step in a theoretical development of a fully coupled thermo-hydro-mechanical model for an unsaturated soil, is choosing the adequate and independent variables which would be able to present all significant interaction effects among the different components involved in a coupled process in a deformable unsaturated porous medium with three phases (skeleton, water and air)under heating. The phase changes between liquid and gas, evaporation, condensation, induced moisture transfer under thermal and pore pressure gradients and the effects of moisture distribution on the heat flow are important aspects in non-deformable unsaturated porous media. If the deformation of porous media is considered, the coupling effects among deformation, moisture, and heat should be also regarded in addition to all above aspects. The governing equations are the equation of equilibrium and constitutive law for solid skeleton, mass conservation and fluid transfer for water and air, and Fourier law and conservation equation for energy. Due to the fact that water phase consists of liquid and vapour two sets of transfer equations are used for water phase: Philip and de Vries law for vapour and Darcy law for liquid. Darcy law is also used for air transfer. In the presented formulations, due to the fact that the medium is assumed to be deformable, the effects of deformation on the temperature and suction distribution in soil and the inverse effects must be included. In order to include

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

    Directory of Open Access Journals (Sweden)

    V. Anes

    2014-10-01

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

  5. Thermo-Mechanical Behaviour of Flax-Fibre Reinforced Epoxy Laminates for Industrial Applications

    Directory of Open Access Journals (Sweden)

    Giuseppe Pitarresi

    2015-11-01

    Full Text Available The present work describes the experimental mechanical characterisation of a natural flax fibre reinforced epoxy polymer composite. A commercial plain woven quasi-unidirectional flax fabric with spun-twisted yarns is employed in particular, as well as unidirectional composite panels manufactured with three techniques: hand-lay-up, vacuum bagging and resin infusion. The stiffness and strength behaviours are investigated under both monotonic and low-cycle fatigue loadings. The analysed material has, in particular, shown a typical bilinear behaviour under pure traction, with a knee yield point occurring at a rather low stress value, after which the material tensile stiffness is significantly reduced. In the present work, such a mechanism is investigated by a phenomenological approach, performing periodical loading/unloading cycles, and repeating tensile tests on previously “yielded” samples to assess the evolution of stiffness behaviour. Infrared thermography is also employed to measure the temperature of specimens during monotonic and cyclic loading. In the first case, the thermal signal is monitored to correlate departures from the thermoelastic behaviour with the onset of energy loss mechanisms. In the case of cyclic loading, the thermoelastic signal and the second harmonic component are both determined in order to investigate the extent of elastic behaviour of the material.

  6. The Behaviour of Various Graphites under Neutron Irradiation

    International Nuclear Information System (INIS)

    The change of graphite properties under neutron irradiation, which is quite important for reactor designers, has been investigated closely for several years, and results have been reported in detail by several authors. The goal of these irradiation experiments was the quantitative determination of property changes as a function of irradiation dose and temperature. The concern of our own irradiation programme, which is sponsored by the Ministry of Atomic Affairs of the Federal Republic of Germany, was to study the behaviour of a wide range of reactor-grade graphites under controlled irradiation conditions. In the first part of the paper, radiation damage as a function of different types of artificial graphite is dealt with. The graphite types differed only by their degree of crystalline order, even though they were produced under the same graphitizing conditions. The differences are caused by the different graphitizabilities of the raw materials. The dependence oí the radiation damage on the graphite type seems to be of fundamental importance for the development of reactor-grade graphites with respect to various applications. Within one group the physical properties are changed in different ways for different graphite types. The differences of the unirradiated samples remain largely unchanged or are even more pronounced after irradiation. Mechanical properties, such as strength, Young's Modulus and thermal expansion, fall into this group. The well-known Wigner growth of various graphites under irradiation was studied systematically. Furthermore, such properties are reported which are levelled out to a final value under the same irradiation conditions even when the raw materials are different. This is true for the thermal and electrical conductivity, the magnetic susceptibility and to some extent for the lattice dimensions of the graphites. Finally, the effect of irradiation on the pore distribution of the various graphites is discussed. The second section ol the

  7. Analysis of the mechanical behaviour of the ITER magnet system

    International Nuclear Information System (INIS)

    The International Thermonuclear Experimental Reactor (ITER) is a tokamak fusion device with the objective of demonstrating controlled ignition and an extended burn for a duration sufficient to achieve stationary conditions. The design of ITER will be based on extensive new design work supported by new physical and technological results. As part of the ITER Engineering Design Activities, the mechanical behaviour of the toroidal field coil (TF coil) system during normal operating conditions and fault conditions has to be analyzed. The displacements and/or stresses in the components must be limited to prevent mechanical failure of parts of the overall structure. These Engineering Design Activities are supported by R and D programs in the European Union. This final report describes the work carried out by ECN to develop a finite element model (FE model) of the TF-coil system which is suitable for the analysis of the mechanical behaviour and presents results obtained with this model. For the analysis of the mechanical behaviour, a large three dimensional (3D) non-linear finite element model has been developed. With this FE model a large number of load cases has been analyzed which correspond with several time points during multiple pulses. (orig./WL)

  8. INPR ACPR utilization in fuel behaviour studies under accidental condition

    Energy Technology Data Exchange (ETDEWEB)

    Negut, Gheorghe; Popov, Mircea [Institute for Nuclear Power Reactors, Pitesti (Romania)

    1990-07-01

    This paper is dedicated to the experimental program, investigating CANDU type fuel behaviour in transient condition, as well as the facilities supporting this program. The tests Reactivity Initiated Accident type. The experiments were performed within TRIGA ACPR facility, installed at INSTITUTE for NUCLEAR POWER REACTORS, Pitesti, ROMANIA. Studies of the safety issues took a great international developement during last years. In USA, Japan, owners of the similar reactors, and USSR there are a big commitment to such programs, intended to establish the nuclear fuel behaviour under RIA-conditions. In our country, too, there are programs aiming a complete testing of the CANDU type fuels. As it is known, RIA is not a CANDU specific accident, but the fuel behaviour in such conditions can give useful informations on the fuel cladding failure threshold and about reflooding post LOCA heat transfer condition. Based on some papers and specific requirements it was initiated and developed a safety research program on CANDU type fuel using the ACPR. The paper describes the reactor,test capsule, instrumentation, fuel samples, tests, post irradiation results. (orig.)

  9. Thermo-hydro-mechanical behaviour of Boom clay

    International Nuclear Information System (INIS)

    This thesis studied the thermo-hydro-mechanical properties of Boom clay, which was chosen to be the host material for the radioactive waste disposal in Mol, Belgium. Firstly, the research was concentrated on the soil water retention properties and the hydro-mechanical coupling by carrying out axial compression tests with suction monitoring. The results obtained permitted elaborating a rational experimental procedure for triaxial tests. Secondly, the systems for high pressure triaxial test at controlled temperature were developed to carry out compression, heating, and shearing tests at different temperatures. The obtained results showed clear visco-elasto-plastic behaviour of the soil. This behaviour was modelled by extending the thermo-elasto-plastic model of Cui et al. (2000) to creep effect. (author)

  10. Spent HIFAR fuel elements behaviour under extended dry storage

    International Nuclear Information System (INIS)

    Previously unpublished observations of the behaviour of HIFAR spent fuel under extended dry storage conditions are reported. The two fuel elements EC802 (Mark III type) were irradiated in 1966, first examined in hot cells in 1967 and again examined in hot cells in 1983 following 16 years of stage, 11 years of which were in the ANSTO engineered dry storage facility. The elements showed negligible deterioration over this extended dry storage period, lending considerable confidence to the viability of dry storage technologies for the long term storage of spent aluminium clad research reactor fuels. 1 tab., 1 fig., 17 ills

  11. Transition in fluctuation behaviour of normal liquids under high pressures

    Science.gov (United States)

    Postnikov, Eugene B.; Chora&¸zdot; ewski, Mirosław

    2016-05-01

    We explore the behaviour of the inverse reduced density fluctuations and the isobaric expansion coefficient using α , ω-dibromoalkanes as an example. Two different states are revealed far from the critical point: the region of exponentially decaying fluctuations near the coexistence curve and the state with longer correlations under sufficiently high pressures. The crossing of the isotherms of the isobaric expansion coefficient occurs within the PVT range of the mentioned transition. We discuss the interplay of this crossing with the changes in molecular packing structure connected with the analysed function of the density, which represents inverse reduced volume fluctuations.

  12. Study on Mechanical and Physical Behaviour of Hybrid GFRP

    OpenAIRE

    Nor Bahiyah Baba; Ahmad Syakirin Suhaimi; Muhamad Asyraf Mohd Amin; Alias Mohd

    2015-01-01

    The paper discusses the mechanical and physical behaviour of hybrid glass fibre reinforced plastic (GFRP). Hybrid GFRP was fabricated by three different types of glass fibre, namely, 3D, woven, and chopped, which were selected and combined with mixture of polyester resin and hardener. The hybrid GFRP was investigated by varying three parameters which were the composite volume fractions, hybrid GFRP arrangement, and single type fibre. The hybrid GFRP was fabricated by using open mould hand lay...

  13. Mechanical behaviour of adhesive joints such as a concrete epoxy

    OpenAIRE

    Aguiar, J. L. Barroso de; Reymond, M. C.; Paillère, A. M.

    1987-01-01

    The sample DCB is separated in two parts then sticked by epoxy to study adhesion between concrete and epoxy resin. The crack propagation was initiated at a notch in a double cantilever beam. The notch of the test sample was opened by an Instron tensile machin. The crack extension was followed through direct optical observations. The displacement was measured by an extensometer. During the fracture test, mechanical behaviour of the sample was monitored with various techniques: the experimental...

  14. Thermo-mechanical behaviour of a compacted swelling clay

    OpenAIRE

    TANG, Anh Minh; Cui, Yu-Jun; Barnel, Nathalie

    2008-01-01

    International audience Compacted unsaturated swelling clay is often considered as a possible buffer material for deep nuclear waste disposal. An isotropic cell permitting simultaneous control of suction, temperature and pressure was used to study the thermo-mechanical behaviour of this clay. Tests were performed at total suctions ranging from 9 to 110 MPa, temperature from 25 to 80 °C, isotropic pressure from 0.1 to 60 MPa. It was observed that heating at constant suction and pressure indu...

  15. Nuclear cooling tower submitted to shrinkage; behaviour under weight and wind

    International Nuclear Information System (INIS)

    A numerical formulation to analyse nuclear cooling tower submitted to creep and shrinkage of concrete is presented in this paper. Both humidity effects and non-linear mechanical behaviour of the constitutive materials are taken into account. Moisture migration is described using a single diffusion equation in which the relative humidity is the driving force and delayed strains are obtained in a phenomenological way. To capture the time-dependent behaviour, an extension of a continuum plasticity model which incorporates viscous behaviour, has been developed and its main parameters are obtained from experimental results. The effects produced by internal stresses that result from time-dependent deformations are finally presented for nuclear tower under services loading

  16. Behaviour of M30 Grade concrete with confinement under axial compression

    OpenAIRE

    C.Vinil Babu; V.K.Visweswara Rao

    2014-01-01

    The strength and durability of concrete have undergone continuous improvement. Over the years and these improved materials are now commonly used. In the present experimental investigation the behaviour of M30 grade concrete with and without confinement for different percentages of replacement of silica fume is studied under axial compression as per IS mix design. The 150mm x 300mm cylindrical specimens were cast with and without confinement and investigating the mechanical prop...

  17. Structural and mechanical behaviour of LLDPE/HNT nanocomposite films

    Science.gov (United States)

    Čermák, M.; Kadlec, P.; Šutta, P.; Polanský, R.

    2016-03-01

    The paper briefly describes structural and mechanical influences of Halloysite nanotubes (HNT) in different level of fulfilment (0, 1, 3, 7 wt%) in the LLDPE commonly used in the cable industry. The influence of HNT on the polymer has been observed and evaluated through the average crystallite size and the micro- deformation by X-Ray diffractometry and the imaging of SEM. Despite the certain inter-phase tension between the polymer and HNT, the influence on the mechanical and combustion behaviour was observed. Measurement showed a higher content of agglomerates in the sample with 7 wt% HNT fulfilment.

  18. To Cooperate or Not to Cooperate: Why Behavioural Mechanisms Matter.

    Science.gov (United States)

    Bernard, Arthur; André, Jean-Baptiste; Bredeche, Nicolas

    2016-05-01

    Mutualistic cooperation often requires multiple individuals to behave in a coordinated fashion. Hence, while the evolutionary stability of mutualistic cooperation poses no particular theoretical difficulty, its evolutionary emergence faces a chicken and egg problem: an individual cannot benefit from cooperating unless other individuals already do so. Here, we use evolutionary robotic simulations to study the consequences of this problem for the evolution of cooperation. In contrast with standard game-theoretic results, we find that the transition from solitary to cooperative strategies is very unlikely, whether interacting individuals are genetically related (cooperation evolves in 20% of all simulations) or unrelated (only 3% of all simulations). We also observe that successful cooperation between individuals requires the evolution of a specific and rather complex behaviour. This behavioural complexity creates a large fitness valley between solitary and cooperative strategies, making the evolutionary transition difficult. These results reveal the need for research on biological mechanisms which may facilitate this transition. PMID:27148874

  19. Study on Mechanical and Physical Behaviour of Hybrid GFRP

    Directory of Open Access Journals (Sweden)

    Nor Bahiyah Baba

    2015-01-01

    Full Text Available The paper discusses the mechanical and physical behaviour of hybrid glass fibre reinforced plastic (GFRP. Hybrid GFRP was fabricated by three different types of glass fibre, namely, 3D, woven, and chopped, which were selected and combined with mixture of polyester resin and hardener. The hybrid GFRP was investigated by varying three parameters which were the composite volume fractions, hybrid GFRP arrangement, and single type fibre. The hybrid GFRP was fabricated by using open mould hand lay-up technique. Mechanical testing was conducted by tensile test for strength and stiffness whereas physical testing was performed using water absorption and hardness. These tests were carried out to determine the effect of mechanical and physical behaviour over the hybrid GFRP. The highest volume fraction of 0.5 gives the highest strength and stiffness of 73 MPa and 821 MPa, respectively. Varying hybrid fibre arrangement which is the arrangement of chopped-woven-3D-woven-chopped showed the best value in strength of 66.2 MPa. The stiffness is best at arrangement of woven-chopped-woven-chopped-woven at 690 MPa. This arrangement also showed the lowest water absorption of 4.5%. Comparing the single fibre type, woven had overtaken the others in terms of both mechanical and physical properties.

  20. Flexural behaviour of selected plants under static load

    Directory of Open Access Journals (Sweden)

    F. J. Sutili

    2010-02-01

    Full Text Available One of the principal purposes of soil bioengineering is the application of vegetation layers from a civil engineering point of view. Living plants are used to reinforce slopes and to control erosion. For a standardised implementation, it is essential to quantify the effectiveness and to assess technical parameters for such bioengineering systems. The objective of this study is to investigate the flexibility of stems and branches of different riparian species of the area of Southern Brazil suitable for soil bioengineering (Phyllanthus sellowianus Müll. Arg., Sebastiania schottiana (Müll. Arg. Müll. Arg., Salix humboldtiana Willd., and Salix×rubens Schrank. Fifty specimens (green stem samples were collected in the surroundings of Santa Maria, state of Rio Grande do Sul, Brazil, and subjected to static bending tests. Their overall deformation behaviour (elastic and plastic is of crucial importance for bioengineering systems. Thus, additional to the state of the art of material parameters, a new parameter is introduced: the "angle of flexibility". This parameter describes the elastic and plastic deformation behaviour of a plant under load in a more engineering practival experience. The results show that the species of Phyllanthus sellowianus is the most flexible species, followed by Sebastiania schottiana, Salix humboldtiana and Salix×rubens.

  1. Behaviour of bituminized ion-exchangers under repository conditions

    International Nuclear Information System (INIS)

    This is a final report containing all the research activities and results from the period 13 July 1997-28 February 2001. The purpose of the research was to study the ageing behaviour of bituminized ion-exchanger product under simulated repository conditions. The chosen temperature in this study was 5-8 deg. C and the equilibration solution used was artificial concrete water to simulate the conditions in the final disposal. The aim was to study the properties of wetted product as a release barrier for such important waste nuclides as Sr-90 and Cs-137, which are normal constituents of the bituminized ion-exchangers. All the nine exchanged waters were analysed by ion chromatography (IC) including the follow-up of the water absorption of the samples. All the samples, which were picked up for microscopic examination, have also been analysed. A saturation-elution test was performed with one diffusion sample using tritium (H-3) as a tracer. The results have been presented and further modelling will be performed later. Further two diffusion samples were tested using H-3, Na-22 and Cl-36 as radioactive tracers. The equilibration solution was artificial concrete ground water spiked with H-3 and Na-22 and in the other case with H-3 and Cl-36. Tritium was an internal reference when comparing the results of the equilibration behaviour of Na-22 and Cl-36. From the radioactive input cells samples were taken as a function of time to monitor the equilibration process. Elution of the samples and modelling of the results will be performed later. Na-22 and Cl-36 were chosen to demonstrate the behaviour of a simple anion and cation. Diffusion tests with important waste nuclides Sr-90 and Cs-137 have been scheduled to years 2001-2002. The aim of the performed research project was to study the barrier properties of the bituminized product. The measured parameters and modelling of the results will reflect the behaviour of the wetted product as a part of the multibarrier system providing

  2. Degradation behaviour of fiber reinforced plastic under electron beam irradiation

    International Nuclear Information System (INIS)

    Various mechanical properties of four kinds of glass fiber-reinforced plastics irradiated with electron beams were examined at three temperatures; room temperature, 123 K and 77 K. Dynamic viscoelastic properties were measured, and fractography by means of scanning electron microscopy was observed in order to clarify degradation behaviour. A considerable decrease in interlaminar shear strength (ILSS) at room temperature was observed above 60 MGy. On the other hand, the three-point bending strength at 77 K and the ILSS at 123 K decreased with increasing irradiation. Fractography reveals that the degradation of the interface layer between matrix resin and fiber plays an important role in the strength reduction at 123 K and 77 K. These findings suggest that the interface between matrix resin and fiber loses its bondability at 123 K arid 77 K after electron beam irradiation. (author)

  3. Calculation of mechanical strength of the bolts of the flanged joints of LWR-type reactor pressure vessels (with particular emphasis on the behaviour under critical internal excess pressure, acting like a ''safety valve''). 5. Technical report

    International Nuclear Information System (INIS)

    The reactor pressure vessel has to be made absolutely fail-safe towards excess primary loads (internal pressure). For this purpose, the vessel is equipped with safety valves (e.g. at the pressurizer) which normally are fully sufficient to master any pressure excursion. Nevertheless, a deterministic safety approach requires additional measures to ensure, in case of safety valve failure, control of the pressure so as to prevent reactor pressure vessel bursting. One way to achieve this is to make the flange joints plastify so strongly in the course of a pressure transient that the flange gap will sufficiently widen and thus behave like a 'safety valve'. In order to keep damage as small as possible, these parts should be easy to replace so that the bolts, or rather the washers, seem to be appropriate for modification. Tests have been made to ascertain whether reduction of bolt cross-sectional area (increase in admissible stress), or insertion of suitable washers is the best way to achieve reliable behaviour under normal conditions and also additional function in terms of a safety valve in case of pressure transients. For this purpose, model calculations have been made for all possible flange joints whith all possible stress variations and bolt dimensions. The event simulated is the ATWS', and the strength computations and stress analyses made for the flange joints of the pressure vessel of the Biblis reactor, unit B, are taken as an example. Main attention has been given to the forces affecting the bolts and to the forces acting between the reactor vessel head flange and the vessel flange under internal excess pressure. For assessment of the thermodynamic processes in case of an ATWS, the calculations made for the Grafenrheinfeld reactor have been taken as a basis. (orig.)

  4. Operational Behaviour of a Complex System Under Priority Repair Echelons

    Directory of Open Access Journals (Sweden)

    Anil Kumar

    1978-10-01

    Full Text Available A mathematical model is set up to evaluate the reliability of a complex system comprising two subsystems (with stand by redundancy in one subsystem. The failure and repair of units for both the subsystems follow exponential and general time distributions respectively. The switching over device for standby subsystem is not perfect and its repair is opportunistic. The repair for both subsystems is carried out under priority. The concept of waiting time for the repair of failed units in staidly subsystem has also been introduced. Supplementary variable and Laplace Transform techniques have been applied to obtain the transient state probabilities for such a system. From these pointwise availability has been evaluated. In the end, a particular case when repair follows exponential time distribution has been derived and asymptotic behaviour of such a system has also been examined.

  5. Molecular Mechanisms Underlying Pituitary Pathogenesis.

    Science.gov (United States)

    Sapochnik, Melanie; Nieto, Leandro Eduardo; Fuertes, Mariana; Arzt, Eduardo

    2016-04-01

    During the last years, progress has been made on the identification of mechanisms involved in anterior pituitary cell transformation and tumorigenesis. Oncogene activation, tumor suppressor gene inactivation, epigenetic changes, and microRNAs deregulation contribute to the initiation of pituitary tumors. Despite the high prevalence of pituitary adenomas, they are mostly benign, indicating that intrinsic mechanisms may regulate pituitary cell expansion. Senescence is characterized by an irreversible cell cycle arrest and represents an important protective mechanism against malignancy. Pituitary tumor transforming gene (PTTG) is an oncogene involved in early stages of pituitary tumor development, and also triggers a senescence response by activating DNA-damage signaling pathway. Cytokines, as well as many other factors, play an important role in pituitary physiology, affecting not only cell proliferation but also hormone secretion. Special interest is focused on interleukin-6 (IL-6) because its dual function of stimulating pituitary tumor cell growth but inhibiting normal pituitary cells proliferation. It has been demonstrated that IL-6 has a key role in promoting and maintenance of the senescence program in tumors. Senescence, triggered by PTTG activation and mediated by IL-6, may be a mechanism for explaining the benign nature of pituitary tumors. PMID:26718581

  6. Effect of Microstructure on the Electro-Mechanical Behaviour of Cu Films on Polyimide

    Science.gov (United States)

    Berger, J.; Glushko, O.; Marx, V. M.; Kirchlechner, C.; Cordill, M. J.

    2016-06-01

    Metal films on polymer substrates are commonly used in flexible electronic devices and may be exposed to large deformations during application. For flexible electronics, the main requirement is to remain conductive while stretching and compressing. Therefore, the electro-mechanical behaviour of 200-nm-thick Cu films on polyimide with two different microstructures (as-deposited and annealed) were studied by executing in situ fragmentation experiments with x-ray diffraction, under an atomic force microscope, and with 4-point probe resistance measurements in order to correlate the plastic deformation with the electrical behaviour. The three in situ techniques clearly demonstrate different behaviours controlled by the microstructure. Interestingly, the as-deposited film with a bi-modal microstructure is more suited for flexible electronic applications than an annealed film with homogenous 1- µm-sized grains. The as-deposited film reaches a higher yield stress, with unchanged electrical conductivity, and does not show extensive surface deformation during straining.

  7. Experimental study on the hydro-mechanical coupling behaviour of highly compacted expansive clay

    OpenAIRE

    Tang, Anh-Minh; Cui, Yu-Jun

    2010-01-01

    Highly compacted expansive clays have been usually considered as a possible material for sealing and backfill in deep geological disposal of radioactive waste. In this condition, the material is simultaneously subjected to water infiltration from the geological barrier and stresses generated by the swelling of engineered barriers in confined conditions. Its behaviour under hydro-mechanical loading is essential to the safe design of the whole storage system. In the present work, MX80 bentonite...

  8. Temperature effect on the poro-mechanical or hydraulic behaviour of a carbonated rock and a mortar: experimental studies

    International Nuclear Information System (INIS)

    The main objective of this study is to evaluate the temperature effect on the hydraulic and poro-mechanical behaviour of a limestone. Many experimental tests (porosity and permeability measurements, uniaxial and hydrostatic compressions tests) were carried out in order to study the thermal treatments effect and so the thermal microcracking effect on rock behaviour. Moreover, an experimental device for permeability measurements under high temperatures (until 200 C) was realized. This experimental device permitted to study the permeability variation of the limestone under thermal stresses. Finally, the behaviour of cementitious materials was studied; the temperature effect on the permeability of a mortar was examined. (author)

  9. Numerical model for thermal and mechanical behaviour of a CANDU 37-element bundle

    International Nuclear Information System (INIS)

    Prediction of transient fuel bundle deformations is important for assessing the integrity of fuel and the surrounding structural components under different operating conditions including accidents. For numerical simulation of the interactions between fuel bundle and pressure tube, a reliable numerical bundle model is required to predict thermal and mechanical behaviour of the fuel bundle assembly under different thermal loading conditions. To ensure realistic representations of the bundle behaviour, this model must include all of the important thermal and mechanical features of the fuel bundle, such as temperature-dependent material properties, thermal viscoplastic deformation in sheath, fuel-to-sheath interactions, endplate constraints and contacts between fuel elements. In this paper, we present a finite element based numerical model for predicting macroscopic transient thermal-mechanical behaviour of a complete 37-element CANDU nuclear fuel bundle under accident conditions and demonstrate its potential for being used to investigate fuel bundle to pressure tube interaction in future nuclear safety analyses. This bundle model has been validated against available experimental and numerical solutions and applied to various simulations involving steady-state and transient loading conditions. (author)

  10. Mechanical behaviour of composite materials made by resin film infusion

    Directory of Open Access Journals (Sweden)

    Casavola C.

    2010-06-01

    Full Text Available Innovative composite materials are frequently used in designing aerospace, naval and automotive components. In the typical structure of composites, multiple layers are stacked together with a particular sequence in order to give specific mechanical properties. Layers are organized with different angles, different sequences and different technological process to obtain a new and innovative material. From the standpoint of engineering designer it is useful to consider the single layer of composite as macroscopically homogeneous material. However, composites are non homogeneous bodies. Moreover, layers are not often perfectly bonded together and delamination often occurs. Other violations of lamination theory hypotheses, such as plane stress and thin material, are not unusual and in many cases the transverse shear flexibility and the thickness-normal stiffness should be considered. Therefore the real behaviour of composite materials is quite different from the predictions coming from the traditional lamination theory. Due to the increasing structural performance required to innovative composites, the knowledge of the mechanical properties for different loading cases is a fundamental source of concern. Experimental characterization of materials and structures in different environmental conditions is extremely important to understand the mechanical behaviour of these new materials. The purpose of the present work is to characterize a composite material developed for aerospace applications and produced by means of the resin film infusion process (RFI. Different tests have been carried out: tensile, open-hole and filled-hole tensile, compressive, openhole and filled-hole compressive. The experimental campaign has the aim to define mechanical characteristics of this RFI composite material in different conditions: environmental temperature, Hot/Wet and Cold.

  11. Metacognitive mechanisms underlying lucid dreaming.

    Science.gov (United States)

    Filevich, Elisa; Dresler, Martin; Brick, Timothy R; Kühn, Simone

    2015-01-21

    Lucid dreaming is a state of awareness that one is dreaming, without leaving the sleep state. Dream reports show that self-reflection and volitional control are more pronounced in lucid compared with nonlucid dreams. Mostly on these grounds, lucid dreaming has been associated with metacognition. However, the link to lucid dreaming at the neural level has not yet been explored. We sought for relationships between the neural correlates of lucid dreaming and thought monitoring. Human participants completed a questionnaire assessing lucid dreaming ability, and underwent structural and functional MRI. We split participants based on their reported dream lucidity. Participants in the high-lucidity group showed greater gray matter volume in the frontopolar cortex (BA9/10) compared with those in the low-lucidity group. Further, differences in brain structure were mirrored by differences in brain function. The BA9/10 regions identified through structural analyses showed increases in blood oxygen level-dependent signal during thought monitoring in both groups, and more strongly in the high-lucidity group. Our results reveal shared neural systems between lucid dreaming and metacognitive function, in particular in the domain of thought monitoring. This finding contributes to our understanding of the mechanisms enabling higher-order consciousness in dreams. PMID:25609624

  12. Molecular Mechanisms Underlying Hepatocellular Carcinoma

    Directory of Open Access Journals (Sweden)

    Christian Trepo

    2009-11-01

    Full Text Available Hepatocarcinogenesis is a complex process that remains still partly understood. That might be explained by the multiplicity of etiologic factors, the genetic/epigenetic heterogeneity of tumors bulks and the ignorance of the liver cell types that give rise to tumorigenic cells that have stem cell-like properties. The DNA stress induced by hepatocyte turnover, inflammation and maybe early oncogenic pathway activation and sometimes viral factors, leads to DNA damage response which activates the key tumor suppressive checkpoints p53/p21Cip1 and p16INK4a/pRb responsible of cell cycle arrest and cellular senescence as reflected by the cirrhosis stage. Still obscure mechanisms, but maybe involving the Wnt signaling and Twist proteins, would allow pre-senescent hepatocytes to bypass senescence, acquire immortality by telomerase reactivation and get the last genetic/epigenetic hits necessary for cancerous transformation. Among some of the oncogenic pathways that might play key driving roles in hepatocarcinogenesis, c-myc and the Wnt/β-catenin signaling seem of particular interest. Finally, antiproliferative and apoptosis deficiencies involving TGF-β, Akt/PTEN, IGF2 pathways for instance are prerequisite for cancerous transformation. Of evidence, not only the transformed liver cell per se but the facilitating microenvironment is of fundamental importance for tumor bulk growth and metastasis.

  13. A possible realization of Einstein's causal theory underlying quantum mechanics

    International Nuclear Information System (INIS)

    It is shown that a new microscopic mechanics formulated earlier can be looked upon as a possible causal theory underlying quantum mechanics, which removes Einstein's famous objections against quantum theory. This approach is free from objections raised against Bohm's hidden variable theory and leads to a clear physical picture in terms of familiar concepts, if self interactions are held responsible for deviations from classical behaviour. The new level of physics unfolded by this approach may reveal novel frontiers in high-energy physics. (author)

  14. Delamination behaviour of GdBCO coated conductor tapes under transverse tension

    Energy Technology Data Exchange (ETDEWEB)

    Gorospe, A. [Department of Mechanical Design Engineering, Andong National University, Andong 760-749 (Korea, Republic of); Department of Engineering, Aurora State College of Technology, Baler 3200 (Philippines); Nisay, A. [Department of Mechanical Design Engineering, Andong National University, Andong 760-749 (Korea, Republic of); Dizon, J.R. [Department of Mechanical Design Engineering, Andong National University, Andong 760-749 (Korea, Republic of); College of Engineering and Architecture, Bataan Peninsula State University, Balanga 2100 (Philippines); Shin, H.S., E-mail: hsshin@andong.ac.kr [Department of Mechanical Design Engineering, Andong National University, Andong 760-749 (Korea, Republic of)

    2013-11-15

    Highlights: •Installation of a test frame which gives precisely aligned transverse load. •Investigation of I{sub c} degradation behaviour depending on the type of sample delamination. •Inhomogeneity of the CC tapes caused large variation on delamination strength. •SEM and EDS analysis of delamination sites under transverse loading. -- Abstract: The electromechanical property behaviour of 2G coated conductor (CC) tapes fabricated by multi-layer deposition process both in the in-plane and transverse direction should be understood. The CC tapes are used in the fabrication of epoxy resin-impregnated coils. In such case, the Lorentz force due to the high magnetic field applied as well as the thermal stress due to the difference in coefficient of thermal expansion (CTE) among constituent layers during cooling to cryogenic temperature will induce transversely applied load to the surface of CC tapes in coils. Hence, the CC tape should have a good mechanical property in the transverse direction in order to maintain its superior performance under magnetic field. In this study, a test frame which gives precisely aligned transverse load was devised. Using the fixture, the delamination behaviours including the delamination strength of the GdBCO CC tapes under transverse tensile loading were investigated. Large variation on the delamination strength of the CC tapes was recorded and might have resulted from the slit edge effect and the inhomogeneity of the CC tapes. The I{sub c} degradation behaviour under transverse load was related to the location where delamination occurred in the sample.

  15. Behaviour of M30 Grade concrete with confinement under axial compression

    Directory of Open Access Journals (Sweden)

    C.Vinil Babu

    2014-09-01

    Full Text Available The strength and durability of concrete have undergone continuous improvement. Over the years and these improved materials are now commonly used. In the present experimental investigation the behaviour of M30 grade concrete with and without confinement for different percentages of replacement of silica fume is studied under axial compression as per IS mix design. The 150mm x 300mm cylindrical specimens were cast with and without confinement and investigating the mechanical properties like axial compressive strength and stress – strain behaviour. It was observed that the confinement of concrete has increased the 28days strength for different percentages of confinement and that the peak stress and corresponding strain at peak stress increased with increase in percentages of confinement

  16. Investigation of the hydro-mechanical behaviour of fouled ballast

    Institute of Scientific and Technical Information of China (English)

    Yu-jun CUI; Trong Vinh DUONG; Anh Minh TANG; Jean-Claude DUPLA; Nicolas CALON; Alain ROBINET

    2013-01-01

    In this study,a fouled ballast taken from the site of Sénissiat,France,was investigated.For the hydraulic behaviour,a large-scale cell was developed allowing drainage and evaporation tests to be carried out with monitoring of both suction and volumetric water content at various positions of the sample.It was observed that the hydraulic conductivity of fouled ballast is decreasing with suction increase,as for common unsaturated soils.The effect of fines content was found to be negligible.For the mechanical behaviour,both monotonic and cyclic triaxial tests were carried out using a large-scale triaxial cell.Various water contents were considered.The results were interpreted in terms of shear strength and permanent axial strain.It appeared that the water content is an important factor to be accounted for since any increase of water content or degree of saturation significantly decreases the shear strength and increases the permanent strain.Constitutive modelling has been attempted based on the experimental results.The model in its current state is capable of describing the effects of stress level,cycle number and water content.

  17. Multi-scale modelling of AISI H11 martensitic tool steel surface anisotropic mechanical behaviour

    Directory of Open Access Journals (Sweden)

    Zouaghi Ahmed

    2014-06-01

    Full Text Available In this work, a numerical investigation is carried out on the anisotropic and heterogeneous behaviour of the AISI H11 martensitic tool steel surface using finite element method and a multi-scale approach. An elasto-viscoplastic model that considers nonlinear isotropic and kinematic hardenings is implemented in the finite elements code ABAQUS using small strain assumption. The parameters of the constitutive equations are identified using macroscopic quasi-static and cyclic material responses by the mean of a localization rule. Virtual realistic microstructures, consisting of laths and grains, are generated using particular Voronoï tessellations. These microstructures consider the specific crystallographic orientations α’/γ. Finite element investigation is then performed. The local heterogeneous and anisotropic behaviour of the surface as well as the subsurface is shown under quasi-static and cyclic mechanical loadings. The laths morphology and crystallographic orientation have an important impact on the local mechanical fields.

  18. Dynamic Behaviour of Concrete Sandwich Panel under Blast Loading

    Directory of Open Access Journals (Sweden)

    Dong Yongxiang

    2009-01-01

    Full Text Available Surface contact explosion experiments were performed to study the dynamic behaviour of concrete sandwich panel subjected to blast loading. Experimental results have shown that there are four damage modes explosion cratering, scabbing of the backside, radial cracking induced failure, and circumferential cracking induced failure. It also illustrates that different foam materials sandwiched in the multi-layered medium have an important effect on damage patterns. Due to the foam material, the stress peak decreases one order of magnitude and the duration is more than four times that of the panel without the soft layer by numerical simulation. Additionally, the multi layered medium with concrete foam demonstrates the favourable protective property compared with that of aluminum foam. Meanwhile, the optimal analysis of the thickness of the foam material in the sandwich panel was performed in terms of experimental and numerical analyseis. The proper thickness proportion of soft layer is about 20 percent to the total thickness of sandwich panel under the conditions in this study.Defence Science Journal, 2009, 59(1, pp.22-29, DOI:http://dx.doi.org/10.14429/dsj.59.1480  

  19. Corrosion behaviour of fireside materials under oxyfuel conditions

    Energy Technology Data Exchange (ETDEWEB)

    Tuurna, Satu; Pohjanne, Pekka; Kinnunen, Tuomo; Jauhiainen, Petra [Research Centre of Finland, Espoo (Finland)

    2010-07-01

    Oxyfuel combustion is widely seen as a major option to facilitate carbon capture and storage (CCS) from future boiler plants utilizing clean coal technologies. Flue gas recirculation can increase the levels of fireside CO{sub 2}, SO{sub 2} and moisture, and thus promote fouling and corrosion. In this work, the oxidation behaviour of typical power plant steels was studied in the simulated oxyfuel conditions (3.6% O{sub 2}-60% CO{sub 2}-30% H{sub 2}O-6,4% Ar). The experiments were carried out in multi-sample furnaces in a temperature range between 580 and 650 C. Test duration was up to 1000 h. Corrosion resistance was evaluated through metallographic examination and mass change measurements. The results are presented and compared to corresponding results from simulated air firing conditions (1.8% O{sub 2}-74.2% N{sub 2}-16% CO{sub 2}O-8%H{sub 2}O Ar). This paper presents the oxidation performance of alloys T22 (10CrMo9-10), X20CrMoV11-1, TP347HFG, HR3C and Sanicro 25 under simulated combustion conditions. (orig.)

  20. Microscopic approaches for understanding the mechanical behaviour of reinforcement in composites

    CERN Document Server

    Durville, Damien

    2012-01-01

    An approach to the mechanical behaviour of textile composites at the scale of their constituting fibres, using an implicit finite element simulation code, is proposed in this chapter. The approach is based on efficient methods and algorithms to detect and take into account contact-friction interactions between elementary fibres. It allows one to model samples of woven textile composites made of a few hundreds of fibres, with an elastic matrix. The approach is employed first to determine the initial configuration of woven fabric samples, before applying to them various loadings in order to identify their mechanical properties under various solicitations

  1. A review of mechanical behaviour and stress effects in hard superconductors

    International Nuclear Information System (INIS)

    The mechanical properties of type II superconducting materials are reviewed as well as the effect of stress on the superconducting properties of these materials. The bcc alloys Nb-Ti and Nb-Zr exhibit good strength and extensive ductility at room temperature. Mechanical tests on these alloys at 4.2 K revealed serrated stress-strain curves, non-linear elastic effects, and reduced ductility. The non-linear behaviour is probably due to twinning and de-twinning or a reversible stress-induced martensitic transformation. The brittle A-15 compound superconductors, such as Nb3Sn and V3Ga, exhibit unusual elastic properties and structural instabilities at cryogenic temperatures. Multifilamentary composites consisting of superconducting filaments in a normal metal matrix are normally used for superconducting devices. The mechanical properties of alloy and compound composites, tapes, as well as composites of niobium carbonitride chemically vapour deposited on high strength carbon fibres are presented. Hysteretic stress-strain behaviour in the metal matrix composites produces significant heat generation, an effect which may lead to degradation in performance of high field magnets. Measurements of the critical current density, Jsub(c), under stress in a magnetic field are reported. Modest stress-reversible degradation in Jsub(c) is observed in Nb-Ti composites while more serious degradation is found in Nb3Sn samples. The importance of mechanical behaviour on device performance is discussed. (author)

  2. Proceedings of a specialist meeting on the behaviour of water reactor fuel elements under accident conditions

    International Nuclear Information System (INIS)

    The contributions of this meeting report experimental, numerical and research investigations on the oxidation behaviour of zircaloy in case of a loss-of-coolant accident (LOCA), analysis of the kinetics of the oxidation rate, very high temperature behaviour of fuel rod claddings (failure mechanics, ballooning), the interaction between cladding and fuel, the mechanical behaviour of zircaloy, etc. Numerous experimental and computer code analysis results are given

  3. Behaviour and failure of C-Mn steel in presence of ageing under strain

    International Nuclear Information System (INIS)

    As carbon-manganese (C-Mn) steels are largely used in various mechanical applications, and more particularly in secondary circuit pipes of pressurized water nuclear reactors (PWR), this research thesis reports the behaviour and failure modelling of such a steel within a large temperature domain (between 20 and 350 deg C). Tensile tests have been performed on smooth samples and on notches axisymmetric samples, and tear tests have been performed on CT samples. The model of Es trin Kubin-McCormick which takes ageing under strain into account has been used to simulate most of the effects of ageing under strain: negative sensitivity of flow stress to strain rate, Luders bands, PLC effect, modification of tensile mechanical properties, so on. The model is applied to the considered samples. In order to predict the failure of notched specimens, a failure local approach has been applied

  4. Tribological behaviour of conventional Al–Sn and equivalent Al–Pb alloys under lubrication

    Indian Academy of Sciences (India)

    J P Pathak; S Mohan

    2003-04-01

    Two compositions of conventional aluminium base alloys were selected and equal amounts of tin and lead as a soft phase were incorporated separately. Impeller mixing and chill casting technique were employed for the preparation of the alloys. Mechanical properties of as cast alloys were evaluated at room temperature. Frictional behaviour of the alloys was studied in detail under lubrication while creating different frictional states by imposing 5–60 kg of normal load on the bearing (bush) mating surface. It was found that aluminium tin and leaded aluminium alloys slightly differ in mechanical properties. Frictional states created during sliding against steel shaft (hardness 55–60 Rc) under oil lubrication were not much different. Leaded aluminium alloy bushes show marginally lower friction than the conventional ones.

  5. Empathy as a driver of prosocial behaviour: highly conserved neurobehavioural mechanisms across species.

    Science.gov (United States)

    Decety, Jean; Bartal, Inbal Ben-Ami; Uzefovsky, Florina; Knafo-Noam, Ariel

    2016-01-19

    Empathy reflects the natural ability to perceive and be sensitive to the emotional states of others, coupled with a motivation to care for their well-being. It has evolved in the context of parental care for offspring, as well as within kinship bonds, to help facilitate group living. In this paper, we integrate the perspectives of evolution, animal behaviour, developmental psychology, and social and clinical neuroscience to elucidate our understanding of the proximate mechanisms underlying empathy. We focus, in particular, on processing of signals of distress and need, and their relation to prosocial behaviour. The ability to empathize, both in animals and humans, mediates prosocial behaviour when sensitivity to others' distress is paired with a drive towards their welfare. Disruption or atypical development of the neural circuits that process distress cues and integrate them with decision value leads to callous disregard for others, as is the case in psychopathy. The realization that basic forms of empathy exist in non-human animals is crucial for gaining new insights into the underlying neurobiological and genetic mechanisms of empathy, enabling translation towards therapeutic and pharmacological interventions. PMID:26644596

  6. Fracture mechanics behaviour of neutron irradiated Alloy A-286

    International Nuclear Information System (INIS)

    The effect of fast-neutron irradiation on the fatigue-crack propagation and fracture toughness behaviour of Alloy A-286 was characterized using fracture mechanics techniques. The fracture toughness was found to decrease continuously with increasing irradiation damage at both 24 deg. C and 427 deg. C. In the unirradiated and low fluence conditions, specimens displayed appreciable plasticity prior to fracture, and equivalent Ksub(Ic) values were determined from Jsub(Ic) fracture toughness results. At high irradiation exposure levels, specimens exhibited a brittle Ksub(Ic) fracture mode. The 427 deg. C fracture toughness fell from 129 MPa√m in the unirradiated condition to 35 MPa√m at an exposure of 16.2 dpa (total fluence of 5.2x1022n/cm2). Room temperature fracture toughness values were consistently 40 to 60 percent higher than the 427 deg. C values. Electron fractography revealed that the reduction in fracture resistance was attributed to a fracture mechanism transition from ductile microvoid coalescence to channel fracture. Fatigue-crack propagation tests were conducted at 427 deg. C on specimens irradiated at 2.4 dpa and 16.2 dpa. Crack growth rates at the lower exposure level were comparable to those in unirradiated material, while those at the higher exposure were slightly higher than in unirradiated material. (author)

  7. MECHANICAL BEHAVIOUR OF ALUMINA-ZIRCONIA COMPOSITE BY SLURRY METHOD

    Directory of Open Access Journals (Sweden)

    JYOTI PRAKASH

    2011-02-01

    Full Text Available Alumina has got some excellent properties like chemical inertness, thermal and mechanical strength against hazardous environment. Alumina is a good ceramic material which is being used for structuralapplications. To enhance the toughness and strength of the body some Zirconia is also used with it. The use of Zirconia in alumina is known as toughening of alumina. One difficulty arises, when alumina and alumina toughened composite are sintered , because the low sinterability of Alumina-Zirconia forced the compact to give very low density body. To overcome this problem alumina and alumina composites are made from slurry method which gives nearly theoretical density. The combined effect of alumina and Zirconia on the phase transformation and microstructure development of heat-treated Alumina-Zirconia composites has been studied. Slurry is prepared by adding water, dispersant, binder and anti-foaming agent. In the present study, Sintering schedule is optimized and kept constant for all samples. After sintering, mechanical behaviour of the composite has been studied.

  8. Microstructural characterisation and constitutive behaviour of alloy RR1000 under fatigue and creep-fatigue loading conditions

    International Nuclear Information System (INIS)

    Mechanical behaviour of a nickel-based superalloy, RR1000, has been investigated at 650 deg. C under cyclic and dwell loading conditions. The microstructural characteristics of the alloy have been studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the distribution patterns of the dislocations and slip planes have been compared between samples tested under fatigue and creep-fatigue loading conditions. Constitutive behaviour of the alloy was described by a unified constitutive model, where both cyclic plastic and viscoplastic strains were represented by one inelastic strain. The results show that the precipitation state is very stable at 650 deg. C and only minor differences exist in the dislocation arrangements formed under pure fatigue and combined creep and fatigue conditions. Hence, a unified constitutive model seems to be justified in describing and predicting the constitutive behaviour in both cases.

  9. Science under pressure: problematic behaviours and social harms

    Directory of Open Access Journals (Sweden)

    Rita Faria

    2014-09-01

    Full Text Available This paper will suggest the use of the Social Harm Approach (Hillyard, Pantazis, Tobs & Gordon, 2004 to problematic behaviours occurring in scientific research and higher education teaching. By analyzing data collected through interviews to scholars, it is possible to state that fabrication, falsification and plagiarism are the most criticized deviant behaviours in science. It is less common for actors to consider other problematic behaviours arising from the pressure (to publish, to get grants felt by them and originated at the heart of the organizations devoted to science. Or problematic behaviours created on the intersection of universities, corporations and/or the state (ex. commissioned research. Also, those interviewed did not have a coherent view on the rules governing science and higher education. Thus, considering the scattering of (individual and organizational problematic behaviours and rules governing them, a new approach will be put forward, one by which processes of scientific production and dissemination must be considered according to the social harms (financial, economic, physical they may cause.

  10. Mechanical behaviour of PEM fuel cell catalyst layers during regular cell operation

    Energy Technology Data Exchange (ETDEWEB)

    Al-Baghdadi, Maher A.R. Sadiq [Fuel Cell Research Center, International Energy & Environment Foundation, Al-Najaf, P.O.Box 39 (Iraq)

    2010-07-01

    Damage mechanisms in a proton exchange membrane fuel cell are accelerated by mechanical stresses arising during fuel cell assembly (bolt assembling), and the stresses arise during fuel cell running, because it consists of the materials with different thermal expansion and swelling coefficients. Therefore, in order to acquire a complete understanding of the mechanical behaviour of the catalyst layers during regular cell operation, mechanical response under steady-state hygro-thermal stresses should be studied under real cell operating conditions and in real cell geometry (three-dimensional). In this work, full three-dimensional, non-isothermal computational fluid dynamics model of a PEM fuel cell has been developed to investigate the behaviour of the cathode and anode catalyst layers during the cell operation. A unique feature of the present model is to incorporate the effect of hygro and thermal stresses into actual three-dimensional fuel cell model. In addition, the temperature and humidity dependent material properties are utilize in the simulation for the membrane. The model is shown to be able to understand the many interacting, complex electrochemical, transport phenomena, and deformation that have limited experimental data.

  11. Mechanical behaviour of PEM fuel cell catalyst layers during regular cell operation

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2010-11-01

    Full Text Available Damage mechanisms in a proton exchange membrane fuel cell are accelerated by mechanical stresses arising during fuel cell assembly (bolt assembling, and the stresses arise during fuel cell running, because it consists of the materials with different thermal expansion and swelling coefficients. Therefore, in order to acquire a complete understanding of the mechanical behaviour of the catalyst layers during regular cell operation, mechanical response under steady-state hygro-thermal stresses should be studied under real cell operating conditions and in real cell geometry (three-dimensional. In this work, full three-dimensional, non-isothermal computational fluid dynamics model of a PEM fuel cell has been developed to investigate the behaviour of the cathode and anode catalyst layers during the cell operation. A unique feature of the present model is to incorporate the effect of hygro and thermal stresses into actual three-dimensional fuel cell model. In addition, the temperature and humidity dependent material properties are utilize in the simulation for the membrane. The model is shown to be able to understand the many interacting, complex electrochemical, transport phenomena, and deformation that have limited experimental data.

  12. Peeling mechanism of tomato under infrared heating

    Science.gov (United States)

    Critical behaviors of peeling tomatoes using infrared heat are thermally induced peel loosening and subsequent cracking. However, the mechanism of peel loosening and cracking due to infrared heating remains unclear. This study aimed at investigating the mechanism of peeling tomatoes under infrared h...

  13. Influence of the mechanical stress and the filler content on the hydrostatic compression behaviour of natural rubber

    International Nuclear Information System (INIS)

    The behaviour of natural rubber (NR) compounds under mechanical stress is often reported in literature. An important and widely discussed effect that occurs is the Mullins effect. During the first loading cycles in a tensile test for example, a stress-softening effect is observed. This and other effects on the mechanical behaviour are investigated for different rubber materials with and without different types of fillers and filler contents. Besides, the hydrostatic compression behaviour is affected by the type and content of filler as well, which is shown for an NR with and without waxes and different contents of carbon black (CB) in this contribution. In contrast to the Mullins effect, there is no dependence of the number of loading cycles on the volumetric behaviour determined in hydrostatic compression tests. Furthermore, the influence of the previous stress-softening due to mechanical stress on the compression behaviour is elaborated. Cyclic uniaxial tensile tests are performed to realize the stress-softening in the rubber materials. The subsequent compression tests are compared to compression tests without any pre-stretching to determine the influence of previous mechanical loading on the compression behaviour of natural rubber with different filler contents

  14. Mechanical behaviour of silicon carbide submitted to high temperature

    International Nuclear Information System (INIS)

    Ceramics (composite ceramics) are considered materials for manufacturing structure pieces of future nuclear reactor cores. In condition of nominal running, the temperature of these components is estimated at 500-800 C and could reach 1600 C in accidental condition. On account of its refractory properties and of its good compatibility with neutron flux, silicon carbide is retained for such applications, particularly for fuel cladding material (SiC/SiC composite). A study aiming to specify the mechanical behaviour of the monolithic αSiC (hexagonal structure) between 1000 and 1500 C as well as its evolution after ionic irradiation is presented. This study presents particularly the mechanical characterizations of SiC in three points bending obtained until 1450 C and surface characterizations led on SiC irradiated with ions. The rupture tests in three points bending carried out in temperature on specimens pre-cracked by indentation show an increase of 85% of the SiC rupture stress between 1000 and 1300 C. Above 1300 C, the damage of SiC induces a significant decrease of the rupture stress. Aniso-thermal creep tests on polished specimens show that the SiC presents a viscoplastic behaviour from 1200 C. Surface characterizations by Raman spectroscopy, micro and nano-indentation, acoustic microscopy led at ambient temperature on fresh and irradiated to Xe ions (94 MeV) SiC at 400 C are presented too. The formation of a structural disorder and of Si-Si homonuclear bonds disorder, suggesting a SiC amorphization, are revealed by Raman spectroscopy between 3*1014 and 3.6*1015 ions/cm2 of fluence. These microstructural changes lead to a macroscopic swelling quantifiable by measuring the height of the step formed during irradiations between the non irradiated and irradiated areas. Measurements by profilometry show that between 3*1014 and 1.2*1015 ions/cm2 of fluence, the height of the step increases of 47 nm to 83 nm, and then is stabilized with the fluence increase. The

  15. Selfish-herd behaviour of sheep under threat

    OpenAIRE

    King, A. J.; Wilson, A. M.; Wilshin, S. D.; J. Lowe; Haddadi, H.; Hailes, S; Morton, A. J.

    2012-01-01

    Flocking is a striking example of collective behaviour that is found in insect swarms, fish schools and mammal herds [1]. A major factor in the evolution of flocking behaviour is thought to be predation, whereby larger and/or more cohesive groups are better at detecting predators (as, for example, in the ‘many eyes theory’), and diluting the effects of predators (as in the ‘selfish-herd theory’) than are individuals in smaller and/or dispersed groups [2]. The former theory assumes that inform...

  16. Mechanical and thermal behaviour of U–Mo and U–Nb–Zr Alloys

    International Nuclear Information System (INIS)

    Nuclear fuels composed of uranium alloys in monolithic and dispersed forms are being considered for research and compact power reactors due to their density properties (greater than 15 g-U/cm3) and fast heat transfer. U–Nb–Zr and U–Mo alloys are the most promising systems for plate fuel elements owing to their broad γ-phase stability field, which shows higher ductility and isotropic behaviour, allowing extensive fabrication capability. In the present work, γ-phase stabilized U–7.5Nb–2.5Zr and U–10Mo alloys were characterized by mechanical and thermal analyses for comparison of their behaviour under deformation and heat-treatment. The results demonstrate that the alloys have substantially different properties regarding deformation, kinetics phase transformation and recovery/recrystallization. The main results show that U–Nb–Zr is superior regarding fabrication capabilities although the γ-phase is less stable than U–Mo alloys

  17. Smooth modeling of oblique contact with friction of turbine blades: behaviour analysis under random excitation

    International Nuclear Information System (INIS)

    This paper deals with modelling of oblique contact with friction generated by touch of shrouds placed at the blade's end of a pressure turbine of nuclear plant. Two phenomenons emerge from the nonlinearity due to contact between shrouds: contact without sliding and with sliding. The nonlinearity is characterized by a nonlinear differential equation based on smooth hysteresis model proposed by BOUC and generalized by WEN. There is contact without sliding up to a level of contact strength and then sliding. This level is a function of normal strength (at contact point) that is linked to system motion. This contact is considered always hold. Here, the blade is considered as a cantilever beam and the shroud as an oblique support on the beam. The dynamical displacement in two perpendicular directions of axis beam are studied. The smooth hysteresis model equation governing contact behaviour couple up vibrations in 2 transverse directions of beam. The paper presents the setting up of modelization of contact with friction, mechanical behaviour of the smooth hysteresis model with contact strength linked to system motion under random excitation. A sensibility analysis is mode on standard deviation in relation to excitation level by means of MONTE CARLO simulation and NEWMARK step-by-step method of integration. This model allows three contact behaviour types: contact without sliding, sliding with constant step dry friction force and sliding with increasing step dry friction force. Results are compared satisfactorily with experimental results. (authors). 3 refs., 8 figs

  18. Study of mechanical properties of nanomaterials under high pressure

    Science.gov (United States)

    Sharma, Jyoti; Kaur, Namrat; Srivastava, A. K.

    2015-08-01

    In the present work, the study of physical properties and behaviour of nanomaterials i.e. n-γ- Al2O3and n-Si3C4 under high pressure is done. For this purpose Murnaghan equation of state is used. The applicability of Murnaghan equation of state is fully tested by calculating mechanical properties of nano materials i.e. volume compression (V/Vo), bulk modulus (KT) and relative isothermal compression coefficient (α(P)/α0) at different pressures. The present calculated values of compression curve for the cited nanomaterials come out to be in reasonable good agreement with the available experimental data.

  19. A study on the mechanical behaviour of WC/Co hardmetals

    OpenAIRE

    Ferreira, J. A. M.; Amaral, M. A. Pina; Antunes, F. V.; Costa, J. D. M.

    2008-01-01

    The hardmetal cutting tools used in machining are submitted to extreme conditions in terms of temperature and mechanical loading. A better understanding of the failure of cutting tools and capability to predict tool life are key factors in the development of new tool materials with improved mechanical behaviour. Main failure mechanisms are wear, thermal-mechanical fatigue and brittle fracture. The aim of present work is to study the mechanical behaviour of two hardmetals. The properties studi...

  20. Nanoscale grain growth behaviour of CoAl intermetallic synthesized by mechanical alloying

    Indian Academy of Sciences (India)

    S N Hosseini; M H Enayati; F Karimzadeh

    2014-05-01

    Grain growth behaviour of the nanocrystalline CoAl intermetallic compound synthesized by mechanical alloying has been studied by isothermal annealing at different temperatures and durations. X-ray diffraction method was employed to investigate structural evolutions during mechanical alloying and annealing processes. The disordered CoAl phase with the grain size of about 6 nm was formed via a gradual reaction during mechanical alloying. The results of isothermal annealing showed that the grain growth behaviour can be explained by the parabolic grain growth law. The grains were at nanometric scale after isothermal annealing up to 0.7 m. The grain growth exponent remained constant above 873 K indicating that grain growth mechanism does not change at high temperatures. The calculated activation energy indicated that the grain growth mechanism in the disordered CoAl phase at high temperatures was diffusing Co and Al atoms in two separate sublattices. Furthermore, an equation has been suggested to describe the grain growth kinetics of nanocrystalline CoAl under isothermal annealing at temperatures above 873 K (/m ≥ 0.5).

  1. Numerical modelling of the time-dependent mechanical behaviour of softwood

    DEFF Research Database (Denmark)

    Engelund, Emil Tang

    2010-01-01

    When using wood as a structural material it is important to consider its time-dependent mechanical behaviour and to predict this behaviour for decades ahead. For this purpose, several rheological mathematical models, spanning from fairly simple to very complex ones, have been developed over the...... microfibrils. This assumption is incorporated in the numerical model by only allowing non-elastic behaviour in shear deformation modes in the local coordinate system. The rate of shearing is described by deformation kinetics. The results indicate that time-dependent behaviour such as creep and relaxation...... mechanisms causing the observed mechanical behaviour. In this study, the mechanical behaviour of softwood tracheids is described using numerical modelling. The basic composition and orientation of the tracheid constituents is incorporated by establishing a local coordinate system aligned with the...

  2. Chaotic behaviour of Zeeman machines at introductory course of mechanics

    Science.gov (United States)

    Nagy, Péter; Tasnádi, Péter

    2016-05-01

    Investigation of chaotic motions and cooperative systems offers a magnificent opportunity to involve modern physics into the basic course of mechanics taught to engineering students. In the present paper it will be demonstrated that Zeeman Machine can be a versatile and motivating tool for students to get introductory knowledge about chaotic motion via interactive simulations. It works in a relatively simple way and its properties can be understood very easily. Since the machine can be built easily and the simulation of its movement is also simple the experimental investigation and the theoretical description can be connected intuitively. Although Zeeman Machine is known mainly for its quasi-static and catastrophic behaviour, its dynamic properties are also of interest with its typical chaotic features. By means of a periodically driven Zeeman Machine a wide range of chaotic properties of the simple systems can be demonstrated such as bifurcation diagrams, chaotic attractors, transient chaos and so on. The main goal of this paper is the presentation of an interactive learning material for teaching the basic features of the chaotic systems through the investigation of the Zeeman Machine.

  3. EDSPA, 1-D Mechanical Displacement for Elastic, Thermoelastic, Viscoelastic Behaviour

    International Nuclear Information System (INIS)

    1 - Description of program or function: EDSPA solves the one dimensional mechanical displacement equation in radial (sphere) axisymmetric cylindrical (infinite cylinder, slab) coordinates. The constitutive laws for the material to be considered can comprise the - elastic and/or - thermoelastic and/or - viscoplastic behaviour. The boundary conditions allow to prescribe displacement and/or stress values. The delivered version of EDSPA is especially suitable for the calculation of borehole problems in rock salt (heater boreholes or free converging boreholes or caverns) where convergence rates and/or contact pressures are of interest. 2 - Method of solution: The coarse-mesh method is used to transform the displacement differential equation (quasi-stationary case: second order ordinary differential equation as a two point boundary value problem) into a system of algebraic equations. This three-diagonal system is solved with the Thomas algorithm (direct solver). 3 - Restrictions on the complexity of the problem: Because of EDSPA's simple one-dimensional formulation there are no restrictions for storage allocation and argument ranges

  4. Metallurgical and mechanical behaviours of PWR fuel cladding tube oxidised at high temperature

    International Nuclear Information System (INIS)

    Zirconium alloys are used as cladding materials in Pressurized Water Reactors (PWR). As they are submitted to very extreme conditions, it is necessary to check their behaviour and especially to make sure they meet the safety criteria. They are therefore studied under typical in service-loadings but also under accidental loadings. In one of these accidental scenarios, called Loss of Coolant Accident (LOCA) the cladding temperature may increase above 800 C, in a steam environment, and decrease before a final quench of the cladding. During this temperature transient, the cladding is heavily oxidised, and the metallurgical changes lead to a decrease of the post quench mechanical properties. It is then necessary to correlate this drop in residual ductility to the metallurgical evolutions. This is the problem we want to address in this study: the oxidation of PWR cladding materials at high temperature in a steam environment and its consequences on post quench mechanical properties. As oxygen goes massively into the metallic part - a zirconia layer grows at the same time - during the high temperature oxidation, the claddings tubes microstructure shows three different phases that are the outer oxide layer (zirconia) and the inner metallic phases (α(O) and 'ex β') - with various mechanical properties. In order to reproduce the behaviour of this multilayered material, the first part of this study consisted in creating samples with different - but homogeneous in thickness - oxygen contents, similar to those observed in the different phases of the real cladding. The study was especially focused on the β-->α phase transformation upon cooling and on the resulting microstructures. A mechanism was proposed to describe this phase transformation. For instance, we conclude that for our oxygen enriched samples, the phase transformation kinetics upon cooling are ruled by the oxygen partitioning between the two allotropic phases. Then, these materials were mechanically tested at

  5. Mechanical and microstructural behaviour of Y2O3 ODS EUROFER 97

    International Nuclear Information System (INIS)

    Two small ingots of the steel EUROFER 97, one containing 0.25 wt% Y2O3 and the other Y2O3 free, have been produced by consolidating mechanically milled powder by hot isostatic pressing at 1373 K for 2 h under 200 MPa. For comparison, a third ingot was consolidated under identical conditions but using un-milled EUROFER powder. Microhardness, tensile and Charpy tests, along with TEM observations, have been performed on these materials in the as-HIPed condition and after different heat treatments. The mechanical behaviour and the microstructural characteristics of these materials suggest that the origin of the reduced impact properties of the oxide dispersion strengthened EUROFER could be the premature formation of carbides during quenching following the HIP process. This would be enhanced by the high density of structural defects produced by milling, as these favour the fast diffusion and segregation of carbon

  6. Sex differences and serotonergic mechanisms in the behavioural effects of psilocin.

    Science.gov (United States)

    Tylš, Filip; Páleníček, Tomáš; Kadeřábek, Lukáš; Lipski, Michaela; Kubešová, Anna; Horáček, Jiří

    2016-06-01

    Psilocybin has recently attracted a great deal of attention as a clinical research and therapeutic tool. The aim of this paper is to bridge two major knowledge gaps regarding its behavioural pharmacology - sex differences and the underlying receptor mechanisms. We used psilocin (0.25, 1 and 4 mg/kg), an active metabolite of psilocybin, in two behavioural paradigms - the open-field test and prepulse inhibition (PPI) of the acoustic startle reaction. Sex differences were evaluated with respect to the phase of the female cycle. The contribution of serotonin receptors in the behavioural action was tested in male rats with selective serotonin receptor antagonists: 5-HT1A receptor antagonist (WAY100635 1 mg/kg), 5-HT2A receptor antagonist (MDL100907 0.5 mg/kg), 5-HT2B receptor antagonist (SB215505 1 mg/kg) and 5-HT2C receptor antagonist (SB242084 1 mg/kg). Psilocin induced dose-dependent inhibition of locomotion and suppression of normal behaviour in rats (behavioural serotonin syndrome, impaired PPI). The effects were more pronounced in male rats than in females. The inhibition of locomotion was normalized by 5-HT1A and 5-HT2B/C antagonists; however, PPI was not affected significantly by these antagonists. Our findings highlight an important issue of sex-specific reactions to psilocin and that apart from 5-HT2A-mediated effects 5-HT1A and 5-HT2C/B receptors also play an important role. These findings have implications for recent clinical trials. PMID:26461483

  7. Experimental study of thermo-hydro-mechanical behaviour of Callovo-Oxfordian Clay-stone

    International Nuclear Information System (INIS)

    During the different phases of the exothermic radioactive waste deep disposal (excavation, operation) and after permanent closure, the host rock is submitted to various coupled mechanical, hydraulic and thermal phenomena. Hence, a thorough investigation of the thermo-hydro-mechanical behaviour of the rock is necessary to complete existing data and to better understand and model the short and long term behaviour of the Callovo-Oxfordian (COx) clay formation in Bure (Meuse/Haute-Marne - M/HM), considered by ANDRA as a potential host rock in France.In this work, the compression - swelling behaviour of the COx Clay-stone was first investigated by carrying out a series of high-pressure oedometric tests. The results, interpreted in terms of coupling between damage and swelling, showed that the magnitude of swelling was linked to the density of the fissures created during compression. In a second step, the hydro-mechanical and thermo-hydro-mechanical behaviour of the saturated Clay-stone under a mean stress close to the in situ one were investigated by using two devices with short drainage path (10 mm), namely a isotropic cell and a newly designed hollow cylinder triaxial cell with local displacement measurements. These devices helped to solve two majors problems related to testing very low permeability materials: i) a satisfactory previous sample saturation (indicated by good Skempton values) and ii) satisfactory drainage conditions. Some typical constitutive parameters (Skempton and Biot's coefficients, drained and undrained compressibility coefficients) have been determined at ambient temperature through isotropic compression tests that also confirmed the transverse isotropy of the Clay-stone. The consistency of the obtained parameters has been checked in a saturated poro-elastic framework. Two aspects of the thermo-hydro-mechanical behaviour of the COx Clay-stone have then been investigated through different heating tests and through drained and undrained isotropic

  8. Mechanical Buckling of Veins under Internal Pressure

    OpenAIRE

    Martinez, Ricky; Fierro, Cesar A.; Shireman, Paula K.; Han, Hai-Chao

    2010-01-01

    Venous tortuosity is associated with multiple disease states and is often thought to be a consequence of venous hypertension and chronic venous disease. However, the underlying mechanisms of vein tortuosity are unclear. We hypothesized that increased pressure causes vein buckling that leads to a tortuous appearance. The specific aim of this study was to determine the critical buckling pressure of veins. We determined the buckling pressure of porcine jugular veins and measured the mechanical p...

  9. Study on the mechanical behaviour of the cold forged niobium as function of the cross section reduction

    International Nuclear Information System (INIS)

    This work aims to study he mechanical behaviour of commercially pure niobium (99.8 % purity) obtained by means of aluminothermic reduction followed by electron beam melting and refining. Eleven groups of specimens were analyzed under tensile tests, with different degrees of reduction (cold working), using rotary forging. Significant alterations were observed in the mechanical properties in all processing steps. Using electron scanning microscopy, the main characteristics of the fracture surface were studied. (author)

  10. Health Behaviours As a Mechanism in the Prospective Relation between Workplace Reciprocity and Absenteeism: A Bridge too Far ?

    Directory of Open Access Journals (Sweden)

    Bart De Clercq

    Full Text Available The persistent lack of evidence on causal mechanisms between social capital and health threatens the credibility of the social capital-health association. The present study aims to address this ongoing problem by investigating whether health behaviours (i.e. smoking, alcohol consumption, and physical activity mediate the prospective relation between workplace reciprocity and future sickness absence.A cohort of 24,402 Belgian employees was followed up during 12 months for sickness absence. Workplace reciprocity was measured with four indicators-colleague help, colleague interest, supervisor help, and supervisor concern. Three types of multilevel mediation models were applied.Overall, workplace reciprocity negatively related to high sickness absence (≥ 10 days mainly independently from health behaviours. Uniquely, colleague interest positively related to smoking (OR = 1.058, 95% CI = 1.019, 1.098 and smoking in turn, positively related to sickness absence (OR = 1.074, 95% CI = 1.047, 1.101. No behavioural pathways could be identified between company-level reciprocity and sickness absence, and company-level health-related behaviours did not mediate the relation between company-level reciprocity and individual sickness absence.These results suggest that both social capital and health behaviours are relevant for employee health, but health behaviours seem not to be the underlying explanatory mechanism between workplace reciprocity and health.

  11. A comparative study of the effects of constructional elements on the mechanical behaviour of dragonfly wings

    Science.gov (United States)

    Rajabi, H.; Rezasefat, M.; Darvizeh, A.; Dirks, J.-H.; Eshghi, Sh.; Shafiei, A.; Mostofi, T. Mirzababaie; Gorb, S. N.

    2016-01-01

    Although wings of insects show a large variation in morphology, they are all made from a network of irregular veins interconnected through membranous areas. Depending on their shape, size, and position, wing veins are usually divided into three different groups: longitudinal veins, cross-veins and ambient veins. The veins together with the membrane and some other elements such as spines, nodus and pterostigma can be considered as the wing's "constructional elements". In spite of rather extensive literature on dragonfly wing structure, the role of each of these elements in determining the wing's function remains mostly unknown. As this question is difficult to answer in vivo using biomechanical experiments on actual wings, this study was undertaken to reveal the effects of the constructional elements on the mechanical behaviour of dragonfly wings by applying numerical simulations. An image processing technique was used to develop 12 finite element models of the insect wings with different constructional elements. The mechanical behaviour of these models was then simulated under normal and shear stresses due to tension, bending and torsion. A free vibration analysis was also performed to determine the resonant frequencies and the mode shapes of the models. For the first time, a quantitative comparison was carried out between the mechanical effects selectively caused by different elements. Our results suggest that the complex interactions of veins, membranes and corrugations may considerably affect the dynamic deformation of the insect wings during flight.

  12. An experimental and constitutive investigation on the chemo-mechanical behaviour of a clay

    OpenAIRE

    Witteveen, Paul Joost; Ferrari, Alessio; LALOUI, Lyesse

    2013-01-01

    Engineering issues for which the understanding of the chemo-mechanical behaviour of soils is relevant include wellbore stability problems, the sali-nification of groundwater and nuclear waste storage, etc. However, despite the vast number of situations in which couplings between chemistry and mechanics occur, the available constitutive models rely on limited experimental evidence. This paper presents the results of an experimental program on the chemo-mechanical behaviour of a non-swelling il...

  13. Modelling of thermal and mechanical behaviour of pebble beds

    International Nuclear Information System (INIS)

    FZK (Forshungzentrum Karlsruhe) is developing a Helium Cooled Pebble Bed (HCPB) Blanket Concept for fusion power reactors based on the use of ceramic breeder materials and beryllium multiplier in the form of pebble beds. The design of such a blanket requires models and computer codes describing the thermal-mechanical behavior of pebble beds to evaluate the temperatures, stresses, deformations and mechanical interactions between pebble beds and the structure with required accuracy and reliability. The objective to describe the beginning of life condition for the HCPB blanket seems near to be reached. Mechanical models that describe the thermo-mechanical behavior of granular materials used in form of pebble beds are implemented in a commercial structure code. These models have been calibrated using the results of a large series of dedicated experiments. The modeling work is practically concluded for ceramic breeder; it will be carried on in the next year for beryllium to obtain the required correlations for creep and the thermal conductivity. The difficulties for application in large components (such as the HCPB blanket) are the limitations of the present commercial codes to manage such a set of constitutive equations under complex load conditions and large mesh number. The further objective is to model the thermal cycles during operation; the present correlations have to be adapted for the release phase. A complete description of the blanket behavior during irradiation is at the present out of our capability; this objective requires an extensive R and D program that at the present is only at the beginning. (Y.Tanaka)

  14. 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.)

  15. Failure mechanisms in thin rubber sheet composites under static solicitation

    Directory of Open Access Journals (Sweden)

    E. Bayraktar

    2007-03-01

    Full Text Available Purpose: Mechanical behaviour and damage mechanisms in thin rubber sheet composites were investigated under static solicitation at room temperature. Two types of rubber are used in this study; Natural rubber, NR vulcanised and reinforced by carbon black and Synthetic rubber (styrene-butadiene-rubber, SBR.Design/methodology/approach: A comprehensive study has been carried out in order to identify a threshold criterion for the damage mechanism to explain a tearing criterion for the concept of tearing energy of the elastomers and also to give a detail for the damage mechanism depending on the loading conditions. A typical type of specimen geometry of thin sheet rubber composite materials was studied under static tensile tests conducted on the smooth and notched specimens with variable depths. In this way, the effects of the plane stress on the damage mechanism are characterized depending on the rubber materials.Findings: Damage mechanisms during tensile test have been described for both of rubber types and the criteria which characterize the tearing resistance, characteristic energy for tearing (T was explained. Damage in the specimens were evaluated just at the beginning of the tearing by means of the observations in the scanning electron microscopy (SEM.Practical implications: A tearing criterion was suggested in the case of simple tension conditions by assuming large strain. In the next step of this study, a finite element analysis (FEA will be applied under the same conditions of this part in order to obtain the agreement between experimental and FEA results.Originality/value: This study propses a threshold criterion for the damage just at the beginning of the tearing for thin sheet rubber composites and gives a detail discussion for explaining the damage mechanisms by SEM results. This type of study gives many facilities for the sake of simplicity in industrial application.

  16. Stress and the social brain: behavioural effects and neurobiological mechanisms.

    Science.gov (United States)

    Sandi, Carmen; Haller, József

    2015-05-01

    Stress often affects our social lives. When undergoing high-level or persistent stress, individuals frequently retract from social interactions and become irritable and hostile. Predisposition to antisocial behaviours - including social detachment and violence - is also modulated by early life adversity; however, the effects of early life stress depend on the timing of exposure and genetic factors. Research in animals and humans has revealed some of the structural, functional and molecular changes in the brain that underlie the effects of stress on social behaviour. Findings in this emerging field will have implications both for the clinic and for society. PMID:25891510

  17. Comportamento mecânico de tendões calcâneo bovino sob informações clínicas Mechanical behaviour of bovine calcaneous tendon under ciclic deformations

    Directory of Open Access Journals (Sweden)

    Sergio Rocha Piedade

    2006-02-01

    Full Text Available Este trabalho teve por finalidade analisar o comportamento de tendões calcâneo bovino submetidos a ensaios mecânicos cíclicos. Para cada corpo de prova foram aplicados três ensaios de dez ciclos de tração e três níveis de deformação: 2,5%, 3% e 4%. Ao término de cada ensaio o tendão era mantido em repouso por 300 s. A velocidade de carregamento adotada foi de 10% do comprimento do corpo de prova, por segundo. Os resultados obtidos foram submetidos à análise de variância com delineamento de parcelas subdivididas no tempo e blocos casualizados nas subparcelas. Conclui-se que o pré-tensionamento de tendões realizado através da deformação relativa permanece como parâmetro mais seguro, por atuar dentro dos limites fisiológicos do tendão, evitando os efeitos nocivos do sobretensionamento.This research work reports an experimental study on the mechanical behavior of bovine calcaneous tendons. A total number of 03 cyclic relaxation tests with 10 cycles respectively at 2,5%, 3%, and 4% of deformation were performed for each specimen. The specimens were kept at rest for 300 s between tests. Deformation rates were maintained at 10% of initial length per second. Cyclic relaxation tests carried on all tendons showed that the average force correspondent to the first cycle was statistically significatively greater than the average force correspondent to the tenth cycle. This also emphasizes the occurrence of a force relaxation phenomena. It can be concluded that tendons pre-tensionning by means of specific deformations stands for a safer parameter because it acts within the tendon biological limits avoyding the overtensioning negative effects.

  18. Behavioural, hormonal and neurobiological mechanisms of aggressive behaviour in human and nonhuman primates.

    Science.gov (United States)

    de Almeida, Rosa Maria Martins; Cabral, João Carlos Centurion; Narvaes, Rodrigo

    2015-05-01

    Aggression is a key component for social behaviour and can have an adaptive value or deleterious consequences. Here, we review the role of sex-related differences in aggressive behaviour in both human and nonhuman primates. First, we address aggression in primates, which varies deeply between species, both in intensity and in display, ranging from animals that are very aggressive, such as chimpanzees, to the nonaggressive bonobos. Aggression also influences the hierarchical structure of gorillas and chimpanzees, and is used as the main tool for dealing with other groups. With regard to human aggression, it can be considered a relevant adaptation for survival or can have negative impacts on social interaction for both sexes. Gender plays a critical role in aggressive and competitive behaviours, which are determined by a cascade of physiological changes, including GABAergic and serotonergic systems, and sex neurosteroids. The understanding of the neurobiological bases and behavioural determinants of different types of aggression is fundamental for minimising these negative impacts. PMID:25749197

  19. Behaviour of a few mode fiber modal pattern under stress

    Science.gov (United States)

    Egalon, Claudio O.; Rogowski, Robert S.

    1991-01-01

    A numerical model was developed to calculate the interference pattern at the end of a multimode weakly guiding optical fiber under stress. Whenever an optical fiber is under stress, the modal phase in the interference term of the intensity formula changes. Plots of the simulated output of a stressed fiber are presented. For multimode fibers, very complicated patterns result. Under stress, lobes in the pattern are generated, displaced and power is exchanged among them.

  20. Fundamentals of soil behaviour

    OpenAIRE

    Gens Solé, Antonio

    2009-01-01

    The paper reviews in summary form the generalised behaviour of soils under nonisothermal and chemically varying conditions. This generalised soil behaviour underlies the performance of a number of ground improvement techniques. The behaviour of frozen soil is examined first showing that some concepts of unsaturated soil mechanics appear to be readily applicable. Afterwards, the observation that volumetric behaviour of saturated and unsaturated soils at high temperature is similar, leads to th...

  1. The behaviour of ferritic steels under fast neutron irradiation

    International Nuclear Information System (INIS)

    Ferritic steels have been irradiated in Rapsodie and Phenix to doses up to 150 dpa F. The swelling and irradiation creep characteristics and the mechanical properties of these materials are reported. (author)

  2. Effect of heat treatment upon the mechanical and poro-mechanical behaviour of cement-based materials: hydraulic properties and morphological changes

    International Nuclear Information System (INIS)

    This work investigates the effects of morphological changes of a cement-based material subjected to heat treatment (up to 400 C). For a model W/C=0.5 mortar, we have characterized experimentally hydraulic behaviour (gas permeability), mechanical behaviour (in uniaxial compression, hydrostatic compression with or without deviatoric stress) and poro-mechanical behaviour (incompressibility moduli Kb, Ks and Biot's coefficient b) after a heating/cooling cycle. We have also developed an original experiment aimed at quantifying the accessible pore space volume under hydrostatic compression. The creation of occluded porosity under high confinement is confirmed, which justifies the observed decrease of solid matrix rigidity Ks under high confinement. A gas retention phenomenon was identified under simultaneous thermal and hydrostatic loadings for mortar, and industrial concretes (provided by CERIB and ANDRA). A predictive thermo-elasto-plastic model with isotropic damage and a micro-mechanical approach, which represents micro-cracking, are coupled in order to analyze or predict the evolution of mechanical and poro-elastic properties after heat cycling. (author)

  3. Mechanical characteristics and microcosmic mechanisms of granite under temperature loads

    Institute of Scientific and Technical Information of China (English)

    XU Xiao-li; GAO Feng; SHEN Xiao-ming; XIE He-ping

    2008-01-01

    The relationships between mechanical characteristics of rock and microcosmic mechanism at high temperatures were investigated by MTS815, as well as the stress-strain behavior of granite under the action of temperatures ranging from room tem-perature to 1200 ℃. Based on a micropore structure analyzer and SEM, the changes in rock porosity and micro'structural mor-phology of sample fractures and brittle-plastic characteristics under high temperatures were analyzed. The results are as follows: 1) Mechanical characteristics do not show obvious variations before 800 ℃; strength decreases suddenly after 800 ℃ and bearing capacity is almost lost at 1200 ℃. 2) Rock porosity increases with rising temperatures; the threshold temperature is about 800 ℃;at this temperature its effect is basically uniform with strength decreasing rapidly. 3) The failure type of granite is a brittle tensile fracture at temperatures below 800 ℃ which transforms into plasticity at temperatures higher than 800 ℃ and crystal formation takes place at this time. Chemical reactions take place at 1200 ℃. Failure of granite under high temperature is a common result of thermal stress as indicated by an increase in the thermal expansion coefficient, transformation to crystal formation of minerals and structural chemical reactions.

  4. A model of multisecond timing behaviour under peak-interval procedures.

    Science.gov (United States)

    Hasegawa, Takayuki; Sakata, Shogo

    2015-04-01

    In this study, the authors developed a fundamental theory of interval timing behaviour, inspired by the learning-to-time (LeT) model and the scalar expectancy theory (SET) model, and based on quantitative analyses of such timing behaviour. Our experiments used the peak-interval procedure with rats. The proposed model of timing behaviour comprises clocks, a regulator, a mixer, a response, and memory. Using our model, we calculated the basic clock speeds indicated by the subjects' behaviour under such peak procedures. In this model, the scalar property can be defined as a kind of transposition, which can then be measured quantitatively. The Akaike information criterion (AIC) values indicated that the current model fit the data slightly better than did the SET model. Our model may therefore provide a useful addition to SET for the analysis of timing behaviour. PMID:25539685

  5. Elastic behaviour of terbium metaphosphate glasses under high pressures

    International Nuclear Information System (INIS)

    The elastic and nonlinear acoustic vibrational properties of terbium metaphosphate glasses (Tb2O3)x(P2O5) 1-x with x = 0.226, 0.247, 0.263 and 0.271 (x is the mole fraction) have been determined from measurements of the effects of temperature, hydrostatic pressure, and uniaxial stress on ultrasonic wave velocity. At temperatures below about 140 K, the elastic stiffness CSIJ of (Tb2O3)x(P2O5) 1x glasses becomes anomalously dependent upon temperature, a behaviour usually associated with interactions between acoustic phonons and two-level systems. Except for the (Tb2O3) 0.271 (P-2O5) 0.729 glass, the hydrostatic pressure derivatives of the elastic stiffness and als of the bulk modulus BS of terbium metaphosphate glasses are small and negative. The third-order elastic stiffness tensor components CIJK of the (TbSO3)0.247(P205)0.753 glass between 77 K and 400 K have also been determined. Both longitudinal and shear acoustic mode Grueneisen parameters are small and negative: the application of pressure softens the long-wavelength acoustic phonon mode frequencies. The mode softening is enhanced as the temperature is reduced. 33 refs., 2 tab., 7 figs

  6. The behaviour of spherical HTR fuel elements under accident conditions

    International Nuclear Information System (INIS)

    Hypothetical accidents may lead to significantly higher temperatures in HTR fuel than during normal operation. In order to obtain meaningful statements on fission product behaviour and release, irradiated spherical fuel elements containing a large number of coated particles (20,000-40,000) with burnups between 6 and 16% FIMA were heated at temperatures between 1400 and 2500 deg. C. HTI-pyrocarbon coating retains the gaseous fission products (e.g. Kr) very well up to about 2400 deg. C if the burnup does not exceed the specified value for THTR (11.5%). Cs diffuses through the pyrocarbon significantly faster than Kr and the diffusion is enhanced at higher fuel burnups because of irradiation induced kernel microstructure changes. Below about 1800 deg. C the Cs release rate is controlled by diffusion in the fuel kernel; above this temperature the diffusion in the pyrocarbon coating is the controlling parameter. An additional SiC coating interlayer (TRISO) ensures Cs retention up to 1600 deg. C. However, the release obtained in the examined fuel elements was only by a factor of three lower than through the HTI pyrocarbon. Solid fission products added to UO2-TRISO particles to simulate high burnup behave in various ways and migrate to attack the SiC coating. Pd migrates fastest and changes the SiC microstructure making it permeable

  7. Loading path effect on the mechanical behaviour and fivefold twinning of copper nanowires

    International Nuclear Information System (INIS)

    The effect of loading path on the mechanical behaviour of single crystalline copper nanowires is investigated with molecular dynamics simulations. Different loading conditions including pre-tensile torsion and pre-torsional tension at different temperatures are taken into consideration. It is found that elastic pre-loading conditions can induce a distinct weakening on the resistance against plastic deformation under later applied loads. Meanwhile, coupled thermal and pre-loading effect can also facilitate the transformation from elasticity to plasticity. Formations of fivefold twins are observed in copper nanowires subjected to the loading path with tension after pre-torsion. These fivefold twins all form at the necking stage before fracture, and are found to be pre-torsion- and size-dependent but insensitive to the change in temperature and cross-sectional shape. The results reported here indicate that the loading path effect on the mechanical behaviour plays an important role in the formation of some special microstructures such as multiple twins in metallic nanowires.

  8. DNA under Force: Mechanics, Electrostatics, and Hydration

    Directory of Open Access Journals (Sweden)

    Jingqiang Li

    2015-02-01

    Full Text Available Quantifying the basic intra- and inter-molecular forces of DNA has helped us to better understand and further predict the behavior of DNA. Single molecule technique elucidates the mechanics of DNA under applied external forces, sometimes under extreme forces. On the other hand, ensemble studies of DNA molecular force allow us to extend our understanding of DNA molecules under other forces such as electrostatic and hydration forces. Using a variety of techniques, we can have a comprehensive understanding of DNA molecular forces, which is crucial in unraveling the complex DNA functions in living cells as well as in designing a system that utilizes the unique properties of DNA in nanotechnology.

  9. Effect of dolomite decomposition under CO2 on its multicycle CO2 capture behaviour under calcium looping conditions.

    Science.gov (United States)

    de la Calle Martos, Antonio; Valverde, Jose Manuel; Sanchez-Jimenez, Pedro E; Perejón, Antonio; García-Garrido, Cristina; Perez-Maqueda, Luis A

    2016-06-28

    One of the major drawbacks that hinder the industrial competitiveness of the calcium looping (CaL) process for CO2 capture is the high temperature (∼930-950 °C) needed in practice to attain full calcination of limestone in a high CO2 partial pressure environment for short residence times as required. In this work, the multicycle CO2 capture performance of dolomite and limestone is analysed under realistic CaL conditions and using a reduced calcination temperature of 900 °C, which would serve to mitigate the energy penalty caused by integration of the CaL process into fossil fuel fired power plants. The results show that the fundamental mechanism of dolomite decomposition under CO2 has a major influence on its superior performance compared to limestone. The inert MgO grains resulting from dolomite decomposition help preserve a nanocrystalline CaO structure wherein carbonation in the solid-state diffusion controlled phase is promoted. The major role played by the dolomite decomposition mechanism under CO2 is clearly demonstrated by the multicycle CaO conversion behaviour observed for samples decomposed at different preheating rates. Limestone decomposition at slow heating rates yields a highly crystalline and poorly reactive CaCO3 structure that requires long periods to fully decarbonate and shows a severely reduced capture capacity in subsequent cycles. On the other hand, the nascent CaCO3 produced after dolomite half-decomposition consists of nanosized crystals with a fast decarbonation kinetics regardless of the preheating rate, thus fully decomposing from the very first cycle at a reduced calcination temperature into a CaO skeleton with enhanced reactivity as compared to limestone derived CaO. PMID:27253328

  10. Behavioural modelling of irrigation decision making under water scarcity

    Science.gov (United States)

    Foster, T.; Brozovic, N.; Butler, A. P.

    2013-12-01

    Providing effective policy solutions to aquifer depletion caused by abstraction for irrigation is a key challenge for socio-hydrology. However, most crop production functions used in hydrological models do not capture the intraseasonal nature of irrigation planning, or the importance of well yield in land and water use decisions. Here we develop a method for determining stochastic intraseasonal water use that is based on observed farmer behaviour but is also theoretically consistent with dynamically optimal decision making. We use the model to (i) analyse the joint land and water use decision by farmers; (ii) to assess changes in behaviour and production risk in response to water scarcity; and (iii) to understand the limits of applicability of current methods in policy design. We develop a biophysical model of water-limited crop yield building on the AquaCrop model. The model is calibrated and applied to case studies of irrigated corn production in Nebraska and Texas. We run the model iteratively, using long-term climate records, to define two formulations of the crop-water production function: (i) the aggregate relationship between total seasonal irrigation and yield (typical of current approaches); and (ii) the stochastic response of yield and total seasonal irrigation to the choice of an intraseasonal soil moisture target and irrigated area. Irrigated area (the extensive margin decision) and per-area irrigation intensity (the intensive margin decision) are then calculated for different seasonal water restrictions (corresponding to regulatory policies) and well yield constraints on intraseasonal abstraction rates (corresponding to aquifer system limits). Profit- and utility-maximising decisions are determined assuming risk neutrality and varying degrees of risk aversion, respectively. Our results demonstrate that the formulation of the production function has a significant impact on the response to water scarcity. For low well yields, which are the major concern

  11. Hybridoma cell behaviour in continuous culture under hyperosmotic stress.

    Science.gov (United States)

    Cherlet, M; Marc, A

    1999-01-01

    In this paper, we propose an alternative strategy to the ones proposed before (Oh et al., 1993; Øyaas et al., 1994a) to get real increases of global final antibody titer and production at hyperosmotic stress, by reducing the detrimental effect of such a stress on cell growth, and conserving the stimulating effect on antibody production. It consists of cultivating the cells in continuous culture and increasing the osmolality stepwise. In this way, the cells could progressively adapt to the higher osmolality at each step and antibody titers could be nearly doubled at 370 and 400 mOsm kg-1, compared to the standard osmolality of 335 mOsm kg-1. Surprisingly, the stimulation of antibody production was not confirmed for higher osmolalities, 425 and 450 mOsm kg- 1, despite the minor negative effect on cell growth. Intracellular IgG analysis by flow cytometry revealed at these osmolalities a significant population of non-producing cells. However, even when taking into account this non-producing population, a stimulating effect on antibody production could not be shown at these highest osmolalities. It seems to us that osmolality has a significant effect on the appearance of these non-producing cells, since they were not observed in continuous cultures at standard osmolality, of comparable duration and at an even higher dilution rate. The appearance of the non-producing cells coincides furthermore with modifications of the synthesised antibody, as shown by electrophoretic techniques. It is however not really clear if these two observations reflect actually the same phenomenon. Hyperosmolality affects the cell behaviour in continuous culture in multiple ways, independently of the growth rate, counting all at least partially for the observed stimulation of antibody production: acceleration of the amino acid, and in particular the glutamine metabolism, increase of the cell volume, increase of the intracellular pH and accumulation of cells in the G1 cell cycle phase. PMID

  12. Mechanical Properties and Fracture Behaviour of Multilayer Alumina Composites

    Institute of Scientific and Technical Information of China (English)

    ZHENG Xinguo; ZHAO Fei; ZHANG Jinyong

    2015-01-01

    Adopting a ceramic/polymer multilayer structure design to simulate the structure of nacre is usually believed to be an effective way to increase the toughness of ceramic composites at the expense of the material's bending strength. However, in this study, we found that both the bending strength and the toughness could be improved simultaneously when using a certain Al2O3/Kevlar multilayer composite design compared to pure alumina samples with the same dimensions. The fracture behaviour of the Al2O3/Kevlar multilayer composite was studied to ifnd a reason for this improvement. The results showed that the complex and asymmetrical stresses occurring in the Kevlar-reinforced layers were the main reason for the differences in fracture behaviour. We expect our results to open up new ways for the design of future high performance ceramic composites.

  13. Aero dynamical and mechanical behaviour of the Savonius rotor

    Energy Technology Data Exchange (ETDEWEB)

    Aouachria, Z. [Batna Univ., (Algeria). Applied Energetic Physics Laboratory

    2009-07-01

    Although the Savonius wind turbine is not as efficient as the traditional Darrieus wind turbine, its rotor design has many advantages such as simple construction; acceptance of wind from all directions; high starting torque; operation at relatively low speed; and easy adaptation to urban sites. These advantages may outweigh its low efficiency and make it suitable for small-scale power requirements such as pumping and rural electrification. This paper presented a study of the aerodynamic behaviour of a Savonius rotor, based on blade pressure measurements. A two-dimensional analysis method was used to determine the aerodynamic strengths, which leads to the Magnus effect and the generation of the vibrations on the rotor. The study explained the vibratory behaviour of the rotor and proposed an antivibration system to protect the machine. 14 refs., 1 tab., 9 figs.

  14. The behaviour of Phenix fuel pin bundle under irradiation

    International Nuclear Information System (INIS)

    An entire Phenix sub-assembly has been mounted and sectioned after irradiation. The examination of cross-sections revealed the effects of mechanical interaction in the bundle (ovalisations and contacts between clads). According to analysis of the sodium channels, cooling of the pin bundle remained uniform. (author)

  15. Microstructural, mechanical and electrochemical behaviour of a 7017 Al–Zn–Mg alloy of different tempers

    International Nuclear Information System (INIS)

    The aim of the investigation is to assess the microstructural features and associated physical, mechanical and electrochemical properties of a 7017 Al–Zn–Mg alloy of various tempers. A 7017 Al–Zn–Mg alloy was subjected to different ageing schedules to produce under-(T4), peak-(T6), over-(T7) and highly over-aged tempers. Optical microscopy, hardness measurement, electrical conductivity measurement, tensile testing and SEM fractographs, differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and electrochemical polarization studies have been used to characterize the alloy tempers. Hardness measurement and tensile testing showed the characteristic age hardening phenomenon of aluminium alloys. Optical and TEM micrographs have revealed the variation in size of matrix strengthening η′ (MgZn2) and also the size and distribution of grain boundary η (MgZn2) precipitate with ageing time. DSC thermograms exhibiting exothermic and endothermic peaks indicated the characteristic solid state reaction sequence of the 7017 alloy. Potentiodynamic polarization study of the 7017 alloy of various tempers in 3.5 wt.% NaCl solution at near neutral pH showed typical active metal dissolution behaviour, but at pH 12 an active–passive–transpassive transition behaviour has been observed. - Graphical abstract: TEM micrograph of the 7017 aluminium alloy of various tempers (a, b) under aged (T4), (c, d) peak aged (T6), (e, f) over aged (T7) and (g, h) highly over-aged. Display Omitted - Highlights: • 7017 Al-Zn-Mg alloy was subjected to different artificial ageing treatments. • Characterization of 7017 alloy tempers by hardness, tensile, DSC, TEM and electrochemical behaviour. • Structure-properties relationship of the 7017 Al-Zn-Mg alloy of various tempers

  16. Microstructural, mechanical and electrochemical behaviour of a 7017 Al–Zn–Mg alloy of different tempers

    Energy Technology Data Exchange (ETDEWEB)

    Rout, Prasanta Kumar, E-mail: prasantonnet55@yahoo.com; Ghosh, M.M.; Ghosh, K.S., E-mail: ksghosh2001@yahoo.co.uk

    2015-06-15

    The aim of the investigation is to assess the microstructural features and associated physical, mechanical and electrochemical properties of a 7017 Al–Zn–Mg alloy of various tempers. A 7017 Al–Zn–Mg alloy was subjected to different ageing schedules to produce under-(T4), peak-(T6), over-(T7) and highly over-aged tempers. Optical microscopy, hardness measurement, electrical conductivity measurement, tensile testing and SEM fractographs, differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and electrochemical polarization studies have been used to characterize the alloy tempers. Hardness measurement and tensile testing showed the characteristic age hardening phenomenon of aluminium alloys. Optical and TEM micrographs have revealed the variation in size of matrix strengthening η′ (MgZn{sub 2}) and also the size and distribution of grain boundary η (MgZn{sub 2}) precipitate with ageing time. DSC thermograms exhibiting exothermic and endothermic peaks indicated the characteristic solid state reaction sequence of the 7017 alloy. Potentiodynamic polarization study of the 7017 alloy of various tempers in 3.5 wt.% NaCl solution at near neutral pH showed typical active metal dissolution behaviour, but at pH 12 an active–passive–transpassive transition behaviour has been observed. - Graphical abstract: TEM micrograph of the 7017 aluminium alloy of various tempers (a, b) under aged (T4), (c, d) peak aged (T6), (e, f) over aged (T7) and (g, h) highly over-aged. Display Omitted - Highlights: • 7017 Al-Zn-Mg alloy was subjected to different artificial ageing treatments. • Characterization of 7017 alloy tempers by hardness, tensile, DSC, TEM and electrochemical behaviour. • Structure-properties relationship of the 7017 Al-Zn-Mg alloy of various tempers.

  17. Behavioural mechanisms behind aggregation in a tritrophic perspective

    OpenAIRE

    Stephan, Jörg

    2016-01-01

    Gregarious organisms need to handle the trade-off between positive effects of group living and increasing food competition. The gregarious Phratora vulgatissima, a specialist leaf beetle on willow in Europe and Asia, frequently reaches outbreak densities in natural stands and short rotation coppices. Outbreaks threaten the yield and plantations therefore rely on omnivorous predators as biocontrol agents, like Anthocoris nemorum and Orthotylus marginalis. I aimed to elucidate behavioural mecha...

  18. Behaviour of Japanese Quail Eggs Under Mechanical Compression

    Czech Academy of Sciences Publication Activity Database

    Buchar, J.; Nedomová, Š.; Trnka, Jan; Strnková, J.

    2015-01-01

    Roč. 18, č. 5 (2015), s. 1110-1118. ISSN 1094-2912 Institutional support: RVO:61388998 Keywords : quail egg * compression * rupture force Subject RIV: GM - Food Processing Impact factor: 0.915, year: 2014 http://www.tandfonline.com/doi/abs/10.1080/10942912.2013.862634#.VNI0aC7z_PM

  19. Influence of different mechanisms on the constitutive behaviour of textile reinforced concrete

    OpenAIRE

    Hartig, Jens; Jesse, Frank; Häußler-Combe, Ulrich

    2009-01-01

    Textile Reinforced Concrete shows a complex load-bearing behaviour, which depends on material properties of the composite constituents and load transfer mechanisms in between. These properties cannot be modified arbitrarily in experimental investigations, which complicates identification of the impact of certain mechanisms on composite’s behaviour. In this respect, theoretical investigations offer the possibility to study the influence of individual parameters. At first, experimental results ...

  20. The behaviour of high-temperature steels under thermal load

    International Nuclear Information System (INIS)

    The different demands made on plants under thermal stress have been the reason for the development of a multitude of high-temperature steels. Mn, Cr, Ni, Mo and, in small amounts, V, W, Nb, and B are used as alloying metals in order to increase temperature and scaling resistance. They induce structural changes and the formation of finely distributed carbides, nitrides, and intermetallic phases which inhibit creep at higher temperatures. The present report discusses the development of this sort of steel, the high-temperature properties of the materials, the calculation of components under thermal stress, as well as testing and control measures. (GSC)

  1. DIFFERENT ROOF BEHAVIOUR UNDER DIFFERENT UPPER MINING BOUNDARY CONDITION IN DATONG

    Institute of Scientific and Technical Information of China (English)

    康立勋

    1997-01-01

    Understanding roof behaviour and immediate roof failure patterns of Iongwall face is a prerequisite for establishing correct roof control theory and appplying effective roof control measures. Roof behaviour and immediate roof failure pattern have a close relationship with upper mining boundary conditions of Iongwall face. According to actual situation of Datong Mining Area, upper mining boundary conditions of Iongwall face have been classified into 5 types in this paper. Roof behaviour and immediate roof failure pattern under each upper mining boundary condition are discussed in details.

  2. Investigation on mechanical behaviour of AM60 magnesium alloys

    Directory of Open Access Journals (Sweden)

    C. Yan

    2008-12-01

    Full Text Available Purpose: In this work, tension, impact, bend and fatigue tests were conducted in an AM60 magnesium alloy. The effects of environmental temperature and loading rates on impact and tension behavior of the alloy were also investigated.Design/methodology/approach: The tests were conducted using an Instron universal testing machine. The loading speed was changed from 1 mm/min to 300 mm/min to gain a better understanding of the effect of strain rate. To understand the failure behavior of this alloy at different environmental temperatures, Charpy impact test was conducted in a range of temperatures (-40~35°C. Plane strain fracture toughness (KIC was evaluated using compact tension (CT specimen. To gain a better understanding of the failure mechanisms, all fracture surfaces were observed using scanning electron microscopy (SEM. In addition, fatigue behavior of this alloy was estimated using tension test under tension-tension condition at 30 Hz. The stress amplitude was selected in the range of 20~50 MPa to obtain the S-N curve.Findings: The tensile test indicated that the mechanical properties were not sensitive to the strain rates applied (3.3x10-4~0.1 and the plastic deformation was dominated by twining mediated slip. The impact energy is not sensitive to the environmental temperature. The plane strain fracture toughness and fatigue limit were evaluated and the average values were 7.6 MPa.m1/2 and 25 MPa, respectively. Practical implications: Tested materials AM60 Mg alloy can be applied among others in automotive industry aerospace, communication and computer industry.Originality/value: Many investigations have been conducted to develop new Mg alloys with improved stiffness and ductility. On the other hand, relatively less attention has been paid to the failure mechanisms of Mg alloys, such as brittle fracture and fatigue, subjected to different environmental or loading conditions. In this work, tension, impact, bend and fatigue tests were conducted

  3. The behaviour of weldable strain gauges under nuclear reactor core conditions

    International Nuclear Information System (INIS)

    Highlights: • Electrical resistance strain gauges can be used in nuclear reactor environments. • Several in-reactor experiments featuring the use of strain gauges are described. • Static and dynamic strain can be measured under the very hostile conditions of nuclear reactor cores. • Irradiation effects can be corrected if they are well understood and precisely quantified. -- Abstract: Electrical resistance strain gauges are a very useful tool to measure mechanical parameters such as deformation, stress, dynamic strain, vibration, etc. This paper presents our experience with strain gauges in nuclear reactor environments. The nature of nuclear applications and the desirable characteristics of nuclear strain gauges are discussed. Several in-reactor experiments featuring the use of strain gauges are described. The behaviour of weldable strain gauges under intense nuclear radiation is discussed. Experimental results and techniques for the successful applications of strain gauges in nuclear environments are presented. It is concluded that weldable stain gauges can be used successfully under the very hostile conditions of nuclear reactor cores if appropriate procedures are followed

  4. Mechanical behaviour of nitrogen-implanted aluminium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Guzman, L. [Centro Materiali e Biofisica Medica, Trento (Italy); Bonini, G. [Dipt. di Ingegneria Nucleare del Politecnico, Milano (Italy); Adami, M. [Dipt. di Meccanica Strutturale, Univ. degli Studi di Trento (Italy); Ossi, P.M. [Dipt. di Ingegneria Nucleare del Politecnico, Milano (Italy)]|[Trento Univ., Povo (Italy). Dipt. di Fisica; Miotello, A. [Ist. Nazionale per la Fisica della Materia, Univ. degli Studi di Trento (Italy)]|[Trento Univ., Povo (Italy). Dipt. di Fisica; Vittori-Antisari, M. [ENEA, C.R. Casaccia, Settore Nuovi Materiali, Roma (Italy); Serventi, A.M. [ENEA, C.R. Casaccia, Settore Nuovi Materiali, Roma (Italy); Voltolini, E. [Centro Materiali e Biofisica Medica, Trento (Italy)

    1996-09-01

    The effect of nitrogen implantation into pure aluminium has been extensively explored, taking into account the variation of several physical and technological properties of the implanted layer. In particular, the formation of aluminium nitride, which occurs under specific choices of the implantation parameters, is associated with an increase in hardness. In this work, we consider two Al alloys (Al-7075 and Al-2011), frequently employed in the mechanical industry, with properties strongly dependent on the thermomechanical treatment. Molecular nitrogen bombardment at 150 keV (75 keV N{sup +}) was employed, up to a total dose of 3.10{sup 17} N cm{sup -2}, varying the substrate temperature from 373 to 473 K. The samples were then characterized with respect to composition, structure, morphology, microhardness, scratch resistance (also performing multi-pass testing) and friction coefficient. The results were interpreted within the framework of micromechanical models describing the hardness of thin coatings deposited onto soft substrates; the microhardness of the implanted layer increased by a factor of five. It appears that nitrogen-implanted aluminium alloy layers, in spite of their shallow thickness, behave better than hard TiN coated surfaces. Care must be taken to implant both alloys at the lowest possible temperature to avoid degradation of the substrate properties. (orig.)

  5. Mechanical behaviour of Bioactive Glass granules and morselized cancellous bone allograft in load bearing defects.

    Science.gov (United States)

    Hulsen, D J W; Geurts, J; van Gestel, N A P; van Rietbergen, B; Arts, J J

    2016-05-01

    Bioactive Glass (BAG) granules are osteoconductive and possess unique antibacterial properties for a synthetic biomaterial. To assess the applicability of BAG granules in load-bearing defects, the aim was to compare mechanical behaviour of graft layers consisting of BAG granules and morselized cancellous bone allograft in different volume mixtures under clinically relevant conditions. The graft layers were mechanically tested, using two mechanical testing modalities with simulated physiological loading conditions: highly controllable confined compression tests (CCT) and more clinically realistic in situ compression tests (ISCT) in cadaveric porcine bone defects. Graft layer impaction strain, residual strain, aggregate modulus, and creep strain were determined in CCT. Graft layer porosity was determined using micro computed tomography. The ISCT was used to determine graft layer subsidence in bone environment. ANOVA showed significant differences (p<0.001) between different graft layer compositions. True strains absolutely decreased for increasing BAG content: impaction strain -0.92 (allograft) to -0.39 (BAG), residual strain -0.12 to -0.01, and creep strain -0.09 to 0.00 respectively. Aggregate modulus increased with increasing BAG content from 116 to 653MPa. Porosity ranged from 66% (pure allograft) to 15% (pure BAG). Subsidence was highest for allograft, and remarkably low for a 1:1 BAG-allograft volume mixture. Both BAG granules and allograft morsels as stand-alone materials exhibit suboptimal mechanical behaviour for load-bearing purpose. BAG granules are difficult to handle and less porous, whereas allograft subsides and creeps. A 1:1 volume mixture of BAG and allograft is therefore proposed as the best graft material in load-bearing defects. PMID:26972764

  6. Reactor and fuel behaviour under severe transient conditions in WAGR

    International Nuclear Information System (INIS)

    The Windscale prototype advanced gas-cooled reactor (WAGR) closed down in 1981. Following the formal shutdown a collaborative series of safety related experiments were performed, jointly funded by the UKAEA, CEGB and SSEB. Reactor transient tests were carried out, simulating aspects of postulated CAGR faults under conditions far beyond those achievable on commercial plant. Modelling of these tests with a CAGR fault study code has shown that a high degree of confidence can be placed in the predictions of the code. The experiments also included pressurised high temperature transients on individual fuel stringers in a loop of the reactor, which were intended to take the fuel pin cladding close to melting. Post-irradiation examination of the fuel has confirmed the success of the experiments, demonstrating the durability of the present CAGR fuel design under such conditions. (author)

  7. Cellular and molecular mechanisms underlying radiation carcinogenesis

    International Nuclear Information System (INIS)

    When considering and analyzing experimental material concerning cellular aspects of the problem of radiation carcinogenesis, the following conclusions can be made: neoplastic transformation of cells in a culture is caused already by small radiation doses, under the effect of which the level of DNA injury is quite insignificant; the frequency of cell transformation depends on the type of radiation, it is particularly pronounced under the effect of radiations with a high linear energy transfer; a correlation between the processes of postradiation recovery and radiogenic transformation of cells is detected, nonrepairable injures of DNA playing the most important role in radiation carcinogenesis; tumour promoters and anticarcinogenic agens produce a modifying effect on the transformation of irradiated cells. Molecular mechanisms of oncogene activation are thoroughly studied using the model of virus carcinogenesis, the problem of the nature of chemical and, in particular, radiation cell transformation remains scantily investigated

  8. Behaviour of Rotating Bose-Einstein Condensates Under Shrinking

    Institute of Scientific and Technical Information of China (English)

    ZHAI Hui; ZHOU Qi

    2005-01-01

    @@ When the repulsive interaction strength between atoms decreases, the size of a rotating Bose-Einstein condensate will consequently shrink. We find that the rotational frequency will increase during the shrinking of condensate,which is a quantum mechanical analogy to ballet dancing. Compared to a non-rotating condensate, the size of a rotating BEC will eventually be satiated at a finite value when the interaction strength is gradually reduced.We also calculate the vortex dynamics induced by the atomic current, and discuss the difference of vortex dynamics in this case and that observed in a recent experiment carried out by the JILA group [Phys. Rev. Lett.90 (2003) 170405].

  9. How does the composition affect the mechanical behaviour of simulated clay-rich fault gouges?

    Science.gov (United States)

    Bakker, Elisenda; Spiers, Christopher J.; Hangx, Suzanne J. T.

    2014-05-01

    CO2 capture and storage (CCS) in depleted oil and gas reservoirs is seen as one of the most promising large-scale CO2-mitigation strategies. Prediction of the effect of fluid-rock interaction on the mechanical integrity and sealing capacity of a reservoir-seal system, on timescales of the order of 1,000 or 10,000 years, is important to ensure the safety and containment of a reservoir in relation to long-term CO2 storage. However, most chemical reactions in rock/CO2/brine systems are slow, which means that long-term effects of fluids on rock composition, microstructure, mechanical properties and transport properties cannot be easily reproduced under laboratory conditions. One way to overcome this problem is to use simulated fault gouges in experiments, investigating a range of possible mineralogical compositions resulting from CO2-exposure. Previous studies have shown that the mechanical and transport properties of clay-rich fault gouges are significantly influenced by the mineralogy, particularly by the presence and relative amount of secondary phases, such as quartz and/or carbonate. In CCS settings, where dissolution and/or precipitation of carbonates may play an important role, the carbonate:clay ratio is expected to influence fault frictional behaviour. This is supported by the different behaviour of phyllosilicates, which generally show stable slip behaviour (aseismic), compared to carbonates, which have shown to become prone to unstable slip (potentially seismic) with increasing temperature. However, little is known about the mechanical and transport properties of carbonate/clay mixtures. We investigated the effect of the carbonate:clay ratio on fault friction, fault reactivation potential and slip stability, i.e. seismic vs. aseismic behaviour, as well as transmissivity evolution during and after fault reactivation. We used two types of starting material, derived from crushed Opalinus Claystone (Mont Terri, Switzerland): i) untreated samples consisting

  10. Mechanical and three-body abrasive wear behaviour of PMMA/TPU blends

    International Nuclear Information System (INIS)

    The blends of poly(methyl methacrlate) (PMMA) and thermoplastic polyurethane (TPU) were prepared by a Brabender co-twin screw extruder. The mechanical and three-body abrasive wear behaviour of PMMA/TPU blends has been studied. Three-body abrasive wear tests were conducted using rubber wheel abrasion tester (RWAT) under different abrading distances at 200 rpm and 22 N load. A significant reduction in tensile strength and tensile modulus with an increase in TPU content in the blend formulation was observed. Three-body abrasive wear results indicate that the wear volume increases with increase in abrading distance for all the samples studied. However, neat PMMA showed better wear resistance as compared to PMMA/TPU blends. The worn surface features, as examined through scanning electron microscope (SEM), show matrix cracking and deep furrows in PMMA/TPU blends

  11. Behaviour of concrete under high confinement: study in triaxial compression and in triaxial extension at the mesoscopic scale

    International Nuclear Information System (INIS)

    This Ph.D. thesis aims at characterising and modeling the mechanical behaviour of concrete under high confinement at the mesoscopic scale. This scale corresponds to that of the large aggregates and the cementitious matrix. The more general scope of this study is the understanding of concrete behaviour under dynamic loading. A dynamic impact can generate mean pressures around 1 GPa. But the characterisation of a material response, in an homogeneous state of stress, can only be achieved through quasi-static tests. The experimentations led in 3S-R Laboratory have underlined the importance of the aggregates in the triaxial response of concrete. Modeling concrete at the mesoscopic level, as a composite of an aggregates phase and a mortar phase, permits a representation of the aggregates effect. An experimental study of the behaviour of mortar phase is performed. Usual tests and hydrostatic and triaxial high confinement tests are realised. The parameters of a constitutive model that couples plasticity with a damage law are identified from these tests. This model is able to reproduce the nonlinear compaction of mortar, the damage behaviour under uniaxial tension or compression, and plasticity under high confinement. The biphasic model uses the finite element method with a cubic and regular mesh. A Monte-Carlo method is used to place quasi-spherical aggregates that respect the given particle size of a reference concrete. Each element is identified by belonging either to the mortar or to the aggregate phase. Numerical simulations are compared with the experimental tests on this concrete. The parameters for these simulations are only identified on the mortar. The simulations reproduce the different phases observed in hydrostatic compression. The evolution of axial moduli under growing confinement is shown, as is the good reproduction of the limit-states experimentally observed under high confinement. The fracture aspect of numerical simulations is comparable with that of

  12. Corrosion products behaviour under VVER primary coolant conditions

    International Nuclear Information System (INIS)

    The aim of this work was to collect data on thermodynamic stability of Cr, Fe, and Ni oxides, mechanisms of hydrothermal corrosion of stainless steels and to compare the real observation with the theory. We found that the electrochemical potential and pH in PWR and VVER are close to the thermodynamic boundary between two fields of stable spinel type oxides. The ways of degradation of the passivating layers due to changes in water chemistry were considered and PWR and VVER systems were found to be potentially endangered by reductive attack. In certain VVER systems the characteristics of the passivating layer on steels and also concentration of soluble corrosion products seem to be in contradiction with the theoretical expectations. (author)

  13. Mechanical behaviour of Nd:YAG laser welded superelastic NiTi

    International Nuclear Information System (INIS)

    Highlights: → The main innovations claimed are: understand rolling direction effect on mechanical cycling of laser welded NiTi. → Functionality confirmed by stabilization of hysteretic response up to 8% strain. → Welds tensile cycled exhibited superior functional mechanical behaviour. → For applied stresses of 50 MPa below UTS the joints showed superelastic behaviour. - Abstract: Joining techniques for shape memory alloys (SMA) has become of great interest, as their functional properties, namely shape memory effect (SME) and superelasticity (SE), present unique solutions for state-of-the-art applications, although limited results concerning mechanical properties are reported. This paper reports experimental work performed with Nd:YAG continuous wave laser welding of superelastic cold-rolled plates of NiTi 1 mm thick. The mechanical behaviour was evaluated by means of tensile tests performed both to failure and to cycling. The superelastic behaviour of the welded joints was observed for applied stresses close to about 50 MPa below the ultimate tensile strength of the welds. The functionality was confirmed by analyzing the stabilization of the mechanical hysteretic response to strain levels up to 8%. For tensile cycling involving strain levels larger than 6%, welded specimens were found to exhibit superior functional mechanical behaviour presenting larger recoverable strain levels. The fracture surfaces were observed by scanning electron microscopy (SEM) and the effect of the rolling direction on mechanical properties was evaluated and discussed, reinforcing the importance of joint design when laser welding these alloys.

  14. Biological mechanisms underlying the role of physical fitness in health and resilience

    OpenAIRE

    Silverman, Marni N.; Deuster, Patricia A.

    2014-01-01

    Physical fitness, achieved through regular exercise and/or spontaneous physical activity, confers resilience by inducing positive psychological and physiological benefits, blunting stress reactivity, protecting against potentially adverse behavioural and metabolic consequences of stressful events and preventing many chronic diseases. In this review, we discuss the biological mechanisms underlying the beneficial effects of physical fitness on mental and physical health. Physical fitness appear...

  15. A nanoscale simulation study of the elastic behaviour in kaolinite clay under pressure

    International Nuclear Information System (INIS)

    Highlights: ► Kaolinite is quite compressible compared to the other clays. This reflects the possible uses in several applications including external constraints. ► The elastic constants such as C33, C13, C23 and C34 have a positive slope under pressure with 15%, 6%, 6% and 1.3%, respectively. ► A decrease of the Young modulus is noticed in a and b directions, whereas an increase in c direction appears with a slope equal to 10%. - Abstract: In this paper, Molecular dynamics simulation based on energy minimization technique has been used to study the structural and mechanical properties of kaolinite under pressure from 0 GPa to 25 GPa. Using the shell model, we have optimized the potential parameters according to Newton–Raphson procedure. Various mechanical properties have been calculated, such as the elastic constants, bulk modulus, shear modulus, Young modulus along a, b and c directions. Moreover the S- and P-wave velocities as well as Poisson ratio were also evaluated. Results reveal that kaolinite is quite compressible compared to the other clays. This reflects the possible uses in several applications including external constraints. In addition, we study the pressure effect on the elasticity of kaolinite. Results show that the elastic constants such as C33, C13, C23 and C34 have a positive slope under pressure with 15%, 6%, 6% and 1.3%, respectively. The remaining elastic constants are almost stable with a small change. A decrease of the Young modulus is noticed in a and b directions, whereas an increase in c direction appears with a slope equal to 10%. The ratio of the S- and P-wave velocities, which are key in the interpretation of seismic behaviours, gives Vp/Vs = 1.787, a value in favourable agreement with experimental data.

  16. Effect of the Young modulus variability on the mechanical behaviour of a nuclear containment vessel

    International Nuclear Information System (INIS)

    This study aims at investigating the influence of the Young modulus variability on the mechanical behaviour of a nuclear containment vessel in case of a loss of cooling agent accident and under the assumption of an elastic behaviour. To achieve this investigation, the Monte-Carlo Method is carried out thanks to a middleware which encapsulates the different components (random field generation, FE simulations) and enables calculations parallelisation. The main goal is to quantify the uncertainty propagation by comparing the maximal values of outputs of interest (orthoradial stress and Mazars equivalent strain) for each realisation of the considered random field with the ones obtained from a reference calculation taking into account uniform field (equal to the expected value of the random field). The Young modulus is supposed to be accurately represented by a weakly homogeneous random field and realisations are provided through its truncated Karhunen-Loeve expansion. This study reveals that the expected value for the maximal equivalent strain in the structure is more important when considering the Young modulus spatial variability than the value obtained from a deterministic approach with a uniform Young modulus field. The influence of the correlation length is investigated too. Finally it is shown that there is no correlation between the maximal values location of equivalent strain and the ones where the Young modulus extreme values are observed for each realisation.

  17. Characterisation and modelling of anisotropic thermo-mechanical behaviour of oriented polyethylene terephthalate

    International Nuclear Information System (INIS)

    The long-term and short-term anisotropic mechanical behaviour of a biaxially stretched polyethylene terephthalate foil is measured. The orientation of the crystalline phase is characterized and the representative foil microstructure is discussed. Using the obtained information, a mean-field model is used to simulate the elasto-viscoplastic behaviour of the oriented polymer foil, taking into account the different constitutive behaviour of the phases. The material is modelled as an aggregate of connected two-phase domains. The parameters of the constitutive behaviour of the crystalline and non-crystalline phases have been determined, and the ability to simulate the large-strain anisotropic behaviour of polyethylene terephthalate in the strain-rate-controlled regime and the long-term creep has been demonstrated. The model is extended to include pre-orientation of the non-crystalline phase. In addition, deformation at the microscopic level is analysed using the model results. (paper)

  18. Behaviour of lindane (gamma HCH) in soil under laboratory conditions

    International Nuclear Information System (INIS)

    The degradation of lindane in solid after multiple application was studied. The rate of disappearance of lindane increased at long periods after application. The dissipation of lindane was more rapid in soil collected from treated a plot than an untreated plot, owing to the degradation by micro-organisms suggesting that microorganisms had become adapted to degrade it. The rates of mineralization, mobility and degradation of lindane were also investigated under laboratory conditions using 14C-labelled lindane. The results showed that most of the applied dose remained on the upper 6cm in the soil columns. Over a periods of three months, extractable residues, bound residues and evolution of 14CO2 were recorded. After 12 weeks, the soil contained about 50% of the initially applied 14C and 20% was bound to the soil. The evolution of 14CO2 increased with time, amounting to 3.1% in non-sterile soil and less than 1% in sterile soil. The hexane 14C-extractable residues were shown, by TLC, to contain lindane as the main product. (author). 5 refs, 4 tabs

  19. Modelling of the mechanical behaviour of a material containing spherical cavities under pressure; example of the aging of a metal tritide; Modelisation du comportement mecanique d'un materiau contenant des cavites sous pression; cas du vieillissement d'un tritiure metallique

    Energy Technology Data Exchange (ETDEWEB)

    Chalon, F

    2001-07-01

    The study aims at modeling the mechanical behaviour of a material containing spherical cavities under pressure (bubbles) of nano-metric size. This work deals with research on tritium storage in metals. In this way, metal tritides are obtained. During time, helium is generated by tritium decay. Helium appears as a gas, which forms bubbles in the metal tritide. These bubbles subsequently cause damage within the material. The purpose of this work was therefore the following: (i) to determine the overall elastic moduli as a function of the volume fraction of cavities. thus providing an information about material damage, (ii) to analyze the macroscopic inflation of the material in order to solve storage problems, (iii) to determine the local stress fields for predicting the evolutions of the bubbles and the matrix. With the help of the scale change methods (homogenization) the macroscopic mechanical properties of the material can be determined as a function of its morphology on a microscopic scale. Thus the damage of the material can be estimated by experimental measurements of the global elastic moduli. Homogenization also allows the elastic inflation to be evaluated as well as the effects of cavity clusters and local variations of the elastic moduli. The internal stresses are determined on the microscopic scale (cavity scale). Two analytical methods (Eshelby-Mura and Legendre polynomials) and one numerical approach (Abaqus) are used to obtain more information and a best description of the material. It is shown that bubbles should attain the same size and same pressure and the plastic strain zones are determined. (author)

  20. Deformation Mechanisms of Gum Metals Under Nanoindentation

    Science.gov (United States)

    Sankaran, Rohini Priya

    defect structures to applied loading, we perform ex-situ nanoindentation. Nanoindentation is a convenient method as the plastic deformation is localized and probes a nominally defect free volume of the material. We subsequently characterize the defect structures in these alloys with both conventional TEM and advanced techniques such as HAADF HRSTEM and nanoprobe diffraction. These advanced techniques allow for a more thorough understanding of the observed deformation features. The main findings from this investigation are as follows. As expected we observe that a non-equilibrium phase, o, is present in the leaner beta-stabilized alloy, ST Ref-1. We do not find any direct evidence of secondary phases in STGM, and we find the beta phase in CWGM, along with lath microstructure with subgrain structure consisting of dislocation cell networks. Upon nanoindentation, we find twinning accompanied by beta nucleation on the twin boundary in ST Ref-1 samples. This result is consistent with previous findings and is reasonable considering the alloy is unstable with respect to beta transformation. We find deformation nanotwinning in cold worked gum metals under nanoindentation, which is initially surprising. We argue that when viewed as a nanocrystalline material, such a deformation mechanism is consistent with previous work, and furthermore, a deformation nanotwinned structure does not preclude an ideal shear mechanism from operating in the alloy. Lastly, we observe continuous lattice rotations in STGM under nanoindentation via nanoprobe diffraction. With this technique, for the first time we can demonstrate that the lattice rotations are truly continuous at the nanoscale. We can quantify this lattice rotation, and find that even though the rotation is large, it may be mediated by a reasonable geometrically necessary dislocation density, and note that similar rotations are typically observed in other materials under nanoindentation. HRSTEM and conventional TEM data confirm the

  1. Numerical and experimental investigation of bump foil mechanical behaviour

    DEFF Research Database (Denmark)

    Larsen, Jon Steffen; Cerda Varela, Alejandro Javier; Santos, Ilmar

    2014-01-01

    Corrugated foils are utilized in air foil bearings to introduce compliance and damping thus accurate mathematical predictions are important. A corrugated foil behaviour is investigated experimentally as well as theoretically. The experimental investigation is performed by compressing the foil......, between two parallel surfaces, both statically and dynamically to obtain hysteresis curves. The theoretical analysis is based on a two dimensional quasi static FE model, including geometrical non-linearities and Coulomb friction in the contact points and neglects the foil mass. A method for implementing...... the friction is suggested. Hysteresis curves obtained via the FE model are compared to the experimental results obtained. Good agreement is observed in the low frequency range and discrepancies for higher frequencies are thoroughly discussed....

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

    International Nuclear Information System (INIS)

    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

  3. Concrete for PCRV's: Mechanical properties at elevated temperatures and residual mechanical behaviour after triaxial preloading

    International Nuclear Information System (INIS)

    During the lifetime of reactor vessels stress states will change as a result of changes in loading and heating, shrinkage and creep. For the design of prestressed concrete reactor vessels information is required about the behaviour of concrete under multiaxial short- and long-term loading at elevated temperatures. Therefore, tests were carried out at the Institut fuer Massivbau of the Technical University of Munich to study the properties of mass concrete under uniaxial loading at 353 K. Additionally, biaxial creep of concrete up to 368 K was investigated. Some of the uniaxial test specimens were sealed with a copper foil to avoid drying. The concrete contained calzite gravel. The thermal expansion coefficient of predried concrete was 9.5 x 10-6, of sealed concrete 13.6 x 10-6 and of unsealed concrete 13.2 x 10-6. The modulus of elasticity at 353 K (393 K) was reduced by 10 (13)% for sealed and by 15 (22)% for unsealed specimens. Total shrinkage deformations of heated concrete were 190 to 225 microstrains for sealed and 250 to 350 microstrains for unsealed specimens. Creep deformations were highly dependent upon temperature being about 3 times higher at 353 K for sealed and unsealed concrete. (orig.)

  4. Evolved Mechanisms Versus Underlying Conditional Relations

    Directory of Open Access Journals (Sweden)

    Astorga Miguel López

    2015-03-01

    Full Text Available The social contracts theory claims that, in social exchange circumstances, human reasoning is not necessarily led by logic, but by certain evolved mental mechanisms that are useful for catching offenders. An emblematic experiment carried out with the intention to prove this thesis is the first experiment described by Fiddick, Cosmides, and Tooby in their paper of 2000. Lopez Astorga has questioned that experiment claiming that its results depend on an underlying conditional logical form not taken into account by Fiddick, Cosmides, and Tooby. In this paper, I propose an explanation alternative to that of Lopez Astorga, which does not depend on logical forms and is based on the mental models theory. Thus, I conclude that this other alternative explanation is one more proof that the experiment in question does not demonstrate the fundamental thesis of the social contracts theory.

  5. An Underlying Geometrical Manifold for Hamiltonian Mechanics

    CERN Document Server

    Horwitz, L P; Levitan, J; Lewkowicz, M

    2015-01-01

    We show that there exists an underlying manifold with a conformal metric and compatible connection form, and a metric type Hamiltonian (which we call the geometrical picture) that can be put into correspondence with the usual Hamilton-Lagrange mechanics. The requirement of dynamical equivalence of the two types of Hamiltonians, that the momenta generated by the two pictures be equal for all times, is sufficient to determine an expansion of the conformal factor, defined on the geometrical coordinate representation, in its domain of analyticity with coefficients to all orders determined by functions of the potential of the Hamilton-Lagrange picture, defined on the Hamilton-Lagrange coordinate representation, and its derivatives. Conversely, if the conformal function is known, the potential of a Hamilton-Lagrange picture can be determined in a similar way. We show that arbitrary local variations of the orbits in the Hamilton-Lagrange picture can be generated by variations along geodesics in the geometrical pictu...

  6. Fatigue behaviour and crack growth of ferritic steel under environmental conditions

    International Nuclear Information System (INIS)

    The assessment of fatigue and cyclic crack growth behaviour of safety relevant components is of importance for the ageing management with regard to safety and reliability. For cyclic stress evaluation different codes and standards provide fatigue analysis procedures to be performed considering the various mechanical and thermal loading histories and geometric complexities of the components. For the fatigue design curves used as a limiting criteria the influence of different factors like e.g. environment, surface finish and temperature must be taken into consideration in an appropriate way. Fatigue tests were performed in the low cycle fatigue (LCF) und high cycle fatigue (HCF) regime with low alloy steels as well as with Nb- and Ti-stabilized German austenitic stainless steels in air and high temperature (HT) boiling water reactor environment to extend the state of knowledge of environmentally assisted fatigue (EAF) as it can occur in boiling water reactor (BWR) plants. Using the reactor pressure vessel (RPV) steel 22NiMoCr3-7 experimental data were developed to verify the influence of BWR coolant environment (high purity water as well as sulphate containing water with 90 ppb SO4 at a test temperature of 240 C and an oxygen content of 400 ppb) on the fatigue life and to extend the basis for a reliable estimation of the remaining service life of reactor components. Corresponding experiments in air were performed to establish reference data to determine the environmental correction factor Fen accounting for the environment. The experimental results are compared with international available mean data curves, the new design curves and on the basis of the environmental factor Fen. Furthermore the behaviour of steel 22NiMoCr3-7 in oxygenated high temperature water under transient loading conditions was investigated with respect to crack initiation and cyclic crack growth. In this process the stress state of the specimen and the chemical composition of the high

  7. Coupling between chemical degradation and mechanical behaviour of leached concrete

    International Nuclear Information System (INIS)

    This work is in the context of the long term behavior of concrete employed in radioactive waste disposal. The objective is to study the coupled chemo-mechanical modelling of concrete. In the first part of this contribution, experimental investigations are described where the effects of the calcium leaching process of concrete on its mechanical properties are highlighted. An accelerated method has been chosen to perform this leaching process by using an ammonium nitrate solution. In the second part, we present a coupled phenomenological chemo-mechanical model that represents the degradation of concrete materials. On one hand, the chemical behavior is described by the simplified calcium leaching approach of cement paste and mortar. Then a homogenization approach using the asymptotic development is presented to take into account the influence of the presence of aggregates in concrete. And on the other hand, the mechanical part of the modelling is given. Here continuum damage mechanics is used to describe the mechanical degradation of concrete. The growth of inelastic strains observed during the mechanical tests is describes by means of a plastic like model. The model is established on the basis of the thermodynamics of irreversible processes framework. The coupled nonlinear problem at hand is addressed within the context of the finite element method. Finally, numerical simulations are compared with the experimental results for validation. (author)

  8. Mechanisms underlying UV-induced immune suppression

    International Nuclear Information System (INIS)

    Skin cancer is the most prevalent form of human neoplasia. Estimates suggest that in excess of one million new cases of skin cancer will be diagnosed this year alone in the United States (www.cancer.org/statistics). Fortunately, because of their highly visible location, skin cancers are more rapidly diagnosed and more easily treated than other types of cancer. Be that as it may, approximately 10,000 Americans a year die from skin cancer. The cost of treating non-melanoma skin cancer is estimated to be in excess of US$ 650 million a year [J.G. Chen, A.B. Fleischer, E.D. Smith, C. Kancler, N.D. Goldman, P.M. Williford, S.R. Feldman, Cost of non-melanoma skin cancer treatment in the United States, Dermatol. Surg. 27 (2001) 1035-1038], and when melanoma is included, the estimated cost of treating skin cancer in the United States is estimated to rise to US$ 2.9 billion annually (www.cancer.org/statistics). Because the morbidity and mortality associated with skin cancer is a major public health problem, it is important to understand the mechanisms underlying skin cancer development. The primary cause of skin cancer is the ultraviolet (UV) radiation found in sunlight. In addition to its carcinogenic potential, UV radiation is also immune suppressive. In fact, data from studies with both experimental animals and biopsy proven skin cancer patients suggest that there is an association between the immune suppressive effects of UV radiation and its carcinogenic potential. The focus of this manuscript will be to review the mechanisms underlying the induction of immune suppression following UV exposure. Particular attention will be directed to the role of soluble mediators in activating immune suppression

  9. Mechanisms underlying UV-induced immune suppression

    Energy Technology Data Exchange (ETDEWEB)

    Ullrich, Stephen E. [Department of Immunology, University of Texas, MD Anderson Cancer Center, South Campus Research Building 1, 7455 Fannin St., P.O. Box 301402, Houston, TX 77030-1903 (United States)]. E-mail: sullrich@mdanderson.org

    2005-04-01

    Skin cancer is the most prevalent form of human neoplasia. Estimates suggest that in excess of one million new cases of skin cancer will be diagnosed this year alone in the United States (www.cancer.org/statistics). Fortunately, because of their highly visible location, skin cancers are more rapidly diagnosed and more easily treated than other types of cancer. Be that as it may, approximately 10,000 Americans a year die from skin cancer. The cost of treating non-melanoma skin cancer is estimated to be in excess of US$ 650 million a year [J.G. Chen, A.B. Fleischer, E.D. Smith, C. Kancler, N.D. Goldman, P.M. Williford, S.R. Feldman, Cost of non-melanoma skin cancer treatment in the United States, Dermatol. Surg. 27 (2001) 1035-1038], and when melanoma is included, the estimated cost of treating skin cancer in the United States is estimated to rise to US$ 2.9 billion annually (www.cancer.org/statistics). Because the morbidity and mortality associated with skin cancer is a major public health problem, it is important to understand the mechanisms underlying skin cancer development. The primary cause of skin cancer is the ultraviolet (UV) radiation found in sunlight. In addition to its carcinogenic potential, UV radiation is also immune suppressive. In fact, data from studies with both experimental animals and biopsy proven skin cancer patients suggest that there is an association between the immune suppressive effects of UV radiation and its carcinogenic potential. The focus of this manuscript will be to review the mechanisms underlying the induction of immune suppression following UV exposure. Particular attention will be directed to the role of soluble mediators in activating immune suppression.

  10. Mechanical behaviour of Astm A 297 grade Hp joints welded using different processes

    International Nuclear Information System (INIS)

    The influence of different arc welding processes on mechanical behaviour was studied for cast heat resistant stainless steel welded joints, in the as welded conditions. ASTM A 297 grade HP with niobium and niobium/titanium additions were welded following three different welding procedures, using shielded metal arc welding gas tungsten arc welding and plasma arc welding, in six welded joints. The welded joint mechanical behaviour was evaluated by ambient temperature and 870 deg C tensile tests; and creep tests at 900 deg C and 50 MPa. Mechanical test results showed that the welding procedure qualification following welding codes is not suitable for high temperature service applications. (author)

  11. Mechanical buckling of veins under internal pressure.

    Science.gov (United States)

    Martinez, Ricky; Fierro, Cesar A; Shireman, Paula K; Han, Hai-Chao

    2010-04-01

    Venous tortuosity is associated with multiple disease states and is often thought to be a consequence of venous hypertension and chronic venous disease. However, the underlying mechanisms of vein tortuosity are unclear. We hypothesized that increased pressure causes vein buckling that leads to a tortuous appearance. The specific aim of this study was to determine the critical buckling pressure of veins. We determined the buckling pressure of porcine jugular veins and measured the mechanical properties of these veins. Our results showed that the veins buckle when the transmural pressure exceeds a critical pressure that is strongly related to the axial stretch ratio in the veins. The critical pressures of the eight veins tested were 14.2 +/- 5.4 and 26.4 +/- 9.0 mmHg at axial stretch ratio 1.5 and 1.7, respectively. In conclusion, veins buckle into a tortuous shape at high lumen pressures or reduced axial stretch ratios. Our results are useful in understanding the development of venous tortuosity associated with varicose veins, venous valvular insufficiency, diabetic retinopathy, and vein grafts. PMID:20094913

  12. Effect of carbonate content on the mechanical behaviour of clay fault-gouges

    Science.gov (United States)

    Bakker, Elisenda; Niemeijer, André; Hangx, Suzanne; Spiers, Chris

    2015-04-01

    Carbon dioxide capture and storage (CCS) in depleted oil and gas reservoirs is considered to be the most promising technology to achieve large-scale reduction in anthropogenic emissions. In order to retain the stored CO2 from the atmosphere for the very long-term, i.e. on timescales of the order of 103-104 years, it is essential to maintain the integrity of the caprock, and more specifically of any faults penetrating the seal. When selecting suitable CO2-storage reservoirs, pre-exisiting faults within the caprock require close attention, as changes in the stress state resulting from CO2-injection may induce fault slip motion which might cause leakage. Little is known about the effect of fluid-rock interactions on the mineral composition, mechanical properties and the integrity and sealing capacity of the caprock. Previous studies on the effect of mineral composition on the frictional properties of fault gouges have shown that friction is controlled by the dominant phase unless there is a frictionally weak, through-going fabric. However, the effect on stability is less clear. Since long-term CO2-exposure might cause chemical reactions, potentially resulting in the dissolution or precipitation of carbonate minerals, a change in mineralogy could affect the mechanical stability of a caprock significantly. Calcite, for example, is known to be prone to micro-seismicity and shows a transition from velocity-strengthening to velocity-weakening behaviour around 100-150°C. Therefore, we investigated the effect of varying clay:carbonate ratios on fault friction behaviour, fault reactivation potential and slip stability, i.e. seismic vs. aseismic behaviour. Three types of simulated fault gouges were used: i) carbonate-free, natural clay-rich caprock samples, consisting of predominantly phyllosilicates (~80%) and quartz ~20%), ii) pure calcite, and iii) mixtures of carbonate-free clay-rich caprock and pure calcite, with predetermined clay:carbonate ratios. For the natural clay

  13. Two distinct neural mechanisms underlying indirect reciprocity.

    Science.gov (United States)

    Watanabe, Takamitsu; Takezawa, Masanori; Nakawake, Yo; Kunimatsu, Akira; Yamasue, Hidenori; Nakamura, Mitsuhiro; Miyashita, Yasushi; Masuda, Naoki

    2014-03-18

    Cooperation is a hallmark of human society. Humans often cooperate with strangers even if they will not meet each other again. This so-called indirect reciprocity enables large-scale cooperation among nonkin and can occur based on a reputation mechanism or as a succession of pay-it-forward behavior. Here, we provide the functional and anatomical neural evidence for two distinct mechanisms governing the two types of indirect reciprocity. Cooperation occurring as reputation-based reciprocity specifically recruited the precuneus, a region associated with self-centered cognition. During such cooperative behavior, the precuneus was functionally connected with the caudate, a region linking rewards to behavior. Furthermore, the precuneus of a cooperative subject had a strong resting-state functional connectivity (rsFC) with the caudate and a large gray matter volume. In contrast, pay-it-forward reciprocity recruited the anterior insula (AI), a brain region associated with affective empathy. The AI was functionally connected with the caudate during cooperation occurring as pay-it-forward reciprocity, and its gray matter volume and rsFC with the caudate predicted the tendency of such cooperation. The revealed difference is consistent with the existing results of evolutionary game theory: although reputation-based indirect reciprocity robustly evolves as a self-interested behavior in theory, pay-it-forward indirect reciprocity does not on its own. The present study provides neural mechanisms underlying indirect reciprocity and suggests that pay-it-forward reciprocity may not occur as myopic profit maximization but elicit emotional rewards. PMID:24591599

  14. The thermal and mechanical behaviour of structural steel piping systems

    OpenAIRE

    Fonseca, E.M.M.; F. J. M. Q. de Melo; Oliveira, C.A.M de

    2005-01-01

    The temperature, the deformation and the stress field in thermo-mechanical problems play a very important role in engineering applications. This paper presents a finite element algorithm developed to perform the thermal and mechanical analysis of structural steel piping systems subjected to elevated temperatures. The new pipe element with 22 degrees of freedom has a displacement field that results from the superposition of a beam displacement, with the displacement field associated w...

  15. Effect of microstructure on the mechanical and damping behaviour of dragonfly wing veins.

    Science.gov (United States)

    Rajabi, H; Shafiei, A; Darvizeh, A; Dirks, J-H; Appel, E; Gorb, S N

    2016-02-01

    Insect wing veins are biological composites of chitin and protein arranged in a complex lamellar configuration. Although these hierarchical structures are found in many 'venous wings' of insects, very little is known about their physical and mechanical characteristics. For the first time, we carried out a systematic comparative study to gain a better understanding of the influence of microstructure on the mechanical characteristics and damping behaviour of the veins. Morphological data have been used to develop a series of three-dimensional numerical models with different material properties and geometries. Finite-element analysis has been employed to simulate the mechanical response of the models under different loading conditions. The modelling strategy used in this study enabled us to determine the effects selectively induced by resilin, friction between layers, shape of the cross section, material composition and layered structure on the stiffness and damping characteristics of wing veins. Numerical simulations suggest that although the presence of the resilin-dominated endocuticle layer results in a much higher flexibility of wing veins, the dumbbell-shaped cross section increases their bending rigidity. Our study further shows that the rubber-like cuticle, friction between layers and material gradient-based design contribute to the higher damping capacity of veins. The results of this study can serve as a reference for the design of novel bioinspired composite structures. PMID:26998340

  16. Mechanical behaviour of textile-reinforced thermoplastics with integrated sensor network components

    International Nuclear Information System (INIS)

    Highlights: → Consideration of two types of integrated bus systems for textile-reinforced thermoplastics with embedded sensor networks. → Specimens with bus systems made of flexible printed circuit boards show good mechanical performance compared to the reference. → Inhomogeneous interface and reduced stiffnesses and strengths for specimens with bus systems basing on single copper wires. -- Abstract: The embedding of sensor networks into textile-reinforced thermoplastics enables the design of function-integrative lightweight components suitable for high volume production. In order to investigate the mechanical behaviour of such functionalised composites, two types of bus systems are selected as exemplary components of sensor networks. These elements are embedded into glass fibre-reinforced polypropylene (GF/PP) during the layup process of unconsolidated weft-knitted GF/PP-preforms. Two fibre orientations are considered and orthotropic composite plates are manufactured by hot pressing technology. Micrograph investigations and computer tomography analyses show different interface qualities between the thermoplastic composite and the two types of bus systems. Mechanical tests under tensile and flexural loading indicate a significant influence of the embedded bus system elements on the structural stiffness and strength.

  17. Modelling and experimental contrast of the mechanical behaviour of structural laminated glass

    Directory of Open Access Journals (Sweden)

    Sanz-Ablanedo, E.

    2010-12-01

    Full Text Available This paper presents a numerical simulation of the mechanical behaviour of laminated glass plates (glass- PVB-glass and its experimental verification. The viscoelastic characterization of the intermediate layer of PVB has been done by means of stress relaxation tests at various temperatures. The consideration of PVB as a viscoelastic material permits to analyze the real response of the structural element of laminated glass under time variations of temperature, of application of loading, of stress state, etc. Displacements obtained with the numerical analysis have been verified experimentally with laminated glass plates under lateral load using close range photogrammetry and dial gauges indicators. The analysis of results confirms the time dependent behaviour of the glass-PVB-glass laminate and suggests the validity of the proposed model.

    Este trabajo presenta la simulación numérica del comportamiento mecánico de placas de vidrio laminado (vidrio-PVB-vidrio y su comprobación experimental. La caracterización viscoelástica de la lámina intermedia de PVB se ha realizado mediante ensayos de relajación de tensiones a diversas temperaturas. La consideración del PVB como material viscoelástico permite analizar la respuesta real del elemento estructural de vidrio laminado ante variaciones en el tiempo de la temperatura, de la velocidad de aplicación de las cargas, del estado tensional, etc. Los desplazamientos obtenidos numéricamente han sido contrastados experimentalmente en placas de vidrio laminado sometidas a carga lateral mediante fotogrametría de objeto cercano y relojes comparadores. Del análisis de los resultados se confirma el comportamiento variable en el tiempo del conjunto vidrio-PVB-vidrio y se deduce la validez de la modelización propuesta.

  18. The behaviour of irradiated fuel under RIA transients: Interpretation of the CABRI experiments

    International Nuclear Information System (INIS)

    Paper presents the results of investigation of highly irradiated PWR fuel behaviour under fast power transients conducted in a sodium loop of CABRI reactor, as well as the results on development and validation of computer code SCANAIR. (author). 8 refs, 9 figs, 2 tabs

  19. Microstructural evolutions and mechanical behaviour of the nickel based alloys 617 and 230 at high temperature

    International Nuclear Information System (INIS)

    properties at 850 C and 950 C have been evaluated using several stress levels (creep), strain rates (tensile) and relaxation duration (fatigue). The effects of initial treatments have also been studied, i.e. ageing treatments effects on creep and tensile properties and cold-work effects on creep properties. At high temperature, the as received Inconel 617 does not show classical creep behaviour. This study shows the importance of the fast carbides precipitation on their mechanical properties, despite the fact that the Inconel 617 and the Haynes 230 are listed as solid solution alloys. Low cycle fatigue tests with and without holding time have been performed at 850 C under air and under vacuum on both alloys. The results showed that cyclic hardening, cyclic stability and life time are closely related to the duration of the holding time. Furthermore, a single thermally activated mechanism operates over a very wide range of strain rates, corresponding to tensile tests, creep and relaxation. The link between microstructure and mechanical behaviour presented in this thesis helps to determine the advantages as the operation limits of each alloy in order to manufacture a nuclear power plant heat exchanger. (author)

  20. Critical current behaviour of superconducting Chevrel phase wires under tensile stress and pressure

    International Nuclear Information System (INIS)

    The Chevrel-phase superconductors PbMo6S8 and SnMo6S8 with the critical magnetic fields Bc2 (4.2 K) = 51 T or 31 T, resp., currently are the most promising materials for applications as superconducting wires in very high magnetic fields, B > 20 T. A new process for industrial-scale production of the Chevrel-phase material using the HIP technique now is available, and the wires made of this material are competitive with otherwise fabricated wires in terms of critical currents: Jc (20 T) ≅ 104 A/cm2. The conductor configurations currently in use need some reinforcing steel in the cladding to guarantee the required mechanical stability. This reinforcing steel proportion and the pre-stressing of the filament have been varied by tests with the PbMo6S8 wires and the SnMo6S8 wires, for examining the critical current behaviour under external, axial tensile stress and transversal pressure, in magnetic fields up to 20 T. The results are compared with corresponding test results obtained with Nb3Sn wires, and are discussed with a view to applications in high magnetic fields. (orig.)

  1. Behaviour of rock-like oxide fuels under reactivity-initiated accident conditions

    International Nuclear Information System (INIS)

    Pulse irradiation tests of three types of un-irradiated rock-like oxide (ROX) fuel - yttria-stabilised zirconia (YSZ) single phase, YSZ and spinel (MgAl2O4) homogeneous mixture and particle-dispersed YSZ/spinel - were conducted in the Nuclear Safety Research Reactor to investigate the fuel behaviour under reactivity-initiated accident conditions. The ROX fuels failed at fuel volumetric enthalpies above 10 GJ/m3, which was comparable to that of un-irradiated UO2 fuel. The failure mode of the ROX fuels, however, was quite different from that of the UO2 fuel. The ROX fuels failed with fuel pellet melting and a part of the molten fuel was released out to the surrounding coolant water. In spite of the release, no significant mechanical energy generation due to fuel/coolant thermal interaction was observed in the tested enthalpy range below∼12 GJ/m3. The YSZ type and homogenous YSZ/spinel type ROX fuels failed by cladding burst when their temperatures peaked, while the particle-dispersed YSZ/spinel type ROX fuel seemed to have failed by cladding local melting. (author)

  2. Mechanical behaviour of ferritic ODS steels - Temperature dependancy and anisotropy

    Science.gov (United States)

    Fournier, B.; Steckmeyer, A.; Rouffie, A.-L.; Malaplate, J.; Garnier, J.; Ratti, M.; Wident, P.; Ziolek, L.; Tournie, I.; Rabeau, V.; Gentzbittel, J. M.; Kruml, T.; Kubena, I.

    2012-11-01

    Ferritic 14%Cr and 18%Cr ODS steels produced at CEA in round bars or plates were tested mechanically. The present paper reports results obtained in tension, impact, fatigue, creep and toughness tests. These tests were carried out at various temperatures and in different directions. These materials show a pronounced anisotropy at all tested temperatures. No matter the loading, the transversal direction is always found to be far less resistant than the longitudinal one. This anisotropy is mainly observed in terms of damage mechanisms, with intergranular fracture preferentially occurring along the extrusion direction. This intergranular fracture mode leads to very low and anisotropic toughness values and to the absence of tertiairy creep stage, pointing out the unstable nature of fracture, even at high temperature. The unrealistically high values of the Norton exponent measured in creep suggests the existence of a threshold stress, which is consistent with the mainly kinematic nature of the stress as revealed by fatigue tests.

  3. Rat behaviour reactions and brain synaptic membrane lipids under the chronical gamma-irradiation

    International Nuclear Information System (INIS)

    The effects of low level chronical ionising irradiation (12.9 cGy/day on the sensory attention to the stimuli of different modalities (somatosensor, visual, odor) of Wistar rats were studied. Analysis of animals behaviour was made after they had received the different doses of irradiation: 4, 6, 8, 10, 15 and 20 Gy. It was founded, that the attention and exploratory activity of rats is significantly decreased up to 20-30% after 4-6 Gy. The irradiation doses 8 Gy did not change animal behaviour as compared to control animals, but doses 10, 15 and 20 Gy decreased the exploratory activity as well as sensory attention of rats to 3-5-times as compared to previous dose. Such a wave-like way of behaviour reflects the functioning of an adaptive mechanism. Biochemical data indicated that after 5 months of the irradiation (dose 20 Gy) the level of phospholipids, lysophosphatidylcholine, phosphatdylethanolamine, phosphatidylcholine, cholesterol were decreased

  4. Experimental creep behaviour determination of cladding tube materials under multi-axial loadings

    International Nuclear Information System (INIS)

    Cladding tubes are structural parts of nuclear plants, submitted to complex thermomechanical loadings. Thus, it is necessary to know and predict their behaviour to preserve their integrity and to enhance their lifetime. Therefore, a new experimental device has been developed to control the load path under multi-axial load conditions. The apparatus is designed to determine the thermomechanical behaviour of zirconium alloys used for cladding tubes. First results are presented. Creep tests with different biaxial loadings were performed. Results are analysed in terms of thermal expansion and of creep strain. The anisotropy of the material is revealed and iso-creep strain curves are given.

  5. Mechanical behaviour of composite materials made by resin film infusion

    OpenAIRE

    Casavola C.; Pappalettere C.; Barile C.; Tursi F.

    2010-01-01

    Innovative composite materials are frequently used in designing aerospace, naval and automotive components. In the typical structure of composites, multiple layers are stacked together with a particular sequence in order to give specific mechanical properties. Layers are organized with different angles, different sequences and different technological process to obtain a new and innovative material. From the standpoint of engineering designer it is useful to consider the single layer of ...

  6. MECHANICAL BEHAVIOUR OF ALUMINA-ZIRCONIA COMPOSITE BY SLURRY METHOD

    OpenAIRE

    JYOTI PRAKASH; DEVENDRA KUMAR; KALYANI MOHANTA

    2011-01-01

    Alumina has got some excellent properties like chemical inertness, thermal and mechanical strength against hazardous environment. Alumina is a good ceramic material which is being used for structuralapplications. To enhance the toughness and strength of the body some Zirconia is also used with it. The use of Zirconia in alumina is known as toughening of alumina. One difficulty arises, when alumina and alumina toughened composite are sintered , because the low sinterability of Alumina-Zirconia...

  7. BIODEGRADABILITY AND MECHANICAL BEHAVIOUR OF SUGAR PALM STARCH BASED BIOPOLYMER

    OpenAIRE

    J. Sahari; S. M. Sapuan; Zainudin, E. S.; Maleque, M A

    2014-01-01

    A new Sugar Palm Starch (SPS) based biopolymer was successfully developed using glycerol as plasticizer. The effect of glycerol concentration (viz., 15, 20, 30 and 40 by weight percent) to the mechanical properties of plasticized SPS biopolymer was investigated. From this investigation, it was found that the 30% glycerol concentrated biopolymer showed the highest flexural strength and impact with the value of 0.13 MPa and 6.13 kJ/m2 respectively. Later, the above 30% gl...

  8. Simulation of disordered systems of cylinders. II. mechanical behaviour

    OpenAIRE

    Stauffer, D.; Herrmann, H. J.; Roux, S

    1987-01-01

    A model is simulated, with non-linear relaxation methods close to molecular dynamics, describing the mechanical behavior of a random array of hard and soft parallel cylinders. Moreover, the hard cylinders fluctuate slightly in their radii. The relation between compression and force is about the same for the whole system as it is for two cylinders (Hertz law), if only soft cylinders exist. Instead, the radius fluctuations of the hard cylinders produce drastic deviations between the macroscopic...

  9. Mechanical behaviour of copper 15% volume niobium microcomposite wires

    Directory of Open Access Journals (Sweden)

    Marcello Filgueira

    2001-01-01

    Full Text Available Cu-Nb microcomposites are attractive in magnet pulsed field technology applications due to their anomalous mechanism of mechanical strength and high electrical conductivity. In this sense, recently it was conceived the use of Cu 15% vol. Nb wires to operate as a high tensile strength cable for a diamond cutting tool (diamond wires for marble and granite slabbing. The multifilamentary Cu 15% vol. Nb composite was obtained using a new processing route, starting with niobium bars bundled into copper tubes, without arc melting. Cold working techniques, such as swaging and wire drawing, combined with heat treatments such as sintering and annealing, and tube restacking were employed. The tensile property of the composite was measured as a function of the niobium filaments dimensions and morphology into the copper matrix, in the several processing steps. An ultimate tensile strength (UTS of 960 MPa was obtained for an areal reduction (R = Ao/A, with Ao-initial cross section area, and A-final cross section area of 4x10(8 X, in which the niobium filaments reached thickness less than 20 nm. The anomalous mechanical strength increase is attributed to the fact that the niobium filaments acts as a barrier to copper dislocations.

  10. SIMPOLE – SIMULATION OF WOOD POLES MECHANICAL BEHAVIOUR

    Directory of Open Access Journals (Sweden)

    Telmo F. M. Morgado,

    2012-06-01

    Full Text Available Generation of virtual poles, based on the statistical distribution of selected visual and physical properties, and the estimation of their mechanical properties are of great help for predicting the quality of the roundwood that a forest stand can provide. With this objective in mind, an algorithm, SIMPOLE (SIMulator of POLEs, was developed. This algorithm allows the generation of pole’s geometry, as well as the mechanical properties of clear wood and the distribution of knots along its length. This generation is made through statistical distributions. The generated poles are simulated, either according to standard EN14251 or according to EN14229, for testing with simple supported beam conditions or with cantilever beam conditions, respectively. The algorithm outputs are: the bending strength, the modulus of elasticity, the location, and cause of failure. The algorithm was calibrated with a sample of 56 maritime pine utility poles and validated with another sample of 57 small diameter maritime pine poles. The results for the validation sample show: for bending strength, a mean error of 16.9%, and for modulus of elasticity, a mean error of 17.2%. Based on these results, the algorithm shows potential to estimate mechanical characteristics of small diameter poles from a forest.

  11. Vascular Adventitia Calcification and Its Underlying Mechanism.

    Directory of Open Access Journals (Sweden)

    Na Li

    Full Text Available Previous research on vascular calcification has mainly focused on the vascular intima and media. However, we show here that vascular calcification may also occur in the adventitia. The purpose of this work is to help elucidate the pathogenic mechanisms underlying vascular calcification. The calcified lesions were examined by Von Kossa staining in ApoE-/- mice which were fed high fat diets (HFD for 48 weeks and human subjects aged 60 years and older that had died of coronary heart disease, heart failure or acute renal failure. Explant cultured fibroblasts and smooth muscle cells (SMCswere obtained from rat adventitia and media, respectively. After calcification induction, cells were collected for Alizarin Red S staining. Calcified lesions were observed in the aorta adventitia and coronary artery adventitia of ApoE-/-mice, as well as in the aorta adventitia of human subjects examined. Explant culture of fibroblasts, the primary cell type comprising the adventitia, was successfully induced for calcification after incubation with TGF-β1 (20 ng/ml + mineralization media for 4 days, and the phenotype conversion vascular adventitia fibroblasts into myofibroblasts was identified. Culture of SMCs, which comprise only a small percentage of all cells in the adventitia, in calcifying medium for 14 days resulted in significant calcification.Vascular calcification can occur in the adventitia. Adventitia calcification may arise from the fibroblasts which were transformed into myofibroblasts or smooth muscle cells.

  12. Molecular Mechanisms Underlying Psychological Stress and Cancer.

    Science.gov (United States)

    Shin, Kyeong Jin; Lee, Yu Jin; Yang, Yong Ryoul; Park, Seorim; Suh, Pann-Ghill; Follo, Matilde Yung; Cocco, Lucio; Ryu, Sung Ho

    2016-01-01

    Psychological stress is an emotion experienced when people are under mental pressure or encounter unexpected problems. Extreme or repetitive stress increases the risk of developing human disease, including cardiovascular disease (CVD), immune diseases, mental disorders, and cancer. Several studies have shown an association between psychological stress and cancer growth and metastasis in animal models and case studies of cancer patients. Stress induces the secretion of stress-related mediators, such as catecholamine, cortisol, and oxytocin, via the activation of the hypothalamic-pituitary-adrenocortical (HPA) axis or the sympathetic nervous system (SNS). These stress-related hormones and neurotransmitters adversely affect stress-induced tumor progression and cancer therapy. Catecholamine is the primary factor that influences tumor progression. It can regulate diverse cellular signaling pathways through adrenergic receptors (ADRs), which are expressed by several types of cancer cells. Activated ADRs enhance the proliferation and invasion abilities of cancer cells, alter cell activity in the tumor microenvironment, and regulate the interaction between cancer and its microenvironment to promote tumor progression. Additionally, other stress mediators, such as glucocorticoids and oxytocin, and their cognate receptors are involved in stress-induced cancer growth and metastasis. Here, we will review how each receptor-mediated signal cascade contributes to tumor initiation and progression and discuss how we can use these molecular mechanisms for cancer therapy. PMID:26916018

  13. Micro-mechanical modeling of alpha/beta two-phased titanium alloy behaviour

    International Nuclear Information System (INIS)

    In order to better describe the mechanical behaviour of the Ti-6246 alloy, a two-phase material where the alpha phase inelastic behaviour is strongly anisotropic, a micro-mechanical approach has been developed to consider the various heterogeneity levels and the role of the various internal stresses induced by its heterogenous character. Among the simulation results, it is shown that the cyclic softening (or over-softening) is not only the consequence of a reduction of transgranular internal stresses (multiplication of the number of slip bands in the alpha phase) but is also related to the inter-cellular-type internal stress redistribution. (A.B.)

  14. Impact of fission gas on irradiated PWR fuel behaviour at extended burnup under RIA conditions

    International Nuclear Information System (INIS)

    With the world-wide trend to increase the fuel burnup at discharge of the LWRs, the reliability of high burnup fuel must be proven, including its behaviour under energetic transient conditions, and in particular during RIAs. Specific aspects of irradiated fuel result from the increasing retention of gaseous and volatile fission products with burnup. The potential for swelling and transient expansion work under rapid heating conditions characterizes the high burnup fuel behaviour by comparison to fresh fuel. This effect is resulting from the steadily increasing amount of gaseous and volatile fission products retained inside the fuel structure. An attempt is presented to quantify the gas behaviour which is motivated by the results from the global tests both in CABRI and in NSRR. A coherent understanding of specific results, either transient release or post transient residual retention has been reached. The early failure of REP Na1 with consideration given to the satisfactory behaviour of the father rod of the test pin at the end of the irradiation (under load follow conditions) is to be explained both by the transient loading from gas driven fuel swelling and from the reduced clad resistance due to hydriding. (R.P.)

  15. Macro-Behaviour of Agents' Opinion under Influence of an External Field

    Science.gov (United States)

    Chang, Yun-Feng; Cai, Xu

    2007-08-01

    We propose a model to study the evolution of opinion under the influence of an external field on small world network. The macro-behaviour of agents' opinion and the relative change rate as time elapses are studied. The external field is found to play an important role in making the opinion s(t) balance or increase, and without the influence of the external field, the relative change rate γ(t) shows nonlinear increasing behaviour as time runs. What is more, this nonlinear increasing behaviour is independent of the initial condition, the strength of the external field and the time that we cancel the external field. The results may reflect some phenomena in our society, such as the function of the macro-control in China or the mass media in our society.

  16. Macro-Behaviour of Agents' Opinion under Influence of an External Field

    Institute of Scientific and Technical Information of China (English)

    CHANG Yun-Feng; CAI Xu

    2007-01-01

    @@ We propose a model to study the evolution of opinion under the influence of an external field on small world network. The macro-behaviour of agents' opinion and the relative change rate as time elapses are studied. The external field is found to play an important role in making the opinion s(t) balance or increase, and without the influence of the external field, the relative change rate γ(t) shows nonlinear increasing behaviour as time runs.What is more, this nonlinear increasing behaviour is independent of the initial condition, the strength of the external field and the time that we cancel the external field. The results may reflect some phenomena in our society, such as the function of the macro-control in China or the mass media in our society.

  17. Mechanical behaviour of new zirconia-hydroxyapatite ceramic materials

    Energy Technology Data Exchange (ETDEWEB)

    Delgado, J.A.; Morejon, L. [La Habana Univ. (Cuba). Centro de Biomateriales; Martinez, S. [Barcelona Univ. (Spain). Dept. Cristallografia, Mineralogia; Ginebra, M.P.; Carlsson, N.; Fernandez, E.; Planell, J.A. [Universidad Politecnica de Cataluna, Barcelona (Spain). CREB; Clavaguera-Mora, M.T.; Rodriguez-Viejo, J. [Universitat Autonoma de Barcelona (Spain). Dept. de Fisica

    2001-07-01

    In this work a new zirconia-hydroxyapatite ceramic material was obtained by uniaxial pressing and sintering in humid environment. The powder X-ray diffraction (XRD) patterns and infrared spectra (FT-IR) showed that the hydroxyapatite (HA) is the only calcium phosphate phase present. The fracture toughness for HA with 20 wt.% of magnesia partially stabilised zirconia (Mg-PSZ) was around 2.5 times higher than those obtained for HA pure, also the highest value of bending strength (160 MPa) was obtained for material reinforced with Mg-PSZ. For the MgPSZ-HA (20%) the fracture mechanism seems to be less transgranular. (orig.)

  18. Mechanical Behaviour of the Short Models of LHC Main Dipole Magnets

    CERN Document Server

    Andreyev, N I; Casarejos, E; Kurtyka, T; Rathjen, C; Perini, D; Siegel, N; Tommasini, D; Vanenkov, I

    1998-01-01

    A series of single and twin aperture 1 metre magnet models has been built and tested in the framework of the R&D program of main superconducting dipole magnets for the Large Hadron Collider project. The se models, designed for a nominal field of 8.3 T at 1.8 K, have been constructed to test the performance of SC coils and to optimise various design options for the full length 15 metre long dipoles. T he models have been extensively equipped with a specially developed mechanical instrumentation, enabling both the control of main assembly parameters - like coil azimuthal and axial pre-load, stress i n the outer shrinking cylinder - and also the monitoring of magnet behaviour during cooling and energising, under the action of electromagnetic forces. The instrumentation used, mainly based on strain gauge transducers, is described and the results of mechanical measurements obtained during power tests of the models are discussed and compared with the design predictions based on Finite Element calc ulations.

  19. Mechanical behaviour of the heel pad: experimental and numerical approach

    DEFF Research Database (Denmark)

    Matteoli, Sara; Fontanella, C. G.; Virga, A.; Wilhjelm, Jens E.; Corvi, A.; Natali, A. N.

    The aim of the present work was to investigate the stress relaxation phenomena of the heel pad region under different loading conditions. A 31-year-old healthy female was enrolled in this study and her left foot underwent both MRI and experimental compression tests. Experimental results were...... compared with those obtained from finite element analysis performed on numerical 3D subject-specific heel pad model built on the basis of MRI. The calcaneal fat pad tissue was described with a visco-hyperelastic model, while a fiber-reinforced hyperelastic model was formulated for the skin. The reliability...

  20. Contribution to the mechanical study of the behaviour of a welded Z3 CN 18-10 steel in service

    International Nuclear Information System (INIS)

    This work contributes to the mechanical study of the behaviour, when in service of a laminated Z3 CN 18-10 stainless steel welded by the electron beam (E.B.) or T.I.G. process. Tensile tests confirm the notch insensitivity of the material and show that the immediate mechanical behaviour of the welded joint is comparable with that of the original material. Besides it is found that as the cross-section of the specimens decreases the ultimate tensile strength increases, these variations being partly due to texture differences in the thickness of the sheet. Tests to estimate the mechanical stability of the welded joints with time, and more especially the behaviour of this stainless steel in service show that: it is deformed under constant stress at room temperature. The deformation is less serious on the welded samples than on the basic material. Fatigue resistance is greater than the standard yield strength and varies according to the direction of sampling, increasing for specimens cut transversely. It is not affected by E.B. welding and increases only with arc welding as the result of a improvement of yield strength. (author)

  1. Influence of Fabrication Technique on Behaviour Under Irradiation of Oxide Fuels

    International Nuclear Information System (INIS)

    Under a contract concluded between EURATOM and the Belgian Government concerning the use of plutonium as a nuclear reactor fuel, the CEN-BelgoNucléaire Joint Plutonium Group has studied the effects of fabrication techniques on the behaviour of UO2-PuO2 fuels under irradiation. The main object of the in-pile experiments has been to determine, by comparing the thermal conditions during irradiation, the influence of the uniformity of PuO2 distribution in UO2-PuO2 fuel elements manufactured by different techniques, with a view to ascertaining the optimum fabrication parameters. The irradiation experiments carried out so far have consisted of: (a) Four irradiation runs on a hydraulic conveyor under both static and dynamic irradiation conditions for the purpose of determining the effect of the plasticity of the constituent fuel on the behaviour under irradiation of elements fabricated by the vibration and vibrocompaction of dense powders; (b) Three irradiation runs in an instrumented capsule for the purpose of determining the temperature distribution during irradiation and the effect of burn-up on behaviour under irradiation. Complementary irradiation experiments are also to be carried out in the DIORIT reactor of the Eidgenössisches Institut für Reaktorforschung at Würenlingen. (author)

  2. Hot deformation of polycrystalline uranium dioxide: from microscopic mechanisms to macroscopic behaviour

    International Nuclear Information System (INIS)

    The improvement of nuclear fuels performances in PWR requires in particular an enhancement of creep ability of uranium dioxide in order to minimise rupture risks of the cladding material during interactions between pellets and cladding. The aim of this study is to investigate the link between the ceramic macroscopic thermo-mechanical behaviour and the changes in the fuel microstructure during deformation. Stoichiometric UO2 pellets with various grains sizes from 9 pm to 36 μm have been deformed by compression at intermediate temperatures, i.e. near TM/2, and quenched under stress. The damage is characterised by the presence of cavities at low stresses and cracks at high stresses, both along grain boundaries parallel to the compression axis. Inside grains, dislocations organise themselves into cellular substructures in which sub-boundaries are made of dislocation hexagonal networks. In these conditions, uranium dioxide deformation is described by grain boundary sliding, which is the main origin of material damage, partially accommodated by dislocational creep inside grains. A steady-state creep model is proposed on a physical basis. It accounts for the almost similar contributions of two mechanisms which are grain boundaries sliding and intragranular creep, and takes into account the grain boundary roughness. In contrast with phenomenological descriptions used up to now, this picture leads to a unique creep law on the whole range of stresses explored here, from 10 MPa to 80 MPa. The creep rate controlling mechanism seems to be the migration of sub-boundaries. The deformation at constant strain rate is controlled by the same mechanisms as creep. (author)

  3. BIODEGRADABILITY AND MECHANICAL BEHAVIOUR OF SUGAR PALM STARCH BASED BIOPOLYMER

    Directory of Open Access Journals (Sweden)

    J. Sahari

    2014-01-01

    Full Text Available A new Sugar Palm Starch (SPS based biopolymer was successfully developed using glycerol as plasticizer. The effect of glycerol concentration (viz., 15, 20, 30 and 40 by weight percent to the mechanical properties of plasticized SPS biopolymer was investigated. From this investigation, it was found that the 30% glycerol concentrated biopolymer showed the highest flexural strength and impact with the value of 0.13 MPa and 6.13 kJ/m2 respectively. Later, the above 30% glycerol biopolymer was undergone through weathering and biodegradation test. The biodegradability test showed 78.09% of tensile strength lost after 72 h of weathering testing period. Meanwhile, the weight loss (% of the same biopolymer was 63.58% after 72 h of biodegradation test.

  4. Mechanical behaviour of tape springs used in the deployment of reflectors around a solar panel

    Science.gov (United States)

    Dewalque, Florence; Collette, Jean-Paul; Brüls, Olivier

    2016-06-01

    In order to increase the production of power on small satellites, solar panels are commonly deployed and, in some cases, reflectors are added to improve the concentration factor on solar cells. In this work, reflectors are deployed by the means of compliant mechanisms known as tape springs. Their attractive characteristics are, among others, their passive behaviour, their self-locking capacity, their elastic deformations and their robustness. However, their mechanical behaviour is highly nonlinear and requires thorough analyses in order to develop predictive numerical models. It is shown here through parametric studies that the nonlinear behaviour of a tape spring is mainly governed by its geometry. Thus, for each specific application, its dimensions can be determined in order to minimise two critical features: the maximum stress affecting the structure and the maximum motion amplitude during deployment. In this paper, an optimisation procedure is proposed to meet these requirements.

  5. Modelling time-dependent mechanical behaviour of softwood using deformation kinetics

    DEFF Research Database (Denmark)

    Engelund, Emil Tang; Svensson, Staffan

    2010-01-01

    The time-dependent mechanical behaviour (TDMB) of softwood is relevant, e.g., when wood is used as building material where the mechanical properties must be predicted for decades ahead. The established mathematical models should be able to predict the time-dependent behaviour. However, these models...... are not always based on the actual physical processes causing time-dependent behaviour and the physical interpretation of their input parameters is difficult. The present study describes the TDMB of a softwood tissue and its individual tracheids. A model is constructed with a local coordinate system that follows...... and inelastic responses. The results of the model are compared with experimental results of different types. It was observed that the model is able to describe the results. Moreover, to some surprise, the introduction of only elastic and viscous properties on the microscopic scale leads to an apparent...

  6. Identification of the mechanical behaviour of biopolymer composites using multistart optimisation technique

    KAUST Repository

    Brahim, Elhacen

    2013-10-01

    This paper aims at identifying the mechanical behaviour of starch-zein composites as a function of zein content using a novel optimisation technique. Starting from bending experiments, force-deflection response is used to derive adequate mechanical parameters representing the elastic-plastic behaviour of the studied material. For such a purpose, a finite element model is developed accounting for a simple hardening rule, namely isotropic hardening model. A deterministic optimisation strategy is implemented to provide rapid matching between parameters of the constitutive law and the observed behaviour. Results are discussed based on the robustness of the numerical approach and predicted tendencies with regards to the role of zein content. © 2013 Elsevier Ltd.

  7. Mechanical design and operating behaviour of advanced LWR fuel elements

    International Nuclear Information System (INIS)

    The development of fuel elements for pressurized and and boiling water reactors during the last years was marked by a reduction of the fuel cycle costs with security and reliability in operation remaining constant. The heightening of fuel discharge burnup and the improvement of neutron economy contributed essentially to that. The latter had been achieved by a reduction of the parasitic absorption within the fuel element and the leakage of neutrons of the reactor cores. These improvements could be obtained under complete observance of the safety-relevant requirements. Due to the change to fuel elements with a higher number of rods and correspondingly lower rod power it was even possible to raise the security margins partly. A survey of the state of experiences of Siemens/KWU is given. (orig./DG)

  8. BEHAVIOUR OF BACKFILL MATERIALS FOR ELECTRICAL GROUNDING SYSTEMS UNDER HIGH VOLTAGE CONDITIONS

    Directory of Open Access Journals (Sweden)

    S. C. LIM

    2015-06-01

    Full Text Available Backfill materials like Bentonite and cement are effective in lowering grounding resistance of electrodes for a considerable period. During lightning, switching impulses and earth fault occurrences in medium and high voltage networks, the grounding system needs to handle extremely high currents either for a short duration or prolonged period respectively. This paper investigates the behaviour of bentonite, cement and sand under impulse and alternating high voltage (50Hz conditions. Fulguritic-formation was observed in all materials under alternating high voltage. The findings reveal that performance of grounding systems under high voltage conditions may significantly change from the outcomes anticipated at design stage.

  9. Predicting the mechanical behaviour of carbon fibre reinforced silicon carbide with interlaminar manufacturing defects

    OpenAIRE

    Hofmann Severin; Koch Dietmar

    2015-01-01

    A finite element approach based on experimental material data is presented in order to compute the mechanical reliability of carbon fibre reinforced silicon carbide, C/C-SiC, taking interlaminar manufacturing defects into account. The approach is evaluated on sample scale by modelling the flexural behaviour of C/C-SiC samples containing delaminations after liquid silicon infiltration (LSI) processing. The non-destructive evaluation methods, determination of fracture mechanical input data and ...

  10. Behaviour of LWR core materials under accident conditions. Proceedings of a technical committee meeting

    International Nuclear Information System (INIS)

    At the invitation of the Government of the Russian Federation, following a proposal of the International Working Group on Water Reactor Fuel Performance and Technology, the IAEA convened a Technical Committee Meeting on Behaviour of LWR Core Materials Under Accident Conditions from 9 to 13 October 1995 in Dimitrovgrad to analyze and evaluate the behaviour of LWR core materials under accident conditions with special emphasis on severe accidents. In-vessel severe accidents phenomena were considered in detail, but specialized thermal hydraulic aspects as well as ex-vessel phenomena were outside the scope of the meeting. Forty participants representing eight countries attended the meeting. Twenty-three papers were presented and discussed during five sessions. Refs, figs, tabs

  11. A semiflexible polymer chain under geometrical restrictions: Only bulk behaviour and no surface adsorption

    Directory of Open Access Journals (Sweden)

    P.K. Mishra

    2014-06-01

    Full Text Available We analyse the conformational behaviour of a linear semiflexible homo-polymer chain confined by two geometrical constraints under a good solvent condition in two dimensions. The constraints are stair shaped impenetrable surfaces. The impenetrable surfaces are lines in a two dimensional space. The infinitely long polymer chain is confined in between such two (A and B surfaces. A lattice model of a fully directed self-avoiding walk is used to calculate the exact expression of the partition function, when the chain has attractive interaction with one or both the constraints. It has been found that under the proposed model, the chain shows only a bulk behaviour. In other words, there is no possibility of adsorption of the chain due to restrictions imposed on the walks of the chain.

  12. CONSUMER BEHAVIOUR PATTERNS: IDENTIFYING BUYING MOTIVES FOR COOL DRINKS AMONGST SOUTH AFRICANS UNDER 35 YEARS OLD

    OpenAIRE

    Tudor Edu; Iliuță Costel Negricea; Alexandru Ionescu

    2013-01-01

    The consumer is in the centre of any marketing endeavour. Finding out what the consumers (individual or organization) need, desire and demand is the starting point of a marketing approach.Our research is focused on determining consumer behaviour coordinates pertaining to cool drinks amongst South Africans under the age of 35. The findings of this study provide significant information concerning the buying motives considered when purchasing cool drinks which can be extended to other categories...

  13. CVD diamond coated silicon nitride self-mated systems : tribological behaviour under high loads

    OpenAIRE

    Abreu, C. S.; Oliveira, F. J.; Belmonte, M.; Fernandes, A. J. S.; Gomes, J. R.; Silva, R. F.

    2006-01-01

    Friction and wear behaviour of self-mated chemical vapour deposited (CVD) diamond films coating silicon nitride ceramics (Si3N4) were investigated in ambient atmosphere. The tribological tests were conducted in a reciprocal motion ball-on-flat type tribometer under applied normal loads up to 80 N (~10 GPa). Several characterisation techniques - including scanning electron microscopy (SEM), atomic force microscopy (AFM) and micro-Raman studies - were used in order to assess the quality, stress s...

  14. Lattice Boltzmann Study of Velocity Behaviour in Binary Mixtures Under Shear

    OpenAIRE

    Xu, Aiguo; Gonnella, G.

    2003-01-01

    We apply lattice Boltzmann methods to study the relaxation of the velocity profile in binary fluids under shear during spinodal decomposition. In simple fluids, when a shear flow is applied on the boundaries of the system, the time required to obtain a triangular profile is inversely proportional to the viscosity and proportional to the square of the size of the system. We find that the same behaviour also occurs for binary mixtures, for any component ratio in the mixture and independently fr...

  15. Non-equilibrium behaviour in coacervate-based protocells under electric-field-induced excitation

    OpenAIRE

    Yin, Yudan; Niu, Lin; Zhu, Xiaocui; Zhao, Meiping; Zhang, Zexin; Mann, Stephen.; Liang, Dehai

    2016-01-01

    Although numerous strategies are now available to generate rudimentary forms of synthetic cell-like entities, minimal progress has been made in the sustained excitation of artificial protocells under non-equilibrium conditions. Here we demonstrate that the electric field energization of coacervate microdroplets comprising polylysine and short single strands of DNA generates membrane-free protocells with complex, dynamical behaviours. By confining the droplets within a microfluidic channel and...

  16. Behaviour of Reverse Channel Connection to Concrete Filled Hollow Tube Columns under fire conditions

    OpenAIRE

    Jafarian, Mostafa

    2013-01-01

    This thesis presents the results of a research project to investigate the behaviour of the two components of a reverse channel connection to concrete filled tubular sections: the reverse channel and the steel tubular section, at both ambient and elevated temperatures. This research forms part of a European Union funded project on the robustness of joints to composite columns under fire conditions. The specific objectives of this research are to develop methods of quantifying the load-deformat...

  17. Experimental Studies on the Mechanical Behaviour of Rock Joints with Various Openings

    Science.gov (United States)

    Li, Y.; Oh, J.; Mitra, R.; Hebblewhite, B.

    2016-03-01

    The mechanical behaviour of rough joints is markedly affected by the degree of joint opening. A systematic experimental study was conducted to investigate the effect of the initial opening on both normal and shear deformations of rock joints. Two types of joints with triangular asperities were produced in the laboratory and subjected to compression tests and direct shear tests with different initial opening values. The results showed that opened rock joints allow much greater normal closure and result in much lower normal stiffness. A semi-logarithmic law incorporating the degree of interlocking is proposed to describe the normal deformation of opened rock joints. The proposed equation agrees well with the experimental results. Additionally, the results of direct shear tests demonstrated that shear strength and dilation are reduced because of reduced involvement of and increased damage to asperities in the process of shearing. The results indicate that constitutive models of rock joints that consider the true asperity contact area can be used to predict shear resistance along opened rock joints. Because rock masses are loosened and rock joints become open after excavation, the model suggested in this study can be incorporated into numerical procedures such as finite-element or discrete-element methods. Use of the model could then increase the accuracy and reliability of stability predictions for rock masses under excavation.

  18. Dynamic Mechanical Behaviour of Ultra-high Performance Fiber Reinforced Concretes

    Institute of Scientific and Technical Information of China (English)

    LAI Jianzhong; SUN Wei

    2008-01-01

    Ultra-high performance fiber reinforced concretes (UHPFRC) were prepared by replacing 60% of cement with ultra-fine industrial waste powder.The dynamic mechanical behaviour of UHPFRC with different fiber volume fraction was researched on repeated compressive impact in four kinds of impact modes through split Hopkinson pressure bar (SHPB).The experimental results show that the peak stress and elastic modulus decrease and the strain rate and peak strain increase gradually with the increasing of impact times.The initial material damage increases and the peak stress of the specimen decreases from the second impact with the increasing of the initial incident wave.Standard strength on repeated impact is defined to compare the ability of resistance against repeated impact among different materials.The rate of reduction of standard strength is decreased by fiber reinforcement under repeated impact.The material damage is reduced and the ability of repeated impact resistance of UHPFRC is improved with the increasing of fiber volume fraction.

  19. Influence of some crystal orientations in mechanical behaviour of zircaloy-4 tubes

    International Nuclear Information System (INIS)

    Zircaloy-4 tubing used in water cooled reactors work under biaxial loading due primarily to the circunferencial swelling of the fuel elements approximating a plane-strain behaviour. The tube is produced to have crystal orientations with high yield strengths under biaxial loading and principally in transverse plane strain. The contribution of individual crystal orientations to that specific yield strength is analysed based on crystallographic lower bound yield loci. (Author)

  20. Mechanical properties and corrosion behaviour of freestanding, precipitate-free magnesium WE43 thin films

    Energy Technology Data Exchange (ETDEWEB)

    Schlueter, Kristina; Zamponi, Christiane; Quandt, Eckhard [Kiel Univ. (Germany). Inst. for Materials Science; Hapke, Julia; Hort, Norbert; Kainer, Karl Ulrich [Helmholtz-Zentrum Geesthacht Centre for Materials and Coastal Research, Geesthacht (Germany). Inst. of Materials Research

    2013-03-15

    Magnetron sputtered freestanding thin films of two modified WE43 alloys (Mg4Y3Nd and Mg4Y3Gd) consist of a supersaturated single phase microstructure with a strong texture in [0001] direction for a wide range of deposition conditions. While the deposition conditions have no significant influence on the corrosion behaviour of these samples, they strongly influence the mechanical properties, which can be tuned between extremely brittle behaviour for high sputtering pressures (2.0 x 10{sup -2} mbar) and ductile behaviour with a maximum strain of about 18% at room temperature for low sputtering pressures (8.0 x 10{sup -4} mbar) for both investigated alloys. (orig.)

  1. Effect of ageing on the mechanical behaviour of aluminium alloy AA2009 reinforced with SIC particles

    International Nuclear Information System (INIS)

    A study of the mechanical behaviour of an aluminium matrix composite (AA2009) reinforced with 15 volume percent of SiC particles has been carried out. The ageing kinetic for this material has been evaluated at two different ageing temperatures (170 and 190 degree centigrade). The hardness peaks for the two different precipitation sequences existing in the matrix alloy have been identified. The mechanical behaviour of the composite was also evaluated for the different thermal conditions (as-received and aged). This research has been completed with the identification of the fracture mechanisms by means of observation with scanning electron microscopy (SEM) both of the fracture surface and transversal sections of them. In addition, transmission electron microscopy (TEM) of the treated composites has been used to determine the influence of the SiC particles on the distribution of strengthening phases precipitated in the matrix. (Author) 14 refs

  2. A framework for modelling the behaviour of a process control operator under stress

    International Nuclear Information System (INIS)

    This paper proposes the basis for a framework for modelling effects of stress on the behaviour of a process control plant operator. The qualitative effects of stress on the cognitive processing ability of the operator are discussed. Stress is thought to mainly decrease the reasoning ability of the operator. The operator will experience increased rigidity in problem solving and the narrowing of his attention and perceptual field. At the same time, the operator will be increasingly reluctant in admitting that wrong decisions have been committed. Furthermore, he will revert to skill-based behaviours. The direct consequence of stress on the decision making mechanism of the operator is the selection of inappropriate choice of action. A formal representation of decision errors is proposed and various techniques are suggested for representing various mechanisms for decision error making. The degree of experience possessed by the operator is also an important factor to the operator's tolerance of stress. The framework also allows the experience of the operator to be integrated into the model. Such an operator model can be linked to a plant simulator and the complete behaviour of the plant then be simulated

  3. Hydro mechanical coupling for non linear behaviour laws. Application to petroleum problems; Couplage hydromecanique pour des lois de comportement non lineaires Application a des problemes petroliers

    Energy Technology Data Exchange (ETDEWEB)

    Longuemare, P.

    1996-11-28

    The aim of this study is to provide a better description of the rock contribution to fluid flows in sedimentary basins and petroleum reservoirs. After a study of the mechanical behaviour of high porosity chalks and shales, we present the elaboration of an elastoplastic constitutive model for the description of their behaviour under various strain and stress paths. This model is introduced in a coupled poro-mechanical approach and used to study the advantages of a good description of strain and stress paths in petroleum reservoirs and sedimentary basins studies. Hydro-mechanical modelling of the behaviour of petroleum reservoir allowed us to analyse the influence of boundary limit conditions on stress paths recovery rates. The study of sedimentary basins showed the importance of the consideration of the evolution of the porosity with time due to the time-scale difference between the laboratory and the field data. (author) 58 refs.

  4. Experimental characterization and mechanical behaviour modelling of MoTiC composite for high temperature applications

    Energy Technology Data Exchange (ETDEWEB)

    Cedat, D.; Rey, C.; Cavel, M. [Ecole Centrale de Paris (MSSMAT), 92 - Chatenay Malabry (France); Fandeur, O. [CEA Saclay, Dept. Modelisation de Systemes et Structures, DEN/DANS/DM2S/SEMT/LM2S, 91 - Gif-sur-Yvette (France); Le Flem, M. [CEA Saclay, Dept. des Materiaux pour le Nucleaire, DEN/DANS/DMN/SRMA, 91 - Gif-sur-Yvette (France)

    2008-07-01

    Complete text of publication follows: In the scope of refractory materials development for structural applications in the core of the future nuclear reactors such as Gas Fast Reactors, materials combining carbide and refractory metals are of great interest to avoid the major drawbacks of monolithic ceramics (poorly damage tolerant) and metals (neutronic incompatibility). This work focuses on the study of the molybdenum-titanium carbide composite processed by hot isostatic pressing. Mo-TiC composites were identified as one of the most promising structural materials in term of mechanical strength to operate at temperatures greater than 800 C (nominal processing) and up to 1650 C (accidental scenarios) under a fast neutron flux. The investigated material is a molybdenum-rich material (MoTiC{sub 30vol%}). Scanning Electron Microscopy picture revealed that titanium carbide (the hard phase) is surrounded by a grey thin-layer, created by diffusion during the forming, and identified as TiC-Mo15% by WDS. The sintered Mo-TiC composite presents a core/rim microstructure. Microstructural characterizations have been investigated: SEM, Transmission Electron Microscopy (TEM) and 3D Tomography focused on the original 3D morphology of this material, induced by the forming process. To get a 3D representation of the material, high energy X-ray tomography at the European Synchrotron Radiation Facility (ESRF, Grenoble, France) has been used. In the aim to investigate the high temperature mechanical behaviour of the cermet compressive tests were carried out in 25-700 C temperature range at constant strain rate ({epsilon}=5.10{sup -4}s{sup -1}). The material shows a slight plastic deformation ({epsilon}max=7%) at room temperature and becomes ductile at 700 C ({epsilon}max=23%). Numerical simulations were performed on a representative 3D aggregate built by 3D-EBSD experiments which were conducted using a joint high-resolution field emission SEM/EBSD set-up together with a FIB system. 20

  5. The failure behaviour of an epoxy glass flake coating/steel system under marine alternating hydrostatic pressure

    International Nuclear Information System (INIS)

    Highlights: • The failure process of the epoxy coating is accelerated by alternating pressure. • The alternating pressure deteriorates the structure of the coating/steel system. • A failure mechanism of the coating/steel system is raised. - Abstract: The failure behaviour of an epoxy glass flake coating/steel system under marine alternating hydrostatic pressure (AHP) was studied by electrochemical impedance spectroscopy (EIS), gravimetric tests, adhesion tests and scanning electron microscopy (SEM). Results reveal that AHP promoted water transportation into the coatings, and deteriorated the interface structures of the coating/steel system, including the coating/steel interface and the pigment/binder interface in the coating body. The failure process of the coating/steel system under marine AHP is discussed in the paper

  6. Laboratory Investigations of the Hydro-Mechanical-Chemical Coupling Behaviour of Sandstone in CO2 Storage in Aquifers

    Science.gov (United States)

    Zhou, Hui; Hu, Dawei; Zhang, Fan; Shao, Jianfu; Feng, Xiating

    2016-02-01

    This paper is devoted to experimental investigations of the hydro-mechanical-chemical coupling behaviour of sandstone in the context of CO2 storage in aquifers. We focused on the evolution of creep strain, the transport properties and the elastic modulus of sandstone under the effect of CO2-brine or CO2 alone. A summary of previous laboratory results is first presented, including mechanical, poromechanical and hydro-mechanical-chemical coupling properties. Tests were then performed to investigate the evolution of the creep strain and permeability during the injection of CO2-brine or CO2 alone. After the injection of CO2-brine or CO2 alone, an instantaneous volumetric dilatancy was observed due to the decrease in the effective confining stress. However, CO2 alone had a significant influence on the creep strain and permeability compared to the small influence of CO2-brine. This phenomenon can be attributed to the acceleration of the CO2-brine-rock reaction by the generation of carbonic acid induced by the dissolution of CO2 into the brine. The original indentation tests on samples after the CO2-brine-rock reaction were also performed and indicated that the elastic modulus decreased with an increasing reaction time. The present laboratory results can advance our knowledge of the hydro-mechanical-chemical coupling behaviour of sandstone in CO2 storage in aquifers.

  7. Behaviour of fourteen exotic ornamental fishes of Bangladesh under starved condition in aquaria

    Directory of Open Access Journals (Sweden)

    ABM Mohsin

    2013-12-01

    Full Text Available The behaviour of fourteen exotic ornamental fishes of Bangladesh under starved condition in aquaria was experimented from January to December, 2011. Fishes were belonging to 13 genera, 09 families and 4 orders. Two treatments each with three replications were used. Four different behavioural phases of fish were monitored through constant observation. Almost all the behavioural phases were seen earlier in the fishes of treatment T1. Marble angel survived more (1022±4.02 hrs; T2 than others. The lowest survival period (116±2.44 hrs; T1 was seen for albino suckermouth. Fishes were died earlier in T1 than T2, due to presence or absence of aeration facilities. Water temperature, dissolved oxygen, free CO2, pH, total alkalinity, ammonia-nitrogen and chlorine level were found to be varied from 25.66±0.17 to 28.66±0.35°C, 3.80±0.06 to 4.73±0.07 mg/l, 9.21±0.05 to 11.75±0.03 mg/l, 7.13±0.05 to 7.47±0.07, 76.66±1.64 to 108.92±3.20 mg/l, 0.0010±0.0006 to 0.0133±0.002 mg/l and 0.0045±0.001 to 0.012±0.0014 mg/l, respectively. The research findings would be helpful in gathering basic knowledge on different behavioural phases through which aquarists can maintain primitive behavioural phase in their aquaria. Further research work is suggested in the aforesaid theme massively.

  8. Behaviour of fibre reinforced polymer confined reinforced concrete columns under fire condition

    Science.gov (United States)

    Chowdhury, Ershad Ullah

    In recent years, fibre reinforced polymer (FRP) materials have demonstrated enormous potential as materials for repairing and retrofitting concrete bridges that have deteriorated from factors such as electro-chemical corrosion and increased load requirements. However, concerns associated with fire remain an obstacle to applications of FRP materials in buildings and parking garages due to FRP's sensitivity to high temperatures as compared with other structural materials and to limited knowledge on their thermal and mechanical behaviour in fire. This thesis presents results from an ongoing study on the fire performance of FRP materials, fire insulation materials and systems, and FRP wrapped reinforced concrete columns. The overall goal of the study is to understand the fire behaviour of FRP materials and FRP strengthened concrete columns and ultimately, provide rational fire safety design recommendations and guidelines for FRP strengthened concrete columns. A combined experimental and numerical investigation was conducted to achieve the goals of this research study. The experimental work consisted of both small-scale FRP material testing at elevated temperatures and full-scale fire tests on FRP strengthened columns. A numerical model was developed to simulate the behaviour of unwrapped reinforced concrete and FRP strengthened reinforced concrete square or rectangular columns in fire. After validating the numerical model against test data available in literature, it was determined that the numerical model can be used to analyze the behaviour of concrete axial compressive members in fire. Results from this study also demonstrated that although FRP materials experience considerable loss of their mechanical and bond properties at temperatures somewhat below the glass transition temperature of the resin matrix, externally-bonded FRP can be used in strengthening concrete structural members in buildings, if appropriate supplemental fire protection system is provided over

  9. Study of austenitic stainless steels behaviour under creep and fatigue crack growth modes at 5500C

    International Nuclear Information System (INIS)

    The behaviour of three austenitic stainless steels used for fast reactor vessels is examined under creep and fatigue crack growth modes. The behaviour of this type of material (ductile characteristic) can be described essentially by a power law (primary creep). No unique correlation can be established between creep crack growth rate and the usual load geometry parameters. An unique correlation exists between the creep crack growth initiation time and a global load geometry parameter C*exp. Time versus C* diagrams were established from the C* calculations with the semi-analytical simulations of load-point displacements, and then used for life prediction purposes in engineering applications. Under fatigue loading, the influence of experimental parameters such as frequency and R ratio has been studied as well as the effects of age hardening and cold work. The latter increases the material resistance to crack growth. A reduction in frequency and an increase in the R ratio result in increasing crack growth rate. The rupture modes of specimens were determined through metallographical examinations. The rupture was intergranular in creep tests, whilst in fatigue tests it was mixed at low Δ K values, becoming intergranular at low frequencies or transgranular at moderate frequencies. Only M23C6 carbides were found in these steels when tested at 5500C. The M23C6 precipitation was found to be accelerated by loading. It is necessay to know the microstructural evolution in order to understand the macroscopic stainless steel behaviour

  10. Simulation of the behaviour of nuclear fuel under high burnup conditions

    International Nuclear Information System (INIS)

    Highlights: • Increasing the time of nuclear fuel into reactor generates high burnup structure. • We analyze model to simulate high burnup scenarios for UO2 nuclear fuel. • We include these models in the DIONISIO 2.0 code. • Tests of our models are in very good agreement with experimental data. • We extend the range of predictability of our code up to 60 MWd/KgU average. - Abstract: In this paper we summarize all the models included in the latest version of the DIONISIO code related to the high burnup scenario. Due to the extension of nuclear fuels permanence under irradiation, physical and chemical modifications are developed in the fuel material, especially in the external corona of the pellet. The codes devoted to simulation of the rod behaviour under irradiation need to introduce modifications and new models in order to describe those phenomena and be capable to predict the behaviour in all the range of a general pressurized water reactor. A complex group of subroutines has been included in the code in order to predict the radial distribution of power density, burnup, concentration of diverse nuclides and porosity within the pellet. The behaviour of gadolinium as burnable poison also is modelled into the code. The results of some of the simulations performed with DIONISIO are presented to show the good agreement with the data selected for the FUMEX I/II/III exercises, compiled in the NEA data bank

  11. High temperature mechanical behaviour of WC-6 wt.% Co cemented carbide

    International Nuclear Information System (INIS)

    The mechanical and fracture behaviour of a cemented carbide WC-6 wt% Co has been studied from room temperature up to 10000C. Elastic modulus, fracture strength and fracture toughness have been measured in inert atmosphere by four point bend tests. Between room temperature and 8000C, there is only limited plasticity and linear elastic mechanics can be applied. Above 8000C, linear fracture mechanics theory is no longer valid on account of significant plasticity. So the material toughness has been characterized with the J integral. Several methods have been used and discussed

  12. Contamination and decontamination behaviour, under operational conditions, of improved surfaces being considered for alpha active environments

    International Nuclear Information System (INIS)

    A range of surface finishes and coatings, both permanent and temporary have been evaluated in terms of their contamination/decontamination behaviour under realistic conditions within four operational glove boxes handling plutonium in a variety of different forms including oxide, metal and solutions. Disc samples housed within tiles were positioned in the glove boxes to represent wall and floor contamination. Examination after periods of exposure up to 150 days revealed relatively low levels of contamination, 2-2 in wall tiles and 2cm2 on the floor tiles, and no consistent trends in behaviour could be related to sample type. Decontamination factors were generally in the range of 2-15 following ultrasonic washing, and residual levels were also found not to be sample specific. Further exposure to higher contamination levels are recommended before reexamination is attempted. (author)

  13. Antidepressant-Resistant Depression and Antidepressant-Associated Suicidal Behaviour: The Role of Underlying Bipolarity

    Directory of Open Access Journals (Sweden)

    Zoltan Rihmer

    2011-01-01

    Full Text Available The complex relationship between the use of antidepressants and suicidal behaviour is one of the hottest topics of our contemporary psychiatry. Based on the literature, this paper summarizes the author's view on antidepressant-resistant depression and antidepressant-associated suicidal behaviour. Antidepressant-resistance, antidepressant-induced worsening of depression, antidepressant-associated (hypomanic switches, mixed depressive episode, and antidepressant-associated suicidality among depressed patients are relatively most frequent in bipolar/bipolar spectrum depression and in children and adolescents. As early age at onset of major depressive episode and mixed depression are powerful clinical markers of bipolarity and the manic component of bipolar disorder (and possible its biological background shows a declining tendency with age antidepressant-resistance/worsening, antidepressant-induced (hypomanic switches and “suicide-inducing” potential of antidepressants seem to be related to the underlying bipolarity.

  14. Non-equilibrium behaviour in coacervate-based protocells under electric-field-induced excitation

    Science.gov (United States)

    Yin, Yudan; Niu, Lin; Zhu, Xiaocui; Zhao, Meiping; Zhang, Zexin; Mann, Stephen; Liang, Dehai

    2016-02-01

    Although numerous strategies are now available to generate rudimentary forms of synthetic cell-like entities, minimal progress has been made in the sustained excitation of artificial protocells under non-equilibrium conditions. Here we demonstrate that the electric field energization of coacervate microdroplets comprising polylysine and short single strands of DNA generates membrane-free protocells with complex, dynamical behaviours. By confining the droplets within a microfluidic channel and applying a range of electric field strengths, we produce protocells that exhibit repetitive cycles of vacuolarization, dynamical fluctuations in size and shape, chaotic growth and fusion, spontaneous ejection and sequestration of matter, directional capture of solute molecules, and pulsed enhancement of enzyme cascade reactions. Our results highlight new opportunities for the study of non-equilibrium phenomena in synthetic protocells, provide a strategy for inducing complex behaviour in electrostatically assembled soft matter microsystems and illustrate how dynamical properties can be activated and sustained in microcompartmentalized media.

  15. Supersymmetric quantum mechanics under point singularities

    International Nuclear Information System (INIS)

    We provide a systematic study on the possibility of supersymmetry (SUSY) for one-dimensional quantum mechanical systems consisting of a pair of lines R or intervals [-l, l] each having a point singularity. We consider the most general singularities and walls (boundaries) at x = ±l admitted quantum mechanically, using a U(2) family of parameters to specify one singularity and similarly a U(1) family of parameters to specify one wall. With these parameter freedoms, we find that for a certain subfamily the line systems acquire an N = 1 SUSY which can be enhanced to N = 4 if the parameters are further tuned, and that these SUSY are generically broken except for a special case. The interval systems, on the other hand, can accommodate N = 2 or N = 4 SUSY, broken or unbroken, and exhibit a rich variety of (degenerate) spectra. Our SUSY systems include the familiar SUSY systems with the Dirac δ(x)-potential, and hence are extensions of the known SUSY quantum mechanics to those with general point singularities and walls. The self-adjointness of the supercharge in relation to the self-adjointness of the Hamiltonian is also discussed

  16. Mechanical behaviour of HTR materials: Developments in support of defect assessment, structural integrity and lifetime evaluation

    International Nuclear Information System (INIS)

    Mod 9Cr-1Mo steel (T91) is a candidate material for pressure vessels and for some internal structures of GCR (Gas Cooled Reactors). In order to validate this choice, it is necessary, firstly to verify that it is able to withstand the planned environmental and operating conditions, and secondly to check if it is covered by the existing design codes, concerning its procurement, fabrication, welding, examination methods and mechanical design rules. A large R and D program on mod 9Cr-1Mo steel has been undertaken at CEA in order to characterize the behaviour of this material and of its welded junctions. In this program, the role of the Laboratory for structural Integrity and Standards (LISN) is to develop high temperature defect assessment procedures under fatigue and creep loadings. Concerning the GCR, complementary studies are conducted in order to validate the existing methods (developed for the fast reactors) and to get new experimental data on Mod 9Cr-1Mo steel. Moreover, if the geometry and the loadings of a standard CT specimen allow performing a 2D analysis, the case of industrial loadings appears much more complicated, notably because of surface defects which propagate and present shapes that can be considered as half ellipse. Therefore, in the frame of the defect assessment methods validation, the LISN undertakes both standard tests on CT specimens to determine the propagation laws and bending tests on large plates under high temperature fatigue and creep loadings. These components present an initial semi-elliptical surface notch normal to the loading direction and its initiation and propagation are studied.

  17. Factors influencing the mechanical behaviour of healthy human descending thoracic aorta

    International Nuclear Information System (INIS)

    In recent times, significant effort has been made to understand the mechanical behaviour of the arterial wall and how it is affected by the different vascular pathologies. However, to be able to interpret the results correctly, it is essential that the influence of other factors, such as aging or anisotropy, be understood. Knowledge of mechanical behaviour of the aorta has been customarily constrained by lack of data on fresh aortic tissue, especially from healthy young individuals. In addition, information regarding the point of rupture is also very limited. In this study, the mechanical behaviour of the descending thoracic aorta of 28 organ donors with no apparent disease, whose ages vary from 17 to 60 years, is evaluated. Tensile tests up to rupture are carried out to evaluate the influence of age and wall anisotropy. Results reveal that the tensile strength and stretch at failure of healthy descending aortas show a significant reduction with age, falling abruptly beyond the age of 30. This fact places age as a key factor when mechanical properties of descending aorta are considered

  18. Identification of the mechanical behaviour and damage mechanisms of a Nextel™610/alumina ceramic matrix composite subjected to tensile loading.

    OpenAIRE

    Ben Ramdane, C.; Jankowiak, A.; Parlier, M.; Valle, R.; Martin, E.; Diss, P.

    2015-01-01

    (x ± y % = 4 words → counted as 1 , z % = 2 words → counted as 1 → total: < 150 words) The present study was aimed at determining the mechanical behaviour of a weak matrix oxide/oxide CMC subjected to monotonic and cyclic tensile loading in fibre direction and in ±45° fibre orientation and at identifying the damage mechanisms. The material consisted of Nextel™610 fibres (8 HSW) embedded in an alumina matrix, with a fibre volume fraction of 49 % and 24 ± 2 % porosity. The average ultimate tens...

  19. Cellular and molecular mechanisms underlying muscular dystrophy

    OpenAIRE

    Rahimov, Fedik; Kunkel, Louis M

    2013-01-01

    The muscular dystrophies are a group of heterogeneous genetic diseases characterized by progressive degeneration and weakness of skeletal muscle. Since the discovery of the first muscular dystrophy gene encoding dystrophin, a large number of genes have been identified that are involved in various muscle-wasting and neuromuscular disorders. Human genetic studies complemented by animal model systems have substantially contributed to our understanding of the molecular pathomechanisms underlying ...

  20. Influence of Water Content on the Mechanical Behaviour of Limestone: Role of the Clay Minerals Content

    Science.gov (United States)

    Cherblanc, F.; Berthonneau, J.; Bromblet, P.; Huon, V.

    2016-06-01

    The mechanical characteristics of various sedimentary stones significantly depend on the water content, where 70 % loss of their mechanical strengths can be observed when saturated by water. Furthermore, the clay fraction has been shown to be a key factor of their hydro-mechanical behaviour since it governs for instance the hydric dilation. This work aims at investigating the correlations between the clay mineral content and the mechanical weakening experienced by limestones when interacting with water. The experimental characterization focuses on five different limestones that exhibit very different micro-structures. For each of them, we present the determination of clay mineral composition, the sorption isotherm curve and the dependences of tensile and compressive strengths on the water content. It emerges from these results that, first, the sorption behaviour is mainly governed by the amount of smectite layers which exhibit the larger specific area and, second, the rate of mechanical strength loss depends linearly on the sorption capacity. Indeed, the clay fraction plays the role of a retardation factor that delays the appearance of capillary bridges as well as the mechanical weakening of stones. However, no correlation was evidenced between the clay content and the amplitude of weakening. Since the mechanisms whereby the strength decreases with water content are not clearly established, these results would help to discriminate between various hypothesis proposed in the literature.

  1. Mechanisms Underlying Induction of Tolerance to Foods.

    Science.gov (United States)

    Berin, M Cecilia; Shreffler, Wayne G

    2016-02-01

    Oral tolerance refers to a systemic immune nonresponsiveness to antigens first encountered by the oral route, and a failure in development of this homeostatic process can result in food allergy. Clinical tolerance induced by allergen immunotherapy is associated with alterations in immune mechanisms relevant to the allergic response, including reduction of basophil reactivity, induction of IgG4, loss of effector Th2 cells, and induction of Tregs. The relative contribution of these immune changes to clinical tolerance to foods, and the duration of these immune changes after termination of immunotherapy, remains to be identified. PMID:26617229

  2. Habitats under Mechanical and Herbicide Management Regimes

    Directory of Open Access Journals (Sweden)

    Wendy-Ann P. Isaac

    2012-01-01

    Full Text Available Commelina diffusa is a colonising species of banana orchard habitats in St. Vincent in the Windward Islands of the Caribbean. In the present study, the population dynamics of C. diffusa were investigated in response to mechanical weed management with either a rotary string trimmer or glufosinate in ruderal and banana habitats. The study focused on density and size distribution of the weed over time and their response to two weed management strategies. The population dynamics of C. diffusa differed between the two habitats. Seedling establishment appeared to be an important factor influencing the dynamics of C. diffusa in banana orchards as there was little recruitment of seeds with less flower production compared with ruderal habitats where plants produced more flowers. Plants of C. diffusa in the banana orchard habitat had a longer growth cycle. In the banana orchard habitat, the C. diffusa population was greater and the plants were shorter with mechanical management than in areas treated with glufosinate. The results suggest that it is possible to manipulate the dynamics of C. diffusa in banana orchards as there is less chance of seed recruitment. Further research is necessary to refine an IPM approach for the management of C. diffusa.

  3. Predicting the mechanical behaviour of carbon fibre reinforced silicon carbide with interlaminar manufacturing defects

    Directory of Open Access Journals (Sweden)

    Hofmann Severin

    2015-01-01

    Full Text Available A finite element approach based on experimental material data is presented in order to compute the mechanical reliability of carbon fibre reinforced silicon carbide, C/C-SiC, taking interlaminar manufacturing defects into account. The approach is evaluated on sample scale by modelling the flexural behaviour of C/C-SiC samples containing delaminations after liquid silicon infiltration (LSI processing. The non-destructive evaluation methods, determination of fracture mechanical input data and the numerical cohesive zone approach are described. The numerical predictions of flexural stiffness and strength of samples with and without interlaminar defects were validated by bending tests of the respective samples. The difference between tensile and bending behaviour is explained by FE modelling for this group of CMC materials.

  4. Long-term behaviour of concretes: pure water chemical damaging and coupling with mechanics

    International Nuclear Information System (INIS)

    The durability of concrete structures represents an essential stake of the safety analysis of nuclear waste disposal centres (containers, sealing, casemates, surveillance galleries). The originality of this study is the coupling between the mechanical behaviour of the material (in particular the crack growth) and a damaging of chemical origin (dissolution of cement hydrates due to pure water trickling). A model has been developed to evaluate this coupling and introduced in a finite-elements calculation code. The calcium content of the interstitial solution is chosen as the status variable of the system. The elasticity modules changes as a function of this variable. The non-linear mechanical behaviour of the concrete is modeled according to the damaging theory. In parallel to this modeling approach, specific procedures and experiments were developed for industrial applications. (J.S.)

  5. Synaptic mechanisms underlying persistent cocaine craving.

    Science.gov (United States)

    Wolf, Marina E

    2016-06-01

    Although it is challenging for individuals with cocaine addiction to achieve abstinence, the greatest difficulty is avoiding relapse to drug taking, which is often triggered by cues associated with prior cocaine use. This vulnerability to relapse persists for long periods (months to years) after abstinence is achieved. Here, I discuss rodent studies of cue-induced cocaine craving during abstinence, with a focus on neuronal plasticity in the reward circuitry that maintains high levels of craving. Such work has the potential to identify new therapeutic targets and to further our understanding of experience-dependent plasticity in the adult brain under normal circumstances and in the context of addiction. PMID:27150400

  6. Mechanical behaviour of alkali-activated blast furnace slag-activated metakaolin blended pastes. Statistical study

    OpenAIRE

    Higuera, I.; Varga, C.; Palomo, J. G.; Gil-Maroto, A.; Vázquez, T.; Puertas, F.

    2012-01-01

    The study and development of alternative, more ecoefficient binders than portland cement are attracting a good deal of scientific and technological interest. Binders obtained from the chemical interaction between calcium silico-aluminous materials and highly alkaline solutions are one of several types of such possible cements. The present paper discusses the mechanical behaviour and mineralogical composition of blended pastes made from NaOH-activated vitreous blast furnace slag and metakaolin...

  7. LOADING RATE EFFECT ON THE MECHANICAL BEHAVIOUR OF A PYROCLASTIC SOIL

    OpenAIRE

    Rojas Vidovic, Juan Carlos

    2008-01-01

    This thesis represents a laboratory-based experimental study into the rate of loading effect on the mechanical behaviour of an unsaturated pyroclastic soil. The study includes equipment design and laboratory testing which are addressed to analyze the rate of loading influence by means of equip-ment modification and suction controlled triaxial tests. The studied material, characterized by its very low density, is typical of the area around Naples where natural slopes are covered by loose s...

  8. Macroscopic and Microscopic Investigation on the History Dependence of the Mechanical Behaviour of Powders

    OpenAIRE

    Kadau, D.; Brendel, L.; Bartels, G.; Wolf, D. E.; Morgeneyer, M.; Schwedes, J.

    2003-01-01

    As an example for history dependent mechanical behaviour of cohesive powders experiments and computer simulations of uniaxial consolidation are compared. Some samples were precompacted transversally to the consolidation direction and hence had a different history. The experiments were done with two carbonyl iron powders, for which the average particle diameters differed by a factor of ca. 2. Whereas the particle diameter was the only characteristic length in the simulations, the evaluation of...

  9. Mechanical properties and creep resistance behaviour of IN-713C alloy castings

    OpenAIRE

    F. Binczyk; J. Śleziona

    2010-01-01

    The paper presents the results of investigations on the effect of modification process on mechanical properties and high-temperature creep resistance behaviour of IN-713C alloy specimens. Two melts modified in volume were made and one melt modified by combined surfacevolume technique. A beneficial modifying effect of filters designed according to the authors’ genuine concept has been proved. As a reference, the results obtained on non-modified castings were used. A very beneficial effect of c...

  10. Effects of mechanical heterogeneity on the tensile and fatigue behaviours in a laser-arc hybrid welded aluminium alloy joint

    International Nuclear Information System (INIS)

    Highlights: • Full field strain evolution was characterized using DIC method in fatigue test. • The differences of fatigue failure mechanism between HAZ and FZ were discussed. • Porosity in FZ significantly influenced high cycle fatigue behaviours of the weld. - Abstract: The effects of mechanical heterogeneity on the tensile and high cycle fatigue (104–107 cycles) properties were investigated for laser-arc hybrid welded aluminium alloy joints. Tensile–tensile cyclic loading with a stress ratio of 0.1 was applied in a direction perpendicular to the weld direction for up to 107 cycles. The local mechanical properties in the tensile test and the accumulated plastic strain in the fatigue test throughout the weld’s different regions were characterized using a digital image correlation technique. The tensile results indicated heterogeneous tensile properties throughout the different regions of the aluminium welded joint, and the heat affected zone was the weakest region in which the strain localized. In the fatigue test, the accumulated plastic strain evolutions in different subzones of the weld were analyzed, and slip bands could be clearly observed in the heat affected zone. A transition of fatigue failure locations from the heat affected zone caused by accumulated plastic strain to the fusion zone induced by fatigue crack at pores could be observed under different cyclic stress levels. The welding porosity in the fusion zone significantly influences the high cycle fatigue behaviour

  11. Alteration mechanisms of UOX spent fuel under water

    International Nuclear Information System (INIS)

    The mechanisms of spent fuel alteration in aqueous media need to be understood on the assumption of a direct disposal of the assemblies in a geological formation or for long duration storage in pool. This work is a contribution to the study of the effects of the alpha and/or beta/gamma radiolysis of water on the oxidation and the dissolution of the UO2 matrix of UOX spent fuel. The effects of the alpha radiolysis, predominant in geological disposal conditions, were quantified by using samples of UO2 doped with plutonium. The leaching experiments highlighted two types of control for the matrix alteration according to the alpha activity. The first is based on the radiolytic oxidation of the surface and leads to a continuous release of uranium in solution whereas the second is based on a control by the solubility of uranium. An activity threshold, between 18 MBq.g-1 and 33 MBq.g-1, was defined in a carbonated water. The value of this threshold is dependent on the experimental conditions and the presence or not of electro-active species such as hydrogen in the system. The effects of the alpha/beta/gamma radiolysis in relation with the storage conditions were also quantified. The experimental data obtained on spent fuel indicate that the alteration rate of the matrix based on the behaviour of tracer elements (caesium and strontium) reached a maximum value of some mg.m-2.d-1, even under very oxidizing conditions. The solubility of uranium and the nature of the secondary phases depend however on the extent of the oxidizing conditions. (author)

  12. Effect of the curing conditions of concrete on the behaviour under freeze-thaw cycles*

    OpenAIRE

    Al‐Assadi, Ghaida; Casati Calzada, María Jesús; Fernandez Gomez, Jaime Antonio; Gálvez Ruíz, Jaime

    2011-01-01

    The aim of this work is to relate the curing conditions of concrete and the addition of an air-entraining admixture with the damage caused by freeze–thaw cycles. In countries with a continental climate, the curing of concrete in summer is performed under climatic conditions of high temperature and low humidity, and during the winter the concrete suffers conditions of freeze–thaw, often accompanied by the use of de-icing salts. This paper shows the experimental results of the behaviour of conc...

  13. Lattice Boltzmann Study of Velocity Behaviour in Binary Mixtures Under Shear

    CERN Document Server

    Xu, A; Xu, Aiguo

    2003-01-01

    We apply lattice Boltzmann methods to study the relaxation of the velocity profile in binary fluids under shear during spinodal decomposition. In simple fluids, when a shear flow is applied on the boundaries of the system, the time required to obtain a triangular profile is inversely proportional to the viscosity and proportional to the square of the size of the system. We find that the same behaviour also occurs for binary mixtures, for any component ratio in the mixture and independently from the time when shear flow is switched on during phase separation.

  14. Analysis of the behaviour of under-clad and surface cracks in cladded components

    International Nuclear Information System (INIS)

    The issue of the contribution is the characterization of under-clad and surface crack behaviour in ferritic steel components with an austenitic welded cladding. The experimental investigations were performed using large-scale samples. The residual stress field was determined in detail by a numerical simulation of the welding and heat treatment processes. These results were used for the numerical simulation of crack initiation and crack arrest. In all evaluated cases the crack was initiated in the ferritic material, while the cladding stayed intact even in case of a crack jump in the base metal. In the frame of case studies the results were transferred to application relevant geometries

  15. Influence of strain rate and temperature on the mechanical behaviour of austenitic steel

    International Nuclear Information System (INIS)

    The mechanical behaviour of austenitic steel Z 6 NCTD 25-15 has been studied in regard to three parameters: strain-rate, temperature and precipitation state. After a structural study to determine the more convenient precipitation states, tensile and compressive tests have been performed between -1960C. and +8000C, in a strain-rate range laying between 10-5 s-1 and 103 s-1. Strain-rate temperature equivalence has been verified, but in some case, other phenomenons in deformation mechanism can occur, such twinning or Portevin Le Chatelier effect, wich make difficult this extrapolation

  16. Effects of fibre content on mechanical properties and fracture behaviour of short carbon fibre reinforced geopolymer matrix composites

    Indian Academy of Sciences (India)

    Tiesong Lin; Dechang Jia; Meirong Wang; Peigang He; Defu Liang

    2009-02-01

    Geopolymer matrix composites reinforced with different volume fractions of short carbon fibres (Cf/geopolymer composites) were prepared and the mechanical properties, fracture behaviour and microstructure of as-prepared composites were studied and correlated with fibre content. The results show that short carbon fibres have a great strengthening and toughening effect at low volume percentages of fibres (3.5 and 4.5 vol.%). With the increase of fibre content, the strengthening and toughening effect of short carbon fibres reduce, possibly due to fibre damage, formation of high shear stresses at intersect between fibres and strong interface cohesion of fibre/matrix under higher forming pressure. The property improvements are primarily based on the network structure of short carbon fibre preform and the predominant strengthening and toughening mechanisms are attributed to the apparent fibre bridging and pulling-out effect.

  17. Poroelastic Mechanical Effects of Hemicelluloses on Cellulosic Hydrogels under Compression

    Science.gov (United States)

    Lopez-Sanchez, Patricia; Cersosimo, Julie; Wang, Dongjie; Flanagan, Bernadine; Stokes, Jason R.; Gidley, Michael J.

    2015-01-01

    Hemicelluloses exhibit a range of interactions with cellulose, the mechanical consequences of which in plant cell walls are incompletely understood. We report the mechanical properties of cell wall analogues based on cellulose hydrogels to elucidate the contribution of xyloglucan or arabinoxylan as examples of two hemicelluloses displaying different interactions with cellulose. We subjected the hydrogels to mechanical pressures to emulate the compressive stresses experienced by cell walls in planta. Our results revealed that the presence of either hemicellulose increased the resistance to compression at fast strain rates. However, at slow strain rates, only xyloglucan increased composite strength. This behaviour could be explained considering the microstructure and the flow of water through the composites confirming their poroelastic nature. In contrast, small deformation oscillatory rheology showed that only xyloglucan decreased the elastic moduli. These results provide evidence for contrasting roles of different hemicelluloses in plant cell wall mechanics and man-made cellulose-based composite materials. PMID:25794048

  18. The ''THERMOST'' for analysing thermo-structural behaviour of LWR fuel rod under PCI conditions

    International Nuclear Information System (INIS)

    As one of the methods for evaluating the fuel rod performances under power ramping or load following operations, the combined ''FROST'' and ''THERMOST'' system has been developed and being brought into practical use. The former had already been presented at Blackpool Meeting in 1978, and the latter is going to be presented in this paper. The major purpose of the THERMOST is to analyse very detailed thermal and structural fuel behaviours in a rather localized part of fuel rod whereas the FROST deals with whole-rod-wide general performances. The code handles 2-dimensional thermal and structural analyses simultaneously by using finite element method, in axial section wide or in lateral section wide. It consists of a fundamental FEM system of generalized constitution and its surrounding subroutine system which characterizes fuel behaviours such as temperature distribution, thermal expansion, elastoplasticity, creep, cracking, swelling, growth, etc. Thermal analysis is handled by heat conduction and heat transfer elements (6 kinds) and structural analysis by axisymmetric ring and lateral plane elements (6 kinds). Boundary problems such as contact, friction and cracking are treated by gap and crack elements. A sample calculation of PCI performance on a PWR fuel rod under ramping condition is presented with some inpile test data. (author)

  19. Heritable variation underlies behavioural types in the mating context in male bluefin killifish

    OpenAIRE

    McGhee, Katie E.; Travis, Joseph

    2013-01-01

    In many species, consistent behavioural differences among individuals are linked to fitness variation. Determining the environmental and genetic factors that mould these behavioural types is crucial to understanding how behaviours might respond to selection. Male bluefin killifish, Lucania goodei, show extensive consistent behavioural variation in their levels of courtship, male-directed aggression and female-directed aggression, resulting in a range of fitness-related behavioural types coexi...

  20. Influence of strain rate on the mechanical behaviour in tension of bovine cortical bone

    Science.gov (United States)

    Latella, C.; Dotta, M.; Forni, D.; Tesio, N.; Cadoni, E.

    2015-09-01

    The mechanical behaviour of bones when subjected to tension loading in a wide range of strain-rates is fundamental to develop protection systems. The paper presents the preliminary tests on the tensile behaviour of bovine cortical bone at medium and high strain rates. Two special apparatus, both installed at the DynaMat Laboratory of the University of Applied Sciences of Southern Switzerland, a Hydro-Pneumatic Machine and a Modified Hopkinson Bar respectively for medium and high strain-rate tests have been used. Flat shape specimens (having 10 mm of gauge length, 5 mm width and 3 mm thickness) have been obtained from 15 bovine femurs with the same age. The paper describes the preparation techniques of the samples and the experimental results obtained. The bovine cortical bone shown a quite important strain rate dependency.

  1. Mechanical Properties and Water Absorption Behaviour of Durian Rind Cellulose Reinforced Poly(lactic acid Biocomposites

    Directory of Open Access Journals (Sweden)

    Patpen Penjumras

    2015-01-01

    Full Text Available Environmental concerns have resulted in replacing petrochemically derived polymer with biodegradable renewable resource. In this study, mechanical properties and water absorption behaviour of durian rind cellulose reinforced poly(lactic acid biocomposites were investigated. Poly(lactic acid was mixed with 25 and 35 wt. % of durian rind cellulose that was derived from durian consumption wastes. The biocomposties were melt-blended at 165 and 175 °C with 15 min using a Brabender internal mixer followed by a hot compression moulding technique. The results showed that impact strength and modulus of Young increased with increasing of cellulose content but decreased at higher mixing temperature. Water absorption behaviour of biocomposites as function of days was also investigated. It was found that the water absorption amount of biocomposites increased with increasing of cellulose content and exposure time.    

  2. Mechanical, thermal, rheological and morphological behaviour of irradiated PP/HA composites

    International Nuclear Information System (INIS)

    Hydroxyapatite (HA) reinforced polypropylene (PP) composites are being developed as bone graft materials. In this research, the effect of γ irradiation on mechanical, rheological, thermal and morphological behaviour of PP-HA composites was studied. The melt flow index of polymer increased markedly when it was exposed to radiation. This is indicative of chain scission reaction as the predominant process. During the tensile testing, the composites exhibited brittle behaviour, showing no fluency point. Elongation at break showed a tendency to decrease with the increase in radiation dose while stress at break did not show significant variation with radiation dose. High HA content (>20%) and radiation dose (25 kGy) had significant influence on thermal stability

  3. Behavioural and hormonal aspects of the oestrous cycle in swamp buffaloes reared under temperate conditions

    International Nuclear Information System (INIS)

    A series of experiments was carried out using a small herd of swamp buffaloes raised in Japan under temperate conditions at 36 deg. N latitude, with a view to determining whether they exhibit peculiar characteristics in their oestrous cycles. The studies on the oestrous behaviour revealed that under adequate feeding and management conditions, buffaloes regularly display oestrous throughout the year, with the cycle length, duration of oestrous and time of ovulation all falling within ranges similar to those reported in cattle. External signs of oestrus were generally less evident, as previously reported. Hormonal analysis showed that there were no remarkable differences between swamp buffaloes and cattle in terms of the secretory patterns of pituitary gonadotrophins and ovarian steroids during the oestrous cycle. (author). 13 refs, 2 figs

  4. Influence of localized plasticity on oxidation behaviour of austenitic stainless steels under primary water reactor

    Energy Technology Data Exchange (ETDEWEB)

    Cissé, Sarata [CEA Saclay, DEN/DANS/DMN/SEMI, 91191 Gif-sur-Yvette Cedex (France); Laffont, Lydia, E-mail: lydia.laffont@ensiacet.fr [Institut CARNOT, CIRIMAT-ENSIACET, 4 allée Emile Monso, 31030 Toulouse Cedex 4 (France); Lafont, Marie-Christine [Institut CARNOT, CIRIMAT-ENSIACET, 4 allée Emile Monso, 31030 Toulouse Cedex 4 (France); Tanguy, Benoit [CEA Saclay, DEN/DANS/DMN/SEMI, 91191 Gif-sur-Yvette Cedex (France); Andrieu, Eric [Institut CARNOT, CIRIMAT-ENSIACET, 4 allée Emile Monso, 31030 Toulouse Cedex 4 (France)

    2013-02-15

    The sensitivity of precipitation-strengthened A286 austenitic stainless steel to stress corrosion cracking was studied by means of slow-strain-rate tests. First, alloy cold working by low cycle fatigue (LCF) was investigated. Fatigue tests under plastic strain control were performed at different strain levels (Δε{sub p}/2 = 0.2%, 0.5%, 0.8% and 2%) to establish correlations between stress softening and the deformation microstructure resulting from the LCF tests. Deformed microstructures were identified through TEM investigations. The interaction between oxidation and localized deformation bands was also studied and it resulted that localized deformation bands are not preferential oxide growth channels. The pre-cycling of the alloy did not modify its oxidation behaviour. However, intergranular oxidation in the subsurface under the oxide layer formed after exposure to PWR primary water was shown.

  5. Influence of localized plasticity on oxidation behaviour of austenitic stainless steels under primary water reactor

    International Nuclear Information System (INIS)

    The sensitivity of precipitation-strengthened A286 austenitic stainless steel to stress corrosion cracking was studied by means of slow-strain-rate tests. First, alloy cold working by low cycle fatigue (LCF) was investigated. Fatigue tests under plastic strain control were performed at different strain levels (Δεp/2 = 0.2%, 0.5%, 0.8% and 2%) to establish correlations between stress softening and the deformation microstructure resulting from the LCF tests. Deformed microstructures were identified through TEM investigations. The interaction between oxidation and localized deformation bands was also studied and it resulted that localized deformation bands are not preferential oxide growth channels. The pre-cycling of the alloy did not modify its oxidation behaviour. However, intergranular oxidation in the subsurface under the oxide layer formed after exposure to PWR primary water was shown

  6. Analyze of phase's mechanical behaviour of a multiphase polycrystalline alloy by X-ray and neutron diffraction

    International Nuclear Information System (INIS)

    The aim of this work is to propose a methodology using diffraction methods and theoretical approaches of self-consistent modeling in order to analyze and better understand the mechanical behavior of each phase of hot-rolled duplex stainless steel. The purpose of the experimental study is to characterize the local mechanical behavior of phases under uniaxial loading. X-ray and neutron diffraction which enable to measure strains in each phase separately were used in this aim. Austenitic and ferritic phase stresses are determined by X-ray diffraction during tensile tests. Evolution of the elastic strains in each phase was measured by neutron diffraction using 'time-of-flight' method during tensile and compression tests. Elastic constants were given using the self-consistent model for a purely elastic deformation. To reproduce the mechanical behaviour of the studied material, self-consistent polycrystalline micro-mechanical model for elastoplastic deformation has been adapted and confronted to experimental results. Crystallographic texture and initial residual stresses were considered in this analysis. Critical shear stresses and hardening parameters of each phase of the studied duplex steel have been identified. Results of this study showed that the austenitic phase represents the softest and the most hardenable phase. Taking into account in calculations the initial residual stresses in the non deformed sample leads to the conclusion that the initial stresses modify considerably the values of phase's yield stresses. Good agreement has been noted comparing results obtained by XRD to those obtained by neutron diffraction. The problem of relaxation of normal stresses in the analysed layer by X-rays was analysed and discussed. Using XRD and self-consistent modelling, the effect of the chemical composition of the duplex stainless steel and the influence of ageing at 400 C degrees for 1000 h on the mechanical behaviour of austenitic and ferritic phases have been established

  7. Understanding and modelling of the aniso-thermal cyclic mechanical behaviour of the AISI 316LN austenitic stainless steel

    International Nuclear Information System (INIS)

    The main subject of this report consists in proposing a mechanical model of the viscoplastic behaviour of an austenitic stainless steel under isothermal and aniso-thermal low cycle fatigue loadings at high temperatures (550-900 K). In this domain, numerous phenomena linked to dynamic strain ageing (DSA) and to dipolar dislocation structure formation may appear. Isothermal and aniso-thermal low cycle fatigue tension-compression tests were performed in order to verify some aspects about the effect of temperature on the mechanical behaviour. The study of the hysteresis loops and the observation of dislocation structures carried on transmission electron microscopy establish two different DSA mechanisms during isothermal tests. The effect of temperature history is shown for for particular temperature sequences. It is demonstrated that the stress amplitude increase when the sample is submitted to cycles at 'high temperature' is linked to the second mechanism of DSA. It comes from the increase of short range interaction between dislocations (chromium segregation), but it is also the consequence of the lack of dipolar structure annihilation at low temperature. From the experimental analysis of DSA mechanisms and dipolar restoration, a macroscopic aniso-thermal model is developed using physical internal variables (densities of dislocations). The equations of a polycrystalline model are rewritten with the aim of getting a simple multi-scale approach which can be used on finite elements analysis software. Between 550 and 873 K, the simulation results are in good accordance with the macroscopic and microscopic observations of low cycle fatigue, relaxation, and 2D-ratchetting tests. (author)

  8. Modeling of the PWR fuel mechanical behaviour and particularly study of the pellet-cladding interaction in a fuel rod

    International Nuclear Information System (INIS)

    In Pressurized Water Reactor (PWR) power plants, fuel cladding constitutes the first containment barrier against radioactive contamination. Computer codes, developed with the help of a large experimental knowledge, try to predict cladding failures which must be limited in order to maintain a maximal safety level. Until now, fuel rod design calculus with unidimensional codes were adequate to prevent cladding failures in standard PWR's operating conditions. But now, the need of nuclear power plant availability increases. That leads to more constraining operating condition in which cladding failures are strongly influenced by the fuel rod mechanical behaviour, mainly at high power level. Then, the pellet-cladding interaction (PCI) becomes important, and is characterized by local effects which description expects a multidimensional modelization. This is the aim of the TOUTATIS 2D-3D code, that this thesis contributes to develop. This code allows to predict non-axisymmetric behaviour too, as rod buckling which has been observed in some irradiation experiments and identified with the help of TOUTATIS. By another way, PCI is influenced by under irradiation experiments and identified with the help of TOUTATIS which includes a densification model and a swelling model. The latter can only be used in standard operating conditions. However, the processing structure of this modulus provides the possibility to include any type of model corresponding with other operating conditions. In last, we show the result of these fuel volume variations on the cladding mechanical conditions. (author). 25 refs., 89 figs., 2 tabs., 12 photos., 5 appends

  9. Effects of suspension-induced osteopenia on the mechanical behaviour of mouse long bones

    Science.gov (United States)

    Simske, S. J.; Greenberg, A. R.; Luttges, M. W.; Spooner, B. S. (Principal Investigator)

    1991-01-01

    Whereas most studies of tail-suspension induced osteopenia have utilized rat femora, the present study investigated the effects of a 14 day tail-suspension on the mechanical behaviour of mice femora, tibiae and humeri. Force-deflection properties were obtained via three-point bending for long bones from suspended and control mice. Whole bone behaviour was characterized by converting the force-deflection values to stiffness, strength, ductility and energy parameters which were not normalized for specimen geometry. The effects of a systematic variation in the deflection rate over the range 0.1-10 mm min-1 were also evaluated. Statistical analysis indicated that the primary effect of the tail-suspension period was lowered bone mass which was manifested mechanically through lower values of the bone strength parameters. These effects were similar in the bones of both the fore and hind limbs. The results also demonstrated that the stiffness, ductility and energy characteristics were much less influenced by the tail-suspension. Whereas a significant dependence of the bone strength values upon deflection rate was observed for the femora and humeri, the other mechanical parameters were less sensitive. Based upon the nature of the physical and mechanical changes observed in the long bones following tail-suspension, the mouse appears to be a suitable animal model for the study of osteopenia.

  10. Study of the hydro-mechanical behaviour of expanded graphite gaskets

    International Nuclear Information System (INIS)

    The poro-mechanical behaviour models developed by O. Coussy permit to consider various phenomena observed experimentally: thermo-hydro-mechanical couplings, plasticity, etc. The aim of this study is to implement the simplest poro-mechanical model (i.e. the isotropic linear poro-elastic model) to model the gasket hydro-mechanical behaviour. First, isotropic poro-elastic characteristics of expanded graphite have been estimated from these tests conducted at Departement Mecanique et Technologie des Composants (MTC) and data from literature. Then, analytical solutions of the tightness tests developed at the MTC Department have been carried out. These calculations provide a first estimation of porosity variations during a tightness tests with metal/metal contact or in elastic recovery, and during a 'hot thermal transient'. Thickness controlled numerical calculations have proved the analytical calculations relevance. With regard to simulation of tests with metal/metal contact or 'hot thermal transient', stress controlled numerical calculations have pointed out: - a greater vertical displacement on the inner side of the graphite ring and - a z dependence of the radial displacement and thus a porous differential variation between the upper and lower faces of the ring. (author)

  11. Influence of temperature on patch residence time in parasitoids: physiological and behavioural mechanisms

    Science.gov (United States)

    Moiroux, Joffrey; Abram, Paul K.; Louâpre, Philippe; Barrette, Maryse; Brodeur, Jacques; Boivin, Guy

    2016-04-01

    Patch time allocation has received much attention in the context of optimal foraging theory, including the effect of environmental variables. We investigated the direct role of temperature on patch time allocation by parasitoids through physiological and behavioural mechanisms and its indirect role via changes in sex allocation and behavioural defences of the hosts. We compared the influence of foraging temperature on patch residence time between an egg parasitoid, Trichogramma euproctidis, and an aphid parasitoid, Aphidius ervi. The latter attacks hosts that are able to actively defend themselves, and may thus indirectly influence patch time allocation of the parasitoid. Patch residence time decreased with an increase in temperature in both species. The increased activity levels with warming, as evidenced by the increase in walking speed, partially explained these variations, but other mechanisms were involved. In T. euproctidis, the ability to externally discriminate parasitised hosts decreased at low temperature, resulting in a longer patch residence time. Changes in sex allocation with temperature did not explain changes in patch time allocation in this species. For A. ervi, we observed that aphids frequently escaped at intermediate temperature and defended themselves aggressively at high temperature, but displayed few defence mechanisms at low temperature. These defensive behaviours resulted in a decreased patch residence time for the parasitoid and partly explained the fact that A. ervi remained for a shorter time at the intermediate and high temperatures than at the lowest temperature. Our results suggest that global warming may affect host-parasitoid interactions through complex mechanisms including both direct and indirect effects on parasitoid patch time allocation.

  12. Investigating mechanisms underlying neurodevelopmental phenotypes of autistic and intellectual disability disorders: a perspective

    OpenAIRE

    Tim eKroon; Martijn eSierksma; Rhiannon Mair Meredith

    2013-01-01

    Brain function and behaviour undergo significant plasticity and refinement, particularly during specific critical and sensitive periods. In autistic and intellectual disability neurodevelopmental disorders (NDDs) and their corresponding genetic mouse models, impairments in many neuronal and behavioural phenotypes are temporally regulated and in some cases, transient. However, the links between neurobiological mechanisms governing typically normal brain and behavioural development (referred to...

  13. Computational analysis of the behaviour of nuclear fuel under steady state, transient and accident conditions

    International Nuclear Information System (INIS)

    Accident analysis is an important tool for ensuring the adequacy and efficiency of the provision in the defence in depth concept to cope with challenges to plant safety. Accident analysis is the milestone of the demonstration that the plant is capable of meeting any prescribed limits for radioactive releases and any other acceptable limits for the safe operation of the plant. It is used, by designers, utilities and regulators, in a number of applications such as: (a) licensing of new plants, (b) modification of existing plants, (c) analysis of operational events, (d) development, improvement or justification of the plant operational limits and conditions, and (e) safety cases. According to the defence in depth concept, the fuel rod cladding constitutes the first containment barrier of the fission products. Therefore, related safety objectives and associated criteria are defined, in order to ensure, at least for normal operation and anticipated transients, the integrity of the cladding, and for accident conditions, acceptable radiological consequences with regard to the postulated frequency of the accident, as usually identified in the safety analysis reports. Therefore, computational analysis of fuel behaviour under steady state, transient and accident conditions constitutes a major link of the safety case in order to justify the design and the safety of the fuel assemblies, as far as all relevant phenomena are correctly addressed and modelled. This publication complements the IAEA Safety Report on Accident Analysis for Nuclear Power Plants (Safety Report Series No. 23) that provides practical guidance for establishing a set of conceptual and formal methods and practices for performing accident analysis. Computational analysis of the behaviour of nuclear fuel under transient and accident conditions, including normal operation (e.g. power ramp rates) is developed in this publication. For design basis accidents, depending on the type of influence on a fuel element

  14. Long term behaviour of polyethylene high integrity containers under repository conditions

    International Nuclear Information System (INIS)

    Polyethylene High Integrity Containers (HICs) were proposed in 1996 for disposal of spent ion-exchange resins and sludge from Nuclear Power Plant Dukovany. Although these containers have been utilized in the USA for low-level radioactive waste storage and disposal since 1983 and have provided a cost effective alternative to waste solidification, they are not licensed in the Czech Republic. The main aim of this project was therefore to prove the suitability of these containers for conditioning of radioactive ion-exchangers and sludge from NPP Dukovany. The unclear issue concerning the polyethylene HIC is its long-term stability under the effect of low dose rates of ionising radiation. The objectives of the project focused therefore mainly on acquiring a deeper knowledge of the long-term behaviour of polyethylene under the low dose rates of ionising radiation of repository conditions. The Differential Scanning Calorimetry (DSC) was chosen as the basic methodology for the evaluation of polyethylene samples properties irradiated by Co-60 at various dose rates, ranging from 8.5 to 8855 Gy/h up to 100 kGy. This method makes possible to quickly evaluate the change of polymers thermo-oxidation stability after irradiation. The gel fraction was determined according to ASTM standard D 2765. The diffusion coefficient was determined in a special static-diffusion cell consisting of two parts divided by the polyethylene foil. The density of polyethylene samples was measured using double weighing method in air and ethanol. It was found that the gel fraction of originally cross-linked high-density polyethylene significantly decreases both with increasing absorbed doses and decreasing dose rates of irradiation. It suggests that the scission of polymer chains is pronounced at low dose rates. The most interesting are the results from the measurements of thermo-oxidation stability of irradiated polyethylene that strongly suggest that even very low absorbed doses of ionising radiation

  15. Modulating mechanical behaviour of 3D-printed cartilage-mimetic PCL scaffolds: influence of molecular weight and pore geometry.

    Science.gov (United States)

    Olubamiji, Adeola D; Izadifar, Zohreh; Si, Jennifer L; Cooper, David M L; Eames, B Frank; Chen, Daniel X B

    2016-06-01

    Three-dimensional (3D)-printed poly(ε)-caprolactone (PCL)-based scaffolds are increasingly being explored for cartilage tissue engineering (CTE) applications. However, ensuring that the mechanical properties of these PCL-based constructs are comparable to that of articular cartilage that they are meant to regenerate is an area that has been under-explored. This paper presents the effects of PCL's molecular weight (MW) and scaffold's pore geometric configurations; strand size (SZ), strand spacing (SS), and strand orientation (SO), on mechanical properties of 3D-printed PCL scaffolds. The results illustrate that MW has significant effect on compressive moduli and yield strength of 3D-printed PCL scaffolds. Specifically, PCL with MW of 45 K was a more feasible choice for fabrication of visco-elastic, flexible and load-bearing PCL scaffolds. Furthermore, pore geometric configurations; SZ, SS, and SO, all significantly affect on tensile moduli of scaffolds. However, only SZ and SS have statistically significant effects on compressive moduli and porosity of these scaffolds. That said, inverse linear relationship was observed between porosity and mechanical properties of 3D-printed PCL scaffolds in Pearson's correlation test. Altogether, this study illustrates that modulating MW of PCL and pore geometrical configurations of the scaffolds enabled design and fabrication of PCL scaffolds with mechanical and biomimetic properties that better mimic mechanical behaviour of human articular cartilage. Thus, the modulated PCL scaffold proposed in this study is a framework that offers great potentials for CTE applications. PMID:27328736

  16. Thermal and mechanical behaviour of the reduced-activation-ferritic-martensitic steel EUROFER

    International Nuclear Information System (INIS)

    Reduced activation ferritic/martensitic (RAFM) steels are being considered for structural application in potential fusion energy systems. Based on the substantial experience with RAFM developmental steels of OPTIFER type, an industrial 3.5 tons batch of a 9CrWVTa-RAFM steel, called EUROFER 97 had been specified and ordered. A characterisation programme has been launched to determine the relevant mechanical and physical-metallurgical properties in order to qualify the steel for fusion application. The hardening, tempering and transformation behaviour of EUROFER is in good agreement with that of other RAFM-steels like OPTIFER and the Japanese industrial scale heat F82H mod. Tensile tests, performed between RT and 750 deg. C, show comparable strength and ductility values that are not strongly affected by different heat treatments and ageing at 580 and 600 deg. C up to 3300 h. Impact bending tests indicate a superior ductile to brittle transition temperature (DBTT) of EUROFER in the as-received condition compared with that of F82H mod. Creep tests between 450 and 650 deg. C up to test times of 15000 h reveal a creep strength similar to other RAFM steels like OPTIFER and F82H mod. EUROFER shows a good low-cycle fatigue behaviour with longer lifetimes than F82H mod. The deformation and softening behaviour is similar

  17. Modeling of the thermo-mechanical behaviour of the PWR fuel

    International Nuclear Information System (INIS)

    This article reviews the various physical phenomena that take place in an irradiated fuel rod and presents the development of the thermo-mechanical codes able to simulate them. Though technically simple the fuel rod is the place where appear 4 types of process: thermal, gas behaviour, mechanical and corrosion that combine involving 5 elements: the fuel pellet, the fuel clad, the fuel-clad gap, the inside volume and the coolant. For instance the pellet is the place where the following mechanical processes took place: thermal dilatation, elastic deformation, creep deformation, densification, solid swelling, gaseous swelling and cracking. The first industrial code simulating the behaviour of the fuel rod was COCCINEL, it was developed by AREVA teams from the American PAD code that was included in the Westinghouse license. Today the GALILEO code has replaced the COPERNIC code that was developed in the beginning of the 2000 years. GALILEO is a synthesis of the state of the art of the different models used in the codes validated for PWR and BWR. GALILEO has been validated on more than 1500 fuel rods concerning PWR, BWR and specific reactors like Siloe, Osiris, HFR, Halden, Studsvik, BR2/3,...) and also for extended burn-ups. (A.C.)

  18. The behaviour of a floating water bridge under reduced gravity conditions

    International Nuclear Information System (INIS)

    When high voltage is applied to pure water filled into two beakers close to each other, a connection forms spontaneously, giving the impression of a floating water bridge (Armstrong 1893 The Electrical Engineer pp 154-45, Uhlig W 2005 personal communication, Fuchs et al 2007 J. Phys. D: Appl. Phys. 40 6112-4, Fuchs et al 2008 J. Phys. D: Appl. Phys. 41 185502, Fuchs et al 2009 J. Phys. D: Appl. Phys. 42 065502, Fuchs et al 2010 J. Phys. D: Appl. Phys. 43 105502, Woisetschlaeger et al 2010 Exp. Fluids 48 121-31, Nishiumi and Honda 2009 Res. Lett. Phys. Chem. 2009 371650). This phenomenon is of special interest, since it comprises a number of phenomena currently tackled in modern water science. In this work, the behaviour of this phenomenon under reduced gravity conditions during a parabolic flight is presented by the means of high speed imaging with fringe projection. An analysis of the behaviour is presented and compared with theoretical considerations.

  19. A CFD analysis of thermal behaviour of transportation cask under fire test conditions

    International Nuclear Information System (INIS)

    Highlights: → Melting and natural convection of lead in cask has been studied using CFD for the first time. → The role of turbulent natural convection on melting was pronounced. → The study establishes the importance of natural convection for accurate thermal design of cask. - Abstract: Thermal design of transportation cask for shipping radioactive waste needs strict compliance with the guidelines of the regulatory bodies. Lead shielding is usually provided in these casks for arresting gamma rays and reducing hazardous emissions to the environment below permissible limits. During transportation, accidental fire may break out and cause melting of lead for a prescribed duration. The present analysis reports, for the first time, a comprehensive CFD analysis of the thermal behaviour of melting of lead under high Rayleigh number convection during the fire test. The study reveals a substantial influence of natural convection on the thermal state and melting behaviour of lead which may have a great bearing on the safety and security of public during transportation of cask.

  20. Study of the behaviour of a reinforced concrete post under aleatory excitation

    International Nuclear Information System (INIS)

    The reactor building of a nuclear power plant must ensure its protection and tightness functions in the most unfavorable conditions of operation, like during an earthquake. The method currently used for the seismic calculation of buildings consists in the determination of the maximum probable response for each of the Eigen-modes of the structure. The aim of this study is to develop a non-linear calculation model for the estimation of the response of reinforced concrete structures. The structure under study is a beam embedded in its base and having a 2 tons load on its top. The structure is excited by a seismic or pulsed signal. In a first step, the global behavioural model of reinforced concrete is determined using the concrete and steel armatures behaviour laws. Then, a computer code is developed for the calculation of the seismic excitation of the beam. The beam is assimilated to a non-linear oscillator. A damaging parameter has been introduced in the model to take into account the damping observed experimentally. Finally, the excitation signal is analyzed in order to determine the parameter responsible for the significant increase of the structure response. (J.S.)

  1. Loosening and Sliding Behaviour of Bolt-Nut Fastener under Transverse Loading

    Directory of Open Access Journals (Sweden)

    Naruse T.

    2010-06-01

    Full Text Available The thread joint has been frequently used for the efficient productivity and maintainability as a machine element. However, many troubles such as loosening of bolted joints or fatigue failure of bolt were often experienced. Many attentions must be paid on the improvement of the strength and the reliability of the thread joints [1, 2]. It is generally said that the fastening axial force rapidly decreases by the rotation loosening of nuts if the relative slippage on the interfaces between nuts and fastened body goes beyond a certain critical limit [3]. This critical relative slippage (Scr that prescribes the upper limit for preventing the loosening behaviour has been estimated according to the theoretically obtained equation considering the bending deformation of bolt and the geometrical constraint condition. In this paper, firstly we present the equation for estimating the Scr based on the fundamental cantilever deformation model. Then we present the investigated results of the deformation behaviour of bolt-nut joint under transverse loading condition considering the reaction moment by nut (Mn. Finaly we can confirmed that these estimated results of critical relative slippage coincided well with the experimental results [4, 5].

  2. Modelling the cracking of pressurised water reactor fuel pellets and its consequences on the mechanical behaviour of the fuel rod

    International Nuclear Information System (INIS)

    This thesis aims to model the cracking of pressurised water reactor fuel pellets and its consequences on the mechanical behaviour of the fuel rod. Fuel cracking has two main consequences. It relieves the stress in the pellet, upon which the majority of the mechanical and physico-chemical phenomena are dependent. It also leads to pellet fragmentation. Taking fuel cracking into account is therefore necessary to adequately predict the mechanical loading of the cladding during the course of an irradiation. The local approach to fracture was chosen to describe fuel pellet cracking. Practical considerations brought us to favour a quasi-static description of fuel cracking by means of a local damage models. These models describe the appearance of cracks by a local loss of rigidity of the material. Such a description leads to numerical difficulties, such as mesh dependency of the results and abrupt changes in the equilibrium state of the mechanical structure during unstable crack propagations. A particular attention was paid to these difficulties because they condition the use of such models in engineering studies. This work was performed within the framework of the ALCYONE fuel performance package developed at CEA/DEC/SESC which relies on the PLEIADES software platform. ALCYONE provides users with various approaches for modelling nuclear fuel behaviour, which differ in terms of the type geometry considered for the fuel rod. A specific model was developed and implemented to describe fuel cracking for each of these approaches. The 2D axisymmetric fuel rod model is the most innovative and was particularly studied. We show that it is able to assess, thanks to an appropriate description of fuel cracking, the main geometrical changes of the fuel rod occurring under normal and off-normal operating conditions. (author)

  3. Behaviour of MZFR-type Zircaloy-4 cans under tensile stress

    International Nuclear Information System (INIS)

    The paper describes the experimental procedure and results from the tensile tests of Zircaloy-4 fuel cans of the MZFR-type, performed at temperatures ranging from 250 to 450 deg C and for a relative deformation velocity of about 0.5%/min. In the representation of the results by a curve of the type sigma = K epsilon/sup n/, two different stages are observed. By statistically fitting the experimental curves, the values for the K and n parameters were obtained for each stage as a function of temperature. The results are discussed and compared with similar data found in current literature. It is concluded that new tests on tubes of different characteristics are necessary in order to obtain a clearer idea about the mechanical behaviour of these materials. (C.A.K.)

  4. Tests and analysis of mechanical behaviours of rock bolt components for China's coal mine roadways

    OpenAIRE

    Hongpu Kang; Jinghe Yang; Xianzhi Meng

    2015-01-01

    A series of laboratory tests were performed to study the mechanical behaviours of newly developed high strength rock bolt components, including rebar, thread, plate, and domed washer. The characteristics of deformation and damage of each component were presented. The stress distribution of plate and domed washer was investigated through finite element modelling. The numerical results show that the yield and tensile strengths of the developed high strength rebar are 33.6%–58.3% and 17.2%–28.7%...

  5. Finite element simulation of mechanical behaviour of nickel-based metallic foam structures

    Energy Technology Data Exchange (ETDEWEB)

    Kaoua, Sid-Ali; Dahmoun, Djaffar; Belhadj, Abd-Elmouneim [Laboratoire des Sciences et de Genie des Materiaux (LSGM), Universite des Sciences et de la Technologie Houari Boumediene (USTHB), BP 32 El-Allia, 16111 Bab Ezzouar, Algiers (Algeria); Azzaz, Mohammed [Laboratoire des Sciences et de Genie des Materiaux (LSGM), Universite des Sciences et de la Technologie Houari Boumediene (USTHB), BP 32 El-Allia, 16111 Bab Ezzouar, Algiers (Algeria)], E-mail: azzaz@wissal.dz

    2009-03-05

    In this paper, numerical simulation by finite elements is performed in order to study the mechanical behaviour of foam structures subjected to tension loading. The anisotropic cellular model of Gibson and Ashby is taken like reference in our simulation. The foam structure, constituted by struts and connection stems, is modelled by space beam finite elements. This led to a parametric analysis showing the evolution of foam Young modulus according to some geometrical parameters of the cellular network structure, such as shape and dimensions of cross-section, connection stem length.

  6. Finite element simulation of mechanical behaviour of nickel-based metallic foam structures

    International Nuclear Information System (INIS)

    In this paper, numerical simulation by finite elements is performed in order to study the mechanical behaviour of foam structures subjected to tension loading. The anisotropic cellular model of Gibson and Ashby is taken like reference in our simulation. The foam structure, constituted by struts and connection stems, is modelled by space beam finite elements. This led to a parametric analysis showing the evolution of foam Young modulus according to some geometrical parameters of the cellular network structure, such as shape and dimensions of cross-section, connection stem length

  7. Order information coding in working memory: Review of behavioural studies and cognitive mechanisms

    Directory of Open Access Journals (Sweden)

    Barbara Dolenc

    2014-06-01

    Full Text Available Executive processes, such as coding for sequential order, are of extreme importance for higher-order cognitive tasks. One of the significant questions is, how order information is coded in working memory and what cognitive mechanisms and processes mediate it. The aim of this review paper is to summarize results of studies that explore whether order and item memory are two separable processes. Furthermore, we reviewed evidence for each of the proposed cognitive mechanism that might mediate order processing. Previous behavioural and neuroimaging data suggest different representation and processing of item and order information in working memory. Both information are maintained and recalled separately and this separation seems to hold for recognition as well as for recall. To explain the result of studies of order coding, numerous cognitive mechanisms were proposed. We focused on four different mechanisms by which order information might be coded and retrieved, namely inter-item associations, direct coding, hierarchical coding and magnitude coding. Each of the mechanisms can explain some of the aspect of order information coding, however none of them is able to explain all of the empirical findings. Due to its complex nature it is not surprising that a single mechanism has difficulties accounting for all the behavioral data and order memory may be more accurately characterized as the result of a set of mechanisms rather than a single one. Moreover, the findings beget a question of whether different types of memory for order information might exist.

  8. Coupling between mechanical behaviour and drying of cementing materials: experimental study on mortars

    International Nuclear Information System (INIS)

    The aim of this work is to understand the desiccation effects on the mechanical behaviour of cement materials. Two mortars of ratio E/C=0.5 and 0.8 have been tested. All the tests have been implemented after a six months maturing in water. The experimental study has been carried out as follows: 1)tests characterizing the differed behaviour and the transport properties have been carried out 2)tests characterizing the short term multiaxial mechanical behaviour have been carried out. The desiccation shrinkage in terms of the weight loss presents three characteristic phases. The permeability measurement on the mortar 05 shows that the permeability of the specimens dried and crept is greater than those of the specimens dried before being crept, and the permeability of the specimens submitted to a desiccation creep and then dried is sensibly the same as the last one in spite of a very important differed deformation. The influence of the desiccation on the uniaxial and deviatoric compressions resistance depends of the binding agent: for a cement paste of good quality (E/C=0.5), the resistances increase with the desiccation because of the capillary depression and of the hydric gradients. For a cement paste of low quality (E/C=0.8), there is a competitive effect between the increase of the microcracks induced and the specimen rigidification; the microcracking becomes then the parameter controlling the rupture process. The elasto-plastic behaviour becomes a damageable elasto-plastic behaviour during desiccation which induces, as the decrease of the E/C ratio, a translation of the elastic limit surfaces and ruptures towards higher stresses. In parallel, the elastic properties and the incompressibility modulus are damaged and the volume deformations increase after the drying. At last, the decrease of the Young modulus and the passage to the third shrinkage phase in terms of the weight loss coincide. This can be attributed to the induced microcracking: this decrease of the

  9. Genetic behaviour of some rice (Oryza sativa L. genotypes under different treatments of nitrogen levels

    Directory of Open Access Journals (Sweden)

    Metwally, T.F., S.E.M. Sedeek., A.F.Abdelkhalik., I.M. El-Rewiny and Ehab. M.R. Metwali

    2010-09-01

    Full Text Available The present investigation was carried out at the experimental farm of Rice Research and Training Center, Sakha, Kafer El-Sheikh, Egypt during 2008 and 2009 seasons to study the physio-morphological behaviour of some rice genotypes under lowand high nitrogen application. Twenty one genotypes were tested under three different nitrogen levels viz, 0, 75 and 150 kgN/ha for ten traits viz, flag leaf area, chlorophyll content, days to heading, panicle weight, , no. of filled grains/panicle, no. ofpanicles/plant ,1000-grain weight, grain yield t ha-1, grain yield efficiency index (GYEI and agronomic nitrogen use efficiency(ANUE. The genotypes were divided into three groups i.e., japonica/japonica (J/J, japonica/indica japonica (J/IJ and indicajaponica/indica japonica (IJ/IJ. GZ6296 x Giza178-1 and GZ6296 x Giza 178-3 gave the highest values of no. of filledgrain/panicle and no. of panicles/hill under low input of nitrogen. Giza177/Sakha101 and Giza176/GZ6944 (J/J gave thehighest grain yield under low input of nitrogen followed by the genotypes derived from Giza178/GZ6296 (IJ/IJ.

  10. Crack growth behaviour of low alloy steels for pressure boundary components under transient light water reactor operating conditions (CASTOC)

    International Nuclear Information System (INIS)

    The CASTOC project addresses environmentally assisted cracking (EAC) phenomena in low alloy steels used for pressure boundary components in both Western type boiling water reactors (BWR) and Russian type pressurised water reactors (VVER). It comprises the four work packages (WP): inter-laboratory comparison test (WP1); EAC behaviour under static load (WP2), EAC behaviour under cyclic load and load transients (WP3); evaluation of the results with regard to their relevance for components in practice (WP4). The use of sophisticated test facilities and measurement techniques for the on-line detection of crack advances have provided a more detailed understanding of the mechanisms of environmentally assisted cracking and provided quantitative data of crack growth rates as a function of loading events and time, respectively. The effect of several major parameters controlling EAC was investigated with particular emphasis on the transferability of the results to components in service. The obtained crack growth rate data were reflected on literature data and on commonly applied prediction curves as presented in the appropriate Code. At relevant stress intensity factors it could be shown that immediate cessation of growing cracks occurs after changing from cyclic to static load in high purity oxygenated BWR water and oxygen-free VVER water corresponding to steady state operation conditions. Susceptibility to environmentally assisted cracking under static load was observed for a heat affected zone material in oxygenated high purity water and also in base materials during a chloride transient representing BWR water condition below Action Level 1 of the EPRI Water Chemistry Guidelines according to the lectrical conductivity of the water but in the range of Action Level 2 according to the content of chlorides. Time based crack growth was also observed in one Russian type base material in oxygenated VVER water and in one Western type base material in oxygenated high purity BWR

  11. A contribution to the study of mechanical behaviour of concrete structures taking into account the effects of desiccation

    International Nuclear Information System (INIS)

    In this work, is given a model of the drying influence on the mechanical behaviour of concrete and a reliable anticipating tool is proposed for engineers. The drying of hardened concrete has several consequences on the mechanical properties of concrete. The desiccation shrinkage is the first sign, generating crack visible at the surface level under the form of crackling and core cracking particularly on the account of the presence of aggregates which prevent the shrinkage of the cement paste to make easily. Then, the elastic parameters are strongly affected (decrease of stiffness, of the Poisson coefficient). A simplified model of the stiffness loss during the drying is proposed under the form of an isotropic hydric damage. The model is validated in the unidimensional case with tests results carried out in the LML. With this model, it is possible to estimate with more accuracy the state of the hydric constraints in concrete. Numerical simulations on 3D structures are then proposed. An application to the case of a wall being manufactured is given. The contributions of the model are tested too in the case where the global mechanical response of cylindrical mortar specimens submitted to drying and to compression tests is simulated. The effect of the capillary suction as well as the increase of the elastic limit during drying are then discussed. At last, the contributions of the model for creep calculations and desiccation are presented. (O.M.)

  12. Coupled Numerical Analysis of the Stability Behaviour of Unsaturated Soil Slopes Under Rainfall Conditions

    Institute of Scientific and Technical Information of China (English)

    WANG Cheng-hua(王成华); THOMAS H R

    2003-01-01

    The stability behaviour of unsaturated soil slopes under rainfall conditions is investigated via a parametric finite element analysis, which is a fully coupled flow and deformation approach linked to a dynamic programming technique for determining the minimum factor of safety as well as its corresponding critical slip surface based on the stress fields from the numerical computation. The effects of rainfall features, soil strength parameters and permeability properties on slope stability are studied. The analyses revealed that the soil matric suction decreased during rainfall, especially in slopes with high permeability and/or with high suction angles of unsaturated soils. The influence of rainfall conditions on such slopes is quite obvious, and soil suction drops rapidly, which leads to a consequent quick reduction in the factor of safety.

  13. Behaviour of LWR Spent Fuel Rods During Storage and Under Accidental Impact Load Conditions

    International Nuclear Information System (INIS)

    The scope of this contribution includes the assessment and evaluation of the structural behaviour of cladding and fuel under extreme transient load conditions encountered in hypothetic transport and handling accidents. The investigation focuses on a broad understanding of the failure (brittle rupture), fragmentation, and on the quantification of the fuel amount released per rod breakage corresponding to different burnup levels and fuel types. Additionally, the contribution aims at characterizing and understanding the evolution of the microstructure subjected to alpha decay and helium build up, in particular to verify extent and stability associated with defects saturation processes occurring at high damage level in the crystalline lattice, and determine if at very high accumulated dose level the decay damage and the radiogenic helium may affect the overall stability of the compound

  14. Behaviour of -glass fibre reinforced vinylester resin composites under impact fatigue

    Indian Academy of Sciences (India)

    Rita Roy; B K Sarkar; N R Bose

    2001-04-01

    An impact fatigue study has been made for the first time on 63.5% glass fibre reinforced vinylester resin notched composites. The study was conducted in a pendulum type repeated impact apparatus especially designed and fabricated for determining single and repeated impact strengths. A well-defined impact fatigue (S–N) behaviour, having a progressive endurance below the threshold single cycle impact fracture stress with decreasing applied stress has been demonstrated. Fractographic analysis revealed fracture by primary debonding having fibre breakage and pullout at the tensile zone, but a shear fracture of fibre bundles at the compressive zone of the specimen. The residual strength, modulus and toughness showed retention of the properties at high impact stress levels up to 1000 impacts followed by a sharp drop. Cumulative residual stresses with each number of impacts not withstanding the static fatigue failure at long endurances have been ascribed for the composite failures under the repeated impact stresses.

  15. ACED mechanical devices for the control of behaviour of nuclear structures to seismic events

    International Nuclear Information System (INIS)

    Treatment of seismic records and the analysis of behaviour of structure indicated that over 80% of the dwelt Romanian territory has a high seismic risk. The earthquakes produced during the last 60 years diminished the structure resistance capacity of most of existent buildings. Consequently, the behaviour control of the existing built structures or of the buildings under construction, particularly for nuclear stations, particularly to seismic events and, generally, to dynamic actions, is extremely important for diminishing as much as possible the consequences of major earthquakes. New ACED devices presented in this paper can be applied both to an efficient consolidation in a short time as well in building new constructions. The ACED devices are easy to achieve and the utilization will increase the quality of consolidation work, will reduce the work expense at the construction site, will improve the environmental protection and will allow an effective control of the behaviour of new and existent structure to dynamical actions. The control of the structure behaviour using ACED devices is achieved by: 1. embodying the ACED devices in the building resistance structure, so obtaining a 'telescoping' system which, within the elastic range of the stresses to which the resistance structure is submitted, dissipates a large amount of seismic energy; by its controlled deformation one gets a increased stiffness of the building structure; 2. emplacing the ACED device between a general raft and the construction's foundation, so obtaining an isolation of the building allowing ground motion under the building without a transmission of the seismic excitation to the building; 3. combined measures of isolation and improving the building behaviour by embodying ACED device in the resistance structure concomitantly with the isolation of the foundation. The ACED device have a compact structure, are reliable and can be guarantied over the life span of the building. The rigidity and damping

  16. Fuel behaviour under transient and LOCA conditions. Proceedings of a technical committee meeting

    International Nuclear Information System (INIS)

    At the invitation of the Government of Norway and in response to a proposal of the IAEA Technical Working Group on Water Reactor Fuel Performance and Technology (TWGFPT), the IAEA convened a Technical Committee Meeting on Fuel Behaviour under Transient and LOCA Conditions in Halden, Norway from 10 to 14 September 2001. The meeting was organized in co-ordination with OECD/NEA and was hosted by the Institutt for Energiteknikk OECD Halden Reactor Project (HRP). This meeting is the seventh in a series of IAEA meetings that were held in 1980 (jointly with OECD/NEA, Helsinki, Finland), 1983 (Riso, Denmark), 1986 (Vienna, Austria), 1988 (Preston, United Kingdom), 1992 (Pembroke, Ontario, Canada) and 1995 (Dimitrovgrad, Russian Federation). All of these activities have significantly contributed to the enhanced understanding of fuel behaviour at accident conditions. In the six years since the last meeting took place, the demands on fuel duties have increased including higher burnup, longer fuel cycles and higher temperatures. To satisfy these demands, fuel vendors develop and introduce new cladding and fuel materials and designs to provide sufficient safety margins, especially under accident conditions. This has incurred a need for assessing the applicability of the database for clarification of safety criteria as well as models for accident evolution predictions. Thus, national and international experimental programmes have been launched, and models are being developed or adapted to consider the changed conditions, e.g. fission gas behaviour, relocation of cracked fuel, and physical property changes of the cladding. Forty-three specialists in experiments and modelling of fuel performance at accident conditions from 15 countries and the OECD Nuclear Energy Agency and 10 observers (Norwegian and foreign representatives to the OECD HRP) took part in the meeting in order to gather and discuss existing knowledge on the subject and to identify the needs for further efforts

  17. Basic investigations on the corrosion behaviour of ferritic components in high temperature water of different chemical composition under static and monotonic external mechanical loading. Final report. Grundlagenuntersuchung zum Korrosionsverhalten ferritischer Bauteile in Hochtemperaturwasser unterschiedlicher chemischer Zusammensetzung bei statischer und zuegiger aeusserer mechanischer Belastung. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Schellenberger, R.; Klenke, K.; Deimel, P.

    1993-07-01

    Wihtin the scope of a respresentative field of parameters (material, mechanical loading, medium) the ferritic material 20 MnMoNi 5 5 (0.003 and 0.011%) was investigated in high temperature water of 240 C with different oxygen contents (0.4 and 8 ppm O[sub 2]) under static and monotonic external mechanical loading. In case of testing in high temperature water, the J[sub R]-curves received under monotonic loading on fracture mechanics specimens were remarkably lower than in air at the same load line displacement rate (1.10[sup -4] mm/s). With lower becoming load line displacement rate the J[sub R]-curve of the low sulphur material converges to the one of the higher sulphur material. In case of testing the fracture mechanics specimens under static active loading, no dependence of the crack growth velocity on the stress intensity factor K[sub I], the sulphur content of the material and the oxygen content of the environmnt in the range of 20 to 50 MPa/m was observed. The reduction of area determined in the slow tensile test at 8 ppm O[sub 2] (spot check 0,4 ppm) and quasi-stagnant as well as flowing conditions showed a dependence on the strain rate. Comapring the two material variants it became obvious, that in the case of the material with 0.011% S the reduction of area was always remarkably lower. The spot check tests of the incubation- and crack initiation phase established simultaneously in all tests holes and cracks for both material variants. (orig.)

  18. Review of experimental data for modelling LWR fuel cladding behaviour under loss of coolant accident conditions

    Energy Technology Data Exchange (ETDEWEB)

    Massih, Ali R. [Quantum Technologies AB, Uppsala Science Park (Sweden)

    2007-02-15

    Extensive range of experiments has been conducted in the past to quantitatively identify and understand the behaviour of fuel rod under loss-of-coolant accident (LOCA) conditions in light water reactors (LWRs). The obtained experimental data provide the basis for the current emergency core cooling system acceptance criteria under LOCA conditions for LWRs. The results of recent experiments indicate that the cladding alloy composition and high burnup effects influence LOCA acceptance criteria margins. In this report, we review some past important and recent experimental results. We first discuss the background to acceptance criteria for LOCA, namely, clad embrittlement phenomenology, clad embrittlement criteria (limitations on maximum clad oxidation and peak clad temperature) and the experimental bases for the criteria. Two broad kinds of test have been carried out under LOCA conditions: (i) Separate effect tests to study clad oxidation, clad deformation and rupture, and zirconium alloy allotropic phase transition during LOCA. (ii) Integral LOCA tests, in which the entire LOCA sequence is simulated on a single rod or a multi-rod array in a fuel bundle, in laboratory or in a tests and results are discussed and empirical correlations deduced from these tests and quantitative models are conferred. In particular, the impact of niobium in zirconium base clad and hydrogen content of the clad on allotropic phase transformation during LOCA and also the burst stress are discussed. We review some recent LOCA integral test results with emphasis on thermal shock tests. Finally, suggestions for modelling and further evaluation of certain experimental results are made.

  19. Review of experimental data for modelling LWR fuel cladding behaviour under loss of coolant accident conditions

    International Nuclear Information System (INIS)

    Extensive range of experiments has been conducted in the past to quantitatively identify and understand the behaviour of fuel rod under loss-of-coolant accident (LOCA) conditions in light water reactors (LWRs). The obtained experimental data provide the basis for the current emergency core cooling system acceptance criteria under LOCA conditions for LWRs. The results of recent experiments indicate that the cladding alloy composition and high burnup effects influence LOCA acceptance criteria margins. In this report, we review some past important and recent experimental results. We first discuss the background to acceptance criteria for LOCA, namely, clad embrittlement phenomenology, clad embrittlement criteria (limitations on maximum clad oxidation and peak clad temperature) and the experimental bases for the criteria. Two broad kinds of test have been carried out under LOCA conditions: (i) Separate effect tests to study clad oxidation, clad deformation and rupture, and zirconium alloy allotropic phase transition during LOCA. (ii) Integral LOCA tests, in which the entire LOCA sequence is simulated on a single rod or a multi-rod array in a fuel bundle, in laboratory or in a tests and results are discussed and empirical correlations deduced from these tests and quantitative models are conferred. In particular, the impact of niobium in zirconium base clad and hydrogen content of the clad on allotropic phase transformation during LOCA and also the burst stress are discussed. We review some recent LOCA integral test results with emphasis on thermal shock tests. Finally, suggestions for modelling and further evaluation of certain experimental results are made

  20. Mechanical and corrosion behaviour of a Ti-Al-Nb alloy after deformation at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Popa, M.V.; Vasilescu, E.; Drob, P.; Vasilescu, C. [Institute of Physical Chemistry ' ' Ilie Murgulescu' ' , Spl. Independentei 202, P.O. Box 12-194, 060021 Bucharest (Romania); Raducanu, D.; Cojocaru, D. [Faculty of Material Science and Engineering, Politehnica University, Spl. Independentei 313, 060042 Bucharest (Romania); Ivanescu, S. [SC R and D Consulting and Services, Str. M. Ghiculeasa 45, 023761 Bucharest (Romania); Rosca, J.C.M. [Mechanical Engineering Department, Las Palmas de Gran Canaria University, 35017 Tafira (Spain)

    2008-12-15

    The mechanical properties of Ti6Al7Nb alloy deformed and heat treated at elevated temperatures were correlated with its microstructure and corrosion behaviour in Ringer (of different pH values: 2.49, 6.9 and 8.9) and Ringer-Brown solutions. Microstructural analysis revealed a Widmanstatten structure for the alloys deformed at 1100 C ({beta} field) and structure with {alpha} grains at 930 C ({alpha}+{beta} field). The thermo-mechanical processing improved the electrochemical behaviour of Ti6Al7Nb alloys, especially their passive state. Open circuit potential variations in time reflected more compact, stable, resistant passive films on the surface of the treated alloys. Open circuit potential gradients simulating the non-uniformities of pH along the implant surface have very low values that cannot generate galvanic corrosion. Corrosion rates and ion release are very much reduced. Impedance spectra were fitted with a two time-constants equivalent circuit for some alloys and with three time-constants equivalent circuit for other alloys. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  1. Mechanical Behaviour of Inconel 718 Thin-Walled Laser Welded Components for Aircraft Engines

    Directory of Open Access Journals (Sweden)

    Enrico Lertora

    2014-01-01

    Full Text Available Nickel alloys are very important in many aerospace applications, especially to manufacture gas turbines and aero engine components, where high strength and temperature resistance are necessary. These kinds of alloys have to be welded with high energy density processes, in order to preserve their high mechanical properties. In this work, CO2 laser overlap joints between Inconel 718 sheets of limited thickness in the absence of postweld heat treatment were made. The main application of this kind of joint is the manufacturing of a helicopter engine component. In particular the aim was to obtain a specific cross section geometry, necessary to overcome the mechanical stresses found in these working conditions without failure. Static and dynamic tests were performed to assess the welds and the parent material fatigue life behaviour. Furthermore, the life trend was identified. This research pointed out that a full joint shape control is possible by choosing proper welding parameters and that the laser beam process allows the maintenance of high tensile strength and ductility of Inconel 718 but caused many liquation microcracks in the heat affected zone (HAZ. In spite of these microcracks, the fatigue behaviour of the overlap welds complies with the technical specifications required by the application.

  2. Evolutionary Psychology: How Psychological Mechanisms Shaped by Natural Selection for Ancestral Environments Produce Current Behaviours

    Institute of Scientific and Technical Information of China (English)

    Charles Crawford

    2009-01-01

    The central purpose of this paper is to explain how Darwin's theory of evolution by natural selection can be used in understanding current human behaviour. First, Darwin's logic is briefly described. Development is an important issue when applying evolutionary theory to human behaviour. The notion of innate developmental orga-nization of psychological mechanisms is introduced. The possible social and political outcomes produced when differ-ent levels of innate developmental organization are paired with different beliefs about it are considered. The notion of psychological mechanisms as evolved adaptations is considered in some detail. Then I discuss different ways evo-htionists think about how genes are involved in the development of adaptations. The paper concludes with a frame-work for considering how ancestral adaptations function in current environments and outlines some ways of studying them. In China and many other parts of the world people desire a more harmonious society. Ⅰ hope that this paper will be of some small help in achieving this great task.

  3. The influence of martensitic transformation on mechanical properties of cast high alloyed CrMnNi-steel under various strain rates and temperatures

    International Nuclear Information System (INIS)

    Metastable austenitic steels show excellent mechanical properties, such as high strength combined with excellent ductility and toughness due to martensitic transformation under mechanical loading (transformation induced plasticity effect). A good energy consumption, and, in the case of high-alloyed metastable austenitic steels, a high corrosion resistance, increase the potential of these materials for diverse applications, also in regard of safety requirements. Up to now, numerous wrought alloys were investigated concerning mechanical behaviour, TRIP-effect, martensitic transformation behaviour and modelling of transformation kinetics or stress-strain behaviour. New high alloyed cast CrMnNi-steels, developed at Technical University Bergakademie Freiberg, provide the chance to reduce processing steps, production time and costs. In order to understand the influence of temperature on the martensitic phase transformation behaviour and therefore on mechanical properties and failure, the mechanical response under tensile loading in a temperature range between -700C and 2000C was investigated. The mechanical behaviour under compressive loading was also examined in a wide range of strain rates between 10-4 s-1 and 103 s-1 to obtain information about the strain rate effect on stress-strain behaviour and microstructural changes.

  4. Review of the expected behaviour of alpha titanium alloys under Yucca Mountain conditions

    Energy Technology Data Exchange (ETDEWEB)

    Shoesmith, D.W

    2000-03-01

    The use of titanium alloys in two different waste package designs has been reviewed under the, conditions anticipated in the Yucca Mountain nuclear waste repository. In the first design. they are considered as one of three barrier materials incorporated into the waste package design and potentially in galvanic contact with the other two waste package materials, 316L stainless steel and Alloy-22. In the second design the Ti alloy is considered as a drip shield placed over, and not in contact with, a dual wall waste package fabricated from the other two materials. The possible failure processes, crevice corrosion, pitting and hydrogen-induced cracking (HIC) have been reviewed for the candidate titanium alloys (Ti-12, Ti-16 and Ti-7). Both pitting and crevice corrosion are very remote possibilities under these conditions. For Ti-12, a limited amount of crevice corrosion is possible but repassivation will occur before substantial damage is sustained. When Ti is considered as part of the triple wall waste package, hydrogen absorption leading to HIC, within an acidified but passive crevice, is the most likely failure mechanism. When the Ti alloy is utilized in the form of a drip shield then hydrogen absorption under potentially alkaline conditions is the major fear. Both Ti-12 and Ti-16 have been shown capable of tolerating substantial amounts of hydrogen ({approx}400 {mu} g{center_dot}g{sup -1} for Ti-12, and > 1000 {mu}g.g{sup -1} for Ti-16) before any effect on the materials fracture toughness is observed. The rate of absorption to a hydrogen content which exceeds these values will be the key feature determining if, or when, the material becomes susceptible to cracking. Once this condition is achieved, whether or not failure occurs will depend on the strength and location of stresses within the structure. For Ti to absorb hydrogen it is inevitably necessary to subject the material to cathodic polarization, either by coupling to a more active material or by the

  5. Review of the expected behaviour of alpha titanium alloys under Yucca Mountain conditions

    International Nuclear Information System (INIS)

    The use of titanium alloys in two different waste package designs has been reviewed under the, conditions anticipated in the Yucca Mountain nuclear waste repository. In the first design. they are considered as one of three barrier materials incorporated into the waste package design and potentially in galvanic contact with the other two waste package materials, 316L stainless steel and Alloy-22. In the second design the Ti alloy is considered as a drip shield placed over, and not in contact with, a dual wall waste package fabricated from the other two materials. The possible failure processes, crevice corrosion, pitting and hydrogen-induced cracking (HIC) have been reviewed for the candidate titanium alloys (Ti-12, Ti-16 and Ti-7). Both pitting and crevice corrosion are very remote possibilities under these conditions. For Ti-12, a limited amount of crevice corrosion is possible but repassivation will occur before substantial damage is sustained. When Ti is considered as part of the triple wall waste package, hydrogen absorption leading to HIC, within an acidified but passive crevice, is the most likely failure mechanism. When the Ti alloy is utilized in the form of a drip shield then hydrogen absorption under potentially alkaline conditions is the major fear. Both Ti-12 and Ti-16 have been shown capable of tolerating substantial amounts of hydrogen (∼400 μ g·g-1 for Ti-12, and > 1000 μg.g-1 for Ti-16) before any effect on the materials fracture toughness is observed. The rate of absorption to a hydrogen content which exceeds these values will be the key feature determining if, or when, the material becomes susceptible to cracking. Once this condition is achieved, whether or not failure occurs will depend on the strength and location of stresses within the structure. For Ti to absorb hydrogen it is inevitably necessary to subject the material to cathodic polarization, either by coupling to a more active material or by the application of galvanic protection

  6. High Strain-Rate Mechanical Behaviour of a Copper Matrix Composite for Nuclear Applications

    CERN Document Server

    Peroni, L

    2012-01-01

    Aim of this work is the investigation of mechanical behaviour of an alumina dispersion strengthened copper, known by the trade name GLIDCOP®, subjected to dynamic loads: it is a composite material with a copper matrix strengthened with aluminium oxide ceramic particles. Since the particle content is quite small the material keeps the OFE copper physical properties, such as thermal and electrical conductivity, but with a higher yield strength, like a mild-carbon steel. Besides, with the addition of aluminium oxide, the good mechanical properties are retained also at high temperatures and the resistance to thermal softening is increased: the second phase blocks the dislocation movement preventing the grain growth. Thanks to these properties GLIDCOP® finds several applications in particle accelerator technologies, where problems of thermal management, combined with structural requirements, play a key role. Currently, it is used for the construction of structural and functional parts of the particle beam collim...

  7. COMETHE III J a computer code for predicting mechanical and thermal behaviour of a fuel pin

    International Nuclear Information System (INIS)

    The design of fuel pins for power reactors requires a realistic evaluation of their thermal and mechanical performances throughout their irradiation life. This evaluation involves the knowledge of a number of parameters, very intricate and interconnected, for example, the temperature, the restructuring and the swelling rates of the fuel pellets, the dimensions, the stresses and the strains in the clad, the composition and the properties of gases, the inner gas pressure etc. This complex problem can only be properly handled by a computer programme which analyses the fuel pin thermal and mechanical behaviour at successive steps of its irradiation life. This report presents an overall description of the COMETHE III-J computer programme, designed to calculate the integral performance of oxide fuel pins with cylindrical metallic cladding irradiated in thermal or fast flux. (author)

  8. Effect of silicon on the structure, tribological behaviour, and mechanical properties of nitrogen-containing chromium-manganese austenitic steels

    International Nuclear Information System (INIS)

    The effect of silicon in quantity of 3.5-4.5 mass. % on tribological behaviour is studied for nitrogen-bearing (0.20-0.52 mass. % of nitrogen) chromium-manganese austenitic steels (10Kh15G23S4A0.20, 10Kh16G17N3S4A0.30, 10Kh19G20NS4A0.50, 12Kh19G19NS2A0.50, 10Kh18G19A0.50, 08Kh16G8N10S4A0.18). Mechanical properties and corrosion resistance of the steels are determined. Using metallographic, x-ray diffraction and electron microscopical methods a study is made into structural transformations running in the steels considered under friction and static tension. It is shown that additional silicon alloying of nitrogen-bearing chromium-manganese austenitic steels results in an essential increase of adhesion wear resistance of the materials on retention of low friction coefficient (f=0.25-0.33). A strong silicon effect on steel tribological behaviour is related with planar slip activation and with an increase of austenite strength and heat resistance

  9. Role of Silicon Dioxide Filler on Mechanical and Dry Sliding Wear Behaviour of Glass-Epoxy Composites

    Directory of Open Access Journals (Sweden)

    Naveed Anjum

    2013-01-01

    Full Text Available The mechanical properties and dry sliding wear behaviour of glass fabric reinforced epoxy (G-E composite with varying weight percentage of silicon dioxide (SiO2 filler have been studied in the present work. The influence of sliding distance, velocity, and applied normal load on dry sliding wear behaviour has been considered using Taguchi's L9 orthogonal array. Addition of SiO2 increased the density, hardness, flexural, and impact strengths of G-E composite. Results of dry sliding wear tests showed increasing wear volume with increase in sliding distance, load, and sliding velocity for G-E and SiO2 filled G-E composites. Taguchi's results indicate that the sliding distance played a significant role followed by applied load, sliding velocity, and SiO2 loading. Scanning electron micrographs of the worn surfaces of composite samples at different test parameters show smooth surface, microploughing, and fine grooves under low load and velocity. However, severe damage of matrix with debonding and fiber breakage was seen at high load and velocity especially in unfilled G-E composite.

  10. Mechanical behaviour of membrane electrode assembly (MEA during cold start of PEM fuel cell from subzero environment temperature

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2015-01-01

    Full Text Available Durability is one of the most critical remaining issues impeding successful commercialization of broad PEM fuel cell transportation energy applications. Automotive fuel cells are likely to operate with neat hydrogen under load-following or load-levelled modes and be expected to withstand variations in environmental conditions, particularly in the context of temperature and atmospheric composition. In addition, they are also required to survive over the course of their expected operational lifetimes i.e., around 5,500 hrs, while undergoing as many as 30,000 startup/shutdown cycles. Cold start capability and survivability of proton exchange membrane fuel cells (PEM in a subzero environment temperature remain a challenge for automotive applications. A key component of increasing the durability of PEM fuel cells is studying the behaviour of the membrane electrode assembly (MEA at the heart of the fuel cell. The present work investigates how the mechanical behaviour of MEA are influenced during cold start of the PEM fuel cell from subzero environment temperatures. Full three-dimensional, non-isothermal computational fluid dynamics model of a PEM fuel cell has been developed to simulate the stresses inside the PEM fuel cell, which are occurring during fuel cell assembly (bolt assembling, and the stresses arise during fuel cell running due to the changes of temperature and relative humidity. The model is shown to be able to understand the many interacting, complex electrochemical, transport phenomena, and stresses distribution that have limited experimental data.

  11. Investigating mechanisms underlying neurodevelopmental phenotypes of autistic and intellectual disability disorders: a perspective

    Directory of Open Access Journals (Sweden)

    Tim eKroon

    2013-10-01

    Full Text Available Brain function and behaviour undergo significant plasticity and refinement, particularly during specific critical and sensitive periods. In autistic and intellectual disability neurodevelopmental disorders (NDDs and their corresponding genetic mouse models, impairments in many neuronal and behavioural phenotypes are temporally regulated and in some cases, transient. However, the links between neurobiological mechanisms governing typically normal brain and behavioural development (referred to also as ‘neurotypical’ development and timing of NDD impairments are not fully investigated.This perspective highlights temporal patterns of synaptic and neuronal impairment, with a restricted focus on autism and intellectual disability types of NDDs. Given the varying known genetic and environmental causes for NDDs, this perspective proposes two strategies for investigation: (1 a focus on neurobiological mechanisms underlying known critical periods in the (typically normal-developing brain (2 investigation of spatio-temporal expression profiles of genes implicated in monogenic syndromes throughout affected brain regions.This approach may help explain why many NDDs with differing genetic causes can result in overlapping phenotypes at similar developmental stages and better predict vulnerable periods within these disorders, with implications for both therapeutic rescue and ultimately, prevention.

  12. Mechanical and failure behaviour of hybrid polymer–metal staked joints

    International Nuclear Information System (INIS)

    Highlights: ► Injection Clinching Joining (ICJ) is a new staking method for hybrid structures. ► Mechanical behaviour of polymer-metal ICJ-staked joints was described. ► Rivet geometry influence on mechanical performance of staked joints is clarified. ► Material properties define ductile or brittle failure modes of joints. ► This study is a base for improvements on staking joining of hybrid structures. - Abstract: Structural applications that use multi-material structures in the transportation industry have increased in recent years. Weight reduction in order to avoid excessive emissions is the driving force of this trend. The current joining technologies for such complex structures have potential for engineering and performance improvement. This preliminary study shows an alternative joining method for hybrid structures, the so-called Injection Clinching Joining (ICJ) [Abibe et al., J Thermoplast Compos 2011;24(2): 233–49], based on the principles of staking, injection moulding, and mechanical fastening. The main objectives of the paper are to exploit the mechanical behaviour of overlap joints produced by this proposed method and assess its potential as an applicable technology. The measurements used in this research are optical and scanning electron microscopy, X-ray computer microtomography, lap-shear strength testing and in situ strain distribution. Different failure modes were found, depending on the joining conditions. Net tension failure had a brittle and catastrophic nature, while rivet pull-out presented a more desirable slow ductile failure mode. The joint strengths were good, ranging from 35.9% to 88.5% of the base material’s experimental ultimate tensile stress. Although there is a lack of studies on structural staking applications, this paper shows potential for these joining techniques and introduces ICJ as a potential focus of future research

  13. Multi-scale approach of the mechanical behaviour of reinforced concrete structures - Application to nuclear plant containment buildings

    International Nuclear Information System (INIS)

    This thesis develops a multi-scale strategy to describe the mechanical behaviour of steel reinforcements and prestressing tendons in a reinforced concrete structure. This strategy is declined in several steps, which allow gradual integration of new physical phenomena. The first asymptotic model represents the effective elastic behaviour of heterogeneities periodically distributed on a surface. It combines an elastic interface behaviour and a membrane behaviour. A second asymptotic model then focuses on the behaviour of rigid fibers distributed on a surface, which may slide with respect to the surrounding volume. These models induce less stress concentrations than the usual truss models. They are implemented in the finite element code Code-Aster, and validated with respect to reference three-dimensional simulations. Their interaction with a macroscopic crack is studied. Finally, this strategy allows the modeling of experimental tests carried out on a portion of a containment building in real scale. (author)

  14. Identifying beliefs underlying pre-drivers' intentions to take risks: An application of the Theory of Planned Behaviour.

    Science.gov (United States)

    Rowe, Richard; Andrews, Elizabeth; Harris, Peter R; Armitage, Christopher J; McKenna, Frank P; Norman, Paul

    2016-04-01

    Novice motorists are at high crash risk during the first few months of driving. Risky behaviours such as speeding and driving while distracted are well-documented contributors to crash risk during this period. To reduce this public health burden, effective road safety interventions need to target the pre-driving period. We use the Theory of Planned Behaviour (TPB) to identify the pre-driver beliefs underlying intentions to drive over the speed limit (N=77), and while over the legal alcohol limit (N=72), talking on a hand-held mobile phone (N=77) and feeling very tired (N=68). The TPB explained between 41% and 69% of the variance in intentions to perform these behaviours. Attitudes were strong predictors of intentions for all behaviours. Subjective norms and perceived behavioural control were significant, though weaker, independent predictors of speeding and mobile phone use. Behavioural beliefs underlying these attitudes could be separated into those reflecting perceived disadvantages (e.g., speeding increases my risk of crash) and advantages (e.g., speeding gives me a thrill). Interventions that can make these beliefs safer in pre-drivers may reduce crash risk once independent driving has begun. PMID:26803598

  15. A Review on Solidification and Change in Mechanical Properties Under Vibratory Welding Condition

    Directory of Open Access Journals (Sweden)

    Jyoti Prakash

    2010-04-01

    Full Text Available Welding has been applied to various industries in particular, automotive, aerospace and microelectronics. Thermal cycle produced near weld line generates residual stress and inhomogeneous plastic deformation in weldments. However there are many methods for welding the workpieces and one of the method among these is vibratory welding. It has the advantages of less investment, more convenient operation, less pollution and shorter manufacturing period. In vibratory welding, workpiece vibrates in the whole welding process and it mainly effects the welding solidification to improve the quality. Vibration facilitates the release of dissolved gases and the resulting weld beads greatly exhibit reduced porosity. Mechanical properties of the welds prepared under vibratory conditions are dependent on the structural changes of the welds This paper presents the solidification behaviour and changes occurs in mechanical properties under vibratory welding condition.

  16. Determination of turbine runner dynamic behaviour under operating condition by a two-way staggered fluid-structureinteraction method

    Science.gov (United States)

    Dompierre, F.; Sabourin, M.

    2010-08-01

    This paper presents the application of the two-way fluid-structure interaction method introduced by ANSYS to calculate the dynamic behaviour of a Francis turbine runner under operating condition. This time-dependant calculation directly takes into account characteristics of the flow and particularly the pressure fluctuations caused by the rotor-stator interaction. This formulation allows the calculation of the damping forces of the whole system implicitly. Thereafter, the calculated dynamic stress can be used for a fatigue analysis. A verification of the mechanical and fluid simulations used as input for the fluid-structure interaction calculation is first performed. Subsequently, a connection of these two independent simulations is made. A validation according to the hydraulic conditions is made with the measurements from the scale model testing. Afterwards, the static displacement of the runner under the hydraulic load is compared with the results of a classical static analysis for verification purposes. Finally, the natural frequencies deduced by the post-processing of the dynamic portion of the runner displacement with respect to time are compared with the natural frequencies obtained from a classical acoustic modal analysis. All comparisons show a good agreement with experimental data or results obtained with conventional methods.

  17. Determination of turbine runner dynamic behaviour under operating condition by a two-way staggered fluid-structureinteraction method

    International Nuclear Information System (INIS)

    This paper presents the application of the two-way fluid-structure interaction method introduced by ANSYS to calculate the dynamic behaviour of a Francis turbine runner under operating condition. This time-dependant calculation directly takes into account characteristics of the flow and particularly the pressure fluctuations caused by the rotor-stator interaction. This formulation allows the calculation of the damping forces of the whole system implicitly. Thereafter, the calculated dynamic stress can be used for a fatigue analysis. A verification of the mechanical and fluid simulations used as input for the fluid-structure interaction calculation is first performed. Subsequently, a connection of these two independent simulations is made. A validation according to the hydraulic conditions is made with the measurements from the scale model testing. Afterwards, the static displacement of the runner under the hydraulic load is compared with the results of a classical static analysis for verification purposes. Finally, the natural frequencies deduced by the post-processing of the dynamic portion of the runner displacement with respect to time are compared with the natural frequencies obtained from a classical acoustic modal analysis. All comparisons show a good agreement with experimental data or results obtained with conventional methods.

  18. Water hydraulic polymer components under irradiation. Mechanical properties

    International Nuclear Information System (INIS)

    Polymers will be used as different sealing and glide components for the hydraulic remote handling systems for lifting and moving activities in ITER. During operation these materials must maintain their properties during prolonged gamma irradiation and in the presence of water at or near room temperature. Preliminary results showed that the irradiation environment could affect the degradation process of the polymers and their hardness increase was different for irradiations carried out to 10 MGy in dry nitrogen or water. Vickers hardness tests were performed to study in detail the change in the mechanical properties of the candidate materials proposed for seals and wipers. Three different polymer materials have been tested as possible seals and O-rings: PEEK, Polyethylene (UHMW-PE), and Polyurethane. Specimens of each material have been irradiated with 60Co gamma rays up to 10 MGy in water. Following irradiation mechanical testing (tensile and microhardness) and also some microstructural observations of the fracture mode were carried out. The main results will be presented and discussed. Of the three materials, PEEK was outstanding, showing excellent mechanical behaviour for the doses and the irradiation conditions studied. Up to 10 MGy, neither hardness nor tensile strength were modified. In the case of polyethylene and polyurethane, the tensil failure mechanism varied with irradiation and give rise to lower ability for bending. However, up to 10 MGy the measured tensile strength and hardness data are acceptable for the working conditions studied. (author)

  19. In-Reactor Creep Behaviour of Zircaloy-2 under Variable Loading Conditions in IFA-585

    International Nuclear Information System (INIS)

    The test assembly IFA-585 is designed to study in-reactor creep behaviour of Zircaloy cladding under variable stress conditions. The first loading of the assembly contained two short rods, one fabricated from pre-irradiated Zr-2 (the BWR rod) and the other from unirradiated Zr-4 (the PWR rod). The diameter gauge on the PWR rod ceased functioning after about 8500 hours, but that on the BWR rod continued to give results until the end of the first loading in October 1995. Diameter change measurements were collected regularly from the BWR rod over its 14,400 hours dwell in reactor. During this time the fast neutron flux averaged 3.2x 1013 ncm-2s-1 whilst the cladding temperature stayed between 300 and 320 oC. The applied hoop stress was changed nine times within the range -160 to +130 MPa, from compression to tension and vice versa. From the measured variation in rod diameter with time at power, the following parameters have been determined for each stress level: elastic loading strain, primary creep strain and secondary creep rate. Although sometimes difficult to detect, primary creep is exhibited after each stress change resulting in a new secondary creep rate. Total primary strain has been shown to be proportional to the preceding change in stress and to exhibit no asymmetry between tension and compression. The stress dependence of the secondary creep rate is nearly linear and it is observed that the creep rate in tension is generally higher than that in compression for a given stress. The loading strain conforms to elastic behaviour and has been removed from the total diameter change measurements in order to obtain inelastic (creep) strain allowing comparison of the experimental results to existing creep models. Comparison is made to two creep models for Zircaloy, one based on in-reactor results, the other thermal creep results. In both cases the agreement is quite good. (author)

  20. [Behaviour of drugs under conditions of ultrasonic thermo aerosols (author's transl)].

    Science.gov (United States)

    Iwainsky, H; Sehrt, I; Lange, A

    1978-02-01

    The behaviour os histamine, acetylcholine, mucosolvine, panthenol, prednisolute and dexamethasone is investigated under conditions of thermoaerosol in the USI 50. The concentration of the drug is estimated in the original solution, in the aerosol and in the solution remaining in the nebulizer by means of specific chemical methods. The concentration in the aerosol is nearly unchanged in the case of acetylcholine, panthenol and dexamethasone. In the case of histamine there is only an insignificant decrease. Using prednisolute and dexamethasone the concentration amounts to 86%. Generally the concentration of the solution in the nebulizer increases. Decompositions or alterations of the drugs are not to be seen spectrophotometrically and by means of thin layer chromatography, nor is the pH-value changed. Signs for reactions or interferences with the nebulizer are to be observed in some cases. Therefore regular controls are necessary. In all cases of changing parts of the apparatus the needed material is to be tested concerning its indifference against the drugs used under conditions of thermoaerosol. PMID:685313

  1. THE INSTITUTIONAL INVESTORS’ BEHAVIOUR UNDER THE IMPACT OF THE GLOBAL FINANCIAL CRISIS

    Directory of Open Access Journals (Sweden)

    PIRTEA MARILEN

    2013-02-01

    Full Text Available On the subject of financial globalization a lot of literature has been written, annalyzing all sorts of effects ithad. Still, the changes induced by globalization at the level of the financial markets are not always clear. The veritableflooding of capitals, constantly moving, created a continuous game of investment opportunities, of arbitrationpossibilities and funding sources, made institutional investors adopt various attitudes, the role of institutional investorsin the activation of capital markets being sustained by the financial globalization and the extension of multinationalfinancial groups, on one side, and by the increased performance of the share and bond markets, on the other side.By the present paper, we propose to underline the behaviour of the main institutional investors (mutual funds,pension funds and hedge funds under the impact of the current global financial crisis, the modifications whichintervened in asset assignment and investment relocation, showing that the instability generated in the global financialsystem had immediate effects on all the portfolios of institutional investors, regardless of their classificationcategory.Under conditions of capital flow increase, adjusted by the global financial crisis, the presented analysis andempirical proofs show a tendency of institutional investors’ asset reallocation on developed markets and thewithdrawal from the emergent ones.

  2. Comparison of mechanical and corrosion behaviour of Alloy 800 H and the new alloy AC 66

    International Nuclear Information System (INIS)

    In coal gasification plants based on nuclear process heat, materials are subjected to high temperature corrosion in process gas atmosphere at 750 to 900 deg. C. The process gas consists of steam, CO, CH4, CO2 and, depending on the gasified coal, low or high H2S-concentrations. The service problems can be divided as follows: 1. Gas-metal interaction: (a) high temperature corrosion; (b) sulphidation; (c) carburization; (d) internal oxidation or internal sulphidation. 2. Ash (slag)-metal interaction: (a) corrosion in molten salts; (b) erosion. 3. Mechanical loading: (a) embrittlement; (b) thermal fluctuations/strain fluctuations; (c) low cycle fatigue; (d) high temperature creep. Therefore materials for heat exchangers must be resistant to these types of high temperature corrosion and they should also have adequate creep rupture strength. Some commercial alloys and various model alloys were exposed to a process gas atmosphere to determine the corrosion behaviour and also stressed mechanically to investigate the interaction of high temperature creep behaviour and corrosion. The tests were carried out for a total period of 10,000 h and specimens were taken out after periods of 1000, 3000, 5000 and 10,000 h. A programme for the development of alloys was started with the aim of optimizing the chemical composition resulting in a good high temperature corrosion resistance and adequate mechanical properties, particularly high creep strength. However, the material must be such that it can be deformed to tubes. Compared with Incoloy 800, one of the new and optimized model alloys (30-32% Ni, 25-27% Cr, and Ce, Fe-balance) exhibits a very good corrosion resistance even when sulphur rich coal is gasified. The creep rupture strength at 900 deg. C is in the range of the creep strength for Incoloy 800. 29 figs

  3. Effects of carbonate content on the mechanical behaviour of stiff clays

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Two deep stiff clays, the Boom and the Ypresian clays are currently investigated by the Belgian radioactive waste management agency Ondraf/Niras as potential host formations for geological disposal. Previous studies on Boom and Ypresian clays have shown significant difference in carbonate contents in Boom and Ypresian clays at different locations. Indeed; Table 1 shows that the carbonate content of the Boom clay at Essen varies with depth and is lower than that at the Mol site. Carbonate content heterogeneity was also recognized in Ypresian clay with a maximum value increasing abruptly up to 10 % in the upper part of the Roubaix member (core YP43). From a practical point of view, it is therefore essential for repository construction to understand the effect of the carbonates content on the mechanical behaviour when comparing the different materials. It is also important to determine to which extent the subsequent evolution of the repository and, possibly, the long term-performance may be affected. Odometer tests with step loading/unloading/reloading paths over low (0.05 - 3.2 MPa) and high (0.125 - 32 MPa) pressure ranges, isotropic consolidation, and consolidated drained (CD) triaxial tests with three different isotropic effective stresses (mean in-situ effective stress, 1 and 0.5 MPa) were carried out on saturated intact Boom and Ypresian clays. An example of the results obtained is shown in Figure 1a (odometer compression curves), Figure 1b (peak shear strength envelope) and Figure 1c (isotropic compression curves). Common loading/unloading/reloading loops were identified in odometer tests. Deeper examination of each path showed that the swelling slope Cs under low stress varies with the carbonate content. Nonetheless, when the sample has undergone higher stresses, the swelling slopes tend to be similar due to the progressive disruption of the fabric and inter-particles bonding as indicated in (Burland, 1990

  4. AN INTRODUCTION TO BEHAVIOURAL ECONOMICS: UNDER SAVING FOR RETIREMENT AND NEW ECONOMIC MODELS FOR PREDICTING SAVINGS

    OpenAIRE

    Marta-Christina SUCIU; Ileana GURAN TEODORESCU

    2013-01-01

    Experimental research done by behavioural economist points out human behavioural “heuristics and biases”, that often result in less than optimal individual economic decisions. These experiments cover a wide range of economic subjects, but one that we found most important to our society is the topic of savings with respect to the retirement behaviours. Evidence suggests that savings for retirement are suboptima, and that, as a result, people experience a drop in their income upon retirement. T...

  5. Tribological behaviour and microscopic wear mechanisms of UHMWPE sliding against thermal oxidation-treated Ti6Al4V

    International Nuclear Information System (INIS)

    Tribological behaviour of ultra-high molecular weight polyethylene (UHMWPE) pins sliding against thermal oxidation (TO)-treated Ti6Al4V alloy discs with different levels of average surface roughness was investigated under water lubrication conditions. When rubbing against a smooth counterface (Ra < 0.030-0.035 μm), UHMWPE was found to be worn predominantly via a micro-fatigue mechanism. To advance the scientific understanding of the microscopic wear mechanisms of UHMWPE, a technique involving permanganic etching coupled with high resolution SEM analyses of wear surfaces and cross-sections was adopted to yield new insight into the micro-fatigue mechanism. It was found that stress-induced preferential orientation of the crystalline lamellae in the UHMWPE led to the origin of ripples containing micro-cracks at their valleys. The cyclic loading promoted lateral propagation and inter-connection of these micro-cracks, thus giving rise to eventual spallation of the surface material as wear debris. Based on the experimental results, a micro-fatigue wear mode is proposed. (orig.)

  6. Fracture mechanical investigations about crack resistance behaviour in non-transforming ceramics in particular aluminum oxide

    International Nuclear Information System (INIS)

    The aim of this work is the clearification of R-curve behaviour of non-transforming ceramics, in particular aluminum oxide exhibiting incrystalline fracture. Investigations of crack growth in controlled bending experiments were performed using 3-Pt- and 4-Pt-bending samples of differing sizes under inert conditions. The fracture experiments were realized using several loading techniques, for example constant and varying displacement rates, load rupture (P = 0) and relaxation tests (v = 0). In addition unloading and reloading experiments were performed to investigate hysteresis curves and residual displacements in accordance with R-curve behaviour. During the crack-growth experiments, the crack extension was measured in situ using a high resolution immersion microscope. With this technique, the fracture processes near the crack tip (crack activity zone) was observed as well. The crack resistance as a function of crack extension (R-curve) was determined using differing calculation methods. All of the methods used resulted in approximately identical R-curves, within the statistical error band. The crack resistance at initiation R0 was 20 N/m. The crack resistance increased during approximately 3 mm of growth to a maximum of 90 N/m. A decrease in the crack resistance was determined for large a/W (crack length normalized with sample height) values, independant of the calculation methods. The R-curve behaviour was interpreted as due to a functional resistance behind the observed crack tip, which arises from a volume dilatation in the crack activity zone while the crack proceeds. (orig.)

  7. Structure, mechanical and thermal behaviour of mixtures of polyester resin and dental ceramic waste

    Science.gov (United States)

    Peña Rodríguez, G.; Martínez Maldonado, L.; Dulce Moreno, H. J.

    2016-02-01

    The tensile strength and bending strength, structure and thermal behaviour of mixtures of polyester resin (P-2000) and powders (ASTM sieve 200, dental ceramic wastes (dentals impressions, alginate and gypsum) was reported. The samples consisted of mixtures with percentage weights of 50-50%, 60-40%, 70-30%, 80-20%, 90-10%, where the resin was the majority phase, the Mekc (4% wt) was used as catalyst. The structure was studied using SEM and XRD, the thermal behaviour using DSC, TGA and DMA, while the mechanical strength was tested using standards ASTM D790 and D638. Irregular morphology and presence of small agglomerations was observed, with particle sizes between 29.63 and 38.67μm, the presence of different phases of calcium sulphate was found, and that to the increasing the concentration of the powder, the materials becomes more crystalline, increasing its density. An average service temperature of 69.15±4.60°C was found. Vickers hardness values are reported in ranges from 18.65 to 27.96. Considering the elastic modules was established that the materials become more rigid by having more powder concentration.

  8. Tribological behaviour of mechanically synthesized titanium-boron carbide nanostructured coating.

    Science.gov (United States)

    Aliofkhazraei, M; Rouhaghdam, A Sabour

    2012-08-01

    In this paper, titanium-boron carbide (Ti/B4C) nanocomposite coatings with different B4C nanoparticles contents were fabricated by surface mechanical attrition treatment (SMAT) method by using B4C nanoparticles with average nanoparticle size of 40 nm. The characteristics of the nanopowder and coatings were evaluated by microhardness test, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Friction and wear performances of nanocomposite coatings and pure titanium substrate were comparatively investigated, with the effect of the boron carbide content on the friction and wear behaviours to be emphasized. The results show the microhardness, friction and wear behaviours of nanocomposite coatings are closely related with boron carbide nanoparticle content. Nanocomposite coating with low B4C content shows somewhat (slight) increased microhardness and wear resistance than pure titanium substrate, while nanocomposite coating with high B4C content has much better (sharp increase) wear resistance than pure titanium substrate. The effect of B4C nanoparticles on microhardness and wear resistance was discussed. PMID:22962832

  9. Modelling the behaviour of mechanical biological treatment outputs in landfills using the GasSim model.

    Science.gov (United States)

    Donovan, S M; Bateson, T; Gronow, J R; Voulvoulis, N

    2010-03-15

    The pretreatment of the biodegradable components of municipal solid waste (MSW) has been suggested as a method of reducing landfill gas emissions. Mechanical biological treatment (MBT) is the technology being developed to provide this reduction in biodegradability, either as an alternative to source segregated collection or for dealing with residual MSW which still contains high levels of biodegradable waste. The compost like outputs (CLOs) from MBT plants can be applied to land as a soil conditioner; treated to produce a solid recovered fuel (SRF) or landfilled. In this study the impact that landfilling of these CLOs will have on gaseous emissions is investigated. It is important that the gas production behaviour of landfilled waste is well understood, especially in European member states where the mitigation of gaseous emissions is a legal requirement. Results of an experiment carried out to characterise the biodegradable components of pretreated biowastes have been used with the GasSim model to predict the long term emissions behaviour of landfills accepting these wastes, in varying quantities. The landfill directive also enforces the mitigation of potential methane emissions from landfills, and the ability of landfill operators to capture gaseous emissions from low emitting landfills of the future is discussed, as well as new techniques that could be used for the mitigation of methane generation. PMID:20092874

  10. A DYNAMIC MECHANICAL ANALYSIS STUDY OF THE TRANSITION BEHAVIOUR OF Ⅰ-PP/EPDM BLENDS

    Institute of Scientific and Technical Information of China (English)

    DONG Lisong; ZHUANG Yugang; LI Shichun; FENG Zhiliu

    1992-01-01

    The transition behaviour of the blends of isotactic polypropylene (i-PP ) with ethylene-propylene terpolymer (EPDM) containing 42 wt% propylene was investigated by dynamic mechanical analysis technique (DMA). Owing to its high propylene content, EPDM is compatible with i-PP to some degree. The interaction between the two components was strengthened. As expected, for partially compatible system the glass transition temperature of i-PP in the blends shifted to lower temperature. It was found that there existed two transitions, αEPDM and βEPDM, for the EPDM used in this work.The former was considered to be the glass transition of the random chain segments of EPDM, while the latter the local motion of the long ethylene sequences in EPDM. The unusual transition behaviour of αEPDM in the blends was explained in terms of the greater thermal expansion of EPDM and the compatibility of the two components. On the other hand, the β EPDM changed with the composition of the blends in a regular manner.

  11. Behaviour of bituminized waste under gamma irradiation. Effect of STE3 decontamination process components

    International Nuclear Information System (INIS)

    Liquid wastes of light and medium activity are treated by chemical co-precipitation and sludge are mixed with bitumen. Irradiation is responsible of gas production and potential swelling of the embedded. It prevails on limitation of filling of storage containers and activity to 140 Ci. The aim of this work is the study of influence of the components of the decontamination process on the behaviour of bituminous wastes, in order to control swelling and to state radiolysis mechanisms, both for production and storage of wastes. For pure bitumen, mechanism of production of H2 and CH4 are specified. Oxygen consumption, localised on the surface of samples, leads to conversion of aromatic oils and resins to asphaltenes, by a chain reaction mechanism. CO2 et CO are reaction products of gaseous oxygen, respectively with bitumen and light hydrocarbons. The composition of bitumen is slightly modified to heavier and higher polarity products, with parallel hardening. NaNO3, Na2SO4, BaSO4, PPFNi, K2SO4, NiSO4, et diatoms DIT3R et DIC3 have strictly a dilution effect towards gas generation. CoS, above 1% embedded, strongly inhibits production of H2, CH4 and light hydrocarbons. Degradation of bitumen being reduced, a radical mechanism with both radicals H· et R· might exist. Kinetic shows that a bi-radicals mechanism (or more) is probable. In the same way, Raney's nickel induces a important decrease of production of H2, CH4 et C2, with a capacity of 7,7 ml/g. Swelling depends on dimension of sample gas production and dose rate. Solid content and particle size are not determining parameters. Low swelling is obtained for penetrability higher than 70 1/10 mm, This can be realised by addition of a solvent as TBP and by increasing temperature above 40 deg C. Rheological characterizations (oscillation and creeping mode) have not been successful to correlate swelling with a physical parameter. (author)

  12. Mechanisms underlying the impacts of exotic plant invasions.

    OpenAIRE

    Levine, Jonathan M; Vilà, Montserrat; D'Antonio, Carla M; Dukes, Jeffrey S; Grigulis, Karl; Lavorel, Sandra

    2003-01-01

    Although the impacts of exotic plant invasions on community structure and ecosystem processes are well appreciated, the pathways or mechanisms that underlie these impacts are poorly understood. Better exploration of these processes is essential to understanding why exotic plants impact only certain systems, and why only some invaders have large impacts. Here, we review over 150 studies to evaluate the mechanisms underlying the impacts of exotic plant invasions on plant and animal community st...

  13. Cooperative Mechanism of Supply Chain Under Asymmetric Information

    Institute of Scientific and Technical Information of China (English)

    郭敏; 王红卫; 瞿坦

    2003-01-01

    The cooperative mechanism is one main issue in the decentralized supply chain system, especially in an asymmetric information structure. We analyze the non-cooperative game behavior of a 2-echelon distribution supply chain, compare the results with the system optimal solution, and give the supplier dominated cooperative mechanisms. We also analyze the validity of our contract under the asymmetric retailers' holding cost information and give some useful conclusions.

  14. Mechanical annealing under low-amplitude cyclic loading in micropillars

    Science.gov (United States)

    Cui, Yi-nan; Liu, Zhan-li; Wang, Zhang-jie; Zhuang, Zhuo

    2016-04-01

    Mechanical annealing has been demonstrated to be an effective method for decreasing the overall dislocation density in submicron single crystal. However, simultaneously significant shape change always unexpectedly happens under extremely high monotonic loading to drive the pre-existing dislocations out of the free surfaces. In the present work, through in situ TEM experiments it is found that cyclic loading with low stress amplitude can drive most dislocations out of the submicron sample with virtually little change of the shape. The underlying dislocation mechanism is revealed by carrying out discrete dislocation dynamic (DDD) simulations. The simulation results indicate that the dislocation density decreases within cycles, while the accumulated plastic strain is small. By comparing the evolution of dislocation junction under monotonic, cyclic and relaxation deformation, the cumulative irreversible slip is found to be the key factor of promoting junction destruction and dislocation annihilation at free surface under low-amplitude cyclic loading condition. By introducing this mechanics into dislocation density evolution equations, the critical conditions for mechanical annealing under cyclic and monotonic loadings are discussed. Low-amplitude cyclic loading which strengthens the single crystal without seriously disturbing the structure has the potential applications in the manufacture of defect-free nano-devices.

  15. A stable enol from a 6-substituted benzanthrone and its unexpected behaviour under acidic conditions

    Directory of Open Access Journals (Sweden)

    Marc Debeaux

    2009-06-01

    Full Text Available Treatment of benzanthrone (1 with biphenyl-2-yl lithium leads to the surprisingly stable enol 4, which is converted by dehydrogenation into the benzanthrone derivative 7. Under acidic conditions 4 isomerises to the spiro compound 11 and the bicyclo[4.3.1]decane derivative 12. Furthermore, the formation of 7 and the hydrogenated compound 13 is observed. A mechanism for the formation of the reaction products is proposed and supported by DFT calculations.

  16. Amphiphilic block copolymers in oil-water-surfactant mixtures: efficiency boosting, structure, phase behaviour and mechanism

    Science.gov (United States)

    Gompper, G.; Richter, D.; Strey, R.

    2001-10-01

    The effect of amphiphilic block copolymers on the phase behaviour and structure of ternary microemulsions in water, oil and non-ionic surfactant mixtures is reviewed. Recent experiments have revealed that the addition of small amounts of polyethylenepropylene-polyethyleneoxide block copolymer to the ternary systems leads to a dramatic increase in the volumes of oil and water solubilized into a bicontinuous microemulsion for a given surfactant volume fraction. While phase diagrams directly show the power of the amphiphilic block copolymers as efficiency boosters, the theoretical analysis in terms of bending energy discloses the mechanism for the efficiency boosting as due to the variation of the surfactant film curvature elasticity by tethered polymers in the form of mushrooms at the interface. Neutron scattering experiments employing a high-precision two-dimensional contrast variation technique confirm this picture and demonstrate that the polymer molecules uniformly decorate the surfactant film.

  17. The effect of interfaces on the mechanical behaviour of multilayered metallic laminates

    Science.gov (United States)

    Sobie, Cameron; McPhie, Mathieu G.; Capolungo, Laurent; Cherkaoui, Mohammed

    2014-06-01

    The mechanical response of multilayered metallic laminates is dominated by size effects through the confinement of dislocation motion within the layers. We deconvolute the contributions to the plastic behaviour resulting from dislocation-dislocation interactions and dislocation-interface interactions, using discrete dislocation dynamics and atomistic simulations. Upper and lower bounds for the material strength are found by considering two limiting cases for the influence of the interfaces: hard and shearable. Hard interfaces, preserving interfacial dislocations, are shown to significantly increase the strength of the multilayered metallic laminates, whereas a deformable interface results in lesser hardening. Molecular dynamics simulations show that the {1 1 1}Cu ∥ {1 1 0}Nb Cu/Nb interface response lies between these two cases. Additionally, the plastic response of Cu/Nb multilayered metallic laminates is studied and shown to be isotropic due to an effect of averaging among layers, despite the plastic anisotropy of the respective layer materials.

  18. The effect of interfaces on the mechanical behaviour of multilayered metallic laminates

    International Nuclear Information System (INIS)

    The mechanical response of multilayered metallic laminates is dominated by size effects through the confinement of dislocation motion within the layers. We deconvolute the contributions to the plastic behaviour resulting from dislocation–dislocation interactions and dislocation–interface interactions, using discrete dislocation dynamics and atomistic simulations. Upper and lower bounds for the material strength are found by considering two limiting cases for the influence of the interfaces: hard and shearable. Hard interfaces, preserving interfacial dislocations, are shown to significantly increase the strength of the multilayered metallic laminates, whereas a deformable interface results in lesser hardening. Molecular dynamics simulations show that the {1 1 1}Cu ∥ {1 1 0}Nb Cu/Nb interface response lies between these two cases. Additionally, the plastic response of Cu/Nb multilayered metallic laminates is studied and shown to be isotropic due to an effect of averaging among layers, despite the plastic anisotropy of the respective layer materials. (paper)

  19. Mechanical Behaviour of Glassy Composite Seals for IT-SOFC Application

    DEFF Research Database (Denmark)

    Nielsen, Karsten Agersted; Solvang, Mette; Nielsen, Sofie Birkedal Lund; Beeaff, Dustin

    2007-01-01

    Glass-based sealants have been developed with emphasis on filler material and surface treatment of the sealing components in order to optimise their mechanical and functional behaviour during the initial sealing process as well as during thermal cycling of the SOFC-stack after exposure to operating...... conditions. The bonding strength and microstructure of the interfaces between composite seals and interconnect materials were investigated as a function of surface treatment of the sealing surfaces, glass matrix composition, sealing pressure and temperature. The initial sealing performance and resistance to...... thermal cycling were then investigated on selected combinations of materials after ageing. Strongest bonding between sodium aluminosilicate glass composite and steel surfaces was obtained for sealing at 850°C. For the strongest interface, having shear strength of 2.35 MPa, rupture occurred in the glass...

  20. Fatigue behaviour and fracture mechanism of cryogenically treated En 353 steel

    International Nuclear Information System (INIS)

    An experimental investigation was conducted for a better understanding of fatigue and fracture behaviour of carburized steel used in the manufacture of vehicle transmission elements such as crown wheel and pinion. An attempt was made to study the fatigue strength of En 353 based on failure at 107 cycles after subjecting to three different treatments namely conventional heat treatment, shallow cryogenic treatment and deep cryogenic treatment. Rotating bending fatigue test was performed in air at room temperature for all specimens. Fractured specimen surfaces were examined by scanning electron microscope to identify the mechanism involved during fatigue. The study concludes that shallow and deep cryogenically treated samples show an improvement with an overall fatigue life of 71% and a reduction of 26% over conventionally heat treated samples respectively. The combined presence of retained austenite and fine carbides has resulted in enhanced fatigue strength of shallow cryogenically treated specimens over the conventionally heat treated and deep cryogenically treated specimens.

  1. Buckling and fracture behaviour of cracked thin plates under shear loading

    International Nuclear Information System (INIS)

    Thin-walled structural components are widely used in several engineering applications such as in aerospace, naval, nuclear power plant, pressure vessel, mechanical and civil fields. Since they are frequently characterised by a high slenderness, the safety assessment of such structural components requires to carefully consider the buckling collapse which can heavily limit their allowable bearing capacity. For very thin plates, buckling collapse can occur under compression, shear, or even under tension. In the present paper, the buckling and fracture collapse mechanisms in an elastic rectangular thin-plate with a central straight crack under shear loading are analysed. Different boundary conditions, crack length and orientation are considered. Through a parametric finite elements (FE) numerical analysis, the crack sensitivity of the collapse load of such a structural component is examined. The obtained results are discussed, and some interesting and useful conclusions are drawn. The collapse mechanism occurring earlier (buckling or fracture) is found by varying the fracture toughness of the material, and some failure-type maps depending on the geometrical parameters of the crack are determined.

  2. Games of School Choice under the Boston Mechanism

    OpenAIRE

    Haluk Ergin; Tayfun Sönmez

    2005-01-01

    Many school districts in the U.S. use a student assignment mechanism that we refer to as the Boston mechanism. Under this mechanism a student loses his priority at a school unless his parents rank it as their first choice. Therefore parents are given incentives to rank high on their list the schools where the student has a good chance of getting in. We characterize the Nash equilibria of the induced preference revelation game. An important policy implication of our result is that a transition...

  3. Mechanical behaviour and failure modes in the Whakaari (White Island volcano) hydrothermal system, New Zealand

    Science.gov (United States)

    Heap, Michael J.; Kennedy, Ben M.; Pernin, Noémie; Jacquemard, Laura; Baud, Patrick; Farquharson, Jamie I.; Scheu, Bettina; Lavallée, Yan; Gilg, H. Albert; Letham-Brake, Mark; Mayer, Klaus; Jolly, Arthur D.; Reuschlé, Thierry; Dingwell, Donald B.

    2015-03-01

    Volcanic hydrothermal systems host a prodigious variety of physico-chemical conditions. The physico-chemical state and mechanical behaviour of rocks within is correspondingly complex and often characterised by vast heterogeneity. Here, we present uniaxial and triaxial compression experiments designed to investigate the breadth of mechanical behaviour and failure modes (dilatant or compactant) for hydrothermally-altered lava and ash tuff deposits from Whakaari (White Island volcano) in New Zealand, a volcano with a well-documented and very active hydrothermal system. Our deformation experiments show that the failure mode of low porosity lava remains dilatant over a range of depths (up to pressures corresponding to depths of about 2 km). Upon failure, shear fractures, the result of the coalescence of dilatational microcracks, are universally present. The high porosity ash tuffs switch however from a dilatant to a compactant failure mode (driven by progressive distributed pore collapse) at relatively low pressure (corresponding to a depth of about 250 m). We capture the salient features of the dynamic conditions (e.g., differential stress, effective pressure) in a schematic cross section for the Whakaari hydrothermal system and map, for the different lithologies, areas susceptible to either dilatant vs. compactive modes of failure. The failure mode will impact, for example, the evolution of rock physical properties (e.g., porosity, permeability, and elastic wave velocity) and the nature of the seismicity accompanying periods of unrest. We outline accordingly the potential implications for the interpretation of seismic signals, outgassing, ground deformation, and the volcanic structural stability for Whakaari and similar hydrothermally-active volcanoes worldwide.

  4. Characterization of the thermo-mechanical behaviour of Hemp fibres intended for the manufacturing oh high performance composites

    CERN Document Server

    Placet, Vincent

    2009-01-01

    In this paper, the thermo-mechanical behaviour of hemp fibres (Cannabis sativa L.) is investigated using a Dynamic Mechanical Analyser. Experiments are performed at a frequency of 1 Hz in the temperature range of 20 to 220\\degree C. When a periodic solicitation is applied to an elementary fibre, an increase of the fibre rigidity and a reduction of the damping capacity are observed. These evolutions aim at stabilization after an identified number of cycles, traducing a phenomenon of "adaptation". This specific mechanical behaviour certainly involves biochemical and/or structural modifications in the material organisation as microfibrils reorientation. In addition, the behaviour of hemp fibres is affected by temperature. Temperature acts as an activation factor but also as a degradation factor of the viscoelastic properties of fibres. The rigidity and the endurance of fibres are highly affected by thermal treatment at temperature above 150\\degree C to 180\\degree C. Taking into account these results, polypropyle...

  5. Experimental approach and modelling of the mechanical behaviour of graphite fuel elements subjected to compression pulses

    Directory of Open Access Journals (Sweden)

    Forquin P.

    2010-06-01

    Full Text Available Among the activities led by the Generation IV International Forum (GIF relative to the future nuclear systems, the improvement of recycling of fuel elements and their components is a major issue. One of the studied systems by the GIF is the graphite-moderated high-temperature gas cooled reactor (HTGR. The fuel elements are composed of fuel roads half-inch in diameter named compacts. The compacts contain spherical particles made of actinide kernels about 500 m in diameter coated with three layers of carbon and silicon carbide, each about 50 m thick, dispersed in a graphite matrix. Recycling of compacts requires first a separation of triso-particles from the graphite matrix and secondly, the separation of the triso-coating from the kernels. This aim may be achieved by using pulsed currents: the compacts are placed within a cell filled by water and exposed to high voltage between 200 – 500 kV and discharge currents from 10 to 20 kA during short laps of time (about 2 µs [1-2]. This repeated treatment leads to a progressive fragmentation of the graphite matrix and a disassembly of the compacts. In order to improve understanding of the fragmentation properties of compacts a series of quasi-static and dynamic experiments have been conducted with similar cylindrical samples containing 10% (volume fraction of SiC particles coated in a graphite matrix. First, quasi-static compression tests have been performed to identify the mechanical behaviour of the material at low strain-rates (Fig.1. The experiments reveal a complex elasto-visco-plastic behaviour before a brittle failure. The mechanical response is characterised by a low yield stress (about 1 MPa, a strong strain-hardening in the loading phase and marked hysteresis-loops during unloading-reloading stages. Brittle failure is observed for axial stress about 13 MPa. In parallel, a series of flexural tests have been performed with the aim to characterise the quasi-static tensile strength of the

  6. Experimental approach and modelling of the mechanical behaviour of graphite fuel elements subjected to compression pulses

    Science.gov (United States)

    Forquin, P.

    2010-06-01

    Among the activities led by the Generation IV International Forum (GIF) relative to the future nuclear systems, the improvement of recycling of fuel elements and their components is a major issue. One of the studied systems by the GIF is the graphite-moderated high-temperature gas cooled reactor (HTGR). The fuel elements are composed of fuel roads half-inch in diameter named compacts. The compacts contain spherical particles made of actinide kernels about 500 m in diameter coated with three layers of carbon and silicon carbide, each about 50 m thick, dispersed in a graphite matrix. Recycling of compacts requires first a separation of triso-particles from the graphite matrix and secondly, the separation of the triso-coating from the kernels. This aim may be achieved by using pulsed currents: the compacts are placed within a cell filled by water and exposed to high voltage between 200 - 500 kV and discharge currents from 10 to 20 kA during short laps of time (about 2 µs) [1-2]. This repeated treatment leads to a progressive fragmentation of the graphite matrix and a disassembly of the compacts. In order to improve understanding of the fragmentation properties of compacts a series of quasi-static and dynamic experiments have been conducted with similar cylindrical samples containing 10% (volume fraction) of SiC particles coated in a graphite matrix. First, quasi-static compression tests have been performed to identify the mechanical behaviour of the material at low strain-rates (Fig.1). The experiments reveal a complex elasto-visco-plastic behaviour before a brittle failure. The mechanical response is characterised by a low yield stress (about 1 MPa), a strong strain-hardening in the loading phase and marked hysteresis-loops during unloading-reloading stages. Brittle failure is observed for axial stress about 13 MPa. In parallel, a series of flexural tests have been performed with the aim to characterise the quasi-static tensile strength of the particulate

  7. Dual mechanical behaviour of hydrogen in stressed silicon nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Volpi, F., E-mail: fabien.volpi@simap.grenoble-inp.fr; Braccini, M.; Pasturel, A. [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France); Devos, A. [IEMN, UMR 8520 CNRS, Avenue Poincarré - CS 60069 - 59652 Villeneuve d' Ascq Cedex (France); Raymond, G. [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France); STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles Cedex (France); Morin, P. [STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles Cedex (France)

    2014-07-28

    In the present article, we report a study on the mechanical behaviour displayed by hydrogen atoms and pores in silicon nitride (SiN) films. A simple three-phase model is proposed to relate the physical properties (stiffness, film stress, mass density, etc.) of hydrogenated nanoporous SiN thin films to the volume fractions of hydrogen and pores. This model is then applied to experimental data extracted from films deposited by plasma enhanced chemical vapour deposition, where hydrogen content, stress, and mass densities range widely from 11% to 30%, −2.8 to 1.5 GPa, and 2.0 to 2.8 g/cm{sup 3}, respectively. Starting from the conventional plotting of film's Young's modulus against film porosity, we first propose to correct the conventional calculation of porosity volume fraction with the hydrogen content, thus taking into account both hydrogen mass and concentration. The weight of this hydrogen-correction is found to evolve linearly with hydrogen concentration in tensile films (in accordance with a simple “mass correction” of the film density calculation), but a clear discontinuity is observed toward compressive stresses. Then, the effective volume occupied by hydrogen atoms is calculated taking account of the bond type (N-H or Si-H bonds), thus allowing a precise extraction of the hydrogen volume fraction. These calculations applied to tensile films show that both volume fractions of hydrogen and porosity are similar in magnitude and randomly distributed against Young's modulus. However, the expected linear dependence of the Young's modulus is clearly observed when both volume fractions are added. Finally, we show that the stiffer behaviour of compressive films cannot be only explained on the basis of this (hydrogen + porosity) volume fraction. Indeed this stiffness difference relies on a dual mechanical behaviour displayed by hydrogen atoms against the film stress state: while they participate to the stiffness in compressive films

  8. Characterisation and behaviour under irradiation of rare-earth doped powellite phases - Application to the long term behaviour of nuclear waste matrices

    International Nuclear Information System (INIS)

    This work deals with the behaviour under irradiation of a glass-ceramic made after heat treatment of a molybdenum rich R7/T7 type glass. Rare earth elements (Eu3+ and Nd3+) are used as surrogates of minor actinides and fission products as well as structural luminescent probes. We will focus on the behaviour of the crystalline phase which is a powellite type calcium molybdate that incorporated other elements including rare earth elements. In order to determine the crystalline-chemical properties of the powellite structure, Raman spectroscopy and photoluminescence analyses are led on natural powellite samples and synthetic ceramics with compositions from pure CaMoO4 to Ca0.76Sr0.1Na0.07Eu0.01La0.02Nd0.02Pr0.02MoO4, a model composition of the crystalline phase of the glass-ceramic. The analyses of synthetic samples irradiated with He, Ar and Pb ions compared to the behaviour of a natural powellite sample that contains uranium indicate that powellite resist strongly to irradiation and never reach the amorphous state. (author)

  9. Mating Behaviour and Copulatory Mechanism in the Scorpionfly Neopanorpa longiprocessa (Mecoptera: Panorpidae)

    OpenAIRE

    Zhong, Wen; Hua, Baozhen

    2013-01-01

    Sexual conflict during copulation may drive morphological and behavioral evolution in insects. Although nuptial feeding behaviour is well studied in Panorpa, whether this behaviour is universal in Panorpidae remains unknown. The scorpionfly Neopanorpa longiprocessa Hua & Chou, 1997 was investigated for its mating behaviour, functional morphology of the notal organ, and external genitalia using light microscopy and scanning electron microscopy. The results show that the mating behaviour is not...

  10. Effects of selected casting methods on mechanical behaviour of Al-Mg-Si alloy

    Directory of Open Access Journals (Sweden)

    Henry Kayode TALABI

    2014-11-01

    Full Text Available This study investigated the effects of selected casting methods on mechanical behaviour of Al-Mg-Si alloy. The casting methods used was spin, sand and die casting, these were done with a view to determine which of the casting methods will produce the best properties. The pure aluminium scrap, magnesium and silicon were subjected to chemical analysis using spectrometric analyzer, thereafter the charge calculation to determine the amount needed to be charged into the furnace was properly worked out and charged into the crucible furnace from which as-cast aluminium was obtained. The mechanical properties of the casting produced were assessed by hardness and impact toughness test. The optical microscopy and experimental density and porosity were also investigated. From the results it was observed that magnesium and silicon were well dispersed in aluminium matrix of the spin casting. It was observed from visual examination after machining that there were minimal defects. It was also observed that out of the three casting methods, spin casting possesses the best mechanical properties (hardness and impact toughness.

  11. Mechanical behaviour and fission product release in overpower transients at entended burnup

    International Nuclear Information System (INIS)

    An important factor for the utilization of water reactor fuel at extended burnup is the PCI behaviour during operational transients. The data from the internationally sponsored RISOE Fission Gas Project have provided significant information regarding the fission product release and swelling of UO2-Zr fuel pins with burnup in the range of 38,000-44,000 MWd/tU, peak pellet, during mild overpower transients (bump tests). The pellet cladding mechanical interaction during the transient tests was large enough to cause permanent deformation down to local heat ratings around 300 W/cm. The mechanical interaction was promoted by very rapid gaseous swelling, which developed during the transients. The local swelling increase during the short transient tests was measured by QIA and found to be as high as 8% at local, calculated temperatures of 800 deg. C. The local release of the volatile fission products Cs and I was measured by radial gamma scanning and found to be very similar to the measured release of noble fission gas. Radial EMPA measurements showed that the Xe release started at local, calculated temperatures of about 700 deg. C. Above 1100 deg. C a release of about 95% was found. Although significant mechanical interaction as well as release of volatile fission products were observed, only one of the twelve tests resulted in cladding failure. This is attributed to the slow approach to the full test power levels, where a power increase rate of 5 W/cm/h (peak pellet) was generally used. (author)

  12. Annealing behaviour and mechanical properties of severely deformed interstitial free steel

    International Nuclear Information System (INIS)

    Highlights: ► Microstructure and micro-texture evolution indicates continuous recrystallisation. ► HAGBs decrease from ∼80 to ∼40% due to texture clustering and orientation pinning. ► Characterisation of correlation between tensile and shear punch tests. ► Tensile behaviour evolves from stress drop to continuous yielding a work hardening. - Abstract: The evolution of microstructure, micro-texture and mechanical properties during isothermal annealing of an ultrafine grained interstitial free (IF) steel processed by Equal Channel Angular Pressing (ECAP) followed by 95% cold rolling (CR) was studied. Microstructure and micro-texture changes were characterised by Electron Back-Scattering Diffraction while mechanical properties were assessed by shear punch and uniaxial tensile testing. During annealing, homogeneous coarsening via continuous recrystallisation is accompanied by the retention of a sharp α-fibre rolling texture and a decrease in area fraction of high angle grain boundaries from ∼80% to ∼40% due to texture clustering and orientation pinning. Failure during uniaxial tension occurred without post-necking elongation after CR. Upon annealing, an evolution from stress-drop soon after yielding to a return to continuous yielding and increased work hardening was observed. Good agreement is found between experimental and estimated strengths and total elongations derived from SPT and tensile data. Tensile characteristics and mechanical properties depend on both, grain size and area fraction of HAGBs.

  13. Mechanical behaviour of ferritic ODS steels – Temperature dependancy and anisotropy

    International Nuclear Information System (INIS)

    Highlights: ► We characterized the anisotropic mechanical behaviour of 3 ferritic ODS steels. ► Creep, tension, fatigue, toughness and impact tests were carried out. ► The tranversal properties are always much poorer than longitudinal ones. ► Fracture modes are highly linked to grain boundaries. - Abstract: Ferritic 14%Cr and 18%Cr ODS steels produced at CEA in round bars or plates were tested mechanically. The present paper reports results obtained in tension, impact, fatigue, creep and toughness tests. These tests were carried out at various temperatures and in different directions. These materials show a pronounced anisotropy at all tested temperatures. No matter the loading, the transversal direction is always found to be far less resistant than the longitudinal one. This anisotropy is mainly observed in terms of damage mechanisms, with intergranular fracture preferentially occurring along the extrusion direction. This intergranular fracture mode leads to very low and anisotropic toughness values and to the absence of tertiairy creep stage, pointing out the unstable nature of fracture, even at high temperature. The unrealistically high values of the Norton exponent measured in creep suggests the existence of a threshold stress, which is consistent with the mainly kinematic nature of the stress as revealed by fatigue tests.

  14. Chemical influence on the hydro-mechanical behaviour of high-density bentonite

    International Nuclear Information System (INIS)

    In radioactive waste disposal schemes, during the operational period of clay barriers, solute transport an d thermal gradients may alter the solute concentration of pore water. These induced changes have important consequences on hydro-mechanical properties and microstructural alterations (mineral composition and pore size distribution changes) of the clay barrier. Chemically induced changes originated by different imbibition fluids and soil mineral compositions have been a subject with a long research tradition. These researches have been mainly focused on the behaviour of reconstituted soils starting from slurry and saturated wit h saline solutions at elevated concentrations, where hydro-mechanical changes (soil compressibility and water permeability changes) are clearly detected. In contrast, available information concerning the response of high-density clays subjected to chemically induced actions with a wide range of pore solution concentrations is very limited in spite of its practical relevance to environmental geotechnics. This situation has been caused, at least in part, by the difficulties in detecting important hydro-mechanical changes when clays with low water storage capacity have been used. Nevertheless, this paper will demonstrate that even in the case of high-density fabrics, considerable changes can be observed when high-activity clays (bentonites) are imbibed with different pore fluid compositions. (authors)

  15. Verification of Dinamika-5 code on experimental data of water level behaviour in PGV-440 under dynamic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Beljaev, Y.V.; Zaitsev, S.I.; Tarankov, G.A. [OKB Gidropress (Russian Federation)

    1995-12-31

    Comparison of the results of calculational analysis with experimental data on water level behaviour in horizontal steam generator (PGV-440) under the conditions with cessation of feedwater supply is presented in the report. Calculational analysis is performed using DIMANIKA-5 code, experimental data are obtained at Kola NPP-4. (orig.). 2 refs.

  16. 12C+12C reactions at astrophysical energies: Tests of targets behaviour under beam bombardment

    International Nuclear Information System (INIS)

    12C(12C,α)20Ne and 12C(12C,p)23Na are the most important reactions during the carbon burning phase in stars. Direct measurements at the relevant astrophysical energy (E=1.5±0.3MeV) are very challenging because of the extremely small cross sections involved and of the high beam-induced background originating from impurities in the targets. In addition, persistent resonant structures at low energies are not well understood and make the extrapolation of the cross section from high energy data very uncertain. As a preliminary step towards the measurements of the 12C(12C,α)20Ne and 12C(12C,p)23Na reactions we intend to investigate the behaviour of targets under beam bombardment, specifically the quantitative measurement of hydrogen and deuterium content of highly pure stable carbon targets in relation to target temperature. Experiments are taking place at the CIRCE accelerator in Caserta, Italy and preliminary results are presented here

  17. Effect of ageing under gamma radiations on the long term behaviour of bitumen material

    International Nuclear Information System (INIS)

    The referential scenario considered for bituminized waste drums is an intermediate storage likely to be followed by a deep geological disposal. Under geological disposal conditions, when site will be re-saturated with water and containers will be corroded, the main phenomenon likely to alter bituminized waste is linked to the presence of water. During intermediate storage conditions, drums will be submitted to the effect of irradiation, and for the external part of the wasteform to the effect of oxidation by surrounding air. The combined effect of air and radiation may increase bitumen oxidation. In further disposal conditions, alteration phenomena of drums will concern aged drums. The aim of these studies dealing with ageing, is to characterise the effect of alteration factors such as irradiation and radio-oxidation on the potential release of radionuclides from bituminized waste in disposal conditions. Radio-oxidation depends on: - the diffusion of O2 in the matrix (diffusion coefficient, solubility), -the intensity of radiation (dose rate), -the time of exposure to radiations. Low dose rates of radiation, near realistic dose rates are here investigated in order to characterise the effect of ageing phenomena on the long term behaviour of bitumen properties. Results concern Infra-red characterization of oxidized bitumen, gases evolution and diffusion of water. The evolution of the thickness of the oxidized layer with the dose and the dose rate for bitumen sample can be deduced from profiles of oxidised compounds concentration obtained with FTIR (Fourier transformed Infrared Spectroscopy). (authors)

  18. High hydrostatic pressure effect on behaviour of SmS crystals under deformation

    International Nuclear Information System (INIS)

    Experiments are carried out on the deformation of SmS monocrystals by uniaxial compression under high (up to 10 kbar) hydrostatic pressure. It is shown that on the whole dependences of mechanical characteristics of samarium monosulfide on the pressure are qualitatively similar to analogous dependences for other materials. While in the quantitative respect effects in samarium monosulfide are much higher, which is evidently connected with high compressibility of semiconducting SmS. It is found that in the result of uniaxial com-- pression of SmS crystals under hydrostatic pressure less than 6.5 kbar, a phase transition analogous to the semiconductor-metal transition under poressure, takes ptace in them

  19. Behaviour of high purity UO2/H2O interfaces under helium beam irradiation in deaerated conditions

    International Nuclear Information System (INIS)

    A question put within the framework of the nuclear fuel storage worn in geological site is what become to them in the presence of water. The aim of a fundamental program, of PRECCI project (ECA), is to highlight the behaviour of interfaces which can be used as models for the interfaces nuclear spent fuel/water if the fuel is uranium UO2 dioxide. This doctorate is interested in the effect of the alpha activity which is the only one that exist in the spent fuel after long periods. The aim is to identify the mechanisms of alteration and of leaching of surfaces under alpha irradiation. A method is developed to irradiate UO2/H2O interfaces in deaerated conditions with the beam of He2+ produced by a cyclotron. The He2+ ions cross an UO2 disc and emerge in water with an energy of 5 MeV. Leachings under irradiation are carried with a large range of particles flux. The post-irradiation characterization of the surface of the discs realised by micro-Raman spectroscopy allowed to identify the alteration layer. It is made up of studtite UO2(O2),4H2O, and of schoepite UO3,xH2O. The analysis of the solutions shows that the uranium release strongly increases. The electrochemical properties of the interfaces under irradiation strongly differ from those before irradiation. This work allows to propose that the radiolytic species seen by the interface are it during the heterogeneous phase of evolution of the traces and are species of short lives. Modeling show that the radiolytic radicals species can migrate toward the interface and react with the UO2 surface. (author)

  20. Study of the damaging mechanisms of a carbon - carbon composite bonded to copper under thermomechanical loading

    International Nuclear Information System (INIS)

    The purpose of this work is to understand and to identify the damaging mechanisms of Carbon-Carbon composite bonded to copper under thermomechanical loading. The study of the composite allowed the development of non-linear models. These ones have been introduced in the finite elements analysis code named CASTEM 2000. They have been validated according to a correlation between simulation and mechanical tests on multi-material samples. These tests have also permitted us to better understand the behaviour of the bonding between composite and copper (damaging and fracture modes for different temperatures) under shear and tensile loadings. The damaging mechanisms of the bond under thermomechanical loading have been studied and identified according to microscopic observations on mock-ups which have sustained thermal cycling tests: some cracks appear in the composite, near the bond between the composite and the copper. The correlation between numerical and experimental results have been improved because of the reliability of the composite modelization, the use of residual stresses and the results of the bond mechanical characterisation. (author)

  1. Study of the damaging mechanisms of a copper / carbon - carbon composite under thermomechanical loading

    International Nuclear Information System (INIS)

    The purpose of this work is to understand and to identify the damaging mechanisms of Carbon-Carbon composite bonded to copper under thermomechanical loading. The study of the composite allowed the development of non-linear models. These ones have been introduced in the finite elements analysis code named CASTEM2000. They have been validated according to a correlation between simulation and mechanical tests on multi-material samples. These tests have also permitted us to better understand the behaviour of the bonding between composite and copper (damaging and fracture modes for different temperatures) under shear and tensile loadings. The damaging mechanisms of the bond under thermomechanical loading have been studied and identified according to microscopic observations on mock-ups which have sustained thermal cycling tests: some cracks appear in the composite, near the bond between the composite and the copper. The correlation between numerical and experimental results have been improved because of the reliability of the composite modelization, the use of residual stresses and the results of the bond mechanical characterization. (author)

  2. Neural Circuitry and Plasticity Mechanisms Underlying Delay Eyeblink Conditioning

    Science.gov (United States)

    Freeman, John H.; Steinmetz, Adam B.

    2011-01-01

    Pavlovian eyeblink conditioning has been used extensively as a model system for examining the neural mechanisms underlying associative learning. Delay eyeblink conditioning depends on the intermediate cerebellum ipsilateral to the conditioned eye. Evidence favors a two-site plasticity model within the cerebellum with long-term depression of…

  3. TRIBOLOGICAL BEHAVIOURS OF ABS AND PA6 POLYMERMETAL SLIDING COMBINATIONS UNDER DRY FRICTION, WATER ABSORBED AND ELECTROPLATED CONDITIONS

    Directory of Open Access Journals (Sweden)

    MITHUN V. KULKARNI

    2016-01-01

    Full Text Available The friction and wear properties of polyamide 6 (PA6 and poly-Acrylonitrile Butadiene Styrene (ABS sliding against metal under dry sliding, water absorption and electroplated (EP conditions were studied by using a pin-ondisc tribometer. The effect of applied load and sliding speed on the tribological behaviours of the polymer–metal sliding combinations under dry sliding, water absorbed and EP conditions were also investigated. The worn surfaces were examined by using Scanning Electron Microscope (SEM. Experimental results showed that ABS samples under water absorbed conditions showed higher wear loss compared to normal samples and the EP samples had exhibited lower wear loss compared to the water absorbed samples. Similarly EP-PA6 samples exhibited excellent wear resistance when compared with EP-ABS samples. Further, it was observed that the frictional heat produced on account of sliding action had a significant effect on the tribological behaviours of samples under dry sliding and water absorbed conditions.

  4. The behaviour of entrainment defects formed in commercial purity Mg alloy cast under a cover gas of SF6

    Science.gov (United States)

    Li, T.; Griffiths, W. D.

    2016-03-01

    In the casting of light alloys, the oxidised film on the melt surface can be folded due to surface turbulence, thus forming entrainment defects that have a significant negative effect on the mechanical properties of castings. Previous researchers reported that the surface film of Mg alloys formed in an atmosphere containing SF6 had a complicated structure composed of MgO and MgF2. The work reported here aims to investigate the behaviour of entrainment defects formed in magnesium alloys protected by SF6-containing atmospheres. Tensile test bars of commercial purity Mg were cast in an unsealed environment under a cover gas of pure SF6. 34Scanning electron microscopy (SEM) of the fracture surface of the test bars indicated entrainment defects that consisted of symmetrical films containing MgO, but also sulphur and fluorine. The results of these examinations of the symmetrical films were used to infer the potential formation and development of entrainment defects in commercial purity Mg alloy.

  5. Multi-scale modelling of the physicochemical-mechanical coupling of fuel behaviour at high temperature in pressurized water reactors

    International Nuclear Information System (INIS)

    Within the frame of the problematic of pellet-sheath interaction in a nuclear fuel rod, a good description of the fuel thermo-mechanical behaviour is required. This research thesis reports the coupling of physics-chemistry (simulation of gas transfers between different cavities) and mechanics (assessment of fuel viscoplastic strains). A new micromechanical model is developed which uses a multi-scale approach to describe the evolution of the double population of cavities (cavities with two different scales) while taking internal pressures as well as the fuel macroscopic viscoplastic behaviour into account. The author finally describes how to couple this micromechanical mode to physics-chemistry models

  6. Structural behaviour and design criteria of under-deck cable-stayed bridges subjected to seismic action

    OpenAIRE

    Cámara Casado, Alfredo; Ruiz Teran, Ana M.; Stafford, Peter J.

    2012-01-01

    SUMMARY: Under-deck cable-stayed bridges are very effective structural systems for which the strong contribution of the stay cables under live loading allows for the design of very slender decks for persistent and transient loading scenarios. Their behaviour when subjected to seismic excitation is investigated herein and a set of design criteria are presented that relate to the type and arrangement of bearings, the number and configuration of struts, and the transverse distribution of stay ca...

  7. Strength behaviour of a gas pressure sintered siliconnitride (GPSSN) under static and cyclostatic loading at 1250 C in air

    Energy Technology Data Exchange (ETDEWEB)

    Lauf, S.; Maier, H.P. [Staatliche Materialpruefungsanstalt (MPA), Universitaet Stuttgart (Germany); Rixecker, G. [Max-Planck-Institut fuer Metallforschung, Pulvermetallurgisches Laboratorium, Stuttgart (Germany); Lohrmann, A. [Welz Industrieprodukte GmbH, Fellbach (Germany)

    2000-07-01

    The strength of ceramic materials shows commonly a great scatter. If the material exhibits distinct subcritical crack growth additionally a great scatter in lifetime occurs at least under tensile loading. Gas pressure sintered siliconnitride is expected to show a less distinct fatigue behaviour as sintered siliconnitride. Therefore, experimental investigations under dynamic, static and cyclostatic loading with 4-point bending specimens at 1250 C in air were performed. (orig.)

  8. A model system to give an insight into the behaviour of gold nanoparticles under ion irradiation

    International Nuclear Information System (INIS)

    Nano-composites fabricated with ion-based techniques have a number of attractive characteristics. However, the main and most crucial difficulty in obtaining commercial NPs-based devices is the inability to produce a suitable narrow size and spatial NP distributions. The objective of this thesis is twofold: i) to go further in the description of the behavior of the ion-driven NPs and ii) to overcome the limitations related to the ion-beam techniques providing a guideline methodology to rationalize the synthesis of NPs when ion-beams are used. Thus, a model system is fabricated. It consists of chemically synthesized metallic nanoparticles sandwiched between two silica layers. We show how the ion irradiation and the temperature can be used to tune the size distribution of the embedded NPs. Moreover, we show that when an initially large NPs size distribution is considered, the study of the growth kinetic of the NPs under irradiation can be problematic. Our model system is than used to investigate in detail the behavior of the NPs under irradiation. We show that the evolution of the precipitate phase under irradiation is successfully described by an Ostwald ripening mechanism in an open system limited by the diffusion. Moreover, the concentration threshold for nucleation as well as the surface tension and the gold diffusivity in silica under irradiation is estimated. Finally, direct and inverse Ostwald ripening processes under irradiation are systematically investigated and the existing theoretical models experimentally checked. (author)

  9. On the modelling of steel thermo-mechanical and metallurgical behaviour. Application to welding and heat treatment process

    International Nuclear Information System (INIS)

    The aim of this research is the prediction of residual stresses and strains in submarine nuclear reactor vessels after a welding operation. In the first part, the author briefly describes the various welding processes, their thermal, metallurgical and mechanical consequences, and gives an overview of the state-of-the-art of computerized modelling of welding. Then, he gives a detailed description of the various proposed models of the thermo-mechanical and metallurgical behaviours of steels. The influence of different phenomena such as plasticity, visco-plasticity, and transformation induced plasticity on the mechanical behaviour of the blend is analysed according to a sequential approach: the behaviour of each metallurgical phase is elastoplastic with linear kinetic cold working, then elasto-viscoplastic. A combined model is presented in which the ferrite phase behaviour is elastoplastic and the austenite behaviour is elasto-viscoplastic. The proposed models are then validated by two computer simulations performed with the COMSOL Multiphysics code. These simulations are simulating two tests which are representative of the phenomena met during a welding operation

  10. Delamination behaviour in differently copper laminated REBCO coated conductor tapes under transverse loading

    Energy Technology Data Exchange (ETDEWEB)

    Gorospe, Alking [Department of Mechanical Design Engineering, Andong National University, 1375 Kyungdong-Ro, Andong 760-749 (Korea, Republic of); Department of Engineering, Aurora State College of Technology, Baler Aurora 3200 (Philippines); Nisay, Arman [Department of Mechanical Design Engineering, Andong National University, 1375 Kyungdong-Ro, Andong 760-749 (Korea, Republic of); Shin, Hyung-Seop, E-mail: hsshin@andong.ac.kr [Department of Mechanical Design Engineering, Andong National University, 1375 Kyungdong-Ro, Andong 760-749 (Korea, Republic of)

    2014-09-15

    Highlights: • I{sub c} degradation behavior under transverse tension loading in different CC tape structure. • Weibull distribution analysis applied on delamination mechanism of CC tape. • Delamination mechanism on CC tapes depending on copper lamination type. • SEM and WDS mapping analysis of delamination sites under transverse loading. - Abstract: Laminated HTS coated conductor (CC) tapes having a unique multi-layer structure made them vulnerable when exposed to transverse loading. Electromechanical transport properties of these CC tapes can be affected by excessive transverse stresses. Due to the coefficient of thermal expansion (CTE) mismatch and incompatibility among constituent materials used in coil applications, delamination among layers occurs and causes critical current, I{sub c} degradation in the CC tapes. In this study, the delamination behaviors in copper (Cu) solder-laminated CC tapes by soldering and surround Cu-stabilized ones by electroplating under transverse tension loading were investigated. Similarly to the surround Cu-stabilized CC tapes in our previous reports, the Cu solder-laminated CC tapes also showed an abrupt and gradual I{sub c} degradation behavior. However, the Cu solder-laminated CC tapes showed different delamination morphologies as compared to the surround Cu-stabilized CC tapes; the superconducting side and the substrate side of the Cu solder laminated CC tapes were totally separated by delamination. On the other hand, the brass laminate did not show any significant effect on the delamination strength when it is added upon the surround Cu-stabilized CC tapes.

  11. Delamination behaviour in differently copper laminated REBCO coated conductor tapes under transverse loading

    International Nuclear Information System (INIS)

    Highlights: • Ic degradation behavior under transverse tension loading in different CC tape structure. • Weibull distribution analysis applied on delamination mechanism of CC tape. • Delamination mechanism on CC tapes depending on copper lamination type. • SEM and WDS mapping analysis of delamination sites under transverse loading. - Abstract: Laminated HTS coated conductor (CC) tapes having a unique multi-layer structure made them vulnerable when exposed to transverse loading. Electromechanical transport properties of these CC tapes can be affected by excessive transverse stresses. Due to the coefficient of thermal expansion (CTE) mismatch and incompatibility among constituent materials used in coil applications, delamination among layers occurs and causes critical current, Ic degradation in the CC tapes. In this study, the delamination behaviors in copper (Cu) solder-laminated CC tapes by soldering and surround Cu-stabilized ones by electroplating under transverse tension loading were investigated. Similarly to the surround Cu-stabilized CC tapes in our previous reports, the Cu solder-laminated CC tapes also showed an abrupt and gradual Ic degradation behavior. However, the Cu solder-laminated CC tapes showed different delamination morphologies as compared to the surround Cu-stabilized CC tapes; the superconducting side and the substrate side of the Cu solder laminated CC tapes were totally separated by delamination. On the other hand, the brass laminate did not show any significant effect on the delamination strength when it is added upon the surround Cu-stabilized CC tapes

  12. Crack growth behaviour of low-alloy steels for pressure boundary components under transient light water reactor operating conditions - CASTOC, Part I: BWR/NWC conditions

    International Nuclear Information System (INIS)

    One of the ageing phenomena of pressure boundary components of light water reactors (LWR) is environmentally-assisted cracking (EAC). The project CASTOC (5. Framework Programme of the EU) was launched September 2000 with six European partners and terminated August 2003. It was focused in particular on the EAC behaviour of low-alloy steels (LAS) and to some extent to weld metal, heat affected zone and the influence of an austenitic cladding. The main objective was directed to the clarification of EAC crack growth behaviour/mechanism of LAS in high-temperature water under steady-state power operation (constant load) and transient operating conditions (e.g., start-up/shut-down, transients in water chemistry and load). Autoclave tests were performed with Western and Russian type reactor pressure vessel steels under simulated boiling water reactor (BWR)/normal water chemistry (NWC) and pressurised water reactor (VVER) conditions. The investigations were performed with fracture mechanics specimens of different sizes and geometries. The applied loading comprised cyclic loads, static loads and load spectra where the static load was periodically interrupted by partial unloading. With regard to water chemistry, the oxygen content (VVER) and impurities of sulphate and chlorides (BWR) were varied beyond allowable limits for continuous operation. The current paper summarises the most important crack growth results obtained under simulated BWR/NWC conditions. The results are discussed in the context of the current crack growth rate curves in the corresponding nuclear codes. (authors)

  13. Liquid-based gating mechanism with tunable multiphase selectivity and antifouling behaviour

    Science.gov (United States)

    Hou, Xu; Hu, Yuhang; Grinthal, Alison; Khan, Mughees; Aizenberg, Joanna

    2015-03-01

    Living organisms make extensive use of micro- and nanometre-sized pores as gatekeepers for controlling the movement of fluids, vapours and solids between complex environments. The ability of such pores to coordinate multiphase transport, in a highly selective and subtly triggered fashion and without clogging, has inspired interest in synthetic gated pores for applications ranging from fluid processing to 3D printing and lab-on-chip systems. But although specific gating and transport behaviours have been realized by precisely tailoring pore surface chemistries and pore geometries, a single system capable of controlling complex, selective multiphase transport has remained a distant prospect, and fouling is nearly inevitable. Here we introduce a gating mechanism that uses a capillary-stabilized liquid as a reversible, reconfigurable gate that fills and seals pores in the closed state, and creates a non-fouling, liquid-lined pore in the open state. Theoretical modelling and experiments demonstrate that for each transport substance, the gating threshold--the pressure needed to open the pores--can be rationally tuned over a wide pressure range. This enables us to realize in one system differential response profiles for a variety of liquids and gases, even letting liquids flow through the pore while preventing gas from escaping. These capabilities allow us to dynamically modulate gas-liquid sorting in a microfluidic flow and to separate a three-phase air-water-oil mixture, with the liquid lining ensuring sustained antifouling behaviour. Because the liquid gating strategy enables efficient long-term operation and can be applied to a variety of pore structures and membrane materials, and to micro- as well as macroscale fluid systems, we expect it to prove useful in a wide range of applications.

  14. Liquid-based gating mechanism with tunable multiphase selectivity and antifouling behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Hou, X; Hu, YH; Grinthal, A; Khan, M; Aizenberg, J

    2015-03-04

    Living organisms make extensive use of micro- and nanometre-sized pores as gatekeepers for controlling the movement of fluids, vapours and solids between complex environments. The ability of such pores to coordinate multiphase transport, in a highly selective and subtly triggered fashion and without clogging, has inspired interest in synthetic gated pores for applications ranging from fluid processing to 3D printing and lab-on-chip systems(1-10). But although specific gating and transport behaviours have been realized by precisely tailoring pore surface chemistries and pore geometries(6,11-17), a single system capable of controlling complex, selective multiphase transport has remained a distant prospect, and fouling is nearly inevitable(11,12). Here we introduce a gating mechanism that uses a capillary-stabilized liquid as a reversible, reconfigurable gate that fills and seals pores in the closed state, and creates a non-fouling, liquid-lined pore in the open state. Theoretical modelling and experiments demonstrate that for each transport substance, the gating threshold-the pressure needed to open the pores-can be rationally tuned over a wide pressure range. This enables us to realize in one system differential response profiles for a variety of liquids and gases, even letting liquids flow through the pore while preventing gas from escaping. These capabilities allow us to dynamically modulate gas-liquid sorting in a microfluidic flow and to separate a three-phase air-water-oil mixture, with the liquid lining ensuring sustained antifouling behaviour. Because the liquid gating strategy enables efficient long-term operation and can be applied to a variety of pore structures and membrane materials, and to micro- as well as macroscale fluid systems, we expect it to prove useful in a wide range of applications.

  15. Mechanical behaviour of chicken quills and chicken feather fibres reinforced polymeric composites

    Directory of Open Access Journals (Sweden)

    M. Uzun

    2011-12-01

    Full Text Available Purpose: The objective of this study is to utilise and evaluate the mechanical properties of the chicken feather quill and fibre reinforced vinylester and polyester composites.Design/methodology/approach: Prior to production of the composites, the chicken feather fibres (CFF were cleaned, tested and analyzed in terms of physical properties; linear density and tensile behaviour. The unidirectional CFF reinforced composites were produced with vinylester and polyester resins with three fibre reinforcement loadings (2.5, 6, 10wt%. Following experiments were conducted to determine physical properties of the control (0% and CFF reinforced composites; tensile, flexural and Charpy impact testing.Findings: It was found that the impact properties of the CFF reinforced composites are significantly better than the control composites however both the tensile and the flexural properties of the CFF reinforced composites have poorer values compared to the control composites. For the 10% CFF reinforced vinylester composite, Charpy impact value was 4.42 kgj/mm2 which was 25% higher than the control vinylester composites (3.31 kgj/mm2 and also for the 10% CFF reinforced polyester (4.56 kgj/mm2 composite had three times better impact resistance than the control composite (1.85 kgj/mm2.Practical implications: The CFF reinforced composite have potential applications due to its improved impact behaviour.Originality/value: If the poultry waste can be utilised and used any engineering applications they will be preferred due to low-cost and superior characteristics and the most importantly they will not cause ecological and health problems.

  16. Using repetitive transcranial magnetic stimulation to study the underlying neural mechanisms of human motor learning and memory

    OpenAIRE

    Censor, Nitzan; Cohen, Leonardo G

    2010-01-01

    In the last two decades, there has been a rapid development in the research of the physiological brain mechanisms underlying human motor learning and memory. While conventional memory research performed on animal models uses intracellular recordings, microfusion of protein inhibitors to specific brain areas and direct induction of focal brain lesions, human research has so far utilized predominantly behavioural approaches and indirect measurements of neural activity. Repetitive transcranial m...

  17. Behaviour of melted tungsten plasma facing components under ITER-like transient heat loads

    International Nuclear Information System (INIS)

    Tungsten in the form of macrobrush structure is foreseen as one of the two candidate materials for the ITER divertor and the dome. Melting and thus melt motion and melt splashing are expected to be main mechanisms of metallic target damage that determine the lifetime of ITER plasma facing components. Experiments carried out at the plasma gun facility QSPA-T for ELM-like heat loads demonstrated a significant erosion of frontal and lateral brush edges, which was confirmed by further numerical simulations. In the experiments and numerical simulations a threshold of brush edge melting was determined. In this paper most important mechanisms of melt splashing and melt bridge formation under ITER transient heat loads are analyzed. Approximate criteria for droplet ejection are obtained and the range of transient events without significant droplet injection is calculated. The critical radius of brush edges rounding which prevents the bridge formation at the macrobrush edges is determined

  18. Behaviour of (Th, U)O2 microspheres under compression tests and pelletization

    International Nuclear Information System (INIS)

    The interrelation between the behaviour of isolated microspheres in compression tests and the microstructure of sintered pellets obtained with these microspheres, was investigated. Various batches of (Th, 5 w/o U)O2 microspheres were produced applying the so-called gel process. The production parameters were diversified both as to the composition and to the heat treatments. The resulting products underwent compression tests in an universal tension and compression machine as single microspheres and, as bulk material, were compacted and sintered. The results of the compression tests revealed the existence of two distinct classes of fragmentation behaviour. Each of these classes causes a distinct behaviour during the pelletization, too, resulting in fuel pellets with quite different microstructures. It was evidenced that there is a relationship between these differences in the microstructure and the behaviour of the single microspheres in the compression test. (Author)

  19. Observations of cod behaviour reveal insights into the function and properties of the swimbladder under pressure

    OpenAIRE

    van der Kooij, Jeroen; Righton, David; Michalsen, Kathrine; Thorsteinsson, Vilhjalmur; Svedäng, Henrik; Neat, Francis

    2006-01-01

    Atlantic cod (Gadus morhua L.) is a highly adaptive boreal species with a broad distribution through different ecosystems in the North Atlantic. Diet, environmental factors and population dynamics vary enormously throughout this range, and behaviours are therefore extremely plastic. However, the behaviour of cod will always be constrained by physiology, be it temperature tolerance, swimming speeds or buoyancy control. Cod, like other gadoids, are physoclists, i.e. they have ...

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

    Directory of Open Access Journals (Sweden)

    Lucie Navrátilová

    2012-01-01

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

  1. Antidepressant-Resistant Depression and Antidepressant-Associated Suicidal Behaviour: The Role of Underlying Bipolarity

    OpenAIRE

    Zoltan Rihmer; Xenia Gonda

    2011-01-01

    The complex relationship between the use of antidepressants and suicidal behaviour is one of the hottest topics of our contemporary psychiatry. Based on the literature, this paper summarizes the author's view on antidepressant-resistant depression and antidepressant-associated suicidal behaviour. Antidepressant-resistance, antidepressant-induced worsening of depression, antidepressant-associated (hypo)manic switches, mixed depressive episode, and antidepressant-associated suicidality among d...

  2. Mechanical Analysis of Concrete Specimen under Restrained Condition

    Institute of Scientific and Technical Information of China (English)

    MA Xinwei; NIU Changren; R D Hooton

    2005-01-01

    In order to quantify the development of the tensile stresses and obtain a reliable estimation of the cracking risk, the concrete was subjected to restrained conditions. The fully restrained condition was achieved by keeping the length constant of a concrete specimen. Comparing the free shrinkage with the restrained shrinkage,tensile creep could be discriminated from shrinkage. The testing method was introduced in details, and the mechanical behaviors under tensile load were analyzed. Results show that concrete exhibits a pronounced viscoelasticity. Under restrained condition, the self induced tensile stress increases with time. The lower the water to cement ratio, the larger the tensile stress at the same age. The tensile creep of hardening concrete is much larger than that of hardened concrete. The relationships among autogenous shrinkage under free condition, elastic strain and creep under restrained condition are described, and the mathematical model for the calculation of elastic strain and creep is proposed.

  3. Permeability and mechanical properties of cracked glass under pressure

    International Nuclear Information System (INIS)

    Crack initiation and growth in brittle solids under tension have been extensively studied by various experimental, theoretical and numerical approaches. If has been established that dynamic brittle fracture is related to fundamental physical parameters and processes, such as crack speed, crack branching, surface roughening, and dynamic instabilities. On the other hand, less studies have been done in the area of compressive fracture despite its vital importance in geology, material science and engineering applications (such as the improvement and the insurance of the nuclear wastes storage). The present work aims to investigate thermo-mechanical cracking effects on elastic wave velocities, mechanical strength and permeability und r pressure to evaluate damage evolution, brittle failure and transport properties on a synthetic glass (SON 68), and to highlight the very different behavior of the glass amorphous structure compared to any rock structure. The original glass, produced in ideal conditions of slow cooling that prevent from any crack formation, exhibits a linear and reversible mechanical behavior and isotropic elastic velocities, as expected. It also presents a high strength as it fails at about 700 MPa of deviatoric stress for a confining pressure of 15 MPa. We choose to apply to some original glass samples a reproducible method (thermal treatment with a thermal shock of T=100,200 and 300 C) which creates cracks with a homogeneous distribution. The impact of the thermal treatment is clearly visible through the elastic wave velocity measurements as we observe crack closure under hydrostatic conditions (at about 30 MPa). For T ≥ 200 C, the glass mechanical behavior becomes non linear and records an irreversible damage. The total damage observed with the acoustic emissions in these samples underlines the combination of the thermal and the mechanical cracks which drive to the sample failure. The results obtained with pore fluid pressure show a very small

  4. Effect of Shading on Physiological, Biochemical and Behaviour Changes in Crossbred Calves Under Hot Climatic Conditions

    International Nuclear Information System (INIS)

    The purpose of this study was to investigate the importance and the effect of shading and non-shading house on physiological changes, body weight (BW), average daily gain (ADG), total antioxidant and thyroid hormones in crossbred calves under hot conditions. Thirty six growing crossbred calves (Friesian x Baladi) aged 8-10 months were divided into two groups (each 18 calves); the first group was maintained in shaded house and the second in house without shade (climatic house). The period of study was 79 days during hot conditions. Performance variables (BW, ADG) were measured and the blood samples were collected to assess some biochemical parameters including antioxidants such as total antioxidant (TA), catalase (CAT), total protein, thyroid hormones (T3, T4) and immunoglobulin factor (IgG). Respiration rates and behaviour parameters (feeding, drinking, standing, lying and agonistic) were also measured during the study. The data indicated that the shaded calves had higher ADG (P<0.05) and final BW than non-shaded ones. Also, a significant improvement in total protein levels and globulins were recorded in shaded house calves as compared to non-shaded ones. The same result was obtained for T3 level whereas non-significant changes were observed for T4 level as well as the level of IgG at different times. The present data indicated that using shaded house will decrease the effect of heat stress on calves which will increase the animal performance through improving BW and ADG as well as some biochemical parameters in addition to T3 hormonal level.

  5. Corrosion behaviour of carbon steel in buffer material under anaerobic condition

    International Nuclear Information System (INIS)

    The deep underground environment for geological disposal of HLW will be relatively oxidizing condition at the initial stage of repository, but it will be returned to reducing as the consumption of oxygen by the corrosion of overpack and the reactions with the minerals in buffer material. It is necessary to understand the corrosion behaviour of carbon steel under such reducing condition for the lifetime prediction of carbon steel overpack. In this study, immersion tests of carbon steel in buffer material were performed in nitrogen atmosphere in which oxygen gas concentration was controlled less than 1 ppm. The corrosion rates of carbon steel were measured by weight loss of the specimens and the corrosion products were analysed by SEM, XRD and EPMA. For investigating the influence of welding of overpack, welded samples by electron-beam welding (EBW) were used for some of the tests. Synthetic sea water (SSW) and aqueous solutions containing bicarbonate ion and chloride ion were chosen as simulated groundwater. According to the experimental results, corrosion products layer contained ferrous carbonate such as FeCO3 and Fe2(OH)2CO3. The average corrosion rates within 1 year were relatively high (4-18 μm/y), but the growths of corrosion after 1 year were decreased rapidly. The increase in average corrosion depths from 1 to 3 (or 4) years was only less than several micro-meters, and the realistic corrosion rates after 1 year were estimated to be less than 1 μm/y in many cases. There was no influence of welding on the corrosion rate of carbon steel up to 3 years of immersion period. The effects of the density of buffer material and the mixing ratio of sand in buffer material on the corrosion rate of carbon steel were also investigated in this study. (author)

  6. Behaviour of radioactive substances in the soil under long-term conditions

    International Nuclear Information System (INIS)

    Within the frame of the project SR 2220 'Safety in the Post-Operation Phase of a Final Disposal of Radioactive Wastes' investigations of the behaviour of radioactive substances in the soil under long-term conditions were carried out on behalf of the Federal Minister for the Environment, Nature Conservation and Nuclear Safety (BMU). The investigations have led to the following results: Following contamination of the soil by irrigation with ground water that has been polluted through a repository, radionuclides migrate downwards because of the activities of burrowing and digging animals; in the case of very mobile radionuclides also the flushing out with rain and irrigation water (bulk flow) into the deeper soil layers plays an important role. Radionuclides absorbed by clay particles are literally freighted in the process of clay displacement into deeply lying soil layers. The radionuclides are brought back out of the lower soil layers and into the upper layers due to the activities of animals. Radionuclides which are readily taken up by plants migrate preferentially upwards through the plants. In the long run, equilibrium occurs between the concentration in the topsoil and in the subsoil. At the same time, a final decrease in soil radionuclide concentration through washout into the ground water and dilution with unpolluted soil takes place due to deposition of atmospheric dust and the weathering of local stone. Equilibrium conditions between inflow and outflow of soil radionuclides are reached over a time-span of up to ca. 30,000 years; the last interim periods between ice ages, which are suitable to overhead irrigation practise, lasted almost long enough to permit the establishment of equilibrium for most of the radionuclides. It is therefore proposed that the concentration in a soil layer of 1 m be calculated for equilibrium conditions. Transfer coefficients as a function of both the Kd-value and transfer factor are given for the migration of selected

  7. Care seeking behaviour and various delays in tuberculosis patients registered under RNTCP in Pune city

    Directory of Open Access Journals (Sweden)

    Jayashree Sachin Gothankar

    2016-03-01

    Full Text Available Introduction: Case finding in tuberculosis is known to be influenced by factors such as patient motivation, care seeking, the degree of diagnostic suspicion by health care provider which could result in a delayed diagnosis.Objective: To determine care seeking behaviour and delay in diagnosis and treatment of new sputum positive tuberculosis patients registered under RNTCP.Material and Methods: Descriptive cross sectional study .283 new sputum positive tuberculosis patients (≥15 yrs of age registered during a period of six months at two randomly selected tuberculosis unit of Pune city. Questionnaire by WHO was modified and used. Interviews were conducted in DOT centres. Statistical analysis: Frequency, mean and standard deviation, chi square test.Results: Mean age of patients was 35(±15 years. Eighteen percent of patients were unemployed and 77% resided in urban slums. The commonest co morbidity in 7.4% and 3.5 % patients was HIV/ AIDS followed by diabetics respectively. Majority of the patients, for the first and second time visited a general practitioner. Median patient, health care system and total delay were 18, 22 and 47 days with mean of 24±21, 32±30 and 56±33 days respectively. Health care system delay was less (p<0.05 in patients who first visited the public health care facility than patients who first visited the a private health care provider.Conclusions: General practitioners are preferred first choice of health care provider for tuberculosis patients. Mean health care system delay is more than patient delay.

  8. Emotional responses to music: the need to consider underlying mechanisms.

    Science.gov (United States)

    Juslin, Patrik N; Västfjäll, Daniel

    2008-10-01

    Research indicates that people value music primarily because of the emotions it evokes. Yet, the notion of musical emotions remains controversial, and researchers have so far been unable to offer a satisfactory account of such emotions. We argue that the study of musical emotions has suffered from a neglect of underlying mechanisms. Specifically, researchers have studied musical emotions without regard to how they were evoked, or have assumed that the emotions must be based on the "default" mechanism for emotion induction, a cognitive appraisal. Here, we present a novel theoretical framework featuring six additional mechanisms through which music listening may induce emotions: (1) brain stem reflexes, (2) evaluative conditioning, (3) emotional contagion, (4) visual imagery, (5) episodic memory, and (6) musical expectancy. We propose that these mechanisms differ regarding such characteristics as their information focus, ontogenetic development, key brain regions, cultural impact, induction speed, degree of volitional influence, modularity, and dependence on musical structure. By synthesizing theory and findings from different domains, we are able to provide the first set of hypotheses that can help researchers to distinguish among the mechanisms. We show that failure to control for the underlying mechanism may lead to inconsistent or non-interpretable findings. Thus, we argue that the new framework may guide future research and help to resolve previous disagreements in the field. We conclude that music evokes emotions through mechanisms that are not unique to music, and that the study of musical emotions could benefit the emotion field as a whole by providing novel paradigms for emotion induction. PMID:18826699

  9. Behaviour and damage of aged austenitic-ferritic steels: a micro-mechanical approach

    International Nuclear Information System (INIS)

    The austenitic-ferritic steels are used in the PWR primary cooling system. At the running temperature (320 C), they are submitted to a slow aging, which leads to the embrittlement of the ferritic phase. This embrittlement leads to a decrease of the mechanical properties, in particular of the crack resistance of the austenitic-ferritic steels. The damage and rupture of the austenitic-ferritic steels have been approached at the ENSMP by the works of P. Joly (1992) and of L. Devilliers-Guerville (1998). These works have allowed to reveal a damage heterogeneity which induces a strong dispersion on the ductilities and the toughnesses as well as on the scale effects. Modeling including the damage growth kinetics measured experimentally, have allowed to verify these effects. Nevertheless, they do not consider the two-phase character of the material and do not include a physical model of the cleavage cracks growth which appear in the embrittled ferrite. In this study, is proposed a description of the material allowing to treat these aspects while authorizing the structure calculation. In a first part, the material is studied. The use of the ESBD allows to specify the complex morphology of these steels and crystal orientation relations between the two phases. Moreover, it is shown that the two phases keep the same crystal orientation in the zones, called bicrystals, whose size varies between 500 μm and 1 mm. The study of the sliding lines, coupled to the ESBD, allows to specify too the deformation modes of the two phases. At last, tensile and tensile-compression tests at various deformation range are carried out to characterize the macroscopic mechanical behaviour of these materials. Then, a micro-mechanical modeling of the material behaviour is proposed. This one takes into account the three scales identified at the preceding chapter. The first scale, corresponding to the laths is described as a monocrystal whose behaviour includes both an isotropic and a kinematic strain

  10. Molten pool behaviour and its physical mechanism during selective laser melting of TiC/AlSi10Mg nanocomposites: simulation and experiments

    International Nuclear Information System (INIS)

    Simulation of temperature evolution and thermal behaviour of the molten pool during selective laser melting (SLM) of TiC/AlSi10Mg nanocomposites was performed, using a finite volume method. Some important physical phenomena, such as a transition from powder to solid, nonlinearities produced by temperature-dependent material properties and fluid flow, were taken into account in the calculation. The effects of Marangoni convection and SLM processing parameters, such as laser power and scan speed, on temperature evolution behaviour, molten pool dimensions and liquid lifetime were thoroughly investigated. The simulation results showed that Marangoni convection played a crucial role in intensifying the convective heat transfer and changing the molten pool geometry. The temperature of laser–powder interaction zone, the molten pool dimensions and liquid lifetime increased with increasing laser power or decreasing scan speed. The maximum temperature gradient within the molten pool increased significantly with increasing the applied laser power, but increased slightly as a higher scan speed was applied. The experimental study on the interlayer bonding and densification behaviour and the surface morphologies and balling effect of the SLM-processed TiC/AlSi10Mg nanocomposites parts was performed. The experimental results validated the thermal behaviour and underlying physical mechanism of the molten pool obtained in the simulations. (paper)

  11. Molten pool behaviour and its physical mechanism during selective laser melting of TiC/AlSi10Mg nanocomposites: simulation and experiments

    Science.gov (United States)

    Yuan, Pengpeng; Gu, Dongdong

    2015-01-01

    Simulation of temperature evolution and thermal behaviour of the molten pool during selective laser melting (SLM) of TiC/AlSi10Mg nanocomposites was performed, using a finite volume method. Some important physical phenomena, such as a transition from powder to solid, nonlinearities produced by temperature-dependent material properties and fluid flow, were taken into account in the calculation. The effects of Marangoni convection and SLM processing parameters, such as laser power and scan speed, on temperature evolution behaviour, molten pool dimensions and liquid lifetime were thoroughly investigated. The simulation results showed that Marangoni convection played a crucial role in intensifying the convective heat transfer and changing the molten pool geometry. The temperature of laser-powder interaction zone, the molten pool dimensions and liquid lifetime increased with increasing laser power or decreasing scan speed. The maximum temperature gradient within the molten pool increased significantly with increasing the applied laser power, but increased slightly as a higher scan speed was applied. The experimental study on the interlayer bonding and densification behaviour and the surface morphologies and balling effect of the SLM-processed TiC/AlSi10Mg nanocomposites parts was performed. The experimental results validated the thermal behaviour and underlying physical mechanism of the molten pool obtained in the simulations.

  12. The mismatch negativity: a review of underlying mechanisms.

    Science.gov (United States)

    Garrido, Marta I; Kilner, James M; Stephan, Klaas E; Friston, Karl J

    2009-03-01

    The mismatch negativity (MMN) is a brain response to violations of a rule, established by a sequence of sensory stimuli (typically in the auditory domain) [Näätänen R. Attention and brain function. Hillsdale, NJ: Lawrence Erlbaum; 1992]. The MMN reflects the brain's ability to perform automatic comparisons between consecutive stimuli and provides an electrophysiological index of sensory learning and perceptual accuracy. Although the MMN has been studied extensively, the neurophysiological mechanisms underlying the MMN are not well understood. Several hypotheses have been put forward to explain the generation of the MMN; amongst these accounts, the "adaptation hypothesis" and the "model adjustment hypothesis" have received the most attention. This paper presents a review of studies that focus on neuronal mechanisms underlying the MMN generation, discusses the two major explanatory hypotheses, and proposes predictive coding as a general framework that attempts to unify both. PMID:19181570

  13. Cellular mechanisms underlying eosinophilic and neutrophilic airway inflammation in asthma.

    Science.gov (United States)

    Pelaia, Girolamo; Vatrella, Alessandro; Busceti, Maria Teresa; Gallelli, Luca; Calabrese, Cecilia; Terracciano, Rosa; Maselli, Rosario

    2015-01-01

    Asthma is a phenotypically heterogeneous chronic disease of the airways, characterized by either predominant eosinophilic or neutrophilic, or even mixed eosinophilic/neutrophilic inflammatory patterns. Eosinophilic inflammation can be associated with the whole spectrum of asthma severity, ranging from mild-to-moderate to severe uncontrolled disease, whereas neutrophilic inflammation occurs mostly in more severe asthma. Eosinophilic asthma includes either allergic or nonallergic phenotypes underlying immune responses mediated by T helper (Th)2 cell-derived cytokines, whilst neutrophilic asthma is mostly dependent on Th17 cell-induced mechanisms. These immune-inflammatory profiles develop as a consequence of a functional impairment of T regulatory (Treg) lymphocytes, which promotes the activation of dendritic cells directing the differentiation of distinct Th cell subsets. The recent advances in the knowledge of the cellular and molecular mechanisms underlying asthmatic inflammation are contributing to the identification of novel therapeutic targets, potentially suitable for the implementation of future improvements in antiasthma pharmacologic treatments. PMID:25878402

  14. Cellular Mechanisms Underlying Eosinophilic and Neutrophilic Airway Inflammation in Asthma

    Directory of Open Access Journals (Sweden)

    Girolamo Pelaia

    2015-01-01

    Full Text Available Asthma is a phenotypically heterogeneous chronic disease of the airways, characterized by either predominant eosinophilic or neutrophilic, or even mixed eosinophilic/neutrophilic inflammatory patterns. Eosinophilic inflammation can be associated with the whole spectrum of asthma severity, ranging from mild-to-moderate to severe uncontrolled disease, whereas neutrophilic inflammation occurs mostly in more severe asthma. Eosinophilic asthma includes either allergic or nonallergic phenotypes underlying immune responses mediated by T helper (Th2 cell-derived cytokines, whilst neutrophilic asthma is mostly dependent on Th17 cell-induced mechanisms. These immune-inflammatory profiles develop as a consequence of a functional impairment of T regulatory (Treg lymphocytes, which promotes the activation of dendritic cells directing the differentiation of distinct Th cell subsets. The recent advances in the knowledge of the cellular and molecular mechanisms underlying asthmatic inflammation are contributing to the identification of novel therapeutic targets, potentially suitable for the implementation of future improvements in antiasthma pharmacologic treatments.

  15. Effect of hydrogen on the mechanical behaviour of carbon-alloyed Fe3Al-based iron aluminides

    Indian Academy of Sciences (India)

    M Sen; R Balasubramaniam

    2002-06-01

    The effect of hydrogen on the mechanical behaviour of two carbon-alloyed iron aluminides was studied. Weakening of some carbide–metal interfaces in the presence of hydrogen was indicated. The effect of cathodic hydrogen charging on the microstructure has also been addressed.

  16. Corrosion behaviour of carbon steel in contact with bentonite under anaerobic condition

    International Nuclear Information System (INIS)

    Full text of publication follows: The geological disposal system of high-level radioactive waste (HLW) consists of vitrified waste, overpack, buffer material and surrounding rock. In this system, overpack is required to prevent the contact of groundwater from vitrified waste for 1000 years. The main factor limiting this function is corrosion due to the contact with groundwater infiltrated to buffer material which is the mixture of bentonite and sand. Carbon steel is selected as one of the candidate materials for overpacks in Japan as a corrosion allowance metal. The deep underground environment for geological disposal of HLW is expected to be relatively oxidizing condition at the initial stage of repository, but it will be returned to reducing as the consumption of oxygen by the corrosion of overpack and the redox reactions with the minerals in buffer material. It is necessary to understand the corrosion behaviour of carbon steel under such anaerobic condition for the lifetime prediction of carbon steel overpack. In this study, immersion tests of carbon steel in buffer material were performed in nitrogen atmosphere in which oxygen gas concentration was controlled less than 1 ppm. The corrosion rates of carbon steel were measured by weight loss of the specimens and the corrosion products were analysed by SEM, XRD and EPMA. For investigating the influence of welding of overpack, welded samples by electron-beam welding (EBW) were used in some of the tests. Synthetic sea water (SSW) and aqueous solutions containing bicarbonate ion and chloride ion were chosen as simulated groundwater. The results indicated that the corrosion form of carbon steel under anaerobic condition was uniform corrosion and no localised corrosion such as pitting, crevice corrosion was found within our experimental conditions. Ferrous carbonate such as FeCO3 or Fe2(OH)2CO3 was identified as crystalline corrosion products by XRD. Although the corrosion rate was affected by test solution and buffer

  17. Corrosion behaviour of carbon steel in contact with bentonite under anaerobic condition

    Energy Technology Data Exchange (ETDEWEB)

    Naoki, Taniguchi; Susumu, Kawakami [Japan Nuclear Cycle Development Institute, Tokai-mura, Ibaraki (Japan); Manabu, Kawasaki; Mitsuru, Kubota [Inspection Development Corporation, Tokai-mura, Ibaraki (Japan)

    2004-07-01

    Full text of publication follows: The geological disposal system of high-level radioactive waste (HLW) consists of vitrified waste, overpack, buffer material and surrounding rock. In this system, overpack is required to prevent the contact of groundwater from vitrified waste for 1000 years. The main factor limiting this function is corrosion due to the contact with groundwater infiltrated to buffer material which is the mixture of bentonite and sand. Carbon steel is selected as one of the candidate materials for overpacks in Japan as a corrosion allowance metal. The deep underground environment for geological disposal of HLW is expected to be relatively oxidizing condition at the initial stage of repository, but it will be returned to reducing as the consumption of oxygen by the corrosion of overpack and the redox reactions with the minerals in buffer material. It is necessary to understand the corrosion behaviour of carbon steel under such anaerobic condition for the lifetime prediction of carbon steel overpack. In this study, immersion tests of carbon steel in buffer material were performed in nitrogen atmosphere in which oxygen gas concentration was controlled less than 1 ppm. The corrosion rates of carbon steel were measured by weight loss of the specimens and the corrosion products were analysed by SEM, XRD and EPMA. For investigating the influence of welding of overpack, welded samples by electron-beam welding (EBW) were used in some of the tests. Synthetic sea water (SSW) and aqueous solutions containing bicarbonate ion and chloride ion were chosen as simulated groundwater. The results indicated that the corrosion form of carbon steel under anaerobic condition was uniform corrosion and no localised corrosion such as pitting, crevice corrosion was found within our experimental conditions. Ferrous carbonate such as FeCO{sub 3} or Fe{sub 2}(OH){sub 2}CO{sub 3} was identified as crystalline corrosion products by XRD. Although the corrosion rate was affected by

  18. Crack arrest saturation model under combined electrical and mechanical loadings

    OpenAIRE

    R.R. Bhargava; A. Setia

    2009-01-01

    Purpose: The investigation aims at proposing a model for cracked piezoelectric strip which is capable to arrest the crack.Design/methodology/approach: Under the combined effect of electrical and mechanical loadings applied at the edges of the strip, the developed saturation zone is produced at each tip of the crack. To arrest further opening of the crack, the rims of the developed saturation zones are subjected to in-plane cohesive, normal uniform constant saturation point electrical displace...

  19. Underlying mechanisms and the evolving influence of diet

    DEFF Research Database (Denmark)

    Larsen, Lesli Hingstrup

    2012-01-01

    to increased risk of developing obesity. Recently, the intestinal microbiome, the collected genome of the bacteria, also has been associated with obesity and with specific dietary profiles. The underlying mechanisms determining the susceptibility to obesity do not only include the genome but also the...... epigenome and the microbiome that can be modified by diet, and by genotype, adding to the complexity of determining the contributors to obesity....

  20. Mechanisms underlying reduced responsiveness of neonatal neutrophils to distinct chemoattractants

    OpenAIRE

    Weinberger, Barry; Laskin, Debra L.; Mariano, Thomas M.; Sunil, Vasanthi R.; DeCoste, Christina J.; Heck, Diane E.; Carol R. Gardner; Laskin, Jeffrey D.

    2001-01-01

    Potential mechanisms underlying impaired chemotactic responsiveness of neonatal neutrophils were investigated. Two distinct chemoattractants were compared: bacterially derived N-formyl-methionyl-leucyl-phenylalanine (fMLP) and a unique chemotactic monoclonal antibody, designated DL1.2, which binds to a neutrophil antigen with an apparent molecular mass of 120 kDa. Chemotaxis of neutrophils toward fMLP, as well as DL1.2, was reduced in neonates when compared with adult cells. This did not appe...

  1. Mechanisms underlying the antidepressant response and treatment resistance

    OpenAIRE

    Levinstein, Marjorie R.; Samuels, Benjamin A.

    2014-01-01

    Depression is a complex and heterogeneous disorder affecting millions of Americans. There are several different medications and other treatments that are available and effective for many patients with depression. However, a substantial percentage of patients fail to achieve remission with these currently available interventions, and relapse rates are high. Therefore, it is necessary to determine both the mechanisms underlying the antidepressant response and the differences between responders ...

  2. Mechanisms Underlying the Antidepressant Response and Treatment Resistance

    OpenAIRE

    Marjorie Rose Levinstein; Benjamin Adam Samuels

    2014-01-01

    Depression is a complex and heterogeneous disorder affecting millions of Americans. There are several different medications and other treatments that are available and effective for many patients with depression. However, a substantial percentage of patients fail to achieve remission with these currently available interventions, and relapse rates are high. Therefore, it is necessary to determine both the mechanisms underlying the antidepressant response and the differences between responders ...

  3. Mechanisms Underlying the Link between Cannabis Use and Prospective Memory

    OpenAIRE

    Carrie Cuttler; McLaughlin, Ryan J.; Peter Graf

    2012-01-01

    While the effects of cannabis use on retrospective memory have been extensively examined, only a limited number of studies have focused on the links between cannabis use and prospective memory. We conducted two studies to examine the links between cannabis use and both time-based and event-based prospective memory as well as potential mechanisms underlying these links. For the first study, 805 students completed an online survey designed to assess cannabis consumption, problems with cannabis ...

  4. Corrosion behaviour and mechanical property changes of AISI 316 SS exposed in liquid sodium environment

    International Nuclear Information System (INIS)

    Under the synergistic influence of high temperature and sodium, different forms of corrosion and mass transfer may occur in the SS components which will have an adverse influence on the mechanical properties. Samples from different sections of the mass transfer loop constructed for this purpose were taken for the present analysis. The purity of the sodium during the course of the experiment was controlled by continuously cold-trapping a part of the sodium. The paper analyses the chemical and mechanical changes and discusses the effect of sodium-exposure from thermal-ageing

  5. Analysis of internal crack healing mechanism under rolling deformation.

    Science.gov (United States)

    Gao, Haitao; Ai, Zhengrong; Yu, Hailiang; Wu, Hongyan; Liu, Xianghua

    2014-01-01

    A new experimental method, called the 'hole filling method', is proposed to simulate the healing of internal cracks in rolled workpieces. Based on the experimental results, the evolution in the microstructure, in terms of diffusion, nucleation and recrystallisation were used to analyze the crack healing mechanism. We also validated the phenomenon of segmented healing. Internal crack healing involves plastic deformation, heat transfer and an increase in the free energy introduced by the cracks. It is proposed that internal cracks heal better under high plastic deformation followed by slow cooling after rolling. Crack healing is controlled by diffusion of atoms from the matrix to the crack surface, and also by the nucleation and growth of ferrite grain on the crack surface. The diffusion mechanism is used to explain the source of material needed for crack healing. The recrystallisation mechanism is used to explain grain nucleation and growth, accompanied by atomic migration to the crack surface. PMID:25003518

  6. Closure mechanisms of ventilated supercavities under steady and unsteady flows

    Science.gov (United States)

    Karn, Ashish; De, Rohan; Hong, Jiarong; Arndt, Roger E. A.

    2015-12-01

    The present work reports some interesting experimental results for ventilated supercavitation in steady and unsteady flows. First, a variety of closure modes obtained as a result of systematic variation in Froude number and air entrainment, are reported. The closure mechanisms were found to differ from the standard criterion reported in the literature. Further, the occurrence of a variety of stable and unstable closure mechanisms were discovered that have not been reported in the literature. Next, a hypothesis is presented to explain the cause behind these different closure mechanisms. The proposed hypothesis is then validated by synchronized high-speed imaging and pressure measurements inside and outside of the supercavity. These measurements show that the supercavity closure is a function of instantaneous cavitation number under unsteady flow conditions. (Research sponsored by Office of Naval Research, USA)

  7. An NMDA Receptor-Dependent Mechanism Underlies Inhibitory Synapse Development

    Directory of Open Access Journals (Sweden)

    Xinglong Gu

    2016-01-01

    Full Text Available In the mammalian brain, GABAergic synaptic transmission provides inhibitory balance to glutamatergic excitatory drive and controls neuronal output. The molecular mechanisms underlying the development of GABAergic synapses remain largely unclear. Here, we report that NMDA-type ionotropic glutamate receptors (NMDARs in individual immature neurons are the upstream signaling molecules essential for GABAergic synapse development, which requires signaling via Calmodulin binding motif in the C0 domain of the NMDAR GluN1 subunit. Interestingly, in neurons lacking NMDARs, whereas GABAergic synaptic transmission is strongly reduced, the tonic inhibition mediated by extrasynaptic GABAA receptors is increased, suggesting a compensatory mechanism for the lack of synaptic inhibition. These results demonstrate a crucial role for NMDARs in specifying the development of inhibitory synapses, and suggest an important mechanism for controlling the establishment of the balance between synaptic excitation and inhibition in the developing brain.

  8. Neural mechanisms underlying morphine withdrawal in addicted patients: a review

    Directory of Open Access Journals (Sweden)

    Nima Babhadiashar

    2015-06-01

    Full Text Available Morphine is one of the most potent alkaloid in opium, which has substantial medical uses and needs and it is the first active principle purified from herbal source. Morphine has commonly been used for relief of moderate to severe pain as it acts directly on the central nervous system; nonetheless, its chronic abuse increases tolerance and physical dependence, which is commonly known as opiate addiction. Morphine withdrawal syndrome is physiological and behavioral symptoms that stem from prolonged exposure to morphine. A majority of brain regions are hypofunctional over prolonged abstinence and acute morphine withdrawal. Furthermore, several neural mechanisms are likely to contribute to morphine withdrawal. The present review summarizes the literature pertaining to neural mechanisms underlying morphine withdrawal. Despite the fact that morphine withdrawal is a complex process, it is suggested that neural mechanisms play key roles in morphine withdrawal.

  9. Understanding molecular mechanism of higher plant plasticity under abiotic stress.

    Science.gov (United States)

    Shao, Hong-Bo; Guo, Qing-Jie; Chu, Li-Ye; Zhao, Xi-Ning; Su, Zhong-Liang; Hu, Ya-Chen; Cheng, Jiang-Feng

    2007-01-15

    Higher plants play the most important role in keeping a stable environment on the earth, which regulate global circumstances in many ways in terms of different levels (molecular, individual, community, and so on), but the nature of the mechanism is gene expression and control temporally and spatially at the molecular level. In persistently changing environment, there are many adverse stress conditions such as cold, drought, salinity and UV-B (280-320 mm), which influence plant growth and crop production greatly. Plants differ from animals in many aspects, but the important may be that plants are more easily influenced by environment than animals. Plants have a series of fine mechanisms for responding to environmental changes, which has been established during their long-period evolution and artificial domestication. These mechanisms are involved in many aspects of anatomy, physiology, biochemistry, genetics, development, evolution and molecular biology, in which the adaptive machinery related to molecular biology is the most important. The elucidation of it will extremely and purposefully promote the sustainable utilization of plant resources and make the best use of its current potential under different scales. This molecular mechanism at least include environmental signal recognition (input), signal transduction (many cascade biochemical reactions are involved in this process), signal output, signal responses and phenotype realization, which is a multi-dimensional network system and contain many levels of gene expression and regulation. We will focus on the molecular adaptive machinery of higher plant plasticity under abiotic stresses. PMID:16914294

  10. Influence of nickel addition on magnetic and electro-mechanical behaviour of permalloys

    Indian Academy of Sciences (India)

    Kiran Gupta; K K Raina; S K Sinha

    2006-08-01

    Magnetic and electro-mechanical investigations have been carried out in two Ni–Fe permalloys under hydrogen atmosphere by varying annealing temperature. These alloys have been characterized for various magnetic parameters like peak permeability, coercivity and core loss under changed annealing profile conditions. The magnetic properties of Ni-rich (Ni ∼ 82%) alloy at 100 Hz were found to be better than the low Ni (Ni ∼ 47%) alloy. The alloys were tested for watch movement and found that the battery life of the watch movement improved by 38% using Ni-rich permalloy.

  11. Giant panda׳s tooth enamel: Structure, mechanical behavior and toughening mechanisms under indentation.

    Science.gov (United States)

    Weng, Z Y; Liu, Z Q; Ritchie, R O; Jiao, D; Li, D S; Wu, H L; Deng, L H; Zhang, Z F

    2016-12-01

    The giant panda׳s teeth possess remarkable load-bearing capacity and damage resistance for masticating bamboos. In this study, the hierarchical structure and mechanical behavior of the giant panda׳s tooth enamel were investigated under indentation. The effects of loading orientation and location on mechanical properties of the enamel were clarified and the evolution of damage in the enamel under increasing load evaluated. The nature of the damage, both at and beneath the indentation surfaces, and the underlying toughening mechanisms were explored. Indentation cracks invariably were seen to propagate along the internal interfaces, specifically the sheaths between enamel rods, and multiple extrinsic toughening mechanisms, e.g., crack deflection/twisting and uncracked-ligament bridging, were active to shield the tips of cracks from the applied stress. The giant panda׳s tooth enamel is analogous to human enamel in its mechanical properties, yet it has superior hardness and Young׳s modulus but inferior toughness as compared to the bamboo that pandas primarily feed on, highlighting the critical roles of the integration of underlying tissues in the entire tooth and the highly hydrated state of bamboo foods. Our objective is that this study can aid the understanding of the structure-mechanical property relations in the tooth enamel of mammals and further provide some insight on the food habits of the giant pandas. PMID:27498423

  12. Peripheral Receptor Mechanisms Underlying Orofacial Muscle Pain and Hyperalgesia

    Science.gov (United States)

    Saloman, Jami L.

    Musculoskeletal pain conditions, particularly those associated with temporomandibular joint and muscle disorders (TMD) are severely debilitating and affect approximately 12% of the population. Identifying peripheral nociceptive mechanisms underlying mechanical hyperalgesia, a prominent feature of persistent muscle pain, could contribute to the development of new treatment strategies for the management of TMD and other muscle pain conditions. This study provides evidence of functional interactions between ligand-gated channels, P2X3 and TRPV1/TRPA1, in trigeminal sensory neurons, and proposes that these interactions underlie the development of mechanical hyperalgesia. In the masseter muscle, direct P2X3 activation, via the selective agonist αβmeATP, induced a dose- and time-dependent hyperalgesia. Importantly, the αβmeATP-induced hyperalgesia was prevented by pretreatment of the muscle with a TRPV1 antagonist, AMG9810, or the TRPA1 antagonist, AP18. P2X3 was co-expressed with both TRPV1 and TRPA1 in masseter muscle afferents confirming the possibility for intracellular interactions. Moreover, in a subpopulation of P2X3 /TRPV1 positive neurons, capsaicin-induced Ca2+ transients were significantly potentiated following P2X3 activation. Inhibition of Ca2+-dependent kinases, PKC and CaMKII, prevented P2X3-mechanical hyperalgesia whereas blockade of Ca2+-independent PKA did not. Finally, activation of P2X3 induced phosphorylation of serine, but not threonine, residues in TRPV1 in trigeminal sensory neurons. Significant phosphorylation was observed at 15 minutes, the time point at which behavioral hyperalgesia was prominent. Similar data were obtained regarding another nonselective cation channel, the NMDA receptor (NMDAR). Our data propose P2X3 and NMDARs interact with TRPV1 in a facilitatory manner, which could contribute to the peripheral sensitization underlying masseter hyperalgesia. This study offers novel mechanisms by which individual pro-nociceptive ligand

  13. Effect of Calcium Sulphate Nanoparticles on Fusion, Mechanical and Thermal Behaviour Polyvinyl Chloride (pvc)

    Science.gov (United States)

    Patil, C. B.; Shisode, P. S.; Kapadi, U. R.; Hundiwale, D. G.; Mahulikar, P. P.

    Calcium Sulphate [CaSO4] was synthesized by in-situ deposition technique and its nano size (60 to 100 nm) was confirmed by Transmission Electron Microscopy (TEM). Composites of the filler CaSO4 (micro and nano) and the matrix poly (vinyl chloride) (PVC) were prepared with different filler loading (0-5 wt. %) by melt mixing. The Brabender torque rheometer equipped with an internal mixer was used for preparation and evaluation of fusion behaviour of composites of different formulations. The effect of nano and micro-CaSO4 content on the structure and properties of composites was studied. The nanostructures and dispersion were studied by wide angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). The mechanical and thermal properties of PVC/ micro and nano-CaSO4 composites were characterized using Universal Testing Machine (UTM) and Thermo Gravimetric Analyzer (TGA). From the results of WAXD and SEM the flocculation of CaSO4 nanoparticles were observed on the surfaces of PVC matrix. The thermal analysis results showed that the first thermal degradation onset (T onset) of PVC/nano-CaSO4 composites for 1 wt. % of filler were higher as compared with corresponding microcomposites and pristine PVC. However, the tensile strength was decreasing with increasing filler content while, it shows increment in magnitude at 1 and 2 wt. % of nano-CaSO4 as compared with corresponding micro-CaSO4 as well as pristine PVC.

  14. Growth behaviour and mechanical properties of PLL/HA multilayer films studied by AFM

    Directory of Open Access Journals (Sweden)

    Cagri Üzüm

    2012-11-01

    Full Text Available Scanning- and colloidal-probe atomic force microscopy were used to study the mechanical properties of poly(L-lysine/hyaluronan (PLL/HAn films as a function of indentation velocity and the number of polymer deposition steps n. The film thickness was determined by two independent AFM-based methods: scratch-and-scan and newly developed full-indentation. The advantages and disadvantages of both methods are highlighted, and error minimization techniques in elasticity measurements are addressed. It was found that the film thickness increases linearly with the bilayer number n, ranging between 400 and 7500 nm for n = 12 and 96, respectively. The apparent Young’s modulus E ranges between 15 and 40 kPa and does not depend on the indenter size or the film bilayer number n. Stress relaxation measurements show that PLL/HA films have a viscoelastic behaviour, regardless of their thickness. If indentation is performed several times at the same lateral position on the film, a viscous/plastic deformation takes place.

  15. Specialists' meeting on LMFBR fuel rod behaviour under operational transients, Kalpakkam, India, 3-6 December 1985

    International Nuclear Information System (INIS)

    IWGFR Specialists' Meeting on ''LMFBR Fuel Rod Behaviour Under Operational Transients'' was held in Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam during 3-6 December 1985. The meeting was attended by the representatives of Belgium, France, FRG, India, Italy, US, USSR, IAEA and observers from India. The purpose of the meeting was to provide a forum for the exchange of information on the subject of LMFBR Fuel Rod Behaviour Under Operational Transients. The meeting presentations were divided into sessions devoted to the following topics: Overview of National Programmes (3 papers); In-pile and out-pile experimental facilities and results (5 papers); Modelling and Code work (5 papers). A separate abstract was prepared for each of these papers

  16. Mechanical and electronical properties of ZnS under pressure

    Directory of Open Access Journals (Sweden)

    M. Bilge

    2008-11-01

    Full Text Available Purpose: The wide-gap semiconductor materials are very important for application in the fields of optical device technology. ZnS is wide-gap semiconductor that is attractive material due to the polymorphic structural transformation and it is suitable semiconductor for applications in infrared optics, ultraviolet laser devices, electronic image display, high-density optical memory, solar cell etc. The goal is to evaluate mechanical and electrical properties of ZnS dunder pressure.Design/methodology/approach: We report ab-initio calculations of lattice constants, bulk modulus and elastic constants of the B1 (rocksalt, B3 (zincblende and B4 (wurtzite structures of ZnS. Ab-initio calculations are based on the density functional theory (DFT within generalized gradient approximation (GGA for the exchange-correlation potential.Findings: Phase transition pressures from B4 phase to B3 phase, from B3 phase to B1 phase and from B4 phase to B1 are predicted from intersection of the enthalpy-pressure data for the three phases. These results are consistent with the experimental and other theoretical calculations. Mechanical properties of ZnS under high pressure are also calculated. It is seen that the mechanical properties of ZnS under high pressure are quite different from those ambient condition. The band structure, density of states (DOS and energy gaps are also given for B3 structure of ZnS.Research limitations/implications: The results are compared with the previous theoretical and experimental data.Originality/value: Evaluation of mechanic and electronical properties of ZnS under pressure.

  17. Electrochemical behaviour of stainless steel under radiation and exposed to representative chemistry in pressurised water reactor conditions

    International Nuclear Information System (INIS)

    The dissertation focuses on the behaviour of stainless steel under irradiation and exposed to primary PWR conditions. The electrochemical potential of austenitic 316L stainless steel and the environmental parameters (hydrogen pressure, temperature, etc.,) have been measured continuously at high temperature (HT) and high pressure (HP) under irradiation, using a unique experimental HTHP working cell. Two sources of irradiation, proton and electron beams, have been employed in the study. A high similarity of electrochemical behaviour under both types of irradiations has been observed: (i) an oxidative potential response under irradiation (few tens of milli-volts); (ii) an increase in the hydrogen pressure reduces the oxidative potential response; (iii) a synergetic effect of thermal ageing and fluence leading to a decrease of the oxidative response under irradiation. The observations of the oxide film showed that without irradiation, metallic nickel in the inner and outer oxide films has been observed under a high hydrogen pressure. Under irradiation, um scale cavities (pits) have been observed in the strongly electron irradiated oxide film formed on 316L stainless steel. These defects are induced by the effect of irradiation of the passive film and water radiolysis. It is also shown that water radiolysis influences the PWR water chemistry by making it become a stronger oxidant at the oxide/solution interface. As a result, the release of metallic cations is increased and a-Fe2O3 hematite has been observed on the irradiated outer oxide film where cavities were formed. (author)

  18. Quasi-morphine abstinence behaviour GABA-ergic mechanisms and their localization

    NARCIS (Netherlands)

    J.W. van der Laan

    1981-01-01

    textabstractDi-n-propylacetate (DPA), generally known to be an anti-epileptic drug, induces a behavioural syndrome in rats resembling morphine abstinence behaviour, which is called, therefore, quasi-morphine abstinence beh~viour. An increase in GABA-ergic activity is probably responsible for this be

  19. Metallurgical and mechanical behaviours of PWR fuel cladding tube oxidised at high temperature; Comportements metallurqigue et mecanique des materiaux de gainage du combustible REP oxydes a haute temperature

    Energy Technology Data Exchange (ETDEWEB)

    Stern, A

    2007-12-15

    Zirconium alloys are used as cladding materials in Pressurized Water Reactors (PWR). As they are submitted to very extreme conditions, it is necessary to check their behaviour and especially to make sure they meet the safety criteria. They are therefore studied under typical in service-loadings but also under accidental loadings. In one of these accidental scenarios, called Loss of Coolant Accident (LOCA) the cladding temperature may increase above 800 C, in a steam environment, and decrease before a final quench of the cladding. During this temperature transient, the cladding is heavily oxidised, and the metallurgical changes lead to a decrease of the post quench mechanical properties. It is then necessary to correlate this drop in residual ductility to the metallurgical evolutions. This is the problem we want to address in this study: the oxidation of PWR cladding materials at high temperature in a steam environment and its consequences on post quench mechanical properties. As oxygen goes massively into the metallic part - a zirconia layer grows at the same time - during the high temperature oxidation, the claddings tubes microstructure shows three different phases that are the outer oxide layer (zirconia) and the inner metallic phases ({alpha}(O) and 'ex {beta}') - with various mechanical properties. In order to reproduce the behaviour of this multilayered material, the first part of this study consisted in creating samples with different - but homogeneous in thickness - oxygen contents, similar to those observed in the different phases of the real cladding. The study was especially focused on the {beta}-->{alpha} phase transformation upon cooling and on the resulting microstructures. A mechanism was proposed to describe this phase transformation. For instance, we conclude that for our oxygen enriched samples, the phase transformation kinetics upon cooling are ruled by the oxygen partitioning between the two allotropic phases. Then, these materials

  20. Contributions to the nonlinear modeling of the mechanical behaviour of concrete and of reinforced and prestressed concrete structures

    International Nuclear Information System (INIS)

    The knowledge of the mechanical behaviour of the material and its loading history (at any point of the structure) is necessary to evaluate the tightness of a containment structure and therefore its durability. An elastic plastic non local damage model is developed for modelling the mechanical behaviour of concrete. A regularization technique is introduced on the part responsible of the strain-softening behaviour in order to avoid the numerical problems due to the phenomenon of localisation of damage. The constitutive law and its numerical implementation are detailed. The consistent tangent matrix is derived, where the numerical differentiation technique is applied to integrate plastic constitutive laws and to obtain a quadratic convergence with the Newton-Raphson method at Gauss-point level and in the solution of the boundary value problem. Simulations have shown the capacity of the model to reproduce the classical and complex structural behaviour of concrete. The comparisons with the isotropic damage models illustrate the improvements achieved by introducing the plasticity to the damage formulation: the mode of failure is reproduced correctly (mode I and mixed mode) and the ultimate load is in good agreement with the experimental data. Finally, we present modifications of the classical non local damage model in order to take into account the boundary effects. Our justification is based on micro-mechanical arguments in which the interactions between microcracks are reduced nearby the free boundary. (author)

  1. Frictional behaviour of megathrust fault gouges under in-situ subduction zone conditions (Utrecht Studies in Earth Sciences 033)

    OpenAIRE

    den Hartog, S.A.M.

    2013-01-01

    Subduction zone megathrusts generate the largest earthquakes and tsunamis known. Understanding and modelling “seismogenesis” on such faults requires an understanding of the frictional processes that control nucleation and propagation of seismic slip. However, experimental data on the frictional behaviour of megathrust fault rocks is limited and almost no experiments have been performed on compositionally realistic materials under relevant in-situ conditions. Data that do exist are usually des...

  2. Influence of the Geometric Parameters on the Mechanical Behaviour of Fabric Reinforced Composite Laminates

    Science.gov (United States)

    Axinte, Andrei; Taranu, Nicolae; Bejan, Liliana

    2016-05-01

    A polymer fabric reinforced composite is a high performance material, which combines strength of the fibres with the flexibility and ductility of the matrix. For a better drapeability, the tows of fibres are interleaved, resulting the woven fabric, used as reinforcement. The complex geometric shape of the fabric is of paramount importance in establishing the deformability of the textile reinforced composite laminates. In this paper, an approach based on Classical Lamination Theory (CLT), combined with Finite Element Methods (FEM), using Failure Analysis and Internal Load Redistribution, is utilised, in order to compare the behaviour of the material under specific loads. The main goal is to analyse the deformability of certain types of textile reinforced composite laminates, using carbon fibre satin as reinforcement and epoxy resin as matrix. This is accomplished by studying the variation of the in-plane strains, given the fluctuation of several geometric parameters, namely the width of the reinforcing tow, the gap between two consecutive tows, the angle of laminae in a multi-layered configuration and the tows fibre volume fraction.

  3. Lattice Boltzmann simulation of behaviour of particles moving in blood vessels under the rolling massage

    International Nuclear Information System (INIS)

    The rolling massage is one of the most important manipulations in Chinese massage, which is expected to eliminate many diseases. Here, the effect of the rolling massage on a pair of particles moving in blood vessels under rolling massage manipulation is studied by the lattice Boltzmann simulation. The simulated results show that the motion of each particle is considerably modified by the rolling massage, and it depends on the relative rolling velocity, the rolling depth, and the distance between particle position and rolling position. Both particles' translational average velocities increase almost linearly as the rolling velocity increases, and obey the same law. The increment of the average relative angular velocity for the leading particle is smaller than that of the trailing one. The result is helpful for understanding the mechanism of the massage and to further develop the rolling techniques. (classical areas of phenomenology)

  4. Mechanical behaviour of alkali-activated blast furnace slag-activated metakaolin blended pastes. Statistical study

    Directory of Open Access Journals (Sweden)

    Higuera, I.

    2012-06-01

    Full Text Available The study and development of alternative, more ecoefficient binders than portland cement are attracting a good deal of scientific and technological interest. Binders obtained from the chemical interaction between calcium silico-aluminous materials and highly alkaline solutions are one of several types of such possible cements. The present paper discusses the mechanical behaviour and mineralogical composition of blended pastes made from NaOH-activated vitreous blast furnace slag and metakaolin. The aim of the study was to determine how parameters such as the slag/metakaolin ratio, activating solution concentration and curing temperature affect strength development in these binders. A statistical study was conducted to establish the impact of each variable and model strength behaviour in these alkaline cements. The conclusion drawn is that activator concentration and the slag/metakaolin ratio are both determinant parameters.

    El estudio y desarrollo de cementos alternativos y más eco-eficientes que el cemento Portland es un tema de gran impacto a nivel científico y tecnológico. Entre esos posibles cementos se encuentran los cementos alcalinos que son materiales conglomerantes obtenidos por la interacción química de materiales silico-aluminosos cálcicos y disoluciones fuertemente alcalinas. En el presente trabajo se estudia el comportamiento mecánico y la composición mineralógica de mezclas de escoria vítrea de horno alto y metacaolín activadas alcalinamente con disoluciones de NaOH. El objetivo de este estudio es conocer cómo afectan parámetros tales como la relación escoria/metacaolín, la concentración de la disolución activadora y la temperatura de curado, al desarrollo resistente de las mezclas. A través del estudio estadístico realizado se ha podido establecer la influencia de cada variable y modelizar el comportamiento resistente de estos cementos alcalinos. Se concluye que la concentración del activador y la relaci

  5. Investigating the mechanism(s) underlying switching between states in bipolar disorder

    OpenAIRE

    Young, Jared W.; Dulcis, Davide

    2015-01-01

    Bipolar Disorder (BD) is a unique disorder that transcends domains of function since the same patient can exhibit depression or mania, states with polar opposite mood symptoms. During depression, people feel helplessness, reduced energy, and risk aversion, while with mania behaviors include grandiosity, increased energy, less sleep, and risk preference. The neural mechanism(s) underlying each state are gaining clarity, with catecholaminergic disruption seen during mania, and cholinergic dysfu...

  6. Adaptive response: some underlying mechanisms and open questions

    Directory of Open Access Journals (Sweden)

    Evgeniya G. Dimova

    2008-01-01

    Full Text Available Organisms are affected by different DNA damaging agents naturally present in the environment or released as a result of human activity. Many defense mechanisms have evolved in organisms to minimize genotoxic damage. One of them is induced radioresistance or adaptive response. The adaptive response could be considered as a nonspecific phenomenon in which exposure to minimal stress could result in increased resistance to higher levels of the same or to other types of stress some hours later. A better understanding of the molecular mechanism underlying the adaptive response may lead to an improvement of cancer treatment, risk assessment and risk management strategies, radiation protection, e.g. of astronauts during long-term space flights. In this mini-review we discuss some open questions and the probable underlying mechanisms involved in adaptive response: the transcription of many genes and the activation of numerous signaling pathways that trigger cell defenses - DNA repair systems, induction of proteins synthesis, enhanced detoxification of free radicals and antioxidant production.

  7. Large Chip Production Mechanism under the Extreme Load Cutting Conditions

    Institute of Scientific and Technical Information of China (English)

    LIU Xianli; HE Genghuang; YAN Fugang; CHENG Yaonan; LIU Li

    2015-01-01

    There has existed a great deal of theory researches in term of chip production and chip breaking characteristics under conventional cutting and high speed cutting conditions, however, there isn’t sufficient research on chip formation mechanism as well as its influence on cutting state regarding large workpieces under extreme load cutting. This paper presents a model of large saw-tooth chip through applying finite element simulation method, which gives a profound analysis about the characteristics of the extreme load cutting as well as morphology and removal of the large chip. In the meantime, a calculation formula that gives a quantitative description of the saw-tooth level regarding the large chip is established on the basis of cutting experiments on high temperature and high strength steel 2.25Cr-1Mo-0.25V. The cutting experiments are carried out by using the scanning electron microscope and super depth of field electron microscope to measure and calculate the large chip produced under different cutting parameters, which can verify the validity of the established model. The calculating results show that the large saw-toothed chip is produced under the squeezing action between workpiece and cutting tools. In the meanwhile, the chip develops a hardened layer where contacts the cutting tool and the saw-tooth of the chip tend to form in transverse direction. This research creates the theoretical model for large chip and performs the cutting experiments under the extreme load cutting condition, as well as analyzes the production mechanism of the large chip in the macro and micro conditions. Therefore, the proposed research could provide theoretical guidance and technical support in improving productivity and cutting technology research.

  8. Analysis of fuel rod behaviour within a rod bundle of a pressurized water reactor under the conditions of a loss of coolant accident (LOCA) using probabilistic methodology

    International Nuclear Information System (INIS)

    The assessment of fuel rod behaviour under PWR LOCA conditions aims at the evaluation of the peak cladding temperatures and the (final) maximum circumferential cladding strains. Moreover, the estimation of the amount of possible coolant channel blockages within a rod bundle is of special interest, as large coplanar clad strains of adjacent rods may result in strong local reductions of coolant channel areas. Coolant channel blockages of large radial extent may impair the long-term coolability of the corresponding rods. A model has been developed to describe these accident consequences using probabilistic methodology. This model is applied to study the behaviour of fuel rods under accident conditions following the double-ended pipe rupture between collant pump and pressure vessel in the primary system of a 1300 MW(el)-PWR. Specifically a rod bundle is considered consisting of 236 fuel rods, that is subjected to severe thermal and mechanical loading. The results obtained indicate that plastic clad deformations with circumferential clad strains of more than 30% cannot be excluded for hot rods of the reference bundle. However, coplanar coolant channel blockages of significant extent seem to be probable within that bundle only under certain boundary conditions which are assumed to be pessimistic. (orig./RW)

  9. Modelling the dynamic behaviour of hard-to-cut alloys under conditions of vibro-impact cutting

    International Nuclear Information System (INIS)

    Industrial applications of titanium alloys have grown significantly over the years primarily due to their high strength, light weight as well as good fatigue and corrosion-resistance properties. Since these alloys are hard-to-machine, there is an obvious demand to develop simulation tools in order to analyse the material's behaviour during machining and, thus, optimise the entire cutting process. Deformation processes in the machining of Ti alloys are typically characterized by high strains, strain rates and temperatures; the material behaviour under such conditions was derived from split Hopkinson pressure-bar (SHPB) tests. In the current study, a computational three-dimensional finite element model of the SHPB test is developed to assess the material's behaviour at high-strain, strain-rate and temperature regimes. The material behaviour derived for high strain rates was used in three-dimensional finite-element modelling of conventional turning and ultrasonically assisted turning of Ti-15333 alloy. A parametric analysis of the studied alloy was carried out using the developed model. Comparisons of simulations with experimental results demonstrate their predictive capability

  10. Chasing behaviour and optomotor following in free-flying male blowflies: flight performance and interactions of the underlying control systems

    Directory of Open Access Journals (Sweden)

    Christine Trischler

    2010-05-01

    Full Text Available The chasing behaviour of male blowflies after small targets belongs to the most rapid and virtuosic visually guided behaviours found in nature. Since in a structured environment any turn towards a target inevitably leads to a displacement of the entire retinal image in the opposite direction, it might evoke optomotor following responses counteracting the turn. To analyse potential interactions between the control systems underlying chasing behaviour and optomotor following, respectively, we performed behavioural experiments on male blowflies and examined the characteristics of the two flight control systems in isolation and in combination. Three findings are particularly striking. (i The characteristic saccadic flight and gaze style – a distinctive feature of blowfly cruising flights – is largely abandoned when the entire visual surroundings move around the fly; in this case flies tend to follow the moving pattern in a relatively continuous and smooth way. (ii When male flies engage in following a small target, they also employ a smooth pursuit strategy. (iii Although blowflies are reluctant to fly at high background velocities, the performance and dynamical characteristics of the chasing system are not much affected when the background moves in either the same or in the opposite direction as the target. Hence, the optomotor following response is largely suppressed by the chasing system and does not much impair chasing performance.

  11. Mechanical properties of cork under contact stresses; Propiedades mecanicas del corcho bajo la accion de tensiones de contacto

    Energy Technology Data Exchange (ETDEWEB)

    Parralejo, A. D.; Guiberteau, F.; Fortes, M. A.; Rosa, M. E.

    2001-07-01

    In this work our interest is focussed on the mechanical behaviour of natural cork under contact stresses. Many of the applications of this curious material are related with its mechanical response under such a stress field, however this topic has not been still sufficiently considered in the scientific literature. For this purpose, we proposed the use of Hertzian indentation tests. By using this mythology we have investigated the cork structure influence on the corresponding mechanical properties. Our results reveal a clear mechanical anisotropy effect. Moreover, the elastic modulus corresponding to specific directions have been estimated. Several are the main advantages of this specific test mythology versus traditional uniaxial compression tests, specially simplicity and local character. (Author) 9 refs.

  12. Moral Development and Behaviour under the Spotlight of the Neurobiological Sciences

    Science.gov (United States)

    Narvaez, Darcia; Vaydich, Jenny L.

    2008-01-01

    With the aid of techniques such as functional magnetic resonance imaging, neuroscience is providing a new perspective on human behaviour. Many areas of psychology have recognised and embraced the new technologies, methodologies and relevant findings. But how do the tools of neuroscience affect the fields of moral development and moral education?…

  13. The behaviour of mosquitoes in relation to humans under holed bednets: the evidence from experimental huts

    Directory of Open Access Journals (Sweden)

    Seth R Irish

    2014-11-01

    Full Text Available The physical integrity of bednets is a concern of national malaria control programs, as it is a key factor in determining the rate of replacement of bednets. It is largely assumed that increased numbers of holes will result in a loss of protection of sleepers from potentially infective bites. Experimental hut studies are valuable in understanding mosquito behaviour indoors, particularly as it relates to blood feeding and mortality. This review summarises findings from experimental hut studies, focusing on two issues: (i the effect of different numbers or sizes of holes in bednets and (ii feeding behaviour and mortality with holed nets as compared with unholed nets. As might be expected, increasing numbers and area of holes resulted in increased blood feeding by mosquitoes on sleepers. However, the presence of holes did not generally have a large effect on the mortality of mosquitoes. Successfully entering a holed mosquito net does not necessarily mean that mosquitoes spend less time in contact with the net, which could explain the lack in differences in mortality. Further behavioural studies are necessary to understand mosquito behaviour around nets and the importance of holed nets on malaria transmission.

  14. Superconductivity of the atomic nucleus and mechanism of memory and behaviour of the man

    International Nuclear Information System (INIS)

    Full text: The mechanism of memory is a key problem in understanding of behaviour of alive entities, including Man. It is considered, that the long term memory is bound to an associative bark. To the important properties of memory is the ability to retin a sequence of happening events and arbitrary to extract it. The population of information in memory determines behaviour of the Man depending on interior needs and exterior actions. The clearing up motivation moments in the behaviour of the Man is bound to a problem of origin of life and mechanism of memory. Origin of life and solution of the mechanism of memory connect to singularities of the line-ups of DNA and ferment protein. However intrinsic to alive plants of property does not imply immediately from physico-chemistry of each of these molecules. The line-ups of DNA and ferment protein cannot be channels of a long-term memory, thought they will execute the important role as a gear link of the information in a brain. Making of methods 'the image of alive brain': a positron emissive tomography, functional magnetic resonance both multichannel progress in understanding of the mechanism of memory. hey have allowed to construct the common plan of handling and transmission of information in motivation centers in a brain. According to existing representations process scheme of information processing in a brain is shown. This plan yields common representations about ring driving of excitation with its recovery to places of tentative projections after after-treatment in other structures of a brain. In outcome the significance of a signal and its ration to this or that need of organism is determined. Then the impulses of excitation came in motivation centers of an intermediate brain. Besides information synthesis, recovery of excitation on diffuse projections ensures also integration of separate indications of stimulus in a fashion. On an example of the man it is possible to note, that the brain of the nan has an

  15. Dielectric strength behaviour and mechanical properties of transparent insulation materials suitable to optical monitoring of partial discharges

    International Nuclear Information System (INIS)

    A novel optical detection method for partial discharge in HV/EHV cable terminations has been proposed. Optical sensor fibres integrated into the HV equipment provide high sensitivity as well as immunity to electromagnetic interference and enable therefore on-line monitoring in electromagnetically noisy environment. The availability of optically transparent silicone rubbers that meet strict dielectric and mechanical criteria is a crucial prerequisite for the implementation of this method. The optically transparent silicone rubbers can be applied for the fabrication of a modern rubber stress cone as well as for the development of a new optical sensing element sensitive to PD activities. In this thesis, AC dielectric strength behaviour and mechanical properties of three types of commercially available silicone rubbers were investigated. One of the characterized silicone rubbers was a translucent type whereas the two others were optically transparent types, however with different chemical curing reactions. The measurements of tensile strength and elongation at break were carried out according to the ISO 37 standard. For investigation of the dielectric strength Eb behaviour of the virgin and modified silicone rubbers, a new methodology was developed. It is, at the same time, highly reliable and efficient, saves time and reduces material consumption in comparison to previously reported methodologies. The key component of this methodology is a specifically developed test facility. Furthermore, the methodology comprises determinations for easy preparation and handling of high-quality test specimens. This test method provides various advantages over other methods that have previously been used for measurement of the fundamental quantity Eb value of silicone rubbers. Both technical and economic demands are satisfied. The new facility also enables cost-effective routine tests in material research laboratories. The high quality of the obtained test results was verified by

  16. Crystal growth behaviour in Au-ZnO nanocomposite under different annealing environments and photoswitchability

    International Nuclear Information System (INIS)

    The growth of gold nanoparticles and ZnO nanorods in atom beam co-sputtered Au-ZnO nanocomposite (NC) system by annealing at two different ambient conditions is demonstrated in this work. Annealing in a furnace at 600 °C (air environment) confirmed the formation of ZnO nanorods surrounded with Au nanoparticles. In-situ annealing inside a transmission electron microscope (TEM) led to the formation of gold nanocrystals with different polygonal shapes. TEM micrographs were obtained in real time at intermediate temperatures of 300 °C, 420 °C, and 600 °C under vacuum. The growth mechanisms of Au nanocrystals and ZnO nanorods are discussed in the framework of Au-Zn eutectic and Zn-melting temperatures in vacuum and air, respectively. Current-voltage responses of Au-ZnO NC nanorods in dark as well as under light illumination have been investigated and photoswitching in Au-ZnO NC system is reported. The photoswitching has been discussed in terms of Au-ZnO band-diagram.

  17. Mechanisms underlying astringency: introduction to an oral tribology approach

    Science.gov (United States)

    Upadhyay, Rutuja; Brossard, Natalia; Chen, Jianshe

    2016-03-01

    Astringency is one of the predominant factors in the sensory experience of many foods and beverages ranging from wine to nuts. The scientific community is discussing mechanisms that explain this complex phenomenon, since there are no conclusive results which correlate well with sensory astringency. Therefore, the mechanisms and perceptual characteristics of astringency warrant further discussion and investigation. This paper gives a brief introduction of the fundamentals of oral tribology forming a basis of the astringency mechanism. It discusses the current state of the literature on mechanisms underlying astringency describing the existing astringency models. The review discusses the crucial role of saliva and its physiology which contributes significantly in astringency perception in the mouth. It also provides an overview of research concerned with the physiological and psychophysical factors that mediate the perception of this sensation, establishing the ground for future research. Thus, the overall aim of the review is to establish the critical roles of oral friction (thin-film lubrication) in the sensation of astringency and possibly of some other specific sensory features.

  18. Quasi-nano wear mechanism under repeated impact contact loading

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A new quasi-nano wear mechanism (QNWM) has been proposed in this paper based on the facts of wear curve turning under high energy impact contact loading.Its characteristic is that the wear rate of QNWM is only 1/10-1/3 that of delamination mechanism at the same energy density.The diameters of wear debris and pits on the worn surfaces fall into the quasi-nanometer scale (about 50-120 nm).The necessary and sufficient conditions,which bring about the QNWM,are:(i) the nano-structure (nano-crystalline + amorphous phase) in impact contact surface layer has formed by the intensive impact strain;(ii) the delamination wear cracking in sub-surface layer must be restrained;(iii) the microcracks of QNWM are produced in amorphous phase of surface nano-structure layer rather than in nano-crystalline.

  19. Nanomaterial-modulated autophagy: underlying mechanisms and functional consequences.

    Science.gov (United States)

    Zheng, Wei; Wei, Min; Li, Song; Le, Weidong

    2016-06-01

    Autophagy is an essential lysosome-dependent process that controls the quality of the cytoplasm and maintains cellular homeostasis, and dysfunction of this protein degradation system is correlated with various disorders. A growing body of evidence suggests that nanomaterials (NMs) have autophagy-modulating effects, thus predicting a valuable and promising application potential of NMs in the diagnosis and treatment of autophagy-related diseases. NMs exhibit unique physical, chemical and biofunctional properties, which may endow NMs with capabilities to modulate autophagy via various mechanisms. The present review highlights the impacts of various NMs on autophagy and their functional consequences. The possible underlying mechanisms for NM-modulated autophagy are also discussed. PMID:27193191

  20. Mechanisms underlying KCNQ1channel cell volume sensitivity

    DEFF Research Database (Denmark)

    Hammami, Sofia

    Cells are constantly exposed to changes in cell volume during cell metabolism, nutrient uptake, cell proliferation, cell migration and salt and water transport. In order to cope with these perturbations, potassium channels in line with chloride channels have been shown to be likely contributors to...... the process of cell volume adjustments. A great diversity of potassium channels being members of either the 6TM, 4 TM or 2 TM K+ channel gene family have been shown to be strictly regulated by small, fast changes in cell volume. However, the precise mechanism underlying the K+ channel sensitivity to...... cell volume alterations is not yet fully understood. The KCNQ1 channel belonging to the voltage gated KCNQ family is considered a precise sensor of volume changes. The goal of this thesis was to elucidate the mechanism that induces cell volume sensitivity. Until now, a number of investigators have...