WorldWideScience

Sample records for thermal stress conditions

  1. TPX vacuum vessel transient thermal and stress conditions

    International Nuclear Information System (INIS)

    Feldshteyn, Y.; Dinkevich, S.; Feng, T.; Majumder, D.

    1995-01-01

    The TPX vacuum vessel provides the vacuum boundary for the plasma and the mechanical support for the internal components. Another function of the vacuum vessel is to contain neutron shielding water in the double wall space during normal operation. This double wall space serves as a heat reservoir for the entire vacuum vessel during bakeout. The vacuum vessel and the internal components are subjected to thermal stresses induced by a nonuniform temperature distribution within the structure during bakeout. A successful Conceptual Design Review in March 1993 has established superheated steam as the heating source of the vacuum vessel. A transient bakeout mode of the vacuum vessel and in-vessel components has been analyzed to evaluate transient period duration, proper temperature level, actual thermal stresses and performance of the steam equipment. Thermally, the vacuum vessel structure may be considered as an adiabatic system because it is perfectly insulated by the strong surrounding vacuum and multiple layers of superinsulation. Important aspects of the analysis are described herein

  2. Effect of the combined stress on the life of components under thermal cycling conditions

    International Nuclear Information System (INIS)

    Zuchowski, R.; Zietkowski, L.

    1987-01-01

    The life of structural components subjected to temperature changes is affected, among other factors, by the nature of the stress field. If life prediction for axially stressed components can be accomplished with a number of well established techniques, the behaviour under a complex state of stress and varying temperature conditions still is the object of intensive research. The present study was aimed at assessing the influence of the stress field upon the life of specimens made of chromium-nickel H23N18 steel under thermal cycling conditions. The designation of steel is in accordance with Polish Standards. The experiments were made on thin-walled tubular specimens loaded with various combinations of a static axial force and a static torque. (orig./GL)

  3. Comparison of different test methods to assess thermal stresses of metal oxide surge arresters under pollution conditions

    International Nuclear Information System (INIS)

    Bargigia, A.; de Nigris, M.; Pigini, A.; Sironi, A.

    1992-01-01

    The report deals with the research conducted by ENEL, the Italian Electricity Board, to assess the performance of zinc oxide surge arresters under pollution condition, with special reference to the consequent thermal stress on internal active parts which can affect the energy handling capabality of the arrester and may lead, in particular conditions, even to thermal runaway

  4. Transient thermal stresses and stress intensity factors induced by thermal stratification in feedwater lines

    International Nuclear Information System (INIS)

    Sanchez Sarmiento, G.; Pardo, E.

    1985-01-01

    General analytical solutions for the thermal stresses and circumferential crack propagation in piping branches of nuclear power plants, that connect two circuits of the same fluid at different temperatures, are presented in this paper. Under certain conditions, two regions of the fluid possessing both temperatures with a separating layer of small thickness are formed ('flow stratification'). Dimensionless analytical expressions for the steady state temperature distribution in the pipe wall and the corresponding thermal stress are here derived, in terms of the basic geometrical and physical parameters. The position and thickness of the separating layer are considered as data of the model. Stress intensity ranges at any point of the tube wall are then determined. Finally, thermally induced stress intensity factors are calculated for hipothetically inside surface cracks. (orig.)

  5. Thermal stress-dependent dilation of concrete

    International Nuclear Information System (INIS)

    Pfeiffer, P.A.; Marchertas, A.H.

    1984-01-01

    Recent studies in nuclear fast reactor safety consider the possibility of concrete containment being subjected to extremely severe environmental conditions. Certain safety scenarios subject the concrete to very high temperatures hence raising the concern of containment integrity. Some of the main detrimental effects of high temperature on concrete are: reduction of strength, redistribution of moisture and etc. Consequently, analytical prediction of concrete response under the high temperature conditions becomes very complex. A rather simple but important experiment of concrete at high temperatures was conducted by Anderberg and Thelandersson. The test samples were small so that moisture was free to evaporate with no appreciable gradient as the temperature increased. Their results revealed that good correlation with analysis could be obtained if thermal expansion was made a function of both temperature and stress. The method of relating the thermal strain to temperature and stress has been integrated into the TEMP-STRESS code. Thus, high temperature concrete computational capability is now available for thermal-stress calculations

  6. Thermal stresses at nozzles of nuclear steel containments under LOCA-conditions

    International Nuclear Information System (INIS)

    Sanchez Sarmiento, G.; Bergmann, A.N.

    1986-01-01

    During a loss of coolant accident (LOCA) of a PWR-nuclear power plant, a considerable heating of the containment atmosphere is expected to occur. Transient thermal stresses will appear at the containment as a consequence of a non-uniform rise of its temperature. Applying computer codes based on the finite element method, dimensionless general thermal stresses at nozzles of spherical steel containment have been calculated, varying the principal geometrical parameters and the Biot number for the containment internal surface. Atmosphere temperature and Biot number are assumed constant after the accident. Several plots of the maximum principal stresses are provided, which constitute general results applicable to stress analysis of any particular containment of this kind. (orig.)

  7. A methodology for on-line calculation of temperature and thermal stress under non-linear boundary conditions

    International Nuclear Information System (INIS)

    Botto, D.; Zucca, S.; Gola, M.M.

    2003-01-01

    In the literature many works have been written dealing with the task of on-line calculation of temperature and thermal stress for machine components and structures, in order to evaluate fatigue damage accumulation and estimate residual life. One of the most widespread methodologies is the Green's function technique (GFT), by which machine parameters such as fluid temperatures, pressures and flow rates are converted into metal temperature transients and thermal stresses. However, since the GFT is based upon the linear superposition principle, it cannot be directly used in the case of varying heat transfer coefficients. In the present work, a different methodology is proposed, based upon CMS for temperature transient calculation and upon the GFT for the related thermal stress evaluation. This new approach allows variable heat transfer coefficients to be accounted for. The methodology is applied for two different case studies, taken from the literature: a thick pipe and a nozzle connected to a spherical head, both subjected to multiple convective boundary conditions

  8. The relationship between bioclimatic thermal stress and subjective thermal sensation in pedestrian spaces

    Science.gov (United States)

    Pearlmutter, David; Jiao, Dixin; Garb, Yaakov

    2014-12-01

    Outdoor thermal comfort has important implications for urban planning and energy consumption in the built environment. To better understand the relation of subjective thermal experience to bioclimatic thermal stress in such contexts, this study compares micrometeorological and perceptual data from urban spaces in the hot-arid Negev region of Israel. Pedestrians reported on their thermal sensation in these spaces, whereas radiation and convection-related data were used to compute the Index of Thermal Stress (ITS) and physiologically equivalent temperature (PET). The former is a straightforward characterization of energy exchanges between the human body and its surroundings, without any conversion to an "equivalent temperature." Although the relation of ITS to subjective thermal sensation has been analyzed in the past under controlled indoor conditions, this paper offers the first analysis of this relation in an outdoor setting. ITS alone can account for nearly 60 % of the variance in pedestrians' thermal sensation under outdoor conditions, somewhat more than PET. A series of regressions with individual contextual variables and ITS identified those factors which accounted for additional variance in thermal sensation, whereas multivariate analyses indicated the considerable predictive power ( R-square = 0.74) of models including multiple contextual variables in addition to ITS. Our findings indicate that pedestrians experiencing variable outdoor conditions have a greater tolerance for incremental changes in thermal stress than has been shown previously under controlled indoor conditions, with a tapering of responses at high values of ITS. However, the thresholds of ITS corresponding to thermal "neutrality" and thermal "acceptability" are quite consistent regardless of context.

  9. Transient stress control of aeroengine disks based on active thermal management

    International Nuclear Information System (INIS)

    Ding, Shuiting; Wang, Ziyao; Li, Guo; Liu, Chuankai; Yang, Liu

    2016-01-01

    Highlights: • The essence of cooling in turbine system is a process of thermal management. • Active thermal management is proposed to control transient stress of disks. • The correlation between thermal load and transient stress of disks is built. • Stress level can be declined by actively adjusting the thermal load distribution. • Artificial temperature gradient can be used to counteract stress from rotating. - Abstract: The physical essence of cooling in the turbine system is a process of thermal management. In order to overcome the limits of passive thermal management based on thermal protection, the concept of active thermal management based on thermal load redistribution has been proposed. On this basis, this paper focuses on a near real aeroengine disk during a transient process and studies the stress control mechanism of active thermal management in transient conditions by a semi-analytical method. Active thermal management is conducted by imposing extra heating energy on the disk hub, which is represented by the coefficient of extra heat flow η. The results show that the transient stress level can be effectively controlled by actively adjusting the thermal load distribution. The decline ratio of the peak equivalent stress of the disk hub can be 9.0% for active thermal management load condition (η = 0.2) compared with passive condition (η = 0), even at a rotation speed of 10,000 r/min. The reason may be that the temperature distribution of the disk turns into an artificial V-shape because of the extra heating energy on the hub, and the resulting thermal stresses induced by the negative temperature gradients counteract parts of the stress from rotating.

  10. Effect of the Evaporative Cooling on the Human Thermal Comfort and Heat Stress in a Greenhouse under Arid Conditions

    Directory of Open Access Journals (Sweden)

    A. M. Abdel-Ghany

    2013-01-01

    Full Text Available Thermal sensation and heat stress were evaluated in a plastic greenhouse, with and without evaporative cooling, under arid climatic conditions in Riyadh, Saudi Arabia. Suitable thermal comfort and heat stress scales were selected for the evaluation. Experiments were conducted in hot sunny days to measure the required parameters (i.e., the dry and wet bulb temperatures, globe temperature, natural wet bulb temperature, and solar radiation flux in the greenhouse. The results showed that in the uncooled greenhouse, workers are exposed to strong heat stress and would feel very hot most of the day time; they are safe from heat stress risk and would feel comfortable during night. An efficient evaporative cooling is necessary during the day to reduce heat stress and to improve the comfort conditions and is not necessary at night. In the cooled greenhouse, workers can do any activity: except at around noon they should follow a proposed working schedule, in which the different types of work were scheduled along the daytimes based on the heat stress value. To avoid heat stress and to provide comfort conditions in the greenhouses, the optimum ranges of relative humidity and air temperature are 48–55% and 24–28°C, respectively.

  11. Effect of thermal exposure on the residual stress relaxation in a hardened cylindrical sample under creep conditions

    Science.gov (United States)

    Radchenko, V. P.; Saushkin, M. N.; Tsvetkov, V. V.

    2016-05-01

    This paper describes the effect of thermal exposure (high-temperature exposure) ( T = 675°C) on the residual creep stress relaxation in a surface hardened solid cylindrical sample made of ZhS6UVI alloy. The analysis is carried out with the use of experimental data for residual stresses after micro-shot peening and exposures to temperatures equal to T = 675°C during 50, 150, and 300 h. The paper presents the technique for solving the boundary-value creep problem for the hardened cylindrical sample with the initial stress-strain state under the condition of thermal exposure. The uniaxial experimental creep curves obtained under constant stresses of 500, 530, 570, and 600 MPa are used to construct the models describing the primary and secondary stages of creep. The calculated and experimental data for the longitudinal (axial) tensor components of residual stresses are compared, and their satisfactory agreement is determined.

  12. Thermal stress analysis of a planar SOFC stack

    Science.gov (United States)

    Lin, Chih-Kuang; Chen, Tsung-Ting; Chyou, Yau-Pin; Chiang, Lieh-Kwang

    The aim of this study is, by using finite element analysis (FEA), to characterize the thermal stress distribution in a planar solid oxide fuel cell (SOFC) stack during various stages. The temperature profiles generated by an integrated thermo-electrochemical model were applied to calculate the thermal stress distributions in a multiple-cell SOFC stack by using a three-dimensional (3D) FEA model. The constructed 3D FEA model consists of the complete components used in a practical SOFC stack, including positive electrode-electrolyte-negative electrode (PEN) assembly, interconnect, nickel mesh, and gas-tight glass-ceramic seals. Incorporation of the glass-ceramic sealant, which was never considered in previous studies, into the 3D FEA model would produce more realistic results in thermal stress analysis and enhance the reliability of predicting potential failure locations in an SOFC stack. The effects of stack support condition, viscous behavior of the glass-ceramic sealant, temperature gradient, and thermal expansion mismatch between components were characterized. Modeling results indicated that a change in the support condition at the bottom frame of the SOFC stack would not cause significant changes in thermal stress distribution. Thermal stress distribution did not differ significantly in each unit cell of the multiple-cell stack due to a comparable in-plane temperature profile. By considering the viscous characteristics of the glass-ceramic sealant at temperatures above the glass-transition temperature, relaxation of thermal stresses in the PEN was predicted. The thermal expansion behavior of the metallic interconnect/frame had a greater influence on the thermal stress distribution in the PEN than did that of the glass-ceramic sealant due to the domination of interconnect/frame in the volume of a planar SOFC assembly.

  13. Coatings influencing thermal stress in photonic crystal fiber laser

    Science.gov (United States)

    Pang, Dongqing; Li, Yan; Li, Yao; Hu, Minglie

    2018-06-01

    We studied how coating materials influence the thermal stress in the fiber core for three holding methods by simulating the temperature distribution and the thermal stress distribution in the photonic-crystal fiber laser. The results show that coating materials strongly influence both the thermal stress in the fiber core and the stress differences caused by holding methods. On the basis of the results, a two-coating PCF was designed. This design reduces the stress differences caused by variant holding conditions to zero, then the stability of laser operations can be improved.

  14. Gene Expression Dynamics Accompanying the Sponge Thermal Stress Response.

    Science.gov (United States)

    Guzman, Christine; Conaco, Cecilia

    2016-01-01

    Marine sponges are important members of coral reef ecosystems. Thus, their responses to changes in ocean chemistry and environmental conditions, particularly to higher seawater temperatures, will have potential impacts on the future of these reefs. To better understand the sponge thermal stress response, we investigated gene expression dynamics in the shallow water sponge, Haliclona tubifera (order Haplosclerida, class Demospongiae), subjected to elevated temperature. Using high-throughput transcriptome sequencing, we show that these conditions result in the activation of various processes that interact to maintain cellular homeostasis. Short-term thermal stress resulted in the induction of heat shock proteins, antioxidants, and genes involved in signal transduction and innate immunity pathways. Prolonged exposure to thermal stress affected the expression of genes involved in cellular damage repair, apoptosis, signaling and transcription. Interestingly, exposure to sublethal temperatures may improve the ability of the sponge to mitigate cellular damage under more extreme stress conditions. These insights into the potential mechanisms of adaptation and resilience of sponges contribute to a better understanding of sponge conservation status and the prediction of ecosystem trajectories under future climate conditions.

  15. SLAC divertor channel entrance thermal stress analysis

    International Nuclear Information System (INIS)

    Johnson, G.L.; Stein, W.; Lu, S.C.; Riddle, R.A.

    1985-01-01

    X-ray beams emerging from the new SLAC electron-positron storage ring (PEP) impinge on the entrance to tangential divertor channels causing highly localized heating in the channel structure. Analyses were completed to determine the temperatures and thermally-induced stresses due to this heating. These parts are cooled with water flowing axially over them at 30 0 C. The current design and operating conditions should result in the entrance to the new divertor channel operating at a peak temperature of 123 0 C with a peak thermal stress at 91% of yield. Any micro-cracks that form due to thermally-induced stresses should not propagate to the coolant wall nor form a path for the coolant to leak into the storage ring vacuum. 34 figs., 4 tabs

  16. Influence of overelastic loading on the stress intensity factor under thermal fatigue conditions

    International Nuclear Information System (INIS)

    Stamm, H.; Munz, D.

    1983-10-01

    Thermal shock loading often creates high thermal stresses which may exceed yield strength of the material in a surface layer. In this report the application of the linear elastic ΔK-concept in the case of cyclic thermal loading within the shakedown region is discussed. To this K-factors for an edge crack in a linear elastic - perfectly plastic plate are calculated using the weight function method and are compared with results obtained with the Finite Element Method. It is shown, that rearrangement stresses during plastic flow in the first cycle must be taken into account developing conservative approximation procedures. (orig.) [de

  17. Thermal Super-Pixels for Bimodal Stress Recognition

    DEFF Research Database (Denmark)

    Irani, Ramin; Nasrollahi, Kamal; Dhall, Abhinav

    2016-01-01

    to be in touch with the body which is not always practical. Contact-free monitoring of the stress by a camera [1, 2] can be an alternative. These systems usually utilize only an RGB or a thermal camera to recognize stress. To the best of our knowledge, the only work on fusion of these two modalities for stress......Stress is a response to time pressure or negative environmental conditions. If its stimulus iterates or stays for a long time, it affects health conditions. Thus, stress recognition is an important issue. Traditional systems for this purpose are mostly contact-based, i.e., they require a sensor...

  18. Human-biometeorological conditions and thermal perception in a Mediterranean coastal park

    Science.gov (United States)

    Saaroni, Hadas; Pearlmutter, David; Hatuka, Tali

    2015-10-01

    This study looks at the interrelation of human-biometeorological conditions, physiological thermal stress and subjective thermal perception in the design and use of a new waterfront park in Tel-Aviv, Israel. Our initial assumption was that the park's design would embody a comprehensive response to the area's ever-increasing heat stress and water shortage. However, almost half of it is covered by grass lawns, irrigated with fresh water, while the remaining area is mainly covered with concrete paving, with minimal shading and sparse trees. We hypothesized that stressful thermal conditions would prevail in the park in the summer season and would be expressed in a high discomfort perception of its users. Thermo-physiological stress conditions in a typical summer month were compared with the subjective comfort perceptions of pedestrians surveyed in the park. It was found that even during mid-day hours, the level of thermal stress tends to be relatively mild, owing largely to the strong sea breeze and despite the high intensity of solar radiation. Moreover, it appears that the largely favorable perception of comfort among individuals may also result from socio-cultural aspects related to their satisfaction with the park's aesthetic attractiveness and in fact its very existence. Adaptive planning is proposed for such vulnerable regions, which are expected to experience further aggravation in thermal comfort due to global as well as localized warming trends.

  19. Nuclear power plant accident simulations of gasket materials under simultaneous radiation plus thermal plus mechanical stress conditions

    International Nuclear Information System (INIS)

    Gillen, K.T.; Malone, G.M.

    1997-07-01

    In order to probe the response of silicone door gasket materials to a postulated severe accident in an Italian nuclear power plant, compression stress relaxation (CSR) and compression set (CS) measurements were conducted under combined radiation (approximately 6 kGy/h) and temperature (up to 230 degrees C) conditions. By making some reasonable initial assumptions, simplified constant temperature and dose rates were derived that should do a reasonable job of simulating the complex environments for worst-case severe events that combine overall aging plus accidents. Further simplification coupled with thermal-only experiments allowed us to derive thermal-only conditions that can be used to achieve CSR and CS responses similar to those expected from the combined environments that are more difficult to simulate. Although the thermal-only simulations should lead to sealing forces similar to those expected during a severe accident, modulus and density results indicate that significant differences in underlying chemistry are expected for the thermal-only and the combined environment simulations. 15 refs., 31 figs., 15 tabs

  20. Investigation of effective factors of transient thermal stress of the MONJU-System components

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, Masaaki; Hirayama, Hiroshi; Kimura, Kimitaka; Jinbo, M. [Toshiba Corp., Kawasaki, Kanagawa (Japan)

    1999-03-01

    Transient thermal stress of each system Component in the fast breeder reactor is an uncertain factor on it's structural design. The temperature distribution in a system component changes over a wide range in time and in space. An unified evaluation technique of thermal, hydraulic, and structural analysis, in which includes thermal striping, temperature stratification, transient thermal stress and the integrity of the system components, is required for the optimum design of tho fast reactor plant. Thermal boundary conditions should be set up by both the transient thermal stress analysis and the structural integrity evaluation of each system component. The reasonable thermal boundary conditions for the design of the MONJU and a demonstration fast reactor, are investigated. The temperature distribution analysis models and the thermal boundary conditions on the Y-piece structural parts of each system component, such as reactor vessel, intermediate heat exchanger, primary main circulation pump, steam generator, superheater and upper structure of reactor core, are illustrated in the report. (M. Suetake)

  1. Thermal stress mitigation by Active Thermal Control

    DEFF Research Database (Denmark)

    Soldati, Alessandro; Dossena, Fabrizio; Pietrini, Giorgio

    2017-01-01

    This work proposes an Active Thermal Control (ATC) of power switches. Leveraging on the fact that thermal stress has wide impact on the system reliability, controlling thermal transients is supposed to lengthen the lifetime of electronic conversion systems. Indeed in some environments...... results of control schemes are presented, together with evaluation of the proposed loss models. Experimental proof of the ability of the proposed control to reduce thermal swing and related stress on the device is presented, too....

  2. Stress induced conditioning and thermal relaxation in the simulation of quasi-static compression experiments

    International Nuclear Information System (INIS)

    Scalerandi, M; Delsanto, P P; Johnson, P A

    2003-01-01

    Local interaction simulation approach simulations of the ultrasonic wave propagation in multi-grained materials have succeeded in reproducing most of the recently observed nonclassical nonlinear effects, such as stress-strain hysteresis and discrete memory in quasi-static experiments and a downwards shift of the resonance frequency and the generation of odd harmonics at specific amplitude rates in dynamics experiments. By including a simple mechanism of thermally activated random transitions, we can predict the occurrence of experimentally observed effects, such as the conditioning and relaxation of the specimen. Experiments are also suggested for a quantitative assessment of the validity of the model

  3. Stress induced conditioning and thermal relaxation in the simulation of quasi-static compression experiments

    CERN Document Server

    Scalerandi, M; Johnson, P A

    2003-01-01

    Local interaction simulation approach simulations of the ultrasonic wave propagation in multi-grained materials have succeeded in reproducing most of the recently observed nonclassical nonlinear effects, such as stress-strain hysteresis and discrete memory in quasi-static experiments and a downwards shift of the resonance frequency and the generation of odd harmonics at specific amplitude rates in dynamics experiments. By including a simple mechanism of thermally activated random transitions, we can predict the occurrence of experimentally observed effects, such as the conditioning and relaxation of the specimen. Experiments are also suggested for a quantitative assessment of the validity of the model.

  4. Coral thermal tolerance: tuning gene expression to resist thermal stress.

    Directory of Open Access Journals (Sweden)

    Anthony J Bellantuono

    Full Text Available The acclimatization capacity of corals is a critical consideration in the persistence of coral reefs under stresses imposed by global climate change. The stress history of corals plays a role in subsequent response to heat stress, but the transcriptomic changes associated with these plastic changes have not been previously explored. In order to identify host transcriptomic changes associated with acquired thermal tolerance in the scleractinian coral Acropora millepora, corals preconditioned to a sub-lethal temperature of 3°C below bleaching threshold temperature were compared to both non-preconditioned corals and untreated controls using a cDNA microarray platform. After eight days of hyperthermal challenge, conditions under which non-preconditioned corals bleached and preconditioned corals (thermal-tolerant maintained Symbiodinium density, a clear differentiation in the transcriptional profiles was revealed among the condition examined. Among these changes, nine differentially expressed genes separated preconditioned corals from non-preconditioned corals, with 42 genes differentially expressed between control and preconditioned treatments, and 70 genes between non-preconditioned corals and controls. Differentially expressed genes included components of an apoptotic signaling cascade, which suggest the inhibition of apoptosis in preconditioned corals. Additionally, lectins and genes involved in response to oxidative stress were also detected. One dominant pattern was the apparent tuning of gene expression observed between preconditioned and non-preconditioned treatments; that is, differences in expression magnitude were more apparent than differences in the identity of genes differentially expressed. Our work revealed a transcriptomic signature underlying the tolerance associated with coral thermal history, and suggests that understanding the molecular mechanisms behind physiological acclimatization would be critical for the modeling of reefs

  5. Transient thermal stresses in an orthotropic finite rectangular plate due to arbitrary surface heat-generations

    International Nuclear Information System (INIS)

    Sugano, Y.

    1980-01-01

    The transient thermal stresses in an orthotropic finite rectangular plate due to arbitrary surface heat-generations on two edges are studied by means of the Airy stress function. The purposes of this paper are to present a method of determing the transient thermal stresses in an orthographic rectangular plate with four edges of distinct thermal boundary condition of the third kind which exactly satisfy the traction-free conditions of shear stress over all boundaries including four corners of the plate, and to consider the effects of the anisotropies of material properties and the convective heat transfer on the upper and lower surfaces on the thermal stress distribution. (orig.)

  6. Universal treatment of plumes and stresses for pressurized thermal shock evaluations

    International Nuclear Information System (INIS)

    Theofanous, T.G.; Angelini, S.; Yan, H.

    1991-01-01

    Thermally-induced stresses in a reactor pressure vessel wall, as a result of high-pressure safety injection, are an essential component of integrated risk analyses of pressurized thermal shock transients. Limiting cooldowns arise when this injection occurs under stagnated loop conditions which, in turn, correspond to a rather narrow range (in size) of small-break loss-of-coolant accidents. Moreover, at these conditions, the flow is thermally stratified, and in addition to the global cooldown, one must be concerned about the additional cooling potential due to the downcomer plumes formed by the cold streams pouring out of the cold legs. In the Nuclear Regulatory Commission's Integrated Pressurized Thermal Shock (IPTS) study, this stratification was calculated with the codes REMIX/NEWMIX. A comprehensive comparison with all available experimental data has currently been compiled. The stress analysis using this input was carried out at Oak Ridge National Laboratory using a one-dimensional approximation with the intent to conservatively bound the magnitude of thermal stresses

  7. Effect of thermal stress on the performance of HgCdTe/Si diodes and FPAs

    International Nuclear Information System (INIS)

    Zhang, Shan; Hu, Xiao-Ning

    2012-01-01

    As a typical hetero-epitaxial material, the HgCdTe film which directly grows on the Si substrate possesses great residual stress for the large lattice and thermal expansion mismatch. Thermal stress caused by the thermal expansion mismatch dominates the stress mechanism after growth and seriously affects the device performance. In this paper, the performance of the HgCdTe/Si material, diodes and focal plane arrays under different thermal stress condition was studied. The experimental results indicate that the performance regularly changes with the thermal stress and all the results can be duplicated and recoverable. By analyzing the changes of the energy band under different stress conditions, it was found that the stress in the HgCdTe film impacts the film's characteristics. The HgCdTe film with tensile stress exhibits higher electron mobility, while with the compressive stress, the film exhibits higher hole mobility than that of the bulk HgCdTe crystal. Finally, the theoretical analysis can explain the experimental results well. (paper)

  8. Thermal stress and seismogenesis

    International Nuclear Information System (INIS)

    Zhou Huilan; Wei Dongping

    1989-05-01

    In this paper, the Fourier stress method was applied to deal with the problem of plane thermal stress, and a computing formula was given. As an example, we set up a variate temperature field to describe the uplifted upper mantle in Bozhong area of China, and the computing results shows that the maximum value of thermal plane shear stress is up to nearly 7x10 7 P α in two regions of this area. Since the Bohai earthquake (18 July, 1969, M s = 7.4) occurred at the edge of one of them and Tangshan earthquake (28 July, 1976, M s = 7.8) within another, their occurrences can be related reasonably to the thermal stress. (author). 15 refs, 7 figs

  9. Moderate Thermal Stress Causes Active and Immediate Expulsion of Photosynthetically Damaged Zooxanthellae (Symbiodinium from Corals.

    Directory of Open Access Journals (Sweden)

    Lisa Fujise

    Full Text Available The foundation of coral reef biology is the symbiosis between corals and zooxanthellae (dinoflagellate genus Symbiodinium. Recently, coral bleaching, which often results in mass mortality of corals and the collapse of coral reef ecosystems, has become an important issue around the world as coral reefs decrease in number year after year. To understand the mechanisms underlying coral bleaching, we maintained two species of scleractinian corals (Acroporidae in aquaria under non-thermal stress (27°C and moderate thermal stress conditions (30°C, and we compared the numbers and conditions of the expelled Symbiodinium from these corals. Under non-thermal stress conditions corals actively expel a degraded form of Symbiodinium, which are thought to be digested by their host coral. This response was also observed at 30°C. However, while the expulsion rates of Symbiodinium cells remained constant, the proportion of degraded cells significantly increased at 30°C. This result indicates that corals more actively digest and expel damaged Symbiodinium under thermal stress conditions, likely as a mechanism for coping with environmental change. However, the increase in digested Symbiodinium expulsion under thermal stress may not fully keep up with accumulation of the damaged cells. There are more photosynthetically damaged Symbiodinium upon prolonged exposure to thermal stress, and corals release them without digestion to prevent their accumulation. This response may be an adaptive strategy to moderate stress to ensure survival, but the accumulation of damaged Symbiodinium, which causes subsequent coral deterioration, may occur when the response cannot cope with the magnitude or duration of environmental stress, and this might be a possible mechanism underlying coral bleaching during prolonged moderate thermal stress.

  10. Moderate Thermal Stress Causes Active and Immediate Expulsion of Photosynthetically Damaged Zooxanthellae (Symbiodinium) from Corals.

    Science.gov (United States)

    Fujise, Lisa; Yamashita, Hiroshi; Suzuki, Go; Sasaki, Kengo; Liao, Lawrence M; Koike, Kazuhiko

    2014-01-01

    The foundation of coral reef biology is the symbiosis between corals and zooxanthellae (dinoflagellate genus Symbiodinium). Recently, coral bleaching, which often results in mass mortality of corals and the collapse of coral reef ecosystems, has become an important issue around the world as coral reefs decrease in number year after year. To understand the mechanisms underlying coral bleaching, we maintained two species of scleractinian corals (Acroporidae) in aquaria under non-thermal stress (27°C) and moderate thermal stress conditions (30°C), and we compared the numbers and conditions of the expelled Symbiodinium from these corals. Under non-thermal stress conditions corals actively expel a degraded form of Symbiodinium, which are thought to be digested by their host coral. This response was also observed at 30°C. However, while the expulsion rates of Symbiodinium cells remained constant, the proportion of degraded cells significantly increased at 30°C. This result indicates that corals more actively digest and expel damaged Symbiodinium under thermal stress conditions, likely as a mechanism for coping with environmental change. However, the increase in digested Symbiodinium expulsion under thermal stress may not fully keep up with accumulation of the damaged cells. There are more photosynthetically damaged Symbiodinium upon prolonged exposure to thermal stress, and corals release them without digestion to prevent their accumulation. This response may be an adaptive strategy to moderate stress to ensure survival, but the accumulation of damaged Symbiodinium, which causes subsequent coral deterioration, may occur when the response cannot cope with the magnitude or duration of environmental stress, and this might be a possible mechanism underlying coral bleaching during prolonged moderate thermal stress.

  11. Thermal stress analysis and operational characteristics of a bellows-seal globe valve

    International Nuclear Information System (INIS)

    Kim, Kwang Su; Kim, Youn Jae

    2005-01-01

    Because of design and manufacturing costs, it is important to predict an expected life of bellows with component stresses of bellows as its design factors and material characteristics. In this study, numerical analyses are carried out to elucidate the thermal and flow characteristics with 0.1 m (4 inch) bellows-seal globe valve for high temperature (max. 600 .deg. C) and for high pressure (max. 104 kgf/cm 2 , 10.2 MPa) conditions. Using commercial codes, FLUENT, which uses FVM and SIMPLE algorithm, and ANSYS, which uses FEM, the pressure and temperature fields are calculated and the results are graphically depicted. In addition, when bellows have an axial displacement, thermal stress affecting bellows life is studied. The pressure and temperature values obtained from the flow analyses are adopted as the boundary conditions for thermal stress analyses. As the result of this study, we get the reasonable coefficients for valve and thermal stress for bellows, compared with existing coefficients and calculated values

  12. Simplified calculation of thermal stresses - on the reduction of effort in the stress analysis of reactor components

    International Nuclear Information System (INIS)

    Karow, K.

    1984-01-01

    The fatigue behaviour of reactor components is predominantly determined from the in-service thermal stresses. The calculation of such stresses for a number of temperature transients in the adjacent fluid may be expensive, particularly with complicated structures. Under certain conditions this expense can be reduced considerably with the aid of a rule, which permits interpolation of thermal stresses from known reference values instead of calculation. This paper presents the derivation and method of application of this interpolation rule. The derivation procedure is based on well-known proportionalities between thermal stress range Δsigma in the structure and temperature change ΔT and rate of change T of the fluid in the extreme cases of an ideal thermal shock and quasi-steady-state conditions, respectively. For the real transients in between the relationship Δsigma proportional (ΔT)sup(x) Tsup(1-x)αsup(y) is proposed, where x is the shock-degree and lies between 0 and 1, and, additionally, y designates the influence of the heat transfer coefficient α. This formula yields the interpolation rule. The rule permits interpolation of stress ranges for additional thermal transients from at least 3 reference stresses via x and y. The procedure is applicable to any metallic structure, reduces fatigue analysis effort considerably and yields excellent results. The paper is split up into 2 parts. In the following the derivation of the rule is presented. The second part describes its application and will be published shortly. (orig.)

  13. Thermal Stress Limit Rafting Migration of Seahorses: Prediction Based on Physiological and Behavioral Responses to Thermal Stress

    Science.gov (United States)

    Qin, G.; Li, C.; Lin, Q.

    2017-12-01

    Marine fish species escape from harmful environment by migration. Seahorses, with upright posture and low mobility, could migrate from unfavorable environment by rafting with their prehensile tail. The present study was designed to examine the tolerance of lined seahorse Hippocampus erectus to thermal stress and evaluate the effects of temperature on seahorse migration. The results figured that seahorses' tolerance to thermal stress was time dependent. Acute thermal stress (30°C) increased breathing rate and HSP genes expression significantly, but didn't affect seahorse feeding behavior. Chronic thermal treatment lead to persistent high expression of HSP genes, higher breathing rate, and decreasing feeding, and final higher mortality, suggesting that seahorse cannot adapt to thermal stress by acclimation. No significant negative effects were found in seahorse reproduction in response to chronic thermal stress. Given that seahorses make much slower migration by rafting on sea surface compared to other fishes, we suggest that thermal stress might limit seahorse migration range. and the influence might be magnified by global warming in future.

  14. Thermal stresses investigation of a gas turbine blade

    Science.gov (United States)

    Gowreesh, S.; Pravin, V. K.; Rajagopal, K.; Veena, P. H.

    2012-06-01

    The analysis of structural and thermal stress values that are produced while the turbine is operating are the key factors of study while designing the next generation gas turbines. The present study examines structural, thermal, modal analysis of the first stage rotor blade of a two stage gas turbine. The design features of the turbine segment of the gas turbine have been taken from the preliminary design of a power turbine for maximization of an existing turbojet engine with optimized dump gap of the combustion chamber, since the allowable temperature on the turbine blade dependents on the hot gas temperatures from the combustion chamber. In the present paper simplified 3-D Finite Element models are developed with governing boundary conditions and solved using the commercial FEA software ANSYS. As the temperature has a significant effect on the overall stress on the rotor blades, a detail study on mechanical and thermal stresses are estimated and evaluated with the experimental values.

  15. Thermal stress relaxation in magnesium composites during thermal cycling

    Energy Technology Data Exchange (ETDEWEB)

    Trojanova, Z.; Lukac, P. (Karlova Univ., Prague (Czech Republic)); Kiehn, J.; Kainer, K.U.; Mordike, B.L. (Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany))

    1998-01-01

    It has been shown that the internal friction of Mg - Saffil metal matrix composites can be influenced by thermal stresses, if MMCc are submitted to thermal cycling between room temperature and an upper temperature of cycling. These stresses can be accommodated by generation and motion of dislocations giving the formation of the microplastic zones. The thermal stress relaxation depends on the upper temperature of cycling, the volume fraction of reinforcement and the matrix composition and can result in plastic deformation and strain hardening of the matrix without applied stress. The internal friction measurements can be used for non destructive investigation of processes which influence the mechanical properties. (orig.)

  16. Effects of location, thermal stress and residual stress on corner cracks in nozzles with cladding

    International Nuclear Information System (INIS)

    McLean, J.L.; Cohen, L.M.; Besuner, P.M.

    1979-01-01

    The stress intensity factors (K 1 ) for corner cracks in a boiling water reactor feedwater nozzle with stainless steel cladding are obtained for loading by internal pressure and a fluid quench in the nozzle. Conditions both with and without residual stress in the component are considered. The residual stress is simulated by means of a reference temperature change. The stress distribution for the uncracked structure is obtained from a three-dimensional finite element model. A three-dimensional influence function (IF) method, in conjunction with the boundary-integral equation method for structural analysis, is employed to compute K 1 values from the uncracked stress distribution. For each type of loading K 1 values are given for cracks at 15 nozzle locations and for 6 crack depths. Reasonable agreement is noted between calculated and previously published pressure-induced K 1 values. Comparisons are made to determine the effect on K 1 of crack location, thermal stress and residual stress, as compared with pressure stress. For the thermal transient it is shown that K 1 for small crack depths is maximised early in the transient, while K 1 for large cracks is maximised later under steady state conditions. Computation should, therefore, be made for several transient time points and the maximum K 1 for a given crack depth should be used for design analysis. It is concluded that the effects on K 1 of location, thermal stresses and residual stresses are significant and generally too complex to evaluate without advanced numerical procedures. The utilised combination of finite element analysis of the uncracked structure and three-dimensional influence function analysis of the cracked structure is demonstrated and endorsed. (author)

  17. Assessment of thermal fatigue damage caused by local fluid temperature fluctuation (part I: characteristics of constraint and stress caused by thermal striation and stratification)

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2014-01-01

    Highlights: • The source of the membrane constraint due to local temperature fluctuation was shown. • Thermal fatigue that occurred at a mixing tee and branched elbow was analyzed. • Cracking occurrence was reasonably explained by the constraint and stress conditions. - Abstract: This study was aimed at identifying the constraint conditions under local temperature fluctuation by thermal striping at a mixing tee and by thermal stratification at an elbow pipe branched from the main pipe. Numerical and analytical approaches were made to derive the thermal stress and its fluctuation. It was shown that an inhomogeneous temperature distribution in a straight pipe caused thermal stress due to a membrane constraint even if an external membrane constraint did not act on the pipe. Although the membrane constraint increased the mean stress at the mixing tee, it did not contribute to fluctuation of the thermal stress. On the other hand, the membrane constraint played an important role in the fatigue damage accumulation near the stratification layer of the branched elbow. Based on the constraint and stress conditions analyzed, the characteristics of the cracking observed in actual nuclear power plants were reasonably explained. Namely, at the mixing tee, where thermal crazing has been found, the lack of contribution of the membrane constraint to stress fluctuation caused a stress gradient in the thickness direction and arrested crack growth. On the other hand, at the branched elbow, where axial through-wall cracks have been found, the relatively large hoop stress fluctuation was brought about by movement of the stratified layer together with the membrane constraint even under a relatively low frequency of stress fluctuation

  18. Evaluation of properties and thermal stress field for thermal barrier coatings

    Institute of Scientific and Technical Information of China (English)

    王良; 齐红宇; 杨晓光; 李旭

    2008-01-01

    In order to get thermal stress field of the hot section with thermal barrier coating (TBCs), the thermal conductivity and elastic modulus of top-coat are the physical key properties. The porosity of top-coat was tested and evaluated under different high temperatures. The relationship between the microstructure (porosity of top-coat) and properties of TBCs were analyzed to predict the thermal properties of ceramic top-coat, such as thermal conductivity and elastic modulus. The temperature and stress field of the vane with TBCs were simulated using two sets of thermal conductivity data and elastic modulus, which are from literatures and this work, respectively. The results show that the temperature and stress distributions change with thermal conductivity and elastic modulus. The differences of maximum temperatures and stress are 6.5% and 8.0%, respectively.

  19. Resistance of functional Lactobacillus plantarum strains against food stress conditions.

    Science.gov (United States)

    Ferrando, Verónica; Quiberoni, Andrea; Reinhemer, Jorge; Suárez, Viviana

    2015-06-01

    The survival of three Lactobacillus plantarum strains (Lp 790, Lp 813 and Lp 998) with functional properties was studied taking into account their resistance to thermal, osmotic and oxidative stress factors. Stress treatments applied were: 52 °C-15 min (Phosphate Buffer pH 7, thermal shock), H2O2 0.1% (p/v) - 30 min (oxidative shock) and NaCl aqueous solution at 17, 25 and 30% (p/v) (room temperature - 1 h, osmotic shock). The osmotic stress was also evaluated on cell growth in MRS broth added of 2, 4, 6, 8 and 10% (p/v) of NaCl, during 20 h at 30 °C. The cell thermal adaptation was performed in MRS broth, selecting 45 °C for 30 min as final conditions for all strains. Two strains (Lp 813 and Lp 998) showed, in general, similar behaviour against the three stress factors, being clearly more resistant than Lp 790. An evident difference in growth kinetics in presence of NaCl was observed between Lp 998 and Lp 813, Lp998 showing a higher optical density (OD570nm) than Lp 813 at the end of the assay. Selected thermal adaptation improved by 2 log orders the thermal resistance of both strains, but cell growth in presence of NaCl was enhanced only in Lp 813. Oxidative resistance was not affected with this thermal pre-treatment. These results demonstrate the relevance of cell technological resistance when selecting presumptive "probiotic" cultures, since different stress factors might considerably affect viability or/and performance of the strains. The incidence of stress conditions on functional properties of the strains used in this work are currently under research in our group. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. Thermal Stress FE Analysis of Large-scale Gas Holder Under Sunshine Temperature Field

    Science.gov (United States)

    Li, Jingyu; Yang, Ranxia; Wang, Hehui

    2018-03-01

    The temperature field and thermal stress of Man type gas holder is simulated by using the theory of sunshine temperature field based on ASHRAE clear-sky model and the finite element method. The distribution of surface temperature and thermal stress of gas holder under the given sunshine condition is obtained. The results show that the thermal stress caused by sunshine can be identified as one of the important factors for the failure of local cracked oil leakage which happens on the sunny side before on the shady side. Therefore, it is of great importance to consider the sunshine thermal load in the stress analysis, design and operation of large-scale steel structures such as the gas holder.

  1. The effects of location, thermal stress, and residual stress on corner cracks in nozzles with cladding

    International Nuclear Information System (INIS)

    Besuner, P.M.; Cohen, L.M.; McLean, J.L.

    1977-01-01

    The stress intensity factors (Ksub(I)) for corner cracks in a boiling water reactor feedwater nozzle with stainless steel cladding are obtained for loading by internal pressure, and a fluid quench in the nozzle. Conditions with and without residual stress in the component are considered. The residual stress is simulated by means of a reference temperature change. The stress distribution for the uncracked structure is obtained from a three-dimensional finite element model. A three-dimensional influence function (IF) method, in conjunction with the boundary-integral equation method for structural analysis, is employed to compute Ksub(I) values from the uncracked structure's stress distribution. For each type of loading Ksub(I) values are given for cracks at 15 nozzle locations and for six crack depths. Reasonable agreement is noted between calculated and previously published pressure-induced Ksub(I) values. Comparisons are made to determine the effect on Ksub(I) of crack location, thermal stress, and residual stress as compared to pressure stress. For the thermal transient it is shown that Ksub(I) for small crack depths is maximized early in the transient while Ksub(I) for large cracks is maximized later, under steady state conditions. Ksub(I) computations should, therefore, be made for several transient time points and the maximum Ksub(I) for a given crack depth should be used for design analysis. It is concluded that the effects on Ksub(I) of location, thermal stresses, and residual stresses are significant and generally too complex to evalute without advanced numerical procedures. The utilized combination of finite element analysis of the uncracked structure and three-dimensional influence function analysis of the cracked structure is demonstrated

  2. Thermal Stress Awareness, Self-Study #18649

    Energy Technology Data Exchange (ETDEWEB)

    Chochoms, Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-11-15

    Thermal stresses can expose individuals to a variety of health hazards at work, home, and play. Every year thermal stresses cause severe injuries and death to a large range of people, from elderly people in cities during summer heat waves to young people engaged in winter mountaineering. Awareness is the key to preventing the health hazards associated with thermal stresses. This course is designed for personnel at Los Alamos National Laboratory (LANL). It addresses both heat and cold stresses and discusses their factors, signs and symptoms, treatments, and controls.

  3. Thermal and mechanical stresses in a functionally graded thick sphere

    International Nuclear Information System (INIS)

    Eslami, M.R.; Babaei, M.H.; Poultangari, R.

    2005-01-01

    In this paper, a general solution for the one-dimensional steady-state thermal and mechanical stresses in a hollow thick sphere made of functionally graded material is presented. The temperature distribution is assumed to be a function of radius, with general thermal and mechanical boundary conditions on the inside and outside surfaces of the sphere. The material properties, except Poisson's ratio, are assumed to vary along the radius r according to a power law function. The analytical solution of the heat conduction equation and the Navier equation lead to the temperature profile, radial displacement, radial stress, and hoop stress as a function of radial direction

  4. Thermal, physiological strain index and perceptual responses in Iranian Muslim women under Thermal Condition in order to Guide in Prevention of Heat Stress

    Directory of Open Access Journals (Sweden)

    Peymaneh Habibi

    2014-09-01

    Full Text Available Heat stress risk assessment, as a harmful agent at workplace, is essential for controlling heat strain. The purpose of this study was relation between physiological and perceptual heat strain responses in Iranian veiled women under laboratory thermal conditions. This experimental study was carried out on 36 healthy females (age 22.3 ± 2.0 yr, height 162.76±5. 57cm, weight 55.82 ± 9.27kg in sitting state under thermal conditions (27 - 38° C in the hot-dry climatic condition for 120 min. In order to calculate the physiological strain index (PSI, oral temperature and heart rate were measured every 5 min. Physiological factors, and Heat Strain Score Index (HSSI questionnaires are simultaneous measurements taken at any 5 min during the exposure and physiological factors, and Heat Strain Score Index (HSSI questionnaires are the initial measurements. The data were analyzed using correlation and line regression by test spss16. The results showed that the average heart rate and oral temperature at resting and sitting were between 83.06 ±9.41bpm, 87.91 ±7.87 bpm and 36.7° C, 37. 1° C respectively. Also, the results have revealed a direct and significant and direct correlation among HSSI with WBGT (R2 = 0.97, P< 0.001, PSI (R2 = 0.96, P< 0.001, oral temperature (R2 = 0.96, P< 0.001 and heart rate (R2 = 0.62, P< 0.01 indices. The results have shown that simultaneously with the increase in valid indices of heat stress evaluation such as WBGT and PSI indices, the amount of HSSI index has also increased with high power. Therefore, it can be conclude that when there is no access to a reliable heat stress method such as WBGT or PSI indices, HSSI index, an objective and subjective heat strain method, can be used as a simple, fast and inexpensive method for evaluating the heat strain in women.

  5. Transient thermal stresses in multiple connected region exhibiting temperature dependence of material properties

    International Nuclear Information System (INIS)

    Sugano, Yoshihiro; Maekawa, Toshiya.

    1983-01-01

    The examples of the analysis of thermal stress in multiple connection regions such as heat exchangers, nuclear reactor cores, ingot cases and polygonal region with elliptic holes are not few, but the temperature dependence of material constants was neglected in these researches because of the difficulty of analysis though the industrial problems related to thermal stress are apt to occur in the condition of relatively large temperature gradient. Also, the analysis of heat conduction problems taking the temperature dependence of material constants into account was limited to one-dimensional problems for which Kirchhoff's transmission can be used. The purpose of this study is to derive the equation of condition which assures the one-value property of rotation and displacement, taking the temperature dependence of material constants into account, and to complete the formulation of the plane thermal stress problems in multiple connection regions by stress function method. Also the method of numerical analysis using difference method is shown to examine the effectiveness of various formulated equations and the effect of the temperature dependence of material constants on temperature and thermal stress. The example of numerical calculation on a thin rectangular plate with a rectangular hole is shown. (Kako, I.)

  6. Modeling of Short-Circuit-Related Thermal Stress in Aged IGBT Modules

    DEFF Research Database (Denmark)

    Bahman, Amir Sajjad; Iannuzzo, Francesco; Uhrenfeldt, Christian

    2017-01-01

    In this paper, the thermal stress on bond wires of aged IGBT modules under short-circuit conditions has been studied with respect to different solder delamination levels. To ensure repeatable test conditions, ad-hoc DBC (direct bond copper) samples with delaminated solder layers have been purposely...... in the surface temperature distribution, which confirms the hypothesis that short-circuit events produce significantly uneven stresses on bond wires....

  7. Prediction of Short-Circuit-Related Thermal Stress in Aged IGBT Modules

    DEFF Research Database (Denmark)

    Bahman, Amir Sajjad; Iannuzzo, Francesco; Uhrenfeldt, Christian

    2016-01-01

    In this paper, the thermal stress on bond wires of aged IGBT modules under short-circuit conditions has been studied with respect to different solder delamination levels. To ensure repeatable test conditions, ad-hoc DBC (direct bond copper) samples with delaminated solder layers have been purposely...... in the surface temperature distribution which confirms the hypothesis that short-circuit events produce significantly uneven stresses on bond wires....

  8. Three dimensional, thermal stress analysis of a welded plate

    International Nuclear Information System (INIS)

    Koening, H.A.; Lai, C.K.-F.; Morral, J.E.

    1985-01-01

    A general finite element thermal stress analysis has been developed. The analysis can be uncoupled to solve either the heat transfer problem or the stress problem independently and it can accommodate non-linear material behavior, initial states of stress and strain, and moving boundary conditions. A unique feature of the model it that it properly accounts for the latent heat effect during phase changes. Applying the moving heat flux boundary condition to simulate arc welding, the model has been used to predict the transient thermal mechanical response of a welded plate. It is the absorption and liberation of latent heat in the fusion zone of a weld which complicates numerical methods of treating welding. For pure materials and eutectic alloys the latent heat effect is less of a problem because phase changes take place at a specific temperature. But for most alloys, phase changes take place over a range of temperatures bounded by the solidus, T S , and liquidus, T L , and the latent heat effect occurs continuously over the temperature range. (author)

  9. Temperature-induced physiological stress and reproductive characteristics of the migratory seahorse Hippocampus erectus during a thermal stress simulation.

    Science.gov (United States)

    Qin, Geng; Johnson, Cara; Zhang, Yuan; Zhang, Huixian; Yin, Jianping; Miller, Glen; Turingan, Ralph G; Guisbert, Eric; Lin, Qiang

    2018-05-15

    Inshore-offshore migration occurs frequently in seahorse species either because of prey opportunities or because it is driven by reproduction, and variations in water temperature may dramatically change migratory seahorse behavior and physiology. The present study investigated the behavioral and physiological responses of the lined seahorse Hippocampus erectus under thermal stress and evaluated the potential effects of different temperatures on its reproduction. The results showed that the thermal tolerance of the seahorses was time dependent. Acute thermal stress (30°C, 2-10 hours) increased the basal metabolic rate (breathing rate) and the expression of stress response genes ( Hsp genes) significantly and further stimulated seahorse appetite. Chronic thermal treatment (30°C, 4 weeks) led to a persistently higher basal metabolic rate, higher stress response gene expression, and higher mortality, indicating that the seahorses could not acclimate to chronic thermal stress and might experience massive mortality due to excessive basal metabolic rates and stress damage. Additionally, no significant negative effects on gonad development or reproductive endocrine regulation genes were observed in response to chronic thermal stress, suggesting that seahorse reproductive behavior could adapt to higher-temperature conditions during migration and within seahorse breeding grounds. In conclusion, this simulation experiment indicated that temperature variations during inshore-offshore migration have no effect on reproduction but promote basal metabolic rates and stress responses significantly. Therefore, we suggest that the high observed tolerance of seahorse reproduction was in line with the inshore-offshore reproductive migration pattern of lined seahorse. © 2018. Published by The Company of Biologists Ltd.

  10. Calculation of thermal stress condition in long metal cylinder under heating by continuous laser radiation

    International Nuclear Information System (INIS)

    Uglov, A.A.; Uglov, S.A.; Kulik, A.N.

    1997-01-01

    The method of determination of temperature field and unduced thermal stresses in long metallic cylinder under its heating by cw-laser normally distributed heat flux is offered. The graphically presented results of calculation show the stress maximum is placed behind of center of laser heat sport along its movement line on the cylinder surface

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

    Directory of Open Access Journals (Sweden)

    Ximin Chen

    2014-01-01

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

  12. Thermal stresses in rectangular plates: variational and finite element solutions

    International Nuclear Information System (INIS)

    Laura, P.A.A.; Gutierrez, R.H.; Sanchez Sarmiento, G.; Basombrio, F.G.

    1978-01-01

    This paper deals with the development of an approximate method for the analysis of thermal stresses in rectangular plates (plane stress problem) and an evaluation of the relative accuracy of the finite element method. The stress function is expanded in terms of polynomial coordinate functions which identically satisfy the boundary conditions, and a variational approach is used to determine the expansion coefficients. The results are in good agreement with a finite element approach. (Auth.)

  13. Degradation tests for C 32/40 concrete used for perimetral wall, reactor base and components of Cernavoda NPP containment, under thermal stress conditions and liner degradation

    International Nuclear Information System (INIS)

    Carlan, P.; Paraschiv, I.; Dinu, A.; Stanciulescu, M.; Olteanu, A. M.; Voica, I.; Stelian, R.; Buc, G.

    2016-01-01

    In order to evaluate the effect of thermal degradation on C 32/40 concrete used in nuclear constructions at Cernavoda NPP, continuous thermal stress tests were performed at 65, 80 and 100°C and cyclic thermal stress tests at 65°C in dry conditions. This paper presents the macroscopic properties of concrete, obtained after these treatments and also the microstructural changes that occur in the cement paste from the concrete composition, which has been tested in the same conditions as the concrete samples. Determinations performed for macroscopic properties of concrete included: compressive strength, loss of density, permeability and modulus of elasticity. Cement paste samples were analysed by XRD (for mineralogical composition) and SEM (for morphology). The obtained results shown an appropriate behaviour of the concrete used in this study; changes are insignificant and follow the normal evolution process of concrete, proving that concrete will preserve its safety functions, as part of the containment structure. (authors)

  14. Effect of fin attachment on thermal stress reduction of exhaust manifold of an off road diesel engine

    Institute of Scientific and Technical Information of China (English)

    Ali; Akbar; Partoaa; Morteza; Abdolzadeh; Masoud; Rezaeizadeh

    2017-01-01

    The effect of fin attachment on the thermal stress reduction of exhaust manifold of an off road diesel engine(Komatsu HD325-6) was investigated.For doing this,coupled thermo-fluid-solid analysis of exhaust manifold of the off road diesel engine was carried out.The thermal analysis,including thermal flow,thermal stress,and the thermal deformation of the manifold was investigated.The flow inside the manifold was simulated and then its properties including velocity,pressure,and temperature were obtained.The flow properties were transferred to the solid model and then the thermal stresses and the thermal deformations of the manifold under different operating conditions were calculated.Finally,based on the predicted thermal stresses and thermal deformations of the manifold body shell,two fin types as well as body shell thickness increase were applied in the critical induced thermal stress area of the manifold to reduce the thermal stress and thermal deformation.The results of the above modifications show that the combined modifications,i.e.the thickness increase and the fin attachment,decrease the thermal stresses by up to 28% and the contribution of the fin attachment in this reduction is much higher compared to the shell thickness increase.

  15. Modelling of Ethanol Production from Red Beet Juice by Saccharomyces cerevisiae under Thermal and Acid Stress Conditions

    Directory of Open Access Journals (Sweden)

    Donaji Jiménez-Islas

    2014-01-01

    Full Text Available In this work the effects of pH and temperature on ethanol production from red beet juice by the strains Saccharomyces cerevisiae ITD00196 and S. cerevisiae ATCC 9763 are studied. Logistic, Pirt, and Luedeking-Piret equations were used to describe quantitatively the microbial growth, substrate consumption, and ethanol production, respectively. The two S. cerevisiae strains used in this study were able to produce ethanol with high yield and volumetric productivity under acid and thermal stress conditions. The equations used to model the fermentation kinetics fit very well with the experimental data, thus establishing that ethanol production was growth associated under the evaluated conditions. The yeast S. cerevisiae ITD00196 had the best fermentative capacity and could be considered as an interesting option to develop bioprocesses for ethanol production.

  16. Coupled transient thermo-fluid/thermal-stress analysis approach in a VTBM setting

    International Nuclear Information System (INIS)

    Ying, A.; Narula, M.; Zhang, H.; Abdou, M.

    2008-01-01

    A virtual test blanket module (VTBM) has been envisioned as a utility to aid in streamlining and optimizing the US ITER TBM design effort by providing an integrated multi-code, multi-physics modeling environment. Within this effort, an integrated simulation approach is being developed for TBM design calculations and performance evaluation. Particularly, integrated thermo-fluid/thermal-stress analysis is important for enabling TBM design and performance calculations. In this paper, procedures involved in transient coupled thermo-fluid/thermal-stress analysis are investigated. The established procedure is applied to study the impact of pulsed operational phenomenon on the thermal-stress response of the TBM first wall. A two-way coupling between the thermal strain and temperature field is also studied, in the context of a change in thermal conductivity of the beryllium pebble bed in a solid breeder blanket TBM due to thermal strain. The temperature field determines the thermal strain in beryllium, which in turn changes the temperature field. Iterative thermo-fluid/thermal strain calculations have been applied to both steady-state and pulsed operation conditions. All calculations have been carried out in three dimensions with representative MCAD models, including all the TBM components in their entirety

  17. DIFFERENTIAL BLOOD COUNT OF TENCH Tinca tinca (Linnaeus, 1758 IN CONDITIONS OF THERMAL STRESS

    Directory of Open Access Journals (Sweden)

    Edhem Hasković

    2014-03-01

    Full Text Available Defining the physiological feature provides an understanding of functional adaptation of species to its ecological niche as well as the various forms of stress factors. This paper gives an overview of changes in certain forms of leukocytes (WBC differential under the influence of thermal stress (increased temperature. In our experiment, we used 46 specimens of tench (Tinca tinca fished in the Jablanica Lake reservoir. Specimens had previously been adapted in specially prepared tanks for 20 days.  The control group of animals (16 was exposed to constant water temperature of 10 0C, while in the treated groups (30, the water temperature was gradually risen to 28 0C and, as such, held for 30 minutes. All specimens were aged 2+ and 3+.It was found that the thermal regime change causes adaptive response of tench specimens by increasing the number of neutrophils and pseudoeosinophils but reduction in the number of lymphocytes. Observed were statistically significant differences in the number of segmented granulocytes, pseudoeosinophils and lymphocytes between the control and the experimental group. However, a significantly higher number of segmented granulocytes and pseudoeosinophils was at the experimental group, while in the control group a number of lymphocytes was significantly higher compared with the experimental group. Neither form of leukocytes showed any significant difference between males and females of the experimental group. It is interesting to note that among individuals from both the control and experimental group, eosinophils and monocytes were rarely noticed, while basophils were not found at all. Key words: thermal stress, tench, Tinca tinca, pseudoeosinophils

  18. Stress assessment in piping under synthetic thermal loads emulating turbulent fluid mixing

    Energy Technology Data Exchange (ETDEWEB)

    Costa Garrido, Oriol, E-mail: oriol.costa@ijs.si; El Shawish, Samir, E-mail: samir.elshawish@ijs.si; Cizelj, Leon, E-mail: leon.cizelj@ijs.si

    2015-03-15

    Highlights: • Generation of complex space-continuous and time-dependent temperature fields. • 1D and 3D thermo-mechanical analyses of pipes under complex surface thermal loads. • Surface temperatures and stress fluctuations are highly linearly correlated. • 1D and 3D results agree for a wide range of Fourier and Biot numbers. • Global thermo-mechanical loading promotes non-equibiaxial stress state. - Abstract: Thermal fatigue assessment of pipes due to turbulent fluid mixing in T-junctions is a rather difficult task because of the existing uncertainties and variability of induced thermal stresses. In these cases, thermal stresses arise on three-dimensional pipe structures due to complex thermal loads, known as thermal striping, acting at the fluid-wall interface. A recently developed approach for the generation of space-continuous and time-dependent temperature fields has been employed in this paper to reproduce fluid temperature fields of a case study from the literature. The paper aims to deliver a detailed study of the three-dimensional structural response of piping under the complex thermal loads arising in fluid mixing in T-junctions. Results of three-dimensional thermo-mechanical analyses show that fluctuations of surface temperatures and stresses are highly linearly correlated. Also, surface stress fluctuations, in axial and hoop directions, are almost equi-biaxial. These findings, representative on cross sections away from system boundaries, are moreover supported by the sensitivity analysis of Fourier and Biot numbers and by the comparison with standard one-dimensional analyses. Agreement between one- and three-dimensional results is found for a wide range of studied parameters. The study also comprises the effects of global thermo-mechanical loading on the surface stress state. Implemented mechanical boundary conditions develop more realistic overall system deformation and promote non-equibiaxial stresses.

  19. Experiments and analysis of thermal stresses around the nozzle of the reactor vessel

    International Nuclear Information System (INIS)

    Song, D.H.; Oh, J.H.; Song, H.K.; Park, D.S.; Shon, K.H.

    1981-01-01

    This report describes the results of analysis and experiments on the thermal stress around the reactor vessel nozzle performed to establish a capability of thermal stress analysis of pressure vessel subjected to thermal loadings. Firstly, heat conduction analysis during reactor design transients and analysis on the experimental model were performed using computer code FETEM-1 for the purpose of verification of FETEM-1 which was developed in 1979 and will be used to obtain the temperature distribution in a solid body under the steady-state and the transient conditions. The results of the analysis was compared to the results in the Stress Report of Kori-1 reactor vessel and those from experiments on the model, respectively

  20. Non-uniform temperature gradients and thermal stresses produced ...

    Indian Academy of Sciences (India)

    thermally-induced stress distributions in a hollow steel sphere heated by a moving uniform ... models to evaluate temperatures according to the frictional heat generation, ... of these thermal effects include thermal stress, strain and deformation.

  1. 40 CFR 90.329 - Catalyst thermal stress test.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Catalyst thermal stress test. 90.329... Equipment Provisions § 90.329 Catalyst thermal stress test. (a) Oven characteristics. The oven used for thermally stressing the test catalyst must be capable of maintaining a temperature of 500 ±5 °C and 1000 ±10...

  2. A method of solution of the elastic-plastic thermal stress problem

    International Nuclear Information System (INIS)

    Rafalski, P.

    1975-01-01

    The purpose of the work is an improvement of the numerical technique for calculating the thermal stress distribution in an elastic-plastic structural element. The work consists of two parts. In the first a new method of solution of the thermal stress problem for the elastic-plastic body is presented. In the second a particular numerical technique, based on the above method, for calculating the stress and strain fields is proposed. A new mathematical approach consists in treating the stress and strain fields as mathematical objects defined in the space-time domain. The methods commonly applied use the stress and strain fields defined in the space domain and establish the relations between them at a given instant t. They reduce the problem to the system of ordinary differential equations with respect to time, which are usually solved with a step-by-step technique. The new method reduces the problem to the system of nonlinear algebraic equations. In the work the Hilbert space of admissible tensor fields is constructed. This space is the orthogonal sum of two subspaces: of statically admissible and kinematically admissible fields. Two alternative orthogonality conditions, which correspond to the equilibrium and compatibility equations with the appropriate boundary conditions, are derived. The results of the work are to be used for construction of the computer program for calculation the stress and strain fields in the elastic-plastic body with a prescribed temperature field in the interior and appropriate displacement and force conditions on the boundary

  3. Physiological Responses to Thermal Stress and Exercise

    Science.gov (United States)

    Iyota, Hiroyuki; Ohya, Akira; Yamagata, Junko; Suzuki, Takashi; Miyagawa, Toshiaki; Kawabata, Takashi

    The simple and noninvasive measuring methods of bioinstrumentation in humans is required for optimization of air conditioning and management of thermal environments, taking into consideration the individual specificity of the human body as well as the stress conditions affecting each. Changes in human blood circulation were induced with environmental factors such as heat, cold, exercise, mental stress, and so on. In this study, the physiological responses of human body to heat stress and exercise were investigated in the initial phase of the developmental research. We measured the body core and skin temperatures, skin blood flow, and pulse wave as the indices of the adaptation of the cardiovascular system. A laser Doppler skin blood flowmetry using an optical-sensor with a small portable data logger was employed for the measurement. These results reveal the heat-stress and exercise-induced circulatory responses, which are under the control of the sympathetic nerve system. Furthermore, it was suggested that the activity of the sympathetic nervous system could be evaluated from the signals of the pulse wave included in the signals derived from skin blood flow by means of heart rate variability assessments and detecting peak heights of velocity-plethysmogram.

  4. Microstructural evolution and stress-corrosion-cracking behavior of thermally aged Ni-Cr-Fe alloy

    International Nuclear Information System (INIS)

    Yoo, Seung Chang; Choi, Kyoung Joon; Kim, Taeho; Kim, Si Hoon; Kim, Ju Young; Kim, Ji Hyun

    2016-01-01

    Highlights: • Effects of long-term thermal aging on the nickel-based Alloy 600 were investigated. • Heat treatments simulating thermal aging were conducted by considering Cr diffusion. • Nano-indentation test results show hardening of thermally aged materials. • Thermally aged materials are more susceptible to stress corrosion cracking. • The property changes are attributed to the formation and evolution of precipitates. - Abstract: To understand the effect of long-term thermal aging in power plant systems, representative thick-walled Alloy 600 was prepared and thermally aged at 400 °C to fabricate samples with thermal aging effects similar to service operating conditions. Changes of microstructures, mechanical properties, and stress corrosion cracking susceptibility were investigated mainly through electron backscatter diffraction, nanoindentation, and high-temperature slow strain rate test. The formation of abundant semi-continuous precipitates with chromium depletion at grain boundaries was observed after thermally aged for 10 equivalent years. Also, alloys thermally aged for 10 equivalent years of thermal aging exhibited the highest susceptibility to stress corrosion cracking.

  5. Numerical simulations on the temperature gradient and thermal stress of a thermoelectric power generator

    International Nuclear Information System (INIS)

    Wu, Yongjia; Ming, Tingzhen; Li, Xiaohua; Pan, Tao; Peng, Keyuan; Luo, Xiaobing

    2014-01-01

    Highlights: • An appropriate ceramic plate thickness is effective in alleviating the thermal stress. • A smaller distance between thermo-pins can help prolong lifecycle of the TE module. • Either a thicker or a thinner copper conducting strip effectively reduces thermal stress. • A suitable tin soldering thickness will alleviate thermal stress intensity and increase thermal efficiency. - Abstract: Thermoelectric generator is a device taking advantage of the temperature difference in thermoelectric material to generate electric power, where the higher the temperature difference of the hot-cold ends, the higher the efficiency will be. However, higher temperature or higher heat flux upon the hot end will cause strong thermal stress which will negatively influence the lifecycle of the thermoelectric module. This phenomenon is very common in industrial applications but seldom has research work been reported. In this paper, numerical analysis on the thermodynamics and thermal stress performance of the thermoelectric module has been performed, considering the variation on the thickness of materials; the influence of high heat flux on thermal efficiency, power output, and thermal stress has been examined. It is found that under high heat flux imposing upon the hot end, the thermal stress is so strong that it has a decisive effect on the life expectation of the device. To improve the module’s working condition, different geometrical configurations are tested and the optimum sizes are achieved. Besides, the side effects on the efficiency, power output, and open circuit voltage output of the thermoelectric module are taken into consideration

  6. Determine variation of poisson ratios and thermal creep stresses and strain rates in an isotropic disc

    Directory of Open Access Journals (Sweden)

    Gupta Nishi

    2016-01-01

    Full Text Available Seth's transition theory is applied to the problem of thermal creep transition stresses and strain rates in a thin rotating disc with shaft having variable density by finite deformation. Neither the yield criterion nor the associated flow rule is assumed here. The results obtained here are applicable to compressible materials. If the additional condition of incompressibility is imposed, then the expression for stresses corresponds to those arising from Tresca yield condition. Thermal effect decreased value of radial stress at the internal surface of the rotating isotropic disc made of compressible material as well as incompressible material and this value of radial stress further much increases with the increase in angular speed. With the introduction of thermal effects, the maximum value of strain rates further increases at the internal surface for compressible materials as compare to incompressible material.

  7. Thermal stresses in long prisms by relaxation methods

    International Nuclear Information System (INIS)

    Cummins, J.D.

    1959-07-01

    A general method is presented for calculating the elastic thermal stresses in long prisms which are producing heat and are not solvable by simple analytical methods. The problem of an inverted lattice i.e. an hexagonal coolant passage surrounded by hexagonal fuel elements is considered and the temperature and principal thermal stress distributions evaluated for the particular case of 20% coolant. The maximum thermal stress for this type of fuel element is about the same as the maximum thermal stress in a cylindrical fuel element surrounded by a sea of coolant assuming the existence of the same maximum temperature drop and material properties. (author)

  8. Thermal stresses in long prisms by relaxation methods

    Energy Technology Data Exchange (ETDEWEB)

    Cummins, J D [Atomic Energy Establishment, Winfrith, Dorchester, Dorset (United Kingdom)

    1959-07-15

    A general method is presented for calculating the elastic thermal stresses in long prisms which are producing heat and are not solvable by simple analytical methods. The problem of an inverted lattice i.e. an hexagonal coolant passage surrounded by hexagonal fuel elements is considered and the temperature and principal thermal stress distributions evaluated for the particular case of 20% coolant. The maximum thermal stress for this type of fuel element is about the same as the maximum thermal stress in a cylindrical fuel element surrounded by a sea of coolant assuming the existence of the same maximum temperature drop and material properties. (author)

  9. Thermal stress analysis of the SLAC moveable mask. Addendum 2

    International Nuclear Information System (INIS)

    Johnson, G.L.

    1985-01-01

    X-ray beams emerging from the new SLAC electron-positron storage ring (PEP) can impinge on the walls of tangential divertor channels. A moveable mask made of 6061-T6 aluminum is installed in the channel to limit wall heating. The mask is cooled with water flowing axially at 30 0 C. Beam strikes on the mask cause highly localized heating in the channel structure. Analyses were completed to determine the temperatures and thermally-induced stresses due to this heating. The current design and operating conditions should result in the entrance to the moveable mask operating at a peak temperature of 88 0 C with a peak thermal stress at 19% of the yield of 6061-T6 aluminum

  10. Evaluation of thermal perception in schoolyards under Mediterranean climate conditions

    Science.gov (United States)

    Antoniadis, D.; Katsoulas, N.; Papanastasiou, D.; Christidou, V.; Kittas, C.

    2016-03-01

    The aim of this paper was to study qualitatively and quantitatively the thermal perception and corresponding heat stress conditions that prevail in two schoolyards in a coastal city in central Greece. For this purpose, meteorological parameters (i.e., wind speed, temperature, relative humidity, solar radiation) were recorded at 70 and 55 measuring points in the schoolyards, from 14:00 to 15:30 local time, during May and June of 2011. The measuring points were distributed so as to get measurements at points (a) directly exposed to the sun, (b) under the shadow of trees and building structures, and (c) near building structures. Cluster analysis was applied to group observations and revealed places that are microclimatically homogeneous. Thermal perception and heat stress conditions were assessed by means of the physiologically equivalent temperature (PET, °C), and the results are presented in relevant charts. The impact of material's albedo, radiation's reflection by structures and obstacles, and different tree species on thermal perception and heat stress conditions was also assessed. The analysis showed that trees triggered a reduction of incident solar radiation that ranged between 79 and 94 % depending on tree's species, crown dimension, tree height, and leaf area. PET values were mainly affected by solar radiation and wind speed. Trees caused a reduction of up to 37 % in PET values, while a 1-m s-1 increase in wind speed triggered a reduction of 3.7-5.0 °C in PET value. The effective shading area in the two schoolyards was small, being 27.5 and 11 %. The results of this study could be exploited by urban planning managers when designing or improving the outdoor environment of a school complex.

  11. 40 CFR 91.427 - Catalyst thermal stress resistance evaluation.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Catalyst thermal stress resistance... Procedures § 91.427 Catalyst thermal stress resistance evaluation. (a)(1) The purpose of the evaluation procedure specified in this section is to determine the effect of thermal stress on catalyst conversion...

  12. 40 CFR 90.427 - Catalyst thermal stress resistance evaluation.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Catalyst thermal stress resistance... Gaseous Exhaust Test Procedures § 90.427 Catalyst thermal stress resistance evaluation. (a) The purpose of... catalyst conversion efficiency for Phase 1 engines. The thermal stress is imposed on the test catalyst by...

  13. Acoustic Emission Analysis of Damage Progression in Thermal Barrier Coatings Under Thermal Cyclic Conditions

    Science.gov (United States)

    Appleby, Matthew; Zhu, Dongming; Morscher, Gregory

    2015-01-01

    Damage evolution of electron beam-physical vapor deposited (EBVD-PVD) ZrO2-7 wt.% Y2O3 thermal barrier coatings (TBCs) under thermal cyclic conditions was monitored using an acoustic emission (AE) technique. The coatings were heated using a laser heat flux technique that yields a high reproducibility in thermal loading. Along with AE, real-time thermal conductivity measurements were also taken using infrared thermography. Tests were performed on samples with induced stress concentrations, as well as calcium-magnesium-alumino-silicate (CMAS) exposure, for comparison of damage mechanisms and AE response to the baseline (as-produced) coating. Analysis of acoustic waveforms was used to investigate damage development by comparing when events occurred, AE event frequency, energy content and location. The test results have shown that AE accumulation correlates well with thermal conductivity changes and that AE waveform analysis could be a valuable tool for monitoring coating degradation and provide insight on specific damage mechanisms.

  14. Theory of thermal stresses

    CERN Document Server

    Boley, Bruno A

    1997-01-01

    Highly regarded text presents detailed discussion of fundamental aspects of theory, background, problems with detailed solutions. Basics of thermoelasticity, heat transfer theory, thermal stress analysis, more. 1985 edition.

  15. Adaptive Responses to Thermal Stress in Mammals

    OpenAIRE

    Yasser Lenis Sanin; Angélica María Zuluaga Cabrera; Ariel Marcel Tarazona Morales

    2015-01-01

    The environment animals have to cope with is a combination of natural factors such as temperature. Extreme changes in these factors can alter homeostasis, which can lead to thermal stress. This stress can be due to either high temperatures or low temperatures. Energy transference for thermoregulation in homoeothermic animals occurs through several mechanisms: conduction, convection, radiation and evaporation. When animals are subjected to thermal stress, physiological mechanisms are activated...

  16. Thermally developing forced convection and the corresponding thermal stresses in a porous plate channel

    Institute of Scientific and Technical Information of China (English)

    YANG Xiao; LIU Xuemei

    2007-01-01

    Based on the Darcy fluid model, by considering the effects of viscous dissipation due to the interaction between solid skeleton and pore fluid flow and thermal conduction in the direction of the fluid flow, the thermally developing forced convection of the local thermal equili- brium and the corresponding thermal stresses in a semi- infmite saturated porous plate channel are investigated in this paper. The expressions of temperature, local Nusselt number and corresponding thermal stresses are obtained by means of the Fourier series, and the distributions of the same are also shown. Furthermore, influences of the Péclet number (Pe) and Brinkman number (Br) on temperature, Nusselt number (Nu) and thermal stress are revealed numerically.

  17. Heat Transfer and Thermal Stress Analysis of a Mandibular Molar Tooth Restored by Different Indirect Restorations Using a Three-Dimensional Finite Element Method.

    Science.gov (United States)

    Çelik Köycü, Berrak; İmirzalıoğlu, Pervin

    2017-07-01

    Daily consumption of food and drink creates rapid temperature changes in the oral cavity. Heat transfer and thermal stress caused by temperature changes in restored teeth may damage the hard and soft tissue components, resulting in restoration failure. This study evaluates the temperature distribution and related thermal stress on mandibular molar teeth restored via three indirect restorations using three-dimensional (3D) finite element analysis (FEA). A 3D finite element model was constructed of a mandibular first molar and included enamel, dentin, pulp, surrounding bone, and indirect class 2 restorations of type 2 dental gold alloy, ceramic, and composite resin. A transient thermal FEA was performed to investigate the temperature distribution and the resulting thermal stress after simulated temperature changes from 36°C to 4 or 60°C for a 2-second time period. The restoration models had similar temperature distributions at 2 seconds in both the thermal conditions. Compared with 60°C exposure, the 4°C condition resulted in thermal stress values of higher magnitudes. At 4ºC, the highest stress value observed was tensile stress (56 to 57 MPa), whereas at 60°C, the highest stress value observed was compressive stress (42 to 43 MPa). These stresses appeared at the cervical region of the lingual enamel. The thermal stress at the restoration surface and resin cement showed decreasing order of magnitude as follows: composite > gold > ceramic, in both thermal conditions. The properties of the restorative materials do not affect temperature distribution at 2 seconds in restored teeth. The pulpal temperature is below the threshold for vital pulp tissue (42ºC). Temperature changes generate maximum thermal stress at the cervical region of the enamel. With the highest thermal expansion coefficient, composite resin restorations exhibit higher stress patterns than ceramic and gold restorations. © 2015 by the American College of Prosthodontists.

  18. Mechanical stress analysis for a fuel rod under normal operating conditions

    International Nuclear Information System (INIS)

    Pino, Eddy S.; Giovedi, Claudia; Serra, Andre da Silva; Abe, Alfredo Y.

    2013-01-01

    Nuclear reactor fuel elements consist mainly in a system of a nuclear fuel encapsulated by a cladding material subject to high fluxes of energetic neutrons, high operating temperatures, pressure systems, thermal gradients, heat fluxes and with chemical compatibility with the reactor coolant. The design of a nuclear reactor requires, among a set of activities, the evaluation of the structural integrity of the fuel rod submitted to different loads acting on the fuel rod and the specific properties (dimensions and mechanical and thermal properties) of the cladding material and coolant, including thermal and pressure gradients produced inside the rod due to the fuel burnup. In this work were evaluated the structural mechanical stresses of a fuel rod using stainless steel as cladding material and UO 2 with a low degree of enrichment as fuel pellet on a PWR (pressurized water reactor) under normal operating conditions. In this sense, tangential, radial and axial stress on internal and external cladding surfaces considering the orientations of 0 deg, 90 deg and 180 deg were considered. The obtained values were compared with the limit values for stress to the studied material. From the obtained results, it was possible to conclude that, under the expected normal reactor operation conditions, the integrity of the fuel rod can be maintained. (author)

  19. Evaluation charts of thermal stresses in cylindrical vessels induced by thermal stratification of contained fluid

    International Nuclear Information System (INIS)

    Furuhashi, Ichiro; Kawasaki, Nobuchika; Kasahara, Naoto

    2008-01-01

    Temperature and thermal stress in cylindrical vessels were analysed for the thermal stratification of contained fluid. Two kinds of temperature analysis results were obtained such as the exact temperature solution of eigenfunction series and the simple approximate one by the temperature profile method. Furthermore, thermal stress shell solutions were obtained for the simple approximate temperatures. Through comparison with FEM analyses, these solutions were proved to be adequate. The simple temperature solution is described by one parameter that is the temperature decay coefficient. The thermal stress shell solutions are described by two parameters. One is the ratio between the temperature decay coefficient and the load decay coefficient. Another is the nondimensional width of stratification. These solutions are so described by few parameters that those are suitable for the simplified thermal stress evaluation charts. These charts enable quick and accurate thermal stress evaluations of cylindrical vessel of this problem compared with conventional methods. (author)

  20. Evaluation charts of thermal stresses in cylindrical vessels induced by thermal stratification of contained fluid

    International Nuclear Information System (INIS)

    Furuhashi, Ichiro; Kawasaki, Nobuchika; Kasahara, Naoto

    2007-01-01

    Temperature and thermal stress in cylindrical vessels were analysed for the thermal stratification of contained fluid. Two kinds of temperature analysis results were obtained such as the exact temperature solution of eigen-function series and the simple approximate one by the temperature profile method. Furthermore, shell solutions of thermal stress were obtained for the simple approximate temperatures. Through comparison with FEM analyses, these solutions were proved to be adequate. The simple temperature solution is described by one parameter that is the temperature decay factor. The shell solutions of thermal stress are described by two parameters. One is the ratio between the temperature decay factor and the local decay factor. Another is the non-dimensional width of stratification. These solution are so described by few parameters that those are suitable for the simplified thermal stress evaluation charts. These charts enable quick and accurate thermal stress evaluations of cylindrical vessel of this problem compared with conventional methods. (author)

  1. Numerical simulation of temperature and thermal stress for nuclear piping by using computational fluid dynamics analysis and Green’s function

    Energy Technology Data Exchange (ETDEWEB)

    Boo, Myung-Hwan [Korea Hydro and Nuclear Power Company, Daejeon (Korea, Republic of); Oh, Chang-Kyun; Kim, Hyun-Su [KEPCO Engineering and Construction Company, Gimcheon (Korea, Republic of); Choi, Choeng-Ryul [ELSOLTEC, Inc., Yongin (Korea, Republic of)

    2017-05-15

    Owing to the fact that thermal fatigue is a well-known damage mechanism in nuclear power plants, accurate stress and fatigue evaluation are highly important. Operating experience shows that the design condition is conservative compared to the actual one. Therefore, various fatigue monitoring methods have been extensively utilized to consider the actual operating data. However, defining the local temperature in the piping is difficult because temperature-measuring instruments are limited. The purpose of this paper is to define accurate local temperature in the piping and evaluate thermal stress using Green’s function (GF) by performing a series of computational fluid dynamics analyses considering the complex fluid conditions. Also, the thermal stress is determined by adopting GF and comparing it with that of the design condition. The fluid dynamics analysis result indicates that the fluid temperature slowly varies compared to the designed one even when the flow rate changes abruptly. In addition, the resulting thermal stress can significantly decrease when reflecting the actual temperature.

  2. Photothermoelastic investigation of transient thermal stresses in circular plates with a hole heated by fluid

    International Nuclear Information System (INIS)

    Tsuji, Masatoshi; Tsujimura, Soichi; Oda, Masanobu.

    1980-01-01

    In this study, the practical use of the method of measuring the unsteady thermal stress in a body subjected to the thermal load due to fluid by photoelastic method and the improvement of accuracy were attempted. The internal wall of a hollow disk was heated with high temperature fluid, and the external wall was cooled with low temperature fluid or thermally insulated. The photoelastic experiment on this hollow disk was carried out in a vacuum tank to given axisymmetric temperature distribution and to prevent heat dissipation due to the convection from both surfaces of the disk, and the temperature distribution and thermal stress were measured. The experimental values were compared with the theoretical values, and the accuracy of the experimental method and measurement was examined. Moreover, the disk with an eccentric hole was tested by the same method, and the effects of the eccentricity and hole diameter on the maximum thermal stress were examined. The experimental apparatus and method, and the experimental results are described. By this method, the condition of thermal loading with fluid was almost attained, and the experimental values of unsteady thermal stress were in good agreement with the theoretical values. (Kako, I.)

  3. Two-dimensional simulation of the thermal stress effect on static and dynamic VDMOS characteristics

    International Nuclear Information System (INIS)

    Alwan, M.; Beydoun, B.; Ketata, K.; Zoaeter, M.

    2005-01-01

    Using a two-dimensional simulator, the effect of the thermal stress on static and dynamic vertical double-diffusion metal oxide semiconductor (VDMOS) characteristics have been investigated. The use of the device under certain thermal stress conditions can produce modifications of its physical and electrical properties. Based on physics and 2D simulations, this paper proposes an analysis of this stress effect observed on the electrical characteristics of the device. Parameters responsible of these modifications are determined. Approximate expressions of the ionization coefficients and breakdown voltage in terms of temperature are proposed. Non-punch-through junction theory is used to express the breakdown voltage and the space charge extension with respect to the impurity concentration and the temperature. The capacitances of the device have been also studied. The effect of the stress on C-V characteristics is observed and analyzed. We notice that the drain-gate, drain-source and gate-source capacitances are shifted due to the degradation of device physical properties versus thermal stress

  4. Thermal stress effects in intermetallic matrix composites

    Science.gov (United States)

    Wright, P. K.; Sensmeier, M. D.; Kupperman, D. S.; Wadley, H. N. G.

    1993-01-01

    Intermetallic matrix composites develop residual stresses from the large thermal expansion mismatch (delta-alpha) between the fibers and matrix. This work was undertaken to: establish improved techniques to measure these thermal stresses in IMC's; determine residual stresses in a variety of IMC systems by experiments and modeling; and, determine the effect of residual stresses on selected mechanical properties of an IMC. X ray diffraction (XRD), neutron diffraction (ND), synchrotron XRD (SXRD), and ultrasonics (US) techniques for measuring thermal stresses in IMC were examined and ND was selected as the most promising technique. ND was demonstrated on a variety of IMC systems encompassing Ti- and Ni-base matrices, SiC, W, and Al2O3 fibers, and different fiber fractions (Vf). Experimental results on these systems agreed with predictions of a concentric cylinder model. In SiC/Ti-base systems, little yielding was found and stresses were controlled primarily by delta-alpha and Vf. In Ni-base matrix systems, yield strength of the matrix and Vf controlled stress levels. The longitudinal residual stresses in SCS-6/Ti-24Al-llNb composite were modified by thermomechanical processing. Increasing residual stress decreased ultimate tensile strength in agreement with model predictions. Fiber pushout strength showed an unexpected inverse correlation with residual stress. In-plane shear yield strength showed no dependence on residual stress. Higher levels of residual tension led to higher fatigue crack growth rates, as suggested by matrix mean stress effects.

  5. 40 CFR 91.329 - Catalyst thermal stress test.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Catalyst thermal stress test. 91.329....329 Catalyst thermal stress test. (a) Oven characteristics. The oven used for termally stressing the test catalyst must be capable of maintaining a temperature of 500 ±5 °C and 1000 ±10 °C. (b) Evaluation...

  6. Temperature distribution and thermal stress

    Indian Academy of Sciences (India)

    Abstract. Thermal effects of a double-end-pumped cubic Nd:YVO4 laser crystal are investigated in this paper. A detailed analysis of temperature distribution and thermal stress in cubic crystal with circular shape pumping is discussed. It has been shown that by considering the total input powers as constant, the ...

  7. Thermal stress ratcheting analysis of a time-hardening structure

    International Nuclear Information System (INIS)

    Hada, Kazuhiko

    1999-01-01

    Thermal stress ratcheting and shakedown is analyzed for a time-hardening structure: the yield stress increases as time goes on under exposure to neutron irradiation or thermal aging. New three modes of ratcheting and shakedown are identified as transition to other deformation modes. Stress regimes and thermal ratchet strains are formulated as a function of time-increasing yield stress. Moreover, a new model of trouble occurrence frequency as a modification to a bath-tube curve is proposed for calculating a time period of a thermal cycle. Application of the proposed formulation tells us a benefit of taking into account the time hardening due to neutron irradiation. (author)

  8. Calculation of the thermal stress and thermal resistance of anisotropic materials. II

    Energy Technology Data Exchange (ETDEWEB)

    Krivko, A I; Epishin, A I; Svetlov, I L; Samoilov, A I; Sukhanov, N N

    1989-04-01

    The stressed state in a wedge and in a family of plates cut from single-crystal ingots of 40 axial orientations is analyzed. It is shown that, in contrast to the case of the wedge, the value of the thermal stress tensor components in the plates depends substantially not only on the axial crystallographic orientation but also on the azimuthal orientation. Requirements on the crystallographic orientation of simple single-crystal parts of plate or wedge type are formulated with the aim of decreasing the detrimental effects of thermal stresses. The correctness of the calculations is confirmed by results of thermal fatigue tests of hollow prismatic specimens, i.e., blade simulators with 001, 011, and 111 axial orientations.

  9. STRESSES IN CEMENT-CONCRETE PAVEMENT SURFACING CAUSED BY THERMAL SHOCK

    Directory of Open Access Journals (Sweden)

    M. K. Pshembaev

    2016-01-01

    Full Text Available It is necessary to mention specially so-called thermal shock among various impacts on highway surface. Ice layer is formed on a concrete surface during the winter period of pavement surfacing operation. Sodium chloride which lowers temperature of water-ice transition temperature and causes ice thawing at negative temperature is usually used to remove ice from the pavement surface. Consequently, temperature in the concrete laying immediately under a thawing ice layer is coming down with a run that leads to significant stresses. Such phenomenon is known as a thermal shock with a meaning of local significant change in temperature. This process is under investigation, it has practical importance for an estimation of strength and longevity of a cement-concrete pavement surfacing and consequently it is considered as rather topical issue. The purpose of investigations is to develop a mathematical model and determination of shock blow permissible gradients for a cementconcrete road covering. Finite difference method has been used in order to determine stressed and deformed condition of the cement-concrete pavement surfacing of highways. A computer program has been compiled and it permits to carry out calculation of a road covering at various laws of temperature distribution in its depth. Regularities in distribution of deformation and stresses in the cement-concrete pavement surfacing of highways at thermal shock have been obtained in the paper. A permissible parameter of temperature distribution in pavement surfacing thickness has been determined in the paper. A strength criterion based on the process of micro-crack formation and development in concrete has been used for making calculations. It has been established that the thermal shock causes significant temperature gradients on the cement-concrete surfacing that lead to rather large normal stresses in the concrete surface layer. The possibility of micro-crack formation in a road covering is

  10. Stress analysis of thermal sprayed coatings using a semi-destructive hole-drilling strain gauge method

    International Nuclear Information System (INIS)

    Dolhof, V.; Musil, J.; Cepera, M.; Zeman, J.

    1995-01-01

    Residual stress is an important parameter in coating technology since it often relates to the maximum coating thickness which can be deposited without spallation, and this applies to coatings produced by different thermal spray and thin film technologies. Indeed, the mechanisms by which residual stress is built up or locked into a coating depends markedly on the deposition process and coating structure (growth structure, phase composition) in the same way too. Methods for determining residual stresses in materials include both destructive and non-destructive methods. This contribution describes semi-destructive hole-drilling strain gauge method modified for measurement of residual stresses in thermal sprayed coatings. This method of stress analysis was used for determination of stress levels in thermal sprayed WC-17% Co coatings onto 13% Cr steel substrates. Results show that deposition conditions and final coating structure influence directly the residual stress level in the coatings. It is proved that semi-destructive hole-tube drilling measurement is effective reproducible method of coating stress analysis and good solution for optimization of deposition process

  11. Simulation of thermal stress and buckling instability in Si/Ge and Ge/Si core/shell nanowires.

    Science.gov (United States)

    Das, Suvankar; Moitra, Amitava; Bhattacharya, Mishreyee; Dutta, Amlan

    2015-01-01

    The present study employs the method of atomistic simulation to estimate the thermal stress experienced by Si/Ge and Ge/Si, ultrathin, core/shell nanowires with fixed ends. The underlying technique involves the computation of Young's modulus and the linear coefficient of thermal expansion through separate simulations. These two material parameters are combined to obtain the thermal stress on the nanowires. In addition, the thermally induced stress is perceived in the context of buckling instability. The analysis provides a trade-off between the geometrical and operational parameters of the nanostructures. The proposed methodology can be extended to other materials and structures and helps with the prediction of the conditions under which a nanowire-based device might possibly fail due to elastic instability.

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

    Science.gov (United States)

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

    2015-01-01

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

  13. Thermal stress microfracturing of crystalline and sedimentary rock. Final report, September 16, 1987--September 15, 1991

    International Nuclear Information System (INIS)

    Wang, H.

    1995-08-01

    Slow uniform heating of crustal rocks is both a pervasive geologic process and an anticipated by-product of radioactive waste disposal. Such heating generates microcracks which alter the strength, elastic moduli, and transport properties of the rock. The research program was to understand mechanisms of thermal cracking in rocks. It included development of a theoretical understanding of cracking due to thermal stresses, laboratory work to characterize crack strain in rocks thermally stressed under different conditions (including natural thermal histories), microscopic work to count and catalog crack occurrences, and geologic application to determine paleostress history of granites from the midcontinent

  14. Exploring the use of thermal infrared imaging in human stress research.

    Directory of Open Access Journals (Sweden)

    Veronika Engert

    Full Text Available High resolution thermal infrared imaging is a pioneering method giving indices of sympathetic activity via the contact-free recording of facial tissues (thermal imprints. Compared to established stress markers, the great advantage of this method is its non-invasiveness. The goal of our study was to pilot the use of thermal infrared imaging in the classical setting of human stress research. Thermal imprints were compared to established stress markers (heart rate, heart rate variability, finger temperature, alpha-amylase and cortisol in 15 participants undergoing anticipation, stress and recovery phases of two laboratory stress tests, the Cold Pressor Test and the Trier Social Stress Test. The majority of the thermal imprints proved to be change-sensitive in both tests. While correlations between the thermal imprints and established stress markers were mostly non-significant, the thermal imprints (but not the established stress makers did correlate with stress-induced mood changes. Multivariate pattern analysis revealed that in contrast to the established stress markers the thermal imprints could not disambiguate anticipation, stress and recovery phases of both tests. Overall, these results suggest that thermal infrared imaging is a valuable method for the estimation of sympathetic activity in the stress laboratory setting. The use of this non-invasive method may be particularly beneficial for covert recordings, in the study of special populations showing difficulties in complying with the standard instruments of data collection and in the domain of psychophysiological covariance research. Meanwhile, the established stress markers seem to be superior when it comes to the characterization of complex physiological states during the different phases of the stress cycle.

  15. Transient thermal stresses in an orthotropic rectangular plate with convective heat transfer at upper and lower surfaces

    International Nuclear Information System (INIS)

    Sugano, Yoshihiro; Nakanishi, Takanori; Ito, Masahiko; Saito, Koichi.

    1982-01-01

    Recently, anisotropic materials have been used widely for reactor core elements and fast flying objects, therefore, the problem of thermal stress in anisotropic bodies has been studied actively. In this study, the unsteady plane thermal stress in an orthotropic rectangular thin plate heated by the temperature of ambient medium was analyzed, taking the heat transfer on both surfaces into account. The influence that the anisotropy of material constants and the heat transfer on both surfaces exert on the temperature and thermal stress of the plate was examined. Moreover, in order to investigate into the effect of the aspect ratio of the plate on the temperature and thermal stress, the unsteady distributions of temperature and thermal stress in an orthotropic semi-infinite band, of which the end surfaces are heated by ambient medium, were analyzed. The numerical calculation was carried out, and the results are shown. Before, it was difficult to satisfy the boundary condition related to shearing stress, accordingly, the analysis has not been performed, but in this study, it was shown that the analysis is possible. (Kako, I.)

  16. Adaptive Responses to Thermal Stress in Mammals

    Directory of Open Access Journals (Sweden)

    Yasser Lenis Sanin

    2015-12-01

    Full Text Available The environment animals have to cope with is a combination of natural factors such as temperature. Extreme changes in these factors can alter homeostasis, which can lead to thermal stress. This stress can be due to either high temperatures or low temperatures. Energy transference for thermoregulation in homoeothermic animals occurs through several mechanisms: conduction, convection, radiation and evaporation. When animals are subjected to thermal stress, physiological mechanisms are activated which may include endocrine, neuroendocrine and behavioral responses. Activation of the neuroendocrine system affects the secretion of hormones and neurotransmitters which act collectively as response mechanisms that allow them to adapt to stress. Mechanisms which have developed through evolution to allow animals to adapt to high environmental temperatures and to achieve thermo tolerance include physiological and physical changes in order to reduce food intake and metabolic heat production, to increase surface area of skin to dissipate heat, to increase blood flow to take heat from the body core to the skin and extremities to dissipate the heat, to increase numbers and activity of sweat glands, panting, water intake and color adaptation of integument system to reflect heat. Chronic exposure to thermal stress can cause disease, reduce growth, decrease productive and reproductive performance and, in extreme cases, lead to death. This paper aims to briefly explain the physical and physiological responses of mammals to thermal stress, like a tool for biological environment adaptation, emphasizing knowledge gaps and offering some recommendations to stress control for the animal production system.

  17. An analytical study on the thermal stress of mass concrete

    International Nuclear Information System (INIS)

    Yoshida, H.; Sawada, T.; Yamazaki, M.; Miyashita, T.; Morikawa, H.; Hayami, Y.; Shibata, K.

    1983-01-01

    The thermal stress in mass concrete occurs as a result of the effect associated with the heat of hydration of the cement. Sometimes, the excessive stresses cause the cracking or other tensile failure in concrete. Therefore it is becoming necessary in the design and construction of mass concrete to predict the thermal stress. The thermal stress analysis of mass concrete requires to take account of the dependence of the elastic modulus on the age of concrete as well as the stress relaxation by creep effect. The studies of those phenomena and the analytical methods have been reported so far. The paper presents the analytical method and discusses its reliability through the application of the method to the actual structure, measuring the temperatures and the thermal stresses. The method is the time dependent thermal stress analysis based on the finite element method, which takes account of creep effect, the aging of concrete and the effect of temperature variation in time. (orig./HP)

  18. Fatigue crack growth behavior under cyclic thermal transient stress

    International Nuclear Information System (INIS)

    Ueda, Masahiro; Kano, Takashi; Yoshitoshi, Atsushi.

    1986-01-01

    Thermal fatigue tests were performed using straight pipe specimens subjected to cyclic thermal shocks of liquid sodium, and crack growth behaviors were estimated using striation patterns observed clearly on any crack surface. Crack growth rate under cyclic thermal strain reaches the maximum at one depth, and after that it decreases gradually with crack depth. The peak location of crack growth rate becomes deeper by superposition of constant primary stress. Parallel cracks co-existing in the neighborhood move the peak to shallower location and decrease the maximum crack growth rate. The equivalent stress intensity factor range calculated by Walker's formula is successfully applied to the case of negative stress ratio. Fatigue crack growth rate under cyclic thermal strain agreed well with that under the constant temperature equal to the maximum value in the thermal cycle. Simplified methods for calculating the stress intensity factor and the crack interference factor have been developed. Crack growth behavior under thermal fatigue could be well predicted using numerical analysis results. (author)

  19. Fatigue crack growth behavior under cyclic transient thermal stress

    International Nuclear Information System (INIS)

    Ueda, Masahiro; Kano, Takashi; Yoshitoshi, Atsushi.

    1987-01-01

    Thermal fatigue tests were performed using straight pipe specimens subjected to cyclic thermal shocks of liquid sodium, and crack growth behaviors were estimated using striation patterns observed clearly on any crack surface. Crack growth rate under cyclic thermal strain reaches the maximum at one depth, and after that it decreases gradually with crack depth. The peak location of crack growth rate becomes deeper by superposition of constant primary stress. Parallel cracks co-existing in the neighborhood move the peak to shallower location and decrease the maximum crack growth rate. The equivalent stress intensity factor range calculated by Walker's formula is successfully applied to the case of negative stress ratio. Fatigue crack growth rate under cyclic thermal strain agreed well with that under the constant temperature equal to the maximum value in the thermal cycle. Simplified methods for calculating the stress intensity factor and the crack interference factor have been developed. Crack growth behavior under thermal fatigue could be well predicted using numerical analysis results. (author)

  20. Modelling and analysis of radial thermal stresses and temperature ...

    African Journals Online (AJOL)

    A theoretical investigation has been undertaken to study operating temperatures, heat fluxes and radial thermal stresses in the valves of a modern diesel engine with and without air-cavity. Temperatures, heat fluxes and radial thermal stresses were measured theoretically for both cases under all four thermal loading ...

  1. Prediction of minimum UO2 particle size based on thermal stress initiated fracture model

    International Nuclear Information System (INIS)

    Corradini, M.

    1976-08-01

    An analytic study was employed to determine the minimum UO 2 particle size that could survive fragmentation induced by thermal stresses in a UO 2 -Na Fuel Coolant Interaction (FCI). A brittle fracture mechanics approach was the basis of the study whereby stress intensity factors K/sub I/ were compared to the fracture toughness K/sub IC/ to determine if the particle could fracture. Solid and liquid UO 2 droplets were considered each with two possible interface contact conditions; perfect wetting by the sodium or a finite heat transfer coefficient. The analysis indicated that particles below the range of 50 microns in radius could survive a UO 2 -Na fuel coolant interaction under the most severe temperature conditions without thermal stress fragmentation. Environmental conditions of the fuel-coolant interaction were varied to determine the effects upon K/sub I/ and possible fragmentation. The underlying assumptions of the analysis were investigated in light of the analytic results. It was concluded that the analytic study seemed to verify the experimental observations as to the range of the minimum particle size due to thermal stress fragmentation by FCI. However the method used when the results are viewed in light of the basic assumptions indicates that the analysis is crude at best, and can be viewed as only a rough order of magnitude analysis. The basic complexities in fracture mechanics make further investigation in this area interesting but not necessarily fruitful for the immediate future

  2. Thermal-stress analysis and testing of DIII-D armor tiles

    International Nuclear Information System (INIS)

    Baxi, C.B.; Anderson, P.M.; Reis, E.E.; Smith, J.P.; Smith, P.D.; Croesmann, C.; Watkins, J.; Whitley, J.

    1987-10-01

    It is planned to install about 1500 new armor tiles in the DIII-D tokamak. The armor tiles currently installed in DIII-D are made by brazing Poco AXF-5Q graphite onto Inconel X-750 stock. A small percentage of these have failed by breakage of graphite. These failures were believed to be related to significant residual stress remaining in graphite after brazing. Hence, an effort was undertaken to improve the design with all-graphite tiles. Three criteria must be satisfied by the armor tiles and the hardware used to attach the tiles to the vessel walls: tiles should not structurally fail, peak tile temperature must be less than 2500 K, and peak vessel stresses must be below acceptable levels. A number of alternate design concepts were first analyzed with the two-dimensional finite element codes TOPAZ2D and NIKE2D. Promising designs were optimized for best parameters such as thicknesses, etc. The two best designs were further analyzed for thermal stresses with the three-dimensional codes P/THERMAL and P/STRESS. Prototype tiles of a number of materials were fabricated by GA and tested at the Plasma Materials Test Facility of the Sandia National Laboratory at Albuquerque. The tests simulated the heat flux and cooling conditions in DIII-D. This paper describes the 2-D and 3-D thermal stress analyses, the test results and logic which led to the selected design of the DIII-D armor tiles. 5 refs., 7 figs., 3 tabs

  3. Temperature and Thermal Stress Analysis of Refractory Products

    Directory of Open Access Journals (Sweden)

    Shaoyang Shi

    2013-05-01

    Full Text Available Firstly current status of temperature and thermal stress research of refractory product at home and aboard are analyzed. Finite element model of two classical refractory products is building by using APDL language. Distribution law of temperature and thermal stress of two typical refractory products-ladles and tundish are analyzed and their structures are optimized. Stress of optimal structure is dropped obviously, and operation life is increased effectively.

  4. An anisotropic thermal-stress model for through-silicon via

    Science.gov (United States)

    Liu, Song; Shan, Guangbao

    2018-02-01

    A two-dimensional thermal-stress model of through-silicon via (TSV) is proposed considering the anisotropic elastic property of the silicon substrate. By using the complex variable approach, the distribution of thermal-stress in the substrate can be characterized more accurately. TCAD 3-D simulations are used to verify the model accuracy and well agree with analytical results (model can be integrated into stress-driven design flow for 3-D IC , leading to the more accurate timing analysis considering the thermal-stress effect. Project supported by the Aerospace Advanced Manufacturing Technology Research Joint Fund (No. U1537208).

  5. Role of high-temperature creep stress in thermally grown oxide growth of thermal barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, K.; Nakao, Y.; Seo, D.; Miura, H.; Shoji, T. [Tohoku Univ., Sendai (Japan)

    2008-07-01

    Thermally grown oxide (TGO) grows at the top / bond coating interface of the thermal barrier coating (TBC) in service. It is supposed that the failures of the TBC occur due to thermal stress and the decrease of adhesive strength caused by the TGO growth. Recently, large local stress has been found to change both the diffusion constant of oxygen through an existing oxide and the rate of chemical reaction at the oxide / oxidized material interface. Since high thermal stress occurs in the TBC, the volume expansion of the newly grown oxide, and centrifugal force, the growth rate of the TGO may change depending on not only temperature but also the stress. The aim of this study is to make clear the influence of stress on the growth rate of the TGO quantitatively. As a result, the thickness of the TGO clearly increases with increase of the amplitude of the applied stress and temperature. The increase rate of the TGO thickness is approximately 23% when the applied stress is increased from 0 to 205 MPa at 900 C, and approximately 29% when the stress is increased from 0 to 150 MPa at 950 C. (orig.)

  6. Finite element analysis of thermal stress distribution in different ...

    African Journals Online (AJOL)

    Nigerian Journal of Clinical Practice. Journal Home ... Von Mises and thermal stress distributions were evaluated. Results: In all ... distribution. Key words: Amalgam, finite element method, glass ionomer cement, resin composite, thermal stress ...

  7. Thermal stress analysis of space shuttle orbiter wing skin panel and thermal protection system

    Science.gov (United States)

    Ko, William L.; Jenkins, Jerald M.

    1987-01-01

    Preflight thermal stress analysis of the space shuttle orbiter wing skin panel and the thermal protection system (TPS) was performed. The heated skin panel analyzed was rectangular in shape and contained a small square cool region at its center. The wing skin immediately outside the cool region was found to be close to the state of elastic instability in the chordwise direction based on the conservative temperature distribution. The wing skin was found to be quite stable in the spanwise direction. The potential wing skin thermal instability was not severe enough to tear apart the strain isolation pad (SIP) layer. Also, the preflight thermal stress analysis was performed on the TPS tile under the most severe temperature gradient during the simulated reentry heating. The tensile thermal stress induced in the TPS tile was found to be much lower than the tensile strength of the TPS material. The thermal bending of the TPS tile was not severe enough to cause tearing of the SIP layer.

  8. FEM thermal and stress analysis of bonded GaN-on-diamond substrate

    Science.gov (United States)

    Zhai, Wenbo; Zhang, Jingwen; Chen, Xudong; Bu, Renan; Wang, Hongxing; Hou, Xun

    2017-09-01

    A three-dimensional thermal and stress analysis of bonded GaN on diamond substrate is investigated using finite element method. The transition layer thickness, thermal conductivity of transition layer, diamond substrate thickness and the area ratio of diamond and GaN are considered and treated appropriately in the numerical simulation. The maximum channel temperature of GaN is set as a constant value and its corresponding heat power densities under different conditions are calculated to evaluate the influences that the diamond substrate and transition layer have on GaN. The results indicate the existence of transition layer will result in a decrease in the heat power density and the thickness and area of diamond substrate have certain impact on the magnitude of channel temperature and stress distribution. Channel temperature reduces with increasing diamond thickness but with a decreasing trend. The stress is reduced by increasing diamond thickness and the area ratio of diamond and GaN. The study of mechanical and thermal properties of bonded GaN on diamond substrate is useful for optimal designs of efficient heat spreader for GaN HEMT.

  9. Estimation of fracture conditions of ceramics by thermal shock with laser beams based on the maximum compressive stress criterion

    International Nuclear Information System (INIS)

    Akiyama, Shigeru; Amada, Shigeyasu.

    1992-01-01

    Structural ceramics are attracting attention in the development of space planes, aircraft and nuclear fusion reactors because they have excellent wear-resistant and heat-resistant characteristics. However, in some applications it is anticipated that they will be exposed to very-high-temperature environments of the order of thousands of degrees. Therefore, it is very important to investigate their thermal shock characteristics. In this report, the distributions of temperatures and thermal stresses of cylindrically shaped ceramics under irradiation by laser beams are discussed using the finite-element computer code (MARC) with arbitrary quadrilateral axisymmetric ring elements. The relationships between spot diameters of laser beams and maximum values of compressive thermal stresses are derived for various power densities. From these relationships, a critical fracture curve is obtained, and it is compared with the experimental results. (author)

  10. Theoretical Research on Thermal Shock Resistance of Ultra-High Temperature Ceramics Focusing on the Adjustment of Stress Reduction Factor

    Directory of Open Access Journals (Sweden)

    Daining Fang

    2013-02-01

    Full Text Available The thermal shock resistance of ceramics depends on not only the mechanical and thermal properties of materials, but also the external constraint and thermal condition. So, in order to study the actual situation in its service process, a temperature-dependent thermal shock resistance model for ultra-high temperature ceramics considering the effects of the thermal environment and external constraint was established based on the existing theory. The present work mainly focused on the adjustment of the stress reduction factor according to different thermal shock situations. The influences of external constraint on both critical rupture temperature difference and the second thermal shock resistance parameter in either case of rapid heating or cooling conditions had been studied based on this model. The results show the necessity of adjustment of the stress reduction factor in different thermal shock situations and the limitations of the applicable range of the second thermal shock resistance parameter. Furthermore, the model was validated by the finite element method.

  11. Calculation of thermal stresses in graphite fuel blocks

    International Nuclear Information System (INIS)

    Lejeail, Y.; Cabrillat, M.T.

    2005-01-01

    This paper presents a parametric study of temperature and thermal stress calculations inside a HTGR core graphite block, taking into account the effect of fluence on the thermal and mechanical properties, up to 4. 10 21 n/cm 2 . The Finite Element model, realized with Cast3M CEA code, includes the effects of irradiation creep, which tends to produce secondary stress relaxation. Then, the Weibull weakest link theory is recalled, evaluating the possible effects of volume, stress field distribution (loading factor), and multiaxiality for graphite-type materials, and giving the methodology to compare the stress to rupture for the structure to the one obtained from characterization, in the general case. The maximum of the Weibull stress in Finite Element calculations is compared to the value for tensile specimens. It is found that the maximum of the stress corresponds to the end of the irradiation cycle, after reactor shutdown, since both thermal conductivity and Young's modulus increase with time. However, this behaviour is partly counterbalanced by the increase of material strength with irradiation. (authors)

  12. Fracture appraisal of large scale glass block under various realistic thermal conditions

    International Nuclear Information System (INIS)

    Laude, F.; Vernaz, E.; Saint-Gaudens, M.

    1982-06-01

    Fracturing of nuclear waste glass caused primarily by thermal and residual stresses during cooling increases the potential leaching surface area and the number of small particles. A theoretical study shows that it is possible to calculate the stresses created but it is difficult to evaluate the state of fracture. Theoretical results are completed by an experimental study with inactive industrial scale glass blocks. The critical stages of its thermal history are simulated and the total surface area of the pieces is measured by comparison of leaching rate of the fractured glass with known samples in the same conditions. Quenching due to water impact, air cooling in a storage fit and experimental reassembly of fractured glass by re-heating are examined

  13. Coherent gradient sensing method for measuring thermal stress field of thermal barrier coating structures

    Directory of Open Access Journals (Sweden)

    Kang Ma

    2017-01-01

    Full Text Available Coherent gradient sensing (CGS method can be used to measure the slope of a reflective surface, and has the merits of full-field, non-contact, and real-time measurement. In this study, the thermal stress field of thermal barrier coating (TBC structures is measured by CGS method. Two kinds of powders were sprayed onto Ni-based alloy using a plasma spraying method to obtain two groups of film–substrate specimens. The specimens were then heated with an oxy-acetylene flame. The resulting thermal mismatch between the film and substrate led to out-of-plane deformation of the specimen. The deformation was measured by the reflective CGS method and the thermal stress field of the structure was obtained through calibration with the help of finite element analysis. Both the experiment and numerical results showed that the thermal stress field of TBC structures can be successfully measured by CGS method.

  14. Thermal and stress analysis of a fuel rod research project 277

    International Nuclear Information System (INIS)

    1975-04-01

    The purpose of this investigation was to perform an analytical evaluation of a postulated loss of coolant incident in a large pressurized water reactor. A coupled thermal and stress finite element analysis of a fuel rod subjected to a hypothetical blow-down transient was carried out. The effect of two gap conditions and two initial stress states on the response of the fuel rod was studied. Both one-dimensional and three-dimensional models were investigated. To study the heat transfer in the gap region one assumes a conductive mode of heat transfer in the gap characterized by an equivalent thermal conductivity, which is dependent on the current gap width. Accordingly, coupled analysis procedure and computational scheme were established. A mesh generation computer program was developed for the three-dimensional model

  15. Thermal hydraulic conditions inducing incipient cracking in the 900 MWe unit 93 D reactor coolant pump shafts

    International Nuclear Information System (INIS)

    Bore, C.

    1995-01-01

    From 1987, 900 MWe plant operating feedback revealed cracking in the lower part of the reactor coolant pump shafts, beneath the thermal ring. Metallurgical examinations established that this was due to a thermal fatigue phenomenon known as thermal crazing, occurring after a large number of cycles. Analysis of thermal hydraulic conditions initiating the cracks does not allow exact quantification of the thermal load inducing cracking. Only qualitative analyses are thus possible, the first of which, undertaken by the pump manufacturer, Jeumont Industrie, showed that the cracks could not be due to the major transients (stop-start, injection cut-off), which were too few in number. Another explanation was then put forward: the thermal ring, shrunk onto the shaft it is required to protect against thermal shocks, loosens to allow an alternating downflow of cold water from the shaft seals and an upflow of hot water from the primary system. However, approximate calculations showed that the flow involved would be too slight to initiate the cracking observed. A more stringent analysis undertaken with the 2D flow analysis code MELODIE subsequently refuted the possibility of alternating flows beneath the ring establishing that only a hot water upflow occurred due to a 'viscosity pump' phenomenon. Crack initiation was finally considered to be due to flowrate variations beneath the ring, with the associated temperature fluctuations. This flowrate fluctuation could be due to an unidentified transient phenomenon or to a variation in pump operating conditions. This analysis of the hydraulic conditions initiating the cracks disregards shaft surface residual stresses. These are tensile stresses and show that loads less penalizing than those initially retained could cause incipient cracking. Thermal ring modifications to reduce these risks were proposed and implemented. In addition, final metallurgical treatment of the shafts was altered and implemented. In addition, final metallurgical

  16. The effects of location, thermal stress, and residual stress on corner cracks in nozzles with cladding

    International Nuclear Information System (INIS)

    Besuner, P.M.; Cohen, L.M.; McLean, J.L.

    1977-01-01

    The stress intensity factors (Ksub(I)) for corner cracks in a boiling water reactor feedwater nozzle with stainless steel cladding are obtained for loading by internal pressure, and a fluid quench in the nozzle. Conditions with and without residual stress in the component are considered. The residual stress is simulated by means of a reference temperature change. The stress distribution for the uncracked structure is obtained from a three-dimensional finite element model. A three-dimensional influence function (IF) method, in conjunction with the boundary-integral equation method for structural analysis is employed to compute Ksub(I) values from the uncracked structure's stress distribution. It is concluded that the effects on Ksub(I) of location, thermal stresses, and residual stresses are significant and generally too complex to evaluate without advanced numerical procedures. The ulilized combination of finite element analysis of the uncracked structure and three-dimensional influence function analysis of the cracked structure is demonstrated and endorsed. (Auth.)

  17. Thermal comfort index and infrared temperatures for lambs subjected to different environmental conditions

    Directory of Open Access Journals (Sweden)

    Tiago do Prado Paim

    2014-10-01

    Full Text Available There is an abundance of thermal indices with different input parameters and applicabilities. Infrared thermography is a promising technique for evaluating the response of animals to the environment and differentiating between genetic groups. Thus, the aim of this study was to evaluate superficial body temperatures of lambs from three genetic groups under different environmental conditions, correlating these with thermal comfort indices. Forty lambs (18 males and 22 females from three genetic groups (Santa Inês, Ile de France × Santa Inês and Dorper × Santa Inês were exposed to three climatic conditions: open air, housed and artificial heating. Infrared thermal images were taken weekly at 6h, 12h and 21h at the neck, front flank, rear flank, rump, nose, skull, trunk and eye. Four thermal comfort indices were calculated using environmental measurements including black globe temperature, air humidity and wind speed. Artificial warming, provided by infrared lamps and wind protection, conserved and increased the superficial body temperature of the lambs, thus providing lower daily thermal ranges. Artificial warming did not influence daily weight gain or mortality. Skin temperatures increased along with increases in climatic indices. Again, infrared thermography is a promising technique for evaluating thermal stress conditions and differentiating environments. However, the use of thermal imaging for understanding animal responses to environmental conditions requires further study.

  18. Calculation of Local Stress and Fatigue Resistance due to Thermal Stratification on Pressurized Surge Line Pipe

    Science.gov (United States)

    Bandriyana, B.; Utaja

    2010-06-01

    Thermal stratification introduces thermal shock effect which results in local stress and fatique problems that must be considered in the design of nuclear power plant components. Local stress and fatique calculation were performed on the Pressurize Surge Line piping system of the Pressurize Water Reactor of the Nuclear Power Plant. Analysis was done on the operating temperature between 177 to 343° C and the operating pressure of 16 MPa (160 Bar). The stagnant and transient condition with two kinds of stratification model has been evaluated by the two dimensional finite elements method using the ANSYS program. Evaluation of fatigue resistance is developed based on the maximum local stress using the ASME standard Code formula. Maximum stress of 427 MPa occurred at the upper side of the top half of hot fluid pipe stratification model in the transient case condition. The evaluation of the fatigue resistance is performed on 500 operating cycles in the life time of 40 years and giving the usage value of 0,64 which met to the design requirement for class 1 of nuclear component. The out surge transient were the most significant case in the localized effects due to thermal stratification.

  19. Impact of thermal stress on evolutionary trajectories of pathogen resistance in three-spined stickleback (Gasterosteus aculeatus).

    Science.gov (United States)

    Schade, Franziska M; Shama, Lisa N S; Wegner, K Mathias

    2014-07-26

    Pathogens are a major regulatory force for host populations, especially under stressful conditions. Elevated temperatures may enhance the development of pathogens, increase the number of transmission stages, and can negatively influence host susceptibility depending on host thermal tolerance. As a net result, this can lead to a higher prevalence of epidemics during summer months. These conditions also apply to marine ecosystems, where possible ecological impacts and the population-specific potential for evolutionary responses to changing environments and increasing disease prevalence are, however, less known. Therefore, we investigated the influence of thermal stress on the evolutionary trajectories of disease resistance in three marine populations of three-spined sticklebacks Gasterosteus aculeatus by combining the effects of elevated temperature and infection with a bacterial strain of Vibrio sp. using a common garden experiment. We found that thermal stress had an impact on fish weight and especially on survival after infection after only short periods of thermal acclimation. Environmental stress reduced genetic differentiation (QST) between populations by releasing cryptic within-population variation. While life history traits displayed positive genetic correlations across environments with relatively weak genotype by environment interactions (GxE), environmental stress led to negative genetic correlations across environments in pathogen resistance. This reversal of genetic effects governing resistance is probably attributable to changing environment-dependent virulence mechanisms of the pathogen interacting differently with host genotypes, i.e. GPathogenxGHostxE or (GPathogenxE)x(GHostxE) interactions, rather than to pure host genetic effects, i.e. GHostxE interactions. To cope with climatic changes and the associated increase in pathogen virulence, host species require wide thermal tolerances and pathogen-resistant genotypes. The higher resistance we found

  20. Thermal stratification and fatigue stress analysis for pressurizer surge line

    International Nuclear Information System (INIS)

    Yu Xiaofei; Zhang Yixiong

    2011-01-01

    Thermal stratification of pressurizer surge line induced by the inside fluid results in the global bending moments, local thermal stresses, unexpected displacements and support loadings of the pipe system. In order to avoid a costly three-dimensional computation, a combined 1D/2D technique has been developed and implemented to analyze the thermal stratification and fatigue stress of pressurize surge line of QINSHAN Phase II Extension Nuclear Power Project in this paper, using the computer codes SYSTUS and ROCOCO. According to the mechanical analysis results of stratification, the maximum stress and cumulative usage factor are obtained. The results indicate that the stress and fatigue intensity considering thermal stratification satisfies RCC-M criterion. (authors)

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

    Science.gov (United States)

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

    2018-02-01

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

  2. Magneto thermal convection in a compressible couple-stress fluid

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Mahinder [Lovely School of Science, Dept. of Mathematics, Lovely Professional Univ., Phagwara (India); Kumar, Pardeep [Dept. of Mathematics, ICDEOL, H.P. Univ., Shimla (India)

    2010-03-15

    The problem of thermal instability of compressible, electrically conducting couple-stress fluids in the presence of a uniform magnetic field is considered. Following the linearized stability theory and normal mode analysis, the dispersion relation is obtained. For stationary convection, the compressibility, couple-stress, and magnetic field postpone the onset of convection. Graphs have been plotted by giving numerical values of the parameters to depict the stability characteristics. The principle of exchange of stabilities is found to be satisfied. The magnetic field introduces oscillatory modes in the system that were non-existent in its absence. The case of overstability is also studied wherein a sufficient condition for the non-existence of overstability is obtained. (orig.)

  3. Modelling of thermal stress in vapor generator supports

    International Nuclear Information System (INIS)

    Halpert, S.; Vazquez, L.

    1997-01-01

    To assure safety and availability of a nuclear power plant components or equipment stress analysis are done. When thermal loads are involved it's necessary to know the temperature field of the component or equipment. This paper describes the structural analysis of a steam generator lug with thermal load including the model used for computer simulation and presents the evolution of the temperature profile, the stress intensity and principal stress during start up and shut down of a nuclear power reactor. Temperature field obtained from code calculation show good agreement with the experimental data while stress analysis results are in agreement with a preview estimation. (author) [es

  4. Non-linear elastic thermal stress analysis with phase changes

    International Nuclear Information System (INIS)

    Amada, S.; Yang, W.H.

    1978-01-01

    The non-linear elastic, thermal stress analysis with temperature induced phase changes in the materials is presented. An infinite plate (or body) with a circular hole (or tunnel) is subjected to a thermal loading on its inner surface. The peak temperature around the hole reaches beyond the melting point of the material. The non-linear diffusion equation is solved numerically using the finite difference method. The material properties change rapidly at temperatures where the change of crystal structures and solid-liquid transition occur. The elastic stresses induced by the transient non-homogeneous temperature distribution are calculated. The stresses change remarkably when the phase changes occur and there are residual stresses remaining in the plate after one cycle of thermal loading. (Auth.)

  5. Average thermal stress in the Al+SiC composite due to its manufacturing process

    International Nuclear Information System (INIS)

    Miranda, Carlos A.J.; Libardi, Rosani M.P.; Marcelino, Sergio; Boari, Zoroastro M.

    2013-01-01

    The numerical analyses framework to obtain the average thermal stress in the Al+SiC Composite due to its manufacturing process is presented along with the obtained results. The mixing of Aluminum and SiC powders is done at elevated temperature and the usage is at room temperature. A thermal stress state arises in the composite due to the different thermal expansion coefficients of the materials. Due to the particles size and randomness in the SiC distribution, some sets of models were analyzed and a statistical procedure used to evaluate the average stress state in the composite. In each model the particles position, form and size are randomly generated considering a volumetric ratio (VR) between 20% and 25%, close to an actual composite. The obtained stress field is represented by a certain number of iso stress curves, each one weighted by the area it represents. Systematically it was investigated the influence of: (a) the material behavior: linear x non-linear; (b) the carbide particles form: circular x quadrilateral; (c) the number of iso stress curves considered in each analysis; and (e) the model size (the number of particles). Each of above analyzed condition produced conclusions to guide the next step. Considering a confidence level of 95%, the average thermal stress value in the studied composite (20% ≤ VR ≤ 25%) is 175 MPa with a standard deviation of 10 MPa. Depending on its usage, this value should be taken into account when evaluating the material strength. (author)

  6. FEM thermal and stress analysis of bonded GaN-on-diamond substrate

    Directory of Open Access Journals (Sweden)

    Wenbo Zhai

    2017-09-01

    Full Text Available A three-dimensional thermal and stress analysis of bonded GaN on diamond substrate is investigated using finite element method. The transition layer thickness, thermal conductivity of transition layer, diamond substrate thickness and the area ratio of diamond and GaN are considered and treated appropriately in the numerical simulation. The maximum channel temperature of GaN is set as a constant value and its corresponding heat power densities under different conditions are calculated to evaluate the influences that the diamond substrate and transition layer have on GaN. The results indicate the existence of transition layer will result in a decrease in the heat power density and the thickness and area of diamond substrate have certain impact on the magnitude of channel temperature and stress distribution. Channel temperature reduces with increasing diamond thickness but with a decreasing trend. The stress is reduced by increasing diamond thickness and the area ratio of diamond and GaN. The study of mechanical and thermal properties of bonded GaN on diamond substrate is useful for optimal designs of efficient heat spreader for GaN HEMT.

  7. Thermal properties of graphene under tensile stress

    Science.gov (United States)

    Herrero, Carlos P.; Ramírez, Rafael

    2018-05-01

    Thermal properties of graphene display peculiar characteristics associated to the two-dimensional nature of this crystalline membrane. These properties can be changed and tuned in the presence of applied stresses, both tensile and compressive. Here, we study graphene monolayers under tensile stress by using path-integral molecular dynamics (PIMD) simulations, which allows one to take into account quantization of vibrational modes and analyze the effect of anharmonicity on physical observables. The influence of the elastic energy due to strain in the crystalline membrane is studied for increasing tensile stress and for rising temperature (thermal expansion). We analyze the internal energy, enthalpy, and specific heat of graphene, and compare the results obtained from PIMD simulations with those given by a harmonic approximation for the vibrational modes. This approximation turns out to be precise at low temperatures, and deteriorates as temperature and pressure are increased. At low temperature, the specific heat changes as cp˜T for stress-free graphene, and evolves to a dependence cp˜T2 as the tensile stress is increased. Structural and thermodynamic properties display non-negligible quantum effects, even at temperatures higher than 300 K. Moreover, differences in the behavior of the in-plane and real areas of graphene are discussed, along with their associated properties. These differences show up clearly in the corresponding compressibility and thermal expansion coefficient.

  8. Stress in piezoelectric hollow sphere with thermal gradient

    International Nuclear Information System (INIS)

    Saadatfar, M.; Rastgoo, A.

    2008-01-01

    The piezoelectric phenomenon has been exploited in science and engineering for decades. Recent advances in smart structures technology have led to a resurgence of interest in piezoelectricity, and in particular, in the solution of fundamental boundary value problems. In this paper, we develop an analytic solution to the axisymmetric problem of a radially polarized, spherically isotropic piezoelectric hollow sphere. The sphere is subjected to uniform internal pressure, or uniform external pressure, or both and thermal gradient. There is a constant thermal difference between its inner and outer surfaces. An analytic solution to the governing equilibrium equations (a coupled system of second-order ordinary differential equations) is obtained. On application of the boundary conditions, the problem is reduced to solving a system of linear algebraic equations. Finally, the stress distributions in the sphere are obtained numerically for two piezoceramics

  9. Assessment of thermal load on transported goats administered with ascorbic acid during the hot-dry conditions

    Science.gov (United States)

    Minka, N. S.; Ayo, J. O.

    2012-03-01

    The major factor in the induction of physiological stress during road transportation of livestock is the complex fluctuations of the thermal transport microenvironment, encountered when animals are transported across different ecological zones. Recommended guidelines on optimum "on-board" conditions in which goats should be transported are lacking, and there are no acceptable ranges and limits for the thermal loads to which goats may be subjected during long-distance road transportation in hot-dry conditions. Panting score (PS), rectal temperature (RT), heart rate (HR) and respiratory rate (RR) were employed as reliable stress indices to assess the effects of different thermal loads, measured as temperature humidity index (THI), encountered in the vehicle during 12 h of road transportation of 40 goats, and to suggest the administration of 100 mg/kg body weight of ascorbic acid (AA) as an ameliorating agent. The results obtained showed that the PS, RT, HR and RR rose above normal reference values with increase in the THI and journey duration. The rise in PS value, which is a visual indicator of the severity of thermal load, was the most pronounced. The results suggest that values of THI in the vehicle up to 94.6 constitute no risk, while at of 100 it presents a moderate risk and above 100 may result in severe stress. The relationships between the thermal load and the physiological variables were positive and significant ( P goats. The results demonstrated that administration of 100 mg/kg body weight of AA before road transportation mitigated the risk of adverse effects of high THI values and other stress factors due to road transportation in goats.

  10. Thermal mechanical stress modeling of GCtM seals

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Steve Xunhu [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Chambers, Robert [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    Finite-element thermal stress modeling at the glass-ceramic to metal (GCtM) interface was conducted assuming heterogeneous glass-ceramic microstructure. The glass-ceramics were treated as composites consisting of high expansion silica crystalline phases dispersed in a uniform residual glass. Interfacial stresses were examined for two types of glass-ceramics. One was designated as SL16 glass -ceramic, owing to its step-like thermal strain curve with an overall coefficient of thermal expansion (CTE) at 16 ppm/ºC. Clustered Cristobalite is the dominant silica phase in SL16 glass-ceramic. The other, designated as NL16 glass-ceramic, exhibited clusters of mixed Cristobalite and Quartz and showed a near-linear thermal strain curve with a same CTE value.

  11. Numerical methods for calculating thermal residual stresses and hydrogen diffusion

    International Nuclear Information System (INIS)

    Leblond, J.B.; Devaux, J.; Dubois, D.

    1983-01-01

    Thermal residual stresses and hydrogen concentrations are two major factors intervening in cracking phenomena. These parameters were numerically calculated by a computer programme (TITUS) using the FEM, during the deposition of a stainless clad on a low-alloy plate. The calculation was performed with a 2-dimensional option in four successive steps: thermal transient calculation, metallurgical transient calculation (determination of the metallurgical phase proportions), elastic-plastic transient (plain strain conditions), hydrogen diffusion transient. Temperature and phase dependence of hydrogen diffusion coefficient and solubility constant. The following results were obtained: thermal calculations are very consistent with experiments at higher temperatures (due to the introduction of fusion and solidification latent heats); the consistency is not as good (by 70 degrees) for lower temperatures (below 650 degrees C); this was attributed to the non-introduction of gamma-alpha transformation latent heat. The metallurgical phase calculation indicates that the heat affected zone is almost entirely transformed into bainite after cooling down (the martensite proportion does not exceed 5%). The elastic-plastic calculations indicate that the stresses in the heat affected zone are compressive or slightly tensile; on the other hand, higher tensile stresses develop on the boundary of the heat affected zone. The transformation plasticity has a definite influence on the final stress level. The return of hydrogen to the clad during the bainitic transformation is but an incomplete phenomenon and the hydrogen concentration in the heat affected zone after cooling down to room temperature is therefore sufficient to cause cold cracking (if no heat treatment is applied). Heat treatments are efficient in lowering the hydrogen concentration. These results enable us to draw preliminary conclusions on practical means to avoid cracking. (orig.)

  12. X-ray diffraction study of thermally and stress-induced phase transformations in single crystalline Ni-Mn-Ga alloys

    International Nuclear Information System (INIS)

    Martynov, V.V.

    1995-01-01

    Using in-situ single crystal X-ray diffraction methods, thermally- and stress-induced crystal structure evolution was investigated in two Ni-Mn-Ga Heusler-type alloys. For the 51at.%Ni-24at.%Mn-25at.%Ga alloy it was found that application of external stress in a temperature range ∼20 C above the M s at first causes intensity changes of X-ray diffuse scattering peaks in β-phase. Further stressing results in stress-induced phase transformations and under the appropriate conditions three successive martensitic transformations (one is parent-to-martensite and two are martensite-to-martensite transformations) can be stress induced. Of these only the parent-to-martensite transformation can be thermally-induced. Two successive structural transformations (thermally-induced parent-to-martensite and stress-induced martensite-to-martensite transformations) were found in 52at.%Ni-25at.%Mn-23at.%Ga alloy. Crystal structure, lattice parameters, type of modulation, and the length of modulation period for all martensites were identified. (orig.)

  13. Transient thermal stress distribution in a circular pipe heated externally with a periodically moving heat source

    International Nuclear Information System (INIS)

    Özışık, Gülşah; Genç, M. Serdar; Yapıcı, Hüseyin

    2012-01-01

    This study presents the effects of periodically moving heat source on a circular steel pipe heated partly from its outer surface under stagnant ambient conditions. While the pipe is heated with this heat source applied on a certain section having a thickness of heat flux, the water flows through it to transfer heat. It is assumed that the flow is a fully-developed laminar flow. The heat source moves along from one end of the outer to the other end with a constant speed and then returns to the first end with the same speed. It is assumed that the heat transfer rate has a constant value, and that the thermo-physical properties of the steel do not change with temperature (elastic analysis). The numerical calculations have been performed individually for a wide range of thermal conductivity of steel and for different thicknesses of heat flux. The moving heat source produces the non-uniform temperature gradient and the non-uniform effective thermal stress, and when it arrives at the ends of the pipe, the temperature and effective thermal stress ratio profiles rise more excessively. The tangential component is more dominant in the effective thermal stress than the radial component. Highlights: ► Moving heat source produces non-uniform temperature gradients and thermal stresses. ► When moving heat source arrives at ends of pipe, temperature gradients rise excessively. ► With increasing of heat flux thickness and thermal conductivity, the temperature gradients reduce. ► Temperature gradients in thermal boundary layers slightly increase. ► Tangential component is more dominant in thermal stress than radial component.

  14. A numerical analysis method on thermal and shrinkage stress of concrete

    International Nuclear Information System (INIS)

    Takiguchi, Katsuki; Hotta, Hisato

    1991-01-01

    Thermal stress often causes cracks in large scale concrete such as that for dam construction. The drying shrinkage of concrete causes cracks in concrete structures. These thermal stress and drying shrinkage stress may be the main reasons cracks occur in concrete, however there is few research which dealt with both stresses together. The problems on the thermal stress and the drying shrinkage are not independent, and should be dealt with together, because both temperature and water content of concrete affect hydration reaction, and the degree of hydration determines all the characteristics of concrete at early age. In this study, the degree of hydration is formulated experimentally, and a numerical stress analysis method taking the hydration reaction in consideration is presented. The formulation of the rate of hydration reaction, the method of analyzing thermal and drying shrinkage stresses, the analytical results for a concrete column and the influence that continuous load exerted to the tensile strength of concrete are reported. The relatively high stress nearly equal to the tensile strength of concrete arises near the surface. (K.I.)

  15. The application of fracture mechanics in thermally stressed structures

    International Nuclear Information System (INIS)

    Cesari, F.; Maitan, A.; Hellen, T.K.

    1981-03-01

    There is considerable interest in calculating stress intensity factors at crack tips in thermally stressed structures, particularly in the power generation industry where the safe operation of both conventional and nuclear plant is founded on rigorous safety cases. Analytical methods to study such problems are of limited scope, although they can be extended by introducing numerical techniques. Purpose built numerical methods, however, offer a much greater and more accurate solution capability and in particular the finite element method is well advanced. Such methods are described, including how stress intensity factors can be obtained from the finite element results. They are then applied to a range of thermally stressed problems including plates with central cracks and cylinders with axial and circumferential cracks. Both steady state and transient temperature distributions arising from typical thermal shocks are considered. (author)

  16. Combined effects of thermal stress and Cd on lysosomal biomarkers and transcription of genes encoding lysosomal enzymes and HSP70 in mussels, Mytilus galloprovincialis

    Energy Technology Data Exchange (ETDEWEB)

    Izagirre, Urtzi; Errasti, Aitzpea; Bilbao, Eider; Múgica, María; Marigómez, Ionan, E-mail: ionan.marigomez@ehu.es

    2014-04-01

    Highlights: • Thermal stress and Cd caused lysosomal enlargement and membrane destabilisation. • hex, gusb and ctsl but not hsp70 were up-regulated at elevated temperature but down-regulated by Cd. • Thermal stress influenced lysosomal responses to Cd exposure. • The presence of Cd jeopardised responsiveness against thermal stress. - Abstract: In estuaries and coastal areas, intertidal organisms may be subject to thermal stress resulting from global warming, together with pollution. In the present study, the combined effects of thermal stress and exposure to Cd were investigated in the endo-lysosomal system of digestive cells in mussels, Mytilus galloprovincialis. Mussels were maintained for 24 h at 18 °C and 26 °C seawater temperature in absence and presence of 50 μg Cd/L seawater. Cadmium accumulation in digestive gland tissue, lysosomal structural changes and membrane stability were determined. Semi-quantitative PCR was applied to reveal the changes elicited by the different experimental conditions in hexosaminidase (hex), β-glucuronidase (gusb), cathepsin L (ctsl) and heat shock protein 70 (hsp70) gene transcription levels. Thermal stress provoked lysosomal enlargement whilst Cd-exposure led to fusion of lysosomes. Both thermal stress and Cd-exposure caused lysosomal membrane destabilisation. hex, gusb and ctsl genes but not hsp70 gene were transcriptionally up-regulated as a result of thermal stress. In contrast, all the studied genes were transcriptionally down-regulated in response to Cd-exposure. Cd bioaccumulation was comparable at 18 °C and 26 °C seawater temperatures but interactions between thermal stress and Cd-exposure were remarkable both in lysosomal biomarkers and in gene transcription. hex, gusb and ctsl genes, reacted to elevated temperature in absence of Cd but not in Cd-exposed mussels. Therefore, thermal stress resulting from global warming might influence the use and interpretation of lysosomal biomarkers in marine pollution

  17. Laser-induced cracks in ice due to temperature gradient and thermal stress

    Science.gov (United States)

    Yang, Song; Yang, Ying-Ying; Zhang, Jing-Yuan; Zhang, Zhi-Yan; Zhang, Ling; Lin, Xue-Chun

    2018-06-01

    This work presents the experimental and theoretical investigations on the mechanism of laser-induce cracks in ice. The laser-induced thermal gradient would generate significant thermal stress and lead to the cracking without thermal melting in the ice. The crack density induced by a pulsed laser in the ice critically depends on the laser scanning speed and the size of the laser spot on the surface, which determines the laser power density on the surface. A maximum of 16 cracks within an area of 17 cm × 10 cm can be generated when the laser scanning speed is at 10 mm/s and the focal point of the laser is right on the surface of the ice with a laser intensity of ∼4.6 × 107 W/cm2. By comparing the infrared images of the ice generated at various experimental conditions, it was found that a larger temperature gradient would result in more laser-induced cracks, while there is no visible melting of the ice by the laser beam. The data confirm that the laser-induced thermal stress is the main cause of the cracks created in the ice.

  18. Mitigation method of thermal transient stress by thermalhydraulic-structure total analysis

    International Nuclear Information System (INIS)

    Kasahara, Naoto; Jinbo, Masakazu; Hosogai, Hiromi

    2003-01-01

    This study proposes a rational evaluation and mitigation method of thermal transient loads in fast reactor components by utilizing relationships among plant system parameters and stresses induced by thermal transients of plants. A thermalhydraulic-structure total analysis procedure helps us to grasp relationship among system parameters and thermal stresses. Furthermore, it enables mitigation of thermal transient loads by adjusting system parameters. In order to overcome huge computations, a thermalhydraulic-structure total analysis code and the Design of Experiments methodology are utilized. The efficiency of the proposed mitigation method is validated through thermal stress evaluation of an intermediate heat exchanger in Japanese demonstration fast reactor. (author)

  19. Thermal stresses in composite tubes using complementary virtual work

    Science.gov (United States)

    Hyer, M. W.; Cooper, D. E.

    1988-01-01

    This paper addresses the computation of thermally induced stresses in layered, fiber-reinforced composite tubes subjected to a circumferential gradient. The paper focuses on using the principle of complementary virtual work, in conjunction with a Ritz approximation to the stress field, to study the influence on the predicted stresses of including temperature-dependent material properties. Results indicate that the computed values of stress are sensitive to the temperature dependence of the matrix-direction compliance and matrix-direction thermal expansion in the plane of the lamina. There is less sensitivity to the temperature dependence of the other material properties.

  20. Lipid biomarkers in Symbiodinium dinoflagellates: new indicators of thermal stress

    KAUST Repository

    Kneeland, J.

    2013-08-30

    Lipid content and fatty acid profiles of corals and their dinoflagellate endosymbionts are known to vary in response to high-temperature stress. To better understand the heat-stress response in these symbionts, we investigated cultures of Symbiodinium goreauii type C1 and Symbiodinium sp. clade subtype D1 grown under a range of temperatures and durations. The predominant lipids produced by Symbiodinium are palmitic (C16) and stearic (C18) saturated fatty acids and their unsaturated analogs, the polyunsaturated fatty acid docosahexaenoic acid (C22:6, n-3; DHA), and a variety of sterols. Prolonged exposure to high temperature causes the relative amount of unsaturated acids within the C18 fatty acids in Symbiodinium tissue to decrease. Thermal stress also causes a decrease in abundance of fatty acids relative to sterols, as well as the more specific ratio of DHA to an algal 4-methyl sterol. These shifts in fatty acid unsaturation and fatty acid-to-sterol ratios are common to both types C1 and D1, but the apparent thermal threshold of lipid changes is lower for type C1. This work indicates that ratios among free fatty acids and sterols in Symbiodinium can be used as sensitive indicators of thermal stress. If the Symbiodinium lipid stress response is unchanged in hospite, the algal heat-stress biomarkers we have identified could be measured to detect thermal stress within the coral holobiont. These results provide new insights into the potential role of lipids in the overall Symbiodinium thermal stress response. © 2013 Springer-Verlag Berlin Heidelberg.

  1. Thermal stress in flexible interdigital transducers with anisotropic electroactive cellulose substrates

    Science.gov (United States)

    Yoon, Sean J.; Kim, Jung Woong; Kim, Hyun Chan; Kang, Jinmo; Kim, Jaehwan

    2017-12-01

    Thermal stress in flexible interdigital transducers a reliability concern in the development of flexible devices, which may lead to interface delamination, stress voiding and plastic deformation. In this paper, a mathematical model is presented to investigate the effect of material selections on the thermal stress in interdigital transducers. We modified the linear relationships in the composite materials theory with the effect of high curvature, anisotropic substrate and small substrate thickness. We evaluated the thermal stresses of interdigital transducers, fabricated with various electrodes, insulators and substrate materials for the comparison. The results show that, among various insulators, organic polymer developed the highest stress level while oxide showed the lowest stress level. Aluminium shows a higher stress level and curvature as an electrode than gold. As substrate materials, polyimide and electroactive cellulose show similar stress levels except the opposite sign convention to each other. Polyimide shows positive curvatures while electroactive cellulose shows negative curvatures, which is attributed to the stress and thermal expansion state of the metal/insulator composite. The results show that the insulator is found to be responsible for the confinement across the metal lines while the substrate is responsible for the confinement along the metal lines.

  2. Effect of the Modification of the Start-Up Sequence on the Thermal Stresses for a Microgas Turbine

    Directory of Open Access Journals (Sweden)

    Oscar Tenango-Pirin

    2016-01-01

    Full Text Available Microgas turbines (MGT are an alternative for small-scale energy production; however, their small size becomes a drawback since it enhances the heat transfer among their components. Moreover, heat transfer drives to temperature gradients which become higher during transient cycles like start-up. The influence of different start-up curves on temperature and thermal stresses of a microgas turbine was investigated. Stationary and rotational blades of the turbine were numerically simulated using CFD and FEM commercial codes. Conjugated heat transfer cases were solved for obtaining heat transfer from fluid toward the blades. Changes of temperature gradients within the blades during the start-ups were calculated under transient state with boundary conditions according to each curve to assess accurate thermal stresses calculations. Results showed that the modification of the start-up curves had an impact on the thermal stresses levels and on the time when highest stresses appeared on each component. Furthermore, zones highly stressed were located near the constraints of blades where thermal strains are restricted. It was also found that the curve that had a warming period at the beginning of the start-up allowed reducing the peaks of stresses making it more feasible and safer for the turbine start-up operation.

  3. Thermal Stress Analysis of Medium-Voltage Converters for Smart Transformers

    DEFF Research Database (Denmark)

    Andresen, Markus; Ma, Ke; De Carne, Giovanni

    2017-01-01

    . To address this concern, this work conducts thermal stress analysis for a modular multilevel converter (MMC), which is a promising solution for the medium voltage stage of the ST. The focus is put on the mission profiles of the transformer and the impact on the thermal stress of power semiconductor devices......A smart transformer (ST) can take over an important managing role in the future electrical distribution grid system and can provide many advanced grid services compared to the traditional transformer. However, the risk is that the advanced functionality is balanced out by a lower reliability....... Normal operation at different power levels and medium voltage grid faults in a feeder fed by a traditional transformer are considered as well as the electrical and the thermal stress of the disconnection and the reconnection procedures. For the validation, the thermal stress of one MMC cell is reproduced...

  4. Thermal stress prediction in mirror and multilayer coatings.

    Science.gov (United States)

    Cheng, Xianchao; Zhang, Lin; Morawe, Christian; Sanchez Del Rio, Manuel

    2015-03-01

    Multilayer optics for X-rays typically consist of hundreds of periods of two types of alternating sub-layers which are coated on a silicon substrate. The thickness of the coating is well below 1 µm (tens or hundreds of nanometers). The high aspect ratio (∼10(7)) between the size of the optics and the thickness of the multilayer can lead to a huge number of elements (∼10(16)) for the numerical simulation (by finite-element analysis using ANSYS code). In this work, the finite-element model for thermal-structural analysis of multilayer optics has been implemented using the ANSYS layer-functioned elements. The number of meshed elements is considerably reduced and the number of sub-layers feasible for the present computers is increased significantly. Based on this technique, single-layer coated mirrors and multilayer monochromators cooled by water or liquid nitrogen are studied with typical parameters of heat-load, cooling and geometry. The effects of cooling-down of the optics and heating of the X-ray beam are described. It is shown that the influences from the coating on temperature and deformation are negligible. However, large stresses are induced in the layers due to the different thermal expansion coefficients between the layer and the substrate materials, which is the critical issue for the survival of the optics. This is particularly true for the liquid-nitrogen cooling condition. The material properties of thin multilayer films are applied in the simulation to predict the layer thermal stresses with more precision.

  5. Thermal stresses in hexagonal materials - heat treatment influence on their mechanical behaviour

    International Nuclear Information System (INIS)

    Gloaguen, D.; Freour, S.; Guillen, R.; Royer, J.; Francois, M.

    2004-01-01

    Internal stresses due to anisotropic thermal and plastic properties were investigated in rolled zirconium and titanium. The thermal stresses induced by a cooling process were predicted using a self-consistent model and compared with experimental results obtained by X-ray diffraction. The study of the elastoplastic response during uniaxial loading was performed along the rolling and the transverse direction of the sheet, considering the influence of the texture and the thermal stresses on the mechanical behaviour. An approach in order to determine the thermal behaviour of phases embedded in two-phase materials is also presented. For zirconium, the residual stresses due to thermal anisotropy are rather important (equivalent to 35% of the yield stress) and consequently they play an important role on the elastoplastic transition contrary to titanium. The study of two-phase material shows the influence and the interaction of the second phase on the thermal behaviour in the studied phase

  6. Verification of thermal-irradiation stress analytical code VIENUS of graphite block

    International Nuclear Information System (INIS)

    Iyoku, Tatsuo; Ishihara, Masahiro; Shiozawa, Shusaku; Shirai, Hiroshi; Minato, Kazuo.

    1992-02-01

    The core graphite components of the High Temperature Engineering Test Reactor (HTTR) show both the dimensional change (irradiation shrinkage) and creep behavior due to fast neutron irradiation under the temperature and the fast neutron irradiation conditions of the HTTR. Therefore, thermal/irradiation stress analytical code, VIENUS, which treats these graphite irradiation behavior, is to be employed in order to design the core components such as fuel block etc. of the HTTR. The VIENUS is a two dimensional finite element viscoelastic stress analytical code to take account of changes in mechanical properties, thermal strain, irradiation-induced dimensional change and creep in the fast neutron irradiation environment. Verification analyses were carried out in order to prove the validity of this code based on the irradiation tests of the 8th OGL-1 fuel assembly and the fuel element of the Peach Bottom reactor. This report describes the outline of the VIENUS code and its verification analyses. (author)

  7. Thermal-stress fatigue behavior of twenty-six superalloys

    Science.gov (United States)

    Bizon, P. T.; Spera, D. A.

    1976-01-01

    The comparative thermal-stress fatigue resistances of 26 nickeland cobalt-base alloys were determined by fluidized bed tests. Cycles to cracking differed by almost three orders of magnitude for these materials, with directional solidification and surface protection showing definite benefit. The alloy-coating combination with the highest thermal-stress fatigue resistance was directionally solidified NASA TAZ-8A with an RT-SP coating. Its oxidation resistance was also excellent, showing approximately a 1/2 percent weight loss after 14,000 fluidized bed cycles.

  8. Prognostics Approach for Power MOSFET Under Thermal-Stress

    Science.gov (United States)

    Galvan, Jose Ramon Celaya; Saxena, Abhinav; Kulkarni, Chetan S.; Saha, Sankalita; Goebel, Kai

    2012-01-01

    The prognostic technique for a power MOSFET presented in this paper is based on accelerated aging of MOSFET IRF520Npbf in a TO-220 package. The methodology utilizes thermal and power cycling to accelerate the life of the devices. The major failure mechanism for the stress conditions is dieattachment degradation, typical for discrete devices with leadfree solder die attachment. It has been determined that dieattach degradation results in an increase in ON-state resistance due to its dependence on junction temperature. Increasing resistance, thus, can be used as a precursor of failure for the die-attach failure mechanism under thermal stress. A feature based on normalized ON-resistance is computed from in-situ measurements of the electro-thermal response. An Extended Kalman filter is used as a model-based prognostics techniques based on the Bayesian tracking framework. The proposed prognostics technique reports on preliminary work that serves as a case study on the prediction of remaining life of power MOSFETs and builds upon the work presented in [1]. The algorithm considered in this study had been used as prognostics algorithm in different applications and is regarded as suitable candidate for component level prognostics. This work attempts to further the validation of such algorithm by presenting it with real degradation data including measurements from real sensors, which include all the complications (noise, bias, etc.) that are regularly not captured on simulated degradation data. The algorithm is developed and tested on the accelerated aging test timescale. In real world operation, the timescale of the degradation process and therefore the RUL predictions will be considerable larger. It is hypothesized that even though the timescale will be larger, it remains constant through the degradation process and the algorithm and model would still apply under the slower degradation process. By using accelerated aging data with actual device measurements and real

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  10. Measurement and analysis of temperature, strain and stress of foundation mat concrete in nuclear and thermal power stations

    International Nuclear Information System (INIS)

    Haraguchi, Akira; Yamakawa, Hidetsugu; Abe, Hirotoshi

    1981-01-01

    The problems of the thermal stress in concrete structures are roughly divided into the initial stress due to setting heat and the stress due to external temperature after hardening. The initial stress exists in every concrete structure, and it is usually neglected in beams and columns, but it must be taken into account in case of the foundation mat structures in nuclear power stations, for example. In this paper, (1) the results of measurement of temperature, strain and stress in each lift at the time of and after placing concrete in the foundation mat of a nuclear power station and the comparison of them with the results of analysis, (2) the results of measurement of the temperature and stress in a foundation mat, which was carried out to rationalize the design method for the raft type foundation mats in thermal power stations, and (3) the results of examination on the analysis model, external force conditions and boundary conditions used for the design are reported. The analysis method for temperature and thermal stress by finite element method, developed by the Central Research Institute of Electric Power Industry, can take the changes in the heat of hydration in placed concrete, the creep phenomenon of concrete and the restraint at construction joints in consideration. It is necessary to collect the data on the measurement of mat concrete and to develop the accurate analysis method. (Kako, I.)

  11. Stress relaxation of thermally bowed fuel pins

    International Nuclear Information System (INIS)

    Crossland, I.G.; Speight, M.V.

    1983-01-01

    The presence of cross-pin temperature gradients in nuclear reactor fuel pins produces differential thermal expansion which, in turn, causes the fuel pin to bow elastically. If the pin is restrained in any way, such thermal bowing causes the pin to be stressed. At high temperatures these stresses can relax by creep and it is shown here that this causes the pin to suffer an additional permanent deflection, so that when the cross-pin temperature difference is removed the pin remains bowed. By representing the cylindrical pin by an equivalent I-beam, the present work examines this effect when it takes place by secondary creep. Two restraint systems are considered, and it is demonstrated that the rate of relaxation depends mainly upon the creep equation, and hence the temperature, and also the magnitude of the initial stresses. (author)

  12. Creep and Environmental Durability of EBC/CMCs Under Imposed Thermal Gradient Conditions

    Science.gov (United States)

    Appleby, Matthew; Morscher, Gregory N.; Zhu, Dongming

    2013-01-01

    Interest in SiC fiber-reinforced SiC ceramic matrix composite (CMC) environmental barrier coating (EBC) systems for use in high temperature structural applications has prompted the need for characterization of material strength and creep performance under complex aerospace turbine engine environments. Stress-rupture tests have been performed on SiC/SiC composites systems, with varying fiber types and coating schemes to demonstrate material behavior under isothermal conditions. Further testing was conducted under exposure to thermal stress gradients to determine the effect on creep resistance and material durability. In order to understand the associated damage mechanisms, emphasis is placed on experimental techniques as well as implementation of non-destructive evaluation; including electrical resistivity monitoring. The influence of environmental and loading conditions on life-limiting material properties is shown.

  13. Dynamic, large-deflection, inelastic and thermal stress analysis by the finite element method

    International Nuclear Information System (INIS)

    Haisler, W.E.; Stricklin, J.A.

    1975-01-01

    A finite element theory and computer program have been developed for predicting the dynamic, large displacement, inelastic and thermal response of stiffened and layered structures. The dependence of material properties on temperature is explicitly accounted for and any arbitrary, transient mechanical or thermal load history is allowed. The shell may have internal or external stiffeners and be constructed with up to three layers. The equations of motion are developed by using the pseudo force approach to represent all nonlinearities and are then solved by using either the Houbolt method or central differences. Moderately large rotations are allowed. The program is based on an incremental theory of plasticity using the Von Mises yield condition and associated flow rule. The post yield or work-hardening behavior is idealized with either the isotropic hardening or mechanical sublayer models. Two models are utilized since it has been found through comparison with experimental results that isotropic hardening is best for simple loading conditions while the mechanical sublayer model is better for reverse and cyclic loading. Strain-rate effects are also accounted for in the program by using a power-law type model based on the strain rate. The dependence of material properties on temperature is taken into account in the pseudo forces. Young's modulus, Poisson's ratio, thermal coefficient of expansion, the yield stress, and the entire stress strain curve are treated as functions of the applied temperature. Containment vessels subjected to transient and shock-type mechanical and thermal loads have been analyzed

  14. Thermal stress comparison in modular power converter topologies for smart transformers in the electrical distribution system

    DEFF Research Database (Denmark)

    Andresen, Markus; Ma, Ke; Liserre, Marco

    2015-01-01

    A Smart Transformer (ST) can cover an important managing role in the future electrical distribution grid. For the moment, the reliability and cost are not competitive with traditional transformers and create a barrier for its application. This work conduct detail designs and analysis...... for a promising modular ST solution, which is composed of Modular Multi-level converter, Quad Active Bridge DC-DC converters, and two-level voltage source converters. The focus is put on the loading conditions and thermal stress of power semiconductor devices in order to discover critical parts of the whole...... system when performing various mission profiles in the realistic distribution grid. It is concluded that the thermal stress for all stages is low during normal operation and especially the isolation stage is stressed least....

  15. Predicted thermal and stress environments in the vicinity of repository openings

    International Nuclear Information System (INIS)

    Bauer, S.J.; Hardy, M.P.; Lin, M.

    1991-01-01

    An understanding of the thermal and stress environment in the vicinity of repository openings is important for preclosure performance considerations and worker health and safety considerations for the proposed high-level radioactive waste repository at Yucca Mountain. This paper presents the results of two and three dimensional numerical analyses which have determined the thermal and stress environments for typical repository openings. In general, it is predicted that openings close to heat sources attain high temperatures and experience a significant stress increase. Openings away from heat sources experience more uniform temperature changes and experience a stress change which results in part from a far-field thermal loading

  16. Human biometeorological analysis of the thermal conditions of the hot Turkish city of Şanliurfa

    Science.gov (United States)

    Toy, Süleyman; Aytaç, Ahmet Serdar; Kántor, Noémi

    2018-01-01

    This paper offers a throughout human biometeorological assessment about the thermal conditions of Şanliurfa in one of the hottest parts of Turkey, in the hottest period of the year (from April to October), and a comparative analysis of three built-up types (urban, suburban and rural). Therefore, the values of physiologically equivalent temperature (PET), one of the most extensively used indices, were calculated from basic climate data with the help of the RayMan model. It was found by regarding the resulted mean PET values and the occurrence frequency of extreme heat stress periods (PET values above 41 °C) that the urban area exhibited the most unfavourable properties, followed by the suburban and rural areas. We also found very severe heat stress conditions in the summer, which may be explained by the torrid and arid climate, calm air conditions and the lack of abundant vegetation. Aiming to optimise human thermal conditions, thereby improving local life quality and facilitating international tourism, increment of vegetated areas and water surfaces would be required and, of course, highlighting the traditional methods taking into account the important aspects of sustainability.

  17. Three-dimensional modelling of thermal stress in floating zone silicon crystal growth

    Science.gov (United States)

    Plate, Matiss; Krauze, Armands; Virbulis, Jānis

    2018-05-01

    During the growth of large diameter silicon single crystals with the industrial floating zone method, undesirable level of thermal stress in the crystal is easily reached due to the inhomogeneous expansion as the crystal cools down. Shapes of the phase boundaries, temperature field and elastic material properties determine the thermal stress distribution in the solid mono crystalline silicon during cylindrical growth. Excessive stress can lead to fracture, generation of dislocations and altered distribution of intrinsic point defects. Although appearance of ridges on the crystal surface is the decisive factor of a dislocation-free growth, the influence of these ridges on the stress field is not completely clear. Here we present the results of thermal stress analysis for 4” and 5” diameter crystals using a quasi-stationary three dimensional mathematical model including the material anisotropy and the presence of experimentally observed ridges which cannot be addressed with axis-symmetric models. The ridge has a local but relatively strong influence on thermal stress therefore its relation to the origin of fracture is hypothesized. In addition, thermal stresses at the crystal rim are found to increase for a particular position of the crystal radiation reflector.

  18. Effect of hall currents on thermal instability of dusty couple stress fluid

    Directory of Open Access Journals (Sweden)

    Aggarwal Amrish Kumar

    2016-09-01

    Full Text Available In this paper, effect of Hall currents on the thermal instability of couple-stress fluid permeated with dust particles has been considered. Following the linearized stability theory and normal mode analysis, the dispersion relation is obtained. For the case of stationary convection, dust particles and Hall currents are found to have destabilizing effect while couple stresses have stabilizing effect on the system. Magnetic field induced by Hall currents has stabilizing/destabilizing effect under certain conditions. It is found that due to the presence of Hall currents (hence magnetic field, oscillatory modes are produced which were non-existent in their absence.

  19. Thermal Stress Behavior of Micro- and Nano-Size Aluminum Films

    International Nuclear Information System (INIS)

    Hanabusa, T.; Kusaka, K.; Nishida, M.

    2008-01-01

    In-situ observation of thermal stresses in thin films deposited on silicon substrate was made by X-ray and synchrotron radiation. Specimens prepared in this experiment were micro- and nano-size thin aluminum films with and without passivation film. The thickness of the film was 1 micrometer for micro-size films and 10, 20 and 50 nanometer for nano-size films. The stress measurement in micro-size films was made by X-ray radiation whereas the measurement of nano-size films was made by synchrotron radiation. Residual stress measurement revealed tensile stresses in all as-deposited films. Thermal stresses were measured in a series of heating- and cooling-stage. Thermal stress behavior of micro-size films revealed hysteresis loop during a heating and cooling process. The width of a hysteresis loop was larger in passivated film that unpassivated film. No hysteresis loops were observed in nano-size films with SiO 2 passivation. Strengthning mechanism in thin films was discussed on a passivation film and a film thickness

  20. Effect of Thermal Stresses on the Failure Criteria of Fiber Composites

    DEFF Research Database (Denmark)

    Leong, Martin Klitgaard; Sankar, Bhavani V.

    2010-01-01

    , the latter, called micro-thermal stresses, has not been given much attention. In this paper the Direct Micromechanics Method is used to investigate the effects of micro-thermal stresses on the failure envelope of composites. Using FEA the unit-cell of the composite is analyzed. Assuming the failure criteria...... for the fiber and matrix are known, the exact failure envelope is developed. Using the micromechanics results, the Tsai-Wu failure envelope is modified to account for the micro-thermal stresses. The approach is demonstrated using two example structures at cryogenic temperature....

  1. Analysis technology in the thick plate free drop impact, heat and thermal stress of the cask for radioactive material transport

    International Nuclear Information System (INIS)

    Lee, Dew Hey; Lee, Young Shin; Ryu, Chung Hyun; Kim, Hyun Su; Choi, Kyung Joo; Choi, Young Jin; Lee, Jae Hyung; Na, Jae Yun; Kim, Seong Jong

    2002-03-01

    In this study, The regulatory condition and analysis condition is analyzed for thick plate free drop, heat and thermal stress analysis to develop the safety assessment technology. Analysis is performed with finite element method which is one of the many analysis methods of the shipping cask. ANSYS, LS-DYNA3D and ABAQUS is suitable for thick plate free drop, heat and thermal stress analysis of the shipping cask. For the analysis model, the KSC-4 that is the shipping cask to transport spent nuclear fuel is investigated. The results of both LS-DYNA3D and ABAQUS for thick plate free drop and the results of ANSYS, LS-DYNA3D and ABAQUS for heat and thermal stress analysis is completely corresponded. And the integrity of the shipping cask is verified. Using this study, the reliable safety assessment technology is supplied to the staff. The efficient and reliable regulatory tasks is performed using the standard safety assessment technology

  2. Analysis technology in the thick plate free drop impact, heat and thermal stress of the cask for radioactive material transport

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dew Hey [Korea Institute of Nuclear and Safety, Taejon (Korea, Republic of); Lee, Young Shin; Ryu, Chung Hyun; Kim, Hyun Su; Choi, Kyung Joo; Choi, Young Jin; Lee, Jae Hyung; Na, Jae Yun; Kim, Seong Jong [Chungnam National Univ., Taejon (Korea, Republic of)

    2002-03-15

    In this study, The regulatory condition and analysis condition is analyzed for thick plate free drop, heat and thermal stress analysis to develop the safety assessment technology. Analysis is performed with finite element method which is one of the many analysis methods of the shipping cask. ANSYS, LS-DYNA3D and ABAQUS is suitable for thick plate free drop, heat and thermal stress analysis of the shipping cask. For the analysis model, the KSC-4 that is the shipping cask to transport spent nuclear fuel is investigated. The results of both LS-DYNA3D and ABAQUS for thick plate free drop and the results of ANSYS, LS-DYNA3D and ABAQUS for heat and thermal stress analysis is completely corresponded. And the integrity of the shipping cask is verified. Using this study, the reliable safety assessment technology is supplied to the staff. The efficient and reliable regulatory tasks is performed using the standard safety assessment technology.

  3. Thermal stress analysis of reactor containment building considering severe weather condition

    International Nuclear Information System (INIS)

    Lee, Yun; Kim, Yun-Yong; Hyun, Jung-Hwan; Kim, Do-Gyeum

    2014-01-01

    Highlights: • We examine that through-wall crack risk in cold weather is high. • It is predicted that cracking in concrete wall will not happen in hot region. • Cracking due to hydration heat can be controlled by appropriate curing condition. • Temperature differences between inner and outer face is relatively small in hot weather. - Abstract: Prediction of concrete cracking due to hydration heat in mass concrete such as reactor containment building (RCB) in nuclear power plant is a crucial issue in construction site. In this study, the numerical analysis for heat transfer and stress development is performed for the containment wall in RCB by considering the severe weather conditions. Finally, concrete cracking risk in hot and cold weather is discussed based on analysis results. In analyses considering severe weather conditions, it is found that the through-wall cracking risk in cold weather is high due to the abrupt temperature difference between inside concrete and the ambient air in cold region. In hot weather, temperature differences between inner and outer face is relatively small, and accordingly the relevant cracking risk is relatively low in contrast with cold weather

  4. Postpartum endocrine activities, metabolic attributes and milk yield are influenced by thermal stress in crossbred dairy cows.

    Science.gov (United States)

    Ihsanullah; Qureshi, Muhammad Subhan; Suhail, Syed Muhammad; Akhtar, Sohail; Khan, Rifat Ullah

    2017-09-01

    This study was conducted on 30 freshly parturated multiparous crossbred dairy cows possessing three levels of Holstein Frisian genetic makeup (62.5, 75.0, and 87.5%). Data on temperature humidity index (THI) were classified into comfortable (≤ 71), mild stress (72-79), moderate stress (80-89), and stressful (≥90) zone. Results showed that serum cortisol concentration increased significantly (P stressful condition irrespective of genetic makeup compared to the other zones. Daily milk yield (DMY) was significantly (P stressful condition. Triglyceride was significantly higher in cows with genetic makeup 87.5% compared to the others, while total serum protein was significantly (P stressful conditions. The mean concentration of cortisol and protein increased linearly from comfort to the stressful condition, while mean serum triglyceride, glucose, progesterone (P 4 ), and luteinizing hormone (LH) decreased by moving from comfort to stressful conditions. Results also indicated that higher cortisol level in higher grade crossbred cows was adversely associated with LH concentration and milk yield under thermal stress conditions. Greater triglyceride in high-grade crossbred (87.5%) cows indicates higher fat mobilization reflecting a negative energy balance. We concluded that heat stress increased blood cortisol and protein, and reduced milk yield in dairy cows irresptive of the genetic makeup. In addition, there was no significant difference in blood metabolites and daily milk yield in the different levels of genetic makeup cows.

  5. Concrete creep and thermal stresses:new creep models and their effects on stress development

    OpenAIRE

    Westman, Gustaf

    1999-01-01

    This thesis deals with the problem of creep in concrete and its influence on thermal stress development. New test frames were developed for creep of high performance concrete and for measurements of thermal stress development. Tests were performed on both normal strength and high performance concretes. Two new models for concrete creep are proposed. Firstly, a viscoelastic model, the triple power law, is supplemented with two additional functions for an improved modelling of the early age cre...

  6. Characteristics of six small heat shock protein genes from Bactrocera dorsalis: Diverse expression under conditions of thermal stress and normal growth.

    Science.gov (United States)

    Dou, Wei; Tian, Yi; Liu, Hong; Shi, Yan; Smagghe, Guy; Wang, Jin-Jun

    2017-11-01

    To explore the functions of small heat shock proteins (sHsps) in relation to thermal stress and development in Bactrocera dorsalis (Hendel), one of the most economically important pest species attacking a wide range of fruits and vegetables, six full-length cDNAs of sHsp genes (BdHsp17.7, 18.4, 20.4, 20.6, 21.6 and 23.8) were cloned, and the expression patterns in different developmental stages and tissues, as well as in response to both thermal and 20-hydroxyecdysone (20E) exposures, were examined using real time quantitative PCR. The open reading frames (ORFs) of six sHsps are 453, 489, 537, 543, 567 and 630bp in length, encoding proteins with molecular weights of 17.7, 18.4, 20.4, 20.6, 21.6 and 23.8kDa, respectively. BdHsp18.4 and BdHsp20.4 maintained lower expression levels in both eggs and larvae, whereas remarkably up-regulated after the larval-pupal transformation, suggesting that these two sHsps may be involved in metamorphosis. Significant tissue specificity exists among sHsps: the highest expression of BdHsp20.6 and BdHsp23.8 in the Malpighian tubules and ovary, respectively, versus a peak in the fat body for others. BdHsp20.4 and BdHsp20.6 were significantly up-regulated by thermal stress. In contrast, BdHsp18.4 and BdHsp23.8 reacted only to heat stress. BdHsp17.7 and BdHsp21.6 were insensitive to both heat and cold stresses. The degree of sHsps response depends on intensity of 20E treatment, i.e., dose and time. These results strongly suggest functional differentiation within the sHsp subfamily in B. dorsalis. The physiological function of sHsp members under thermal stress and normal growth remains the subjects of further investigation. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Stress and Thermal Analysis of the In-Vessel RMP Coils in HL-2M

    International Nuclear Information System (INIS)

    Cen Yishun; Li Qiang; Cai Lijun; Jiang Jiaming; Li Guangsheng; Liu Yi; Ding Yonghua

    2013-01-01

    A set of in-vessel resonant magnetic perturbation (RMP) coils for MHD instability suppression is proposed for the design of a HL-2M tokamak. Each coil is to be fed with a current of up to 5 kA, operated in a frequency range from DC to about 1 kHz. Stainless steel (SS) jacketed mineral insulated cables are proposed for the conductor of the coils. In-vessel coils must withstand large electromagnetic (EM) and thermal loads. The support, insulation and vacuum sealing in a very limited space are crucial issues for engineering design. Hence finite element calculations are performed to verify the design, optimize the support by minimizing stress caused by EM forces on the coil conductors and work out the temperature rise occurring on the coil in different working conditions, the corresponding thermal stress caused by the thermal expansion of materials is evaluated to be allowable. The techniques to develop the in-vessel RMP coils, such as support, insulation and cooling, are discussed

  8. Analysis of the Slab Temperature, Thermal Stresses and Fractures Computed with the Implementation of Local and Average Boundary Conditions in the Secondary Cooling Zones

    Directory of Open Access Journals (Sweden)

    Hadała B.

    2016-12-01

    Full Text Available The numerical simulations of the temperature fields have been accomplished for slab casting made of a low carbon steel. The casting process of slab of 1500 mm in width and 225 mm in height has been modeled. Two types of boundary condition models of heat transfer have been employed in numerical simulations. The heat transfer coefficient in the first boundary condition model was calculated from the formula which takes into account the slab surface temperature and water flow rate in each secondary cooling zone. The second boundary condition model defines the heat transfer coefficient around each water spray nozzle. The temperature fields resulting from the average in zones water flow rate and from the nozzles arrangement have been compared. The thermal stresses and deformations resulted from such temperature field have given higher values of fracture criterion at slab corners.

  9. Stress and Displacement Analysis of Microreactors during Thermal and Vacuum Loading

    Science.gov (United States)

    2017-09-07

    ARL-TR-8121 ● SEP 2017 US Army Research Laboratory Stress and Displacement Analysis of Microreactors during Thermal and Vacuum...is no longer needed. Do not return it to the originator. ARL-TR-8121 ● SEP 2017 US Army Research Laboratory Stress and...TITLE AND SUBTITLE Stress and Displacement Analysis of Microreactors during Thermal and Vacuum Loading 5a. CONTRACT NUMBER 5b. GRANT NUMBER

  10. Thermal stresses in an orthotropic rectangular plate with a rigid ribbonlike inclusion

    International Nuclear Information System (INIS)

    Sumi, N.

    1981-01-01

    On the basis of the complex variable method for determining the stationary two-dimensional thermal stresses, the thermal stresses in an orthotropic rectangular plate with a rigid ribbonlike inclusion under a steady state temperature field is considered. The solution is found by the analytic continuation argument and the modified mapping-collocation technique. Numerical results indicate a dependence of the orthotropic stress intensity factors on the thermal, elastic and geometrical constants over a certain parameter range. (orig.)

  11. Stress hysteresis during thermal cycling of plasma-enhanced chemical vapor deposited silicon oxide films

    Science.gov (United States)

    Thurn, Jeremy; Cook, Robert F.

    2002-02-01

    The mechanical response of plasma-enhanced chemical vapor deposited SiO2 to thermal cycling is examined by substrate curvature measurement and depth-sensing indentation. Film properties of deposition stress and stress hysteresis that accompanied thermal cycling are elucidated, as well as modulus, hardness, and coefficient of thermal expansion. Thermal cycling is shown to result in major plastic deformation of the film and a switch from a compressive to a tensile state of stress; both athermal and thermal components of the net stress alter in different ways during cycling. A mechanism of hydrogen incorporation and release from as-deposited silanol groups is proposed that accounts for the change in film properties and state of stress.

  12. Thermal stress analysis of gravity support system for ITER based on ANSYS

    International Nuclear Information System (INIS)

    Liang Shangming; Yan Xijiang; Huang Yufeng; Wang Xianzhou; Hou Binglin; Li Pengyuan; Jian Guangde; Liu Dequan; Zhou Caipin

    2009-01-01

    A method for building the finite element model of the gravity support system for International Thermonuclear Experimental Reactor (ITER) was proposed according to the characteristics of the gravity support system with the cyclic symmetry. A mesh dividing method, which has high precision and an acceptable calculating scale, was used, and a three dimensional finite element model for the toroidal 20 degree sector of the gravity support system was built by using ANSYS. Meantime, the steady-state thermal analysis and thermal-structural coupling analysis of the gravity support system were performed. The thermal stress distributions and the maximal thermal stress values of all parts of the gravity support system were obtained, and the stress intensity of parts of the gravity support system was analyzed. The results of thermal stress analysis lay the solid foundation for design and improvement for gravity supports system for ITER. (authors)

  13. Development of thermal stress screening method. Application of green function method

    International Nuclear Information System (INIS)

    Furuhashi, Ichiro; Shibamoto, Hiroshi; Kasahara, Naoto

    2004-01-01

    This work was achieved for the development of the screening method of thermal transient stresses in FBR components. We proposed an approximation method for evaluations of thermal stress under variable heat transfer coefficients (non-linear problems) using the Green functions of thermal stresses with constant heat transfer coefficients (linear problems). Detailed thermal stress analyses provided Green functions for a skirt structure and a tube-sheet of Intermediate Heat Exchanger. The upper bound Green functions were obtained by the analyses using those upper bound heat transfer coefficients. The medium and the lower bound Green functions were got by the analyses of those under medium and the lower bound heat transfer coefficients. Conventional evaluations utilized the upper bound Green functions. On the other hand, we proposed a new evaluation method by using the upper bound, medium and the lower bound Green functions. The comparison of above results gave the results as follows. The conventional evaluations were conservative and appropriate for the cases under one fluid thermal transient structure such as the skirt. The conventional evaluations were generally conservative for the complicated structures under two or more fluids thermal transients such as the tube-sheet. But the danger locations could exists for the complicated structures under two or more fluids transients, namely the conventional evaluations were non-conservative. The proposed evaluations gave good estimations for these complicated structures. Though above results, we have made the basic documents of the screening method of thermal transient stresses using the conventional method and the new method. (author)

  14. Thermal stress analysis for fatigue damage evaluation at a mixing tee

    International Nuclear Information System (INIS)

    Kamaya, Masayuki; Nakamura, Akira

    2011-01-01

    Highlights: → Thermal stress and fatigue damage have been analyzed for a mixing tee. → Fatigue damage was accumulated near boundaries of the cold spot. → It was found that fatigue damage was brought about by fluctuation of cold spot. → Simple one-dimensional analysis could derive stress for fatigue evaluation. - Abstract: Fatigue cracks have been found at mixing tees where fluids of different temperature flow in. In this study, the thermal stress at a mixing tee was calculated by the finite element method using temperature transients obtained by a fluid dynamics simulation. The simulation target was an experiment for a mixing tee, in which cold water flowed into the main pipe from a branch pipe. The cold water flowed along the main pipe wall and caused a cold spot, at which the membrane stress was relatively large. Based on the evaluated thermal stress, the magnitude of the fatigue damage was assessed according to the linear damage accumulation rule and the rain-flow procedure. Precise distributions of the thermal stress and fatigue damage could be identified. Relatively large axial stress occurred downstream from the branch pipe due to the cold spot. The variation ranges of thermal stress and fatigue damage became large near the position 20 o from the symmetry line in the circumferential direction. The position of the cold spot changed slowly in the circumferential direction, and this was the main cause of the fatigue damage. The fatigue damage was investigated for various differences in the temperature between the main and branch pipes. Since the magnitude of accumulated damage increased abruptly when the temperature difference exceeded the value corresponding to the fatigue limit, it was suggested that the stress amplitude should be suppressed less than the fatigue limit. In the thermal stress analysis for fatigue damage assessment, it was found that the detailed three-dimensional structural analysis was not required. Namely, for the current case, a one

  15. Mechanism of laser ablation for aqueous media irradiated under confined-stress conditions

    International Nuclear Information System (INIS)

    Oraevsky, A.A.; Jacques, S.L.; Tittel, F.K.

    1995-01-01

    Pulsed laser ablation of aqueous medium irradiated under conditions of temporal confinement of thermal stress is described. Time-resolved measurements of laser-induced transient stress waves with simultaneous imaging of ablation process by laser-flash photography were performed. Stress transients induced in aqueous solution of K 2 CrO 4 by ablative nanosecond laser pulses at 355 nm were studied by a broad-band lithium niobate acoustic transducer. Recoil momentum upon material ejection was measured from the temporal profiles of the acoustic transducer signal as a function of incident laser fluence. Cavitation bubbles produced in the irradiated volume during the tensile phase of thermoelastic stress were shown to drive material ejection at temperatures substantially below 100 degree C. Experimental data are evident that nanosecond-pulse laser ablation of aqueous media (when temporal stress-confinement conditions are satisfied) include the following two main stages of material ejection: (1) ejection of water microdroplets due to expansion and rupture of subsurface cavitation bubbles; (2) ejection of liquid streams with substantial volume upon collapse of initial crater and large cavitation bubbles in the depth of irradiated volume (after coalescence of smaller bubbles). copyright 1995 American Institute of Physics

  16. Heat transfer and thermal stress analysis in fluid-structure coupled field

    International Nuclear Information System (INIS)

    Li, Ming-Jian; Pan, Jun-Hua; Ni, Ming-Jiu; Zhang, Nian-Mei

    2015-01-01

    In this work, three-dimensional simulation on conjugate heat transfer in a fluid-structure coupled field was carried out. The structure considered is from the dual-coolant lithium-lead (DCLL) blanket, which is the key technology of International Thermo-nuclear Experimental Reactor (ITER). The model was developed based on finite element-finite volume method and was employed to investigate mechanical behaviours of Flow Channel Insert (FCI) and heat transfer in the blanket under nuclear reaction. Temperature distribution, thermal deformation and thermal stresses were calculated in this work, and the effects of thermal conductivity, convection heat transfer coefficient and flow velocity were analyzed. Results show that temperature gradients and thermal stresses of FCI decrease when FCI has better heat conductivity. Higher convection heat transfer coefficient will result in lower temperature, thermal deformations and stresses in FCI. Analysis in this work could be a theoretical basis of blanket optimization. - Highlights: • We use FVM and FEM to investigate FCI structural safety considering heat transfer and FSI effects. • Higher convective heat transfer coefficient is beneficial for the FCI structural safety without much affect to bulk flow temperature. • Smaller FCI thermal conductivity can better prevent heat leakage into helium, yet will increase FCI temperature gradient and thermal stress. • Three-dimensional simulation on conjugate heat transfer in a fluid-structure coupled field was carried out

  17. Numerical Study on the Thermal Stress and its Formation Mechanism of a Thermoelectric Device

    Science.gov (United States)

    Pan, Tao; Gong, Tingrui; Yang, Wei; Wu, Yongjia

    2018-06-01

    The strong thermo-mechanical stress is one of the most critical failure mechanisms that affect the durability of thermoelectric devices. In this study, numerical simulations on the formation mechanism of the maximum thermal stress inside the thermoelectric device have been performed by using finite element method. The influences of the material properties and the thermal radiation on the thermal stress have been examined. The results indicate that the maximum thermal stress was located at the contact position between the two materials and occurred due to differential thermal expansions and displacement constraints of the materials. The difference in the calculated thermal stress value between the constant and the variable material properties was between 3% and 4%. At a heat flux of 1 W·cm-2 and an emissivity of 0.5, the influence of the radiation heat transfer on the thermal stress was only about 5%; however, when the heat flux was 20 W·cm-2 and the emissivity was 0.7, the influence of the radiation heat transfer was more than 30%.

  18. Dynamic characteristics of rotating pretwisted clamped-clamped beam under thermal stress

    International Nuclear Information System (INIS)

    Zhang, Bo; Li, Yueming; Lu, Wei Zhen

    2016-01-01

    Effects of thermal stress on the vibration characteristics, buckling limit and critical speed of a rotating pretwisted beam clamped to rigid hub at a stagger angle were investigated. By considering the work done by thermal stress, the thermal influence on stiffness matrix was introduced in the dynamic model. The motion equations were derived based on Lagrange equation by employing three pure Cartesian deformation variables combined with nonlinear von Karman strain formula. Numerical investigations studied the modal characteristics of the beam. Numerical results calculated from a commercial finite element code and obtained with the present modeling method were in good agreement with the previous results reported in the literature. The combined softening effects due to the thermal stress and the rotation motion were observed. Furthermore, it is shown that the inclusion of thermal stress is necessary for blades operating under a high temperature field. Buckling thermal loads and the critical rotating speed were calculated through solving the corresponding nonlinear equations numerically, and some pertinent conclusions are outlined. It is also found that the peak value position of the first mode shape approaches to the tip of blade with the increment of rotating speed and hub radius. However, the variation in the environment temperature causes only a slight alteration in the mode shape

  19. Dynamic characteristics of rotating pretwisted clamped-clamped beam under thermal stress

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Bo; Li, Yueming [State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Key Laboratory of Environment and Control for Flight Vehicle, School of Aerospace, Xi' an Jiaotong UniversityXi' an (China); Lu, Wei Zhen [Dept. of Civil and Architectural Engineering, City University of Hong Kong, Hong Kong (China)

    2016-09-15

    Effects of thermal stress on the vibration characteristics, buckling limit and critical speed of a rotating pretwisted beam clamped to rigid hub at a stagger angle were investigated. By considering the work done by thermal stress, the thermal influence on stiffness matrix was introduced in the dynamic model. The motion equations were derived based on Lagrange equation by employing three pure Cartesian deformation variables combined with nonlinear von Karman strain formula. Numerical investigations studied the modal characteristics of the beam. Numerical results calculated from a commercial finite element code and obtained with the present modeling method were in good agreement with the previous results reported in the literature. The combined softening effects due to the thermal stress and the rotation motion were observed. Furthermore, it is shown that the inclusion of thermal stress is necessary for blades operating under a high temperature field. Buckling thermal loads and the critical rotating speed were calculated through solving the corresponding nonlinear equations numerically, and some pertinent conclusions are outlined. It is also found that the peak value position of the first mode shape approaches to the tip of blade with the increment of rotating speed and hub radius. However, the variation in the environment temperature causes only a slight alteration in the mode shape.

  20. Heat transfer and thermal stress analysis in grooved tubes

    Indian Academy of Sciences (India)

    ANSYS (1997) computer code has been used to analyse the thermal ... The numerical method is used succesfully to solve the governing equations ... thermal stress is an important criterion for consideration in the design of new compact heat.

  1. Postpartum endocrine activities, metabolic attributes and milk yield are influenced by thermal stress in crossbred dairy cows

    Science.gov (United States)

    Ihsanullah; Qureshi, Muhammad Subhan; Suhail, Syed Muhammad; Akhtar, Sohail; Khan, Rifat Ullah

    2017-09-01

    This study was conducted on 30 freshly parturated multiparous crossbred dairy cows possessing three levels of Holstein Frisian genetic makeup (62.5, 75.0, and 87.5%). Data on temperature humidity index (THI) were classified into comfortable (≤ 71), mild stress (72-79), moderate stress (80-89), and stressful (≥90) zone. Results showed that serum cortisol concentration increased significantly ( P cows during stressful condition irrespective of genetic makeup compared to the other zones. Daily milk yield (DMY) was significantly ( P cows during stressful condition. Triglyceride was significantly higher in cows with genetic makeup 87.5% compared to the others, while total serum protein was significantly ( P cows during both moderate and stressful conditions. The mean concentration of cortisol and protein increased linearly from comfort to the stressful condition, while mean serum triglyceride, glucose, progesterone (P4), and luteinizing hormone (LH) decreased by moving from comfort to stressful conditions. Results also indicated that higher cortisol level in higher grade crossbred cows was adversely associated with LH concentration and milk yield under thermal stress conditions. Greater triglyceride in high-grade crossbred (87.5%) cows indicates higher fat mobilization reflecting a negative energy balance. We concluded that heat stress increased blood cortisol and protein, and reduced milk yield in dairy cows irresptive of the genetic makeup. In addition, there was no significant difference in blood metabolites and daily milk yield in the different levels of genetic makeup cows.

  2. Thermal-stress analysis of HTGR fuel and control rod fuel blocks in in-block carbonization and annealing furnace

    International Nuclear Information System (INIS)

    Gwaltney, R.C.; McAfee, W.J.

    1977-01-01

    A new method for performing thermal stress analyses in structures with multiple penetrations was applied to these analyses. This method couples the development of an equivalent thermal conductivity for the blocks, a technique that has been used extensively for modeling the thermal characteristics of reactor cores, with the use of the equivalent solid plate method for stress analysis. Using this equivalent thermal conductivity, which models as one material the heat transfer characteristics of the fuel, coolant, and graphite two-dimensional, steady-state thermal analyses of the fuel and control rod fuel blocks were performed to establish all temperature boundaries required for the stress analyses. In applying the equivalent solid plate method, the region of penetrations being modeled was replaced by a pseudo material having the same dimensions but whose materials properties were adjusted to account for the penetration. The peak stresses and strains were determined by applying stress and strain intensification factors to the calculated distributions. The condition studied was where the blocks were located near the center of the furnace. In this position, the axial surface of the block is heated near one end and cooled near the other. The approximate axial surface temperatures ranged from 1521 0 C at both the heated and the cooled ends to a peak of 1800 0 C near the center. Five specific cases were analyzed: plane (two-dimensional thermal, plane stress strain) analyses of each end of a standard fuel block (2 cases), plane analyses of each end of a control rod fuel block (2 cases), and a two-dimensional analysis of a fuel block treated as an axisymmetric cylind

  3. Stress in film/substrate system due to diffusion and thermal misfit effects

    International Nuclear Information System (INIS)

    Shao Shanshan; Xuan Fuzhen; Wang Zhengdong; Tu Shantung

    2009-01-01

    The stress in film/substrate systems has been analysed taking into consideration the coupling effects of diffusion and thermal misfit within the framework of Fick's second law. The solution of diffusion-induced stress in a film/substrate system involving the thermal misfit stress feedback is developed. The effects of modulus ratios, diffusivity ratios, thickness ratios of the substrate and the film and the partial molar volume of the diffusing component on the stress distribution in the film/substrate system are then discussed with the help of the finite difference method. Results indicate that the stresses in the film/substrate system vary with diffusion time. Diffusion enhances the magnitudes of film stress when the thermal misfit stress is compressive in the film. Furthermore, the absolute values of stress in the film increase with the increasing modulus ratios of the substrate and film, while they reduce with the increasing partial molar volume of the diffusing component and the diffusivity ratio of the substrate and the film.

  4. Finite element simulation of stress evolution in thermal barrier coating systems

    Energy Technology Data Exchange (ETDEWEB)

    Bednarz, P.

    2007-07-01

    Gas turbine materials exposed to extreme high temperature require protective coatings. To design reliable components, a better understanding of the coating failure mechanisms is required. Damage in Thermal Barrier Coating Systems (TBCs) is related to oxidation of the Bond Coat, sintering of the ceramic, thermal mismatch of the material constituents, complex shape of the BC/TGO/TBC interface, redistribution of stresses via creep and plastic deformation and crack resistance. In this work, experimental data of thermo-mechanical properties of CMSX-4, MCrAlY (Bond Coat) and APS-TBC (partially stabilized zirconia), were implemented into an FE-model in order to simulate the stress development at the metal/ceramic interface. The FE model reproduced the specimen geometry used in corresponding experiments. It comprises a periodic unit cell representing a slice of the cylindrical specimen, whereas the periodic length of the unit cell equals an idealized wavelength of the rough metal/ceramic interface. Experimental loading conditions in form of thermal cycling with a dwelltime at high temperature and consideration of continuous oxidation were simulated. By a stepwise consideration of various material properties and processes, a reference model was achieved which most realistically simulated the materials behavior. The influences of systematic parameter variations on the stress development and critical sites with respect to possible crack paths were shown. Additionally, crack initiation and propagation at the peak of asperity at BC/TGO interface was calculated. It can be concluded that a realistic modeling of stress development in TBCs requires at least reliable data of i) BC and TGO plasticity, ii) BC and TBC creep, iii) continuous oxidation including in particular lateral oxidation, and iv) critical energy release rate for interfaces (BC/TGO, TGO/TBC) and for each layer. The main results from the performed parametric studies of material property variations suggest that

  5. Prior stress exposure increases pain behaviors in a rat model of full thickness thermal injury.

    Science.gov (United States)

    Nyland, Jennifer E; McLean, Samuel A; Averitt, Dayna L

    2015-12-01

    Thermal burns among individuals working in highly stressful environments, such as firefighters and military Service Members, are common. Evidence suggests that pre-injury stress may exaggerate pain following thermal injury; however current animal models of burn have not evaluated the potential influence of pre-burn stress. This sham-controlled study evaluated the influence of prior stress exposure on post-burn thermal and mechanical sensitivity in male Sprague-Dawley rats. Rats were exposed to 20 min of inescapable swim stress or sham stress once per day for three days. Exposure to inescapable swim stress (1) increased the intensity and duration of thermal hyperalgesia after subsequent burn and (2) accelerated the onset of thermal hyperalgesia and mechanical allodynia after subsequent burn. This stress-induced exacerbation of pain sensitivity was reversed by pretreatment and concurrent treatment with the serotonin-norepinephrine reuptake inhibitor (SNRI) duloxetine. These data suggest a better understanding of mechanisms by which prior stress augments pain after thermal burn may lead to improved pain treatments for burn survivors. Copyright © 2015 Elsevier Ltd and ISBI. All rights reserved.

  6. Thermal stress relieving of dilute uranium alloys

    International Nuclear Information System (INIS)

    Eckelmeyer, K.H.

    1981-01-01

    The kinetics of thermal stress relieving of uranium - 2.3 wt % niobium, uranium - 2.0 wt % molybdenum, and uranium - 0.75 wt % titanium are reported and discussed. Two temperature regimes of stress relieving are observed. In the low temperature regime (T 0 C) the process appears to be controlled by an athermal microplasticity mechanism which can be completely suppressed by prior age hardening. In the high temperature regime (300 0 C 0 C) the process appears to be controlled by a classical diffusional creep mechanism which is strongly dependent on temperature and time. Stress relieving is accelerated in cases where it occurs simultaneously with age hardening. The potential danger of residual stress induced stress corrosion cracking of uranium alloys is discussed

  7. Thermal stress evaluation of the Viking RTG heat shield

    International Nuclear Information System (INIS)

    Stadter, J.T.; Weiss, R.O.

    1976-03-01

    Thermal stress analyses of the Viking RTG heat shield are presented. The primary purpose of the analyses was to determine the effects of the end cap and the finite length of the heat shield on the peak tensile stress in the barrel wall. The SAAS III computer code was used to calculate the thermal stresses; axisymmetric and plane section analyses were performed for a variety of temperature distributions. The study consisted of three parts. In the first phase, the influence of the end cap on the barrel wall stresses was examined by parametrically varying the modulus of elasticity of the contact zone between the end cap and the barrel. The second phase was concerned with stresses occurring as a result of an orbital decay reentry trajectory, and the effects of the magnitude and shape of the axial temperature gradient. The final part of the study was concerned with the circumferentially nonuniform temperature distribution which develops during a side-on stable reentry. The last part includes a comparison of stresses generated for a hexagonal cross section with those generated for a circular cross section

  8. Optical stimulation of the hearing and deaf cochlea under thermal and stress confinement condition

    Science.gov (United States)

    Schultz, M.; Baumhoff, P.; Kallweit, N.; Sato, M.; Krüger, A.; Ripken, T.; Lenarz, T.; Kral, A.

    2014-03-01

    There is a controversy, to which extend cochlear stimulation with near infrared laser pulses at a wavelength of 1860 nm is based on optoacoustic stimulation of intact hair cells or -in contrast- is based on direct stimulation of the nerve cells in absence of functional hair cells. Thermal and stress confinement conditions apply, because of the pulse duration range (5 ns, 10 μs-20 ms) of the two lasers used. The dependency of the signal characteristics on pulse peak power and pulse duration was investigated in this study. The compound action potential (CAP) was measured during stimulation of the cochlea of four anaesthetized guinea pigs, which were hearing at first and afterwards acutely deafened using intracochlear neomycin-rinsing. For comparison hydrophone measurements in a water tank were performed to investigate the optoacoustic signals at different laser interaction regimes. With rising pulse peak power CAPs of the hearing animals showed first a threshold, then a positively correlated and finally a saturating dependency. CAPs also showed distinct responses at laser onset and offset separated with the pulse duration. At pulse durations shorter than physiological response times the signals merged. Basically the same signal characteristics were observed in the optoacoustic hydrophone measurements, scaled with the sensitivity and response time of the hydrophone. Taking together the qualitative correspondence in the signal response and the absence of any CAPs in deafened animals our results speak in favor of an optoacoustic stimulation of intact hair cells rather than a direct stimulation of nerve cells.

  9. Dietary live yeast alters metabolic profiles, protein biosynthesis and thermal stress tolerance of Drosophila melanogaster.

    Science.gov (United States)

    Colinet, Hervé; Renault, David

    2014-04-01

    The impact of nutritional factors on insect's life-history traits such as reproduction and lifespan has been excessively examined; however, nutritional determinant of insect's thermal tolerance has not received a lot of attention. Dietary live yeast represents a prominent source of proteins and amino acids for laboratory-reared drosophilids. In this study, Drosophila melanogaster adults were fed on diets supplemented or not with live yeast. We hypothesized that manipulating nutritional conditions through live yeast supplementation would translate into altered physiology and stress tolerance. We verified how live yeast supplementation affected body mass characteristics, total lipids and proteins, metabolic profiles and cold tolerance (acute and chronic stress). Females fed with live yeast had increased body mass and contained more lipids and proteins. Using GC/MS profiling, we found distinct metabolic fingerprints according to nutritional conditions. Metabolite pathway enrichment analysis corroborated that live yeast supplementation was associated with amino acid and protein biosyntheses. The cold assays revealed that the presence of dietary live yeast greatly promoted cold tolerance. Hence, this study conclusively demonstrates a significant interaction between nutritional conditions and thermal tolerance. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. Thermal Stress and Toxicity | Science Inventory | US EPA

    Science.gov (United States)

    Elevating ambient temperature above thermoneutrality exacerbates toxicity of most air pollutants, insecticides, and other toxic chemicals. On the other hand, safety and toxicity testing of toxicants and drugs is usually performed in mice and rats maintained at subthermoneutral temperatures of —22 °C. When exposed to chemical toxicants under these relatively cool conditions, rodents typically undergo a regulated hypothermic response, characterized by preference for cooler ambient temperatures and controlled reduction in core temperature. Reducing core temperature delays the clearance of most toxicants from the body; however, a mild hypothermia also improves recovery and survival from the toxicant. Raising ambient temperature to thermoneutrality and above increases the rate of clearance of the toxicant but also exacerbates toxicity. Furthermore, heat stress combined with work or exercise is likely to worsen toxicity. Body temperature of large mammals, including humans, does not decrease as much in response to exposure to a toxicant. However, heat stress tan nonetheless worsen toxic outcome in humans through a variety of mechanisms. For example, heat-induced sweating and elevation in skin blood flow accelerates uptake of some insecticides. Epidemiological studies suggest that thermal stress may exacerbate the toxicity of airborne pollutants such as ozone and particulate matter. Overall, translating results of studies in rodents to that of humans is a formidable

  11. Thermal stress measurement in continuous welded rails using the hole-drilling method

    Science.gov (United States)

    Zhu, Xuan; Lanza di Scalea, Francesco; Fateh, Mahmood

    2016-04-01

    The absence of expansion joints in Continuous Welded Rail (CWR) has created the need for the railroad industry to determine the in-situ level of thermal stresses so as to prevent train accidents caused by rail buckling in hot weather and by rail breakage in cold weather. The development of non-destructive or semi-destructive methods for determining the level of thermal stresses in rails is today a high research priority. This study explores the known hole-drilling method as a possible solution to this problem. A new set of calibration coefficients to compute the relieved stress field with the finer hole depth increments was determined by a 3D Finite Element Analysis that modeled the entire hole geometry, including the mechanics of the hole bottom and walls. To compensate the residual stress components, a linear relationship was experimentally established between the longitudinal and the vertical residual stresses of two common sizes of rails, the 136RE and the 141RE, with statistical significance. This result was then utilized to isolate the longitudinal thermal stress component in hole-drilling tests conducted on the 136RE and 141RE thermally-loaded rails at the Large-scale CWR Test-bed of UCSD's Powell Research Laboratories. The results from the Test-bed showed that the hole-drilling procedure, with the appropriate residual stress compensation, can indeed estimate the in-situ thermal stresses to achieve a +/-5°F accuracy of Neutral Temperature determination with a 90% statistical confidence, which is the desired industry gold standard.

  12. Design of durability and lifetime assessment method under thermomechanical stress for thermal barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Hyun Gyoo; Choi, Young Kue; Jeon, Seol; Lee, Hee Soo [Pusan National University, Busan (Korea, Republic of); Jeon, Min Seok [Korea Testing Laboratory, Seoul (Korea, Republic of)

    2014-01-15

    A durability testing method under thermo-mechanical stress for thermal barrier coatings (TBC) specimens was designed by a combination of an electric furnace and a tensile testing machine, which was done on TBCs on NIMONIC 263 substrates by an atmospheric plasma spraying (APS) deposition method. The testing conditions were chosen according to a preliminary experiment that identified the elastic deformation region of the top coating and the substrate during mechanical loading. Surface cracking and a decrease in the thickness of the top coating, which are typical degradation behaviors under conventional thermal shock testing, were observed after the designed thermal fatigue test, and delamination at the top coating-bond coating interface occurred by the mechanical load. Lifetime assessment was conducted by statistical software using life cycle data which were obtained after the thermal fatigue test.

  13. Numerical Study of Thermal Stresses for the Semiconductor CdZnTe in Vertical Bridgman

    OpenAIRE

    Jamai , Hanen; El Ganaoui , M.; Sammouda , Habib; Pateyron , Bernard

    2015-01-01

    International audience; The aim of this work is to present a numerical simulation of thermal stress in directional solidification of CdZnTe in vertical Bridgman apparatus. Especial attention will be attributed to show the importance of cooling temperature and time's growth affecting the thermal stress. Furthermore, we will focus on investigating the thermal stress' components and their distribution in crystal, which gives a detailed about the stress distribution and consequently on the distri...

  14. Quaternion Based Thermal Condition Monitoring System

    Science.gov (United States)

    Wong, Wai Kit; Loo, Chu Kiong; Lim, Way Soong; Tan, Poi Ngee

    In this paper, we will propose a new and effective machine condition monitoring system using log-polar mapper, quaternion based thermal image correlator and max-product fuzzy neural network classifier. Two classification characteristics namely: peak to sidelobe ratio (PSR) and real to complex ratio of the discrete quaternion correlation output (p-value) are applied in the proposed machine condition monitoring system. Large PSR and p-value observe in a good match among correlation of the input thermal image with a particular reference image, while small PSR and p-value observe in a bad/not match among correlation of the input thermal image with a particular reference image. In simulation, we also discover that log-polar mapping actually help solving rotation and scaling invariant problems in quaternion based thermal image correlation. Beside that, log-polar mapping can have a two fold of data compression capability. Log-polar mapping can help smoother up the output correlation plane too, hence makes a better measurement way for PSR and p-values. Simulation results also show that the proposed system is an efficient machine condition monitoring system with accuracy more than 98%.

  15. Numerical evaluation of stress intensity factor for vessel and pipe subjected to thermal shock

    International Nuclear Information System (INIS)

    Kim, Y.W.; Lee, H.Y.; Yoo, B.

    1994-01-01

    The thermal weight function method and the finite element method were employed in the numerical computation of the stress intensity factor for a cracked vessel and the cracked pipe subjected to thermal shock. A wall subjected to thermal shock was analyzed, and it has been shown that the effect of thermal shock on the stress intensity factor is dominant for the crack with small crack length to thickness ratio. Convection at the crack face had an influence on the stress intensity factor in the early stage of thermal shock. (Author)

  16. Thermal Stress Cracking of Slide-Gate Plates in Steel Continuous Casting

    Science.gov (United States)

    Lee, Hyoung-Jun; Thomas, Brian G.; Kim, Seon-Hyo

    2016-04-01

    The slide-gate plates in a cassette assembly control the steel flow through the tundish nozzle, and may experience through-thickness cracks, caused by thermal expansion and/or mechanical constraint, leading to air aspiration and safety concerns. Different mechanisms for common and rare crack formation are investigated with the aid of a three-dimensional finite-element model of thermal mechanical behavior of the slide-gate plate assembly during bolt pretensioning, preheating, tundish filling, casting, and cooling stages. The model was validated with previous plant temperature measurements of a ladle plate during preheating and casting, and then applied to a typical tundish-nozzle slide-gate assembly. The formation mechanisms of different types of cracks in the slide-gate plates are investigated using the model and evaluated with actual slide-gate plates at POSCO. Common through-thickness radial cracks, found in every plate, are caused during casting by high tensile stress on the outside surfaces of the plates, due to internal thermal expansion. In the upper plate, these cracks may also arise during preheating or tundish filling. Excessive bolt tightening, combined with thermal expansion during casting may cause rare radial cracks in the upper and lower plates. Rare radial and transverse cracks in middle plate appear to be caused during tundish filling by impingement of molten steel on the middle of the middle plate that generates tensile stress in the surrounding refractory. The mechanical properties of the refractory, the bolt tightening conditions, and the cassette/plate design are all important to service life.

  17. Growth stress buildup in ion beam sputtered Mo thin films and comparative study of stress relaxation upon thermal annealing or ion irradiation

    International Nuclear Information System (INIS)

    Debelle, A.; Abadias, G.; Michel, A.; Jaouen, C.; Pelosin, V.

    2007-01-01

    In an effort to address the understanding of the origin of growth stress in thin films deposited under very energetic conditions, the authors investigated the stress state and microstructure of Mo thin films grown by ion beam sputtering (IBS) as well as the stress relaxation processes taking place during subsequent thermal annealing or ion irradiation. Different sets of samples were grown by varying the IBS deposition parameters, namely, the energy E 0 and the flux j of the primary ion beam, the target-to-sputtering gas mass ratio M 1 /M 2 as well as film thickness. The strain-stress state was determined by x-ray diffraction using the sin 2 ψ method and data analyzed using an original stress model which enabled them to correlate information at macroscopic (in terms of stress) and microscopic (in terms of defect concentration) levels. Results indicate that these refractory metallic thin films are characterized by a high compressive growth stress (-2.6 to -3.8 GPa), resulting from the creation of a large concentration (up to ∼1.4%) of point or cluster defects, due to the atomic peening mechanism. The M 1 /M 2 mass ratio enables tuning efficiently the mean deposited energy of the condensing atoms; thus, it appears to be the more relevant deposition parameter that allows modifying both the microstructure and the stress level in a significant way. The growth stress comes out to be highly unstable. It can be easily relaxed either by postgrowth thermal annealing or ion irradiation in the hundred keV range at very low dose [<0.1 dpa (displacement per atom)]. It is shown that thermal annealing induces deleterious effects such as oxidation of the film surface, decrease of the film density, and in some cases adhesion loss at the film/substrate interface, while ion irradiation allows controlling the stress level without generating any macroscopic damage

  18. Toward Improved Lifetimes of Organic Solar Cells under Thermal Stress: Substrate-Dependent Morphological Stability of PCDTBT:PCBM Films and Devices.

    Science.gov (United States)

    Li, Zhe; Ho Chiu, Kar; Shahid Ashraf, Raja; Fearn, Sarah; Dattani, Rajeev; Cheng Wong, Him; Tan, Ching-Hong; Wu, Jiaying; Cabral, João T; Durrant, James R

    2015-10-15

    Morphological stability is a key requirement for outdoor operation of organic solar cells. We demonstrate that morphological stability and lifetime of polymer/fullerene based solar cells under thermal stress depend strongly on the substrate interface on which the active layer is deposited. In particular, we find that the stability of benchmark PCDTBT/PCBM solar cells under modest thermal stress is substantially increased in inverted solar cells employing a ZnO substrate compared to conventional devices employing a PSS substrate. This improved stability is observed to correlate with PCBM nucleation at the 50 nm scale, which is shown to be strongly influenced by different substrate interfaces. Employing this approach, we demonstrate remarkable thermal stability for inverted PCDTBT:PC70BM devices on ZnO substrates, with negligible (humidity exposure as widely reported previously, can also demonstrate enhanced morphological stability. As such we show that the choice of suitable substrate interfaces may be a key factor in achieving prolonged lifetimes for organic solar cells under thermal stress conditions.

  19. EXAMINATION OF THE SIMULATED THERMAL CONDITIONS IN A POPULAR PLAYGROUND RELATED TO THE HUMAN REACTIONS AND THE JUDGMENT OF THE AREA DESIGN

    Directory of Open Access Journals (Sweden)

    L.A. ÉGERHÁZI

    2013-03-01

    Full Text Available In the field of urban bioclimatology an important and timely research direction today is to examine the thermal conditions of public places. In our study, human thermal comfort analysis was performed in a modern and well-attended children playground located in Szeged (Hungary. The aim of the paper is to reveal the changes in the thermal comfort conditions between two seasons and also the resulting subjective thermal reactions of visitors in this relatively small area. Thermal comfort conditions were quantified by the Physiologically Equivalent Temperature (PET. For typical summer and autumn days of 2011 numerical simulations of thermal comfort conditions in the playground were carried out by means of the urban microclimate model ENVI-met. Spatial distribution of the simulated PET, i.e. thermal stress maps were created in two different times of the selected days in order to characterize the distinct microclimatological conditions appearing in the area. The relationship between the momentary spatial patterns of visitors and the thermal conditions was also under investigation. Additionally, onsite questionnaire survey was implemented which highlights the people’s subjective evaluation related to the design of the playground.

  20. Analytical method for thermal stress analysis of plasma facing materials

    Science.gov (United States)

    You, J. H.; Bolt, H.

    2001-10-01

    The thermo-mechanical response of plasma facing materials (PFMs) to heat loads from the fusion plasma is one of the crucial issues in fusion technology. In this work, a fully analytical description of the thermal stress distribution in armour tiles of plasma facing components is presented which is expected to occur under typical high heat flux (HHF) loads. The method of stress superposition is applied considering the temperature gradient and thermal expansion mismatch. Several combinations of PFMs and heat sink metals are analysed and compared. In the framework of the present theoretical model, plastic flow and the effect of residual stress can be quantitatively assessed. Possible failure features are discussed.

  1. Analytical method for thermal stress analysis of plasma facing materials

    International Nuclear Information System (INIS)

    You, J.H.; Bolt, H.

    2001-01-01

    The thermo-mechanical response of plasma facing materials (PFMs) to heat loads from the fusion plasma is one of the crucial issues in fusion technology. In this work, a fully analytical description of the thermal stress distribution in armour tiles of plasma facing components is presented which is expected to occur under typical high heat flux (HHF) loads. The method of stress superposition is applied considering the temperature gradient and thermal expansion mismatch. Several combinations of PFMs and heat sink metals are analysed and compared. In the framework of the present theoretical model, plastic flow and the effect of residual stress can be quantitatively assessed. Possible failure features are discussed

  2. Rapid thermal conditioning of sewage sludge

    Science.gov (United States)

    Zheng, Jianhong

    Rapid thermal conditioning (RTC) is a developing technology recently applied to sewage sludge treatment. Sludge is heated rapidly to a reaction temperature (up to about 220sp°C) under sufficient pressure to maintain the liquid phase. Reaction is quenched after 10 to 30 seconds when the mixture of sludge and steam pass through a pressure let-down valve. This process reduces the amount of sludge requiring land disposal, eliminates the need for polymer coagulant, improves dewaterability, increases methane production, and further reduces the concentration of pathogens. The odor problem associated with traditional thermal conditioning processes is largely minimized. Ammonia removal is readily integrated with the process. For this research, a pilot unit was constructed capable of processing 90 liters of sludge per hour. Over 22 runs were made with this unit using sludge from New York City Water Pollution Control Plants (WPCP). Sludges processed in this equipment were tested to determine the effect of RTC operating conditions on sludge dewaterability, biodegradability, and other factors affecting the incorporation of RTC into wastewater treatment plants. Dewaterability of thermally conditioned sludge was assessed for cetrifugeability and filterability. Bench scale centrifugation was used for evaluating centrifugeability, pressure filtration and capillary suction time (CST) for filterability. A mathematical model developed for centrifuge dewatering was used to predict the effect of RTC on full scale centrifuge performance. Particle size distribution and solids density of raw and treated PDS were also analyzed. An observed increase in sludge solids density at least partially explains its improved centrifugeability. An investigation of thermally conditioned amino acids showed that the L-isomer is highly biodegradable while the D-isomers are generally less so. Glucose is highly biodegradable, but rapidly becomes refractory as thermal conditioning time is lengthened. This

  3. Thermal stress relieving of dilute uranium alloys

    International Nuclear Information System (INIS)

    Eckelmeyer, K.H.

    1980-01-01

    The kinetics of thermal stress relieving of uranium - 2.3 wt. % niobium, uranium - 2.0 wt. % molybdenum, and uranium - 0.75 wt. % titanium are reported and discussed. Two temperature regimes of stress relieving are observed. In the low temperature regime (T 0 C) the process appears to be controlled by an athermal microplasticity mechanism which can be completely suppressed by prior age hardening. In the high temperature regime (300 0 C 0 C) the process appears to be controlled by a classical diffusional creep mechanism which is strongly dependent on temperature and time. Stress relieving is accelerated in cases where it occurs simultaneously with age hardening. The potential danger of residual stress induced stress corrosion cracking of uranium alloys is discussed. It is shown that the residual stress relief which accompanies age hardening of uranium - 0.75% titanium more than compensates for the reduction in K/sub ISCC/ caused by aging. As a result, age hardening actually decreases the susceptibility of this alloy to residual stress induced stress corrosion cracking

  4. Pipe cracking due to thermal stresses produced by valve opening

    International Nuclear Information System (INIS)

    Sanchez Sarmiento, G.

    1982-01-01

    The thermal stresses produced in a tube whose internal surface is abrupt cooled during a valve opening so that the water volume increases linearly with time are studied. A general solution for these stresses and its stress intensity factors in terms of non-dimensional parameters is presented. (E.G.) [pt

  5. Simulation of thermal stresses in anode-supported solid oxide fuel cell stacks. Part II: Loss of gas-tightness, electrical contact and thermal buckling

    Science.gov (United States)

    Nakajo, Arata; Wuillemin, Zacharie; Van herle, Jan; Favrat, Daniel

    Structural stability issues in planar solid oxide fuel cells arise from the mismatch between the coefficients of thermal expansion of the components. The stress state at operating temperature is the superposition of several contributions, which differ depending on the component. First, the cells accumulate residual stresses due to the sintering phase during the manufacturing process. Further, the load applied during assembly of the stack to ensure electric contact and flatten the cells prevents a completely stress-free expansion of each component during the heat-up. Finally, thermal gradients cause additional stresses in operation. The temperature profile generated by a thermo-electrochemical model implemented in an equation-oriented process modelling tool (gPROMS) was imported into finite-element software (ABAQUS) to calculate the distribution of stress and contact pressure on all components of a standard solid oxide fuel cell repeat unit. The different layers of the cell in exception of the cathode, i.e. anode, electrolyte and compensating layer were considered in the analysis to account for the cell curvature. Both steady-state and dynamic simulations were performed, with an emphasis on the cycling of the electrical load. The study includes two different types of cell, operation under both thermal partial oxidation and internal steam-methane reforming and two different initial thicknesses of the air and fuel compressive sealing gaskets. The results generated by the models are presented in two papers: Part I focuses on cell cracking. In the present paper, Part II, the occurrences of loss of gas-tightness in the compressive gaskets and/or electrical contact in the gas diffusion layer were identified. In addition, the dependence on temperature of both coefficients of thermal expansion and Young's modulus of the metallic interconnect (MIC) were implemented in the finite-element model to compute the plastic deformation, while the possibilities of thermal buckling

  6. Temperature and thermal stress analysis of a switching tube anode

    International Nuclear Information System (INIS)

    Sutton, S.B.

    1979-01-01

    In the design of high power density switching tubes which are subjected to cyclic thermal loads, the temperature induced stresses must be minimized in order to maximize the life expectancy of the tube. Following are details of an analysis performed for the Magnetic Fusion Program at the Lawrence Livermore Laboratory on a proposed tube. The tube configuration is given. The problem was simplified to one-dimensional approximations for both the thermal and stress analyses. The underlying assumptions and their implications are discussed

  7. Combined thermal and herbicide stress in functionally diverse coral symbionts

    International Nuclear Information System (INIS)

    Dam, J.W. van; Uthicke, S.; Beltran, V.H.; Mueller, J.F.; Negri, A.P.

    2015-01-01

    Most reef building corals rely on symbiotic microalgae (genus Symbiodinium) to supply a substantial proportion of their energy requirements. Functional diversity of different Symbiodinium genotypes, endorsing the host with physiological advantages, has been widely reported. Yet, the influence of genotypic specificity on the symbiont's susceptibility to contaminants or cumulative stressors is unknown. Cultured Symbiodinium of presumed thermal-tolerant clade D tested especially vulnerable to the widespread herbicide diuron, suggesting important free-living populations may be at risk in areas subjected to terrestrial runoff. Co-exposure experiments where cultured Symbiodinium were exposed to diuron over a thermal stress gradient demonstrated how fast-growing clade C1 better maintained photosynthetic capability than clade D. The mixture toxicity model of Independent Action, considering combined thermal stress and herbicide contamination, revealed response additivity for inhibition of photosynthetic yield in both tested cultures, emphasizing the need to account for cumulative stressor impacts in ecological risk assessment and resource management. - Highlights: • Water quality influences thermal stress thresholds in different Symbiodinium types. • Photosystem of clade D tested more sensitive than C1 to a common herbicide. • Increased thermal tolerance quickly countered in presence of herbicide. • Mixture toxicity approach demonstrated response additivity for combined stressors. • Symbiotic partnership may be compromised in areas subjected to terrestrial runoff. - Thermal-tolerant Symbiodinium type D tested especially vulnerable to a common herbicide, emphasizing the significance of cumulative stressors in ecological risk management

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

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2013-01-01

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

  9. Effective stress coefficient for uniaxial strain condition

    DEFF Research Database (Denmark)

    Alam, M.M.; Fabricius, I.L.

    2012-01-01

    one dimensional rock mechanical deformation. We further investigated the effect of boundary condition on the stress dependency of effective stress coefficient and discussed its application in reservoir study. As stress field in the reservoirs are most unlikely to be hydrostatic, effective stress...... determined under uniaxial strain condition will be more relevant in reservoir studies. Copyright 2012 ARMA, American Rock Mechanics Association....

  10. First wall thermal stress analysis for suddenly applied heat fluxes

    International Nuclear Information System (INIS)

    Dalessandro, J.A.

    The failure criterion for a solid first wall of an inertial confinement reactor is investigated. Analytical expressions for induced thermal stresses in a plate are given. Two materials have been chosen for this investigation: grade H-451 graphite and chemically vapor deposited (CVD) β-silicon carbide. Structural failure can be related to either the maximum compressive stress produced on the surface or the maximum tensile stress developed in the interior of the plate; however, it is shown that compressive failure would predominate. A basis for the choice of the thermal shock figure of merit, k(1 - ν) sigma/E α kappa/sup 1/2/, is identified. The result is that graphite and silicon carbide rank comparably

  11. Human power output during repeated sprint cycle exercise: the influence of thermal stress

    NARCIS (Netherlands)

    Ball, D.; Burrows, C.; Sargeant, A.J.

    1999-01-01

    Thermal stress is known to impair endurance capacity during moderate prolonged exercise. However, there is relatively little available information concerning the effects of thermal stress on the performance of high-intensity short-duration exercise. The present experiment examined human power output

  12. Thermal residual stress evaluation based on phase-shift lateral shearing interferometry

    Science.gov (United States)

    Dai, Xiangjun; Yun, Hai; Shao, Xinxing; Wang, Yanxia; Zhang, Donghuan; Yang, Fujun; He, Xiaoyuan

    2018-06-01

    An interesting phase-shift lateral shearing interferometry system was proposed to evaluate the thermal residual stress distribution in transparent specimen. The phase-shift interferograms was generated by moving a parallel plane plate. Based on analyzing the fringes deflected by deformation and refractive index change, the stress distribution can be obtained. To verify the validity of the proposed method, a typical experiment was elaborately designed to determine thermal residual stresses of a transparent PMMA plate subjected to the flame of a lighter. The sum of in-plane stress distribution was demonstrated. The experimental data were compared with values measured by digital gradient sensing method. Comparison of the results reveals the effectiveness and feasibility of the proposed method.

  13. Investigation of stress in a circular tunnel due to overburden and thermal loading of horizontally placed 21 PWR multi purpose canisters

    International Nuclear Information System (INIS)

    Kandalaft-Ladkany, N.; Wyman, R.V.

    1994-01-01

    The drift of a High Level Nuclear Waste (HLNW) Repository were subjected to 2-D thermal loading resulting from the horizontal emplacement of 125 Ton Multi-Purpose Canisters (MPC). Ten 2-D temperature profiles, resulting from 57 Kw/acre and 114 Kw/acre thermal loading conditions, were used in a finite element analysis of the drift; in which a quadrant of the drift and surrounding rock ±100m above and below the drift were modeled. Our analysis shows that the 114 Kw/acre thermal loading results in compressive stresses around the drift, 60 years after emplacement, that exceed the unconfined compressive strength of the TSW tuff analyzed. Stresses resulting from a 57 Kw/acre thermal loading are within the acceptable limit in tunnel rock. A parametric analysis of the invert backfill material showed that Young's modulus for the invert backfill should closely match that of the surrounding unconfined rock in the tunnel in order to prevent an unacceptable stress rise in both rock and backfill

  14. The effect of atmospheric thermal conditions and urban thermal pollution on all-cause and cardiovascular mortality in Bangladesh

    International Nuclear Information System (INIS)

    Burkart, Katrin; Schneider, Alexandra; Breitner, Susanne; Khan, Mobarak Hossain; Kraemer, Alexander; Endlicher, Wilfried

    2011-01-01

    This study assessed the effect of temperature and thermal atmospheric conditions on all-cause and cardiovascular mortality in Bangladesh. In particular, differences in the response to elevated temperatures between urban and rural areas were investigated. Generalized additive models (GAMs) for daily death counts, adjusted for trend, season, day of the month and age were separately fitted for urban and rural areas. Breakpoint models were applied for determining the increase in mortality above and below a threshold (equivalent) temperature. Generally, a 'V'-shaped (equivalent) temperature-mortality curve with increasing mortality at low and high temperatures was observed. Particularly, urban areas suffered from heat-related mortality with a steep increase above a specific threshold. This adverse heat effect may well increase with ongoing urbanization and the intensification of the urban heat island due to the densification of building structures. Moreover, rising temperatures due to climate change could aggravate thermal stress. - Highlights: → Temperature exhibits a strong influence on mortality in Bangladesh. → Mortality increases at low and high end of the temperature range. → Temperature is increased in the urban area of Dhaka, particular during summer. → Urban areas are facing increased risk of heat-related mortality. → Urbanization and climate change are likely to increase heat-related mortality. - Mortality in Bangladesh is strongly affected by thermal atmospheric conditions with particularly urban areas facing excess mortality above a specific threshold temperature.

  15. Rock properties and their effect on thermally-induced displacements and stresses

    International Nuclear Information System (INIS)

    Chan, T.; Hood, M.; Board, M.

    1980-02-01

    A discussion is given of the importance of material properties in the finite-element calculations for thermally induced displacements and stresses resulting from a heating experiment in an in-situ granitic rock, at Stripa, Sweden. Comparisons are made between field measurements and finite element method calculations using (1) temperature independent, (2) temperature dependent thermal and thermomechanical properties and (3) in-situ and laboratory measurements for Young's modulus. The calculations of rock displacements are influenced predominantly by the temperature dependence of the thermal expansion coefficient, whereas the dominant factor affecting predictions for rock stresses is the in-situ modulus

  16. Effects of thermal aging and stress triaxiality on PWSCC initiation susceptibility of nickel-based Alloy 600

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Seung Chang; Choi, Kyoung Joon; Kim, Tae Ho; Kim, Ji Hyun [Dept. of Nuclear Science and Engineering, School of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

    2016-10-15

    In present study, effects of thermal aging and triaxial stress were investigated in terms of primary water stress corrosion cracking susceptibility. The thermal aging was applied via heat treatment at 400°C and triaxial stress was applied via notched tensile test specimen. The crack initiation time of each specimen were then measured by direct current potential drop method during slow strain rate test at primary water environment. Alloys with 10 years thermal aging exhibited the highest susceptibility to stress corrosion cracking and asreceived specimen shows lowest susceptibility. The trend was different with triaxial stress applied; 20 years thermal aging specimen shows highest susceptibility and as-received specimen shows lowest. It would be owing to change of precipitate morphology during thermal aging and different activated slip system in triaxial stress state.

  17. Non-Contact Smartphone-Based Monitoring of Thermally Stressed Structures

    Science.gov (United States)

    Ozturk, Turgut; Mas, David; Rizzo, Piervincenzo

    2018-01-01

    The in-situ measurement of thermal stress in beams or continuous welded rails may prevent structural anomalies such as buckling. This study proposed a non-contact monitoring/inspection approach based on the use of a smartphone and a computer vision algorithm to estimate the vibrating characteristics of beams subjected to thermal stress. It is hypothesized that the vibration of a beam can be captured using a smartphone operating at frame rates higher than conventional 30 Hz, and the first few natural frequencies of the beam can be extracted using a computer vision algorithm. In this study, the first mode of vibration was considered and compared to the information obtained with a conventional accelerometer attached to the two structures investigated, namely a thin beam and a thick beam. The results show excellent agreement between the conventional contact method and the non-contact sensing approach proposed here. In the future, these findings may be used to develop a monitoring/inspection smartphone application to assess the axial stress of slender structures, to predict the neutral temperature of continuous welded rails, or to prevent thermal buckling. PMID:29670034

  18. Transient thermal stresses of work roll by coupled thermoelasticity

    Science.gov (United States)

    Lai, W. B.; Chen, T. C.; Weng, C. I.

    1991-01-01

    A numerical method, based on a two-dimensional plane strain model, is developed to predict the transient responses (that include distributions of temperature, thermal deformation, and thermal stress) of work roll during strip rolling by coupled thermoelasticity. The method consists of discretizing the space domain of the problem by finite element method first, and then treating the time domain by implicit time integration techniques. In order to avoid the difficulty in analysis due to relative movement between work roll and its thermal boundary, the energy equation is formulated with respect to a fixed Eulerian reference frame. The effect of thermoelastic coupling term, that is generally disregarded in strip rolling, can be considered and assessed. The influences of some important process parameters, such as rotational speed of the roll and intensity of heat flux, on transient solutions are also included and discussed. Furthermore, since the stress history at any point of the roll in both transient and steady state could be accurately evaluated, it is available to perform the analysis of thermal fatigue for the roll by means of previous data.

  19. Time-dependent analytical thermal model to investigate thermally induced stresses in quasi-CW-pumped laser rods

    CSIR Research Space (South Africa)

    Bernhardi, EH

    2008-01-01

    Full Text Available that determines the temperature and the thermally induced stresses in isotropic rods is presented. Even though the model is developed for isotropic rods, it is shown that it can also be used to accurately estimate the thermal effects in anisotropic rods...

  20. Thermoregulatory responses to environmental toxicants: The interaction of thermal stress and toxicant exposure

    International Nuclear Information System (INIS)

    Leon, Lisa R.

    2008-01-01

    Thermal stress can have a profound impact on the physiological responses that are elicited following environmental toxicant exposure. The efficacy by which toxicants enter the body is directly influenced by thermoregulatory effector responses that are evoked in response to high ambient temperatures. In mammals, the thermoregulatory response to heat stress consists of an increase in skin blood flow and moistening of the skin surface to dissipate core heat to the environment. These physiological responses may exacerbate chemical toxicity due to increased permeability of the skin, which facilitates the cutaneous absorption of many environmental toxicants. The core temperature responses that are elicited in response to high ambient temperatures, toxicant exposure or both can also have a profound impact on the ability of an organism to survive the insult. In small rodents, the thermoregulatory response to thermal stress and many environmental toxicants (such as organophosphate compounds) is often biphasic in nature, consisting initially of a regulated reduction in core temperature (i.e., hypothermia) followed by fever. Hypothermia is an important thermoregulatory survival strategy that is used by small rodents to diminish the effect of severe environmental insults on tissue homeostasis. The protective effect of hypothermia is realized by its effects on chemical toxicity as molecular and cellular processes, such as lipid peroxidation and the formation of reactive oxygen species, are minimized at reduced core temperatures. The beneficial effects of fever are unknown under these conditions. Perspective is provided on the applicability of data obtained in rodent models to the human condition

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

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2013-01-01

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

  2. Thermal stress state of cryogenic HP vessels under freezing and pressurization

    International Nuclear Information System (INIS)

    Tsybenko, A.S.; Kuranov, B.A.; Chepurnoj, A.D.; Shaposhnikov, V.A.; Krishchuk, N.G.

    1986-01-01

    A mathematical model is developed for thermomechanical processes in cryogenic HP vessels under freezing either by liquid and (or) gaseous cryogen and under pressurization. Equations of nonlinear nonstationary thermal conductivity and nonisothermal thermoelastoplasticity are used for the case of the theory off low with isotropic hardening. Semiempiricaldependences of nonstationary heat exchange for gaseous medium, experimental curves of cryogenic liquid boiling, mass exchange relationships are allowed for when formulating boundary conditions. The mathematical modelis realized on the basi of the finite element method in the form of highly automated program complex TERSOD (heat resistanceof vessels), oriented for computer of the Unified System. Heat and stress-strained states for three constructions of vessels are thoroughly studied under different conditions of gaseous, liquid and combined freezing with subsequent pressurization

  3. Changes in the performance characteristics of a GaAs near infrared light emitting diode when exposed to various current and thermal stresses

    Science.gov (United States)

    Thomas, E. F., Jr.

    1974-01-01

    The changes that occurred in the optical and electrical characteristics of a near infrared, GaAs light emitting diode, when operated under various levels and combinations of current and thermal stresses are discussed. A total of forty parts were operated for two thousand hours under eight different sets of dc current and ambient temperature conditions. Degradation in the radiant optical power of these devices was thirty-four percent when operated at their rated current and an ambient temperature of 298K (25 C). Derating the current and/or the thermal stress reduced the degradation of this parameter in approximately a linear manner. All degraded devices behaved similarly, exhibiting rapid nonlinear degradation followed by a gradual linear degradation and finally a period of stable operation. An attempt was made to correlate initial device condition to degradation during stress testing, but met with little success.

  4. The application of linear elastic fracture mechanics to thermally stressed welded components

    International Nuclear Information System (INIS)

    Green, D.

    1981-01-01

    Linear Elastic Fracture Mechanics techniques are applied to components constructed from brittle materials and operating at low or ambient temperatures. It is argued that these techniques can justifiably be applied to components at high temperature provided that stresses are thermally induced, self-equilibrating and cyclic. Such loading conditions occur for example in an LMFBR and a simple welded detail containing a crevice is taken as an example. Theoretical and experimental estimates of crack growth in this component are compared and good agreement is shown. (author)

  5. Polyp bailout in Pocillopora damicornis following thermal stress [version 2; referees: 2 approved

    Directory of Open Access Journals (Sweden)

    Alexander J Fordyce

    2017-08-01

    Full Text Available Polyp bailout is an established but understudied coral stress response that involves the detachment of individual polyps from the colonial form as a means of escaping unfavourable conditions. This may influence both the mortality and asexual recruitment of coral genotypes across a range of species. It has been observed in response to numerous stressors including high salinity and low pH. Polyp expulsion in association with thermal stress has once been described in a geographically restricted, temperate species. We therefore cannot reliably apply this observation to tropical coral reefs around the world, which are increasingly under threat from thermal stress events. We present the first qualitative observation of polyp bailout following acute temperature shock  in a near-natural mesocosm experiment. Detached polyps show similar characteristics to those described in previous studies, including the retention of endosymbiotic zooxanthellae and the ability to disperse across short distances. This finding strongly suggests that polyp bailout occurs in tropical coral reef environments and warrants further detailed research into the implication of this response in terms of individual survival, rapid migration into cooler micro-habitats and local recruitment within the reef environment and its coral community.

  6. Investigation on in-vessel thermal transients in a fast breeder reactor

    International Nuclear Information System (INIS)

    Muramatsu, Toshiharu; Kasahara, Naoto

    1999-01-01

    Thermal stratification phenomena are observed in an upper plenum of liquid metal fast breeder reactors (LMFBRs) under reactor scram conditions, which give rise to thermal stress on structural components. Therefore it is important to evaluate characteristics of the phenomena in the design of the internal structures in an LMFBR plenum. To evaluate thermal stress characteristics for the inner barrel in a typical LMFBR upper plenum, numerical analysis was carried out with a multi-dimensional thermohydraulics code AQUA for a scram condition from full power operation conditions. Thereafter, thermal stress conditions for the inner barrel were evaluated by the use of a structural analysis code FINAS with the thermohydraulic results calculated by the AQUA code as boundary conditions. From the thermohydraulic analysis and the thermal stress analysis, the following results have been obtained. (1) A large axial temperature gradient was calculated at the region between the upper and lower flow holes located on the inner barrel. The axial position of the thermal stratification interface was fixed in the various circumferential directions. As for the comparison with a 40% operation condition, maximum temperature gradients at the lower flow hole region indicated a 2 times value of that in the 40% operation condition. (2) Transient thermal stratification phenomena were observed after 120 sec from the reactor scram in the numerical results. These tendencies on thermal stratification phenomena were sameness with the transient results from the 40% operation condition. (3) During the reactor trip from full power operation, large temperature gradient in both vertical and sectional direction are enforced around the lower flow hole, since there exists flow pass of low temperature sodium through this hole. As a result, the maximum thermal stress within 32.6 kg/mm 2 was predicted at the lower flow hole when considering stress concentration at the hole edge. (J.P.N.)

  7. Transient thermal stress problem for a circumferentially cracked hollow cylinder

    Science.gov (United States)

    Nied, H. F.; Erdogan, F.

    1982-01-01

    The transient thermal stress problem for a hollow elasticity cylinder containing an internal circumferential edge crack is considered. It is assumed that the problem is axisymmetric with regard to the crack geometry and the loading, and that the inertia effects are negligible. The problem is solved for a cylinder which is suddenly cooled from inside. First the transient temperature and stress distributions in an uncracked cylinder are calculated. By using the equal and opposite of this thermal stress as the crack surface traction in the isothermal cylinder the crack problem is then solved and the stress intensity factor is calculated. The numerical results are obtained as a function of the Fourier number tD/b(2) representing the time for various inner-to-outer radius ratios and relative crack depths, where D and b are respectively the coefficient of diffusivity and the outer radius of the cylinder.

  8. Thermal stress intensity factor for an axial crack in a clad cylinder

    International Nuclear Information System (INIS)

    Kuo, An Yu; Deardorf, A.F.; Riccardella, P.C.

    1993-01-01

    Many clad pressure vessels have been found to have cracks running through the inside surface cladding and into the base material. Although Young's moduli and Poisson's ratios of the clad and base materials are about the same for most of the industrial applications, coefficients of thermal expansion of the two dissimilar materials, clad and base materials, are usually quite different. For example, low alloy ferritic steel is a common base material for reactor pressure vessels (RPV) and the vessels are usually clad with austenitic stainless steel. Young's moduli for the low alloy steel and stainless steel at 350 F are 29,000 ksi and 28,000 ksi, respectively, while their coefficients of thermal expansion are 7.47x10 -6 in/in and 9.50x10 -6 in/in-degree F, respectively. The mismatch in coefficients of thermal expansion will cause high residual thermal stress even when the entire vessel is at a uniform temperature. This residual stress is one of the primary reasons why so many cracks have been found in the cladded components. In performing reactor pressure vessel integrity evaluation, such as computing probability of brittle fracture of the RPV, it is necessary to calculate stress intensity factors for cracks, which initiate from the clad material and run into the base metal. This paper presents a convenient method of calculating stress intensity factor for an axial crack emanating from the inside surface of a cladded cylinder under thermal loading. A J-integral like line integral was derived and used to calculate the stress intensity factors from finite element stress solutions of the problem

  9. Tasco®, a Product of Ascophyllum nodosum, Imparts Thermal Stress Tolerance in Caenorhabditis elegans

    Directory of Open Access Journals (Sweden)

    Franklin Evans

    2011-11-01

    Full Text Available Tasco®, a commercial product manufactured from the brown alga Ascophyllum nodosum, has been shown to impart thermal stress tolerance in animals. We investigated the physiological, biochemical and molecular bases of this induced thermal stress tolerance using the invertebrate animal model, Caenorhabiditis elegans. Tasco® water extract (TWE at 300 µg/mL significantly enhanced thermal stress tolerance as well as extended the life span of C. elegans. The mean survival rate of the model animals under thermal stress (35 °C treated with 300 µg/mL and 600 µg/mL TWE, respectively, was 68% and 71% higher than the control animals. However, the TWE treatments did not affect the nematode body length, fertility or the cellular localization of daf-16. On the contrary, TWE under thermal stress significantly increased the pharyngeal pumping rate in treated animals compared to the control. Treatment with TWE also showed differential protein expression profiles over control following 2D gel-electrophoresis analysis. Furthermore, TWE significantly altered the expression of at least 40 proteins under thermal stress; among these proteins 34 were up-regulated while six were down-regulated. Mass spectroscopy analysis of the proteins altered by TWE treatment revealed that these proteins were related to heat stress tolerance, energy metabolism and a muscle structure related protein. Among them heat shock proteins, superoxide dismutase, glutathione peroxidase, aldehyde dehydrogenase, saposin-like proteins 20, myosin regulatory light chain 1, cytochrome c oxidase RAS-like, GTP-binding protein RHO A, OS were significantly up-regulated, while eukaryotic translation initiation factor 5A-1 OS, 60S ribosomal protein L18 OS, peroxiredoxin protein 2 were down regulated by TWE treatment. These results were further validated by gene expression and reporter gene expression analyses. Overall results indicate that the water soluble components of Tasco® imparted thermal stress

  10. Behavioural responses to thermal conditions affect seasonal mass change in a heat-sensitive northern ungulate.

    Directory of Open Access Journals (Sweden)

    Floris M van Beest

    Full Text Available BACKGROUND: Empirical tests that link temperature-mediated changes in behaviour (activity and resource selection to individual fitness or condition are currently lacking for endotherms yet may be critical to understanding the effect of climate change on population dynamics. Moose (Alces alces are thought to suffer from heat stress in all seasons so provide a good biological model to test whether exposure to non-optimal ambient temperatures influence seasonal changes in body mass. Seasonal mass change is an important fitness correlate of large herbivores and affects reproductive success of female moose. METHODOLOGY/PRINCIPAL FINDINGS: Using GPS-collared adult female moose from two populations in southern Norway we quantified individual differences in seasonal activity budget and resource selection patterns as a function of seasonal temperatures thought to induce heat stress in moose. Individual body mass was recorded in early and late winter, and autumn to calculate seasonal mass changes (n = 52 over winter, n = 47 over summer. We found large individual differences in temperature-dependent resource selection patterns as well as within and between season variability in thermoregulatory strategies. As expected, individuals using an optimal strategy, selecting young successional forest (foraging habitat at low ambient temperatures and mature coniferous forest (thermal shelter during thermally stressful conditions, lost less mass in winter and gained more mass in summer. CONCLUSIONS/SIGNIFICANCE: This study provides evidence that behavioural responses to temperature have important consequences for seasonal mass change in moose living in the south of their distribution in Norway, and may be a contributing factor to recently observed declines in moose demographic performance. Although the mechanisms that underlie the observed temperature mediated habitat-fitness relationship remain to be tested, physiological state and individual variation in

  11. Behavioural responses to thermal conditions affect seasonal mass change in a heat-sensitive northern ungulate.

    Science.gov (United States)

    van Beest, Floris M; Milner, Jos M

    2013-01-01

    Empirical tests that link temperature-mediated changes in behaviour (activity and resource selection) to individual fitness or condition are currently lacking for endotherms yet may be critical to understanding the effect of climate change on population dynamics. Moose (Alces alces) are thought to suffer from heat stress in all seasons so provide a good biological model to test whether exposure to non-optimal ambient temperatures influence seasonal changes in body mass. Seasonal mass change is an important fitness correlate of large herbivores and affects reproductive success of female moose. Using GPS-collared adult female moose from two populations in southern Norway we quantified individual differences in seasonal activity budget and resource selection patterns as a function of seasonal temperatures thought to induce heat stress in moose. Individual body mass was recorded in early and late winter, and autumn to calculate seasonal mass changes (n = 52 over winter, n = 47 over summer). We found large individual differences in temperature-dependent resource selection patterns as well as within and between season variability in thermoregulatory strategies. As expected, individuals using an optimal strategy, selecting young successional forest (foraging habitat) at low ambient temperatures and mature coniferous forest (thermal shelter) during thermally stressful conditions, lost less mass in winter and gained more mass in summer. This study provides evidence that behavioural responses to temperature have important consequences for seasonal mass change in moose living in the south of their distribution in Norway, and may be a contributing factor to recently observed declines in moose demographic performance. Although the mechanisms that underlie the observed temperature mediated habitat-fitness relationship remain to be tested, physiological state and individual variation in thermal tolerance are likely contributory factors. Climate-related effects on animal

  12. Thermal expansion coefficients of obliquely deposited MgF2 thin films and their intrinsic stress.

    Science.gov (United States)

    Jaing, Cheng-Chung

    2011-03-20

    This study elucidates the effects of columnar angles and deposition angles on the thermal expansion coefficients and intrinsic stress behaviors of MgF2 films with columnar microstructures. The behaviors associated with temperature-dependent stresses in the MgF2 films are measured using a phase-shifting Twyman-Green interferometer with a heating stage and the application of a phase reduction algorithm. The thermal expansion coefficients of MgF2 films at various columnar angles were larger than those of glass substrates. The intrinsic stress in the MgF2 films with columnar microstructures was compressive, while the thermal stress was tensile. The thermal expansion coefficients of MgF2 films with columnar microstructures and their intrinsic stress evidently depended on the deposition angle and the columnar angle.

  13. Survival of juvenile fishes receiving thermal and mechanical stresses in a simulated power plant condenser

    International Nuclear Information System (INIS)

    Kedl, R.J.; Coutant, C.C.

    Experiments were conducted in a water-recirculating loop to determine the effects of fluid-induced stresses (e.g., turbulence, pressure, and vacuum) on six species of larval fish and one species each of frog tadpoles and zooplankton. These stresses simulate the insults developed in the condenser portion, but not including the pump, of a steam power plant. Some experiments were conducted with thermal stresses superimposed on fluid-induced stresses. Fluid-induced stresses of the magnitude developed in these experiments were generally not fatal to the larval fish within the precision of the experiments, although some sublethal effects were noted. When thermal stress was superimposed on the fluid-induced stresses, the mortalities were equivalent to those resulting from thermal stress alone. Fluid-induced stresses of low magnitude were not fatal to Daphnia magna, but fluid-induced stresses of higher magnitude were responsible for significant mortalities. (U.S.)

  14. Prediction of deformation and hygro-thermal stresses distribution in PEM fuel cell vehicle using three-dimensional CFD model

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-07-01

    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. The damage mechanisms in a PEM 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 damage mechanisms in the membrane, 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 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. 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 stresses distribution that have limited experimental data. This model is used to study and analyse the effect of operating parameters on the

  15. Transient thermal stresses in composite hollow circular cylinder due to partial heat generation

    International Nuclear Information System (INIS)

    Goshima, Takahito; Miyao, Kaju

    1979-01-01

    Clad materials are adopted for the machines and structures used in contact with high temperature, corrosive atmosphere in view of their strength and economy. Large thermal stress sometimes arises in clad cylinders due to uneaven temperature field and the difference in linear thermal expansion. Vessels are often heated uneavenly, and shearing stress occurs, which is not observed in uniform heating. In this study, infinitely long, concentric cylinders of two layers were analyzed, when the internal heat changing in stepped state is generated in cylindrical form. The unsteady thermal stress occurred was determined, using thermo-elastic potential and stress functions, and assuming the thermal properties and elastic modulus of materials as constant regardless of the temperature. Laplace transformation was used, and the basic equations for thermo-elastic displacement were employed as the basis of calculation. The analysis of the temperature distribution and stress is explained. Numerical calculation was carried out on the example of an internal cylinder of SUS 304 stainless steel and an external cylinder of mild steel. The maximum shearing stress occurred in the direction of 40 deg from the heat source, and was affected largely by the position of heat generation. The effect became remarkable as time elapsed. (Kako, I.)

  16. Effect of thermal stresses on the mechanism of tooth pain.

    Science.gov (United States)

    Oskui, Iman Z; Ashtiani, Mohammed N; Hashemi, Ata; Jafarzadeh, Hamid

    2014-11-01

    Daily hot and cold thermal loadings on teeth may result in structural deformation, mechanical stress, and pain signaling. The aim of this study was to compare the adverse effects of hot and cold beverages on an intact tooth and, then, to provide physical evidence to support the hydrodynamic theory of tooth pain sensation mechanism. Three-dimensional finite element analysis was performed on a premolar model subjected to hot and cold thermal loadings. Elapsed times for heat diffusion and stress detection at the pulp-dentin junction were calculated as measures of the pain sensation. Extreme tensile stress within the enamel resulted in damage in cold loadings. Also, extreme values of stress at the pulpal wall occurred 21.6 seconds earlier than extreme temperatures in hot and cold loadings. The intact tooth was remarkably vulnerable to cold loading. Earlier changes in mechanical stress rather than temperature at the pulp-dentin junction indicate that the dental pain caused by hot or cold beverages may be based on the hydrodynamic theory. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  17. Evaluation of thermal stress in the anode chamber wall of a large volume magnetic bucket ion source

    International Nuclear Information System (INIS)

    Wells, Russell; Horiike, Hiroshi; Kuriyama, Masaaki; Ohara, Yoshihiro

    1984-02-01

    Thermal stress analysis was performed on the plasma chamber of the Large Volume Magnetic Multipole Bucket Ion Source (LVB) designed for use on the JT-60 NBI system. The energy absorbed by the walls of the plasma chambers of neutral beam injectors is of the order of 1% of the accelerator electrical drain power. A previous study indicates that a moderately high heat flux, of about 600W/cm 2 , is concentrated on the magnetic field cusp lines during normal full power operation. Abnormal arc discharges during conditioning of a stainless steel LVB produced localized melting of the stainless steel at several locations near the cusps lines. The power contained in abnormal arc discharges (arc spots) was estimated from the observed melting. Thermal stress analysis was performed numerically on representative sections of the copper LVB design for both stable and abnormal arc discharge conditions. Results show that this chamber should not fail due to thermal fatigue stesses arising from normal arc discharges. However, fatigue failure may occur after several hundred to a few thousand arc spots of 30mS duration at any one location. Limited arc discharge operation of the copper bucket was performed to partially verify the chamber's durability. (author)

  18. Mosaic-shaped cathode for highly durable solid oxide fuel cell under thermal stress

    Science.gov (United States)

    Joo, Jong Hoon; Jeong, Jaewon; Kim, Se Young; Yoo, Chung-Yul; Jung, Doh Won; Park, Hee Jung; Kwak, Chan; Yu, Ji Haeng

    2014-02-01

    In this study, we propose a novel "mosaic structure" for a SOFC (solid oxide fuel cell) cathode with high thermal expansion to improve the stability against thermal stress. Self-organizing mosaic-shaped cathode has been successfully achieved by controlling the amount of binder in the dip-coating solution. The anode-supported cell with mosaic-shaped cathode shows itself to be highly durable performance for rapid thermal cycles, however, the performance of the cell with a non-mosaic cathode exhibits severe deterioration originated from the delamination at the cathode/electrolyte interface after 7 thermal cycles. The thermal stability of an SOFC cathode can be evidently improved by controlling the surface morphology. In view of the importance of the thermal expansion properties of the cathode, the effects of cathode morphology on the thermal stress stability are discussed.

  19. Effects of chronic thermal stress on growth performance, carcass traits, antioxidant indices and the expression of HSP70, growth hormone and superoxide dismutase genes in two broiler strains.

    Science.gov (United States)

    Roushdy, Elshimaa M; Zaglool, Asmaa W; El-Tarabany, Mahmoud S

    2018-05-01

    The objective was to investigate the effects of genetic type and the duration of chronic thermal stress (36 °C) on the growing efficiency, carcass traits, antioxidant status, and the expression of liver heat shock protein 70 (HSP70), growth hormone (GH) and superoxide dismutase (SOD) genes. Two hundred and seventy one-day-old chicks (135 male chicks of each breed; Ross 308 and Cobb 500) were used in this work. On the 21st day of age, birds were allocated randomly into 3 equal groups till the 42 days of age (CON:raised in a thermoneutral condition; HS 1 and HS 2 groups were subjected to 4 and 6 h of daily thermal stress, respectively). Regardless of genetic type, thermal stress decreased the dressing percentage in broilers when compared with the thermoneutral conditions (p = 0.039). In both broiler strains, thermal stress for 6 h (HS 2 ) increased the heterophil to lymphocyte ratio (p = 0.036) and the serum albumin, cholesterol and triglyceride levels (p = 0.023, 0.012 and 0.005, respectively) compared with the thermoneutral group. Under the thermonuteral and heat stress conditions, the Ross broiler chickens showed a significant lower serum triiodothyronine level compared with the Cobb boilers (p = 0.042). It is interesting to note that the expression of HSP70 in the liver of heat-stressed Ross broilers, either 4 or 6 h, was significantly (p = 0.002) higher than that reported in the heat-stressed Cobb broilers. In both broiler strains, the thermal stress for 6 h up-regulate the expression of SOD gene (p = 0.001), but down-regulate the expression of GH gene (p = 0.021) when compared with the CON group. In conclusion, chronic thermal stress down-regulate the mRNA expression of liver GH, concomitantly with an increase in the expression of HSP70 and SOD genes in both broiler strains. This could be useful in the identification of molecular genetic markers to assist in selecting broilers that are more tolerant to heat stress

  20. Lipocalin 2 regulation by thermal stresses: Protective role of Lcn2/NGAL against cold and heat stresses

    International Nuclear Information System (INIS)

    Roudkenar, Mehryar Habibi; Halabian, Raheleh; Roushandeh, Amaneh Mohammadi; Nourani, Mohammad Reza; Masroori, Nasser; Ebrahimi, Majid; Nikogoftar, Mahin; Rouhbakhsh, Mehdi; Bahmani, Parisa; Najafabadi, Ali Jahanian; Shokrgozar, Mohammad Ali

    2009-01-01

    Environmental temperature variations are the most common stresses experienced by a wide range of organisms. Lipocalin 2 (Lcn2/NGAL) is expressed in various normal and pathologic conditions. However, its precise functions have not been fully determined. Here we report the induction of Lcn2 by thermal stresses in vivo, and its role following exposure to cold and heat stresses in vitro. Induction of Lcn2 in liver, heart and kidney was detected by RT-PCR, Western blot and immunohistochemistry following exposure of mice to heat and cold stresses. When CHO and HEK293T cells overexpressing NGAL were exposed to cold stress, cell proliferation was higher compared to controls. Down-regulatrion of NGAL by siRNA in A549 cells resulted in less proliferation when exposed to cold stress compared to control cells. The number of apoptotic cells and expression of pro-apoptotic proteins were lower in the NGAL overexpressing CHO and HEK293T cells, but were higher in the siRNA-transfected A549 cells compared to controls, indicating that NGAL protects cells against cold stress. Following exposure of the cells to heat stress, ectopic expression of NGAL protected cells while addition of exogenous recombinant NGAL to the cell culture medium exacerbated the toxicity of heat stress specially when there was low or no endogenous expression of NGAL. It had a dual effect on apoptosis following heat stress. NGAL also increased the expression of HO-1. Lcn2/NGAL may have the potential to improve cell proliferation and preservation particularly to prevent cold ischemia injury of transplanted organs or for treatment of some cancers by hyperthermia.

  1. Lipocalin 2 regulation by thermal stresses: Protective role of Lcn2/NGAL against cold and heat stresses

    Energy Technology Data Exchange (ETDEWEB)

    Roudkenar, Mehryar Habibi, E-mail: roudkenar@ibto.ir [Research Center, Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Halabian, Raheleh [Research Center, Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Roushandeh, Amaneh Mohammadi [Department of Anatomy, Faculty of Medicine, Medical University of Tabriz, Tabriz (Iran, Islamic Republic of); Nourani, Mohammad Reza [Chemical Injury Research Center, Baqiyatallah Medical Science University, Tehran (Iran, Islamic Republic of); Masroori, Nasser [Research Center, Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Ebrahimi, Majid [Research Center, Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Chemical Injury Research Center, Baqiyatallah Medical Science University, Tehran (Iran, Islamic Republic of); Nikogoftar, Mahin; Rouhbakhsh, Mehdi; Bahmani, Parisa [Research Center, Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Najafabadi, Ali Jahanian [Department of Molecular Biology, Pasteur Institute of Iran, Tehran (Iran, Islamic Republic of); Shokrgozar, Mohammad Ali [National Cell Bank of Iran, Pasteur institute of Iran, Tehran (Iran, Islamic Republic of)

    2009-11-01

    Environmental temperature variations are the most common stresses experienced by a wide range of organisms. Lipocalin 2 (Lcn2/NGAL) is expressed in various normal and pathologic conditions. However, its precise functions have not been fully determined. Here we report the induction of Lcn2 by thermal stresses in vivo, and its role following exposure to cold and heat stresses in vitro. Induction of Lcn2 in liver, heart and kidney was detected by RT-PCR, Western blot and immunohistochemistry following exposure of mice to heat and cold stresses. When CHO and HEK293T cells overexpressing NGAL were exposed to cold stress, cell proliferation was higher compared to controls. Down-regulatrion of NGAL by siRNA in A549 cells resulted in less proliferation when exposed to cold stress compared to control cells. The number of apoptotic cells and expression of pro-apoptotic proteins were lower in the NGAL overexpressing CHO and HEK293T cells, but were higher in the siRNA-transfected A549 cells compared to controls, indicating that NGAL protects cells against cold stress. Following exposure of the cells to heat stress, ectopic expression of NGAL protected cells while addition of exogenous recombinant NGAL to the cell culture medium exacerbated the toxicity of heat stress specially when there was low or no endogenous expression of NGAL. It had a dual effect on apoptosis following heat stress. NGAL also increased the expression of HO-1. Lcn2/NGAL may have the potential to improve cell proliferation and preservation particularly to prevent cold ischemia injury of transplanted organs or for treatment of some cancers by hyperthermia.

  2. Coupling analysis of the target temperature and thermal stress due to pulsed ion beam

    International Nuclear Information System (INIS)

    Yan Jie; Liu Meng; Lin Jufang; An Li; Long Xinggui

    2013-01-01

    Background: Target temperature has an important effect on the target life for the sealed neutron generator without cooling system. Purpose: To carry out the thermal-mechanical coupling analysis of the film-substrate target bombarded by the pulsed ion beam. Methods: The indirect coupling Finite Element Method (FEM) with a 2-dimensional time-space Gaussian axisymmetric power density as heat source was used to simulate the target temperature and thermal stress fields. Results: The effects of the target temperature and thermal stress fields under difference pulse widths and beam sizes were analyzed in terms of the FEM results. Conclusions: Combining with the temperature requirement and the thermal stress inducing film thermal mechanical destruction effect of the sealed neutron generator film-substrate targets, an optimized pulsed ion beam work status was proposed. (authors)

  3. Thermal stresses and cyclic creep-fatigue in fusion reactor blanket

    International Nuclear Information System (INIS)

    Liu, K.C.

    1977-01-01

    Thermal stresses in the first walls of fusion reactor blankets were studied in detail. ORNL multibucket modules are emphasized. Practicality of using the bucket module rather than other blanket designs is examined. The analysis shows that applying intelligent engineering judgment in design can reduce the thermal stresses significantly. Arrangement of coolant flow and distribution of temperature are reviewed. Creep-fatigue property requirements for a first wall are discussed on the basis of existing design rules and criteria. Some major questions are pointed out and experiments needed to resolve basic uncertainties relative to key design decisions are discussed

  4. Finite element analysis of thermal stresses of the reactor vessel in a severe light water reactor accident

    International Nuclear Information System (INIS)

    Borovkov, A.I.; Semenov, A.S.; Granovsky, V.S.; Kovtunova, S.V.

    1995-01-01

    The thermal stress and damage analysis of the light water reactor (LWR) vessel is considered in a severe accident conditions. The high temperature corium accumulates on the vessel bottom and necessary condition of its holding is intensive cooling of vessel. External flooding with outside cooling of the LWR vessel is one of the accident management strategies being proposed to ensure the integrity of the vessel after a severe accident. (author). 8 refs., 5 figs

  5. Finite element analysis of thermal stresses of the reactor vessel in a severe light water reactor accident

    Energy Technology Data Exchange (ETDEWEB)

    Borovkov, A.I.; Semenov, A.S. [St. Petersburg State Technical Univ. (Russian Federation); Granovsky, V.S.; Kovtunova, S.V. [Research Inst. of Technology, Sosnovy Bor (Russian Federation)

    1995-12-31

    The thermal stress and damage analysis of the light water reactor (LWR) vessel is considered in a severe accident conditions. The high temperature corium accumulates on the vessel bottom and necessary condition of its holding is intensive cooling of vessel. External flooding with outside cooling of the LWR vessel is one of the accident management strategies being proposed to ensure the integrity of the vessel after a severe accident. (author). 8 refs., 5 figs.

  6. Transient thermal stresses in a transversely isotropic finite hollow circular cylinder due to arbitrary surface heat generations

    International Nuclear Information System (INIS)

    Sugano, Yoshihiro; Nakanishi, Takanori.

    1980-01-01

    The materials macroscopically regarded as anisotropic materials such as fiber-reinforced composite materials have become to be used for the structural elements at elevated temperature, and the studies on the problem of thermal stress in anisotropic bodies are carried out actively. The unsteady thermal stress in anisotropic finite circular cylinders has not been analyzed so far. In this study, the problem of unsteady thermal stress in an anisotropic finite circular cylinder having arbitrary surface heat generation in axial direction on the internal and external surfaces, and emitting heat from both ends and the internal and external surfaces, was analyzed. For the analysis of temperature distribution, generalized finite Fourier transformation and finite Hankel transformation were used, and thermal stress and thermal displacement were analyzed by the use of the stress function of Singh. By adopting the function used for the transformation nucleus in generalized finite Fourier transformation as the stress function, the analysis was made without separating symmetric and opposite symmetric problems. Numerical calculation was carried out on the basis of the analytical results, and the effects of the anisotropy in thermal conductivity, Young's modulus and linear expansion on unsteady temperature distribution, thermal stress and thermal displacement were quantitatively examined. (Kako, I.)

  7. Geographic variation in responses of European yellow dung flies to thermal stress.

    Science.gov (United States)

    Bauerfeind, Stephanie S; Sørensen, Jesper G; Loeschcke, Volker; Berger, David; Broder, E Dale; Geiger, Madeleine; Ferrari, Manuela; Blanckenhorn, Wolf U

    2018-04-01

    Climatic conditions can be very heterogeneous even over small geographic scales, and are believed to be major determinants of the abundance and distribution of species and populations. Organisms are expected to evolve in response to the frequency and magnitude of local thermal extremes, resulting in local adaptation. Using replicate yellow dung fly (Scathophaga stercoraria; Diptera: Scathophagidae) populations from cold (northern Europe) and warm climates (southern Europe), we compared 1) responses to short-term heat and cold shocks in both sexes, 2) heat shock protein (Hsp70) expression in adults and eggs, and 3) female reproductive traits when facing short-term heat stress during egg maturation. Contrary to expectations, thermal traits showed minor geographic differentiation, with weak evidence for greater heat resistance of southern flies but no differentiation in cold resistance. Hsp70 protein expression was little affected by heat stress, indicating systemic rather than induced regulation of the heat stress response, possibly related to this fly group's preference for cold climes. In contrast, sex differences were pronounced: males (which are larger) endured hot temperatures longer, while females featured higher Hsp70 expression. Heat stress negatively affected various female reproductive traits, reducing first clutch size, overall reproductive investment, egg lipid content, and subsequent larval hatching. These responses varied little across latitude but somewhat among populations in terms of egg size, protein content, and larval hatching success. Several reproductive parameters, but not Hsp70 expression, exhibited heritable variation among full-sib families. Rather than large-scale clinal geographic variation, our study suggests some local geographic population differentiation in the ability of yellow dung flies to buffer the impact of heat stress on reproductive performance. Copyright © 2018 Elsevier Ltd. All rights reserved.

  8. The effect of atmospheric thermal conditions and urban thermal pollution on all-cause and cardiovascular mortality in Bangladesh.

    Science.gov (United States)

    Burkart, Katrin; Schneider, Alexandra; Breitner, Susanne; Khan, Mobarak Hossain; Krämer, Alexander; Endlicher, Wilfried

    2011-01-01

    This study assessed the effect of temperature and thermal atmospheric conditions on all-cause and cardiovascular mortality in Bangladesh. In particular, differences in the response to elevated temperatures between urban and rural areas were investigated. Generalized additive models (GAMs) for daily death counts, adjusted for trend, season, day of the month and age were separately fitted for urban and rural areas. Breakpoint models were applied for determining the increase in mortality above and below a threshold (equivalent) temperature. Generally, a 'V'-shaped (equivalent) temperature-mortality curve with increasing mortality at low and high temperatures was observed. Particularly, urban areas suffered from heat-related mortality with a steep increase above a specific threshold. This adverse heat effect may well increase with ongoing urbanization and the intensification of the urban heat island due to the densification of building structures. Moreover, rising temperatures due to climate change could aggravate thermal stress. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Low-stress photosensitive polyimide suspended membrane for improved thermal isolation performance

    Science.gov (United States)

    Fan, J.; Xing, R. Y.; Wu, W. J.; Liu, H. F.; Liu, J. Q.; Tu, L. C.

    2017-11-01

    In this paper, we introduce a method of isolating thermal conduction from silicon substrate for accommodating thermal-sensitive micro-devices. This method lies in fabrication of a low-stress photosensitive polyimide (PSPI) suspension structure which has lower thermal conductivity than silicon. First, a PSPI layer was patterned on a silicon wafer and hard baked. Then, a cavity was etched from the backside of the silicon substrate to form a membrane or a bridge-shape PSPI structure. After releasing, a slight deformation of about 20 nm was observed in the suspended structures, suggesting ultralow residual stress which is essential for accommodating micro-devices. In order to investigate the thermal isolation performance of the suspended PSPI structures, micro Pirani vacuum gauges, which are thermal-sensitive, had been fabricated on the PSPI structures. The measurement results illustrated that the Pirani gauges worked as expected in the range from 1- 470 Pa. Moreover, the results of the Pirani gauges based on the membrane and bridge structures were comparable, indicating that the commonly used bridge-shape structure for further reducing thermal conduction was unnecessary. Due to the excellent thermal isolation performance of PSPI, the suspended PSPI membrane is promising to be an outstanding candidate for thermal isolation applications.

  10. Stress and reliability analyses of multilayered composite cylinder under thermal and mechanical loads

    Science.gov (United States)

    Wang, Xiaohua

    The coupling resulting from the mutual influence of material thermal and mechanical parameters is examined in the thermal stress analysis of a multilayered isotropic composite cylinder subjected to sudden axisymmetric external and internal temperature. The method of complex frequency response functions together with the Fourier transform technique is utilized. Because the coupling parameters for some composite materials, such as carbon-carbon, are very small, the effect of coupling is neglected in the orthotropic thermal stress analysis. The stress distributions in multilayered orthotropic cylinders subjected to sudden axisymmetric temperature loading combined with dynamic pressure as well as asymmetric temperature loading are also obtained. The method of Fourier series together with the Laplace transform is utilized in solving the heat conduction equation and thermal stress analysis. For brittle materials, like carbon-carbon composites, the strength variability is represented by two or three parameter Weibull distributions. The 'weakest link' principle which takes into account both the carbon-carbon composite cylinders. The complex frequency response analysis is performed on a multilayered orthotropic cylinder under asymmetrical thermal load. Both deterministic and random thermal stress and reliability analyses can be based on the results of this frequency response analysis. The stress and displacement distributions and reliability of rocket motors under static or dynamic line loads are analyzed by an elasticity approach. Rocket motors are modeled as long hollow multilayered cylinders with an air core, a thick isotropic propellant inner layer and a thin orthotropic kevlar-epoxy case. The case is treated as a single orthotropic layer or a ten layered orthotropic structure. Five material properties and the load are treated as random variable with normal distributions when the reliability of the rocket motor is analyzed by the first-order, second-moment method (FOSM).

  11. Effects of thermal residual stresses and fiber packing on deformation of metal-matrix composites

    International Nuclear Information System (INIS)

    Nakamura, T.; Suresh, S.

    1993-01-01

    The combined effects of thermal residual stresses and fiber spatial distribution on the deformation of a 6061 aluminum alloy containing a fixed concentration unidirectional boron fibers have been analyzed using detailed finite element models. The geometrical structure includes perfectly periodic, uniformly space fiber arrangements in square and hexagonal cells, as well as different cells in which either 30 or 60 fibers are randomly placed in the ductile matrix. The model involves an elastic-plastic matrix, elastic fibers, and mechanically bonded interfaces. The results indicate that both fiber packing and thermal residual stresses can have a significant effect on the stress-strain characteristics of the composite. The thermal residual stresses cause pronounced matrix yielding which also influences the apparent overall stiffness of the composite during the initial stages of subsequent far-field loading along the axial and transverse direction. Furthermore, the thermal residual stresses apparently elevate the flow stress of the composite during transverse tension. Such effects can be traced back to the level of constraint imposed on the matrix by local fiber spacing. The implications of the present results to the processing of the composites are also briefly addressed

  12. Alternative body sites for heat stress measurement in milking cows under tropical conditions and their relationship to the thermal discomfort of the animals

    Science.gov (United States)

    Martello, Luciane S.; Savastano Junior, Holmer; Silva, Saulo L.; Balieiro, Júlio Cesar C.

    2010-11-01

    This study was conducted to determine the relationship among temperatures measured at different anatomical sites of the animal body and their daily pattern as indicative of the thermal stress in lactating dairy cows under tropical conditions. Environmental dry bulb (DBT) and black globe (BGT) temperatures and relative humidity (RH) were recorded. Rectal temperature (RT), respiratory frequency (RF), body surface (BST), internal base of tail (TT), vulva (VT) and auricular temperatures (AT) were collected, from 37 Black and White Holstein cows at 0700, 1300 and 1800 hours. RT showed a moderately and positive correlations with all body temperatures, ranging from 0.59 with TT to 0.64 with BST. Correlations among AT, VT and TT with RF were very similar (from 0.63 to 0.64) and were greater than those observed for RF with RT (0.55) or with BST (0.54). RF and RT were positively correlated to TT (0.63 and 0.59, respectively), AT (r = 0.63 for both) and VT ( r = 0.64 and 0.63, respectively). Positive and very high correlations were observed among AT, VT and TT (from 0.94 to 0.97) indicating good association of temperatures measured in these anatomical sites. Correlations of BST with AT and VT were positive and very similar (0.71 and 0.72, respectively) and lower with TT (0.66). The AT, TT, VT and BST presented similar patterns and follow the variations of DBT through the day. Temperatures measured at different anatomical sites of the animal body have the potential to be used as indicative of the thermal stress in lactating dairy cows.

  13. Modelling and analysis of radial thermal stresses and temperature ...

    African Journals Online (AJOL)

    user

    The temperature field, heat transfer rate and thermal stresses were investigated with numerical simulation models using FORTRAN FE (finite element) software. ...... specific heats, International Communications in Heat and Mass Transfer, Vol.

  14. Residual stress determination in thermally sprayed metallic deposits by neutron diffraction

    International Nuclear Information System (INIS)

    Keller, Thomas; Margadant, Nikolaus; Pirling, Thilo; Riegert-Escribano, Maria J.; Wagner, Werner

    2004-01-01

    Neutron diffraction was used to obtain spatially resolved strain and stress profiles in thermally sprayed metallic 'NiCrAlY' deposits (chemical composition 67 wt.% Ni, 22 wt.% Cr, 10 wt.% Al, 1 wt.% Y) and the underlying steel substrates. Samples of four different spray techniques were analyzed: atmospheric and water stabilized plasma spraying (APS and WSP), flame spraying (FS) and wire arc spraying (WAS). The results are quantitatively compared with the average in-plane residual stress determined by complementary bending tests and the hole drilling technique. While the stress profiles from the surface to the interface in the deposits are similar for all investigated spray techniques, their absolute values and gradients vary strongly. This is attributed to different quenching stresses from the impinging particles, different thermal histories the deposit/substrate systems undergo during the spraying and subsequent cooling, and also to different coating properties. In the water stabilized plasma sprayed and the wire arc sprayed deposits, a gradient in the stress-free lattice parameter was observed. Crack formation is found to be a dominant mechanism for stress relaxation in the surface plane

  15. Haemoglobin-mediated response to hyper-thermal stress in the keystone species Daphnia magna.

    Science.gov (United States)

    Cuenca Cambronero, Maria; Zeis, Bettina; Orsini, Luisa

    2018-01-01

    Anthropogenic global warming has become a major geological and environmental force driving drastic changes in natural ecosystems. Due to the high thermal conductivity of water and the effects of temperature on metabolic processes, freshwater ecosystems are among the most impacted by these changes. The ability to tolerate changes in temperature may determine species long-term survival and fitness. Therefore, it is critical to identify coping mechanisms to thermal and hyper-thermal stress in aquatic organisms. A central regulatory element compensating for changes in oxygen supply and ambient temperature is the respiratory protein haemoglobin (Hb). Here, we quantify Hb plastic and evolutionary response in Daphnia magna subpopulations resurrected from the sedimentary archive of a lake with known history of increase in average temperature and recurrence of heat waves. By measuring constitutive changes in crude Hb protein content among subpopulations, we assessed evolution of the Hb gene family in response to temperature increase. To quantify the contribution of plasticity in the response of this gene family to hyper-thermal stress, we quantified changes in Hb content in all subpopulations under hyper-thermal stress as compared to nonstressful temperature. Further, we tested competitive abilities of genotypes as a function of their Hb content, constitutive and induced. We found that Hb-rich genotypes have superior competitive abilities as compared to Hb-poor genotypes under hyper-thermal stress after a period of acclimation. These findings suggest that whereas long-term adjustment to higher occurrence of heat waves may require a combination of plasticity and genetic adaptation, plasticity is most likely the coping mechanism to hyper-thermal stress in the short term. Our study suggests that with higher occurrence of heat waves, Hb-rich genotypes may be favoured with potential long-term impact on population genetic diversity.

  16. A Lumped Thermal Model Including Thermal Coupling and Thermal Boundary Conditions for High Power IGBT Modules

    DEFF Research Database (Denmark)

    Bahman, Amir Sajjad; Ma, Ke; Blaabjerg, Frede

    2018-01-01

    Detailed thermal dynamics of high power IGBT modules are important information for the reliability analysis and thermal design of power electronic systems. However, the existing thermal models have their limits to correctly predict these complicated thermal behavior in the IGBTs: The typically used...... thermal model based on one-dimensional RC lumps have limits to provide temperature distributions inside the device, moreover some variable factors in the real-field applications like the cooling and heating conditions of the converter cannot be adapted. On the other hand, the more advanced three......-dimensional thermal models based on Finite Element Method (FEM) need massive computations, which make the long-term thermal dynamics difficult to calculate. In this paper, a new lumped three-dimensional thermal model is proposed, which can be easily characterized from FEM simulations and can acquire the critical...

  17. Numerical simulation of time-dependent deformations under hygral and thermal transient conditions

    International Nuclear Information System (INIS)

    Roelfstra, P.E.

    1987-01-01

    Some basic concepts of numerical simulation of the formation of the microstructure of HCP are outlined. The aim is to replace arbitrary terms like aging by more realistic terms like bond density in the xerogel and bonds between hydrating particles of HCP. Actual state parameters such as temperature, humidity and degree of hydration can be determined under transient hygral and thermal conditions by solving numerically a series of appropriate coupled differential equations with given boundary conditions. Shrinkage of a composite structure without crack formation, based on calculated moisture distributions, has been determined with numerical concrete codes. The influence of crack formation, tensile strain-hardening and softening on the total deformation of a quasi-homogeneous drying material has been studied by means of model based on FEM. The difference between shrinkage without crack formation and shrinkage with crack formation can be quantified. Drying shrinkage and creep of concrete cannot be separated. The total deformation depends on the superimposed stress fields. Transient hygral deformation can be realistically predicted if the concept of point properties is applied rigorously. Transient thermal deformation has to be dealt with in the same way. (orig./HP)

  18. Thermal and stress analyses in thermoelectric generator with tapered and rectangular pin configurations

    International Nuclear Information System (INIS)

    Yilbas, Bekir Sami; Akhtar, S.S.; Sahin, A.Z.

    2016-01-01

    Thermal stress developed in thermoelectric generators is critical for long service applications. High temperature gradients, due to a large temperature difference across the junctions, causes excessive stress levels developed in the device pins and electrodes at the interfaces. In the present study, a thermoelectric generator with horizontal pin configuration is considered and thermal stress analysis in the device is presented. Ceramic wafer is considered to resemble the high temperature plate and copper electrodes are introduced at the pin junctions to reduce the electrical resistance between the pins and the high and low temperature junction plates during the operation. Finite element code is used to simulate temperature and stress fields in the thermoelectric generator. In the simulations, convection and radiation losses from the thermoelectric pins are considered and bismuth telluride pin material with and without tapering is incorporated. It is found that von Mises stress attains high values at the interface between the hot and cold junctions and the copper electrodes. Thermal stress developed in tapered pin configuration attains lower values than that of rectangular pin cross-section. - Highlights: • Different cold junction temperatures improves thermoelectric generator performance. • von Mises stress remains high across copper electrodes and hot junction ceramics. • von Mises stress reduces along pin length towards cold junction. • Pin tapering lowers stress levels in thermoelectric generator.

  19. Thermal Stress of Surface of Mold Cavities and Parting Line of Silicone Molds

    Directory of Open Access Journals (Sweden)

    Bajčičák Martin

    2014-06-01

    Full Text Available The paper is focused on the study of thermal stress of surface of mold cavities and parting line of silicone molds after pouring. The silicone mold White SD - THT was thermally stressed by pouring of ZnAl4Cu3 zinc alloy with pouring cycle 20, 30 and 40 seconds. The most thermally stressed part of surface at each pouring cycle is gating system and mold cavities. It could be further concluded that linear increase of the pouring cycle time leads to the exponential increasing of the maximum temperature of mold surface after its cooling. The elongated pouring cycle increases the temperature accumulated on the surface of cavities and the ability of silicone mold to conduct the heat on its surface decreases, because the low thermal conductivity of silicone molds enables the conduction of larger amount of heat into ambient environment.

  20. Effect of Thermal cycles and Dimensions of the Geometry on Residual stress of the Alumina-Kovar Joint

    Science.gov (United States)

    Mishra, Srishti; Pal, Snehanshu; Karak, Swapan Kumar; Shah, Sejal; Venakata Nagaraju, M.; Chakraborty, Arun Kumar

    2018-03-01

    Finite element method is employed to determine the effect of variation of residual stress with dimension and the stress generated under its working condition along the Kovar. 3 different dimensions of Alumina-Kovar joint with height to diameter ratio of 3/10, using TiCuSil as a filler material. Transient Structural Analysis is carried out for three different dimensions (diameter × height) (i) 60mm × 20mm (Geometry 1) (ii) 90mm × 20mm (Geometry 2) (iii) 120mm × 20mm (Geometry 3). A comparative study has been carried out between the residual stresses developed in the brazed joint that have undergone 5 thermal cycles subsequent to brazing and that between the brazed joint. The heating and cooling rates from the brazed temperature is 10°C/up to room temperature. The brazing temperature and holding time considered for the analysis are 900°C and 10 minutes. Representative Volume Element (RVE) model is used for simulation. Sparse Matrix Direct Solver method is used to evaluate the results, using Augmented Lagrange method formulation in the contact region. All the simulations are performed in ANSYS Workbench 15.0, using solver target Mechanical APDL. From, the above simulations it is observed high concentration of residual stress is observed along the filler region i.e. in between Alumina and Kovar, as a result of difference in coefficient of thermal expansion between Alumina and Kovar. The residual stress decreases with increasing dimensions of the geometry and upon application of thermal cycles, subsequent to brazing.

  1. Remote detection of canopy water stress in coniferous forests using the NS001 Thematic Mapper Simulator and the thermal infrared multispectral scanner

    Science.gov (United States)

    Pierce, Lars L.; Running, Steven W.; Riggs, George A.

    1990-01-01

    Water stress was induced in two coniferous forest stands in West Germany by severing tree sapwood. Leaf water potential, Psi(L), measurements indicated that maximum, naturally occurring levels of water stress developed in the stressed plots while control plots exhibited natural diurnal trends. Images of each site were obtained with the Thematic Mapper Simulator (NS001) and the Thermal Infrared Multispectral Scanner (TIMS) 12 to 15 days after stress induction. NS001 bands 2 to 6, NS001 indices combining bands 4 and 6, and NS001 and TIMS thermal bands showed significant radiance differences between stressed and control plots when large differences in Psi(L) and relative water content (RWC) existed during the morning overflights at Munich. However, the NS001 and TIMS sensors could not detect the slightly smaller differences in Psi(L) and RWC during the Munich afternoon and Frankfurt overflights. The results suggest that routine detection of canopy water stress under operational conditions is difficult utilizing current sensor technology.

  2. Differential gene expression during thermal stress and bleaching in the Caribbean coral Montastraea faveolata.

    Science.gov (United States)

    DeSalvo, M K; Voolstra, C R; Sunagawa, S; Schwarz, J A; Stillman, J H; Coffroth, M A; Szmant, A M; Medina, M

    2008-09-01

    The declining health of coral reefs worldwide is likely to intensify in response to continued anthropogenic disturbance from coastal development, pollution, and climate change. In response to these stresses, reef-building corals may exhibit bleaching, which marks the breakdown in symbiosis between coral and zooxanthellae. Mass coral bleaching due to elevated water temperature can devastate coral reefs on a large geographical scale. In order to understand the molecular and cellular basis of bleaching in corals, we have measured gene expression changes associated with thermal stress and bleaching using a complementary DNA microarray containing 1310 genes of the Caribbean coral Montastraea faveolata. In a first experiment, we identified differentially expressed genes by comparing experimentally bleached M. faveolata fragments to control non-heat-stressed fragments. In a second experiment, we identified differentially expressed genes during a time course experiment with four time points across 9 days. Results suggest that thermal stress and bleaching in M. faveolata affect the following processes: oxidative stress, Ca(2+) homeostasis, cytoskeletal organization, cell death, calcification, metabolism, protein synthesis, heat shock protein activity, and transposon activity. These results represent the first medium-scale transcriptomic study focused on revealing the cellular foundation of thermal stress-induced coral bleaching. We postulate that oxidative stress in thermal-stressed corals causes a disruption of Ca(2+) homeostasis, which in turn leads to cytoskeletal and cell adhesion changes, decreased calcification, and the initiation of cell death via apoptosis and necrosis.

  3. Expression of heat shock proteins (HSPs) in Aedes aegypti (L) and Aedes albopictus (Skuse) (Diptera: Culicidae) larvae in response to thermal stress.

    Science.gov (United States)

    Sivan, Arun; Shriram, Ananganallur Nagarajan; Muruganandam, Nagarajan; Thamizhmani, Ramanathan

    2017-03-01

    Climatic changes are responsible, to a certain extent for the occurrence and spread of arboviral pathogens world over. Temperature is one of the important abiotic factors influencing the physiological processes of mosquitoes. Several genes of heat shock protein (HSP) families are known to be expressed in mosquitoes, which aid in overcoming stress induced by elevated temperature. In order to understand expression of HSP family genes in the Andaman population of Aedes aegypti and Aedes albopictus, we used quantitative real-time polymerase chain reaction (qPCR) to examine expression levels of HSPs in response to thermal stress under laboratory and in actual field conditions. HSP genes AeaHsp26, AeaHsp83 and AeaHsc70 were examined by comparing relative transcript expression levels at 31°C, 33°C, 34°C, 37°C and 39°C respectively. Enhanced up-regulation of HSPs was evident in third instar larvae of Ae. aegypti with rise in water temperatures (31°C, 33°C, 34°C) in the containers in the nature and thermally stressed (37°C and 39°C) in laboratory conditions. In Ae. albopictus up-regulation of HSPs was observed in field conditions at 34°C only and when thermally treated at 37°C, while down regulation was evident in larvae subjected to thermal stress in laboratory at 39°C. Data on expression levels revealed that larvae of Ae. aegypti was tolerant to thermal stress, while Ae. albopictus larvae was sensitive to heat shock treatment. Statistical analysis indicated that AeaHsp83 genes were significantly up-regulated in Ae. aegypti larvae after 360min exposure to high temperature (39°C). The difference in expression levels of AeaHsp26, AeaHsc70 and AeaHsp83 genes in Ae. albopictus larvae was statistically significant between different exposure temperatures. All of these genes were significantly up-regulated at 37°C. These results indicate that AeaHsp26, AeaHsc70 and AeaHsp83 are important markers of stress and perhaps function as proteins conferring protection and

  4. Using High-Resolution Hyperspectral and Thermal Airborne Imagery to Assess Physiological Condition in the Context of Wheat Phenotyping

    Directory of Open Access Journals (Sweden)

    Victoria Gonzalez-Dugo

    2015-10-01

    Full Text Available There is a growing need for developing high-throughput tools for crop phenotyping that would increase the rate of genetic improvement. In most cases, the indicators used for this purpose are related with canopy structure (often acquired with RGB cameras and multispectral sensors allowing the calculation of NDVI, but using approaches related with the crop physiology are rare. High-resolution hyperspectral remote sensing imagery provides optical indices related to physiological condition through the quantification of photosynthetic pigment and chlorophyll fluorescence emission. This study demonstrates the use of narrow-band indicators of stress as a potential tool for phenotyping under rainfed conditions using two airborne datasets acquired over a wheat experiment with 150 plots comprising two species and 50 varieties (bread and durum wheat. The flights were performed at the early stem elongation stage and during the milking stage. Physiological measurements made at the time of flights demonstrated that the second flight was made during the terminal stress, known to largely determine final yield under rainfed conditions. The hyperspectral imagery enabled the extraction of thermal, radiance, and reflectance spectra from 260 spectral bands from each plot for the calculation of indices related to photosynthetic pigment absorption in the visible and red-edge regions, the quantification of chlorophyll fluorescence emission, as well as structural indices related to canopy structure. Under the conditions of this study, the structural indices (i.e., NDVI did not show a good performance at predicting yield, probably because of the large effects of terminal water stress. Thermal indices, indices related to chlorophyll fluorescence (calculated using the FLD method, and carotenoids pigment indices (PRI and CAR demonstrated to be better suited for screening complex traits such as crop yield. The study concludes that the indicators derived from high

  5. Modelling of thermal stresses in bearing steel structure generated by electrical current impulses

    Science.gov (United States)

    Birjukovs, M.; Jakovics, A.; Holweger, W.

    2018-05-01

    This work is the study of one particular candidate for white etching crack (WEC) initiation mechanism in wind turbine gearbox bearings: discharge current impulses flowing through bearing steel with associated thermal stresses and material fatigue. Using data/results from previously published works, the authors develop a series of models that are utilized to simulate these processes under various conditions/local microstructure configurations, as well as to verify the results of the previous numerical studies. Presented models show that the resulting stresses are several orders of magnitude below the fatigue limit/yield strength for the parameters used herein. Results and analysis of models provided by Scepanskis, M. et al. also indicate that certain effects predicted in their previous work resulted from a physically unfounded assumption about material thermodynamic properties and numerical model implementation issues.

  6. Assessment of bioclimatic conditions within the area of Szczecin agglomeration

    Directory of Open Access Journals (Sweden)

    Jadwiga Nidzgorska-Lencewicz

    2013-10-01

    Full Text Available The aim of this paper is to characterise the bioclimatic conditions in the city of Szczecin, particularly the recognition of the frequency of occurrence of the conditions unfavourable to humans. The analysis is based on the hourly values of particular meteorological elements and pollutant concentrations in the period 2005?2010 taken at the three measuring stations located in various settlement structures in Szczecin metropolitan area. The Universal Thermal Climate Index (UTCI was used to assess heat stress of human organism and the assessment of thermal sensation was based on the Effective Temperature index (ET. It was established that on a yearly basis the most favourable biothermal conditions are observed in the centre of the city and in its southern districts ? categories no thermal stress (UTCI and thermal comfort (ET are most frequently recorded there. However, in the northern parts of the city the most common class of thermal stress (UTCI is moderate cold stress and thermal sensation category (ET cool and cold. Among the situations which thermal stress, the conditions connected with discomfort related to cold rather than heat are more frequent. Throughout the year, the strong cold stress (UTCI < 13 ° C and sensations (ET related to cold stress occurred in 12.5% and 25% of time respectively, whereas thermal discomfort related to strong heat stress with UTCI values over 32 ° C and ET thermal sensations hot and very hot were observed incomparably less frequently ? 0.3% and 3.7% respectively. However, heat-related discomfort is more frequently observed in the city centre, and cold-related discomfort is most frequently experienced by residents of the outskirts of the city, particularly its northern parts. The statistically strongest relationships were observed between biothermal sensation and ozone (O3 and particulate matter PM2.5 immissions. During the analysed period, the most unfavourable bioclimatic conditions occurred predominantly in

  7. Thermal stress in the edge cladding of Nova glass laser disks

    International Nuclear Information System (INIS)

    Pitts, J.H.; Kong, M.K.; Gerhard, M.A.

    1987-01-01

    We calculated thermal stresses in Nova glass laser disks having light-absorbing edge cladding glass attached to the periphery with an epoxy adhesive. Our closed-form solutions indicated that, because the epoxy adhesive is only 25 μm across, it does not significantly affect the thermal stress in the disk or cladding glass. Our numerical results showed a peak tensile stress in the cladding glass of 24 MPa when the cladding glass had a uniform absorption coefficient of 7.5 cm -1 . This peak value is reduced to 19 MPa if surface parasitic oscillation heating is eliminated by tilting the disk edges. The peak tensile stresses exceed the typical 7 to 14-MPa working stress for glass; however, we have not observed any disk or cladding glass failures at peak Nova fluences of 20 J/cm 2 . We have observed delamination of the epoxy adhesive bond at fluences several times that which would occur on Nova. Replacement laser disks will incorporate cladding with a reduced absorption coefficient of 4.5 cm -1 . Recent experiments show that this reduced absorption coefficient is satisfactory

  8. Residual stress determination in thermally sprayed metallic deposits by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Keller, Thomas; Margadant, Nikolaus; Pirling, Thilo; Riegert-Escribano, Maria J.; Wagner, Werner

    2004-05-25

    Neutron diffraction was used to obtain spatially resolved strain and stress profiles in thermally sprayed metallic 'NiCrAlY' deposits (chemical composition 67 wt.% Ni, 22 wt.% Cr, 10 wt.% Al, 1 wt.% Y) and the underlying steel substrates. Samples of four different spray techniques were analyzed: atmospheric and water stabilized plasma spraying (APS and WSP), flame spraying (FS) and wire arc spraying (WAS). The results are quantitatively compared with the average in-plane residual stress determined by complementary bending tests and the hole drilling technique. While the stress profiles from the surface to the interface in the deposits are similar for all investigated spray techniques, their absolute values and gradients vary strongly. This is attributed to different quenching stresses from the impinging particles, different thermal histories the deposit/substrate systems undergo during the spraying and subsequent cooling, and also to different coating properties. In the water stabilized plasma sprayed and the wire arc sprayed deposits, a gradient in the stress-free lattice parameter was observed. Crack formation is found to be a dominant mechanism for stress relaxation in the surface plane.

  9. Finite element analysis of thermal stress distribution in different ...

    African Journals Online (AJOL)

    Nigerian Journal of Clinical Practice • Jan-Feb 2016 • Vol 19 • Issue 1. Abstract ... Key words: Amalgam, finite element method, glass ionomer cement, resin composite, thermal stress ... applications for force analysis and assessment of different.

  10. Heat stress and sudden infant death syndrome--stress gene expression after exposure to moderate heat stress

    DEFF Research Database (Denmark)

    Rohde, Marianne Cathrine; Corydon, Thomas Juhl; Hansen, Jakob

    2013-01-01

    The aim of the present study was to investigate stress gene expression in cultured primary fibroblasts established from Achilles tendons collected during autopsies from sudden infant death syndrome (SIDS) cases, and age-matched controls (infants dying in a traumatic event). Expression of 4 stress...... responsive genes, HSPA1B, HSPD1, HMOX1, and SOD2, was studied by quantitative reverse transcriptase PCR analysis of RNA purified from cells cultured under standard or various thermal stress conditions. The expression of all 4 genes was highly influenced by thermal stress in both SIDS and control cells. High...... interpersonal variance found in the SIDS group indicated that they represented a more heterogeneous group than controls. The SIDS group responded to thermal stress with a higher expression of the HSPA1B and HSPD1 genes compared to the control group, whereas no significant difference was observed...

  11. Regulation of apoptotic pathways by Stylophora pistillata (Anthozoa, Pocilloporidae to survive thermal stress and bleaching.

    Directory of Open Access Journals (Sweden)

    Hagit Kvitt

    Full Text Available Elevated seawater temperatures are associated with coral bleaching events and related mortality. Nevertheless, some coral species are able to survive bleaching and recover. The apoptotic responses associated to this ability were studied over 3 years in the coral Stylophora pistillata from the Gulf of Eilat subjected to long term thermal stress. These include caspase activity and the expression profiles of the S. pistillata caspase and Bcl-2 genes (StyCasp and StyBcl-2-like cloned in this study. In corals exposed to thermal stress (32 or 34°C, caspase activity and the expression levels of the StyBcl-2-like gene increased over time (6-48 h and declined to basal levels within 72 h of thermal stress. Distinct transcript levels were obtained for the StyCasp gene, with stimulated expression from 6 to 48 h of 34°C thermal stress, coinciding with the onset of bleaching. Increased cell death was detected in situ only between 6 to 48 h of stress and was limited to the gastroderm. The bleached corals survived up to one month at 32°C, and recovered back symbionts when placed at 24°C. These results point to a two-stage response in corals that withstand thermal stress: (i the onset of apoptosis, accompanied by rapid activation of anti-oxidant/anti-apoptotic mediators that block the progression of apoptosis to other cells and (ii acclimatization of the coral to the chronic thermal stress alongside the completion of symbiosis breakdown. Accordingly, the coral's ability to rapidly curb apoptosis appears to be the most important trait affecting the coral's thermotolerance and survival.

  12. Dynamic thermal environment and thermal comfort.

    Science.gov (United States)

    Zhu, Y; Ouyang, Q; Cao, B; Zhou, X; Yu, J

    2016-02-01

    Research has shown that a stable thermal environment with tight temperature control cannot bring occupants more thermal comfort. Instead, such an environment will incur higher energy costs and produce greater CO2 emissions. Furthermore, this may lead to the degeneration of occupants' inherent ability to combat thermal stress, thereby weakening thermal adaptability. Measured data from many field investigations have shown that the human body has a higher acceptance to the thermal environment in free-running buildings than to that in air-conditioned buildings with similar average parameters. In naturally ventilated environments, occupants have reported superior thermal comfort votes and much greater thermal comfort temperature ranges compared to air-conditioned environments. This phenomenon is an integral part of the adaptive thermal comfort model. In addition, climate chamber experiments have proven that people prefer natural wind to mechanical wind in warm conditions; in other words, dynamic airflow can provide a superior cooling effect. However, these findings also indicate that significant questions related to thermal comfort remain unanswered. For example, what is the cause of these phenomena? How we can build a comfortable and healthy indoor environment for human beings? This article summarizes a series of research achievements in recent decades, tries to address some of these unanswered questions, and attempts to summarize certain problems for future research. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  13. Thermal stress resistance of ion implanted sapphire crystals

    International Nuclear Information System (INIS)

    Gurarie, V.N.; Jamieson, D.N.; Szymanski, R.; Orlov, A.V.; Williams, J.S.; Conway, M.

    1999-01-01

    Monocrystals of sapphire have been subjected to ion implantation with 86 keV Si - and 80 keV Cr - ions to doses in the range of 5x10 14 -5x10 16 cm -2 prior to thermal stress testing in a pulsed plasma. Above a certain critical dose ion implantation is shown to modify the near-surface structure of samples by introducing damage, which makes crack nucleation easier under the applied stress. The effect of ion dose on the stress resistance is investigated and the critical doses which produce a noticeable change in the stress resistance are determined. The critical dose for Si ions is shown to be much lower than that for Cr - ions. However, for doses exceeding 2x10 16 cm -2 the stress resistance parameter decreases to approximately the same value for both implants. The size of the implantation-induced crack nucleating centers and the density of the implantation-induced defects are considered to be the major factors determining the stress resistance of sapphire crystals irradiated with Si - and Cr - ions

  14. Thermal effects in concrete members

    International Nuclear Information System (INIS)

    Kar, A.K.

    1977-01-01

    The proposed method of analysis for concrete members subjected to temperature changes is consistent with the requirements of ultimate strength design. This also facilitates the provision of the same safety margin as for other loads. Due to cracks and creep in concrete, thermal stresses are nonlinear; they are dependent on the effective member stiffness, which in turn vary with the magnitude of loading. Therefore it is inconsistent to have an ultimate strength design in conjunction with an analysis based on the linear elastic theory. It is proposed that when the requirements of serviceability are met, the neutral axis corresponding to the ultimate load capacity conditions be considered for temperature-induced loadings. This conforms with the fact that the thermal load, because of creep and formation of cracks in the member, can be self-relieving as the failure load condition or ultimate capacity is approached. The maximum thermal load that can develop in dependent on the effective cross section of the member. Recommendations are made for determining the average effective member stiffness, which lies between the stiffness corresponding to the cracked (at ultimate condition) and the uncracked sections. In the proposed method, thermal stresses are not considered completely self-relieving. The stresses are considered simultaneously with stresses resulting from other causes. A step-by-step approach is presented for analysis and design of concrete members subjected to temperature changes

  15. Influence of solder joint length to the mechanical aspect during the thermal stress analysis

    Science.gov (United States)

    Tan, J. S.; Khor, C. Y.; Rahim, Wan Mohd Faizal Wan Abd; Ishak, Muhammad Ikman; Rosli, M. U.; Jamalludin, Mohd Riduan; Zakaria, M. S.; Nawi, M. A. M.; Aziz, M. S. Abdul; Ani, F. Che

    2017-09-01

    Solder joint is an important interconnector in surface mount technology (SMT) assembly process. The real time stress, strain and displacement of the solder joint is difficult to observe and assess the experiment. To tackle these problems, simulation analysis was employed to study the von Mises stress, strain and displacement in the thermal stress analysis by using Finite element based software. In this study, a model of leadless electronic package was considered. The thermal stress analysis was performed to investigate the effect of the solder length to those mechanical aspects. The simulation results revealed that solder length gives significant effect to the maximum von Mises stress to the solder joint. Besides, changes in solder length also influence the displacement of the solder joint in the thermal environment. The increment of the solder length significantly reduces the von Mises stress and strain on the solder joint. Thus, the understanding of the physical parameter for solder joint is important for engineer prior to designing the solder joint of the electronic component.

  16. Transcriptome analysis and identification of significantly differentially expressed genes in Holstein calves subjected to severe thermal stress

    Science.gov (United States)

    Srikanth, Krishnamoorthy; Lee, Eunjin; Kwan, Anam; Lim, Youngjo; Lee, Junyep; Jang, Gulwon; Chung, Hoyoung

    2017-11-01

    RNA-Seq analysis was used to characterize transcriptome response of Holstein calves to thermal stress. A total of eight animals aged between 2 and 3 months were randomly selected and subjected to thermal stress corresponding to a temperature humidity index of 95 in an environmentally controlled house for 12 h consecutively for 3 days. A set of 15,787 unigenes were found to be expressed and after a threshold of threefold change, and a Q value physiological and metabolic processes to survive. Many of the genes identified in this study have not been previously reported to be involved in thermal stress response. The results of this study extend our understanding of the animal's response to thermal stress and some of the identified genes may prove useful in the efforts to breed Holstein cattle with superior thermotolerance, which might help in minimizing production loss due to thermal stress.

  17. Stochastic thermal stress analysis of clad cylindrical fuel elements

    International Nuclear Information System (INIS)

    Barrett, P.R.

    1975-01-01

    After a review of deterministic elastic thermal stress analysis by means of the displacement method for a cylindrical system in which the temperature distribution is not only radially variable but azimuthally and axially variable also, a method is shown for the determination of the statistical moments of the stress components when (a) the outer boundary of the cladding is a stochastic quantity, and (b) the uncertainties in the elastic and thermal constants of the materials and in the magnitude of the heat generation term are taken into account. A typical model is proposed for describing the statistics of the outer radius of the cladding which is a stochastic variable owing to uncertainties produced by the extrusion process. The theory is illustrated by means of a simple example by examining a meaningful reliability index and the relative importance of each of the uncertainties. (Auth.)

  18. Thermal stresses in the space shuttle orbiter: Analysis versus test

    International Nuclear Information System (INIS)

    Grooms, H.R.; Gibson, W.F. Jr.; Benson, P.L.

    1984-01-01

    Significant temperature differences occur between the internal structure and the outer skin of the Space Shuttle Orbiter as it returns from space. These temperature differences cause important thermal stresses. A finite element model containing thousands of degrees of freedom is used to predict these stresses. A ground test was performed to verify the prediction method. The analysis and test results compare favorably. (orig.)

  19. Early life thermal stress: Impact on future thermotolerance, stress response, behavior, and intestinal morphology in piglets exposed to a heat stress challenge during simulated transport

    Science.gov (United States)

    Study objectives were to evaluate the impact of early life thermal stress (ELTS) on thermoregulation, stress, and intestinal health of piglets subjected to a future heat stress (HS) challenge during simulated transport. Approximately 7 d after farrowing, 12 first parity gilts and their litters were ...

  20. Methods of evaluating protective clothing relative to heat and cold stress: thermal manikin, biomedical modeling, and human testing.

    Science.gov (United States)

    O'Brien, Catherine; Blanchard, Laurie A; Cadarette, Bruce S; Endrusick, Thomas L; Xu, Xiaojiang; Berglund, Larry G; Sawka, Michael N; Hoyt, Reed W

    2011-10-01

    Personal protective equipment (PPE) refers to clothing and equipment designed to protect individuals from chemical, biological, radiological, nuclear, and explosive hazards. The materials used to provide this protection may exacerbate thermal strain by limiting heat and water vapor transfer. Any new PPE must therefore be evaluated to ensure that it poses no greater thermal strain than the current standard for the same level of hazard protection. This review describes how such evaluations are typically conducted. Comprehensive evaluation of PPE begins with a biophysical assessment of materials using a guarded hot plate to determine the thermal characteristics (thermal resistance and water vapor permeability). These characteristics are then evaluated on a thermal manikin wearing the PPE, since thermal properties may change once the materials have been constructed into a garment. These data may be used in biomedical models to predict thermal strain under a variety of environmental and work conditions. When the biophysical data indicate that the evaporative resistance (ratio of permeability to insulation) is significantly better than the current standard, the PPE is evaluated through human testing in controlled laboratory conditions appropriate for the conditions under which the PPE would be used if fielded. Data from each phase of PPE evaluation are used in predictive models to determine user guidelines, such as maximal work time, work/rest cycles, and fluid intake requirements. By considering thermal stress early in the development process, health hazards related to temperature extremes can be mitigated while maintaining or improving the effectiveness of the PPE for protection from external hazards.

  1. Study on Stress Development in the Phase Transition Layer of Thermal Barrier Coatings

    Directory of Open Access Journals (Sweden)

    Yijun Chai

    2016-09-01

    Full Text Available Stress development is one of the significant factors leading to the failure of thermal barrier coating (TBC systems. In this work, stress development in the two phase mixed zone named phase transition layer (PTL, which grows between the thermally grown oxide (TGO and the bond coat (BC, is investigated by using two different homogenization models. A constitutive equation of the PTL based on the Reuss model is proposed to study the stresses in the PTL. The stresses computed with the proposed constitutive equation are compared with those obtained with Voigt model-based equation in detail. The stresses based on the Voigt model are slightly higher than those based on the Reuss model. Finally, a further study is carried out to explore the influence of phase transition proportions on the stress difference caused by homogenization models. Results show that the stress difference becomes more evident with the increase of the PTL thickness ratio in the TGO.

  2. Residual stress of particulate polymer composites with reduced thermal expansion

    International Nuclear Information System (INIS)

    Nishino, T; Kotera, M; Sugiura, Y

    2009-01-01

    Thermal expansion behavior was investigated for tangusten zirconium phosphate (Zr 2 (WO 4 )(PO 4 ) 2 (ZWP)) particulate filled poly(ether ether ketone) (PEEK) composite. ZWP is known as ceramic filler with a negative thermal expansion. By incorporating ZWP with 40 volume %, the linear thermal expansion coefficient of the PEEK composite was reduced to almost same value (2.53 X 10 -5 K -1 ) with that of aluminum. This decrease was found to be quite effective for the decrease of the residual stress at the interface between aluminum plate and the composite.

  3. Human Thermal Comfort and Heat Stress in an Outdoor Urban Arid Environment: A Case Study

    Directory of Open Access Journals (Sweden)

    A. M. Abdel-Ghany

    2013-01-01

    Full Text Available To protect humans from heat stress risks, thermal comfort and heat stress potential were evaluated under arid environment, which had never been made for such climate. The thermal indices THI, WBGT, PET, and UTCI were used to evaluate thermal comfort and heat stress. RayMan software model was used to estimate the PET, and the UTCI calculator was used for UTCI. Dry and wet bulb temperatures (Td, Tw, natural wet bulb temperature (Tnw, and globe temperature (Tg were measured in a summer day to be used in the calculation. The results showed the following. (i The thermal sensation and heat stress levels can be evaluated by either the PET or UTCI scales, and both are valid for extremely high temperature in the arid environment. (ii In the comfort zone, around 75% of individuals would be satisfied with the surrounding environment and feel comfortable during the whole day. (iii Persons are exposed to strong heat stress and would feel uncomfortable most of the daytime in summer. (iv Heat fatigue is expected with prolonged exposure to sun light and activity. (v During the daytime, humans should schedule their activities according to the highest permissible values of the WBGT to avoid thermal shock.

  4. Thermal hydraulic conditions inducing incipient cracking in the 900 MWe unit 93 D reactor coolant pump shafts; Pompes primaires 93 D des tranches de 900 MW. Conditions thermo-hydrauliques d`amorcage des fissures d`arbres

    Energy Technology Data Exchange (ETDEWEB)

    Bore, C.

    1995-12-31

    From 1987, 900 MWe plant operating feedback revealed cracking in the lower part of the reactor coolant pump shafts, beneath the thermal ring. Metallurgical examinations established that this was due to a thermal fatigue phenomenon known as thermal crazing, occurring after a large number of cycles. Analysis of thermal hydraulic conditions initiating the cracks does not allow exact quantification of the thermal load inducing cracking. Only qualitative analyses are thus possible, the first of which, undertaken by the pump manufacturer, Jeumont Industrie, showed that the cracks could not be due to the major transients (stop-start, injection cut-off), which were too few in number. Another explanation was then put forward: the thermal ring, shrunk onto the shaft it is required to protect against thermal shocks, loosens to allow an alternating downflow of cold water from the shaft seals and an upflow of hot water from the primary system. However, approximate calculations showed that the flow involved would be too slight to initiate the cracking observed. A more stringent analysis undertaken with the 2D flow analysis code MELODIE subsequently refuted the possibility of alternating flows beneath the ring establishing that only a hot water upflow occurred due to a `viscosity pump` phenomenon. Crack initiation was finally considered to be due to flowrate variations beneath the ring, with the associated temperature fluctuations. This flowrate fluctuation could be due to an unidentified transient phenomenon or to a variation in pump operating conditions. This analysis of the hydraulic conditions initiating the cracks disregards shaft surface residual stresses. These are tensile stresses and show that loads less penalizing than those initially retained could cause incipient cracking. Thermal ring modifications to reduce these risks were proposed and implemented. In addition, final metallurgical treatment of the shafts was altered and implemented. (Abstract Truncated)

  5. Further study on the wheel-rail impact response induced by a single wheel flat: the coupling effect of strain rate and thermal stress

    Science.gov (United States)

    Jing, Lin; Han, Liangliang

    2017-12-01

    A comprehensive dynamic finite-element simulation method was proposed to study the wheel-rail impact response induced by a single wheel flat based on a 3-D rolling contact model, where the influences of the structural inertia, strain rate effect of wheel-rail materials and thermal stress due to the wheel-rail sliding friction were considered. Four different initial conditions (i.e. pure mechanical loading plus rate-independent, pure mechanical loading plus rate-dependent, thermo-mechanical loading plus rate-independent, and thermo-mechanical loading plus rate-dependent) were involved into explore the corresponding impact responses in term of the vertical impact force, von-Mises equivalent stress, equivalent plastic strain and shear stress. Influences of train speed, flat length and axle load on the flat-induced wheel-rail impact response were discussed, respectively. The results indicate that the maximum thermal stresses are occurred on the tread of the wheel and on the top surface of the middle rail; the strain rate hardening effect contributes to elevate the von-Mises equivalent stress and restrain the plastic deformation; and the initial thermal stress due to the sliding friction will aggravate the plastic deformation of wheel and rail. Besides, the wheel-rail impact responses (i.e. impact force, von-Mises equivalent stress, equivalent plastic strain, and XY shear stress) induced by a flat are sensitive to the train speed, flat length and axle load.

  6. Pressurized-thermal-shock technology

    International Nuclear Information System (INIS)

    Dickson, T.L.

    1991-01-01

    It was recognized at the time the original Issues on Pressurized Thermal Shock (IPTS) studies were conducted that distinct vertical plumes of cooling water form beneath the cold leg inlet nozzles during those particular transients that exhibit fluid/thermal stratification. The formation of these plumes (referred to as thermal streaming) induces a time-dependent circumferential temperature variation on the inner surface of the Reactor Pressure Vessel (RPV) wall that creates an axial stress component. This axial stress component is in addition to the axial stress components induced by time-dependent radial temperature variation through the wall thickness and the time-dependent pressure transient. This additional axial stress component will result in a larger axial stress resultant that results in a larger stress-intensity factor acting on circumferential flaws, thus reducing the fracture margin for circumferential flaws. Although this was recognized at the time of the original IPTS study, the contribution appeared to be relatively small; therefore, it was neglected. The original IPTS studies were performed with OCA-P, a computer program developed at ORNL to analyze the cleavage fracture response of a nuclear RPV subjected to PTS loading. OCA-P is a one-dimensional (1-D) finite-element code that analyzes the stresses and stress-intensity factors (axial and tangential) resulting from the pressure and the radial temperature variation through the wall thickness only. The HSST Program is investigating the potential effects of thermal-streaming-induced stresses in circumferential welds on the reactor vessel PTS analyses. The initial phase of this investigation focused on an evaluation of the available thermal-hydraulic data and analyses results. The objective for the initial phase of the investigation is to evaluate thermal-streaming behavior under conditions relevant to the operation of U.S. PWRs and chracterize any predicted thermal-streaming plumes

  7. Flexible thermal cycle test equipment for concentrator solar cells

    Science.gov (United States)

    Hebert, Peter H [Glendale, CA; Brandt, Randolph J [Palmdale, CA

    2012-06-19

    A system and method for performing thermal stress testing of photovoltaic solar cells is presented. The system and method allows rapid testing of photovoltaic solar cells under controllable thermal conditions. The system and method presents a means of rapidly applying thermal stresses to one or more photovoltaic solar cells in a consistent and repeatable manner.

  8. A method for the dynamic and thermal stress analysis of space shuttle surface insulation

    Science.gov (United States)

    Ojalvo, I. U.; Levy, A.; Austin, F.

    1975-01-01

    The thermal protection system of the space shuttle consists of thousands of separate insulation tiles bonded to the orbiter's surface through a soft strain-isolation layer. The individual tiles are relatively thick and possess nonuniform properties. Therefore, each is idealized by finite-element assemblages containing up to 2500 degrees of freedom. Since the tiles affixed to a given structural panel will, in general, interact with one another, application of the standard direct-stiffness method would require equation systems involving excessive numbers of unknowns. This paper presents a method which overcomes this problem through an efficient iterative procedure which requires treatment of only a single tile at any given time. Results of associated static, dynamic, and thermal stress analyses and sufficient conditions for convergence of the iterative solution method are given.

  9. Thermal Stress Analyses for a Multislug Beam NLC Positron Target(LCC-0090)

    International Nuclear Information System (INIS)

    Stein, W.

    2003-01-01

    The power deposition of an incident multislug electron beam in a tungsten-rhenium target and the resultant thermal shock stresses in the material have been modeled with a transient, dynamic, structural response finite element code. The Next Linear Collider electron beam is assumed split into two parts, with each part impinging on a 4 radiation lengths thick target. Two targets are required to avoid excessive thermal stresses in the targets. Each of the two beam parts is assumed broken up into four slugs, each two microseconds apart. Energy deposition from each slug occurs over 265 nanoseconds and results in heating of the target and pressure pulses straining the material. The rapid power deposition of the electron beam and the resultant temperature profile in the target generates stress and pressure waves in the material that are considerably larger than those calculated by a static analysis. The 6.22 GeV electron beam has a spot radius size of 1.6 mm and results in a maximum temperature jump of 438 C. Stress pressure pulses are induced in the material from the rapid thermal expansion of the hotter material with peak effective stresses reaching 78 ksi (5.3 x 10 8 Pa) on the back side of the target, which is less than one half of the yield strength of the tungsten/rhenium alloy and below the material fatigue limit

  10. Temperature field and thermal stress analysis of the HT-7U vacuum vessel

    International Nuclear Information System (INIS)

    Song Yuntao; Yao Damao; Wu Songtao; Weng Peide

    2000-01-01

    The HT-7U vacuum vessel is an all-metal-welded double-wall interconnected with toroidal and poloidal stiffening ribs. The channels formed between the ribs and walls are filled with boride water as a nuclear shielding. On the vessel surface facing the plasma are installed cable-based Ohmic heaters. Prior to plasma operation the vessel is to be baked out and discharge cleaned at about 250 degree C. During baking out the non-uniformity of temperature distribution on the vacuum vessel will bring about serious thermal stress that can damage the vessel. In order to determine and optimize the design of the HT-7U vacuum vessel, a three-dimensional finite element model was performed to analyse its temperature field and thermal stress. the maximal thermal stress appeared on the round of lower vertical port and maximal deformation located just on the region between the upper vertical port and the horizontal port. The results show that the reinforced structure has a good capability of withstanding the thermal loads

  11. Perceived Thermal Discomfort and Stress Behaviours Affecting Students’ Learning in Lecture Theatres in the Humid Tropics

    Directory of Open Access Journals (Sweden)

    Tamaraukuro Tammy Amasuomo

    2016-04-01

    Full Text Available The study investigated the relationship between students’ perceived thermal discomfort and stress behaviours affecting their learning in lecture theatres in the humid tropics. Two lecture theatres, LTH-2 and 3, at the Niger Delta University, Nigeria, were used for the study. Two groups of students from the Faculties of Agriculture and Engineering and the Department of Technology Education constituted the population. The sample size selected through random sampling for Groups A and B was 210 and 370 students, respectively. Objective and self-report instruments were used for data collection. The objective instrument involved physical measurement of the two lecture theatres and of the indoor temperature, relative humidity and air movement. The self-report instrument was a questionnaire that asked for the students perceived indoor thermal discomfort levels and the effect of indoor thermal comfort level on perceived stress behaviours affecting their learning. The objective indoor environmental data indicated thermal discomfort with an average temperature of 29–32 °C and relative humidity of 78% exceeding the ASHARE [1] and Olgyay [2].The students’ experienced a considerable level of thermal discomfort and also perceived that stress behaviours due to thermal discomfort affected their learning. Further, there were no significant differences in the perceived thermal discomfort levels of the two groups of students in LTH-2 and 3. Furthermore, stress behaviours affecting learning as perceived by the two groups of students did not differ significantly. In addition, no correlation existed between the perceived indoor thermal discomfort levels and stress behaviour levels affecting learning for students in LTH-2, because the arousal level of the students in the thermal environment was likely higher than the arousal level for optimal performance [3,4]. However, a correlation existed in the case of students in LTH-3, which was expected because it only

  12. The effect of water on thermal stresses in polymer composites

    Science.gov (United States)

    Sullivan, Roy M.

    1994-01-01

    The fundamentals of the thermodynamic theory of mixtures and continuum thermochemistry are reviewed for a mixture of condensed water and polymer. A specific mixture which is mechanically elastic with temperature and water concentration gradients present is considered. An expression for the partial pressure of water in the mixture is obtained based on certain assumptions regarding the thermodynamic state of the water in the mixture. Along with a simple diffusion equation, this partial pressure expression may be used to simulate the thermostructural behavior of polymer composite materials due to water in the free volumes of the polymer. These equations are applied to a specific polymer composite material during isothermal heating conditions. The thermal stresses obtained by the application of the theory are compared to measured results to verify the accuracy of the approach.

  13. Renal sympathetic nerve, blood flow, and epithelial transport responses to thermal stress.

    Science.gov (United States)

    Wilson, Thad E

    2017-05-01

    Thermal stress is a profound sympathetic stress in humans; kidney responses involve altered renal sympathetic nerve activity (RSNA), renal blood flow, and renal epithelial transport. During mild cold stress, RSNA spectral power but not total activity is altered, renal blood flow is maintained or decreased, and epithelial transport is altered consistent with a sympathetic stress coupled with central volume loaded state. Hypothermia decreases RSNA, renal blood flow, and epithelial transport. During mild heat stress, RSNA is increased, renal blood flow is decreased, and epithelial transport is increased consistent with a sympathetic stress coupled with a central volume unloaded state. Hyperthermia extends these directional changes, until heat illness results. Because kidney responses are very difficult to study in humans in vivo, this review describes and qualitatively evaluates an in vivo human skin model of sympathetically regulated epithelial tissue compared to that of the nephron. This model utilizes skin responses to thermal stress, involving 1) increased skin sympathetic nerve activity (SSNA), decreased skin blood flow, and suppressed eccrine epithelial transport during cold stress; and 2) increased SSNA, skin blood flow, and eccrine epithelial transport during heat stress. This model appears to mimic aspects of the renal responses. Investigations of skin responses, which parallel certain renal responses, may aid understanding of epithelial-sympathetic nervous system interactions during cold and heat stress. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. An investigation of characteristics of thermal stress caused by fluid temperature fluctuation at a T-junction pipe

    International Nuclear Information System (INIS)

    Miyoshi, Koji; Nakamura, Akira; Utanohara, Yoichi

    2014-01-01

    Thermal fatigue cracking may initiate at a T-junction pipe where high and low temperature fluids flow in from different directions and mix. Thermal stress is caused by a temperature gradient in a structure and by its variation. It is possible to obtain stress distributions if the temperature distributions at the pipe inner surface are obtained by experiments. The wall temperature distributions at a T-junction pipe were measured by experiments. The thermal stress distributions were calculated using the experimental data. The circumferential and axial stress fluctuations were larger than the radial stress fluctuation range. The stress fluctuation at the position of the maximum stress fluctuation had 10sec period. The distribution of the stress fluctuation was similar to that of the temperature fluctuation. The large stress fluctuations were caused by the time variation of the heating region by the hot jet flow. (author)

  15. Thermal stress estimation in relation to spalling of HSC restrained with steel rings at high temperatures

    Directory of Open Access Journals (Sweden)

    Tanibe T.

    2013-09-01

    Full Text Available This paper reports on an experimental study regarding the behavior of steel ring-restrained concrete in response to fire exposure. The study was conducted to enable estimation of thermal stress based on steel ring strain in such concrete under the conditions of a RABT 30 heating curve. The specimens used were made from high-strength concrete (Fc: 80 MPa restrained using steel rings with thicknesses of 0.5, 8 and 18 mm.

  16. Coupled thermal stress analysis of a hollow circular cylinder with transversely isotropic properties

    International Nuclear Information System (INIS)

    Tanigawa, Y.; Ootao, Y.

    1987-01-01

    If we shall analyze the thermal stress problems exactly in a transient state in continuum media, discussed with both the coupling and inertia effect, it has be shown that the thermomechanical coupling term shows a significant role than the inertia term for the common commercial alloys. In the present paper, we have considered the continuum medium with transversely isotropic material property, which has an isotropic property in r-θ plane, and analyzed the transient thermal stress problem of an infinitely long hollow circular cylinder due to an axisymmetrical partial heating. In order to get the thermal and thermoelastic fundamental differential equations separated in each field, we have introduced a perturbation technique. And then, we have carried out numerical calculations for several values of thermal and thermoelastic orthotropical parameters. (orig./GL)

  17. Heat transfer and thermal stress analysis in grooved tubes

    Indian Academy of Sciences (India)

    Heat transfer and thermal stresses, induced by temperature differencesin the internally grooved tubes of heat transfer equipment, have been analysed numerically. The analysis has been conducted for four different kinds of internally grooved tubes and three different mean inlet water velocities. Constant temperature was ...

  18. Mucus sugar content shapes the bacterial community structure in thermally stressed Acropora muricata

    Directory of Open Access Journals (Sweden)

    Sonny T.M. Lee

    2016-03-01

    Full Text Available It has been proposed that the chemical composition of a coral’s mucus can influence the associated bacterial community. However, information on this topic is rare, and non-existent for corals that are under thermal stress. This study therefore compared the carbohydrate composition of mucus in the coral Acropora muricata when subjected to increasing thermal stress from 26°C to 31°C, and determined whether this composition correlated with any changes in the bacterial community. Results showed that, at lower temperatures, the main components of mucus were N-acetyl glucosamine and C6 sugars, but these constituted a significantly lower proportion of the mucus in thermally-stressed corals. The change in the mucus composition coincided with a shift from a γ-Proteobacteria- to a Verrucomicrobiae- and α-Proteobacteria-dominated community in the coral mucus. Bacteria in the class Cyanobacteria also started to become prominent in the mucus when the coral was thermally stressed. The increase in the relative abundance of the Verrucomicrobiae at higher temperature was strongly associated with a change in the proportion of fucose, glucose and mannose in the mucus. Increase in the relative abundance of α-Proteobacteria were associated with GalNAc and glucose, while the drop in relative abundance of γ-Proteobacteria at high temperature coincided with changes in fucose and mannose. Cyanobacteria were highly associated with arabinose and xylose. Changes in mucus composition and the bacterial community in the mucus layer occurred at 29°C, which were prior to visual signs of coral bleaching at 31°C. A compositional change in the coral mucus, induced by thermal stress could therefore be a key factor leading to a shift in the associated bacterial community. This, in turn, has the potential to impact the physiological function of the coral holobiont.

  19. Thermal residual stresses in amorphous thermoplastic polymers

    Science.gov (United States)

    Grassia, Luigi; D'Amore, Alberto

    2010-06-01

    An attempt to calculate the internal stresses in a cylindrically shaped polycarbonate (LEXAN-GE) component, subjected to an arbitrary cooling rate, will be described. The differential volume relaxation arising as a result of the different thermal history suffered by each body point was considered as the primary source of stresses build up [1-3]. A numerical routine was developed accounting for the simultaneous stress and structural relaxation processes and implemented within an Ansys® environment. The volume relaxation kinetics was modeled by coupling the KAHR (Kovacs, Aklonis, Hutchinson, Ramos) phenomenological theory [4] with the linear viscoelastic theory [5-7]. The numerical algorithm translates the specific volume theoretical predictions at each body point as applied non-mechanical loads acting on the component. The viscoelastic functions were obtained from two simple experimental data, namely the linear viscoelastic response in shear and the PVT (pressure volume temperature) behavior. The dimensionless bulk compliance was extracted from PVT data since it coincides with the memory function appearing in the KAHR phenomenological theory [7]. It is showed that the residual stress scales linearly with the logarithm of the Biot's number.

  20. Simulation of global warming effect on outdoor thermal comfort conditions

    Energy Technology Data Exchange (ETDEWEB)

    Roshan, G.R.; Ranjbar, F. [Univ. of Tehran (IR). Dept. of Physical Geography; Orosa, J.A. [Univ. of A Coruna (Spain). Dept. of Energy

    2010-07-01

    In the coming decades, global warming and increase in temperature, in different regions of the world, may change indoor and outdoor thermal comfort conditions and human health. The aim of this research was to study the effects of global warming on thermal comfort conditions in indoor ambiences in Iran. To study the increase in temperature, model for assessment of greenhouse-gas induced climate change scenario generator compound model has been used together with four scenarios and to estimate thermal comfort conditions, adaptive model of the American Society of Heating, Refrigerating and Air-Conditioning Engineers has been used. In this study, Iran was divided into 30 zones, outdoor conditions were obtained using meteorological data of 80 climatological stations and changes in neutral comfort conditions in 2025, 2050, 2075 and 2100 were predicted. In accordance with each scenario, findings from this study showed that temperature in the 30 zones will increase by 2100 to between 3.4 C and 5.6 C. In the coming decades and in the 30 studied zones, neutral comfort temperature will increase and be higher and more intense in the central and desert zones of Iran. The low increase in this temperature will be connected to the coastal areas of the Caspian and Oman Sea in southeast Iran. This increase in temperature will be followed by a change in thermal comfort and indoor energy consumption from 8.6 % to 13.1 % in air conditioning systems. As a result, passive methods as thermal inertia are proposed as a possible solution.

  1. Physiological and lactation responses of Egyptian dairy Baladi goats to natural thermal stress under subtropical environmental conditions.

    Science.gov (United States)

    El-Tarabany, Mahmoud S; El-Tarabany, Akram A; Atta, Mostafa A

    2017-01-01

    The objective of this study was to evaluate the impact of thermal stress on milk production and physiological traits of Baladi goats under subtropical Egyptian conditions. Sixty dairy Baladi goats were exposed to three different levels of temperature-humidity index (THI), including low (less than 70), moderate (over 70 and up to 80), and high levels (over 80). The influence of THI on the milk composition and physiological, hematological, and biochemical traits was investigated. Rectal temperature and respiration rate were significantly greater at the higher THI than at low and moderate THI (p = 0.016 and 0.002, respectively). Baladi goats had decreased daily milk yield in a rate of 27.3 and 19.3 % at high THI level, compared with low and moderate THI, respectively (p = 0.031). On the contrary, no significant differences have been reported in protein, fat, and total solids percentages at different THI levels. Total leucocyte count, serum glucose, and total protein were significantly reduced at high THI in comparison with low and moderate THI levels (p = 0.043, 0.001, and 0.001, respectively). However, dairy goats maintained relatively stable estimates for erythrocytes count, hemoglobin, serum triglycerides, cholesterol, catalase, total antioxidant capacity, and triiodothyronine at different THI levels. Our results indicate that dairy Baladi goats can tolerate THI levels up to 80; however, variable reduction in milk yield and few biochemical (serum total protein and glucose) and hematological (leucocytes count) parameters have been reported at a THI level higher than 80.

  2. Finite element formulation for thermal stress analysis of thin reactor structures

    International Nuclear Information System (INIS)

    Kulak, R.F.; Kennedy, J.M.; Belytschko, T.B.

    1978-01-01

    This paper describes the formulation of a finite-element procedure for the thermal stress analysis of thin wall reactor components. A general temperature-dependent constituent relationship is derived from a Gibbs potential function and a temperature-dependent yield surface. This form of constitutive relationship is applicable to problems of small strain. A similar form of a hypoelastic-plastic type is also developed for large strains. The variation of the yield surface with temperature is based upon a temperature-dependent, work-hardening model. The model uses a temperature-equivalent stress-plastic strain diagram which is generated from isothermal unaxial stress-strain data. The above constitutive relationships are incorporated into two computer codes and a previously developed numerical algorithm is used with minor modifications. A set of problems is presented validating the thermal analysis capability of the computer codes to a variety of problem types. (Auth.)

  3. Effect of power history on the shape and the thermal stress of a large sapphire crystal during the Kyropoulos process

    Science.gov (United States)

    Nguyen, Tran Phu; Chuang, Hsiao-Tsun; Chen, Jyh-Chen; Hu, Chieh

    2018-02-01

    In this study, the effect of the power history on the shape of a sapphire crystal and the thermal stress during the Kyropoulos process are numerically investigated. The simulation results show that the thermal stress is strongly dependent on the power history. The thermal stress distributions in the crystal for all growth stages produced with different power histories are also studied. The results show that high von Mises stress regions are found close to the seed of the crystal, the highly curved crystal surface and the crystal-melt interface. The maximum thermal stress, which occurs at the crystal-melt interface, increases significantly in value as the crystal expands at the crown. After this, there is reduction in the maximum thermal stress as the crystal lengthens. There is a remarkable enhancement in the maximum von Mises stress when the crystal-melt interface is close to the bottom of the crucible. There are two obvious peaks in the maximum Von Mises stress, at the end of the crown stage and in the final stage, when cracking defects can form. To alleviate this problem, different power histories are considered in order to optimize the process to produce the lowest thermal stress in the crystal. The optimal power history is found to produce a significant reduction in the thermal stress in the crown stage.

  4. Thermal Stress Analysis for Ceramics Stalk in the Low Pressure Die Casting Machine

    Science.gov (United States)

    Noda, Nao-Aki; Hendra, Nao-Aki; Takase, Yasushi; Li, Wenbin

    Low pressure die casting (LPDC) is defined as a net shape casting technology in which the molten metal is injected at high speeds and pressure into a metallic die. The LPDC process is playing an increasingly important role in the foundry industry as a low-cost and high-efficiency precision forming technique. The LPDC process is that the permanent die and filling systems are placed over the furnace containing the molten alloy. The filling of the cavity is obtained by forcing the molten metal by means of a pressurized gas in order to rise into a ceramic tube, which connects the die to the furnace. The ceramics tube called stalk has high temperature resistance and high corrosion resistance. However, attention should be paid to the thermal stress when the stalk is dipped into the molten aluminum. It is important to develop the design of the stalk to reduce the risk of fracture because of low fracture toughness of ceramics. In this paper, therefore, the finite element method is applied to calculate the thermal stresses when the stalk is dipped into the crucible by varying the dipping speeds and dipping directions. It is found that the thermal stress can be reduced by dipping slowly if the stalk is dipped into the crucible vertically, while the thermal stress can be reduced by dipping fast if it is dipped horizontally.

  5. Rooting and early growth of red mangrove seedlings from thermally stressed trees

    International Nuclear Information System (INIS)

    Banus, M.D.; Kolehmainen, S.E.

    At Guayanilla on the south coast of Puerto Rico a fossil fueled electric generating station of 1100 MW(e) discharges its cooling water into a nearly enclosed lagoon of about 25 hectares area. The plume and lagoon typically have water temperatures 10 0 C and 8 0 C above ambient so that the winter and summer lagoon temperatures are 34 and 39 0 C, respectively. The north, east, and south shores of this lagoon have extensive stands of red and black mangrove trees which are visibly stressed by the elevated temperatures. Ripe red mangrove seedlings from the bearing trees are significantly smaller than those from trees in Guayanilla Bay not thermally stressed and in unpolluted bays from western Puerto Rico. Seedlings from thermally stressed trees developed negative buoyancy and initial roots faster but first pair of leaves slower than seedlings from control areas. This behavior will be discussed in relation to the propagation of seedlings from non-stressed areas. (U.S.)

  6. A thermal model for photovoltaic panels under varying atmospheric conditions

    International Nuclear Information System (INIS)

    Armstrong, S.; Hurley, W.G.

    2010-01-01

    The response of the photovoltaic (PV) panel temperature is dynamic with respect to the changes in the incoming solar radiation. During periods of rapidly changing conditions, a steady state model of the operating temperature cannot be justified because the response time of the PV panel temperature becomes significant due to its large thermal mass. Therefore, it is of interest to determine the thermal response time of the PV panel. Previous attempts to determine the thermal response time have used indoor measurements, controlling the wind flow over the surface of the panel with fans or conducting the experiments in darkness to avoid radiative heat loss effects. In real operating conditions, the effective PV panel temperature is subjected to randomly varying ambient temperature and fluctuating wind speeds and directions; parameters that are not replicated in controlled, indoor experiments. A new thermal model is proposed that incorporates atmospheric conditions; effects of PV panel material composition and mounting structure. Experimental results are presented which verify the thermal behaviour of a photovoltaic panel for low to strong winds.

  7. Study on application of green's function method in thermal stress rapid calculation

    International Nuclear Information System (INIS)

    Zhang Guihe; Duan Yuangang; Xu Xiao; Chen Rong

    2013-01-01

    This paper presents a quick and accuracy thermal stress calculation method, the Green's Function Method, which is a combination of finite element method and numerical algorithm method. Thermal stress calculation of Safe Injection Nozzle of Reactor Coolant Line of PWR plant is performed with Green's function method for heatup and cooldown thermal transients as a demonstration example, and the result is compared with finite element method to verify the rationality and accuracy of this method. The advantage and disadvantage of the Green's function method and the finite element method are also compared. (authors)

  8. Monitoring Thermal Conditions in Footwear

    Science.gov (United States)

    Silva-Moreno, Alejandra. A.; Lopez Vela, Martín; Alcalá Ochoa, Noe

    2006-09-01

    Thermal conditions inside the foot were evaluated on a volunteer subject. We have designed and constructed an electronic system which can monitors temperature and humidity of the foot inside the shoe. The data is stored in a battery-powered device for later uploading to a host computer for data analysis. The apparatus potentially can be used to provide feedback to patients who are prone to having skin breakdowns.

  9. Three-dimensional multi-phase flow computational fluid dynamics model for analysis of transport phenomena and thermal stresses in PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Maher, A.R.; Al-Baghdadi, S. [International Technological Univ., London (United Kingdom). Dept. of Mechanical Engineering; Haroun, A.K.; Al-Janabi, S. [Babylon Univ., Babylon (Iraq). Dept. of Mechanical Engineering

    2007-07-01

    Fuel cell technology is expected to play an important role in meeting the growing demand for distributed generation because it can convert the chemical energy of a clean fuel directly into electrical energy. An operating fuel cell has varying local conditions of temperature, humidity, and power generation across the active area of the fuel cell in 3D. This paper presented a model that was developed to improve the basic understanding of the transport phenomena and thermal stresses in PEM fuel cells, and to investigate the behaviour of polymer membrane under hygro and thermal stresses during the cell operation. This comprehensive 3D, multiphase, non-isothermal model accounts for the major transport phenomena in a PEM fuel cell, notably convective and diffusive heat and mass transfer; electrode kinetics; transport and phase change mechanism of water; and potential fields. The model accounts for the liquid water flux inside the gas diffusion layers by viscous and capillary forces and can therefore predict the amount of liquid water inside the gas diffusion layers. This study also investigated the key parameters affecting fuel cell performance including geometry, materials and operating conditions. The model considers the many interacting, complex electrochemical, transport phenomena, thermal stresses and deformation that cannot be studied experimentally. It was concluded that the model can provide a computer-aided tool for the design and optimization of future fuel cells with much higher power density and lower cost. 21 refs., 2 tabs., 14 figs.

  10. Residual stress change by thermal annealing in amorphous Sm-Fe-B thin films

    International Nuclear Information System (INIS)

    Na, S.M.; Suh, S.J.; Kim, H.J.; Lim, S.H.

    2002-01-01

    The change in the residual stress and its effect on mechanical bending and magnetic properties of sputtered amorphous Sm-Fe-B thin films are investigated as a function of annealing temperature. Two stress components of intrinsic compressive stress and tensile stress due to the difference of the thermal expansion coefficients between the substrate and thin film are used to explain the stress state in as-deposited thin films, and the annealing temperature dependence of residual stress, mechanical bending and magnetic properties

  11. A protocol for analysing thermal stress in insects using infrared thermography.

    Science.gov (United States)

    Gallego, Belén; Verdú, José R; Carrascal, Luis M; Lobo, Jorge M

    2016-02-01

    The study of insect responses to thermal stress has involved a variety of protocols and methodologies that hamper the ability to compare results between studies. For that reason, the development of a protocol to standardize thermal assays is necessary. In this sense, infrared thermography solves some of the problems allowing us to take continuous temperature measurements without handling the individuals, an important fact in cold-blooded organisms like insects. Here, we present a working protocol based on infrared thermography to estimate both cold and heat thermal stress in insects. We analyse both the change in the body temperature of individuals and their behavioural response. In addition, we used partial least squares regression for the statistical analysis of our data, a technique that solves the problem of having a large number of variables and few individuals, allowing us to work with rare or endemic species. To test our protocol, we chose two species of congeneric, narrowly distributed dung beetles that are endemic to the southeastern part of the Iberian Peninsula. With our protocol we have obtained five variables in the response to cold and twelve in the response to heat. With this methodology we discriminate between the two flightless species of Jekelius through their thermal response. In response to cold, Jekelius hernandezi showed a higher rate of cooling and reached higher temperatures of stupor and haemolymph freezing than Jekelius punctatolineatus. Both species displayed similar thermoregulation ranges before reaching lethal body temperature with heat stress. Overall, we have demonstrated that infrared thermography is a suitable method to assess insect thermal responses with a high degree of sensitivity, allowing for the discrimination between closely related species. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Contrasting Patterns of Coral Bleaching Susceptibility in 2010 Suggest an Adaptive Response to Thermal Stress

    Science.gov (United States)

    Guest, James R.; Baird, Andrew H.; Maynard, Jeffrey A.; Muttaqin, Efin; Edwards, Alasdair J.; Campbell, Stuart J.; Yewdall, Katie; Affendi, Yang Amri; Chou, Loke Ming

    2012-01-01

    Background Coral bleaching events vary in severity, however, to date, the hierarchy of susceptibility to bleaching among coral taxa has been consistent over a broad geographic range and among bleaching episodes. Here we examine the extent of spatial and temporal variation in thermal tolerance among scleractinian coral taxa and between locations during the 2010 thermally induced, large-scale bleaching event in South East Asia. Methodology/Principal Findings Surveys to estimate the bleaching and mortality indices of coral genera were carried out at three locations with contrasting thermal and bleaching histories. Despite the magnitude of thermal stress being similar among locations in 2010, there was a remarkable contrast in the patterns of bleaching susceptibility. Comparisons of bleaching susceptibility within coral taxa and among locations revealed no significant differences between locations with similar thermal histories, but significant differences between locations with contrasting thermal histories (Friedman = 34.97; pSingapore, where only 5% and 12% of colonies died. Conclusions/Significance The pattern of susceptibility among coral genera documented here is unprecedented. A parsimonious explanation for these results is that coral populations that bleached during the last major warming event in 1998 have adapted and/or acclimatised to thermal stress. These data also lend support to the hypothesis that corals in regions subject to more variable temperature regimes are more resistant to thermal stress than those in less variable environments. PMID:22428027

  13. Stress analysis in curved composites due to thermal loading

    Science.gov (United States)

    Polk, Jared Cornelius

    Many structures in aircraft, cars, trucks, ships, machines, tools, bridges, and buildings, consist of curved sections. These sections vary from straight line segments that have curvature at either one or both ends, segments with compound curvatures, segments with two mutually perpendicular curvatures or Gaussian curvatures, and segments with a simple curvature. With the advancements made in multi-purpose composites over the past 60 years, composites slowly but steadily have been appearing in these various vehicles, compound structures, and buildings. These composite sections provide added benefits over isotropic, polymeric, and ceramic materials by generally having a higher specific strength, higher specific stiffnesses, longer fatigue life, lower density, possibilities in reduction of life cycle and/or acquisition cost, and greater adaptability to intended function of structure via material composition and geometry. To be able to design and manufacture a safe composite laminate or structure, it is imperative that the stress distributions, their causes, and effects are thoroughly understood in order to successfully accomplish mission objectives and manufacture a safe and reliable composite. The objective of the thesis work is to expand upon the knowledge of simply curved composite structures by exploring and ascertaining all pertinent parameters, phenomenon, and trends in stress variations in curved laminates due to thermal loading. The simply curved composites consist of composites with one radius of curvature throughout the span of the specimen about only one axis. Analytical beam theory, classical lamination theory, and finite element analysis were used to ascertain stress variations in a flat, isotropic beam. An analytical method was developed to ascertain the stress variations in an isotropic, simply curved beam under thermal loading that is under both free-free and fixed-fixed constraint conditions. This is the first such solution to Author's best knowledge

  14. Investigations in thermal fields and stress fields induced by electron beam welding

    International Nuclear Information System (INIS)

    Basile, G.

    1979-12-01

    This document presents the thermal study of electron beam welding and identifies stresses and strains from welding: description of the operating principles of the electron gun and characterization of various welding parameters, examination of the temperature fields during electron beam welding development of various mathematic models and comparison with experimental results, measurement and calculation of stresses and strains in the medium plane of the welding assembly, residual stresses analysis [fr

  15. Cyclic Thermal Stress-Induced Degradation of Cu Metallization on Si3N4 Substrate at -40°C to 300°C

    Science.gov (United States)

    Lang, Fengqun; Yamaguchi, Hiroshi; Nakagawa, Hiroshi; Sato, Hiroshi

    2015-01-01

    The high-temperature reliability of active metal brazed copper (AMC) on Si3N4 ceramic substrates used for fabricating SiC high-temperature power modules was investigated under harsh environments. The AMC substrate underwent isothermal storage at 300°C for up to 3000 h and a thermal cycling test at -40°C to 300°C for up to 3000 cycles. During isothermal storage at 300°C, the AMC substrate exhibited high reliability, characterized by very little deformation of the copper (Cu) layer, low crack growth, and low oxidation rate of the Cu layer. Under thermal cycling conditions at -40°C to 300°C, no detachment of the Cu layer was observed even after the maximum 3000 cycles of the experiment. However, serious deformation of the Cu layer occurred and progressed as the number of thermal cycles increased, thus significantly roughening the surface of the Cu metallized layer. The cyclic thermal stress led to a significant increase in the crack growth and oxidation of the Cu layer. The maximum depth of the copper oxides reached up to 5/6 of the Cu thickness. The deformation of the Cu layer was the main cause of the decrease of the bond strength under thermal cycling conditions. The shear strength of the SiC chips bonded on the AMC substrate with a Au-12 wt.%Ge solder decreased from the original 83 MPa to 14 MPa after 3000 cycles. Therefore, the cyclic thermal stress destroyed the Cu oxides and enhanced the oxidation of the Cu layer.

  16. Effect of Thermal Mechanical Behaviors of Cu on Stress Distribution in Cu-Filled Through-Silicon Vias Under Heat Treatment

    Science.gov (United States)

    Zhao, Xuewei; Ma, Limin; Wang, Yishu; Guo, Fu

    2018-01-01

    Through-silicon vias (TSV) are facing unexpected thermo-mechanical reliability problems due to the coefficient of thermal expansion (CTE) mismatch between various materials in TSVs. During applications, thermal stresses induced by CTE mismatch will have a negative impact on other devices connecting with TSVs, even leading to failure. Therefore, it is essential to investigate the stress distribution evolution in the TSV structure under thermal loads. In this report, TSVs were heated to 450°C at different heating rates, then cooled down to room temperature after a 30-min dwelling. After heating treatment, TSV samples exhibited different Cu deformation behaviors, including Cu intrusion and protrusion. Based on the different Cu deformation behaviors, stress in Si around Cu vias of these samples was measured and analyzed. Results analyzed by Raman spectrums showed that the stress distribution changes were associated with Cu deformation behaviors. In the area near the Cu via, Cu protrusion behavior might aggravate the stress in Si obtained from the Raman measurement, while Cu intrusion might alleviate the stress. The possible reason was that in this area, the compressive stress σ_{θ } induced by thermal loads might be the dominant stress. In the area far from the Cu via, thermal loads tended to result in a tensile stress state in Si.

  17. Primary productivity, heterotrophy, metabolic indicators of stress and interactions in algal-bacterial mat communities affected by a fluctuating thermal regime

    International Nuclear Information System (INIS)

    Tison, D.L.

    1980-01-01

    Thermal habitats in effluent cooling waters from production nuclear reactors at the Savannah River Plant are unlike natural thermal habitats in that reactor operations are periodically halted, exposing the organisms growing in these thermal habitats to ambient temperatures for unpredictable lengths of time. Rates of primary production, glucose heterotrophy, and the composition of algal-bacterial mat communities growing along a thermal gradient from about 50 to 35 0 C during periods of reactor operation were studied. Cyanobacteria were the only photoautotrophs in mat communities above 40 0 C while cyanobacteria and eucaryotic algae comprised the photoautotrophic component of mat communities below 40 0 C. The heterotrophic component of these communities above 40 0 C was made up of stenothermic and eurythermic thermophilic bacteria while both eurythermic thermophiles and mesophilic bacteria were found in communities below 40 0 C. Net CO 2 -fixation rates during thermal conditions dropped after initial exposure to ambient temperatures. After prolonged exposure of the thermal communities to ambient temperatures, adaptation and colonization by mesophilic algae occurred. Rates of glucose utilization under varying degrees of thermal influence suggested that the heterotrophic component may not have been optimally adapted to thermal conditions. During periods of changing thermal conditions, an increase in the percentage extracellular release of photosynthetically fixed 14 CO 2 by cyanobacteria and algae and an increase in the percentage of glucose mineralized (respired) by the heterotrophic component of the mat communities was observed. Results of temperature shift experiments indicated that the short-term response of the photoautotrophic component of these communities to thermal stress was an increase in the percentage of photosynthate released extracellularly

  18. Spalling stress in oxidized thermal barrier coatings evaluated by X-ray diffraction method

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, K. [Faculty of Education and Human Sciences, Niigata Univ., Niigata (Japan); Tanaka, K. [Dept. of Mechanical Engineering, Nagoya Univ., Furoh-cho, Chikusa-ku, Nagoya (Japan)

    2005-07-01

    The spallation of thermal barrier coatings (TBCs) is promoted by thermally grown oxide (TGO). To improve TBCs, it is very important to understand the influence of TGO on the spalling stress. In this study 'the TBCs were oxidized at 1373 K for four different periods: 0, 500,1000 and 2000 h. The distribution of the in-plane stress in oxidized TBCs, {sigma}{sub 1}, was obtained by repeating the X-ray stress measurement with low energy X-rays after successive removal of the surface layer. The distribution of the out-of-plane stress, {sigma}{sub 1} - {sigma}{sub 3}, was measured with hard synchrotron X-rays, because high energy X-rays have a large penetration depth. From the results by the low and high energy X-rays, the spalling stress in the oxidized TBCs, {sigma}{sub 3}, was evaluated. The evaluated value of the spalling stress for the oxidized TBC was a small tension beneath the surface, but steeply increased near the interface between the top and bond coating. This large tensile stress near the interface is responsible for the spalling of the top coating. (orig.)

  19. Quasi-Static Transient Thermal Stresses in an Elliptical Plate due to Sectional Heat Supply on the Curved Surfaces over the Upper Face

    Directory of Open Access Journals (Sweden)

    Lalsingh Khalsa

    2018-01-01

    Full Text Available This paper is an attempt to determine quasi-static thermal stresses in a thin elliptical plate which is subjected to transient temperature on the top face with zero temperature on the lower face and the homogeneous boundary condition of the third kind on the fixed elliptical curved surface. The solution to conductivity equation is elucidated by employing a classical method. The solution of stress components is achieved by using Goodier’s and Airy’s potential function involving the Mathieu and modified functions and their derivatives. The obtained numerical results are accurate enough for practical purposes, better understanding of the underlying elliptic object, and better estimates of the thermal effect on the thermoelastic problem. The conclusions emphasize the importance of better understanding of the underlying elliptic structure, improved understanding of its relationship to circular object profile, and better estimates of the thermal effect on the thermoelastic problem.

  20. A study on the bonding residual thermal stress analysis of dissimilar materials using boundary element method

    International Nuclear Information System (INIS)

    Yi, Won; Yu, Yeong Chul; Jeong, Eui Seob; Lee, Chang Ho

    1995-01-01

    It is very important to evaluate the bonding residual thermal stress in dissimilar materials such as LSI package. In this study, the bonding residual thermal stress was calculated using the boundary element method, varing with the sub-element, geometry of specimen and adhesive thickness. The present results reveal a stress singularity at the edge of the interface, therefore the bonding strength of metal/resin interface can be estimated by taking into account it.

  1. Thermal Analysis for Condition Monitoring of Machine Tool Spindles

    International Nuclear Information System (INIS)

    Clough, D; Fletcher, S; Longstaff, A P; Willoughby, P

    2012-01-01

    Decreasing tolerances on parts manufactured, or inspected, on machine tools increases the requirement to have a greater understanding of machine tool capabilities, error sources and factors affecting asset availability. Continuous usage of a machine tool during production processes causes heat generation typically at the moving elements, resulting in distortion of the machine structure. These effects, known as thermal errors, can contribute a significant percentage of the total error in a machine tool. There are a number of design solutions available to the machine tool builder to reduce thermal error including, liquid cooling systems, low thermal expansion materials and symmetric machine tool structures. However, these can only reduce the error not eliminate it altogether. It is therefore advisable, particularly in the production of high value parts, for manufacturers to obtain a thermal profile of their machine, to ensure it is capable of producing in tolerance parts. This paper considers factors affecting practical implementation of condition monitoring of the thermal errors. In particular is the requirement to find links between temperature, which is easily measureable during production and the errors which are not. To this end, various methods of testing including the advantages of thermal images are shown. Results are presented from machines in typical manufacturing environments, which also highlight the value of condition monitoring using thermal analysis.

  2. Thermal sensations and comfort investigations in transient conditions in tropical office.

    Science.gov (United States)

    Dahlan, Nur Dalilah; Gital, Yakubu Yau

    2016-05-01

    The study was done to identify affective and sensory responses observed as a result of hysteresis effects in transient thermal conditions consisting of warm-neutral and neutral - warm performed in a quasi-experiment setting. Air-conditioned building interiors in hot-humid areas have resulted in thermal discomfort and health risks for people moving into and out of buildings. Reports have shown that the instantaneous change in air temperature can cause abrupt thermoregulation responses. Thermal sensation vote (TSV) and thermal comfort vote (TCV) assessments as a consequence of moving through spaces with distinct thermal conditions were conducted in an existing single-story office in a hot-humid microclimate, maintained at an air temperature 24 °C (± 0.5), relative humidity 51% (± 7), air velocity 0.5 m/s (± 0.5), and mean radiant temperature (MRT) 26.6 °C (± 1.2). The measured office is connected to a veranda that showed the following semi-outdoor temperatures: air temperature 35 °C (± 2.1), relative humidity 43% (± 7), air velocity 0.4 m/s (± 0.4), and MRT 36.4 °C (± 2.9). Subjective assessments from 36 college-aged participants consisting of thermal sensations, preferences and comfort votes were correlated against a steady state predicted mean vote (PMV) model. Local skin temperatures on the forehead and dorsal left hand were included to observe physiological responses due to thermal transition. TSV for veranda-office transition showed that no significant means difference with TSV office-veranda transition were found. However, TCV collected from warm-neutral (-0.24, ± 1.2) and neutral-warm (-0.72, ± 1.3) conditions revealed statistically significant mean differences (p thermal transition after travel from warm-neutral-warm conditions did not replicate the hysteresis effects of brief, slightly cool, thermal sensations found in previous laboratory experiments. These findings also indicate that PMV is an acceptable alternative to predict thermal

  3. Initial assessment of the thermal stresses around a radioactive waste depository in hard rock

    International Nuclear Information System (INIS)

    Hodgkinson, D.P.; Bourke, P.J.

    1980-01-01

    The disposal of heat emitting radioactive waste into hard rock should result in temperature rises and thermal gradients over distances of several hundred metres for several centuries. The consequent constrained thermal expansion of the rock would induce stresses which have important implications for possible water-borne leakage of radionuclides and for depository design. These problems are assessed by considering a simplified mathematical model for which analytic solutions to the temperature and stress fields are derived. (author)

  4. Effects of Thermal Annealing Conditions on Cupric Oxide Thin Film

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyo Seon; Oh, Hee-bong; Ryu, Hyukhyun [Inje University, Gimhae (Korea, Republic of); Lee, Won-Jae [Dong-Eui University, Busan (Korea, Republic of)

    2015-07-15

    In this study, cupric oxide (CuO) thin films were grown on fluorine doped tin oxide(FTO) substrate by using spin coating method. We investigated the effects of thermal annealing temperature and thermal annealing duration on the morphological, structural, optical and photoelectrochemical properties of the CuO film. From the results, we could find that the morphologies, grain sizes, crystallinity and photoelectrochemical properties were dependent on the annealing conditions. As a result, the maximum photocurrent density of -1.47 mA/cm{sup 2} (vs. SCE) was obtained from the sample with the thermal annealing conditions of 500 ℃ and 40 min.

  5. Estimation of thermal sensation during varied air temperature conditions.

    Science.gov (United States)

    Katsuura, T; Tabuchi, R; Iwanaga, K; Harada, H; Kikuchi, Y

    1998-03-01

    Seven male students were exposed to four varied air temperature environments: hot (37 degrees C) to neutral (27 degrees C) (HN), neutral to hot (NH), cool (17 degrees C) to neutral (CN), and neutral to cool (NC). The air temperature was maintained at the first condition for 20 min, then was changed to the second condition after 15 min and was held there for 20 min. Each subject wore a T-shirt, briefs, trunks, and socks. Each sat on a chair and was continuously evaluated for thermal sensation, thermal comfort, and air velocity sensation. Some physiological and thermal parameters were also measured every 5 s during the experiment. The correlation between thermal sensation and skin temperature at 15 sites was found to be poor. The subjects felt much warmer during the rising phase of the air temperature (CN, NH) than during the descending phase (HN, NC) at a given mean skin temperature. However, thermal sensation at the same heat flux or at the same value of the difference between skin and air temperature (delta(Tsk - Ta)) was not so different among the four experimental conditions, and the correlation between thermal sensation and heat flux or delta(Tsk - Ta) was fairly good. The multiple regression equation of the thermal sensation (TS) on 15 sites of skin temperature (Tsk; degrees C) was calculated and the coefficient of determination (R*2) was found to be 0.656. Higher coefficients of determination were found in the equations of thermal sensation for the heat flux (H; kcal.m-2.h-1) at the right and left thighs of the subjects and on delta(Tsk - Ta) (degrees C) at 4 sites. They were as follows: TS = 2.04 - 0.016 Hright - 0.036 Hleft; R*2 = 0.717, TS = 1.649 + 0.013 delta(Tsk - Ta)UpperArm - 0.036 delta(Tsk - Ta)Chest - 0.223 delta(Tsk - Ta)Thigh-0.083 delta(Tsk - Ta)LowerLeg; R*2 = 0.752, respectively.

  6. Modelling and analysis of radial thermal stresses and temperature ...

    African Journals Online (AJOL)

    user

    it acts as an insulating medium and prevents the heat flow, hence the need of providing insulation coating on valves is ... geometry metal components (piston, liner and cylinder head) and found a satisfactory .... model. Step8: Find the radial thermal stress at all the nodal point with the use of temperature ..... Cast iron St. 70.

  7. The stress and stress intensity factors computation by BEM and FEM combination for nozzle junction under pressure and thermal loads

    International Nuclear Information System (INIS)

    Du, Q.; Cen, Z.; Zhu, H.

    1989-01-01

    This paper reports linear elastic fracture analysis based upon the stress intensity factor evaluation successfully applied to safety assessments of cracked structures. The nozzle junction are usually subjected to high pressure and thermal loads simultaneously. In validity of linear elastic fracture analysis, K can be decomposed into K P (caused by mechanic loads) and K τ (caused by thermal loads). Under thermal transient loading, explicit analysis (say by the FEM or BEM) of K tracing an entire history respectively for a range of crack depth may be much more time consuming. The techniques of weight function provide efficient means for transforming the problem into the stress computation of the uncracked structure and generation of influence function (for the given structure and size of crack). In this paper, a combination of BE-FEM has been used for the analysis of the cracked nozzle structure by techniques of weight function. The influence functions are obtained by coupled BE-FEM and the uncracked structure stress are computed by finite element methods

  8. Thermal stress analysis of an Am/Cm stabilization bushing melter

    International Nuclear Information System (INIS)

    Gong, C.; Hardy, B.J.

    1996-01-01

    Decades of nuclear material production at the Savannah River Site (SRS) has resulted in the generation of large quantities of the isotopes Am 243 and Cm 244 . Currently, the Am and Cm isotopes are stored as a nitric acid solution in a tank. The Am and Cm isotopes have great commercial value but must be transferred to the Oak Ridge National Laboratory (ORNL) for processing. The nitric acid solution contains other isotopes and is intensely radioactive, which makes storage a problem and precludes shipment in the liquid form. In order to stabilize the material for onsite storage and to permit transport the material from SRS to ORNL, it has been proposed that the Am and Cm be separated from other isotopes in the solution and vitrified. The vitrification process in the Platinum-Rhodium alloy vessel generates a wide spectrum of temperature distributions. The melter is partially supported by a suspension system and confined by the flexible insulation. The combination of the fluctuation of temperature distribution and variable boundary conditions, induces stresses and strains in the melter. The thermal stress analysis is carried out with the finite element code ABAQUS. This analysis is closely associated with the design, manufacture and testing of the melter. The results were compared with the test data

  9. Study on mitigation of stress corrosion cracking by peening

    International Nuclear Information System (INIS)

    Maeguchi, Takaharu; Tsutsumi, Kazuya; Toyoda, Masahiko; Ohta, Takahiro; Okabe, Taketoshi; Sato, Tomonobu

    2010-01-01

    In order to verify stability of residual stress improvement effect of peeing for mitigation of stress corrosion cracking in components of PWR plant, relaxation behavior of residual stress induced by water jet peening (WJP) and ultrasonic shot peening (USP) on surface of alloy 600 and its weld metal was investigated under various thermal aging and stress condition considered for actual plant operation. In the case of thermal aging at 320-380degC, surface residual stress relaxation was observed at the early stage of thermal aging, but no significant stress relaxation was observed after that. Applied stress below yield stress does not significantly affect stress relaxation behavior of surface residual stress. Furthermore, it was confirmed that cyclic stress does not accelerate stress relaxation. (author)

  10. Mitochondrial terminal alternative oxidase and its enhancement by thermal stress in the coral symbiont Symbiodinium

    Science.gov (United States)

    Oakley, Clinton A.; Hopkinson, Brian M.; Schmidt, Gregory W.

    2014-06-01

    A terminal electron acceptor alternative to mitochondrial cytochrome c oxidase (COX), mitochondrial alternative oxidase (AOX), is ubiquitous in higher plants and represented in nearly every algal taxon but is poorly documented in dinoflagellates. AOX competes for electrons with the conventional COX and has been hypothesized to function as a means of reducing oxidative stress in mitochondria, as well as a potential mechanism for ameliorating thermal and other physiological stressors. Here, the presence of an active AOX in cultured Symbiodinium was assayed by the response of oxygen consumption to the AOX inhibitor salicylhydroxamic acid (SHAM) and the COX inhibitor cyanide (CN). CN-insensitive, SHAM-sensitive oxygen consumption was found to account for a large portion (26 %) of Symbiodinium dark respiration and is consistent with high levels of AOX activity. This experimental evidence of the existence of a previously unreported terminal oxidase was further corroborated by analysis of publicly available Symbiodinium transcriptome data. The potential for enhanced AOX expression to play a compensatory role in mediating thermal stress was supported by inhibitor assays of cultured Symbiodinium at low (18 °C), moderate (26 °C), and high (32 °C) temperature conditions. Maximum capacity of the putative AOX pathway as a proportion of total dark oxygen consumption was found to increase from 26 % at 26 °C to 45 % and 53 % at 18 °C and 32 °C, respectively, when cells were acclimated to the treatment temperatures. Cells assayed at 18 and 32 °C without acclimation exhibited either the same or lower AOX capacity as controls, suggesting that the AOX protein is upregulated under temperature stress. The physiological implications for the presence of AOX in the coral/algal symbiosis and its potential role in response to many forms of biotic and abiotic stress, particularly oxidative stress, are discussed.

  11. Effective Stress Law in Unconventional Reservoirs under Different Boundary Conditions

    Science.gov (United States)

    Saurabh, S.; Harpalani, S.

    2017-12-01

    Unconventional reservoirs have attracted a great deal of research interest worldwide during the past two decades. Low permeability and specialized techniques required to exploit these resources present opportunities for improvement in both production rates and ultimate recovery. Understanding subsurface stress modifications and permeability evolution are valuable when evaluating the prospects of unconventional reservoirs. These reservoir properties are functions of effective stress. As a part of this study, effective stress law, specifically the variation of anisotropic Biot's coefficient under various boundary conditions believed to exist in gas reservoirs by different researchers, has been established. Pressure-dependent-permeability (PdK) experiments were carried out on San Juan coal under different boundary conditions, that is, uniaxial strain condition and constant volume condition. Stress and strain in the vertical and horizontal directions were monitored throughout the experiment. Data collected during the experiments was used to determine the Biot's coefficient in vertical and horizontal directions under these two boundary conditions, treating coal as transversely isotropic. The variation of Biot's coefficient was found to be well correlated with the variation in coal permeability. Based on the estimated values of Biot's coefficients, a theory of variation in its value is presented for other boundary conditions. The findings of the study shed light on the inherent behavior of Biot's coefficient under different reservoir boundary conditions. This knowledge can improve the modeling work requiring estimation of effective stress in reservoirs, such as, pressure-/stress- dependent permeability. At the same time, if the effective stresses are known with more certainty by other methods, it enables assessment of the unknown reservoir boundary conditions.

  12. Expression of genes involved in energy mobilization and osmoprotectant synthesis during thermal and dehydration stress in the Antarctic midge, Belgica antarctica.

    Science.gov (United States)

    Teets, Nicholas M; Kawarasaki, Yuta; Lee, Richard E; Denlinger, David L

    2013-02-01

    The Antarctic midge, Belgica antarctica, experiences sub-zero temperatures and desiccating conditions for much of the year, and in response to these environmental insults, larvae undergo rapid shifts in metabolism, mobilizing carbohydrate energy reserves to promote synthesis of low-molecular-mass osmoprotectants. In this study, we measured the expression of 11 metabolic genes in response to thermal and dehydration stress. During both heat and cold stress, we observed upregulation of phosphoenolpyruvate carboxykinase (pepck) and glycogen phosphorylase (gp) to support rapid glucose mobilization. In contrast, there was a general downregulation of pathways related to polyol, trehalose, and proline synthesis during both high- and low-temperature stress. Pepck was likewise upregulated in response to different types of dehydration stress; however, for many of the other genes, expression patterns depended on the nature of dehydration stress. Following fast dehydration, expression patterns were similar to those observed during thermal stress, i.e., upregulation of gp accompanied by downregulation of trehalose and proline synthetic genes. In contrast, gradual, prolonged dehydration (both at a constant temperature and in conjunction with chilling) promoted marked upregulation of genes responsible for trehalose and proline synthesis. On the whole, our data agree with known metabolic adaptations to stress in B. antarctica, although a few discrepancies between gene expression patterns and downstream metabolite contents point to fluxes that are not controlled at the level of transcription.

  13. Transient thermal stresses in a circular cylinder with constrained ends

    International Nuclear Information System (INIS)

    Goshima, Takahito; Miyao, Kaju

    1986-01-01

    This paker deals with the transient thermal stresses in a finite circular cylinder constrained at both end surfaces and subjected to axisymmetric temperature distribution on the lateral surface. The thermoelastic problem is formulated in terms of a thermoelastic displacement potential and three harmonic stress functions. Numerical calculations are carried out for the case of the uniform temperature distribution on the lateral surface. The stress distributions on the constrained end and the free suface are shown graphically, and the singularity in stresses appearing at the circumferencial edge is considered. Moreover, the approximate solution based upon the plane strain theory is introduced in order to compare the rigorous one, and it is considered how the length of the cylinder and the time proceeds affect on the accuracy of the approximation. (author)

  14. THERMAL COMFORT STUDY OF AN AIR-CONDITIONED DESIGN STUDIO IN TROPICAL SURABAYA

    Directory of Open Access Journals (Sweden)

    Agus Dwi Hariyanto

    2005-01-01

    Full Text Available This paper evaluates the current thermal comfort condition in an air-conditioned design studio using objective measurement and subjective assessment. Objective measurement is mainly to quantify the air temperature, MRT, relative humidity, and air velocity. Subjective assessment is conducted using a questionnaire to determine the occupants thermal comfort sensations and investigate their perception of the thermal comfort level. A design studio in an academic institution in Surabaya was chosen for the study. Results show that more than 80% of the occupants accepted the indoor thermal conditions even though both the environmental and comfort indices exceeded the limit of the standard (ASHRAE Standard 55 and ISO 7730. In addition, non-uniformity of spatial temperature was present in this studio. Some practical recommendations were made to improve the thermal comfort in the design studio.

  15. Design of an RF window for L-band CW klystron based on thermal-stress analysis

    International Nuclear Information System (INIS)

    Yamaguchi, Seiya; Sato, Isamu; Konashi, Kenji; Ohshika, Junji.

    1993-01-01

    Design of klystron RF window has been performed based on a thermal-stress analysis for L-band CW electron linac for nuclear wastes transmutation. It was shown that the hoop stress for a modified disk is 46% of that of normal disk. Thermal load test has been done which indicated that the modified disk is proof against power twice as much as that for the normal disk. (author)

  16. Bandgap tuning with thermal residual stresses induced in a quantum dot.

    Science.gov (United States)

    Kong, Eui-Hyun; Joo, Soo-Hyun; Park, Hyun-Jin; Song, Seungwoo; Chang, Yong-June; Kim, Hyoung Seop; Jang, Hyun Myung

    2014-09-24

    Lattice distortion induced by residual stresses can alter electronic and mechanical properties of materials significantly. Herein, a novel way of the bandgap tuning in a quantum dot (QD) by lattice distortion is presented using 4-nm-sized CdS QDs grown on a TiO2 particle as an application example. The bandgap tuning (from 2.74 eV to 2.49 eV) of a CdS QD is achieved by suitably adjusting the degree of lattice distortion in a QD via the tensile residual stresses which arise from the difference in thermal expansion coefficients between CdS and TiO2. The idea of bandgap tuning is then applied to QD-sensitized solar cells, achieving ≈60% increase in the power conversion efficiency by controlling the degree of thermal residual stress. Since the present methodology is not limited to a specific QD system, it will potentially pave a way to unexplored quantum effects in various QD-based applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Numerical Analysis of Thermal Stresses around Fasteners in Composite Metal Foils

    Science.gov (United States)

    Nammi, S. K.; Butt, J.; –L Mauricette, J.; Shirvani, H.

    2017-12-01

    The process of composite metal foil manufacturing (CMFM) has reduced a number of limitations associated with commercial additive manufacturing (AM) methods. The existing metal AM machines are restricted by their build envelope and there is a growing market for the manufacture of large parts using AM. These parts are subsequently manufactured in fragments and are fastened together. This paper analyses the thermal stresses around cylindrical fasteners for three layered metal composite parts consisting of aluminium foil, brazing paste and copper foil layers. The investigation aims to examine the mechanical integrity of the metallurgically bonded aluminium/copper foils of 100 micron thickness manufactured in a disc shape. A cylindrical fastener set at an elevated temperature of 100 °C is fitted in the middle of the disc which results in a steady-state thermal distribution. Radial and shear stresses are computed using finite element method which shows that non-zero shear stresses developed by the copper layer inhibit the axial slippage of the fastener and thereby establishing the suitability of rivet joints for CMFM parts.

  18. Perturbation of baseline thermal stress in the Mound 9516 Shipping Package primary containment vessel

    International Nuclear Information System (INIS)

    Sansalone, K.H.F.

    1995-01-01

    Full-capacity loading of heat sources into the Mound 9516 Shipping Package primary containment vessel (PCV) results in temperature gradients which are symmetric, due to the axisymmetry of the package design. Concern over the change in thermal gradients (and therefore, stress) in the PCV due to sub-capacity loading led to the analytical examination of this phenomenon. The PCVs are cylindrical in shape and are loaded into the package such that they and all containment components are concentrically arranged along a common longitudinal axis. If the design full-capacity loading of the PCVs in this package assumes the axisymmetric (or more precisely, cyclicly symmetric) arrangement of its heat-producing contents, then sub-capacity loading implies that in many cases, the load arrangement could be asymmetric with respect to the longitudinal axis. It is then feasible that the departure from heat load axisymmetry could perturb the nominal thermal gradients so that thermally-induced stress within the PCV might increase to levels deemed unacceptable. This study applies Finite Element analysis (FEA) to the problem and demonstrates that no such unacceptable thermal stress increase occurs in the PCV material due to the asymmetric arrangement of contents. copyright 1995 American Institute of Physics

  19. Avaliação do estresse térmico em condição simulada de transporte de frangos de corte Evaluation of thermal stress in simulated condition of transportation on broiler chickens

    Directory of Open Access Journals (Sweden)

    Marco Aurélio Neves da Silva

    2007-08-01

    Full Text Available Objetivou-se simular, em câmara climática, a condição ambiental de estresse térmico durante o transporte de aves até o abatedouro para avaliação da influência do estresse térmico sobre parâmetros fisiológicos e as características de carcaça de frangos de corte. Trinta frangos machos com 42 dias de idade foram pesados, alocados em caixas de transporte (10 aves/caixa e submetidos a condição de alto estresse térmico (35ºC e 85% UR para simular o transporte até o abatedouro. A cada tempo de exposição às condições de estresse (0, 30, 60, 90 e 120 minutos, foram retiradas duas aves de cada caixa para análises posteriores. Foram mensurados o peso corporal, a temperatura retal, a freqüência respiratória e o hematócrito e, em seguida, as aves foram abatidas para avaliação das características de carcaça (pesos da carcaça eviscerada, do peito, das pernas (coxa e sobrecoxa, do dorso e das vísceras. As características fisiológicas e de carcaça (perda de peso corporal e pesos de pernas, asas e dorso diferiram após a exposição das aves à condição de alto estresse. O tempo de exposição e a condição ambiental de transporte afetaram negativamente o metabolismo e o equilíbrio térmico corporal das aves.This experiment aimed to simulate thermal-stress-environment conditions in climatic chamber during the transportation of birds to slaughterhouse to evaluate the influence of these conditions on physiological parameters and carcass conformation in broiler chickens. Thirty chicks with 42 days old were weighted and distributed to transportation crates (10 chicks by crate, and submitted to high stress conditions (35ºC and 85% RH to simulate the transport to the slaughterhouse. At each time of exposition to the stress conditions (0, 30, 60, 90 and 120 minutes, two birds from each crate was withdrawn for further analyses. Body weight, rectal temperature, respiratory frequency and hematocrit value were measured, and after

  20. Latitudinal discontinuity in thermal conditions along the nearshore of central-northern Chile.

    Science.gov (United States)

    Tapia, Fabian J; Largier, John L; Castillo, Manuel; Wieters, Evie A; Navarrete, Sergio A

    2014-01-01

    Over the past decade, evidence of abrupt latitudinal changes in the dynamics, structure and genetic variability of intertidal and subtidal benthic communities along central-northern Chile has been found consistently at 30-32°S. Changes in the advective and thermal environment in nearshore waters have been inferred from ecological patterns, since analyses of in situ physical data have thus far been missing. Here we analyze a unique set of shoreline temperature data, gathered over 4-10 years at 15 sites between 28-35°S, and combine it with satellite-derived winds and sea surface temperatures to investigate the latitudinal transition in nearshore oceanographic conditions suggested by recent ecological studies. Our results show a marked transition in thermal conditions at 30-31°S, superimposed on a broad latitudinal trend, and small-scale structures associated with cape-and-bay topography. The seasonal cycle dominated temperature variability throughout the region, but its relative importance decreased abruptly south of 30-31°S, as variability at synoptic and intra-seasonal scales became more important. The response of shoreline temperatures to meridional wind stress also changed abruptly at the transition, leading to a sharp drop in the occurrence of low-temperature waters at northern sites, and a concurrent decrease in corticated algal biomass. Together, these results suggest a limitation of nitrate availability in nearshore waters north of the transition. The localized alongshore change results from the interaction of latitudinal trends (e.g., wind stress, surface warming, inertial period) with a major headland-bay system (Punta Lengua de Vaca at 30.25°S), which juxtaposes a southern stretch of coast characterized by upwelling with a northern stretch of coast characterized by warm surface waters and stratification. This transition likely generates a number of latitude-dependent controls on ecological processes in the nearshore that can explain species

  1. Growth form-dependent response to physical disturbance and thermal stress in Acropora corals

    Science.gov (United States)

    Muko, S.; Arakaki, S.; Nagao, M.; Sakai, Kazuhiko

    2013-03-01

    To predict the community structure in response to changing environmental conditions, it is necessary to know the species-specific reaction and relative impact strength of each disturbance. We investigated the coral communities in two sites, an exposed and a protected site, at Iriomote Island, Japan, from 2005 to 2008. During the study period, a cyclone and thermal stress were observed. All Acropora colonies, classified into four morphologies (arborescent, tabular, corymbose, and digitate), were identified and tracked through time to calculate the annual mortality and growth rate. The mortality of all Acropora colonies in the protected site was lower than that in the exposed site during the period without disturbances. Extremely higher mortality due to bleaching was observed in tabular and corymbose Acropora, compared to other growth forms, at the protected sites after thermal stress. In contrast, physical disturbance by a tropical cyclone induced the highest mortality in arborescent and digitate corals at the exposed site. Moreover, arborescent corals exhibited a remarkable decline 1 year after the tropical cyclone at the exposed site. The growth of colonies that survived coral bleaching did not decrease in the following year compared to previous year for all growth forms, but the growth of arborescent and tabular remnant corals at the exposed site declined severely after the tropical cyclone compared to previous year. The delayed mortality and lowered growth rate after the tropical cyclone were probably due to the damage caused by the tropical cyclone. These results indicate that the cyclone had a greater impact on fragile corals than expected. This study provides useful information for the evaluation of Acropora coral response to progressing global warming conditions, which are predicted to increase in frequency and intensity in the near future.

  2. Transient thermal stresses in circular cylinder under intermittently sudden heat generation

    International Nuclear Information System (INIS)

    Sugano, Y.; Saito, K.; Takeuti, Y.

    1975-01-01

    The thermal stresses associated with the transient temperature distribution arising in a circular cylinder under intermittently changing sudden heat generation over a finite band and with heat loss to a surrounding medium on the remainder of the cylinder surface are exactly analysed. For the first time the temperature field in a circular cylinder under sudden heat generation over a finite band of the cylinder surface is determined by combined use of Fourier cosine, Laplace transforms in axial position and time, respectively. Secondly it is assumed that the temperature fields in a circular cylinder subjected to heat generation Qsub(i) (i=0, 1, 2, ...) independently over a finite band are given by T 0 (r,z,t), T 1 (r,z,t), T 2 (r,z,t),... respectively. Tsub(i)(r,z,t) indicates the temperature field before the i-th heat generation Qsub(i). The thermal stresses associated with the temperature field described above are analysed by using the Hoyle stress functions. Numerical calculations are carried out for the extensive case of the ratio of the heat-generating length to the diameter of cylinder. It is found that the time in which the maximum stresses occur on the cylinder surface does not depend on the heat-generating length-to-diameter ratio

  3. Differential responses of the coral host and their algal symbiont to thermal stress.

    Directory of Open Access Journals (Sweden)

    William Leggat

    Full Text Available The success of any symbiosis under stress conditions is dependent upon the responses of both partners to that stress. The coral symbiosis is particularly susceptible to small increases of temperature above the long term summer maxima, which leads to the phenomenon known as coral bleaching, where the intracellular dinoflagellate symbionts are expelled. Here we for the first time used quantitative PCR to simultaneously examine the gene expression response of orthologs of the coral Acropora aspera and their dinoflagellate symbiont Symbiodinium. During an experimental bleaching event significant up-regulation of genes involved in stress response (HSP90 and HSP70 and carbon metabolism (glyceraldehyde-3-phosphate dehydrogenase, α-ketoglutarate dehydrogenase, glycogen synthase and glycogen phosphorylase from the coral host were observed. In contrast in the symbiont, HSP90 expression decreased, while HSP70 levels were increased on only one day, and only the α-ketoglutarate dehydrogenase expression levels were found to increase. In addition the changes seen in expression patterns of the coral host were much larger, up to 10.5 fold, compared to the symbiont response, which in all cases was less than 2-fold. This targeted study of the expression of key metabolic and stress genes demonstrates that the response of the coral and their symbiont vary significantly, also a response in the host transcriptome was observed prior to what has previously been thought to be the temperatures at which thermal stress events occur.

  4. Thermal shock fracture of graphite armor plate under the heat load of plasma disruption

    International Nuclear Information System (INIS)

    Horie, Tomoyoshi; Seki, Masahiro; Ohmori, Junji

    1989-01-01

    Experiments on the thermal shock brittle fracture of graphite plates were performed. Thermal loading which simulated a plasma disruption was produced by an electron beam facility. Pre-cracks produced on the surface propagated to the inside of the specimen even if the thermal stress on the surface was compressive. Two mechanisms are possible to produce tensile stress around the crack tip under thermal shock conditions. Temperature, thermal stress, and the stress intensity factor for the specimen were analyzed based on the finite element method for various heating conditions. The trend of experimental results under the asymmetric heating agrees qualitatively with the analytical results. This phenomenon is important for the design of plasma facing components made of graphite. Establishment of a lifetime prediction procedure including fatigue, fatigue crack growth, and brittle fracture is needed for graphite armors. (orig.)

  5. Cemented carbide cutting tool: Laser processing and thermal stress analysis

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S. [Mechanical Engineering Department, KFUPM, Box 1913, Dhahran 31261 (Saudi Arabia)]. E-mail: bsyilbas@kfupm.edu.sa; Arif, A.F.M. [Mechanical Engineering Department, KFUPM, Box 1913, Dhahran 31261 (Saudi Arabia); Karatas, C. [Engineering Faculty, Hacettepe University, Ankara (Turkey); Ahsan, M. [Mechanical Engineering Department, KFUPM, Box 1913, Dhahran 31261 (Saudi Arabia)

    2007-04-15

    Laser treatment of cemented carbide tool surface consisting of W, C, TiC, TaC is examined and thermal stress developed due to temperature gradients in the laser treated region is predicted numerically. Temperature rise in the substrate material is computed numerically using the Fourier heating model. Experiment is carried out to treat the tool surfaces using a CO{sub 2} laser while SEM, XRD and EDS are carried out for morphological and structural characterization of the treated surface. Laser parameters were selected include the laser output power, duty cycle, assisting gas pressure, scanning speed, and nominal focus setting of the focusing lens. It is found that temperature gradient attains significantly high values below the surface particularly for titanium and tantalum carbides, which in turn, results in high thermal stress generation in this region. SEM examination of laser treated surface and its cross section reveals that crack initiation below the surface occurs and crack extends over the depth of the laser treated region.

  6. Simulasi Thermal Stress Pada Tube Superheater Package Boiler

    OpenAIRE

    Hamdani

    2013-01-01

    This project investigates the thermal stress behavior and the mechanisms of superheater tube failure with experimental method and numerical analysis. First of all the procedures for failure analysis were applied to determine the root cause of them. A visual assessment of boiler critical pressure parts was carried out, and then the failed tube is examined by nondestructive evaluation. For the numerical domain, initially the elastic solution for a superheater tube subjected to an internal press...

  7. The relationships between environmental and physiological heat stress indices in Muslim women under the controlled thermal conditions

    Directory of Open Access Journals (Sweden)

    Peymaneh Habibi

    2015-01-01

    Full Text Available Aims: The aim of this study was to evaluate the relationship between environmental and physiological heat stress indices based on heart rate (HR, oral temperature for the estimation of heat strain, in veiled women in hot-dry condition in the climate chamber. Materials and Methods: The experimental study was carried out on 36 healthy Muslim women in hot-dry climatic conditions (wet bulb globe temperature (WBGT = 22-32°C in low workload for 2 h. The HR, oral temperature and WBGT index were measured. The obtained data were analyzed using descriptive statistics and Pearson correlation tests. Results: The results of the Pearson test indicated that physiological strain index was a high correlation (r = 0.975 with WBGT index (P < 0.05. Also, there was a good correlation among WBGT and HR (r = 0.779 and oral temperature (r = 0.981. Conclusion: The findings of this study illustrated that there is a good correlation between environmental and physiological heat stress indices in veiled women with Islamic clothing at the low workload over the action limit (WBGT = 31°C. So that it can be concluded that the WBGT 22-32°C is a good indicator of the heat strain in veiled women with Islamic clothing.

  8. A study on thermal residual stresses in the matrix and fiber of a misoriented short fiber composite

    International Nuclear Information System (INIS)

    Son, Bong Jin; Lee, Joon Hyun

    1994-01-01

    An elastic model is developed to predict the average thermal residual stresses in the matrix and fiber of a misoriented short fiber composite. The thermal residual stresses are induced by the mismatch in the coefficient of the thermal expansion of the matrix and fiber when the composite is subjected to a uniform temperature change. The model considers two special cases of fiber misorientation; two-dimensional in-plane and three-dimensional axisymmetric. The analytical formulation of the model is based on Eshelby's equivalent inclusion method and is unique in that it is able to account for interactions among fibers. The model is more general than past models and it is able to treat prior analyses of the simpler composite systems as extream cases. The present model is to investigate the effects of fiber volume fraction, distribution type, distribution cut-off angle, and aspect ratio on thermal residual stress for both in-plane and axisymmetric fiber misorientation. Fiber volume fraction, aspect ratio, and disturbution cut-off angle are shown to have more significant effects on the magnitude of the thermal residual stresses than fiber distrubution type for both in-plane and axisymmetric misorientation.

  9. Thermal Conditions in a Simulated Office Environment with Convective and Radiant Cooling Systems

    DEFF Research Database (Denmark)

    Mustakallio, Panu; Bolashikov, Zhecho Dimitrov; Kostov, Kalin

    2013-01-01

    velocity and turbulent intensity were measured and draft rate levels calculated in the room. Manikin-based equivalent temperature (MBET) was determined by two thermal manikins to identify the impact of the local thermal conditions generated by the studied systems on occupants’ thermal comfort. The results......The thermal conditions in a two person office room were measured with four air conditioning systems: chilled beam (CB), chilled beam with radiant panel (CBR), chilled ceiling with ceiling installed mixing ventilation (CCMV) and four desk partition mounted local radiant cooling panels with mixing...

  10. Effect of processing conditions and methods on residual stress in CeO2 buffer layers and YBCO superconducting films

    International Nuclear Information System (INIS)

    Xiong Jie; Qin Wenfeng; Cui Xumei; Tao Bowan; Tang Jinlong; Li Yanrong

    2006-01-01

    CeO 2 layers have been fabricated by pulsed laser deposition (PLD) technique on (1 1 0 2) sapphire substrate. Microstructure of CeO 2 layers is characterized by X-ray diffraction as functions of substrate temperature. The effects of the substrate temperature on the residual stress have been studied. The results show that residual stress in CeO 2 film decreased with increasing substrate temperature, not the same development tendency as that of thermal stress. This means that the thermal stress is only a fraction of the residual stress. Moreover, YBCO superconducting films were prepared by direct current (DC) sputtering and pulsed laser deposition (PLD) technique. The residual stress and thermal stress of both YBCO films were measured. PLD processing apparently generated higher intrinsic compressive stresses in comparison to DC sputtering

  11. Thermally activated low temperature creep and primary water stress corrosion cracking of NiCrFe alloys

    International Nuclear Information System (INIS)

    Hall, M.M. Jr.

    1993-01-01

    A phenomenological SCC-CGR model is developed based on an apriori assumption that the SCC-CGR is controlled by low temperature creep (LTC). This mode of low temperature time dependent deformation occurs at stress levels above the athermal flow stress by a dislocation glide mechanism that is thermally activated and may be environmentally assisted. The SCC-CGR model equations developed contain thermal activation parameters descriptive of the dislocation creep mechanism. Thermal activation parameters are obtained by fitting the CGR model to SCC-CGR data obtained on Alloy 600 and Alloy X-750. These SCC-CGR activation parameters are compared to LTC activation parameters obtained from stress relaxation tests. When the high concentration of hydrogen at the tip of an SCC crack is considered, the SCC-CGR activation energies and rate sensitivities are shown to be quantitatively consistent with hydrogen reducing the activation energy and increasing the strain rate sensitivity in LTC stress relaxation tests. Stress dependence of SCC-CGR activation energy consistent with that found for the LTC activation energy. Comparisons between temperature dependence of the SCC-CGR stress sensitivity and LTC stress sensitivity provide a basis for speculation on effects of hydrogen and solute carbon on SCC crack growth rates

  12. Verification of OCA-P and VISA-II on behalf of strains and stresses induced during HDR-TEMB thermal mixing tests

    International Nuclear Information System (INIS)

    Geiss, M.

    1987-01-01

    The reactor pressure (RPV) in a pressurized water reactor is normally subjected to operating conditions which do not allow propagation of flaws that have to be postulated in the vessel wall. However in the last years a class of severe overcooling transients referred to as pressurized thermal shock transients have come into discussion. Such transients might have a potential for instable growth of preexisting inner surface flaws thus introducing the possibility of vessel failure. However such conditions are supposed to be critical only in very highly embrittled vessels. The beltline region of the reactor pressure vessel is most critical within this respect since the thermal stresses caused by the transient are very high in this area and the material ductility may be considerably reduced due to the cooldown and the neutron embrittlement. (orig.)

  13. Temperature-time distribution and thermal stresses on the RTG fins and shell during water cooling

    Science.gov (United States)

    Turner, R. H.

    1983-01-01

    Radioisotope thermoelectric generator (RTG) packages designed for space missions generally do not require active cooling. However, the heat they generate cannot remain inside of the launch vehicle bay and requires active removal. Therefore, before the Shuttle bay door is closed, the RTG coolant tubes attached to the heat rejection fins must be filled with water, which will circulate and remove most of the heat from the cargo bay. There is concern that charging a system at initial temperature around 200 C with water at 24 C can cause unacceptable thermal stresses in the RTG shell and fins. A computer model is developed to estimate the transient temperature distribution resulting from such charging. The thermal stresses resulting from the temperature gradients do not exceed the elastic deformation limit for the material. Since the simplified mathematical model for thermal stresses tends to overestimate stresses, it is concluded that the RTG can be cooled by introducing water at 24 C to the initially hot fin coolant tubes while the RTG is in the Shuttle cargo bay.

  14. Bond strength and stress measurements in thermal barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Gell, M.; Jordan, E. [Univ. of Connecticut, Storrs, CT (United States)

    1995-10-01

    Thermal barrier coatings have been used extensively in aircraft gas turbines for more than 15 years to insulate combustors and turbine vanes from the hot gas stream. Plasma sprayed thermal barrier coatings (TBCs) provide metal temperature reductions as much as 300{degrees}F, with improvements in durability of two times or more being achieved. The introduction of TBCs deposited by electron beam physical vapor deposition (EB-PVD) processes in the last five years has provided a major improvement in durability and also enabled TBCs to be applied to turbine blades for improved engine performance. To meet the aggressive Advanced Turbine Systems goals for efficiency, durability and the environment, it will be necessary to employ thermal barrier coatings on turbine airfoils and other hot section components. For The successful application of TBCs to ATS engines with 2600{degrees}F turbine inlet temperatures and required component lives 10 times greater than those for aircraft gas turbine engines, it is necessary to develop quantitative assessment techniques for TBC coating integrity with time and cycles in ATS engines. Thermal barrier coatings in production today consist of a metallic bond coat, such as an MCrAlY overlay coating or a platinum aluminide (Pt-Al) diffusion coating. During heat treatment, both these coatings form a thin, tightly adherent alumina (Al{sub 2}O{sub 3}) film. Failure of TBC coatings in engine service occurs by spallation of the ceramic coating at or near the bond coat to alumina or the alumina to zirconia bonds. Thus, it is the initial strength of these bonds and the stresses at the bond plane, and their changes with engine exposure, that determines coating durability. The purpose of this program is to provide, for the first time, a quantitative assessment of TBC bond strength and bond plane stresses as a function of engine time and cycles.

  15. THERMAL COMFORT STUDY OF AN AIR-CONDITIONED DESIGN STUDIO IN TROPICAL SURABAYA

    OpenAIRE

    Agus Dwi Hariyanto

    2005-01-01

    This paper evaluates the current thermal comfort condition in an air-conditioned design studio using objective measurement and subjective assessment. Objective measurement is mainly to quantify the air temperature, MRT, relative humidity, and air velocity. Subjective assessment is conducted using a questionnaire to determine the occupants thermal comfort sensations and investigate their perception of the thermal comfort level. A design studio in an academic institution in Surabaya was chosen ...

  16. Study by X-ray diffraction and mechanical analysis of the residual stress generation during thermal spraying

    International Nuclear Information System (INIS)

    Pina, J.; Dias, A.; Lebrun, J.L.

    2003-01-01

    Thermally sprayed coatings are formed by the deposition of molten or partially molten particles, propelled onto a substrate where they impact, spread and solidify rapidly. Residual stresses are expected within the sprayed deposit as a consequence of the release of thermal and kinetic energies. A wide range of materials and two spraying techniques are considered in this study, namely atmospheric plasma spraying (APS) and high-velocity oxygen fuel. Stresses were determined by the X-ray diffraction (XRD) method. The results were compared with those calculated by mechanical analysis of stress relief in coatings detached from the substrate. Comparison of the results for adherent and free-standing coatings shows that the residual stress state can be resolved in terms of the components suggested by models that propose two stages of stress generation: quenching stresses and secondary-cooling stresses. The in-depth distribution of residual stresses, through the coating thickness, is discussed in terms of the nature of the coating system

  17. Development of residual thermal stress-relieving structure of CFC monoblock target for JT-60SA divertor

    Energy Technology Data Exchange (ETDEWEB)

    Tsuru, Daigo, E-mail: tsuru.daigo@jaea.go.jp; Sakurai, Shinji; Nakamura, Shigetoshi; Ozaki, Hidetsugu; Seki, Yohji; Yokoyama, Kenji; Suzuki, Satoshi

    2015-10-15

    Highlights: • We carried out numerical simulations on residual thermal stress of targets for the JT-60SA divertor. • We developed three measures to reduce residual thermal stress. • We proposed two structures of CFC monoblock target for the JT-60SA divertor. • We confirmed the effectiveness of the structure by infrared thermography inspection and high heat flux test. - Abstract: Carbon fibre-reinforced carbon composite (CFC) monoblock target for JT-60SA divertor is under development towards the mass-production. CFC monoblocks, WCu interlayers and a CuCrZr cooling tube at the centre of the monoblocks were bonded by vacuum brazing in a high temperature, to a target. If residual thermal stress due to difference of thermal expansions between CFC and CuCrZr exceeds the maximum allowable stress of the CFC after the bonding, cracks are generated in the CFC monoblock and heat removal capacity of the target degrades. In this paper, new structures of the targets were proposed, to reduce residual thermal stress and to mitigate the degradation of heat removal capacity of the targets. Some measures, including slitting of the CFC monoblock aside of the cooling tube, replacement of the interlayer material and shifting the position of the cooling tube, were implemented. The effectiveness of the measures was evaluated by numerical simulations. Target mock-ups with the proposed structures were manufactured. Infrared thermography inspection and high heat flux test were carried out on the mock-ups in order to evaluate the heat removal capacity.

  18. Crop water-stress assessment using an airborne thermal scanner

    Science.gov (United States)

    Millard, J. P.; Jackson, R. D.; Reginato, R. J.; Idso, S. B.; Goettelman, R. C.

    1978-01-01

    An airborne thermal scanner was used to measure the temperature of a wheat crop canopy in Phoenix, Arizona. The results indicate that canopy temperatures acquired about an hour and a half past solar noon were well correlated with presunrise plant water tension, a parameter directly related to plant growth and development. Pseudo-colored thermal images reading directly in stress degree days, a unit indicative of crop irrigation needs and yield potential, were produced. The aircraft data showed significant within-field canopy temperature variability, indicating the superiority of the synoptic view provided by aircraft over localized ground measurements. The standard deviation between airborne and ground-acquired canopy temperatures was 2 C or less.

  19. Proposal on the mitigation methods of thermal stress near the sodium

    International Nuclear Information System (INIS)

    Ando, Masanori; Kasahara, Naoto

    2003-09-01

    A Reactor vessel of fast rector plants contains high temperature liquid sodium in its inside and its upper end is supported by a low temperature structures. Therefore, a significant temperature gradient will arise at the vessel wall near the sodium surface. For this reason, a large thermal stress will be generated around this part. To lower this stress and to protect the vessel, a number of methods have been applied the plants. Generally, these mitigation methods by protection equipments for thermal stress also have some problems such as, increase a mount of materials or to be complicate for control, hard to maintenance and so on. In this research, authors suggested another simple methods for thermal stress, and evaluated their effects using computer analysis. The results obtained in this research are as follows. Authors suggested one method, circulate high temperature gas around outside of the vessel and evaluated the effects of this method by analysis. In case of using this method, Sn (one of index values of design) value might be getting lower about 45%. Authors also suggested another method by setting up a heat transfer plate outside of the vessel and evaluated the effects of this method by analysis. Effects of this method depend on material of the plate. In case of using Carbon as material of plate, Sn value might be 27% lower and in case of using 12Cr steel as material of plate, Sn value might be 15% lower. Authors also suggested another method by changing material of the guard vessel to be the one which has good ability of heat transfer and evaluated the effects of this method by analysis. In case of changing material of guard vessel to 12Cr steel, Sn value might be lower about 12%. (author)

  20. Investigations on the effect of creep stress on the thermal properties of metallic materials

    International Nuclear Information System (INIS)

    Radtke, U.; Crostack, H.A.; Winschuh, E.

    1995-01-01

    Using thermal wave analysis with front side infrared detection on sample material damaged by creep, one examines whether the creep stress has an effect on the thermal material properties and to what effect this can be used to estimate the remaining service life. (orig.) [de

  1. Theoretical basis for a transient thermal elastic-plastic stress analysis of nuclear reactor fuel elements

    International Nuclear Information System (INIS)

    Hsu, T.R.; Bertels, A.W.M.; Banerjee, S.; Harrison, W.C.

    1976-07-01

    This report presents the theoretical basis for a transient thermal elastic-plastic stress analysis of a nuclear reactor fuel element subject to severe transient thermo-mechanical loading. A finite element formulation is used for both the non-linear stress analysis and thermal analysis. These two major components are linked together to form an integrated program capable of predicting fuel element transient behaviour in two dimensions. Specific case studies are presented to illustrate capabilities of the analysis. (author)

  2. Nutritional mitigation of winter thermal stress in gilthead seabream: Associated metabolic pathways and potential indicators of nutritional state.

    Science.gov (United States)

    Richard, Nadège; Silva, Tomé S; Wulff, Tune; Schrama, Denise; Dias, Jorge P; Rodrigues, Pedro M L; Conceição, Luís E C

    2016-06-16

    with diet WF, by undertaking a comparative analysis of fish liver proteome at the end of winter. This study brings information relative to biological processes that are involved in gilthead seabream winter thermal stress and shows that these can be mitigated through a nutritional strategy, assisting gilthead seabream to deal better with winter thermal conditions. Furthermore, the results show that proteomic information not only clearly distinguishes the two dietary groups from each other, but also captures heterogeneities that reflect intra-group differences in nutritional state. This was exploited in this work to refine the variable selection strategy so that protein spots displaying a stronger correlation with “nutritional state” could be identified as possible indicators of gilthead seabream metabolic and nutritional state. Finally, this study shows that gel-based proteomics seems to provide more reliable information than transmissive FT-IR spectroscopy, for the purposes of nutritional and metabolic profiling.

  3. Emotional memory consolidation under lower versus higher stress conditions

    Directory of Open Access Journals (Sweden)

    Inna eKogan

    2010-12-01

    Full Text Available An exposure to stress can enhance memory for emotionally arousing experiences. The phenomenon is suggested to be amygdala-dependent and in accordance with that view the amygdala was found to modulate mnemonic processes in other brain regions. Previously, we illustrated increased amygdala activation and reduced activation of CA1 following spatial learning under high versus low emotionality conditions. When spatial learning was followed by reversal training interference, impaired retention was detected only under high emotionality conditions. Here we further evaluate the potential implications of the difference in the level of amygdala activation on the quality of the memory formed under these stress conditions. We attempted to affect spatial memory consolidation under low or high stress conditions by either introducing a foot shock interference following massed training in the water maze; by manipulating the threshold for acquisition employing either brief (3 trials or full (12 trials training sessions; or by employing a spaced training (over three days rather than massed training protocol. The current findings reveal that under heightened emotionality, the process of consolidation seems to become less effective and more vulnerable to interference; however, when memory consolidation is not interrupted, retention is improved. These differential effects might underlie the complex interactions of stress, and, particularly, of traumatic stress with memory formation processes.

  4. Enhancement of wind stress evaluation method under storm conditions

    Science.gov (United States)

    Chen, Yingjian; Yu, Xiping

    2016-12-01

    Wind stress is an important driving force for many meteorological and oceanographical processes. However, most of the existing methods for evaluation of the wind stress, including various bulk formulas in terms of the wind speed at a given height and formulas relating the roughness height of the sea surface with wind conditions, predict an ever-increasing tendency of the wind stress coefficient as the wind speed increases, which is inconsistent with the field observations under storm conditions. The wave boundary layer model, which is based on the momentum and energy conservation, has the advantage to take into account the physical details of the air-sea interaction process, but is still invalid under storm conditions without a modification. By including the energy dissipation due to the presence of sea spray, which is speculated to be an important aspect of the air-sea interaction under storm conditions, the wave boundary layer model is improved in this study. The improved model is employed to estimate the wind stress caused by an idealized tropical cyclone motion. The computational results show that the wind stress coefficient reaches its maximal value at a wind speed of about 40 m/s and decreases as the wind speed further increases. This is in fairly good agreement with the field data.

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

    Science.gov (United States)

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

    2017-12-01

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

  6. Qinshan phase II extension nuclear power project thermal stratification and fatigue stress analysis for pressurizer surge line

    International Nuclear Information System (INIS)

    Yu Xiaofei; Zhang Yixiong; Ai Honglei

    2010-01-01

    Thermal stratification of pressurizer surge line induced by the inside fluid brings on global bending moments, local thermal stresses, unexpected displacements and support loadings of the pipe system. In order to avoid a costly three-dimensional computation, a combined 1D/2D technique has been developed and implemented to analyze the thermal stratification and fatigue stress of pressurize surge line of QINSHAN Phase II Extension Nuclear Power Project in this paper, using the computer codes SYSTUS and ROCOCO. According to the mechanical analysis results of stratification, the maximum stress and cumulative usage factor, the loadings at connections of surge line to main pipe and RCP and the displacements of surge line at supports are obtained. (authors)

  7. A prediction method of temperature distribution and thermal stress for the throttle turbine rotor and its application

    Directory of Open Access Journals (Sweden)

    Yang Yu

    2017-01-01

    Full Text Available In this paper, a prediction method of the temperature distribution for the thermal stress for the throttle-regulated steam turbine rotor is proposed. The rotor thermal stress curve can be calculated according to the preset power requirement, the operation mode and the predicted critical parameters. The results of the 660 MW throttle turbine rotor show that the operators are able to predict the operation results and to adjust the operation parameters in advance with the help of the inertial element method. Meanwhile, it can also raise the operation level, thus providing the technical guarantee for the thermal stress optimization control and the safety of the steam turbine rotor under the variable load operation.

  8. Thermal–mechanical stress analysis of pressurized water reactor pressure vessel with/without a preexisting crack under grid load following conditions

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, Subhasish, E-mail: smohanty@anl.gov; Soppet, William K.; Majumdar, Saurin; Natesan, Krishnamurti

    2016-12-15

    Highlights: • Use of intermittent renewable-energy source in power grid is becoming a trend. • Gird load-following can leads to variable power demand from Nuclear power plant. • Reactor components can be stressed differently under gird load-following mode. • Estimation of stress–strain state under grid load-following condition is essential. - Abstract: In this paper, we present thermal–mechanical stress analysis of a pressurized water reactor pressure vessel and its hot-leg and cold-leg nozzles. Results are presented from thermal and thermal–mechanical stress analysis under reactor heat-up, cool-down, and grid load-following conditions. Analysis results are given with and without the presence of preexisting crack in the reactor nozzle (axial crack in hot leg nozzle). From the model results it is found that the stress–strain states are significantly higher in case of presence of crack than without crack. The stress–strain state under grid load following condition are more realistic compared to the stress–strain state estimated assuming simplified transients.

  9. Thermal–mechanical stress analysis of pressurized water reactor pressure vessel with/without a preexisting crack under grid load following conditions

    International Nuclear Information System (INIS)

    Mohanty, Subhasish; Soppet, William K.; Majumdar, Saurin; Natesan, Krishnamurti

    2016-01-01

    Highlights: • Use of intermittent renewable-energy source in power grid is becoming a trend. • Gird load-following can leads to variable power demand from Nuclear power plant. • Reactor components can be stressed differently under gird load-following mode. • Estimation of stress–strain state under grid load-following condition is essential. - Abstract: In this paper, we present thermal–mechanical stress analysis of a pressurized water reactor pressure vessel and its hot-leg and cold-leg nozzles. Results are presented from thermal and thermal–mechanical stress analysis under reactor heat-up, cool-down, and grid load-following conditions. Analysis results are given with and without the presence of preexisting crack in the reactor nozzle (axial crack in hot leg nozzle). From the model results it is found that the stress–strain states are significantly higher in case of presence of crack than without crack. The stress–strain state under grid load following condition are more realistic compared to the stress–strain state estimated assuming simplified transients.

  10. Thermal and Energy Performance of Conditioned Building Due To Insulated Sloped Roof

    Science.gov (United States)

    Irwan, Suhandi Syiful; Ahmed, Azni Zain; Zakaria, Nor Zaini; Ibrahim, Norhati

    2010-07-01

    For low-rise buildings in equatorial region, the roof is exposed to solar radiation longer than other parts of the envelope. Roofs are to be designed to reject heat and moderate the thermal impact. These are determined by the design and construction of the roofing system. The pitch of roof and the properties of construction affect the heat gain into the attic and subsequently the indoor temperature of the living spaces underneath. This finally influences the thermal comfort conditions of naturally ventilated buildings and cooling load of conditioned buildings. This study investigated the effect of insulated sloping roof on thermal energy performance of the building. A whole-building thermal energy computer simulation tool, Integrated Environmental Solution (IES), was used for the modelling and analyses. A building model with dimension of 4.0 m × 4.0 m × 3.0 m was designed with insulated roof and conventional construction for other parts of the envelope. A 75 mm conductive insulation material with thermal conductivity (k-value) of 0.034 Wm-1K-1 was installed underneath the roof tiles. The building was modelled with roof pitch angles of 0° , 15°, 30°, 45°, 60° and simulated for the month of August in Malaysian climate conditions. The profile for attic temperature, indoor temperature and cooling load were downloaded and evaluated. The optimum roof pitch angle for best thermal performance and energy saving was identified. The results show the pitch angle of 0° is able to mitigate the thermal impact to provide the best thermal condition with optimum energy savings. The maximum temperature difference between insulated and non-insulted roof for attic (AtticA-B) and indoor condition (IndoorA-B) is +7.8 °C and 0.4 °C respectively with an average energy monthly savings of 3.9 %.

  11. Thermal Stress Analyses for an NLC Positron Target with a 3 mm Spot Radius Beam

    International Nuclear Information System (INIS)

    Stein, W.; Sunwoo, A.; Sheppard, J. C.; Bharadwaj, V.; Schultz, D.

    2002-01-01

    The power deposition of an incident electron beam in a tungsten-rhenium target and the resultant thermal shock stresses in the material have been modeled with a transient, dynamic, structural response finite element code. The Next Linear Collider electron beam is assumed split into three parts, with each part impinging on a 4 radiation lengths thick target. Three targets are required to avoid excessive thermal stresses in the targets. Energy deposition from each beam pulse occurs over 265 nanoseconds and results in heating of the target and pressure pulses straining the material. The rapid power deposition of the electron beam and the resultant temperature profile in the target generates stress and pressure waves in the material that are considerably larger than those calculated by a static analysis. The 6.22 GeV electron beam has a spot radius size of 3 mm and results in a maximum temperature jump of 147 C. Stress pressure pulses are induced in the material from the rapid thermal expansion of the hotter material with peak effective stresses reaching 83 ksi (5.77 x 10 8 Pa) on the back side of the target, which is less than one half of the yield strength of the tungsten/rhenium alloy and below the material fatigue limit

  12. Contrasting patterns of coral bleaching susceptibility in 2010 suggest an adaptive response to thermal stress.

    Science.gov (United States)

    Guest, James R; Baird, Andrew H; Maynard, Jeffrey A; Muttaqin, Efin; Edwards, Alasdair J; Campbell, Stuart J; Yewdall, Katie; Affendi, Yang Amri; Chou, Loke Ming

    2012-01-01

    Coral bleaching events vary in severity, however, to date, the hierarchy of susceptibility to bleaching among coral taxa has been consistent over a broad geographic range and among bleaching episodes. Here we examine the extent of spatial and temporal variation in thermal tolerance among scleractinian coral taxa and between locations during the 2010 thermally induced, large-scale bleaching event in South East Asia. Surveys to estimate the bleaching and mortality indices of coral genera were carried out at three locations with contrasting thermal and bleaching histories. Despite the magnitude of thermal stress being similar among locations in 2010, there was a remarkable contrast in the patterns of bleaching susceptibility. Comparisons of bleaching susceptibility within coral taxa and among locations revealed no significant differences between locations with similar thermal histories, but significant differences between locations with contrasting thermal histories (Friedman = 34.97; pBleaching was much less severe at locations that bleached during 1998, that had greater historical temperature variability and lower rates of warming. Remarkably, Acropora and Pocillopora, taxa that are typically highly susceptible, although among the most susceptible in Pulau Weh (Sumatra, Indonesia) where respectively, 94% and 87% of colonies died, were among the least susceptible in Singapore, where only 5% and 12% of colonies died. The pattern of susceptibility among coral genera documented here is unprecedented. A parsimonious explanation for these results is that coral populations that bleached during the last major warming event in 1998 have adapted and/or acclimatised to thermal stress. These data also lend support to the hypothesis that corals in regions subject to more variable temperature regimes are more resistant to thermal stress than those in less variable environments.

  13. Thermal Stress and Heat Transfer Coefficient for Ceramics Stalk Having Protuberance Dipping into Molten Metal

    Science.gov (United States)

    Noda, Nao-Aki; Hendra; Li, Wenbin; Takase, Yasushi; Ogura, Hiroki; Higashi, Yusuke

    Low pressure die casting is defined as a net shape casting technology in which the molten metal is injected at high speeds and pressure into a metallic die. The low pressure die casting process plays an increasingly important role in the foundry industry as a low-cost and high-efficiency precision forming technique. In the low pressure die casting process is that the permanent die and filling systems are placed over the furnace containing the molten alloy. The filling of the cavity is obtained by forcing the molten metal, by means of a pressurized gas, to rise into a ceramic tube having protuberance, which connects the die to the furnace. The ceramics tube, called stalk, has high temperature resistance and high corrosion resistance. However, attention should be paid to the thermal stress when the stalk having protuberance is dipped into the molten aluminum. It is important to reduce the risk of fracture that may happen due to the thermal stresses. In this paper, thermo-fluid analysis is performed to calculate surface heat transfer coefficient. The finite element method is applied to calculate the thermal stresses when the stalk having protuberance is dipped into the crucible with varying dipping speeds. It is found that the stalk with or without protuberance should be dipped into the crucible slowly to reduce the thermal stress.

  14. A unified momentum equation approach for computing thermal residual stresses during melting and solidification

    Science.gov (United States)

    Yeo, Haram; Ki, Hyungson

    2018-03-01

    In this article, we present a novel numerical method for computing thermal residual stresses from a viewpoint of fluid-structure interaction (FSI). In a thermal processing of a material, residual stresses are developed as the material undergoes melting and solidification, and liquid, solid, and a mixture of liquid and solid (or mushy state) coexist and interact with each other during the process. In order to accurately account for the stress development during phase changes, we derived a unified momentum equation from the momentum equations of incompressible fluids and elastoplastic solids. In this approach, the whole fluid-structure system is treated as a single continuum, and the interaction between fluid and solid phases across the mushy zone is naturally taken into account in a monolithic way. For thermal analysis, an enthalpy-based method was employed. As a numerical example, a two-dimensional laser heating problem was considered, where a carbon steel sheet was heated by a Gaussian laser beam. Momentum and energy equations were discretized on a uniform Cartesian grid in a finite volume framework, and temperature-dependent material properties were used. The austenite-martensite phase transformation of carbon steel was also considered. In this study, the effects of solid strains, fluid flow, mushy zone size, and laser heating time on residual stress formation were investigated.

  15. Determination of the optimum temperature history of inlet water for minimizing thermal stresses in a pipe by the multiphysics inverse analysis

    International Nuclear Information System (INIS)

    Kubo, S; Uchida, K; Ishizaka, T; Ioka, S

    2008-01-01

    It is important to reduce the thermal stresses for managing and extending the lives of pipes in plants. In this problem, heat conduction, elastic deformation, heat transfer, liquid flow should be considered, and therefore the problem is of a multidisciplinary nature. An inverse method was proposed by the present authors for determining the optimum thermal load history which reduced transient thermal stress considering the multidisciplinary physics. But the obtained solution had a problem that the temperature increasing rate of inner surface of the pipe was discontinuous at the end time of heat up. In this study we introduce temperature history functions that ensure the continuity of the temperature increasing rate. The multidisciplinary complex problem is decomposed into a heat conduction problem, a heat transfer problem, and a thermal stress problem. An analytical solution of the temperature distribution of radial thickness and thermal hoop stress distribution is obtained. The maximum tensile and compressive hoop stresses are minimized for the case where inner surface temperature T s (t) is expressed in terms of the 4th order polynomial function of time t. Finally, from the temperature distributions, the optimum fluid temperature history is obtained for reducing the thermal stresses.

  16. Induced thermal stress on serotonin levels in the blue swimmer crab, Portunus pelagicus

    Directory of Open Access Journals (Sweden)

    Saravanan Rajendiran

    2016-03-01

    Full Text Available The temperature of habitat water has a drastic influence on the behavioral, physiological and biochemical mechanisms of crustaceans. Hyperglycemia is a typical response of many aquatic animals to harmful physical and chemical environmental changes. In crustaceans increased circulating crustacean hyperglycemic hormone (CHH and hyperglycemia are reported to occur following exposure to several environmental stress. The biogenic amine, serotonin has been found to modulate the CHH levels and oxidation of serotonin into its metabolites is catalysed by monoamine oxidase. The blue swimmer crab, Portunus pelagicus is a dominant intertidal species utilized throughout the indo-pacific region and is a particularly important species of Palk bay. It has high nutritional value and delicious taste and hence their requirements of capture and cultivation of this species are constantly increasing. This species experiences varying and increasing temperature levels as it resides in an higher intertidal zone of Thondi coast. The present study examines the effect of thermal stress on the levels of serotonin and crustacean hyperglycemic hormone in the hemolymph of P. pelagicus and analyzes the effect of the monoamine oxidase inhibitor, pargyline on serotonin and CHH level after thermal stress. The results showed increased levels of glucose, CHH and serotonin on exposure to 26 °C in control animals. Pargyline injected crabs showed highly significant increase in the levels of CHH and serotonin on every 2 °C increase or decrease in temperature. A greater CHH level of 268.86±2.87 fmol/ml and a greater serotonin level of 177.69±10.10 ng/ml was observed at 24 °C. This could be due to the effect of in maintaining the level of serotonin in the hemolymph and preventing its oxidation, which in turn induces hyperglycemia by releasing CHH into hemolymph. Thus, the study demonstrates the effect of thermal stress on the hemolymph metabolites studied and the role of

  17. Induced thermal stress on serotonin levels in the blue swimmer crab, Portunus pelagicus.

    Science.gov (United States)

    Rajendiran, Saravanan; Muhammad Iqbal, Beema Mahin; Vasudevan, Sugumar

    2016-03-01

    The temperature of habitat water has a drastic influence on the behavioral, physiological and biochemical mechanisms of crustaceans. Hyperglycemia is a typical response of many aquatic animals to harmful physical and chemical environmental changes. In crustaceans increased circulating crustacean hyperglycemic hormone (CHH) and hyperglycemia are reported to occur following exposure to several environmental stress. The biogenic amine, serotonin has been found to modulate the CHH levels and oxidation of serotonin into its metabolites is catalysed by monoamine oxidase. The blue swimmer crab, Portunus pelagicus is a dominant intertidal species utilized throughout the indo-pacific region and is a particularly important species of Palk bay. It has high nutritional value and delicious taste and hence their requirements of capture and cultivation of this species are constantly increasing. This species experiences varying and increasing temperature levels as it resides in an higher intertidal zone of Thondi coast. The present study examines the effect of thermal stress on the levels of serotonin and crustacean hyperglycemic hormone in the hemolymph of P. pelagicus and analyzes the effect of the monoamine oxidase inhibitor, pargyline on serotonin and CHH level after thermal stress. The results showed increased levels of glucose, CHH and serotonin on exposure to 26 °C in control animals. Pargyline injected crabs showed highly significant increase in the levels of CHH and serotonin on every 2 °C increase or decrease in temperature. A greater CHH level of 268.86±2.87 fmol/ml and a greater serotonin level of 177.69±10.10 ng/ml was observed at 24 °C. This could be due to the effect of in maintaining the level of serotonin in the hemolymph and preventing its oxidation, which in turn induces hyperglycemia by releasing CHH into hemolymph. Thus, the study demonstrates the effect of thermal stress on the hemolymph metabolites studied and the role of pargyline in elevating the

  18. Leuconostoc strains isolated from dairy products: Response against food stress conditions.

    Science.gov (United States)

    D'Angelo, Luisa; Cicotello, Joaquín; Zago, Miriam; Guglielmotti, Daniela; Quiberoni, Andrea; Suárez, Viviana

    2017-09-01

    A systematic study about the intrinsic resistance of 29 strains (26 autochthonous and 3 commercial ones), belonging to Leuconostoc genus, against diverse stress factors (thermal, acidic, alkaline, osmotic and oxidative) commonly present at industrial or conservation processes were evaluated. Exhaustive result processing was made by applying one-way ANOVA, Student's test (t), multivariate analysis by Principal Component Analysis (PCA) and Matrix Hierarchical Cluster Analysis. In addition, heat adaptation on 4 strains carefully selected based on previous data analysis was assayed. The strains revealed wide diversity of resistance to stress factors and, in general, a clear relationship between resistance and Leuconostoc species was established. In this sense, the highest resistance was shown by Leuconostoc lactis followed by Leuconostoc mesenteroides strains, while Leuconostoc pseudomesenteroides and Leuconostoc citreum strains revealed the lowest resistance to the stress factors applied. Heat adaptation improved thermal cell survival and resulted in a cross-resistance against the acidic factor. However, all adapted cells showed diminished their oxidative resistance. According to our knowledge, this is the first study regarding response of Leuconostoc strains against technological stress factors and could establish the basis for the selection of "more robust" strains and propose the possibility of improving their performance during industrial processes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Flux Balance Analysis of Escherichia coli under Temperature and pH Stress Conditions

    KAUST Repository

    Xu, Xiaopeng

    2015-05-12

    An interesting discovery in biology is that most genes in an organism are dispensable. That means these genes have minor effects on survival of the organism in standard laboratory conditions. One explanation of this discovery is that some genes play important roles in specific conditions and are essential genes under those conditions. E. coli is a model organism, which is widely used. It can adapt to many stress conditions, including temperature, pH, osmotic, antibiotic, etc. Underlying mechanisms and associated genes of each stress condition responses are usually different. In our analysis, we combined protein abundance data and mutant conditional fitness data into E. coli constraint-based metabolic models to study conditionally essential metabolic genes under temperature and pH stress conditions. Flux Balance Analysis was employed as the modeling method to analysis these data. We discovered lists of metabolic genes, which are E. coli dispensable genes, but conditionally essential under some stress conditions. Among these conditionally essential genes, atpA in low pH stress and nhaA in high pH stress found experimental evidences from previous studies. Our study provides new conditionally essential gene candidates for biologists to explore stress condition mechanisms.

  20. Thermal Aging Effects on Residual Stress and Residual Strain Distribution on Heat Affected Zone of Alloy 600 in Dissimilar Metal Weld

    Energy Technology Data Exchange (ETDEWEB)

    Ham, Junhyuk; Choi, Kyoung Joon; Kim, Ji Hyun [UNIST, Ulsan (Korea, Republic of)

    2016-10-15

    Dissimilar metal weld (DMW), consisting of Alloy 600, Alloy 182, and A508 Gr.3, has been widely used as a joining material of the reactor pressure vessel penetration nozzle and the steam generator tubing for pressurized water reactors (PWR) because of its good mechanical strength, thermal conductivity, and corrosion resistance. Residual tensile stress is mainly nominated as a cause of SCC in light water reactors by IAEA report. So, to relax the residual stress, post-weld heat treatment is required after manufacturing process such as welding. However, thermal treatment has a great effect on the microstructure and the chromium depletion profile on Alloy 600, so called sensitization. By this reason, HAZ on Alloy 600 is critical to crack. According to G.A. Young et al., Crack growth rates (CGR) in the Alloy 600 HAZ were about 30 times faster than those in the Alloy 600 base metal tested under the same conditions. And according to Z.P. Lu et al., CGR in the Alloy 600 HAZ can be more than 20 times higher than that in its base metal. There are some methods to measure the exact value of residual stress on the material surface. The most common way is X-ray diffraction method (XRD). The principle of XRD is based on lattice strains and depends on the changes in the spacing of the atomic planes in material. And there is a computer simulation method to estimate residual stress distribution which is called ANSYS. This study was conducted to investigate how thermal aging affects residual stress and residual strain distribution of Alloy 600 HAZ. Following conclusions can be drawn from this study. According to preceding researches and this study, both the relaxation of residual stress and the change of residual strain follow as similar way, spreading out from concentrated region. The result of Vickers micro-hardness tester shows that tensile residual stresses are distributed broadly on the material aged by 15 years. Therefore, HT400{sub Y}15 material is weakest state for PWSCC. The

  1. Thermal stress analysis of sulfur deactivated solid oxide fuel cells

    Science.gov (United States)

    Zeng, Shumao; Parbey, Joseph; Yu, Guangsen; Xu, Min; Li, Tingshuai; Andersson, Martin

    2018-03-01

    Hydrogen sulfide in fuels can deactivate catalyst for solid oxide fuel cells, which has become one of the most critical challenges to stability. The reactions between sulfur and catalyst will cause phase changes, leading to increase in cell polarization and mechanical mismatch. A three-dimensional computational fluid dynamics (CFD) approach based on the finite element method (FEM) is thus used to investigate the polarization, temperature and thermal stress in a sulfur deactivated SOFC by coupling equations for gas-phase species, heat, momentum, ion and electron transport. The results indicate that sulfur in fuels can strongly affect the cell polarization and thermal stresses, which shows a sharp decrease in the vicinity of electrolyte when 10% nickel in the functional layer is poisoned, but they remain almost unchanged even when the poisoned Ni content was increased to 90%. This investigation is helpful to deeply understand the sulfur poisoning effects and also benefit the material design and optimization of electrode structure to enhance cell performance and lifetimes in various hydrocarbon fuels containing impurities.

  2. Sustainability of compressive residual stress by stress improvement processes

    International Nuclear Information System (INIS)

    Nishikawa, Satoru; Okita, Shigeru; Yamaguchi, Atsunori

    2013-01-01

    Stress improvement processes are countermeasures against stress corrosion cracking in nuclear power plant components. It is necessary to confirm whether compressive residual stress induced by stress improvement processes can be sustained under operation environment. In order to evaluate stability of the compressive residual stress in 60-year operating conditions, the 0.07% cyclic strains of 200 times at 593 K were applied to the welded specimens, then a thermal aging treatment for 1.66x10 6 s at 673 K was carried out. As the result, it was confirmed that the compressive residual stresses were sustained on both surfaces of the dissimilar welds of austenitic stainless steel (SUS316L) and nickel base alloy (NCF600 and alloy 182) processed by laser peening (LP), water jet peening (WJP), ultrasonic shot peening (USP), shot peening (SP) and polishing under 60-year operating conditions. (author)

  3. A fracture mechanics method of evaluating structural integrity of a reactor vessel due to thermal shock effects following LOCA condition

    International Nuclear Information System (INIS)

    Ramani, D.T.

    1977-01-01

    The importance of knowledge of structural integrity of a reactor vessel due to thermal shock effects, is related to safety and operational requirements in assessing the adequacy and flawless functioing of the nuclear power systems. Followig a loss-of-coolant accident (LOCA) condition the integrity of the reactor vessel due to a sudden thermal shock induced by actuation of emergency core cooling system (ECCS), must be maintained to ensure safe and orderly shutdown of the reactor and its components. The paper encompasses criteria underlaying a fracture mechanics method of analysis to evaluate structural integrity of a typical 950 MWe PWR vessel as a result of very drastic changes in thermal and mechanical stress levels in the reactor vessel wall. The main object of this investigation therefore consists in assessing the capability of a PWR vessel to withstand the most critical thermal shock without inpairing its ability to conserve vital coolant owing to probable crack propagation. (Auth.)

  4. Thermal stress in UO2 during sintering as a possible cause of cracking

    International Nuclear Information System (INIS)

    Aragones, M.A.; Tobias, E.; Tulli, I.; Naquid, C.

    1980-01-01

    Thermal stresses arising during sintering of UO 2 pellets are evaluated numerically by the solution of coupled equations for heat transfer through the sample. Results are compared with those of a semiempirical approach reported in the literature. Better insight into the heat transfer process is obtained from the solution of the coupled equations rather than from the empirical approach. The two approaches give different results for the thermal stresses arising during sintering. The use of heating and cooling rates of approximately 0.5 0 Cs -1 is found to prevent the possibility of cracking in UO 2 pellets of radii varying from 0.6 cm to 1 cm during sintering in hydrogen or argon-hydrogen atmospheres. (author)

  5. Thermal Analysis Evaluation of Spent Fuel Storage Rack for Research Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sangjin; Oh, Jinho; Kwak, Jinsung; Lee, Jongmin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    Spent fuel storage rack is to store spent fuel assemblies. The spent fuel storage rack is submerged in the designated pool for cooling. Due to the condition change of the pool water, the effect of thermal load on spent fuel storage rack must be analyzed and evaluated. In this paper, thermal stress analysis is performed and evaluated on a spent fuel storage rack. For thermal stress evaluation of the spent fuel storage rack, load combinations and allowable criteria in ASME Sec. III NB-3220 are applied. In cases of A-1 and B-1, the same temperature applied on the whole model, thermal stress doesn't occur because there is no constraint about the thermal expansion. The support frame is located on the pool bottom in free standing type and the racks are located in the support frame with enough space. Thermal expansion was considered and reflected in the design of spent fuel storage rack in advance. Thermal stress analysis is performed and evaluated on a spent fuel storage rack with consideration of pool water temperature variation. The thermal analysis including a linear heat transfer and the thermal stress analysis is performed for the racks and support frame and resulted stresses are within allowable criteria.

  6. Location-specific responses to thermal stress in larvae of the reef-building coral Montastraea faveolata.

    Directory of Open Access Journals (Sweden)

    Nicholas R Polato

    2010-06-01

    Full Text Available The potential to adapt to a changing climate depends in part upon the standing genetic variation present in wild populations. In corals, the dispersive larval phase is particularly vulnerable to the effects of environmental stress. Larval survival and response to stress during dispersal and settlement will play a key role in the persistence of coral populations.To test the hypothesis that larval transcription profiles reflect location-specific responses to thermal stress, symbiont-free gametes from three to four colonies of the scleractinian coral Montastraea faveolata were collected from Florida and Mexico, fertilized, and raised under mean and elevated (up 1 to 2 degrees C above summer mean temperatures. These locations have been shown to exchange larvae frequently enough to prevent significant differentiation of neutral loci. Differences among 1,310 unigenes were simultaneously characterized using custom cDNA microarrays, allowing investigation of gene expression patterns among larvae generated from wild populations under stress. Results show both conserved and location-specific variation in key processes including apoptosis, cell structuring, adhesion and development, energy and protein metabolism, and response to stress, in embryos of a reef-building coral.These results provide first insights into location-specific variation in gene expression in the face of gene flow, and support the hypothesis that coral host genomes may house adaptive potential needed to deal with changing environmental conditions.

  7. Thermal fatigue behavior of a SUS304 pipe under longitudinal cyclic movement of axial temperature distribution

    International Nuclear Information System (INIS)

    Yamauchi, Masafumi; Ohtani, Tomomi; Takahashi, Yukio

    1996-01-01

    In a structural thermal fatigue test which imposed an oscillating axial temperature distribution on a SUS 304 pipe specimens, different crack initiation lives were observed between the inner and the outer surfaces, although the values of the von-Mises equivalent strain range calculated by FEM inelastic analysis were almost the same for both surfaces. The outer surface condition was an in-phase thermal cycle and an almost uniaxial cyclic stress (low hydrostatic stress). The inner surface condition was an out-of-phase thermal cycle and an almost equibiaxial cyclic stress (high hydrostatic stress). A uniaxial thermal fatigue test was performed under the simulated conditions of the outer and inner surfaces of the pipe specimen. The in-phase uniaxial thermal fatigue test result was in good agreement with the test result of the pipe specimen for the outer surface. The out-of-phase uniaxial thermal fatigue test which simulated the inner surface condition, showed a longer life than the in-phase uniaxial test, and thus contradicted the result of the structural model test. However, the structural model test life for the inner surface agreed well with the uniaxial experimental measurement when the strain range of the inner surface was corrected by a triaxiality factor

  8. Physics Based Electrolytic Capacitor Degradation Models for Prognostic Studies under Thermal Overstress

    Science.gov (United States)

    Kulkarni, Chetan S.; Celaya, Jose R.; Goebel, Kai; Biswas, Gautam

    2012-01-01

    Electrolytic capacitors are used in several applications ranging from power supplies on safety critical avionics equipment to power drivers for electro-mechanical actuators. This makes them good candidates for prognostics and health management research. Prognostics provides a way to assess remaining useful life of components or systems based on their current state of health and their anticipated future use and operational conditions. Past experiences show that capacitors tend to degrade and fail faster under high electrical and thermal stress conditions that they are often subjected to during operations. In this work, we study the effects of accelerated aging due to thermal stress on different sets of capacitors under different conditions. Our focus is on deriving first principles degradation models for thermal stress conditions. Data collected from simultaneous experiments are used to validate the desired models. Our overall goal is to derive accurate models of capacitor degradation, and use them to predict performance changes in DC-DC converters.

  9. Analysis of thermal stress of the piston during non-stationary heat flow in a turbocharged Diesel engine

    Science.gov (United States)

    Gustof, P.; Hornik, A.

    2016-09-01

    In the paper, numeric calculations of thermal stresses of the piston in a turbocharged Diesel engine in the initial phase of its work were carried out based on experimental studies and the data resulting from them. The calculations were made using a geometrical model of the piston in a five-cylinder turbocharged Diesel engine with a capacity of about 2300 cm3, with a direct fuel injection to the combustion chamber and a power rating of 85 kW. In order to determine the thermal stress, application of own mathematical models of the heat flow in characteristic surfaces of the piston was required to show real processes occurring on the surface of the analysed component. The calculations were performed using a Geostar COSMOS/M program module. A three-dimensional geometric model of the piston was created in this program based on a real component, in order to enable the calculations and analysis of thermal stresses during non-stationary heat flow. Modelling of the thermal stresses of the piston for the engine speed n=4250 min-1 and engine load λ=1.69 was carried out.

  10. Response of coral assemblages to thermal stress: are bleaching intensity and spatial patterns consistent between events?

    Science.gov (United States)

    Penin, Lucie; Vidal-Dupiol, Jeremie; Adjeroud, Mehdi

    2013-06-01

    Mass bleaching events resulting in coral mortality are among the greatest threats to coral reefs, and are projected to increase in frequency and intensity with global warming. Achieving a better understanding of the consistency of the response of coral assemblages to thermal stress, both spatially and temporally, is essential to determine which reefs are more able to tolerate climate change. We compared variations in spatial and taxonomic patterns between two bleaching events at the scale of an island (Moorea Island, French Polynesia). Despite similar thermal stress and light conditions, bleaching intensity was significantly lower in 2007 (approximately 37 % of colonies showed signs of bleaching) than in 2002, when 55 % of the colonies bleached. Variations in the spatial patterns of bleaching intensity were consistent between the two events. Among nine sampling stations at three locations and three depths, the stations at which the bleaching response was lowest in 2002 were those that showed the lowest levels of bleaching in 2007. The taxonomic patterns of susceptibility to bleaching were also consistent between the two events. These findings have important implications for conservation because they indicate that corals are capable of acclimatization and/or adaptation and that, even at small spatial scales, some areas are consistently more susceptible to bleaching than others.

  11. Genotypic variation influences reproductive success and thermal stress tolerance in the reef building coral, Acropora palmata

    Science.gov (United States)

    Baums, I. B.; Devlin-Durante, M. K.; Polato, N. R.; Xu, D.; Giri, S.; Altman, N. S.; Ruiz, D.; Parkinson, J. E.; Boulay, J. N.

    2013-09-01

    The branching coral Acropora palmata is a foundation species of Caribbean reefs that has been decimated in recent decades by anthropogenic and natural stressors. Declines in population density and genotypic diversity likely reduce successful sexual reproduction in this self-incompatible hermaphrodite and might impede recovery. We investigated variation among genotypes in larval development under thermally stressful conditions. Six two-parent crosses and three four-parent batches were reared under three temperatures and sampled over time. Fertilization rates differed widely with two-parent crosses having lower fertilization rates (5-56 %, mean 22 % ± 22 SD) than batches (from 31 to 87 %, mean 59 % ± 28 SD). Parentage analysis of larvae in batch cultures showed differences in gamete compatibility among parents, coinciding with significant variation in both sperm morphology and egg size. While all larval batches developed more rapidly at increased water temperatures, rate of progression through developmental stages varied among batches, as did swimming speed. Together, these results indicate that loss of genotypic diversity exacerbates already severe limitations in sexual reproductive success of A. palmata. Nevertheless, surviving parental genotypes produce larvae that do vary in their phenotypic response to thermal stress, with implications for adaptation, larval dispersal and population connectivity in the face of warming sea surface temperatures.

  12. Apparatus and method for thermal power generation

    International Nuclear Information System (INIS)

    Cohen, P.; Redding, A.H.

    1978-01-01

    An improved thermal power plant and method of power generation is described which minimizes thermal stress and chemical impurity buildup in the vaporizing component, particularly beneficial under loss of normal feed fluid and startup conditions. The invention is particularly applicable to a liquid metal fast breeder reactor plant

  13. Influence of thermal buoyancy on vertical tube bundle thermal density head predictions under transient conditions

    International Nuclear Information System (INIS)

    Lin, H.C.; Kasza, K.E.

    1984-01-01

    The thermal-hydraulic behavior of an LMFBR system under various types of plant transients is usually studied using one-dimensional (1-D) flow and energy transport models of the system components. Many of the transient events involve the change from a high to a low flow with an accompanying change in temperature of the fluid passing through the components which can be conductive to significant thermal bouyancy forces. Thermal bouyancy can exert its influence on system dynamic energy transport predictions through alterations of flow and thermal distributions which in turn can influence decay heat removal, system-response time constants, heat transport between primary and secondary systems, and thermal energy rejection at the reactor heat sink, i.e., the steam generator. In this paper the results from a comparison of a 1-D model prediction and experimental data for vertical tube bundle overall thermal density head and outlet temperature under transient conditions causing varying degrees of thermal bouyancy are presented. These comparisons are being used to generate insight into how, when, and to what degree thermal buoyancy can cause departures from 1-D model predictions

  14. Assessing heat-related health risk in Europe via the Universal Thermal Climate Index (UTCI)

    Science.gov (United States)

    Di Napoli, Claudia; Pappenberger, Florian; Cloke, Hannah L.

    2018-03-01

    In this work, the potential of the Universal Thermal Climate Index (UTCI) as a heat-related health risk indicator in Europe is demonstrated. The UTCI is a bioclimate index that uses a multi-node human heat balance model to represent the heat stress induced by meteorological conditions to the human body. Using 38 years of meteorological reanalysis data, UTCI maps were computed to assess the thermal bioclimate of Europe for the summer season. Patterns of heat stress conditions and non-thermal stress regions are identified across Europe. An increase in heat stress up to 1 °C is observed during recent decades. Correlation with mortality data from 17 European countries revealed that the relationship between the UTCI and death counts depends on the bioclimate of the country, and death counts increase in conditions of moderate and strong stress, i.e., when UTCI is above 26 and 32 °C. The UTCI's ability to represent mortality patterns is demonstrated for the 2003 European heatwave. These findings confirm the importance of UTCI as a bioclimatic index that is able to both capture the thermal bioclimatic variability of Europe, and relate such variability with the effects it has on human health.

  15. Experimentally Reproducing Thermal Breakdown of Rock at Earth's Surface

    Science.gov (United States)

    Eppes, M. C.; Griffiths, L.; Heap, M. J.; Keanini, R.; Baud, P.

    2016-12-01

    Thermal stressing induces microcrack growth in rock in part due to thermal expansion mismatch between different minerals, mineral phases, or crystalline axes and/or thermal gradients in the entire rock mass. This knowledge is largely derived from experimental studies of thermal microcracking, typically under conditions of very high temperatures (hundreds of °C). Thermal stressing at lower temperatures has received significantly less attention despite the fact that it may play an important role in rock breakdown at and near Earth's surface (Aldred et al., 2015; Collins and Stock, 2016). In particular, Eppes et al. (2016) attribute recorded Acoustic Emissions (AE) from a highly instrumented granite boulder sitting on the ground in natural conditions to subcritical crack growth driven by thermal stresses arising from a combination of solar- and weather-induced temperature changes; however the maximum temperature the boulder experienced was just 65 °C. In order to better understand these results without complicating factors of a natural environment, we conducted controlled laboratory experiments on cylindrical samples (40 mm length and 20 mm diameter) cored from the same granite as the Eppes et al. (2016) experiment, subjecting them to temperature fluctuations that reproduced the field measurements. We used a novel experimental configuration whereby two high temperature piezo-transducers are each in contact with an opposing face of the sample. The servo-controlled uniaxial press compensates for the thermal expansion and contraction of the pistons and the sample, keeping the coupling between the transducers and the sample, and the axial force acting on the sample, constant throughout. The system records AE, as well as P-wave velocity, both independent proxies for microfracture, as well as strain and temperature. Preliminary tests, heating and cooling granite at a rate of 1 °C/min, show that a large amount of AE occurs at temperatures as low as 100 °C. Ultimately, by

  16. Sensitivity of calcification to thermal stress varies among genera of massive reef-building corals.

    Directory of Open Access Journals (Sweden)

    Juan P Carricart-Ganivet

    Full Text Available Reductions in calcification in reef-building corals occur when thermal conditions are suboptimal, but it is unclear how they vary between genera in response to the same thermal stress event. Using densitometry techniques, we investigate reductions in the calcification rate of massive Porites spp. from the Great Barrier Reef (GBR, and P. astreoides, Montastraea faveolata, and M. franksi from the Mesoamerican Barrier Reef (MBR, and correlate them to thermal stress associated with ocean warming. Results show that Porites spp. are more sensitive to increasing temperature than Montastraea, with calcification rates decreasing by 0.40 g cm(-2 year(-1 in Porites spp. and 0.12 g cm(-2 year(-1 in Montastraea spp. for each 1°C increase. Under similar warming trends, the predicted calcification rates at 2100 are close to zero in Porites spp. and reduced by 40% in Montastraea spp. However, these predictions do not account for ocean acidification. Although yearly mean aragonite saturation (Ω(ar at MBR sites has recently decreased, only P. astreoides at Chinchorro showed a reduction in calcification. In corals at the other sites calcification did not change, indicating there was no widespread effect of Ω(ar changes on coral calcification rate in the MBR. Even in the absence of ocean acidification, differential reductions in calcification between Porites spp. and Montastraea spp. associated with warming might be expected to have significant ecological repercussions. For instance, Porites spp. invest increased calcification in extension, and under warming scenarios it may reduce their ability to compete for space. As a consequence, shifts in taxonomic composition would be expected in Indo-Pacific reefs with uncertain repercussions for biodiversity. By contrast, Montastraea spp. use their increased calcification resources to construct denser skeletons. Reductions in calcification would therefore make them more susceptible to both physical and biological

  17. In situ thermal residual stress evolution in ultrathin ZnO and Ag films studied by synchrotron x-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Renault, P.O., E-mail: Pierre.olivier.renault@univ-poitiers.fr [Institut P' , CNRS, Universite de Poitiers, UPR 3346, 86962 Futuroscope (France); Krauss, C.; Le Bourhis, E.; Geandier, G. [Institut P' , CNRS, Universite de Poitiers, UPR 3346, 86962 Futuroscope (France); Benedetto, A. [Saint-Gobain Recherche (SGR), 93303 Aubervilliers (France); Grachev, S.Y.; Barthel, E. [Lab. Surface du Verre et Interfaces (SVI), UMR-CNRS 125, 93303 Aubervilliers (France)

    2011-12-30

    Residual-stress evolution in sputtered encapsulated ZnO/Ag/ZnO stack has been studied in-situ by synchrotron x-ray diffraction when heat treated. The ZnO/Ag/ZnO stack encapsulated into Si{sub 3}N{sub 4} layers and deposited on (001) Si substrates was thermally heated from 25 Degree-Sign C to 600 Degree-Sign C and cooled down to 25 Degree-Sign C. X-ray diffraction 2D patterns captured continuously during the heat treatment allowed monitoring the diffraction peak shifts of both Ag (15 nm thick) and ZnO (10 nm and 50 nm thick) sublayers. Due to the mismatch between the coefficients of thermal expansion, the silicon substrate induced compressive thermal stresses in the films during heating. We first observed a linear increase of the compressive stress state in both Ag and ZnO films and then a more complex elastic-stress evolution starts to operate from about 100 Degree-Sign C for Ag and about 250 Degree-Sign C for ZnO. Thermal contraction upon cooling seems to dominate so that the initial compressive film stresses relax by about 300 and 700 MPa after thermal treatment for ZnO and Ag, respectively. The overall behavior is discussed in terms of structural changes induced by the heat treatment.

  18. Carbon-Starvation Induces Cross-Resistance to Thermal, Acid, and Oxidative Stress in Serratia marcescens

    Science.gov (United States)

    Pittman, Joseph R.; Kline, La’Kesha C.; Kenyon, William J.

    2015-01-01

    The broad host-range pathogen Serratia marcescens survives in diverse host and non-host environments, often enduring conditions in which the concentration of essential nutrients is growth-limiting. In such environments, carbon and energy source starvation (carbon-starvation) is one of the most common forms of stress encountered by S. marcescens. Related members of the family Enterobacteriaceae are known to undergo substantial changes in gene expression and physiology in response to the specific stress of carbon-starvation, enabling non-spore-forming cells to survive periods of prolonged starvation and exposure to other forms of stress (i.e., starvation-induced cross-resistance). To determine if carbon-starvation also results in elevated levels of cross-resistance in S. marcescens, both log-phase and carbon-starved cultures, depleted of glucose before the onset of high cell-density stationary-phase, were grown in minimal media at either 30 °C or 37 °C and were then challenged for resistance to high temperature (50 °C), low pH (pH 2.8), and oxidative stress (15 mM H2O2). In general, carbon-starved cells exhibited a higher level of resistance to thermal stress, acid stress, and oxidative stress compared to log-phase cells. The extent of carbon-starvation-induced cross-resistance was dependent on incubation temperature and on the particular strain of S. marcescens. In addition, strain- and temperature-dependent variations in long-term starvation survival were also observed. The enhanced stress-resistance of starved S. marcescens cells could be an important factor in their survival and persistence in many non-host environments and within certain host microenvironments where the availability of carbon sources is suboptimal for growth. PMID:27682115

  19. Carbon-Starvation Induces Cross-Resistance to Thermal, Acid, and Oxidative Stress in Serratia marcescens

    Directory of Open Access Journals (Sweden)

    Joseph R. Pittman

    2015-10-01

    Full Text Available The broad host-range pathogen Serratia marcescens survives in diverse host and non-host environments, often enduring conditions in which the concentration of essential nutrients is growth-limiting. In such environments, carbon and energy source starvation (carbon-starvation is one of the most common forms of stress encountered by S. marcescens. Related members of the family Enterobacteriaceae are known to undergo substantial changes in gene expression and physiology in response to the specific stress of carbon-starvation, enabling non-spore-forming cells to survive periods of prolonged starvation and exposure to other forms of stress (i.e., starvation-induced cross-resistance. To determine if carbon-starvation also results in elevated levels of cross-resistance in S. marcescens, both log-phase and carbon-starved cultures, depleted of glucose before the onset of high cell-density stationary-phase, were grown in minimal media at either 30 °C or 37 °C and were then challenged for resistance to high temperature (50 °C, low pH (pH 2.8, and oxidative stress (15 mM H2O2. In general, carbon-starved cells exhibited a higher level of resistance to thermal stress, acid stress, and oxidative stress compared to log-phase cells. The extent of carbon-starvation-induced cross-resistance was dependent on incubation temperature and on the particular strain of S. marcescens. In addition, strain- and temperature-dependent variations in long-term starvation survival were also observed. The enhanced stress-resistance of starved S. marcescens cells could be an important factor in their survival and persistence in many non-host environments and within certain host microenvironments where the availability of carbon sources is suboptimal for growth.

  20. Conditioned pain modulation dampens the thermal grill illusion.

    Science.gov (United States)

    Harper, D E; Hollins, M

    2017-10-01

    The thermal grill illusion (TGI) refers to the perception of burning heat and often pain that arises from simultaneous cutaneous application of innocuous warm and cool stimuli. This study utilized conditioned pain modulation (CPM) to help elucidate the TGI's underlying neural mechanisms, including the debated role of ascending nociceptive signals in generating the illusion. To trigger CPM, subjects placed the left hand in noxious cold (6 °C) water before placing the right volar forearm onto a thermal grill. Lower pain and unpleasantness ratings of the grill in this CPM run compared to those in a control run (i.e. 33 °C water) were taken as evidence of CPM. To determine whether CPM reduces noxious heat pain and illusory heat pain equally, an experimental group of subjects rated pain and unpleasantness of a grill consisting of innocuous alternating warm (42 °C) and cool (18 °C) bars, while a control group rated a grill with all bars controlled to a noxious temperature (45 °C). CPM produced significant and comparable reductions in pain, unpleasantness and perceived heat of both noxious heat and the TGI. This result suggests that the TGI results from signals in nociceptive dorsal horn convergent neurons, since CPM involves descending inhibition with high selectivity for this neuronal population. More broadly, CPM's ability to produce a shift in perceived thermal sensation of both noxious heat and the TGI from 'hot' to 'warm' implies that nociceptive signals generated by a cutaneous stimulus can contribute to its perceived thermal intensity. Conditioned pain modulation reduces the perceived painfulness, unpleasantness and heat of the thermal grill illusion and noxious heat similarly. The results have important theoretical implications for both types of pain. © 2017 European Pain Federation - EFIC®.

  1. Thermal stress, human performance, and physical employment standards.

    Science.gov (United States)

    Cheung, Stephen S; Lee, Jason K W; Oksa, Juha

    2016-06-01

    Many physically demanding occupations in both developed and developing economies involve exposure to extreme thermal environments that can affect work capacity and ultimately health. Thermal extremes may be present in either an outdoor or an indoor work environment, and can be due to a combination of the natural or artificial ambient environment, the rate of metabolic heat generation from physical work, processes specific to the workplace (e.g., steel manufacturing), or through the requirement for protective clothing impairing heat dissipation. Together, thermal exposure can elicit acute impairment of work capacity and also chronic effects on health, greatly contributing to worker health risk and reduced productivity. Surprisingly, in most occupations even in developed economies, there are rarely any standards regarding enforced heat or cold safety for workers. Furthermore, specific physical employment standards or accommodations for thermal stressors are rare, with workers commonly tested under near-perfect conditions. This review surveys the major occupational impact of thermal extremes and existing employment standards, proposing guidelines for improvement and areas for future research.

  2. Ice thermal storage air conditioning system for electric load leveling; Denryoku heijunka to hyochikunetsu system

    Energy Technology Data Exchange (ETDEWEB)

    Shigenaga, Y. [Daikin Industries Ltd., Osaka (Japan)

    1998-08-15

    Thermal storage air conditioning system is the one to use energy stored into thermal storing materials by using night electric power and to operate effective air conditioning. Therefore, as load can be treated by the stored energy, volume of the apparatus can be reduced. And, by reduction of the consumed power at day time, it can contribute to leveling of electric power demand. In general, there are two types in the thermal storage method: one is a method to store as thermal energy, and the other is that to store as chemical energy. For conditions required for the storing materials, important elements on their actual uses are not only physical properties such as large thermal storage per unit and easy thermal in- and out-puts, but also safety, long-term reliability, and easy receiving and economics containing future. The ice thermal storage air conditioning system is classified at the viewpoint of type of ice, kind of thermal storing medium, melting method on using cooling and heating, kinds of thermal medium on cooling and heating. 3 refs., 5 figs., 2 tabs.

  3. Functional analysis of atfA gene to stress response in pathogenic thermal dimorphic fungus Penicillium marneffei.

    Directory of Open Access Journals (Sweden)

    Panjaphorn Nimmanee

    Full Text Available Penicillium marneffei, the pathogenic thermal dimorphic fungus is a causative agent of a fatal systemic disease, penicilliosis marneffei, in immunocompromised patients especially HIV patients. For growth and survival, this fungus has to adapt to environmental stresses outside and inside host cells and this adaptation requires stress signaling pathways and regulation of gene expression under various kinds of stresses. In this report, P. marneffei activating transcription factor (atfA gene encoding bZip-type transcription factor was characterized. To determine functions of this gene, atfA isogenic mutant strain was constructed using the modified split marker recombination method. The phenotypes and susceptibility to varieties of stresses including osmotic, oxidative, heat, UV, cell wall and cell membrane stresses of the mutant strain were compared with the wild type and the atfA complemented strains. Results demonstrated that the mRNA expression level of P. marneffei atfA gene increased under heat stress at 42°C. The atfA mutant was more sensitive to sodium dodecyl sulphate, amphotericin B and tert-butyl hydroperoxide than the wild type and complemented strains but not hydrogen peroxide, menadione, NaCl, sorbitol, calcofluor white, itraconazole, UV stresses and heat stress at 39°C. In addition, recovery of atfA mutant conidia after mouse and human macrophage infections was significantly decreased compared to those of wild type and complemented strains. These results indicated that the atfA gene was required by P. marneffei under specific stress conditions and might be necessary for fighting against host immune cells during the initiation of infection.

  4. Development of relative thermal stress index (RTSI) for Monitoring and Management of Dry Deciduous Ecosystem

    Science.gov (United States)

    Gupta, R. K.; Vijayan, D.

    Gir wildlife sanctuary located between 20 r 57 to 21 r 20 N and 70 r 28 to 71 r 13 E is the last home of Asiatic lions Its biodiversity comprises of 450 recorded flowering plant species 32 species of mammals 26 species of reptiles about 300 species of birds and more than 2000 species of insects As per 1995 census it has 304 lions and 268 leopards The movement of wildlife to thermally comfortable zones to reduce stress conditions forces the changes in management plan with reference to change in localized water demand This necessitates the use of space based thermal data available from AVHRR MODIS etc to monitor temperature of Gir-ecosystem for meso-scale level operational utility As the time scale of the variability of NDVI parameter is much higher than that for lower boundary temperature LBT the dense patch in riverine forest having highest NDVI value would not experience change in its vigour with the change in the season NDVI value of such patch would be near invariant over the year and temperature of this pixel could serve as reference temperature for developing the concept of relative thermal stress index RTSI which is defined as RTSI T p -T r T max -T r wherein T r T max and T p refer to LBT over the maximum NDVI reference point maximum LBT observed in the Gir ecosystem and the temperature of the pixel in the image respectively RTSI images were computed from AVHRR images for post-monsoon leaf-shedded and summer seasons Scatter plot between RTSI and NDVI for summer seasons

  5. Thermal stress promotes host mitochondrial degradation in symbiotic cnidarians: are the batteries of the reef going to run out?

    Directory of Open Access Journals (Sweden)

    Simon R Dunn

    Full Text Available The symbiotic relationship between cnidarians and their dinoflagellate symbionts, Symbiodinium spp, which underpins the formation of tropical coral reefs, can be destabilized by rapid changes to environmental conditions. Although some studies have concluded that a breakdown in the symbiosis begins with increased reactive oxygen species (ROS generation within the symbiont due to a decoupling of photosynthesis, others have reported the release of viable symbionts via a variety of host cell derived mechanisms. We explored an alternative model focused upon changes in host cnidarian mitochondrial integrity in response to thermal stress. Mitochondria are often likened to being batteries of the cell, providing energy in the form of ATP, and controlling cellular pathway activation and ROS generation. The overall morphology of host mitochondria was compared to that of associated symbionts under an experimental thermal stress using confocal and electron microscopy. The results demonstrate that hyperthermic stress induces the degradation of cnidarian host mitochondria that is independent of symbiont cellular deterioration. The potential sites of host mitochondrial disruption were also assessed by measuring changes in the expression of genes associated with electron transport and ATP synthesis using quantitative RT-PCR. The primary site of degradation appeared to be downstream of complex III of the electron transport chain with a significant reduction in host cytochrome c and ATP synthase expression. The consequences of reduced expression could limit the capacity of the host to mitigate ROS generation and maintain both organelle integrity and cellular energy supplies. The disruption of host mitochondria, cellular homeostasis, and subsequent cell death irrespective of symbiont integrity highlights the importance of the host response to thermal stress and in symbiosis dysfunction that has substantial implications for understanding how coral reefs will survive

  6. Effect of Young's modulus evolution on residual stress measurement of thermal barrier coatings by X-ray diffraction

    International Nuclear Information System (INIS)

    Chen, Q.; Mao, W.G.; Zhou, Y.C.; Lu, C.

    2010-01-01

    Subjected to thermal cycling, the apparent Young's modulus of air plasma-sprayed (APS) 8 wt.% Y 2 O 3 -stabilized ZrO 2 (8YSZ) thermal barrier coatings (TBCs) was measured by nanoindentation. Owing to the effects of sintering and porous microstructure, the apparent Young's modulus follows a Weibull distribution and changes from 50 to 93 GPa with an increase of thermal cycling. The evolution of residual stresses in the top coating of an 8YSZ TBC system was determined by X-ray diffraction (XRD). The residual stresses derived from the XRD data are well consistent with that obtained by the Vickers indention. It is shown that the evolution of Young's modulus plays an important role in improving the measurement precision of residual stresses in TBCs by XRD.

  7. Numerical study on lithium titanate battery thermal response under adiabatic condition

    International Nuclear Information System (INIS)

    Sun, Qiujuan; Wang, Qingsong; Zhao, Xuejuan; Sun, Jinhua; Lin, Zijing

    2015-01-01

    Highlights: • The thermal behavior of lithium titanate battery during cycling was investigated. • The temperature rate in charging was less than that of discharging in the cycling. • The temperature difference was less than 0.02 °C at 0.5 C in adiabatic condition. • The temperature distribution and thermal runaway of the battery were predicted. - Abstract: To analyze the thermal behavior of 945 mA h lithium titanate battery during charging and discharging processes, the experimental and numerical studies are performed in this work. The cathode and anode of the 945 mA h lithium titanate soft package battery are the lithium nickel–cobalt–manganese-oxide and lithium titanate, respectively. In the experiment, an Accelerating Rate Calorimeter combined with battery cycler is employed to investigate the electrochemical–thermal behavior during charge–discharge cycling under the adiabatic condition. In numerical simulation, one electrochemical-thermal model is adopted to predict the thermal response and validated with the experimental results. From both experimental and simulated results, the profile of potential and current, the heat generation, the temperature, the temperature changing rate and the temperature distribution in the cell are obtained and thermal runaway is predicted. The analysis of the electrochemical and thermal behavior is beneficial for the commercial application of lithium titanate battery in the fields of electric vehicles and hybrid electric vehicles

  8. Impact of thermal stress on the growth, size-distribution and biomass ...

    African Journals Online (AJOL)

    This paper reports an in-vivo account of the impact of thermal stress on the biomass and sizedistribution of estuarine populations of Pachymelania aurita in Epe Lagoon, Nigeria. Off all physicochemical variables investigated only water temperature was statistically different among study stations. A total of 7626 individuals of ...

  9. Packaging strategies for printed circuit board components. Volume I, materials & thermal stresses.

    Energy Technology Data Exchange (ETDEWEB)

    Neilsen, Michael K. (Kansas City Plant, Kansas City, MO); Austin, Kevin N.; Adolf, Douglas Brian; Spangler, Scott W.; Neidigk, Matthew Aaron; Chambers, Robert S.

    2011-09-01

    Decisions on material selections for electronics packaging can be quite complicated by the need to balance the criteria to withstand severe impacts yet survive deep thermal cycles intact. Many times, material choices are based on historical precedence perhaps ignorant of whether those initial choices were carefully investigated or whether the requirements on the new component match those of previous units. The goal of this program focuses on developing both increased intuition for generic packaging guidelines and computational methodologies for optimizing packaging in specific components. Initial efforts centered on characterization of classes of materials common to packaging strategies and computational analyses of stresses generated during thermal cycling to identify strengths and weaknesses of various material choices. Future studies will analyze the same example problems incorporating the effects of curing stresses as needed and analyzing dynamic loadings to compare trends with the quasi-static conclusions.

  10. Effects of Thermal Exposure on Structures of DD6 Single Crystal Superalloy with Thermal Barrier Coatings

    Directory of Open Access Journals (Sweden)

    DONG Jianmin

    2016-10-01

    Full Text Available In order to investigate the effect of water grit-blasting and high temperature thermal exposure on the microstructures of DD6 alloy with TBCs, DD6 single crystal superalloy specimens were water grit-blasted with 0.3 MPa pressure, then the specimens were coated with thermal barrier coatings by electron beam physical vapor deposition (EB-PVD. Specimens with TBCs were exposed at 1100℃ for 50 and 100 hours in the air respectively, and then these specimens were subjected to stress-rupture tests under the condition of 1100℃/130 MPa. The results show that grit-blasting doesn't lead into the recrystallization, thermal exposure can induce element interdiffusion between the bond coat and alloy substrate, the residual stress and element diffusion lead into the changes of γ' phase coarsing direction. After stress rupture tests, the secondary reaction zone emerges into a local area.

  11. Numerical investigation into thermal load responses of steel railway bridge

    Science.gov (United States)

    Saravana Raja Mohan, K.; Sreemathy, J. R.; Saravanan, U.

    2017-07-01

    Bridge design requires consideration of the effects produced by temperature variations and the resultant thermal gradients in the structure. Temperature fluctuation leads to expansion and contraction of bridges and these movements are taken care by providing expansion joints and bearings. Free movements of a member can be restrained by imposing certain boundary condition but at the same time considerable allowances should be made for the stresses resulting from this restrained condition since the additional deformations and stresses produced may affect the ultimate and serviceability limit states of the structure. If the reaction force generated by the restraints is very large, then its omission can lead to unsafe design. The principal objective of this research is to study the effects of temperature variation on stresses and deflection in a steel railway bridge. A numerical model, based on finite element analysis is presented for evaluating the thermal performance of the bridge. The selected bridge is analyzed and the temperature field distribution and the corresponding thermal stresses and strains are calculated using the finite element software ABAQUS. A thorough understanding of the thermal load responses of a structure will result in safer and dependable design practices.

  12. Ocean acidification increases the sensitivity of and variability in physiological responses of an intertidal limpet to thermal stress

    Science.gov (United States)

    Wang, Jie; Russell, Bayden D.; Ding, Meng-Wen; Dong, Yun-Wei

    2018-05-01

    Understanding physiological responses of organisms to warming and ocean acidification is the first step towards predicting the potential population- and community-level ecological impacts of these stressors. Increasingly, physiological plasticity is being recognized as important for organisms to adapt to the changing microclimates. Here, we evaluate the importance of physiological plasticity for coping with ocean acidification and elevated temperature, and its variability among individuals, of the intertidal limpet Cellana toreuma from the same population in Xiamen. Limpets were collected from shaded mid-intertidal rock surfaces. They were acclimated under combinations of different pCO2 concentrations (400 and 1000 ppm, corresponding to a pH of 8.1 and 7.8) and temperatures (20 and 24 °C) in a short-term period (7 days), with the control conditions (20 °C and 400 ppm) representing the average annual temperature and present-day pCO2 level at the collection site. Heart rates (as a proxy for metabolic performance) and expression of genes encoding inducible and constitutive heat-shock proteins (hsp70 and hsc70) at different heat-shock temperatures (26, 30, 34, and 38 °C) were measured. Hsp70 and Hsc70 play important roles in protecting cells from heat stresses, but have different expression patterns, with Hsp70 significantly increased in expression during stress and Hsc70 constitutively expressed and only mildly induced during stress. Analysis of heart rate showed significantly higher temperature coefficients (Q10 rates) for limpets at 20 °C than at 24 °C and post-acclimation thermal sensitivity of limpets at 400 ppm was lower than at 1000 ppm. Expression of hsp70 linearly increased with the increasing heat-shock temperatures, with the largest slope occurring in limpets acclimated under a future scenario (24 °C and 1000 ppm pCO2). These results suggested that limpets showed increased sensitivity and stress response under future conditions. Furthermore, the

  13. Role of thermal stresses on pulsed laser irradiation of thin films under conditions of microbump formation and nonvaporization forward transfer

    Science.gov (United States)

    Meshcheryakov, Yuri P.; Shugaev, Maxim V.; Mattle, Thomas; Lippert, Thomas; Bulgakova, Nadezhda M.

    2013-11-01

    This paper presents a theoretical analysis of the processes in thin solid films irradiated by short and ultrashort laser pulses in the regimes of film structuring and laser-induced forward transfer. The regimes are considered at which vaporization of the film materials is insignificant and film dynamics is governed mainly by mechanical processes. Thermoelastoplastic modeling has been performed for a model film in one- and two-dimensional geometries. A method has been proposed to estimate the height of microbumps produced by nanosecond laser irradiation of solid films. Contrary to femtosecond laser pulses, in nanosecond pulse regimes, stress waves across the film are weak and cannot induce film damage. The main role in laser-induced dynamics of irradiated films is played by radial thermal stresses which lead to the formation of a bending wave propagating along the film and drawing the film matter to the center of the irradiation spot. The bending wave dynamics depends on the hardness of the substrate underlying the film. The causes of the receiver substrate damage sometimes observed upon laser-induced forward transfer in the scheme of the direct contact between the film and the receiver are discussed.

  14. Numerical analysis of thermal stress and dislocation density distributions in large size multi-crystalline silicon ingots during the seeded growth process

    Science.gov (United States)

    Nguyen, Thi Hoai Thu; Chen, Jyh-Chen; Hu, Chieh; Chen, Chun-Hung; Huang, Yen-Hao; Lin, Huang-Wei; Yu, Andy; Hsu, Bruce

    2017-06-01

    In this study, a global transient numerical simulation of silicon growth from the beginning of the solidification process until the end of the cooling process is carried out modeling the growth of an 800 kg ingot in an industrial seeded directional solidification furnace. The standard furnace is modified by the addition of insulating blocks in the hot zone. The simulation results show that there is a significant decrease in the thermal stress and dislocation density in the modified model as compared to the standard one (a maximal decrease of 23% and 75% along the center line of ingot for thermal stress and dislocation density, respectively). This modification reduces the heating power consumption for solidification of the silicon melt by about 17% and shortens the growth time by about 2.5 h. Moreover, it is found that adjusting the operating conditions of modified model to obtain the lower growth rate during the early stages of the solidification process can lower dislocation density and total heater power.

  15. Psychosocial working conditions and stress in UK social workers

    OpenAIRE

    Ravalier, J.M

    2018-01-01

    It is well documented that exposure to chronic negative working conditions leads to stress. This subsequently impacts sickness absence and attrition, making it a key consideration for policymakers and academics alike. This study therefore seeks to investigate the influence of psychosocial working conditions on stress and related outcomes: sickness presenteeism, job satisfaction, and turnover intentions in UK social workers (SWs). A cross-sectional survey was used, in addition to a single open...

  16. Recovery in dc and rf performance of off-state step-stressed AlGaN/GaN high electron mobility transistors with thermal annealing

    International Nuclear Information System (INIS)

    Kim, Byung-Jae; Hwang, Ya-Hsi; Ahn, Shihyun; Zhu, Weidi; Dong, Chen; Lu, Liu; Ren, Fan; Holzworth, M. R.; Jones, Kevin S.; Pearton, Stephen J.; Smith, David J.; Kim, Jihyun; Zhang, Ming-Lan

    2015-01-01

    The recovery effects of thermal annealing on dc and rf performance of off-state step-stressed AlGaN/GaN high electron mobility transistors were investigated. After stress, reverse gate leakage current and sub-threshold swing increased and drain current on-off ratio decreased. However, these degradations were completely recovered after thermal annealing at 450 °C for 10 mins for devices stressed either once or twice. The trap densities, which were estimated by temperature-dependent drain-current sub-threshold swing measurements, increased after off-state step-stress and were reduced after subsequent thermal annealing. In addition, the small signal rf characteristics of stressed devices were completely recovered after thermal annealing

  17. Computational analysis of heat transfer, thermal stress and dislocation density during resistively Czochralski growth of germanium single crystal

    Science.gov (United States)

    Tavakoli, Mohammad Hossein; Renani, Elahe Kabiri; Honarmandnia, Mohtaram; Ezheiyan, Mahdi

    2018-02-01

    In this paper, a set of numerical simulations of fluid flow, temperature gradient, thermal stress and dislocation density for a Czochralski setup used to grow IR optical-grade Ge single crystal have been done for different stages of the growth process. A two-dimensional steady state finite element method has been applied for all calculations. The obtained numerical results reveal that the thermal field, thermal stress and dislocation structure are mainly dependent on the crystal height, heat radiation and gas flow in the growth system.

  18. The design of bonded reinforcement for thermal stresses in prestressed concrete reactor vessels

    International Nuclear Information System (INIS)

    Kotulla, B.; Hansson, V.

    1977-01-01

    This paper deals with examples of thermal loadings where instationary growth of tensile zones and redistribution of stresses by cracking are of importance. Temperatures produce, in addition to prestressing and internal pressure, the most important stresses in a prestressed concrete reactor pressure vessel. Characteristic of thermal stresses is that they are influenced to a large extent by creep of concrete and that they influence stress redistributions by temperature dependent creep data. Computations show that during the first instationary heating process of the vessel stresses are reduced by creep effects to about fifty percent of the values of the stationary elastic case at the hot face. With a following cooling, creep effects are generally much less, so this case may produce tensile stresses on the internal face of the wall which lead to cracking of the concrete. Tensile stresses first occur due to the instationary growth of the temperature field in a narrow zone near the liner. If outside this zone compressive stresses exist due to prestressing then crack spreading is limited and restraint by the parts of the wall under compression causes crack distribution even without reinforcement in this zone. Growth of cracks with the instationary spreading of tensile zones according to temperature development was calculated. These calculations take into account discrete cracks, reinforcement and different assumptions for tensile strength. Reinforcement of small diameter near the surface has the best influence on crack spacing. Calculations show that for the stationary state of cooling the forces in the reinforcement may be as low as twenty to thirty percent of the tensile force not taking into account cracking of the concrete

  19. Stability of dye-sensitized solar cells under extended thermal stress.

    Science.gov (United States)

    Yadav, Surendra K; Ravishankar, Sandheep; Pescetelli, Sara; Agresti, Antonio; Fabregat-Santiago, Francisco; Di Carlo, Aldo

    2017-08-23

    In the last few decades, dye-sensitized solar cell (DSC) technology has been demonstrated to be a promising candidate for low cost energy production due to cost-effective materials and fabrication processes. Arguably, DSC stability is the biggest challenge for making this technology appealing for industrial exploitation. This work provides further insight into the stability of DSCs by considering specific dye-electrolyte systems characterized by Raman and impedance spectroscopy analysis. In particular, two ruthenium-based dyes, Z907 and Ru505, and two commercially available electrolytes, namely, the high stability electrolyte (HSE) and solvent-free Livion 12 (L-12), were tested. After 4700 h of thermal stress at 85 °C, the least stable device composed of Z907/HSE showed an efficiency degradation rate of ∼14%/1000 h, while the Ru505/L-12 system retained 96% of its initial efficiency by losing ∼1% each 1000 h. The present results show a viable route to stabilize the DSC technology under prolonged annealing conditions complying with the IEC standard requirements.

  20. Thermal-buckling analysis of an LMFBR overflow vessel

    International Nuclear Information System (INIS)

    Severud, L.K.

    1983-01-01

    During a reactor scram, cold sodium flows into the hot overflow vessel. The effect on the vessel is a compressive thermal stress in a zone just above the sodium level. This condition must be sufficiently controlled to preclude thermal buckling. Also, under repeated scrams, the vessel should not suffer thermal stress low cycle fatigue. To evaluate the closeness to buckling and satisfaction of ASMA Code limits, a combination of simple approximations, detailed elastic shell buckling analyses, and correlations to results of thermal buckling tests were employed. This paper describes the analysis methods, special considerations, and evaluations accomplished for this FFTF vessel to assure satisfaction of ASME buckling design criteria, rules, and limits

  1. Enthalpy estimation for thermal comfort and energy saving in air conditioning system

    International Nuclear Information System (INIS)

    Chu, C.-M.; Jong, T.-L.

    2008-01-01

    The thermal comfort control of a room must consider not only the thermal comfort level but also energy saving. This paper proposes an enthalpy estimation that is conducive for thermal comfort control and energy saving. The least enthalpy estimator (LEE) combines the concept of human thermal comfort with the theory of enthalpy to predict the load for a suitable setting pair in order to maintain more precisely the thermal comfort level and save energy in the air conditioning system

  2. Investigation on the Temporal Surface Thermal Conditions for Thermal Comfort Researches Inside A Vehicle Cabin Under Summer Season Climate

    Directory of Open Access Journals (Sweden)

    Zhang Wencan

    2016-01-01

    Full Text Available With the proposes of improving occupant's thermal comfort and reducing the air conditioning power consumption, the present research carried out a comprehensive study on the surface thermal conductions and their influence parameters. A numerical model was built considering the transient conduction, convective and radiation heat transfer inside a vehicle cabin. For more accurate simulation of the radiation heat transfer behaviors, the radiation was considered into two spectral bands (short wave and long wave radiation, and the solar radiation was calculated by two solar fluxes (beam and diffuse solar radiation. An experiment was conducted to validate the numerical approach, showing a good agreement with the surface temperature. The surface thermal conditions were numerically simulated. The results show that the solar radiation is the most important factor in determining the internal surface thermal conditions. Effects of the window glass properties and the car body surface conditions were investigated. The numerical calculation results indicate that reducing the transitivity of window glass can effectively reduce the internal surface temperature. And the reflectivity of the vehicle cabin also has an important influence on the surface temperature, however, it's not so obvious as comparison to the window glass.

  3. A 1-D Analytical Model for the Thermally Induced Stresses in the Mould Surface During Die Casting

    DEFF Research Database (Denmark)

    Hattel, Jesper; Hansen, Preben

    1994-01-01

    This paper presents an anlytically based method for predicting the normal stresses in a die mold surface exposed to a thermal load. A example of application of the method is the high-pressure di casting process where the surface stresses in critical cases lead to cracks. Expressions for the normal...... stresses as afunction of the thermal and mechanical properties have been developed for a casting both without and with a coating. Finally, the resulting relationships are derived and evaluated, with particular emphasis on the effect of the heat transfer coefficient between the casting and the mold....

  4. INVESTIGATION OF NONAXISYMMETRIC STRESS STATE FOR QUASI-STATIC THERMAL POWER LOADING UNDER CONDITIONS OF HIGHEST-ENERGY PARTICLE IRRADIATION

    Directory of Open Access Journals (Sweden)

    A. V. Chigarev

    2013-01-01

    Full Text Available The paper contains a virtual modeling 2D(r, θ for deformation of singly-connected cylindrical solid under conditions of thermo-irradiation impact. Influence of a circumferential distortion on nonaxisymmetric strain-stress state for various values of temperature amplitudes has been investigated in the paper. A solid cylinder  with internal heat sources has been considered as a model body. Properties of the model body correspond to cermet fuel (40 % UO2 + 60 % Cr. 

  5. Numerical method for analysis of temperature rises and thermal stresses around high level radioactive waste repository in granite

    International Nuclear Information System (INIS)

    Shimooka, Hiroshi

    1982-01-01

    The disposal of high-level radioactive waste should result in temperature rises and thermal stresses which change the hydraulic conductivity of the rock around the repository. For safety analysis on disposal of high-level radioactive waste into hard rock, it is necessary to find the temperature rises and thermal stresses distributions around the repository. In this paper, these distribution changes are analyzed by the use of the finite difference method. In advance of numerical analysis, it is required to simplify the shapes and properties of the repository and the rock. Several kinds of numerical models are prepared, and the results of this analysis are examined. And, the waste disposal methods are discussed from the stand-points of the temperature rise and thermal stress analysis. (author)

  6. The effect of allometric scaling in coral thermal microenvironments.

    Directory of Open Access Journals (Sweden)

    Robert H Ong

    Full Text Available A long-standing interest in marine science is in the degree to which environmental conditions of flow and irradiance, combined with optical, thermal and morphological characteristics of individual coral colonies, affects their sensitivity of thermal microenvironments and susceptibility to stress-induced bleaching within and/or among colonies. The physiological processes in Scleractinian corals tend to scale allometrically as a result of physical and geometric constraints on body size and shape. There is a direct relationship between scaling to thermal stress, thus, the relationship between allometric scaling and rates of heating and cooling in coral microenvironments is a subject of great interest. The primary aim of this study was to develop an approximation that predicts coral thermal microenvironments as a function of colony morphology (shape and size, light or irradiance, and flow velocity or regime. To do so, we provided intuitive interpretation of their energy budgets for both massive and branching colonies, and then quantified the heat-size exponent (b* and allometric constant (m using logarithmic linear regression. The data demonstrated a positive relationship between thermal rates and changes in irradiance, A/V ratio, and flow, with an interaction where turbulent regime had less influence on overall stress which may serve to ameliorate the effects of temperature rise compared to the laminar regime. These findings indicated that smaller corals have disproportionately higher stress, however they can reach thermal equilibrium quicker. Moreover, excellent agreements between the predicted and simulated microscale temperature values with no significant bias were observed for both the massive and branching colonies, indicating that the numerical approximation should be within the accuracy with which they could be measured. This study may assist in estimating the coral microscale temperature under known conditions of water flow and irradiance

  7. Thermal tests of a transport / Storage cask in buried conditions

    International Nuclear Information System (INIS)

    Yamakawa, H.; Gomi, Y.; Saegusa, T.; Ito, C.

    1998-01-01

    Thermal tests for a hypothetical accident which simulated accidents caused by building collapse in case of an earthquake were conducted using a full-scale dry type transport and storage cask (total heat load: 23 kW). The objectives of these tests were to clarify the heat transfer features of the buried cask under such accidents and the time limit for maintaining the thermal integrity of the cask. Moreover, thermal analyses of the test cask under the buried conditions were carried out on basis of experimental results to establish methodology for the thermal analysis. The characteristics of the test cask are described as well as the test method used. The heat transfer features of the buried cask under such accidents and a time for maintaining the thermal integrity of the cask have been obtained. (O.M.)

  8. Dietary lecithin potentiates thermal tolerance and cellular stress protection of milk fish (Chanos Chanos) reared under low dose endosulfan-induced stress.

    Science.gov (United States)

    Kumar, Neeraj; Minhas, P S; Ambasankar, K; Krishnani, K K; Rana, R S

    2014-12-01

    Endosulfan is an organochlorine pesticide commonly found in aquatic environments that has been found to reduce thermal tolerance of fish. Lipotropes such as the food additive, Lecithin has been shown to improve thermal tolerance in fish species. This study was conducted to evaluate the role of lipotropes (lecithin) for enhancing the thermal tolerance of Chanos chanos reared under sublethal low dose endosulfan-induced stress. Two hundred and twenty-five fish were distributed randomly into five treatments, each with three replicates. Four isocaloric and isonitrogenous diets were prepared with graded levels of lecithin: normal water and fed with control diet (En0/L0), endosulfan-treated water and fed with control diet (En/L0), endosulfan-treated water and fed with 1% (En/L1%), 1.5% (En/L 1.5%) and 2% (En/L 2%) lecithin supplemented feed. The endosulfan in treated water was maintained at the level of 1/40th of LC50 (0.52ppb). At the end of the five weeks, critical temperature maxima (CTmax), lethal temperature maxima (LTmax), critical temperature minima (CTmin) and lethal temperature minima (LTmin) were Determined. There was a significant (Plecithin on temperature tolerance (CTmax, LTmax, CTmin and LTmin) of the groups fed with 1, 1.5 and 2% lecithin-supplemented diet compared to control and endosulfan-exposed groups. Positive correlations were observed between CT max and LTmax (R(2)=0.934) as well as between CTmin and LTmin (R(2)=0.9313). At the end of the thermal tolerance study, endosulfan-induced changes in cellular stress enzymes (Catalase, SOD and GST in liver and gill and neurotansmitter enzyme, brain AChE) were significantly (plecithin. We herein report the role of lecithin in enhancing the thermal tolerance and protection against cellular stress in fish exposed to an organochlorine pesticide. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Baking system for ports of experimental advanced super-conducting tokamak vacuum vessel and thermal stress analysis

    International Nuclear Information System (INIS)

    Cheng Yali; Bao Liman; Song Yuntao; Yao Damao

    2006-01-01

    The baking system of Experimental Advanced Super-Conducting Toakamk (EAST) vacuum vessel is necessary to obtain the baking temperature of 150 degree C. In order to define suitable alloy heaters and achieve their reasonable layouts, thermal analysis was carried out with ANSYS code. The analysis results indicate that the temperature distribution and thermal stress of most parts of EAST vacuum vessel ports are uniform, satisfied for the requirement, and are safe based on ASME criterion. Feasible idea on reducing the stress focus is also considered. (authors)

  10. Development of intergranular thermal residual stresses in beryllium during cooling from processing temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Brown, D.W. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)], E-mail: dbrown@lanl.gov; Sisneros, T.A.; Clausen, B.; Abeln, S.; Bourke, M.A.M.; Smith, B.G.; Steinzig, M.L.; Tome, C.N.; Vogel, S.C. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2009-02-15

    The intergranular thermal residual stresses in texture-free solid polycrystalline beryllium were determined by comparison of crystallographic lattice parameters in solid and powder samples measured by neutron diffraction during cooling from 800 deg. C. The internal stresses are not significantly different from zero >575 deg. C and increase nearly linearly <525 deg. C. At room temperature, the c axis of an average grain is under {approx}200 MPa of compressive internal stress, and the a axis is under 100 MPa of tensile stress. For comparison, the stresses have also been calculated using an Eshelby-type polycrystalline model. The measurements and calculations agree very well when temperature dependence of elastic constants is accounted for, and no plastic relaxation is allowed in the model.

  11. X-ray diffraction study of thermal stress relaxation in ZnO films deposited by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Conchon, F. [Institut P' , Universite de Poitiers-Ensma-UPR CNRS 3346, 86962 Futuroscope (France); Renault, P.O., E-mail: pierre.olivier.renault@univ-poitiers.f [Institut P' , Universite de Poitiers-Ensma-UPR CNRS 3346, 86962 Futuroscope (France); Le Bourhis, E.; Krauss, C.; Goudeau, P. [Institut P' , Universite de Poitiers-Ensma-UPR CNRS 3346, 86962 Futuroscope (France); Barthel, E.; Grachev, S. Yu.; Sondergard, E. [Lab. Surface du Verre et Interfaces (SVI), UMR 125, 93303 Aubervilliers (France); Rondeau, V.; Gy, R. [Lab. Recherche de Saint-Gobain (SGR), 93303 Aubervilliers (France); Lazzari, R.; Jupille, J. [Institut des Nanosciences de Paris (INSP), UMR 7588, 75015 Paris (France); Brun, N. [Lab. Physique des Solides (LPS), UMR 8502, 91405 Orsay (France)

    2010-12-30

    X-ray diffraction stress analyses have been performed on two different thin films deposited onto silicon substrate: ZnO and ZnO encapsulated into Si{sub 3}N{sub 4} layers. We showed that both as-deposited ZnO films are in a high compressive stress state. In situ X-ray diffraction measurements inside a furnace revealed a relaxation of the as-grown stresses at temperatures which vary with the atmosphere in the furnace and change with Si{sub 3}N{sub 4} encapsulation. The observations show that Si{sub 3}N{sub 4} films lying on both sides of the ZnO film play an important role in the mechanisms responsible for the stress relaxation during heat treatment. The different temperatures observed for relaxation in ambient and argon atmospheres suggest that the thermally activated stress relaxation may be attributed to a variation of the stoichiometry of the ZnO films. The present observations pave the way to fine tuning of the residual stresses through thermal treatment parameters.

  12. Aprediction study for the behaviour of fuel cell membrane subjected to hygro and thermal stresses in running PEM fuel cell

    OpenAIRE

    Maher A.R. Sadiq Al-Baghdadi

    2016-01-01

    A three-dimensional, multi–phase, non-isothermal computational fluid dynamics model of a proton exchange membrane fuel cell has been used and developed to investigate the hygro and thermal stresses in polymer membrane, which developed during the cell operation due to the changes of temperature and relative humidity. The behaviour of the membrane during operation of a unit cell has been studied and investigated under real cell operating conditions. The results show that the non-uniform distrib...

  13. Deposition stress effects on thermal barrier coating burner rig life

    Science.gov (United States)

    Watson, J. W.; Levine, S. R.

    1984-01-01

    A study of the effect of plasma spray processing parameters on the life of a two layer thermal barrier coating was conducted. The ceramic layer was plasma sprayed at plasma arc currents of 900 and 600 amps onto uncooled tubes, cooled tubes, and solid bars of Waspalloy in a lathe with 1 or 8 passes of the plasma gun. These processing changes affected the residual stress state of the coating. When the specimens were tested in a Mach 0.3 cyclic burner rig at 1130 deg C, a wide range of coating lives resulted. Processing factors which reduced the residual stress state in the coating, such as reduced plasma temperature and increased heat dissipation, significantly increased coating life.

  14. Amelioration of Heat-Stress Conditions of Egyptian Summer Season on Friesian Calves Using Air Condition

    International Nuclear Information System (INIS)

    Nessim, M.Z.; Kamal, T.H.; Khalil, W.K.B.

    2010-01-01

    Male Friesian calves were used to evaluate cool air condition (AC) in alleviating heat stress (HS) determined by Heat Shock Protein genes expression (HSP), hormonal, biochemical and physiological parameters. The animals were exposed to summer heat stress (HS) under shade for two weeks (control). The maximum temperature humidity index (THI) during summer HS was from 81 to 88. Afterward the animals were exposed to AC, inside a climatic chamber for 6 hours daily for two weeks, where, the THI was from 70 to 71. The results revealed that expression level of the Hsp genes (Hsp72, Hsp70.1, Hsp70 and Hsp47) was lower under air condition treatment than under summer heat stress. Rectal temperature and respiration rate were significantly lower (p< 0.01) under air condition treatment than those under heat stress. Total triiodothyronin (T3) level was significantly higher (P< 0.05) in AC cooling treatments than in HS, while cortisol level was significantly lower (P < 0.01) in AC cooling treatment than in HS calves. Creatinine and Urea -N levels were significantly lower (P < 0.01) in AC cooling treatment than in HS calves. Triglycerides, ALT and AST levels were significantly lower (p<0.01), (P< 0.01) and (p<0.05), respectively in AC cooling treatment than in HS calves. These results demonstrated that there is a relationship between the molecular weight of HSPs and the level of HSPs gene exprisson. The higher the molecular weight (HSP 72) the lower is the HSPs gene expression level (0.82 in HS and 0.39 in AC) and vise versa. This holds true in both heat stress and air condition. AC treatment is capable to ameliorate heat stress of Friesian calves under hot summer climate

  15. Propagation of internal stresses in composite materials during heating and cooling according to thermal cycles of welding

    International Nuclear Information System (INIS)

    Gukasyan, L.E.; Belov, V.V.

    1977-01-01

    Investigations of free thermal expansion of a composite material, of fibre and matrix during welding thermal cycle make it possible to estimate mean internal strain and stress in the composite components, as well as the residual internal stress and strain present in the composite material after manufacturing. The samples investigated consisted of nickel-chromium EhI445 alloy, reinforced by tungsten-rhenium alloy fibres. As the composite material was cooled and heated in course of welding, the stress and strain changed their sign twice, the first time upon heating, the second time upon cooling. After complete cooling of the composite material residual stresses in the fibre stay at the proportionality level, while those in the matrix are lower. Experimental evidence of internal stress and strain appearing in the composite material during heating are fairly consistent with calculations in the elastic region, if account is taken of the temperature of internal residual stress relaxation upon heating

  16. Thermal Stress Analysis and Structure Parameter Selection for a Bi2Te3-Based Thermoelectric Module

    Science.gov (United States)

    Gao, Jun-Ling; Du, Qun-Gui; Zhang, Xiao-Dan; Jiang, Xin-Qiang

    2011-05-01

    The output power and conversion efficiency of thermoelectric modules (TEMs) are mainly determined by their material properties, i.e., Seebeck coefficient, electrical resistivity, and thermal conductivity. In practical applications, due to the influence of the harsh environment, the mechanical properties of TEMs should also be considered. Using the finite-element analysis (FEA) model in ANSYS software, we present the thermal stress distribution of a TEM based on the anisotropic mechanical properties and thermoelectric properties of hot-pressed materials. By analyzing the possibilities of damage along the cleavage plane of Bi2Te3-based thermoelectric materials and by optimizing the structure parameters, a TEM with better mechanical performance is obtained. Thus, a direction for improving the thermal stress resistance of TEMs is presented.

  17. Analysis of electrical and thermal stress effects on PCBM:P3HT solar cells by photocurrent and impedance spectroscopy modeling

    DEFF Research Database (Denmark)

    Torto, Lorenzo; Rizzo, Antonio; Cester, Andrea

    2017-01-01

    We investigated the effects of electrical stress and thermal storage by means of photocurrent, Impedance Spectroscopy and Open Circuit Voltage Decay models. The electrical stress damages only the active layer, by reducing the generation rate, the polaron separation probability and the carrier...... lifetime. The thermal stress also degrades the anode interface. This reflects on the appearance of an inflection in the I-V photocurrent shape close to the operative region....

  18. Influence of anomalous thermal losses of ignition conditions

    International Nuclear Information System (INIS)

    Coppi, B.; Tang, W.M.

    1986-05-01

    In the process of achieving ignition conditions, it is likely that microinstabilities, which lead to anomalous thermal transport of the fusing nuclei, will be present. When such phenomena are taken into account, an appropriate formulation of ignition criteria becomes necessary. In particular, a new type of plasma density limit is identified

  19. On the determination of the thermal comfort conditions of a metropolitan city underground railway.

    Science.gov (United States)

    Katavoutas, George; Assimakopoulos, Margarita N; Asimakopoulos, Dimosthenis N

    2016-10-01

    Although the indoor thermal comfort concept has received increasing research attention, the vast majority of published work has been focused on the building environment, such as offices, residential and non-residential buildings. The present study aims to investigate the thermal comfort conditions in the unique and complex underground railway environment. Field measurements of air temperature, air humidity, air velocity, globe temperature and the number of passengers were conducted in the modern underground railway of Athens, Greece. Environmental monitoring was performed in the interior of two types of trains (air-conditioned and forced air ventilation cabins) and on selected platforms during the summer period. The thermal comfort was estimated using the PMV (predicted mean vote) and the PPD (predicted percentage dissatisfied) scales. The results reveal that the recommended thermal comfort requirements, although at relatively low percentages are met only in air-conditioned cabins. It is found that only 33% of the PPD values in air-conditioned cabins can be classified in the less restrictive comfort class C, as proposed by ISO-7730. The thermal environment is "slightly warm" in air-conditioned cabins and "warm" in forced air ventilation cabins. In addition, differences of the thermal comfort conditions on the platforms are shown to be associated with the depth and the design characteristics of the stations. The average PMV at the station with small depth is 0.9 scale points higher than that of the station with great depth. The number of passengers who are waiting at the platforms during daytime reveals a U-shaped pattern for a deep level station and an inverted course of PMV for a small depth station. Further, preliminary observations are made on the distribution of air velocity on the platforms and on the impact of air velocity on the thermal comfort conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Research on suitable heating conditions during local PWHT. Pt. 1. Influence of heating conditions on temperature distribution

    International Nuclear Information System (INIS)

    Tanaka, Jinkichi; Horii, Yukihiko; Sato, Masanobu; Murakawa, Hidekazu; Wang Jianhua

    1999-01-01

    To improve weld joint properties a heat treatment so called post weld heat treatment (PWHT) is often implemented for steel weldment. Generally, the PWHT is conducted in a furnace at a factory. But in site welds such as the girth joint of pipe, a local PWHT is applied using electric heater and so on. In the local PWHT steep temperature gradient occurs depending on the heating condition and it leads to rise of the thermal stress in addition to the welding residual stress. However, heating condition is not always defined the same in some standards. Therefore, suitable heat conditions for the local PWHT were studied supposing the power plant and so on experimentally and theoretically. Temperature distribution and thermal strains under different heating conditions were measured during the local PWHT using carbon steel pipes of 340 mm in diameter and 53 mm in wall thickness. The temperature gradient, thermal strain were also analyzed using Finite Element Method (FEM) as axis-symmetric model. Further, the influences of pipe size and heat transfer coefficient on the temperature distribution were analyzed and suitable heating source widths for various pipe sizes were proposed from the viewpoint of temperature distribution. (orig.)

  1. Poor working conditions and work stress among Canadian sex workers.

    Science.gov (United States)

    Duff, P; Sou, J; Chapman, J; Dobrer, S; Braschel, M; Goldenberg, S; Shannon, K

    2017-10-01

    While sex work is often considered the world's oldest profession, there remains a dearth of research on work stress among sex workers (SWs) in occupational health epidemiological literature. A better understanding of the drivers of work stress among SWs is needed to inform sex work policy, workplace models and standards. To examine the factors that influence work stress among SWs in Metro Vancouver. Analyses drew from a longitudinal cohort of SWs, known as An Evaluation of Sex Workers' Health Access (AESHA) (2010-14). A modified standardized 'work stress' scale, multivariable linear regression with generalized estimating equations was used to longitudinally examine the factors associated with work stress. In multivariable analysis, poor working conditions were associated with increased work stress and included workplace physical/sexual violence (β = 0.18; 95% confidence interval (CI) 0.06, 0.29), displacement due to police (β = 0.26; 95% CI 0.14, 0.38), working in public spaces (β = 0.73; 95% CI 0.61, 0.84). Older (β = -0.02; 95% CI -0.03, -0.01) and Indigenous SWs experienced lower work stress (β = -0.25; 95% CI -0.43, -0.08), whereas non-injection (β = 0.32; 95% CI 0.14, 0.49) and injection drug users (β = 0.17; 95% CI 0.03, 0.31) had higher work stress. Vancouver-based SWs' work stress was largely shaped by poor work conditions, such as violence, policing, lack of safe workspaces. There is a need to move away from criminalized approaches which shape unsafe work conditions and increase work stress for SWs. Policies that promote SWs' access to the same occupational health, safety and human rights standards as workers in other labour sectors are also needed. © The Author 2017. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oup.com

  2. Thermal creep and stress-affected precipitation of 20% cold-worked 316 stainless steel

    International Nuclear Information System (INIS)

    Puigh, R.J.; Lovell, A.J.; Garner, F.A.

    1984-01-01

    Measurements of the thermal creep of 20% cold-worked 316 stainless steel have been performed for temperatures from 593 to 760 0 C, stress levels as high as 138 MPa and exposure times as long as 15,000 hours. The creep strains exhibit a complex behavior arising from the combined action of true creep and stress-affected precipitation of intermetallic phases. The latter process is suspected to be altered by neutron irradiation. (orig.)

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

    Directory of Open Access Journals (Sweden)

    Abdulhadi Hassan A.

    2016-01-01

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

  4. Residual thermal stresses in a solid sphere cast from a thermosetting material

    Science.gov (United States)

    Levitsky, M.; Shaffer, B. W.

    1975-01-01

    Expressions are developed for the residual thermal stresses in a solid sphere cast from a chemically hardening thermosetting material in a rigid spherical mold. The description of the heat generation rate and temperature variation is derived from a first-order chemical reaction. Solidification is described by the continuous transformation of the material from an inviscid liquidlike state into an elastic solid, with intermediate properties determined by the degree of chemical reaction. Residual stress components are obtained as functions of the parameters of the hardening process and the properties of the hardening material. Variation of the residual stresses with a nondimensionalized reaction rate parameter and the relative compressibility of the hardened material is discussed in detail.

  5. Thermal resistivity of tungsten grades under fusion relevant conditions

    Energy Technology Data Exchange (ETDEWEB)

    Wirtz, M.; Linke, J.; Pintsuk, G. [Forschungszentrum Juelich (Germany). EURATOM Association

    2010-05-15

    Controlled nuclear fusion on earth is a very promising but also a very challenging task. Fusion devices like ITER and DEMO are major steps on the way of solving the energy problems of the future. However, the realisation of such thermonuclear fusion reactors still needs high efforts in many areas of research. One of the most critical issues is the field of in - vessel materials and components and in particular the plasma facing material (PFM). This not only has to be compatible to the heat sink material being able to withstand thermal fatigue loading conditions during steady state heat loading (up to 20 MW/m{sup 2}) but also has to withstand extreme thermal loads during transient events. The latter are divided into normal and off normal events, such as plasma disruptions or vertical displacement events (VDEs), resulting in irreversible damage of the material. Therefore they have to be avoided in future fusion devices by an improved plasma control. In contrast, edge localized modes (ELMs) occur during normal operation and are the result of complex plasma configuration. In the next step experiment ITER they are generated with a frequency of {>=} 1 Hz and a duration of 200 - 500 {mu}s depositing energies of {<=} 1 MJ/m{sup 2}. One of the most promising materials for the application as PFM in particular in the divertor region is tungsten. Its main advantages are a high thermal conductivity, a high melting temperature, a low tritium inventory and a low erosion rate. However there are some drawbacks like a high ductile to brittle transitions temperature (DBTT), its high atomic number Z and the remarkable neutron irradiation induced activation and degradation of its mechanical properties. The main aim of future R and D will be to understand the mechanisms of thermal induced damages and subsequently to minimize these types of damages. Therefore various tungsten grades have to be tested under fusion relevant conditions, e.g. by electron, ion or plasma beam exposure; the

  6. Simple method of calculating the transient thermal performance of composite material and its applicable condition

    Institute of Scientific and Technical Information of China (English)

    张寅平; 梁新刚; 江忆; 狄洪发; 宁志军

    2000-01-01

    Degree of mixing of composite material is defined and the condition of using the effective thermal diffusivity for calculating the transient thermal performance of composite material is studied. The analytical result shows that for a prescribed precision of temperature, there is a condition under which the transient temperature distribution in composite material can be calculated by using the effective thermal diffusivity. As illustration, for the composite material whose temperatures of both ends are constant, the condition is presented and the factors affecting the relative error of calculated temperature of composite materials by using effective thermal diffusivity are discussed.

  7. A Theoretical Study on Quantitative Prediction and Evaluation of Thermal Residual Stresses in Metal Matrix Composite (Case 1 : Two-Dimensional In-Plane Fiber Distribution)

    International Nuclear Information System (INIS)

    Lee, Joon Hyun; Son, Bong Jin

    1997-01-01

    Although discontinuously reinforced metal matrix composite(MMC) is one of the most promising materials for applications of aerospace, automotive industries, the thermal residual stresses developed in the MMC due to the mismatch in coefficients of thermal expansion between the matrix and the fiber under a temperature change has been pointed out as one of the serious problem in practical applications. There are very limited nondestructive techniques to measure the residual stress of composite materials. However, many difficulties have been reported in their applications. Therefore it is important to establish analytical model to evaluate the thermal residual stress of MMC for practical engineering application. In this study, an elastic model is developed to predict the average thermal residual stresses in the matrix and fiber of a misoriented short fiber composite. The thermal residual stresses are induced by the mismatch in the coefficient of the thermal expansion of the matrix and fiber when the composite is subjected to a uniform temperature change. The model considers two-dimensional in-plane fiber misorientation. The analytical formulation of the model is based on Eshelby's equivalent inclusion method and is unique in that it is able to account for interactions among fibers. This model is more general than past models to investigate the effect of parameters which might influence thermal residual stress in composites. The present model is to investigate the effects of fiber volume fraction, distribution type, distribution cut-off angle, and aspect ratio on thermal residual stress for in-plane fiber misorientation. Fiber volume fraction, aspect ratio, and distribution cut-off angle are shown to have more significant effects on the magnitude of the thermal residual stresses than fiber distribution type for in-plane misorientation

  8. Human thermal comfort conditions and urban planning in hot-humid climates-The case of Cuba.

    Science.gov (United States)

    Rodríguez Algeciras, José Abel; Coch, Helena; De la Paz Pérez, Guillermo; Chaos Yeras, Mabel; Matzarakis, Andreas

    2016-08-01

    Climate regional characteristics, urban environmental conditions, and outdoors thermal comfort requirements of residents are important for urban planning. Basic studies of urban microclimate can provide information and useful resources to predict and improve thermal conditions in hot-humid climatic regions. The paper analyzes the thermal bioclimate and its influence as urban design factor in Cuba, using Physiologically Equivalent Temperature (PET). Simulations of wind speed variations and shade conditions were performed to quantify changes in thermal bioclimate due to possible modifications in urban morphology. Climate data from Havana, Camagüey, and Santiago of Cuba for the period 2001 to 2012 were used to calculate PET with the RayMan model. The results show that changes in meteorological parameters influence the urban microclimate, and consequently modify the thermal conditions in outdoors spaces. Shade is the predominant strategy to improve urban microclimate with more significant benefits in terms of PET higher than 30 °C. For climatic regions such as the analyzed ones, human thermal comfort can be improved by a wind speed modification for thresholds of PET above 30 °C, and by a wind speed decreases in conditions below 26 °C. The improvement of human thermal conditions is crucial for urban sustainability. On this regards, our study is a contribution for urban designers, due to the possibility of taking advantage of results for improving microclimatic conditions based on urban forms. The results may enable urban planners to create spaces that people prefer to visit, and also are usable in the reconfiguration of cities.

  9. Metabolite profiling of symbiont and host during thermal stress and bleaching in the coral Acropora aspera

    Science.gov (United States)

    Hillyer, Katie E.; Dias, Daniel A.; Lutz, Adrian; Wilkinson, Shaun P.; Roessner, Ute; Davy, Simon K.

    2017-03-01

    Rising seawater temperatures pose a significant threat to the persistence of coral reefs. Despite the importance of these systems, major gaps remain in our understanding of how thermal stress and bleaching affect the metabolic networks that underpin holobiont function. We applied gas chromatography-mass spectrometry (GC-MS) metabolomics to detect changes in the intracellular free metabolite pools (polar and semi-polar compounds) of in hospite dinoflagellate symbionts and their coral hosts (and any associated microorganisms) during early- and late-stage thermal bleaching (a reduction of approximately 50 and 70% in symbiont density, respectively). We detected characteristic changes to the metabolite profiles of each symbiotic partner associated with individual cellular responses to thermal, oxidative and osmotic stress, which progressed with the severity of bleaching. Alterations were also indicative of changes to energy-generating and biosynthesis pathways in both partners, with a shift to the increased catabolism of lipid stores. Specifically, in symbiont intracellular metabolite pools, we observed accumulations of multiple free fatty acids, plus the chloroplast-associated antioxidant alpha-tocopherol. In the host, we detected a decline in the abundance of pools of multiple carbohydrates, amino acids and intermediates, in addition to the antioxidant ascorbate. These findings further our understanding of the metabolic changes that occur to symbiont and host (and its associated microorganisms) during thermal bleaching. These findings also provide further insight into the largely undescribed roles of free metabolite pools in cellular homeostasis, signalling and acclimation to thermal stress in the cnidarian-dinoflagellate symbiosis.

  10. Investigation of analytical methods in thermal stratification analysis. Evaluation of flow rates through flow holes for normal and scram conditions of 40% power operation with AQUA code

    International Nuclear Information System (INIS)

    Doi, Yoshihiro; Muramatsu, Toshiharu

    1997-08-01

    Thermal stratification phenomena are observed in an upper plenum of liquid metal fast breeder reactors (LMFBRs) under reactor scram conditions, which give rise to thermal stress on structural components. Therefore it is important to evaluate characteristics of phenomena in the design of the internal structure in an LMFBR plenum. To evaluate flow rates through flow holes of the prototype fast breeder reactor, MONJU, numerical analyses were carried out with AQUA code for normal and scram conditions with 40% power operation. Through comparison of analysis results and measured temperature, thermal stratification phenomena in 300 second period after the scram was evaluated. Flow rate through the upper flow holes, the lower flow holes and annular gap between the inner barrel and the reactor vessel were evaluated with the measured temperature and the analysis results individually. (J.P.N.)

  11. Development of Methodologies for the Estimation of Thermal Properties Associated with Aerospace Vehicles

    Science.gov (United States)

    Scott, Elaine P.

    1996-01-01

    A thermal stress analysis is an important aspect in the design of aerospace structures and vehicles such as the High Speed Civil Transport (HSCT) at the National Aeronautics and Space Administration Langley Research Center (NASA-LaRC). These structures are complex and are often composed of numerous components fabricated from a variety of different materials. The thermal loads on these structures induce temperature variations within the structure, which in turn result in the development of thermal stresses. Therefore, a thermal stress analysis requires knowledge of the temperature distributions within the structures which consequently necessitates the need for accurate knowledge of the thermal properties, boundary conditions and thermal interface conditions associated with the structural materials. The goal of this proposed multi-year research effort was to develop estimation methodologies for the determination of the thermal properties and interface conditions associated with aerospace vehicles. Specific objectives focused on the development and implementation of optimal experimental design strategies and methodologies for the estimation of thermal properties associated with simple composite and honeycomb structures. The strategy used in this multi-year research effort was to first develop methodologies for relatively simple systems and then systematically modify these methodologies to analyze complex structures. This can be thought of as a building block approach. This strategy was intended to promote maximum usability of the resulting estimation procedure by NASA-LARC researchers through the design of in-house experimentation procedures and through the use of an existing general purpose finite element software.

  12. effect of thermal stress of short duration on the red blood cell

    African Journals Online (AJOL)

    Dr Ivanc

    2013-05-01

    May 1, 2013 ... an acute increase of temperature and metabolic rate on basic blood parameters as oxygen transport system. The effect of thermal stress was studied on the Barbus balcanicus, a species inhabiting smaller water bodies often exposed to temperature fluctuatiation. During the experiment, the fish were ...

  13. Thermal stability of nafion membranes under mechanical stress

    Energy Technology Data Exchange (ETDEWEB)

    Quintilii, M; Struis, R [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The feasibility of adequately modified fluoro-ionomer membranes (NAFION{sup R}) is demonstrated for the selective separation of methanol synthesis products from the raw reactor gas at temperatures around 200{sup o}C. For an economically relevant application of this concept on a technical scale the Nafion membranes should be thin ({approx_equal}10 {mu}m) and thermally stable over a long period of time (1-2 years). In cooperation with industry (Methanol Casale SA, Lugano (CH)), we test the thermal stability of Nafion hollow fibers and supported Nafion thin sheet membranes at temperatures between 160 and 200{sup o}C under mechanical stress by applying a gas pressure difference over the membrane surface ({Delta}P{<=} 40 bar). Tests with the hollow fibers revealed that Nafion has visco-elastic properties. Tests with 50 {mu}m thin Nafion sheets supported by a porous metal carrier at 200{sup o}C and {Delta}P=39 bar showed no mechanical defects over a period of 92 days. (author) 5 figs., 4 refs.

  14. Study of thermal stress in heat affected zones during welding

    International Nuclear Information System (INIS)

    Devaux, J.C.

    1979-01-01

    The importance of applications of welding in the nuclear industry leads to the study of the main problem concerning metal welding: sensibility to cracking. The development of computation methods allows the numerical simulation of welding effects. Due to the complexity of this problem, it is divided in three steps: thermal, metallurgical and mechanical calculus. Interactions between the 3 steps are examined. Mathematical models necessary to get residual stress (i.e. stress remaining when welding is completed and structure at ambient temperature) are described. Then parameters for metallurgical structure determination are given and compared to experiments. A508 and A533 type steels of primary coolant circuit of PWR reactors are taken as examples and the numerical simulation of a test is presented [fr

  15. Tremor frequency characteristics in Parkinson's disease under resting-state and stress-state conditions.

    Science.gov (United States)

    Lee, Hong Ji; Lee, Woong Woo; Kim, Sang Kyong; Park, Hyeyoung; Jeon, Hyo Seon; Kim, Han Byul; Jeon, Beom S; Park, Kwang Suk

    2016-03-15

    Tremor characteristics-amplitude and frequency components-are primary quantitative clinical factors for diagnosis and monitoring of tremors. Few studies have investigated how different patient's conditions affect tremor frequency characteristics in Parkinson's disease (PD). Here, we analyzed tremor characteristics under resting-state and stress-state conditions. Tremor was recorded using an accelerometer on the finger, under resting-state and stress-state (calculation task) conditions, during rest tremor and postural tremor. The changes of peak power, peak frequency, mean frequency, and distribution of power spectral density (PSD) of tremor were evaluated across conditions. Patients whose tremors were considered more than "mild" were selected, for both rest (n=67) and postural (n=25) tremor. Stress resulted in both greater peak powers and higher peak frequencies for rest tremor (pstate condition. The distributions of PSD of tremor were symmetrical, regardless of conditions. Tremor is more evident and typical tremor characteristics, namely a lower frequency as amplitude increases, are different in stressful condition. Patient's conditions directly affect neural oscillations related to tremor frequencies. Therefore, tremor characteristics in PD should be systematically standardized across patient's conditions such as attention and stress levels. Copyright © 2016. Published by Elsevier B.V.

  16. Changes in fatty acid composition in the giant clam Tridacna maxima in response to thermal stress.

    Science.gov (United States)

    Dubousquet, Vaimiti; Gros, Emmanuelle; Berteaux-Lecellier, Véronique; Viguier, Bruno; Raharivelomanana, Phila; Bertrand, Cédric; Lecellier, Gaël J

    2016-10-15

    Temperature can modify membrane fluidity and thus affects cellular functions and physiological activities. This study examines lipid remodelling in the marine symbiotic organism, Tridacna maxima, during a time series of induced thermal stress, with an emphasis on the morphology of their symbiont Symbiodinium First, we show that the French Polynesian giant clams harbour an important proportion of saturated fatty acids (SFA), which reflects their tropical location. Second, in contrast to most marine organisms, the total lipid content in giant clams remained constant under stress, though some changes in their composition were shown. Third, the stress-induced changes in fatty acid (FA) diversity were accompanied by an upregulation of genes involved in lipids and ROS pathways. Finally, our microscopic analysis revealed that for the giant clam's symbiont, Symbiodinium, thermal stress led to two sequential cell death processes. Our data suggests that the degradation of Symbiodinium cells could provide an additional source of energy to T maxima in response to heat stress. © 2016. Published by The Company of Biologists Ltd.

  17. Occupants' adaptive responses and perception of thermal environment in naturally conditioned university classrooms

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Runming [The School of Construction Management and Engineering, The University of Reading, Whiteknights, PO Box 219, Reading RG6 6AW (United Kingdom); The Faculty of Urban Construction and Environmental Engineering, Chongqing University, Chongqing 400042 (China); Liu, Jing [The School of Construction Management and Engineering, The University of Reading, Whiteknights, PO Box 219, Reading RG6 6AW (United Kingdom); Li, Baizhan [The Faculty of Urban Construction and Environmental Engineering, Chongqing University, Chongqing 400042 (China); Key Laboratory of the Three Gorges Reservoir Region' s Eco-Environment (Ministry of Education), Chongqing University, Chongqing 400042 (China)

    2010-03-15

    A year-long field study of the thermal environment in university classrooms was conducted from March 2005 to May 2006 in Chongqing, China. This paper presents the occupants' thermal sensation votes and discusses the occupants' adaptive response and perception of the thermal environment in a naturally conditioned space. Comparisons between the Actual Mean Vote (AMV) and Predicted Mean Vote (PMV) have been made as well as between the Actual Percentage of Dissatisfied (APD) and Predicted Percentage of Dissatisfied (PPD). The adaptive thermal comfort zone for the naturally conditioned space for Chongqing, which has hot summer and cold winter climatic characteristics, has been proposed based on the field study results. The Chongqing adaptive comfort range is broader than that of the ASHRAE Standard 55-2004 in general, but in the extreme cold and hot months, it is narrower. The thermal conditions in classrooms in Chongqing in summer and winter are severe. Behavioural adaptation such as changing clothing, adjusting indoor air velocity, taking hot/cold drinks, etc., as well as psychological adaptation, has played a role in adapting to the thermal environment. (author)

  18. Heat exchange studies on coconut oil cells as thermal energy storage for room thermal conditioning

    Science.gov (United States)

    Sutjahja, I. M.; Putri, Widya A.; Fahmi, Z.; Wonorahardjo, S.; Kurnia, D.

    2017-07-01

    As reported by many thermal environment experts, room air conditioning might be controlled by thermal mass system. In this paper we discuss the performance of coconut oil cells as room thermal energy storage. The heat exchange mechanism of coconut oil (CO) which is one of potential organic Phase Change Material (PCM) is studied based on the results of temperature measurements in the perimeter and core parts of cells. We found that the heat exchange performance, i.e. heat absorption and heat release processes of CO cells are dominated by heat conduction in the sensible solid from the higher temperature perimeter part to the lower temperature core part and heat convection during the solid-liquid phase transition and sensible liquid phase. The capability of heat absorption as measured by the reduction of air temperature is not influenced by CO cell size. Besides that, the application of CO as the thermal mass has to be accompanied by air circulation to get the cool sensation of the room’s occupants.

  19. 3D analysis of thermal and stress evolution during laser cladding of bioactive glass coatings.

    Science.gov (United States)

    Krzyzanowski, Michal; Bajda, Szymon; Liu, Yijun; Triantaphyllou, Andrew; Mark Rainforth, W; Glendenning, Malcolm

    2016-06-01

    Thermal and strain-stress transient fields during laser cladding of bioactive glass coatings on the Ti6Al4V alloy basement were numerically calculated and analysed. Conditions leading to micro-cracking susceptibility of the coating have been investigated using the finite element based modelling supported by experimental results of microscopic investigation of the sample coatings. Consecutive temperature and stress peaks are developed within the cladded material as a result of the laser beam moving along the complex trajectory, which can lead to micro-cracking. The preheated to 500°C base plate allowed for decrease of the laser power and lowering of the cooling speed between the consecutive temperature peaks contributing in such way to achievement of lower cracking susceptibility. The cooling rate during cladding of the second and the third layer was lower than during cladding of the first one, in such way, contributing towards improvement of cracking resistance of the subsequent layers due to progressive accumulation of heat over the process. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Occupational stress, working condition and nutritional status of military police officers.

    Science.gov (United States)

    Santana, Angela Maria C; Gomes, Josiane Keila V; De Marchi, Dione; Girondoli, Yassana M; Rosado, Lina E F P de Lima; Rosado, Gilberto Paixão; de Andrade, Isabel Maria

    2012-01-01

    This study aimed to investigate the relationship between stress, working conditions and the nutritional status of 53 military police officers in a Southeast city of Brazil. In order to evaluate the symptomatology and the stress phase, the Inventory of Stress Symptoms Lipp for Adults - ISSL was utilized. The assessment of the working conditions was performed by means of socio-demographic questionnaire, direct observation and interviews. The nutritional and health conditions were assessed through anthropometric measures, biochemical tests, blood pressure measurements and cardiovascular disease risk calculator. The sample is of the male gender (92.5%) and aging below 40 years old (73.6%). From these, 35.8% showed stress and 68.4% were in the resistance phase, with 31.6% almost burned out. Through the calculation of Chi-square we could find positive association between the BMI and tiredness (P = 0.0188), between the BMI and irritation (P = 0.0005) and the BMI and the appearance of nervous system problems or emotional problems (P = 0.0304), indicating that these statuses or problems could be related to work. We can conclude then, the stress is present among military police officers. No case of critical stress was found, and the stress phases identified are still susceptible to intervention.

  1. Study on durability for thermal cycle of planar SOFC

    Energy Technology Data Exchange (ETDEWEB)

    Ando, Motoo; Nakata, Kei-ichi; Wakayama, Sin-ichi [Tonen Corp., Saitama (Japan)] [and others

    1996-12-31

    TONEN CORPORATION has developed planar type SOFC since 1986. We demonstrated the output of 1.3 kW in 1991 and 5.1 kW in 1995. Simultaneously we have studied how to raise electric efficiency and reliability utilizing hydrogen and propane as fuel. Durability for thermal cycle is one of the most important problems of planar SOFC to make it more practical. The planar type SOFC is made up of separator, zirconia electrolyte and glass sealant. The thermal expansion of these components are expected to be the same value, however, they still possess small differences. In this situation, a thermal cycle causes a thermal stress due to the difference of the cell components and is often followed by a rupture in cell components, therefore, the analysis of the thermal stress should give us much useful information. The thermal cycle process consists of a heating up and cooling down procedure. Zirconia electrolyte is not bonded to the separator under the condition of the initial heating up procedure, and glass sealant becomes soft or melts and glass seals spaces between the zirconia and separator. The glass sealant becomes harder with the cooling down procedure. Moreover, zirconia is tightly bonded with separator below a temperature which is defined as a constraint temperature and thermal stress also occurs. This indicates that the heating up process relaxes the thermal stress and the cooling down increases it. In this paper, we simulated dependence of the stress on the sealing configuration, thermal expansion of sealant and constraint temperature of sealant glass. Furthermore, we presented SOFC electrical properties after a thermal cycle.

  2. Thermal Dehydration Kinetics of Gypsum and Borogypsum under Non-isothermal Conditions

    Institute of Scientific and Technical Information of China (English)

    I.Y.Elbeyli; S.Piskin

    2004-01-01

    Thermal dehydration of gypsum and borogypsum was investigated under nonisothermal conditions in air by using simultaneous thermogravimetric-differential thermal analyzer. Nonisothermal experiments were carried out at various linear heating rates. Kinetics of dehydration in the temperature range of 373-503 K were evaluated from the DTA (differential thermal analysis)-TGA (thermogravimetric analysis) data by means of Coats-Redfern,Kissinger and Doyle Equations. Values of the activation energy and the pre-exponential factor of the dehydration were calculated. The results of thermal experiments and kinetic parameters indicated that borogypsum is similar to gypsum from dehydration mechanism point of view although it consists of boron and small amount of alkali metal oxides.

  3. Theoretical and experimental investigations of thermal conditions of household biogas plant

    Directory of Open Access Journals (Sweden)

    Zhelykh Vasil

    2016-06-01

    Full Text Available The construction of domestic continuous bioreactor is proposed. The modeling of thermal modes of household biogas plant using graph theory was done. The correction factor taking into account with the influence of variables on its value was determined. The system of balance equations for the desired thermal conditions in the bioreactor was presented.

  4. Thermal Stress-Induced Depolarization Loss in Conventional and Panda-Shaped Photonic Crystal Fiber Lasers

    Science.gov (United States)

    Mousavi, Seyedeh Laleh; Sabaeian, Mohammad

    2016-10-01

    We report on the modeling of the depolarization loss in the conventional and panda-shaped photonic crystal fiber lasers (PCFLs) due to the self-heating of the fiber, which we call it thermal stress-induced depolarization loss (TSIDL). We first calculated the temperature distribution over the fiber cross sections and then calculated the thermal stresses/strains as a function of heat load per meter. Thermal stress-induced birefringence (TSIB), which is defined as | n x - n y |, in the core and cladding regions was calculated. Finally, TSIDL was calculated for the conventional and panda-shaped PCFLs as a function of fiber length and, respectively, saturated values of 22 and 25 % were obtained which were independent of heat load per meter. For panda-shaped PCFLs, prior to being saturated, an oscillating and damping behavior against the fiber length was seen where in some lengths reached 35 %. The results are close to an experimental value of 30 % reported for a pulsed PCFL (Limpert et al., Opt Express 12:1313-1319, 2004) where the authors reported a degree of polarization of 70 % (i.e., a depolarization of 30 %). The most important result of this work is a saturation behavior of TSIDL at long-enough lengths of the fiber laser which is independent of heat load per meter. To our knowledge, this the first report of TSIBL for PCFLs.

  5. Thermal properties of bentonite under extreme conditions

    Energy Technology Data Exchange (ETDEWEB)

    Vasicek, R. [Czech Technical Univ., Centre of Experimental Geotechnics, Faculty of Civil Engineering, Prague (Czech Republic)

    2005-07-01

    Centre of Experimental Geotechnics (CEG) deals with the research of the behaviour of bentonite and clays. The measurement of thermal properties is not so frequent test in geotechnical laboratory but in relation to deep repository it is a part which should not be overlooked. The reason is the heat generated by canister with spent nuclear fuel and possible influence of the heat on the materials of the engineered barrier. In the initial stages following the burial of canister with the waste the barrier materials will be exposed to elevated temperature. According to existing information, these temperatures should not exceed 90 C. That heat can induce a creation of cracks and opening of joint between highly compacted blocks. It will predispose the bentonite barrier to penetration of water from surrounding towards to canister. Therefore easy removal of heat through the barrier is required. It is essential that the tests aimed at determining the real values of measured parameters are carried out in conditions identical with those anticipated in a future disposal system. These relatively complicated thermophysical tests are logical continuation of the simple ones, carried out under laboratory temperature and on not fully saturated samples without possibility to measure the swelling pressure. Thermophysical properties and swelling pressure are dominantly influenced by water content (which is influenced by temperature). Therefore is important to realize the tests under different moisture and thermal conditions. These tests are running at the APT-PO1 Analyser, designed to fulfill mentioned requirements - it allows measurement of thermal properties under temperature up to 200 C and swelling pressure up to 20 MPa. The device is capable to register the evolution of temperature, swelling and vapor pressure. The measurement of thermal conductivity and volume heat capacity is realized by the dynamic impulse method with point source of heat. Four types of tests are possible: at

  6. Open stack thermal battery tests

    Energy Technology Data Exchange (ETDEWEB)

    Long, Kevin N. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Roberts, Christine C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Grillet, Anne M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Headley, Alexander J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Fenton, Kyle [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Wong, Dennis [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ingersoll, David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-04-17

    We present selected results from a series of Open Stack thermal battery tests performed in FY14 and FY15 and discuss our findings. These tests were meant to provide validation data for the comprehensive thermal battery simulation tools currently under development in Sierra/Aria under known conditions compared with as-manufactured batteries. We are able to satisfy this original objective in the present study for some test conditions. Measurements from each test include: nominal stack pressure (axial stress) vs. time in the cold state and during battery ignition, battery voltage vs. time against a prescribed current draw with periodic pulses, and images transverse to the battery axis from which cell displacements are computed. Six battery configurations were evaluated: 3, 5, and 10 cell stacks sandwiched between 4 layers of the materials used for axial thermal insulation, either Fiberfrax Board or MinK. In addition to the results from 3, 5, and 10 cell stacks with either in-line Fiberfrax Board or MinK insulation, a series of cell-free “control” tests were performed that show the inherent settling and stress relaxation based on the interaction between the insulation and heat pellets alone.

  7. Guidelines on Thermal Comfort of Air Conditioned Indoor Environment

    Science.gov (United States)

    Miura, Toyohiko

    The thermal comfort of air conditioned indoor environment for workers depended, of course, on metabolic rate of work, race, sex, age, clothing, climate of the district and state of acclimatization. The attention of the author was directed to the seasonal variation and the sexual difference of comfortable temperature and a survey through a year was conducted on the thermal comfort, and health conditions of workers engaged in light work in a precision machine factory, in some office workers. Besides, a series of experiments were conducted for purpose of determinning the optimum temperature of cooling in summer time in relation to the outdoor temperature. It seemed that many of workers at present would prefer somewhat higher temperature than those before the World War II. Forty years ago the average homes and offices were not so well heated as today, and clothing worn on the average was considerably heavier.

  8. Thermal conductivity of hydrate-bearing sediments

    Science.gov (United States)

    Cortes, Douglas D.; Martin, Ana I.; Yun, Tae Sup; Francisca, Franco M.; Santamarina, J. Carlos; Ruppel, Carolyn D.

    2009-01-01

    A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate–saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate–bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces.

  9. Ecology of anuran populations inhabiting thermally stressed aquatic ecosystems, with emphasis on larval Rana pipiens and Bufo terrestris

    International Nuclear Information System (INIS)

    Nelson, D.H.

    1974-01-01

    Field and laboratory studies were conducted to determine the responses of anuran populations to thermally stressed aquatic ecosystems. Adult and larval amphibians were sampled in and around a cool arm of a 67 ha reservoir that receives high temperature effluent from a nuclear production reactor on the Savannah River Plant (SRP) in South Carolina. Patterns for some species were compared with data from nearby unheated areas and analyzed in terms of the thermal gradient (16-45 C) extending the length of the reservoir's cool arm. The adaptation to breeding during nocturnal rainfall fortuitously confers a double advantage especially to anurans breeding in thermally stressed waters. (U.S.)

  10. What is the best clothing to prevent heat and cold stress? Experiences with thermal manikin.

    Science.gov (United States)

    Magyar, Z; Tamas, R

    2013-02-01

    The present study summarizes the current knowledge of the heat and cold stress which might significantly affect military activities and might also occur among travellers who are not well adapted to weather variations during their journey. The selection of the best clothing is a very important factor in preserving thermal comfort. Our experiences with thermal manikin are also represented in this paper.

  11. Global Transcriptional Responses to Osmotic, Oxidative, and Imipenem Stress Conditions in Pseudomonas putida.

    Science.gov (United States)

    Bojanovič, Klara; D'Arrigo, Isotta; Long, Katherine S

    2017-04-01

    Bacteria cope with and adapt to stress by modulating gene expression in response to specific environmental cues. In this study, the transcriptional response of Pseudomonas putida KT2440 to osmotic, oxidative, and imipenem stress conditions at two time points was investigated via identification of differentially expressed mRNAs and small RNAs (sRNAs). A total of 440 sRNA transcripts were detected, of which 10% correspond to previously annotated sRNAs, 40% to novel intergenic transcripts, and 50% to novel transcripts antisense to annotated genes. Each stress elicits a unique response as far as the extent and dynamics of the transcriptional changes. Nearly 200 protein-encoding genes exhibited significant changes in all stress types, implicating their participation in a general stress response. Almost half of the sRNA transcripts were differentially expressed under at least one condition, suggesting possible functional roles in the cellular response to stress conditions. The data show a larger fraction of differentially expressed sRNAs than of mRNAs with >5-fold expression changes. The work provides detailed insights into the mechanisms through which P. putida responds to different stress conditions and increases understanding of bacterial adaptation in natural and industrial settings. IMPORTANCE This study maps the complete transcriptional response of P. putida KT2440 to osmotic, oxidative, and imipenem stress conditions at short and long exposure times. Over 400 sRNA transcripts, consisting of both intergenic and antisense transcripts, were detected, increasing the number of identified sRNA transcripts in the strain by a factor of 10. Unique responses to each type of stress are documented, including both the extent and dynamics of the gene expression changes. The work adds rich detail to previous knowledge of stress response mechanisms due to the depth of the RNA sequencing data. Almost half of the sRNAs exhibit significant expression changes under at least one

  12. The competition between thermal contraction and differentiation in the stress history of the moon

    Science.gov (United States)

    Kirk, Randolph L.; Stevenson, David J.

    1989-01-01

    The stress history of the moon is discussed, taking into consideration the effects of thermal contraction and differentiation. The amount of expansion caused by extracting basalt from undifferentiated lunar material is estimated taking account of the uncertainty in the knowledge of the appropriate compositions, and the resulting estimate of the expansion is used to compare the relative importance of the thermal and differentiation effects in the moon's volumetric history. The results of calculations show that differentiation is likely to be of major importance and, thus, thermal expansion is not the sole possible contributor to evolutionary changes in the lunar radius.

  13. Effect of abiotic stress under light and dark conditions on carotenoid ...

    African Journals Online (AJOL)

    The aim of this study was to observe the effect of abiotic stress under light and dark conditions on pumpkin calluses carotenoid. Plant elicitors used to create abiotic stress in this study were Polyethylene Glycol 4000 for drought stress, Jasmonic Acid and Salicylic Acid for hormones stress and Murashige and Skoog Salt for ...

  14. Radial lip seals, thermal aspects

    NARCIS (Netherlands)

    Stakenborg, M.J.L.; van Ostaijen, R.A.J.; Dowson, D.

    1989-01-01

    In this paper the influence of temperature on tne seal-snarc contact is studied, using coupled temperature-stress FEH analysis. A thermal network model is used to calculate the seal-shaft contact temperature for steady-state and transient conditions. Contact temperatures were measured under the seal

  15. Techniques for the thermal/hydraulic analysis of LMFBR check valves

    International Nuclear Information System (INIS)

    Cho, S.M.; Kane, R.S.

    1979-01-01

    A thermal/hydraulic analysis of the check valves in liquid sodium service for LMFBR plants is required to provide temperature data for thermal stress analysis of the valves for specified transient conditions. Because of the complex three-dimensional flow pattern within the valve, the heat transfer analysis techniques for less complicated shapes could not be used. This paper discusses the thermal analysis techniques used to assure that the valve stress analysis is conservative. These techniques include a method for evaluating the recirculating flow patterns and for selecting appropriately conservative heat transfer correlations in various regions of the valve

  16. Parametric Assessment of Stress Development and Cracking in Internally Cured Restrained Mortars Experiencing Autogenous Deformations and Thermal Loading

    Directory of Open Access Journals (Sweden)

    Kambiz Raoufi

    2011-01-01

    Full Text Available A finite element model is used to examine how the properties of cementitious mortar are related to the stress development in the dual ring test. The results of this investigation are used to explain the thermal cracking behavior of mixtures containing prewetted lightweight aggregates (LWA by quantifying the contribution of several material properties individually. In addition to the beneficial effects of using the LWA as an internal curing agent to reduce the autogenous shrinkage of concrete, the LWA also helps to reduce the potential for thermal cracking due to a lower elastic modulus and increased stress relaxation. The rate of stress development, age of cracking, and magnitude of the temperature drop n