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Sample records for thermal creep properties

  1. Transitional Thermal Creep of Early Age Concrete

    DEFF Research Database (Denmark)

    Hauggaard-Nielsen, Anders Boe; Damkilde, Lars; Freiesleben Hansen, Per

    1999-01-01

    Couplings between creep of hardened concrete and temperature/water effects are well-known. Both the level and the gradients in time of temperature or water content influence the creep properties. In early age concrete the internal drying and the heat development due to hydration increase the effect...... of these couplings. The purpose of this work is to set up a mathematical model for creep of concrete which includes the transitional thermal effect. The model govern both early age concrete and hardened concrete. The development of the material properties in the model are assumed to depend on the hydration process...... termed the microprestresses, which reduces the stiffness of the concrete and increase the creep rate. The aging material is modelled in an incremental way reflecting the hydration process in which new layers of cement gel solidifies in a stress free state and add stiffness to the material. Analysis...

  2. Transitional Thermal Creep of Early Age Concrete

    DEFF Research Database (Denmark)

    Hauggaard, A. B.; Damkilde, L.; Hansen, Per Freiesleben

    1999-01-01

    Couplings between creep of hardened concrete and temperature/water effects are well-known. Both the level and the gradients in time of temperature or water content influence the creep properties. In early age concrete the internal drying and the heat development due to hydration increase the effect...... of these couplings. The purpose of this work is to set up a mathematical model for creep of concrete that includes the transitional thermal effect. The model governs both early age concrete and hardened concrete. The development of the material properties in the model is assumed to depend on the hydration process...... termed the microprestresses, which reduce the stiffness of the concrete and increase the creep rate. The aging material is modeled in an incremental way reflecting the hydration process in which new layers of cement gel solidify in a stress free state and add stiffness to the material. Analysis...

  3. Creep damage and hardness properties for 9Cr steel by SP-creep test technique

    Energy Technology Data Exchange (ETDEWEB)

    Baek, Seung Se; Yu, Hyo Sun; Kwon, Il Hyun; Chung, Se Hee [Chonbuk National Univ., Jeonju (Korea, Republic of); Lyu, Dae Young; Kim, Jeong Ki [Jeonju Technical College, Jeonju (Korea, Republic of)

    2001-07-01

    It has recently been raised main issue how solve the problem of insufficient energy. One of the solution is to increase the thermal efficiency of power generation system. For the purpose of high efficiency, it is necessary to increase the steam temperature and pressure. So, the use of modified 9{approx}12%Cr steel having superior creep rupture strength and oxidation resistance is required to endure such severe environment. The evaluation of creep properties of those heat resistance material is very important to secure the reliability of high temperature and pressure structural components. Since creep properties are determined by microstructural change such as carbide precipitation and coarsening. It is certain that there are some relationship between creep properties and hardness affected by microstructure. In this study, SP-creep ruptured test for newly developed 9Cr steel being used as boiler valve material was performed, and creep properties of the material were evaluated. Also, hardness test were performed and hardness results were related to the creep properties such as LMP and creep strength to verify the availability of SP-creep test as creep test method.

  4. Study on impact properties of creep-resistant steel thermally simulated heat affected zone

    Directory of Open Access Journals (Sweden)

    Mitrović Radivoje M.

    2012-01-01

    Full Text Available The steam pipe line (SPL and steam line material, along with its welded joints, subject to damage that accumulates during operation in coal power plants. As a result of thermal fatigue, dilatation of SPL at an operating temperature may lead to cracks initiation at the critical zones within heat affected zone (HAZ of steam pipe line welded joints. By registration of thermal cycle during welding and subsequent HAZ simulation is possible to obtain target microstructure. For the simulation is chosen heat resisting steel, 12H1MF (designation 13CrMo44 according to DIN standard. From the viewpoint of mechanical properties, special attention is on impact toughness mostly because very small number of available references. After simulation of single run and multi run welding test on instrumented Charpy pendulum. Metallographic and fractographic analysis is also performed, on simulated 12H1MF steel from service and new, unused steel. The results and correlation between microstructure and impact toughness is discussed, too.

  5. Biaxial Thermal Creep of Alloy 617 and Alloy 230 for VHTR Applications

    Energy Technology Data Exchange (ETDEWEB)

    Mo, Kun; Lv, Wei; Tung, Hsiao-Ming; Yun, Di; Miao, Yinbin; Lan, Kuan-Che; Stubbins, James F.

    2016-05-18

    In this study, we employed pressurized creep tubes to investigate the biaxial thermal creep behavior of Inconel 617 (alloy 617) and Haynes 230 (alloy 230). Both alloys are considered to he the primary candidate structural materials for very high-temperature reactors (VITITRs) due to their exceptional high-temperature mechanical properties. The current creep experiments were conducted at 900 degrees C for the effective stress range of 15-35 MPa. For both alloys, complete creep strain development with primary, secondary, and tertiary regimes was observed in all the studied conditions. Tertiary creep was found to he dominant over the entire creep lives of both alloys. With increasing applied creep stress, the fraction of the secondary creep regime decreases. The nucleation, diffusion, and coarsening of creep voids and carbides on grain boundaries were found to be the main reasons for the limited secondary regime and were also found to be the major causes of creep fracture. The creep curves computed using the adjusted creep equation of the form epsilon= cosh 1(1 rt) + P-sigma ntm agree well with the experimental results for both alloys at die temperatures of 850-950 degrees C.

  6. Tracing Thermal Creep Through Granular Media

    Science.gov (United States)

    Steinpilz, Tobias; Teiser, Jens; Koester, Marc; Schywek, Mathias; Wurm, Gerhard

    2017-08-01

    A temperature gradient within a granular medium at low ambient pressure drives a gas flow through the medium by thermal creep. We measured the resulting air flow for a sample of glass beads with particle diameters between 290 μ m and 420 μ m for random close packing. Ambient pressure was varied between 1 Pa and 1000 Pa. The gas flow was quantified by means of tracer particles during parabolic flights. The flow varies systematically with pressure between 0.2 cm/s and 6 cm/s. The measured flow velocities are in quantitative agreement to model calculations that treat the granular medium as a collection of linear capillaries.

  7. Some numerical approaches of creep, thermal shock, damage and ...

    Indian Academy of Sciences (India)

    Some numerical approaches of creep, thermal shock, damage and delayed failure of ceramics and refractories ... Ceramic; refractories; creep; thermal stock; damage; delayed failure; numerical simulation. Abstract. Numerical simulation is now very often used to predict the behaviour of components in service conditions.

  8. Thermal creep properties of Ti-stabilized DIN 1.4970 (15-15Ti) austenitic stainless steel pressurized cladding tubes

    Science.gov (United States)

    Cautaerts, Niels; Delville, Rémi; Dietz, Wolfgang; Verwerft, Marc

    2017-09-01

    This paper presents a large database of thermal creep data from pressurized unirradiated DIN 1.4970 Ti-stabilized austenitic stainless steel (i.e. EN 1515CrNiMoTiB or ;15-15Ti;) cladding tubes from more than 1000 bi-axial creep tests conducted during the fast reactor R&D program of the DeBeNe (Deutschland-Belgium-Netherlands) consortium between the 1960's to the late 1980's. The data comprises creep rate and time-to-rupture between 600 and 750 °C and a large range of stresses. The data spans tests on material from around 70 different heats and 30 different melts. Around one fourth of the data was obtained from cold worked material, the rest was obtained on cold worked + aged (800 °C, 2 h) material. The data are graphically presented in log-log graphs. The creep rate data is fit with a sinh correlation, the time to rupture data is fit with a modified exponential function through the Larson-Miller parameter. Local equivalent parameters to Norton's law are calculated and compared to literature values for these types of steels and related to possible creep mechanisms. Some time to rupture data above 950 °C is compared to literature dynamic recrystallization data. Time to rupture data between 600 and 750 °C is also compared to literature data from 316 steel. Time to rupture was correlated directly to creep rate with the Monkman-Grant relationship at different temperatures.

  9. Influence of stress on creep deformation properties of 9-12Cr ferritic creep resistant steels

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, K.; Sawada, K.; Kushima, H. [National Institute for Materials Science (Japan)

    2008-07-01

    Creep deformation property of 9-12Cr ferritic creep resistant steels was investigated. With decrease in stress, a magnitude of creep strain at the onset of accelerating creep stage decreased from about 2% in the short-term to less than 1% in the longterm. A time to 1% total strain was observed in the transient creep stage in the short term regime, however, it shifted to the accelerating creep stage in the long-term regime. Life fraction of the times to 1% creep strain and 1% total strain tended to increase with decrease in stress. Difference in stress dependence of the minimum creep rate was observed in the high- and low-stress regimes with a boundary condition of 50% of 0.2% offset yield stress. Stress dependence of the minimum creep rate in the high stress regime was equivalent to a strain rate dependence of the flow stress evaluated by tensile test, and a magnitude of stress exponent, n, in the high stress regime decreased with increase in temperature from 20 at 550 C to 10 at 700 C. On the other hand, n value in the low stress regime was about 5, and creep deformation in the low stress regime was considered to be controlled by dislocation climb. Creep rupture life was accurately predicted by a region splitting method by considering a change in stress dependence of creep deformation. (orig.)

  10. The Creep Properties of Fine Sandstone under Uniaxial Tensile Stress

    Directory of Open Access Journals (Sweden)

    Jiang Haifei

    2015-09-01

    Full Text Available A graduated uniaxial direct tensile creep test for fine sandstone is conducted by adopting a custom-designed direct tensile test device for rock. The experiment shows that the tensile creep of fine sandstone has similar creep curve patterns to those of compression creep, while the ratios of the creep strain to the total strain obtained in the tensile tests are substantially higher than those obtained for similar compression tests, which indicates that the creep ability of rock in the tensile process is higher than that in the uniaxial compression process. Based on the elastic modulus in the approximately linear portion of the obtained isochronous stress-strain curves of the tensile creep, the time dependence of the elasticity modulus for the Kelvin model is evaluated, and a revised generalized Kelvin model is obtained by substitution into the generalized Kelvin model. A new viscousplastic model is proposed to describe the accelerated creep properties, and this model is combined in series with the revised generalized Kelvin model to form a new nonlinear viscoelastic-plastic creep model that can describe the properties of attenuation creep, steady creep, and accelerated creep. Comparison of the test and theoretical curves demonstrates that they are nearly identical, which verifies the performance of the model.

  11. Microstructure and creep behaviour of plasma sprayed yttria stabilized zirconia thermal barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Soltani, R.; Coyle, T.W.; Mostaghimi [Toronto Univ., ON (Canada)

    2008-07-01

    The purpose of this study was to determine the creep/sintering characteristics of thermally sprayed zirconia coatings and attempt to understand the influence of microstructure on the creep resistance of deposits. The major modification, compared with more typical practice, was employment of powder feedstock with agglomerated sub-micron size particles (Nanox), which is compared to one of the best commercially available powders (HOSP). Thick plasma sprayed coatings were prepared and their physical and mechanical properties were characterized. Creep/sintering experiments were then conducted to investigate the response of the materials when exposed to high temperatures under load. The results showed that it could be possible to correlate the splat thickness to the creep behaviour of the coatings. (orig.)

  12. Creep properties and microstructure of the new wrought austenitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Vlasak, T.; Hakl, J.; Novak, P. [SVUM a.s., Prague (Czech Republic); Vyrostkova, A. [Slovak Academy of Sciences, Kosice (Slovakia). Inst. of Materials Research

    2010-07-01

    The contribution is oriented on the new wrought austenitic steel BGA4 (Cr23Ni15Mn6Cu3W1.5NbVMo) developed by the British Corus Company. Our main aim is to present creep properties studied in SVUM a.s. Prague during COST 536 programme. The dependencies of the creep strength, strength for specific creep strain and minimum creep strain rate were evaluated on the basis of long term creep tests carried out at temperature interval (625; 725) C. Important part of a paper is metallographic analysis. (orig.)

  13. Effect of Post-Weld Heat Treatment on Creep Rupture Properties of Grade 91 Steel Heavy Section Welds

    Energy Technology Data Exchange (ETDEWEB)

    Li, Leijun

    2012-11-02

    This project will conduct a systematic metallurgical study on the effect of post-weld heat treatment (PWHT) on the creep rupture properties of P91 heavy section welds. The objective is to develop a technical guide for selecting PWHT parameters, and to predict expected creep-rupture life based on the selection of heat treatment parameters. The project consists of four interdependent tasks: Experimentally and numerically characterize the temperature fields of typical post-weld heat treatment procedures for various weld and joint configurations to be used in Gen IV systems. Characterize the microstructure of various regions, including the weld fusion zone, coarse-grain heat-affected zone, and fine-grain heat affected zone, in the welds that underwent the various welding and PWHT thermal histories. Conduct creep and creep-rupture testing of coupons extracted from actual and physically simulated welds. Establish the relationship among PWHT parameters, thermal histories, microstructure, creep, and creep-rupture properties.

  14. Degradation of mechanical properties of CrMo creep resistant steel operating under conditions of creep

    Directory of Open Access Journals (Sweden)

    J. Michel

    2012-01-01

    Full Text Available Mechanical properties of a steam tube made of CrMo creep resistant steel are analysed in this contribution after up to 2,6•105 hours service life in creep conditions at temperature 530 °C and calculated stress level in the tube wall 46,5 MPa. During service life there were in the steel gradual micro structure changes, fi rst pearlite spheroidization, precipitation, coaugulation and precipitate coarsening. Nevertheless the strength and deformation properties of the steel (Re, Rm, A5, Z, and the resistance to brittle fracture and the creep strength limit, were near to unchanged after 2,1•105 hours in service. The steam tube is now in service more than 2,6•105 h.

  15. MICROSTRUCTURE AND MECHANICAL PROPERTIES DEGRADATION OF CrMo CREEP RESISTANT STEEL OPERATING UNDER CREEP CONDITIONS

    Directory of Open Access Journals (Sweden)

    Ján Micheľ

    2011-07-01

    Full Text Available In this contribution microstructure degradation of a steam tube is analysed. The tube is made of CrMo creep resistant steel and was in service under creep conditions at temperature 530°C and calculated stress level in the tube wall 46.5 MPa. During service life in the steel gradual micro structure changes were observed, first pearlite spheroidization, precipitation, coagulation and precipitate coarsening. Despite the fact that there were evident changes in the micro structure the strength and deformation properties of the steel (Re, Rm, A5, Z, the resistance to brittle fracture and the creep strength limit, were near to unchanged after 2.1x10 5 hours in service. The steam tube is now in service more than 2.6x10 5 h.

  16. Experimental Study on the Porosity Creep Properties of Broken Limestone

    Directory of Open Access Journals (Sweden)

    Li Shun-cai

    2016-01-01

    Full Text Available In the underground engineering, the long-term stability of the surrounding rocks (especially the broken rocks containing water and the ground settlement resulted from the seepage-creep coupling above goaf have been the important research subjects concerning the deep mining. For the broken rock, its porosity is an important structural parameter determining its creep properties, and the porosity change rate is more superior to describe the creep characteristics compared with the strain change rate at a certain direction. In this paper, MTS815.02 Rock Mechanics Test System is used to carry out the creep experiments on water-saturated broken limestone, and then the time curves of porosity and of the porosity change rate are obtained. By regression, we have got the relation equation between the porosity change rate with the instant porosity and the stress level during the creep. The study indicates that when the stress retains a constant level, the relation between the porosity change rate and the instant porosity can be fitted with a cubical polynomial. The obtained creep relation equation between the porosity change rate and the instant porosity and the instant stress provides a necessary state equation for studying the coupling between the seepage and the creep of the broken rock. Furthermore, the seepage in the broken rock has been verified to satisfy the Forchheimer’s non-Darcy flow according to our previous studies, and its seepage properties, k, β and ca can all be expressed respectively as the polynomial of the porosity, so, by combining with these three state equations we have obtained the four essential state equations for solving the coupling problems of the seepage and the creep for the broken rocks.

  17. Thermal activated grain boundary creep in polycrystalline copper ...

    African Journals Online (AJOL)

    Creep deformation in metals and alloys at intermediate temperatures and low stresses are attributed to power-law and diffusion mechanisms. ... By superposition of the rate equations, the net strain rate is determined as the sum of three independent creep mechanisms of Cobble diffusion creep, gra-in boundary sliding and ...

  18. Thermal creep and stress-affected precipitation of 20% cold-worked 316 stainless steel

    Science.gov (United States)

    Puigh, R. J.; Lovell, A. J.; Garner, F. A.

    1984-05-01

    Measurements of the thermal creep of 20% cold-worked 316 stainless stpel have been performed for temperatures from 593 to 760°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.

  19. Creep and thermal rounding close to the elastic depinning threshold.

    Science.gov (United States)

    Purrello, V H; Iguain, J L; Kolton, A B; Jagla, E A

    2017-08-01

    We study the slow stochastic dynamics near the depinning threshold of an elastic interface in a random medium by solving a particularly suited model of hopping interacting particles that belongs to the quenched-Edwards-Wilkinson depinning universality class. The model allows us to compare the cases of uniformly activated and Arrhenius activated hops. In the former case, the velocity accurately follows a standard scaling law of the force and noise intensity with the analog of the thermal rounding exponent satisfying a modified "hyperscaling" relation. For the Arrhenius activation, we find, both numerically and analytically, that the standard scaling form fails for any value of the thermal rounding exponent. We propose an alternative scaling incorporating logarithmic corrections that appropriately fits the numerical results. We argue that this anomalous scaling is related to the strong correlation between activated hops that, alternated with deterministic depinning-like avalanches, occur below the depinning threshold. We rationalize the spatiotemporal patterns by making an analogy of the present model in the near-threshold creep regime with some well-known models with extremal dynamics, particularly the Bak-Sneppen model.

  20. Creep and thermal rounding close to the elastic depinning threshold

    Science.gov (United States)

    Purrello, V. H.; Iguain, J. L.; Kolton, A. B.; Jagla, E. A.

    2017-08-01

    We study the slow stochastic dynamics near the depinning threshold of an elastic interface in a random medium by solving a particularly suited model of hopping interacting particles that belongs to the quenched-Edwards-Wilkinson depinning universality class. The model allows us to compare the cases of uniformly activated and Arrhenius activated hops. In the former case, the velocity accurately follows a standard scaling law of the force and noise intensity with the analog of the thermal rounding exponent satisfying a modified "hyperscaling" relation. For the Arrhenius activation, we find, both numerically and analytically, that the standard scaling form fails for any value of the thermal rounding exponent. We propose an alternative scaling incorporating logarithmic corrections that appropriately fits the numerical results. We argue that this anomalous scaling is related to the strong correlation between activated hops that, alternated with deterministic depinning-like avalanches, occur below the depinning threshold. We rationalize the spatiotemporal patterns by making an analogy of the present model in the near-threshold creep regime with some well-known models with extremal dynamics, particularly the Bak-Sneppen model.

  1. A Numerical Procedure to Obtain the Creep Parameters of the Thermal Barrier Coating

    Directory of Open Access Journals (Sweden)

    Shifeng Wen

    2014-05-01

    Full Text Available Three-point bending creep test was used to understand the creep behavior of typical thin film/substrate systems—thermal barrier coating (TBC systems. Firstly, a simplified model, which does not consider the local effect, has been set up to get an analytical relationship. The important result is that creep stress exponent of materials is equal to the creep load exponent of the steady-state deflection rate of BC specimens. Secondly, in order to consider the local effect of bending, the finite element method (FEM has been carried out. FEM calculation shows that there is a steady stage of the creep deflection under a constant applied load. And the exponent of the steady-state creep deflection rate to the applied load is found to be equal to the creep stress exponent of materials. The creep constant of the materials can be obtained by a set of trials with assumed creep constants of materials and can be finally determined by the best fit method. Finally, the finite element results show that the influences of the friction, the thickness of TBCs, and the modulus ratio of TBC to the substrate on stress distribution are important.

  2. Effect of matrix hardness on the creep properties of a 12CrMoVNb steel

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y.S.; Yu, J. [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Materials Science and Engineering

    1999-09-01

    Using a creep-ductile 12CrMoVNb steel, constant-load creep tests were conducted in air at 650 C, and the effects of matrix hardness on the creep properties were investigated. Specimens with a matrix hardness (Rc) of 30, 25, and 20 were prepared using different tempering conditions. The creep behaviors were well described by the power-law creep equation, with the stress exponents of strain rate (n) and rupture time ({chi}) decreasing with matrix hardness. Rupture-time analyses showed that creep rupture occurred by the nucleation of creep cavities on second-phase particles and growth by creep flow of the surrounding matrix. A hardness decrease tends to lower the rupture time and increase the strain rate ({dot {var_epsilon}}), and the effect of hardness was quite distinct at high applied stresses due to the short creep times, but not so at low applied stresses due to elongated creep times. After 10{sup 4} hours, there were almost no effects. The hardness decrease during the creep test was more severe for the specimens with higher hardness and was also more severe in the gage section than in the head section, the latter due to the stress-assisted diffusion in the coarsening of carbides. Microstructural examinations showed that subgrain boundaries grew during creep, and equiaxed carbide particles coarsened during the creep test, the rates of coarsening being greater for specimens with a higher hardness.

  3. The effect of different content of Al, RE and Si element on the microstructure, mechanical and creep properties of Mg-Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Meshinchi Asl, Kaveh, E-mail: kaveh_mesh@yahoo.co.uk [School of Materials Science and Engineering, Clemson University, Clemson, SC 29634 (United States); Tari, Alireza; Khomamizadeh, Farzad [Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Tehran (Iran, Islamic Republic of)

    2009-10-15

    The effect of Al content and Si addition on the microstructural and creep properties of Mg-Al-RE alloys was investigated in this study. The steady state creep rates were specified and it was found that the creep behavior of the alloy, which is dependent on the stability of the near grain boundary microstructure, was improved by the RE and Si addition. For the AZ91 alloy, the results indicate a mixed mode of creep behavior, with some grain boundary effects contributing to the overall behavior. However for the RE and Si added samples, sliding of grain boundaries was greatly suppressed and the dislocation climb controlled creep was the dominant deformation mechanism. Analysis of creep rates also showed that the Si addition resulted in formation of Mg{sub 2}Si particles (in Chinese Script form) which have a high thermal stability. After Si addition the steady state creep rates were decreased and the creep resistance was improved. This was due to formation of Mg{sub 2}Si particles which change the deformation mechanism at elevated temperatures. Addition of cerium rich misch metal to AZ91 alloy resulted in formation of needle shape particles, which also had a very high thermal stability, providing increased creep resistance and superior mechanical properties compared to AZ91 magnesium alloy. As a result, the grain boundaries were less susceptible for grain boundary sliding at high temperatures. By decreasing the Al content of the alloy having 2 wt.% RE from 9 to 4 wt.%, the steady state creep rate was also decreased compared to AZ91 + 2% RE alloy. The fracture mechanism was also investigated and it was observed that although the Si addition improves the creep resistance, it can make the alloy brittle at ambient temperature.

  4. Post Preloading Creep Properties of Highly Compressible Harbor Marine Sediments

    Directory of Open Access Journals (Sweden)

    Franciscus Xaverius Toha

    2017-07-01

    Full Text Available A laboratory experimental research in creep behavior of soft clay marine sediments was done to investigate creep strain under reloading. A total of 52 oedometer tests were carried out with 16 slurry sediment samples subjected to cycles of unloading at preload removal pressure and reloading to higher design pressures. Common practice as well as more recent advanced methods of creep deformation analysis were used to refine the predictions. The study indicates that although preloading substantially reduces post construction creep, the analysis is very sensitive to creep indices at slight overconsolidation and the resulting creep may not be negligible at previously established limits of primary to secondary compression ratios.

  5. Some numerical approaches of creep, thermal shock, damage and ...

    Indian Academy of Sciences (India)

    Unknown

    Ecole des Mines de Paris – Centre des Matériaux P.M. Fourt, B.P. 87, 91003 EVRY Cedex, France. Abstract. Numerical simulation is now very often used to predict the behaviour of components in service conditions. This paper is interested in specific approaches concerning ceramic materials and refractories. Creep.

  6. Creep Properties of Walikukun (Schouthenia ovata Timber Beams

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    Ali Awaludin

    2016-09-01

    Full Text Available This study presents an evaluation of creep constants of Walikukun (Schoutheniaovata timber beams when rheological model of four solid elements, which is obtained byassembling Kelvin and Maxwell bodies in parallel configuration, was adopted. Creep behaviorobtained by this method was further discussed and compared with creep behavior developedusing phenomenological model of the previous study. Creep data of previous study was deformationmeasurement of Walikukun beams having cross-section of 15 mm by 20 mm with a clearspan of 550 mm loaded for three weeks period under two different room conditions: with andwithout Air Conditioner. Creep behavior given by both four solid elements model and phenomenological(in this case are power functions had good agreement during the period of creepmeasurement, but they give different prediction of creep factor beyond this period. The powerfunction of phenomenological model could give a reasonable creep prediction, while for the foursolid elements model a necessary modification is required to adjust its long-term creep behavior.

  7. Effect of Long-Term Thermal Exposures on Microstructure and Impression Creep in 304HCu Grade Austenitic Stainless Steel

    Science.gov (United States)

    Dash, Manmath Kumar; Karthikeyan, T.; Mythili, R.; Vijayanand, V. D.; Saroja, S.

    2017-10-01

    This paper presents the results of microstructural evolution and mechanical properties in 304H Cu grade austenite stainless (SS 304HCu) during long-term exposure at high temperatures. The predicted phase composition as a function of temperature obtained using JMatPro® software was confirmed in conjunction with the microstructural evolution characterized by scanning and transmission electron microscopy. Microstructures revealed primary Nb(C,N), M23C6 precipitates at γ-grain boundaries, fine secondary Nb(C,N) intragranular carbides, and a uniform precipitation of <40-nm-sized spherical Cu-rich phase after thermal aging for 10,000 hours at 903 K (630 °C). The impression creep rate at 300 MPa increased by a factor of 20 between 873 K and 923 K (600 °C and 650 °C). The creep rate at 903 K (630 °C) was found to moderately reduce with aging time, signifying the role of Cu-rich phase in improving the creep resistance. The deformation zones and the recrystallization behavior of the plastic zone in creep tested specimen was assessed using Electron backscatter diffraction technique.

  8. Longitudinal Heat Conduction Effects on a Conjugate Thermal Creep Flow in a Microchannel

    Science.gov (United States)

    Monsivais, Ian; Lizardi, José J.; Méndez, Federico

    2017-11-01

    In this work, we use asymptotic and numerical techniques to analyze the conjugate heat transfer between a rarified gas flow and the lower wall of a thin horizontal microchannel exposed to a uniform heat flux, when the laminar motion of the gas is only caused by the thermal creep or transpiration effect on the lower wall of the microchannel. Usually, it is enough to impose a linear temperature profile as a boundary condition to produce the thermal creep effect. However, we prefer to avoid this arbitrary simplification taking into account that for real cases, the temperature profile at the lower wall can be unknown. We can assume then that the lower face of this heat sink with finite thermal conductivity and thickness is exposed to a uniform heat flux, while the upper wall of the microchannel is subject to a well-known prescribed thermal boundary condition. The resulting governing equations are written in dimensionless form, assuming that the Reynolds number associated with the characteristic velocity of the thermal creep and the aspect ratio of the microchannel, are both very small. Thermal creep effect depends strongly on a dimensionless conjugate parameter that represents the competition between the heat driven by the gas and the heat that longitudinally conducts the lower wall.

  9. Survey of creep properties of copper intended for nuclear waste disposal

    Energy Technology Data Exchange (ETDEWEB)

    Andersson-Oestling, Henrik C.M. (Swerea KIMAB AB, Stockholm (Sweden)); Sandstroem, Rolf (Materials Science and Engineering, School of Industrial Engineering and Management, Royal Inst. of Technology (KTH), Stockholm (Sweden))

    2009-12-15

    Creep in copper for application in canisters for nuclear waste disposal is surveyed. The importance of phosphorus doping to obtain adequate properties is demonstrated experimentally as well as explained theoretically. Creep tests results for electron beam and friction stir welds are compared. The latter type of welds has properties that are close to those of parent metal. The relation between slow strain rate tensile and creep is described. Fundamental constitutive equations are presented that are suitable for finite element modelling. These equations are used to simulate creep deformation in canisters

  10. Effect of Ti content on creep properties of Ni-base single crystal superalloys

    Science.gov (United States)

    Choi, Baig Gyu; Kim, In Soo; Hong, Hyun Uk; Do, Jeonghyeon; Jung, Joong Eun; Jo, Chang Yong

    2017-09-01

    The effect of Ti content on the creep properties and microstructures of experimental Ni-base single crystal superalloys has been investigated. The experimental alloys were designed to provide better high temperature properties than the commercial single crystal alloy CMSX-4. The creep properties of the experimental alloys, Alloy 2 and Alloy 3, were superior to those of CMSX-4. Alloy 3 showed a longer creep life than Alloy 2 at 900 °C and 950 °C, while it has similar creep life with Alloy 2 at 982 °C. Transmission electron microscopy micrographs of the experimental alloys after the creep test showed distinct deformation features as a function of temperature and Ti content. The dissociation of dislocations into partial dislocations with stacking faults in Alloy 3 was found to improve resistance to creep deformation at 950 °C. The effect of Ti on the creep deformation mechanism was not evident at 982 °C, which resulted in similar creep properties in both experimental alloys. The transition of the γ' cutting mechanism from dislocations coupled with stacking faults to anti-phase boundary coupled pairs occurred both in Alloy 2 and Alloy 3. However, the transition temperature was higher in Alloy 3 than in Alloy 2 because of the difference in Ti contents.

  11. Microstructure and Creep Property of a GH4169 Nickel-based Superalloy

    Directory of Open Access Journals (Sweden)

    LIU Chen

    2017-06-01

    Full Text Available By means of direct aging (DA heat treatment, creep properties measurement and microstructure observation, the microstructure and creep behaviors of the GH4169 superalloy were investigated. Results show that the microstructure of the alloy consists of γ, γ', γ" and δ phases, and the coherent interfaces exist between the phases. The creep life of the alloy at 660℃/700 MPa is predicted to be 123h, and 39h at 680℃/700MPa. Under the testing temperature and stress range, the creep activation energy of the alloy is calculated to be 588.0 kJ/mol. The deformation mechanisms of the alloy during creep are dislocation slipping and twin deformation. The granular carbides precipitated along the grain boundaries may restrain the slipping of the boundary, which is thought to be the main reason of the good creep resistance. As the creep goes on, the slipping dislocations activated within the grains are hindered and blocked by the boundaries to cause the stress concentration, which may promote the initiation and propagation of the crack occurring along the boundaries perpendicular to the stress axis, when the value of stress concentration is higher than the bonding strength of the boundaries, up to the occurrence of creep fracture. This is thought to be the fracture mechanism of alloy during creep.

  12. Thermal fatigue and creep evaluation for the bed in tritium SDS

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Woo-seok, E-mail: wschoi@kaeri.re.kr [Korea Atomic Energy Research Institute, Yuseong, Daejeon (Korea, Republic of); Park, Chang-gyu [Korea Atomic Energy Research Institute, Yuseong, Daejeon (Korea, Republic of); Ju, Yong-sun [KOASIS, Yuseong, Daejeon (Korea, Republic of); Kang, Hyun-goo; Jang, Min-ho; Yun, Sei-hun [National Fusion Research Institute, Yuseong, Daejeon (Korea, Republic of)

    2016-11-01

    Highlights: • To evaluate the integrity of the ITER tritium SDS bed, three kinds of assessments were conducted. • The structural analysis showed that the stress induced from the thermal load and the internal pressure is within the design stress intensity. • The combined fatigue and creep assessment was also performed according to the procedure of ASME code Subsection NH. • A new operation procedure to obtain more integrity margin was recommended. • The other operation procedure could be considered which makes the rapid operation possible giving up the marginal integrity. - Abstract: The primary vessel of ITER tritium SDS bed is made of stainless steel. It is heated beyond 500 °C to desorb tritium. During this process the primary vessel is subject to thermal stress. And it is also subject to thermal fatigue by the iterative process of absorption and desorption. In addition, its operation temperature range is in the thermal creep temperature region. Therefore, the tritium SDS bed should have sufficient design stress intensity under the high temperature operating conditions. It should also be free of damage due to fatigue during the design life. Thermal analysis and structural analysis was performed using a finite element method to calculate the temperature and the stress distribution of the ITER tritium SDS bed due to the internal pressure and thermal loads. The thermal fatigue and creep effects were also evaluated since the tritium SDS bed was heated to hot temperature region where creep occurs. Based on the distribution of the primary stress and secondary stress results, two evaluation cross-sections were selected. The evaluation showed that the calculated value on the cross-sections satisfied all of the limits of the design code requirements.

  13. Microstructure, creep properties, and rejuvenation of service-exposed alloy 713C turbine blades

    Science.gov (United States)

    Maccagno, T. M.; Koul, A. K.; Immarigeon, J.-P.; Cutler, L.; Allem, R.; L'Espérance, G.

    1990-12-01

    A study was carried out on the microstructure and creep properties of aero engine first-stage turbine blades made from Alloy 713C nickel-base superalloy. Results are reported for new blades, blades in two service-exposed conditions, and service-exposed blades subjected to one of three rejuvenation treatments: a recoating heat treatment, a hot isostatic pressing (HIP) + recoating heat treatment, and a HIP + controlled cooling + recoating heat treatment. The blade microstructure undergoes significant change during service, and this leads to a loss in creep properties exhibited by specimens machined from the blade airfoils. Good correlations were observed between the rupture time and the amount of blade airfoil untwist and between the minimum creep rate and the amount of untwist. The recoating heat treatment and the HIP + controlled cooling + recoating treatment were moderately successful in restoring the microstructure and creep properties of the service-exposed blades. In comparison, the HIP + recoating treatment was very successful in rejuvenating creep properties but only for blades having a chemical composition with a lower propensity to form σ phase. For the blades with an unfavorable composition, σ phase was found to form preferentially near the grain boundaries during creep testing, and this had a detrimental effect on the creep properties. Nonetheless, the degree of rejuvenation for these blades was always at least as good as that obtained through the recoating heat treatment alone.

  14. Study of the temperature dependence of the uniaxial creep property of similar material of new soft rock

    Science.gov (United States)

    Wang, Y. Y.; Wu, Y.; Fan, X. Y.; Zhang, J. L.; Guo, P.; Li, J. G.

    2017-11-01

    Using the experimental method, the experimental research of creep properties were conducted under different temperature ranging from 10°C to 60°C. The similar material of new soft rock consists of paraffin, which can obtain that the deformation contains the instantaneous elastic deformation and creep deformation through the uniaxial creep experimental results. And thus the increase of temperature has great influence on the creep characteristics of similar soft rock according to the creep curve of similar soft rock at 10°C to 60°C. With the increase of temperature, the slope of the stress-strain curve of similar soft rock is increasing, while the average of the creep modulus is decreasing, which means that the capacity of resist deformation is reduced. Therefore, the creeps law of high-temperature and short-time can be shown the creep phenomenon of low-temperature and long-time, and further shorten the creep experimental cycle.

  15. 3-D stochastic finite elements for thermal creep analysis of piping structures with spatial material inhomogeneities

    NARCIS (Netherlands)

    Appalanaidu, Y.; Roy, A.; Gupta, S.

    2017-01-01

    A stochastic finite element-based methodology is developed for creep damage assessment in pipings carrying high-temperature fluids. The material properties are assumed to be spatially randomly inhomogeneous and are modelled as 3-D non-Gaussian fields. A spectral-based approach for random field

  16. Thermal Properties Measurement Report

    Energy Technology Data Exchange (ETDEWEB)

    Carmack, Jon [Idaho National Lab. (INL), Idaho Falls, ID (United States); Braase, Lori [Idaho National Lab. (INL), Idaho Falls, ID (United States); Papesch, Cynthia [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hurley, David [Idaho National Lab. (INL), Idaho Falls, ID (United States); Tonks, Michael [Idaho National Lab. (INL), Idaho Falls, ID (United States); Zhang, Yongfeng [Idaho National Lab. (INL), Idaho Falls, ID (United States); Gofryk, Krzysztof [Idaho National Lab. (INL), Idaho Falls, ID (United States); Harp, Jason [Idaho National Lab. (INL), Idaho Falls, ID (United States); Fielding, Randy [Idaho National Lab. (INL), Idaho Falls, ID (United States); Knight, Collin [Idaho National Lab. (INL), Idaho Falls, ID (United States); Meyer, Mitch [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-08-01

    The Thermal Properties Measurement Report summarizes the research, development, installation, and initial use of significant experimental thermal property characterization capabilities at the INL in FY 2015. These new capabilities were used to characterize a U3Si2 (candidate Accident Tolerant) fuel sample fabricated at the INL. The ability to perform measurements at various length scales is important and provides additional data that is not currently in the literature. However, the real value of the data will be in accomplishing a phenomenological understanding of the thermal conductivity in fuels and the ties to predictive modeling. Thus, the MARMOT advanced modeling and simulation capability was utilized to illustrate how the microstructural data can be modeled and compared with bulk characterization data. A scientific method was established for thermal property measurement capability on irradiated nuclear fuel samples, which will be installed in the Irradiated Material Characterization Laboratory (IMCL).

  17. Thermal properties of nanofluids.

    Science.gov (United States)

    Philip, John; Shima, P D

    2012-11-15

    Colloidal suspensions of fine nanomaterials in the size range of 1-100 nm in carrier fluids are known as nanofluids. For the last one decade, nanofluids have been a topic of intense research due to their enhanced thermal properties and possible heat transfer applications. Miniaturization and increased operating speeds of gadgets warranted the need for new and innovative cooling concepts for better performance. The low thermal conductivity of conventional heat transfer fluid has been a serious impediment for improving the performance and compactness of engineering equipments. Initial studies on thermal conductivity of suspensions with micrometer-sized particles encountered problems of rapid settling of particles, clogging of flow channels and increased pressure drop in the fluid. These problems are resolved by using dispersions of fine nanometer-sized particles. Despite numerous experimental and theoretical studies, it is still unclear whether the thermal conductivity enhancement in nanofluids is anomalous or within the predictions of effective medium theory. Further, many reports on thermal conductivity of nanofluids are conflicting due to the complex issues associated with the surface chemistry of nanofluids. This review provides an overview of recent advances in the field of nanofluids, especially the important material properties that affect the thermal properties of nanofluids and novel approaches to achieve extremely high thermal conductivities. The background information is also provided for beginners to better understand the subject. Copyright © 2012 Elsevier B.V. All rights reserved.

  18. Mechanism-based modeling of solute strengthening: application to thermal creep in Zr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Tome, Carlos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wen, Wei [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Capolungo, Laurent [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-08-01

    This report focuses on the development of a physics-based thermal creep model aiming to predict the behavior of Zr alloy under reactor accident condition. The current models used for this kind of simulations are mostly empirical in nature, based generally on fits to the experimental steady-state creep rates under different temperature and stress conditions, which has the following limitations. First, reactor accident conditions, such as RIA and LOCA, usually take place in short times and involve only the primary, not the steady-state creep behavior stage. Moreover, the empirical models cannot cover the conditions from normal operation to accident environments. For example, Kombaiah and Murty [1,2] recently reported a transition between the low (n~4) and high (n~9) power law creep regimes in Zr alloys depending on the applied stress. Capturing such a behavior requires an accurate description of the mechanisms involved in the process. Therefore, a mechanism-based model that accounts for the evolution with time of microstructure is more appropriate and reliable for this kind of simulation.

  19. Thermal properties examples

    OpenAIRE

    Bantle, Michael

    2017-01-01

    Thermal properties of selected organic products were investigated using novel DSC technique and methods of determination. The report includes determination of freezing temperatures, glass transition temperatures, amount of ice, and end of freezing point, heat capacity and thermal conductivity for selected cases. One part of the experimental work was devoted to investigate the difference between oils extracted from organic and conventional salmon. The main aim of the investigation was to u...

  20. Effect of Impurity Tin on the Creep Properties of a P91 Heat-Resistant Steel

    Science.gov (United States)

    Song, S.-H.; Xu, Y.-W.; Yang, H.-F.

    2014-09-01

    The creep properties of P91 steel specimens undoped and doped with 0.058 wt pct tin, which was normalized from 1328 K (1055 °C) and tempered at 1033 K (760 °C), were examined under different engineering stresses (150 to 210 MPa) and temperatures [873 K to 923 K (600 °C to 650 °C)]. The creep behavior followed the temperature-compensated power law and Monkman-Grant equations. In the temperature-compensated power law equation, the apparent activation energy and stress exponent for creep were approximately 541 kJ/mol and 12 for the undoped steel and 527 kJ/mol and 11 for the Sn-doped one, respectively. In the Monkman-Grant relation, the values of constants m and C were around 1.062 and 0.0672 for the undoped steel, and 1.012 and 0.0650 for the Sn-doped one, respectively. The 100 MPa stress creep lifetime at 873 K (600 °C) was estimated as 100641 hours for the undoped steel and 35290 hours for the Sn-doped steel, respectively. These indicated that Sn substantially deteriorated the creep properties of the steel. It was found that grain or subgrain boundary segregation of Sn could promote the nucleation of cavities or microcracks, thereby leading to the deterioration of the steel creep properties.

  1. Properties of aluminum alloys tensile, creep, and fatigue data at high and low temperatures

    CERN Document Server

    1999-01-01

    This book compiles more than 300 tables listing typical average properties of a wide range of aluminum alloys. The individual test results were compiled, plotted in various ways, and analyzed. The average values from the tensile and creep tests were then normalized to the published typical room-temperature tensile properties of the respective alloys for easy comparison. This extensive project was done by Alcoa Laboratories over a period of several years. The types of data presented include: Typical Mechanical Properties of Wrought and Cast Aluminum Alloys at Various Temperatures, including tensile properties at subzero temperatures, at temperature after various holding times at the test temperature, and at room temperature after exposure at various temperatures for various holding times; creep rupture strengths for various times at various temperatures; stresses required to generate various amounts of creep in various lengths of time; rotating-beam fatigue strengths; modulus of elasticity as a function of t...

  2. Time evolution of damage in thermally induced creep rupture

    KAUST Repository

    Yoshioka, N.

    2012-01-01

    We investigate the time evolution of a bundle of fibers subject to a constant external load. Breaking events are initiated by thermally induced stress fluctuations followed by load redistribution which subsequently leads to an avalanche of breakings. We compare analytic results obtained in the mean-field limit to the computer simulations of localized load redistribution to reveal the effect of the range of interaction on the time evolution. Focusing on the waiting times between consecutive bursts we show that the time evolution has two distinct forms: at high load values the breaking process continuously accelerates towards macroscopic failure, however, for low loads and high enough temperatures the acceleration is preceded by a slow-down. Analyzing the structural entropy and the location of consecutive bursts we show that in the presence of stress concentration the early acceleration is the consequence of damage localization. The distribution of waiting times has a power law form with an exponent switching between 1 and 2 as the load and temperature are varied.

  3. Fiber creep rate and high-temperature properties of SiC/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Lewinsohn, C.A.; Jones, R.H.; Youngblood, G.E.; Henager, C.H. Jr. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    Results of studies aimed at relating the fiber creep rate to the subcritical crack growth rate and fracture properties of SiC/SiC composites have demonstrated that the crack growth rate in a bulk composite is controlled by the fiber creep rate. This result was demonstrated for Nicalon-CG and Hi-Nicalon fiber reinforced material where a 50--75 c shift in the creep strength of the fiber resulted in a similar shift in the crack growth rate of the composite. Irradiation enhanced creep of SiC fibers and matrix must also be considered in the performance assessment of SiC/SiC composites. The shape of the displacement versus time curve for composites containing Hi-Nicalon fibers were similar to those of the previously tested materials, containing Ceramic-grade fibers, that exhibited subcritical crack growth controlled by time-dependent relaxation of the fiber-bridging stresses due to fiber creep. The crack velocity in the CG-C composites at 1100 C in argon was very close to that of the Hi-C materials at 1150--1175 C, this roughly corresponds to the temperature differential shown by DiCarlo et al. to obtain the same relaxation in 1 hour bend stress relaxation (BSR) tests in the two fibers. This supports the hypothesis that subcritical crack growth in SiC/SiC composites is controlled by fiber creep.

  4. Tracing Thermal Creep and Thermophoresis in Porous Structures at Low Ambient Pressure and Low Gravity

    Science.gov (United States)

    Schywek, Mathias; Teiser, Jens; Wurm, Gerhard

    2017-12-01

    We carried out two types of drop tower experiments to quantify gas and particle motion induced by temperature gradients inside a porous structure in a low pressure environment. In one setup 400 μm sized particles were traced inside heated channels at pressures of a few Pascal. Their motion is consistent with pure thermophoresis. In the second setup tracer particles were used to track the thermal creep gas flow through a porous dust bed. Here, the flow was traced outside of the dust bed and without thermophoretic motion. The results are consistent with a simple capillary model of the dust bed.

  5. Tracing Thermal Creep and Thermophoresis in Porous Structures at Low Ambient Pressure and Low Gravity

    Science.gov (United States)

    Schywek, Mathias; Teiser, Jens; Wurm, Gerhard

    2017-11-01

    We carried out two types of drop tower experiments to quantify gas and particle motion induced by temperature gradients inside a porous structure in a low pressure environment. In one setup 400 μm sized particles were traced inside heated channels at pressures of a few Pascal. Their motion is consistent with pure thermophoresis. In the second setup tracer particles were used to track the thermal creep gas flow through a porous dust bed. Here, the flow was traced outside of the dust bed and without thermophoretic motion. The results are consistent with a simple capillary model of the dust bed.

  6. An anisotropic linear thermo-viscoelastic constitutive law - Elastic relaxation and thermal expansion creep in the time domain

    Science.gov (United States)

    Pettermann, Heinz E.; DeSimone, Antonio

    2017-09-01

    A constitutive material law for linear thermo-viscoelasticity in the time domain is presented. The time-dependent relaxation formulation is given for full anisotropy, i.e., both the elastic and the viscous properties are anisotropic. Thereby, each element of the relaxation tensor is described by its own and independent Prony series expansion. Exceeding common viscoelasticity, time-dependent thermal expansion relaxation/creep is treated as inherent material behavior. The pertinent equations are derived and an incremental, implicit time integration scheme is presented. The developments are implemented into an implicit FEM software for orthotropic material symmetry under plane stress assumption. Even if this is a reduced problem, all essential features are present and allow for the entire verification and validation of the approach. Various simulations on isotropic and orthotropic problems are carried out to demonstrate the material behavior under investigation.

  7. Thermal Volume Changes and Creep in the Callovo-Oxfordian Claystone

    Science.gov (United States)

    Belmokhtar, Malik; Delage, Pierre; Ghabezloo, Siavash; Conil, Nathalie

    2017-09-01

    The Callovo-Oxfordian (COx) claystone is considered as a potential host rock for high-level radioactive waste disposal at great depth in France. Given the exothermic nature of radioactive wastes, a temperature elevation planned to be smaller than 100 °C will affect the host rock around the disposal cells. To gain better understanding of the thermal volumetric response of the COx claystone, a new thermal isotropic compression cell was developed with particular attention devoted to monitoring axial and radial strains. To do so, a high-precision LVDTs system ensuring direct contact between the LVDT stem and the claystone sample through the membrane was developed. A short drainage length (10 mm) was also ensured so as to allow full saturation of the sample under stress conditions close to in situ, and fully drained conditions during compression. High-precision strain monitoring allowed to observe a volumetric creep under stress conditions close to in situ. A drained heating test under constant stress carried out afterwards up to 80 °C exhibited a thermoelastic expansion up to a temperature of 48 °C, followed by thermoplastic contraction at higher temperature. Creep volume changes, that appeared to be enhanced by temperature, were modelled by using a simple Kelvin-Voigt model, so as to estimate the instantaneous response of the COx claystone and to determine its thermal expansion coefficient. The temperature at which the transition between thermal expansion and contraction appeared is close to the maximum burial temperature of the Callovo-Oxfordian claystone, estimated at 50 °C. This is in agreement with what has been already observed on the Opalinus Clay by Monfared et al. (2012) that was interpreted as a thermal hardening phenomenon, showing that the material kept the memory of the highest temperature supported during its geological history.

  8. Investigation of creep rupture properties in air and He environments of alloy 617 at 800 °C

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woo-Gon, E-mail: wgkim@kaeri.re.k [Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Ekaputra, I.M.W.; Park, Jae-Young [Pukyong National University, Busan 608-739 (Korea, Republic of); Kim, Min-Hwan; Kim, Yong-Wan [Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of)

    2016-09-15

    Creep rupture properties for Alloy 617 were investigated by a series of creep tests under different applied stresses in air and He environments at 800 °C. The creep rupture time in air and He environments exhibited almost similar life in a short rupture time. However, when the creep rupture time reaches above 3000 h, the creep life in the He environment reduced compared with those of the air environment. The creep strain rate in the He environment was a little faster than that in the air environment above 3000 h. The reduction of creep life in the He environment was due to the difference of various microstructure features such as the carbide depleted zone, oxidation structures, surface cracking, voids below the surface, and voids in the matrix in air and He environments. Alloy 617 followed Norton’s power law and the Monkman–Grant relationship well. As the stress decreased, the creep ductility decreased slightly. The thickness of the outer and internal oxide layers presented the trend of a parabolic increase with an increase in creep rupture time in both the air and He environments. The thickness in the He environment was found to be thicker than in the air environment, although pure helium gas of 99.999% was used in the present investigation. The differences in the oxide-layer thickness caused detrimental effects on the creep resistance, even in a low oxygen-containing He agent.

  9. Recovery of creep properties of the nickel-base superalloy nimonic 105

    CSIR Research Space (South Africa)

    Girdwood, RB

    1996-01-01

    Full Text Available of the creep properties of Nimonic 105. The general microstructural observations show that there is a clear change in the morphology of the y? with time and temperature (Ostwald ripening). The y? elongation is more pronounced in the longer tests...

  10. Stiffness modulus and creep properties of the coconut shell in an ...

    African Journals Online (AJOL)

    Coconut shell (CS) is an agricultural waste engineered into a road construction material. This study was conducted to evaluate the stiffness modulus and dynamic creep properties of the asphaltic concrete containing CS as an aggregate replacement. A mixture design incorporating the bitumen penetration grade 60/70 was ...

  11. CREEP AGE FORMING OF Al-Zn-Mg ALLOYS WITH OPTIMIZATION OF MECHANICALl PROPERTIES

    Directory of Open Access Journals (Sweden)

    M. Ershadi Khameneh

    2015-12-01

    Full Text Available Creep age forming (CAF is one of the novel methods in aerospace industry that has been used to manufacture components of panels with improved mechanical properties and reduced fabrication cost. CAF is a combined age-hardening and stress-relaxation that are responsible for strengthening and forming, respectively. This paper deals with the experimental investigations of mechanical and springback properties of Al-Zn-Mg Al alloy in creep forming process. Creep forming experiments have been performed at temperatures of 120◦C and 180◦C for 6–72 h. Results indicated that yield stress and hardness of creep age formed specimens increased with increasing forming time and temperature,  simultaneously induced deflection by stress-relaxation increased. Incorporating spring back and mechanical properties, it can be found that the appropriate forming cycle was 180 ◦C/24 h among all forming conditions. CAF Time increase to a certain extent increased mechanical properties. This can be attributed to presence of stress in CAF that causes the precipitates be finer because of creation more nucleation sites. Therefor the growth of precipitates, takes place at long time and postpones the decreasing of the yield stress

  12. Creep properties of three low temperature-curing bone cements: a preclinical assessment.

    Science.gov (United States)

    Verdonschot, N; Huiskes, R

    2000-09-01

    The mechanical characteristics of new bone cements should be assessed before these cements are released on the orthopedic market in great quantities. In this study, we present the deformational response of 3 relatively new, low-curing temperature bone cements (Cemex RX, Cemex System, and Cemex Isoplastic) to a dynamic compressive force in comparison to Simplex P bone cement. For this purpose, dynamic compressive creep tests were performed on cylindrical shaped specimens at a maximal load level of 20 MPa for a period of 250,000 cycles. The results showed that Cemex System and Cemex RX produced creep rates that were higher (20% and 30%, respectively) as compared to Simplex P bone cement. The creep behavior of Cemex Isoplastic was very similar to that of Simplex P. It was concluded that although Cemex RX and Cemex System produced higher creep rates than Simplex P, these differences were not considered excessive. Hence, although other tests are required to assess the safety and efficacy of these new cements, the dynamic creep properties under compression can be considered adequate for clinical use. Copyright 2000 John Wiley & Sons, Inc.

  13. Mechanical Properties, Short Time Creep, and Fatigue of an Austenitic Steel

    Directory of Open Access Journals (Sweden)

    Josip Brnic

    2016-04-01

    Full Text Available The correct choice of a material in the process of structural design is the most important task. This study deals with determining and analyzing the mechanical properties of the material, and the material resistance to short-time creep and fatigue. The material under consideration in this investigation is austenitic stainless steel X6CrNiTi18-10. The results presenting ultimate tensile strength and 0.2 offset yield strength at room and elevated temperatures are displayed in the form of engineering stress-strain diagrams. Besides, the creep behavior of the steel is presented in the form of creep curves. The material is consequently considered to be creep resistant at temperatures of 400 °C and 500 °C when subjected to a stress which is less than 0.9 of the yield strength at the mentioned temperatures. Even when the applied stress at a temperature of 600 °C is less than 0.5 of the yield strength, the steel may be considered as resistant to creep. Cyclic tensile fatigue tests were carried out at stress ratio R = 0.25 using a servo-pulser machine and the results were recorded. The analysis shows that the stress level of 434.33 MPa can be adopted as a fatigue limit. The impact energy was also determined and the fracture toughness assessed.

  14. High temperature creep properties of directionally solidified CM-247LC Ni-based superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Chiou, Mau-Sheng [Department of Materials Science and Engineering, I-Shou University, Kaohsiung 840, Taiwan (China); Jian, Sheng-Rui, E-mail: srjian@gmail.com [Department of Materials Science and Engineering, I-Shou University, Kaohsiung 840, Taiwan (China); Yeh, An-Chou [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan (China); Kuo, Chen-Ming [Department of Mechanical and Automation Engineering, I-Shou University, Kaohsiung 840, Taiwan (China); Juang, Jenh-Yih [Department of Electrophysics, National Chiao Tung University, Hsinchu 300, Taiwan (China)

    2016-02-08

    This study explores the effects of cooling rate after solution heat treatment on the high temperature/low stress (982 °C/200 MPa) creep properties of CM-247LC Nickel base superalloy. Cooling rate was controlled by blowing argon gas, air cooling, and furnace cooling, which, in turn, gave rise to corresponding cooling rates (from 1260 °C to 800 °C) of 18.7, 7.4, and 0.19 °C/s, respectively. The results indicated that higher cooling rate from the solution heat treatment temperature led to finer γ′ precipitates and much improved tertiary creep as well as rupture life time in high-temperature creep test. The microstructural analyses using both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that finer γ′ precipitates and narrower γ channel width could result in denser rafting structure which might have hindered the climb of dislocations across the precipitates rafts.

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

    Directory of Open Access Journals (Sweden)

    B. Piekarski

    2007-12-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-04-15

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

  17. Effect of nitrogen on creep properties of type 316L stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D.W.; Lee, Y.K.; Kuk, I.H.; Ryu, W.S. [Korea Atomic Energy Research Institute, Taejon (Korea)

    1999-03-01

    The effect of nitrogen on the creep properties of type 316L stainless steels with three different nitrogen contents from 0.04 to 0.15% was investigated. The plate was solution treated for 1 hr at 1100 deg C and then water quenched. Specimens were obtained from the plate parallel to the rolling direction. The geometry of specimen was 4mm diameter and 30mm gauge length. Creep tests were carried out using constant-load single-lever machines in the initial stress range from 120 to 380MPa at 550, 600 and 650 deg C and in air. The temperature deviation along the gauge length of the specimen was strictly controlled less than {+-}2 deg C. The time to rupture increased and the minimum creep strain rate decreased with the addition of nitrogen. On the other hand, the rupture elongation and fracture mode was not strongly influenced by the nitrogen content. The effect of nitrogen content on the creep properties were found to be more pronounced at higher temperatures. The intergranular fracture mode was found in all specimens and increased with decreasing applied stress. (author). 7 refs., 41 figs.

  18. The Mechanical Properties and Modeling of Creep Behavior of UHMWPE/Nano-HA Composites

    Science.gov (United States)

    Li, Fan; Gao, Lilan; Gao, Hong; Cui, Yun

    2017-09-01

    Composites with different levels of hydroxyapatite (HA) content and ultra-high molecular weight polyethylene (UHMWPE) were prepared in this work. Mechanical properties of the composites were examined here, and to evaluate the effect of HA particles on the time-dependent behavior of the pure matrix, the creep and recovery performance of composites at various stress levels were also researched. As expected, the addition of HA influenced the time-dependent response of the UHMWPE and the effect had a strong dependence on the HA content. The creep and recovery strain of the composites significantly decreased with increasing HA content, and tensile properties were also impaired, which was due to the concentration of HA fillers. The mechanism and effect of HA dispersed into the UHMWPE matrix were examined by scanning electron microscopy. Additionally, since variations in the adjusted parameters revealed the impact of HA on the creep behavior of the UHMWPE matrix, Findley's model was employed. The results indicated that the analytical model was accurate for the prediction of creep of the pure matrix and its composites.

  19. Thermal, creep-recovery and viscoelastic behavior of high density polyethylene/hydroxyapatite nano particles for bone substitutes: effects of gamma radiation.

    Science.gov (United States)

    Alothman, Othman Y; Fouad, H; Al-Zahrani, S M; Eshra, Ayman; Al Rez, Mohammed Fayez; Ansari, S G

    2014-08-28

    High Density Polyethylene (HDPE) is one of the most often used polymers in biomedical applications. The limitations of HDPE are its visco-elastic behavior, low modulus and poor bioactivity. To improve HDPE properties, HA nanoparticles can be added to form polymer composite that can be used as alternatives to metals for bone substitutes and orthopaedic implant applications. In our previous work (BioMedical Engineering OnLine 2013), different ratios of HDPE/HA nanocomposites were prepared using melt blending in a co-rotating intermeshing twin screw extruder. The accelerated aging effects on the tensile properties and torsional viscoelastic behavior (storage modulus (G') and Loss modulus (G")) at 80°C of irradiated and non-irradiated HDPE/HA was investigated. Also the thermal behavior of HDPE/HA were studied. In this study, the effects of gamma irradiation on the tensile viscoelastic behavior (storage modulus (E') and Loss modulus (E")) at 25°C examined for HDPE/HA nanocomposites at different frequencies using Dynamic Mechanical Analysis (DMA). The DMA was also used to analyze creep-recovery and relaxation properties of the nanocomposites. To analyze the thermal behavior of the HDPE/HA nanocomposite, Differential Scanning Calorimetry (DSC) was used. The microscopic examination of the cryogenically fractured surface revealed a reasonable distribution of HA nanoparticles in the HDPE matrix. The DMA showed that the tensile storage and loss modulus increases with increasing the HA nanoparticles ratio and the test frequency. The creep-recovery behavior improves with increasing the HA nanoparticle content. Finally, the results indicated that the crystallinity, viscoelastic, creep recovery and relaxation behavior of HDPE nanocomposite improved due to gamma irradiation. Based on the experimental results, it is found that prepared HDPE nanocomposite properties improved due to the addition of HA nanoparticles and irradiation. So, the prepared HDPE/HA nanocomposite appears to

  20. Creep of chemically vapour deposited SiC fibres

    Science.gov (United States)

    Dicarlo, J. A.

    1986-01-01

    The creep, thermal expansion, and elastic modulus properties for chemically vapor deposited SiC fibers were measured between 1000 and 1500 C. Creep strain was observed to increase logarithmically with time, monotonically with temperature, and linearly with tensile stress up to 600 MPa. The controlling activation energy was 480 + or - 20 kJ/mole. Thermal pretreatments near 1200 and 1450 C were found to significantly reduce fiber creep. These results coupled with creep recovery observations indicate that below 1400 C fiber creep is anelastic with negligible plastic component. This allowed a simple predictive method to be developed for describing fiber total deformation as a function of time, temperature, and stress. Mechanistic analysis of the property data suggests that fiber creep is the result of beta-SiC grain boundary sliding controlled by a small percent of free silicon in the grain boundaries.

  1. Comparison of the Tensile, Creep, and Rupture Strength Properties of Stoichiometric SiC Fibers

    Science.gov (United States)

    Yun, H. M.; DiCarlo, J. A.

    1999-01-01

    Tensile strength, creep strength, and rupture strength properties were measured for the following types of polymer-derived stoichiometric SiC fibers: Hi-Nicalon Type S from Nippon Carbon, Tyranno SA from Ube, and Sylramic from Dow Corning. Also included in this study were an earlier version of the SA fiber plus two recent developmental versions of the Sylramic fiber. The tensile strength measurements were made at room temperature on as-received fibers and on fibers after high-temperature inert exposure. The creep-rupture property data were obtained at 1400 deg C in air as well as, argon. Some fiber types showed strong effects of environment on their strength properties. These results are compared and discussed in terms of underlying mechanisms and implications for ceramic composites.

  2. Creep properties and simulation of weld repaired low alloy heat resistant CrMo and Mo steels at 540 deg C. Sub project 1 - Ex-serviced parent metal and virgin weld metals

    Energy Technology Data Exchange (ETDEWEB)

    Rui Wu; Storesund, Jan; Borggreen, Kjeld; Weilin Zang

    2006-10-15

    Many existing power generating and process plants, where low alloy heat resistant CrMo(V) steels are extensively used for critical components, have exceeded their design lifetime of usually 100,000 hours. Assessment of residual lifetime and extension of economic life by weld repair have become increasingly important and attractive. This project aims at i) performing weld repair and determining the degree of mismatching, ii) evaluating the creep properties of weld repairs, iii) analysing creep behaviour of weld repair and providing necessary data for further reliable simulations of weld repair creep behaviour in long term service, and iv), simulating and assessing lifetime and creep damage evolution of weld repair. Weld repair using 10 CrMo 9 10, 13 CrMo 4 4 and 15 Mo 3 consumables has been carried out in a service-exposed 10 CrMo 9 10 pipe. Creep specimens have been extracted from the service-exposed 10 CrMo 9 10 parent metal (PM), from the virgin 10 CrMo 9 10 weld metal (WM), from the virgin 13 CrMo 4 4 WM as well as from the virgin 15 Mo 3 WM. Iso-thermal uniaxial creep tests have been performed at 540 deg C in air. Pre- and post-metallography are carried out on the selected samples. FEM simulations using obtained creep data are executed. Pre-test metallography shows normal and acceptable weld repairs at given welding conditions. Creep tests demonstrate that the virgin 10 CrMo 9 10, 13 CrMo 4 4 and 15 Mo 3 WMs have apparently longer creep lifetime than the service-exposed CrMo 9 10 PM at higher stresses than 110 MPa. Among the weld metals, the longest creep lifetime is found in 10 CrMo 9 10. Higher creep strength and lower creep strain rate in the weld metals indicate an overmatch weld. At 95 MPa, however, lifetime of 13 CrMo 4 4 WM is surprisingly short (factors which may shorten lifetime are discussed and one more test will start to verify creep strength at low stress) and tests are still running for other two weld metals. More results regarding low stress

  3. Effect of prior creep at 1365 K on the room temperature tensile properties of several oxide dispersion strengthened alloys

    Science.gov (United States)

    Whittenberger, J. D.

    1977-01-01

    An experimental study was conducted to determine whether oxide dispersion-strengthened (ODS) Ni-base alloys in wrought bar form are subject to creep degradation effects similar to those found in thin-gage sheet. The bar products evaluated included ODS-Ni, ODS-NiCr, and advanced ODS-NiCrAl types; the alloys included microstructures ranging from an essentially perfect single crystal to a structure consisting of very small elongated grains. Tensile test specimens were exposed to creep at various stress levels at 1365 K and then tensile tested at room temperature. Low residual tensile properties, change in fracture mode, appearance of dispersoid free bands, grain boundary cavitation, and/or internal oxidation are interpreted as creep degradation effects. The amount of degradation depends on creep strain, and degradation appears to be due to diffusional creep which produces dispersoid free bands around grain boundaries acting as vacancy sources.

  4. Effect of boron addition and ESR process on the creep properties of type 316L(N) stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, W. K.; Kim, D. H.; Jang, J. S.; Kook, I. H.; Ryu, W. S. [KAERI, Taejon (Korea, Republic of)

    1999-10-01

    The effects of B-addition and ESR(electroslag remelting) process on the creep properties of 316L(N) stainless steel were investigated at 550 deg C in air. High temperature tensile strength for three heats was similar, but creep rupture time of B-doped and ESR-processed 316L(N) steels increased significantly in comparison with B-undoped steels. Also, the creep rupture elongation increased and minimum creep rate decreased inversely. Cross section of crept specimen showed the typical wedge cracks regardless of B-addition or ESR. The size and spacing of grain boundary cavitation in B-doped and ESR-processed steels were smaller than those of B-undoped steels. It was concluded that 0.0025% boron addition increases creep rupture time by delaying the onset of the tertiary stage due to suppression of grain boundary cavitation and wedge cracking.

  5. Real-time simulation of thermal stresses and creep in plates subjected to transient heat input

    DEFF Research Database (Denmark)

    Hattel, Jesper Henri; Jacobsen, Torben Krogsdal; Hansen, P.N.

    1997-01-01

    -difference approach. It applies a general formulation which takes into account nonconstant material properties (e.g. temperature, material, or time dependency), heat-transfer coefficients, and creep. The temperature calculation applies a one-dimensional numerical model, whereas the stress analysis is semi......This paper presents a novel numerical technique for solving the temperature and stress fields in a plate subjected to arbitrarily varying transient boundary conditions (transient temperature and heat-flux variations) on a surface. The numerical method is based on the control-volume finite......-two-dimensional. Both plane stress and plane strain conditions are considered as extreme cases. It is shown that, by using the developed numerical technique, very fast real-time simulations can be performed. The method has proved its applicability in e.g. high-pressure die-casting, and applications to this industrial...

  6. Vesta surface thermal properties map

    Science.gov (United States)

    Capria, Maria Teresa; Tosi, F.; De Santis, Maria Cristina; Capaccioni, F.; Ammannito, E.; Frigeri, A.; Zambon, F; Fonte, S.; Palomba, E.; Turrini, D.; Titus, T.N.; Schroder, S.E.; Toplis, M.J.; Liu, J.Y.; Combe, J.-P.; Raymond, C.A.; Russell, C.T.

    2014-01-01

    The first ever regional thermal properties map of Vesta has been derived from the temperatures retrieved by infrared data by the mission Dawn. The low average value of thermal inertia, 30 ± 10 J m−2 s−0.5 K−1, indicates a surface covered by a fine regolith. A range of thermal inertia values suggesting terrains with different physical properties has been determined. The lower thermal inertia of the regions north of the equator suggests that they are covered by an older, more processed surface. A few specific areas have higher than average thermal inertia values, indicative of a more compact material. The highest thermal inertia value has been determined on the Marcia crater, known for its pitted terrain and the presence of hydroxyl in the ejecta. Our results suggest that this type of terrain can be the result of soil compaction following the degassing of a local subsurface reservoir of volatiles.

  7. Development of creep damage assessment system for aged thermal power plant; Karyoku koon buzai no creep sonsho shindan system no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, T.; Misono, S.; Nonaka, I.; Umaki, H. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan)

    1997-11-01

    A `creep damage assessment system` deriving a diagnostic result immediately on the spot was developed and practically used as a method to measure non-destructively damages in aged thermal power plants. This system develops the weld creep void area rate method for high-temperature members, observes directly portions to be diagnosed by using a small laser microscope, and uses an automatic void identifying process using image processing, which has been developed originally. The main device used in boilers is the small laser microscope which observes metallic structures in portions to be diagnosed. This microscope is a new type microscope which scans laser beams on the observation surface to produce the observation results into images. The microscope can derive clean focus scan memory images with the focus placed on the whole observation field of vision by not only memorizing and synthesizing real-time images which project only the focused portions, but also doing the same for real-time images derived by scanning an object lens in the focus axial direction. A test to apply the system to a practical device was performed to evaluate and identify its operability, applicability to different environments and diagnostic accuracy. Good results were obtained from the test. 1 ref., 12 figs.

  8. Numerical modeling of physical vapor transport under microgravity conditions: Effect of thermal creep and stress

    Science.gov (United States)

    Mackowski, Daniel W.; Knight, Roy W.

    1993-01-01

    One of the most promising applications of microgravity (micro-g) environments is the manufacture of exotic and high-quality crystals in closed cylindrical ampoules using physical vapor transport (PVT) processes. The quality enhancements are believed to be due to the absence of buoyant convection in the weightless environment - resulting in diffusion-limited transport of the vapor. In a typical experiment, solid-phase sample material is initially contained at one end of the ampoule. The sample is made to sublime into the vapor phase and deposit onto the opposite end by maintaining the source at an elevated temperature with respect to the deposit. Identification of the physical factors governing both the rates and uniformity of crystal growth, and the optimization of the micro-g technology, will require an accurate modeling of the vapor transport within the ampoule. Previous micro-g modeling efforts have approached the problem from a 'classical' convective/diffusion formulation, in which convection is driven by the action of buoyancy on thermal and solutal density differences. The general conclusion of these works have been that in low gravity environments the effect of buoyancy on vapor transport is negligible, and vapor transport occurs in a diffusion-limited mode. However, it has been recently recognized than in the non-isothermal (and often low total pressure) conditions encountered in ampoules, the commonly-assumed no-slip boundary condition to the differential equations governing fluid motion can be grossly unrepresentative of the actual situation. Specifically, the temperature gradients can give rise to thermal creep flows at the ampoule side walls. In addition, temperature gradients in the vapor itself can, through the action of thermal stress, lead to bulk fluid convection.

  9. Thermal stability and creep behaviour of MgNiYCe-rich mischmetal alloys processed by a powder metallurgy route

    Czech Academy of Sciences Publication Activity Database

    Peréz, P.; Milička, Karel; Badia, J. M.; Garcés, G.; Antoranz, J. M.; Gonzáles, S.; Dobeš, Ferdinand; Adeva, P.

    289-292, - (2009), s. 127-136 ISSN 1012-0386. [DIMAT 2008, International Conference on Diffusion in Materials /7./. Lanzarote, Canary Islands, 28.10.2008-31.10.2008] Grant - others:Ministerio de Ciencia y Tecnologia(ES) MAT2006-11731-C02 Institutional research plan: CEZ:AV0Z20410507 Keywords : magnesium alloys * powder metallurgy * microstructure * thermal stability * creep Subject RIV: JG - Metallurgy

  10. Martensitic stainless steel AISI 420—mechanical properties, creep and fracture toughness

    Science.gov (United States)

    Brnic, J.; Turkalj, G.; Canadija, M.; Lanc, D.; Krscanski, S.

    2011-11-01

    In this paper some experimental results and analyses regarding the behavior of AISI 420 martensitic stainless steel under different environmental conditions are presented. That way, mechanical properties like ultimate tensile strength and 0.2 percent offset yield strength at lowered and elevated temperatures as well as short-time creep behavior for selected stress levels at selected elevated temperatures of mentioned material are shown. The temperature effect on mentioned mechanical properties is also presented. Fracture toughness was calculated on the basis of Charpy impact energy. Experimentally obtained results can be of importance for structure designers.

  11. Influence of Constituents on Creep Properties of SiC/SiC Composites

    Science.gov (United States)

    Bhatt, R.; DiCarlo, J.

    2016-01-01

    SiC-SiC composites are being considered as potential candidate materials for next generation turbine components such as combustor liners, nozzle vanes and blades because of their low density, high temperature capability, and tailorable mechanical properties. These composites are essentially fabricated by infiltrating matrix into a stacked array of fibers or fiber preform by one or a combination of manufacturing methods such as, Melt Infiltration (MI) of molten silicon metal, Chemical Vapor Infiltration (CVI), Polymer Infiltration and Pyrolysis (PIP). To understand the influence of constituents, the SiC-SiC composites fabricated by MI, CVI, and PIP methods were creep tested in air between 12000 and 14500 degrees Centigrade for up to 500 hours. The failed specimens were analyzed under a scanning electron microscope to assess damage mechanisms. Also, knowing the creep deformation parameters of the fiber and the matrix under the testing conditions, the creep behavior of the composites was modeled and compared with the measured data. The implications of the results on the long term durability of these composites will be discussed.

  12. Transient Liquid Phase Bonding Single-Crystal Superalloys with Orientation Deviations: Creep Properties

    Science.gov (United States)

    Sheng, Naicheng; Liu, Jide; Jin, Tao; Sun, Xiaofeng; Hu, Zhuangqi

    2015-12-01

    Superalloys single crystals with various orientation deviations were bonded using transient liquid phase bonding method, then the creep properties of the bonded specimens were tested at 1033 K (760 °C)/780 MPa. It is found that the creep life of the bonded specimens decreases with the increase of the relative orientation deviations. Despite the fracture of the specimens appears on the bonding region, the deformation mechanism changes from specimens with low angle boundary to high angle boundary. In low angle boundary specimens, cleavage originated from the defects grows perpendicularly to the tensile stress and connects through the different slip planes around the cleavage planes. In this case, the deformation proceeds by the dislocations and stacking faults on multi-planes. With increasing orientation deviation, dislocation and stacking faults moved on single plane. As a result, the dislocations interact with the grain boundary and lead to fracture. Based on the present investigation, the orientation of the bonded superalloys single crystal should be controlled so that the introduced grain boundaries are relatively small and exhibit higher creep strength.

  13. A unified analysis of kinetic models for the problem of thermal creep based on the boundary conditions of Cercignani-Lampis for heterogeneous plates

    Energy Technology Data Exchange (ETDEWEB)

    Rosa, Cinara Ewerling da, E-mail: cinara@pb.ifarroupilha.edu.br [Universidade Federal do Rio Grande do Sul (IFF/UFRS), Porto Alegre, RS (Brazil); Instituto Federal Farroupilha, Panambi, RS (Brazil); Knackfuss, Rosenei Felippe, E-mail: knackfuss@smail.ufsm.br [Universidade Federal de Santa Maria (UFSM), Santa Maria, RS (Brazil)

    2013-07-01

    In this work is presented a series of numerical results and graphical comparisons of the physical quantities of interest such as: the velocity profile and the heat on profile. This formulation is developed for the problem of Thermal Creep, where the gas is moving between two parallel plates with different chemical constitutions (heterogeneous plates) due to a temperature gradient. The flow of a rarefied gas, is investigated with special attention to the gas-surface interaction, modeled by the Cercignani-Lampis kernel, that unlike Maxwell's scattering kernel, is defined in terms of two accommodation coefficients (normal and tangential) to represent the physical properties of the gas. The kinetic theory for rarefied gas dynamics, derived from the linearized Boltzmann equation, is developed in an unified approach, to the BGK model, S model, GJ model and MRS model. In the search for solutions to solve the problem of Thermal Creep with kernel of the Cercignani-Lampis, we used a analytical version of the discrete ordinates method (ADO) based on an arbitrary quadrature scheme, under which is determined a problem of eigenvalues and their respective separation constants. Numerical results are developed by the computer program FORTRAN. (author)

  14. Viscoelastic properties, creep behavior and degree of conversion of bulk fill composite resins.

    Science.gov (United States)

    Papadogiannis, D; Tolidis, K; Gerasimou, P; Lakes, R; Papadogiannis, Y

    2015-12-01

    The aim of this study was to investigate the viscoelastic properties and creep behavior of bulk fill composites under different conditions and evaluate their degree of conversion. Seven bulk fill composites were examined: everX Posterior (EV), SDR (SD), SonicFill (SF), Tetric EvoCeram Bulk Fill (TE), Venus Bulk Fill (VE), x-tra base (XB) and x-tra fil (XF). Each material was tested at 21°C, 37°C and 50°C under dry and wet conditions by applying a constant torque for static and creep testing and dynamic torsional loading for dynamic testing. Degree of conversion (%DC) was measured on the top and bottom surfaces of composites with ATR-FTIR spectroscopy. Statistical analysis was performed with two-way ANOVA, Bonferroni's post hoc test and Pearson's correlation coefficient. Shear modulus G ranged from 2.17GPa (VE) to 8.03GPa (XF) and flexural modulus E from 6.16GPa (VE) to 23GPa (XF) when the materials were tested dry at 21°C. The increase of temperature and the presence of water lead to a decline of these properties. Flowable materials used as base composites in restorations showed significantly lower values (p<0.05) than non-base composites, while being more prone to creep deformation. %DC ranged from 47.25% (XF) to 66.67% (SD) at the top material surface and 36.06% (XF) to 63.20% (SD) at the bottom. Bulk fill composites exhibited significant differences between them with base flowable materials showing in most cases inferior mechanical properties and higher degree of conversion than restorative bulk fill materials. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  15. A physics-based crystallographic modeling framework for describing the thermal creep behavior of Fe-Cr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Wei [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Capolungo, Laurent [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Patra, Anirban [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tome, Carlos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-02-02

    This Report addresses the Milestone M2MS-16LA0501032 of NEAMS Program (“Develop hardening model for FeCrAl cladding), with a deadline of 09/30/2016. Here we report a constitutive law for thermal creep of FeCrAl. This Report adds to and complements the one for Milestone M3MS-16LA0501034 (“Interface hardening models with MOOSE-BISON”), where we presented a hardening law for irradiated FeCrAl. The last component of our polycrystal-based constitutive behavior, namely, an irradiation creep model for FeCrAl, will be developed as part of the FY17 Milestones, and the three regimes will be coupled and interfaced with MOOSE-BISON.

  16. [Nondestructive applanation technique to measure the elasticity moduli and creep properties of ocular cornea in vivo].

    Science.gov (United States)

    Zhang, Xueyong; Liu, Dong; Tang, Zhen; Liao, Rongfeng; Ma, Jianguo

    2015-02-01

    Due to lack of the practical technique to measure the biomechanical properties of the ocular cornea in vivo, clinical ophthalmologists have some difficulties in understanding the deformation mechanism of the cornea under the action of physiological intraocular pressures. Using Young's theory analysis of the corneal deformation during applanation tonometry, the relation between the elasticity moduli of the cornea and the applanated corneal area and the measured and true intraocular pressures can be obtained. A new applanation technique has been developed for measuring the biomechanical properties of the ocular cornea tissue in vivo, which can simultaneously acquire the data of the applanation area and displacement of the corneal deformation as well as the exerted applanation force on the cornea. Experimental results on a rabbit's eyeball demonstrated that the present technique could be used to measure the elasticity moduli and creep properties of the ocular cornea nondestructively in vivo.

  17. Thermally activated low temperature creep and primary water stress corrosion cracking of NiCrFe alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hall, M.M. Jr.

    1993-10-01

    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.

  18. Effect of fine {gamma}' precipitation on non-isothermal creep and creep-fatigue behaviour of nickel base superalloy MC2

    Energy Technology Data Exchange (ETDEWEB)

    Le Graverend, J.-B., E-mail: jean-briac.le_graverend@onera.fr [Office National d' Etudes et de Recherches Aerospatiales, 29 avenue de la Division Leclerc, BP 72, 92322 Chatillon (France); Institut Pprime CNRS-ENSMA-Universite de Poitiers, Departement Physique et Mecanique des Materiaux, ENSMA-Teleport 2, 1 avenue Clement Ader, BP 40109, F86961 FUTUROSCOPE CHASSENEUIL cedex (France); Cormier, J.; Jouiad, M. [Institut Pprime CNRS-ENSMA-Universite de Poitiers, Departement Physique et Mecanique des Materiaux, ENSMA-Teleport 2, 1 avenue Clement Ader, BP 40109, F86961 FUTUROSCOPE CHASSENEUIL cedex (France); Gallerneau, F.; Paulmier, P. [Office National d' Etudes et de Recherches Aerospatiales, 29 avenue de la Division Leclerc, BP 72, 92322 Chatillon (France); Hamon, F. [Institut Pprime CNRS-ENSMA-Universite de Poitiers, Departement Physique et Mecanique des Materiaux, ENSMA-Teleport 2, 1 avenue Clement Ader, BP 40109, F86961 FUTUROSCOPE CHASSENEUIL cedex (France)

    2010-07-25

    A novel technique, combining on the one hand creep-fatigue tests with an overheating and creep tests with thermal cycling in the other hand, performed on {gamma}/{gamma}' nickel base single crystal superalloy MC2 have led to an increased understanding of fine {gamma}' precipitation and its strengthening effect. Both creep and creep-fatigue tests were conducted at 1050 deg. C with 1200 deg. C overheating for creep-fatigue experiments and with repeated overheatings at 1100 deg. C and 1150 deg. C for creep. The resulting microstructures of these experiments were examined using both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It appears, both on creep or creep-fatigue, once an overheating is experienced a fine {gamma}' precipitation occurs in {gamma} matrix. These precipitates seem to have a transient strengthening effect on the mechanical properties. For the creep-fatigue experiments a decrease of the plastic strain rate was measured at once after the temperature peak. In the case of the creep tests under thermal cycling, no extra deformation induced by the overheating at 1100 deg. C was recorded. However, overheatings at 1150 deg. C lead to a plastic strain jump which progressively decreases upon thermal cycling, due to the formation of fine {gamma}' precipitates. Furthermore, the {gamma}' fine particles seem to have a hardening effect that vanishes once they dissolve.

  19. Effects of repeated biaxial loads on the creep properties of cardinal ligaments.

    Science.gov (United States)

    Baah-Dwomoh, Adwoa; De Vita, Raffaella

    2017-10-01

    The cardinal ligament (CL) is one of the major pelvic ligaments providing structural support to the vagina/cervix/uterus complex. This ligament has been studied mainly with regards to its important function in the treatment of different diseases such as surgical repair for pelvic organ prolapse and radical hysterectomy for cervical cancer. However, the mechanical properties of the CL have not been fully determined, despite the important in vivo supportive role of this ligament within the pelvic floor. To advance our limited knowledge about the elastic and viscoelastic properties of the CL, we conducted three consecutive planar equi-biaxial tests on CL specimens isolated from swine. Specifically, the CL specimens were divided into three groups: specimens in group 1 (n = 7) were loaded equi-biaxially to 1 N, specimens in group 2 (n = 8) were loaded equi-biaxially to 2N, and specimens in group 3 (n = 7) were loaded equi-biaxially to 3N. In each group, the equi-biaxial loads of 1N, 2N, or 3N were applied and kept constant for 1200s three times. The two axial loading directions were selected to be the main in-vivo loading direction of the CL and the direction that is perpendicular to it. Using the digital image correlation (DIC) method, the in-plane Lagrangian strains in these two loading directions were measured throughout the tests. The results showed that CL was elastically anisotropic, as statistical differences were found between the mean strains along the two axial loading directions for specimens in group 1, 2, or 3 when the equi-biaxial load reached 1N, 2N, or 3N, respectively. For specimens in group 1 and 2, no statistical differences were detected in the mean normalized strains (or, equivalently, the increase in strain over time) between the two axial loading directions for each creep test. For specimens in group 3, some differences were noted but, by the end of the 3rd creep test, there were no statistical differences in the mean normalized strains between

  20. Thermal insulation properties of walls

    Directory of Open Access Journals (Sweden)

    Zhukov Aleksey Dmitrievich

    2014-05-01

    Full Text Available Heat-protective qualities of building structures are determined by the qualities of the used materials, adequate design solutions and construction and installation work of high quality. This rule refers both to the structures made of materials similar in their structure and nature and mixed, combined by a construction system. The necessity to ecaluate thermal conductivity is important for a product and for a construction. Methods for evaluating the thermal protection of walls are based on the methods of calculation, on full-scale tests in a laboratory or on objects. At the same time there is a reason to believe that even deep and detailed calculation may cause deviation of the values from real data. Using finite difference method can improve accuracy of the results, but it doesn’t solve all problems. The article discusses new approaches to evaluating thermal insulation properties of walls. The authors propose technique of accurate measurement of thermal insulation properties in single blocks and fragments of walls and structures.

  1. Physicochemical properties and creep strength of a single crystal of nickel-base superalloy containing rhenium and ruthenium

    Energy Technology Data Exchange (ETDEWEB)

    Petrushin, Nikolay V.; Svetlow, Igor L.; Samoylov, Andrey I.; Morozova, Galina I. [All-Russia Institute of Aviation Materials, Moscow (Russian Federation)

    2010-05-15

    The influence of alloying elements, including rhenium and ruthenium, on the physicochemical and structural parameters of single crystal nickel-base superalloys has been analyzed. The results were used in computer designing of a single crystal nickel-base superalloy containing rhenium and ruthenium. The optimized alloy composition, providing the best physicochemical properties and longest creep lifetime, contains 6 wt.% rhenium and 4 wt.% ruthenium. <001> single crystals of the designed superalloy were directionally solidified and investigated in as-cast, heat treated and creep deformed conditions. The investigations included: characterization of the superalloy microstructure, dendritic segregation of alloying elements, their partition between the {gamma}- and {gamma}'-phases etc. Creep rupture tests were performed in the temperature interval of 900-1100 C and included tests longer 1000 h. (orig.)

  2. Measurement of Creep Properties of Ultra-High-Temperature Materials by a Novel Non-Contact Technique

    Science.gov (United States)

    Hyers, Robert W.; Lee, Jonghyun; Rogers, Jan R.; Liaw, Peter K.

    2007-01-01

    A non-contact technique for measuring the creep properties of materials has been developed and validated as part of a collaboration among the University of Massachusetts, NASA Marshall Space Flight Center Electrostatic Levitation Facility (ESL), and the University of Tennessee. This novel method has several advantages over conventional creep testing. The sample is deformed by the centripetal acceleration from the rapid rotation, and the deformed shapes are analyzed to determine the strain. Since there is no contact with grips, there is no theoretical maximum temperature and no concern about chemical compatibility. Materials may be tested at the service temperature even for extreme environments such as rocket nozzles, or above the service temperature for accelerated testing of materials for applications such as jet engines or turbopumps for liquid-fueled engines. The creep measurements have been demonstrated to 2400 C with niobium, while the test facility, the NASA MSFC ESL, has processed materials up to 3400 C. Furthermore, the ESL creep method employs a distribution of stress to determine the stress exponent from a single test, versus the many tests required by conventional methods. Determination of the stress exponent from the ESL creep tests requires very precise measurement of the surface shape of the deformed sample for comparison to deformations predicted by finite element models for different stress exponents. An error analysis shows that the stress exponent can be determined to about 1% accuracy with the current methods and apparatus. The creep properties of single-crystal niobium at 1985 C showed excellent agreement with conventional tests performed according to ASTM Standard E-139. Tests on other metals, ceramics, and composites relevant to rocket propulsion and turbine engines are underway.

  3. The microstructure and impression creep behavior of cast Mg–4Sn–4Ca alloy

    Energy Technology Data Exchange (ETDEWEB)

    Khalilpour, Hamid, E-mail: Ha.Khalilpoorster@gmail.com [Shahid Rajaee Teacher Training University, Faculty of Mechanical Engineering, Lavizan, Tehran (Iran, Islamic Republic of); Mahdi Miresmaeili, Seyed, E-mail: s_m_miresmaeily@yahoo.com [Shahid Rajaee Teacher Training University, Faculty of Mechanical Engineering, Lavizan, Tehran (Iran, Islamic Republic of); Baghani, Amir, E-mail: amir-baghani@uiowa.edu [University of Iowa, Department of Mechanical and Industrial Engineering, Iowa City, IA (United States)

    2016-01-15

    Because of low creep properties of magnesium–aluminum alloys, magnesium–tin alloys have received much attention in applications where high mechanical properties in high temperatures required. In this study creep properties of Mg–4Sn–4Ca alloy were investigated by the aim of impression creep test, scanning electron microscopy, energy dispersion spectrometry and X-ray diffraction analysis. The impression creep tests were carried out under different shear modulus normalized stress at high temperatures. According to the measured stress exponent values and activation energies the climb-controlled dislocation creep was determined as the dominant mechanism. The creep resistance of this alloy was related to the presence of Ca–Mg–Sn and Mg{sub 2}Ca phases which are distributed uniformly in the matrix and exhibit high thermal stability.

  4. Creep of fibrous composite materials

    DEFF Research Database (Denmark)

    Lilholt, Hans

    1985-01-01

    Models are presented for the creep behaviour of fibrous composite materials with aligned fibres. The models comprise both cases where the fibres remain rigid in a creeping matrix and cases where the fibres are creeping in a creeping matrix. The treatment allows for several contributions...... to the creep strength of composites. The advantage of combined analyses of several data sets is emphasized and illustrated for some experimental data. The analyses show that it is possible to derive creep equations for the (in situ) properties of the fibres. The experiments treated include model systems...

  5. CREEP PROPERTIES EVALUATION AT 600°C OF MARAGING 300 STEEL SOLUTION TREATED

    Directory of Open Access Journals (Sweden)

    Adriano Gonçalves dos Reis

    2014-03-01

    Full Text Available Maraging steels are alloys with Ni-Co-Mo-Ti with ultra-high resistance and broad application, with fundamental interest in the aerospace sector due to high mechanical resistance combined with a good fracture toughness. This steel has been proposed to replace the steels 300M and 4340 in the Brazilian rocket engine case for Satellite Launcher Vehicles. Maraging steels have a metastable martensitic structure that can revert to austenite when heated in temperatures close to the aging temperature, and this effect can be enhanced with the temperature increasing and time of treatment. Therefore, the study of creep behavior in elevated temperatures has technological importance to the development of this material. In this work the creep behavior of a 300 grade commercial maraging steel solution treated is evaluated by carrying out creep tests at 600ºC and in a stress range of 200MPa to 500 MPa. Creep parameters, such as steady state creep rate (ε·s, final creep time (tf, and stress exponent from secondary creep (n are determined, considering that they are important to evaluate the creep resistance of the material.

  6. Effect of Solution Treatment on Precipitation Behaviors, Age Hardening Response and Creep Properties of Elektron21 Alloy Reinforced by AlN Nanoparticles

    Directory of Open Access Journals (Sweden)

    Abdollah Saboori

    2017-12-01

    Full Text Available In the present study, the solution and ageing treatments behavior of Mg-RE-Zr-Zn alloy (Elektron21 and its nano-AlN reinforced nanocomposites have been evaluated. The properties of the thermal-treated materials were investigated in terms of Vickers hardness, the area fraction of precipitates, microstructure and phase composition. The solution treatments were performed by treating at 520 °C, 550 °C and 580 °C in argon atmosphere. The outcomes show that the hardness of the solutionized alloys was slightly affected by the solution temperature. X-ray diffraction and image analysis revealed that the complete dissolution of precipitates was not possible, neither for Elektron21 (El21 nor for its AlN containing nanocomposites. The ageing treatment of El21 led to a significant improvement in hardness after 20 h, while for longer times, it progressively decreased. The effect of ageing on the hardness of El21–AlN composites was found to be much less than this effect on the hardness of the host alloy. Electron backscatter diffraction (EBSD analysis of El21 and El21–1%AlN after solution treatment confirm the random orientation of grains with a typical texture of random distribution. The as-cast creep results showed that the incorporation of nanoparticles could effectively improve the creep properties, while the results after solution treatment at 520 °C for 12 h followed by ageing treatment at 200 °C for 20 h confirmed that the minimum creep rate of T6-El21 was almost equal to the as-cast El21–AlN.

  7. Effect of Solution Treatment on Precipitation Behaviors, Age Hardening Response and Creep Properties of Elektron21 Alloy Reinforced by AlN Nanoparticles.

    Science.gov (United States)

    Saboori, Abdollah; Padovano, Elisa; Pavese, Matteo; Dieringa, Hajo; Badini, Claudio

    2017-12-02

    In the present study, the solution and ageing treatments behavior of Mg-RE-Zr-Zn alloy (Elektron21) and its nano-AlN reinforced nanocomposites have been evaluated. The properties of the thermal-treated materials were investigated in terms of Vickers hardness, the area fraction of precipitates, microstructure and phase composition. The solution treatments were performed by treating at 520 °C, 550 °C and 580 °C in argon atmosphere. The outcomes show that the hardness of the solutionized alloys was slightly affected by the solution temperature. X-ray diffraction and image analysis revealed that the complete dissolution of precipitates was not possible, neither for Elektron21 (El21) nor for its AlN containing nanocomposites. The ageing treatment of El21 led to a significant improvement in hardness after 20 h, while for longer times, it progressively decreased. The effect of ageing on the hardness of El21-AlN composites was found to be much less than this effect on the hardness of the host alloy. Electron backscatter diffraction (EBSD) analysis of El21 and El21-1%AlN after solution treatment confirm the random orientation of grains with a typical texture of random distribution. The as-cast creep results showed that the incorporation of nanoparticles could effectively improve the creep properties, while the results after solution treatment at 520 °C for 12 h followed by ageing treatment at 200 °C for 20 h confirmed that the minimum creep rate of T6-El21 was almost equal to the as-cast El21-AlN.

  8. Development of creep damage assessment system for aged thermal power plant

    Energy Technology Data Exchange (ETDEWEB)

    Nonaka, Isamu [IshikawaJima-Harima Heavy Industries Co., Ltd., Tokyo (Japan); Umaki, Hideo [Ishikawajima-Harima Heavy Industries Co., Ltd., Tokyo (Japan); Nishida, Hidetalca [The Chugoku Electric Power Co., Inc., Hiroshima (Japan); Yamaguchi, Hiroshi [The Chugoku Electric Power Co., Inc., Hiroshima (Japan)

    1998-12-31

    IHI has developed the Creep Damage Assessment System to identify voids by processing an image observed by a small laser microscope with an advanced image processing technique jointly with Chugoku Electric Power Co., Inc. The result can be obtained immediately on the spot. Application tests of the system at the Unit No.3 boiler of the Kudamatsu Power Station showed good operability, adaptability to the environment, and accuracy. The new system can easily indicate damage conditions in parts during the periodical inspection, allowing rapid maintenance. Time reduction required for assessment and increased reliability of equipment can be also achieved. (orig.)

  9. Effects of Cr, Mo, W, Mn and Ni on creep properties of 2. 25Cr-Mo-V rotor steel. 2. 25Cr-Mo-V tanko no creep tokusei ni oyobosu Cr, Mo, W, Mn oyobi Ni no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Kadoya, Y. (Mitsubishi Heavy Industries Ltd., Tokyo (Japan). Takasago Research and Development Center); Kitai, T.; Matsuo, A.; Tsuji, I. (Mitsubishi Heavy Industries Ltd., Tokyo (Japan)); Azuma, T.; Tanaka, Y. (The Japan Steel Works Ltd., Tokyo (Japan). Muroran Research Lab. ); Ikeda, Y. (The Japan Steel Works Ltd., Tokyo (Japan))

    1993-08-01

    2.2SCr-Mo-V rotor steel is developed and put into practical use as a high and low pressure suitable rotor steel and the gas turbine disk materials. In this study, the creep experiments subjected to stresses of the levels of 220, 250 and 280 MPa at 565[degree]C for 2.25Cr-Mo-V steel were carried out, effect of the alloying elements on creep properties was examined, and effect of the alloying elements on the precipitation of carbides was investigated. Main results obtained were as follows: Cr, Ni and Mn additions decreased the creep rupture strength of 2.25Cr-Mo-V steel, and W addition increased the creep rupture strength. Mo addition did not give a remarkable change on the seep rupture strength. Ni addition up to 1.8% did not exert a significant effect on the creep rupture strength, and its addition more than that value remarkably decreased the creep rupture strength. 20 refs., 12 figs., 2 tabs.

  10. Viscoelastic properties of tablets from Osborne fractions, pentosans, flour and bread evaluated by creep tests

    Science.gov (United States)

    Escalante-Aburto, Anayansi; de Dios Figueroa-Cárdenas, Juan; Véles-Medina, José Juan; Ponce-García, Néstor; Hernández-Estrada, Zorba Josué; Rayas-Duarte, Patricia; Simsek, Senay

    2017-07-01

    Little attention has been given to the influence of non-gluten components on the viscoelastic properties of wheat flour dough, bread making process and their products. The aim of this study was to evaluate by creep tests the viscoelastic properties of tablets manufactured from Osborne solubility fractions (globulins, gliadins, glutenins, albumins and residue), pentosans, flour and bread. Hard and soft wheat cultivars were used to prepare the reconstituted tablets. Sintered tablets (except flour and bread) showed similar values to those obtained from the sum of the regression coefficients of the fractions. Gliadins and albumins accounted for about 54% of the total elasticity. Gliadins contributed with almost half of the total viscosity (45.7%), and showed the highest value for the viscosity coefficient of the viscous element. When the effect of dilution was evaluated, the residue showed the highest instantaneous elastic modulus (788.2 MPa). Retardation times of the first element (λ1 3.5 s) were about 10 times lower than the second element (λ2 39.3 s). The analysis of compliance of data corrected by protein content in flour showed that the residue fraction presented the highest values. An important contribution of non-gluten components (starch, albumins and globulins) on the viscoelastic performance of sintered tablets from Osborne fractions, flour and bread was found.

  11. The use of indentor testing in determining the creep properties locally - a review; Nyttjande av indentorteknik foer bestaemning av krypegenskaper lokalt - litteraturstudie

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Peder [Det Norske Veritas AB, Stockholm (Sweden)

    2000-07-01

    A review has been performed with the purpose of examining what has been published regarding the creep indentation technique. In the reference list a selected choice of published papers is presented. Furthermore, the use of the technique is explained, a presentation is made of the parameters that are possible to determine and, finally, the limitations of the technique are discussed. In the investigated publications, the theoretical aspects of the indentation technique are discussed, as well as the possibilities of applying the technique in practice. From the published material, it is obvious that creep indentation testing is a technique suitable when the creep deformation properties of a material are to be determined. It seems though, that the technique so far mostly has been used in academically designed experiments and not in a larger industrial scale. The creep indentation testing technique seems to be a good complement to conventional uniaxial creep testing in determining the creep deformation properties of a material. Especially in testing of the creep deformation properties of weldments and parts of weldments, such as HAZ, the indentation testing technique can prove to be advantageous, as only a small amount of material is needed. In the line of business of plants operating in the high temperature range, where materials experience creep, there should be an interest in seeing a development of a testing standard for the creep indentation technique. This could be performed by doing a more comprehensive analysis of a selected choice of published papers, putting together their differences and similarities after which verifying experiments are pursued. In the end, it should be possible to come up with a draft standard for creep indentation testing.

  12. Creep properties of PWC-11 base metal and weldments as affected by heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Titran, R.H.; Moore, T.J.; Grobstein, T.L. [Lewis Research Center, Cleveland, OH (United States)

    1994-09-01

    In a preliminary study using single specimens for each condition, PWC-11 (a niobium-base alloy with a nominal composition of Nb-1%Zr-0.1%C) was creep tested at 1350 K and 40 MPa. Base metal specimens and specimens with transverse electrode beam welds were tested with and without a 1000 hr, 1350 K aging treatment prior to testing. In the annealed condition (1 hr at 1755 K + 2 hr at 1475 K), the base metal exhibited superior creep strength compared to the aged condition, reaching 1 percent strain in 3480 hr. A 1000 hr, 1350 K aging treatment prior to creep testing had a severe detrimental effect on creep strength of the base metal and transverse electron beam weldments, reducing the time to attain 1 percent strain by an order of magnitude. Extrapolated temperature compensated creep rates indicate that the present heat of PWC-11 may be four times as creep resistance as similarly tested Nb-1%Zr. The extrapolated stress to achieve 1 percent creep strain in 7 yr at 1350 K is 0.6 MPa for annealed Nb-1%Zr and 2.8 MPa for annealed and aged PWC-11 base metal with and without a transverse electron beam weld.

  13. Creep-Rupture Properties and Corrosion Behaviour of 21/4 Cr-1 Mo Steel and Hastelloy X-Alloys in Simulated HTGR Environment

    DEFF Research Database (Denmark)

    Lystrup, Aage; Rittenhouse, P. L.; DiStefano, J. R.

    Hastelloy X and 2/sup 1///sub 4/ Cr-1 Mo steel are being considered as structural alloys for components of a High-Temperature Gas-Cooled Reactor (HTGR) system. Among other mechanical properties, the creep behavior of these materials in HTGR primary coolant helium must be established to form part...... of the design criteria. This report describes the simulated HTGR-helium environmental creep facilities, summarizes preliminary creep properties of 2/sup 1///sub 4/ Cr-1 Mo steel and Hastelloy X generated in HTGR helium and compares these with data obtained by testing in air. Some corrosion characteristics...

  14. Creep properties of phosphorus alloyed oxygen free copper under multiaxial stress state

    Energy Technology Data Exchange (ETDEWEB)

    Rui Wu; Sandstroem, Rolf; Seitisleam, Facredin

    2009-10-15

    Phosphorus alloyed oxygen free copper (Cu-OFP) canisters are planned to be used for spent nuclear fuel in Sweden. The copper canisters will be subjected to creep under multiaxial stress states in the repository. Creep tests have therefore been carried out at 75 deg C using double notch specimens with notch acuities of 0.5, 2, 5, and 18.8, respectively. The creep lifetime for notched specimens is considerably longer than that for the smooth one at a given net section stress, indicating that the investigated Cu-OFP is notch insensitive (notch strengthening). The notch strengthening factor in time is, for instance, greater than 70 at 180 MPa for the bluntest notch (notch acuity = 0.5). The creep lifetime is notch acuity dependent. The sharper the notch, the longer the creep lifetime is. The creep deformation is to a significant extent concentrated to the region around the notches. Different deformation on the two notches is observed. Both axial and radial strains on the failed notch are several times larger than those on the unbroken one. Linear relation between the axial and the radial strains on the notches is found. Transgranular failure is predominant, independent of stress, rupture time, and notch acuity. Adjacent to fracture, elongated grains along the stress direction, separate pores and cavities are often visible. On the unbroken notch, fewer separate cavities and cracks are only seen intergranularly for the sharper notches (notch acuity > 2). To interpret the tests for the notched creep specimens, finite element computations have been performed. A fundamental model for primary and secondary creep without fitting parameters has been used as constitutive equation. The FEM-modelling could represent the creep strain versus time curves for the notched specimens in a satisfactory way. In these curves the strain on loading is included. From the FEM-computations a stationary creep stress could be assessed, which is close to the reference stress. For a given

  15. Creep properties and microstructure evaluation of weld joint of the pipe made of P92 steel

    Energy Technology Data Exchange (ETDEWEB)

    Kasl, Josef; Jandova, Dagmar; Chvostova, Eva [SKODA VYZKUM s.r.o., Plzen (Czech Republic); Folkova, Eva [SKODA POWER a.s., Plzen (Czech Republic)

    2010-07-01

    One-side weld joint of W type was prepared from P92 type steel using GTAW and SMAW method. Creep test to the rupture of smooth cross-weld samples has been carried out at temperatures ranging from 575 to 650 C and at stresses from 70 to 240 MPa. Fractographic analysis, hardness measurement and detailed study of submicrostructure have been performed using light, scanning and transmission electron microscopy. Changes of microstructure were correlated with the creep strength. Increase in size of secondary phases and cavities formation were evident after creep tests at temperatures above 575 C. Voids were concentrated in the fine prior austenite grain heat affected zones, where fracture occurred. In addition, a sporadic occurrence of individual cavities was found out in the base material and the weld metal after tests at 625 and 650 C. During creep exposures at temperatures above 600 C Laves phase precipitated. (orig.)

  16. Creep properties in similar weld joint of a thick-walled P92 steel pipe

    Czech Academy of Sciences Publication Activity Database

    Sklenička, Václav; Kuchařová, Květa; Svobodová, M.; Kvapilová, Marie; Král, Petr; Horváth, P.

    2016-01-01

    Roč. 119, č. 1 (2016), s. 1-12 ISSN 1044-5803 R&D Projects: GA ČR(CZ) GA16-09518S; GA MPO FR-TI4/406 Institutional support: RVO:68081723 Keywords : 9–12%Cr steels * Creep testing * High temperature creep * Thick-walled pipe * Welding Subject RIV: JG - Metallurgy Impact factor: 2.714, year: 2016

  17. Theory of transformation thermal convection for creeping flow in porous media: Cloaking, concentrating, and camouflage

    Science.gov (United States)

    Dai, Gaole; Shang, Jin; Huang, Jiping

    2018-02-01

    Heat can transfer via thermal conduction, thermal radiation, and thermal convection. All the existing theories of transformation thermotics and optics can treat thermal conduction and thermal radiation, respectively. Unfortunately, thermal convection has seldom been touched in transformation theories due to the lack of a suitable theory, thus limiting applications associated with heat transfer through fluids (liquid or gas). Here, we develop a theory of transformation thermal convection by considering the convection-diffusion equation, the equation of continuity, and the Darcy law. By introducing porous media, we get a set of equations keeping their forms under coordinate transformation. As model applications, the theory helps to show the effects of cloaking, concentrating, and camouflage. Our finite-element simulations confirm the theoretical findings. This work offers a transformation theory for thermal convection, thus revealing novel behaviors associated with potential applications; it not only provides different hints on how to control heat transfer by combining thermal conduction, thermal convection, and thermal radiation, but also benefits mass diffusion and other related fields that contain a set of equations and need to transform velocities at the same time.

  18. Low Temperature Creep of Hot-Extruded Near-Stoichiometric NiTi Shape Memory Alloy. Part 2; Effect of Thermal Cycling

    Science.gov (United States)

    Raj, S. V.; Noebe, R. D.

    2013-01-01

    This paper is the first report on the effect prior low temperature creep on the thermal cycling behavior of NiTi. The isothermal low temperature creep behavior of near-stoichiometric NiTi between 300 and 473 K was discussed in Part I. The effect of temperature cycling on its creep behavior is reported in the present paper (Part II). Temperature cycling tests were conducted between either 300 or 373 K and 473 K under a constant applied stress of either 250 or 350 MPa with hold times lasting at each temperature varying between 300 and 700 h. Each specimen was pre-crept either at 300 or at 473 K for several months under an identical applied stress as that used in the subsequent thermal cycling tests. Irrespective of the initial pre-crept microstructures, the specimens exhibited a considerable increase in strain with each thermal cycle so that the total strain continued to build-up to 15 to 20 percent after only 5 cycles. Creep strains were immeasurably small during the hold periods. It is demonstrated that the strains in the austenite and martensite are linearly correlated. Interestingly, the differential irrecoverable strain, in the material measured in either phase decreases with increasing number of cycles, similar to the well-known Manson-Coffin relation in low cycle fatigue. Both phases are shown to undergo strain hardening due to the development of residual stresses. Plots of true creep rate against absolute temperature showed distinct peaks and valleys during the cool-down and heat-up portions of the thermal cycles, respectively. Transformation temperatures determined from the creep data revealed that the austenitic start and finish temperatures were more sensitive to the pre-crept martensitic phase than to the pre-crept austenitic phase. The results are discussed in terms of a phenomenological model, where it is suggested that thermal cycling between the austenitic and martensitic phase temperatures or vice versa results in the deformation of the austenite and

  19. Thermal properties of methyltrimethoxysilane aerogel thin films

    Directory of Open Access Journals (Sweden)

    Leandro N. Acquaroli

    2016-10-01

    Full Text Available Aerogels are light and porous solids whose properties, largely determined by their nanostructure, are useful in a wide range of applications, e.g., thermal insulation. In this work, as-deposited and thermally treated air-filled silica aerogel thin films synthesized using the sol-gel method were studied for their thermal properties using the 3-omega technique, at ambient conditions. The thermal conductivity and diffusivity were found to increase as the porosity of the aerogel decreased. Thermally treated films show a clear reduction in thermal conductivity compared with that of as-deposited films, likely due to an increase of porosity. The smallest thermal conductivity and diffusivity found for our aerogels were 0.019 W m−1 K−1 and 9.8 × 10-9 m2 s−1. A model was used to identify the components (solid, gaseous and radiative of the total thermal conductivity of the aerogel.

  20. Room-Temperature Indentation Creep and the Mechanical Properties of Rapidly Solidified Sn-Sb-Pb-Cu Alloys

    Science.gov (United States)

    Kamal, Mustafa; El-Bediwi, A.; Lashin, A. R.; El-Zarka, A. H.

    2016-05-01

    In this paper, we study the room-temperature indentation creep and the mechanical properties of Sn-Sb-Pb-Cu alloys. Rapid solidification from melt using the melt-spinning technique is applied to prepare all the alloys. The experimental results show that the magnitude of the creep displacement increases with the increase in both time and applied load, and the stress exponent increases with the increase in the copper content in the alloys which happens primarily due to the existence of the intermetallic compounds SbSn and Cu6Sn5. The calculated values of the stress exponent are in the range of 2.82 to 5.16, which are in good agreement with the values reported for the Sn-Sb-Pb-Cu alloys. We have also studied and analyzed the structure, elastic modulus, and internal friction of the Sn-Sb-Pb-Cu alloys.

  1. Creep rupture properties of P122 and P92 steel HAZs simulated by heat treatments and by a weld simulator

    Energy Technology Data Exchange (ETDEWEB)

    Albert, S.K. [IGCAR, Kalpakkam (India); Matsui, M. [Mitsubushi Heavy Industries, Nagasaki (Japan); Watanabe, T.; Hongo, H.; Kubo, K.; Tabuchi, M. [National Inst. for Materials Science, Ibaraki (Japan)

    2002-07-01

    In the present study, creep rupture properties of the heat affected zones (HAZs) of P122 and P92 steels, simulated by a heat treatments and by a weld simulator, are studied and compared with those of the actual weld joint. Specimen blanks cut out from steel plates were heated to different peak temperatures that corresponds to intercritical HAZ (ICHAZ), fine grained HAZ (FGHAZ) and coarse grained HAZ (CGHAZ) both by heat treatment and by employing a weld simulator. These were then subjected to post weld heat treatment (PWHT) and creep specimens prepared from these blanks were tested at 923 K for various stress levels. Microstructure was uniform for the specimens with HAZ simulated by heat treatment while for those produced by weld simulator, the uniform microstructures corresponding to the peak temperature of simulation was confined to only {proportional_to}10 mm at the center of the specimens. (orig.)

  2. Investigation on Long-term Creep Rupture Properties and Microstructure Stability of Fe-Ni based Alloy Ni-23Cr-7W at 700°C

    DEFF Research Database (Denmark)

    Tokairin, Tsuyoshi; Dahl, Kristian Vinter; Danielsen, Hilmar Kjartansson

    2013-01-01

    Long-term creep rupture properties and microstructural stability of Fe–Ni based alloy Ni–23Cr–7W (HR6W, ASME Code Case 2684) were experimentally investigated. Crept specimens at 700 °C for durations up to 37,667 h were chosen, the microstructure evolution during creep was characterized. Besides...... for the main strengthening precipitate, Laves phase. The alloy was proven to have good microstructural stability without observable coarsening of strengthening precipitates during long-term creep up to around 37,667 h. It was also verified that the growth kinetics of Laves phase can be well described...

  3. Influence of textile properties on thermal comfort

    Science.gov (United States)

    Marolleau, A.; Salaun, F.; Dupont, D.; Gidik, H.; Ducept, S.

    2017-10-01

    This study reports on the impact of textile properties on thermal comfort. The fabric weight, thickness, porosity, moisture regain, air permeability and density have been considered and correlated to the thermal and water vapour resistance, permeability index, thermal conductivity and effusivity, and moisture management capacity. Results suggest that moisture transfer is affected by thickness, density and moisture regain whereas thermal transfer by air permeability and density.

  4. Damage Assessment of Creep Tested and Thermally Aged Metallic Alloys Using Acousto-Ultrasonics

    Science.gov (United States)

    Gyekenyesi, Andrew L.; Kautz, Harold E.; Baaklini, George Y.

    2001-01-01

    In recent years emphasis has been placed on the early detection of material changes experienced in turbine powerplant components. During the scheduled overhaul of a turbine, the current techniques of examination of various hot section components aim to find flaws such as cracks, wear, and erosion, as well as excessive deformations. Thus far, these localized damage modes have been detected with satisfactory results. However, the techniques used to find these flaws provide no information on life until the flaws are actually detected. Major improvements in damage assessment, safety, as well as more accurate life prediction could be achieved if nondestructive evaluation (NDE) techniques could be utilized to sense material changes that occur prior to the localized defects mentioned. Because of elevated temperatures and excessive stresses, turbine components may experience creep behavior. As a result, it is desirable to monitor and access the current condition of such components. Research at the NASA Glenn Research Center involves developing and utilizing an NDE technique that discloses distributed material changes that occur prior to the localized damage detected by the current methods of inspection. In a recent study, creep processes in a nickel-base alloy were the life-limiting condition of interest, and the NDE technique was acousto-ultrasonics (AU). AU is an NDE technique that utilizes two ultrasonic transducers to interrogate the condition of a test specimen. The sending transducer introduces an ultrasonic pulse at a point on the surface of the specimen while a receiving transducer detects the signal after it has passed through the material. The goal of the method is to correlate certain parameters of the detected waveform to characteristics of the material between the two transducers. Here, the waveform parameter of interest is the attenuation due to internal damping for which information is being garnered from the frequency domain. The parameters utilized to

  5. Phase Evolution in and Creep Properties of Nb-Rich Nb-Si-Cr Eutectics

    Science.gov (United States)

    Gang, Florian; Kauffmann, Alexander; Heilmaier, Martin

    2017-10-01

    In this work, the Nb-rich ternary eutectic in the Nb-Si-Cr system has been experimentally determined to be Nb-10.9Si-28.4Cr (in at. pct). The eutectic is composed of three main phases: Nb solid solution (Nbss), β-Cr2Nb, and Nb9(Si,Cr)5. The ternary eutectic microstructure remains stable for several hundred hours at a temperature up to 1473 K (1200 °C). At 1573 K (1300 °C) and above, the silicide phase Nb9(Si,Cr)5 decomposes into α-Nb5Si3, Nbss, and β-Cr2Nb. Under creep conditions at 1473 K (1200 °C), the alloy deforms by dislocation creep while the major creep resistance is provided by the silicide matrix. If the silicide phase is fragmented and, thus, its matrix character is destroyed by prior heat treatment [e.g., at 1773 K (1500 °C) for 100 hours], creep is mainly controlled by the Laves phase β-Cr2Nb, resulting in increased minimum strain rates. Compared to state of the art Ni-based superalloys, the creep resistance of this three-phase eutectic alloy is significantly higher.

  6. Understanding effects of microstructural inhomogeneity on creep response – New approaches to improve the creep resistance in magnesium alloys

    Directory of Open Access Journals (Sweden)

    Yuanding Huang

    2014-06-01

    Full Text Available Previous investigations indicate that the creep resistance of magnesium alloys is proportional to the stability of precipitated intermetallic phases at grain boundaries. These stable intermetallic phases were considered to be effective to suppress the deformation by grain boundary sliding, leading to the improvement of creep properties. Based on this point, adding the alloying elements to form the stable intermetallics with high melting point became a popular way to develop the new creep resistant magnesium alloys. The present investigation, however, shows that the creep properties of binary Mg–Sn alloy are still poor even though the addition of Sn possibly results in the precipitation of thermal stable Mg2Sn at grain boundaries. That means other possible mechanisms function to affect the creep response. It is finally found that the poor creep resistance is attributed to the segregation of Sn at dendritic and grain boundaries. Based on this observation, new approaches to improve the creep resistance are suggested for magnesium alloys because most currently magnesium alloys have the commonality with the Mg–Sn alloys.

  7. Characterization of intrinsic material properties of a model lipoproteic emulsion gel by oscillatory and creep compliance rheometry.

    Science.gov (United States)

    Okada, Kyle S; Kuo, Wan-Yuan; Lee, Youngsoo

    2018-02-01

    The effects of varying formulation and processing parameters on rheological properties in a model lipid/protein-based emulsion gel were studied. Heat-set model lipoproteic emulsion gels were prepared with varying levels of protein, lipid, and NaCl contents and high pressure homogenization treatments. Small deformation oscillatory rheometry, creep compliance, and pore size analysis experiments were used to characterize intrinsic structural properties, matrix interactions, and microstructure. Creep compliance behavior of the gel system was successfully modeled by a four-component Burgers model. Shear storage and loss moduli and Newtonian viscosity increased while instantaneous compliance, retarded compliance, and pore size decreased with increasing protein or fat content or homogenization pressure. The data obtained in this study provide information on factors affecting protein network structure and strength, properties may be useful for creating desirable attributes in lipid/protein-based foods with a further optimization process. This research evaluates the effects of formulation and processing factors on the properties of a protein/fat-based food system. These properties may be related to sodium mobility and salty taste perception. This research provides information on strategies that can be used to control factors influencing the physical properties of protein/fat-based food systems targeting sodium reduction. © 2017 Wiley Periodicals, Inc.

  8. Research on Construction Optimization of Three-Connected-Arch Hydraulic Underground Cavities Considering Creep Property

    Directory of Open Access Journals (Sweden)

    Bao-yun Zhao

    2014-01-01

    Full Text Available In order to prevent the creep of surrounding rock in long-term construction, with consideration of different construction methods and other factors during the construction of large-scale underground cavity, three different construction schemes are designed for specific projects and a nonlinear viscoelastic-plastic creep model which can describe rock accelerated creeping is introduced and applied to construction optimization calculation of the large-scale three-connected-arch hydraulic underground cavity through secondary development of FLAC3D. The results show that the adoption of middle cavity construction method, the second construction method, enables the maximum vault displacement of 16.04 mm. This method results in less stress redistribution and plastic zone expansion to the cavity’s surrounding rock than the other two schemes, which is the safest construction scheme. The conclusion can provide essential reference and guidance to similar engineering for construction optimization.

  9. Microstructure and properties degradation of P/T 91, 92 steels weldments in creep conditions

    Directory of Open Access Journals (Sweden)

    Falat L.

    2012-01-01

    Full Text Available The studies were performed on dissimilar ferritic/austenitic weldments between 9Cr tempered martensitic steels of the grades either P/T 91 or 92 and unstabilised AISI316H austenitic steel. The welded joints were fabricated using the fusion welding by tungsten inert gas (TIG method with Ni-based filler metal. Microstructural analyses were performed using light and electron microscopy. Microstructural gradient in heat-affected zone (HAZ of 9Cr steels remained preserved during creep exposure. All weldments fractured by the type IV failure within their intercritical HAZ (ICHAZ regions. The most remarkable microstructural change during creep was the precipitation of intermetallic Laves phase. Experimentally determined phases of the samples after creep exposure are in good agreement with equilibrium thermodynamic calculations.

  10. Microstructure and long-term creep properties of 9–12% Cr steels

    DEFF Research Database (Denmark)

    Hald, John

    2008-01-01

    Advanced microstructure characterisation and microstructure modelling has demonstrated that long-term microstructure stability in 9–12% Cr steels under technical loading conditions is equivalent to precipitate stability. Mo and W can have a positive influence on long-term creep strength of 9–12% Cr...... steels by Laves phase precipitation hardening. Unexpected breakdown of long-term creep stability of a number of alloys is caused by precipitation of the complex Z-phase nitride, which may completely dissolve fine V and Nb containing MX nitrides. High Cr contents of 10% and above in the steels accelerate...

  11. Creep in amorphous metals

    Directory of Open Access Journals (Sweden)

    Michael E. Kassner

    2015-01-01

    Full Text Available This paper reviews the work on creep behavior of amorphous metals. There have been, over the past several years, a few reviews of the mechanical behavior of amorphous metals. Of these, the review of the creep properties of amorphous metals by Schuh et al. though oldest of the three, is particularly noteworthy and the reader is referred to this article published in 2007. The current review of creep of amorphous metals particularly focuses on those works since that review and places the work prior to 2007 in a different context where new developments warrant.

  12. Investigation of thermally activated deformation in amorphous PMMA and Zr-Cu-Al bulk metallic glasses with broadband nanoindentation creep

    Science.gov (United States)

    J.B. Puthoff; J.E. Jakes; H. Cao; D.S. Stone

    2009-01-01

    The development of nanoindentation test systems with high data collection speeds has made possible a novel type of indentation creep test: broadband nanoindentation creep (BNC). Using the high density of data points generated and analysis techniques that can model the instantaneous projected indent area at all times during a constant-load indentation experiment, BNC...

  13. Microstructure, Tensile and Creep Properties of Ta20Nb20Hf20Zr20Ti20High Entropy Alloy.

    Science.gov (United States)

    Larianovsky, Natalya; Katz-Demyanetz, Alexander; Eshed, Eyal; Regev, Michael

    2017-07-31

    This paper examines the microstructure and mechanical properties of Ta 20 Nb 20 Hf 20 Zr 20 Ti 20 . Two casting processes, namely, gravity casting and suction-assisted casting, were applied, both followed by Hot Isostatic Pressing (HIP). The aim of the current study was to investigate the creep and tensile properties of the material, since the literature review revealed no data whatsoever regarding these properties. The main findings are that the HIP process is responsible for the appearance of a Hexagonal Close Packed (HCP) phase that is dispersed differently in these two castings. The HIP process also led to a considerable increase in the mechanical properties of both materials under compression, with values found to be higher than those reported in the literature. Contrary to the compression properties, both materials were found to be highly brittle under tension, either during room temperature tension tests or creep tests conducted at 282 °C. Fractography yielded brittle fracture without any evidence of plastic deformation prior to fracture.

  14. Thermal properties of alkali-activated aluminosilicates

    Science.gov (United States)

    Florian, Pavel; Valentova, Katerina; Fiala, Lukas; Zmeskal, Oldrich

    2017-07-01

    The paper is focused on measurements and evaluation of thermal properties of alkali-activated aluminosilicates (AAA) with various carbon admixtures. Such composites consisting of blast-furnace slag, quartz sand, water glass as alkali activator and small amount of electrically conductive carbon admixture exhibit better electric and thermal properties than the reference material. Such enhancement opens up new practical applications, such as designing of snow-melting, de-icing or self-sensing systems that do not need any external sensors to detect current condition of building material. Thermal properties of the studied materials were measured by the step-wise transient method and mutually compared.

  15. Creep properties of simulated heat-affected zone of HR3C austenitic steel

    Czech Academy of Sciences Publication Activity Database

    Sklenička, Václav; Kuchařová, Květa; Kvapilová, Marie; Svoboda, Milan; Král, Petr; Dvořák, Jiří

    2017-01-01

    Roč. 128, JUN (2017), s. 238-247 ISSN 1044-5803 R&D Projects: GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 Keywords : HR3C steel * Welding * Heat affected zone * Creep * Microstructure * Fractography Subject RIV: JG - Metallurgy Impact factor: 2.714, year: 2016

  16. Effect of hot corrosion on the creep properties of types 321 and 347 stainless steels

    Science.gov (United States)

    González-Rodríguez, J. G.; Luna-Ramírez, A.; Martínez-Villafañe, A.

    1999-02-01

    Problems caused by hot corrosion and creep damage on superheater and reheater tubes of power plants using heavy oil as fuel inhibit the continuous service of the boilers and shorten their design lives. The acceleration of hot corrosion attack of boilers is caused by the presence of fuel ash deposits containing V, Na, and S, in the form of Na2SO4 and V2O5, which form low melting point phases. In addition to this, the tubes are exposed to the action of both high stresses and high temperatures, producing a continuous plastic deformation of the tube walls called creep damage. Creep rupture tests were carried out in the temperature range 620 to 670 °C in static air in the presence of corrosive environments using 321H and 347H type stainless steels used in superheater and reheater tubes under hot corrosion and creep environments. The corrosive environment includes synthetic Na2SO4, V2O5, and the mixture 80% V2O5-20%Na2SO4. Also, the role of the different elements present in the environments on corrosion was investigated using electronic microscopy and x-ray diffraction techniques.

  17. Impurity Antimony-Induced Creep Property Deterioration and Its Suppression by Rare Earth Ceriumfor a 9Cr-1Mo Ferritic Heat-Resistant Steel

    Directory of Open Access Journals (Sweden)

    Yewei Xu

    2016-08-01

    Full Text Available The high temperature creep properties of three groups of modified 9Cr-1Mo steel samples, undoped, doped with Sb, and doped with Sb and Ce, are evaluated under the applied stresses from 150 MPa to 210 MPa and at the temperatures from 873–923 K. The creep behavior follows the temperature-compensated power law as well as the Monkman-Grant relation. The creep activation energy for the Sb-doped steel (519 kJ/mol is apparently lower than that for the undoped one (541 kJ/mol, but it is considerably higher for the Sb+Ce-doped steel (621 kJ/mol. Based on the obtained relations, both the creep lifetimes under 50 MPa, 80 MPa, and 100 MPa in the range 853–923 K and the 105 h creep rupture strengths at 853 K, 873 K, and 893 K are predicted. It is demonstrated that the creep properties of the Sb-doped steel are considerably deteriorated but those of the Sb+Ce-doped steel are significantly improved as compared with the undoped steel. Microstructural and microchemical characterizations indicate that the minor addition of Ce can stabilize the microstructure of the steel by segregating to grain boundaries and dislocations, thereby offsetting the deleterious effect of Sb by coarsening the microstructure and weakening the grain boundary.

  18. Creep Resistant Zinc Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Frank E. Goodwin

    2002-12-31

    This report covers the development of Hot Chamber Die Castable Zinc Alloys with High Creep Strengths. This project commenced in 2000, with the primary objective of developing a hot chamber zinc die-casting alloy, capable of satisfactory service at 140 C. The core objectives of the development program were to: (1) fill in missing alloy data areas and develop a more complete empirical model of the influence of alloy composition on creep strength and other selected properties, and (2) based on the results from this model, examine promising alloy composition areas, for further development and for meeting the property combination targets, with the view to designing an optimized alloy composition. The target properties identified by ILZRO for an improved creep resistant zinc die-casting alloy were identified as follows: (1) temperature capability of 1470 C; (2) creep stress of 31 MPa (4500 psi); (3) exposure time of 1000 hours; and (4) maximum creep elongation under these conditions of 1%. The project was broadly divided into three tasks: (1) Task 1--General and Modeling, covering Experimental design of a first batch of alloys, alloy preparation and characterization. (2) Task 2--Refinement and Optimization, covering Experimental design of a second batch of alloys. (3) Task 3--Creep Testing and Technology transfer, covering the finalization of testing and the transfer of technology to the Zinc industry should have at least one improved alloy result from this work.

  19. Structural, thermal and spectroscopic properties of supramolecular ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 118; Issue 6. Structural, thermal and spectroscopic properties of supramolecular coordination solids. Birinchi Kumar Das Sanchay Jyoti Bora Monideepa Chakrabortty Laksheswar Kalita Rajesh Chakrabarty Ramakanta Barman. Volume 118 Issue 6 November 2006 ...

  20. Thermal to electricity conversion using thermal magnetic properties

    Science.gov (United States)

    West, Phillip B [Idaho Falls, ID; Svoboda, John [Idaho Falls, ID

    2010-04-27

    A system for the generation of Electricity from Thermal Energy using the thermal magnetic properties of a Ferromagnetic, Electrically Conductive Material (FECM) in one or more Magnetic Fields. A FECM is exposed to one or more Magnetic Fields. Thermal Energy is applied to a portion of the FECM heating the FECM above its Curie Point. The FECM, now partially paramagnetic, moves under the force of the one or more Magnetic Fields. The movement of the FECM induces an electrical current through the FECM, generating Electricity.

  1. Creep properties of advanced heat-resistant martensitic steels strengthened by L1{sub 0} type ordered intermetallic phase

    Energy Technology Data Exchange (ETDEWEB)

    Igarashi, M.; Muneki, S.; Abe, F. [National Res. Inst. for Metals, Tsukuba (Japan). Frontier Res. Center for Struct. Mater.

    2000-07-01

    Creep properties of advanced heat-resistant martensitic steels with the compositions of 0.08C-0.3Si-0.5Mn-9Cr-3.3W-(0/3)Pd-0.2V-0.05Nb-0.05N-Fe (in mass%) have been studied to explore the fundamental guiding principles for the development of new steels with improved creep strength at higher temperatures over 650 C. The steel with 3%Pd exhibits higher creep strength than that of the base steel, in particular, at higher temperatures. The microstructure of the steel with Pd is characterized by fine precipitation of a FePd based L1{sub 0} type ordered phase, {alpha}{sup ''} phase. The {alpha}{sup ''} phase forms in the tempered martensitic matrix, {alpha}, along with the existing phases such as MX (M; V, Nb, X; C, N) carbonitride and M{sub 23}C{sub 6} (M; Cr, Fe, W) carbide after normalizing at 1100 C and tempering at 770 C. A detailed TEM observation has shown that the {alpha}{sup ''} phase precipitates in a plate-shaped with the habit plane parallel to {l_brace}001{r_brace}{sub {alpha}} and with a crystallographic orientation relationship with the matrix, {l_brace}001{r_brace}{sub {alpha}}//{l_brace}001{r_brace}{sub {alpha}{sup ''}} and left angle 100 right angle {sub {alpha}}// left angle 110 right angle {sub {alpha}{sup ''}}. The {alpha}{sup ''} phase is found to be a most effective precipitate to increase creep resistance of the steel in terms of the inter-particle spacing estimated. The {alpha}{sup ''} phase is stable even after aging at 700 C and hence is more useful at higher temperatures. It is thus concluded that the creep resistance of the ferritic steels can be increased further by optimizing the combination of fine precipitation such as the {alpha}{sup ''} phase and MX carbonitride. (orig.)

  2. Thermal properties of simulated Hanford waste glasses

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, Carmen P. [Pacific Northwest National Laboratory, Richland Washington USA; Chun, Jaehun [Pacific Northwest National Laboratory, Richland Washington USA; Crum, Jarrod V. [Pacific Northwest National Laboratory, Richland Washington USA; Canfield, Nathan L. [Pacific Northwest National Laboratory, Richland Washington USA; Rönnebro, Ewa C. E. [Pacific Northwest National Laboratory, Richland Washington USA; Vienna, John D. [Pacific Northwest National Laboratory, Richland Washington USA; Kruger, Albert A. [U.S. Department of Energy, Office of River Protection, Richland Washington

    2017-03-20

    The Hanford Tank Waste Treatment and Immobilization Plant (WTP) will vitrify the mixed hazardous wastes generated from 45 years of plutonium production. The molten glasses will be poured into stainless steel containers or canisters and subsequently quenched for storage and disposal. Such highly energy-consuming processes require precise thermal properties of materials for appropriate facility design and operations. Key thermal properties (heat capacity, thermal diffusivity, and thermal conductivity) of representative high-level and low-activity waste glasses were studied as functions of temperature in the range of 200 to 800°C (relevant to the cooling process), implementing simultaneous differential scanning calorimetry-thermal gravimetry (DSC-TGA), Xe-flash diffusivity, pycnometry, and dilatometry. The study showed that simultaneous DSC-TGA would be a reliable method to obtain heat capacity of various glasses at the temperature of interest. Accurate thermal properties from this study were shown to provide a more realistic guideline for capacity and time constraint of heat removal process, in comparison to the design basis conservative engineering estimates. The estimates, though useful for design in the absence measured physical properties, can now be supplanted and the measured thermal properties can be used in design verification activities.

  3. Thermal properties of the Cobourg Limestone

    Science.gov (United States)

    Pitts, Michelle

    The underground storage of used nuclear fuel in Deep Geologic Repositories (DGRs) has been a subject of research in Canada for decades. One important technical aspect of repository design is the accommodation of the mechanical impacts of thermal inputs (heating) from the fuel as it goes through the remainder of its life cycle. Placement room spacing, a major factor in project cost, will be determined by the ability of the host rock to dissipate heat. The thermal conductivity and linear thermal expansion will determine the evolution of the temperature and thermally-induced stress fields. Thermal processes must be well understood to design a successful DGR. This thesis examines the thermal properties of rocks, how they are influenced by factors such as temperature, pressure, mineralogy, porosity, and saturation; and common methods for calculating and/or measuring these properties. A brief overview of thermal and thermally-coupled processes in the context of DGRs demonstrates the degree to which they would impact design, construction, and operation of these critical structures. Several case histories of major in situ heating experiments are reviewed to determine how the lessons learned could be applied to a Canadian Underground Demonstration Facility (UDF). A mineralogy investigation using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) examines samples of the Cobourg Limestone from the Bowmanville and Bruce sites, and demonstrates geographical variability within the Cobourg Formation. The thermal properties of samples from the Bowmanville site are determined. A divided bar apparatus was constructed and used to measure thermal conductivity. The temperature measurement component of the divided bar apparatus was used to measure linear thermal expansion. Finally, the past investigations into the thermal impact of a DGR are reviewed, and the implications of the laboratory testing results on similar analyses are discussed.

  4. Creep behaviour and creep mechanisms of normal and healing ligaments

    Science.gov (United States)

    Thornton, Gail Marilyn

    Patients with knee ligament injuries often undergo ligament reconstructions to restore joint stability and, potentially, abate osteoarthritis. Careful literature review suggests that in 10% to 40% of these patients the graft tissue "stretches out". Some graft elongation is likely due to creep (increased elongation of tissue under repeated or sustained load). Quantifying creep behaviour and identifying creep mechanisms in both normal and healing ligaments is important for finding clinically relevant means to prevent creep. Ligament creep was accurately predicted using a novel yet simple structural model that incorporated both collagen fibre recruitment and fibre creep. Using the inverse stress relaxation function to model fibre creep in conjunction with fibre recruitment produced a superior prediction of ligament creep than that obtained from the inverse stress relaxation function alone. This implied mechanistic role of fibre recruitment during creep was supported using a new approach to quantify crimp patterns at stresses in the toe region (increasing stiffness) and linear region (constant stiffness) of the stress-strain curve. Ligament creep was relatively insensitive to increases in stress in the toe region; however, creep strain increased significantly when tested at the linear region stress. Concomitantly, fibre recruitment was evident at the toe region stresses; however, recruitment was limited at the linear region stress. Elevating the water content of normal ligament using phosphate buffered saline increased the creep response. Therefore, both water content and fibre recruitment are important mechanistic factors involved in creep of normal ligaments. Ligament scars had inferior creep behaviour compared to normal ligaments even after 14 weeks. In addition to inferior collagen properties affecting fibre recruitment and increased water content, increased glycosaminoglycan content and flaws in scar tissue were implicated as potential mechanisms of scar creep

  5. Non-contact measurements of creep properties of niobium at 1985 °C

    Science.gov (United States)

    Lee, J.; Wall, J. J.; Rogers, J. R.; Rathz, T. J.; Choo, H.; Liaw, P. K.; Hyers, R. W.

    2015-01-01

    The stress exponent in the power-law creep of niobium at 1985 °C was measured by a non-contact technique using an electrostatic levitation facility at NASA MSFC. This method employs a distribution of stress to allow the stress exponent to be determined from each test, rather than from the curve fit through measurements from multiple samples that is required by conventional methods. The sample is deformed by the centripetal acceleration from the rapid rotation, and the deformed shapes are analyzed to determine the strain. Based on a mathematical proof, which revealed that the stress exponent was determined uniquely by the ratio of the polar to equatorial strains, a series of finite-element analyses with the models of different stress exponents were also performed to determine the stress exponent corresponding to the measured strain ratio. The stress exponent from the ESL experiment showed a good agreement with those from the literature and the conventional creep test.

  6. Graphene Thermal Properties: Applications in Thermal Management and Energy Storage

    Directory of Open Access Journals (Sweden)

    Jackie D. Renteria

    2014-11-01

    Full Text Available We review the thermal properties of graphene, few-layer graphene and graphene nanoribbons, and discuss practical applications of graphene in thermal management and energy storage. The first part of the review describes the state-of-the-art in the graphene thermal field focusing on recently reported experimental and theoretical data for heat conduction in graphene and graphene nanoribbons. The effects of the sample size, shape, quality, strain distribution, isotope composition, and point-defect concentration are included in the summary. The second part of the review outlines thermal properties of graphene-enhanced phase change materials used in energy storage. It is shown that the use of liquid-phase-exfoliated graphene as filler material in phase change materials is promising for thermal management of high-power-density battery parks. The reported experimental and modeling results indicate that graphene has the potential to outperform metal nanoparticles, carbon nanotubes, and other carbon allotropes as filler in thermal management materials.

  7. Comparative investigation of creep behavior of ceramic fiber-reinforced alumina and silica aerogel

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaoguang; Wei, Jing [School of Energy and Power Engineering, Beihang University, P.O. Box 405, Beijing 100191 (China); Shi, Duoqi, E-mail: shdq@buaa.edu.cn [School of Energy and Power Engineering, Beihang University, P.O. Box 405, Beijing 100191 (China); Sun, Yantao; Lv, Shuangqi [School of Energy and Power Engineering, Beihang University, P.O. Box 405, Beijing 100191 (China); Feng, Jian; Jiang, Yonggang [National Key Laboratory of Science and Technology on Advanced Ceramic Fibers and Composites, College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

    2014-07-15

    Ambient and high temperature creep experiments at constant stresses of 0.05 MPa and 0.2 MPa were conducted on a ceramic fiber-reinforced alumina aerogel. Experimental results show that at low temperature (below 300 °C), there is no significant creep phenomenon at low stress level (0.05 MPa), but time-dependent creep deformation is found at high stress level (0.2 MPa) for the material. Scanning Electron Microscope (SEM) analysis was also conducted to understand the micro mechanism of the creep behavior. Crack initiation and propagation in matrix are the key factors that change the creep property. Comparative investigation of creep properties was also carried out between ceramic fiber-reinforced alumina and silica aerogel. Finally the application prospect of the two composites was discussed. The result shows that alumina aerogel has excellent creep resistance, thermal stability and heat insulation properties at high temperature (above 800 °C), and it has a good application prospect in high temperature insulation fields, while the ceramic fiber-reinforced silica aerogel, limited by the sintering and poor creep resistance under high temperature, is more suitable for low temperature (below 600 °C) insulation field.

  8. Microstructure and properties degradation of P/T 91, 92 steels weldments in creep conditions

    OpenAIRE

    Falat L.; Homolová V.; Kepič J.; Svoboda M; Výrostková A.

    2012-01-01

    The studies were performed on dissimilar ferritic/austenitic weldments between 9Cr tempered martensitic steels of the grades either P/T 91 or 92 and unstabilised AISI316H austenitic steel. The welded joints were fabricated using the fusion welding by tungsten inert gas (TIG) method with Ni-based filler metal. Microstructural analyses were performed using light and electron microscopy. Microstructural gradient in heat-affected zone (HAZ) of 9Cr steels remained preserved during creep expo...

  9. Thermal properties of selected cheeses samples

    Directory of Open Access Journals (Sweden)

    Monika BOŽIKOVÁ

    2016-02-01

    Full Text Available The thermophysical parameters of selected cheeses (processed cheese and half hard cheese are presented in the article. Cheese is a generic term for a diverse group of milk-based food products. Cheese is produced throughout the world in wide-ranging flavors, textures, and forms. Cheese goes during processing through the thermal and mechanical manipulation, so thermal properties are one of the most important. Knowledge about thermal parameters of cheeses could be used in the process of quality evaluation. Based on the presented facts thermal properties of selected cheeses which are produced by Slovak producers were measured. Theoretical part of article contains description of cheese and description of plane source method which was used for thermal parameters detection. Thermophysical parameters as thermal conductivity, thermal diffusivity and volume specific heat were measured during the temperature stabilisation. The results are presented as relations of thermophysical parameters to the temperature in temperature range from 13.5°C to 24°C. Every point of graphic relation was obtained as arithmetic average from measured values for the same temperature. Obtained results were statistically processed. Presented graphical relations were chosen according to the results of statistical evaluation and also according to the coefficients of determination for every relation. The results of thermal parameters are in good agreement with values measured by other authors for similar types of cheeses.

  10. Thermal Properties of Lignocellulose Pellets

    Science.gov (United States)

    Wachter, Igor; Hirle, Siegfried; Balog, Karol

    2017-06-01

    This article deals with the characterization of biomass pellets using Differential Scanning Calorimetry. We used three types of industrially produced and commercially available pellets as samples: wood pellets containing grass, wood pellet containing bark and wood pellets without bark. Each of the samples were examined using the DSC method. Based on the measurements in atmosphere of air and nitrogen temperature, the changes caused by thermal degradation of various kinds of test fuels were observed. Subsequently, limits of exothermic processes, reaction enthalpy changes and the temperature at which exothermic reactions reached peaks were determined.

  11. Thermal Properties of Lignocellulose Pellets

    Directory of Open Access Journals (Sweden)

    Wachter Igor

    2017-06-01

    Full Text Available This article deals with the characterization of biomass pellets using Differential Scanning Calorimetry. We used three types of industrially produced and commercially available pellets as samples: wood pellets containing grass, wood pellet containing bark and wood pellets without bark. Each of the samples were examined using the DSC method. Based on the measurements in atmosphere of air and nitrogen temperature, the changes caused by thermal degradation of various kinds of test fuels were observed. Subsequently, limits of exothermic processes, reaction enthalpy changes and the temperature at which exothermic reactions reached peaks were determined.

  12. Mechanical and Thermal Properties of Epoxy Composites Containing Zirconium Oxide Impregnated Halloysite Nanotubes

    Directory of Open Access Journals (Sweden)

    Moon il Kim

    2017-12-01

    Full Text Available Liquid epoxy resins have received much attention from both academia and the chemical industry as eco-friendly volatile organic compound (VOC-free alternatives for applications in coatings and adhesives, especially in those used in households. Epoxy resins show high chemical resistance and high creep resistance. However, due to their brittleness and lack of thermal stability, additional fillers are needed for improving the mechanical and thermal properties. Halloysite nanotubes (HNTs are naturally abundant, inexpensive, and eco-friendly clay minerals that are known to improve the mechanical and thermal properties of epoxy composites after suitable surface modification. Zirconium is well known for its high resistance to heat and wear. In this work, zirconium oxide-impregnated HNTs (Zr/HNTs were added to epoxy resins to obtain epoxy composites with improved mechanical and thermal properties. Zr/HNTs were characterized by field-emission transmission electron microscopy, transmission electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Changes in the thermal properties of the epoxy composites were characterized by thermo mechanical analysis and differential scanning calorimetry. Furthermore, flexural properties of the composites were analyzed using a universal testing machine.

  13. Some properties of zirconium alloys determinated by differential stress techniques during creep tests

    Energy Technology Data Exchange (ETDEWEB)

    Novak, M.; Hamersky, M. (Universita J.E. Purkyne, Brno (Czechoslovakia). Prirodovedecka Fakulta); Cadek, J. (Ceskoslovenska Akademie Ved, Brno. Ustav Fyzikalni Metalurgie)

    1982-01-01

    The creep behaviour of Zr-4.5Sn, Zr-4.5Sn-1Mo and Zr-4.5Sn-2Mo in the temperature range 300 to 800 K was studied. Both the yield and fracture stresses are temperature independent in the temperature range 540 to 660 K. The stress sensitivity parameter also exhibits its maximum in this temperature range. Sn and Mo atoms have a strong strengthening effect but they do not markedly influence the temperature range 540 to 660 K, where the athermal deformation mechanism is important. This mechanism most probably exists due to the presence of oxygen atoms in the specimens.

  14. Analysis of elevated-temperature tensile and creep properties of normalized and tempered 2 1/4 Cr-1 Mo steel

    Energy Technology Data Exchange (ETDEWEB)

    Booker, M.K.; Booker, B.L.P.; Swindeman, R.W.

    1982-01-01

    Tensile and creep data were collected for normalized and tempered 2 1/4 Cr-1 Mo steel from American, Japanese, British, French, and German sources. These included creep data obtained at temperatures from 427 to 600/sup 0/C (800 to 1112/sup 0/F) and tensile data from room temperature to 550/sup 0/C (1022/sup 0/F). Properties examined included yield strength, ultimate tensile strength, 10/sup 5/-h creep-rupture strength, and 10/sup -5/%/h creep strength. These are the properties used in setting allowable stresses for Section VIII, Division 1, of the ASME Boiler and Pressure Vessel Code. The data were analyzed by using lot-centered regression approaches that yielded expressions for the variations in the above properties with loading condition, as well as accounting for lot-to-lot variations in properties. No indications were found of systematic differences in any of the properties examined for data from the different countries. However, the estimated allowable stresses from this investigation fell up to 10% below those currently given for this material in the ASME Code. Several possible reasons were cited for the differences, and we concluded that our results are not overly conservative. On the other hand, there is no direct evidence that the current code allowable stresses are insufficiently conservative, since those stresses rely on factors (such as service experience) other than experimental data.

  15. Thermal and thermoelectric properties of graphene.

    Science.gov (United States)

    Xu, Yong; Li, Zuanyi; Duan, Wenhui

    2014-06-12

    The subject of thermal transport at the mesoscopic scale and in low-dimensional systems is interesting for both fundamental research and practical applications. As the first example of truly two-dimensional materials, graphene has exceptionally high thermal conductivity, and thus provides an ideal platform for the research. Here we review recent studies on thermal and thermoelectric properties of graphene, with an emphasis on experimental progresses. A general physical picture based on the Landauer transport formalism is introduced to understand underlying mechanisms. We show that the superior thermal conductivity of graphene is contributed not only by large ballistic thermal conductance but also by very long phonon mean free path (MFP). The long phonon MFP, explained by the low-dimensional nature and high sample purity of graphene, results in important isotope effects and size effects on thermal conduction. In terms of various scattering mechanisms in graphene, several approaches are suggested to control thermal conductivity. Among them, introducing rough boundaries and weakly-coupled interfaces are promising ways to suppress thermal conduction effectively. We also discuss the Seebeck effect of graphene. Graphene itself might not be a good thermoelectric material. However, the concepts developed by graphene research might be applied to improve thermoelectric performance of other materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Thermal Properties of Aliphatic Polypeptoids

    KAUST Repository

    Fetsch, Corinna

    2013-01-29

    A series of polypeptoid homopolymers bearing short (C1-C5) side chains of degrees of polymerization of 10-100 are studied with respect to thermal stability, glass transition and melting points. Thermogravimetric analysis of polypeptoids suggests stability to >200 °C. The study of the glass transition temperatures by differential scanning calorimetry revealed two dependencies. On the one hand an extension of the side chain by constant degree of polymerization decrease the glass transition temperatures (Tg) and on the other hand a raise of the degree of polymerization by constant side chain length leads to an increase of the Tg to a constant value. Melting points were observed for polypeptoids with a side chain comprising not less than three methyl carbon atoms. X-ray diffraction of polysarcosine and poly(N-ethylglycine) corroborates the observed lack of melting points and thus, their amorphous nature. Diffractograms of the other investigated polypeptoids imply that crystalline domains exist in the polymer powder. © 2013 by the authors.

  17. Microbial Properties of Composts That Suppress Damping-Off and Root Rot of Creeping Bentgrass Caused by Pythium graminicola.

    Science.gov (United States)

    Craft, C M; Nelson, E B

    1996-05-01

    Composts prepared from a variety of feedstocks were tested for their ability to suppress seedling and root diseases of creeping bentgrass caused by Pythium graminicola. Among the most suppressive materials in laboratory experiments were different batches of a brewery sludge compost and a biosolids compost from Endicott, N.Y. Batches of these composts that were initially not suppressive to Pythium damping-off became more suppressive with increasing compost age. Leaf, yard waste, food, and spent mushroom composts as well as certain biosolids, cow manure, chicken-cow manure, and leaf-chicken manure composts were not suppressive to Pythium damping-off. In some cases, turkey litter, chicken manure, chicken-leaf, and food waste composts were inhibitory to creeping bentgrass seed germination in laboratory experiments. Microbial populations varied among all of the composts tested. Bacterial populations were high in all composts except the turkey litter compost, in which populations were 1,000- to 10,000-fold lower than in the other composts tested. Among the highest populations of heterotrophic fungi and antibiotic-producing actinomycetes were those found in all batches of the brewery sludge compost, whereas the lowest populations were found in turkey litter, chicken manure, and food waste composts. Heat treatment of suppressive composts reduced populations of bacteria, fungi, and actinomycetes in all composts tested. Disease suppressiveness was also reduced or eliminated in heated composts. Amending heated composts with small amounts of nonheated compost restored suppressive properties and partially restored microbial populations to wild-type levels. A strong negative relationship between compost microbial activity (as measured by the hydrolysis of fluorescein diacetate) and Pythium damping-off severity was observed. When composts were applied to creeping bentgrass in field experiments, a significant level of suppressiveness was evident with some composts when disease

  18. Effect of Laves phase on the creep rupture properties of P92 steel

    Energy Technology Data Exchange (ETDEWEB)

    Maddi, Lakshmiprasad, E-mail: prasadmlp@gmail.com [Department of Metallurgical and Materials Engineering, Visvesvaraya National Institute of Technology, Nagpur 440010 (India); GMR Institute of Technology, GMR Nagar, Rajam 532127 (India); Deshmukh, G.S.; Ballal, A.R.; Peshwe, D.R.; Paretkar, R.K. [Department of Metallurgical and Materials Engineering, Visvesvaraya National Institute of Technology, Nagpur 440010 (India); Laha, K.; Mathew, M.D. [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

    2016-06-21

    Stress rupture tests of normalized and tempered P92 (9Cr–0.5Mo–1.8 W) steel were performed in the range of 135–215 MPa at 650 °C. Effect of tempering temperature in the range of 740–780 °C on the creep rupture life was investigated. Resulting rupture times varied from 100 to 3000 h, and creep rate by one order of magnitude. In the high stress regime, lower tempering temperature resulted in the highest rupture time due to initial high dislocation density and fine laths. However, at lower stresses, highest rupture time was observed for highest tempering temperature. Formation of Laves phase (Fe{sub 2}Mo, Fe{sub 2}W) adjacent to M{sub 23}C{sub 6} carbides was responsible for increase in rupture time. Back scattered electron imaging (BSE) in scanning electron microscopy (SEM) was used to identify Laves phases, and study their distribution. Reduction in dislocation density and coarsening of laves phase precipitates result in decrease in stress exponent value ‘n’ at higher test temperatures of 650 °C.

  19. Creep of service-aged welds

    OpenAIRE

    Sun, Wei

    1996-01-01

    The creep behaviour of welds in service-aged pipes are studied. The aims of the research have been achieved using analytical, numerical and experimental approaches to the relevant subjects. Several features of the work are presented: (i) a systematic parametric study of the creep of two-material test specimens including a stress singularity analysis, (ii) an impression creep testing method using a rectangular indenter, which can be applied to study the creep properties in welds, and (iii) met...

  20. Effects of composition and heat treatment at 1150{degrees}C on creep-rupture properties of Fe{sub 3}Al-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    McKamey, C.G.; Maziasz, P.J.; Marrero-Santos, Y. [Oak Ridge National Lab., TN (United States)

    1995-08-01

    The effects of composition and heat treatment at 1150{degrees}C on the creep-rupture properties of Fe3Al-based alloys were studied. Tests of alloy FA-180 (Fe-28Al-5Cr-0.5Nb-0.8Mo-0.025Zr-0.05C-0.005B, at.%) with this heat treatment were performed in air using various test temperatures and stresses in order to obtain creep activation energies and constants. An activation energy for creep of approximately 150 kcal/mole was determined, a value which is approximately twice that obtained earlier for the binary alloy heat treated at 750{degrees}C. Tests were also conducted on alloys containing various combinations of Cr, Mo, Nb, Zr, C, and B in order to better understand the effect of composition on the improved creep resistance with heat treating at 1150{degrees}C. The results suggest an interaction of Mo with Zr and Nb to produce increased creep life.

  1. Seismic Creep

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Seismic creep is the constant or periodic movement on a fault as contrasted with the sudden erupture associated with an earthquake. It is a usually slow deformation...

  2. Native Cellulose: Structure, Characterization and Thermal Properties

    Directory of Open Access Journals (Sweden)

    Matheus Poletto

    2014-08-01

    Full Text Available In this work, the relationship between cellulose crystallinity, the influence of extractive content on lignocellulosic fiber degradation, the correlation between chemical composition and the physical properties of ten types of natural fibers were investigated by FTIR spectroscopy, X-ray diffraction and thermogravimetry techniques. The results showed that higher extractive contents associated with lower crystallinity and lower cellulose crystallite size can accelerate the degradation process and reduce the thermal stability of the lignocellulosic fibers studied. On the other hand, the thermal decomposition of natural fibers is shifted to higher temperatures with increasing the cellulose crystallinity and crystallite size. These results indicated that the cellulose crystallite size affects the thermal degradation temperature of natural fibers. This study showed that through the methods used, previous information about the structure and properties of lignocellulosic fibers can be obtained before use in composite formulations.

  3. Modelling the impact of creep on the probability of failure of a solid oxidefuel cell stack

    DEFF Research Database (Denmark)

    Greco, Fabio; Frandsen, Henrik Lund; Nakajo, Arata

    2014-01-01

    In solid oxide fuel cell (SOFC) technology a major challenge lies in balancing thermal stresses from an inevitable thermal field. The cells are known to creep, changing over time the stress field. The main objective of this study was to assess the influence of creep on the failure probability...... of an SOFC stack. A finite element analysis on a single repeating unit of the stack was performed, in which the influence of the mechanical interactions,the temperature-dependent mechanical properties and creep of the SOFC materials are considered. Moreover, stresses from the thermo-mechanical simulation...... of sintering of the cells have been obtained and were implemented into the model of the single repeating unit. The significance of the relaxation of the stresses by creep in the cell components and its influence on the probability of cell survival was investigated. Finally, the influence of cell size...

  4. Effect of heat treatment on elevated temperature tensile and creep properties of the extruded Mg–6Gd–4Y–Nd–0.7Zr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Lin, E-mail: yuanlin@hit.edu.cn; Shi, Wenchao; Jiang, WenMao; Zhao, Zhe; Shan, Debin

    2016-03-21

    The light and heavy rare earth elements are added to the magnesium alloys to improve the strengths and the creep resistance. The age hardening behaviors of the extruded Mg–6Gd–4Y–Nd–0.7Zr alloy aged at 200, 225 and 250 °C were investigated. Tensile tests and creep tests of the extruded and extruded-T5 Mg–6Gd–4Y–Nd–0.7Zr were carried out at 150–300 °C. The relationship between the microstructure and the properties of the extruded-T5 Mg–6Gd–4Y–Nd–0.7Zr alloy was studied. The result shows that the extruded Mg–6Gd–4Y–Nd–0.7Zr (contained less than 10 wt% Gd) peak aged at 225 °C for 72 h has the excellent creep resistance and high strengths with the UTS more than 350 MPa from room temperature to 200 °C, which are correlative with the precipitates. The high dense and uniform distribution of β′ phase with good heat stability precipitates inhibiting the dislocation motion contributes to age hardening, accelerates the ageing hardening response and increases the creep resistance. The artificially aged (T5) at low temperature further creep tested and tensile tested at higher temperatures decreases the resistance to the dislocation motion and the grain boundary sliding, resulting in the reduction in creep properties and strengths of the extruded-T5 Mg–6Gd–4Y–Nd–0.7Zr alloy above 225 °C.

  5. Fractal Geometry-Based Hypergeometric Time Series Solution to the Hereditary Thermal Creep Model for the Contact of Rough Surfaces Using the Kelvin-Voigt Medium

    Directory of Open Access Journals (Sweden)

    Osama M. Abuzeid

    2010-01-01

    Full Text Available This paper aims at constructing a continuous hereditary creep model for the thermoviscoelastic contact of a rough punch and a smooth surface of a rigid half-space. The used model considers the rough surface as a function of the applied load and temperatures. The material of the rough punch surface is assumed to behave as Kelvin-Voigt viscoelastic material. Such a model uses elastic springs and viscous dashpots in parallel. The fractal-based punch surface is modelled using a deterministic Cantor structure. An asymptotic power law, deduced using approximate iterative relations, is used to express the punch surface creep which is a time-dependent inelastic deformation. The suggested law utilized the hypergeometric time series to relate the variables of creep as a function of remote forces, body temperatures, and time. The model is valid when the approach of punch surface and half space is in the order of the size of the surface roughness. The closed-form results are obtained for selected values of the system parameters; the fractal surface roughness and various material properties. The obtained results show good agreement with published experimental results, and the methodology can be further extended to other structures such as the Kelvin-Voigt medium within electronic circuits and systems.

  6. Thermal properties of spinel based solid solutions

    Science.gov (United States)

    O'Hara, Kelley Rae

    Solid solution formation in spinel based systems proved to be a viable approach to decreasing thermal conductivity. Samples with systematically varied additions of MgGa2O4 to MgAl2O 4 were prepared and thermal diffusivity was measured using the laser flash technique. Additionally, heat capacity was measured using differential scanning calorimetry and modeled for the MgAl2O4-MgGa 2O4 system. At 200°C thermal conductivity decreased 24% with a 5 mol% addition of MgGa2O4 to the system. The solid solution continued to decrease the thermal conductivity by 13% up to 1000°C with 5 mol% addition. The decrease in thermal conductivity ultimately resulted in a decrease in heat flux when applied to a theoretical furnace lining, which could lead to energy savings in industrial settings. The MgAl2O4-Al2O3 phase equilibria was investigated to fully understand the system and the thermal properties at elevated temperatures. The solvus line between MgAl2O4 and Al2O3 has been defined at 79.6 wt% Al 2O3 at 1500°C, 83.0 wt% Al2O4 at 1600°C, and 86.5 wt% Al2O3 at 1700°C. A metastable region has been identified at temperatures up to 1700°C which could have significant implications for material processing and properties. The spinel solid solution region has been extended to form an infinite solid solution with Al2O3 at elevated temperatures. A minimum in melting at 1975°C and a chemistry of 96 wt% Al2O3 rather than a eutectic is present. Thermal properties in the MgAl2O4-Al2O 3 system were investigated in both the single phase solid solution region and the two phase region. The thermal diffusivity decreased through the MgAl 2O4 solid solution region and was at a minimum through the entire metastable (nucleation and growth) region. As Al2O 3 became present as a second phase the thermal diffusivity increased with Al2O3 content. There was an 11.7% increase in thermal diffusivity with a change in overall chemistry of 85.20 wt% Al2O 3 to 87.71 wt% Al2O3, due to the drastic change in

  7. Characterization of cohesion, adhesion and creep-properties of dynamically loaded coatings through the impact tester

    Energy Technology Data Exchange (ETDEWEB)

    Bouzakis, K.D.; Michailidis, N.; Lontos, A.; Siganos, A.; Hadjiyiannis, S.; Giannopoulos, G.; Maliaris, G. [Aristoteles Univ., Thessaloniki (Greece). Lab. for Machine Tools and Mfg. Engineering; Erkens, G. [CemeCon GmbH, Wuerselen (Germany)

    2001-10-01

    The coating impact test, in combination with finite elements method (FEM) simulation, is successfully used to characterize the fatigue performance of coatings. Critical values for stress components, responsible for distinctive fatigue failure modes of the coating, are obtained and the fatigue limits of various coatings are illustrated in form of generally applicable Smith and Woehler diagrams, determined through a developed evaluation software. This software takes into account the impact test experimental data, as well as coating and substrate constitutive laws. Herewith coating adhesive and cohesive failure modes are elucidated and a cutting performance prediction of coated tools can be carried out. On the other hand, creep phenomena of plasma sprayed coatings are quantitatively interpreted. (orig.)

  8. Relationship between Creep Property and Loading-Rate Dependence of Strength of Artificial Methane-Hydrate-Bearing Toyoura Sand under Triaxial Compression

    Directory of Open Access Journals (Sweden)

    Kuniyuki Miyazaki

    2017-09-01

    Full Text Available Methane hydrate is anticipated to be a promising energy resource. It is essential to consider the mechanical properties of a methane hydrate reservoir to ensure sustainable production, since its mechanical behavior may affect the integrity of the production well, the occurrence of geohazards, and gas productivity. In particular, the creep property of methane-hydrate-bearing sediment is thought to have great significance in the long-term prediction of the mechanical behaviors of a reservoir. In earlier studies, triaxial compression tests were conducted on artificial methane-hydrate-bearing Toyoura sand under three axial-loading conditions, i.e., constant-strain-rate test, constant-stress-rate test, and creep (constant-stress test. In this paper, the time-dependent properties of the methane-hydrate-bearing Toyoura sand observed in these tests were quantitatively discussed and found to be almost in agreement. The creep life obtained from the creep tests had a reasonably strong correlation with the loading-rate dependencies of strength, obtained from the constant-strain-rate tests and constant-stress-rate tests based on a simple hypothesis. The findings are expected to be used to develop a constitutive model considering the time-dependent behaviors of hydrate-bearing soil in future studies, and to improve the reliability of long-term prediction of the geomechanical response to gas extraction from a reservoir.

  9. Assessment of long-term creep strength of grade 91 steel

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, Kazuhiro; Sawada, Kota; Kushima, Hideaki [National Inst. for Materials Science, Tsukuba, Ibaraki (Japan)

    2010-07-01

    In 2004 and 2005 long-term creep rupture strength of ASME Grade 91 type steels of plate, pipe, forging and tube materials was evaluated in Japan by means of region splitting analysis method in consideration of 50% of 0.2% offset yield stress. According to the evaluated 100,000h creep rupture strength of 94MPa for plate, pipe and forging steels and 92MPa for tube steel at 600 C, allowable tensile stress of the steels regulated in the Interpretation for the Technical Standard for Thermal Power Plant was slightly reduced. New creep rupture data of the steels obtained in the long-term indicate further reduction of long-term creep rupture strength. Not only creep rupture strength, but also creep deformation property of the ASME Grade 91 steel was investigated and need of reevaluation of long-term creep strength of Grade 91 steel was indicated. A refinement of region splitting analysis method for creep rupture like prediction was discussed. (orig.)

  10. Thermal properties of food and pharmaceutical powders

    Science.gov (United States)

    Abiad, Mohamad Ghassan

    Foods and pharmaceuticals are complex systems usually exposed to various environmental conditions during processing and thus storage, stability, functionality and quality are key attributes that deserve careful attention. The quality and stability of foods and pharmaceuticals are mainly affected by environmental conditions such as temperature, humidity, time, and processing conditions (e.g. shear, pressure) under which they may undergo physical and/or chemical transformations. Glass transition as well as other thermal properties is a key to understand how external conditions affect physical changes of such materials. Development of new materials and understanding the physico-chemical behavior of existing ones require a scientific foundation that translates into safe and high quality foods, improved quality of pharmaceuticals and nutraceuticals with lower risk to patients and functional efficacy of polymers used in food and medicinal products. This research provides an overview of the glass transition and other thermal properties and introduces novel methods developed to characterize such properties.

  11. influence of relative humidity on tensile and compressive creep of ...

    African Journals Online (AJOL)

    HOD

    While creep is as a result of sustained stress, shrinkage is due to hygrometric conditions [1]. According to Neville et al [2], a typical concrete element creeps up to twice its initial strain after a year of loading. Concrete creep can occur in tension and also in compression. The properties of tensile and compressive creep are ...

  12. Optimization of APS-ZrO{sub 2}-thermal barrier coatings by variations of creep strength and interface roughness; Optimierung von APS-ZrO{sub 2}-Waermedaemmschichten durch Variationen der Kriechfestigkeit und der Grenzflaechenrauhigkeit

    Energy Technology Data Exchange (ETDEWEB)

    Schweda, Mario

    2011-07-01

    Gas turbines operate at combustion chamber temperatures up to 1400 C. Therefore the blades and the combustion chamber lining, which consist of Ni-superalloys for highest loads, are coated with a thermal barrier coating (TBC) of zirconium oxide and an underlying oxidation protection coating of MCrAlY-alloys (M=Ni, Co). At high temperature the MCrAlY-coating oxidizes and an Al{sub 2}O{sub 3}-scale (thermally grown oxide, TGO) forms between MCrAlY-coating and TBC, what constrains the oxidation of the base material. At plasma sprayed TBCs, the MCrAlY-coating provides a bond coat (BC) for the TBC at the same time and therefore is roughened by sandblasting before the deposition of the TBC. By the growth of the Al{sub 2}O{sub 3}-scale and the start up and run down of the gas turbine, stresses arise in the TBC, which lead to lateral crack formation in the field of the TBC-BC-interface and finally to the spallation of the TBC. Thereby other parts of the turbine can be damaged, what causes high costs. Therefrom the aim is to delay the crack growth as strong as possible or rather to maximize the lifetime of the TBC. For this purpose the material properties of the coating components have to be optimized. In the present work, the influence of creep strength of BC and TGO and the influence of TBC-BC-interface-roughness on the lifetime and damage evolution of plasma sprayed ZrO{sub 2}-TBCs are investigated. To determine the lifetime, cylindrical specimens with plasma sprayed ZrO{sub 2}-TBC were produced and thermally cycled with a minimum and maximum temperature of 60 C and 1050 C and a dwell time at maximal temperature of 2h. To exclude the interdiffusion and thermal mismatch between BC and Ni-superalloy, a model system was used: The Ni-superalloy was left and the substrate material consists completely of a BC-like FeCrAlY-alloy. The model system was simulated by the project partner TU Braunschweig with the FE-method. The TBC-BC-interface-roughness was abstracted by a 2

  13. EXPERIMENTAL MEASUREMENT OF NANOFLUIDS THERMAL PROPERTIES

    Directory of Open Access Journals (Sweden)

    Adnan M. Hussein

    2013-07-01

    Full Text Available Solid particles dispersed in a liquid with sizes no larger than 100nm, known as nanofluids, are used to enhance Thermophysical properties compared to the base fluid. Preparations of alumina (Al2O3, titania (TiO2 and silica (SiO2 in water have been experimentally conducted in volume concentrations ranging between 1 and 2.5%. Thermal conductivity is measured by the hot wire method and viscosity with viscometer equipment. The results of thermal conductivity and viscosity showed an enhancement (0.5–20% and 0.5–60% respectively compared with the base fluid. The data measured agreed with experimental data of other researchers with deviation of less than 5%. The study showed that alumina has the highest thermal conductivity, followed silica and titania, on the other hand silica has the highest viscosity followed alumina and titania.

  14. Thermal properties of methane gas hydrates

    Science.gov (United States)

    Waite, William F.

    2007-01-01

    Gas hydrates are crystalline solids in which molecules of a “guest” species occupy and stabilize cages formed by water molecules. Similar to ice in appearance (fig. 1), gas hydrates are stable at high pressures and temperatures above freezing (0°C). Methane is the most common naturally occurring hydrate guest species. Methane hydrates, also called simply “gas hydrates,” are extremely concentrated stores of methane and are found in shallow permafrost and continental margin sediments worldwide. Brought to sea-level conditions, methane hydrate breaks down and releases up to 160 times its own volume in methane gas. The methane stored in gas hydrates is of interest and concern to policy makers as a potential alternative energy resource and as a potent greenhouse gas that could be released from sediments to the atmosphere and ocean during global warming. In continental margin settings, methane release from gas hydrates also is a potential geohazard and could cause submarine landslides that endanger offshore infrastructure. Gas hydrate stability is sensitive to temperature changes. To understand methane release from gas hydrate, the U.S. Geological Survey (USGS) conducted a laboratory investigation of pure methane hydrate thermal properties at conditions relevant to accumulations of naturally occurring methane hydrate. Prior to this work, thermal properties for gas hydrates generally were measured on analog systems such as ice and non-methane hydrates or at temperatures below freezing; these conditions limit direct comparisons to methane hydrates in marine and permafrost sediment. Three thermal properties, defined succinctly by Briaud and Chaouch (1997), are estimated from the experiments described here: - Thermal conductivity, λ: if λ is high, heat travels easily through the material. - Thermal diffusivity, κ: if κ is high, it takes little time for the temperature to rise in the material. - Specific heat, cp: if cp is high, it takes a great deal of heat to

  15. Adsorption properties of thermally sputtered calcein film

    Science.gov (United States)

    Kruglenko, I.; Burlachenko, J.; Kravchenko, S.; Savchenko, A.; Slabkovska, M.; Shirshov, Yu.

    2014-05-01

    High humidity environments are often found in such areas as biotechnology, food chemistry, plant physiology etc. The controlling of parameters of such ambiences is vitally important. Thermally deposited calcein films have extremely high adsorptivity at exposure to water vapor of high concentration. This feature makes calcein a promising material for humidity sensing applications. The aim of this work is to explain high sensitivity and selectivity of calcein film to high humidity. Quartz crystal microbalance sensor, AFM and ellipsometry were used for calcein film characterization and adsorption properties investigation. The proposed model takes into account both the molecular properties of calcein (the presence of several functional groups capable of forming hydrogen bonds, and their arrangement) and the features of structure of thermally deposited calcein film (film restructuring due to the switching of bonds "calcein-calcein" to "calcein-water" in the course of water adsorption).

  16. Effect of normalizing temperature on microstructural stability and mechanical properties of creep strength enhanced ferritic P91 steel

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, C.; Giri, A.; Mahapatra, M.M.

    2016-03-07

    Mechanical properties of creep enhanced ferritic (CSEF) steels is affected by various parameters, the solutionizing temperature is one of them. The present work demonstrates the effect of solutionizing temperature on microstructure and mechanical properties of CSEF P91 steel. Optical metallography (OM) and Scanning electron microscopy (SEM) were carried out to study the microstructure of P91 steel in different heat treatment conditions. In order to determine the precipitates present in microstructure; X-ray analysis was performed. Moreover, the influence of solutionizing temperature on the mechanical properties (strength, hardness and impact toughness) has also been studied. - Highlights: • SEM-EDS analysis of P91 steel precipitates present at grain boundary and grain interior were carried out. • For constant tempering time effect of normalizing temperature on precipitate size, particle-to particle distance, and grain size were carried out. • Effect of normalizing temperature on tensile strength, yield strength, hardness, % elongation and % reduction of area of P91 steel were studied. • For constant tempering time effect of normalizing temperature on room temperature impact toughness of P91 steel were studied. Fracture surface after impact testing were also characterized by using SEM. • Fracture surface after room temperature tensile testing were also characterized by using SEM to study the effect of normalizing temperature on fracture surface.

  17. Thermal properties of an erythritol derivative

    Science.gov (United States)

    Trhlikova, Lucie; Prikryl, Radek; Zmeskal, Oldrich

    2016-06-01

    Erythritol (C4H10O4) is a sugar alcohol (or polyol) that is commonly used in the food industry. Its molar mass is 122.12 g.mol-1 and mass density 1450 kg.m-3. Erythritol, an odorless crystalline powder, can also be characterized by other physical parameters like melting temperature (121 °C) and boiling temperature (329 °C). The substance can be used for the accumulation of energy in heat exchangers based on various oils or water. The PlusICE A118 product manufactured by the PCM Products Ltd. company (melting temperature Θ = 118 °C, specific heat capacity cp = 2.70 kJ.K-1.kg-1, mass density 1450 kg.m-3, latent heat capacity 340 kJ.kg-1, volumetric heat capacity 493 MJ.m-3) is based on an erythritol-type medium. Thermal properties of the PlusICE A118 product in both solid and liquid phase were investigated for this purpose in terms of potential applications. Temperature dependences of its thermal parameters (thermal diffusivity, thermal conductivity, and specific heat) were determined using a transient (step-wise) method. A fractal model of heat transport was used for determination of the above thermal parameters. This model is independent of geometry and type of sample heating. Moreover, it also considers heat losses. The experiment confirmed the formerly declared value of phase change temperature, about 120 °C.

  18. Mechanical and thermal properties of crab chitin reinforced carboxylated SBR composites

    Directory of Open Access Journals (Sweden)

    C. Santulli

    2012-05-01

    Full Text Available The addition of small amounts (up to 9 wt% of chitin microsized particles, originating from shellfish waste, to carboxylated styrene-butadiene rubber (XSBR matrix (as received and annealed to 100°C has been studied. In particular, this study concentrated on their mechanical (creep investigation by nanoindentation and dynamical-mechanical analysis, thermal (differential scanning calorimetry and thermogravimetry and swelling behaviour (toluene absorption and was completed by morphological characterisation by scanning electron microscopy and atomic force microscopy. The results show that annealing has a limited effect on materials properties, effects which are further reduced by the addition of growing amounts of crab chitin. It should be noted that the limited filler content used in the study does not substantially modify the linear creep behaviour of XSBR for sufficiently long loading times. The thermal stability of the system does also appear to be preserved even with the maximum chitin content added, while it serves sufficiently as an effective barrier against aromatic solvent absorption.

  19. Creep Resistance of VM12 Steel

    Directory of Open Access Journals (Sweden)

    Zieliński A.

    2016-09-01

    Full Text Available This article presents selected material characteristics of VM12 steel used for elements of boilers with super- and ultra-critical steam parameters. In particular, abridged and long-term creep tests with and without elongation measurement during testing and investigations of microstructural changes due to long-term impact of temperature and stress were carried out. The practical aspect of the use of creep test results in forecasting the durability of materials operating under creep conditions was presented. The characteristics of steels with regard to creep tests developed in this paper are used in assessment of changes in functional properties of the material of elements operating under creep conditions.

  20. Elevated Temperature Creep Properties of Conventional 50Au-50Cu and 47Au 50Cu-3Ni Braze Alloys

    Energy Technology Data Exchange (ETDEWEB)

    STEPHENS JR.,JOHN J.; SCHMALE,DAVID T.

    2000-12-18

    The elevated temperature creep properties of the 50Au-50Cu wt% and 47Au-50Cu-3Ni braze alloys have been evaluated over the temperature range 250-850 C. At elevated temperatures, i.e., 450-850 C, both alloys were tested in the annealed condition (2 hrs. 750 C/water quenched). The minimum strain rate properties over this temperature range are well fit by the Garofalo sinh equation. At lower temperatures (250 and 350 C), power law equations were found to characterize the data for both alloys. For samples held long periods of time at 375 C (96 hrs.) and slowly cooled to room temperature, an ordering reaction was observed. For the case of the 50Au-50Cu braze alloy, the stress necessary to reach the same, strain rate increased by about 15% above the baseline data. The limited data for ordered 47Au-50Cu-3Ni alloy reflected a,smaller strength increase. However, the sluggishness of this ordering reaction in both alloys does not appear to pose a problem for braze joints cooled at reasonable rates following brazing.

  1. Biodegradable compounds: Rheological, mechanical and thermal properties

    Science.gov (United States)

    Nobile, Maria Rossella; Lucia, G.; Santella, M.; Malinconico, M.; Cerruti, P.; Pantani, R.

    2015-12-01

    Recently great attention from industry has been focused on biodegradable polyesters derived from renewable resources. In particular, PLA has attracted great interest due to its high strength and high modulus and a good biocompatibility, however its brittleness and low heat distortion temperature (HDT) restrict its wide application. On the other hand, Poly(butylene succinate) (PBS) is a biodegradable polymer with a low tensile modulus but characterized by a high flexibility, excellent impact strength, good thermal and chemical resistance. In this work the two aliphatic biodegradable polyesters PBS and PLA were selected with the aim to obtain a biodegradable material for the industry of plastic cups and plates. PBS was also blended with a thermoplastic starch. Talc was also added to the compounds because of its low cost and its effectiveness in increasing the modulus and the HDT of polymers. The compounds were obtained by melt compounding in a single screw extruder and the rheological, mechanical and thermal properties were investigated. The properties of the two compounds were compared and it was found that the values of the tensile modulus and elongation at break measured for the PBS/PLA/Talc compound make it interesting for the production of disposable plates and cups. In terms of thermal resistance the compounds have HDTs high enough to contain hot food or beverages. The PLA/PBS/Talc compound can be, then, considered as biodegradable substitute for polystyrene for the production of disposable plates and cups for hot food and beverages.

  2. Thermal power sludge – properties, treatment, utilization

    Directory of Open Access Journals (Sweden)

    Martin Sisol

    2005-11-01

    Full Text Available In this paper a knowledge about properties of thermal power sludge from coal combustion in smelting boilers is presented. The physical and technological properties of slag – granularity, density, specific, volume and pouring weight, hardness and decoupling – together with chemical properties influence its exploitation. The possibility of concentrating the Fe component by the mineral processing technologies (wet low-intenzity magnetic separation is verified. An industrial use of the slag in civil engineering, e.g. road construction, was realised. The slag-fly ashes are directly utilized in the cement production as a substitute of a part of natural raw materials. For the use of slag as the stoneware in the road construction, all the criteria are fulfilled.

  3. Extreme creep resistance in a microstructurally stable nanocrystalline alloy

    Science.gov (United States)

    Darling, K. A.; Rajagopalan, M.; Komarasamy, M.; Bhatia, M. A.; Hornbuckle, B. C.; Mishra, R. S.; Solanki, K. N.

    2016-09-01

    Nanocrystalline metals, with a mean grain size of less than 100 nanometres, have greater room-temperature strength than their coarse-grained equivalents, in part owing to a large reduction in grain size. However, this high strength generally comes with substantial losses in other mechanical properties, such as creep resistance, which limits their practical utility; for example, creep rates in nanocrystalline copper are about four orders of magnitude higher than those in typical coarse-grained copper. The degradation of creep resistance in nanocrystalline materials is in part due to an increase in the volume fraction of grain boundaries, which lack long-range crystalline order and lead to processes such as diffusional creep, sliding and rotation. Here we show that nanocrystalline copper-tantalum alloys possess an unprecedented combination of properties: high strength combined with extremely high-temperature creep resistance, while maintaining mechanical and thermal stability. Precursory work on this family of immiscible alloys has previously highlighted their thermo-mechanical stability and strength, which has motivated their study under more extreme conditions, such as creep. We find a steady-state creep rate of less than 10-6 per second—six to eight orders of magnitude lower than most nanocrystalline metals—at various temperatures between 0.5 and 0.64 times the melting temperature of the matrix (1,356 kelvin) under an applied stress ranging from 0.85 per cent to 1.2 per cent of the shear modulus. The unusual combination of properties in our nanocrystalline alloy is achieved via a processing route that creates distinct nanoclusters of atoms that pin grain boundaries within the alloy. This pinning improves the kinetic stability of the grains by increasing the energy barrier for grain-boundary sliding and rotation and by inhibiting grain coarsening, under extremely long-term creep conditions. Our processing approach should enable the development of

  4. Extreme creep resistance in a microstructurally stable nanocrystalline alloy.

    Science.gov (United States)

    Darling, K A; Rajagopalan, M; Komarasamy, M; Bhatia, M A; Hornbuckle, B C; Mishra, R S; Solanki, K N

    2016-09-15

    Nanocrystalline metals, with a mean grain size of less than 100 nanometres, have greater room-temperature strength than their coarse-grained equivalents, in part owing to a large reduction in grain size. However, this high strength generally comes with substantial losses in other mechanical properties, such as creep resistance, which limits their practical utility; for example, creep rates in nanocrystalline copper are about four orders of magnitude higher than those in typical coarse-grained copper. The degradation of creep resistance in nanocrystalline materials is in part due to an increase in the volume fraction of grain boundaries, which lack long-range crystalline order and lead to processes such as diffusional creep, sliding and rotation. Here we show that nanocrystalline copper-tantalum alloys possess an unprecedented combination of properties: high strength combined with extremely high-temperature creep resistance, while maintaining mechanical and thermal stability. Precursory work on this family of immiscible alloys has previously highlighted their thermo-mechanical stability and strength, which has motivated their study under more extreme conditions, such as creep. We find a steady-state creep rate of less than 10(-6) per second-six to eight orders of magnitude lower than most nanocrystalline metals-at various temperatures between 0.5 and 0.64 times the melting temperature of the matrix (1,356 kelvin) under an applied stress ranging from 0.85 per cent to 1.2 per cent of the shear modulus. The unusual combination of properties in our nanocrystalline alloy is achieved via a processing route that creates distinct nanoclusters of atoms that pin grain boundaries within the alloy. This pinning improves the kinetic stability of the grains by increasing the energy barrier for grain-boundary sliding and rotation and by inhibiting grain coarsening, under extremely long-term creep conditions. Our processing approach should enable the development of

  5. Gamma Prime Morphology and Creep Properties of Nickel Based Superalloys With Platinum Group Metal Additions (Preprint)

    Science.gov (United States)

    2008-04-01

    decreas the poin [2 [1 [3 D1 Figure I alloy wt%) compo the gra oils were prepa to the applie ss using grit olishing at a t used for al ), 10...383-417. 4. B. Gleeson, “Thermal Barrier Coatings for Aeroengine Applications,” Journal of Propulsion and Power , 22 (2) (2006), 375-383. 5

  6. Microstructure and mechanical properties of high temperature creep resisting superalloy René 77 modified CoAl2O4

    OpenAIRE

    M. Poręba; J. Sieniawski; Zielinska, M.

    2007-01-01

    Purpose: Nickel based superalloys are widely used for turbine and stator blades of compressor in aero-engines. The objective of this work is to determine the influence of the inoculant’s content (cobalt aluminate) in the surface layer of the ceramic mould on the microstructure and mechanical properties of high temperature creep resisting superalloy René 77.Design/methodology/approach: Experimentally investigated castings have been made of commercially produced nickel superalloy René 77. Stepp...

  7. Study of Thermal Properties of Cast Metal- Ceramic Composite Foams

    OpenAIRE

    Gawdzińska K.; Chybowski L.; Przetakiewicz W.

    2017-01-01

    Owing to its properties, metallic foams can be used as insulation material. Thermal properties of cast metal-ceramic composite foams have applications in transport vehicles and can act as fire resistant and acoustic insulators of bulkheads. This paper presents basic thermal properties of cast and foamed aluminum, the values of thermal conductivity coefficient of selected gases used in foaming composites and thermal capabilities of composite foams (AlSi11/SiC). A certificate of non-combustibil...

  8. The effect of cold rolling on the grain boundary character and creep rupture properties of INCONEL alloy 718

    Energy Technology Data Exchange (ETDEWEB)

    Boehlert, C.J. [Alfred Univ., School of Ceramic Engineering and Materials Science, Alfred, NY (United States); Civelekoglu, S. [Alfred Univ., School of Ceramic Engineering and Materials Science, Alfred, NY (United States); Eisinger, N.; Smith, G.; Crum, J. [Special Metals Corp., Huntington (United States)

    2003-07-01

    In order to evaluate the effects of sheet processing on the grain boundary character distribution (GBCD) of INCONEL trademark alloy 718 (IN 718), electron backscattered diffraction (EBSD) mapping was performed on samples cold rolled between 0-40%. Increased cold rolling increased the fraction of low-angle boundaries at the expense of the coincident site lattice boundaries. The tensile-creep rupture life (T{sub r}) and elongation-to-failure ({epsilon}{sub f}) were evaluated at 649 C and 758 MPa, and the data indicated that increased cold rolling significantly increased both the T{sub r} and {epsilon}{sub f} values. In addition the GBCD and room-temperature (RT) tensile properties were evaluated for superplastically formed INCONEL trademark alloy 718 (IN 718SPF). The tensile results indicated the exceptional strength of the fine-grained IN 718SPF material, however the GBCD parameters were intermediate to those of the 10% and 20% cold rolled IN 718 materials. (orig.)

  9. In Vivo Static Creep Loading of the Rat Forelimb Reduces Ulnar Structural Properties at Time-Zero and Induces Damage-Dependent Woven Bone Formation

    Science.gov (United States)

    Lynch, Jennifer A.; Silva, Matthew J.

    2008-01-01

    Periosteal woven bone forms in response to stress fractures and pathological overload. The mechanical factors that regulate woven bone formation are poorly understood. Fatigue loading of the rat ulna triggers a woven bone response in proportion to the level of applied fatigue displacement. However, because fatigue produces damage by application of cyclic loading it is unclear if the osteogenic response is due to bone damage (injury response) or dynamic strain (adaptive response). Creep loading, in contrast to fatigue, involves application of a static force. Our objectives were to use static creep loading of the rat forelimb to produce discrete levels of ulnar damage, and subsequently to determine the bone response over time. We hypothesized that 1) increases in applied displacement during loading correspond to ulnae with increased crack number, length and extent, as well as decreased mechanical properties; and 2) in vivo creep loading stimulates a damage-dependent dose-response in periosteal woven bone formation. Creep loading of the rat forelimb to progressive levels of sub-fracture displacement led to progressive bone damage (cracks) and loss of whole-bone mechanical properties (especially stiffness) at time-zero. For example, loading to 60% of fracture displacement caused a 60% loss of ulnar stiffness and a 25% loss of strength. Survival experiments showed that woven bone formed in a dose-dependent manner, with greater amounts of woven bone in ulnae that were loaded to higher displacements. Furthermore, after 14 days the mechanical properties of the loaded limb were equal or superior to control, indicating functional repair of the initial damage. We conclude that bone damage created without dynamic strain triggers a woven bone response, and thus infer that the woven bone response reported after fatigue loading and in stress fractures is in large part a response to bone damage. PMID:18295561

  10. Investigation Of Thermal Properties Of Naturally Seasoned Dry ...

    African Journals Online (AJOL)

    Steady-state thermal conductivity measurements of naturally seasoned African thorn tree (Macaranga barteri) timer boards were carried out. Other thermal and physical properties such as specific heat capacity, thermal resistivity, density, thermal absorptivity and diffusivity as well as percentage of dead air space (v/v) were ...

  11. Thermal properties of hemp fibre non-woven materials

    Science.gov (United States)

    Freivalde, Liga; Kukle, Silvija; Russell, Stephen

    2013-12-01

    This review considers the thermal properties analysis of hemp fiber non-woven materials made by three different manufacturing technologies - thermal bonding, needle-punching and hydro-entanglement. For non-wovens development two hemp fibers cultivars grown in Latvia were used - Purini and Bialobrzeskie. Thermal resistance, conductivity and the effects of several parameters on thermal performance are revised.

  12. Some Physco-thermal properties of Rice Bran | Obetta | Global ...

    African Journals Online (AJOL)

    Some of these properties were combined for study on their effect on thermal conductivity which was one of the thermal properties studied. Mean values of the thermal conductivity determined ranged from 0.2456 to 0.5764 W/m oC depending on the moisture content of the raw rice bran and the variety. The two major varieties ...

  13. The Influence of Lath, Block and Prior Austenite Grain (PAG Size on the Tensile, Creep and Fatigue Properties of Novel Maraging Steel

    Directory of Open Access Journals (Sweden)

    Thomas Simm

    2017-06-01

    Full Text Available The influence of martensitic microstructure and prior austenite grain (PAG size on the mechanical properties of novel maraging steel was studied. This was achieved by looking at two different martensitic structures with PAG sizes of approximately 40 µm and 80 µm, produced by hot rolling to different reductions. Two ageing heat-treatments were considered: both heat-treatments consisted of austenisation at 960 °C, then aging at 560 °C for 5 h, but while one was rapidly cooled the other was slow cooled and then extended aged at 480 °C for 64 h. It is shown that for the shorter ageing treatment the smaller PAG size resulted in significant improvements in strength (increase of more than 150 MPa, ductility (four times increase, creep life (almost four times increase in creep life and fatigue life (almost doubled. Whereas, the extended aged sample showed similar changes in the fatigue life, elongation and hardness it displayed yet showed no difference in tensile strength and creep. These results display the complexity of microstructural contributions to mechanical properties in maraging steels.

  14. The Influence of Lath, Block and Prior Austenite Grain (PAG) Size on the Tensile, Creep and Fatigue Properties of Novel Maraging Steel.

    Science.gov (United States)

    Simm, Thomas; Sun, Lin; McAdam, Steven; Hill, Paul; Rawson, Martin; Perkins, Karen

    2017-06-30

    The influence of martensitic microstructure and prior austenite grain (PAG) size on the mechanical properties of novel maraging steel was studied. This was achieved by looking at two different martensitic structures with PAG sizes of approximately 40 µm and 80 µm, produced by hot rolling to different reductions. Two ageing heat-treatments were considered: both heat-treatments consisted of austenisation at 960 °C, then aging at 560 °C for 5 h, but while one was rapidly cooled the other was slow cooled and then extended aged at 480 °C for 64 h. It is shown that for the shorter ageing treatment the smaller PAG size resulted in significant improvements in strength (increase of more than 150 MPa), ductility (four times increase), creep life (almost four times increase in creep life) and fatigue life (almost doubled). Whereas, the extended aged sample showed similar changes in the fatigue life, elongation and hardness it displayed yet showed no difference in tensile strength and creep. These results display the complexity of microstructural contributions to mechanical properties in maraging steels.

  15. Novel elastomer dye-functionalised POSS nanocomposites: Enhanced colourimetric, thermomechanical and thermal properties

    Directory of Open Access Journals (Sweden)

    R. A. Shanks

    2012-05-01

    Full Text Available Nanocomposites consisting of poly(styrene-b-butadiene-b-styrene (SBS and polyhedral oligomeric silsesquioxanes (POSS were prepared using a solvent dispersion method. POSS molecules were functionalised with two dichlorotriazine reactive dyes (CI Reactive Blue 4, CI Reactive Red 2 prior to compounding. Infrared spectroscopy confirmed functionalisation.Scanning electron microscopy revealed an increase in filler aggregation with concentration, with preferential phase selectivity. Ultraviolet spectroscopy and colourimetry confirmed colour uniformity and suggested that colour intensity could be controlled. Functionalised POSS improved thermal stability by imparting restrictions on SBS chain motions. Tensile stress-strain analysis revealed an increase in modulus with filler concentration, while creep deformation decreased and permanent strain increased with POSS content. Storage modulus, loss modulus and glass transition temperature increased with filler content due to effective SBS-POSS interaction. Nanocomposite properties were influenced by the phase the filler was dispersed throughout and the structure of the dye chromophore.

  16. Temperature-dependent thermal properties of spark plasma sintered alumina

    Directory of Open Access Journals (Sweden)

    Saheb Nouari

    2017-01-01

    Full Text Available In this work, we report temperature-dependent thermal properties of alumina powder and bulk alumina consolidated by spark plasma sintering method. The properties were measured between room temperature and 250ºC using a thermal constants analyzer. Alumina powder had very low thermal properties due to the presence of large pores and absence of bonding between its particles. Fully dense alumina with a relative density of 99.6 % was obtained at a sintering temperature of 1400°C and a holding time of 10 min. Thermal properties were found to mainly dependent on density. Thermal conductivity, thermal diffusivity, and specific heat of the fully dense alumina were 34.44 W/mK, 7.62 mm2s-1, and 1.22 J/gK, respectively, at room temperature. Thermal conductivity and thermal diffusivity decreased while specific heat increased with the increase in temperature from room temperature to 250ºC.

  17. Semiconductor nanowires: Controlled growth and thermal properties

    Science.gov (United States)

    Wu, Yiying

    This dissertation presents an experimental study of the controlled growth of semiconductor nanowires and their thermophysical properties. The synthesis of nanowires was based on the well-known Vapor-Liquid-Solid (VLS) mechanism in which the growth of nanowire is initiated by a nanosized liquid droplet. The prepared nanowires are single-crystalline with certain preferred growth direction. Nanowires with different compositions have been synthesized, including Si, Ge, boron and MgB2. The control of nanowire composition, diameter and orientation has also been achieved. In addition, a Pulsed Laser Ablation-Chemical Vapor Deposition (PLA-CVD) hybrid process was developed to synthesize Si/SiGe longitudinally superlattice nanowires. The thermal conductivity of individual pure Si nanowire and Si/SiGe nanowire was measured using a microfabricated suspended device over a temperature range of 20--320 K. The thermal conductivities of individual 22, 37, 56, and 115 nm diameter single crystalline intrinsic Si nanowires were much lower than the bulk value due to the strong phonon boundary scattering. Except for the 22 nm diameter nanowire, theoretical predictions using a modified Callaway model fit the experimental data very well. The data for the 22 nm diameter wire suggest that changes in phonon dispersion due to confinement can cause additional thermal conductivity reduction. The Si/SiGe superlattice nanowires with diameters of 83 run and 58 nm were also measured. Their thermal conductivities are smaller than pure Si nanowire with similar diameter, as well as Si/SiGe superlattice thin film with comparable period. Both the alloying scattering and the boundary scattering are believed to contribute to this reduction. Size dependent melting-recrystallization study of the carbon-sheathed semiconductor Ge nanowires was carried out in in-situ high temperature transmission electron microscope (TEM). Significant depression in melting temperature with decreasing size of the nanowires as

  18. Influence of creep damage on the low cycle thermal-mechanical fatigue behavior of two tantalum base alloys

    Science.gov (United States)

    Sheffler, K. D.; Doble, G. S.

    1972-01-01

    Low cycle fatigue tests have been performed on the tantalum base alloys T-111 and ASTAR 811C with synchronized, independently programmed temperature and strain cycling. The thermal-mechanical cycles applied fell into three basic categories: these were isothermal cycling, in-phase thermal cycling, and out-of-phase thermal cycling. In-phase cycling was defined as tensile deformation associated with high temperature and compressive deformation with low temperature, while out-of-phase thermal cycling was defined as the reverse case. The in-phase thermal cycling had a pronounced detrimental influence on the fatigue life of both alloys, with the life reduction being greater in the solid solution strengthened T-111 alloy than in the carbide strengthened ASTAR 811C alloy. The out-of-phase tests also showed pronounced effects on the fatigue life of both alloys, although not as dramatic.

  19. High temperature tensile and creep properties of a cast AIM and ESR intermetallic alloy based on Fe{sub 3}Al

    Energy Technology Data Exchange (ETDEWEB)

    Baligidad, R.G. [Defence Metallurgical Research Lab., Hyderabad (India); Prakash, U. [Defence Metallurgical Research Lab., Hyderabad (India); Radhakrishna, A. [Defence Metallurgical Research Lab., Hyderabad (India)

    1997-07-15

    A high carbon intermetallic Fe-16 wt.% A1-1.1 wt.% C alloy based on Fe{sub 3}Al was melted under a flux cover by air induction melting (AIM). The AIM ingots exhibited excellent elevated temperature tensile properties in the temperature range (600-800 C) studied, in contrast to poor properties expected in ingots melted without a flux cover. Subsequent processing of the AIM ingots through electroslag remelting (ESR) resulted in improvement in ductility. However, the AIM ingots exhibited better creep properties because of their coarser gain structure. The presence of large (1.1 wt.%) amount of carbon in the alloy resulted in significant improvement in elevated temperature tensile as well as creep properties over those reported for Fe{sub 3}Al based intermetallic alloys with lower carbon contents. These improvements in mechanical properties are attributed to the extensive precipitation of Fe{sub 3}AlC phase and to the formation of a duplex Fe{sub 3}Al-Fe{sub 3}AlC structure at such high levels of carbon. It is suggested that carbon may be an important alloying addition to Fe{sub 3}Al-based intermetallic alloys. (orig.)

  20. Constraining Non-thermal and Thermal properties of Dark Matter

    Directory of Open Access Journals (Sweden)

    Bhupal eDev

    2014-05-01

    Full Text Available We describe the evolution of Dark Matter (DM abundance from the very onset of its creation from inflaton decay under the assumption of an instantaneous reheating. Based on the initial conditions such as the inflaton mass and its decay branching ratio to the DM species, the reheating temperature, and the mass and interaction rate of the DM with the thermal bath, the DM particles can either thermalize (fully/partially with the primordial bath or remain non-thermal throughout their evolution history. In the thermal case, the final abundance is set by the standard freeze-out mechanism for large annihilation rates, irrespective of the initial conditions. For smaller annihilation rates, it can be set by the freeze-in mechanism which also does not depend on the initial abundance, provided it is small to begin with. For even smaller interaction rates, the DM decouples while being non-thermal, and the relic abundance will be essentially set by the initial conditions. We put model-independent constraints on the DM mass and annihilation rate from over-abundance by exactly solving the relevant Boltzmann equations, and identify the thermal freeze-out, freeze-in and non-thermal regions of the allowed parameter space. We highlight a generic fact that inflaton decay to DM inevitably leads to an overclosure of the Universe for a large range of DM parameter space, and thus poses a stringent constraint that must be taken into account while constructing models of DM. For the thermal DM region, we also show the complementary constraints from indirect DM search experiments, Big Bang Nucleosynthesis, Cosmic Microwave Background, Planck measurements, and theoretical limits due to the unitarity of S-matrix. For the non-thermal DM scenario, we show the allowed parameter space in terms of the inflaton and DM masses for a given reheating temperature, and compute the comoving free-streaming length to identify the hot, warm and cold DM regimes.

  1. Thermal Properties of G-348 Graphite

    Energy Technology Data Exchange (ETDEWEB)

    McEligot, Donald M. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Swank, W. David [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cottle, David L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Valentin, Francisco I. [City Univ. (CUNY), NY (United States)

    2017-04-01

    Fundamental measurements have been obtained in the INL Graphite Characterization Laboratory to deduce the temperature dependence of thermal conductivity for G-348 isotropic graphite, which has been used by City College of New York in thermal experiments related to gas-cooled nuclear reactors. Measurements of thermal diffusivity, mass, volume and thermal expansion were converted to thermal conductivity in accordance with ASTM Standard Practice C781-08 (R-2014). Data are tabulated and a preliminary correlation for the thermal conductivity is presented as a function of temperature from laboratory temperature to 1000C.

  2. On sound absorption and thermal properties of non-wovens

    OpenAIRE

    Chen Jin-Jing; Yu Hong-Qin; Guo Zheng; You Jin-Zhang; Song Wen-Fang

    2015-01-01

    Non-woven is widely used as auxiliary materials of automobile industry due to its excellent sound absorption capability and good thermal property. The paper concludes that its density greatly affects sound absorption and thermal resistance, and an aluminum evaporated film can enhance the thermal resistance.

  3. On sound absorption and thermal properties of non-wovens

    Directory of Open Access Journals (Sweden)

    Chen Jin-Jing

    2015-01-01

    Full Text Available Non-woven is widely used as auxiliary materials of automobile industry due to its excellent sound absorption capability and good thermal property. The paper concludes that its density greatly affects sound absorption and thermal resistance, and an aluminum evaporated film can enhance the thermal resistance.

  4. experimental determination of some thermal properties of raphia ...

    African Journals Online (AJOL)

    NIJOTECH

    OF RAPHIA VINIFERA GUM by. DAVID C. ONYEJEKWE. Department of Mechanical Engineering,. University of Nigeria, Nsukka. Abstract. The thermal properties - thermal conductivity, specific heat capacity and viscosity of raphia gum are studied experimentally. The results show that thermal conductivity varies from 0.0164 ...

  5. SOME MOISTURE DEPENDENT THERMAL PROPERTIES AND ...

    African Journals Online (AJOL)

    The thermal heat conductivity, specific heat capacity, thermal heat diffusivity and bulk density of Prosopis africana seeds were determined as a function of moisture content. Specific heat capacity was measured by the method of mixture while the thermal heat conductivity was measured by the guarded hot plate method.

  6. Thermal-Insulation Properties of Multilayer Textile Packages

    Directory of Open Access Journals (Sweden)

    Matusiak Małgorzata

    2014-12-01

    Full Text Available Thermal-insulation properties of textile materials play a significant role in material engineering of protective clothing. Thermal-insulation properties are very important from the point of view of thermal comfort of the clothing user as well as the protective efficiency against low or high temperature. Thermal protective clothing usually is a multilayer construction. Its thermal insulation is a resultant of a number of layers and their order, as well as the thermalinsulation properties of a single textile material creating particular layers. The aim of the presented work was to investigate the relationships between the thermal-insulation properties of single materials and multilayer textile packages composed of these materials. Measurement of the thermal-insulation properties of single and multilayer textile materials has been performed with the Alambeta. The following properties have been investigated: thermal conductivity, resistance and absorptivity. Investigated textile packages were composed of two, three and four layers made of woven and knitted fabrics, as well as nonwovens. On the basis of the obtained results an analysis has been carried out in order to assess the dependency of the resultant values of the thermal-insulation properties of multilayer packages on the appropriate values of particular components.

  7. Thermal Properties of Asphalt Mixtures Modified with Conductive Fillers

    Directory of Open Access Journals (Sweden)

    Byong Chol Bai

    2015-01-01

    Full Text Available This paper investigates the thermal properties of asphalt mixtures modified with conductive fillers used for snow melting and solar harvesting pavements. Two different mixing processes were adopted to mold asphalt mixtures, dry- and wet-mixing, and two conductive fillers were used in this study, graphite and carbon black. The thermal conductivity was compared to investigate the effects of asphalt mixture preparing methods, the quantity, and the distribution of conductive filler on thermal properties. The combination of conductive filler with carbon fiber in asphalt mixture was evaluated. Also, rheological properties of modified asphalt binders with conductive fillers were measured using dynamic shear rheometer and bending beam rheometer at grade-specific temperatures. Based on rheological testing, the conductive fillers improve rutting resistance and decrease thermal cracking resistance. Thermal testing indicated that graphite and carbon black improve the thermal properties of asphalt mixes and the combined conductive fillers are more effective than the single filler.

  8. Optothermal Raman Studies of Thermal Properties of Graphene Based Films

    OpenAIRE

    Malekpour, Hoda

    2016-01-01

    Efficient thermal management is becoming a critical issue for development of the next generation of electronics. As the size of electronic devices shrinks, the dissipated power density increases, demanding a better heat removal. The discovery of graphene’s unique electrical and thermal properties stimulated interest of electronic industry to development of graphene based technologies. In this dissertation, I report the results of my investigation of thermal properties of graphene derivatives ...

  9. Thermal properties of WC-10 wt. (% Co alloys

    Directory of Open Access Journals (Sweden)

    Francisco de Assis Léo Machado

    2008-03-01

    Full Text Available In this article, photothermal techniques were used in order to determine some thermal properties: diffusivity, conductivity, effusivity and specific heat capacity of WC-10 wt. (% Co six samples subjected to different sintering processes. The samples were sintered using high pressure - high temperature (HPHT sintering system. The open cell photoacoustic (OPC used to measure thermal diffusivity is described in detail. The values of thermal properties here measured and evaluated are consistent to those previously reported in the literature.

  10. Thermal Coatings Seminar Series Training Part 1: Properties of Thermal Coatings

    Science.gov (United States)

    Triolo, Jack

    2015-01-01

    This course will present an overview of a variety of thermal coatings-related topics, including: coating types and availability, thermal properties measurements, environmental testing (lab and in-flight), environmental impacts, contamination impacts, contamination liabilities, determination of BOLEOL values, and what does specularity mean to the thermal engineer.

  11. Young’s modulus and creep compliance of GaAs and Ga1-xMnxAs ferromagnetic thin films under thermal stress at varied manganese doping levels

    Directory of Open Access Journals (Sweden)

    Kemei S.K.

    2015-06-01

    Full Text Available Dynamical mechanical analysis yields information about the mechanical properties of a material as a function of deforming factors, such as temperature, oscillating stress and strain amplitudes. GaAs and Mn-doped GaAs at varied levels, used in making electronic devices, suffer from damage due to changes in environmental temperatures. This is a defective factor experienced during winter and summer seasons. Hence, there was a need to establish the best amount of manganese to be doped in GaAs so as to obtain a mechanically stable spin injector material to make electronic devices. Mechanical properties of Ga1-xMnxAs spin injector were studied in relation to temperatures above room temperature (25 °C. Here, creep compliance, Young’s moduli and creep recovery for all studied samples with different manganese doping levels (MDLs were determined using DMA 2980 Instrument from TA instruments Inc. The study was conducted using displace-recover programme on DMA creep mode with a single cantilever clamp. The samples were prepared using RF sputtering techniques. From the creep compliance study it was found that MDL of 10 % was appropriate at 30 °C and 40 °C. The data obtained can be useful to the spintronic and electronic device engineers in designing the appropriate devices to use at 30 °C and above or equal to 40 °C.

  12. Creep characterization of solder bumps using nanoindentation

    Science.gov (United States)

    Du, Yingjie; Liu, Xiao Hu; Fu, Boshen; Shaw, Thomas M.; Lu, Minhua; Wassick, Thomas A.; Bonilla, Griselda; Lu, Hongbing

    2017-08-01

    Current nanoindentation techniques for the measurement of creep properties are applicable to viscoplastic materials with negligible elastic deformations. A new technique for characterization of creep behavior is needed for situations where the elastic deformation plays a significant role. In this paper, the effect of elastic deformation on the determination of creep parameters using nanoindentation with a self-similar nanoindenter tip is evaluated using finite element analysis (FEA). It is found that the creep exponent measured from nanoindentation without taking into account of the contribution of elastic deformation tends to be higher than the actual value. An effective correction method is developed to consider the elastic deformation in the calculation of creep parameters. FEA shows that this method provides accurate creep exponent. The creep parameters, namely the creep exponent and activation energy, were measured for three types of reflowed solder bumps using the nanoindentation method. The measured parameters were verified using FEA. The results show that the new correction approach allows extraction of creep parameters with precision from nanoindentation data.

  13. Eutectic mixtures of some fatty acids for latent heat storage: Thermal properties and thermal reliability with respect to thermal cycling

    Energy Technology Data Exchange (ETDEWEB)

    Sari, Ahmet [Department of Chemistry, Gaziosmanpasa University, 60240 Tokat (Turkey)]. E-mail: asari@gop.edu.tr

    2006-06-15

    Accelerated thermal cycle tests have been conducted to study the change in melting temperatures and latent heats of fusion of the eutectic mixtures of lauric acid (LA)-myristic acid (MA), lauric acid (LA)-palmitic acid (PA) and myristic acid (MA)-stearic acid (SA) as latent heat storage materials. The thermal properties of these materials were determined by the differential scanning calorimetry (DSC) analysis method. The thermal reliability of the eutectic mixtures after melt/freeze cycles of 720, 1080 and 1460 was also evaluated using the DSC curves. The accelerated thermal cycle tests indicate that the melting temperatures usually tend to decrease, and the variations in the latent heats of fusion are irregular with increasing number of thermal cycles. Moreover, the probable reasons for the change in thermal properties of the eutectic mixtures after repeated thermal cycles were investigated. Fourier Transform Infrared (FT-IR) spectroscopic analysis indicates that the accelerated melt/freeze processes do not cause any degradation in the chemical structure of the mixtures. The change in thermal properties of the eutectic mixtures with increasing number of thermal cycles is only because of the presence of certain amounts of impurities in the fatty acids used in their preparation. It is concluded that the tested eutectic mixtures have reasonable thermal properties and thermal reliability as phase change materials (PCMs) for latent heat storage in any solar heating applications that include a four year utilization period.

  14. Creep stresses in a spherical shell under steady state temperature

    Science.gov (United States)

    Verma, Gaurav; Rana, Puneet

    2017-10-01

    The paper investigates the problem of creep of a spherical structure under the influence of steady state temperature. The problem of creep in spherical shell is solved by using the concept of generalized strain measures and transition hypothesis given by Seth. The problem has reduced to non-linear differential equation for creep transition. This paper deals with the non-linear behaviour of spherical shell under thermal condition. The spherical shell structures are easily vulnerable to creep, shrinkage and thermal effects; a thorough understanding of their time-dependent behaviour has been fully established. The paper aims to provide thermal creep analysis to enhance the effective design and long life of shells, and a theoretical model is developed for calculating creep stresses and strains in a spherical shell with purpose. Results obtained for the problem are depicted graphically.

  15. Mechanical properties of thermal protection system materials.

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, Robert Douglas; Bronowski, David R.; Lee, Moo Yul; Hofer, John H.

    2005-06-01

    An experimental study was conducted to measure the mechanical properties of the Thermal Protection System (TPS) materials used for the Space Shuttle. Three types of TPS materials (LI-900, LI-2200, and FRCI-12) were tested in 'in-plane' and 'out-of-plane' orientations. Four types of quasi-static mechanical tests (uniaxial tension, uniaxial compression, uniaxial strain, and shear) were performed under low (10{sup -4} to 10{sup -3}/s) and intermediate (1 to 10/s) strain rate conditions. In addition, split Hopkinson pressure bar tests were conducted to obtain the strength of the materials under a relatively higher strain rate ({approx}10{sup 2} to 10{sup 3}/s) condition. In general, TPS materials have higher strength and higher Young's modulus when tested in 'in-plane' than in 'through-the-thickness' orientation under compressive (unconfined and confined) and tensile stress conditions. In both stress conditions, the strength of the material increases as the strain rate increases. The rate of increase in LI-900 is relatively small compared to those for the other two TPS materials tested in this study. But, the Young's modulus appears to be insensitive to the different strain rates applied. The FRCI-12 material, designed to replace the heavier LI-2200, showed higher strengths under tensile and shear stress conditions. But, under a compressive stress condition, LI-2200 showed higher strength than FRCI-12. As far as the modulus is concerned, LI-2200 has higher Young's modulus both in compression and in tension. The shear modulus of FRCI-12 and LI-2200 fell in the same range.

  16. Synthesis, mechanical, thermal and chemical properties of ...

    Indian Academy of Sciences (India)

    Cardanol, an excellent monomer for polymer production, has been isolated from CNSL and allowed to react with formaldehyde in a particular mole ratio in the presence of glutaric acid catalyst to give ... Differential thermal analysis (DTA) and thermo-gravimetric analysis (TGA) were undertaken for thermal characterization.

  17. Summary of thermal properties for casting alloys and mold materials

    Science.gov (United States)

    Pehlke, R. D.; Jeyarajan, A.; Wada, H.

    1982-12-01

    A review of thermal properties of casting alloys and mold materials was conducted for the purpose of stimulating activity in computer aided design for castings. A summary of thermal data; thermal conductivity, specific heat, density, and heats of fusion was prepared for metals and casting alloys, and for primary molding materials. This summary represents an initial step in the development of data bases for support of computer aided design systems for castings. Additional information is required, in particular for thermal properties of commercial casting alloy systems.

  18. Properties of thick welded joints on superheater collectors made from new generation high alloy martensitic creep-resisting steels for supercritical parameters

    Energy Technology Data Exchange (ETDEWEB)

    Dobrzanski, Janusz; Zielinski, Adam [Institute for Ferrous Metallurgy, Gliwice (Poland); Pasternak, Jerzy [Boiler Engineering Company RAFAKO S.A., Raciborz (Poland)

    2010-07-01

    The continuously developing power generation sector, including boilers with supercritical parameters, requires applications of new creep-resistant steel grades for construction of boilers steam superheater components. This paper presents selected information, experience within the field of research and implementation of a new group of creep-resistant as X10CrMoVNb9-1(P91), X10CrWMoVNb9-2(P92) and X12CrCoWVNb12-2-2(VM12) grades, containing 9-12%Cr. During welding and examination process the results of mechanical properties, requested level for base material and welded joints, as well as: tensile strength, impact strength and technological properties have been evaluated. Additional destructive examinations, with evaluation of structure stability, hardness distribution, for base material and welded joints after welding, heat treatment, again process have been determined. Recommendations due to the implementation influence of operating parameters of the main boiler components are part of this paper. (orig.)

  19. On the prediction of long term creep strength of creep resistant steels

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Mi; Wang, Qiao; Song, Xin-Li; Jia, Juan; Xiang, Zhi-Dong [Wuhan University of Science and Technology (China). The State Key Laboratory of Refractories and Metallurgy

    2016-02-15

    When the conventional power law creep equation is applied to rationalise the creep data of creep resistant steels, its parameters depend strongly on stress and temperature and hence cannot be used to predict long term creep properties. Here, it is shown that this problem can be resolved if it is modified to satisfy two boundary conditions, i.e. when σ (stress) = 0, ε{sub min} (minimum creep rate) = 0, and when σ = σ{sub TS} (tensile stress at creep temperature T), ε{sub min} = ∞. This can be achieved by substituting the reference stress σ{sub 0} in the conventional equation by the term (σ{sub TS} - σ). The new power law creep equation describing the stress and temperature dependence of minimum creep rate can then be applied to predict long term creep strength from data of short term measurements. This is demonstrated using the creep and tensile strength data measured for 11Cr-2W-0.4Mo-1Cu-Nb-V steel (tube).

  20. Nanomechanical properties and thermal decomposition of Cu-Al2O3 composites for FGM applications

    Directory of Open Access Journals (Sweden)

    Koumoulos Elias P.

    2016-01-01

    Full Text Available It is widely reported that copper-alumina (Cu-Al2O3 nanocomposite materials exhibit high potential for use in structural applications in which enhanced mechanical characteristics are required. The investigation of Cu-Al2O3 nanocomposites which are to form a functionally graded material (FGM structure in terms of nanomechanical/structural integrity and thermal stability is still scarce. In this work, fully characterized nanosized Al2O3 powder has been incorporated in Cu matrix in various compositions (2, 5 and 10 wt.% of Al2O3 content. The produced composites were evaluated in terms of their morphology, structural analysis, thermal behavior, nanomechanical properties and their extent of viscoplasticity. The results reveal that all nanocomposites degrade at elevated temperatures; increased surface mass gain with decreasing Al2O3 content was observed, while no such difference of % mass gain in 5 and 10 wt.% of Al and Al2O3 content in Cu was observed. The increase of Al2O3 wt.% content results in thermal stability enhancement of the nanocomposites. The thermal decomposition process of the material is reduced in the presence of 10 wt.% of Al2O3 content. This result for the matrix decomposition can be explained by a decrease in the diffusion of oxygen and volatile degradation products throughout the composite material due to the incorporation of Al and Al2O3. The Al2O3 powder enhances the overall thermal stability of the system. All samples exhibited significant pile-up of the materials after nanoindentation testing. Increasing the wt.% of Al2O3 content was found to increase the creep deformation of the samples as well as the hardness and elastic modulus values.

  1. Thermal transport properties of grey cast irons

    Energy Technology Data Exchange (ETDEWEB)

    Hecht, R.L. [Ford Motor Co., Dearborn, MI (United States). Ford Research Lab.; Dinwiddie, R.B.; Porter, W.D.; Wang, Hsin [Oak Ridge National Lab., TN (United States)

    1996-10-01

    Thermal diffusivity and thermal conductivity of grey cast iron have been measured as a function of graphite flake morphology, chemical composition, and position in a finished brake rotor. Cast iron samples used for this investigation were cut from ``step block`` castings designed to produce iron with different graphite flake morphologies resulting from different cooling rates. Samples were also machined from prototype alloys and from production brake rotors representing a variation in foundry practice. Thermal diffusivity was measured at room and elevated temperatures via the flash technique. Heat capacity of selected samples was measured with differential scanning calorimetry, and these results were used to calculate the thermal conductivity. Microstructure of the various cast iron samples was quantified by standard metallography and image analysis, and the chemical compositions were determined by optical emission spectroscopy.

  2. Creep deformation and rupture behavior of CLAM steel at 823 K and 873 K

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Boyu [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Huang, Bo, E-mail: bo.huang@fds.org.cn [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Li, Chunjing; Liu, Shaojun; Xu, Gang [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Zhao, Yanyun; Huang, Qunying [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); University of Science and Technology of China, Hefei, Anhui 230027 (China)

    2014-12-15

    China Low Activation Martensitic (CLAM) steel is selected as the candidate structural material in Fusion Design Study (FDS) series fusion reactor conceptual designs. The creep property of CLAM steel has been studied in this paper. Creep tests have been carried out at 823 K and 873 K over a stress range of 150–230 MPa. The creep curves showed three creep regimes, primary creep, steady-state creep and tertiary creep. The relationship between minimum creep rate (ε-dot{sub min}) and the applied stress (σ) could be described by Norton power law, and the stress exponent n was decreased with the increase of the creep temperature. The creep mechanism was analyzed with the fractographes of the rupture specimens which were examined by scanning electron microscopy (SEM). The coarsening of precipitates observed with transmission electron microscope (TEM) indicated the microstructural degradation after creep test.

  3. Computational Design of Creep-Resistant Alloys and Experimental Validation in Ferritic Superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, Peter

    2014-12-31

    -principles calculations, providing deep insight of creep mechanisms of the creep-resistant ferritic superalloys. With the above investigations, the HPSFA has been proved with superior creep resistance, and its microstructure, creep mechanism, and thermal/mechanical properties have been well studied and understood. In the future, HPSFAs with different additions and sizes of precipitates will be investigated and developed to further enhance the creep resistance of the ferritic superalloys and provide promising applications of the fossil-energy power plants.

  4. Contribution to the thermal properties of selected steels

    Directory of Open Access Journals (Sweden)

    P. Jonšta

    2015-01-01

    Full Text Available The paper deals with the influence of structural changes on heat transport phenomena of steels samples. Three samples of 10GN2MFA steel were thermally treated at quenching temperatures equal to 900 °C, 1 000 °C and 1 100 °C, and temperature of the tempering was 670 °C. Both thermal diffusivity and thermal conductivity increase with the quenching temperature. Specific heat capacity of steel samples after thermal treatment does not change significantly. Further three different high manganese steels were measured. Maximal content of Mn and C was 27 and 0,5 mass percent. From results of thermophysical properties after ageing, one can see the increase of thermal diffusivity up to 20 percent, thermal conductivity up to 15 percent, decrease of specific heat capacity is not significant. All measured values of thermophysical properties are in good agreement with literary data (before ageing.

  5. Investigation of thermal properties of raw materials of asphalt mixtures

    Science.gov (United States)

    Géber, R.; Simon, A.; Kocserha, I.

    2017-02-01

    Asphalt mixtures are composite materials, which are made of different grades of mineral aggregates and bitumen. During the mixing process mineral materials were blended with bitumen at relatively high temperature (∼200 °C). As the binding process come off in these higher temperature range, thermal properties of asphaltic materials are important. The aim of this project is to reveal the thermal properties of raw materials. During our research two types of mineral aggregates were tested (limestone and dolomite) by different methods. Differential thermal analysis, thermal expansion and thermal conductivity were investigated at technologically important temperatures. The results showed that the structure of mineral materials did not change at elevated temperatures, expansion of samples was neglible, while thermal conductivity changed by temperature.

  6. Method and apparatus for implementing material thermal property measurement by flash thermal imaging

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Jiangang

    2017-11-14

    A method and apparatus are provided for implementing measurement of material thermal properties including measurement of thermal effusivity of a coating and/or film or a bulk material of uniform property. The test apparatus includes an infrared camera, a data acquisition and processing computer coupled to the infrared camera for acquiring and processing thermal image data, a flash lamp providing an input of heat onto the surface of a two-layer sample with an enhanced optical filter covering the flash lamp attenuating an entire infrared wavelength range with a series of thermal images is taken of the surface of the two-layer sample.

  7. Thermal properties of epoxy composites filled with boric acid

    Science.gov (United States)

    Visakh, P. M.; Nazarenko, O. B.; Amelkovich, Yu A.; Melnikova, T. V.

    2015-04-01

    The thermal properties of epoxy composites filled with boric acid fine powder at different percentage were studied. Epoxy composites were prepared using epoxy resin ED-20, boric acid as flame-retardant filler, hexamethylenediamine as a curing agent. The prepared samples and starting materials were examined using methods of thermal analysis, scanning electron microscopy and infrared spectroscopy. It was found that the incorporation of boric acid fine powder enhances the thermal stability of epoxy composites.

  8. Effects of Heat-Treated Wood Particles on the Physico-Mechanical Properties and Extended Creep Behavior of Wood/Recycled-HDPE Composites Using the Time–Temperature Superposition Principle

    Directory of Open Access Journals (Sweden)

    Teng-Chun Yang

    2017-03-01

    Full Text Available This study investigated the effectiveness of heat-treated wood particles for improving the physico-mechanical properties and creep performance of wood/recycled-HDPE composites. The results reveal that the composites with heat-treated wood particles had significantly decreased moisture content, water absorption, and thickness swelling, while no improvements of the flexural properties or the wood screw holding strength were observed, except for the internal bond strength. Additionally, creep tests were conducted at a series of elevated temperatures using the time–temperature superposition principle (TTSP, and the TTSP-predicted creep compliance curves fit well with the experimental data. The creep resistance values of composites with heat-treated wood particles were greater than those having untreated wood particles due to the hydrophobic character of the treated wood particles and improved interfacial compatibility between the wood particles and polymer matrix. At a reference temperature of 20 °C, the improvement of creep resistance (ICR of composites with heat-treated wood particles reached approximately 30% over a 30-year period, and it increased significantly with increasing reference temperature.

  9. Effects of Heat-Treated Wood Particles on the Physico-Mechanical Properties and Extended Creep Behavior of Wood/Recycled-HDPE Composites Using the Time-Temperature Superposition Principle.

    Science.gov (United States)

    Yang, Teng-Chun; Chien, Yi-Chi; Wu, Tung-Lin; Hung, Ke-Chang; Wu, Jyh-Horng

    2017-03-30

    This study investigated the effectiveness of heat-treated wood particles for improving the physico-mechanical properties and creep performance of wood/recycled-HDPE composites. The results reveal that the composites with heat-treated wood particles had significantly decreased moisture content, water absorption, and thickness swelling, while no improvements of the flexural properties or the wood screw holding strength were observed, except for the internal bond strength. Additionally, creep tests were conducted at a series of elevated temperatures using the time-temperature superposition principle (TTSP), and the TTSP-predicted creep compliance curves fit well with the experimental data. The creep resistance values of composites with heat-treated wood particles were greater than those having untreated wood particles due to the hydrophobic character of the treated wood particles and improved interfacial compatibility between the wood particles and polymer matrix. At a reference temperature of 20 °C, the improvement of creep resistance ( ICR ) of composites with heat-treated wood particles reached approximately 30% over a 30-year period, and it increased significantly with increasing reference temperature.

  10. Thermal properties of graphite oxide, thermally reduced graphene and chemically reduced graphene

    Science.gov (United States)

    Jankovský, Ondřej; Sedmidubský, David; Lojka, Michal; Sofer, Zdeněk

    2017-07-01

    We compared thermal behavior and other properties of graphite oxide, thermally reduced graphene and chemically reduced graphene. Graphite was oxidized according to the Hofmann method using potassium chlorate as oxidizing agent in strongly acidic environment. In the next step, the formed graphite oxide was chemically or thermally reduced yielding graphene. The mechanism of thermal reduction was studied using STA-MS. Graphite oxide and both thermally and chemically reduced graphenes were analysed by SEM, EDS, elemental combustion analysis, XPS, Raman spectroscopy, XRD and BET. These findings will help for the large scale production of graphene with appropriate chemical composition.

  11. Control of Early Age Concrete. Phase 3: Creep in Concrete

    DEFF Research Database (Denmark)

    Hauggaard-Nielsen, Anders Boe; Damkilde, Lars; Hansen, Per Freiesleben

    1997-01-01

    The mechanical properties of the "Road Directorate Concrete" at early ages are studied. Creep in tension at 24 and 72 maturity hours are measured on dogbone shaped specimens. The development of tensile modulus of elasticity and strength are measured with a method developed here. The results...... are compared to compression values and splitting strengths. It is found that the properties of creep in tension are similar to the properties in compression. Further the influence form temperature on creep is found to be significant....

  12. Thermal Transport Properties of Dry Spun Carbon Nanotube Sheets

    Directory of Open Access Journals (Sweden)

    Heath E. Misak

    2016-01-01

    Full Text Available The thermal properties of carbon nanotube- (CNT- sheet were explored and compared to copper in this study. The CNT-sheet was made from dry spinning CNTs into a nonwoven sheet. This nonwoven CNT-sheet has anisotropic properties in in-plane and out-of-plane directions. The in-plane direction has much higher thermal conductivity than the out-of-plane direction. The in-plane thermal conductivity was found by thermal flash analysis, and the out-of-plane thermal conductivity was found by a hot disk method. The thermal irradiative properties were examined and compared to thermal transport theory. The CNT-sheet was heated in the vacuum and the temperature was measured with an IR Camera. The heat flux of CNT-sheet was compared to that of copper, and it was found that the CNT-sheet has significantly higher specific heat transfer properties compared to those of copper. CNT-sheet is a potential candidate to replace copper in thermal transport applications where weight is a primary concern such as in the automobile, aircraft, and space industries.

  13. Marine aerosol properties and thermal imager performance (MAPTIP): an overview

    NARCIS (Netherlands)

    Leeuw, G. de; Eijk, A.M.J. van; Jensen, D.R.

    1996-01-01

    The MAPTIP (marine aerosol properties and thermal imager performance) experiment was organized as part of a project to assess atmospheric effects on the detection and identification of targets using thermal imagers in coastal areas. The experiment took place at the North Sea from 11 October - 5

  14. Laboratory measurements of gravel thermal properties. A methodology proposal

    Science.gov (United States)

    Cultrera, Matteo; Peron, Fabio; Bison, Paolo; Dalla Santa, Giorgia; Bertermann, David; Muller, Johannes; Bernardi, Adriana; Galgaro, Antonio

    2017-04-01

    Gravel thermal properties measurements at laboratory level is quite challenging due to several technical and logistic issues, mainly connected to the sediment sizes and the variability of their mineralogical composition. The direct measurement of gravel thermal properties usually are not able to involve a representative volume of geological material, consequently the thermal measurements performed produce much dispersed results and not consistent due to the large interstitial voids and the poor physical contact with the measuring sensors. With the aim of directly provide the measurement of the gravel thermal properties, a new methodology has been developed and some results are already available on several gravel deposits samples around Europe. Indeed, a single guarded hot plate Taurus Instruments TLP 800 measured the gravel thermal properties. Some instrumental adjustments were necessary to adapt the measuring devices and to finalize the thermal measurements on gravels at the IUAV FISTEC laboratory (Environmental Technical Physics Laboratory of Venice University). This device usually provides thermal measurements according to ISO 8302, ASTM C177, EN 1946-2, EN 12664, EN 12667 and EN 12939 for building materials. A preliminary calibration has been performed comparing the outcomes obtained with the single guarded hot plate with a needle probe of a portable thermal conductivity meter (ISOMET). Standard sand (ISO 67:2009) is used as reference material. This study is provided under the Cheap-GSHPs project that has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement no. 657982

  15. Densely crosslinked polycarbosiloxanes .2. Thermal and mechanical properties

    NARCIS (Netherlands)

    Flipsen, T.A C; Derks, R.; van der Vegt, H.A.; Stenekes, R.; Pennings, A.J; Hadziioannou, G

    1997-01-01

    The thermal and mechanical properties of two densely crosslinked polycarbosiloxane systems were investigated in relation to the molecular structure. The networks were prepared from functional branched prepolymers and crosslinked via a hydrosilylation curing reaction. The prepolymers having only

  16. The effect of electron beam welding on the creep rupture properties of a Nb-Zr-C alloy

    Science.gov (United States)

    Moore, T. J.; Titran, R. H.; Grobstein, T. L.

    1986-01-01

    Creep rupture tests of electron beam welded PWC-11 sheet were conducted at 1350 K. Full penetration, single pass welds were oriented transverse to the testing direction in 1 mm thick sheet. With this orientation, stress was imposed equally on the base metal, weld metal, and heat-affected zone. Tests were conducted in both the postweld annealed and aged conditions. Unwelded specimens with similar heat treatments were tested for comparative purposes. It was found that the weld region is stronger than the base metal for both the annealed and aged conditions and that the PWC-11 material is stronger in the annealed condition than in the aged condition.

  17. Simultaneous consolidation and creep

    DEFF Research Database (Denmark)

    Krogsbøll, Anette

    1997-01-01

    Materials that exhibit creep under constant effective stress typically also show rate dependent behavior. The creep deformations and the rate sensitive behavior is very important when engineering and geological problems with large time scales are considered. When stress induced compaction (consol...... (consolidation) is retarded by slow drainage of excess pore pressure it is expected that consolidation and creep occur simultaneously. A constitutive model adressing the problems of rate sensitive behavior and simultaneous consolidation and creep is presented....

  18. Creep rupture strength of microalloyed steels

    Energy Technology Data Exchange (ETDEWEB)

    Foldyna, V.; Kubon, Z.; Schellong, T.

    2001-07-01

    The superior creep resistance of the microalloyed steels compared to the carbon steels originates in the presence of very fine particles of minor phases based on vanadium or niobium. These steels are delivered either after controlled rolling or in the normalized state. The creep strength of these microalloyed steels reaches nearly that of low alloy 0.15C-0.3Mo steel type. The best creep properties are detected in steels after controlled rolling, while after normalizing creep rupture strength slightly decreases, especially in heats alloyed with niobium. This is the result of the microstructure of the steel when in steel with niobium originally fine particles of niobium carbonitride coarsen during normalizing with corresponding changes in their interparticle spacing. When compared the creep rupture strength attained experimentally with the data stated in the standard CSN 41 2025, it is clear that the data stated in the standard corresponds the creep properties of this steel after normalizing but do not take into account creep properties attained after controlled rolling (normalizing forming). (orig.)

  19. Dependence of Glass Mechanical Properties on Thermal and Pressure History

    DEFF Research Database (Denmark)

    Smedskjær, Morten Mattrup; Bauchy, Mathieu

    Predicting the properties of new glasses prior to manufacturing is a topic attracting great industrial and scientific interest. Mechanical properties are currently of particular interest given the increasing demand for stronger, thinner, and more flexible glasses in recent years. However, as a non......-equilibrium material, the structure and properties of glass depend not only on its composition, but also on its thermal and pressure histories. Here we review our recent findings regarding the thermal and pressure history dependence of indentation-derived mechanical properties of oxide glasses....

  20. Creep and Creep-Fatigue of Alloy 617 Weldments

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Jill K. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Carroll, Laura J. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Wright, Richard N. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2014-08-01

    Alloy 617 is the primary candidate material for the heat exchanger of a very high temperature gas cooled reactor intended to operate up to 950°C. While this alloy is currently qualified in the ASME Boiler and Pressure Vessel Code for non-nuclear construction, it is not currently allowed for use in nuclear designs. A draft Code Case to qualify Alloy 617 for nuclear pressure boundary applications was submitted in 1992, but was withdrawn prior to approval. Prior to withdrawal of the draft, comments were received indicating that there was insufficient knowledge of the creep and creep-fatigue behavior of Alloy 617 welds. In this report the results of recent experiments and analysis of the creep-rupture behavior of Alloy 617 welds prepared using the gas tungsten arc process with Alloy 617 filler wire. Low cycle fatigue and creep-fatigue properties of weldments are also discussed. The experiments cover a range of temperatures from 750 to 1000°C to support development of a new Code Case to qualify the material for elevated temperature nuclear design. Properties of the welded material are compared to results of extensive characterization of solution annealed plate base metal.

  1. Preparation, thermal properties and thermal reliability of microencapsulated n-eicosane as novel phase change material for thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Alkan, Cemil; Sari, Ahmet; Karaipekli, Ali [Department of Chemistry, Gaziosmanpasa University, 60240 Tokat (Turkey)

    2011-01-15

    This study deals with preparation, characterization, thermal properties and thermal reliability of n-eicosane microcapsules as novel phase change material (PCM) for thermal energy storage. The microcapsulated PCMs were prepared by coating n-eicosane with polymethylmethacrylate (PMMA) shell. Fourier transform infrared (FT-IR), scanning electron microscope (SEM) and particle size distribution (PSD) analysis were used to characterize the PMMA/eicosane microcapsules as microcapsulated PCMs. The PSD analysis indicated that the average diameter of microcapsules was found to be 0.70 {mu}m under the stirring speed of 2000 rpm. Thermal properties and thermal reliability of the microcapsules were determined using differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA) methods. From DSC analysis, the melting and freezing temperatures and the latent heats of the microcapsules were measured as 35.2 C and 34.9 C, 84.2 and -87.5 J/g, respectively. TGA analysis indicated that PMMA/eicosane microcapsules degrade in three steps at considerably high temperatures. Accelerated thermal cycling tests have been also applied to show the thermal reliability of the microcapsules. All results showed that thermal properties make the PMMA/eicosane microcapsules potential PCM for thermal energy storage. (author)

  2. Thermal, electrochemical and mechanical properties of shape

    African Journals Online (AJOL)

    T. Ahmad

    2017-05-01

    May 1, 2017 ... He also discussed the uses of superelastic NiTi powder for the resistance of SnPdAg solder against failure due to thermal stresses. European has been recently using NiTiNb plug for sealing high-pressure fuel passages in diesel engine injectors made of SMA actuators. This research is aimed to develop ...

  3. Thermal conductivity and other properties of cementitious grouts

    Energy Technology Data Exchange (ETDEWEB)

    Allan, M.

    1998-08-01

    The thermal conductivity and other properties cementitious grouts have been investigated in order to determine suitability of these materials for grouting vertical boreholes used with geothermal heat pumps. The roles of mix variables such as water/cement ratio, sand/cement ratio and superplasticizer dosage were measured. In addition to thermal conductivity, the cementitious grouts were also tested for bleeding, permeability, bond to HDPE pipe, shrinkage, coefficient of thermal expansion, exotherm, durability and environmental impact. This paper summarizes the results for selected grout mixes. Relatively high thermal conductivities were obtained and this leads to reduction in predicted bore length and installation costs. Improvements in shrinkage resistance and bonding were achieved.

  4. THERMAL CONDUCTIVITY AND OTHER PROPERTIES OF CEMENTITIOUS GROUTS

    Energy Technology Data Exchange (ETDEWEB)

    ALLAN,M.

    1998-05-01

    The thermal conductivity and other properties cementitious grouts have been investigated in order to determine suitability of these materials for grouting vertical boreholes used with geothermal heat pumps. The roles of mix variables such as water/cement ratio, sand/cement ratio and superplasticizer dosage were measured. In addition to thermal conductivity, the cementitious grouts were also tested for bleeding, permeability, bond to HDPE pipe, shrinkage, coefficient of thermal expansion, exotherm, durability and environmental impact. This paper summarizes the results for selected grout mixes. Relatively high thermal conductivities were obtained and this leads to reduction in predicted bore length and installation costs. Improvements in shrinkage resistance and bonding were achieved.

  5. In situ thermally reduced graphene oxide/epoxy composites: thermal and mechanical properties

    Science.gov (United States)

    Olowojoba, Ganiu B.; Eslava, Salvador; Gutierrez, Eduardo S.; Kinloch, Anthony J.; Mattevi, Cecilia; Rocha, Victoria G.; Taylor, Ambrose C.

    2016-10-01

    Graphene has excellent mechanical, thermal, optical and electrical properties and this has made it a prime target for use as a filler material in the development of multifunctional polymeric composites. However, several challenges need to be overcome to take full advantage of the aforementioned properties of graphene. These include achieving good dispersion and interfacial properties between the graphene filler and the polymeric matrix. In the present work, we report the thermal and mechanical properties of reduced graphene oxide/epoxy composites prepared via a facile, scalable and commercially viable method. Electron micrographs of the composites demonstrate that the reduced graphene oxide (rGO) is well dispersed throughout the composite. Although no improvements in glass transition temperature, tensile strength and thermal stability in air of the composites were observed, good improvements in thermal conductivity (about 36 %), tensile and storage moduli (more than 13 %) were recorded with the addition of 2 wt% of rGO.

  6. In situ thermally reduced graphene oxide/epoxy composites: thermal and mechanical properties

    Directory of Open Access Journals (Sweden)

    Ganiu B. Olowojoba

    2016-01-01

    Full Text Available Abstract Graphene has excellent mechanical, thermal, optical and electrical properties and this has made it a prime target for use as a filler material in the development of multifunctional polymeric composites. However, several challenges need to be overcome to take full advantage of the aforementioned properties of graphene. These include achieving good dispersion and interfacial properties between the graphene filler and the polymeric matrix. In the present work, we report the thermal and mechanical properties of reduced graphene oxide/epoxy composites prepared via a facile, scalable and commercially viable method. Electron micrographs of the composites demonstrate that the reduced graphene oxide (rGO is well dispersed throughout the composite. Although no improvements in glass transition temperature, tensile strength and thermal stability in air of the composites were observed, good improvements in thermal conductivity (about 36 %, tensile and storage moduli (more than 13 % were recorded with the addition of 2 wt% of rGO.

  7. In situ thermally reduced graphene oxide/epoxy composites: thermal and mechanical properties

    National Research Council Canada - National Science Library

    Olowojoba, Ganiu B; Eslava, Salvador; Gutierrez, Eduardo S; Kinloch, Anthony J; Mattevi, Cecilia; Rocha, Victoria G; Taylor, Ambrose C

    2016-01-01

    Graphene has excellent mechanical, thermal, optical and electrical properties and this has made it a prime target for use as a filler material in the development of multifunctional polymeric composites...

  8. Measurement of thermal properties of magnetic nanoparticles using infrared thermal microscopy

    DEFF Research Database (Denmark)

    Kim, Jae Young; Chang, Ki Soo; Kook, Myung Ho

    2013-01-01

    Magnetic nanoparticles (MNPs) are considered promising for biomedical applications such as hyperthermia treatment and disease diagnosis owing to their distinctive thermal properties. For these applications, it is essential to screen the temperature distribution in the targeted disease site...

  9. Influence of defects on thermal properties of stanene

    Science.gov (United States)

    Das, Sourav; Rakib, Tawfiqur; Mojumder, Satyajit; Islam, Md Mahbubul; Motalab, Mohammad Abdul

    2017-06-01

    Stanene is a two-dimensional, graphene-like honeycomb structure material, has been synthesized in a recent experimental study. Theoretically, it is expected to have a super conductive property near room temperature due to its spin orbital coupling effect. It is a potential material for the next generation nano-electronics application. Therefore, studying its thermal property is of particular interest. In this paper, we investigated the effect of different types of defects on the thermal conductivity of stanene nanosheets. Molecular Dynamics simulations are performed to calculate the thermal conductivity as a function of various types of defects. MEAM potential is used to describe the inter-atomic forces. It has been found that the presence of defects reduces the thermal conductivity significantly. Finally, vibrational density of states (DOS) are calculated to elucidate the underlying mechanisms of the reduction of thermal conductivity.

  10. Thermal characterization and properties of a copper-diamond composite

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Pin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Chavez, Thomas P. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); DiAntonio, Christopher Brian [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Coker, Eric Nicholas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-09-01

    The thermal properties of a commercial copper-diamond composite were measured from below -50°C to above 200°C. The results of thermal expansion, heat capacity, and thermal diffusivity were reported. These data were used to calculate the thermal conductivity of the composite as a function of temperature in the thickness direction. These results are compared with estimated values based on a simple mixing rule and the temperature dependence of these physical properties is represented by curve fitting equations. These fitting equations can be used for thermal modeling of practical devices/systems at their operation temperatures. The results of the mixing rule showed a consistent correlation between the amount of copper and diamond in the composite, based on density, thermal expansion, and heat capacity measurements. However, there was a disparity between measured and estimated thermal diffusivity and thermal conductivity. These discrepancies can be caused by many intrinsic material issues such as lattice defects and impurities, but the dominant factor is attributed to the large uncertainty of the interfacial thermal conductance between diamond and copper.

  11. Creep in ceramics

    CERN Document Server

    Pelleg, Joshua

    2017-01-01

    This textbook is one of its kind, since there are no other books on Creep in Ceramics. The book consist of two parts: A and B. In part A general knowledge of creep in ceramics is considered, while part B specifies creep in technologically important ceramics. Part B covers creep in oxide ceramics, carnides and nitrides. While covering all relevant information regarding raw materials and characterization of creep in ceramics, the book also summarizes most recent innovations and developments in this field as a result of extensive literature search.

  12. Synthesis, characterization, thermal and electrical properties of ...

    Indian Academy of Sciences (India)

    The anticorrosive property of a coating of PANI/[Co(mea)2(H2O)2Cl2] composite on mild steel coupon in 3 M HNO3 was evaluated using weight loss measurement and compared with pure polyaniline coating. The said composite has shown anticorrosive property and can thus, act as a potent dopant for enhancing corrosion ...

  13. Nonlinear creep damage constitutive model for soft rocks

    Science.gov (United States)

    Liu, H. Z.; Xie, H. Q.; He, J. D.; Xiao, M. L.; Zhuo, L.

    2017-02-01

    In some existing nonlinear creep damage models, it may be less rigorous to directly introduce a damage variable into the creep equation when the damage variable of the viscous component is a function of time or strain. In this paper, we adopt the Kachanov creep damage rate and introduce a damage variable into a rheological differential constitutive equation to derive an analytical integral solution for the creep damage equation of the Bingham model. We also propose a new nonlinear viscous component which reflects nonlinear properties related to the axial stress of soft rock in the steady-state creep stage. Furthermore, we build an improved Nishihara model by using this new component in series with the correctional Nishihara damage model that describes the accelerating creep, and deduce the rheological constitutive relation of the improved model. Based on superposition principle, we obtain the damage creep equation for conditions of both uniaxial and triaxial compression stress, and study the method for determining the model parameters. Finally, this paper presents the laboratory test results performed on mica-quartz schist in parallel with, or vertical to the schistosity direction, and applies the improved Nishihara model to the parameter identification of mica-quartz schist. Using a comparative analysis with test data, results show that the improved model has a superior ability to reflect the creep properties of soft rock in the decelerating creep stage, the steady-state creep stage, and particularly within the accelerating creep stage, in comparison with the traditional Nishihara model.

  14. Thermal properties of composite materials: a complex systems approximation

    Science.gov (United States)

    Carrillo, J. L.; Bonilla, Beatriz; Reyes, J. J.; Dossetti, Victor

    We propose an effective media approximation to describe the thermal diffusivity of composite samples made of polyester resin and magnetite inclusions. By means of photoacoustic spectroscopy, the thermal diffusivity of the samples were experimentally measured. The volume fraction of the inclusions was systematically varied in order to study the changes in the effective thermal diffusivity of the composites. For some samples, a static magnetic field was applied during the polymerization process, resulting in anisotropic inclusion distributions. Our results show a significant difference in the thermal properties of the anisotropic samples, compared to the isotropic randomly distributed. We correlate some measures of the complexity of the inclusion structure with the observed thermal response through a multifractal analysis. In this way, we are able to describe, and at some extent predict, the behavior of the thermal diffusivity in terms of the lacunarity and other measures of the complexity of these samples Partial Financial Support by CONACyT México and VIEP-BUAP.

  15. Whole Year Optimization of Building Thermal Properties

    OpenAIRE

    Naeimi, Homa

    2014-01-01

    Along with improvement in buildings structure, developments in thermal design allow decreasing the energy demand of heating, cooling, and air conditioning of buildings. This thesis distinguishes and optimizes design elements that are essential in minimizing building heating /cooling loads. Optimum designs vary significantly for different areas due to different meteorological conditions between locations and seasonal changes at the same location. Considering the typical meteorological conditio...

  16. Pressure dependence of thermal transport properties.

    Science.gov (United States)

    Hofmeister, Anne M

    2007-05-29

    Pressure (P) derivatives of thermal conductivity (k) and thermal diffusivity (D) are important to geophysics but are difficult to measure accurately because minerals, being hard and partially transparent, likely incur systematic errors through thermal losses at interfaces and spurious radiative transfer. To evaluate accuracy, repeat experiments for olivine [(Mg(0.9)Fe(0.1))(2)SiO4], quartz (SiO2), and NaCl are examined in detail: these and other data on electrical insulators are compared with theory. At ambient conditions, D is underestimated in proportion to the number of contacts. As temperature (T) increases, spurious radiative transfer more than offsets contact loss. Compression of pore space and contact losses affect pressure derivatives, but these seem independent of T. Accurate (+/-2%) values of D(T) at 1 atm are obtained with the contact-free, laser-flash method. Other optical techniques do not pinpoint D but provide useful pressure derivatives. Published data on (partial differential)(lnk)/(partial differential)P at ambient conditions agree roughly with all available models, the simplest of which predicts (partial differential)(lnk)/(partial differential)P approximately (partial differential)(lnK(T))/(partial differential)P, where K(T) is the bulk modulus. However, derivatives verified by multiple measurements are reproduced accurately only by the damped harmonic oscillator model. An improved database is needed to refine this model and to confidently extrapolate these difficult measurements to geophysically relevant conditions.

  17. Physical and chemical properties of the creeping fault ruptured in the 2008 Mw 7.9 Wenchuan earthquake from the WFSD-3P cores, eastern Tibet

    Science.gov (United States)

    He, X.; Li, H.; Wang, H.; Zhang, L., Jr.; Chevalier, M. L.

    2016-12-01

    The Anxian-Guanxian Fault (AGF) is a frontal fault of the Longmen Shan thrust belt, which ruptured during the 2008 Mw 7.9 Wenchuan earthquake in the eastern margin of the Tibetan Plateau. This study focuses on the 551.54 m-depth cores from the shallow hole of the Wenchuan earthquake Fault Scientific Drilling Project WFSD-3P which drilled across the AGF. Detailed core petrological study, geophysical downhole logs, rock magnetism and XRF analyses were conducted to explore the physical and chemical properties of the AGF, which is helpful to reveal the faulting mechanism and provides a reference to determine behaviors of other faults. The AGF zone in the WFSD-3p mainly consists of fault gouge and fault breccia from 442.41-510.14 m depth cores ( 48 m thick), with a dip angle of 45°. Fine-grained fault gouge and pressolution structures are commonly observed under optical microscope, which indicate the AGF is in creeping. The average magnetic susceptibility value of the fault gouge is slightly less than that of the country rock and the main magnetic carriers are pyrrhotite on the basis of low-temperature magnetic measurement. This phenomenon is different from the characteristics of other seismic faults with high magnetic susceptibility value due to heating by rapid slip friction. In terms of chemical properties, the fault gouge is characterized by relatively low concentration of iron, manganese and calcium, as well as high concentration of copper, vanadium and sulfur according to XRF analyses. In addition, the fluid samples are reductive, with a PH value of 10 and a negative value for redox potential. Combined with the grey-green sandstone along the rupture zone, they indicate that the AGF creeping is in a reducing environment. There are partly locked areas with clasts by rapid slip during the earthquake in the AGF zone. This observation was present at the boundary of the Triassic and Jurassic units ( 507 m depth), near the bottom of the fault zone. It represents the

  18. Comparative study of physicochemical and thermal properties of the ...

    African Journals Online (AJOL)

    Three indigenous cucurbit seeds from Ivory Coast namely Cucumeropsis mannii Naudin, Citrullus lanatus var. Citroides (Thrumb.) Matsum & Nakai and Cucumis melo var. Agrestis were investigated for the physicochemical properties. Thermal properties of their crude oils extracted by a cold solvent method were also tested.

  19. Structural, thermal and optical properties of Cu 2 doped methacrylic ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 40; Issue 5. Structural, thermal and optical properties ... UV–Vis absorption spectra in the wavelength region200–900 nm were used to evaluate the optical properties like direct band gap, indirect band gap and absorption edge. Theoptical band gap decreased with the ...

  20. Compilation of properties data for Li{sub 2}TiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Roux, N. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France)

    1998-03-01

    Properties data obtained at CEA for Li{sub 2}TiO{sub 3} are reported. The compilation includes : stability of Li{sub 2}TiO{sub 3} {beta} phase, specific heat, thermal diffusivity, thermal conductivity, linear thermal expansion, thermal creep, interaction with water and acid. (author)

  1. Phenylethynyl Silsesquioxanes: Monomer Synthesis, Characterization,Thermolysis and Thermal Properties

    Science.gov (United States)

    2016-12-14

    Increased weight Monitoring Repair Modify Oligomer Chemistry Reduce backbone polarity Reduction in thermal and mechanical properties Blend/IPN...PA Clearance Number 16586 Effects of Water Uptake on Viscoelastic Properties Dynamic TMA experiments performed at high heating rate (50 °C/min...it greatly reduces saturated moisture content  POSS improves wet thermomechanical properties and could prevent shock associated with water release

  2. In-situ Creep Testing Capability Development for Advanced Test Reactor

    Energy Technology Data Exchange (ETDEWEB)

    B. G. Kim; J. L. Rempe; D. L. Knudson; K. G. Condie; B. H. Sencer

    2010-08-01

    Creep is the slow, time-dependent strain that occurs in a material under a constant strees (or load) at high temperature. High temperature is a relative term, dependent on the materials being evaluated. A typical creep curve is shown in Figure 1-1. In a creep test, a constant load is applied to a tensile specimen maintained at a constant temperature. Strain is then measured over a period of time. The slope of the curve, identified in the figure below, is the strain rate of the test during Stage II or the creep rate of the material. Primary creep, Stage I, is a period of decreasing creep rate due to work hardening of the material. Primary creep is a period of primarily transient creep. During this period, deformation takes place and the resistance to creep increases until Stage II, Secondary creep. Stage II creep is a period with a roughly constant creep rate. Stage II is referred to as steady-state creep because a balance is achieved between the work hardening and annealing (thermal softening) processes. Tertiary creep, Stage III, occurs when there is a reduction in cross sectional area due to necking or effective reduction in area due to internal void formation; that is, the creep rate increases due to necking of the specimen and the associated increase in local stress.

  3. Thermal properties of alkali-activated aluminosilicates with CNT admixture

    Science.gov (United States)

    Zmeskal, Oldrich; Trhlikova, Lucie; Fiala, Lukas; Florian, Pavel; Cerny, Robert

    2017-07-01

    Material properties of electrically conductive cement-based materials with increased attention paid on electric and thermal properties were often studied in the last years. Both electric and thermal properties play an important role thanks to their possible utilization in various practical applications (e.g. snow-melting systems or building structures monitoring systems without the need of an external monitoring system). The DC/AC characteristics depend significantly on the electrical resistivity and the electrical capacity of bulk materials. With respect to the DC/AC characteristics of cement-based materials, such materials can be basically classified as electric insulators. In order to enhance them, various conductive admixtures such as those based on different forms of carbon, can be used. Typical representatives of carbon-based admixtures are carbon nanotubes (CNT), carbon fibers (CF), graphite powder (GP) and carbon black (CB). With an adequate amount of such admixtures, electric properties significantly change and new materials with higher added value can be prepared. However, other types of materials can be enhanced in the same way. Alkali-activated aluminosilicates (AAA) based on blast furnace slag are materials with high compressive strength comparable with cement-based materials. Moreover, the price of slag is lower than of Portland cement. Therefore, this paper deals with the study of thermal properties of this promising material with different concentrations of CNT. Within the paper a simple method of basic thermal parameters determination based on the thermal transient response to a heat power step is presented.

  4. Thermal and electrical properties of silicon nitride substrates

    Directory of Open Access Journals (Sweden)

    H. S. Dow

    2017-09-01

    Full Text Available This work presents the results of studies on the thermal and electrical properties of sintered silicon nitride to investigate the effects of non-oxide additives. With regard to electrical transport properties, a high electrical resistivity of 1014 ∼ 1015 Ωcm at 323 K was observed with Si3N4 substrates. Typical electrical resistivity and thermal conductivity values of the Si3N4 substrates were 1015 Ωcm and 90 W/mK at room temperature, respectively. Based on the results of XPS measurement, it is suggested that the addition of Nb significantly improved oxygen gettering by the phases of Nb2O5. Based on the analysis of the thermal conductivity of Si3N4 substrates, it appears that the interaction between oxygen and Nb in Si3N4, enhanced the thermal conduction rate of Si3N4.

  5. Structural, thermal and spectroscopic properties of supramolecular ...

    Indian Academy of Sciences (India)

    (H2O)4 have been reported.18 No general synthetic methodology for metal isonicotinate tetrahydrates has been reported so far. Detailed magnetic and spectroscopic properties of the compounds have not also been studied. Herein we report their high yield syntheses ... purpose of quantitative metal analysis by the gra-.

  6. Thermal, electrochemical and mechanical properties of shape ...

    African Journals Online (AJOL)

    ... resemblance with structure of casted shape memory alloy obtained from the vacuum induction process. The Vickers hardness test was also performed. Quenched microstructure with improved hardness than pre-quenched structure was observed. Keywords: Shape Memory Alloy, Microstructure, Mechanical Properties ...

  7. Synthesis, mechanical, thermal and chemical properties of ...

    Indian Academy of Sciences (India)

    Unknown

    Department of Chemistry, Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli 627 012, India. MS received 28 August 2003; ... thanes were characterized with respect to their resistance to chemical reagents and mechanical properties such as tensile strength, ..... Recent advances (ed.) I S. Bhardwajj (New ...

  8. Creep behavior of tantalum alloy T-222 at 1365 to 1700 K

    Science.gov (United States)

    Titran, R. H.

    1974-01-01

    High vacuum creep tests on the tantalum T-222 alloy at 0.42 to 0.52 T sub m show that the major portion of the creep curves, up to at least 1 percent strain, can be best described by an increasing creep rate, with strain varying linearly with time. Correlation and extrapolation of the creep curves on the basis of increasing creep rates results in more accurate engineering design data than would use of approximated linear rates. Based on increasing creep rates, the stress for 1 percent strain in 10,000 hours for T-222 is about four times greater than for the Ta-10W alloy. Increasing the grain size results in increased creep strength. Thermal aging prior to testing caused precipitation of the hexagonal close packed (Hf,Ta) sub 2 C, which initially increased creep strength. However, this dimetal carbide was converted during creep testing to face-centered cubic (Hf,Ta)C.

  9. Thermal Properties of Anionic Polyurethane Composition for Leather Finishing

    Directory of Open Access Journals (Sweden)

    Olga KOVTUNENKO

    2016-09-01

    Full Text Available Thermal properties of anionic polyurethane composition mixed with collagen product and hydrophilic sodium form of montmorillonite for use in the finishing of leather were studied by thermogravimetric method. The thermal indices of processes of thermal and thermo-oxidative destruction depending on the polyurethane composition were determined. The influence of anionic polyurethane composition on thermal behavior of chromium tanned gelatin films that imitate the leather were studied. APU composition with natural compounds increases their thermal stability both in air and in nitrogen atmosphere due to the formation of additional bonds between active groups of APU, protein and chrome tanning agent as the result of chemical reactions between organic and inorganic parts with the new structure formation.DOI: http://dx.doi.org/10.5755/j01.ms.22.3.10043

  10. Preparation, characterization, and thermal properties of microencapsulated phase change material for thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Alkan, Cemil; Sari, Ahmet; Karaipekli, Ali [Department of Chemistry, Gaziosmanpasa University, 60240 Tokat (Turkey); Uzun, Orhan [Department of Physics, Gaziosmanpasa University, 60240 Tokat (Turkey)

    2009-01-15

    This study is focused on the preparation, characterization, and determination of thermal properties of microencapsulated docosane with polymethylmethacrylate (PMMA) as phase change material for thermal energy storage. Microencapsulation of docosane has been carried out by emulsion polymerization. The microencapsulated phase change material (MEPCM) was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Thermal properties and thermal stability of MEPCM were measured by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). DSC analysis indicated that the docosane in the microcapsules melts at 41.0 C and crystallizes at 40.6 C. It has latent heats of 54.6 and -48.7 J/g for melting and crystallization, respectively. TGA showed that the MEPCM degraded in three distinguishable steps and had good chemical stability. Accelerated thermal cycling tests also indicated that the MEPCM had good thermal reliability. Based on all these results, it can be concluded that the microencapsulated docosane as MEPCMs have good potential for thermal energy storage purposes such as solar space heating applications. (author)

  11. Comparison of Thermal Properties Measured by Different Methods

    Energy Technology Data Exchange (ETDEWEB)

    Sundberg, Jan [Geo Innova AB, Linkoeping (Sweden); Kukkonen, Ilmo [Geological Survey of Finland, Helsinki (Finland); Haelldahl, Lars [Hot Disk AB, Uppsala (Sweden)

    2003-04-01

    A strategy for a thermal site descriptive model of bedrock is under development at SKB. In the model different kinds of uncertainties exist. Some of these uncertainties are related to the potential errors in the methods used for determining thermal properties of rock. In two earlier investigations thermal properties of rock samples were analysed according to the TPS method (transient plane source). Thermal conductivity and thermal diffusivity were determined using the TPS method. For a comparison, the same samples have been measured at the Geological Survey of Finland (GSF), using different laboratory methods. In this later investigation, the thermal conductivity was determined using the divided-bar method and the specific heat capacity using a calorimetric method. The mean differences between the results of different methods are relatively low but the results of individual samples show large variations. The thermal conductivity measured by the divided bar method gives for most samples slightly higher values, in average about 3%, than the TPS method. The specific heat capacity measured by the calorimetric method gives lower values, in average about 2%, than the TPS method. Consequently, the thermal diffusivity calculated from thermal conductivity and specific heat capacity gives higher values, in average about 6%, than the TPS method. Reasons for the differences are estimated mainly to be dependent on differences between the samples, errors in the temperature dependence of specific heat and in the transformation from volumetric to specific heat. The TPS measurements are performed using two pieces (sub-samples) of rock. Only one of these two sub-samples was measured using the divided bar method and the calorimetric method. Further, sample preparation involved changes in the size of some of the samples. The mean differences between the results of different methods are within the margins of error reported by the measuring laboratories. However, systematic errors in

  12. Thermal properties of a cylindrical YBa2Cu3O x superconductor in a levitation system: triggered by nonlinear dynamics

    Science.gov (United States)

    Huang, Yi; Zhang, Xingyi; Zhou, You-He

    2016-07-01

    The vibration of a permanent magnet (PM) levitated upon a high temperature superconductor (HTS) shows anomalous motion under external disturbance. In this paper we construct a cantilevered beam experimental setup composed of a bulk PM and a thermally insulated cylindrical YBa2Cu3O x superconductor. When the levitation system is disturbed by vertical excitation, the thermal character of the superconductor surface could be measured directly. Our experiments on a clean and large single-domain superconductor show that a giant temperature spike appears once the levitated PM experiences period doubling oscillation. We develop a numerical simulation for the analysis of the nonlinear vibration of the levitated PM coupled with the nonlinear electromagnetic force between the PM and HTS, taking into account heat diffusion. Using this procedure, we explore the electromagnetic and thermal properties at the thermally insulated HTS surface when the levitated PM shows a period doubling vibration. We find a remarkable difference between the experimental results and simulation. In order to interpret this temperature difference, we suggest a type of flux motion triggered by the electromagnetic force when it is far larger than the pinning force of the superconductor. The quantitative approach is based on the analysis process of the partial flux jump as a result of the flux creep. Finally, the calculated result is shown to be very close to the experimental result.

  13. Creep analysis of silicone for podiatry applications.

    Science.gov (United States)

    Janeiro-Arocas, Julia; Tarrío-Saavedra, Javier; López-Beceiro, Jorge; Naya, Salvador; López-Canosa, Adrián; Heredia-García, Nicolás; Artiaga, Ramón

    2016-10-01

    This work shows an effective methodology to characterize the creep-recovery behavior of silicones before their application in podiatry. The aim is to characterize, model and compare the creep-recovery properties of different types of silicone used in podiatry orthotics. Creep-recovery phenomena of silicones used in podiatry orthotics is characterized by dynamic mechanical analysis (DMA). Silicones provided by Herbitas are compared by observing their viscoelastic properties by Functional Data Analysis (FDA) and nonlinear regression. The relationship between strain and time is modeled by fixed and mixed effects nonlinear regression to compare easily and intuitively podiatry silicones. Functional ANOVA and Kohlrausch-Willians-Watts (KWW) model with fixed and mixed effects allows us to compare different silicones observing the values of fitting parameters and their physical meaning. The differences between silicones are related to the variations of breadth of creep-recovery time distribution and instantaneous deformation-permanent strain. Nevertheless, the mean creep-relaxation time is the same for all the studied silicones. Silicones used in palliative orthoses have higher instantaneous deformation-permanent strain and narrower creep-recovery distribution. The proposed methodology based on DMA, FDA and nonlinear regression is an useful tool to characterize and choose the proper silicone for each podiatry application according to their viscoelastic properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Optothermal Raman Studies of Thermal Properties of Graphene Based Films

    Science.gov (United States)

    Malekpour, Hoda

    Efficient thermal management is becoming a critical issue for development of the next generation of electronics. As the size of electronic devices shrinks, the dissipated power density increases, demanding a better heat removal. The discovery of graphene's unique electrical and thermal properties stimulated interest of electronic industry to development of graphene based technologies. In this dissertation, I report the results of my investigation of thermal properties of graphene derivatives and their applications in thermal management. The dissertation consists of three parts. In the first part, I investigated thermal conductivity of graphene laminate films deposited on thermally insulating polyethylene terephthalate substrates. Graphene laminate is made of chemically derived graphene and few layer graphene flakes packed in overlapping structure. Two types of graphene laminate were studied: as deposited and compressed. The thermal conductivity of the laminate was found to be in the range from 40 W/mK to 90 W/mK at room temperature. It was established that the average size and the alignment of graphene flakes are parameters dominating the heat conduction. In the second part of this dissertation, I investigated thermal conductivity of chemically reduced freestanding graphene oxide films. It was found that the in-plane thermal conductivity of graphene oxide can be increased significantly using chemical reduction and temperature treatment. Finally, I studied the effect of defects on thermal conductivity of suspended graphene. The knowledge of the thermal conductivity dependence on the concentration of defects can shed light on the strength of the phonon - point defect scattering in two-dimensional materials. The defects were introduced to graphene in a controllable way using the low-energy electron beam irradiation. It was determined that as the defect density increases the thermal conductivity decreases down to about 400 W/mK, and then reveal saturation type behavior

  15. Creep in metals

    OpenAIRE

    Saarinen, Juho

    2013-01-01

    Creep is time dependent plastic malformation of solids, that happen in static stress and temperature when threshold values are met. Creep occurs at high temperature, meaning temperature more than 30% of material's absolute melting temperature (this limit is a little lower with plastics, and higher in ceramics). The malformations it causes can lead to rupture, which usually happen in a short time compared to the duration of the whole process. The creep effect itself is known from already t...

  16. POLYMER CONCRETE CREEP

    OpenAIRE

    Yu. М. Borisov; I. S. Surovtsev; Yu. B. Potapov

    2012-01-01

    Problem statement. It is well known that creep is the tendency of a solid material to move slowly or deform permanently under the influence of stresses. The aim of the paper is to study the process of creep in polymer concretes. Results and conclusions. It is shown that creep in polymer concrete occurs according to the same pattern as in many other polymer composites with the elastic core. Equations which indirectly es-tablish the relation between complete deformations of polymer concrete, in...

  17. Study of Thermal Properties of Cast Metal- Ceramic Composite Foams

    Directory of Open Access Journals (Sweden)

    Gawdzińska K.

    2017-12-01

    Full Text Available Owing to its properties, metallic foams can be used as insulation material. Thermal properties of cast metal-ceramic composite foams have applications in transport vehicles and can act as fire resistant and acoustic insulators of bulkheads. This paper presents basic thermal properties of cast and foamed aluminum, the values of thermal conductivity coefficient of selected gases used in foaming composites and thermal capabilities of composite foams (AlSi11/SiC. A certificate of non-combustibility test of cast aluminum-ceramic foam for marine applications was included inside the paper. The composite foam was prepared by the gas injection method, consisting in direct injection of gas into liquid metal. Foams with closed and open cells were examined. The foams were foaming with foaming gas consisting of nitrogen or air. This work is one of elements of researches connected with description of properties of composite foams. In author's other works acoustic properties of these materials will be presented.

  18. Investigation on Thermal Properties of Composite of Rice Husk, Corncob and Baggasse for Building Thermal Insulation

    OpenAIRE

    Kyauta E.E. Dauda D.M; Justin E

    2014-01-01

    The thermal properties of some Agricultural waste ( Rice Husk, Bagasse and Corncob) was investigated with the purpose of determining their use as insulators. Using varied composite percentages of each sample wastes at increasing and decreasing quantities to determine best mixtures has assisted in accurate recommendation. The work has explored the potentials for using composite samples of Rice Husk, Bagasse and Corncob as materials for thermal insulation, a solution which offers a reduction...

  19. Thermal Properties for the Thermal-Hydraulics Analyses of the BR2 Maximum Nominal Heat Flux

    Energy Technology Data Exchange (ETDEWEB)

    Dionne, B. [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Bergeron, A. [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Licht, J. R. [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Kim, Y. S. [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Hofman, G. L. [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division

    2015-02-01

    This memo describes the assumptions and references used in determining the thermal properties for the various materials used in the BR2 HEU (93% enriched in 235U) to LEU (19.75% enriched in 235U) conversion feasibility analysis. More specifically, this memo focuses on the materials contained within the pressure vessel (PV), i.e., the materials that are most relevant to the study of impact of the change of fuel from HEU to LEU. Section 2 provides a summary of the thermal properties in the form of tables while the following sections and appendices present the justification of these values. Section 3 presents a brief background on the approach used to evaluate the thermal properties of the dispersion fuel meat and specific heat capacity. Sections 4 to 7 discuss the material properties for the following materials: i) aluminum, ii) dispersion fuel meat (UAlx-Al and U-7Mo-Al), iii) beryllium, and iv) stainless steel. Section 8 discusses the impact of irradiation on material properties. Section 9 summarizes the material properties for typical operating temperatures. Appendix A elaborates on how to calculate dispersed phase’s volume fraction. Appendix B provides a revised methodology for determining the thermal conductivity as a function of burnup for HEU and LEU.

  20. Thermal properties of soils: effect of biochar application

    Science.gov (United States)

    Usowicz, Boguslaw; Lukowski, Mateusz; Lipiec, Jerzy

    2014-05-01

    Thermal properties (thermal conductivity, heat capacity and thermal diffusivity) have a significant effect on the soil surface energy partitioning and resulting in the temperature distribution. Thermal properties of soil depend on water content, bulk density and organic matter content. An important source of organic matter is biochar. Biochar as a material is defined as: "charcoal for application as a soil conditioner". Biochar is generally associated with co-produced end products of pyrolysis. Many different materials are used as biomass feedstock for biochar, including wood, crop residues and manures. Additional predictions were done for terra preta soil (also known as "Amazonian dark earth"), high in charcoal content, due to adding a mixture of charcoal, bone, and manure for thousands of years i.e. approximately 10-1,000 times longer than residence times of most soil organic matter. The effect of biochar obtained from the wood biomass and other organic amendments (peat, compost) on soil thermal properties is presented in this paper. The results were compared with wetland soils of different organic matter content. The measurements of the thermal properties at various water contents were performed after incubation, under laboratory conditions using KD2Pro, Decagon Devices. The measured data were compared with predictions made using Usowicz statistical-physical model (Usowicz et al., 2006) for biochar, mineral soil and soil with addition of biochar at various water contents and bulk densities. The model operates statistically by probability of occurrence of contacts between particular fractional compounds. It combines physical properties, specific to particular compounds, into one apparent conductance specific to the mixture. The results revealed that addition of the biochar and other organic amendments into the soil caused considerable reduction of the thermal conductivity and diffusivity. The mineral soil showed the highest thermal conductivity and diffusivity

  1. Effect of precipitates on long-term creep deformation properties of P92 and P122 type advanced ferritic steels for USC power plants

    Energy Technology Data Exchange (ETDEWEB)

    Yoshizawa, M., E-mail: yoshizaw-mtr@sumitomometals.co.jp [Corporate Research and Development Laboratories, Sumitomo Metal Industries, Ltd., 1-8 Fuso-cho, Amagasaki, Hyogo 660-0891 (Japan); Igarashi, M.; Moriguchi, K. [Corporate Research and Development Laboratories, Sumitomo Metal Industries, Ltd., 1-8 Fuso-cho, Amagasaki, Hyogo 660-0891 (Japan); Iseda, A. [Tubular Products Technology Department, Sumitomo Metal Industries, Ltd., 1-8-11 Harumi, Chuo-ku, Tokyo 104-6111 (Japan); Armaki, Hassan Ghassemi; Maruyama, K. [Graduate School of Environmental Studies, Tohoku University, 6-6-02 Aobayama, Sendai 980-8579 (Japan)

    2009-06-15

    Long-term creep rupture strengths and the microstructural stability of ASME P92 and P122 pipes have been studied using creep testing at the temperatures from 550 to 700 deg. C and detailed scanning transmission electron microscopy. Creep rupture strength of P92 is found to be more stable than that of P122 at temperatures over 600 deg. C, which is mainly due to the difference in their Cr content. P122 type model steel with reduced Cr content, 9%Cr, has been prepared to explore the effect of Cr on the stability of MX and formation of Z-phase during creep deformation. MX in 9%Cr steel is found to be stable even after prolonged exposure at 650 deg. C, while Cr and Fe concentration to MX without marked coarsening has been observed in 10.5%Cr steel after aging for 10,000 h at 650 deg. C. This seems to lead to the transition of MX carbonitride into the Z-phase after aging for 23,000 h, which requires ordering in a M{sub 2}N lattice to achieve a tetragonal Z-phase to be stable. Creep deformation behavior in the transient creep region of the steels is almost same up to about 7000 h, while in the acceleration creep region the creep rate of 10.5%Cr steel becomes much faster than that of 9%Cr steel, resulting in shorter rupture life. It is obvious that the creep rupture strength degradation starts prior to the formation of Z-phase in 10.5%Cr steel. It is thus concluded that Z-phase is not a necessary factor for degradation of creep rupture strength but the instability of the fine precipitates such as Cr{sub 2}(C, N) caused by the compositions change like Cr supply to MX carbonitride is more essential.

  2. Thermal properties. Site descriptive modelling Forsmark - stage 2.2

    Energy Technology Data Exchange (ETDEWEB)

    Back, Paer-Erik; Wrafter, John; Sundberg, Jan [Geo Innova AB (Sweden); Rosen, L ars [Sweco Viak AB (Sweden)

    2007-09-15

    The lithological data acquired from boreholes and mapping of the rock surface need to be reclassified into thermal rock classes, TRCs. The main reason is to simplify the simulations. The lithological data are used to construct models of the transition between different TRCs, thus describing the spatial statistical structure of each TRC. The result is a set of transition probability models that are used in the simulation of TRCs. The intermediate result of this first stochastic simulation is a number of realisations of the geology, each one equally probable. Based on the thermal data, a spatial statistical thermal model is constructed for each TRC. It consists of a statistical distribution and a variogram for each TRC. These are used in the stochastic simulation of thermal conductivity and the result is a number of equally probable realisations of thermal conductivity for the domain. In the next step, the realisations of TRCs (lithology) and thermal conductivity are merged, i.e. each realisation of geology is filled with simulated thermal conductivity values. The result is a set of realisations of thermal conductivity that considers both the difference in thermal properties between different TRCs, and the variability within each TRC. If the result is desired in a scale different from the simulation scale, i.e. the canister scale, upscaling of the realisations can be performed. The result is a set of equally probable realisations of thermal properties. The presented methodology was applied to rock domain RFM029 and RFM045. The main results are sets of realisations of thermal properties that can be used for further processing, most importantly for statistical analysis and numerical temperature simulations for the design of repository layout (distances between deposition holes). The main conclusions of the thermal modelling are: The choice of scale has a profound influence on the distribution of thermal conductivity values. The variance decreases and the lower tail

  3. Cellular and Porous Materials Thermal Properties Simulation and Prediction

    CERN Document Server

    Öchsner, Andreas; de Lemos, Marcelo J S

    2008-01-01

    Providing the reader with a solid understanding of the fundamentals as well as an awareness of recent advances in properties and applications of cellular and porous materials, this handbook and ready reference covers all important analytical and numerical methods for characterizing and predicting thermal properties. In so doing it directly addresses the special characteristics of foam-like and hole-riddled materials, combining theoretical and experimental aspects for characterization purposes.

  4. Rare Earth Borohydrides—Crystal Structures and Thermal Properties

    Directory of Open Access Journals (Sweden)

    Christoph Frommen

    2017-12-01

    Full Text Available Rare earth (RE borohydrides have received considerable attention during the past ten years as possible hydrogen storage materials due to their relatively high gravimetric hydrogen density. This review illustrates the rich chemistry, structural diversity and thermal properties of borohydrides containing RE elements. In addition, it highlights the decomposition and rehydrogenation properties of composites containing RE-borohydrides, light-weight metal borohydrides such as LiBH4 and additives such as LiH.

  5. Temperature-dependent thermal properties of ex vivo liver undergoing thermal ablation.

    Science.gov (United States)

    Guntur, Sitaramanjaneya Reddy; Lee, Kang Il; Paeng, Dong-Guk; Coleman, Andrew John; Choi, Min Joo

    2013-10-01

    Thermotherapy uses a heat source that raises temperatures in the target tissue, and the temperature rise depends on the thermal properties of the tissue. Little is known about the temperature-dependent thermal properties of tissue, which prevents us from accurately predicting the temperature distribution of the target tissue undergoing thermotherapy. The present study reports the key thermal parameters (specific heat capacity, thermal conductivity and heat diffusivity) measured in ex vivo porcine liver while being heated from 20 ° C to 90 ° C and then naturally cooled down to 20 ° C. The study indicates that as the tissue was heated, all the thermal parameters resulted in plots with asymmetric quasi-parabolic curves with temperature, being convex downward with their minima at the turning temperature of 35-40 ° C. The largest change was observed for thermal conductivity, which decreased by 9.6% from its initial value (at 20 ° C) at the turning temperature (35 ° C) and rose by 45% at 90 ° C from its minimum (at 35 ° C). The minima were 3.567 mJ/(m(3) ∙ K) for specific heat capacity, 0.520 W/(m.K) for thermal conductivity and 0.141 mm(2)/s for thermal diffusivity. The minimum at the turning temperature was unique, and it is suggested that it be taken as a characteristic value of the thermal parameter of the tissue. On the other hand, the thermal parameters were insensitive to temperature and remained almost unchanged when the tissue cooled down, indicating that their variations with temperature were irreversible. The rate of the irreversible rise at 35 ° C was 18% in specific heat capacity, 40% in thermal conductivity and 38.3% in thermal diffusivity. The study indicates that the key thermal parameters of ex vivo porcine liver vary largely with temperature when heated, as described by asymmetric quasi-parabolic curves of the thermal parameters with temperature, and therefore, substantial influence on the temperature distribution of the tissue undergoing

  6. Comparison of creep of the cement pastes included fly ash

    Directory of Open Access Journals (Sweden)

    Padevět Pavel

    2017-01-01

    Full Text Available The paper is devoted to comparison of creep of cement pastes containing fly ash admixture. The size of creep in time depends on the amount of components of the cement paste. Attention is paid to the content of classical fly ash in cement paste and its impact on the size of creep. The moisture of cement pastes is distinguished because it significantly affects the rheological properties of the material.

  7. Thermal properties of solids at room and cryogenic temperatures

    CERN Document Server

    Ventura, Guglielmo

    2014-01-01

    This book is a guide for materials scientists, physicists, chemists and engineers who wish to explore the field of low-temperature material properties. The focus is on heat capacity, thermal expansion and electrical and thermal conductivity. The authors report a wide range of experimental details and data, and have compiled useful tables of low-temperature data. Each chapter of the book starts by addressing the theoretical basis of the phenomena. This is a concise presentation, but it helps the reader to develop a deeper understanding of the experiments. The second part of the chapters is dedicated to describing the main experimental techniques to measure thermal properties at low and very low temperature ranges. The final part of each chapter provides a wealth of relevant experimental data in the form of tables and graphs.

  8. Investigation of thermo-physical properties of thermal insulation coating

    Science.gov (United States)

    Kopčok, Michal; Lukovičová, Jozefa; Kačur, Jozef; Pavlendová, Gabriela

    2017-07-01

    This paper examines the thermal properties of thermal insulation coating applied to the building materials surfaces. The main objective is to determine the insulation coating impact on the heat flux transfer. The heat flux is modelled in terms of the heat transfer coefficient on the surface of a solid body. The thermal conductivity and heat transfer coefficient are obtained from the solution of the inverse heat conduction problem in 3D, based on the temperature measurements. The real temperature evolution is perturbed due to intrinsic properties of the measuring apparatus. We correct this situation via modelling a thermocouple function. Afterwards the determination procedure of the heat flux transfer parameters is a standard solution of the inverse problem based on the minimization of discrepancy between corrected measured data and computed temperature data.

  9. Structural Properties of Dwelling and Thermal Comfort in Tropical ...

    African Journals Online (AJOL)

    The structural properties of dwelling units, in particular “window types” in 1, 250 apartments and their indoor temperature levels were collected. One hypothesis was formulated: (HO) There is no significant variation in effective temperature index and thus thermal comfort between dwellings built with wooden windows and ...

  10. Phonon and thermal properties of achiral single wall carbon ...

    Indian Academy of Sciences (India)

    A detailed theoretical study of the phonon and thermal properties of achiral single wall carbon nanotubes has been carried out using force constant model considering up to third nearest-neighbor interactions. We have calculated the phonon dispersions, density of states, radial breathing modes (RBM) and the specific heats ...

  11. Chemical and thermal properties of VIP latrine sludge

    African Journals Online (AJOL)

    2015-07-04

    Jul 4, 2015 ... thermal conductivity; calorific value and heat capacity. These properties will facilitate the design of faecal sludge emptying and treatment equipment. A manual sorting of the pit contents was carried out to determine the categories and amounts of household waste present. There was a significant difference ...

  12. Chemical and thermal properties of VIP latrine sludge | Zuma | Water ...

    African Journals Online (AJOL)

    The samples were analysed for: moisture content; volatile solids; chemical oxygen demand; ammonia; total Kjeldahl nitrogen; pH; orthophosphate; thermal conductivity; calorific value and heat capacity. These properties will facilitate the design of faecal sludge emptying and treatment equipment. A manual sorting of the pit ...

  13. Crystal growth and comparison of vibrational and thermal properties ...

    Indian Academy of Sciences (India)

    86, No. 3. — journal of. March 2016 physics pp. 719–722. Comments on: “Crystal growth and comparison of vibrational and thermal properties of semi-organic nonlinear optical materials” ... and urea ligands, the title paper by Gunasekaran et al [1] reporting on the growth of the so-called urea thiourea mercuric chloride ...

  14. Ferritic Alloys with Extreme Creep Resistance via Coherent Hierarchical Precipitates

    National Research Council Canada - National Science Library

    Song, Gian; Sun, Zhiqian; Li, Lin; Xu, Xiandong; Rawlings, Michael; Liebscher, Christian H; Clausen, Bjørn; Poplawsky, Jonathan; Leonard, Donovan N; Huang, Shenyan; Teng, Zhenke; Liu, Chain T; Asta, Mark D; Gao, Yanfei; Dunand, David C; Ghosh, Gautam; Chen, Mingwei; Fine, Morris E; Liaw, Peter K

    2015-01-01

    There have been numerous efforts to develop creep-resistant materials strengthened by incoherent particles at high temperatures and stresses in response to future energy needs for steam turbines in thermal-power plants...

  15. Foldable dome climate measurements and thermal properties

    Science.gov (United States)

    Sliepen, Guus; Jägers, Aswin P. L.; Hammerschlag, Robert H.; Bettonvil, Felix C. M.

    2010-07-01

    As part of a larger project for measuring various aspects of foldable domes in the context of EST and with support of the Dutch Technology Foundation STW, we have collected over a year of continuous temperature and humidity measurements, both inside and outside the domes of the Dutch Open Telescope (DOT) on La Palma5 and the GREGOR telescope on Tenerife.6 In addition, we have measured the wind field around each dome. Although the structure of both domes is similar, the DOT dome has a single layer of cloth, and is situated on top of an open tower. In contrast, the GREGOR dome has a double layer of cloth, and is situated on top of a tower-shaped building. These differences result in large differences in temperature and humidity insulation when the dome is closed. We will present the changes in temperature and humidity one can expect for each dome within one day, and the statistics for the variations throughout a year. In addition, we will show that the main advantage of a foldable dome is the near instantaneous equilibration of the air inside the volume originally enclosed by the dome and that of the environment outside the dome. This property allows one to operate a telescope without needing expensive air conditioning and dome skin temperature control in order to limit dome and shell seeing effects. The measurements give also information about the weather fluctuations at the sites of the domes. It was observed that on small time scales the temperature fluctuations are significantly greater during the day than during the night.

  16. Tailoring Thermal Radiative Properties with Doped-Silicon Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhuomin [Georgia Inst. of Technology, Atlanta, GA (United States)

    2017-08-28

    Aligned doped-silicon nanowire (D-SiNW) arrays form a hyperbolic metamaterial in the mid-infrared and have unique thermal radiative properties, such as broadband omnidirectional absorption, low-loss negative refraction, etc. A combined theoretical and experimental investigation will be performed to characterize D-SiNW arrays and other metamaterials for tailoring thermal radiative properties. Near-field thermal radiation between anisotropic materials with hyperbolic dispersions will also be predicted for potential application in energy harvesting. A new kind of anisotropic metamaterial with a hyperbolic dispersion in a broad infrared region has been proposed and demonstrated based on aligned doped-silicon nanowire (D-SiNW) arrays. D-SiNW-based metamaterials have unique thermal radiative properties, such as broadband omnidirectional absorption whose width and location can be tuned by varying the filling ratio and/or doping level. Furthermore, high figure of merit (FOM) can be achieved in a wide spectral region, suggesting that D-SiNW arrays may be used as a negative refraction material with much less loss than other structured materials, such as layered semiconductor materials. We have also shown that D-SiNWs and other nanostructures can significantly enhance near-field thermal radiation. The study of near-field radiative heat transfer between closely spaced objects and the electromagnetic wave interactions with micro/nanostructured materials has become an emerging multidisciplinary field due to its importance in advanced energy systems, manufacturing, local thermal management, and high spatial resolution thermal sensing and mapping. We have performed extensive study on the energy streamlines involving anisotropic metamaterials and the applicability of the effective medium theory for near-field thermal radiation. Graphene as a 2D material has attracted great attention in nanoelectronics, plasmonics, and energy harvesting. We have shown that graphene can be used to

  17. Thermal and Electrical Properties of Electrides

    Science.gov (United States)

    Moeggenborg, Kevin James

    1990-01-01

    A method to determine the stability and decomposition kinetics of electrides was developed. The method uses DSC and was applied to two electrides. A sample of Li ^+(PMPCY)e^- underwent a first-order decomposition reaction with a half life of 110 hrs at 23^circC while a sample of K^+(C222)e ^- decomposed autocatalytically in under 2 days at -57^circ C. The results point to two different mechanisms of decomposition in electrides. The electrical properties of several electrides were investigated through Impedance Spectroscopy and a.c. and d.c. conductivity methods. D.C. conductivity studies of K^+(C222)e^- indicated a low band gap but high apparent resistivity and marked non-Ohmic behavior for the compound. The high resistivity and non-Ohmic behavior were found to be due to a Schottky barrier at the sample-electrode interface. Four probe a.c. conductivity experiments on a cylindrical sample pellet revealed a band gap of 0.086 eV for the compound and placed an upper limit of 0.189 Omega cm at 130 K on its resistivity. The band gap of the compound may be due to the activated transfer of electrons across grain boundaries in the polycrystalline samples. The electrides Cs^+(15C5) _2e^- and Cs^+(18C6)_2e ^- were shown to exhibit the first ionic conductivity ever seen in electrides. Cs ^+(15C5)_2e ^- undergoes a transition from defect electronic conductivity to ionic conductivity, the latter having an activation energy of 0.7 eV. Cs^+(18C6) _2e^- also exhibited ionic conduction with an activation energy of 1.0 eV. Both compounds exhibited electrochemical cell behavior when placed between one cesium and one stainless steel electrode. The mechanism of the ionic conductivity may involve the release of the cesium cation from its crown ether cage and its reduction by an electron anion of the compound followed by Cs^+ transfer between anionic sites in the crystal lattice. The semiconductor behavior previously seen in Cs^+(18C6) _2e^- was shown to be due to the doping of the

  18. Creep in buffer clay

    Energy Technology Data Exchange (ETDEWEB)

    Pusch, R. [Geodevelopment AB, Lund (Sweden); Adey, R. [Computational Mechanics BEASY, Southampton (United Kingdom)

    1999-12-01

    The study involved characterization of the microstructural arrangement and molecular forcefields in the buffer clay for getting a basis for selecting suitable creep models. It is concluded that the number of particles and wide range of the particle bond spectrum require that stochastical mechanics and thermodynamics will be considered and they are basic to the creep model proposed for predicting creep settlement of the canisters. The influence of the stress level on creep strain of MX-80 clay is not well known but for the buffer creep is approximately proportional to stress. Theoretical considerations suggest a moderate impact for temperatures up to 90 deg C and this is supported by model experiments. It is believed that the assumption of strain being proportional to temperature is conservative. The general performance of the stochastic model can be illustrated in principle by use of visco-elastic rheological models implying a time-related increase in viscosity. The shear-induced creep settlement under constant volume conditions calculated by using the proposed creep model is on the order of 1 mm in ten thousand years and up to a couple of millimeters in one million years. It is much smaller than the consolidation settlement, which is believed to be on the order of 10 mm. The general conclusion is that creep settlement of the canisters is very small and of no significance to the integrity of the buffer itself or of the canisters.

  19. Thermal Properties and Phonon Spectral Characterization of Synthetic Boron Phosphide for High Thermal Conductivity Applications.

    Science.gov (United States)

    Kang, Joon Sang; Wu, Huan; Hu, Yongjie

    2017-12-13

    Heat dissipation is an increasingly critical technological challenge in modern electronics and photonics as devices continue to shrink to the nanoscale. To address this challenge, high thermal conductivity materials that can efficiently dissipate heat from hot spots and improve device performance are urgently needed. Boron phosphide is a unique high thermal conductivity and refractory material with exceptional chemical inertness, hardness, and high thermal stability, which holds high promises for many practical applications. So far, however, challenges with boron phosphide synthesis and characterization have hampered the understanding of its fundamental properties and potential applications. Here, we describe a systematic thermal transport study based on a synergistic synthesis-experimental-modeling approach: we have chemically synthesized high-quality boron phosphide single crystals and measured their thermal conductivity as a record-high 460 W/mK at room temperature. Through nanoscale ballistic transport, we have, for the first time, mapped the phonon spectra of boron phosphide and experimentally measured its phonon mean free-path spectra with consideration of both natural and isotope-pure abundances. We have also measured the temperature- and size-dependent thermal conductivity and performed corresponding calculations by solving the three-dimensional and spectral-dependent phonon Boltzmann transport equation using the variance-reduced Monte Carlo method. The experimental results are in good agreement with that predicted by multiscale simulations and density functional theory, which together quantify the heat conduction through the phonon mode dependent scattering process. Our finding underscores the promise of boron phosphide as a high thermal conductivity material for a wide range of applications, including thermal management and energy regulation, and provides a detailed, microscopic-level understanding of the phonon spectra and thermal transport mechanisms of

  20. Mechanical and thermal properties of the Czech marbles

    Science.gov (United States)

    Čáchová, Monika; Koňáková, Dana; Vejmelková, Eva; Keppert, Martin; Černý, Robert

    2016-06-01

    The paper is dealing with selected parameters of four marbles with respect to their utilization as building materials. Stones from four function quarries in the Czech Republic were chosen and scopes of physical properties were determined. Basic physical, mechanical and thermal properties belong among studied characteristics. Bulk density of studied marbles is in average 2750 kg/m3, matrix density 2770 kg/m3, open porosity 0.7%. Pore structure show similar distributions. Mechanical properties show more differences; however minimal value of compressive strength was 66.5 MPa, while maximum was 174 MPa. Thermal conductivity of studied marbles was about 2.955 W/mK. Last measured characteristic was specific heat capacity; its average value was 609 J/kgK.

  1. Thermal properties of carbon black aqueous nanofluids for solar absorption

    Directory of Open Access Journals (Sweden)

    Han Dongxiao

    2011-01-01

    Full Text Available Abstract In this article, carbon black nanofluids were prepared by dispersing the pretreated carbon black powder into distilled water. The size and morphology of the nanoparticles were explored. The photothermal properties, optical properties, rheological behaviors, and thermal conductivities of the nanofluids were also investigated. The results showed that the nanofluids of high-volume fraction had better photothermal properties. Both carbon black powder and nanofluids had good absorption in the whole wavelength ranging from 200 to 2,500 nm. The nanofluids exhibited a shear thinning behavior. The shear viscosity increased with the increasing volume fraction and decreased with the increasing temperature at the same shear rate. The thermal conductivity of carbon black nanofluids increased with the increase of volume fraction and temperature. Carbon black nanofluids had good absorption ability of solar energy and can effectively enhance the solar absorption efficiency.

  2. Improved creep resistance and thermal behavior of Ni-doped Sn–3.0Ag–0.5Cu lead-free solder

    Energy Technology Data Exchange (ETDEWEB)

    El-Daly, A.A., E-mail: dreldaly11@yahoo.com [Physics Department, Faculty of Science, Zagazig Univ., Zagazig (Egypt); El-Taher, A.M. [Physics Department, Faculty of Science, Zagazig Univ., Zagazig (Egypt); Dalloul, T.R. [Physics Department, Faculty of Science, Islamic Univ. of Gaza, Gaza, Palestine (Country Unknown)

    2014-02-25

    Highlights: • Small amounts of Ni (x = 0–1.0) have been added into SAC(305) solder. • Ni additions enhanced the formation of new (Cu, Ni){sub 6}Sn{sub 5} IMCs. • Ni can effectively reduce the undercooling and solidus melting temperature. • The SAC(305)–0.5%Ni solder reveals the maximum creep resistance and total fracture time. • Correlations between the microstructure and creep parameters were analyzed. -- Abstract: To develop lead-free solders for advance electrical components, a series of Sn–3.0Ag–0.5Cu (SAC 305) solders containing small amounts of Ni have been investigated. Results showed that the addition of Ni not only decreased the amount of undercooling by about 7.9–8.5 °C, but also reduced the solidus temperature of SAC(305) solder from 219.9 to 216.2 °C. Microstructure analysis revealed that Ni could replace the Cu atoms in the Cu{sub 6}Sn{sub 5} phase and generates a new η-(Cu, Ni){sub 6}Sn{sub 5} IMC phase containing large amount of Ni after 0.5%Ni addition. The high solubility of Ni in Cu{sub 6}Sn{sub 5} increased the substitutional defects and generated inter-atomic stress around Ni atoms, which in turn impeded the dislocation movements in different crystal directions, resulting in an increase in the creep resistance and total fracture time of 0.5%Ni-doped SAC(305) solder. In addition, the formation of fine fiber-like Ag{sub 3}Sn and finer dot-shaped precipitates at the surface of β-Sn matrix could provide more obstacles for dislocation pile up in the adjacent grains and enhanced the creep resistance. However, when the concentration of Ni exceeded 0.5 wt%, the benefits of creep behavior and fracture time were reduced due to the formation of small amount of abrasive Ag{sub 3}Sn and coarsening of (Cu, Ni){sub 6}Sn{sub 5} IMCs in the eutectic colony.

  3. Thermal properties of flax fiber scoured by different methods

    Directory of Open Access Journals (Sweden)

    Zheng Dong

    2015-01-01

    Full Text Available Thermal properties of flax roves untreated and treated were characterized by differential scanning calorimetry (DSC and thermal gravity analyzer (TGA in order to understand their thermal behavior in more detail and to evaluate the effect of scouring processing on the thermal behavior. Flax roves were treated with six kinds of methods including biological scouring, one bath, two bath, bleaching, alkali scouring and industry chemical scouring as standards. Results showed that all treatments improved thermal stability of flax roves. The results indicated that glass transition temperature (Tg decreased after scouring besides the sample by directly bleaching. It is more difficult to determine the endothermic peak of flax treated by chemical scouring in industry because it takes a very flat course. A distinct endothermic peak was observed for the untreated flax rove, while a distinct exothermic peak in different temperature interval was revealed for other four treated flax rove samples. For TGA analysis, thermal degradation of flax roves studied consists of three regions of the initial, main, and char decomposition, and the third stage consists of secondary weight loss and carbonization for flax roves with biological scouring, one-bath and two-bath. Besides, different residue left indicates that the bio-scoured flax roves are lost with volatile products and does not contribute to char formation. These results provide valuable preferences for mechanism and top value added application of bio-scouring in flax roves.

  4. High Temperature Thermal Properties of Bentonite Foundry Sand

    Directory of Open Access Journals (Sweden)

    Krajewski P.K.

    2015-06-01

    Full Text Available The paper presents results of measuring thermal conductivity and heat capacity of bentonite foundry sand in temperature range ambient - 900­­°C. During the experiments a technical purity Cu plate was cast into the green-sand moulds. Basing on measurements of the mould temperature field during the solidification of the casting, the temperature relationships of the measured properties were evaluated. It was confirmed that water vaporization strongly influences thermal conductivity of the moulding sand in the first period of the mould heating by the poured casting.

  5. Measurement of thermal properties of soil and concrete samples

    DEFF Research Database (Denmark)

    Pagola, Maria Alberdi; Jensen, Rasmus Lund; Madsen, Søren

    Centrum Pæle A/S, Aalborg University, VIA University College and INSERO Horsens are partners in an industrial PhD project within the field of shallow geothermal energy systems based on pile heat exchangers. Pile heat exchangers, also known as energy piles, are thermally active building foundation...... elements with embedded geothermal pipes fixed to the steel reinforcement in which a circulating fluid exchanges heat with the pile and the surrounding soil. As such, the foundation of the building both serves as a structural component and a heating/cooling supply element. The thermal properties of the pile...

  6. Creep strength and ductility of 9 to 12% chromium steels

    DEFF Research Database (Denmark)

    Hald, John

    2004-01-01

    The present paper focuses in on long-term creep properties of parent material of the new 9-12%Cr creep resistant steels, P91, E911 and P92 developed for use in advanced ultrasupercritical power plants. These steels have been at the center of activities in the ECCC Working Group 3A (WG3A) "Ferritic...... Steels", which covers creep data development and analysis for parent materials and welds of all ferritic creep resistant steels ranging from low alloy steels up to 12%Cr steels. The opinions stated in the paper represent the views of the author rather than the whole ECCC WG3A group....

  7. Thermal and Thermoelectric Properties of Nanostructured Materials and Interfaces

    Science.gov (United States)

    Liao, Hao-Hsiang

    Many modern technologies are enabled by the use of thin films and/or nanostructured composite materials. For example, many thermoelectric devices, solar cells, power electronics, thermal barrier coatings, and hard disk drives contain nanostructured materials where the thermal conductivity of the material is a critical parameter for the device performance. At the nanoscale, the mean free path and wavelength of heat carriers may become comparable to or smaller than the size of a nanostructured material and/or device. For nanostructured materials made from semiconductors and insulators, the additional phonon scattering mechanisms associated with the high density of interfaces and boundaries introduces additional resistances that can significantly change the thermal conductivity of the material as compared to a macroscale counterpart. Thus, better understanding and control of nanoscale heat conduction in solids is important scientifically and for the engineering applications mentioned above. In this dissertation, I discuss my work in two areas dealing with nanoscale thermal transport: (1) I describe my development and advancement of important thermal characterization tools for measurements of thermal and thermoelectric properties of a variety of materials from thin films to nanostructured bulk systems, and (2) I discuss my measurements on several materials systems done with these characterization tools. First, I describe the development, assembly, and modification of a time-domain thermoreflectance (TDTR) system that we use to measure the thermal conductivity and the interface thermal conductance of a variety of samples including nanocrystalline alloys of Ni-Fe and Co-P, bulk metallic glasses, and other thin films. Next, a unique thermoelectric measurement system was designed and assembled for measurements of electrical resistivity and thermopower of thermoelectric materials in the temperature range of 20 to 350 °C. Finally, a commercial Anter Flashline 3000 thermal

  8. Nano-indentation creep properties of the S2 cell wall lamina and compound corner middle lamella [abstract

    Science.gov (United States)

    Joseph E. Jakes; Charles R. Frihart; James F. Beecher; Donald S. Stone

    2010-01-01

    Bulk wood properties are derived from an ensemble of processes taking place at the micron-scale, and at this level the properties differ dramatically in going from cell wall layers to the middle lamella. To better understand the properties of these micron-scaled regions of wood, we have developed a unique set of nano-indentation tools that allow us to measure local...

  9. Enhanced mechanical, thermal, and electric properties of graphene aerogels via supercritical ethanol drying and high-temperature thermal reduction

    OpenAIRE

    Yehong Cheng; Shanbao Zhou; Ping Hu; Guangdong Zhao; Yongxia Li; Xinghong Zhang; Wenbo Han

    2017-01-01

    Graphene aerogels with high surface areas, ultra-low densities and thermal conductivities have been prepared to exploit their wide applications from pollution adsorption to energy storage, supercapacitor, and thermal insulation. However, the low mechanical properties, poor thermal stability and electric conductivity restrict these aerogels? applications. In this paper, we prepared mechanically strong graphene aerogels with large BET surface areas, low thermal conductivities, high thermal stab...

  10. AGC 2 Irradiation Creep Strain Data Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Windes, William E. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Rohrbaugh, David T. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Swank, W. David [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-08-01

    The Advanced Reactor Technologies Graphite Research and Development Program is conducting an extensive graphite irradiation experiment to provide data for licensing of a high temperature reactor (HTR) design. In past applications, graphite has been used effectively as a structural and moderator material in both research and commercial high temperature gas cooled reactor designs. Nuclear graphite H-451, used previously in the United States for nuclear reactor graphite components, is no longer available. New nuclear graphite grades have been developed and are considered suitable candidates for new HTR reactor designs. To support the design and licensing of HTR core components within a commercial reactor, a complete properties database must be developed for these current grades of graphite. Quantitative data on in service material performance are required for the physical, mechanical, and thermal properties of each graphite grade, with a specific emphasis on data accounting for the life limiting effects of irradiation creep on key physical properties of the HTR candidate graphite grades. Further details on the research and development activities and associated rationale required to qualify nuclear grade graphite for use within the HTR are documented in the graphite technology research and development plan.

  11. Thermal properties of poly(3-hydroxybutyrate)/vegetable fiber composites

    Science.gov (United States)

    Vitorino, Maria B. C.; Reul, Lízzia T. A.; Carvalho, Laura H.; Canedo, Eduardo L.

    2015-05-01

    The present work studies the thermal properties of composites of poly(3-hydroxybutyrate) (PHB) - a fully biodegradable semi-crystalline thermo-plastic obtained from renewable resources through low-impact biotechno-logical process, biocompatible and non-toxic - and vegetable fiber from the fruit (coconut) of babassu palm tree. PHB is a highly crystalline resin and this characteristic leads to suboptimal properties in some cases. Consequently, thermal properties, in particular those associated with the crystallization of the matrix, are important to judge the suitability of the compounds for specific applications. PHB/babassu composites with 0-50% load were prepared in an internal mixer. Two different types of babassu fibers with two different particle size ranges were compounded with PHB and test specimens molded by compression. Melting and crystallization behavior were studied by differential scanning calorimetry (DSC) at heating/cooling rates between 2 and 30°C/min. Several parameters, including melting point, crystallization temperature, crystallinity, and rate of crystallization, were estimated as functions of load and heating/cooling rates. Results indicate that fibers do not affect the melting process, but facilitate crystallization from the melt. Crystallization temperatures are 30 to 40°C higher for the compounds compared with the neat resin. However, the amount of fiber added has little effect on crystallinity and the degree of crystallinity is hardly affected by the load. Fiber type and initial particle size do not have a significant effect on thermal properties.

  12. Characterization of the thermal insulating properties of vacuum glazing

    Energy Technology Data Exchange (ETDEWEB)

    Ng, N. [School of Physics, University of Sydney, New South Wales 2006 (Australia)]. E-mail: n.ng@Physics.usyd.edu.au; Collins, R.E. [School of Physics, University of Sydney, New South Wales 2006 (Australia); So, L. [School of Physics, University of Sydney, New South Wales 2006 (Australia)

    2007-03-25

    Methods are described for characterizing the thermal insulating properties of vacuum glazing-two flat sheets of glass, hermetically sealed together around the edges containing a highly evacuated space, and separated by small pillars. The small-area guarded hot plate apparatus gives absolute measurements of the different heat flows through the glazing due to radiation, gaseous conduction and thermal conduction through the pillars. In the transient technique, a step temperature increase is applied to one side of the glazing, and the resultant slow temperature rise of the other glass sheet is measured. This method can be used in ageing studies to characterize glazings at elevated temperatures. In the cool-down method, one glass sheet of a glazing that is initially at high temperature is insulated, the opposite glass sheet is rapidly cooled, and the rate of cooling of the thermally insulated sheet is then measured.

  13. Multi-scale investigation of tensile creep of ultra-high performance concrete for bridge applications

    Science.gov (United States)

    Garas Yanni, Victor Youssef

    Ultra-high performance concrete (UHPC) is relatively a new generation of concretes optimized at the nano and micro-scales to provide superior mechanical and durability properties compared to conventional and high performance concretes. Improvements in UHPC are achieved through: limiting the water-to-cementitious materials ratio (i.e., w/cm ≤ 0.20), optimizing particle packing, eliminating coarse aggregate, using specialized materials, and implementing high temperature and high pressure curing regimes. In addition, and randomly dispersed and short fibers are typically added to enhance the material's tensile and flexural strength, ductility, and toughness. There is a specific interest in using UHPC for precast prestressed bridge girders because it has the potential to reduce maintenance costs associated with steel and conventional concrete girders, replace functionally obsolete or structurally deficient steel girders without increasing the weight or the depth of the girder, and increase bridge durability to between 75 and 100 years. UHPC girder construction differs from that of conventional reinforced concrete in that UHPC may not need transverse reinforcement due to the high tensile and shear strengths of the material. Before bridge designers specify such girders without using shear reinforcement, the long-term tensile performance of the material must be characterized. This multi-scale study provided new data and understanding of the long-term tensile performance of UHPC by assessing the effect of thermal treatment, fiber content, and stress level on the tensile creep in a large-scale study, and by characterizing the fiber-cementitious matrix interface at different curing regimes through nanoindentation and scanning electron microscopy (SEM) in a nano/micro-scale study. Tensile creep of UHPC was more sensitive to investigated parameters than tensile strength. Thermal treatment decreased tensile creep by about 60% after 1 year. Results suggested the possibility of

  14. Enhanced mechanical, thermal, and electric properties of graphene aerogels via supercritical ethanol drying and high-temperature thermal reduction.

    Science.gov (United States)

    Cheng, Yehong; Zhou, Shanbao; Hu, Ping; Zhao, Guangdong; Li, Yongxia; Zhang, Xinghong; Han, Wenbo

    2017-05-03

    Graphene aerogels with high surface areas, ultra-low densities and thermal conductivities have been prepared to exploit their wide applications from pollution adsorption to energy storage, supercapacitor, and thermal insulation. However, the low mechanical properties, poor thermal stability and electric conductivity restrict these aerogels' applications. In this paper, we prepared mechanically strong graphene aerogels with large BET surface areas, low thermal conductivities, high thermal stability and electric conductivities via hydrothermal reduction and supercritical ethanol drying. Annealing at 1500 °C resulted in slightly increased thermal conductivity and further improvement in mechanical properties, oxidation temperature and electric conductivity of the graphene aerogel. The large BET surface areas, together with strong mechanical properties, low thermal conductivities, high thermal stability and electrical conductivities made these graphene aerogels feasible candidates for use in a number of fields covering from batteries to sensors, electrodes, lightweight conductor and insulation materials.

  15. Effective Thermal Expansion Property of Consolidated Granular Materials.

    Science.gov (United States)

    Küçük, Gülşad; Gonzalez, Marcial; Cuitiño, Alberto M

    2017-11-09

    Thermally-assisted compaction of granular materials is of keen interest in many engineering applications. A proper estimation of the material behavior of compacted granular materials is contingent upon the knowledge of microstructure formation, which is highly dependent on the bulk material properties and processing conditions, during the deformation stage. Originating from the pair interactions between particles, the macroscopic properties are obtained using various homogenization techniques and postulating continuum constitutive laws. While pioneers in this field have laid fundamental groundwork regarding effective medium descriptions, there exists a discrepancy between discrete and continuum level solutions. In our previous work, we elaborated a Particle Mechanics Approach (PMA) that integrates thermal contact and Hertzian deformation models to understand the thermo-mechanically-coupled consolidation problem. We also considered the analogous problem from the perspective of the conventional Continuum Mechanics Approach (CMA). In this study, following the multi-scale modeling framework, we propose an effective thermal expansion coefficient for the thermally-assisted compaction of granular materials.

  16. Thermal properties of graphene from path-integral simulations

    Science.gov (United States)

    Herrero, Carlos P.; Ramírez, Rafael

    2018-03-01

    Thermal properties of graphene monolayers are studied by path-integral molecular dynamics simulations, which take into account the quantization of vibrational modes in the crystalline membrane and allow one to consider anharmonic effects in these properties. This system was studied at temperatures in the range from 12 to 2000 K and zero external stress, by describing the interatomic interactions through the LCBOPII effective potential. We analyze the internal energy and specific heat and compare the results derived from the simulations with those yielded by a harmonic approximation for the vibrational modes. This approximation turns out to be rather precise up to temperatures of about 400 K. At higher temperatures, we observe an influence of the elastic energy due to the thermal expansion of the graphene sheet. Zero-point and thermal effects on the in-plane and "real" surface of graphene are discussed. The thermal expansion coefficient α of the real area is found to be positive at all temperatures, in contrast to the expansion coefficient αp of the in-plane area, which is negative at low temperatures and becomes positive for T ≳ 1000 K.

  17. Handbook on dielectric and thermal properties of microwaveable materials

    CERN Document Server

    Komarov, Vyacheslav V

    2012-01-01

    The application of microwave energy for thermal processing of different materials and substances is a rapidly growing trend in modern science and engineering. In fact, optimal design work involving microwaves is impossible without solid knowledge of the properties of these materials. Here s a practical reference that collects essential data on the dielectric and thermal properties of microwaveable materials, saving you countless hours on projects in a wide range of areas, including microwave design and heating, applied electrodynamics, food science, and medical technology. This unique book provides hard-to-find information on complex dielectric permittivity of media at industrial, scientific, and medical frequencies (430 MHz, 915MHz, 2.45GHz, 5.8 GHz, and 24.125GHz). Written by a leading expert in the field, this authoritative book does an exceptional job at presenting critical data on various materials and explaining what their key characteristics are concerning microwaves.

  18. Thermal properties of SFR-HPC exposed to high temperatures

    Science.gov (United States)

    Scheinherrová, Lenka; Pavlík, Zbyšek

    2017-07-01

    In this paper, a non-adiabatic method was used for the assessment of specific heat capacity of steel fibre reinforced high performance concrete in the temperature range 105-1000 °C. The tested SFR-HPC mix was produced from CEM II 42.5 R, ground granulated blast furnace slag, silica sand with maximum particle size of 2 mm, silica fume, brass-coated steel fibres, superplasticizer on polycarboxylate ether basis and batch water. For the studied material, properties after 2 hours thermal treatment at the temperatures of 105 °C, 200 °C, 400 °C, 600 °C, 800 °C, and 1000 °C respectively were tested. Among them, bulk density, matrix density, total open porosity and thermal parameters as thermal conductivity, thermal diffusivity and specific heat capacity were measured. The measured specific heat capacity exhibited high dependence on temperature and pointed to the structural changes that studied material underwent at high temperatures. Accordingly, the obtained residual parameters revealed the thermally induced damage of SFR-HPC and critical temperatures for its functionality.

  19. Thermal properties of degraded lowland peat-moorsh soils

    Science.gov (United States)

    Gnatowski, Tomasz

    2016-04-01

    Soil thermal properties, i.e.: specific heat capacity (c), thermal conductivity (K), volumetric heat capacity (C) govern the thermal environment and heat transport through the soil. Hence the precise knowledge and accurate predictions of these properties for peaty soils with high amount of organic matter are especially important for the proper forecasting of soil temperature and thus it may lead to a better assessment of the greenhouse gas emissions created by microbiological activity of the peatlands. The objective of the study was to develop the predictive models of the selected thermal parameters of peat-moorsh soils in terms of their potential applicability for forecasting changes of soil temperature in degraded ecosystems of the Middle Biebrza River Valley area. Evaluation of the soil thermal properties was conducted for the parameters: specific heat capacity (c), volumetric heat capacities of the dry and saturated soil (Cdry, Csat) and thermal conductivities of the dry and saturated soil (Kdry, Ksat). The thermal parameters were measured using the dual-needle probe (KD2-Pro) on soil samples collected from seven peaty soils, representing total 24 horizons. The surface layers were characterized by different degrees of advancement of soil degradation dependent on intensiveness of the cultivation practises (peaty and humic moorsh). The underlying soil layers contain peat deposits of different botanical composition (peat-moss, sedge-reed, reed and alder) and varying degrees of decomposition of the organic matter, from H1 to H7 (von Post scale). Based on the research results it has been shown that the specific heat capacity of the soils differs depending on the type of soil (type of moorsh and type of peat). The range of changes varied from 1276 J.kg-1.K-1 in the humic moorsh soil to 1944 J.kg-1.K-1 in the low decomposed sedge-moss peat. It has also been stated that in degraded peat soils with the increasing of the ash content in the soil the value of specific heat

  20. Electrical and thermal properties of PLA/CNT composite films

    OpenAIRE

    Ceregatti, Thayara; Pecharki, Paloma; PACHEKOSKI, Wagner M.; Becker,Daniela; Dalmolin, Carla

    2017-01-01

    ABSTRACT Conducting polymers presents many potential applications such as biosensors and biofuelcells. However, to be used in those devices, a thin film must be deposited onto a conducting and biocompatible substrate. In this work, carbon nanotubes (CNT) were mixed in a poly (lactic acid) - PLA - matrix with different compositions (from 0.25 to 5.0 %) in order to form conducting composites suitable to the deposition of a conducting polymer. Thermal properties of PLA/CNT composites were evalua...

  1. Electrical and thermal properties of graphite/polyaniline composites

    Energy Technology Data Exchange (ETDEWEB)

    Bourdo, Shawn E., E-mail: sxbourdo@ualr.edu [Center for Integrative Nanotechnology Sciences, University of Arkansas at Little Rock, 2801 South University Avenue, Little Rock, AR 72204 (United States); Warford, Brock A.; Viswanathan, Tito [Department of Chemistry, University of Arkansas at Little Rock, 2801 South University Avenue, Little Rock, AR 72204 (United States)

    2012-12-15

    A composite of a carbon allotrope (graphite) and an inherently conducting polymer, polyaniline (PANI), has been prepared that exhibits an electrical conductivity greater than either of the two components. An almost 2-fold increase in the bulk conductivity occurs when only a small mass fraction of polyaniline exists in the composite (91% graphite/ 9% polyaniline, by mass). This increase in dc electrical conductivity is curious since in most cases a composite material will exhibit a conductivity somewhere between the two individual components, unless a modification to the electronic nature of the material occurs. In order to elucidate the fundamental electrical properties of the composite we have performed variable temperature conductivity measurements to better understand the nature of conduction in these materials. The results from these studies suggest a change in the mechanism of conduction as the amount of polyaniline is increased in the composite. Along with superior electrical properties, the composites exhibit an increase in thermal stability as compared to the graphite. - Graphical abstract: (Left) Room temperature electrical conductivity of G-PANI composites at different mass ratios. (Right) Electrical conductivity of G-PANI composites at temperatures from 5 K to 300 K. Highlights: Black-Right-Pointing-Pointer Composites of graphite and polyaniline have been synthesized with unique electrical and thermal properties. Black-Right-Pointing-Pointer Certain G-PANI composites are more conductive and more thermally stable than graphite alone. Black-Right-Pointing-Pointer G-PANI composites exhibit a larger conductivity ratio with respect to temperature than graphite alone.

  2. Suppression of creep-regime dynamics in epitaxial ferroelectric BiFeO3 films.

    Science.gov (United States)

    Shin, Y J; Jeon, B C; Yang, S M; Hwang, I; Cho, M R; Sando, D; Lee, S R; Yoon, J-G; Noh, T W

    2015-05-27

    Switching dynamics of ferroelectric materials are governed by the response of domain walls to applied electric field. In epitaxial ferroelectric films, thermally-activated 'creep' motion plays a significant role in domain wall dynamics, and accordingly, detailed understanding of the system's switching properties requires that this creep motion be taken into account. Despite this importance, few studies have investigated creep motion in ferroelectric films under ac-driven force. Here, we explore ac hysteretic dynamics in epitaxial BiFeO3 thin films, through ferroelectric hysteresis measurements, and stroboscopic piezoresponse force microscopy. We reveal that identically-fabricated BiFeO3 films on SrRuO3 or La0.67Sr0.33MnO3 bottom electrodes exhibit markedly different switching behaviour, with BiFeO3/SrRuO3 presenting essentially creep-free dynamics. This unprecedented result arises from the distinctive spatial inhomogeneities of the internal fields, these being influenced by the bottom electrode's surface morphology. Our findings further highlight the importance of controlling interface and defect characteristics, to engineer ferroelectric devices with optimised performance.

  3. Determination Of Thermal And Mechanical Properties Of Packaging Materials For The Use In FEM-Simulations

    Science.gov (United States)

    Roellig, Mike; Boehme, Bjoern; Meier, Karsten; Metasch, René

    2011-09-01

    Conventional and future electronic packages merge several different materials. Polymers, metals, solders, dielectrics, glasses, silicon, composites come together and show strong mechanical and material interaction. These interfacial effects increase if the miniaturization and diversification keep on rising as it is proposed. Many efforts have to be done to assure the system reliability of new electronic packages. The Finite Element Simulation has the ability to support the development process of new packages. The application of the FEM-analysis requires the knowledge about the precise mechanical and thermal behaviour of the materials. The paper presents different measurement methods to determine accurate mechanical material properties of moulding compound polymers, underfillers, solder mask, and wafer photo resist and solder joints. The temperature dependency is essential to be respected. The polymer materials moulding compound as well as solder mask were characterized by Dynamic Mechanical Analysis under humidity influences to determine mechanical properties as function of moisture and temperature. Further experiments on polymer were conducted to extract the cure kinetics by Differential Scanning Calorimetry and to determine Bulk Modulus by Pressure-Volume-Temperature experiments (PVT). Altogether, these material properties need to be modeled in a comprehensive way fitting to each other. The common practice of just compiling data from different sources has been found to fail yielding in reliable and accurate results. The conditions under which the data were determined may cause mismatches between them and cause inconsistencies within the model. If a convergent solution was obtained at all, much simulation time would be needed as many iterations with small time steps were needed. In order to avoid this, the paper reports an approach of characterizing the temperature and time dependent mechanical material properties in one comprehensive scheme. The solder

  4. Effect of prior-austenite grain refinement on microstructure, mechanical properties and thermal embrittlement of 9Cr-1Mo-0.1C steel

    Science.gov (United States)

    Karthikeyan, T.; Dash, Manmath Kumar; Ravikirana; Mythili, R.; Panneer Selvi, S.; Moitra, A.; Saroja, S.

    2017-10-01

    The effect of 'conventional normalizing and tempering' (CNT) and 'double austenitization based normalizing and tempering' (DNT) heat treatments on the microstructure, tensile, creep and impact toughness properties of 9Cr-1Mo steel has been studied. The tempered martensite microstructure obtained through DNT treatment exhibited smaller sizes of prior-austenite grains/martensite packets (28 μm/11 μm) compared to the CNT treatment (44 μm/14 μm). The tempered martensite morphology was largely retained after long-term thermal aging at 550 °C/5000 h, while the M23C6 and M2(C,N) type of precipitates were found to act as nucleation sites for precipitation of brittle Fe2Mo Laves phase. The grain refinement by DNT was found to be beneficial for minimizing the ductile-to-brittle transition characteristics (25 °C lower ductile-to-brittle transition temperature and 70 J higher upper shelf energy) over the CNT. Thermal embrittlement occurred in both heated treated steels, but the transition temperature of aged DNT steel remained below room temperature. Fractured Charpy specimens revealed ductile failure by void coalescence for high temperature tests, and a quasi-cleavage fracture at low temperatures with few isolated occurrence of intergranular crack in thermal embrittled steel. The DNT treated steel resulted in similar or better tensile and creep properties, when compared to the CNT treatment. The homogeneous fine grained tempered martensite microstructure obtained by DNT treatment resulted in improved embrittlement resistance and mechanical properties over the conventional treatment.

  5. XFEM for Thermal Crack of Massive Concrete

    Directory of Open Access Journals (Sweden)

    Guowei Liu

    2013-01-01

    Full Text Available Thermal cracking of massive concrete structures occurs as a result of stresses caused by hydration in real environment conditions. The extended finite element method that combines thermal fields and creep is used in this study to analyze the thermal cracking of massive concrete structures. The temperature field is accurately simulated through an equivalent equation of heat conduction that considers the effect of a cooling pipe system. The time-dependent creep behavior of massive concrete is determined by the viscoelastic constitutive model with Prony series. Based on the degree of hydration, we consider the main properties related to cracking evolving with time. Numerical simulations of a real massive concrete structure are conducted. Results show that the developed method is efficient for numerical calculations of thermal cracks on massive concrete. Further analyses indicate that a cooling system and appropriate heat preservation measures can efficiently prevent the occurrence of thermal cracks.

  6. Creep Behavior of UFG CP Ti at Room Temperature

    Science.gov (United States)

    Luo, Lei; Zhao, Xicheng; Liu, XiaoYan; Yang, Xirong

    2017-10-01

    Ultra-fine grained commercial purity titanium (UFG CP Ti) is processed by Composite refining process (Equal channel angular pressing (ECAP), cold rolling and rotary swaging) at room temperature. The grain size is refined from 19 μm to 180 nm, and the ultimate tensile strength increase to 870 MPa. Creep tests were carried out on Ultra-fine grained commercial purity titanium with the stresses of 640, 660, 680, 700, 720, 740, 760 MPa at room temperature. Steady state creep rate and stress exponent n at various stresses were calculated for Ultra-fine grained commercial purity titanium, and creep deformation mechanism was also investigated. (With the rise of stress, the steady creep rate increases while the creep time decrease). The steady state creep rate reached maximum 1.416×10-6 s-1 (under) stress of 760 MPa. The stress exponent is 17.3 when the stress was 640 ∼ 700MPa, while the stress exponent is 55.7 when the stress was 700 ∼ 760MPa, UFG CP Ti shows good creep property at room temperature. The creep deformation mechanism of UFG CP Ti is the dislocation creep.

  7. Thermal property measurement of thin fibers by complementary methods

    Science.gov (United States)

    Munro, Troy Robert

    To improve measurement reliability and repeatability and resolve the orders of magnitude discrepancy between the two different measurements (via reduced model transient electrothermal and lock-in IR thermography), this dissertation details the development of three complementary methods to accurately measure the thermal properties of the natural and synthetic Nephila (N.) clavipes spider dragline fibers. The thermal conductivity and diffusivity of the dragline silk of the (N.) clavipes spider has been characterized by one research group to be 151-416 W m-1 K-1 and 6.4-12.3 x 10-5 m2 s -1, respectively, for samples with low to high strains (zero to 19.7%). Thermal diffusivity of the dragline silk of a different spider species, Araneus diadematus, has been determined by another research group as 2 x 10-7 m2 s-1 for un-stretched silk. This dissertation seeks to resolve this discrepancy by three complementary methods. The methods detailed are the transient electrothermal technique (in both reduced and full model versions), the 3o method (for both current and voltage sources), and the non-contact, photothermal, quantum-dot spectral shape-based fluorescence thermometry method. These methods were also validated with electrically conductive and non-conductive fibers. The resulting thermal conductivity of the dragline silk is 1.2 W m-1 K-1, the thermal diffusivity is 6 x 10-7 m2 s -1 and the volumetric heat capacity is 2000 kJ m-3 K-1, with an uncertainty of about 12% for each property.

  8. Input Correlations for Irradiation Creep of FeCrAl and SiC Based on In-Pile Halden Test Results

    Energy Technology Data Exchange (ETDEWEB)

    Terrani, K. A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Karlsen, T. M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Yamamoto, Yukinori [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-05-01

    Swelling and creep behavior of wrought FeCrAl alloys and CVD-SiC, two candidate accident tolerant fuel cladding materials, are being examined using in-pile tests at the Halden reactor. The outcome of these tests are material property correlations that are inputs into fuel performance analysis tools. The results are discussed and compared with what is available in literature from irradiation experiments in other reactors or out-of-pile tests. Specific recommendation on what correlations should be used for swelling, thermal, and irradiation creep for each material are provided in this document.

  9. Seismic Creep, USA Images

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Seismic creep is the constant or periodic movement on a fault as contrasted with the sudden rupture associated with an earthquake. It is a usually slow deformation...

  10. Biaxial Creep Specimen Fabrication

    Energy Technology Data Exchange (ETDEWEB)

    JL Bump; RF Luther

    2006-02-09

    This report documents the results of the weld development and abbreviated weld qualification efforts performed by Pacific Northwest National Laboratory (PNNL) for refractory metal and superalloy biaxial creep specimens. Biaxial creep specimens were to be assembled, electron beam welded, laser-seal welded, and pressurized at PNNL for both in-pile (JOYO reactor, O-arai, Japan) and out-of-pile creep testing. The objective of this test campaign was to evaluate the creep behavior of primary cladding and structural alloys under consideration for the Prometheus space reactor. PNNL successfully developed electron beam weld parameters for six of these materials prior to the termination of the Naval Reactors program effort to deliver a space reactor for Project Prometheus. These materials were FS-85, ASTAR-811C, T-111, Alloy 617, Haynes 230, and Nirnonic PE16. Early termination of the NR space program precluded the development of laser welding parameters for post-pressurization seal weldments.

  11. Irradiation Creep in Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Ubic, Rick; Butt, Darryl; Windes, William

    2014-03-13

    An understanding of the underlying mechanisms of irradiation creep in graphite material is required to correctly interpret experimental data, explain micromechanical modeling results, and predict whole-core behavior. This project will focus on experimental microscopic data to demonstrate the mechanism of irradiation creep. High-resolution transmission electron microscopy should be able to image both the dislocations in graphite and the irradiation-induced interstitial clusters that pin those dislocations. The team will first prepare and characterize nanoscale samples of virgin nuclear graphite in a transmission electron microscope. Additional samples will be irradiated to varying degrees at the Advanced Test Reactor (ATR) facility and similarly characterized. Researchers will record microstructures and crystal defects and suggest a mechanism for irradiation creep based on the results. In addition, the purchase of a tensile holder for a transmission electron microscope will allow, for the first time, in situ observation of creep behavior on the microstructure and crystallographic defects.

  12. Morphology and the physical and thermal properties of thermoplastic polyurethane reinforced with thermally reduced graphene oxide

    Directory of Open Access Journals (Sweden)

    Strankowski Michał

    2015-12-01

    Full Text Available In this study, thermally reduced graphene oxide (TRG-containing polyurethane nanocomposites were obtained by the extrusion method. The content of TRG incorporated into polyurethane elastomer systems equaled 0.5, 1.0, 2.0 and 3.0 wt%. The morphology, static and dynamic mechanical properties, and thermal stability of the modified materials were investigated. The application of TRG resulted in a visible increase in material stiffness as confirmed by the measurements of complex compression modulus (E′ and glass transition temperature (Tg. The Tg increased with increasing content of nanofiller in the thermoplastic system. The addition of thermally reduced graphene oxide had a slight effect on thermal stability of the obtained materials. The incorporation of 0.5, 1.0, 2.0 and 3.0 wt% of TRG into a system resulted in increased char residues compared to unmodified PU elastomer. Also, this study demonstrated that after exceeding a specific amount of TRG, the physicomechanical properties of modified materials start to deteriorate.

  13. Thermal Properties Capability Development Workshop Summary to Support the Implementation Plan for PIE Thermal Conductivity Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Braase, Lori [Idaho National Lab. (INL), Idaho Falls, ID (United States); Papesch, Cynthia [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hurley, David [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-04-01

    The Department of Energy (DOE)-Office of Nuclear Energy (NE), Idaho National Laboratory (INL), and associated nuclear fuels programs have invested heavily over the years in infrastructure and capability development. With the current domestic and international need to develop Accident Tolerant Fuels (ATF), increasing importance is being placed on understanding fuel performance in irradiated conditions and on the need to model and validate that performance to reduce uncertainty and licensing timeframes. INL’s Thermal Properties Capability Development Workshop was organized to identify the capability needed by the various nuclear programs and list the opportunities to meet those needs. In addition, by the end of fiscal year 2015, the decision will be made on the initial thermal properties instruments to populate the shielded cell in the Irradiated Materials Characterization Laboratory (IMCL).

  14. Comparative study of hygrothermal properties of five thermal insulation materials

    Directory of Open Access Journals (Sweden)

    Laure Ducoulombier

    2017-09-01

    Full Text Available The objective of this article is to carry out a comparative study of the main hygrothermal properties of five thermal insulation materials for buildings. These properties are necessary for a correct prediction of heat and moisture transfers through the walls and the selection of the most appropriate materials according to the specific buildings. The studied materials were glass wool, rock wool, expanded polystyrene, wood fiberboard and polyester fiberfill. The article is divided into three parts. The first part presents the phenomena of hygrothermal transfers in walls in order to understand the need for determining specific properties of the insulating materials. The second part describes in details the five studied insulating materials and the methods used for the characterization and identification of their main properties. Finally, the last part presents the experimental results and makes comparisons between materials. The differences between the insulating materials are brought out, such as the strong dependence of the thermal conductivity of polystyrene on temperature, or the good permeability of fibrous insulating materials to water vapor. A detailed analysis of the obtained results is presented.

  15. Thermal Properties of Hybrid Carbon Nanotube/Carbon Fiber Polymer

    Science.gov (United States)

    Kang, Jin Ho; Cano, Roberto J.; Luong, Hoa; Ratcliffe, James G.; Grimsley, Brian W.; Siochi, Emilie J.

    2016-01-01

    Carbon fiber reinforced polymer (CFRP) composites possess many advantages for aircraft structures over conventional aluminum alloys: light weight, higher strength- and stiffness-to-weight ratio, and low life-cycle maintenance costs. However, the relatively low thermal and electrical conductivities of CFRP composites are deficient in providing structural safety under certain operational conditions such as lightning strikes. One possible solution to these issues is to interleave carbon nanotube (CNT) sheets between conventional carbon fiber (CF) composite layers. However, the thermal and electrical properties of the orthotropic hybrid CNT/CF composites have not been fully understood. In this study, hybrid CNT/CF polymer composites were fabricated by interleaving layers of CNT sheets with Hexcel (Registered Trademark) IM7/8852 prepreg. The CNT sheets were infused with a 5% solution of a compatible epoxy resin prior to composite fabrication. Orthotropic thermal and electrical conductivities of the hybrid polymer composites were evaluated. The interleaved CNT sheets improved the in-plane thermal conductivity of the hybrid composite laminates by about 400% and the electrical conductivity by about 3 orders of magnitude.

  16. High-field thermal transport properties of REBCO coated conductors

    Science.gov (United States)

    Bonura, Marco; Senatore, Carmine

    2015-02-01

    The use of REBCO coated conductors (CCs) is envisaged for many applications, extending from power cables to high-field magnets. Whatever the case, thermal properties of REBCO tapes play a key role for the stability of superconducting devices. In this work, we present the first study on the longitudinal thermal conductivity (κ) of REBCO CCs in magnetic fields up to 19 T applied both parallel and perpendicularly to the thermal-current direction. Copper-stabilized tapes from six industrial manufacturers have been investigated. We show that zero-field κ of CCs can be calculated with an accuracy of +/- 15% from the residual resistivity ratio of the stabilizer and the Cu/non-Cu ratio. Measurements performed at high fields have allowed us to evaluate the consistency of the procedures generally used for estimating in-field κ in the framework of the Wiedemann-Franz law from an electrical characterization of the materials. In-field data are intended to provide primary ingredients for the thermal stability analysis of high-temperature superconductor-based magnets.

  17. Topical Problems and Applications of Creep Theory

    Science.gov (United States)

    Altenbach, H.

    2003-06-01

    A historical review of achievements in creep theory is given. Primary attention is focused on the phenomenological approach. Different constitutive equations are discussed for primary and secondary creep as well as for creep with damage. New creep problems are examined

  18. Physical, thermal and structural properties of Calcium Borotellurite glass system

    Energy Technology Data Exchange (ETDEWEB)

    Paz, E.C. [CCSST – UFMA, Imperatriz, MA (Brazil); IFMA, Açailândia, MA (Brazil); Dias, J.D.M. [CCSST – UFMA, Imperatriz, MA (Brazil); Melo, G.H.A. [CCSST – UFMA, Imperatriz, MA (Brazil); IFMA, Imperatriz, MA (Brazil); Lodi, T.A. [CCSST – UFMA, Imperatriz, MA (Brazil); Carvalho, J.O. [CCSST – UFMA, Imperatriz, MA (Brazil); IFTO, Araguaína, TO (Brazil); Façanha Filho, P.F.; Barboza, M.J.; Pedrochi, F. [CCSST – UFMA, Imperatriz, MA (Brazil); Steimacher, A., E-mail: steimacher@hotmail.com [CCSST – UFMA, Imperatriz, MA (Brazil)

    2016-08-01

    In this work the glass forming ability in Calcium Borotellurite (CBTx) glass system was studied. Six glass samples were prepared by melt-quenching technique and the obtained samples are transparent, lightly yellowish, with no visible crystallites. The structural studies were carried out by using XRD, FTIR, Raman Spectra, density measurements, and the thermal analysis by using DTA and specific heat. The results are discussed in terms of tellurium oxide content and their changes in structural and thermal properties of glass samples. The addition of TeO{sub 2} increased the density and thermal stability values and decreased glass transition temperature (Tg). Raman and FTIR spectroscopies indicated that the network structure of CBTx glasses is formed by BO{sub 3}, BO{sub 4}, TeO{sub 3}, TeO{sub 3+1} and TeO{sub 4} units. CBTx system showed good glass formation ability and good thermal stability, which make CBTx glasses suitable for manufacturing process and a candidate for rare-earth doping for several optical applications. - Highlights: • Glass forming ability on Calcium Borotellurite system was studied. • The glass structure was investigated by XRD, Raman and FTIR. • The glass network structure of the CBTx glasses is formed by BO{sub 3}, BO{sub 4}, TeO{sub 3}, TeO{sub 3+1} and TeO{sub 4} units. • The density and thermal stability of the CBTx glass decreases with TeO{sub 2} while the Cp and the Tg decreases. • The obtained CBTx glasses are suitable for manufacturing process and rare-earth doping for several optical applications.

  19. Nano-scale simulation based study of creep behavior of bimodal nanocrystalline face centered cubic metal.

    Science.gov (United States)

    Meraj, Md; Pal, Snehanshu

    2017-10-11

    In this paper, the creep behavior of nanocrystalline Ni having bimodal grain structure is investigated using molecular dynamics simulation. Analysis of structural evolution during the creep process has also been performed. It is observed that an increase in size of coarse grain causes improvement in creep properties of bimodal nanocrystalline Ni. Influence of bimodality (i.e., size difference between coarse and fine grains) on creep properties are found to be reduced with increasing creep temperature. The dislocation density is observed to decrease exponentially with progress of creep deformation. Grain boundary diffusion controlled creep mechanism is found to be dominant at the primary creep region and the initial part of the secondary creep region. After that shear diffusion transformation mechanism is found to be significantly responsible for deformation as bimodal nanocrystalline Ni transforms to amorphous structure with further progress of the creep process. The presence of , , and  distorted icosahedra has a significant influence on creep rate in the tertiary creep regime according to Voronoi cluster analysis.

  20. Comparison of experimental and theoretical thermal fatigue lives for five nickel base alloys

    Science.gov (United States)

    Spera, D. A.

    1972-01-01

    The alloys Nimonic 90, IN 100, coated IN 100, B 1900, coated B 1900, MAR M200, and MAR M200DS (directionally solidified) were studied. Maximum temperatures ranged from 770 C to 1120 C (1420 F to 2050 F). Specimen geometries included tapered disks, double-edged wedges, and cambered airfoils. The disks and wedges were heated and cooled in fluidized beds. The airfoil specimens were heated by a Mach 1 natural gas burner and rapid-air-cooled, with and without spanwise loading. Life calculations included two distinct failure modes: conventional low cycle fatigue and cyclic creep. Required material properties were limited to conventional thermal, tensile, and creep rupture data. The complete life calculation system included the calculation of transient temperature distributions, thermal strains, stresses, creep damage, fatigue damage, and cycles to first crack. Calculated lives were within a factor of two for 76 of the 86 data points analyzed. Cyclic creep accounted for 81% of all the calculated damage.

  1. Hemp Thermal Insulation Concrete with Alternative Binders, Analysis of their Thermal and Mechanical Properties

    Science.gov (United States)

    Sinka, M.; Sahmenko, G.; Korjakins, A.; Radina, L.; Bajare, D.

    2015-11-01

    One of the main challenges that construction industry faces today is how to address the demands for more sustainable, environmentally friendly and carbon neutral construction materials and building upkeep processes. One of the answers to these demands is lime-hemp concrete (LHC) building materials - carbon negative materials that have sufficient thermal insulation capabilities to be used as thermal insulation materials for new as well as for existing buildings. But one problem needs to be overcome before these materials can be used on a large scale - current manufacturing technology allows these materials to be used only as self-bearing thermal insulation material with large labour intensity in the manufacturing process. In order to lower the labour intensity and allow the material to be used in wider applications, a LHC block and board production is necessary, which in turn calls for the binders different from the classically used ones, as they show insufficient mechanical strength for this new use. The particular study focuses on alternative binders produced using gypsum-cement compositions ensuring they are usable in outdoor applications together with hemp shives. Physical, mechanical, thermal and water absorption properties of hemp concrete with various binders are addressed in the current study.

  2. The thermal properties of a carbon nanotube-enriched epoxy: Thermal conductivity, curing, and degradation kinetics

    KAUST Repository

    Ventura, Isaac Aguilar

    2013-05-31

    Multiwalled carbon nanotube-enriched epoxy polymers were prepared by solvent evaporation based on a commercially available epoxy system and functionalized multiwalled carbon nanotubes (COOH-MWCNTs). Three weight ratio configurations (0.05, 0.5, and 1.0 wt %) of COOH-MWCNTs were considered and compared with neat epoxy and ethanol-treated epoxy to investigate the effects of nano enrichment and processing. Here, the thermal properties of the epoxy polymers, including curing kinetics, thermal conductivity, and degradation kinetics were studied. Introducing the MWCNTs increased the curing activation energy as revealed by differential scanning calorimetry. The final thermal conductivity of the 0.5 and 1.0 wt % MWCNT-enriched epoxy samples measured by laser flash technique increased by up to 15% compared with the neat material. The activation energy of the degradation process, investigated by thermogravimetric analysis, was found to increase with increasing CNT content, suggesting that the addition of MWCNTs improved the thermal stability of the epoxy polymers. © 2013 Wiley Periodicals, Inc.

  3. Basic thermal-mechanical properties and thermal shock, fatigue resistance of swaged + rolled potassium doped tungsten

    Science.gov (United States)

    Zhang, Xiaoxin; Yan, Qingzhi; Lang, Shaoting; Xia, Min; Ge, Changchun

    2014-09-01

    The potassium doped tungsten (W-K) grade was achieved via swaging + rolling process. The swaged + rolled W-K alloy exhibited acceptable thermal conductivity of 159.1 W/m K and ductile-to-brittle transition temperature of about 873 K while inferior mechanical properties attributed to the coarse pores and small deformation degree. Then the thermal shock, fatigue resistance of the W-K grade were characterized by an electron beam facility. Thermal shock tests were conducted at absorbed power densities varied from 0.22 to 1.1 GW/m2 in a step of 0.22 GW/m2. The cracking threshold was in the range of 0.44-0.66 GW/m2. Furthermore, recrystallization occurred in the subsurface of the specimens tested at 0.66-1.1 GW/m2 basing on the analysis of microhardness and microstructure. Thermal fatigue tests were performed at 0.44 GW/m2 up to 1000 cycles and no cracks emerged throughout the tests. Moreover, recrystallization occurred after 1000 cycles.

  4. Photophysical, electrochemical, thermal and aggregation properties of new metal phthalocyanines

    Science.gov (United States)

    Jeong, Jaemyeng; Kumar, Rangaraju Satish; Mergu, Naveen; Son, Young-A.

    2017-11-01

    In this study, the synthesis of di(ethylene glycol) naphthalene substituted metal-phthalocyanines was reported. These novel phthalocyanines were characterized by elemental and spectroscopic analysis, including 1H NMR, FT-IR, UV-Vis spectral and MALDI-TOF mass data. The aggregation behavior of these phthalocyanines was examined in chloroform at different concentrations, and we confirmed that the phthalocyanines were non-aggregated. Further thermal stability, electrochemical, theoretical studies and metal sensing properties also investigated. In addition, we successfully prepared phthalocyanine (6d) blended polyurethane electrospun (ES) nanofibers.

  5. Lipophilic phytosterol derivatives: synthesis, thermal property and nanoemulsion behavior

    DEFF Research Database (Denmark)

    Panpipat, Worawan; Xu, Xuebing; Guo, Zheng

    the productive yield of a series of -sitosteryl fatty acid esters (C2-C18) and to investigate the thermal property and nano-emulsion behaviors of those compounds. This work reported a novel approach to synthesize phytosterol (-sitosterol as a model) fatty acid ester by employing Candida antarctica lipase...... of -sitosterol fatty acid esters was governed by the carbon chain length of fatty acid incorporated. The nano-emulsions of a series of -sitosteryl fatty acid esters were prepared by probe-sonication method. The particle size distributions, zeta potentials and TEM images of those emulsions were different...

  6. Creep of trabecular bone from the human proximal tibia

    Energy Technology Data Exchange (ETDEWEB)

    Novitskaya, Ekaterina, E-mail: eevdokim@ucsd.edu [Mechanical and Aerospace Engineering, UC, San Diego, La Jolla, CA 92093 (United States); Materials Science and Engineering Program, UC, San Diego, La Jolla, CA 92093 (United States); Zin, Carolyn [Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218 (United States); Chang, Neil; Cory, Esther; Chen, Peter [Departments of Bioengineering and Orthopaedic Surgery, UC, San Diego, La Jolla, CA 92093 (United States); D’Lima, Darryl [Shiley Center for Orthopaedic Research and Education, Scripps Health, La Jolla, CA 92037 (United States); Sah, Robert L. [Materials Science and Engineering Program, UC, San Diego, La Jolla, CA 92093 (United States); Departments of Bioengineering and Orthopaedic Surgery, UC, San Diego, La Jolla, CA 92093 (United States); McKittrick, Joanna [Mechanical and Aerospace Engineering, UC, San Diego, La Jolla, CA 92093 (United States); Materials Science and Engineering Program, UC, San Diego, La Jolla, CA 92093 (United States)

    2014-07-01

    Creep is the deformation that occurs under a prolonged, sustained load and can lead to permanent damage in bone. Creep in bone is a complex phenomenon and varies with type of loading and local mechanical properties. Human trabecular bone samples from proximal tibia were harvested from a 71-year old female cadaver with osteoporosis. The samples were initially subjected to one cycle load up to 1% strain to determine the creep load. Samples were then loaded in compression under a constant stress for 2 h and immediately unloaded. All tests were conducted with the specimens soaked in phosphate buffered saline with proteinase inhibitors at 37 °C. Steady state creep rate and final creep strain were estimated from mechanical testing and compared with published data. The steady state creep rate correlated well with values obtained from bovine tibial and human vertebral trabecular bone, and was higher for lower density samples. Tissue architecture was analyzed by micro-computed tomography (μCT) both before and after creep testing to assess creep deformation and damage accumulated. Quantitative morphometric analysis indicated that creep induced changes in trabecular separation and the structural model index. A main mode of deformation was bending of trabeculae. - Highlights: • Compressive creep tests of human trabecular bone across the tibia were performed. • The creep rate was found to be inversely proportional to the density of the samples. • μ-computed tomography before and after testing identified regions of deformation. • Bending of the trabeculae was found to be the main deformation mode.

  7. Predicting creep strengths and lifetimes of creep resistant engineering alloys

    Science.gov (United States)

    Zhao, Yanrong; Yao, Hongpeng; Song, Xinli; Jia, Juan; Xiang, Zhidong

    2018-01-01

    The physical basis for predicting the long-term creep strengths and lifetimes at application temperatures using creep parameters determined from short-term creep tests is investigated for complex creep resistant engineering alloys. It is shown that the seemingly unpredictable stress and temperature dependence of minimum creep rate of such alloys can be rationalised using an approach based on the new power law creep equation that incorporate the tensile strength. This is demonstrated using the tensile and creep data measured for two completely different types of alloys: steel 11Cr-2W-0.4Mo-1Cu-Nb-V and Ni base superalloy 15Cr-28Co-4Mo-2.5Ti-3Al. For both alloys, the stress exponent n determined does not depend on temperature and activation energy of creep does not depend on stress. Consequently, it becomes possible to use the new power law creep equation in combination with the Monkman-Grant relationship to predict the long term creep rupture strengths and lifetimes and microstructure stability of the two alloys from short term creep test data. The implications of the results for creep mechanism identification and future microstructure analysis are discussed.

  8. Structural, thermal, and electrical properties of CrSi2

    Science.gov (United States)

    Dasgupta, T.; Etourneau, J.; Chevalier, B.; Matar, S. F.; Umarji, A. M.

    2008-06-01

    Stoichiometric CrSi2 was prepared by arc melting and compacted by uniaxial hot pressing for property measurements. The crystal structure of CrSi2 was investigated using the powder x-ray diffraction method. From the Rietveld refinement, the lattice parameters were found to be a =4.42757 (7) and c =6.36804 (11)Å, respectively. The thermal expansion measurement revealed an anisotropic expansion in the temperature range from room temperature 800K with αa=14.58×10-6/K, αc=7.51×10-6/K, and αV=12.05×10-6/K. The volumetric thermal expansion coefficient shows an anomalous decrease in the temperature range of 450-600K. The measured electrical resistivity ρ and thermoelectric power S have similar trends with a maxima around 550K. Thermal conductivity measurements show a monotonic decrease with increasing temperature from a room temperature value of 10Wm-1K-1. The ZT values increase with temperature and have a maximum value of 0.18 in the temperature range studied. An analysis of the electronic band structure is provided.

  9. High-field thermal transports properties of REBCO coated conductors

    CERN Document Server

    Bonura, M

    2015-01-01

    The use of REBCO coated conductors is envisaged for many applications, extending from power cables to high-field magnets. Whatever the case, thermal properties of REBCO tapes play a key role for the stability of superconducting devices. In this work, we present the first study on the longitudinal thermal conductivity (k) of REBCO coated conductors in magnetic fields up to 19 T applied both parallelly and perpendicularly to the thermal-current direction. Copper-stabilized tapes from six industrial manufacturers have been investigated. We show that zero-field k of coated conductors can be calculated with an accuracy of ‡ 15% from the residual resistivity ratio of the stabilizer and the Cu/non-Cu ratio. Measurements performed at high fields have allowed us to evaluate the consistency of the procedures generally used for estimating in-field k in the framework of the Wiedemann-Franz law from an electrical characterization of the materials. In-field data are intended to provide primary ingredients for the ...

  10. Effect of hardness values on the creep rupture strength in a Mod.9Cr1Mo steel

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y. S.; Ryu, S. H.; Kong, B. O.; Kim, J. T. [Doosan Heavy Industries and Construction, Changwon (Korea, Republic of)

    2003-07-01

    The modified 9Cr-1Mo steel identified as T91, P91 and F91 in the ASME specification has been widely used for the construction of modern power plants. The available data on the influence of process parameters during manufacturing and fabrication on its properties are not sufficient. In this study, the influence of various thermal cycles on the hardness and the creep rupture strength was analyzed in the base metal and the weldments made in tube and pipe of a Mod.9Cr-1Mo steel. The low hardness, 155Hv, showed low creep rupture strength below the allowable stresses of T91 base metal in the ASME specification. This low value was attributed to the fully recovered dislocation structure and the weakening of precipitation hardening associated with the abnormal thermal cycles.

  11. Determination of the Creep Parameters of Linear Viscoelastic Materials

    Directory of Open Access Journals (Sweden)

    Alibay Iskakbayev

    2016-01-01

    Full Text Available Creep process of linear viscoelastic materials is described by the integral equation of Boltzmann-Volterra in which creep kernel is approximated by Rabotnov’s fractional exponential function. The creep equation contains four unknown parameters: α, singularity parameter; β, fading parameter; λ, rheological parameter; and ε0, conditionally instantaneous strain. Two-stage determination method of creep parameters is offered. At the first stage, taking into account weak singularity properties of Abel’s function at the initial moment of loading, parameters ε0 and α are determined. At the second stage, using already known parameters ε0 and α, parameters β and λ are determined. Analytical expressions for calculating these parameters are obtained. An accuracy evaluation of the offered method with using experimentally determined creep strains of material Nylon 6 and asphalt concrete showed its high accuracy.

  12. Thermophysical properties of fluids: dynamic viscosity and thermal conductivity

    Science.gov (United States)

    Latini, G.

    2017-11-01

    Thermophysical properties of fluids strongly depend upon atomic and molecular structure, complex systems governed by physics laws providing the time evolution. Theoretically the knowledge of the initial position and velocity of each atom, of the interaction forces and of the boundary conditions, leads to the solution; actually this approach contains too many variables and it is generally impossible to obtain an acceptable solution. In many cases it is only possible to calculate or to measure some macroscopic properties of fluids (pressure, temperature, molar volume, heat capacities...). The ideal gas “law,” PV = nRT, was one of the first important correlations of properties and the deviations from this law for real gases were usefully proposed. Moreover the statistical mechanics leads for example to the “hard-sphere” model providing the link between the transport properties and the molecular size and speed of the molecules. Further approximations take into account the intermolecular interactions (the potential functions) which can be used to describe attractions and repulsions. In any case thermodynamics reduces experimental or theoretical efforts by relating one physical property to another: the Clausius-Clapeyron equation provides a classical example of this method and the PVT function must be known accurately. However, in spite of the useful developments in molecular theory and computers technology, often it is usual to search for physical properties when the existing theories are not reliable and experimental data are not available: the required value of the physical or thermophysical property must be estimated or predicted (very often estimation and prediction are improperly used as synonymous). In some cases empirical correlations are useful, if it is clearly defined the range of conditions on which they are based. This work is concerned with dynamic viscosity µ and thermal conductivity λ and is based on clear and important rules to be respected

  13. Verification of the thermal insulation properties and determination the optimal position of the reflective thermal insulation layer in the wood based envelope

    National Research Council Canada - National Science Library

    Martin Labovský; Martin Lopušniak

    2016-01-01

    To achieve thinner wood based envelope is necessary look for an alternative thermal insulation material, which will have the best possible thermal insulation properties while maintaining affordability...

  14. Adjustment of Sensor Locations During Thermal Property Parameter Estimation

    Science.gov (United States)

    Milos, Frank S.; Marschall, Jochen; Rasky, Daniel J. (Technical Monitor)

    1996-01-01

    The temperature dependent thermal properties of a material may be evaluated from transient temperature histories using nonlinear parameter estimation techniques. The usual approach is to minimize the sum of the squared errors between measured and calculated temperatures at specific locations in the body. Temperature measurements are usually made with thermocouples and it is customary to take thermocouple locations as known and fixed during parameter estimation computations. In fact, thermocouple locations are never known exactly. Location errors on the order of the thermocouple wire diameter are intrinsic to most common instrumentation procedures (e.g., inserting a thermocouple into a drilled hole) and additional errors can be expected for delicate materials, difficult installations, large thermocouple beads, etc.. Thermocouple location errors are especially significant when estimating thermal properties of low diffusively materials which can sustain large temperature gradients during testing. In the present work, a parameter estimation formulation is presented which allows for the direct inclusion of thermocouple positions into the primary parameter estimation procedure. It is straightforward to set bounds on thermocouple locations which exclude non-physical locations and are consistent with installation tolerances. Furthermore, bounds may be tightened to an extent consistent with any independent verification of thermocouple location, such as x-raying, and so the procedure is entirely consonant with experimental information. A mathematical outline of the procedure is given and its implementation is illustrated through numerical examples characteristic of light-weight, high-temperature ceramic insulation during transient heating. The efficacy and the errors associated with the procedure are discussed.

  15. Structural and thermal properties of carboxylic acid functionalized polythiophenes

    Directory of Open Access Journals (Sweden)

    Ariane de França Mescoloto

    2014-01-01

    Full Text Available Polythiophenes functionalized with polar groups at the end of side-chain have emerged as an alternative method to obtain good compatibility between this class of conjugated polymers and electron acceptor compounds. The aim is to prevent phase segregation and to improve the efficiency of the polythiophene technological devices. However, homopolymers synthesized from thiophene rings with high polar groups at the end of the side-chain, such as hydroxyl and carboxylic acid groups, are poorly soluble in common volatile organic solvents. We report on a systematic preparation of copolymers of 3-hexylthiophene (HT and thiophene-3-acetic acid (TAA, using different feed ratios. The chemical structures of the copolymers were confirmed by FTIR and ¹H-NMR. The TAA content in these copolymers were 33, 38 and 54 mol %. HPSEC results did not show any remarkable correlation with TAA contents in the copolymers. In contrast, the thermal analyses showed a decrease in the thermal stability and an increase in rigidity of their backbones, for the copolymers with high amounts of TAA. The solubility and optical property of copolymers were also related to the TAA contents. Thus, the properties of these copolymers can be modulated by a simple control of feed ratio of TAA in the copolymerization.

  16. Accelerated Creep Testing of High Strength Aramid Webbing

    Science.gov (United States)

    Jones, Thomas C.; Doggett, William R.; Stnfield, Clarence E.; Valverde, Omar

    2012-01-01

    A series of preliminary accelerated creep tests were performed on four variants of 12K and 24K lbf rated Vectran webbing to help develop an accelerated creep test methodology and analysis capability for high strength aramid webbings. The variants included pristine, aged, folded and stitched samples. This class of webbings is used in the restraint layer of habitable, inflatable space structures, for which the lifetime properties are currently not well characterized. The Stepped Isothermal Method was used to accelerate the creep life of the webbings and a novel stereo photogrammetry system was used to measure the full-field strains. A custom MATLAB code is described, and used to reduce the strain data to produce master creep curves for the test samples. Initial results show good correlation between replicates; however, it is clear that a larger number of samples are needed to build confidence in the consistency of the results. It is noted that local fiber breaks affect the creep response in a similar manner to increasing the load, thus raising the creep rate and reducing the time to creep failure. The stitched webbings produced the highest variance between replicates, due to the combination of higher local stresses and thread-on-fiber damage. Large variability in the strength of the webbings is also shown to have an impact on the range of predicted creep life.

  17. Creeping Viscous Flow around a Heat-Generating Solid Sphere

    DEFF Research Database (Denmark)

    Krenk, Steen

    1981-01-01

    The velocity field for creeping viscous flow around a solid sphere due to a spherically symmetric thermal field is determined and a simple thermal generalization of Stokes' formula is obtained. The velocity field due to an instantaneous heat source at the center of the sphere is obtained in close...... form and an application to the storage of heat-generating nuclear waste is discussed....

  18. Nano-Localized Thermal Analysis and Mapping of Surface and Sub-Surface Thermal Properties Using Scanning Thermal Microscopy (SThM).

    Science.gov (United States)

    Pereira, Maria J; Amaral, Joao S; Silva, Nuno J O; Amaral, Vitor S

    2016-12-01

    Determining and acting on thermo-physical properties at the nanoscale is essential for understanding/managing heat distribution in micro/nanostructured materials and miniaturized devices. Adequate thermal nano-characterization techniques are required to address thermal issues compromising device performance. Scanning thermal microscopy (SThM) is a probing and acting technique based on atomic force microscopy using a nano-probe designed to act as a thermometer and resistive heater, achieving high spatial resolution. Enabling direct observation and mapping of thermal properties such as thermal conductivity, SThM is becoming a powerful tool with a critical role in several fields, from material science to device thermal management. We present an overview of the different thermal probes, followed by the contribution of SThM in three currently significant research topics. First, in thermal conductivity contrast studies of graphene monolayers deposited on different substrates, SThM proves itself a reliable technique to clarify the intriguing thermal properties of graphene, which is considered an important contributor to improve the performance of downscaled devices and materials. Second, SThM's ability to perform sub-surface imaging is highlighted by thermal conductivity contrast analysis of polymeric composites. Finally, an approach to induce and study local structural transitions in ferromagnetic shape memory alloy Ni-Mn-Ga thin films using localized nano-thermal analysis is presented.

  19. Guided-wave technique for the measurement of dielectric thin-film materials' thermal properties.

    Science.gov (United States)

    Huguet-Chantĵme, Pascal; Escoubas, Ludovic; Flory, François

    2002-06-01

    A pump-and-probe setup that uses a totally reflecting prism coupler is presented. Its electromagnetic and thermal models are described. To our knowledge, the first results are given concerning the measurement of thermal properties of thin films.

  20. Transformation-Induced Creep and Creep Recovery of Shape Memory Alloy.

    Science.gov (United States)

    Takeda, Kohei; Tobushi, Hisaaki; Pieczyska, Elzbieta A

    2012-05-22

    If the shape memory alloy is subjected to the subloop loading under the stress-controlled condition, creep and creep recovery can appear based on the martensitic transformation. In the design of shape memory alloy elements, these deformation properties are important since the deflection of shape memory alloy elements can change under constant stress. The conditions for the progress of the martensitic transformation are discussed based on the kinetics of the martensitic transformation for the shape memory alloy. During loading under constant stress rate, temperature increases due to the stress-induced martensitic transformation. If stress is held constant during the martensitic transformation stage in the loading process, temperature decreases and the condition for the progress of the martensitic transformation is satisfied, resulting in the transformation-induced creep deformation. If stress is held constant during the reverse transformation stage in the unloading process, creep recovery appears due to the reverse transformation. The details for these thermomechanical properties are investigated experimentally for TiNi shape memory alloy, which is most widely used in practical applications. The volume fraction of the martensitic phase increases in proportion to an increase in creep strain.

  1. Non-destructive thermal wave method applied to study thermal properties of fast setting time endodontic cement

    Science.gov (United States)

    Picolloto, A. M.; Mariucci, V. V. G.; Szpak, W.; Medina, A. N.; Baesso, M. L.; Astrath, N. G. C.; Astrath, F. B. G.; Santos, A. D.; Moraes, J. C. S.; Bento, A. C.

    2013-11-01

    The thermal wave method is applied for thermal properties measurement in fast endodontic cement (CER). This new formula is developed upon using Portland cement in gel and it was successfully tested in mice with good biocompatibility and stimulated mineralization. Recently, thermal expansion and setting time were measured, conferring to this material twice faster hardening than the well known Angelus Mineral trioxide aggregate (MTA) the feature of fast hardening (˜7 min) and with similar thermal expansion (˜12 μstrain/ °C). Therefore, it is important the knowledge of thermal properties like thermal diffusivity, conductivity, effusivity in order to match thermally the tissue environment upon its application in filling cavities of teeth. Photothermal radiometry technique based on Xe illumination was applied in CER disks 600 μm thick for heating, with prepared in four particle sizes (25, 38, 45, and 53) μm, which were added microemulsion gel with variation volumes (140, 150, 160, and 170) μl. The behavior of the thermal diffusivity CER disks shows linear decay for increase emulsion volume, and in contrast, thermal diffusivity increases with particles sizes. Aiming to compare to MTA, thermal properties of CER were averaged to get the figure of merit for thermal diffusivity as (44.2 ± 3.6) × 10-3 cm2/s, for thermal conductivity (228 ± 32) mW/cm K, the thermal effusivity (1.09 ± 0.06) W s0.5/cm2 K and volume heat capacity (5.2 ± 0.7) J/cm3 K, which are in excellent agreement with results of a disk prepared from commercial MTA-Angelus (grain size < 10 μm using 57 μl of distilled water).

  2. Non-destructive thermal wave method applied to study thermal properties of fast setting time endodontic cement

    Energy Technology Data Exchange (ETDEWEB)

    Picolloto, A. M.; Mariucci, V. V. G.; Szpak, W.; Medina, A. N.; Baesso, M. L.; Astrath, N. G. C.; Astrath, F. B. G.; Bento, A. C., E-mail: acbento@uem.br [Departamento de Física, Grupo de Espectroscopia Fotoacústica e Fototérmica, Universidade Estadual de Maringá – UEM, Av. Colombo 5790, 87020-900 Maringá, Paraná (Brazil); Santos, A. D.; Moraes, J. C. S. [Departamento de Física e Química, Universidade Estadual Paulista Júlio de Mesquita Filho – UNESP, Av. Brasil 56, 15385-000 Ilha Solteira, SP (Brazil)

    2013-11-21

    The thermal wave method is applied for thermal properties measurement in fast endodontic cement (CER). This new formula is developed upon using Portland cement in gel and it was successfully tested in mice with good biocompatibility and stimulated mineralization. Recently, thermal expansion and setting time were measured, conferring to this material twice faster hardening than the well known Angelus Mineral trioxide aggregate (MTA) the feature of fast hardening (∼7 min) and with similar thermal expansion (∼12 μstrain/ °C). Therefore, it is important the knowledge of thermal properties like thermal diffusivity, conductivity, effusivity in order to match thermally the tissue environment upon its application in filling cavities of teeth. Photothermal radiometry technique based on Xe illumination was applied in CER disks 600 μm thick for heating, with prepared in four particle sizes (25, 38, 45, and 53) μm, which were added microemulsion gel with variation volumes (140, 150, 160, and 170) μl. The behavior of the thermal diffusivity CER disks shows linear decay for increase emulsion volume, and in contrast, thermal diffusivity increases with particles sizes. Aiming to compare to MTA, thermal properties of CER were averaged to get the figure of merit for thermal diffusivity as (44.2 ± 3.6) × 10{sup −3} cm{sup 2}/s, for thermal conductivity (228 ± 32) mW/cm K, the thermal effusivity (1.09 ± 0.06) W s{sup 0.5}/cm{sup 2} K and volume heat capacity (5.2 ± 0.7) J/cm{sup 3} K, which are in excellent agreement with results of a disk prepared from commercial MTA-Angelus (grain size < 10 μm using 57 μl of distilled water)

  3. Creep in generation IV nuclear applications

    Energy Technology Data Exchange (ETDEWEB)

    Rissanen, L. (VTT Technical Research Centre of Finland, Espoo (Finland))

    2010-05-15

    Nuclear power has an important role in fulfilling the world's growing energy needs and reducing the carbon dioxide emission. Six new, innovative nuclear energy systems have been identified and selected for further development by the international Generation Four International Forum (GIF). These generation four (Gen IV) nuclear energy systems include a variety of reactor, energy conversion and fuel cycle technologies. The successful development and deployment of these largely depend on the performance and reliability of the available structural materials. These potential materials need to sustain their mechanical properties up to high temperatures, high neutron doses and corrosive environments of the new or enhanced types of coolants. Current knowledge on material properties, material-coolant interaction and especially material degradation processes in these new environments are limited. This paper gives an overview of the Gen IV material issues with special emphasis on European design of supercritical light water reactor concept high performance light water reactor (HPLWR). The challenges for the structural materials and the components most likely to suffer from creep and creep-irradiation are highlighted. Some results from relatively short term creep testing in supercritical water are presented for AISI 316NG, 347H and 1.4970 steels. The 1.4970 steel was superior in creep and oxidation resistance (orig.)

  4. Improved Inversion of Needle Probe Data for the Determination of Rock Thermal Properties

    DEFF Research Database (Denmark)

    Bording, Thue Sylvester; Balling, N.; Nielsen, S.B.

    Heat flow, thermal conductivity and thermal diffusivity are essential properties in subsurface temperature modelling. We present initial results of a novel inversion approach for laboratory measurements of rock thermal conductivity and thermal diffusivity by the needle probe method. Instead...... of analytical expressions, we use a numerical finite element procedure for the forward temperature response. A Markov Chain Monte Carlo Metropolis Hastings inversion procedure produces estimates of rock thermal parameters with uncertainties. .....

  5. Creep of timber joints

    NARCIS (Netherlands)

    Van de Kuilen, J.W.G.

    2008-01-01

    A creep analysis has been performed on nailed, toothed-plates and split-ring joints in a varying uncontrolled climate. The load levels varied between 30% and 50% of the average ultimate short term strength of these joints, tested in accordance with ISO 6891. The climate in which the tests were

  6. Analysis of indentation creep

    Science.gov (United States)

    Don S. Stone; Joseph E. Jakes; Jonathan Puthoff; Abdelmageed A. Elmustafa

    2010-01-01

    Finite element analysis is used to simulate cone indentation creep in materials across a wide range of hardness, strain rate sensitivity, and work-hardening exponent. Modeling reveals that the commonly held assumption of the hardness strain rate sensitivity (mΗ) equaling the flow stress strain rate sensitivity (mσ...

  7. Development of vacuum glazing with advanced thermal properties - Final report

    Energy Technology Data Exchange (ETDEWEB)

    Koebel, M.; Manz, H.

    2009-03-15

    Windows constitute a weak link in the building envelope and hence contribute significantly to the total heating energy demand in buildings. By evacuating the glazing cavity a vacuum glazing is created and heat transfer can be significantly reduced. This project was designed to build knowledge and technology necessary to fabricate vacuum glazing with advanced thermal properties. More specifically, various strategies for improvement of conventional technology were investigated. Of central importance was the development of a novel edge sealing approach which can in theory circumvent the main limitation of conventional glass soldering technology. This approach which is rapid, low temperature, low cost and completely vacuum compatible was filed for patenting in 2008. With regards to thermal insulation performance and glazing deflection, numerical studies were performed demonstrating the importance of nonlinear behavior with glazing size and the results published. A detailed service life prediction model was elaborated which defines a set of parameters necessary to keep the expected pressure increase below a threshold value of 0.1 Pa after 30 years. The model takes into account four possible sources of pressure increase and a getter material which acts as a sink. For the production of 0.5 m by 0.5 m glazing assembly prototypes, a high vacuum chamber was constructed and a first sealing prototype realized therein. The manufacture of improved prototypes and optimization of the anodic bonding edge sealing technology with emphasis on process relevant aspects is the goal of a follow-up project. (authors)

  8. Mechanical, Thermal and Functional Properties of Green Lightweight Foamcrete

    Directory of Open Access Journals (Sweden)

    Md Azree Othuman Mydin

    2012-09-01

    Full Text Available In recent times, the construction industry has revealed noteworthy attention in the use of lightweight foamcrete as a building material due to its many favourable characteristics such as lighter weight, easy to fabricate, durable and cost effective. Foamcrete is a material consisting of Portland cement paste or cement filler matrix (mortar with a homogeneous pore structure created by introducing air in the form of small bubbles. With a proper control in dosage of foam and methods of production, a wide range of densities (400 – 1600 kg/m 3 of foamcrete can be produced thus providing flexibility for application such as structural elements, partition, insulating materials and filling grades. Foamcrete has so far been applied primarily as a filler material in civil engineering works. However, its good thermal and acoustic performance indicates its strong potential as a material in building construction. The focus of this paper is to classify literature on foamcrete in terms of its mechanical, thermal and functional properties.

  9. Mechanical and Thermal Properties of Praseodymium Monopnictides: AN Ultrasonic Study

    Science.gov (United States)

    Bhalla, Vyoma; Kumar, Raj; Tripathy, Chinmayee; Singh, Devraj

    2013-09-01

    We have computed ultrasonic attenuation, acoustic coupling constants and ultrasonic velocities of praseodymium monopnictides PrX(X: N, P, As, Sb and Bi) along the , , in the temperature range 100-500 K using higher order elastic constants. The higher order elastic constants are evaluated using Coulomb and Born-Mayer potential with two basic parameters viz. nearest-neighbor distance and hardness parameter in the temperature range of 0-500 K. Several other mechanical and thermal parameters like bulk modulus, shear modulus, Young's modulus, Poisson ratio, anisotropic ratio, tetragonal moduli, Breazeale's nonlinearity parameter and Debye temperature are also calculated. In the present study, the fracture/toughness (B/G) ratio is less than 1.75 which implies that PrX compounds are brittle in nature at room temperature. The chosen material fulfilled Born criterion of mechanical stability. We also found the deviation of Cauchy's relation at higher temperatures. PrN is most stable material as it has highest valued higher order elastic constants as well as the ultrasonic velocity. Further, the lattice thermal conductivity using modified approach of Slack and Berman is determined at room temperature. The ultrasonic attenuation due to phonon-phonon interaction and thermoelastic relaxation mechanisms have been computed using modified Mason's approach. The results with other well-known physical properties are useful for industrial applications.

  10. Thermal properties of a ferromagnetic superconductor UGe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Tateiwa, Naoyuki [Osaka Univ., Graduate School of Engineering Science, Suita, Osaka (Japan); Kobayashi, Tatsuo C.; Amaya, Kichi [Osaka Univ., Research Center for Materials Science at Extreme Conditions, Toyonaka, Osaka (Japan); Haga, Yoshinori [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Settai, Rikio; Onuki, Yoshichika [Osaka Univ., Graduate School of Science, Toyonaka, Osaka (Japan)

    2002-11-01

    Thermal properties of a ferromagnetic superconductor UGe{sub 2} were investigated by the heat capacity measurements. The bulk nature of the superconductivity was confirmed by the observation of a peak in the heat capacity at the superconducting transition temperature T{sub SC}. From the pressure dependence of the linear heat capacity coefficient {gamma}, it is suggested that the low energy magnetic excitation near the critical point P{sub C}{sup *}, where T* becomes 0 K, might play an important role on the superconductivity. The pressure dependence of the superconducting peak and the temperature dependence of C/T above T{sub SC} suggest that the order parameter of the superconducting state might be different between the phases below and above P{sub C}{sup *}. (author)

  11. From Tomography to Material Properties of Thermal Protection Systems

    Science.gov (United States)

    Mansour, Nagi N.; Panerai, Francesco; Ferguson, Joseph C.; Borner, Arnaud; Barnhardt, Michael; Wright, Michael

    2017-01-01

    A NASA Ames Research Center (ARC) effort, under the Entry Systems Modeling (ESM) project, aims at developing micro-tomography (micro-CT) experiments and simulations for studying materials used in hypersonic entry systems. X-ray micro-tomography allows for non-destructive 3D imaging of a materials micro-structure at the sub-micron scale, providing fiber-scale representations of porous thermal protection systems (TPS) materials. The technique has also allowed for In-situ experiments that can resolve response phenomena under realistic environmental conditions such as high temperature, mechanical loads, and oxidizing atmospheres. Simulation tools have been developed at the NASA Ames Research Center to determine material properties and material response from the high-fidelity tomographic representations of the porous materials with the goal of informing macroscopic TPS response models and guiding future TPS design.

  12. Microfabricated thermal conductivity sensor: a high resolution tool for quantitative thermal property measurement of biomaterials and solutions.

    Science.gov (United States)

    Liang, Xin M; Ding, Weiping; Chen, Hsiu-hung; Shu, Zhiquan; Zhao, Gang; Zhang, Hai-feng; Gao, Dayong

    2011-10-01

    Obtaining accurate thermal properties of biomaterials plays an important role in the field of cryobiology. Currently, thermal needle, which is constructed by enclosing a manually winded thin metal wire with an insulation coating in a metallic sheath, is the only available device that is capable of measuring thermal conductivity of biomaterials. Major drawbacks, such as macroscale sensor size, lack of versatile format to accommodate samples with various shapes and sizes, neglected effects of heat transfer inside the probe and thermal contact resistance between the sensing element and the probe body, difficult to mass produce, poor data repeatability and reliability and labor-intense sensor calibration, have significantly reduced their potential to be an essential measurement tool to provide key thermal property information of biological specimens. In this study, we describe the development of an approach to measure thermal conductivity of liquids and soft bio-tissues using a proof-of-concept MEMS based thermal probe. By employing a microfabricated closely-packed gold wire to function as the heater and the thermistor, the presented thermal sensor can be used to measure thermal conductivities of fluids and natural soft biomaterials (particularly, the sensor may be directly inserted into soft tissues in living animal/plant bodies or into tissues isolated from the animal/plant bodies), where other more standard approaches cannot be used. Thermal standard materials have been used to calibrate two randomly selected thermal probes at room temperature. Variation between the obtained system calibration constants is less than 10%. By incorporating the previously obtained system calibration constant, three randomly selected thermal probes have been successfully utilized to measure the thermal conductivities of various solutions and tissue samples under different temperatures. Overall, the measurements are in agreement with the recommended values (percentage error less than 5

  13. Thermal properties of radiolytically synthesized PVA/Ag nanocomposites

    Directory of Open Access Journals (Sweden)

    Krklješ Aleksandra N.

    2007-01-01

    Full Text Available The radiolytic method was used to synthesize two types of nanocomposites with silver, PVA/Ag by film casting and PVA hydrogel/Ag nanocomposites. This method is particularly suitable for generating metal nanoparticles in solution. The radiolytic species (solvated electrons and secondary radicals exhibit strong reducing properties such that metal ions are reduced at each encounter. Metal atoms then tend to grow into larger clusters. It was found that solid or swollen polymers are able to stabilize small crystallites against spontaneous growth via aggregation. Using differential scanning calorimetry (DSC, the melting behavior and kinetics of the PVA/Ag nanocomposites were investigated and compared to those of pure PVA. The melting as well as crystallization behavior of polymers is crucial because it governs the thermal properties, impact resistance and stress strain properties. Understanding the melting behavior is significant not only to tailor the properties of nanocomposites but to investigate the interactions between the constituents. The DSC curves of pure PVA and prepared nanocomposites show only one melting peak between 175 and 230°C, indicating that the melting behavior of these two systems are analogous. In both cases, with increasing heating rate, the melting peak shifts to a higher temperature, but with increasing Ag content the peak melting temperature is lower. When specimens are heated at high heating rate, the motion of PVA molecular chains cannot follow the heating temperature on time due to the influence of heat hysteresis, which leads to a higher peak melting temperature. When Ag nanoparticles are added they increase the heat transfer among the PVA molecular chains decreasing the melting temperature. The Ag content is a major factor affecting the degree of crystallinity. It was observed that at low nanofiller content, up to the 0.5 wt%, the degree of crystallinity of the nanocomposites increased, while at a higher content the

  14. CREEP LIFE ASSESSMENT OF 2.25Cr-1Mo PIPING STEEL AND OF ITS SIMULATED HAZ MATERIAL

    OpenAIRE

    Kazunari, FUJIYAMA; Takashi, ISEKI; Atsushi, KOMATSU; Nagatoshi, OKABE; Heavy Apparatus Engineering Laboratory, Toshiba Corporation; Keihin Product Operations, Toshiba Corporation; Keihin Product Operations, Toshiba Corporation; Department of Mechanical Engineering, Ehime University

    1997-01-01

    A creep life assessment method was proposed for base metal and HAZ of 2.25Cr-1Mo steel STPA24 used in high temperature steam piping of fossil power plants. Microstructuiral observations and hardness measurements were carried out for base metal and simulated HAZ after thermal aging and creep testing. Simulated HAZ material showed significant softening during thermal and creep exposure, but base metal showed less softening. Hardness equation was established based on the kinetics of carbide coar...

  15. Verification of the thermal insulation properties and determination the optimal position of the reflective thermal insulation layer in the wood based envelope

    Directory of Open Access Journals (Sweden)

    Labovský Martin

    2016-06-01

    Full Text Available To achieve thinner wood based envelope is necessary look for an alternative thermal insulation material, which will have the best possible thermal insulation properties while maintaining affordability. One such material is also reflective thermal insulation layer, but it is necessary to verify the thermal insulation properties and determine the optimal position in the wood based envelope.

  16. Computation of Effective Steady-State Creep of Porous Ni–YSZ Composites with Reconstructed Microstructures

    DEFF Research Database (Denmark)

    Kwok, Kawai; Jørgensen, Peter Stanley; Frandsen, Henrik Lund

    2015-01-01

    This paper investigates the effective steady-state creep response of porous Ni–YSZ composites used in solid oxide fuel cell applications by numerical homogenization based on three-dimensional microstructural reconstructions and steadystate creep properties of the constituent phases. The Ni phase...... is found to carry insignificant stress in the composite and has a negligible role in the effective creep behavior. Thus, when determining effective creep, porous Ni–YSZ composites can be regarded as porous YSZ in which the Ni phase is counted as additional porosity. The stress exponents of porous YSZ...... are the same as that of dense YSZ, but the effective creep rate increases by a factor of 8–10 due to porosity. The relationship of creep rate and volume fraction of YSZ computed by numerical homogenization is underestimated by most existing analytical models. The Ramakrishnan–Arunchalam creep model provides...

  17. Thermal Storage Properties of Molten Nitrate Salt-Based Nanofluids with Graphene Nanoplatelets

    National Research Council Canada - National Science Library

    Xie, Qiangzhi; Zhu, Qunzhi; Li, Yan

    2016-01-01

    .... For both solar salt and resultant nanofluids, differential scanning calorimetry was employed to measure the thermal storage properties, including characteristic temperatures of phase change, startup...

  18. Experimental study and modelling of high temperature creep flow and damage behaviour of 9Cr1Mo-NbV steel weldments; Etude experimentale et modelisation, du comportement, de l'endommagement et de la rupture en fluage a haute temperature de joint soudes en acier 9Cr1Mo-NbV

    Energy Technology Data Exchange (ETDEWEB)

    Gaffard, V

    2004-12-15

    Chromium martensitic stainless steels are under development since the 70's with the prospect of using them as structural components in thermal and nuclear power plants. The modified 9Cr1Mo-NbV steel is already used, especially in England and Japan, as a material for structural components in thermal power plants where welding is a commonly used joining technique. New generations of chromium martensitic stainless steels with improved mechanical properties for high pressure and temperature use are currently under development. However, observations of several in-service premature failures of welded components in 9Cr1Mo-NbV steel, outline a strong need for understanding the high temperature creep flow and damage behaviour of 9Cr1Mo-NbV steels and weldments. The present study aimed at experimentally determining and then modelling the high temperature creep flow and damage behaviour of both 9Cr1Mo-NbV steels and weldments (typically in the temperature range from 450 C to 650 C). The base metal was first studied as the reference material. It was especially evidenced that tempered chromium martensitic steels exhibit a change in both creep flow and damage behaviour for long term creep exposure. As a consequence, the classically performed extrapolation of 1,000 hours creep data to 100,000 hours creep lifetime predictions might be very hazardous. Based on experimental observations, a new model, integrating and coupling multiple creep flow and damage mechanisms, was developed in the framework of the mechanics of porous media. It was then successfully used to represent creep flow and damage behaviour of the base metal from high to low stress levels even for complex multiaxial loading conditions. Although the high temperature creep properties of the base metal are quite good, the occurrence of premature failure in weldments in high temperature creep conditions largely focused the attention of the scientific community. The lower creep strength of the weld component was also

  19. Optical properties of mineral dust aerosol in the thermal infrared

    Science.gov (United States)

    Köhler, Claas H.

    2017-02-01

    The optical properties of mineral dust and biomass burning aerosol in the thermal infrared (TIR) are examined by means of Fourier Transform Infrared Spectrometer (FTIR) measurements and radiative transfer (RT) simulations. The measurements were conducted within the scope of the Saharan Mineral Dust Experiment 2 (SAMUM-2) at Praia (Cape Verde) in January and February 2008. The aerosol radiative effect in the TIR atmospheric window region 800-1200 cm-1 (8-12 µm) is discussed in two case studies. The first case study employs a combination of IASI measurements and RT simulations to investigate a lofted optically thin biomass burning layer with emphasis on its potential influence on sea surface temperature (SST) retrieval. The second case study uses ground based measurements to establish the importance of particle shape and refractive index for benchmark RT simulations of dust optical properties in the TIR domain. Our research confirms earlier studies suggesting that spheroidal model particles lead to a significantly improved agreement between RT simulations and measurements compared to spheres. However, room for improvement remains, as the uncertainty originating from the refractive index data for many aerosol constituents prohibits more conclusive results.

  20. Healing mechanism of nanocrack in nanocrystalline metals during creep process

    Science.gov (United States)

    Meraj, Md.; Pal, Snehanshu

    2017-02-01

    Molecular dynamics (MD) simulation has been performed to demonstrate the fate of cracks present inside ultrafine-grained (grain size 7 nm) nanocrystalline Ni specimen during creep deformation process. It is observed that internal nanocracks are healed within a few pico-seconds of initial part of creep process even if the constant applied load on the specimen is tensile in nature and acting normal to crack surface in the outward direction. This kind of crack-healing phenomenon can be accounted by the facts such as stress-driven grain boundary migration, grain boundary diffusion and amorphization of specimen as per results obtained from this MD simulation. This MD study also reveals that the presence of nanocrack inside ultrafine-grained NC Ni in fact slightly improves creep properties and such enhancement of the creep properties is intensified as the size of internal crack increases.

  1. Improved methods of creep-fatigue life assessment of components

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, Alfred; Berger, Christina [Inst. fuer Werkstoffkunde (IfW), Technische Univ. Darmstadt (Germany)

    2009-07-01

    The improvement of life assessment methods contributes to a reduction of efforts at design and an effective long term operation of high temperature components, reduces technical risk and increases high economical advantages. Creep-fatigue at multi-stage loading, covering cold start, warm start and hot start cycles in typical loading sequences e.g. for medium loaded power plants, was investigated here. At hold times creep and stress relaxation, respectively, lead to an acceleration of crack initiation. Creep fatigue life time can be calculated by a modified damage accumulation rule, which considers the fatigue fraction rule for fatigue damage and the life fraction rule for creep damage. Mean stress effects, internal stress and interaction effects of creep and fatigue are considered. Along with the generation of advanced creep data, fatigue data and creep fatigue data as well scatter band analyses are necessary in order to generate design curves and lower bound properties inclusive. Besides, in order to improve lifing methods the enhancement of modelling activities for deformation and life time are important. For verification purposes, complex experiments at variable creep conditions as well as at creep fatigue interaction under multi-stage loading are of interest. Generally, the development of methods to transfer uniaxial material properties to multiaxial loading situations is a current challenge. For specific design purposes, a constitutive material model is introduced which is implemented as an user subroutine for Finite Element applications due to start-up and shut-down phases of components. Identification of material parameters have been performed by Neural Networks. (orig.)

  2. Thermal properties of high temperature vacuum receivers used for parabolic trough solar thermal power system

    Directory of Open Access Journals (Sweden)

    Qinghe Yu

    2017-08-01

    Full Text Available The receiver's emittance and vacuum pressure are the two of great significance issues on the heat-loss which is the main factor reducing the efficiency of the parabolic though systems. In this paper, the thermal steady-state equilibrium method was used to test the receivers’ heat-loss. The receivers with increasing emittance were tested to study the variation of heat-loss. Meanwhile, the variable vacuum pressure in the annulus that affects the efficiency of the system was investigated. The influence of vacuumizing rate and getters on the vacuum pressure and heat-loss were discussed. The result shows that the emittance and vacuum pressure affect the receiver's heat-loss dramatically, and the emittance is the major influence factor on the thermal properties. The receiver with 0.08 emittance and 10−3 Pa vacuum pressure has a satisfactory heat-loss of 215.6 W/m at 400 °C. The analysis further reveals that the synergistic effect of both emittance and vacuum pressure on the heat-loss can be reflected by the packaging temperature of the glass tube, and a fitting formula has been established to estimate the receivers’ heat-loss according to the packaging temperature of the glass tube.

  3. Creep of Two-Phase Microstructures for Microelectronic Applications

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, Heidi Linch [Univ. of California, Berkeley, CA (United States)

    1998-12-01

    The mechanical properties of low-melting temperature alloys are highly influenced by their creep behavior. This study investigates the dominant mechanisms that control creep behavior of two-phase, low-melting temperature alloys as a function of microstructure. The alloy systems selected for study were In-Ag and Sn-Bi because their eutectic compositions represent distinctly different microstructure.” The In-Ag eutectic contains a discontinuous phase while the Sn-Bi eutectic consists of two continuous phases. In addition, this work generates useful engineering data on Pb-free alloys with a joint specimen geometry that simulates microstructure found in microelectronic applications. The use of joint test specimens allows for observations regarding the practical attainability of superplastic microstructure in real solder joints by varying the cooling rate. Steady-state creep properties of In-Ag eutectic, Sn-Bi eutectic, Sn-xBi solid-solution and pure Bi joints have been measured using constant load tests at temperatures ranging from O°C to 90°C. Constitutive equations are derived to describe the steady-state creep behavior for In-Ageutectic solder joints and Sn-xBi solid-solution joints. The data are well represented by an equation of the form proposed by Dom: a power-law equation applies to each independent creep mechanism. Rate-controlling creep mechanisms, as a function of applied shear stress, test temperature, and joint microstructure, are discussed. Literature data on the steady-state creep properties of Sn-Bi eutectic are reviewed and compared with the Sn-xBi solid-solution and pure Bi joint data measured in the current study. The role of constituent phases in controlling eutectic creep behavior is discussed for both alloy systems. In general, for continuous, two-phase microstructure, where each phase exhibits significantly different creep behavior, the harder or more creep resistant phase will dominate the creep behavior in a lamellar microstructure. If a

  4. Electronic and Thermal Properties of Puckered Orthorhombic Materials

    Science.gov (United States)

    Fei, Ruixiang

    Puckered orthorhombic crystals, such as black phosphorus and group IV monochalcogenides, are attracting tremendous attention because of their new exotic properties, which are of great interests for fundamental science and novel applications. Unlike those well studied layered hexagonal materials such as graphene and transition metal dichalcogenides, the puckered orthorhombic crystals possess highly asymmetrical in-plane crystal structures. Understanding the unique properties emerginge from their low symmetries is an intriguing and useful process, which gives insight into experimental observation and sheds light on manipulating their properties. In this thesis, we study and predict various properties of orthorhombic materials by using appropriate theoretical techniques such as first-principles calculations, Monte-Carlo simulations, and k · p models. In the first part of the thesis, we deal with the anisotropic electric and thermal properties of a typical puckered orthorhombic crystal, black phosphorus. We first study the electric properties in monolayer and few-layer black phosphorus, where the unique, anisotropic electrical conductance is founded. Furthermore, we find that the anisotropy of the electrical conductance can be rotated by 90° through applying appropriate uniaxial or biaxial strain. Beyond electrical conductance, we, for the first time, predict that the thermal conductance of black phosphorus is also anisotropic and, particularly, the preferred conducting direction is perpendicular to the preferred electrical conducting direction. Within the reasonable estimation regime, the thermoelectric figure of merit (ZT) ultimately reaches 1 at room temperature using only moderate doping. The second part of this thesis focuses on the electronic polarization of non-centrosymmetric puckered materials-group IV monochalcogenide. We propose that monolayer group IV monochalcogenides are a new class of two-dimensional (2D) ferroelectric materials with spontaneous in

  5. Technique for measuring irradiation creep in polycrystalline SiC fibers

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Hamilton, M.L.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-10-01

    A bend stress relaxation (BSR) test has been designed to examine irradiation enhanced creep in polycrystalline SiC fibers being considered for fiber reinforcement in SiC/SiC composite. Thermal creep results on Nicalon-CG and Hi-Nicalon were shown to be consistent with previously published data with Hi-Nicalon showing about a 100{degrees}C improvement in creep resistance. Preliminary data was also obtained on Nicalon-S that demonstrated that its creep resistance is greater than that of Hi-Nicalon.

  6. Review of data on irradiation creep of monolithic SiC

    Energy Technology Data Exchange (ETDEWEB)

    Garner, F.A.; Youngblood, G.E.; Hamilton, M.L. [Pacific Northwest National Laboratory, Richland, WA (United States)

    1996-04-01

    An effort is now underway to design an irradiation creep experiment involving SiC composites to SiC fibers. In order to successfully design such an experiment, it is necessary to review and assess the available data for monolithic SiC to establish the possible bounds of creep behavior for the composite. The data available show that monolithic SiC will indeed creep at a higher rate under irradiation compared to that of thermal creep, and surprisingly, it will do so in a temperature-dependant manner that is typical of metals.

  7. Vortex creep and the internal temperature of neutron stars. I - General theory

    Science.gov (United States)

    Alpar, M. A.; Pines, D.; Anderson, P. W.; Shaham, J.

    1984-01-01

    The theory of a neutron star superfluid coupled to normal matter via thermal creep against pinning forces is developed in some detail. General equations of motion for a pinned rotating superfluid and their form for vortex creep are given. Steady state creep and the way in which the system approaches the steady state are discussed. The developed formalism is applied to the postglitch relaxation of a pulsar, and detailed models are developed which permit explicit calculation of the postglitch response. The energy dissipation associated with creep and glitches is considered.

  8. Multiscale Modeling of Carbon/Phenolic Composite Thermal Protection Materials: Atomistic to Effective Properties

    Science.gov (United States)

    Arnold, Steven M.; Murthy, Pappu L.; Bednarcyk, Brett A.; Lawson, John W.; Monk, Joshua D.; Bauschlicher, Charles W., Jr.

    2016-01-01

    Next generation ablative thermal protection systems are expected to consist of 3D woven composite architectures. It is well known that composites can be tailored to achieve desired mechanical and thermal properties in various directions and thus can be made fit-for-purpose if the proper combination of constituent materials and microstructures can be realized. In the present work, the first, multiscale, atomistically-informed, computational analysis of mechanical and thermal properties of a present day - Carbon/Phenolic composite Thermal Protection System (TPS) material is conducted. Model results are compared to measured in-plane and out-of-plane mechanical and thermal properties to validate the computational approach. Results indicate that given sufficient microstructural fidelity, along with lowerscale, constituent properties derived from molecular dynamics simulations, accurate composite level (effective) thermo-elastic properties can be obtained. This suggests that next generation TPS properties can be accurately estimated via atomistically informed multiscale analysis.

  9. Soil thermal properties at Kalpakkam in coastal south India

    Indian Academy of Sciences (India)

    . ... two locations in Kalpakkam, coastal southeast India. The data were analysed to estimate soil thermal di usivity, thermal conductivity, volumetric heat capacity and soil heat ux. This paper describes the results and discusses their implications.

  10. Investigation of the relationship between negative thermal expansion and other thermal properties of framework oxides

    Science.gov (United States)

    Kennedy, Catherine Anne

    2005-07-01

    Several framework solids exhibit negative thermal expansion (NTE) over a wide temperature range, e.g. ZrW2O 8 exhibits NTE from 0.3 to 1050 K. Although NTE is observed in other materials, it occurs over much smaller temperature ranges. NTE in ZrW 2O8 is associated with the low-energy modes corresponding to the correlated vibrations of the [WO4]2- tetrahedra and their three nearest [ZrO6]8- octahedra. This involves translation as well as libration, and low-energy optic modes play a central role. Thermal expansion and resistance to heat flow both originate in the anharmonic terms of the lattice dynamics. The influence of NTE in these framework materials on thermal conductivity was investigated by measuring thermal properties (thermal conductivity, kappa, from ca. 2 to 390 K and heat capacity, CP, from ca. 0.4 to 300 K) of ZrW2O8 and HfMo2O8. Literature values of the CP of ZrW2 O8 showed more disagreement than one might expect. In this research, it was found that the discrepancy could be due to low thermal conductivity of ZrW2O8. The CP of HfMo 2O8 is reported here for the first time. Analysis of CP reveals low-frequency modes that are not present in the binary oxides. A calculation of CP of HfMo 2O8 from HfMo2O8, ZrW2O 8, and ZrMo2O8 fits experimental C P of HfMo2O8 better since each AB 2O8 compound exhibits NTE and therefore has the low-frequency modes attributed to NTE. The thermodynamic calculations of the production of ZrW2O8 and HfMo2O8 from the appropriate oxides confirm that both are thermodynamically unstable with respect to the oxides. The kappa values of both ZrW2O8 and HfMo 2O8 are exceptionally low: kappadense(ZrW 2O8) is 0.91 W m-1 K-1 and kappadense(HfMo2O8) is 0.64 W m-1 K-1 at T = 300 K. Temperature-dependent kappa values of ZrW2O8 and HfMo2O8 are glass-like, despite polycrystalline morphology. Through consideration of the CP, phonon mean free path, and Gruneisen parameter, the kappa behavior is attributed to the low-frequency modes which are also

  11. Effect of Nanoparticles on the Morphology, Thermal, and Electrical Properties of Low-Density Polyethylene after Thermal Aging

    Directory of Open Access Journals (Sweden)

    Youyuan Wang

    2017-10-01

    Full Text Available This paper investigates the morphology, thermal, and electrical properties of LDPE (low-density polyethylene-based nanocomposites after thermal aging. The FTIR (Fourier transform infrared spectroscopy spectra results show that thermo-oxidative reactions occur in neat LDPE and LDPE/SiO2 nanocomposites when the aging time is 35 days and in LDPE/MgO nanocomposites when the aging time is 77 days. Specifically, LDPE/MgO nanocomposites delay the appearance of thermo-oxidative reactions, showing anti-thermal aging ability. Furthermore, nanocomposites present lower onset degradation temperature than neat LDPE, showing better thermal stabilization. With regard to the electrical properties, nanocomposites maintain the ability to suppress space charge accumulation after thermal aging. Additionally, in comparison with SiO2 nanocomposites and neat LDPE, the permittivity of LDPE/MgO nanocomposites changes slightly after thermal aging. It is concluded that LDPE/MgO nanocomposites have better insulation properties than neat LDPE after thermal aging, which may be caused by the interface introduced by the nanoparticles.

  12. Effect of Nanoparticles on the Morphology, Thermal, and Electrical Properties of Low-Density Polyethylene after Thermal Aging.

    Science.gov (United States)

    Wang, Youyuan; Wang, Can; Zhang, Zhanxi; Xiao, Kun

    2017-10-12

    This paper investigates the morphology, thermal, and electrical properties of LDPE (low-density polyethylene)-based nanocomposites after thermal aging. The FTIR (Fourier transform infrared spectroscopy) spectra results show that thermo-oxidative reactions occur in neat LDPE and LDPE/SiO₂ nanocomposites when the aging time is 35 days and in LDPE/MgO nanocomposites when the aging time is 77 days. Specifically, LDPE/MgO nanocomposites delay the appearance of thermo-oxidative reactions, showing anti-thermal aging ability. Furthermore, nanocomposites present lower onset degradation temperature than neat LDPE, showing better thermal stabilization. With regard to the electrical properties, nanocomposites maintain the ability to suppress space charge accumulation after thermal aging. Additionally, in comparison with SiO₂ nanocomposites and neat LDPE, the permittivity of LDPE/MgO nanocomposites changes slightly after thermal aging. It is concluded that LDPE/MgO nanocomposites have better insulation properties than neat LDPE after thermal aging, which may be caused by the interface introduced by the nanoparticles.

  13. Thermal Insulating Properties of Straw-Filled Environmentally Friendly Building Materials

    Science.gov (United States)

    Petkova-Slipets, Rositsa; Zlateva, Penka

    2017-06-01

    The paper presents results of a research for determination of a few general thermal-physical properties of environmentally friendly building materials made by clay, sand and straw. The aim of this study is to establish their heat insulating and energy-efficient capacity. All specific measurements were carried out by using the newest generation thermal conductivity analyser Mathis TCi. The results showed that the studied composite materials are good thermal insulators with thermal conductivity less than 0.5 W/m.K, which depends on the straw amount. Even less than 0.5 wt.% straw reflects on the insulating properties by decreasing the thermal conductivity coefficient with nearly 50 %.

  14. Properties of Starch Based Foams Made by Thermal Pressure Forming

    Directory of Open Access Journals (Sweden)

    J. Štancl

    2008-01-01

    Full Text Available Packaging materials based on expanded polystyrene can be substituted by biodegradable foam, manufactured by direct or indirect electrical heating of a potato starch suspension in a closed mold. This paper deals with an experimental evaluation of selected properties of potato starch and starch foam related to this technology: density, specific heat capacity and specific electrical conductivity of a water suspension of potato starch within the temperature range up to 100 °C, and mass fraction from 5 to 65 %. The electric conductivity and heat capacity changes were observed during direct ohmic heating of a starch suspension between electrodes in a closed cell (feeding voltage 100 V, frequency 50 Hz. Specific electric conductivity increases with temperature, with the exception of the gelatinization region at 60 to 70 °C, and decreases with increasing concentration of starch (the temperature and concentration dependencies were approximated using the Lorentz equation. Direct ohmic heating is restricted by a significant decrease in effective electrical conductivity above a temperature of 100 °C, when evaporated steam worsens the contact with the electrodes. Experiments show that when direct ohmic heating is not combined with indirect contact heating, only 20 % of the water can be evaporated from manufactured samples and the starch foam is not fully formed. This is manifested by only a slight expansion of the heated sample. Only the indirect contact heating from the walls of the mold, with the wall temperature above 180 °C, forms a fixed porous structure (expansion of about 300 % and a crust, ensuring suitable mechanical and thermal insulation properties of the manufactured product. The effective thermal conductivity of the foamed product (sandwich plates with a porous core and a compact crust was determined by the heated wire method, while the porosity of the foam and the thickness of the crust were evaluated by image analysis of colored cross

  15. Hydrogeological properties of the thermal source Rimske Toplice

    Directory of Open Access Journals (Sweden)

    Andrej Lapanje

    2002-12-01

    Full Text Available The Rimske Toplice thermal resort has been sadly abandoned since 1991. However, the mechanism of the thermal source is again earning greater attention of general public through recent efforts of Spa revitalisation. In this paper the history of thermal water research inthe area is presented along with results of the research conducted in 2001 and 2002.

  16. Mechanical, Hygric and Thermal Properties of Flue Gas Desulfurization Gypsum

    Directory of Open Access Journals (Sweden)

    P. Tesárek

    2004-01-01

    Full Text Available The reference measurements of basic mechanical, thermal and hygric parameters of hardened flue gas desulfurization gypsum are carried out. Moisture diffusivity, water vapor diffusion coefficient, thermal conductivity, volumetric heat capacity and linear thermal expansion coefficient are determined with the primary aim of comparison with data obtained for various types of modified gypsum in the future. 

  17. Thermophysical and mechanical properties of Fe-(8-9)%Cr reduced activation steels

    Energy Technology Data Exchange (ETDEWEB)

    Zinkle, S.J.; Robertson, J.P.; Klueh, R.L. [Oak Ridge National Lab., TN (United States)

    1998-09-01

    The key thermophysical and mechanical properties for 8--9%Cr reduced activation ferritic/martensitic steels are summarized, including temperature-dependent tensile properties in the unirradiated and irradiated conditions, stress-rupture behavior, elastic constants, thermal conductivity, thermal expansion, specific heat, and ductile-to-brittle transition temperature. The estimated lower and upper temperatures limits for structural applications are 250 and 550 C due to radiation hardening/embrittlement and thermal creep considerations, respectively.

  18. Simultaneous Measurement of Thermal Diffusivity and Thermal Conductivity by Means of Inverse Solution for One-Dimensional Heat Conduction (Anisotropic Thermal Properties of CFRP for FCEV)

    Science.gov (United States)

    Kosaka, Masataka; Monde, Masanori

    2015-11-01

    For safe and fast fueling of hydrogen in a fuel cell electric vehicle at hydrogen fueling stations, an understanding of the heat transferred from the gas into the tank wall (carbon fiber reinforced plastic (CFRP) material) during hydrogen fueling is necessary. Its thermal properties are needed in estimating heat loss accurately during hydrogen fueling. The CFRP has anisotropic thermal properties, because it consists of an adhesive agent and layers of the CFRP which is wound with a carbon fiber. In this paper, the thermal diffusivity and thermal conductivity of the tank wall material were measured by an inverse solution for one-dimensional unsteady heat conduction. As a result, the thermal diffusivity and thermal conductivity were 2.09 × 10^{-6}{ m}2{\\cdot }{s}^{-1} and 3.06{ W}{\\cdot }{m}{\\cdot }^{-1}{K}^{-1} for the axial direction, while they were 6.03 × 10^{-7} {m}2{\\cdot }{s}^{-1} and 0.93 {W}{\\cdot }{m}^{-1}{\\cdot }{K}^{-1} for the radial direction. The thermal conductivity for the axial direction was about three times higher than that for the radial direction. The thermal diffusivity shows the same trend in both directions because the thermal capacity, ρ c, is independent of direction, where ρ is the density and c is the heat capacity.

  19. Thermal capacitator design rationale. Part 1: Thermal and mechanical property data for selected materials potentially useful in thermal capacitor design and construction

    Science.gov (United States)

    Bailey, J. A.; Liao, C. K.

    1975-01-01

    The thermal properties of paraffin hydrocarbons and hydrocarbon mixtures which may be used as the phase change material (PCM) in thermal capacitors are discussed. The paraffin hydrocarbons selected for consideration are those in the range from C11H24 (n-Undecane) to C20H42 (n-Eicosane). A limited amount of data is included concerning other properties of paraffin hydrocarbons and the thermal and mechanical properties of several aluminum alloys which may find application as constructional materials. Data concerning the melting temperature, transition temperature, latent heat of fusion, heat of transition, specific heat, and thermal conductivity of pure and commercial grades of paraffin hydrocarbons are given. An index of companies capable of producing paraffin hydrocarbons and information concerning the availability of various grades (purity levels) is provided.

  20. Creep Behavior of ABS Polymer in Temperature-Humidity Conditions

    Science.gov (United States)

    An, Teagen; Selvaraj, Ramya; Hong, Seokmoo; Kim, Naksoo

    2017-04-01

    Acrylonitrile-Butadiene-Styrene (ABS), also known as a thermoplastic polymer, is extensively utilized for manufacturing home appliances products as it possess impressive mechanical properties, such as, resistance and toughness. However, the aforementioned properties are affected by operating temperature and atmosphere humidity due to the viscoelasticity property of an ABS polymer material. Moreover, the prediction of optimum working conditions are the little challenging task as it influences the final properties of product. This present study aims to develop the finite element (FE) models for predicting the creep behavior of an ABS polymeric material. In addition, the material constants, which represent the creep properties of an ABS polymer material, were predicted with the help of an interpolation function. Furthermore, a comparative study has been made with experiment and simulation results to verify the accuracy of developed FE model. The results showed that the predicted value from FE model could agree well with experimental data as well it can replicate the actual creep behavior flawlessly.

  1. Thermal properties of bodies in fractal and cantorian physics

    Energy Technology Data Exchange (ETDEWEB)

    Zmeskal, Oldrich [Institute of Physical and Applied Chemistry, Brno University of Technology, Purkynova 118, 612 00 Brno (Czech Republic)] e-mail: zmeskal@fch.vutbr.cz; Buchnicek, Miroslav [Institute of Physical and Applied Chemistry, Brno University of Technology, Purkynova 118, 612 00 Brno (Czech Republic); Vala, Martin [Institute of Physical and Applied Chemistry, Brno University of Technology, Purkynova 118, 612 00 Brno (Czech Republic)

    2005-09-01

    fractal dimensions (the energy density is real-valued). Again, it is shown that above the critical temperature (kT > K h c) and for fractal dimension D {sub m} > 2.0269 the results are comparable to the kinetics theory of real (ideal) gas (van der Waals equation of state, compressibility factor, Boyle's temperature). For the critical temperature (K h c = kT {sub r}) the compressibility factor gains Z = 1 (except for the ideal gas case D = 3) also for the fractal dimension D = 1/{phi} = 1.618033989, where {phi} is the golden mean value of the El Naschie's golden mean field theory. To determine the minimum it is also possible to employ the Lambert's W- Function u(A) = A + W[-Aexp(-A)], whereA {approx} 0.6779 and u {approx} -0.7330. The thermal properties of fractal structures (thermal capacity, thermal conductivity, diffusivity) and additional parameters (enthalpy, entropy, etc.) will be defined using the mathematic apparatus in the future. Good agreement of the fractal model with experimental data is documented on the compressibility factor of various gases.

  2. Investigation of Thermal and Electrical Properties for Conductive Polymer Composites

    Science.gov (United States)

    Juwhari, Hassan K.; Abuobaid, Ahmad; Zihlif, Awwad M.; Elimat, Ziad M.

    2017-10-01

    This study addresses the effects of temperature ranging from 300 K to 400 K on thermal ( κ) and electrical ( σ) conductivities, and Lorenz number ( L) for different conductive polymeric composites (CPCs), as tailoring the ratios between both conductivities of the composites can be influential in the design optimization of certain thermo-electronic devices. Both κ and σ were found to have either a linear or a nonlinear (2nd and 3rd degree polynomial function) increasing behavior with increased temperatures, depending on the conduction mechanism occurring in the composite systems studied. Temperature-dependent behavior of L tends to show decreasing trends above 300 K, where at 300 K the highest and the lowest values were found to be 3 × 103 W Ω/K2 for CPCs containing iron particles and 3 × 10-2 W Ω/K2 for CPCs-containing carbon fibers respectively. Overall, temperature-dependent behavior of κ/ σ and L can be controlled by heterogeneous structures produced via mechanical-molding-compression. These structures are mainly responsible for energy-transfer processes or transport properties that take place by electrons and phonons in the CPCs' bulks. Hence, the outcome is considered significant in the development process of high performing materials for the thermo-electronic industry.

  3. Thermal Properties of Trogamid by Conventional and Fast Scanning Calorimetry

    Science.gov (United States)

    Cebe, Peggy; Merfeld, John; Mao, Bin; Wurm, Andreas; Zhuravlev, Evgeny; Schick, Christoph

    We use conventional slow scan rate differential scanning calorimetry, and fast scanning chip-based calorimetry (FSC), to investigate the crystallization and melting behavior of Trogamid, a chemical relative of nylon. Fundamental thermal properties of Trogamid were studied, including the melt crystallization kinetics, heat of fusion, and the solid and liquid state heat capacities. Using slow scan DSC (at 5 K/min), Trogamid displays a glass transition relaxation process at ~133 C, melting endotherm peak at 250 C, and is stable upon repeated heating to 310 C. When using slow scan DSC, the isothermal melt crystallization temperatures were restricted to 225 C or above. Trogamid crystallizes rapidly from the melt and conventional calorimetry is unable to cool sufficiently fast to prevent nucleation and crystal growth prior to stabilization at lower crystallization temperatures. Using FSC we were able to cool nano-gram sizes samples at 2000 K/s to investigate a much lower range of melt crystallization temperatures, from 205-225 C. The experimental protocol for performing FSC on semicrystalline polymers to obtain liquid state heat capacity data will be presented. National Science Foundation, Polymers Program DMR-1206010; DAAD; Tufts Faculty Supported Leave.

  4. Thermally and Electrically Conductive Nanopapers from Reduced Graphene Oxide: Effect of Nanoflakes Thermal Annealing on the Film Structure and Properties

    Directory of Open Access Journals (Sweden)

    M. Mar Bernal

    2017-12-01

    Full Text Available In this study, we report a novel strategy to prepare graphene nanopapers from direct vacuum filtration. Instead of the conventional method, i.e., thermal annealing nanopapers at extremely high temperatures prepared from graphene oxide (GO or partially reduced GO, we fabricate our graphene nanopapers directly from suspensions of fully reduced graphene oxide (RGO, obtained after RGO and thermal annealing at 1700 °C in vacuum. By using this approach, we studied the effect of thermal annealing on the physical properties of the macroscopic graphene-based papers. Indeed, we demonstrated that the enhancement of the thermal and electrical properties of graphene nanopapers prepared from annealed RGO is strongly influenced by the absence of oxygen functionalities and the morphology of the nanoflakes. Hence, our methodology can be considered as a valid alternative to the classical approach.

  5. Effect of thermal-treatment sequence on sound absorbing and mechanical properties of porous sound-absorbing/thermal-insulating composites

    Directory of Open Access Journals (Sweden)

    Huang Chen-Hung

    2016-01-01

    Full Text Available Due to recent rapid commercial and industrial development, mechanical equipment is supplemented massively in the factory and thus mechanical operation causes noise which distresses living at home. In livelihood, neighborhood, transportation equipment, jobsite construction noises impact on quality of life not only factory noise. This study aims to preparation technique and property evaluation of porous sound-absorbing/thermal-insulating composites. Hollow three-dimensional crimp PET fibers blended with low-melting PET fibers were fabricated into hollow PET/low-melting PET nonwoven after opening, blending, carding, lapping and needle-bonding process. Then, hollow PET/low-melting PET nonwovens were laminated into sound-absorbing/thermal-insulating composites by changing sequence of needle-bonding and thermal-treatment. The optimal thermal-treated sequence was found by tensile strength, tearing strength, sound-absorbing coefficient and thermal conductivity coefficient tests of porous composites.

  6. Isothermal and aniso-thermal creep in the {alpha} phase domain, {beta} phase domain and {alpha}+{beta} two phase domain in a Zr-1%NbO alloy; Fluage isotherme et anisotherme dans les domaines monophases ({alpha} et {beta}) et biphases ({alpha} et {beta}) d'un alliage Zr-1%NbO

    Energy Technology Data Exchange (ETDEWEB)

    Kaddour, D

    2004-12-15

    The coupling between phase transformation and mechanical behaviour of a Zr-1%NbO alloy was studied using an original experimental device already used in a previous study devoted to the Zy-4 alloy. The Zr-1%NbO alloy undergoes a phase transformation {alpha} (hc) {r_reversible} (cc) typically between 750 and 1000 C. The transformation temperatures were measured in situ by using the resistivity and dilatometry techniques. The isothermal creep behaviour of fuel cladding tubes was studied, first after heating, in the {alpha} phase domain between 650 and 760 C, in the {beta} phase domain between 960 and 1100 C, as well as in the ({alpha} + {beta}) two phase domain between 800 and 900 C. The results are summarized in Ashby deformation mechanism maps. It is confirmed that the {beta} phase is much more sensitive to creep flow than the {alpha} phase. The effect of microstructure on the isothermal creep flow behaviour was then investigated by first applying a thermal cycle involving either a full or a partial transformation from {alpha} to {beta}. It was investigated both in the {alpha} phase domain, and after direct cooling into the ({alpha} + {beta}) phase domain. The behaviour in aniso-thermal conditions was finally studied at heating and cooling rates of 10 and 200 C/min. In both cases, we showed that there is no significant transformation plasticity in the stress range under investigation ({<=} 5 MPa). A finite element model using Voronoi polyhedra and eventually meshing a film of intergranular {beta} phase was used to describe the behaviour of material in the ({alpha} + {beta}) domain in various microstructural states. The model predictions are in good agreement with the experimental results for the microstructure obtained after cooling, but the model underestimates creep deformation in the as-received state. This difference is probably related to the fact that interface sliding is not taken into account in the model. (author)

  7. Comparison of the Characteristics of Solid Type and Annular Type Nuclear Fuels Using Thermoelastic-Plastic-Creep FEM

    Directory of Open Access Journals (Sweden)

    Young-Doo Kwon

    2016-01-01

    Full Text Available The purpose of this study is to compare the characteristics of two types of nuclear fuel using the finite element program of thermoelastic-plastic-creep analysis. The analyzed fuel rods are of two types, solid and annular ones, and their thermomechanical characteristics are compared. Thermoelastic-plastic-creep analyses were made using an in-house finite element analysis program that adopts the “effective-stress-function” algorithm. The temperature-dependent material properties, which were obtained from the experiments for actual nuclear reactors, are adopted. The effects of type of fuel systems are revealed in both stresses and temperature distributions. The maximum tensile and compressive hoop stress of pellet and cladding are monitored to evaluate the mechanical behavior, and the maximum temperature is used to evaluate the thermal behavior. Although the annular type of fuel has certain disadvantage, it would be used very effectively or safely in future nuclear power plants.

  8. Preparation, thermal properties and thermal reliabilities of microencapsulated n-octadecane with acrylic-based polymer shells for thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Xiaolin [Advanced Materials Institute and Clearer Production Key Laboratory, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Key Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Haidian District, Beijing 100084 (China); Song, Guolin; Chu, Xiaodong; Li, Xuezhu [Advanced Materials Institute and Clearer Production Key Laboratory, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Tang, Guoyi, E-mail: tanggy@tsinghua.edu.cn [Advanced Materials Institute and Clearer Production Key Laboratory, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Key Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Haidian District, Beijing 100084 (China)

    2013-01-10

    Highlights: Black-Right-Pointing-Pointer n-Octadecane was encapsulated by p(butyl methacrylate) (PBMA) and p(butyl acrylate). Black-Right-Pointing-Pointer Microcapsules using divinylbenzene as crosslinking agent have better quality. Black-Right-Pointing-Pointer Microcapsule with butyl methacrylate-divinylbenzene has highest latent heat. Black-Right-Pointing-Pointer Microcapsule with butyl methacrylate-divinylbenzene has greatest thermal stability. Black-Right-Pointing-Pointer Phase change temperatures and enthalpies of the microcapsules varied little after thermal cycle. - Abstract: Microencapsulation of n-octadecane with crosslinked p(butyl methacrylate) (PBMA) and p(butyl acrylate) (PBA) as shells for thermal energy storage was carried out by a suspension-like polymerization. Divinylbenzene (DVB) and pentaerythritol triacrylate (PETA) were employed as crosslinking agents. The surface morphologies of the microencapsulated phase change materials (microPCMs) were studied by scanning electron microscopy (SEM). Thermal properties, thermal reliabilities and thermal stabilities of the as-prepared microPCMs were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The microPCMs prepared by using DVB exhibit greater heat capacities and higher thermal stabilities compared with those prepared by using PETA. The thermal resistant temperature of the microPCM with BMA-DVB polymer was up to 248 Degree-Sign C. The phase change temperatures and latent heats of all the as-prepared microcapsules varied little after 1000 thermal cycles.

  9. Behaviour of Epoxy Silica Nanocomposites Under Static and Creep Loading

    Science.gov (United States)

    Constantinescu, Dan Mihai; Picu, Radu Catalin; Sandu, Marin; Apostol, Dragos Alexandru; Sandu, Adriana; Baciu, Florin

    2017-12-01

    Specific manufacturing technologies were applied for the fabrication of epoxy-based nanocomposites with silica nanoparticles. For dispersing the fillers in the epoxy resin special equipment such as a shear mixer and a high energy sonicator with temperature control were used. Both functionalized and unfunctionalized silica nanoparticles were added in three epoxy resins. The considered filling fraction was in most cases 0.1, 0.3 and 0.5 wt%.. The obtained nanocomposites were subjected to monotonic uniaxial and creep loading at room temperature. The static mechanical properties were not significantly improved regardless the filler percentage and type of epoxy resin. Under creep loading, by increasing the stress level, the nanocomposite with 0.1 wt% silica creeps less than all other materials. Also the creep rate is reduced by adding silica nanofillers.

  10. Study on the creep and recovery behaviors of ferrofluids

    Science.gov (United States)

    Li, Zhenkun; Li, Decai; Hao, Du; Cheng, Yanhong

    2017-10-01

    The creep and recovery behaviors of lubrication oil based ferrofluids of different particle concentration were systematically investigated to understand the viscoelasticity of ferrofluids. The influence of stress level, magnetic field strength and temperature on creep and recovery behaviors of ferrofliuids was studied experimentally and the microscopic mechanisms behind the rheological phenomenon were discussed. Linear viscoelasticity theory and generalized Burgers models were employed to analyze the experimental results. The experimental results demonstrate that the ferrofluids exhibits unique creep and recovery properties significantly different from other stimuli responsive materials both in the linear and nonlinear viscoelastic region. Furthermore, structures larger than single chains are supposed to be responsible for many experimental results, including the extended relaxation process in recovery phase and the nonlinear increasing trend of creep strain with magnetic field strength and temperature. These findings contribute to a better understanding of the microscopic mechanism of magnetorheology of ferrofluids and also provide guidance for many practical applications.

  11. Microstructure evolution of CLAM steel during creep at 923K

    Science.gov (United States)

    Ye, S.; Zhao, F.; Huang, F.; He, J.; Wang, J. L.

    2017-08-01

    The microstructure change of CLAM steel during creep testing process was investigated at the temperature of 923K with different stress. The results show that the fragmentation and polygonization of martensite lath, as well as the degeneration of dislocation structure are the main factors to deteriorate the creep performance. The stability of MX precipitates in CLAM steel during high temperature creep is good, but the amount and size of M23C6 precipitates are increased. The Laves phase was not found in all samples, which may be due to the experimental temperature is close to the dissolution temperature of Laves phase. The higher temperature accelerates the microstructure evolution of CLAM steel, which results in the degradation of creep properties.

  12. NASALIFE - Component Fatigue and Creep Life Prediction Program

    Science.gov (United States)

    Gyekenyesi, John Z.; Murthy, Pappu L. N.; Mital, Subodh K.

    2014-01-01

    NASALIFE is a life prediction program for propulsion system components made of ceramic matrix composites (CMC) under cyclic thermo-mechanical loading and creep rupture conditions. Although the primary focus was for CMC components, the underlying methodologies are equally applicable to other material systems as well. The program references empirical data for low cycle fatigue (LCF), creep rupture, and static material properties as part of the life prediction process. Multiaxial stresses are accommodated by Von Mises based methods and a Walker model is used to address mean stress effects. Varying loads are reduced by the Rainflow counting method or a peak counting type method. Lastly, damage due to cyclic loading and creep is combined with Minor's Rule to determine damage due to cyclic loading, damage due to creep, and the total damage per mission and the number of potential missions the component can provide before failure.

  13. Finite Element Modeling of Thermo Creep Processes Using Runge-Kutta Method

    OpenAIRE

    Yu. I. Dimitrienko; E. A. Gubareva; Yu. V. Yurin

    2015-01-01

    Thermo creep deformations for most heat-resistant alloys, as a rule, nonlinearly depend on stresses and are practically non- reversible. Therefore, to calculate the properties of these materials the theory of plastic flow is most widely used. Finite-element computations of a stress-strain state of structures with account of thermo creep deformations up to now are performed using main commercial software, including ANSYS package. However, in most cases to solve nonlinear creep equations, one s...

  14. High temperature deformation characteristics of Zirlo{sup TM} tubing via ring-creep and burst tests

    Energy Technology Data Exchange (ETDEWEB)

    Seok, C.S. [Mechanical Engineering Department, Sungkyunkwan University, Suwon (Korea, Republic of); Marple, B.; Song, Y.J.; Gollapudi, S. [Nuclear Engineering Department, North Carolina State University, Raleigh, NC (United States); Charit, I., E-mail: icharit@uidaho.ed [Materials Science and Engineering Department, University of Idaho, Moscow, ID (United States); Murty, K.L. [Nuclear Engineering Department, North Carolina State University, Raleigh, NC (United States)

    2011-03-15

    Fuel cladding tubing acting as a barrier between coolant and radioactive fuel pellets in light water reactors undergo a combination of mechanical and thermal effects along with corrosive conditions during normal operations as well as accident situations, such as LOCA, etc. Therefore, the mechanical integrity of the cladding tubing is of critical importance. In this study, high temperature deformation characteristics of niobium-containing zirconium alloy cladding materials (Zirlo{sup TM}) have been evaluated via both ring-creep and burst tests. Creep-rupture data are presented in terms of Larson-Miller parameters (LMP). Data (creep rate vs. stress) from ring-creep and burst tests are analyzed, and operating deformation mechanisms are elucidated. This study demonstrates that the hoop creep data obtained from ring-creep and burst tests are equivalent, and one can be replaced with the other, if needed, in order to evaluate creep life.

  15. Thermophysical properties of selected powders for thermal barrier coatings

    OpenAIRE

    M. Drajewicz; M. Góral; M. Pytel; J. Sieniawski

    2012-01-01

    Purpose: Plasma-sprayed thermal barrier coatings often have the problems of spallation and cracking in service owing to their poor bond strength and high residual stresses. Functionally graded thermal barrier coatings with a gradual compositional variation from heat resistant ceramics to fracture-resistant metals are proposed to mitigate these problems.Design/methodology/approach: The results of measurements of thermal diffusivity by using one of the most modern experimental sets LFA 427 (Las...

  16. Method of remotely characterizing thermal properties of a sample

    Science.gov (United States)

    Heyman, Joseph S. (Inventor); Heath, D. Michele (Inventor); Welch, Christopher (Inventor); Winfree, William P. (Inventor); Miller, William E. (Inventor)

    1992-01-01

    A sample in a wind tunnel is radiated from a thermal energy source outside of the wind tunnel. A thermal imager system, also located outside of the wind tunnel, reads surface radiations from the sample as a function of time. The produced thermal images are characteristic of the heat transferred from the sample to the flow across the sample. In turn, the measured rates of heat loss of the sample are characteristic of the flow and the sample.

  17. Thermal transport properties of uranium dioxide by molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Taku; Sinnott, Susan B. [Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States); Tulenko, James S. [Department of Nuclear and Radiological Engineering, University of Florida, Gainesville, FL 32611 (United States); Grimes, Robin W. [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Schelling, Patrick K. [AMPAC and Department of Physics, University of Central Florida, Orlando, FL 32816 (United States); Phillpot, Simon R. [Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States)], E-mail: sphil@mse.ufl.edu

    2008-04-30

    The thermal conductivities of single crystal and polycrystalline UO{sub 2} are calculated using molecular dynamics simulations, with interatomic interactions described by two different potential models. For single crystals, the calculated thermal conductivities are found to be strongly dependent on the size of the simulation cell. However, a scaling analysis shows that the two models predict essentially identical values for the thermal conductivity for infinite system sizes. By contrast, simulations with the two potentials for identical fine polycrystalline structures yield estimated thermal conductivities that differ by a factor of two. We analyze the origin of this difference.

  18. Enhanced mechanical and thermal properties of regenerated cellulose/graphene composite fibers.

    Science.gov (United States)

    Tian, Mingwei; Qu, Lijun; Zhang, Xiansheng; Zhang, Kun; Zhu, Shifeng; Guo, Xiaoqing; Han, Guangting; Tang, Xiaoning; Sun, Yaning

    2014-10-13

    In this study, a wet spinning method was applied to fabricate regenerated cellulose fibers filled with low graphene loading which was systematically characterized by SEM, TEM, FTIR and XRD techniques. Subsequently, the mechanical and thermal properties of the resulting fibers were investigated. With only 0.2 wt% loading of graphene, a ∼ 50% improvement of tensile strength and 25% enhancement of Young's modulus were obtained and the modified Halpin-Tsai model was built to predict the mechanical properties of composite fibers. Thermal analysis of the composite fibers showed remarkably enhanced thermal stability and dynamic heat transfer performance of graphene-filled cellulose composite fiber, also, the presence of graphene oxide can significantly enhance the thermal conductivity of the composite fiber. This work provided a facile way to improve mechanical and thermal properties of regenerated cellulose fibers. The resultant composite fibers have potential application in thermal insulation and reinforced fibrous materials. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Effect of Heat Flux on Creep Stresses of Thick-Walled Cylindrical Pressure Vessels

    Directory of Open Access Journals (Sweden)

    Mosayeb Davoudi Kashkoli

    2014-06-01

    Full Text Available Assuming that the thermo-creep response of the material is governed by Norton’s law, an analytical solution is presented for the calculation of time-dependent creep stresses and displacements of homogeneous thick-walled cylindrical pressure vessels. For the stress analysis in a homogeneous pressure vessel, having material creep behavior, the solutions of the stresses at a time equal to zero (i.e. the initial stress state are needed. This corresponds to the solution of materials with linear elastic behavior. Therefore, using equations of equilibrium, stress-strain and strain-displacement, a differential equation for displacement is obtained and then the stresses at a time equal to zero are calculated. Using Norton’s law in the multi-axial form in conjunction with the above-mentioned equations in the rate form, the radial displacement rate is obtained and then the radial, circumferential and axial creep stress rates are calculated. When the stress rates are known, the stresses at any time are calculated iteratively. The analytical solution is obtained for the conditions of plane strain and plane stress. The thermal loading is as follows: inner surface is exposed to a uniform heat flux, and the outer surface is exposed to an airstream. The heat conduction equation for the one-dimensional problem in polar coordinates is used to obtain temperature distribution in the cylinder. The pressure, inner radius and outer radius are considered constant. Material properties are considered as constant. Following this, profiles are plotted for the radial displacements, radial stress, circumferential stress and axial stress as a function of radial direction and time.

  20. Mineralogy and thermal properties of clay from Slatina (Ub, Serbia)

    Science.gov (United States)

    Milosevic, Maja; Logar, Mihovil; Kaludjerovic, Lazar; Jelic, Ivana

    2017-04-01

    The "Slatina" deposit, Ub, Serbia was opened in 1965 and represents one of few deposits exploited by "Kopovi" a.d., Ub, company. Deposit is composed of clay layers belonging to Neogene sediments that are widespread transgressive over granitoid rocks of Cer mountain and Paleozoic and Mesozoic sediments. Clay is mostly of illite-montmorillonite-kaolinite type and they are generally used as ceramic materials while some of the layers are used as fire-resistant materials. In this study we present mineralogical and thermal characterization of two samples to determine their application as industrial materials. Chemical and mineral composition was determined using inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD) on powder and oriented samples, infrared spectroscopy (IR) and granulometry. Cationic exchange capacity (CEC) and specific surface area (SSA) was determined using spectrophotometry and methylene blue (MB). Thermal properties where determined by gravimetry (120, 350, 600 and 1000 oC) and differential thermal analysis (DTA). Quantitative mineral composition obtained by Rietveld refinement of combined chemical and XRD data shows that the sample 1(SC) is mainly smectite-illite (45%) and kaolinite (14%) clay with 19% of quartz, 10% feldspars and 7% of limonite, while sample 2(SV) is smectite-illite (43%) and kaolinite (11%) clay with 10% of quartz, 15% feldspars and 7% of limonite. Both samples have low content of impurities (carbonate minerals). Medium grain size (μm) goes from 1.02 (SSA = 104 m2/g) for sample 1(SC) to 0.71 (SSA = 117 m2/g) for sample 2(SV) while their CEC is 12.7 and 14.9 mmol/100g for 1(SC) and 2(SV) respectively. IR spectra of the samples shows larger amount of smectite clays with quartz and carbonate minerals for both samples which is in accordance with XRD data. DTA data shows couple of events that are endothermic. First one (100-200 oC) is associated with loss of moisture and constitutive water, second

  1. Fabrication, thermal properties and thermal stabilities of microencapsulated n-alkane with poly(lauryl methacrylate) as shell

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Xiaolin, E-mail: shirleyqiu2009@gmail.com [Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology, School of Mechanical Engineering, Jiangnan University, Wuxi 214122 (China); Lu, Lixin; Wang, Ju [Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology, School of Mechanical Engineering, Jiangnan University, Wuxi 214122 (China); Tang, Guoyi [Advanced Materials Institute and Clearer Production Key Laboratory, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Key Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Haidian District, Beijing 100084 (China); Song, Guolin [Advanced Materials Institute and Clearer Production Key Laboratory, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China)

    2015-11-20

    Highlights: • Microencapsulation of octadecane and paraffin by crosslinked poly(lauryl methacrylate). • Octadecane microcapsules have a melting enthalpy of about 118 J g{sup −1}. • Weight loss temperatures of the microcapsules were increased by 67 °C and 28 °C. • Phase change enthalpies decreased by around 10 wt% after 500 thermal cycles. • Foams with microcapsules can be applied for passive temperature control. - Abstract: Microencapsulation of n-octadecane or paraffin with poly(lauryl methacrylate) (PLMA) shell was performed by a suspension-like polymerization. The polymer shell was crosslinked by pentaerythritol tetraacrylate (PETRA). The surface morphologies of microcapsules were investigated by scanning electron microscopy (SEM). Phase change properties, thermal reliabilities and thermal stabilities of microcapsules were determined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The n-octadecane microcapsule exhibits higher melting enthalpy (118.0 J g{sup −1}) and crystallization enthalpy (108.3 J g{sup −1}) compared with the paraffin microcapsule. The thermal resistant temperatures were enhanced by more than 25 °C when n-alkanes were microencapsulated by PLMA. The PCM contents of microcapsules decreased by less than 4 wt% and 6 wt% after 500 and 1000 thermal cycles, respectively. Heat-up experiments indicated that microcapsule-treated foams exhibited upgraded thermal regulation capacities. Consequently, microencapsulated n-octadecane or paraffin with PLMA as shell possesses good potentials for heat storage and thermal regulation.

  2. Thermal, creep-recovery and viscoelastic behavior of high density polyethylene/hydroxyapatite nano particles for bone substitutes: effects of gamma radiation

    OpenAIRE

    Alothman, Othman Y; Fouad, H; Al-Zahrani, S M; Eshra, Ayman; Al Rez, Mohammed Fayez; Ansari, S G

    2014-01-01

    Background High Density Polyethylene (HDPE) is one of the most often used polymers in biomedical applications. The limitations of HDPE are its visco-elastic behavior, low modulus and poor bioactivity. To improve HDPE properties, HA nanoparticles can be added to form polymer composite that can be used as alternatives to metals for bone substitutes and orthopaedic implant applications. Method In our previous work (BioMedical Engineering OnLine 2013), different ratios of HDPE/HA nanocomposites w...

  3. Characterisation of advanced windows. Determination of thermal properties by measurements

    Energy Technology Data Exchange (ETDEWEB)

    Duer, K.

    2001-04-01

    optically inhomogeneous materials). Therefor an outdoor test facility has been constructed in order to facilitate the measurement of direct solar transmittance of optically inhomogeneous samples under natural solar radiation and under any chosen angle of incidence. The test facility is based on a scanning pyranometer mounted in a tracking device. Utilising the equipment and the procedures for measurements and data treatment described in this report will in most cases allow a full thermal characterisation of advanced windows and glazings to be carried out by measurements and with good accuracy. As an example of this the thermal and optical properties of a prototypical aerogel glazing have been determined by means of measurements. (au)

  4. Mechanical and thermal properties of tungsten carbide – graphite nanoparticles nanocomposites

    Directory of Open Access Journals (Sweden)

    Kornaus Kamil

    2016-06-01

    Full Text Available Previous studies concerning pure tungsten carbide polycrystalline materials revealed that nanolayers of graphite located between WC grains improve its thermal properties. What is more, pressure-induced orientation of graphene nano platelets (GNP in hot pressed silicon nitride-graphene composites results in anisotropy of thermal conductivity. Aim of this study was to investigate if addition of GNP to WC will improve its thermal properties. For this purpose, tungsten carbide with 0.5–6 wt.% of GNP(12-additive underwent hot pressing. The microstructure observations performed by SEM microscopy. The anisotropy was determined via ultrasonic measurements. The following mechanical properties were evaluated: Vickers hardness, bending strength, fracture toughness KIc. The influence of GNP(12 addition on oxidation resistance and thermal conductivity was examined. It was possible to manufacture hot-pressed WC-graphene composites with oriented GNP(12 particles, however, the addition of graphene decreased both thermal and mechanical properties of the material.

  5. Another Demo of the Unusual Thermal Properties of Rubber

    Science.gov (United States)

    Liff, Mark I.

    2010-01-01

    The unusual thermal behavior of rubbers, though discovered a long time ago, can still be mind-boggling for students and teachers who encounter this class of polymeric systems. Unlike other solids, stretched elastic polymers shrink upon heating. This is a manifestation of the Gough-Joule (G-J) effect. Joule in the 1850s studied the thermal behavior…

  6. Thermal Properties of Kerstingiella geocarpa Seeds as Influenced ...

    African Journals Online (AJOL)

    The specific heat capacity, thermal conductivity and thermal diffusivity of Kerstingiella geocarpa seeds were determined as a function of moisture content. The initial moisture content of the seeds determined using the ASAE standard test was 10.0 % (d.b). The specific heat capacity of Kerstingiella geocarpa seed increased ...

  7. Thermal Properties of Some Organic Liquids Using Ultrasonic Velocity Measurements

    Directory of Open Access Journals (Sweden)

    P. Ramadoss

    2011-01-01

    Full Text Available Debye temperature and thermal relaxation time has been calculated in normal and boiling temperature. Using thermal relaxation time, the heat of fusion has been calculated for nineteen organic liquids and the results throw light on the method of calculating heat of fusion.

  8. Simulation of thermo-Elastics Properties of Thermal Barrier Coatings ...

    African Journals Online (AJOL)

    Thermal barrier coatings are used to protect different parts in compressors and turbines from heat. They are generally composed of two layers, one metallic layer providing resistance to heat corrosion and oxidation, and one thermally insulating ceramic layer. Two different techniques are industrially used. Plasma spray ...

  9. Preconsolidation Pressure and Creep Settlements

    DEFF Research Database (Denmark)

    Thorsen, Grete

    1995-01-01

    of oedometer tests with undisturbed samples have been analysed by means of different methods to determine the pre-consolidation pressure. An attempt is made to estimate the creep rates on the basis of AMS 14C-datings of the sediments and a model for creep determination proposed by Moust Jacobsen....

  10. Nanogranular origin of concrete creep

    Science.gov (United States)

    Vandamme, Matthieu; Ulm, Franz-Josef

    2009-01-01

    Concrete, the solid that forms at room temperature from mixing Portland cement with water, sand, and aggregates, suffers from time-dependent deformation under load. This creep occurs at a rate that deteriorates the durability and truncates the lifespan of concrete structures. However, despite decades of research, the origin of concrete creep remains unknown. Here, we measure the in situ creep behavior of calcium–silicate–hydrates (C–S–H), the nano-meter sized particles that form the fundamental building block of Portland cement concrete. We show that C–S–H exhibits a logarithmic creep that depends only on the packing of 3 structurally distinct but compositionally similar C–S–H forms: low density, high density, ultra-high density. We demonstrate that the creep rate (≈1/t) is likely due to the rearrangement of nanoscale particles around limit packing densities following the free-volume dynamics theory of granular physics. These findings could lead to a new basis for nanoengineering concrete materials and structures with minimal creep rates monitored by packing density distributions of nanoscale particles, and predicted by nanoscale creep measurements in some minute time, which are as exact as macroscopic creep tests carried out over years. PMID:19541652

  11. Influence of S, P, C on grain boundary diffusion and creep properties of Alloy 800; Einfluss von S, P, C auf die Korngrenzendiffusion und Kriecheigenschaften von Alloy 800

    Energy Technology Data Exchange (ETDEWEB)

    Lindemann, J.; Hannesen, K.; Mast, R.; Viefhaus, H. [Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany); Grabke, H.J.

    1998-12-31

    The paper reports examinations of Alloy 800 and specific commercially available variants known under the names of 800H, 800HT, and 800LC, differing in their concentrations of C, Al, and Ti. In addition, melts also containing phosphorus (0.09 wt-%) or sulfur (0.04 wt-%) as additional alloying materials have been prepared for the experiments. The volume diffusion and the grain boundary diffusion of {sup 59}Fe in those alloys was measured at temperatures between 800 and 1000 C by means of a radioactive tracer method combined with residual activity measurements. It was found that accompanying elements like phosphorus and sulfur increase the activation energy of the grain boundary diffusion of the iron and thus delay the grain boundary self-diffusion in Alloy 800. Creep curves were measured of the same materials after age-hardening treatment for 100 hours at 800 C, measurements performed at constant temperature but at three different, constant creep stress loads. The results showed that addition of phosphorus markedly increases the lifetime of Alloy 800, and reduces the creep rupture strain. The minimum strain rate in Alloy 800 containing 0.09 wt-% of phosphorus was found to be lower by a factor of 100, as compared to the other Alloy 800 materials used. (orig./CB) [Deutsch] Alloy 800 ist ein austenitischer Fe-Ni-Cr Stahl, der relativ geringe, aber wichtige Konzentrationen von Kohlenstoff, Aluminium und Titan enthaelt. Besondere Varianten von Alloy 800, bekannt als 800H, 800HT und 800LC, unterscheiden sich in den Konzentrationen dieser Elemente. Diese kommerziellen Legierungen wurden untersucht, und zusaetzlich wurden Schmelzen mit zulegiertem Phosphor (0,09 Gew-%) bzw. Schwefel (0,04 Gew-%) hergestellt. Mittels einer radioaktiven Tracermethode in Verbindung mit Restaktivitaetsmessungen wurde die Volumen- und Korngrenzendiffusion von {sup 59}Fe in diesen Legierungen im Temperaturbereich 800-1000 C gemessen. Es wurde gefunden, dass Begleitelemente wie Phosphor und

  12. Evaluating the effect of spinning systems on thermal comfort properties of modal fabrics

    Science.gov (United States)

    Seçil Aydın, İ.; Kertmen, M.; Marmarali, A.

    2017-10-01

    In recent years the importance of clothing comfort became one of the most important feature of the fabrics. The aim of this study is to characterize thermal comfort properties of single jersey fabrics were knitted using 100% modal yarns which were spun in various types of yarn spinning methods such as ring spinning, compact spinning, rotor spinning and airjet spinning. Thermal comfort properties like air permeability, thermal resistance, thermal absorptivity and water vapour permeability of fabrics were tested. The results indicate that compact spinning technology will be appropriate for the summer climate casual wear.

  13. Creep-induced anisotropy in covalent adaptable network polymers.

    Science.gov (United States)

    Hanzon, Drew W; He, Xu; Yang, Hua; Shi, Qian; Yu, Kai

    2017-10-11

    Anisotropic polymers with aligned macromolecule chains exhibit directional strengthening of mechanical and physical properties. However, manipulating the orientation of polymer chains in a fully cured thermoset is almost impossible due to its permanently crosslinked nature. In this paper, we demonstrate that rearrangeable networks with bond exchange reactions (BERs) can be utilized to tailor the anisotropic mechanical properties of thermosetting polymers. When a constant force is maintained at BER activated temperatures, the malleable thermoset creeps in the direction of stress, and macromolecule chains align themselves in the same direction. The aligned polymer chains result in an anisotropic network with a stiffer mechanical behavior in the direction of creep, while with a more compliant behavior in the transverse direction. The degree of network anisotropy is proportional to the amount of creep strain. A multi-length scale constitutive model is developed to study the creep-induced anisotropy of thermosetting polymers. The model connects the micro-scale BER kinetics, orientation of polymer chains, and directional mechanical properties of network polymers. Without any fitting parameters, it is able to predict the evolution of creep strain at different temperatures and anisotropic stress-strain behaviors of CANs after creep. Predictions on the chain orientation are verified by molecular dynamics (MD) simulation. Based on parametric studies, it is shown that the influences of creep time and temperature on the network anisotropy can be generalized into a single parameter, and the evolution of directional modulus follows an Arrhenius type time-temperature superposition principle (TTSP). The presented work provides a facile approach to transform isotropic thermosets into anisotropic ones using simple heating, and their directional properties can be readily tailored by the processing conditions.

  14. Creep of zirconia/nickel composites

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Rodriguez, A.; Bravo-Leon, A.; Dominguez-Rodriguez, A.; Jimenez-Melendo, M. [Dept. de Fisica de la Materia Condensada, Univ. de Sevilla, Sevilla (Spain)

    2004-07-01

    The creep properties of wet-processed 3 mol% Y{sub 2}O{sub 3}-stabilized ZrO{sub 2}/Ni composites (20 and 40 vol% of nickel content) have been studied by compressive constant load tests in the temperature range 900 C-1250 C under argon atmosphere. The microstructural characterization of these cermets has been performed using scanning and transmission electron microscopy. The composites consist of nickel particles (1 {mu}m in size) uniformly distributed throughout a fine-grained zirconia matrix (0.13 {mu}m in size). The mechanical and microstructural results indicate that the overall creep behavior of the cermets is controlled primarily by the zirconia matrix; metal additions increase the ductility of the material. (orig.)

  15. Thermal Properties of Carbon Nanotube–Copper Composites for Thermal Management Applications

    Directory of Open Access Journals (Sweden)

    Jia Chengchang

    2010-01-01

    Full Text Available Abstract Carbon nanotube–copper (CNT/Cu composites have been successfully synthesized by means of a novel particles-compositing process followed by spark plasma sintering (SPS technique. The thermal conductivity of the composites was measured by a laser flash technique and theoretical analyzed using an effective medium approach. The experimental results showed that the thermal conductivity unusually decreased after the incorporation of CNTs. Theoretical analyses revealed that the interfacial thermal resistance between the CNTs and the Cu matrix plays a crucial role in determining the thermal conductivity of bulk composites, and only small interfacial thermal resistance can induce a significant degradation in thermal conductivity for CNT/Cu composites. The influence of sintering condition on the thermal conductivity depended on the combined effects of multiple factors, i.e. porosity, CNTs distribution and CNT kinks or twists. The composites sintered at 600°C for 5 min under 50 MPa showed the maximum thermal conductivity. CNT/Cu composites are considered to be a promising material for thermal management applications.

  16. Mechanical and thermal properties of HSC with fine natural pozzolana as SCM

    Science.gov (United States)

    KoÅ¥átková, Jaroslava; Čáchová, Monika; KoÅáková, Dana; Vejmelková, Eva; Reiterman, Pavel

    2017-07-01

    The paper is dealing with an influence of fine pozzolanic admixture supplementing a part of cement on various properties of high-strength concrete. The measured characteristics were basic physical properties, compressive strength and thermal properties (thermal conductivity and specific heat capacity). Replacing the cement by the natural pozzolana in higher dosages leads to the higher porosity and thus to the lower compressive strength of the developed material. Conversely, in case of lower amounts of pozzolana (up to 10% of weight) such replacement has an opposite consequence, the open porosity decreases which results in the higher compressive strength. Taking into account thermal properties which are enhanced by an increase of amount of pores, it is evident that it is necessary to optimize the amount of pozzolana (pozzolanic) admixture in order to obtain reasonable mechanical and thermal properties.

  17. Measurement on the Thermal Properties of Graphene Powder

    Science.gov (United States)

    Zhang, Wenchan; Dong, Hua; Wang, Yongchun; Zhang, Jingkui

    2017-08-01

    We report on an in-plane thermal diffusivity study of suspended graphene powder (GP) measured by the transient electro-thermal (TET) technique. The GP with a density of 0.24 \\hbox {g} \\cdot \\hbox {cm}^{-3} is made up of five-six-layer graphene. And the average size of graphene flakes used in our study is 0.98 \\upmu m. The intrinsic thermal conductivity perpendicular to in-plane of GP is determined at 18.8 \\hbox {W} \\cdot (\\hbox {m} \\cdot \\hbox {K})^{-1} using the thermal conductivity instrument, and the range of the in-plane thermal diffusivity of GP is identified from 0.86× 10^{-5 } \\hbox {m}^{2 } \\cdot \\hbox {s}^{-1} to 1.52× 10^{-5 } \\hbox {m}2 \\cdot \\hbox {s}^{-1} measured by the TET technique. Accordingly, the corresponding intrinsic thermal conductivity is 13.5 \\hbox {W} \\cdot (\\hbox {m} \\cdot \\hbox {K})^{-1}-23.8 \\hbox {W} \\cdot (\\hbox {m} \\cdot \\hbox {K})^{-1}. It is obvious that the two methods used in the experimental research on the intrinsic thermal conductivity of GP in different directions are not only the same order of magnitude but also have a maximum difference of only 5 \\hbox {W} \\cdot (\\hbox {m} \\cdot \\hbox {K})^{-1}. The results of our experiments are about one order of magnitude lower than those reported for four-five-layer graphene. There are various porosities in the whole sample after the compaction steps in the preparation of the samples, which gives rise to a large thermal contact resistance. And widely uneven surface defects observed under an optical microscope for the studied GP lead to substantial phonon scattering. Those factors combine together to give the observed significant reduction in the thermal conductivity.

  18. The effectiveness of shearography and digital image correlation for the study of creep in elastomers

    Science.gov (United States)

    Benito Pascual-Francisco, Juan; Barragán-Pérez, Omar; Susarrey-Huerta, Orlando; Michtchenko, Alexandre; Martínez-García, Amalia; Israel Farfán-Cabrera, Leonardo

    2017-11-01

    In this paper, authors present a study of the application of speckle shearing interferometry (shearography) and digital image correlation to measure viscoelasticity in terms of creep compliance of elastomeric materials. The creep tests were performed using two different elastomers (neoprene and EPDM) by applying a constant tensile stress to a specimen during 3 h. First, a shearography setup was implemented to measure directly the in-plane strains produced in the specimens and thus determining creep strains. Secondly, digital image correlation was also used to measure the creep strains in similar creep tests. The results obtained were compared each other to see the effectiveness of each measurement technique for the assessment of this property. It was demonstrated that these techniques can be potentially and successfully applied to the creep analysis of these kind of materials. Moreover, advantages and drawbacks of both measurement methods are discussed.

  19. Mechanisms Governing the Creep Behavior of High Temperature Alloys for Generation IV Nuclear Energy Systems

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, Vijay [Univ. of Cincinnati, OH (United States); Carroll, Laura [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sham, Sam [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-04-06

    This research project, which includes collaborators from INL and ORNL, focuses on the study of alloy 617 and alloy 800H that are candidates for applications as intermediate heat exchangers in GEN IV nuclear reactors, with an emphasis on the effects of grain size, grain boundaries and second phases on the creep properties; the mechanisms of dislocation creep, diffusional creep and cavitation; the onset of tertiary creep; and theoretical modeling for long-term predictions of materials behavior and for high temperature alloy design.

  20. Creep-Rupture Data Analysis - Engineering Application of Regression Techniques. Ph.D. Thesis - North Carolina State Univ.

    Science.gov (United States)

    Rummler, D. R.

    1976-01-01

    The results are presented of investigations to apply regression techniques to the development of methodology for creep-rupture data analysis. Regression analysis techniques are applied to the explicit description of the creep behavior of materials for space shuttle thermal protection systems. A regression analysis technique is compared with five parametric methods for analyzing three simulated and twenty real data sets, and a computer program for the evaluation of creep-rupture data is presented.

  1. Reassembling Surveillance Creep

    DEFF Research Database (Denmark)

    Bøge, Ask Risom; Lauritsen, Peter

    2017-01-01

    We live in societies in which surveillance technologies are constantly introduced, are transformed, and spread to new practices for new purposes. How and why does this happen? In other words, why does surveillance “creep”? This question has received little attention either in theoretical developm......We live in societies in which surveillance technologies are constantly introduced, are transformed, and spread to new practices for new purposes. How and why does this happen? In other words, why does surveillance “creep”? This question has received little attention either in theoretical...... development or in empirical analyses. Accordingly, this article contributes to this special issue on the usefulness of Actor-Network Theory (ANT) by suggesting that ANT can advance our understanding of ‘surveillance creep’. Based on ANT’s model of translation and a historical study of the Danish DNA database......, we argue that surveillance creep involves reassembling the relations in surveillance networks between heterogeneous actors such as the watchers, the watched, laws, and technologies. Second, surveillance creeps only when these heterogeneous actors are adequately interested and aligned. However...

  2. Creep and crack growth of zircon and mullite base materials

    Energy Technology Data Exchange (ETDEWEB)

    Carbonneau, X.; Olagnon, C.; Fantozzi, G. [INSA, Villeurbanne (France). GEMPPM

    1999-03-01

    The creep and crack propagation properties of mullite and zircon ceramics were compared. In the investigated temperature range, mullite presents a simple crack propagation of a unique macrocracks, although a change of mechanism is observed at 1200 C. The zircon material present a rather more complex crack propagation, with multicracking and branching, due to a significant crack healing. The creep behaviours also appeared as different for both materials. The mullite creep curves present only two stages, even when fracture occurs, while a tertiary regime is observed in the case of zircon. The results show that grain boundary sliding is the main deformation mechanism for the two different materials. In fact, they exhibit similar overall real behaviours with a different characteristic temperature. At low stress, the minimum creep rate can be considered as a stationary creep, but at a higher stress, generalised or localised damage interfere, leading to a higher apparent stationary creep exponent. Sub-critical crack growth and deformation act as parallel mechanisms for mullite, while the interaction is more complex in zircon where crack healing induce multi-cracking. (orig.) 9 refs.

  3. A Critical Analysis of the Conventionally Employed Creep Lifing Methods

    Directory of Open Access Journals (Sweden)

    Zakaria Abdallah

    2014-04-01

    Full Text Available The deformation of structural alloys presents problems for power plants and aerospace applications due to the demand for elevated temperatures for higher efficiencies and reductions in greenhouse gas emissions. The materials used in such applications experience harsh environments which may lead to deformation and failure of critical components. To avoid such catastrophic failures and also increase efficiency, future designs must utilise novel/improved alloy systems with enhanced temperature capability. In recognising this issue, a detailed understanding of creep is essential for the success of these designs by ensuring components do not experience excessive deformation which may ultimately lead to failure. To achieve this, a variety of parametric methods have been developed to quantify creep and creep fracture in high temperature applications. This study reviews a number of well-known traditionally employed creep lifing methods with some more recent approaches also included. The first section of this paper focuses on predicting the long-term creep rupture properties which is an area of interest for the power generation sector. The second section looks at pre-defined strains and the re-production of full creep curves based on available data which is pertinent to the aerospace industry where components are replaced before failure.

  4. Verification of creep performance of a ceramic gas turbine blade

    Energy Technology Data Exchange (ETDEWEB)

    Lin, H.T.; Becher, P.F.; Ferber, M.K. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.; Parthasarathy, V. [Solar Turbines Inc., San Diego, CA (United States)

    1998-03-01

    Tensile creep tests were carried out on a Norton NT164 silicon nitride ceramic turbine blade containing 4 wt. % Y{sub 2}O{sub 3} sintering additive at 1,370 C in air under selected stress levels. The objective of this study was to measure the creep properties of test specimens extracted from a complex shaped ceramic gas turbine blade to verify the response of actual components. The creep results indicated that specimens from both the airfoil and dovetail sections exhibited creep rates that were about 4 to 100 times higher than those obtained from both the buttonhead and dogbone creep specimens machined from the developmental billets fabricated with the same composition and processing procedures. Electron microscopy analyses suggested that high creep rates and short lifetimes observed in specimens extracted from the turbine blade resulted from a higher glassy phase(s) content and smaller number density of elongated grain microstructure. Silicon nitride ceramics with an in-situ reinforced elongated microstructure have been the primary candidates for both advanced automotive and land-based gas turbine engine applications.

  5. Assessment of spatial variability of soil thermal properties in cultivated field

    Science.gov (United States)

    Usowicz, Boguslaw; Lipiec, Jerzy

    2017-04-01

    Most of soil physical properties are spatially variable both in regional and field scale. Spatial heterogeneity of soil properties in the field is related to the nature of the soil itself, but some of the variation is caused by tillage and other management practices. The aim of this work was to determine spatial variability of thermal properties on the cultivated field (40 x 350 m) using geostatistical method. The present work used data obtained from the measurements of topsoil soil texture (sand, silt and clay content), organic carbon, water content, bulk density, particle density, thermal conductivity, heat capacity and thermal diffusivity after harvest of triticale. The measurements were done in 45 points using TDR and KD2Pro for soil water content and thermal properties, respectively. Moreover, measurements of the thermal properties were performed in the laboratory at dry and saturated soil. The coefficient of variations (CV) varied from 1.6% for the particle density to 67% for the clay content. Among the thermal properties the most variable was thermal diffusivity at saturation (24%) and the least variable thermal conductivity in dry state (8.4%). The exponential semivariogram models matched well with empirical semivariogram. The range of the thermal properties measured in the field varied from 10 m for the thermal diffusivity to 23 m for the thermal conductivity. The ranges in dry and saturated soil were greater than at field water content. Among the remaining properties the largest range of the semivariograms was for soil textural fractions (100-250 m) and bulk density (145 m) and the lowest water content (14 m). This indicates that the thermal properties were resultant of both soil water content and bulk density. Most of the soil properties exhibited strong and moderate spatial dependency. Heterogeneity and variation of soil physical and thermal parameters in a field due to soil cultivation should be taken into consideration for a successful agricultural

  6. Thermal and Transport Properties of Mafic and Ultramafic Rocks of Oman Ophiolite

    Directory of Open Access Journals (Sweden)

    Sayyadul Arafin

    2016-11-01

    Full Text Available Thermal and other physical properties of rocks and minerals are of considerable significance for deriving mineralogical and compositional models of the Earth's mantle. We have determined these properties for the mafic rock such as gabbro and ultramafic rock like harzburgite of the Oman ophiolite suite by utilizing the Debye characteristic property ,Θ-

  7. Thermal properties of metals alloy by electrical pyroelectric method (EPE)

    Energy Technology Data Exchange (ETDEWEB)

    Bennaji, N; Mellouki, I; Yacoubi, N, E-mail: bennajin@yahoo.f

    2010-03-01

    In present work, we propose a new technique based on uniform electrical heating of pyroelectric detector which investigated simultaneous thermal conductivity and diffusivity of samples. A new one-dimensional theoretical model was developed to determinate thermal proprieties of steel alloy. The obtained values of thermal conductivity are 13 Wm{sup -1}K{sup -1}, 18 Wm{sup -1}K{sup -1} and 24 Wm{sup -1}K{sup -1} and of thermal diffusivity are 7x10{sup -6} m{sup 2}s{sup -1}, 15x10{sup -6} m{sup 2}s{sup -1} and 8x10{sup -6} m{sup 2}s{sup -1} respectively for sheet steel, galvanized steel and stainless steel. These results are given with an uncertainty at the 1{sigma} level.

  8. Boron effects on creep rupture strength of W containing advanced ferritic creep resistant steels

    Energy Technology Data Exchange (ETDEWEB)

    Mito, N.; Hasegawa, Y. [Tohoku Univ., Sendai (Japan)

    2010-07-01

    The creep strength in ferritic creep resistant steels is increased by boron addition. However, the strengthening mechanisms have not yet been studied. This study clarifies the strengthening mechanism of 9% chromium steels with 10{proportional_to}100ppm boron and 0.5{proportional_to}2.0mass% tungsten in the laboratory. The strengthening effect of simultaneous addition of boron and tungsten was analyzed by hardenability, room-temperature strength and creep tests at 650 C. Changes in the microstructure as a result of the addition of boron and tungsten were also examined by optical microscope and transmission electron microscope (TEM). In addition, Alpha-ray Track Etching (ATE) method was used to detect the boron distribution and analyze the mechanisms change in the mechanical properties. Boron addition did not affect room-temperature strength, however, simultaneous addition of boron and tungsten increased room-temperature and high-temperature strength. According to ATE analysis, boron exists at the grain boundary. Therefore, synergistic effects of boron and tungsten on the creep strength suggest the tungsten precipitates stabilization by boron at the grain boundary. (orig.)

  9. Effect of tuber skin on the thermal properties of whole tubers of potato and sweet potato

    Science.gov (United States)

    Oluwo, A. A.; Khan, R. M.; Salami, M. J. E.

    2013-12-01

    Temperature-dependent thermal coefficients of mathematical models of the postharvest storage process play an important role in determining the models accuracy. Thermal properties of tubers under storage available in literature are generally of those in semi processed form (skinless) such as those having undergone peeling, dicing and cutting actions. This study investigates the effect of tuber skin on the thermal properties of whole tubers of potato and sweet potato. A direct approach was used to measure the tubers' density and thermal conductivity and thermal diffusivity by the transient heat transfer method. Indirect approach was used to measure the tubers' specific heat. Experimental data were used to develop empirical models of the thermal coefficients as a function of temperature. Results of the study should find great use in the modeling of potato and sweet potato storage process.

  10. Heat pipes with variable thermal conductance property for space applications

    Energy Technology Data Exchange (ETDEWEB)

    Kravets, V.; Alekseik, Ye.; Alekseik, O.; Khairnasov, S. [National Technical University of Ukraine, Kyiv (Ukraine); Baturkin, V.; Ho, T. [Explorationssysteme RY-ES, Bremen (Germany); Celotti, L. [Active Space Technologies GmbH, Berlin (Germany)

    2017-06-15

    The activities presented in this paper demonstrate a new approach to provide passive thermal control using heat pipes, as demonstrated on the electronic unit of DLR’s MASCOT lander, which embarked on the NEA sample return mission Hayabusa 2 (JAXA). The focus is on the development and testing of heat pipes with variable thermal conductance in a predetermined temperature range. These heat pipes act as thermal switches. Unlike standard gasloaded heat pipes and thermal-diode heat pipes construction of presented heat pipes does not include any additional elements. Copper heat pipes with metal fibrous wicks were chosen as baseline design. We obtained positive results by choosing the heat carrier and structural parameters of the wick (i.e., pore diameter, porosity, and permeability). The increase in the thermal conductivity of the heat pipes from 0.04 W/K to 2.1 W/K was observed in the temperature range between −20 °C and +55 °C. Moreover, the heat pipes transferred the predetermined power of not less than 10 W within the same temperature range. The heat pipes have been in flight since December 2014, and the supporting telemetry data were obtained in September 2015. The data showed the nominal operation of the thermal control system.

  11. Characterization of thermal, hydraulic, and gas diffusion properties in variably saturated sand grades

    DEFF Research Database (Denmark)

    Deepagoda Thuduwe Kankanamge Kelum, Chamindu; Smits, Kathleen; Ramirez, Jamie

    2016-01-01

    porous media transport properties, key transport parameters such as thermal conductivity and gas diffusivity are particularly important to describe temperature-induced heat transport and diffusion-controlled gas transport processes, respectively. Despite many experimental and numerical studies focusing....../70) in relation to physical properties, water retention, hydraulic conductivity, thermal conductivity, and gas diffusivity. We used measured basic properties and transport data to accurately parameterize the characteristic functions (particle- and pore-size distributions and water retention) and descriptive...... transport models (thermal conductivity, saturated hydraulic conductivity, and gas diffusivity). An existing thermal conductivity model was improved to describe the distinct three-region behavior in observed thermal conductivity–water saturation relations. Applying widely used parametric models for saturated...

  12. Thermal and corrosion properties of silicon nitride for copper die casting components

    OpenAIRE

    Khader, I.; Renz, A.; Kailer, A.; Haas, D.

    2013-01-01

    Due to the high melting temperature of copper and copper alloys, conventional die-steel components used in pressure die casting these materials exhibit short service lifetimes and undergo thermal fatigue. Thermal and corrosion properties of silicon nitride were studied to assess the material's applicability in substituting conventional die-steels in casting copper and copper alloys. In this study, experiments were conducted to test the thermal shock resistance and corrosion behaviour of a com...

  13. Laser-Interferometric Creep Rate Spectroscopy of Polymers

    Science.gov (United States)

    Bershtein, Vladimir A.; Yakushev, Pavel N.

    Laser-interferometric creep rate meter (LICRM) and creep rate spectroscopy (CRS), as an original high-resolution method for discrete relaxation spectrometry and thermal analysis, were developed in the authors' Materials Dynamics Laboratory at Ioffe Physical-Technical Institute of the Russian Academy of Sciences (Saint-Petersburg). In the last few decades they have been successfully applied to solving various problems of polymer physics and materials science, especially being combined with DSC, structural, and other techniques. CRS involves measuring ultra-precisely a creep rate at small tensile or compressive stress, typically much lower than the yield stress, as a function of temperature, over the range from 100 to 800 K. LICRM setup allows one to register precisely creep rates on the basis of deformation increment of 150-300 nm. The survey describes this method and summarizes the results of numerous studies performed with the LICRM setup and CRS technique for different bulk polymeric materials, films, or thin fibers. This approach provided new experimental possibilities superior in resolution and sensitivity compared to the conventional relaxation spectrometry techniques. Among such possibilities are discrete analysis of dynamics; creep on submicro-, micro- and meso-scales; revealing relations between stepwise microplasticity and morphology; kinetic information on creep at any temperature and deformation; polymer dynamics at interfaces; analysis of microplasticity, relaxations, and phase transitions in brittle materials; using creep rate spectra for non-destructive prediction of temperature anomalies in mechanical behavior of materials, etc. Considerable attention has been paid to combined CRS/DSC analysis of the peculiarities of segmental dynamics, nanoscale dynamic, and compositional heterogeneity in different kinds of complex polymer systems and nanocomposites.

  14. A review of wood thermal pretreatments to improve wood composite properties

    Science.gov (United States)

    Manuel Raul Pelaez-Samaniego; Vikram Yadama; Eini Lowell; Raul. Espinoza-Herrera

    2013-01-01

    The objective of this paper is to review the published literature on improving properties of wood composites through thermal pretreatment of wood. Thermal pretreatment has been conducted in moist environments using hot water or steam at temperatures up to 180 and 230 ˚C, respectively, or in dry environments using inert gases at temperatures up to 240 ...

  15. Thermal Insulating Properties of Straw-Filled Environmentally Friendly Building Materials

    Directory of Open Access Journals (Sweden)

    Petkova-Slipets Rositsa

    2017-06-01

    Full Text Available The paper presents results of a research for determination of a few general thermal-physical properties of environmentally friendly building materials made by clay, sand and straw. The aim of this study is to establish their heat insulating and energy-efficient capacity. All specific measurements were carried out by using the newest generation thermal conductivity analyser Mathis TCi.

  16. MAPTIP - Marine Aerosol Properties and Thermal Imager Performance : Summary and initial results

    NARCIS (Netherlands)

    Eijk, A.M.J. van; Leeuw, G. de; Jensen, D.R.

    1995-01-01

    The marine aerosol properties and thermal imager performance trial (MAPTIP) was conducted by NATO AC/243 Panel 04/RSG.8 and 04/RSG.5 in the Dutch coastal waters during the fall of 1993. The main objectives of the trial were (1) to assess marine boundary layer effects on thermal imaging systems and

  17. Tribological properties of the two-step thermally deposited chromium films

    NARCIS (Netherlands)

    Lazauskas, A.; Baltrusaitis, Jonas; Grigaliunas, V.; Baltusnikas, A.; Abakeviciene, B.; Polcar, T.

    2013-01-01

    Chromium thin films were prepared on glass substrate via a two-step thermal deposition and their structural, chemical and tribological properties were determined. The X-ray diffraction pattern of the two-step thermally deposited chromium film showed the presence of well-defined body-centered cubic

  18. Microstructural and thermal properties of piston aluminum alloy reinforced by nano-particles

    Science.gov (United States)

    Azadi, Mohammad; Safarloo, Sama; Loghman, Fatemeh; Rasouli, Roham

    2018-01-01

    Aluminum alloys have been widely utilized in engine pistons of automotive industries. Under such loading conditions, thermal stresses were applied to the piston material, due to the combustion process. Knowing the thermal behavior and microstructural properties of the material has an important rule for designers. Besides, the used material should withstand these thermal expansions and one way to increase this thermal strength is to add nano-particles for reinforcing the material. In the present article, the thermal behavior of piston aluminum alloys has been analyzed. This objective has been performed by thermal dilatometric measuring to find the thermal expansion coefficient. Then, the effect of adding nano-particles for reinforcing the aluminum alloy has been also investigated. In addition, the distribution of nano-particles in the aluminum matrix was also studied by the field emission scanning electron microscopy (FE-SEM). Besides, the microstructure of the piston aluminum alloy, with and without SiO2 nano-particles, was investigated.

  19. Design and Fabrication of a Soil Moisture Meter Using Thermal Conductivity Properties of Soil

    National Research Council Canada - National Science Library

    Subir Das; Biplab Bag; T S Sarkar; Nisher Ahmed; B Chakrabrty

    2011-01-01

    ... of soil moisture modeling. In this present work design of a soil moisture measurement meter using thermal conductivity properties of soil has been proposed and experimental results are reported...

  20. Basement Construction of Measurement Standardization for Thermal Property and Basement Preparation of Industrial Technology

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Kweon Ho; Song, Kee Chan; Park, Chang Je

    2007-02-15

    There are three main categories in this report : 1)Basement construction of measurement standardization for nuclear material thermal property, 2) Reliability evaluation of measurement instrument, and 3) Standardization and industrial propagation.

  1. Long-term aging effect on the creep strength of the T92 steel

    Energy Technology Data Exchange (ETDEWEB)

    Panait, C. [MINES ParisTech, UMR CNRS, Evry (France). Centre des Materiaux; V et M France CEV, Aulnoye-Aymeries (France); Gourgues-Lorenzon, A.F.; Besson, J. [MINES ParisTech, UMR CNRS, Evry (France). Centre des Materiaux; Fuchsmann, A.; Gabrel, J.; Piette, M. [V et M France CEV, Aulnoye-Aymeries (France); Bendick, W. [Salzgitter Mannesmann Forschung GmbH (SZMF), Duisburg (Germany)

    2010-07-01

    Creep strength loss of T92 steel after long-term creep exposure at 600 C and 650 C is partially due to a thermal aging of the steel during the first part of the test. In order to quantify the effect of long-term aging on the creep strength loss, creep tests were conducted at 600 and 650 C on T92 steel thermally aged for 10,000h at the same temperature and on as-received T92 steel. Laves phases precipitates were found after thermal aging at 600 C and 650 C with an average equivalent diameter of about 200nm and of about 350nm, respectively. No significant change in hardness and in the matrix substructure as revealed by electron backscatter diffraction occurred during aging. For stresses higher than 170MPa at 600 C and higher than 110MPa at 650 C the time to rupture is four times lower in the aged steels compared to the as-received steel, this is correlated to a secondary creep rate four times higher for the aged specimens compared to that of the as-received steel. Creep tests conducted at 650 C under lower stresses revealed a creep lifetime only twice lower after aging. (orig.)

  2. Eutectic mixtures of some fatty acids for low temperature solar heating applications: Thermal properties and thermal reliability

    Energy Technology Data Exchange (ETDEWEB)

    Sari, Ahmet [Department of Chemistry, Gaziosmanpasa University, 60240 Tokat (Turkey)]. E-mail: asari@gop.edu.tr

    2005-10-01

    The thermal properties and thermal reliability of the eutectic mixtures of lauric acid-myristic acid (LA-MA), lauric acid-palmitic acid (LA-PA), myristic acid-stearic acid (MA-SA) as phase change material (PCM) were determined after repeated melt/freeze cycles by the method of differential scanning calorimeter (DSC). The DSC thermal analysis results indicate that the binary systems of LA-MA in ratio of 66.0:34.0 wt.%, LA-PA in ratio of 69.0:31.0 wt.% and MA-SA in ratio of 64.0:36.0 wt.% form eutectic mixture with a melting temperature of 34.2 deg. C, 35.2 deg. C and 44.1 deg. C, and with a latent heat of fusion of 166.8 J g{sup -1}, 166.3 J g{sup -1} and 182.4 J g{sup -1}, respectively. The changes in the melting temperatures and the latent heats of fusion are in the range of -0.31 deg. C-0.14 deg. C and 0.9%-2.4% for LA-MA, -0.40 deg. C-0.23 deg. C and 1.5%-3.0% for LA-PA, and 1.11 deg. C-0.26 deg. C and -1.10%-2.2% for MA-SA during the 1460 thermal cycles. Based on the results, it can be concluded that the studied PCMs have good thermal properties and thermal reliability for a four-year energy storage period, which corresponds to 1460 thermal cycles, in terms of the change in their melting temperatures and latent heats of fusion.

  3. A Comprehensive Study on the Mechanical and Thermal Properties of Nanoclay Reinforced Polymers at Various Temperatures

    Science.gov (United States)

    2010-03-04

    A Comprehensive Study on the Mechanical and Thermal Properties of Nanoclay Reinforced Polymers at Various Temperatures*† Selen Bayar, Ph.D...thermal properties of nanoclay reinforced polymer resins are investigated at various temperatures. The effect of nanoclay reinforcement was elicited by...The results indicate that the addition of nanoclay to PP leads to a stronger and stiffer nanocomposite. It was also found that the strength and

  4. Experimental approach and micro-mechanical modeling of the creep behavior of irradiated zirconium alloys; Approche experimentale et modelisation micromecanique du comportement en fluage des alliages de zircomium irradies

    Energy Technology Data Exchange (ETDEWEB)

    Ribis, J

    2007-12-15

    The fuel rod cladding, strongly affected by microstructural changes due to irradiation such as high density of dislocation loops, is strained by the end-of-life fuel rod internal pressure and the potential release of fission gases and helium during dry storage. Within the temperature range that is expected during dry interim storage, cladding undergoes long term creep under over-pressure. So, in order to have a predictive approach of the behavior of zirconium alloys cladding in dry storage conditions it is essential to take into account: initial dislocation loops, thermal annealing of loops and creep straining due to over pressure. Specific experiments and modelling for irradiated samples have been developed to improve our knowledge in that field. A Zr-1%Nb-O alloy was studied using fine microstructural investigations and mechanical testing. The observations conducted by transmission electron microscopy show that the high density of loops disappears during a heat treatment. The loop size becomes higher and higher while their density falls. The microhardness tests reveal that the fall of loop density leads to the softening of the irradiated material. During a creep test, both temperature and applied stress are responsible of the disappearance of loops. The loops could be swept by the activation of the basal slip system while the prism slip system is inhibited. Once deprived of loops, the creep properties of the irradiated materials are closed to the non irradiated state, a result whose consequence is a sudden acceleration of the creep rate. Finally, a micro-mechanical modeling based on microscopic deformation mechanisms taking into account experimental dislocation loop analyses and creep test, was used for a predictive approach by constructing a deformation mechanism map of the creep behavior of the irradiated material. (author)

  5. Nanoporous Carbon Monoliths with Tunable Thermal Insulation and Mechanical Properties.

    Science.gov (United States)

    Wang, Xiaopeng; Chen, Fenghua; Luo, Zhenhua; Li, Hao; Zhao, Tong

    2016-01-01

    In this work, nanoscale porous carbon monoliths, with excellent compressive strength and thermal insulation, were obtained with a simple method of carbonizing cured phenol-formaldehyde resin/poly(methyl methacrylate) blends. Apparent density, pore size and morphology of the carbon monoliths were tailored by changing the composition, curing process and carbonization temperature. The continuous nanopores played a key role in enhancing mechanical and thermal performance of the carbon materials. When PMMA concentration was 25%, apparent density and thermal conductivity of the nanoporous carbonaceous monoliths were obtained as low as 1.07 g · cm⁻³ and 0.42 W/(m · K), decreasing by 29.4% and 35.4% than that of carbonaceous monoliths obtained from pure PF; while compressive strength of the nanoporous carbonaceous monoliths was as high as 34 MPa, which was improved over five times than that of pure PF carbon monoliths.

  6. Experimental measurements of thermal properties of high-temperature refractory materials used for thermal energy storage

    Science.gov (United States)

    El-Leathy, Abdelrahman; Jeter, Sheldon; Al-Ansary, Hany; Abdel-Khalik, Said; Golob, Matthew; Danish, Syed Noman; Saeed, Rageh; Djajadiwinata, Eldwin; Al-Suhaibani, Zeyad

    2016-05-01

    This paper builds on studies conducted on thermal energy storage (TES) systems that were built as a part of the work performed for a DOE-funded SunShot project titled "High Temperature Falling Particle Receiver". In previous studies, two small-scale TES systems were constructed for measuring heat loss at high temperatures that are compatible with the falling particle receiver concept, both of which had shown very limited heat loss. Through the course of those studies, it became evident that there was a lack of information about the thermal performance of some of the insulating refractory materials used in the experiments at high temperatures, especially insulating firebrick and perlite concrete. This work focuses on determining the thermal conductivities of those materials at high temperatures. The apparatus consists of a prototype cylindrical TES bin built with the same wall construction used in previous studies. An electric heater is placed along the centerline of the bin, and thermocouples are used to measure temperature at the interfaces between all layers. Heat loss is measured across one of the layers whose thermal conductivity had already been well established using laboratory experiments. This value is used to deduce the thermal conductivity of other layers. Three interior temperature levels were considered; namely, 300°C, 500°C, and 700°C. Results show that the thermal conductivity of insulating firebrick remains low (approximately 0.22 W/m.K) at an average layer temperature as high as 640°C, but it was evident that the addition of mortar had an impact on its effective thermal conductivity. Results also show that the thermal conductivity of perlite concrete is very low, approximately 0.15 W/m.K at an average layer temperature of 360°C. This is evident by the large temperature drop that occurs across the perlite concrete layer. These results should be useful for future studies, especially those that focus on numerical modeling of TES bins.

  7. Studies on Mechanical, Thermal, and Morphological Properties of Glass Fibre Reinforced Polyoxymethylene Nanocomposite

    Directory of Open Access Journals (Sweden)

    K. Mohan Babu

    2014-01-01

    Full Text Available Polyoxymethylene is a material which has excellent mechanical properties similar to Nylon-6 filled with 30% GF. 75% POM and 25% glass fibre (POMGF were blended with nanoclay to increase the tensile and flexural properties. Samples were extruded in twin screw extruder to blend POMGF and (1%, 3%, and 5% Cloisite 25A nanoclay and specimens were prepared by injection moulding process. The tensile properties, flexural properties, impact strength, and hardness were investigated for the nanocomposites. The fibre pull-outs, fibre matrix adhesion, and cracks in composites were investigated by using scanning electron microscopy. 1% POMGF nanocomposite has low water absorption property. Addition of nanoclay improves the mechanical properties and thermal properties marginally. Improper blending of glass fibre and nanoclay gives low tensile strength and impact strength. SEM image shows the mixing of glass fibre and nanoclay among which 1% POMGF nanocomposite shows better properties compared to others. The thermal stability decreased marginally only with the addition of nanoclay.

  8. Creep in electronic ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Routbort, J. L.; Goretta, K. C.; Arellano-Lopez, A. R.

    2000-04-27

    High-temperature creep measurements combined with microstructural investigations can be used to elucidate deformation mechanisms that can be related to the diffusion kinetics and defect chemistry of the minority species. This paper will review the theoretical basis for this correlation and illustrate it with examples from some important electronic ceramics having a perovskite structure. Recent results on BaTiO{sub 3}, (La{sub 1{minus}x}Sr){sub 1{minus}y}MnO{sub 3+{delta}}, YBa{sub 2}Cu{sub 3}O{sub x}, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}, (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and Sr(Fe,Co){sub 1.5}O{sub x} will be presented.

  9. Understanding the mechanisms of amorphous creep through molecular simulation.

    Science.gov (United States)

    Cao, Penghui; Short, Michael P; Yip, Sidney

    2017-12-26

    Molecular processes of creep in metallic glass thin films are simulated at experimental timescales using a metadynamics-based atomistic method. Space-time evolutions of the atomic strains and nonaffine atom displacements are analyzed to reveal details of the atomic-level deformation and flow processes of amorphous creep in response to stress and thermal activations. From the simulation results, resolved spatially on the nanoscale and temporally over time increments of fractions of a second, we derive a mechanistic explanation of the well-known variation of creep rate with stress. We also construct a deformation map delineating the predominant regimes of diffusional creep at low stress and high temperature and deformational creep at high stress. Our findings validate the relevance of two original models of the mechanisms of amorphous plasticity: one focusing on atomic diffusion via free volume and the other focusing on stress-induced shear deformation. These processes are found to be nonlinearly coupled through dynamically heterogeneous fluctuations that characterize the slow dynamics of systems out of equilibrium.

  10. Effects of ageing and moisture content on thermal properties of ...

    African Journals Online (AJOL)

    The mean thermal conductivity ranged from 0.4770 to 0.5654, 0.4804 to 0.5530 and 0.4302 to 0.6102 W/mK at these ages respectively. The thermal diffusivity also ranged from 1.588 to 2.426, 1.614 to 0.1972 and 1.610 to 2.020m2/s while the specific heat capacity ranged from 2.3626 to 3.1495, 2.4900 to 3.7538 and 3.4222 ...

  11. Some aspects of anelastic and microplastic creep of pure Al and two Al-alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sgobba, S. (Lab. de Metallurgie Mecanique, Dept. des Materiaux, Ecole Polytechnique Federale de Lausanne (Switzerland)); Kuenzi, H.U. (Lab. de Metallurgie Mecanique, Dept. des Materiaux, Ecole Polytechnique Federale de Lausanne (Switzerland)); Ilschner, B. (Lab. de Metallurgie Mecanique, Dept. des Materiaux, Ecole Polytechnique Federale de Lausanne (Switzerland))

    1993-11-01

    Anelastic creep of pure Al, commercial Al-Cu and a binary Al-Cu alloy has been measured at room temperature by means of a high resolution laser interferometer. The irreversible component of the deformation was also quantified from measurements of the anelastic creep recovery. The dependence of the deformation-time curves on thermal treatment and cold work is analyzed. The mechanisms responsible for the room temperature anelastic creep are discussed. Materials loaded below their elastic limit can present either a pure anelastic behavior (commercial Al-Cu) or additional viscoelastic creep (pure Al, high purity Al-Cu). For commercial Al-Cu, the presence of an irreversible deformation appears to be mainly related to the state of the surface. A viscoelastic after effect has been measured for this alloy after a Cu-electroplating treatment. As a typical result for room temperature creep, the irreversible deformation depends logarithmically on load time. (orig.).

  12. Irradiation creep lifetime analysis on first wall structure materials for CFETR

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Bing; Peng, Lei, E-mail: penglei@ustc.edu.cn; Zhang, Xiansheng; Shi, Jingyi; Zhan, Jie

    2017-05-15

    Fusion reactor first wall services on the conditions of high surface heat flux and intense neutron irradiation. For China Fusion Engineering Test Reactor (CFETR) with high duty time factor, it is important to analyze the irradiation effect on the creep lifetime of the main candidate structure materials for first wall, i.e. ferritic/martensitic steel, austenite steel and oxide dispersion strengthened steel. The allowable irradiation creep lifetime was evaluated with Larson-Miller Parameter (LMP) model and finite element method. The results show that the allowable irradiation creep lifetime decreases with increasing of surface heat flux, first wall thickness and inlet coolant temperature. For the current CFETR conceptual design, the lifetime is not limited by thermal creep or irradiation creep, which indicated the room for design parameters optimization.

  13. Benefits of high gradient solidification for creep and low cycle fatigue of AM1 single crystal superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Steuer, S., E-mail: Susanne.Steuer@ensma.fr [Institut Pprime, CNRS – ENSMA – Université de Poitiers, UPR CNRS 3346, Department of Physics and Mechanics of Materials, ENSMA – Téléport 2, 1 avenue Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France); Villechaise, P. [Institut Pprime, CNRS – ENSMA – Université de Poitiers, UPR CNRS 3346, Department of Physics and Mechanics of Materials, ENSMA – Téléport 2, 1 avenue Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France); Pollock, T.M. [Materials Department, University of California Santa Barbara, Santa Barbara, CA 93106-5050 (United States); Cormier, J. [Institut Pprime, CNRS – ENSMA – Université de Poitiers, UPR CNRS 3346, Department of Physics and Mechanics of Materials, ENSMA – Téléport 2, 1 avenue Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France)

    2015-10-01

    The influence of high thermal gradient processing on the creep and low cycle fatigue properties of the AM1 Ni-based single crystal superalloy has been studied. Isothermal creep (from 750 °C up to 1200 °C) and low cycle fatigue (750 °C and 950 °C) experiments were performed for AM1 alloy solidified with a conventional radiation cooled (Bridgman) and higher thermal gradient liquid-metal cooled (LMC) casting process to produce coarse and finer-scaled dendritic structures, respectively. There was no significant effect of the casting technique on creep properties, due to the very similar microstructures (γ′-size and γ-channel width) established after full heat treatment of both Bridgman and LMC samples. For low cycle fatigue properties, the benefit of the higher gradient LMC process was dependent on the testing temperature. At 750 °C, cracks primarily initiated at pores created by solidification shrinkage in both Bridgman and LMC samples. Samples produced by the LMC technique demonstrated fatigue lives up to 4 times longer, compared to the Bridgman samples, due to refined porosity. At 950 °C the low cycle fatigue properties of the LMC and conventionally solidified material were not distinguishable due to a shift of crack initiation sites from internal pores to oxidized surface layers or near-surface pores. The benefit of the LMC approach was, however, apparent in fatigue at 950 °C when testing in a vacuum environment. Based on these results, a crack initiation model based on the local slip activity close to casting defect is proposed.

  14. Moisture dependent thermal properties of hydrophilic mineral wool: application of the effective media theory

    Directory of Open Access Journals (Sweden)

    Iñigo Antepara

    2015-09-01

    Full Text Available Thermal properties of mineral wool based materials appear to be of particular importance for their practical applications because the majority of them is used in the form of thermal insulation boards. Every catalogue list of any material producer of mineral wool contains thermal conductivity, sometimes also specific heat capacity, but they give only single characteristic values for dry state of material mostly. Exposure to outside climate or any other environment containing moisture can negatively affect the thermal insulation properties of mineral wool. Nevertheless, the mineral wool materials due to their climatic loading and their environmental exposure contain moisture that can negatively affect their thermal insulation properties. Because the presence of water in mineral wool material is undesirable for the majority of applications, many products are provided with hydrophobic substances. Hydrophilic additives are seldom used in mineral wool products. However, this kind of materials has a good potential for application for instance in interior thermal insulation systems, masonry desalination, green roofs, etc. For these materials, certain moisture content must be estimated and thus their thermal properties will be different than for the dry state. On this account, moisture dependent thermal properties of hydrophilic mineral wool (HMW are studied in a wide range of moisture content using a pulse technique. The experimentally determined thermal conductivity data is analysed using several homogenization formulas based on the effective media theory. In terms of homogenization, a porous material is considered as a mixture of two or three phases. In case of dry state, material consists from solid and gaseous phase. When moistened, liquid phase is also present. Mineral wool consists of the solid phase represented by basalt fibers, the liquid phase by water and the gaseous phase by air. At first, the homogenization techniques are applied for the

  15. Tracking the thermal properties of the lower continental crust

    DEFF Research Database (Denmark)

    Ray, Labani; Förster, Hans-Jürgen; Förster, Andrea

    2015-01-01

    In this study, the bulk thermal conductivity (TC) of 26 rock samples representing different types of granulite-facies rocks, i.e., felsic, intermediate and mafic granulites, from the Southern Granulite Province, India, is measured at dry and saturated conditions with the optical-scanning method. ...

  16. Soil thermal properties at Kalpakkam in coastal south India

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging Solutions)

    2012-02-01

    Feb 1, 2012 ... face energy balance. Such estimates are, however, not easily available. The purpose of this paper is to report a study carried out at Kalpakkam, located on the south east coast of India. Using measured soil temperature and soil heat flux, site specific thermal parameters are estimated. The soil heat flux was ...

  17. Preparation and investigations of thermal properties of copper oxide ...

    Indian Academy of Sciences (India)

    the porous network of the graphite, Al2O3 and CuO. According to the supporting materials, the graphite had the minimum porosity and the maximum crystallite size. Keywords. Composite materials; DSC; thermal energy storage. 1. Introduction. Phase change materials (PCMs), also called latent heat- storage materials, are a ...

  18. Phonon and thermal properties of achiral single wall carbon ...

    Indian Academy of Sciences (India)

    This exceptionally high value of thermal conductivity reflects the one-dimensional conduction behavior of nanotubes with least phonon scattering. Recent ..... In this way one can interpret the double peak structure of the high-energy sub-band of carbon nanotubes. In the case of achiral tubes it was found that the magnitude ...

  19. Crack propagation studies and bond coat properties in thermal ...

    Indian Academy of Sciences (India)

    Ceramic based thermal barrier coatings (TBC) are currently considered as a candidate material for advanced stationary gas turbine components. Crack propagation studies under bending are described that were performed on plasma sprayed ZrO2, bonded by MCrAlY layer to Ni base superalloy. The crack propagation ...

  20. Worldwide distribution of soil dielectric and thermal properties

    NARCIS (Netherlands)

    Hendrickx, J.M.H.; Dam, R.L. van; Borchers, B.; Curtis, J.; Lensen, H.A.; Harmon, R.

    2003-01-01

    Ground penetrating radar and thermal sensors hold much promise for the detection of non-metallic land mines. In previous work we have shown that the performance of ground penetrating radar strongly depends on field soil conditions such as texture, water content, and soil-water salinity since these

  1. Mechanical and Thermal Properties of Polymethyl Methacrylate-BN Nanotube Composites

    Directory of Open Access Journals (Sweden)

    C. Y. Zhi

    2008-01-01

    Full Text Available Polymethyl methacrylate (PMMA-BN nanotube (BNNT composites were fabricated and their mechanical and thermal properties were analyzed. Using a 1 wt.% BNNTs fraction in a polymer, the elastic modulus of PMMA was increased up to 19%. In addition, thermal stability and glass transition temperature of PMMA were also positively affected. The thermal conductivity of PMMA with BNNT additions increased three times. The resultant BNNT-PMMA composites possess the high electrical breakover voltages. Thus our studies clearly indicate that BNNTs are promising nanofillers for improvement of mechanical and thermal conductivity of dielectric polymers under preservation of their electrical insulation.

  2. Viscoelastic and thermal properties of woven sisal fabric reinforced natural rubber biocomposites

    CSIR Research Space (South Africa)

    John, MJ

    2009-01-01

    Full Text Available . They observed that the use of organophilic MMT resulted in a higher Tg and enhanced thermal stability. The properties of man made cellulose and abaca fibres were investigated by Bledzki et al6.The storage modulus of PLA-based composites was found to be much... VISCOELASTIC AND THERMAL PROPERTIES OF WOVEN SISAL FABRIC REINFORCED NATURAL RUBBER BIOCOMPOSITES Journal: Journal of Applied Polymer Science Manuscript ID: APP-2009-08-2614.R1 Wiley - Manuscript type: Research Article Keywords: composites, thermal...

  3. Thermal properties of solid oxide fuel cell perovskite LaCrO3

    Science.gov (United States)

    Parey, Vanshree; Shukla, Aarti; Parveen, Atahar; Bano, Amreen; Khare, Preeti; Gaur, N. K.

    2016-05-01

    The effect of temperature on elastic, cohesive and thermal properties of LaCrO3 in orthorhombic, rhombohedral and cubic phases has been investigated using Modified Rigid Ion Model (MRIM). We present the elastic constants (C11, C12, C44) and other elastic properties like bulk modulus (BT), Young's modulus (E) and shear modulus (G). We have computed the specific heat and volume thermal expansion coefficient as a function of temperature (0K ≤ T ≤ 2000K). The specific heat results are in reasonable agreement with the available experimental data. A check on thermal stability of this compound is made by computing other properties like Debye temperature (θD), cohesive energy (ϕ), Reststrahlen frequency (υ) and Gruneisen parameter (γ). The computed properties reproduce well with the available experimental results. To our knowledge some of the properties are reported for the first time.

  4. Modification and Performance Evaluation of a Low Cost Electro-Mechanically Operated Creep Testing Machine

    Directory of Open Access Journals (Sweden)

    John J. MOMOH

    2010-12-01

    Full Text Available Existing mechanically operated tensile and creep testing machine was modified to a low cost, electro-mechanically operated creep testing machine capable of determining the creep properties of aluminum, lead and thermoplastic materials as a function of applied stress, time and temperature. The modification of the testing machine was necessitated by having an electro-mechanically operated creep testing machine as a demonstration model ideal for use and laboratory demonstrations, which will provide an economical means of performing standard creep experiments. The experimental result is a more comprehensive understanding of the laboratory experience, as the technology behind the creep testing machine, the test methodology and the response of materials loaded during experiment are explored. The machine provides a low cost solution for Mechanics of Materials laboratories interested in creep testing experiment and demonstration but not capable of funding the acquisition of commercially available creep testing machines. Creep curves of strain versus time on a thermoplastic material were plotted at a stress level of 1.95MPa, 3.25MPa and 4.55MPa and temperature of 20oC, 40oC and 60oC respectively. The machine is satisfactory since it is always ready for operation at any given time.

  5. Development of Creep Resistant Mg-Al-Sr Alloys

    Science.gov (United States)

    Pekguleryuz, Mihriban O.; Baril, Eric

    There have been attempts since in the 70's to develop creep resistant magnesium diecasting alloys for automotive applications such as automatic-transmission case and engine components. The earliest die casting alloys developed as a result of these activities were the Mg-Al- RE and Mg-Al-Si systems (AE and AS alloys). The shortcomings of these two alloy systems related to high cost or borderline properties have led to renewed activity in the 90's in the development of magnesium alloys with improved elevaied-temperature properties. This paper presents the development of a new family of creep-resistant Mg alloys based on the Mg-Al-Sr system. Creep resistance, the tensile yield strength and the bolt-load-retention of these alloys at 150°C and 175°C show improvement over Mg-Al-RE and Mg-Al-Si system. The microstructure of the alloys is characterized by Al-Sr-(Mg) containing intermetallic second phases. The absence of the Mg17Al12 phase in the microstructure, either creep-induced or as-cast, is one of the factors that contribute to improved creep-resistance of these alloys over the Mg-Al based diecasting alloys. Furthermore, the alloys exhibit better salt-spray corrosion resistance (0.09-0.15mg/cm2/day) than other commercial magnesium diecasting alloys such as AM60B, AS41, AE42 and the aluminum diecasting alloy A380.

  6. Plasticity and creep of metals

    CERN Document Server

    Rusinko, Andrew

    2011-01-01

    Here is a systematic presentation of the postulates, theorems and principles of mathematical theories of plasticity and creep in metals, and their applications. Special attention is paid to analysis of the advantages and shortcomings of the classical theories.

  7. Spray freeze-dried nanofibrillated cellulose aerogels with thermal superinsulating properties.

    Science.gov (United States)

    Jiménez-Saelices, Clara; Seantier, Bastien; Cathala, Bernard; Grohens, Yves

    2017-02-10

    Nanofibrillated cellulose (NFC) aerogels were prepared by spray freeze-drying (SFD). Their structural, mechanical and thermal insulation properties were compared to those of NFC aerogels prepared by conventional freeze-drying (CFD). The purpose of this investigation is to develop superinsulating bioaerogels by reducing their pore size. Severe reduction of the aerogel pore size and skeleton architecture were observed by SEM, aerogels prepared by SFD method show a fibril skeleton morphology, which defines a mesoporous structure. BET analyses confirm the appearance of a new organization structure with pores of nanometric sizes. As a consequence, the thermal insulation properties were significantly improved for SFD materials compared to CFD aerogel, reaching values of thermal conductivity as low as 0.018W/(mK). Moreover, NFC aerogels have a thermal conductivity below that of air in ambient conditions, making them one of the best cellulose based thermal superinsulating material. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Thermal properties measurements of a silica/pyrocarbon composite at the microscale

    Science.gov (United States)

    De, Indrayush; Battaglia, Jean-Luc; Vignoles, Gérard L.

    2016-12-01

    Laminar pyrocarbons are used as interphases or matrices of carbon/carbon and ceramic-matrix composites in several high-temperature aerospace applications. Depending on their organization at the microscale, they can have a variety of mechanical and thermal properties. Hence, it is important to know, before thermal processing, the properties of these matrices at the micrometer scale in order to improve and control the composite behavior in a macroscopic scale. We use the scanning thermal microscopy on a silica fiber/regenerative laminar pyrocarbon matrix composite to provide an insight into the effective thermal conductivity of pyrocarbon as well as the thermal contact resistance at the interface between fiber and matrix. The conductivity of pyrocarbon is discussed as a function of its nanostructural organization.

  9. Effect of interfacial treatment on the thermal properties of thermal conductive plastics

    Directory of Open Access Journals (Sweden)

    2007-09-01

    Full Text Available In this paper, ZnO, which is processed by different surface treatment approaches, is blended together with polypropylene to produce thermal conductive polymer composites. The composites are analyzed by Fourier transform infrared (FTIR spectroscopy and scanning electron microscopy (SEM to investigate the surface modification of filler, their distribution in the matrix and the condition of two-phase interface. Optimized content of filler surface modifier is investigated as well. The results showed that using low-molecular coupling agent produces positive effect to improve the interface adhesion between filler and matrix, and the thermal conductivity of the composite as well. Macro-molecular coupling agent can strongly improve two-phase interface, but it is not beneficial at obtaining a high thermal conductivity. The blend of ZnO without modification and polypropylene has many defects in the two-phase interface, and the thermal conductivity of the composite is between those of composites produced by previous two approaches. The surface treatment of the filler also allowed producing the composites with lower coefficient of thermal expansion (CTE. As for the content of low-molecular coupling agent, it obtains the best effect at 1.5 wt%.

  10. Photothermal model fitting in the complex plane for thermal properties determination in solids.

    Science.gov (United States)

    Zambrano-Arjona, M A; Peñuñuri, F; Acosta, M; Riech, I; Medina-Esquivel, R A; Martínez-Torres, P; Alvarado-Gil, J J

    2013-02-01

    Thermal properties of solids are obtained by fitting the exact complex photothermal model to the normalized photoacoustic (PA) signal in the front configuration. Simple closed-form expressions for the amplitude and phase are presented in all frequency ranges. In photoacoustic it has been common practice to assume that all the absorptions of radiation take place in the sample. However, in order to obtain the accurate thermal properties it is necessary to consider the PA signal contributions produced at the cell walls. Such contributions were considered in our study. To demonstrate the usefulness of the proposed methodology, commercial stainless steel layers AISI 302 were analyzed. It is shown that using our approach the obtained thermal diffusivity and effusivity were in good agreement with those reported in the literature. Also, a detailed procedure for the calculation of the standard error in the thermal properties is discussed.

  11. Dynamic measurement of coal thermal properties and elemental composition of volatile matter during coal pyrolysis

    Directory of Open Access Journals (Sweden)

    Rohan Stanger

    2014-01-01

    Full Text Available A new technique that allows dynamic measurement of thermal properties, expansion and the elemental chemistry of the volatile matter being evolved as coal is pyrolysed is described. The thermal and other properties are measured dynamically as a function of temperature of the coal without the need for equilibration at temperature. In particular, the technique allows for continuous elemental characterisation of tars as they are evolved during pyrolysis and afterwards as a function of boiling point. The technique is demonstrated by measuring the properties of maceral concentrates from a coal. The variation in heats of reaction, thermal conductivity and expansion as a function of maceral composition is described. Combined with the elemental analysis, the results aid in the interpretation of the chemical processes contributing to the physical and thermal behaviour of the coal during pyrolysis. Potential applications in cokemaking studies are discussed.

  12. Influence of Textile Structure and Silica Based Finishing on Thermal Insulation Properties of Cotton Fabrics

    Directory of Open Access Journals (Sweden)

    G. Rosace

    2016-01-01

    Full Text Available The aim of this work is to investigate the influence of weave structures and silica coatings obtained via sol-gel process on the thermal insulation properties of cotton samples. For this reason three main weave structures (plain, satin, and piqué of cotton fabric were selected with different yarn count, threads per cm, and mass per square meter values. Thereafter, only for the plain weave, the samples were padded using silica sol formed by hydrolysis and subsequent condensation of 3-glycidoxypropyltrimethoxysilane under acidic conditions. The silanized plain weave samples were characterized by TGA and FT-IR techniques. The thermal properties were measured with a home-made apparatus in order to calculate thermal conductivity, resistance, and absorption of all the treated fabric samples. The relationship between the thermal insulation properties of the plain weave fabrics and the concentration of sol solutions has been investigated. Fabrics weave and density were found to strongly influence the thermal properties: piqué always shows the lowest values and satin shows the highest values while plain weave lies in between. The thermal properties of treated high-density cotton plain weave fabric were proved to be strongly influenced by finishing agent concentration.

  13. Measurement of thermal properties of white radish (R. raphanistrum using easily constructed probes.

    Directory of Open Access Journals (Sweden)

    Mfrekemfon Samuel Obot

    Full Text Available Thermal properties are necessary for the design and control of processes and storage facilities of food materials. This study proposes the measurement of thermal properties using easily constructed probes with specific heat capacity calculated, as opposed to the use of Differential Scanning Calorimeter (DSC or other. These probes were constructed and used to measure thermal properties of white radish in the temperature range of 80-20°C and moisture content of 91-6.1% wb. Results showed thermal properties were within the range of 0.71-0.111 Wm-1 C-1 for thermal conductivity, 1.869×10-7-0.72×10-8 m2s-1 for thermal diffusivity and 4.316-1.977 kJ kg-1C-1for specific heat capacity. These results agree with reports for similar products studied using DSC and commercially available line heat source probes. Empirical models were developed for each property through linear multiple regressions. The data generated would be useful in modeling and control of its processing and equipment design.

  14. Thermal Creep Force: Analysis And Application

    Science.gov (United States)

    2016-06-01

    pressure does exist, it produces a small force and would tend to move the vanes with the black side leading contrary to the observed motion . The same year...the simulation. After the particles have completed their motion , particles are randomly selected for collision . The probability that an individual...of the mean free time between collisions at lower pressures. Each simulation ran 100 thousand time steps. We calculated the force by multiplying

  15. Biological properties of a thermally crosslinked gelatin film as a novel anti-adhesive material: Relationship between the biological properties and the extent of thermal crosslinking.

    Science.gov (United States)

    Tsujimoto, Hiroyuki; Tanzawa, Ayumi; Miyamoto, Hiroe; Horii, Tsunehito; Tsuji, Misaki; Kawasumi, Akari; Tamura, Atsushi; Wang, Zhen; Abe, Rie; Tanaka, Shota; Yamanaka, Kouki; Matoba, Mari; Torii, Hiroko; Ozamoto, Yuki; Takamori, Hideki; Suzuki, Shuko; Morita, Shinichiro; Ikada, Yoshito; Hagiwara, Akeo

    2015-10-01

    In order to prevent postoperative adhesion and the related complications, a thermally crosslinked gelatin (TCG) film was developed and the basic biological properties were examined, paying special attention to the relationship between these properties and the extent of crosslinking of the film. The gelatin films crosslinked thermally for five different time periods (0, 1, 3, 8, and 14 hours) were developed and the following tests were performed. Regarding the material characterization of the films, the water content, the water solubility, and the enzymatic degradation for collagenase were found to be closely related to the duration of thermal crosslinking. In an in vitro study conducted to examine the cell growth of fibroblasts cultured on the films, the degree of cell growth, except no crosslinked film, was less than that observed in the control group, thus suggesting that such effects of the films on fibroblast cell growth may be related with their anti-adhesive effects. In in vivo tests, the films crosslinked for longer time periods (3, 8, and 14 hours) were retained for longer after being implanted into the abdominal cavity in rats and showed a significant anti-adhesive effect in the rat cecum adhesion models, indicating that the biodegradability and anti-adhesive effects of the TCG films depend on the duration of thermal crosslinking. In order to develop useful and effective anti-adhesive gelatin film, it is very important to optimize duration of the thermal crosslinking. © 2014 Wiley Periodicals, Inc.

  16. Creep in dispersion strengthened aluminium

    Energy Technology Data Exchange (ETDEWEB)

    Orlova, A.; Kucharova, K.; Cadek, J.; Besterci, M.; Slesar, M.

    1986-01-01

    Results of an investigation of creep at 623 and 723 K in two DISPAL type dispersion strengthened aluminium alloys containing nominal concentrations of 2.5 and 10 vol. pct of dispersed Al4C3 and 2.1 and 3.8 vol. pct of Al2O3, respectively, are presented. The dispersoid particles 25-85 nm in diameter are situated predominantly in grain boundaries and to a less extent as clusters inside the grains. Steady state creep rate, which is strongly applied stress dependent, is most probably controlled by lattice diffusion. A threshold stress characterizing the creep can be identified with the Orowan bowing stress for lattice dislocations. It is shown that creep can be described in terms of lattice diffusion controlled climb of Orowan dislocation loops around dispersed particles. A comparison with creep behavior of dispersion strengthened alloys SAP and NOVAMET shows better resistance of DISPAL as compared to these alloys though its creep ductility is relatively low. 27 references.

  17. Thermal and mechanical properties of PVDF/PANI blends

    Directory of Open Access Journals (Sweden)

    Luiz Francisco Malmonge

    2010-12-01

    Full Text Available Poly(vinylidene fluoride/polyaniline blends of different composition were synthesized by chemical polymerization of aniline in a mixture of Poly(vinylidene fluoride and N,N-dimethylformamide and their thermal and mechanical behavior was investigated as a function of the polyaniline doping level and the composition using thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis and tensile tests techniques. The results showed the blend obtained presents a good thermal stability with low weight loss up to 300 ºC, assigned to water and solvents evaporation. The glass transition and melting point is not affected by the PANI content in the blend, showing that polymers are no miscible. The films produced present a good sustainability; however the presence of the conducting polymer in the blend increases the tensile strength and the Young modulus, while diminishes the elongation at break, as compared to pure PVDF.

  18. Preparation and thermal properties of polystyrene/silica nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Bera, O., E-mail: oskarbera@gmail.com [Faculty of Technology, University of Novi Sad, Bulevar cara Lazara 1, 21000 Novi Sad (Serbia); Pilic, B.; Pavlicevic, J.; Jovicic, M. [Faculty of Technology, University of Novi Sad, Bulevar cara Lazara 1, 21000 Novi Sad (Serbia); Hollo, B.; Szecsenyi, K. Meszaros [Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovica 3, 2100 Novi Sad (Serbia); Spirkova, M. [Institute of Macromolecular Chemistry AS CR v.v.i., Heyrovskeho Nam. 2, 16206 Prague (Czech Republic)

    2011-03-10

    A series of polystyrene/silica nanocomposites with different inorganic nanofiller content were prepared by evaporating of toluene solvent. The weight fraction of silica nanoparticles of an average diameter of 7 nm treated with hexamethyldisilazane was varied (2, 5, 10, 15 and 30 wt.%). The polystyrene nanocomposite morphology was studied by scanning electron microscopy. The thermal stability of the samples was determined using thermogravimetry, coupled with differential scanning calorimetry. The influence of the filler content on glass transition temperature of polystyrene/silica nanocomposites was followed by differential scanning calorimetry. It was found that the polystyrene glass transition temperature was influenced by the hydrophobic silica content. A mathematical method to describe the glass transition temperature dependence on the polystyrene/silica ratio is proposed. According to the experimental results and calculations, the highest thermal stability of the nanocomposite belongs to 18% silica content.

  19. Surfactant assisted surface morphology and thermal properties of polythiophene composites

    Science.gov (United States)

    Vijeth, H.; Niranjana, M.; Yesappa, L.; Chapi, Sharanappa; Raghu, S.; Ashokkumar, S. P.; Devendrappa, H.

    2017-06-01

    Conducting polythiophene (PTH)/aluminium oxide (Al2O3) composites was prepared with camphor sulphonic acid (CSA) as s anionic surfactant by means of in situ chemical oxidation polymerization. The morphology and material phase of PTH/Al2O3 (PTHA) composites were investigated by Field-Emission Scanning Electron Microscopy (FESEM) and Energy-dispersive X-ray spectroscopy (EDX). The FESEM image shows alter the size of grain and EDX results consistent with the presence of Al2O3 and CSA chemical composition. Thermal stability of composites was characterized using TGA/DSC, the results indicate that the PTP/Al2O3 composites have higher thermal stability than that of PTP and decompose at higher temperatures due to addition of anionic surfactant.

  20. Thermal Effect of Ceramic Nanofiller Aluminium Nitride on Polyethylene Properties

    Directory of Open Access Journals (Sweden)

    Omer Bin Sohail

    2012-01-01

    Full Text Available Ethylene polymerization was done to form polyethylene nano-composite with nanoaluminum nitride using zirconocene catalysts. Results show that the catalytic activity is maximum at a filler loading of 15 mg nanoaluminum nitride. Differential scanning calorimeter (DSC and X-ray diffraction (XRD results show that percentage crystallinity was also marginally higher at this amount of filler. Thermal behavior of polyethylene nanocomposites (0, 15, 30, and 45 mg was studied by DSC and thermal gravimetric analyzer (TGA. Morphology of the component with 15 mg aluminium nitride is more fibrous as compared to 0 mg aluminium nitride and higher filler loading as shown by SEM images. In order to understand combustibility behavior, tests were performed on microcalorimeter. Its results showed decrease in combustibility in polyethylene nanocomposites as the filler loading increases.

  1. Role of Defects in Swelling and Creep of Irradiated SiC

    Energy Technology Data Exchange (ETDEWEB)

    Szlufarska, Izabela [Univ. of Wisconsin, Madison, WI (United States); Voyles, Paul [Univ. of Wisconsin, Madison, WI (United States); Sridharan, Kumar [Univ. of Wisconsin, Madison, WI (United States); Katoh, Yutai [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-01-16

    Silicon carbide is a promising cladding material because of its high strength and relatively good corrosion resistance. However, SiC is brittle and therefore SiC-based components need to be carefully designed to avoid cracking and failure by fracture. In design of SiC-based composites for nuclear reactor applications it is essential to take into account how mechanical properties are affected by radiation and temperature, or in other words, what strains and stresses develop in this material due to environmental conditions. While thermal strains in SiC can be predicted using classical theories, radiation-induced strains are much less understood. In particular, it is critical to correctly account for radiation swelling and radiation creep, which contribute significantly to dimensional instability of SiC under radiation. Swelling typically increases logarithmically with radiation dose and saturates at relatively low doses (damage levels of a few dpa). Consequently, swelling-induced stresses are likely to develop within a few months of operation of a reactor. Radiation-induced volume swelling in SiC can be as high as 2%, which is significantly higher than the cracking strain of 0.1% in SiC. Swelling-induced strains will lead to enormous stresses and fracture, unless these stresses can be relaxed via some other mechanism. An effective way to achieve stress relaxation is via radiation creep. Although it has been hypothesized that both radiation swelling and radiation creep are driven by formation of defect clusters, existing models for swelling and creep in SiC are limited by the lack of understanding of specific defects that form due to radiation in the range of temperatures relevant to fuel cladding in light water reactors (LWRs) (<1000°C). For example, defects that can be detected with traditional transmission electron microscopy (TEM) techniques account only for 10-45% of the swelling measured in irradiated SiC. Here, we have undertaken an integrated experimental and

  2. Extended-time-scale creep measurement on Maraging cantilever blade springs

    Energy Technology Data Exchange (ETDEWEB)

    Virdone, Nicole [Mayfield Senior High School, 500 Bellefontaine Street, Pasadena, CA 91105 (United States); LIGO Observatories, California Institute of Technology, Pasadena, CA 91125 (United States)], E-mail: nvirdone@ucla.edu; Agresti, Juri [LIGO Observatories, California Institute of Technology, Pasadena, CA 91125 (United States); Dipartimento di Fisica ' Enrico Fermi' and INFN Sezione di Pisa, Universita di Pisa, Largo Bruno Pontecorvo, I-56127 Pisa (Italy); Bertolini, Alessandro [Chalmers University of Technology, SE-412 96 Goteborg (Sweden); DeSalvo, Riccardo [LIGO Observatories, California Institute of Technology, Pasadena, CA 91125 (United States); Stellacci, Rosalia [LIGO Observatories, California Institute of Technology, Pasadena, CA 91125 (United States); Dipartimento di Fisica ' Enrico Fermi' and INFN Sezione di Pisa, Universita di Pisa, Largo Bruno Pontecorvo, I-56127 Pisa (Italy); Kamp, Justin [DESY, Forschung Linear Collider Division, Notkestrasse 85, D-22607 Hamburg (Germany); Mantovani, Maddalena [LIGO Observatories, California Institute of Technology, Pasadena, CA 91125 (United States); Dipartimento di Fisica ' Enrico Fermi' and INFN Sezione di Pisa, Universita di Pisa, Largo Bruno Pontecorvo, I-56127 Pisa (Italy); Sannibale, Virginio [LIGO Observatories, California Institute of Technology, Pasadena, CA 91125 (United States); Tarallo, Marco [LIGO Observatories, California Institute of Technology, Pasadena, CA 91125 (United States); Dipartimento di Fisica ' Enrico Fermi' and INFN Sezione di Pisa, Universita di Pisa, Largo Bruno Pontecorvo, I-56127 Pisa (Italy); Kaltenegger, Lisa [Harvard Smithsonian Institute for Astrophysics (CfA), 60 Garden Street, Cambridge, MA 02138 (United States)

    2008-08-11

    Two controlled temperature facilities were built to induce an accelerated creep rate in a Maraging steel GAS spring and to measure the material's creep over an artificially extended period of time. The data acquisition of the first experiment lasted for almost a year, but then the blades were allowed to creep for six more years before measuring the permanent deformation integrated over time. The data from this first experiment was polluted by a defect in the data acquisition software, but yielded overall creep limits and an evaluation of the Arrhenius acceleration of creep speed with temperature (1.28{+-}0.13 deg. C{sup -1}). The duration of the second experiment was only 1 year but more free of systematic errors. The effective test period of this second experiment (normalized with the Arrhenius acceleration measured in the first experiment) extends in billions of years showing no sign of anomalous creep. The result of both experiments also produced a simple procedure capable of eliminating all practical effects of creep from the Advanced LIGO seismic isolation and suspensions. Measurements of creep under various stress levels, and of the thermal variations of Young's modulus (2.023 ({+-}0.013)x10{sup -4} deg. C{sup -1}) are reported as well.

  3. Thermal Optical Properties of Lunar Dust Simulants and Their Constituents

    Science.gov (United States)

    Gaier, James R.; Ellis, Shaneise; Hanks, Nichole

    2011-01-01

    The total reflectance spectra of lunar simulant dusts (< 20 mm particles) were measured in order to determine their integrated solar absorptance (alpha) and their thermal emittance (epsilon) for the purpose of analyzing the effect of dust on the performance of thermal control surfaces. All of the simulants except one had a wavelength-dependent reflectivity (p (lambda)) near 0.10 over the wavelength range of 8 to 25 microns and so are highly emitting at room temperature and lower. The 300 K emittance (epsilon) of all the lunar simulants except one ranged from 0.78 to 0.92. The exception was Minnesota Lunar Simulant 1 (MLS-1), which has little or no glassy component. In all cases the epsilon was lower for the < 20 micron particles than for larger particles reported earlier. There was considerably more variation in the lunar simulant reflectance in the solar spectral range (250 to 2500 nm) than in the thermal infrared. As expected, the lunar highlands simulants were more reflective in this wavelength range than the lunar mare simulants. The integrated solar absorptance (alpha) of the simulants ranged from 0.39 to 0.75. This is lower than values reported earlier for larger particles of the same simulants (0.41 to 0.82), and for representative mare and highlands lunar soils (0.74 to 0.91). Since the of some mare simulants more closely matched that of highlands lunar soils, it is recommended that and values be the criteria for choosing a simulant for assessing the effects of dust on thermal control surfaces, rather than whether a simulant has been formulated as a highlands or a mare simulant.

  4. The equivalent thermal properties of a single fracture

    Science.gov (United States)

    Adler, P. M.; Sangare, D.; Thovert, J. F.

    2009-04-01

    The major objective of this communication is to determine in a steady state the equivalent thermal resistance of a fracture embedded in a conducting medium when a constant temperature gradient is imposed far away from the fracture. This gradient is either perpendicular or parallel to the fracture plane. In the first situation, the fracture corresponds roughly to a layer of conductivity lambdaf in between two blocks with the same conductivity lambda; it is equivalent to an additional resistance (which can be negative) in series with the two solid blocks. In the second situation, the fracture corresponds to an element in parallel with the two solid blocks; therefore, it is more straightforward to study the tangential conductivity rather than the tangential resistance. These two quantities are systematically addressed. Of course, the thermal resistance is the inverse of the thermal conductivity and these quantities can be easily derived one from another. It is important to notice that this work is not limited to thermal problems, but to problems which are governed by Laplace equations in the fracture and in the surrounding solid. For instance, consider a fracture filled by debris embedded in a porous medium; the flow on the Darcy scale in these two media are governed by elliptic equations with different coefficients. Therefore, all the methodology and results apply to this case as well. The normal resistance and the tangential conductivity of a single fracture with Gaussian or self affine surfaces are systematically studied as functions of the nature of the materials in contact and of the geometrical parameters. Analytical formulae are provided in the lubrication limit for fractures with sinusoidal apertures; these formulae are used to substantiate empirical formulae for resistance and conductivity. Other approximations based on the combination of series and parallel formulae are tested.

  5. Thermal properties of African yam bean seeds as influenced by ...

    African Journals Online (AJOL)

    The specific heat capacity of African yam bean seeds, measured using copper calorimeter, increased from 2.035 to 2.816 KJ kg-1 k-1, as the moisture content and temperatures increased from 9.6 to 30 % (w.b) and 30 to 50oC respectively. The thermal conductivity of the seed was determined using the line heat source and ...

  6. Analysis of the thermal properties of nanomodified epoxy composite

    Directory of Open Access Journals (Sweden)

    FOMIN Nikolay Egorovich

    2014-02-01

    Full Text Available The paper presents the results of experimental research of epoxy composites modified by nanoparticles. The results were obtained by the method of thermogravimetric analysis. The dependences between the intensity of the processes of thermal degradation in the air and technological factors and content of nanoparticles have been determined. The optimal concentration of 5 types of nanomodifiers besed on carbon nanoclusters adducts, which are functionalized carbon compounds has been revealed. The obvious advantage of these modifiers is their high solubility in polar solvents, that makes the use of these modifiers easier and allows disusing the additional sonication. Investigation of thermooxidation processes of modified epoxy resins was performed in a dynamic mode using TGA/SDTA851e module of STARe System in the temperature range 25÷800⁰C in air atmosphere with simultaneous removal of the gaseous decomposition products. Aluminum oxide (Al₂O₃ was used as the etalon, the temperature speed set was 10 deg./min. It was found out that the process of thermal degradation consists of two stages. The first step is characterized by the main oxidative degradation of polymer and the loss of up to 80% of the original sample weight, the second step is accompanied by the further oxidative decomposition of epoxy composite related to the carbon skeleton destruction. It was proved experimentally that injection of modifiers changes thermal-oxidative decomposition processes and also changes specific energy of epoxy composite according to the type and concentration of nanomodifier. It was shown that the injection of optimal amounts of modifier allows increase of the thermal and energy characteristics, and as a result, the durability of epoxy coatings exposed to aggressive climatic factors.

  7. Synthesis, thermal properties and photoisomerization of trans-[Ru ...

    Indian Academy of Sciences (India)

    chemsci

    ALEXANDER N MAKHINYAa,b,∗, ILYA V KOROLKOVa,b, MAXIM A IL'INa,b,. IRAIDA A BAIDINAa ... log10(k0/sec. −1. ) = 18.9±0.6, and Td = 217 K. Keywords. Ruthenium nitrosyl complexes; pyridine; X-ray crystallography-thermal analysis; photoinduced linkage isomer ... Trans-[Ru(NO)(Py)4Cl](PF6)2·0.5H2O10 and trans-.

  8. Contemporary overview of soil creep phenomenon

    Science.gov (United States)

    Kaczmarek, Łukasz; Dobak, Paweł

    2017-06-01

    Soil creep deformation refers to phenomena which take place in many areas and research in this field of science is rich and constantly developing. The article presents an analysis of the literature on soil creep phenomena. In light of the complexity of the issues involved and the wide variety of perspectives taken, this attempt at systematization seeks to provide a reliable review of current theories and practical approaches concerning creep deformation. The paper deals with subjects such as definition of creep, creep genesis, basic description of soil creep dynamics deformation, estimation of creep capabilities, various fields of creep occurrence, and an introduction to creep modeling. Furthermore, based on this analysis, a new direction for research is proposed.

  9. Thermal and optical properties of electron beam irradiated cellulose triacetate

    Science.gov (United States)

    Nouh, S. A.; Mohamed, Amal; El Hussieny, H. M.

    2009-06-01

    Samples from Cellulose triacetate (CTA) sheets were irradiated with electron beam in the dose range 10-200 kGy. Non-isothermal studies were carried out using thermogravimetric analysis (TGA) to obtain the activation energy of thermal decomposition for CTA polymer. The CTA samples decompose in one main break down stage. The results indicate that the irradiation by electron beam in the dose range 80-200 kGy increases the thermal stability of the polymer samples. Also, the variation of melting temperatures with the electron dose has been determined using differential thermal analysis (DTA). The CTA polymer is characterized by the appearance of one endothermic peak due to melting. It is found that the irradiation in the dose range 10-80 kGy causes defects generation that splits the crystals depressing the melting temperature, while at higher doses (80-200 kGy), the thickness of crystalline structure (lamellae) is increased, thus the melting temperature increases. In addition, the transmission of these samples in the wavelength range 200-2500 nm, as well as any color changes, were studied. The color intensity Δ E* was greatly increased on increasing the electron beam dose, and accompanied by a significant increase in the blue color component.

  10. The thermal properties of the subsurface – key parameters for geothermal energy utilization

    DEFF Research Database (Denmark)

    Norden, Ben; Bording, Thue Sylvester; Balling, N.

    Often the investigation of petrophysical properties is far behind the capabilities of sophisticated modelling techniques applied in basin and geothermal modelling and for which these data serve as an input. Therefore, more in-depth investigations especially of thermal properties are requested. We...

  11. Antimicrobial properties of uncapped silver nanoparticles synthesized by DC arc thermal plasma technique.

    Science.gov (United States)

    Shinde, Manish; Patil, Rajendra; Karmakar, Soumen; Bhoraskar, Sudha; Rane, Sunit; Gade, Wasudev; Amalnerkar, Dinesh

    2012-02-01

    We, herein, report the antimicrobial properties of uncapped silver nanoparticles for a Gram positive model organism, Bacillus subtilis. Uncapped silver nanoparticles have been prepared using less-explored DC arc thermal plasma technique by considering its large scale generation capability. It is observed that the resultant nanoparticles show size as well as optical property dependent antimicrobial effect.

  12. Mechanical, thermal, and moisture properties of plastics with bean as filler

    Science.gov (United States)

    Experiments on polymers using beans as fillers are reported herein. We are looking for desirable mechanical, thermal and moisture properties at economical costs. Poly(lactic acid) (PLA) is studied as the polymeric matrix because it is available and biodegradable. Although the physical properties are...

  13. Effect of Functionalization of Graphene Nanoplatelets on the Mechanical and Thermal Properties of Silicone Rubber Composites

    Directory of Open Access Journals (Sweden)

    Guangwu Zhang

    2016-02-01

    Full Text Available This study investigated the effect of silane and surfactant treatments of graphene nanoplatelets (GnPs on the mechanical and thermal properties of silicone rubber (SR composites. GnPs were modified with aminopropyltriethoxysilane (APTES, vinyltrimethoxysilane (VTMS, and Triton X-100, and then the pristine GnPs and functionalized GnPs were individually incorporated into the SR. Compared with the pristine GnP/SR composite, the composites reinforced with modified GnP showed better tensile strength, elongation at break, and thermal conductivity properties due to better dispersion of modified GnPs and stronger interfacial interactions between the modified GnPs and matrix. The mechanical properties and thermal conductivity of the VTMS-GnP/SR composite were comparable to the properties of the Triton-GnP counterpart, but better than that of the APTES-GnP/SR composite. In addition, the VTMS-GnP/SR composite demonstrated the highest thermal stability and crystallization temperature among the four types of composites. The remarkable improvement of mechanical and thermal properties of the VTMS-GnP/SR composite was mainly due to the covalent linkage of VTMS-GnP with SR. The VTMS treatment was a more appropriate modification of GnP particles to improve the multifunctional properties of SR.

  14. Effects of Thermal Exposure on Properties of Al-Li Alloys

    Science.gov (United States)

    Shah, Sandeep; Wells, Doug; Stanton, William; Lawless, Kirby; Russell, Carolyn; Wagner, John; Domack, Marcia; Babel, Henry; Farahmand, Bahram; Schwab, David; hide

    2002-01-01

    This paper presents viewgraphs on the effects of thermal exposure on the mechanical properties of both developmental and production mature Al-Li alloys. The topics include: 1) Aluminum-Lithium Alloys Composition and Features; 2) Key Characteristics of Al-Li Alloys; 3) Research Approach; 4) Available and Tested Material; and 5) Thermal Exposure Matrix. The alloy temperatures, gage thickness and product forms show that there is no deficit in mechanical properties at lower exposure temperatures in some cases, and a significant deficit in mechanical properties at higher exposure temperatures in all cases.

  15. Mechanical, thermal, and barrier properties of methylcellulose/cellulose nanocrystals nanocomposites

    Directory of Open Access Journals (Sweden)

    Hudson Alves Silvério

    2014-12-01

    Full Text Available In this work, the effects of incorporating cellulose nanocrystals from soy hulls (WSH30 on the mechanical, thermal, and barrier properties of methylcellulose (MC nanocomposites were evaluated. MC/WSH30 nanocomposite films with different filler levels (2, 4, 6, 8, and 10% were prepared by casting. Compared to neat MC film, improvements in the mechanical and barrier properties were observed, while thermal stability was retained. The improved mechanical properties of nanocomposites prepared may be attributed to mechanical percolation of WSH30, formation of a continuous network of WSH30 linked by hydrogen interactions and a close association between filler and matrix.

  16. Mechanical, thermal, and barrier properties of methylcellulose/cellulose nanocrystals nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Silverio, Hudson Alves; Flauzino Neto, Wilson Pires; Silva, Ingrid Souza Vieira da; Rosa, Joyce Rover; Pasquini, Daniel, E-mail: pasquini@iqufu.ufu.br, E-mail: danielpasquini2005@yahoo.com.br [Universidade de Uberlandia (USU), MG (Brazil). Instituto de Quimica; Assuncao, Rosana Maria Nascimento de [Universidade de Uberlandia (USU), Ituiutaba, MG (brazil). Fac. de Ciencias Integradas do Pontal; Barud, Hernane da Silva; Ribeiro, Sidney Jose Lima [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Araraquara, SP (Brazil). Instituto de Quimica

    2014-11-15

    In this work, the effects of incorporating cellulose nanocrystals from soy hulls (WSH{sub 30}) on the mechanical, thermal, and barrier properties of methylcellulose (MC) nanocomposites were evaluated. MC/WSH{sub 30} nanocomposite films with different filler levels (2, 4, 6, 8, and 10%) were prepared by casting. Compared to neat MC film, improvements in the mechanical and barrier properties were observed, while thermal stability was retained. The improved mechanical properties of nanocomposites prepared may be attributed to mechanical percolation of WSH{sub 30}, formation of a continuous network of WSH{sub 30} linked by hydrogen interactions and a close association between filler and matrix. (author)

  17. Soil thermal diffusivity estimated from data of soil temperature and single soil component properties

    Directory of Open Access Journals (Sweden)

    Quirijn de Jong van Lier

    2013-02-01

    Full Text Available Under field conditions, thermal diffusivity can be estimated from soil temperature data but also from the properties of soil components together with their spatial organization. We aimed to determine soil thermal diffusivity from half-hourly temperature measurements in a Rhodic Kanhapludalf, using three calculation procedures (the amplitude ratio, phase lag and Seemann procedures, as well as from soil component properties, for a comparison of procedures and methods. To determine thermal conductivity for short wave periods (one day, the phase lag method was more reliable than the amplitude ratio or the Seemann method, especially in deeper layers, where temperature variations are small. The phase lag method resulted in coherent values of thermal diffusivity. The method using properties of single soil components with the values of thermal conductivity for sandstone and kaolinite resulted in thermal diffusivity values of the same order. In the observed water content range (0.26-0.34 m³ m-3, the average thermal diffusivity was 0.034 m² d-1 in the top layer (0.05-0.15 m and 0.027 m² d-1 in the subsurface layer (0.15-0.30 m.

  18. Study of the Thermal Properties of Raffia Bamboo Vinifera L. Arecaceae

    Directory of Open Access Journals (Sweden)

    E. Foadieng

    2017-01-01

    Full Text Available Raffia is a kind of fast-growing palm tree, from the family of Arecaceae, encountered in marshy areas and along rivers. In this study, the “Raffia Bamboo” is the stalk of a palm, made of a fragile marrow inside a thin shell, smooth and hard to protect the latter. In our region, this material is widely used to build all the low-cost traditional houses and furniture, to make granaries storage of dry products, to build chicken coops, to make decoration. Thus, various jobs are organized around this material, with the fight against poverty. To our knowledge, information on its thermal properties is almost nonexistent. The experimental determination of the transverse thermal properties of the dry shell, the dry marrow, and the whole dry bamboo helped to find, for each, a specific heat, a thermal diffusivity, a thermal conductivity, and finally a thermal effusivity. From the analysis of results, we deduce that the thermal properties of raffia bamboo vinifera L. Arecacea make it a very good thermal insulator.

  19. Impact of biochar addition on thermal properties of a sandy soil: modelling approach

    Science.gov (United States)

    Usowicz, Boguslaw; Lipiec, Jerzy; Lukowski, Mateusz; Bis, Zbigniew; Marczewski, Wojciech; Usowicz, Jerzy

    2017-04-01

    Adding biochar can alter soil thermal properties and increase the water holding capacity and reduce the mineral soil fertilization. Biochar in the soil can determine the heat balance on the soil surface and the temperature distribution in the soil profile through changes in albedo and the thermal properties. Besides, amendment of soil with biochar results in improvement of water retention, fertility and pH that are of importance in sandy and acid soils, widely used in agriculture. In this study we evaluated the effects of wood-derived biochar (0, 10, 20, and 40 Mg ha-1) incorporated to a depth of 0-15 cm on the thermal conductivity, heat capacity, thermal diffusivity and porosity in sandy soil under field conditions. In addition, soil-biochar mixtures of various percentages of biochar were prepared to determine the thermal properties in function of soil water status and density in laboratory. It was shown that a small quantity of biochar added to the soil does not significantly affect all the thermal properties of the soil. Increasing biochar concentration significantly enhanced porosity and decreased thermal conductivity and diffusivity with different rate depending on soil water status. The soil thermal conductivity and diffusivity varied widely and non-linearly with water content for different biochar content and soil bulk density. However, the heat capacity increased with biochar addition and water content linearly and was greater at higher than lower soil water contents. The measured and literature thermal data were compared with those obtained from the analytic model of Zhang et al. (2013) and statistical-physical model (Usowicz et al., 2016) based on soil texture, biochar content, bulk density and water content.

  20. Standard test method for measurement of creep crack growth times in metals

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 This test method covers the determination of creep crack growth (CCG) in metals at elevated temperatures using pre-cracked specimens subjected to static or quasi-static loading conditions. The time (CCI), t0.2 to an initial crack extension δai = 0.2 mm from the onset of first applied force and creep crack growth rate, ˙a or da/dt is expressed in terms of the magnitude of creep crack growth relating parameters, C* or K. With C* defined as the steady state determination of the crack tip stresses derived in principal from C*(t) and Ct (1-14). The crack growth derived in this manner is identified as a material property which can be used in modeling and life assessment methods (15-25). 1.1.1 The choice of the crack growth correlating parameter C*, C*(t), Ct, or K depends on the material creep properties, geometry and size of the specimen. Two types of material behavior are generally observed during creep crack growth tests; creep-ductile (1-14) and creep-brittle (26-37). In creep ductile materials, where cr...