To predicate the temperature distribution of concrete-filled steel tubes(CFSTs) being exposure to fire,a finite element analysis model was developed using a finite element package,ANSYS.A suggested value of contact th...To predicate the temperature distribution of concrete-filled steel tubes(CFSTs) being exposure to fire,a finite element analysis model was developed using a finite element package,ANSYS.A suggested value of contact thermal resistance was therefore proposed with the supporting of massive numbers of collected test data.Parametric analysis was conducted subsequently towards the cross-sectional temperature distribution of CFST columns in four-side fire,in which the exposure time,width of the cross section,steel ratio were taken into account with considering contact thermal resistance.It was found that contact thermal resistance has little effect on the overall temperature regulation with the exposure time,the width of cross-section or the change of steel ratio.However,great temperature dropping at the concrete adjacent to the contact interface,and gentle temperature increase at steel tube,exist if considering contact thermal resistance.The results of the study are expected to provide theoretical basis for the fire resistance behavior and design of the CFST columns being exposure to fire.展开更多
Thermal contact resistance plays a very important role in heat transfer efficiency and thermomechanical coupling response between two materials,and a common method to reduce the thermal contact resistance is to fill a...Thermal contact resistance plays a very important role in heat transfer efficiency and thermomechanical coupling response between two materials,and a common method to reduce the thermal contact resistance is to fill a soft interface material between these two materials.A testing system of high temperature thermal contact resistance based on INSTRON 8874 is established in the present paper,which can achieve 600 C at the interface.Based on this system,the thermal contact resistance between superalloy GH600 material and three-dimensional braid C/C composite material is experimentally investigated,under different interface pressures,interface roughnesses and temperatures,respectively.At the same time,the mechanism of reducing the thermal contact resistance with carbon fiber sheet as interface material is experimentally investigated.Results show that the present testing system is feasible in the experimental research of high temperature thermal contact resistance.展开更多
To obtain thermal contact resistance(TCR) between the vertical double-diffused metal-oxide-semiconductor(VDMOS) and the heat sink, we derived the relationship between the total thermal resistance and the contact f...To obtain thermal contact resistance(TCR) between the vertical double-diffused metal-oxide-semiconductor(VDMOS) and the heat sink, we derived the relationship between the total thermal resistance and the contact force imposed on the VDMOS. The total thermal resistance from the chip to the heat sink is measured under different contact forces, and the TCR can be extracted nondestructively from the derived relationship. Finally, the experimental results are compared with the simulation results.展开更多
The study is carried out in imperfect contact with a concrete slab wall attached to a panel based on rice straw compressed in a dynamic frequency regime. We will propose the characterization of thermal insulation for ...The study is carried out in imperfect contact with a concrete slab wall attached to a panel based on rice straw compressed in a dynamic frequency regime. We will propose the characterization of thermal insulation for thermal resistance of contact (<i><span style="font-family:Verdana;">x</span></i><span style="font-family:Verdana;"> = 0.05 m). The impact of heat exchange coefficients on the front face (</span><i><span style="font-family:Verdana;">x</span></i><span style="font-family:Verdana;"> = 0 m) and the rear face (</span><i><span style="font-family:Verdana;">x</span></i><span style="font-family:Verdana;"> = 0.1 m) on these resistors is shown.</span>展开更多
Several theoretical models have been developed so far to predict the thermal conductivities of carbon nanotube(CNT)networks.However,these models overestimated the thermal conductivity significantly.In this paper,we cl...Several theoretical models have been developed so far to predict the thermal conductivities of carbon nanotube(CNT)networks.However,these models overestimated the thermal conductivity significantly.In this paper,we claimed that a CNT network can be considered as a contact thermal resistance network.In the contact thermal resistance network,the temperature of an individual CNT is nonuniform and the intrinsic thermal resistance of CNTs can be ignored.Compared with the previous models,the model we proposed agrees well with the experimental results of single-walled CNT networks.展开更多
In the process of two-pass micro plasma arc welding of titanium alloy sheet,based on the thermal contact resistance theory,a three-dimensional transient heat transfer finite element model of contact heat transfer betw...In the process of two-pass micro plasma arc welding of titanium alloy sheet,based on the thermal contact resistance theory,a three-dimensional transient heat transfer finite element model of contact heat transfer between titanium alloy sheet and flexible fixture was established.The effects of contact upper surface temperature,micro-contact thermal resistance,micro-gap thermal resistance,DC and pulse welding on thermal contact resistance were investigated,and the simulation and experimental results were compared.The results show that the thermal contact resistance increases as the temperature increases when the temperature of the contact upper surface (titanium alloy sheet) is in the range of 290-350 K.The effect of micro-contact thermal resistance on the thermal contact resistance is 26.1%-46.3% larger than the micro-gap thermal resistance.The thermal contact resistance of pulse welding is 3.1%-3.5% larger than DC welding.The error of simulation and experimental results of weld pool depth is 8.6%,which verifies the reliability of the model.展开更多
The method of reliability is proposed for the investigation of thermal contact conductance (TCC) in this study. A new defini- tion is introduced, namely reliability thermal contact conductance (RTCC), which is def...The method of reliability is proposed for the investigation of thermal contact conductance (TCC) in this study. A new defini- tion is introduced, namely reliability thermal contact conductance (RTCC), which is defined as the TCC value that meets the reliability design requirement of the structural materials under consideration. An experimental apparatus with the compensation heater to test the TCC is introduced here. A practical engineering example is utilized to demonstrate the applicability of the pro- posed approach. By using a statistical regression model along with experimental data obtained from the interfaces of the struc- tural materials GH4169 and K417 used in aero-engine, the estimate values and the confidence level of TCC and RTCC values are studied and compared. The results show that the testing values of TCC increase with interface pressure and the proposed RTCC model matches the test results better at high interface pressure.展开更多
As electronic devices continue to evolve toward miniaturization and integration,traditional thermal interface materials(TIMs)are no longer able to meet the ever-tougher thermal management challenges.Owing to their hig...As electronic devices continue to evolve toward miniaturization and integration,traditional thermal interface materials(TIMs)are no longer able to meet the ever-tougher thermal management challenges.Owing to their high thermal conductivity and excellent conformability within a highly confined space,liquid metals have great potential for advanced thermal management in various cutting-edge devices and have become a key candidate for next-generation high-performance TIMs.In addition to already known materials,such as liquid metal alloy TIMs,particle-filled liquid metal TIMs,and liquid metal-filled TIMs,more TIMs are still being developed.This review presents a systematic classification of the liquid metal TIMs developed thus far,interprets the fundamental mechanisms underlying material innovation and in-situ heat transfer enhancement,and comparatively evaluates their respective advantages and shortcomings.Subsequently,a series of representative theoretical models for characterizing the thermal conductivities of composites are summarized,and the limits of the thermal conductivity of liquid metal TIMs are predicted to guide practical R&D efforts.To address the urgent need for higher-performance TIMs to overcome future thermal management challenges of electronic devices,a roadmap is outlined for the development of high-performance liquid metal TIMs,and a strategy for running these technologies is demonstrated.展开更多
Considering the thermal contact resistance and elastic wave impedance at the interface,in this paper we theoretically investigate the thermo-hydro-mechanical(THM)coupling dynamic response of bilayered saturated porous...Considering the thermal contact resistance and elastic wave impedance at the interface,in this paper we theoretically investigate the thermo-hydro-mechanical(THM)coupling dynamic response of bilayered saturated porous media.Fractional thermoelastic theory is applied to porous media with imperfect thermal and mechanical contact.The analytical solutions of the dynamic response of the bilayered saturated porous media are obtained in frequency domain.Furthermore,the effects of fractional derivative parameters and thermal contact resistance on the dynamic response of such media are systematically discussed.Results show that the effects of fractional derivative parameters on the dynamic response of bilayered saturated porous media are related to the thermal contact resistance at the interface.With increasing thermal contact resistance,the displacement,pore water pressure,and stress decrease gradually.展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No.50708028)the Postdoctoral Foundation of Heilongjiang Province(GrantNo.LBH-Q07048)
文摘To predicate the temperature distribution of concrete-filled steel tubes(CFSTs) being exposure to fire,a finite element analysis model was developed using a finite element package,ANSYS.A suggested value of contact thermal resistance was therefore proposed with the supporting of massive numbers of collected test data.Parametric analysis was conducted subsequently towards the cross-sectional temperature distribution of CFST columns in four-side fire,in which the exposure time,width of the cross section,steel ratio were taken into account with considering contact thermal resistance.It was found that contact thermal resistance has little effect on the overall temperature regulation with the exposure time,the width of cross-section or the change of steel ratio.However,great temperature dropping at the concrete adjacent to the contact interface,and gentle temperature increase at steel tube,exist if considering contact thermal resistance.The results of the study are expected to provide theoretical basis for the fire resistance behavior and design of the CFST columns being exposure to fire.
基金supported by the Fundamental Research Funds for the Central Universities (FRF-BR-10-007A and FRF-AS-09-001A)the National Natural Science Foundation of China (10872104)
文摘Thermal contact resistance plays a very important role in heat transfer efficiency and thermomechanical coupling response between two materials,and a common method to reduce the thermal contact resistance is to fill a soft interface material between these two materials.A testing system of high temperature thermal contact resistance based on INSTRON 8874 is established in the present paper,which can achieve 600 C at the interface.Based on this system,the thermal contact resistance between superalloy GH600 material and three-dimensional braid C/C composite material is experimentally investigated,under different interface pressures,interface roughnesses and temperatures,respectively.At the same time,the mechanism of reducing the thermal contact resistance with carbon fiber sheet as interface material is experimentally investigated.Results show that the present testing system is feasible in the experimental research of high temperature thermal contact resistance.
基金Project supported by the National Natural Science Foundation of China(Grant No.61204081)
文摘To obtain thermal contact resistance(TCR) between the vertical double-diffused metal-oxide-semiconductor(VDMOS) and the heat sink, we derived the relationship between the total thermal resistance and the contact force imposed on the VDMOS. The total thermal resistance from the chip to the heat sink is measured under different contact forces, and the TCR can be extracted nondestructively from the derived relationship. Finally, the experimental results are compared with the simulation results.
文摘The study is carried out in imperfect contact with a concrete slab wall attached to a panel based on rice straw compressed in a dynamic frequency regime. We will propose the characterization of thermal insulation for thermal resistance of contact (<i><span style="font-family:Verdana;">x</span></i><span style="font-family:Verdana;"> = 0.05 m). The impact of heat exchange coefficients on the front face (</span><i><span style="font-family:Verdana;">x</span></i><span style="font-family:Verdana;"> = 0 m) and the rear face (</span><i><span style="font-family:Verdana;">x</span></i><span style="font-family:Verdana;"> = 0.1 m) on these resistors is shown.</span>
基金Project support by the National Natural Science Foundation of China(Grant No.52127811)Department of Science and Technology of Jiangsu Province,China(Grant No.BK20220032)。
文摘Several theoretical models have been developed so far to predict the thermal conductivities of carbon nanotube(CNT)networks.However,these models overestimated the thermal conductivity significantly.In this paper,we claimed that a CNT network can be considered as a contact thermal resistance network.In the contact thermal resistance network,the temperature of an individual CNT is nonuniform and the intrinsic thermal resistance of CNTs can be ignored.Compared with the previous models,the model we proposed agrees well with the experimental results of single-walled CNT networks.
基金This work was supported by the Hebei Provincial Natural Science Fund Key Project(F2017202243)Hebei Provincial Natural Science Fund(E2019202132)+3 种基金Tianjin Natural Science Foundation(18JCTPJC54700)Hebei Province Higher Education Science and Technology Research Project(BJ2019049)China Postdoctoral Science Foundation(2018M641616)National Natural Science Foundation of China(51705128).
文摘In the process of two-pass micro plasma arc welding of titanium alloy sheet,based on the thermal contact resistance theory,a three-dimensional transient heat transfer finite element model of contact heat transfer between titanium alloy sheet and flexible fixture was established.The effects of contact upper surface temperature,micro-contact thermal resistance,micro-gap thermal resistance,DC and pulse welding on thermal contact resistance were investigated,and the simulation and experimental results were compared.The results show that the thermal contact resistance increases as the temperature increases when the temperature of the contact upper surface (titanium alloy sheet) is in the range of 290-350 K.The effect of micro-contact thermal resistance on the thermal contact resistance is 26.1%-46.3% larger than the micro-gap thermal resistance.The thermal contact resistance of pulse welding is 3.1%-3.5% larger than DC welding.The error of simulation and experimental results of weld pool depth is 8.6%,which verifies the reliability of the model.
基金National Natural Science Foundation of China (11001005)Innovation Foundation of BUAA for PhD Graduates (YWF-12-RBYJ-03)
文摘The method of reliability is proposed for the investigation of thermal contact conductance (TCC) in this study. A new defini- tion is introduced, namely reliability thermal contact conductance (RTCC), which is defined as the TCC value that meets the reliability design requirement of the structural materials under consideration. An experimental apparatus with the compensation heater to test the TCC is introduced here. A practical engineering example is utilized to demonstrate the applicability of the pro- posed approach. By using a statistical regression model along with experimental data obtained from the interfaces of the struc- tural materials GH4169 and K417 used in aero-engine, the estimate values and the confidence level of TCC and RTCC values are studied and compared. The results show that the testing values of TCC increase with interface pressure and the proposed RTCC model matches the test results better at high interface pressure.
文摘As electronic devices continue to evolve toward miniaturization and integration,traditional thermal interface materials(TIMs)are no longer able to meet the ever-tougher thermal management challenges.Owing to their high thermal conductivity and excellent conformability within a highly confined space,liquid metals have great potential for advanced thermal management in various cutting-edge devices and have become a key candidate for next-generation high-performance TIMs.In addition to already known materials,such as liquid metal alloy TIMs,particle-filled liquid metal TIMs,and liquid metal-filled TIMs,more TIMs are still being developed.This review presents a systematic classification of the liquid metal TIMs developed thus far,interprets the fundamental mechanisms underlying material innovation and in-situ heat transfer enhancement,and comparatively evaluates their respective advantages and shortcomings.Subsequently,a series of representative theoretical models for characterizing the thermal conductivities of composites are summarized,and the limits of the thermal conductivity of liquid metal TIMs are predicted to guide practical R&D efforts.To address the urgent need for higher-performance TIMs to overcome future thermal management challenges of electronic devices,a roadmap is outlined for the development of high-performance liquid metal TIMs,and a strategy for running these technologies is demonstrated.
基金Project supported by the National Natural Science Foundation of China(Nos.52108347 and 51779217)the Primary Research and Development Plan of Zhejiang Province(Nos.2019C03120 and 2020C01147),China。
文摘Considering the thermal contact resistance and elastic wave impedance at the interface,in this paper we theoretically investigate the thermo-hydro-mechanical(THM)coupling dynamic response of bilayered saturated porous media.Fractional thermoelastic theory is applied to porous media with imperfect thermal and mechanical contact.The analytical solutions of the dynamic response of the bilayered saturated porous media are obtained in frequency domain.Furthermore,the effects of fractional derivative parameters and thermal contact resistance on the dynamic response of such media are systematically discussed.Results show that the effects of fractional derivative parameters on the dynamic response of bilayered saturated porous media are related to the thermal contact resistance at the interface.With increasing thermal contact resistance,the displacement,pore water pressure,and stress decrease gradually.