A new method was proposed for preparing AZ31/1060 composite plates with a corrugated interface,which involved cold-pressing a corrugated surface on the Al plate and then hot-pressing the assembled Mg/Al plate.The resu...A new method was proposed for preparing AZ31/1060 composite plates with a corrugated interface,which involved cold-pressing a corrugated surface on the Al plate and then hot-pressing the assembled Mg/Al plate.The results show that cold-pressing produces intense plastic deformation near the corrugated surface of the Al plate,which promotes dynamic recrystallization of the Al substrate near the interface during the subsequent hot-pressing.In addition,the initial corrugation on the surface of the Al plate also changes the local stress state near the interface during hot pressing,which has a large effect on the texture components of the substrates near the corrugated interface.The construction of the corrugated interface can greatly enhance the shear strength by 2−4 times due to the increased contact area and the strong“mechanical gearing”effect.Moreover,the mechanical properties are largely depended on the orientation relationship between corrugated direction and loading direction.展开更多
The Richtmyer-Meshkov instability ofa ‘V＇ shaped air/helium gaseous interface subjected to a weak shock wave is experimentally studied. A soap film technique is adopted to create a ‘V＇ shaped interface with accura...The Richtmyer-Meshkov instability ofa ‘V＇ shaped air/helium gaseous interface subjected to a weak shock wave is experimentally studied. A soap film technique is adopted to create a ‘V＇ shaped interface with accurate initial conditions. Five kinds of ‘V＇ shaped interfaces with different vertex angles are formed to highlight the effects of initial conditions on the flow characteristics. The results show that a spike is generated after the shock impact, and grows constantly with time. As the vertex angle increases, vortices generated on the interface become less noticeable, and the spike develops less pronouncedly. The linear growth rate of interface width after compression phase is estimated by a linear model and a revised linear model, and the latter is proven to be more effective for the interface with high initial amplitudes. The linear growth rate of interface width is, for the first time in a heavy/light interface configuration, found to be a non-monotonous function of the initial perturbation amplitude-wavelength ratio.展开更多
NiTi particles reinforced aluminum （NiTip/Al） composite was prepared via friction stir processing, elimi- nating interfacial reaction and/or elemental diffusion. The NiTip in the composite maintained the intrinsic c...NiTi particles reinforced aluminum （NiTip/Al） composite was prepared via friction stir processing, elimi- nating interfacial reaction and/or elemental diffusion. The NiTip in the composite maintained the intrinsic characteristic of a reversible thermoelastic phase transformation even after heat-treatment. The shape memory characteristic of the NiTip decreased the coefficient of thermal expansion of the Al matrix, and an apparent two-way shape memory effect was observed in the composite. The composite owned a good combination of adjustable damping and thermal physical properties.展开更多
This paper describes the analysis of the thermal stress concentration and the effects of geometrical shape in the interfacial edge by FEM. It is shown that the elevated stress in a dissim...This paper describes the analysis of the thermal stress concentration and the effects of geometrical shape in the interfacial edge by FEM. It is shown that the elevated stress in a dissimilar material caused by temperature is only restricted in a minor region of the interfacial edge, where the stress peak value and and the stress gradient are high. It is also found that narrowing the boundary angle can effectively reduce the peak value of stress components on the interfacial layer, especially the peeling stress σ y , which is a condition of the debonding failure in the interface.θ=60, an obvious variation, proves that selecting a reasonable edge geometrical shape helps to reduce the value of the maximum stress. At last the methods of relaxing stress concentration and effects of the geometric blunt are also discussed.展开更多
The uniformity of impurity distribution in a melt growth process is significantly determined by the melt convection and melt/crystal interface.Therefore,it is important to investigate the coupling effects of convectio...The uniformity of impurity distribution in a melt growth process is significantly determined by the melt convection and melt/crystal interface.Therefore,it is important to investigate the coupling effects of convection,segregation and growth interface shapes in order to largely improve the crystal quality. In this paper,we employ a finite element algorithm to study the vertical Bridgman growth process of Te doped GaSb crystals.The calculation model consists of unsteady state equations of heat transfer,mass transfer and momentum transfer,as well as their correspondingly boundary and initial conditions.A boundary conformal mapping technique is used to obtain the free melt/crystal interface shape and position which is a prior unknown.The set of algebraic equations obtained after finite element discretion is iteratively solved by Newton Raphson method until a given criterion is reached.展开更多
Wet gas can form liquid loading at the lower line pipe sections,so the transportation efficiency will be impacted and the line pipes will be corroded and even blocked.Therefore,to accurately predict the critical liqui...Wet gas can form liquid loading at the lower line pipe sections,so the transportation efficiency will be impacted and the line pipes will be corroded and even blocked.Therefore,to accurately predict the critical liquid-carrying velocity of gas is of great significance to preventing the liquid loading in wet gas line pipes.In view of the gaseliquid two-phase stratified flow in micro-tilting line pipes with low liquid content,this paper newly established a critical liquid-carrying velocity prediction model considering droplet entrainment according to the momentum balance equation of a gaseliquid two-phase flow and the closure relationship of a new gaseliquid interface shape.Then,based on the experimental data,the new model,FLAT model,ARS model,double-circle model and MARS model were verified and their prediction results were compared.Finally,the new model was applied to analyze the effects of pipe dip,operational pressure,liquid density and gas component on the critical liquid-carrying velocity and critical liquid content of natural gasewater and natural gase-60%glycerine with water stratified flow in a microtilting line pipe.And the following research results were obtained.First,with the increase of pipe dip and liquid density,the critical liquidcarrying velocity increases continuously and the critical liquid content decreases gradually.Second,with the increase of operational pressure and heavy component content,the critical liquid-carrying velocity decreases continuously and the critical liquid content increases gradually.In conclusion,the new model is higher in prediction accuracy and its prediction result is better accordant with the experimental value,so it can be used to predict the critical liquid-carrying velocity in wet gas line pipes.展开更多
The DS(directional solidification) polycrystalline silicon ingot is the most important photovoltaic material today,and the conversion efficiency of solar cells is affected by the morphology and organization of the cry...The DS(directional solidification) polycrystalline silicon ingot is the most important photovoltaic material today,and the conversion efficiency of solar cells is affected by the morphology and organization of the crystal.Uniform grains with larger size are conducive to get high-quality wafer,so improving the cell conversion efficiency.However,grains sizes that are less than 1 mm2 can be observed frequently in the central district of mc-Si ingots,which bring negative effect to the quality of the mc-Si ingot and decrease the electrical performance of wafer.In this paper,we make an attempt to explain the formation mechanism and influence factors of microcrystal in mc-Si ingot with computer simulation technology and theory of component supercooling.It was found that:to avoid production of microcrystal,it's better to increase the value of G/V(V is the growth rate and G is the near-interface temperature gradient),strengthen the melt convection front in the solidification interface and keep a fairly flat solid/melt interface in producing mc-Si ingot.展开更多
基金supported by Guangdong Major Project of Basic and Applied Basic Research, China (No. 2020B0301030006)Fundamental Research Funds for the Central Universities, China (No. SWU-XDJH202313)+1 种基金Chongqing Postdoctoral Science Foundation Funded Project, China (No. 2112012728014435)the Chongqing Postgraduate Research and Innovation Project, China (No. CYS23197)。
文摘A new method was proposed for preparing AZ31/1060 composite plates with a corrugated interface,which involved cold-pressing a corrugated surface on the Al plate and then hot-pressing the assembled Mg/Al plate.The results show that cold-pressing produces intense plastic deformation near the corrugated surface of the Al plate,which promotes dynamic recrystallization of the Al substrate near the interface during the subsequent hot-pressing.In addition,the initial corrugation on the surface of the Al plate also changes the local stress state near the interface during hot pressing,which has a large effect on the texture components of the substrates near the corrugated interface.The construction of the corrugated interface can greatly enhance the shear strength by 2−4 times due to the increased contact area and the strong“mechanical gearing”effect.Moreover,the mechanical properties are largely depended on the orientation relationship between corrugated direction and loading direction.
基金supported by the National Natural Science Foundation of China(U1530103,11302219,and 11272308)
文摘The Richtmyer-Meshkov instability ofa ‘V＇ shaped air/helium gaseous interface subjected to a weak shock wave is experimentally studied. A soap film technique is adopted to create a ‘V＇ shaped interface with accurate initial conditions. Five kinds of ‘V＇ shaped interfaces with different vertex angles are formed to highlight the effects of initial conditions on the flow characteristics. The results show that a spike is generated after the shock impact, and grows constantly with time. As the vertex angle increases, vortices generated on the interface become less noticeable, and the spike develops less pronouncedly. The linear growth rate of interface width after compression phase is estimated by a linear model and a revised linear model, and the latter is proven to be more effective for the interface with high initial amplitudes. The linear growth rate of interface width is, for the first time in a heavy/light interface configuration, found to be a non-monotonous function of the initial perturbation amplitude-wavelength ratio.
基金the National Natural Science Foundation of China(Nos.51101155 and 51331008)the National Basic Research Program of China(No.2012CB619600)
文摘NiTi particles reinforced aluminum （NiTip/Al） composite was prepared via friction stir processing, elimi- nating interfacial reaction and/or elemental diffusion. The NiTip in the composite maintained the intrinsic characteristic of a reversible thermoelastic phase transformation even after heat-treatment. The shape memory characteristic of the NiTip decreased the coefficient of thermal expansion of the Al matrix, and an apparent two-way shape memory effect was observed in the composite. The composite owned a good combination of adjustable damping and thermal physical properties.
文摘This paper describes the analysis of the thermal stress concentration and the effects of geometrical shape in the interfacial edge by FEM. It is shown that the elevated stress in a dissimilar material caused by temperature is only restricted in a minor region of the interfacial edge, where the stress peak value and and the stress gradient are high. It is also found that narrowing the boundary angle can effectively reduce the peak value of stress components on the interfacial layer, especially the peeling stress σ y , which is a condition of the debonding failure in the interface.θ=60, an obvious variation, proves that selecting a reasonable edge geometrical shape helps to reduce the value of the maximum stress. At last the methods of relaxing stress concentration and effects of the geometric blunt are also discussed.
文摘The uniformity of impurity distribution in a melt growth process is significantly determined by the melt convection and melt/crystal interface.Therefore,it is important to investigate the coupling effects of convection,segregation and growth interface shapes in order to largely improve the crystal quality. In this paper,we employ a finite element algorithm to study the vertical Bridgman growth process of Te doped GaSb crystals.The calculation model consists of unsteady state equations of heat transfer,mass transfer and momentum transfer,as well as their correspondingly boundary and initial conditions.A boundary conformal mapping technique is used to obtain the free melt/crystal interface shape and position which is a prior unknown.The set of algebraic equations obtained after finite element discretion is iteratively solved by Newton Raphson method until a given criterion is reached.
基金supported by National Natural Science Foundation of China“Thermodynamic behavior investigation,energy efficiency analysis and structural optimization of longitudinal finned tubes of air-heated vaporizer in the integrated cold energy thermoelectric generator”and“Enhanced heat transfer mechanism and structural optimization of innovative heat transfer tube of open rack vaporizer”(No.:51774237 and 51304160)Shaanxi Provincial Scientific Project for Postdoctors“Study on kinetic behaviors of gaseliquid two-phase swirling flow caused by helical tape in vortex borehole”(No.:20168630)Special Research Program of the Education Department of Shaanxi Province“Integration and optimization of cold energy utilization and light hydrocarbon recycling processes at LNG receiving terminal based on the multi-objective comprehensive evaluation method”(No.:15JK1581).
文摘Wet gas can form liquid loading at the lower line pipe sections,so the transportation efficiency will be impacted and the line pipes will be corroded and even blocked.Therefore,to accurately predict the critical liquid-carrying velocity of gas is of great significance to preventing the liquid loading in wet gas line pipes.In view of the gaseliquid two-phase stratified flow in micro-tilting line pipes with low liquid content,this paper newly established a critical liquid-carrying velocity prediction model considering droplet entrainment according to the momentum balance equation of a gaseliquid two-phase flow and the closure relationship of a new gaseliquid interface shape.Then,based on the experimental data,the new model,FLAT model,ARS model,double-circle model and MARS model were verified and their prediction results were compared.Finally,the new model was applied to analyze the effects of pipe dip,operational pressure,liquid density and gas component on the critical liquid-carrying velocity and critical liquid content of natural gasewater and natural gase-60%glycerine with water stratified flow in a microtilting line pipe.And the following research results were obtained.First,with the increase of pipe dip and liquid density,the critical liquidcarrying velocity increases continuously and the critical liquid content decreases gradually.Second,with the increase of operational pressure and heavy component content,the critical liquid-carrying velocity decreases continuously and the critical liquid content increases gradually.In conclusion,the new model is higher in prediction accuracy and its prediction result is better accordant with the experimental value,so it can be used to predict the critical liquid-carrying velocity in wet gas line pipes.
基金supported by the Natural Science Foundation of Jiangsu Province of China (Grant No BK2008548)
文摘The DS(directional solidification) polycrystalline silicon ingot is the most important photovoltaic material today,and the conversion efficiency of solar cells is affected by the morphology and organization of the crystal.Uniform grains with larger size are conducive to get high-quality wafer,so improving the cell conversion efficiency.However,grains sizes that are less than 1 mm2 can be observed frequently in the central district of mc-Si ingots,which bring negative effect to the quality of the mc-Si ingot and decrease the electrical performance of wafer.In this paper,we make an attempt to explain the formation mechanism and influence factors of microcrystal in mc-Si ingot with computer simulation technology and theory of component supercooling.It was found that:to avoid production of microcrystal,it's better to increase the value of G/V(V is the growth rate and G is the near-interface temperature gradient),strengthen the melt convection front in the solidification interface and keep a fairly flat solid/melt interface in producing mc-Si ingot.
