轨道式电磁发射器电枢在高速滑动受到摩擦热的影响熔化产生金属液化层,从而发生转捩。因此研究电枢熔化特性对避免转捩十分重要。针对枢轨接触界面不同粗糙度对电枢熔化特性的影响,建立了传热模型和流体模型,并结合磁扩散模型和电枢弹...轨道式电磁发射器电枢在高速滑动受到摩擦热的影响熔化产生金属液化层,从而发生转捩。因此研究电枢熔化特性对避免转捩十分重要。针对枢轨接触界面不同粗糙度对电枢熔化特性的影响,建立了传热模型和流体模型,并结合磁扩散模型和电枢弹性形变模型,耦合构建了热磁弹流动压模型,采用COMSOL Multiphysics with MATLAB联合仿真软件,迭代求解电枢形变、传热量等参数,分析了枢轨相对速度、粗糙度量级以及粗糙表面纹理分布对枢轨接触界面液化层厚度分布和电枢熔化速度分布的影响。仿真表明,在设定粗糙度不变的发射过程中,枢轨相对速度越大,电枢熔化速度越大,液化层膜厚也越厚;在设定枢轨相对速度不变的发射过程中,枢轨间越粗糙,电枢熔化速度越大且变化趋势不断增大,液化层膜厚也越厚。分析结果对研究转捩发生机理,提高发射效率有重要参考价值。展开更多
This study proposes a general imperfect thermal contact model to predict the thermal contact resistance at the interface among multi-layered composite structures.Based on the Green-Lindsay(GL)thermoelastic theory,semi...This study proposes a general imperfect thermal contact model to predict the thermal contact resistance at the interface among multi-layered composite structures.Based on the Green-Lindsay(GL)thermoelastic theory,semi analytical solutions of temperature increment and displacement of multi-layered composite structures are obtained by using the Laplace transform method,upon which the effects of thermal resistance coefficient,partition coefficient,thermal conductivity ratio and heat capacity ratio on the responses are studied.The results show that the generalized imperfect thermal contact model can realistically describe the imperfect thermal contact problem.Accordingly,it may degenerate into other thermal contact models by adjusting the thermal resistance coefficient and partition coefficient.展开更多
In this paper,the springback of TC4 titanium alloy under hot stamping condition was studied by means of experiment and numerical analysis.Firstly,an analytical model was established to predict the V-shaped springback ...In this paper,the springback of TC4 titanium alloy under hot stamping condition was studied by means of experiment and numerical analysis.Firstly,an analytical model was established to predict the V-shaped springback angleΔαunder the stretch-bending conditions.The model took into account of blank holder force,friction,property of the material,thickness of the sheet and the neutral layer shift.Then,the influence of several process parameters on springback was studied by experiment and finite element simulation using a V-shaped stamping tool.In the hot stamping tests,the titanium alloy sheet fractured seriously at room temperature.The titanium alloy has good formability when the initial temperature of the sheet is 750–900°C.However,the springback angle of formed parts is large and decreases with increasing temperature.The springback angleΔαdecreased by 50%from 0.5°to 0.25°,and the angleΔβdecreased by 46.7%from 1.5°to 0.8°when the initial temperature of sheet increased from 750°C to 900°C.The springback angle of titanium alloy sheet increases gradually with the increase of the punch radius,because of the increase of elastic recovery,the complex distribution of stress,the length of forming region and the decreasing degree of stress.Compared with the simulation results,the analytical model can better predict the springback angleΔα.展开更多
Without considering the influence of heat,existing fractal contact models are not applicable to analyze the contacts when the temperature changes.For this problem,the normal load model and the normal stiffness model o...Without considering the influence of heat,existing fractal contact models are not applicable to analyze the contacts when the temperature changes.For this problem,the normal load model and the normal stiffness model of thermal elasto-plastic contact of rough surfaces are developed respectively in this paper.The proposed model is based on the normal contact mechanics model of fractal theory of anisotropic and thermal elasto-plastic contact theory which can be used to characterize the rough surface thermodynamic properties.Then the validity of the model is verified.Finally,the influence of main parameters on the total normal load and the whole normal stiffness of thermal elasto-plastic contact at the interface is analyzed by contact simulation.The results show that the total normal load of thermal elasto-plastic contact increases with the increases of temperature.The whole normal stiffness of thermal elasto-plastic contact increases with increasing coefficient of linear expansion,scale factor,temperature difference or fractal dimension,but decreases with increasing fractal roughness.This model expands basic theory and applications of traditional models,and can be used to calculate and analyze the contacts when the temperature changes.展开更多
文摘轨道式电磁发射器电枢在高速滑动受到摩擦热的影响熔化产生金属液化层,从而发生转捩。因此研究电枢熔化特性对避免转捩十分重要。针对枢轨接触界面不同粗糙度对电枢熔化特性的影响,建立了传热模型和流体模型,并结合磁扩散模型和电枢弹性形变模型,耦合构建了热磁弹流动压模型,采用COMSOL Multiphysics with MATLAB联合仿真软件,迭代求解电枢形变、传热量等参数,分析了枢轨相对速度、粗糙度量级以及粗糙表面纹理分布对枢轨接触界面液化层厚度分布和电枢熔化速度分布的影响。仿真表明,在设定粗糙度不变的发射过程中,枢轨相对速度越大,电枢熔化速度越大,液化层膜厚也越厚;在设定枢轨相对速度不变的发射过程中,枢轨间越粗糙,电枢熔化速度越大且变化趋势不断增大,液化层膜厚也越厚。分析结果对研究转捩发生机理,提高发射效率有重要参考价值。
基金Projects(42477162,52108347,52178371,52168046,52178321,52308383)supported by the National Natural Science Foundation of ChinaProjects(2023C03143,2022C01099,2024C01219,2022C03151)supported by the Zhejiang Key Research and Development Plan,China+6 种基金Project(LQ22E080010)supported by the Exploring Youth Project of Zhejiang Natural Science Foundation,ChinaProject(LR21E080005)supported by the Outstanding Youth Project of Natural Science Foundation of Zhejiang Province,ChinaProject(2022M712964)supported by the Postdoctoral Science Foundation of ChinaProject(2023AFB008)supported by the Natural Science Foundation of Hubei Province for Youth,ChinaProject(202203)supported by Engineering Research Centre of Rock-Soil Drilling&Excavation and Protection,Ministry of Education,ChinaProject(202305-2)supported by the Science and Technology Project of Zhejiang Provincial Communication Department,ChinaProject(2021K256)supported by the Construction Research Founds of Department of Housing and Urban-Rural Development of Zhejiang Province,China。
文摘This study proposes a general imperfect thermal contact model to predict the thermal contact resistance at the interface among multi-layered composite structures.Based on the Green-Lindsay(GL)thermoelastic theory,semi analytical solutions of temperature increment and displacement of multi-layered composite structures are obtained by using the Laplace transform method,upon which the effects of thermal resistance coefficient,partition coefficient,thermal conductivity ratio and heat capacity ratio on the responses are studied.The results show that the generalized imperfect thermal contact model can realistically describe the imperfect thermal contact problem.Accordingly,it may degenerate into other thermal contact models by adjusting the thermal resistance coefficient and partition coefficient.
基金Projects(U1564202,51705018)supported by the National Natural Science Foundation of ChinaProject supported by the Beijing Laboratory of Modern Transportation Metal Materials and Processing Technology and the Beijing Key Laboratory of Metal Forming Lightweight,China。
文摘In this paper,the springback of TC4 titanium alloy under hot stamping condition was studied by means of experiment and numerical analysis.Firstly,an analytical model was established to predict the V-shaped springback angleΔαunder the stretch-bending conditions.The model took into account of blank holder force,friction,property of the material,thickness of the sheet and the neutral layer shift.Then,the influence of several process parameters on springback was studied by experiment and finite element simulation using a V-shaped stamping tool.In the hot stamping tests,the titanium alloy sheet fractured seriously at room temperature.The titanium alloy has good formability when the initial temperature of the sheet is 750–900°C.However,the springback angle of formed parts is large and decreases with increasing temperature.The springback angleΔαdecreased by 50%from 0.5°to 0.25°,and the angleΔβdecreased by 46.7%from 1.5°to 0.8°when the initial temperature of sheet increased from 750°C to 900°C.The springback angle of titanium alloy sheet increases gradually with the increase of the punch radius,because of the increase of elastic recovery,the complex distribution of stress,the length of forming region and the decreasing degree of stress.Compared with the simulation results,the analytical model can better predict the springback angleΔα.
基金Project(52130501)supported by the National Natural Science Foundation of ChinaProject(LY20E050012)supported by the Natural Science Foundation of Zhejiang Province,ChinaProject(Y201942581)supported by the Scientific Research Project of Education Department of Zhejiang Province,China。
文摘Without considering the influence of heat,existing fractal contact models are not applicable to analyze the contacts when the temperature changes.For this problem,the normal load model and the normal stiffness model of thermal elasto-plastic contact of rough surfaces are developed respectively in this paper.The proposed model is based on the normal contact mechanics model of fractal theory of anisotropic and thermal elasto-plastic contact theory which can be used to characterize the rough surface thermodynamic properties.Then the validity of the model is verified.Finally,the influence of main parameters on the total normal load and the whole normal stiffness of thermal elasto-plastic contact at the interface is analyzed by contact simulation.The results show that the total normal load of thermal elasto-plastic contact increases with the increases of temperature.The whole normal stiffness of thermal elasto-plastic contact increases with increasing coefficient of linear expansion,scale factor,temperature difference or fractal dimension,but decreases with increasing fractal roughness.This model expands basic theory and applications of traditional models,and can be used to calculate and analyze the contacts when the temperature changes.
