The phenomenon of heat accumulation and transportation in the composite materials is a very typical and critical issue during drilling process.In this study,a three-dimensional temperature field prediction model is pr...The phenomenon of heat accumulation and transportation in the composite materials is a very typical and critical issue during drilling process.In this study,a three-dimensional temperature field prediction model is proposed using finite difference method,based on the partly homogenization hypothesis of material,to predict temperature field in the process of drilling unidirectional carbon fiber/epoxy(C/E)composites.According to the drilling feed motion,drilling process is divided into four stages to study the temperature distributing characteristics.The results show that the temperature distribution predicted by numerical study has a good agreement with the experimental results.The temperature increases with increasing the drilling depth,and the burn phenomena is observed due to the heat accumulation,especially at the drill exit.Due to the fiber orientation,an elliptical shape of the temperature field along the direction is found for both numerical and experimental studies of C/E composites drilling process.展开更多
Research has been conducted about the hardness prediction for the carburizing and quenching process based on an optimized hardness simulation model,in accordance with the calculation rule of mixed phases.The coupling ...Research has been conducted about the hardness prediction for the carburizing and quenching process based on an optimized hardness simulation model,in accordance with the calculation rule of mixed phases.The coupling field model incorporates carburizing field analysis,temperature field analysis,phase transformation kinetics analysis and a modified hardness calculation model.In determination of the calculation model for hardness,calculation equations are given to be applied to low carbon content(x(C)<0.5%) for the child phases and the martensite hardness is calculated for high carbon content(x(C)>0.5%) in alloy.Then,the complete carburizing-quenching hardness calculation model is built,and the hardness simulation data are corrected considering the influence of residual austenite(RA) on hardness.Hardness simulations of the carburizing and quenching process of 17CrNiMo6 samples have been performed using DEFORM-HT_V10.2 and MATLAB R2013 a.Finally,a series of comparisons of simulation results and measured values show a good agreement between them,which validates the accuracy of the proposed mathematical model.展开更多
This study investigated the temperature field and thawing depth of wide embankment for expressway in permafrost regions based on numerical analysis by using finite element method(FEM).According to specific embankment ...This study investigated the temperature field and thawing depth of wide embankment for expressway in permafrost regions based on numerical analysis by using finite element method(FEM).According to specific embankment section of Qinghai-Tibet highway,computational region for numerical analysis was defined.And numerical model was developed through FEM software named as ABAQUS and was verified by field observed data.The effects by width and height of embankment on the thermal regime of computational region were analyzed based on FEM modeling.Numerical analysis showed that embankment construction has serious disturbance on the thermal stability of ground permafrost showing as annual average ground temperature and the maximum thawing depth keeps increasing with service time increasing.And larger embankment width leads to poorer thermal stability and more serious uneven temperature field of embankment.Raising embankment height can improve the thermal stability; however,the improvement is restricted for wide embankment and it cannot change the degradation trend of thermal stability with service life increasing.Thus,to construct expressway with wide embankment in permafrost regions of Qinghai-Tibet Plateau,effective measures need to be considered to improve the thermal stability of underlying permafrost.展开更多
基金Projects(51475073,51605076,51875079)supported by the National Natural Science Foundation of ChinaProject(2017YFB1301701)supported by the National Key Research and Development Program of China
文摘The phenomenon of heat accumulation and transportation in the composite materials is a very typical and critical issue during drilling process.In this study,a three-dimensional temperature field prediction model is proposed using finite difference method,based on the partly homogenization hypothesis of material,to predict temperature field in the process of drilling unidirectional carbon fiber/epoxy(C/E)composites.According to the drilling feed motion,drilling process is divided into four stages to study the temperature distributing characteristics.The results show that the temperature distribution predicted by numerical study has a good agreement with the experimental results.The temperature increases with increasing the drilling depth,and the burn phenomena is observed due to the heat accumulation,especially at the drill exit.Due to the fiber orientation,an elliptical shape of the temperature field along the direction is found for both numerical and experimental studies of C/E composites drilling process.
基金Projects(51535012,U1604255)supported by the National Natural Science Foundation of ChinaProject(2016JC2001)supported by the Key Research and Development Program of Hunan Province,China
文摘Research has been conducted about the hardness prediction for the carburizing and quenching process based on an optimized hardness simulation model,in accordance with the calculation rule of mixed phases.The coupling field model incorporates carburizing field analysis,temperature field analysis,phase transformation kinetics analysis and a modified hardness calculation model.In determination of the calculation model for hardness,calculation equations are given to be applied to low carbon content(x(C)<0.5%) for the child phases and the martensite hardness is calculated for high carbon content(x(C)>0.5%) in alloy.Then,the complete carburizing-quenching hardness calculation model is built,and the hardness simulation data are corrected considering the influence of residual austenite(RA) on hardness.Hardness simulations of the carburizing and quenching process of 17CrNiMo6 samples have been performed using DEFORM-HT_V10.2 and MATLAB R2013 a.Finally,a series of comparisons of simulation results and measured values show a good agreement between them,which validates the accuracy of the proposed mathematical model.
基金Project(2014BAG05B04)supported by the National Science and Technology Support Program,ChinaProject(51378006)supported by the National Natural Science Foundation of ChinaProject(2242015R30027)supported by the Excellent Young Teacher Program of Southeast University,China
文摘This study investigated the temperature field and thawing depth of wide embankment for expressway in permafrost regions based on numerical analysis by using finite element method(FEM).According to specific embankment section of Qinghai-Tibet highway,computational region for numerical analysis was defined.And numerical model was developed through FEM software named as ABAQUS and was verified by field observed data.The effects by width and height of embankment on the thermal regime of computational region were analyzed based on FEM modeling.Numerical analysis showed that embankment construction has serious disturbance on the thermal stability of ground permafrost showing as annual average ground temperature and the maximum thawing depth keeps increasing with service time increasing.And larger embankment width leads to poorer thermal stability and more serious uneven temperature field of embankment.Raising embankment height can improve the thermal stability; however,the improvement is restricted for wide embankment and it cannot change the degradation trend of thermal stability with service life increasing.Thus,to construct expressway with wide embankment in permafrost regions of Qinghai-Tibet Plateau,effective measures need to be considered to improve the thermal stability of underlying permafrost.
