The accurate description of friction is critical in the finite element(FE)simulation of the sheet metal forming process.Usually,friction is oversimplified through the use of a constant Coulomb friction coefficient.In ...The accurate description of friction is critical in the finite element(FE)simulation of the sheet metal forming process.Usually,friction is oversimplified through the use of a constant Coulomb friction coefficient.In this study,the application of an existing multiscale friction model is extended to the hot stamping process.The model accounts for the effects of tool and sheet metal surface topography as well as the evolution of contact pressure,temperature,and bulk strain during hot stamping.Normal load flattening and strip drawing experiments are performed to calibrate the model.The results show that the model can relatively well predict friction in strip draw experiments when the tool surface evolution due to wear is incorporated.Finally,the application of the formulated multiscale friction model was demonstrated in the FE simulation of a hot-stamped part.展开更多
Understanding asperity flattening is vital for a reliable macro-scale modeling of friction and wear.In sheet metal forming processes,sheet surface asperities are deformed due to contact forces between the tools and th...Understanding asperity flattening is vital for a reliable macro-scale modeling of friction and wear.In sheet metal forming processes,sheet surface asperities are deformed due to contact forces between the tools and the workpiece.In addition,as the sheet metal is strained while retaining the normal load,the asperity deformation increases significantly.Deformation of the asperities determines the real area of contact which influences the friction and wear at the tool-sheet metal contact.The real area of contact between two contacting rough surfaces depends on type of loading,material behavior,and topography of the contacting surfaces.In this study,an experimental setup is developed to investigate the effect of a combined normal load and sub-surface strain on real area of contact.Uncoated and zinc coated steel sheets(GI)with different coating thicknesses,surface topographies,and substrate materials are used in the experimental study.Finite element(FE)analyses are performed on measured surface profiles to further analyze the behavior observed in the experiments and to understand the effect of surface topography,and coating thickness on the evolution of the real area of contact.Finally,an analytical model is presented to determine the real area contact under combined normal load and sub-surface strain.The results show that accounting for combined normal load and sub-surface straining effects is necessary for accurate predictions of the real area of contact.展开更多
文摘The accurate description of friction is critical in the finite element(FE)simulation of the sheet metal forming process.Usually,friction is oversimplified through the use of a constant Coulomb friction coefficient.In this study,the application of an existing multiscale friction model is extended to the hot stamping process.The model accounts for the effects of tool and sheet metal surface topography as well as the evolution of contact pressure,temperature,and bulk strain during hot stamping.Normal load flattening and strip drawing experiments are performed to calibrate the model.The results show that the model can relatively well predict friction in strip draw experiments when the tool surface evolution due to wear is incorporated.Finally,the application of the formulated multiscale friction model was demonstrated in the FE simulation of a hot-stamped part.
文摘Understanding asperity flattening is vital for a reliable macro-scale modeling of friction and wear.In sheet metal forming processes,sheet surface asperities are deformed due to contact forces between the tools and the workpiece.In addition,as the sheet metal is strained while retaining the normal load,the asperity deformation increases significantly.Deformation of the asperities determines the real area of contact which influences the friction and wear at the tool-sheet metal contact.The real area of contact between two contacting rough surfaces depends on type of loading,material behavior,and topography of the contacting surfaces.In this study,an experimental setup is developed to investigate the effect of a combined normal load and sub-surface strain on real area of contact.Uncoated and zinc coated steel sheets(GI)with different coating thicknesses,surface topographies,and substrate materials are used in the experimental study.Finite element(FE)analyses are performed on measured surface profiles to further analyze the behavior observed in the experiments and to understand the effect of surface topography,and coating thickness on the evolution of the real area of contact.Finally,an analytical model is presented to determine the real area contact under combined normal load and sub-surface strain.The results show that accounting for combined normal load and sub-surface straining effects is necessary for accurate predictions of the real area of contact.
