Study On The Mechanism And Numerical Modelling Of Punch Wear In Sheet Extrusion Process

Sheet extrusion is often combined with the fine blanking process to create complex and high-quality parts.However,the work conditions of sheet extrusion process is very complex,and tool wear is easy to occur,which will reduce the tool life.Over the years,a lot of research work and experiments for tool wear have been done by many scholars.However,the wear process is affected by many factors and the period of wear test is time consuming and high cost,so that most of the wear test are only used as verification.The study on the tool wear regulations is still insufficient.This paper focus on the punch wear in sheet extrusion process.Accompanied with numerical modelling,the wear mechanism of the punch in sheet extrusion process were discussed.The main research contents are as follows.The tensile test of ASSAB88 and 42CrMo4 were carried out,and the stress-strain relationship of each material was derived.At the same time,a detailed introduction about the sheet extrusion process,and experimental plan was provided.Base on the sheet extrusion experiment,qualitative analysis and characterization of the punch wear morphology were carried out.The results show that the typical characteristics of punch wear includes scratches,adhesion and depression points.The depression point gradually merged as the increase of extrusion strokes,which resulted in the decline of surface quality of the punch.After different sheet extrusion strokes,the quantitative characterization of the punch wear profile and the distribution of wear depth were carried out.The results show that the wear of punch edge is the highest,the punch face is the second,and the punch side is the smallest.The wear of the punch in the circular zone shows a ‘three-stage' regulation,while the wear in straight zone has basically gone through the initial stage and the stable stage,but there is no obvious trend of destruction stage.By using DEFORM,the distribution of wear depth and the effect of wear coefficient on punch wear under different sheet extrusion strokes were studied.The results show that the wear depth of the punch edge presented a ‘parabolic' distribution,and the maximum wear depth located in the middle zone of the edge.By adjusting the wear coefficient in abrasive wear model,more accurate prediction of the punch wear in sheet extrusion could be achieved.