| Because of its fast and efficient characteristics,urban rail vehicles have become the first choice for people to travel,and successfully solved the problem of traffic congestion in larger cities.At present,there are two main materials for the rail vehicle body: stainless steel and aluminum alloy.Stainless steel bodywork was widely used in the manufacture of urban rail body,because of its excellent mechanical properties,high temperature resistance,corrosion resistance and other advantages.The SUS301 L series austenitic stainless steels with nano/ultrafine grain structures have the characteristics of high strength and good plasticity.The excellent comprehensive performance is beneficial for the lightweight design of urban rail vehicle body,which has become one of the main materials of the body.The corner part is mainly used to connect the cross beam and the side column of the door,with excellent high and low temperature mechanical properties.The space structure of the corner part is complex,and the metal flow rate varies from the sheet in different parts of the forming process.The flow rate of sheets varies in each position during the forming process.It is difficult for the sheet to flow at the joint,and it is prone to wrinkle defects.The plane part of the corner part is not fully deformed and has a large area of insufficient drawing defects.And stainless steel has a good resistance to deformation.After unloading,the springback of the corner part is large.In the traditional forming method,parts with shape and size are required to meet the requirements by the shaping process.In order to optimize the stamping process,save mould design time and improve the shape accuracy,CATIA software was used to design the forming mould for the corner part of urban rail vehicle with SUS301 L stainless steel in this paper.The finite element software Auto Form was used to simulate the forming process of this kind ofparts with large drawing depth,complex spatial structure and large thickness.Firstly,influences of drawbead with different arrangement and drawbead coefficient on the forming quality of sheet were studied.Then,by adjusting the blank holder force,die clearance,die radius and friction coefficient,the influence of each parameter on the forming quality of the corner part was analyzed to optimize the process.And an effective method to control forming defects was put forward.The results showed that the optimized forming process could eliminate drawing defects,including insufficient drawing and wrinkling.And it improved the contour accuracy of the corner part,so that the springback of the part was controlled within a reasonable range.Through the forming test,qualified forming parts were obtained,and the accuracy of the simulation results was verified. |
