Car Roof Stamping Numerical Simulation Studies

Because of the automobile panels' characteristics,the development cycle of new style car lies on the stamping processes of the automobile panel.It needs a rapid, effective and reliable method to replace the traditional methods for designing automobile panels' die.It is a very complicated mechanics process of the automobile panels' stamping. For involving the multiple non-linear processes,various questions of stamping are very stubborn.People adopt numerical simulation technology to calculate the forming process,which makes it possible,that making accurate analysis of various phenomena during the process.While,stamping forming simulation involves several key theory technologies,such as yield criterion of materials,contact and friction,finite element method,element technology,judgment and prediction of products' failure,etc.So,it is the decisive factors for accuracy and validity of simulation results,that how to select the above technologies reasonably and adopt proper parameters.In this paper,based on large amount of literature and practice,assisted by the CAD software Pro/E,carrying on simulation experimental design by orthogonal design and uniform design technology,adopting the CAE software Dynaform, research on numerical simulation for stamping forming process of a automobile roof panel was done.The main research work and conclusions were as follows:Firstly,to formability,die clearance of the big covering panel should neither be too small nor be too large,while,there is an optimum value.In the paper,simulation was carried out under different die clearance values 0.10mm,0.15mm and 0.20mm,as a result,it was found that the value 0.15mm was appropriate for the roof panel.Secondly,the frictionfactor has great influence on panel's stamping formability. In the paper,the frictionfactors of blank & die,blank & punch,and blank & blank-hold surface,were given different values respectively,simulation experimental design was carried out by orthogonal design technology;By analyzing the forming results,the gradation of the third frictionfactors' influence on the roof's stamping formability and deformation uniformity was confirmed.Thirdly,plastic strain ratio r and strain hardening index n are the two key parameters of material's formability.In the paper,r and n were given different values respectively,simulation experimental design was carried out by orthogonal design technology.Finally,the influence of r and n on the roof's formability were found out,and the request of the blank material was:r≥1.7,n≥0.23.Fourthly,a new way for optimization design of drawbeads was gained:firstly adopting equivalent drawbead of Dynaform,each drawbead was given different equivalent restraining forces,and simulation experimental design was carried out by uniform design technology;secondly analysis of the forming result was carried out, and a optimum set of equivalent drawbead restraining forces was gained;finally,each drawbead's geometric parameters were inversely sought using drawbead restraining force predicting system of Dynaform.It was an innovation of the paper.All above provided theoretical base for establishing stamping craft of automobile panel.