Investigations And Applications Of Finite Element Inverse Approach In The Numerical Simulation Of Auto Panel Stamping Processes

As an important part of automobiles, the auto-body has an important influence on the market competition of automobile products. Since the quality of the auto-body is greatly controlled by the quality of the auto panel, many investigations have been carried out to probe into the panel stamping process. As a result, the sheet forming theory and the forming technology are significantly developed. However, the auto panel almost has the complex 3D shape, the short life cycle and the high-quality standard, some effective and reliable techniques are urgently needed to deal with these design problems. Fortunately, the last developed finite element approach for sheet metal forming simulation exactly provides such an effective analysis technology.The emphasis of this thesis is to investigate the application of An effective finite element method called the inverse approach in automobile sheet forming simulations. Firstly, the basic theory of sheet forming is briefly introduced. Then the constitutive relation based on the plastic deformation theory for plane stress is adapted. The workpiece which final geometry is known is discretized by flat triangular membrane elements of constant thickness having three nodes. Assumptions are made regarding the actions of the tools (punch and die) on the sheet at the end of forming process, and then equivalent computation model of external nodal force is put forward. In the third chapter, the finite element inverse approach has been applied to an L-shaped cup drawing simulation. Compared with the experimental result and incremental FEM result, the numerical results of inverse approach validate the efficiency and accuracy of inverse approach.In the fourth chapter, a rear fender has been chosen to be an example of 3D complicated auto panel. Numerical simulation is carried out by finite element inverse approach. The initial blank shape and stress, strain states have been obtained. At the same time, the formability of the fender has been analyzed. The possible defects in the sheet metal forming process are estimated, and several ways are provided to prevent and control these forming defects.