CAE Analysis And Optimization Design Of Automobile Hemming Mould

Hemming is a joining method that is used to connect two metal sheets, such as the inner and outer panels of automobile door, hood and trunk lid. Hemming has a direct impact on the quality of automotive body assembly and appearance. Sheet metal hemming process is complexity complicated. Which make the hemming mould design and production difficult. The small hemming zone and large deformation make analysis more difficult, so the current study of hemming mould is relatively little and not perfect.In order to make some useful attempts and exploration, a series of studies with a view to kinematics in the hemming, finite element analysis and optimization method design of hemming mould are carried out. The work is mainly about kinematics analysis of pre-hemming mechanism, to analyze the kinematic characteristics for selection; The finite element method of sheet metal hemming is introduced to check defects and guide the production; Optimal design method is used to hemming mould design. The method makes sense for control roll-in after hemming. Based on the above ideas, the following research work is carried out by his paper:(1) Pre-hemming is an important step of hemming, which has an important effect to the quality of sheet metal hemming. A variety of pre-hemming such as translational pre-hemming mechanism, pure rotating pre-hemming mechanism and two kinds of composite pre-hemming mechanism are taken kinematics analysis. Two kinds of composite pre-hemming movements uncertainty is found by changing spring stiffness. The uncertainty of mechanism movements do harm to the production of hemming debugging and cutting down the reject rate. The movement principle of four-bar mechanism and single-arm mechanism are analysed. And hemming interference inspection methods are introduced.(2) Forming analysis is done to sheet metal. The car trunk lid hemming mould finite element model is established. The calculation results of the thickness variation, stress, strain and springback are analysed. In order to give the guide to production, the hemming defects are studied.(3) Sensitivity analysis and interval number uncertain optimization method are applied to sheet metal hemming. The hemming process brings roll-in, which is the basic reason leading to un-uniform assembly gap between door and door-fame. Therefore how to control the roll-in is the key factor in design and manufacture of the hemming mould. In this paper, a variety of parameters which may influence roll-in in hemming are generalized. FEM mode is created to find the sensitive parameters. The effect of sensitive parameters in hemming is analysed, which offer direction to the design and debugging in hemming. Uncertainty optimization problem is established. The interval optimization method is applied to objective function approximation model. The small area of sheet metal hemming lead to low efficiency, while the approximation hemming model can solve the problem, which make hemming optimization possible. Based on interval number optimization method, the approximation hemming model offers a new method to control the roll-in in hemming.