Research On Die Surface Designing Method Compensating Springback In Sheet Metal Forming

The sheet metal stamping forming is an advanced, highquality, efficient, low consumption and low cost manufacture technology, and is widely applied in automobile, aircraft, electronic instrument and other industries. But because sheet metal forming is a complicated elastic and plastic mechanical process with large deformation, which includes non-liner problem of geometry, material models and boundary conditions, so there are lots of defects in the forming process, for instance: sheet metal's rupture, wrinkle and springback, etc.Spingback is one of the common defects in sheet metal forming, and have not been solved yet. In order to improve quality of forming parts and reduce production cycle, springback must be controled. A theoretical-analytical method of die's surface designing compensating springback is proposed in this paper.The dispersing method by constant arc length to solve die's surface compensating springback of varied curvature bending for sheet metal is proposed, after that the sheet metal is dispersed as lots of infinitesimal cells. Based on classical theory about springback of arc curvature bending, the formula of bending curvature before springback in elastic-plastic arc bending is derived. Cubic polynomial interpolation is established, combining this formula with nodes' information of every infinitesimal cell, and then part's shape before springback is described by iterative calculation in MATLAB, finally the punch and die's figure compensating springback are gained by offsetting this curve.In order to test if this theoretical-analytical method can meet engineering need, dynamic stamping forming numerical simulation with the die compensating springback designed in Chapter 3 by ANSYS/LS-DYNA is carried in Chapter 4, and then after implicit analysis of springback, part's shape curve is finally gained. Compare with part's true shape in UG, the maximal normal diviation of this two curves is analyzed.By a train of analysis and demonstration, a conclusion can be reached: die's surface compensating springback can be directly gained by this method based on part's ture shape of varied curvature bending, and this method is directly and exactly to solve die's surface with springback compensation. It can not only eliminate springback largely, but also reduce the work to trial and repair die, cut cost and shorten the development cycle of new products.At last, in order to reduce crack, wrinkle and other defects, stamping forming simulation of an automobile covering panel is carried based on Dynaform to expound the processes of simulation and discuss how to forecast defects and do modification to eliminate these defects.