Numerical Simulation Of The Sheet Metal Stretch-Forming Process Based On The Multi-Point Digital Die

Multi-point forming (MPF) is a new means for sheet metal forming. Its main idea is dividing the curved surface of the traditional stamping dies into many pairs of matrices of elements, and then the three-dimensional shape of sheet metal is formed by the curved surface of elements. Relative to the traditional stamping technique, the MPF has saved a lot of time for die designing, die manufacturing and debugging. It has shortened the exploiting cycle and reduced the costs. Now, the MPF technology can be applied extensively in many fields, such as the skin of high-speed locomotive, ship shell plates, automobile panels, and large sculpture pieces in the city. The craft skin stretching technology is an important developing direction for MPF. To realize the craft skin production with MPF, has great impact on our country aero industry.With more and more applications of computer and the maturity of nonlinear finite element, the numerical simulation technology of sheet metal forming has developed quickly. Now the technology is widely adopted in the die design for forecasting forming defects.There are some different loading modes which can be used in the Multi-Point Stretch-Forming (MPSF) for sheet metal forming and may influence the simulation results much. The elastic-cushion technology in the MPF can constrain the dimple defects effectively, but non-uniform deformation of the elastic-cushion also has great impact on the precision of the part. The spring-back of sheet-metal after unloading is unavoidable. It is emergent to solve the problem that how to modify the shape of multi-point die to compensate the non-uniform deformation of the elastic-cushion and spring-back of forming part after unloading. The main contents and results are as follows:1) The foundation for FEM in craft skin MPSF and the determination of the virtual loading velocity...