Contents I. Introduction
Sheet metals usually undergo elastic deformation during plastic bending; as a result, springback often occurs after the bending process. Springback is a main defect of bending formation; however, the amount of springback is hard to determine [1], [2]. In addition, from mechanics viewpoint, the seemingly simple bending process is in fact a complex plastic formation process including non-linear, geometric non-linear and contact non-linear processes in the material. Therefore, it is difficult to address the springback problem by theoretical method[3]. Engineers typically determine springback values by empirical data, then test and modify the die accordingly. This empirical method is hardly able to take into consideration the various factors affecting sheet formation, thus lacking quantitative analysis necessary for efficient die design. This leads to blindness in design works, causing waste in manpower, material and time. Finite element (FE) analysis is seen as an effective way in addressing this problem. In particular, FE analysis for large elastic-plastic deformation has been widely used in die design and processing design. Numerical simulation technology is also used in design. Sheet formation process can be simulated with input such as material parameters, process and geometrical parameters. Such analyses and data offer comprehensive and valuable evaluation information for die design and modifications [4].
