Forming Limit of Al-Mg-Si Based Alloy Automotive Outer Sheet and Its Numerical Application

The forming limit of Al-Mg-Si based alloy sheet was tested and the forming limit diagram (FLD) was determined by using FLD test and automated strain analysis and measurement system (ASAME).The result of comparison analysis showed that the forming limit of Al-Mg-Si based alloy sheet was higher than that of AA6111 sheet at the same thickness and heat treatment state (T4).The above result was also applied to the commercial finite element analysis to serve for the fracture criterion during forming.Automotive door panel was investigated in order to test the application formability of Al-Mg-Si based alloy sheet.Through analysing the distribution of principal strain in FLD,it was found that the shape and position of brake bead played vital role in forming processing and the rigidity problem could be solved by using the double surface designing method.