Thermoforming process optimization for B pillar of 7075 aluminum alloy based on damage factor

To overcome the difficulty in judging the thermoforming failure of 7075 aluminum alloy, a damage factor is introduced as a failure judgment parameter. Firstly, the thermal damage constitutive equation of 7075 aluminum alloy is established, with a corresponding user-defined material subroutine in Ls-dyna created with FORTRAN language. Then a finite element analysis is conducted on the thermoforming of B pillar to study the effects of single parameter change on the maximum forming damage of B pillar. Finally, the forming parameters are optimized by using orthogonal experiment, and a set of optimal parameters of forming process is determined: an initial sheet temperature of 420℃, an initial die temperature of 60℃, a friction coefficient of 0.15, a blank-holder force of 6000N and a stamping speed of 230mm/s. © 2015, Society of Automotive Engineers of China. All right reserved.