Estimating Forming Conditions for Deep Drawn SUS304 Square Cups Having no Delayed Cracks Using FE Simulation

Forming conditions for deep drawn SUS304 square cups having no delayed cracks are determined using finite element (FE) simulations based on the threshold % of wall thickening for delay cracking obtained from deep drawing tests of SUS304 cylindrical cups. The maximum drawing ratio and the initial blank thickness are fixed at 1.87 and 0.8 mm, respectively in this study taken into the considerations of the capacity of the press machine i.e., 100 kN. The blank holding forces (BHF), punch corner radius, rp and die corner radius, rd are varied to obtain 75 mm x 75 mm square cups having % of local thickening less than the threshold value i.e., 47% in the cracking zones located adjacent to the top corners of the cups. A quarter 3D FE simulation model of the deep drawing process is constructed, the wall thickness distributions of the cups are calculated. The simulation results showed that the forming conditions for the crack-free cups could be obtained with BHF ≥ 47 kN, rp ≥ 8.5 mm and 6.8 mm ≤ rd ≤ 9.5 mm. A method for designing the forming conditions of deep drawn SUS304 square cups is proposed in this study.