3.2. Process parameters analysis
In this paper, Pam-stamp software was adopted as the simulation for forming and quenching. The process was
subdivided into three steps. The first step is cooling down of the hot blank by transferring from the furnace about
5-6 seconds. In the second step, the hot forming begins. The third step is a quenching stage due to heat transfer
between blank and tools. The friction force at 650-700 0
C was considered with a static friction coefficient of μ =
0.4. The initial temperature of the blank was set as 930 0
C and metallurgical structure was 100% austenite. First,
the simulation without movable pad design, thickness, temperature, and microstructure distribution of the sheet
was observed. It could be seen that the thickness changes with the minimum value of 0.93 mm at the central corner
between twin-U. The thinning ratio is about 34%, can be judged as having risk to cause rupture at the corner as
shown in Fig. 5.