Limiting Drawing Ratio Analysis of Deep Drawing with Servo Pulse Motion

A servo deep drawing test device was developed in this study to analyze the limiting drawing ratio (LDR) of SPCD metal sheets. This designed deep drawing apparatus was mounted onto the platform of a servo-controlled tensile testing machine, with a hydraulic system managing the blank holder force (BHF). The punch, positioned above the tensile testing machine, was precisely controlled by its integrated servo motion system. The LDR was investigated using two distinct punch motion profiles: a servo pulse motion curve (characterized by multiple motion recovery phases) and a constant velocity motion. Both experimental results and finite element analysis (FEA) confirmed that the servo pulse motion curve yielded a superior LDR compared to the constant velocity motion. Specifically, the LDR was approximately 2.25 for the servo motion curve, whereas it was around 2.187 for the constant speed motion. Furthermore, the forming force and LDR values predicted by FEA closely matched the experimental data, demonstrating that the deep drawing process with the servo motion curve of the punch can be accurately simulated using FEA. Stress distributions within the sheet metal were also observed through FEA for both punch motion profiles. Compared to the constant speed motion, the stress distribution resulting from the servo pulse curve was found to be more uniform and of a lower magnitude, indicating improved material flow and reduced localized stress concentrations.