Design modification in a multi-stage rectangular cup drawing process with a large aspect ratio by an elasto-plastic finite element analysis

Finite element analysis of multi-stage deep drawing processes is carried out for the process design of rectangular cup drawing with a large aspect ratio. The analysis incorporates shell elements for an elasto-plastic finite element method with an explicit time integration scheme using LS-DYNA3D. Simulation is performed for thorough investigation of failures such as tearing and wrinkling during the forming process. The analysis reveals that the difference of the drawing ratio within the cross-section produces non-uniform metal flow to cause wrinkling and severe extension. The irregular contact condition between the blank and the die also induces non-uniform metal flow. This paper identifies such an unfavorable mechanism in rectangular cup drawing and proposes a modification guideline in the design of the process and the tool shape. The analysis result confirms that the modified design not only improves the quality of a deep-drawn product but also reduces the possibility of failure.