Experimental and numerical investigations of the drawing combined with ironing process for a relay barrel-shaped shell cover

The relay shell cover features a complex geometry with stringent requirements for dimensional accuracy, typically necessitating a four-stage PreDs-I forming process: three drawing stages followed by an ironing stage. To enhance metal formability, an intermediate annealing process is conventionally employed between forming stages; however, this significantly increases production costs. This study aims to eliminate the need for annealing by optimizing key process parameters, including the friction coefficient, die clearance, and blank shape. The effects of these parameters on the PreDs-I process are investigated through finite element (FE) simulations and experiments. A high-fidelity FE model is developed using the commercial software DEFORM-3D to simulate the forming process. Additionally, a custom friction-testing apparatus is designed to evaluate tool-workpiece friction under various lubrication conditions. The friction coefficients of different lubricants-palm oil, SCAK-CU355, and SCAK-CU377are measured, revealing that palm oil exhibits superior lubrication performance, resulting in a more uniform thickness distribution in the formed part. Die clearance is found to significantly influence blank formability due to its correlation with frictional effects. Furthermore, an optimized blank shape is determined by analyzing thickness variations at the part’s round corner for different radial offset distances. By implementing these optimized parameters, the relay barrel-shaped shell cover can be successfully manufactured without the annealing process, thereby reducing production costs while maintaining high forming quality.