Combining the pressure effect with local heat treatment for improving the sheet metal forming process
CHALLENGE - The massive adoption of light alloys is becoming an unavoidable step for respecting the limitations of harmful emissions. Aluminium (Al) alloys, a largely adopted light material, despite providing good resistance to weight ratio, present poor formability at room temperature: the adoption of such alloys thus needs deep investigations aimed at improving the stamping process. The present work deals with the numerical investigation of the advantages of Hydromechanical Deep Drawing (HDD) when AA5754 Tailored Heat Treated Blanks (THTBs) are adopted.
SOLUTION - When non heat-treatable alloys are considered, the THTB approach can be successfully applied to increase the Limit Drawing Ratio (LDR) by changing the peripheral zone into the annealed state starting from a cold-worked blank. If this approach is combined with the advantages of a counterpressure, even more remarkable improvements can be achieved. Due to the large number of involved parameters, the optimized design of both the local treatment and the pressure profile were investigated coupling an axial symmetric Finite Element model with optimization platform modeFRONTIER.
BENEFITS - The improvement of the HDD process when THTBs are adopted has been numerically demonstrated using a two-step multi-objective optimization. Results confirmed the possibility of increasing the LDR from 2.0 up to about 3.0 if combining the adoption of a THTB with the optimal pressure profile. The DD process can be improved even if performed at room temperature, thus needing less complex equipment and leading to a consequent higher tool saving.