Effect of Sheet Thickness and Punch Roughness on Formability of Sheets in Hydromechanical Deep Drawing

The importance of hydromechanical deep drawing is due to certain advantages over conventional deep drawing such as better formability, reduced number of manufacturing steps, improved surface finish, etc. Due to this, the potential applications of hydromechanical deep drawing have increased in the recent years. In this process, sheet metal parts are formed with the assistance of fluid pressure. The present work addresses the effect of sheet thickness and punch roughness on the formability of interstitial-free steel sheets in hydromechanical deep drawing. Experimental work has been done to study the influence of counter pressure on drawability by varying the sheet thickness and punch roughness. Finite element method has been used to simulate the process, and the results have been found to be in good agreement with the experimental results. It has been found out that the minimum required counter pressure for successful drawing increases with increase in sheet thickness. Drawability of 1.2 mm thick sheet improved with increase in punch roughness. As the punch roughness increases, the minimum required counter pressure decreases because of improved friction holding effect. For the same punch roughness, the minimum required counter pressure increases with increase in draw ratio.