Analysis of the effects of tool and process parameters in hydrodynamic deep drawing assisted by radial pressure

Abstract

Among the various techniques of sheet hydroforming, hydrodynamic deep drawing assisted by radial pressure (HDDRP) has showed good results to shape parts with uniform thickness distribution and high drawing ratio. In this paper, improving formability of the parts in HDDRP is taken into consideration and the effects of some geometrical parameters such as the die profile radius and the gap between the die and the blank holder, and some process parameters such as pressure path and friction coefficient are investigated on thickness distribution of cylindrical cups and punch force. The pressure path has a great effect on the formability. The results showed that increasing the maximum pressure reduces part thinning in the critical regions. Increasing the pressure above a certain value does not have a significant effect on the part forming, but it increases the punch force. The most appropriate pressure path for forming the part studied in this paper is 27 MPa. Furthermore, thinning of the part and maximum punch force decreases by decreasing the friction between the sheet and blank holder. Moreover, increasing the friction coefficient between the punch and sheet to a certain value (0.2) improves forming condition that results in decreasing thinning of the part. Increasing the friction coefficient more than this value does not have a significant effect on forming the part. Friction between the punch and the sheet does not affect the maximum punch force. The results also illustrated that by increasing the gap between the blank holder and the die to 1.2 mm which is more than the thickness of the sheet, thickness reduction of the part and maximum punch force decreases. Increasing the gap above this value does not have a significant effect on ease of sheet flow and improving part formability.