Enhancement on plastic deformation of curved surface shell by sheet hydroforming with optimized pre-bulging process

Abstract

For sheet metal components, the enhancement of formability during plastic deformation is a key criterion in the evaluation of forming quality. To realize homogenous deformation during the forming of curved surface shells, a pre-bulging process combined with sheet hydroforming technology was designed. The pre-bulging shape was optimized using response surface methodology. An experimental setup was manufactured to conduct pre-bulging and sheet hydroforming process. The distribution of strain and thickness were measured to present the formability of the parts. The stress distribution was calculated to analyze the deformation mechanism. Results show that when using appropriate pre-bulging and sheet hydroforming process, the average strain value and uniform deformation parameter can be improved simultaneously. The microhardness of formed shell is increased. The stress state in the center region after pre-bulging is changed to biaxial compression state. It can be concluded that the combination between optimized pre-bulging effect and sheet hydroforming process is a potential method for the enhancement of formability including deformation value and uniformity.