Quick establishment of backpressure path in sheet hydroforming process

Abstract

Backpressure path is a vital parameter for the control of dimensional accuracy and shape integrity of the fabricated part and the improvement of material formability in sheet hydroforming. The optimal backpressure path is closely related to the unsupported wall region between the punch and the die, which is determined by the geometric characteristic of the fabricated part. To clarify the relation between the optimal backpressure path and part feature, the workpieces are classified into three types according to the various change patterns of the unsupported area during the hydroforming deformation. To establish the correlation of unsupported region with the reasonable loading locus, three different types of workpieces including a cylindrical part with constant unsupported area, a conical part owning continuous variable noncontact region and an irregular part with composite vacant area were selected to be produced via sheet hydroforming. The forming quality of the three parts was analyzed under different backpressure loci, and the relationship between the optimal backpressure path and the unsupported region was built.