An analysis of the superplastic forming of a circular sheet diaphragm

Abstract A general method of analysis has been formulated for the study of superplastic forming of a sheet diaphragm into a circular cavity. In this analysis, the bulge shape is assumed to be ellipsoidal, whereas most of the previous analyses have assumed that the bulge surface remains spherical during forming. Results suggest that a low strain-rate sensitivity (m) value of the forming material gives rise to a prolate shape, which is consistent with experimental observations. Stress and strain distributions and pressurization profiles during forming at a constant strain rate at the pole were examined for materials with different m values and for ellipsoidal bulges with various aspect ratios. Experimental work has also been done to assess the validity of the model.