Prediction of Negative Bulge in Two Point Incremental Forming of an Asymmetric Shape Part

Abstract

The bulging effect in incremental sheet forming (ISF) has been explained by the build-up of compressive stresses during forming resulting in the material at the center to bulge inward or outward. In this study, effect of step size on the formation of a bulge in an asymmetric shape in two point incremental forming (TPIF) is examined. Experimentally validated finite element models were developed to simulate the forming at both the macro scale, and using a finer mesh to generate the surface profile. The formation of the bulge is determined to be due to a combination of compressive stresses and an instability created by the material in the underformed area during the forming operation.