Experimental and numerical studies on formability of extra-deep drawing steel in incremental sheet metal forming

This paper focuses on the formability and thickness distribution in incremental sheet forming (ISF) of extra-deep drawing steel (EDD). In ISF, the formability of the material is primarily measured by the maximum formable wall angle and maximum allowable thinning. The maximum wall angle is generally obtained by forming frustum of cones and square pyramids having different wall angles till fracture, which requires a large number of experiments. Therefore in the present study, a continuously varying wall angle conical frustum (VWACF) was used to predict the maximum wall angle to minimize the number of experiments. VWACF is generated using circular, parabolic, elliptical and exponential generatrices. In order to get the maximum allowable thinning, the thickness of the formed geometry has been measured at various points along the depth. In addition, the thickness distribution has been computed theoretically based on the sine law and also using finite element code LS-DYNA. Theoretical and simulated thickness values have been compared with measured thickness values. It was found from the results that the finite element model was more accurate than theoretical model in predicting thickness distribution.