Deformation Behavior of Extra Deep Drawing Steel in Single-Point Incremental Forming

Abstract

This paper focuses on investigation of formability, thickness distribution, strain distribution, and microstructural changes of extra deep drawing (EDD) steel in the single-point incremental forming (SPIF) process. For this, pyramidal frustums with varying wall angle along the depth were formed till the fracture. The parts were designed by rotating circular, elliptic, parabolic, and exponential curve segments. The varying wall angle pyramidal frustums (VWAPF) can minimize the number of experiments required to find the maximum wall angle compared to conventional constant wall angle pyramidal frustums. The maximum wall angle corresponding to fracture depth and thickness distribution along the depth was measured for parts with different generatrices. The maximum formable wall angle was found to be 73 ± 2°. Experimental thickness distribution was compared with the thickness distribution obtained from numerical simulations using the LS-DYNA software. A good correlation was found between experimental and numerical results. Furthermore, the distribution of strains obtained from numerical simulations revealed that the faces of the pyramid were under plane strain conditions, while the corners were toward biaxial stretching. The microstructural study showed that there was a grain refinement after incremental forming of the sheet.