Setting Residual Stresses in Tensile Stress-Superposed Incremental Sheet Forming

Incremental sheet metal sheet forming (ISF) is a flexible forming process to manufacture sheet metal parts. ISF processes allow a control of residual stresses depending on the process parameters and the acting forming mechanisms. These forming-induced residual stresses highly influence the product properties. This paper presents numerical and experimental results demonstrating the influence of biaxial tensile stress-superposed incremental forming (TSSIF) on the residual stress of truncated cones. An adjustable clamping frame is used to apply defined tensile stresses over the sheet plane in biaxial direction during forming. Residual stresses are evaluated by means of x-ray diffraction on both sides of the cone wall. Tensile stress-superposition shifts the residual stress amplitudes to the tensile residual stress region, depending on the amount of initial tensile stress. TSSIF can be used to improve the product properties of compressive stress-imposed components.