Experimental investigation and finite element modelling of residual stress control in disc springs made of metastable austenitic stainless steel (MASS) using incremental sheet forming (ISF)

Abstract The current study presents a novel methodology to generate compressive residual stresses in disc springs made of metastable austenitic stainless steel by using incremental sheet forming. Conventional disc spring manufacturing uses a forming operation and a subsequent shot peening treatment to generate residual stresses. Shot peening changes the shape of the springs and the spring characteristics. In this contribution, incremental sheet forming is used to form the disc springs and to control the residual stress in a single set-up. As an alternative, pre-formed disc springs are treated using incremental sheet forming to induce the desired residual stresses. The changes in the spring properties are due to the formation of deformation-induced martensite, which is characterized using metallographic investigations and disc compression tests. A significant enhancement of the spring properties is observed. Further, a numerical model considering the transformation induced plasticity effect is used to simulate the process. The process parameters of incremental sheet forming, i.e., tool diameter and tool step-down, are varied to characterize the influence on the spring properties. The numerical results are compared to the experimental observations. It is found that the proposed forming process can be used for controlling the shape and residual stresses in disc springs.