Characterization of residual stresses in austenitic disc springs induced by martensite formation during incremental forming using micromagnetic methods

Disc springs are very common and important machine elements used in almost all fields of mechanical engineering. They are applied when high spring forces are required and only a small mounting space is available, for example, in clutches or rolling bearings. Residual stresses induced by shot peening improve the performance significantly, at the same time shot peening increases the production time and cost. This paper investigates an incremental forming process that allows forming of the spring geometry and generation of residual stresses in a single setup. Accurate measurements of the spring performance are needed to control the product properties, especially when new processes are introduced. The possibility to apply magnetic measurements to control the spring properties is evaluated. A relation between spring characteristics and magnetic Barkhausen noise envelope is established. The findings are supported by residual stress measurements and light optical microscopy, showing martensite islands caused by incremental forming.