Low cycle constant amplitude fully reversed strain controlled testing of low carbon and stainless sheet steels for simulation of straightening operations

Ten sheet steel grades have been tested in fully reversed constant strain amplitude loading. Seven low carbon steels with proof stresses from 240 MPa to 1500 MPa were included together with one austenitic stainless steel and two duplex stainless steels. For each steel grade, tests at three different strain levels have been performed and hysteresis loops were recorded during twenty subsequent cycles. The development of cyclic hardening and softening was illustrated both as a function of strain amplitude and as a function of cycle number. Different constitutive models were evaluated to describe the cyclic flow data. It was found that the best fit was obtained with a constitutive model of the type σa=σ0−C·e−k·εpl,a+σx. σa and εpl,a are stress amplitude and plastic strain amplitude respectively in the hysteresis loops. σ0, C and k are material constants. The variable σx is a function of imposed strain amplitude and cycle number.