Cyclic deformation behavior of non-oriented electrical steel sheets

The cyclic deformation behavior of a fully processed, non-oriented electrical steel sheet is investigated in dependence on loading condition and control mode. Therefore, strain- and stress-controlled fatigue tests are performed to determine cyclic deformation curves in the low- and high-cycle fatigue regimes. With symmetric strain control, continuous cyclic hardening occurs, while in asymmetric stress control with non-zero mean stress, pronounced ratcheting takes place. Depending on the loading condition, the material can exhibit a transitional period with cyclic softening. This effect is present at intermediate amplitudes in the yield point region. It emerges as the dislocation movement is initially inhibited, while at higher amplitudes, cyclic hardening occurs from the very beginning. The evolving dislocation structures are characterized by the predominantly planar slip behavior of the alloy.