DIFFERENCES IN THE CYCLIC DEFORMATION-BEH AVIOR OF QUENCHED AND TEMPERED STEEL 42-CRMO-4 (AISI-4140) DUE TO STRESS-CONTROL AND STRAIN-CONTROL

Cyclic stress-strain-curves and Manson-Coffin-plots of quenched and te mpered steel 42 CrMo 4 (AISI 4140) strongly depend on whether they are determined under stress- or total-strain-control. At total-strain-con trolled experiments. this is caused on the: one hand by comparatively high initial stress-amplitudes which lead to distinctive cyclic workso ftening. On the other hand, the occurring differences in the evolution of inhomogeneous deformation patterns at both types of loading, which can be recorded by means of photoelasticity and microscopy, lead to d ifferently distributed plastic deformations and to different integral values of plastic strain.