COMPARISON OF A CYCLIC BEHAVIOR OF 316L STEEL IN UNIAXIAL AND MULTIAXIAL CYCLIC LOADING

A study of the cyclic behavior of austenitic stainless steel 316L was carried out in uniaxial loading, pure torsional loading and multiaxial in phase loading. Experiments were performed on hollow cylindrical specimens with polished surface. The specimens were cyclically loaded at room temperature with constant total strain amplitude. The specimen surface was observed by scanning electron microscopy and the microstructure was investigated by transmission electron microscopy. Differences in the mechanical response in different loading modes are discussed. It was found that the exhibited secondary hardening is caused by both the phase transformation and the appearance of alpha' martensite. The phase transformation is more intense in the case of torsional loading as compared to axial loading. The crack initiation mechanism does not change considerably in individual modes. Persistent slip bands occur and fatigue cracks initiate along them.