Experimental and numerical analysis of short fatigue cracks in LEAN DSS

M.C. MARINELLI; R. STRUBBIA; S. HEREÑU; I. ALVAREZ

Verbania, Lake Maggiore

Encuentro; XVII International Colloquium "mechanical fatigue of metals" (ICMFM-XVII); 2014

Transmission (TEM) and scanning electron microscopy (SEM) in combination with automated electron back-scattered diffraction (EBSD) techniques is used to study the surface damage as well as the initiation and propagation of short fatigue cracks during low cycle fatigue in the LDSS AL 2003 in two different thermal conditions. Whereas in the as received (AR) condition the initial deformation lines appear in the ferrite phase, in the heat treated (HT) condition the deformation lines appear in both phases at the same time. Moreover, although in the AR condition the short cracks nucleate along intrusion/extrusions in the ferrite phase, in the HT condition the nucleation crack sites are at grain boundaries or along extrusions in the ferritic phase. Additionally, the analysis of cyclic plastic slip activation and short crack propagation behaviour is discussed by applying a numerical model. The path of a short crack not only depends on the Schmid Factor but also through this model is found to be conditioned by the angles of the crack-plane deflection at a grain boundary.