CONICET | Buscador de Institutos y Recursos Humanos

In this paper we study the fatigue crack propagation behavior of an austenitic metastable stainless steel in the near threshold region. The steel used in this research is investigated in two different microstructural conditions: annealed and cold rolled. The fatigue crack propagation tests were conducted using the procedure of ΔK decreasing constant R, and ΔK decreasing constant Kmax. The assessment of the fatigue crack propagation curves using the crack growth trajectory map proposed by Sadananda and Vasudevan [Int. J. Fatigue 26 (2004) 39-47] points out that the mechanism that controls the fatigue crack advance in this material changes as a function of the level of ΔK applied. On the other side, the analysis of the fatigue crack propagation curves shows that the behavior of this material cannot be explained entirely by the concepts of two driving forces. The contribution of the crack closure to the decrease in the fatigue crack growth rate is quantified using two methods, and the measurement of the crack opening load is done using the standard method proposed in the ASTM E647-08ɛ1 and the ACRn2 method. In basis of this last method and in the crack profiles, which are uncharacteristic in materials with austenite/martensite interface, it is established that in this material the crack closure is induced by roughness. At the end of the paper an explanation is suggested for the load ratio effects using the two driving forces and taking into account the contribution of the crack closure.