Research on fatigue crack propagation in CT specimens subjected to loading modes I, II or III

Abstract

The main purpose of the research presented herein was to study the fatigue crack propagation under loading modes I, II or III, either for plane strain or plain stress state. Therefore, several finite element analyses (FEA) were carried out and some experimental tests were performed in a bi-axial servo-hydraulic machine. J-integral values were determined through numerical simulations and stress intensity factors, KI, KII and KIII were inferred at the crack tip of both thick and thin C(T) specimens, assuming several crack’s lengths, and either for plane strain or plane stress state. Load opening-mode I shown to be the predominant mode of crack propagation under plane-strain state, leading to the highest J-integral values calculated, followed by Mode III. In addition, shearing load (mode II) induced the lowest stress intensity factor values at the crack tip both for plane stress state and for plane strain state. Finally, some fatigue crack growth rates (FCG) were determined under loading modes I or III, for thin specimens, at room temperature. C(T) specimens used in the experimental tests were made of two austenitic stainless steels, namely the AISI 316L and the Cr-Mn stainless steel, which are commonly used in several specific engineering applications. Results were compared and some conclusions could be drawn.