Fatigue crack growth; Steels; Three point bend; Pivot point; Compliance
Constant load amplitude fatigue crack growth rate (FCGR) behaviour of A533B steel was studied using compact tension (CT) and three point bend (TPB) specimens. TPB specimens belonged to two categories, namely, span to width (S/W) ratio equal to 4 and 2 respectively. The thickness of TPB
specimens was 10 mm while CT specimens were of 10 and 20 mm thickness. Paris law constants were obtained for the different geometries of CT and TPB specimens. It has been confirmed that size effects are absent for the test conditions investigated. During the fatigue testing of TPB specimens, unloading compliance was determined using a crack mouth opening displacement (CMOD) gauge fitted at the level of the notch mouth. An expression was derived to calculate the crack length in S/W = 2 type of TPB specimens using the unloading compliance values.