FATIGUE-CRACK PROPAGATION IN A HIGH-STRESS CONCENTRATION AREA

The behaviour of fatigue crack propagation in a high stress concentrat ion area caused by a geometrical notch in the structure is studied. Lo w cycle fatigue tests in two kinds of materials and a total of six spe cimens of double-through cracks emanating from the edges of an ellipti cal hole were carried out. For reducing errors in the parameter calcul ation, a calculation formula for the stress intensity factor K of a fi nite width panel with double-through cracks emanating from the edges o f a central elliptical hole is first established, and then, a large pl astic zone correction method is introduced to take account of the elas tic-plastic behaviour. Finite element analyses were carried out to con firm the accuracy of the formula and the method. Both the stress inten sity factor K and the large plastic zone correction form of K are used as correlating parameters. The results show that the large plastic zo ne correction form of K developed by the present studies which success fully represents the J integral for the problem studied is a suitable parameter to explore the behaviour of fatigue crack propagation in a h igh stress concentration area.