FATIGUE SHAPE-ANALYSIS FOR CORNER CRACKS AT FASTENER HOLES

Fatigue crack shape is simulated in this paper by a step-by-step finit e element technique for corner cracks emanating from fastener holes in plates under cyclic tension loading. The numerical technique calculat es the local growth increments at a set of points defining a crack fro nt by employing a Paris type fatigue growth law, and permits the growt h to be automatically advanced on a step-by-step basis. Hence, it can directly predict the shape development of propagating cracks. The fati gue shape analysis is concentrated on the growth simulation for severa l assumed initially quarter-elliptical corner cracks at three fastener holes of different hole radius. An initially irregular corner crack i s also modelled to examine its shape development characteristic. The c rack shape deviation from the widely-assumed quarter ellipse is numeri cally investigated by both the proposed relative residual and standard deviation criteria. The aspect ratio changes during crack growth are obtained and compared with limited experimental data found in the lite rature. Moreover, the influence of the power contained in the Paris la w on the aspect ratio variation is studied. (C) 1997 Elsevier Science Ltd.