SHAPE GROWTH SIMULATION OF SURFACE CRACKS IN TENSION FATIGUED ROUND BARS

The step-by-step three-dimensional finite element technique, developed recently by the present authors, was used to simulate fatigue crack s hape developments, beginning from several elliptical-arc cracks with d ifferent aspect ratios and an irregular crack, in round bars under axi al tension. A Paris type crack growth relation was employed as the bas is of the simulating computations. The shape of growing cracks was qua ntitatively examined by two proposed measures: the relative residual a nd relative standard deviation, in order to reveal the shape differenc e between the numerically predicted crack profiles and the widely-assu med circular-arc shape. The aspect ratio changes for the initially par t-elliptical cracks were predicted, and compared with some published e xperimental results. In addition, the effect of the exponent in the Pa ris law on the aspect ratio variation was investigated. (C) 1997 Elsev ier Science Ltd.