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 shape developments, beginning from several elliptical-arc cracks with different aspect ratios and an irregular crack, in round bars under axial tension. A Paris type crack growth relation was employed as the basis of the simulating computations. The shape of growing cracks was quantitatively examined by two proposed measures: the relative residual and relative standard deviation, in order to reveal the shape difference between the numerically predicted crack profiles and the widely-assumed circular-arc shape. The aspect ratio changes for the initially part-elliptical cracks were predicted, and compared with some published experimental results. In addition, the effect of the exponent in the Paris law on the aspect ratio variation was investigated.

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