This paper presents an investigation of the fatigue crack growth (FCG) behavior at fastener holes in a high strength steel, 3OCrMnSiNiZA, before and after a cold-expansion process. The fatigue life of coldworked specimens was significantly increased compared to non-coldworked ones and increased the lower applied stress level.From a study of the residual stress distribution near the edge of the hole, it was found that the experimental residual compressive stresses in absolute values were much less than the calculated values derived by previous analytical methods. Thus, a simplified residual stress model for describing the FCG behavior at coldworked fastener holes is proposed, from which, the AKeR and fatigue lives of specimens after cold-expansion can be predicted satisfactorily for engineering applications.
The fracture behavior of acrylonitrile-butadiene-styrene (ABS) was investigated using the J-integral method under monotonic loading. Two ways were used to monitor the onset of crack growth: the dyeing method and the length of craze region ahead of initial notch. The blunting at the crack tip and crack growth mechanism for ABS was observed using a scanning electron microscope. Before the onset of crack growth, the energy put into material was dissipated to create crazes ahead of the initial notch and to deform the material at the crack tip. A part of the energy was released to create a new crack surface after the onset of crack growth.
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