A photoelastic analysis of crescent-shaped cracks in bolts

Three-dimensional photoelasticity was used to analyse the effect of crack s hape on the stress intensity factors (SIFs) at the tips of cracks in thread ed connectors under axial and eccentric loads. The results show that the sh ape of the crack does not affect the maximum SIF occurring at the middle of the crack front. However, it does influence the distribution around the cr ack front, with the K-I/K-0 values decreasing more rapidly towards the end of the crack front for more crescent-shaped cracks. Despite the complexity of the geometry, the SIFs were found to be predominantly mode I. Eccentric loading was found to increase the SIFs at the centre of the crack front sli ghtly. The crack shape employed in this study was different from those used by earlier investigators but was based on evidence from fatigue tests.