Stress intensity factors under combined tension and torsion loadings

Abstract

This paper numerically discusses the stress intensity factor (SIF) calculations for surface cracks in round bars subjected to combined loadings. Different crack aspect ratios,&nbsp;<i style="mso-bidi-font-style:normal">a/b</i> ranged from 0.0 to 1.2 and the relative crack depth, <i style="mso-bidi-font-style:normal">a/D</i> in the range of&nbsp;0.1 to&nbsp;0.6 are considered. Since the loading is non-symmetrical, the whole finite element model is constructed. Then, both tension and torsion loadings are remotely applied to the finite element model and the SIFs are determined along the crack front of various crack geometries. An equivalent SIF method is then explicitly used to combine the individual SIF obtained using different loadings. A comparison is made between the combined SIFs obtained using the equivalent SIF method and finite element analysis (FEA) under similar loadings. It is found that the equivalent SIF method successfully predicted the combined SIF for Mode I. However, discrepancies between the results, which have been determined from the different approaches, occurred when <i style="mso-bidi-font-style:normal">F_III</i> is involved. Meanwhile, it is also noted that the predicted SIF using FEA is higher than the predicted through the equivalent SIF method due to the crack face interactions.