Stress intensity factors for surface cracks in round bar under single and combined loadings

Abstract

This paper numerically discusses stress intensity factor (SIF) calculations for surface cracks in round bars subjected to single and combined loadings. Different crack aspect ratios, a/b, ranging from 0.0 to 1.2 and the relative crack depth, a/D, in the range of 0.1 to 0.6 are considered. Since the torsion loading is non-symmetrical, the whole finite element model has been constructed, and the loadings have been remotely applied to the model. The equivalent SIF, $F^{*}_{EQ}$ is then used to combine the individual SIF from the bending or tension with torsion loadings. Then, it is compared with the combined SIF, $F^{*}_{FE}$ obtained numerically using the finite element analysis under similar loadings. It is found that the equivalent SIF method successfully predicts the combined SIF, $F^{*}_{EQ}$ for Mode I when compared with $F^{*}_{FE}$ . However, some discrepancies between the results, determined from the two different approaches, occur when F III is involved. Meanwhile, it is also noted that the $F^{*}_{FE}$ is higher than the $F^{*}_{EQ}$ due to the difference in crack face interactions and deformations.