A modified 3D G-criterion for the prediction of crack propagation under mixed mode I-III loadings

A modified 3D G-criterion is proposed for the crack under mixed mode I-III loadings, by differentiating the volumetric and distortional energy release rates (ERRs) and considering the influence of T-stress. The modified 3D G-criterion is validated by comparing the predicted tilt angle, twist angle and critical stress intensity factors (SIFs) with the experimental results for different materials. Then the effects of critical volumetric to distortional ERR ratio, Poisson ratio and dimensionless T-stress on the tilt angle, twist angle and critical SIFs are discussed. The tilt angle will be nonzero only when the dimensionless T-stress reaches a certain threshold, while the twist angle increases first and then gradually decreases as the dimensionless T-stress increases. Besides, the twist angle gets increased while the corresponding critical SIFs slightly decrease as the Poisson ratio increases. Finally, the critical SIFs are found to noticeably reduce as the critical volumetric to distortional ERR ratio increases, and get enhanced (decreased) when the dimensionless T-stress is negative (positive).

Automated summary

A modified 3D G-criterion is proposed for crack under mixed mode I-III loadings, which considers the influence of T-stress and differentiates the volumetric and distortional ERRs. The criterion is validated by comparing predicted and experimental results, and the effects of ERR ratio, Poisson ratio, and T-stress on tilt angle, twist angle, and critical SIF are discussed. The results showed that the tilt angle is nonzero only when a certain threshold of T-stress is reached, and the twist angle increases and then decreases with increasing T-stress. Moreover, an increase in Poisson ratio leads to an increase in the twist angle and a slight decrease in critical SIF.