Multiaxial crack growth rate under variable T-stress

• Fatigue crack growth rate are studied through experiments and computations.
• Different biaxial and mixed-mode loading conditions are considered.
• A method is suggested for calculating the mixed mode plastic stress intensity factor.
• It is demonstrated that the plastic SIF can characterize the crack growth rate.

Fatigue crack growth rate are studied through experiments and numerical computations under different biaxial and mixed-mode loading conditions. Cruciform specimens under biaxial loading and compact tension–shear specimens are considered. The different degrees of mode mixity from pure mode I to pure mode II are given by the combinations of the far-field stress level, load biaxiality and inclined crack angle. For the particular specimen geometries considered, the T-stress and the numerical constant of the plastic stress field distributions In are obtained as a function of the dimensionless crack length, load biaxiality and mode mixity. A method is also suggested for calculating the plastic stress intensity factor for any mixed-mode I/II loading based on the T-stress and power law solutions. It is further demonstrated that the plastic stress intensity factor accounting for the in-plane and out-of-plane constraint effect can be used to characterize the multiaxial crack growth rate for a variety of specimen geometries.