On Evaluation of Stress Intensity Factor from In-Plane and Transverse Surface Displacements

Experimental approaches to the evaluation of stress intensity factor (SIF) of through-cracked plate components are currently based on the classical plane stress (2D) asymptotic power series expansion of strains or displacements near the crack tip (Williams’ solution). Besides the plasticity effects, the quantitative evaluation of SIF has to take into account a finite domain of convergence of the series expansion as well as three-dimensional (3D) effects, which prevail in the close vicinity of the crack tip. In this paper we demonstrate and confirm that attempts to fit Williams’ solution to experimental data in the near crack tip region can provide misleading results. In addition, it is verified that the SIF can be linked to the transverse displacements in the region controlled by 3D effects, and in particular, by 3D corner singularity. Under mode I loading, the transverse displacement field in this region is uniform, and largely unaffected by the higher order terms of the asymptotic power series expansion, which make this way of the evaluation of SIF particularly attractive for experimental measurements.