Experimental validation of mixed-mode and non-crack-concentrator predictions

Verify experimentally whether the length scale parameters identified using simplified strain gradient elasticity provide reliable predictions for cracks under mixed-mode loading within the adopted maximum-principal-stress failure criterion, and for specimens containing other stress concentrators such as sharp notches or small holes.

Background

The paper develops procedures for identifying the single length scale parameter of simplified strain gradient elasticity from standard pure Mode I fracture tests involving centre-cracked tension, single-edge-notched tension, and single-edge-notched bending specimens. These procedures use either a maximum-principal-stress criterion applied to regularized crack-tip stresses or regression relations fitted to numerical solutions.

The authors explicitly restrict the study to pure Mode I loading and recognize that mixed-mode fracture may require more sophisticated failure criteria or more general strain-gradient constitutive relations. They also leave unresolved whether the identified parameters remain predictive for mixed-mode cracks and for other stress concentrators, including sharp notches and small holes.