Mode II fracture toughness for non-planar frictional cracks

Traction-free and planar cracks represent a rather idealized picture of the physical reality, commonly used in fracture mechanics problems. In the present paper, the influence of roughness and friction of crack surfaces is examined in relation to both the resulting near-tip stress field and the fracture resistance under monotonic mixed-mode loading. A two-dimensional model is presented where an elastic-plastic-like constitutive interface law is adopted to describe the Mode I/II coupling between displacements and tractions along the crack surfaces. The solution is obtained using the Distributed Dislocation Technique (DDT). By considering a linear piecewise periodic profile of the crack, the present model is employed to quantify the mode II fracture toughness of different types of natural stones under varying mode I compressive load.