Issue 47

A. Spagnoli et alii, Frattura ed Integrità Strutturale, 47 (2019) 401-407; DOI: 10.3221/IGF-ESIS.47.30 406 In the present paper a numerical algorithm, based on the distributed dislocation technique, is used in combination with a non-linear interface model to characterise the near-tip stress field of rough and frictional cracks. The interface roughness and the frictional effects are included through a rigid-plastic constitutive relationship between stresses and relative displacements along the crack. The stress intensity factors are computed through a numerical solution of singular integral equations, adopting an iterative algorithm developed by the authors, which has proved to be effective in different geometries and loading scenarios. Specifically, the model is used here to examine the influence of a size effect parameter, related to the ratio between the crack roughness period and the length of the crack. The results confirm a crack shielding effect due to roughness and friction, that is, a reduction in the mode II stress intensity factor for increasing roughness (notably, the asperity angle). Moreover, we show that the crack shielding is more pronounced for longer cracks. Figure 3: Variation of the normalised SIF K II with respect to the roughness angle, for q/p =1. Figure 4: (a) Variation of the normalised SIF K II with respect to the relative crack length c/L , for q/p =1. The angle of the surface asperity is kept constant. (b) Variation of the normalised SIF K II with respect to the relative crack length c/L , for q/p =1. The height of the surface asperity is kept constant. The coefficient of friction is equal to 0.5 in all the simulations.