Towards a New Concept of Crack Path: A Tribute to James R. Rice

Abstract

This paper tries to advance towards a new concept of crack path covering different length scales (multi-scale approach) and distinct points of view (multi-perspective approach). With regard to the fracture/crack path profile in a vertical plane of analysis (i.e., perpendicular to the crack front), it can be studied by means of fracto-materialographic analysis to obtain the physical crack path that can be evaluated at different length scales: (i) microstructurally-induced crack paths, (ii) crack paths micro-roughness, (iii) crack-path micro-deflections, (iv) locally multi-axial crack paths, (v) kinked crack paths; (vi) deflected crack paths, (vii) bifurcated crack paths. In all these phenomena, material microstructure plays a relevant role producing the local deviations of the otherwise straight crack path (macroscopic crack path), thereby increasing the real (physical) crack path length and increasing the material resistance to fatigue and fracture. In the matter of the crack shape in a horizontal plane, the crack aspect ratio evolution (with the existence or not of a preferential propagation path) is the object of analysis, thereby representing another aspect of crack paths. Examples of the different approaches are provided in the framework of previous research by the author in the field of fatigue, fracture, stress corrosion cracking and hydrogen embrittlement. In addition, the reverse approach to the concept of crack paths (crack paths versus paths near cracks) provides the idea of paths in cracks, or paths near cracks, in the framework of the mathematical formulation of a path independent integral near a crack tip (a path near a crack, and an integral whose value is independent of the particular path), so that this paper is a heartfelt tribute to James R. Rice and his J-Integral.