Effects of T-stresses on fracture initiation for a closed crack in compression with frictional crack faces

Abstract

This paper studies crack extension resulting from a closed crack in compression. The crack-tip field of such a crack contains a singular field relative to K II and non-singular T-stresses T x and T y parallel and perpendicular to the crack plane, respectively. Using a modified maximum tensile stress criterion with the singular and non-singular terms, the kinking angle at the onset of crack growth is determined by a two parameter field involving the mode-II stress intensity factors and T-stresses, and at fracture initiation a wing crack may be created at an arbitrary angle from 0 • to 90 • . A compressive T y increases the kinking angle and reinforces apparent mode-II fracture toughness, while a compressive T x decreases the kinking angle and enhances apparent mode-II fracture toughness. The direction and resistance of fracture onset is strongly affected by T-stresses as well as frictional stress. The von Mises effective stress is determined for small-scale yielding near the crack tip. The effective stress contour shape exhibits a marked asymmetrical behavior unless 2T x = T y ≤ 0 for plane stress state. Coulomb friction between two crack faces generally increases the kinking angle, shrinks the size enclosed by the effective stress contour and enhances apparent fracture toughness. Field evidence and experimental observations of many phenomena involving the growth of closed cracks in compression agree well with theoretical predictions of the present model.

Brittle fracture of rock under combined tensile and compressive loading conditions

“…Then, the parameters K I , K II , T x and T y in Fig. 2 can be defined as Li et al (2009) investigated the role of the T y component on crack growth. However, they did not study the effects of the crack orientation angle and confining pressure ratio on the crack growth.…”

Fatigue crack growth in bearing steel under cyclic mode II + static biaxial compression

“…Classical bifurcation criteria do not allow a reliable prediction of the crack path for this kind of loading [11][12][13][14][15]. Theoretical or numerical works on the influence of biaxial compression on the bifurcation of a closed crack loaded in mode II can be found in the literature, among which those of Melin [16], Frelat and Leblond [17], Li et al [18]. However, these works, which analyze static mode II, and not reversed cyclic shearing with static compression, do not agree regarding the impact of compression on the kink angle.…”

Stress intensify factors for an external circular crack at the interface of a bi-material in shear–compression

“…A tensile wing crack grows near the tip of a closed crack or strike-slip fault in a lower angle owing to confining pressure of the ambient structure arising from change in temperature in field observations of structural geology (Myers and Aydin, 2004;Mutlu and Pollard, 2008). In addition, two elastic T-stresses are present at a crack tip for a closed crack in compression, whereas only one an elastic T-stress for an opening crack (Li and Xu, 2007), and the apparent fracture toughness and small-scale yielding zone are strongly affected by these two T-stresses (Li et al, 2009). Up to now, the advance mechanism of a flaw in shear-compression has been expounded based on the concept of fracture mechanics (NematNasser and Horii, 1982;Shen and Stephansson, 1994).…”