A micromechanical model is developed for grain bridging in monolithic ceramics. Specifically, bridge formation of a single, non-equiaxed grain spanning adjacent grains is addressed. A cohesive zone framework enables crack initiation and propagation along grain boundaries. The evolution of the bridge is investigated through a variance in both grain angle and aspect ratio. We propose that the bri...

Shear-wave splitting, observed in microearthquake records at The NW and SE Geysers geothermal fields, CA has proved to be effective in the detection of subsurface crack orientations and crack densities. Crust anisotropy due to patterns of stress-aligned fractures causes approaching shear-waves to split into fast and slow arrivals. Within the shear-wave window of a given seismic station, the mea...

In this paper, the use of a cohesive-zone approach to model the mode-I fracture of adhesive joints made from a polymer-matrix composite is demonstrated. Cohesive-zone parameters were obtained by matching numerical results to experimental observations. It is shown that there is a distinction between the characteristic strength of the interface associated with the toughness, and the intrinsic coh...

For a crack impinging upon a bimaterial interface at an angle, the singular stress field is a linear superposition of two modes, usually of unequal exponents, either a pair of complex conjugates, or two unequal real numbers. In the latter case, a stronger and a weaker singularity coexist (known as split singularities). We define a dimensionless parameter, called the local mode mixity, to charac...

This paper presents the fracture analyses conducted on the FAA/NASA stiffened and unstiffened panels using the STAGS (STructural Analysis of General Shells) code with the critical crack-tip-opening angle (CTOA) fracture criterion. The STAGS code with the “plane-strain” core option was used in all analyses. Previous analyses of wide, flat panels have shown that the high-constraint conditions aro...

The energy balance associated with the transmission of cleavage front across high angle grain boundary is analysed theoretically. On the one hand, if the distance between adjacent breakthrough points is small, their crack trapping effect tends to be pronounced. On the other hand, decreasing this distance promotes the separation of persistent grain boundary areas. The effective grain boundary to...

The stress singularity near the Mode III interface end of isotropic and orthotropic bi-material was studied. Based on arbitrary angle boundary conditions, by solving a class of harmonic equations we discussed the root of the characteristic equation with the help of complex function method of material fracture. The expression and variation of the singularity index λ of the tip of interfacial cra...

Abstract-A plate with a pre-existent through crack is considered under the action of a remote bending moment and a remote in-plane force. The problem statement is reduced to the solution of two coupled integral equations with strongly singular kernels. The independent variables in the latter equations are the closure displacement and rotation angle. The corresponding closure force and moment di...

In this paper, a fracto-metallographic analysis was performed on the cracked specimens of cold drawn pearlitic steel subjected to fatigue tests. Fatigue cracks are transcollonial and exhibit a preference for fracturing pearlitic lamellae, with non-uniform crack opening displacement values, micro-discontinuities, branchings, bifurcations and frequent local deflections that create microstructural...

In this paper we address the issue of a creeping wave by investigating a twodimensional configuration which involves a surface-braking crack in a traction free planar backwall. We assume that this back-wall is irradiated by a shear Gaussian beam which is incident at a critical angle and hits the wall away from the crack edge. We show that the generated wave known in the engineering literature a...