the cracked brazilian disc (cbd) specimen is widely used in order to determine mode-i/ii and mixed-mode fracture toughness of a rock medium. in this study, the stress intensity factor (sif) on the crack-tip in this specimen is calculated for various geometrical crack conditions using the extended-finite element method (x-fem). this method is based upon the finite element method (fem). in this m...

It has long been observed that brittle fracture of materials can lead to emission of high energy electrons and UV photons, but an atomistic description of the origin of such processes has lacked. We report here on simulations using a first-principles-based electron force field methodology with effective core potentials to describe the nonadiabatic quantum dynamics during brittle fracture in sil...

The problem of dynamic symmetric branching of a tensile crack propagating in a brittle material is studied within Linear Elastic Fracture Mechanics theory. The Griffith energy criterion and the principle of local symmetry provide necessary conditions for the onset of dynamic branching instability and for the subsequent paths of the branches. The theory predicts a critical velocity for branching...

A recent theoretical model (Blumenfeld, Phys. Rev. Lett. 76 (1996) 3703) is described for modes I and III crack propagation dynamics in noncrystalline materials on mesoscopic lengthscales. Fracture has been one of the longest standing problems in physics and materials science, and despite much e€ort, several fundamental issues have stubbornly resisted resolution: (i) Running cracks reach a stea...

The scaling properties of post-mortem fracture surfaces of brittle (silica glass), ductile (aluminum alloy) and quasi-brittle (mortar and wood) materials have been investigated. These surfaces, studied far from the initiation, were shown to be self-affine. However, the Hurst exponent measured along the crack direction is found to be different from the one measured along the propagation directio...

A modified ray approach isused to model the slot lens for determining V(z) and the results are compared with experiment for several materials. The slot lens is also used to obtain V(z) of ycut quartz for a number of slot orientations relative to the crystalline x axis. The Rayleigh wave velocity as a function of propagation direction is then deduced from these measurements and compared with acc...

Finite element calculations of dynamic fracture based on embedding cohesive surfaces in a continuum indicate that the predictions are sensitive to the cohesive law used. Simulations were performed on a square block in plane strain with an initial edge crack loaded at a constant rate of strain. Cohesive laws that have an initial elastic response were observed to produce spontaneous branching at ...