The behaviour of microcracks in silicon during thermal annealing has been studied using in situ X-ray diffraction imaging. Initial cracks are produced with an indenter at the edge of a conventional Si wafer, which was heated under temperature gradients to produce thermal stress. At temperatures where Si is still in the brittle regime, the strain may accumulate if a microcrack is pinned. If a cr...

The matched asymptotic (MA) approach of the coupled criterion (CC) enables studying crack initiation at a pore located near free edge, which leads to competition between three possible mechanisms, namely in ligament, side opposite edge or simultaneously both sides. mechanism that is most likely occur depends on pore-to-free ligament size and material characteristic length diameter ratio. Simult...

We present an experimental study of the dynamics of rapid tensile fracture in brittle amorphous materials. We first compare the dynamic behavior of “standard” brittle materials (e.g. glass) with the corresponding features observed in “model” materials, polyacrylamide gels, in which the relevant sound speeds can be reduced by 2-3 orders of magnitude. The results of this comparison indicate unive...

In this study, single-edge cracked uniaxial specimens with an initial crack length of 0.1 in or 0.3 in and wedge-shaped sheet specimens with an initial crack length of 0.3 in were tested at a constant displacement rate of 50 in/min under 1000 psi confining pressure. The specimens were made of a highly filled polymeric material, containing 86% by weight of hard particles embedded in a rubbery ma...

There are prevailing concerns with the critical dimensions when conventional theories break down. Here we find that the Griffith criterion remains valid for cracks down to 10 nm but overestimates the strength of shorter cracks. We observe the preferred crack extension along the zigzag edge in graphene, and explain this phenomenon by local strength-based failure rather than energy-based Griffith...

A combined experimental/analytical work is carried out to elucidate the fracture resistance of a thin, hard coating bonded to a semi-infinite substrate due to indentation by a cylindrical surface. The bending of the coating under the softer substrate induces concentrated tensile stress regions at the lower and upper surfaces of the coating, from which cracks may ensue. The evolution of such dam...

Introduction Transverse matrix cracking in cross-ply gr/ep laminates was studied with advanced acoustic emission (AE) techniques. The primary goal of this research was to measure the load required to initiate the first transverse matrix crack in cross-ply laminates of different thicknesses. Other methods had been previously used for these measurements including penetrant enhanced radiography, o...

In the present study, fracture toughness of functionally graded steels in crack divider configuration has been modeled. By utilizing plain carbon and austenitic stainless steels slices with various thicknesses and arrangements as electroslag remelting electrodes, functionally graded steels were produced. The fracture toughness of the functionally graded steels in crack divider configuration has...