A puzzling question in dynamic fracture has been why cracks in amorphous brittle materials always travel at velocities smaller than the Rayleigh wave speed. The answer is that the energy per length needed for the crack to propagate depends strongly on velocity. As the energy flux to the crack tip increases, the crack chooses new modes of dissipation such as micro-cracking and the creation of su...

Several stress analysis methods were used to find the energy release rate for initiation of an interfacial crack in a microbond specimen. First, we used a recently derived variational mechanics analysis of the stresses in a microbond specimen. Previous studies for analysis of crack growth have used shear-lag methods. For a second analysis, we present a new, and more complete, shear-lag analysis...

The primary objective of this work was to analyse the adequacy of the Double Cantilever Beam (DCB) test in determining fracture toughness under pure mode I loading of cortical bone tissue. A new data reduction scheme based on specimen compliance and the crack equivalent concept was used to overcome the difficulties inherent in crack monitoring during its growth. It provides a complete resistanc...

Recent analysis of gas outflow histories at wellheads shows that the hydraulic crack spacing must be of the order of 0.1 m (rather than 1 m or 10 m). Consequently, the existing models, limited to one or several cracks, are unrealistic. The reality is 10(5)-10(6) almost vertical hydraulic cracks per fracking stage. Here, we study the growth of two intersecting near-orthogonal systems of parallel...

Since concrete is used for marine and hydraulic structures, pipe coatings and channel walls, its wear due to the attack of fast flowing water is a problem (1). The first systematic investigations on the resistance of concrete against wear in marine structures were carried out in the 1940s (2). Investigations carried out in the fields of water flow erosion, cavitation and abrasion have been revi...

In this study, in order to investigate crack retardation behavior and the variability of retardation cycles, crack growth tests are conducted on 7075-T6 aluminum alloy under a single tensile overload. A retardation coefficient D is introduced herein as the ratio of the crack growth rate under constant amplitude loading and the crack growth rate after an overload. This coefficient D is separatel...

Studies on the growth of small cracks have led to the observation that fatigue life of many engineering materials is primarily “crack growth” from micro-structural features, such as inclusion particles, voids, slip-bands or from manufacturing defects. This paper reviews the capabilities of a plasticity-induced crack-closure model to predict fatigue lives of metallic materials using “small-crack...

Studies on the growth of small cracks have led to the observation that fatigue life of many engineering materials is primarily “crack growth” from micro-structural features, such as inclusion particles, voids, slip-bands or from manufacturing defects. This paper reviews the capabilities of a plasticity-induced crack-closure model to predict fatigue lives of metallic materials using “small-crack...

An understanding of how fatigue cracks grow in bone is of importance as fatigue is thought to be the main cause of clinical stress fractures. This study presents new results on the fatigue-crack growth behavior of small surface cracks (approximately 75-1000 microm in size) in human cortical bone, and compares their growth rates with data from other published studies on the behavior of both surf...

In an earlier paper it was suggested that a knowledge of the elastic-stress variation in the neighborhood of an angular corner of an infinite plate would perhaps be of value in analyzing the stress distribution at the base of a V-notch. As a part of a more general study, the specific case of a zero-angle notch, or crack, was carried out to supplement results obtained by other investigators. Thi...