In previous studies, enamel showed indications to occlude small cracks in-vivo and exhibited R-curve behaviors for bigger cracks ex-vivo. This study quantifies the crack tip's toughness (K(I0),K(III0)), the crack's closure stress and the cohesive zone size at the crack tip of enamel and investigates the toughening mechanisms near the crack tip down to the length scale of a single enamel crystal...

This paper (Part II), which is the second in a series of two papers, presents new closed-form solutions for net-section-collapse (NSC) analysis of circumferentially cracked pipes for several idealized crack shapes subjected to combined bending and tension (pressure-induced) loads. They are based on further simpli®cations of generalized NSC equations developed in a parallel study. Analytical sol...

Fatigue crack growth behavior of AZ61 magnesium alloy was investigated in low humidity (55% relative humidity) and 3.5% NaCl spray environments under various stress ratios. Fatigue crack growth rates became higher with increasing load ratio for both environments. However, the results of fatigue crack growth test under 3.5% NaCl spray environment showed lower fatigue crack propagation rate compa...

The interaction between an edge dislocation and a crack in the presence of uniform applied tension and shear is considered. Emphasis is placed on the effects of partial closure and crack-face friction. Representative results are given.

A 2-dimensional, elastic-plastic finite element model has been developed to simulate plasticity induced crack closure in slanted and deflected cracks growing outside the small scale yielding (SSY) regime. The finite element model allows for contact between deformable surfaces to capture the complex contact interaction between the crack faces. Coulomb’s friction law has been used to model fricti...

It is necessary to manage the fatigue crack growth (FCG) once those cracks are detected during in-service inspections. In this paper, a simulation program (FCG-System) is developed utilizing the commercial software ABAQUS with its object-oriented programming interface to simulate the fatigue crack path and to compute the corresponding fatigue life. In order to apply FCG-System in large-scale ma...

Effect of Cracks on Elastic Properties of Low Porosity Rocks by Terrence Patrick Todd Submitted to the Department of Earth and Planetary Sciences on May 1, 1973, in partial fulfillment of the requirements for the degree of Doctor of Philosophy Microcracks in terrestrial and lunar rocks significantly alter elastic, thermal, and mechanical properties. The degree to which microcracks alter physica...

Failure analysis and fatigue life prediction are necessary and critical for engineering structural materials. In this paper, a general methodology is proposed to predict fatigue life of smooth and circular-hole specimens, in which the crack closure model and equivalent initial flaw size (EIFS) concept are employed. Different effects of crack closure on small crack growth region and long crack g...

A thorough examination of the quasi-static penetration of a floating elastic-brittle plate via a fracture mechanics approach has been presented by Bažant and Kim. Bažant and Kim reach the conclusion that there is a size effect (in terms of the plate thickness, h). A few of the assumptions made by these authors will be examined in this discussion. The formulation presented by Bažant and Kim assu...