Progressive radial cracking of a clamped plate subjected to crack-face closure is studied. The material behavior is assumed to be elastic-brittle. The cracks are assumed to be relatively long in the sense that the three-dimensional contact problem can be described via a statically equivalent two-dimensional idealization. The number of cracks is supposed large enough to permit a quasi-continuum ...

BACKGROUND The aim of this study was to compare sociodemographic characteristics, patterns of drug use, and risky sexual behaviour among female and male users of crack cocaine. METHODS Between 2012 and 2013, we conducted a cross-sectional study of 919 crack cocaine users (783 men and 136 women) in Central Brazil using face-to-face interviews. Blood samples were collected to test for syphilis....

Artificial aging degrades the fatigue crack growth (FCG) resistance of heat treatable aluminum alloys, particularly in the near-threshold regime. Consequently, applications of aluminum alloys in tensiondominated structures that require fatigue damage tolerance are limited to the naturally aged T3 temper. Degraded FCG resistance compromises the benefit from higher strength by artificial aging. W...

Reliable and quantitative non-destructive evaluation for small fatigue cracks, in particular those in hard-to-inspect locations, is a challenging problem. Guided waves are advantageous for structural health monitoring due to their slow geometrical decay of amplitude with propagating distance, which is ideal for rapid wide-area inspection. This paper presents a 3D laser vibrometry experimental a...

Turbo-generator shafts are often subjected to complex dynamic torsional loadings, resulting in generation and propagation of circumferential cracks. Mode III fatigue crack growth generally results in a fracture surface consisting of peaks and valleys, resembling a factory roof. The fracture surface roughness depends on the material microstructure, the material yield strength, and the applied cy...

A novel method for preparing and testing bending specimens in-situ the TEM has been developed. This method provides high visibility of the crack front and its associated plastic zone. This is significant because energy release rates can now be calculated at many points throughout the test based on crack tip opening displacement (CTOD), crack opening angle (COA), and crack advance. Further refin...

In this work, the plastic deformation mechanisms responsible for mechanical properties and fracture toughness in nanotwinned (NT) magnesium is studied by molecular dynamics (MD) simulation. The influence of twin boundary (TBs) spacing and crack position on deformation behaviors are investigated. The microstructure evolution at the crack tip are not exactly the same for the left edge crack (LEC)...

THE GENERAL weight function expressions given in GAO (J. Mech. Phys. Solids 37, 133, 1989). referred to here as part I, for combined-mode crack-dislocation interaction problems in the three-dimensional regime are applied to solve for the stress field and energy of a shear dislocation loop emerging from the tip of a half-plane crack. The results are compared to the previously proposed approximat...