A major part of fracture mechanics is concerned with studying the initiation and propagation of fatigue cracks. This typically requires constant monitoring of crack growth during fatigue cycles which necessitates automation of the whole process. If the rate of crack growth can be determined the experimenter can vary externally controlled parameters such as load level, load cycle frequency and s...

In this paper, the problem of calculating the stress intensity factor (SIF) for an orthotropic thick-walled cylinder with a small radial crack subject to internal pressure is considered. The crack is assumed to be an edge crack on the external radius of the cylinder. The stress intensity factor is calculated by superposition of an uncracked cylinder with uniform stress distribution and a cylind...

The multiscale nature of cracking in ferroelectric ceramics is explored in relation to the crack growth enhancement and retardation behavior when the direction of applied electric ®eld is reversed with reference to that of poling. An a priori knowledge of the prevailing fracture behavior is invoked for the energy dissipated in exchange of the macroand micro-crack surface. To avoid the formalism...

introduction: supplies of illegal drugs play determinant roles in developing new cases, relapse after treatment and some health criteria. recently, iran has encountered an illicit new coming drug which belongs to opioids. this article presents the crack supply in retail market in tehran.   method: this qualitative study was conducted in 2009 in tehran. in-depth interviews with drug dealers, dru...

The propagation of cracks in graded materials under monotonic and cyclic loading was investigated via experiment and simulation. Graded alumina/epoxy composite specimens exhibiting a variation in composition from 5% to 65% epoxy, representing a twenty-fold variation in Young’s modulus, across a region of width between 6 and 20 mm, were produced by a multistep infiltration technique. Crack initi...

Crack tip deformations and fracture parameters in functionally graded glass-filled epoxy beams are experimentally evaluated under static and dynamic loading conditions. Beams with unidirectional, monotonic elastic gradients and cracks along the gradient are examined. SEN samples with increasing or decreasing Young’s modulus ahead of the crack tip are studied in symmetric four-point bending and ...

In this work, fracture behavior of multilayered unidirectional graphite/epoxy composite (T800/3900-2) materials is investigated. Rectangular coupons with a single-edged notch are studied under geometrically symmetric loading configurations and impact loading conditions. The notch orientation parallel to or at an angle to the fiber orientation is considered to produce mode-I or mixed-mode (mode-...

Based on the analytical solution of Crouch to the problem of a constant discontinuity in displacement over a finite line segment in an infinite elastic solid, in the present paper, the crack-tip displacement discontinuity elements, which can be classified as the left and the right crack-tip elements, are presented to model the singularity of stress near a crack tip. Furthermore, the crack-tip e...

Plate impact experiments are conducted to study the dynamic fracture processes in 4340 VAR steel which occur on submicrosecond timescales. These experiments involve the plane strain loading of a planar crack by a plane tensile pulse with a duration of approximately 1 /xs. The loading is achieved by impacting a precracked, disk-shaped specimen by a thin flyer plate. Motion of the rear surface of...