The long-lifetime fatigue regime is suggested to be a probabilistic realization of sequentially occurring mechanisms. We associate these mechanisms with the development of a ranking of heterogeneity scales in the material, with decreasing probability of occurrence in the order of increasing scale, at any given loading condition. The underlying drivers for these heterogeneity levels are an array...

The objective of this study was the development of the automated system for crack detection on square steel bars used in the automotive industry for axle and shaft construction. The automated system for thermographic crack detection uses brief pulsed eddy currents to heat steel components under inspection. Cracks, if present, will disturb the current flow and so generate changes in the temperat...

The mechanism of spoiling failure in rolling contact is modeled by an elastic halfplane with a subsurface crack parallel to the surface, loaded by a compressive normal force which moves over the surface. Coulomb friction at the crack faces reduces the Mode II Stress Intensity Factors and results in a number of historydependent slip-stick configurations. The formulation used to study these invol...

Available microwave techniques for crack detection have some challenges, such as design complexity and working at a high frequency. These challenges make the sensing apparatus design complex and relatively very expensive. This paper presents a simple method for surface and subsurface crack detection in metallic and non-metallic materials based on complementary split-ring resonators (CSRRs). A C...

Managing subsurface damage during the shaping process and removing subsurface damage during the polishing process is essential in the production of low damage density optical components, such as those required for use on high peak power lasers. Removal of subsurface damage, during the polishing process, requires polishing to a depth which is greater than the depth of the residual cracks present...

This paper proposes a novel Lamb wave line sensing technique for crack detection in a welded stiffener. The proposed technique overcomes one of the biggest technical challenges of Lamb wave crack detection for real structure applications: crack-induced Lamb waves are often mixed with multiple reflections from complex waveguides. In particular, crack detection in a welded joint, one of the struc...

The Mode I and II stress intensity factors (K„ Kn) at the two tips of a subsurface crack subjected to a moving compressive load are studied. Coulomb friction along the crack faces results in a number of history dependent slip-stick configurations and nonsymmetric variation in K7 and K/7. The formulation used to study this variation involves a singular integral equation in two variables which mu...

An investigation of the friction and sliding wear of gray cast iron against chromium plated cast irons was carried out on a newly constructed reciprocating friction and wear tester. The tests were the first to be done on the test rig under dry conditions and at the speed of 170 cm/min, and variable loads of 20-260 N for a duration of 15 min. to 3 hours. The gray cast iron surfaces worn by a pro...

Shear-wave splitting, observed in microearthquake records at The NW and SE Geysers geothermal fields, CA has proved to be effective in the detection of subsurface crack orientations and crack densities. Crust anisotropy due to patterns of stress-aligned fractures causes approaching shear-waves to split into fast and slow arrivals. Within the shear-wave window of a given seismic station, the mea...

Vertisols have unique morphology and the capacity to change volume with changes in water content; therefore, they are well known for their spatial and temporal variability. Our objectives were to address the spatial variability of Vertisol surface and subsurface features, as well as the spatial and temporal variability of Vertisol cracking. First, we discuss surface and subsurface features of V...