Laser ultrasonic system is a non-contact inspection device with a high spatial resolution and it is applicable to hard-to-access locations like in a nuclear power plant. In this paper, we have attempted to detect the depth of a surface-breaking crack by using the surface wave of a laser ultrasound. We have investigated a variation of the peak-to-valley value in the time domain and the spectrum ...

There are many ways that women support their use of crack cocaine, including sex-for-crack bartering and other forms of prostitution. Empirical studies conducted in the mid-1970s and in the mid-1980s in New York City, and in Chicago in the late 1980s to early 1990s are compared, analyzing similarities and differences between the contemporary crack-prostitution scene and previous prostitution sc...

Fatigue properties and cracking behavior of cold-drawn commercially pure aluminum wires (CPAWs) widely used as the overhead transmission conductors were investigated. It was found that the fracture surface of the CPAWs shows an obvious four-stage fracture characteristic, i.e., crack initiation, planar crack propagation, 45°-inclined crack propagation and final rapid fracture. The crack growth m...

(FBRs). The factors influencing fatigue lifetime in sodium compared with that in air were investigated by observation of surface cracks in 316FR steel. Furthermore, the effects of sodium environment on fatigue were investigated based on examining the results of thermal striping tests, etc., obtained up to now. The results of the fatigue tests show that many micro cracks in the shearing directio...

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-...

2 Notation This paper introduces a new detection method of crack and structural objects, whiteline , joint and manhole of the road surface image based on morphological t,echnique . Crack and structural objects are difficult to detect directly at the pixel level because of the noise and the vagueness. Some kind of structural information is needed. In the proposed method, we have used morphologca...

We have extended our earlier investigation of scattering from surface cracks. In particular, we have studied the change in the reflection coefficient of a Rayleigh wave incident on a half-penny shaped surface crack along with the corresponding change in the acoustic crack size estimates as the cracked sample is stressed to fracture. We have examined in this manner both cracks in annealed sample...

RESTRICTIONS on the quasi-static extension, or healing, of Griffith cracks are developed in the framework of irreversible thermodynamics. It is emphasized that thermodynamics requires that (G 2r)I > 0, where i is crack speed, G the Irwin energy release rate, and 2y the work of reversible separation of the surfaces to be fractured. Implications for ‘lattice trapping’ models of cracks and for the...

Crack front waves are nonlinear localized waves that propagate along the leading edge of a crack. They are generated by both the interaction of a crack with a localized material inhomogeneity and the intrinsic formation of microbranches. Front waves are shown to transport energy, generate surface structure, and lead to localized velocity fluctuations. Their existence locally imparts inertia, wh...

Fatigue and stress crack detection in metallic structures is of utmost importance to the in-service inspections of metallic components. Beside the crack detection, the prediction of the crack size leads to a better estimation of the useful life of the metal in service. Currently, there are several prominent nondestructive testing (NDT) techniques for detecting and sizing surface cracks in metal...