A crack detection (CD) paint was applied to weld lines of a transverse rib welded joint specimen of a rolled steel for welded structures, and the effects of the paint on visual detection of fatigue cracks were evaluated by performing a fatigue test. Remarkable color development was observed in the CD paint when fatigue cracks propagated along the weld toe lines. At intervals in the fatigue test...

The corrosion fatigue crack growth characteristics of small (>35pm) surface and corner cracks in aluminum alloy 7075 is established. The early stage of crack growth is studied by performing in situ long focal length microscope (500X) crack length measurements in laboratory air and 1% NaCl environments. To quantify the “small crack effect” in the corrosive environment, the corrosion fatigue crac...

Nondestructive testing of concrete allows the inspection of larger areas of concrete members at lesser cost than coring and provides more information than visual inspection. This paper addresses a new approach for determining the positions and size of cracks in concrete members by using ultrasonic pulse velocity test. Three plain concrete beams, containing artificial cracks (30 – 60% of the bea...

-This paper presents an overview of the finite element alternating technique for the analysis of interacting cracks. To illustrate the ease and accuracy of this method the technique is used to analyse several problems associated with both widespread fatigue and multi-site damage, a problem which is attracting worldwide attention. Whilst this paper presents an overview of the technique for both ...

Paris law constants are commonly obtained with a well established procedure based on standard specimens, notched and pre-cracked. Pre-cracking produces through cracks with stable shapes, nearly straight, similar during all propagation. However, in several situations specimens with corner and surface cracks are recommended. In these cases cracks having significant propagation will continuously m...

Cracks appeared in GaN epitaxial layers which were grown by a novel method combining metal organic vapor-phase epitaxy (MOCVD) and hydride vapor-phase epitaxy (HVPE) in one chamber. The origin of cracks in a 22-μm thick GaN film was fully investigated by high-resolution X-ray diffraction (XRD), micro-Raman spectra, and scanning electron microscopy (SEM). Many cracks under the surface were first...

We report on recent developments in the detection of surface breaking cracks using flying laser spot thermography. Application of an infrared camera for mapping the thermal radiation after excitation with a diode laser equipped with an optical scanner allows us to examine a surface containing cracks in an entirely non-destructive, contactless and fast way, without even moving the camera. We dev...

An improved single sided Rayleigh wave (R-wave) measurement was suggested to characterize surface breaking crack in steel reinforced concrete structures. Numerical simulations were performed to clarify the behavior of R-waves interacting with surface breaking crack with different depths and degrees of inclinations. Through analysis of simulation results, correlations between R-wave parameters o...

Abstract: DCPD technique is powerful tool for quantitative NDE of cracks. The technique using four probes which are in close proximity to each other has been proposed for NDE of surface cracks; that is the closely coupled probes potential drop (CCPPD) technique. It has been shown that the sensitivity of the CCPPD technique is enhanced significantly in comparison with the usual method. The objec...

In this p;y)cr , ;I new crack detection rnethod in ro;ul surface inlagc based on morphological t,echniqrlr is proposed. Cracks arc difficult, t,o dct.ect directly at t.hc pixel level because of t , l ~ noise and the vagueness. Some kind of st,r~lct.ural information is needed. A crack is t,hought, tlo be ;I siiccession of dark saddle points with t,he linear feature. In the proposed met.hod , t,h...