Vibrothermography often employs a high-power actuator to generate heat on a specimen to reveal damage, however, the high-power actuator brings inconvenience to the application and possibly introduces additional damage to the inspected objects. This study uses a low-power piezoceramic transducer as the actuator of vibrothermography and explores its ability to detect multiple surface cracks in a ...

Evaluation of the critical nature of interior cracks in turbine rotor component web regions in order to assess the remaining service life of the parts requires accurate determination of the crack sizes in order to perform fracture mechanics analysis. This analysis is important both in order to retire critically defective parts and in order to return components to service if detected flaws are s...

Sand-®lled cracks from the Lower Fine-grained Quartzite of Dalradian (late Proterozoic) age on the Island of Islay, western Scotland, may be divided into two main types, both of which form orthogonal and non-orthogonal closed patterns on bedding surfaces. Type 1 cracks are short and lenticular in cross-section, contain sand which had been injected downwards, and are found on the bottoms of cros...

A newly developed computational approach is proposed in the paper for the analysis of multiple crack problems based on the eigen crack opening displacement (COD) boundary integral equations. The eigen COD particularly refers to a crack in an infinite domain under fictitious traction acting on the crack surface. With the concept of eigen COD, the multiple cracks in great number can be solved by ...

Cracks often arise in an aeroengine labyrinth disc, which endanger flight security. Non-destructive testing (NDT) must been carried out in the labyrinth disc during the aeroengine working time. In situ detecting cracks in the labyrinth disc, the probe need pass through three layers narrow holes of aircraft skin, engine shell and outlet duct. Ultrasonic, radiography and liquid penetrant inspecti...

Recent analysis of gas outflow histories at wellheads shows that the hydraulic crack spacing must be of the order of 0.1 m (rather than 1 m or 10 m). Consequently, the existing models, limited to one or several cracks, are unrealistic. The reality is 10(5)-10(6) almost vertical hydraulic cracks per fracking stage. Here, we study the growth of two intersecting near-orthogonal systems of parallel...

The numerical manifold method (NMM), based on the finite covers, unifies the continuum analyses and discontinuum analyses without changing a predefined mathematical mesh of the uncracked solid, and has the advantages of being concise in theory as well as being clear in concept. It provides a natural method to analyze complex shaped strong discontinuities as well as weak discontinuities such as ...

In service, cracks or microcracks are usually present in concrete as a result of several mechanisms, for example the drying shrinkage, thermal gradients, freezing-thawing cycles, alkali-aggregate reaction and external loading. It has been realized that cracking can significantly accelerate the ingress of chlorides into concrete since it provides preferential flow channels and allow more chlorid...

Aging aircraft may develop multiple-site damage (MSD) that can reduce the structural integrity of fuselage structures. The existence of small cracks emanating from adjacent rivet holes in a fuselage lap-splice joint is of major concern. Small collinear cracks greatly reduce the residual strength of a panel with a lead crack. Recent studies predicting the residual strength of flat and curvilinea...