Case Studies in Nondestructive Testing and Evaluation最新文献

Soil anchors with their guy lines are employed in a wide variety of applications. Anchor support for utility poles is the focus of the present study. A nonintrusive measuring system is proposed to monitor the integrity of such guy line ground anchors. The natural longitudinal frequency of the partially buried anchor rod with a terminal buried plate attached can be measured periodically with an accelerometer. An increase in this frequency over time would indicate a possible corrosion-induced loosening of the ground anchor from its buried terminal plate, and the need for anchor replacement. A case study involving an aging and failed utility pole anchor illustrates the need for such frequency monitoring.

This work aims at applying the laser-ultrasonic method for nondestructive evaluation of the depth of the subsurface damage in machined silicon wafers. It is based on different mechanisms of laser excitation of ultrasound by absorption of Q-switched Nd:YAG laser pulses at the fundamental wavelength: the concentration–deformation mechanism in the single-crystalline silicon and the thermoelastic one in the damaged layer. Due to the uniform heating of the whole damaged layer during the laser pulse action the amplitude of the compression phase of the laser-induced ultrasonic signal is proportional to the damaged depth. The rarefaction phase of this signal arises by absorption of the rest of laser energy in the single-crystalline silicon beneath the damaged layer. The empirical relation between the depth of the subsurface damage and the ratio of the amplitudes of compression and rarefaction phases of the laser-induced ultrasonic signal can be fitted by a linear function within the depth variation and the corresponding spread of the signal amplitudes. This relation can be used for in situ quantitative nondestructive evaluation of the depth of the subsurface damage in machined silicon wafers; the minimal reliably detectable depth is estimated at the level of 0.15–0.2 μm.

‘Big data’ obtained from wayside detection systems and sensors installed on board a train show that actual loading history for a railway track is rather dynamic and transient. The dynamic loadings due to train and track interactions redistribute from the rails to the rail pad, from the rail pad to the railway sleeper, and from the railway sleeper to the underlying ground. Dynamic content redistributed onto each layer of track is also filtered by energy dissipation characteristic of materials and structures. As a critical infrastructure, railway turnout is a structural grillage system used to divert a train to other directions or other tracks. The wheel–rail contact over the crossing transfer zone often causes detrimental impact loads that rapidly deteriorate the turnout and its components. The dynamic responses of wheel–rail interaction depend largely on the non-smooth trajectory or wearing condition of crossing geometry. In reality, a railway line spreads over a large distance and monitoring such rail infrastructure is one of the challenges in rail industry. This paper presents a methodology and application to evaluate and monitor the structural deterioration of railway turnout systems in an Australian urban rail network. The method has integrated numerical train/track simulations, axle box acceleration and ride quality data obtained from the calibrated track inspection vehicle “AK Car”.

A novel inspection system which incorporates a low-profile flexible ultrasonic array and a shape sensing fibre is presented in this paper. The system is shown to be able to directly measure the location of the elements in the array as it conforms to a curved surface. This enables the accurate ultrasonic imaging and inspection of components with complex geometries for sub-surface defects. The system offers many significant advantages over other inspection approaches and is particularly applicable to in situ inspections where access is limited.