Simulation of Layer Thickness Measurement in Thin Multi-Layered Material by Variable-Focus Laser Ultrasonic Testing.

Thin multi-layered materials are widely used in key structures of many high technology industries. To ensure the quality and safety of structures, layer thickness measurement by non-destructive testing (NDT) techniques is essential. In this paper, a novel approach for the measurement of each layer's thickness in thin multi-layered material is proposed by using ring-shaped laser generated focused ultrasonic bulk waves.

Fully noncontact inspection of closed surface crack with nonlinear laser ultrasonic testing method.

Nonlinear ultrasonic testing method is one of few techniques that are effective for evaluating early material degradation and micro-crack initiation by analysing the nonlinear effects of ultrasonic waves. This study presents a noncontact nonlinear ultrasonic testing method based on lasers for closed surface crack inspection. A pulsed laser grating source by grating mask is applied to generate narrowband surface acoustic wave of a chosen frequency.

A new method for plastic strain measurement with Rayleigh wave polarization.

In this work, a new non-contact and coupling-free ultrasound method with measuring Rayleigh wave polarization (RWP) by electromagnetic acoustic transducers (EMATs) is applied for plastic strain measurement, which can provide a very promising alternative and reference-free ultrasonic testing technique with high spatial resolution. Two specially designed EMAT receivers are developed to measure the polarization of Rayleigh wave generated by an enhanced meander-line-coil EMAT. The change in RWP due to the plastic strain has been successfully measured.

Image enhancement for on-site X-ray nondestructive inspection of reinforced concrete structures.

The use of portable and high-energy X-ray system can provide a very promising approach for on-site nondestructive inspection of inner steel reinforcement of concrete structures. However, the noise properties and contrast of the radiographic images for thick concrete structures do often not meet the demands. To enhance the images, we present a simple and effective method for noise reduction based on a combined curvelet-wavelet transform and local contrast enhancement based on neighborhood operation.

A study of internal defect testing with the laser-EMAT ultrasonic method.

This paper studies the ultrasonic detection and evaluation of internal volume defects in metals using laser generation and electromagnetic acoustic transducer (EMAT) detection. A finite element model is developed to simulate the interaction of laser-generated ultrasonic waves with the defect in the material. Not only have the directly scattered shear waves been observed, but also the mode-converted creeping waves on the defect surface.

Correction of chemical shift misregistration by images from two different bandwidths.

One major effect caused by the different chemical shift frequencies of water and fat is the misregistration between the two components in MR images. Methods to correct misregistration are required in clinical MRI for accurate localization and artifact reduction. One of the methods uses the images scanned at opposite readout gradients to separate water and fat signal in the k-space.