Ultrasonic Wave Parameters Research Articles

Nonreciprocity effect upon propagation of ultrasonic waves in a La0.825Sr0.175MnO3 single crystal

The temperature dependences of the parameters of ultrasonic waves propagating in a La0.825Sr0.175MnO3 single crystal at a frequency of 770 MHz are investigated experimentally in the temperature range T = 285–330 K. It is found that the ultrasonic waves propagating in the sample in opposite directions have different velocities (the nonreciprocity effect). It is assumed that the acoustic nonreciprocity observed at these temperatures is most likely associated with the existence of structural and magnetic multiphase states, as well as with the formation of structural microinhomogeneities.

Quantitative Estimation of Bone Density and Bone Quality Using Acoustic Parameters of Cancellous Bone for Fast and Slow Waves

In previous studies, two longitudinal waves, the fast and slow waves, were observed in cancellous bone. The propagation speed of the fast wave increases with bone density and that of the slow wave remains almost constant. The attenuation constant of the fast wave is much higher than that of the slow wave and is independent of bone density, but the attenuation constant of the slow wave increases with bone density. In the present study, experimental results on ultrasonic waves transmitted through cancellous bone show that the fast wave amplitude increases proportionally and the slow wave amplitude decreases inversely with bone density. The dependence of the fast wave amplitude on bone density cannot be explained by the attenuation constant. The ultrasonic wave propagation path through cancellous bone is modeled to specify the causality between ultrasonic wave parameters and bone density. Then bone density and bone elasticity are quantitatively formulated.

Application of ultrasound reflection tomography for nondestructive evaluation of objects with a complex geometry

In the case of solid objects with complex geometry, conventional ultrasound tomography techniques tend not to be efficient enough. The objective of the paper is the development and experimental verification of an ultrasound tomography approach suitable for objects with non-flat boundaries. The reconstructed images in ultrasound reflection tomography usually are imperfect because of ultrasound wavefront curvature, which is significantly affected by wave refraction and mode conversion phenomena at the boundaries. In order to achieve better resolution of reconstructed images in the ultrasound reflection tomography, the curvature of the wavefronts has to be known and taken into account performing backprojection. Ultrasonic wavefronts were reconstructed from measured ultrasonic wave parameters. Obtained results were taken into account performing backprojection in the ultrasound refection tomography. When the curvature of the wavefront is known, the shape and the size of the defects can be reconstructed with greater accuracy. In order to determine accuracy of the proposed method, computer simulations and experimental measurements have been carried out and sources of possible errors were detected. From the results presented it can be seen that the method proposed increases accuracy of the ultrasonic reflection tomography.

Laser-modulated phase-stepping digital shearography for quantitative full-field imaging of ultrasonic waves

Measurement of surface displacements due to ultrasonic wave propagation in elastic solids has traditionally been studied using single-point measurement techniques such as ultrasonic transducers or interferometers. Full-field methods, excluding scanning techniques, are uncommon; examples include holographic interferometry and Schlieren imaging. In many cases, these techniques have been used to yield qualitative results due to inherent difficulties in processing the data. Laser-modulated phase-stepping digital shearography is a full-field, common-path, interferometric method which can be used to quickly visualize ultrasonic wave fields. A shearography system will be described that provides not only whole-field images of ultrasonic waves, but quantitative displacement data within these fields. Images are shown of propagating plate and bar waves, and mathematics relating the calculated optical phase to the ultrasonic wave parameters are presented.

Bond strength measurement by ultrasonic guided waves

A quasi-static model is proposed for ultrasonic guided waves interaction with imperfect interfaces. Incomplete bonding and the effect of this condition on the velocity is comprehensively discussed. The theoretical model, serves as reference for extracting ultrasonic wave parameters from experimental data. These parameters are correlated to adhesion strength. This work presents the results of a series of experiments with bonds of varying quality and thickness. Ultrasonic surface waves have been generated by a piezoelectric transducer and the detection was performed using an optical interferometer. The optical sensing of the ultrasonic surface waves is used to provide information about the ultrasonic guided waves which propagates along the boundaries between solids. Specifically, the normal component of the ultrasonic wave has been measured for providing information about the bond strength. The challenge of discriminating imperfect bonds was achieved.