Measurements of Elastic Properties of Plasma-Sprayed Coatings Using Bulk Ultrasonic Pulses

Abstract

A new theory is proposed to extend the limit of the application of bulk ultrasonic pulses, which have been thought to be unsuitable for the evaluation of sound velocity in thin coating layers because of interference with echoes. This extension is accomplished by introducing the new concept of the group delay spectrum. We first made a model representing waves reflected from a coating layer and found that many acoustic properties, for example, sound velocity, acoustic impedance, and coating density, can be derived easily by a group delay analysis. Next, the theory was applied to the analysis of a layer plasmasprayed coated with alumina particles on a stainless steel substrate. To confirm the validity of the theory, we prepared coated specimens of varying thicknesses which covered from 0.16 mm to 0.48 mm, and we succeeded in evaluating sound velocity and coating density.

Analysis of Propagation of Ultrasonic Pulses in Dispersive Media Using Group Delay Concept

“…The author has discovered a useful application of the group delay concept in the analysis of bulk wave propagation in plasma-sprayed coatings, 9) which are regarded to be thin materials. The author believes that this application is not limited to thin materials, and that the time has come to further develop the studies on group delay and velocity.…”

“…However, it is difficult to apply this method when the change of phase is rapid as, for example, in thin materials. 9) We used the phase slope and analytic cross-correlation methods in the analysis of plasma-sprayed coatings mentioned above. However, because these methods have the disadvantages described above, we have had to develop a theory to overcome these disadvantages to improve analysis.…”

Evaluation of Elastic Constants of Antifouling Paint Film Using Group Delay Spectrum Method

“…However, it is difficult to apply the conventional pulseecho method 2) to the analysis of such thin films because of the interference between bottom echoes in thin layers like films. In our previous study, 3) we have developed a new analytical technique called the group delay spectrum method and succeeded in evaluating the sound velocity of plasmasprayed coatings. Therefore, in the case in which the conventional method is not applicable, we can use the group delay spectrum method 3,4) to analyze wave propagation in thin films.…”

“…In our previous study, 3) we have developed a new analytical technique called the group delay spectrum method and succeeded in evaluating the sound velocity of plasmasprayed coatings. Therefore, in the case in which the conventional method is not applicable, we can use the group delay spectrum method 3,4) to analyze wave propagation in thin films.…”

Elastography Using Graph Cut Algorithm

“…Elastography is examined as a new application of ultrasound in medical diagnostic imaging. [3][4][5][6][7][8][9] This method utilizes signals observed in different situations (for example, with additional static pressure). Therefore, we expected to be able to apply the GC algorithm to elastography successfully.…”