In a first stage, we exploit characteristic the ultrasonic Rayleigh waves have of spreading on the surface of a sample in a depth proportional to the wavelength. On the basis of an experimental device with variable incidence and re-emission angles, and with localized immersion coupling, we generate non generalized surface waves by means of a couple of large bandwith transmitter-receiver transducers. Variating the distance covered by the wave and measuring the corresponding times for each of the signal frequencies permit, by two different methods of calculation, to get the distribution in relation to the depth (incremental calculus and least error squares method). These calculations imply, on the one hand the time measurements by inter-correlation or by the cross density phase, and on the other hand the analysis of the distribution of the wave energy in relation to the depth. Wave train and impulse wave tests allow the validation of the experimental measurements.
In a second stage, we determine the evolution of the elasticity modulus. This requires the measurement of several parameters: i.e. the density and the residual stresses that evolve with the depth as well as the acousto-elastic and Poisson coefficients.
The presented results show the evolutions of the ultrasonic wave velocity with the frequency and with the depth, then the value of the elasticity modulus in relation to the depth for the two steels in different states: treated or non-treated. An analysis justifies some of these evolutions and insists on the limited amplitude of these variations.
Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00
Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:
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