Comparison between elastic and porous elastic material models for sediment acoustical behavior in an aluminum-sediment double layer

Abstract

In this paper, Lamb waves dispersion curves are extracted for a double layer aluminum-sediment (gypsum) plate, both numerically and experimentally. For this purpose, the gypsum elastic properties are approximately calculated using ultrasonic bulk waves method. Then, by using the porous elastic behavior model for the gypsum, as well as the elastic model, available in ABAQUS commercial software, the dispersion curves are calculated numerically in the frequency range of 100–200 kHz for the sedimentary plate. In order to validate the numerical dispersion curves, an experimental setup consists of a 1-mm-thick aluminum plate covered by a 1.5 mm thick sediment (gypsum) area, equipped with two piezoelectric disks has been provided. The experimental dispersion curves for two fundamental symmetric and anti-symmetric modes, S0 and A0, have been extracted, using the time of flight method, applied on filtered experimental signals. Results show that the relative error between porous elastic and experimental models is 5.26% and 3.56% while relative error between numerical elastic model and the experimental model is 5.9% and 4.3%, for S0 and A0 modes, respectively. It is concluded that for dry sediments, the elastic mechanical behavior is acceptable. However, in case of wet sediments, dispersion curves should be extracted using a porous elastic model before defect detection in sedimentary structures. The unique capability of the porous elastic model is the possibility of wet sediment consideration, for dispersion curves evaluation.