Modelling of gradients in elastic properties for acoustic microscopy characterizations

¹ LIM, Faculté des Sciences, Université Ibnou Zohr, B.P. 28/S, Agadir, Morocco
² LAIN, Université Montpellier II, 34095 Montpellier Cedex 05, France

Corresponding author: cros@lain.univ-montp2.fr

Received: 8 December 1998
Revised: 23 February 1999
Accepted: 4 March 1999
Published online: 15 June 1999

Abstract

In order to allow non-destructive characterizations by acoustic microscopy, the materials presenting in their properties a gradient perpendicular to the surface are modelled. The method consists in regarding the material as built of a succession of homogeneous layers numerous enough for the acoustic parameters to vary quasi-continuously. The gradient in Young modulus existing in the material is related to a gradient in acoustic properties measurable by acoustic microscopy. The role of the shape of the gradient profile is taken into account in the study of the convergence of the velocity of the surface mode V_S. The dispersion of the velocity V_S versus d/λ (d is the depth of the gradient area and λ is the wavelength) is studied as a function of the gradient profile. The shape of the curves shows that the best sensitivity to the profile is obtained for d/λ≈1.