Interaction of a monochromatic ultrasonic beam with a finite length defect at the interface between two anisotropic layers: kirchhoff approximation and fourier representation

This paper presents a fast computation method to simulate the interaction between a bounded acoustic beam and a 2-layered anisotropic structure with a finite defect on the internal interface. The method uses the classical Fourier decomposition of the fields into plane waves, and the Kirchhoff approximation is introduced to calculate the diffusion by the defect. The validity of the approximation is estimated by comparison with the Keller Geometrical Theory of Diffraction and with results obtained by boundary element methods. The quickness of the method allows testing several geometrical configurations (varying incident angle, thickness of the layers or the physical nature of the defect). These studies may be used to foresee what experimental configurations would be adequate to have a chance to detect the defect.