Elastodynamic models for extending GTD to penumbra and finite size flaws

A.K. Djakou (1) , Michel Darmon (1) , Catherine Potel (2, 3)

1 LSMA (CEA, LIST) - Laboratoire Simulation et Modélisation Acoustique (CEA, LIST)
2 LAUM - Laboratoire d'Acoustique de l'Université du Mans
3 FANO - Fédération Acoustique du Nord-Ouest

The scattering of elastic waves from an obstacle is of great interest in ultrasonic Non Destructive Evaluation (NDE). There exist two main scattering phenomena: specular reflection and diffraction. This paper is especially focused on possible improvements of the Geometrical Theory of Diffraction (GTD), one classical method used for modelling diffraction from scatterer edges. GTD notably presents two important drawbacks: it is theoretically valid for a canonical infinite edge and not for a finite one and presents discontinuities around the direction of specular reflection. In order to address the first drawback, a 3D hybrid method using both GTD and Huygens secondary sources has been developed to deal with finite flaws. ITD (Incremental Theory of Diffraction), a method developed in electromagnetism, has also been developed in elastodynamics to deal with small flaws. Experimental validation of these methods has been performed. As to the second drawback, a GTD uniform correction, the UTD (Uniform Theory of Diffraction) has been developed in the view of designing a generic model able to correctly simulate both specular reflection and diffraction. A comparison has been done between UTD numerical results and UAT (Uniform Asymptotic Theory of Diffraction) which is another uniform solution of GTD.

Mots clés: Diffraction; Elastic waves; Nondestructive examination; Experimental validations; Geometrical theory of diffraction; Incremental theory of diffractions; Non destructive evaluation; Scattering of elastic waves; Scattering phenomenon; Uniform asymptotic theories; Uniform theory of diffraction; Ultrasonic testing

Domaines: Physique [physics]

A.K. Djakou, Michel Darmon, Catherine Potel. Elastodynamic models for extending GTD to penumbra and finite size flaws. Journal of Physics: Conference Series, 2016, 684, pp.012002. ⟨10.1088/1742-6596/684/1/012002⟩. ⟨cea-01820749⟩