A new technique for ultrasonic nondestructive evaluation of adhesive joints: Part I. Theory

In this paper we proposed a new technique for ultrasonic nondestructive evaluation (UNDE) of adhesively bonded joints. We report an exact solution to the problem of reflection and tarnsmission of a plane, time-harmonic, longitudinal wave through anN-layered medium. The solution is valid for perfectly elastic as well as linear-viscoelastic materials, and for isotropic as well as anisotropic materials (for example, fiber-reinforced composite) so long as the wavepropagation vector coincids with one of the material coordinates. The transfer function,H ^*() is defined as the trans-mitted (or reflected) field normalized with respect to the incident field. A closed-form solution forH ^*() for the case of an adhesive joint (consisting of two adherends joined by an adhesive layer) immersed in an elastic fluid is derived. A detailed analysis of the sensitivity ofH ^*() to the wave speed and thickness of the adherends and the adhesive is carried out. An experimental verification of the analysis is the subject of Part II of this paper.Paper was presented at the 1991 SEM Spring Confernce on Experimental Mechanics held in Milwaukee, WI on June 9–13.