Nonlinear ultrasonic testing

There have been a number of previous attempts to relate the appearance of higher harmonics in the transmission of ultrasound through bonded structures to the quahty of the bonds [2-9]. Commonly used is the so-called nonhnearity parameter y 2, a measure of the generation of only the second harmonic [2], and the distortion factor K which describes the complete nonlinear content of the response [7]. In this paper cahbrated measurements on samples consisting of two aluminum plates joined together by a thin epoxy layer are presented and discussed. The amphtudes and phases of the ultrasonic waves transmitted through the bond are considered. The measurements are related to the results of destructive tensile tests of the adhesive layer. 

In order to allow both ultrasonic transmission experiments and tensile loading, the ultrasonic set-up was integrated into a small laboratory-scale tensile test stage (Fig. 25.9). The incentive for these experiments originated from the results of combined ultrasonic transmission and dynamic and quasi-static tensile tests of bonded steel tubes [14] and the data shown above. We wanted to test whether there is a correlation of any of the following parameters the second-order nonlinearity parameter y 2, the third-order nonlinearity parameter / 3, the distortion factor K, or the interaction force Fip to the destractively determined tensile strengths. 

---