The effect of a middle layer on ultrasonic wave propagating in a three-layered structure

Abstract

In this paper the focus is on the effect of an elastic middle layer on the propagation of ultrasonic waves. Systematic parametric studies are conducted to quantify the effects of the middle layer upon the ultrasonic wave propagation, including its thickness and acoustic impedance. We treat this problem analytically and numerically. The three-layered structure is also used to investigate the influence of the imperfect interfaces between two outer layers and a middle layer on the ultrasonic wave propagation. The theoretical analysis considers successive reflections of waves radiated by the transmitting transducer. The output signal is a superposition of successive reflections. Our results demonstrate clearly that there is significant influence of the middle layer in our three-layered problem. Various aspects of our approach are discussed and numerical examples are used to illustrate the suitability of our approach. Some details about the numerical methods employed are also given. The results are presented and discussed. © 2013 Acoustical Society of America.