Research On Propagation Of Ultrasonic In Multilayer Structure With Dissimilar Materials

In order to get a reliable result, it's necessary to control the field distribution of ultrasonic in ultrasonic testing. For that reason, people design some coupling medium to affect the propagating characteristic of ultrasonic, between probe and testing structure, which all contribute to the propagation and the field distribution of the ultrasonic.In this paper, we take copper-steel multilayer structure as an example and build a multilayer model. In this model, ultrasonic propagating through lens, water, copper, steel, the interfaces and the multi heterogeneous materials which all contribute to the propagation and the field distribution of the ultrasonic. In order to present the inner condition, the propagation of the ultrasonic wave should be researched firstly to guide the test. In this article, the distribution of acoustic pressure field has been studied using the principle of geometric acoustic and the Gaussian beam model in copper-steel multilayer structure. The characteristic of propagation has also been researched when the acoustic propagates through the multilayer. Applying the theoretical analysis, the flaws which parallel and incline to the interface have been successfully found by use of point focus transducer.The characteristic of the ultrasonic propagation along the interface of multi materials have further been researched by solving the Stoneley's secular equation. Using the theoretical conclusion, the tiny flaws which are perpendicular to the interface have also been successfully tested by use of flat transducer.In order to increase the testing efficiency, high efficiency C-scan has been realized by means of phase array transducer. This testing result is in good consistent to the result by the single element transducer, but in much shorter period of time because of the simplified of the mechanical system.At last, to meet the practice requirement in industry, a set of ultrasonic auto-testing system has been develop and researched which possesses the specialty of low cost, high efficiency, great reliability.