Analytical Modelling of Magnetostrictive Transducers used for Non-Destructive Evaluation

摘要

Magnetostrictive transducers have been intensively used for filters, delay lines and power transducers in sonar systems [1]-[6]. When the propagation medium has magnetic properties its intrinsic magnetostriction can been used for designing specific actuators and sensors which allow to evaluate the material parameters of the material [7]-[11]. For each application, a dedicated model has been develop to describe the performances of the transducer in term of transient [2], [4] or harmonic propagation [10]-[12]. Transient analysis of delay lines has been first developed by A. Rothbart, L. Rosenberg [2], Williams [4] and by Thomson [6]. They obtained an analytical model of the wave generation which help understanding the transduction phenomena inside the magnetostrictive transducer. Mason [1] and Onoe [5] give electrical equivalent circuits of the delay line magnetostrictive transducers. Jacobsen [13] first established a transient model for piezoelectric transducers vibrating on longitudinal mode. Based on Green function, Jacobsen's approach leads to a very simple and useful important understanding of the electromechanical conversion inside piezoelectric materials. This paper is devoted to the modelling of a non destructive magnetostrictive device used for monitoring the cables and strands of bridges. This model based on Green function approach emphasizes on the electro-mechanical conversion process and the location of the generated waves inside magnetostrictive materials. The transfer function of the monitoring system can be deduced of this modelling.