Simulation of wave ultrasonic propagation to characterize material properties

MESSINEO, MARIA GABRIELA; FRONTINI, GLORIA L.; GAETE GARRETÓN, L.; VARGAS, YOLANDA; ELIÇABE, GUILLERMO E.

Santiago de Chile-Chile

Congreso; International Congress on Ultrasonics, ICU, 2009; 2009

Abstract: In this work we present some contributions to the analysis and simulation of the ultrasonic propagation in a layered material. The main objective is the ultrasonic characterization of the material. We use plane ustrasonic pulses in a structure assumed to be composed of layers with plane parallel interfaces. The wave equation is assumed to be the exact mathematical formulation for the problem. We use also analogous mechanical impedance as an approximate representation useful under certain circumstances. Numerical simulations are performed by means of a software  (Wave2000, Cyberlogic) based in a finite difference method and the results are compared to those obtained by specific programs developed using Matlab. The determination of the material properties is accomplished solving an inverse problem in which the unknowns are the parameters that characterize the material. A non linear least squares method is implemented to minimize the discrepancy between the synthetic measurements and the signal stemmed from the solution of the forward problem, i.e., the ultrasonic propagation model. The minimization is made involving the time domain models. We use the impulse response of the specimen as a function of interest for the characterization. The estimation of the impulse response is done in a parametric manner using the least square approach. Besides, we explored the possibility to solve the problem assuming free-form for the function  by means of deconvolution techniques.  The results show that the calculated values are in good agreement with the real parameters even in the case where added noise is considered. For the deconvolution approach, noise effect is important due to the ill-conditioned nature of the problem.