COVER SHEET Title: Predictive modeling of ultrasonics SHM with PWAS transducers Authors: Matthieu Gresil

This paper presents a set of analytical and numerical results on the use of guided waves for structural health monitoring application. The aim of the work presented in this paper is to provide tools to extend modeling capacities and improve quality and reliability of guided wave propagation models using commercially available finite element (FE) packages. Predictive simulation of ultrasonic non-destructive evaluation (NDE) and structural health monitoring (SHM) in realistic structures is challenging. The principle of guided wave propagation is studied and an analytical model is developed to obtain the analytical waveform and theoretical frequency contents solution of arbitrary engineering situations. Two benchmark problems, one 1-D and the other 2-D to achieve reliable and trustworthy predictive simulation of ultrasonic guided wave SHM with FEM codes have been proposed. The proposed 1-D benchmark problem will be a simple pitch-catch arrangement between a transmitter PWAS and receiver PWAS in a plate. The proposed 2-D benchmark problem will be the pitch-catch arrangement in a full 2-D plate involving circular-crested guided waves between a transmitter PWAS and receiver PWAS. In addition, a circular through hole of defined size ratio could be added to the 2-D problem to simulate the detection of damage, and assess the detectability threshold since closed-form solution exists for this problem too. The paper finishes with summary, conclusion, and suggestions for further work. INTRODUCTION Predictive simulation of ultrasonic non-destructive evaluation (NDE) and structural health monitoring (SHM) in realistic structures is challenging [1]. Analytical methods (e.g., ray-tracing, beam/pencil, Green functions, etc.) [2] can perform efficiently modeling of wave propagation but are limited to simple geometries. 1 Matthieu Gresil, LAMSS, Univ. of South Carolina, SC 29208, USA, [email protected] Yanfeng Shen, LAMSS, Univ. of South Carolina, SC 29208, USA Victor Giurgiutiu, LAMSS, Univ. of South Carolina, SC 29208, USA Realistic structures with complicated geometries are usually modeled with the finite element method (FEM). Commercial FEM codes offer convenient built-in resources for automated meshing, frequency analysis, as well as time integration of dynamic events. Even a relatively rough FE model would yield a ‘wave propagation’ animated output that is illustrative and interesting to watch. However, to obtain accurate wave propagation solution at ultrasonic frequencies is computationally intensive and may become prohibitive for realistic structures. Several investigators have previously addressed the convergence of FEM solutions for NDE-type ultrasonic inspection (bulk waves) and have developed useful guidelines [3, 4]. This paper addresses this issue in the context of guided-waves for SHM with piezoelectric wafer active sensors (PWAS) using the pitch-catch method.