Finite element study of Lamb waves: modeling techniques and applications

Abstract

The intent of this thesis research is to investigate Lamb waves numerically and to establish PC-based finite element modeling techniques, using a commercial code, for Lamb waves. This investigation provides concurrent support for the development of experimental laser based NDE techniques and applications. Experimental results are compared to some of the finite element techniques used for modeling the Lamb waves. Methods that are used for developing acceptable models are discussed. A numerical exercise is also included that checks the validity of the model parameters, such as mesh size, time step, and other assumptions, to ensure efficient modeling of these waves. When possible, frequency characteristics and wave velocities are compared to experimental and theoretical results. In addition, other finite element work shows the viability of using these modeling techniques as a tool for understanding the interaction of Lamb waves with physical defects. As a signal processing tool, neural networks will process model displacement time histories to determine defect geometries in a thin plate. Recommendations are presented for the future continuation of this type of work in finite element wave propagation.