Identification of Stiffness Coefficients in Resonant Ultrasound Spectroscopy Using Particle Swarm Optimization

Resonant ultrasound spectroscopy (RUS) is an experimental method for measuring the full elastic tensor of a small solid sample from the free resonant frequencies. One important step of the method is to adjust the stiffness coefficients in a model to minimize the difference between computed and measured frequencies. This inverse problem is traditionally solved with the Levenberg-Marquardt (LM) minimization algorithm. The convergence rate and accuracy of the method depend on the initial guess of the elastic tensor that should be relatively close to the sought solution in order to reach the global minimum (as opposed to a local one). To overcome this limitation, we introduce in this paper the particle swarm optimization (PSO) algorithm for its potential in finding a global solution without the need for an accurate initial guess for the model parameters.