Our aim is to develope precise non-invasive acoustic tools to characterize material properties. In collaboration with Fernando Lund, Felipe Barra and coworkers we are also interested in exploring the dependence of these properties on the density of dislocations in solids.

We are currently exploring two techniques, the traditional ultrasonic pulse propagation technique, and the presumably more sensitive Resonant Ultrasonic Spectroscopy (RUS) technique. Measurements in copper using 5 MHz ultrasonic longitudinal pulses have been done, though diffraction effects still have to be minimized in order to get more precise measurements of the longitudinal sound speed. We also plan to measure by the same procedure the transverse sound speed in the same samples in order to completely characterize the elastic constants of this isotropic material. The RUS setup is currently being constructed. The forward and inverse codes for estimation and iteration of the resonant frequencies and elastic constants of samples of different sample shapes are under study (These codes exist as open-source programs, which we are learning to use). The piezoelectric ceramics that will be used for ultrasonic generation have been tested in the RUS configuration and resonance spectra have been obtained, though we have not yet minimized the applied stress to the sample, a necessary condition in order to apply the RUS technique. In order to do so we have to use the complete RUS setup, which will be ready soon.

People Involved
- Andrés Caru (Universidad de Valdivia)
- Nicolás Mujica (Universidad de Chile)