Two problems in dislocation dynamics are under study, tunneling of a dislocation (how it occurs) and a dislocation model for martensite phase transformations. In both cases detailed ultrasonic measurements are employed to examine the structural changes that occur during the process. The first part is an attempt to define the conditions under which tunneling of dislocations through pinning points can occur in dilute superconductor alloys as a function of impurity segregation to dislocations. If definitive evidence of tunneling is found, it can be used to test current theories of the effect of viscosity on tunneling of macroscopic systems. The second part is an attempt to obtain parameters for a detailed dislocation model for the martensite transformation in cobalt, which involves a change from the face-centered cubic structure to hexagonal close-packed structure. In this research ultrasonic measurements are ideally suited for examination of the mechanisms involved because of the sensitivity available for small structural changes, the discrimination possible from polarization dependence measurements, and the fact that the technique measures dynamic aspects of dislocation behavior.
