Ultrasonic focusing using a stacked thin-plate region

This paper describes a stacked thin-plate region for focusing the transmitted waves. The region was designed to focus the wave field in the bulk medium by utilizing the dispersion nature of Lamb waves. The first numerical calculation proved that an incident plane wave changes the wavefront in a stacked thin-plate region because of the different phase velocities in plates with different thicknesses, and the resulting transmitted wave was focused at the target. Second, when a delayed longitudinal wave was applied to the edge of the stacked thin-plate region with identical thickness, the numerical calculations showed that the delayed wavefront of the S0 mode was preserved in the stacked plate region, and that the transmitted longitudinal wave was appropriately focused at the target. The focusing devise consisting of a stacked thin-plate structure is useful for the buffer for phased array inspection.