An experimental/numeric study will be carried out for acquiring the understanding of the basic mechanics of the generation and propagation of thermoelastically generated Lamb waves that is needed to exploit these waves for nondestructive evaluation of wafers, plates and panels. Since Lamb waves propagate in the plane of a plate and affect the whole thickness, they are excellent for determining the extent and severity of defects such as surface cracks, delaminations and local changes in material properties. Broadband transient Lamb waves will be generated by irradiating a small area on the surface of a plate with a short duration fiber guided laser pulse. The resultant thermal shock generates a wave which is then sensed by a fiber-optic interferometer. Data analysis will be in the frequency domain where the imprints that defects leave on the wave are most clearly evident. The numeric and experimental methods will be combined to study the basic parameters involved in the generation and propagation of these waves and in the ways in which they are influenced by defects. The resultant knowledge will be used to design efficient means for generating waves with desirable characteristics and to optimize the overall system for identifying and characterizing defects both for quality control and safety assurance.
