Karpur 9523342 Ultrasonic techniques have been found to be very effective in detecting small defects in comparatively small samples. However, in big civil infrastructure type specimens such as bridges, columns, poles and pipelines use of ultrasonic techniques has been limited because of high absorption and scattering of body waves (longitudinal and shear waves which are used in ultrasonic experiments) in such big objects. In this project unconventional Lamb waves at very low frequencies (30 kHz - 200 kHz) will be used to detect internal defects in civil infrastructures. Initial investigations have shown that for detecting weak bonds and partially damaged internal interfaces, Lamb waves are much more efficient than body waves. However, Lamb wave sensors have not been developed yet to its full potential because of the lack of expertise in this field in sensor industries. In this research the theory necessary to develop efficient Lamb wave or guided wave sensors will be developed first. Then the new sensor will be fabricated with the help of transducer manufacturing industries. These sensors will be tested at the Wright-Patterson Material Laboratory and will be used to detect internal damages in concrete and metal slabs and pipeline type civil infrastructures. Two companion projects are supported to carry out the above described research: University of Arizona which will develop the basic lamb wave theory and conduct initial sensor design and testing, and University of Dayton/Wright- Patterson Laboratory which will test the fabricated sensors and evaluate the results. ***
