Abstract
A description is given of the application of the pulsed light emitting diode illumination of ultrasonic wavefronts to experiments where the sound, viewed in a visualizing block, first passes through steel containing a small hole. Marked improvements are reported for the system illumination, ultrasonic transducer drive and efficiency, interfacing of transducer to specimen and specimen to glass, and optimizing procedures to give clear sharp fringes. Photographs are included showing fringe patterns obtained at 2 MHz and 4 MHz which contain information derived from holes in the range 1–4 mm radius. The experimental arrangement is inexpensive and compact and accurate location of the simple defects studies done (holes) is quite obvious from the geometry of the mode converted distortional (shear) wave form.
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