Flexural resonance measurements of clamped and partially clamped disks excited by nanosecond laser pulses

Nanosecond pulses from a Nd:YAG laser are used to excite clamped aluminum disks to resonance. The first two flexural vibration modes are shown to be in agreement with classical plate theory. This theory is then applied to the case of flat-bottomed holes in aluminum plates, when the remainder of the plate below the hole may be said to be partially clamped. It is shown that the theory can still be used over a well-defined regime. In addition, the depth of the hole can be obtained from the ring-around longitudinal ultrasonic pulse generated by the laser. A combination of these two techniques, therefore, allows a sizing of circularlike flaws in laminations lying close to a sample’s surface.