Our Buzz-o-sonic NDT systems use the Impulse Excitation Technique (IET), or Ping test, to excite and measure resonant frequencies. The test is described in detail in ASTM E1876 and C1259. Buzz-o-sonic complies with these standards.
In the above example, a rectangular prism or bar is made to vibrate by tapping it lightly with a small hammer (impulse tool). These vibrations will resolve to standing waves in the sample, the frequency of which will depend on the sample shape, the sample dimensions and density, the sample's elastic properties, and on the mode of vibration. In this case, the resulting standing wave has nodes at 0.224 of the length from each end of the sample for the fundamental out-of-plane flexural mode of vibration; so the sample is supported on a parallel knife-edge span of 0.552 of the length.
This is a movie illustrating the fundamental out-of-plane flexural mode of vibration for a rectangular bar: the sample is supported and excited so that the sample vibrates up and down in a bending or flexural mode.
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