Measuring and testing – Vibration – By mechanical waves
Patent
1987-09-04
1989-07-11
Levy, Stewart J.
Measuring and testing
Vibration
By mechanical waves
7386138, G01H 500
Patent
active
048459895
ABSTRACT:
Method and apparatus for determining Young's Modulus of a specimen by measuring the speed at which stress waves, either P-waves or S-waves, propagate therein. An embodiment of the apparatus includes two fixtures which are removably affixed to opposite ends of the specimen. A hammer having an accelerometer affixed to its head is used to strike the first fixture to produce stress waves in the specimen. A timer starts counting in response to an output generated by the accelerometer when the hammer strikes the first fixture. A second accelerometer affixed to the second fixture detects the stress waves and generates an output which causes the timer to stop counting. Further circuitry extracts the measured time, calculates a dispersion time delay based on material and length, and subtracts the dispersion time delay and a predetermined constant, both dependent on the material in the specimen, from the measured time to form a corrected transit time. The circuitry uses the corrected transit time to determine the propagation speed of the stress waves and Young's Modulus therefrom.
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Brost Wilmut
Hahn David T.
Titlow Joseph D.
Bell Robert R.
Levy Stewart J.
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