Boots – shoes – and leggings
Patent
1989-03-14
1990-12-04
Lall, Parshotam S.
Boots, shoes, and leggings
36455102, 73581, 73622, 340680, G01N 2782, G01R 3312
Patent
active
049758551
ABSTRACT:
The presence, size and location of a crack in a shaft is determined by comparing actual measured natural frequencies of the shaft with the results of an analytical model. From a multistation analytical model of an uncracked shaft, natural frequencies and associated mode shapes are derived. A suspected axial location of a crack is defined and a natural frequency of interest is selected which has an associated mode shape exhibiting maximum deflection at the supected axial location of the crack and at a site of excitation. The analytical model is modified to include a representation of an asymmetric crack, at the suspected crack location, and the predicted split and downward shift of the natural frequency of interest as a function of crack depth is calculated from the modified model. The actual shaft is subjected to a radial excitation force, and vibrational response measurements are taken with an accelerometer along multiple radial directions. A fast Fourier transform analyzer derives a frequency response function from the measurements for each radial direction. The frequency response functions indicate the actual natural frequencies of the shaft. A comparison of these actual natural frequencies with those predicted by the modified model is employed to determine the presence and severity of a crack in the shaft.
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Brook Warren R.
Miller William H.
Lall Parshotam S.
Mattson Brian M.
REM Technologies, Inc.
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