Shaft crack detection method
US4975855A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 14, 1989 |
| Grant date | Dec 4, 1990 |
| Priority date | — |
| Expiry date | Mar 14, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2291/2696
- WIPO fieldMeasurement
- WIPO sectorInstruments
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…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.