Crack detection method for operating shaft
US5159563A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 19, 1990 |
| Grant date | Oct 27, 1992 |
| Priority date | — |
| Expiry date | Sep 19, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2291/2693
- 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 operating shaft system with the results of an analytical model. From a multi-station analytical model of an uncracked operating shaft system, 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 significant localized bending at the suspected axial location of the crack and at a site of response measurement. The analytical model is modified to include a representation of an asymmetric crack at the suspected crack location. A predicted split and downward shift of a lateral natural frequency of interest as a function of crack depth and/or a predicted downward shift of a torsional natural frequency of interest as a function of crack depth is calculated from the modified model. The actual shaft system is subjected to an operating force excitation, and vibrational response measurements are taken with strain gages and then output through a short range telemetry system. A fast Fourier transform analyzer derives frequenc…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.