DEMODULATED RESONANCE ANALYSIS SYSTEM

• US 3,842,663 A
• Filed: 12/01/1972
• Issued: 10/22/1974
• Est. Priority Date: 12/01/1972
• Status: Expired due to Term

• Current Assignee: Darrell R. Harting, John W. Taylor
• Original Assignee: Darrell R. Harting, John W. Taylor
• Inventors: Harting, Darrell R., Taylor, John W.
• Primary Examiner(s): Queisser, Richard C.
• Assistant Examiner(s): Kreitman, Stephen A.
• Application Number:
  US05/311,284
• Time in Patent Office: 690 Days
• Field of Search: 73/67,71.4,67.2,69,71.2
• US Class Current: 73/593
• CPC Class Codes: G01H 1/003 of rotating machines G01H1/10 takes precedence
• CPC Class Codes: G01M 13/028 Acoustic or vibration analysis
• CPC Class Codes: G01M 13/045 Acoustic or vibration analysis

Abstract

An apparatus for detecting defects or flaws in mechanical systems with rotating and/or reciprocating components, such as gears or bearings. The scheme utilizes a transducer, which is excited at its mounted natural frequency by the vibrations caused by the impacting of components of a device across a flaw in a bearing or the like, a filter to eliminate background noise and signals other than the natural resonant frequency of the transducer, and a demodulator which converts the resulting signal into a series of pulses in which each pulse represents an individual impact. A spectral analysis is then performed on the series of pulses to obtain the location and nature of the surface defect in the bearing or other rotating and/or reciprocating component.

Claims

1. An apparatus for detecting flaws in mechanical components of machines, wherein the flaws and the natural vibration of the mechanical components in operation are a source of mechanical energy, comprising:

means for transforming the mechanicAl energy produced by the flaws and the natural vibration of the mechanical components into representative electrical signals, wherein said transforming means includes at least one transducer having a mounted natural resonant frequency sufficiently removed from the frequency of the natural vibration of the mechanical components such that said transducer is substantially only excited at its natural resonant frequency by the flaws in the mechanical components;

means for eliminating that portion of said electrical signals having frequencies with substantial energy other than said resonant frequency of said transforming means while retaining that portion of said electrical signals having frequencies substantially equal to said resonant frequency of said transforming means; and

means for analyzing said retained signals to determine the existence of a flaw in a mechanical component of a machine.

2. An apparatus in accordance with claim 1, including means for demodulating the output of said frequency elimination means.

3. An apparatus in accordance with claim 2 wherein said mechanical defect causes the transducer to vibrate at its mounted natural resonant frequency, said transducer producing an electrical output frequency spectrum containing said natural resonant frequency of the transducer in addition to other vibrations and noise associated with the mechanical structure.

4. An apparatus in accordance with claim 3 wherein the amplitude of an electrical signal associated with the said natural resonant frequency of the transducer by said transducer is a function of the severity of said mechanical defect.

5. An apparatus in accordance with claim 4 wherein said transducer produces an electrical signal output each time said mechanical defect is impacted by another part of the mechanical structure.

6. An apparatus in accordance with claim 5 wherein said frequency elimination means is a filter.

7. An apparatus in accordance with claim 6 wherein said filter is a band-pass filter, the mounted natural resonant frequency of the transducer being the center of the pass-band.

8. An apparatus in accordance with claim 7 wherein said demodulating means is a peak follower circuit, the output signal of which is the signal envelope of the output of said band-pass filter.

9. An apparatus in accordance with claim 8 wherein said transducer is piezo-electric accelerometer.

10. An apparatus in accordance with claim 9, including an amplifier, connected to said accelerometer and said filter for amplifying the output of said accelerometer.

11. An apparatus in accordance with claim 10, including an integrator, connected to said demodulator, said integrator integrating the output of said demodulator, to determine the area under the curve provided by said demodulator.

12. A method for detecting flaws in mechanical components of machines comprising the steps of:

exciting a transducer at its mounted natural resonant frequency, wherein said natural resonant frequency is sufficiently removed from the frequency of the natural vibration of the mechanical components such that said transducer is substantially only excited at its natural resonant frequency by the flaws in the mechanical components;

transforming said mechanical energy into representative electrical signals;

eliminating electrical signals not associated with the mechanical flaws; and

recognizing the presence of a remaining electrical signal which is associated with the mechanical flaws to obtain information concerning the flaws.

13. A process in accordance with claim 12, including the step of amplifying said representative electrical signals.

14. A process in accordance with claim 13, wherein the step of eliminating electrical signals includes eliminating electrical signals having frequencies other than the mounted natural resonant frequency of said transducer.

15. A process in accordance with claim 14, including demodulating said mounted natural resonant frequency signaL of said transducer.

16. A process in accordance with claim 15, wherein the step of recognizing includes integrating the demodulated resonant frequency signal.