REMOTE TRANSMISSION SYSTEM AND METHOD FOR DETECTING ONSET OF STRUCTURAL FAILURE

• US 20100001874A1
• Filed: 07/01/2008
• Published: 01/07/2010
• Est. Priority Date: 07/01/2008
• Status: Abandoned Application

• Current Assignee: Pratt & Whitney Rocketdyne Incorporated (L3Harris Technologies, Inc.)
• Original Assignee: Pratt & Whitney Rocketdyne Incorporated (L3Harris Technologies, Inc.)
• Inventors: Cipra, Dale O.
• Application Number:
  US12/165,695
• Publication Number:
  US 20100001874A1
• Time in Patent Office: Days
• US Class Current: 340/683
• CPC Class Codes: G01N 2291/0258 Structural degradation, e.g. fatigue of composites, ageing of oils
• CPC Class Codes: G01N 2291/042 Wave modes
• CPC Class Codes: G01N 29/12 by measuring frequency or resonance of acoustic waves measuring frequency or resonant frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04, G01H13/00; acoustic resonators G10K11/04; vibration or shock testing of structures G01M7/00
• CPC Class Codes: G01N 3/34 generated by mechanical means, e.g. hammer blows

Abstract

A method for monitoring a structure subject to a mechanical load comprises measuring physical parameters associated with natural oscillations of the structure, transforming the physical parameters into normal mode spectra, and broadcasting an alarm as a function of a change in the normal mode spectra near a critical point. The normal mode spectra represent the natural oscillations of the structure.

Claims

1. A method for monitoring a structure subject to a mechanical load, the method comprising:

measuring physical parameters associated with natural oscillations of the structure when subject to the mechanical load;

transforming the physical parameters into a normal mode spectrum, such that the normal mode spectrum represents the natural oscillations of the structure; and

broadcasting a structural failure alarm as a function of a change in the normal mode spectrum near a critical point.

2. The method of claim 1, wherein transforming the physical parameters into the normal mode spectrum comprises transforming the physical parameters such that the normal mode spectrum represents a natural mode of oscillation having a frequency of less than one hundred hertz.

3. The method of claim 1, wherein transforming the physical parameters into the normal mode spectrum comprises transforming the physical parameters such that the normal mode spectrum represents a natural mode of oscillation having a subsonic frequency.

4. The method of claim 1, wherein transforming the physical parameters into the normal mode spectrum comprises transforming the physical parameters such that the normal mode spectrum represents a natural mode of oscillation having an order of less than ten.

5. The method of claim 1, wherein transforming the physical parameters into the normal mode spectrum comprises transforming the physical parameters such that the normal mode spectrum represents a fundamental mode of oscillation.

6. The method of claim 1, wherein broadcasting an alarm as a function of a change in the normal mode spectra comprises broadcasting the alarm as a function of an approach to a zero or unbounded value near the critical point.

7. The method of claim 6, wherein the approach to a zero or unbounded value comprises a change of greater than ten percent in an oscillation frequency or an oscillation period.

8. The method of claim 1, wherein broadcasting an alarm as a function of a change in the normal mode spectra comprises broadcasting the alarm as a function of an approach to an unbounded or zero slope of a frequency or period curve.

9. The method of claim 8, wherein the approach to a zero or unbounded slope comprises a change of greater than twenty percent in the slope of the frequency or period curve.

10. The method of claim 1, wherein broadcasting an alarm as a function of a change in the normal mode spectrum comprises broadcasting the alarm as a function of a deviation from an analytical model of the natural oscillation.

11. The method of claim 1, wherein the deviation from the analytical model comprises a deviation of at least three sigma in a frequency, a period or a slope, as compared to the analytical model.

12. The method of claim 1, wherein measuring physical parameters associated with natural oscillations of the structure comprises measuring physical parameters associated with natural oscillations of a bridge.

13. The method of claim 12, wherein broadcasting an alarm comprises directing traffic to stay off the bridge.

14. A method for warning of impending structural collapse, the method comprising:

measuring physical quantities associated with subsonic modes of oscillation in a structure subject to a mechanical load;

transforming the measured physical quantities into a normal mode spectrum, wherein the normal mode spectrum characterizes the subsonic modes of oscillation; and

transmitting a warning of impending collapse, wherein the warning is a function of a shift in the normal mode spectrum near a critical point.

15. The method of claim 14, wherein transmitting the warning of impending collapse is a function of a shift toward zero frequency in one of the subsonic modes of oscillation.

16. The method of claim 14, wherein transmitting the warning of impending collapse is a function of a shift toward a zero slope in one of the subsonic modes of oscillation.

17. The method of claim 14, wherein transmitting the warning of impending collapse is a function of a shift toward an undefined slope in one of the subsonic modes of oscillation.

18. The method of claim 14, wherein transforming the measured physical quantities into the normal mode spectrum comprises transforming the physical quantities such that the normal mode spectrum characterizes a fundamental mode of oscillation.

19. The method of claim 18, wherein transmitting the warning of impending collapse comprises transmitting the warning to emergency response personnel in order to evacuate the structure.

20. The method of claim 18, wherein transmitting the warning of impending collapse comprises transmitting a warning signal to direct persons to evacuate the structure.

21. A system for detecting onset of structural failure in a structural element, the system comprising:

a sensor for sensing a physical parameter associated with a normal mode of natural oscillation in the structural element;

a signal processor for transforming the physical parameter into an oscillation function representing the normal mode; and

a transmitter for transmitting an alarm indicating the onset of structural failure based on a shift in the oscillation function as the oscillation approaches a critical point.

22. The system of claim 21, wherein the normal mode has an order of less then ten.

23. The system of claim 22, wherein the shift comprises a shift of greater than ten percent in a period or frequency of the oscillation function.

24. The system of claim 22, wherein the shift comprises a shift of greater than twenty percent in a slope of the oscillation function.

25. The system of claim 22, wherein the shift comprises a deviation of at least three sigma between the oscillation function and an analytical model of the normal mode.

26. The system of claim 21, wherein the shift in the oscillation function occurs before failure of local components of the structural element.

27. The system of claim 21, wherein the shift in the oscillation function is indicative of the onset of a buckling failure.