STRUCTURAL HEALTH MONITORING SYSTEM UTILIZING GUIDED LAMB WAVES EMBEDDED ULTRASONIC STRUCTURAL RADAR

• US 20050228597A1
• Filed: 06/16/2003
• Published: 10/13/2005
• Est. Priority Date: 06/14/2002
• Status: Active Grant

• Current Assignee: University of South Carolina
• Original Assignee: University of South Carolina
• Inventors: Giurgiutiu, Victor, Zagrai, Andrei N., Bao, Jingjing
• Granted Patent: US 6,996,480 B2
• Time in Patent Office: Days
• US Class Current: 702/35
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 5/0066 by exciting or detecting vibration or acceleration vibration testing of structures G01M7/00
• CPC Class Codes: G01N 2291/0231 Composite or layered materials
• CPC Class Codes: G01N 2291/0237 Thin materials, e.g. paper, membranes, thin films
• CPC Class Codes: G01N 2291/0258 Structural degradation, e.g. fatigue of composites, ageing of oils
• CPC Class Codes: G01N 2291/0289 Internal structure, e.g. defects, grain size, texture
• CPC Class Codes: G01N 2291/0425 Parallel to the surface, e.g. creep waves
• CPC Class Codes: G01N 2291/0427 Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 2291/106 one or more transducer arrays
• CPC Class Codes: G01N 2291/2694 Wings or other aircraft parts
• CPC Class Codes: G01N 29/041 on the surface of the material, e.g. using Lamb, Rayleigh or shear waves
• CPC Class Codes: G01N 29/069 Defect imaging, localisation and sizing using, e.g. time of flight diffraction [TOFD], synthetic aperture focusing technique [SAFT], Amplituden-Laufzeit-Ortskurven [ALOK] technique
• CPC Class Codes: G01N 29/2475 Embedded probes, i.e. probes incorporated in objects to be inspected
• CPC Class Codes: G01N 29/262 by electronic orientation or focusing, e.g. with phased arrays phased arrays per se G10K11/34

Abstract

A method and device for performing ultrasonic damage detection in a thin-wall structure using an array of embedded Piezoelectric Wafer Active Sensors (PWAS) for the transmission and reception of guided waves and a signal processing methodology based on the beamforming process. The beamforming signal processing has been adapted to the specifics of guided elastic waves traveling in thin-wall structures.

Claims

1. A system operative to detect a damage feature in a thin wall structure, said system comprising:

a plurality of piezoelectric sensors embedded on said structure in a predetermined pattern;

a generator operative to impress a pulse having a predetermined carrier frequency upon at least one of said sensors to produce guided ultrasonic waves that travel along said thin wall structure;

a signal processor operative to process received signals at said sensors resulting from an echo from said damage feature;

said processor implementing a synthetic beamforming methodology for determining an angular position of said damage feature spaced apart from said plurality of sensors along a plane of said thin wall structure; and

said processor further calculating a distance to said damage feature.

2. A system as set forth in claim 1, wherein said plurality of sensors are linearly arranged.

3. A system as set forth in claim 2, wherein said sensors are separated by a spacing equal to approximately one-half a signal wavelength at said predetermined carrier frequency.

4. A system as set forth in claim 3, wherein said predetermined carrier frequency is at least 100 KHz.

5. A system as set forth in claim 4, wherein said predetermined carrier frequency is at least approximately 300 kHz.

6. A system as set forth in claim 2, wherein said plurality of sensors includes at least three sensors.

7. A system as set forth in claim 6, wherein said plurality of sensors includes no more than twenty-one sensors.

8. A system as set forth in claim 2, wherein said generator impresses said pulse on only one of said sensors per reading.

9. A system as set forth in claim 8, wherein said generator is operative to impress successive signals on respective sensors in round-robin fashion.

10. A system as set forth in claim 9, wherein a set of received signals for all sensors acting as a receiver for each of said sensors acting as a transmitter in round-robin fashion are collected so as to produce an enhanced signal.

11. A system as set forth in claim 10, wherein said angular position of said damage feature is determined via an energy calculation assuming a plurality of angles throughout a selected angular range.

12. A system as set forth in claim 1, wherein a set of received signals for all sensors acting as a receiver for each of said sensors acting as a transmitter in round-robin fashion are collected so as to determine said angular position of said damage feature.

13. A system as set forth in claim 1, wherein said processor is operative to time shift and superimpose signals received at respective sensors to create an enhanced signal.

14. A system as set forth in claim 1, wherein said sensors respectively comprise piezoelectric wafer active sensors.

15. A system as set forth in claim 14, wherein said sensors are adhered to a surface of said thin wall structure.

26. A system as set forth in claim 10, wherein said enhanced signal is produced in subsequent processing based on a set of primitive signals received at each of said sensors.

27. A system as set forth in claim 10, wherein said synthetic beamforming methodology operates by applying time delays corresponding to selected angles to a set of primitive signals received at each of said sensors.

16. A system operative to detect a damage feature in a thin wall structure, said system comprising:

a plurality of piezoelectric sensors embedded on said structure in a linear pattern;

a generator operative to impress a pulse having a predetermined carrier frequency upon said sensors so as to produce guided ultrasonic waves that travel along said thin wall structure at a predetermined azimuth;

a signal processor operative to process received signals at said sensors resulting from an echo from said damage feature, said damage feature being spaced apart from said sensors along a plane of said thin wall structure; and

said processor calculating a distance to said damage feature.

17. A system as set forth in claim 16, wherein said generator is operative to impress said pulse on respective of said sensors with a predetermined time delay so as to produce constructive interference at said predetermined azimuth.

18. A system as set forth in claim 17, wherein said sensors are separated by a spacing equal to approximately one-half a signal wavelength at said predetermined carrier frequency.

19. A system as set forth in claim 18, wherein said predetermined carrier frequency is at least 100 KHz.

20. A system as set forth in claim 19, wherein said predetermined carrier frequency of approximately 300 kHz.

21. A system as set forth in claim 16, wherein said plurality of sensors includes at least three sensors.

22. A system as set forth in claim 16, wherein said plurality of sensors includes no more than twenty-one sensors.

23. A system as set forth in claim 16, wherein said sensors respectively comprise piezoelectric wafer active sensors.

24. A system as set forth in claim 23, wherein said sensors are permanently adhered to a surface of said thin wall structure.

25. A system as set forth in claim 16, wherein said generator is operative to sweep said azimuth over a predetermined angular range.