Miniaturized contactless sonic IR device for remote non-destructive inspection

• US 6,399,948 B1
• Filed: 09/15/2000
• Issued: 06/04/2002
• Est. Priority Date: 09/16/1999
• Status: Expired due to Term

• Current Assignee: Siemens Westinghouse Power Corporation, Wayne State University
• Original Assignee: Wayne State University
• Inventors: Sun, Gang, Ouyang, Zhong, Zombo, Paul John, Sui, Hua, Shannon, Robert Edward, Han, Xiaoyan, Thomas, Robert L., Favro, Lawrence D.
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Gabor, Otilia
• Application Number:
  US09/663,295
• Time in Patent Office: 627 Days
• Field of Search: 250/341.6, 250/334, 250/338.1, 250/338.3
• US Class Current: 250/341.6
• CPC Class Codes: G01N 2291/02881 Temperature
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 2291/0423 Surface waves, e.g. Rayleigh waves, Love waves
• CPC Class Codes: G01N 2291/0427 Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever
• CPC Class Codes: G01N 2291/101 one transducer
• CPC Class Codes: G01N 25/72 Investigating presence of flaws
• CPC Class Codes: G01N 29/2412 using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]; investigating the presence of flaws using eddy currents G01N27/90, magnetostrictive transducers B06B1/08, measuring magnetostrictive properties G01R33/18
• CPC Class Codes: G01N 29/28 providing acoustic coupling , e.g. water impedance matching G10K11/02
• CPC Class Codes: G01N 29/346 with amplitude characteristics, e.g. modulated signal
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00
• CPC Class Codes: G01N 29/449 Statistical methods not provided for in G01N29/4409, e.g. averaging, smoothing and interpolation
• CPC Class Codes: G01N 29/46 by spectral analysis, e.g. Fourier analysis or wavelet analysis spectral signal processing per se G06F17/14

Abstract

A thermal imaging system for detecting cracks and defects in a component. An electromagnetic acoustic transducer (EMAT) is coupled to the component, and introduces pulsed sound signals therein. The sound signals cause the defects to heat up. The IR radiation from the heated pulses is detected by a thermal camera. The amplitude of the pulsed signals are substantially constant, and the frequency of the pulsed signal can be changed within each pulse. A control unit is employed to provide timing and control for the operation of the EMAT and the camera.

Claims

1. A thermal imaging system for detecting defects in a component, said system comprising:

at least one electromagnetic acoustic transducer (EMAT) for exciting the component;

a thermal imaging camera for generating thermal images of the component; and

a controller coupled to the EMAT and the camera, said controller directing at least one time varying signal pulse at a predetermined frequency and for a predetermined duration to the EMAT and causing the camera to generate sequential images of the component, said EMAT inducing sound waves in the component, said signal pulse having a substantially constant amplitude, wherein vibrational energy generated by the EMAT causes the defects in the component to heat up and be visible in the images generated by the camera.

2. The system according to claim 1 wherein the controller operates to change the frequency of the signal pulse applied to the EMAT.

3. The system according to claim 2 wherein the controller provides a change in frequency of the signal pulse as a step frequency change or a sweep frequency change.

4. The system according to claim 1 wherein the controller provides the time varying signal pulse as a square wave signal or a spiked pulse signal.

5. The system according to claim 1 wherein the at least one EMAT is a plurality of EMATs.

6. The system according to claim 5 wherein the controller provides the time varying signal pulse to each EMAT in a sequential manner.

7. The system according to claim 1 wherein the signal pulse has a duration of one-half of a second or less.

8. A defect detection system for detecting defects in a structure, said system comprising:

at least one EMAT for generating a sound signal in the structure for a predetermined period of time, said sound signal having a predetermined frequency and a substantially constant amplitude;

a camera directed towards the structure and generating images of the structure when the EMAT generates the sound signal; and

a controller coupled to the EMAT and the camera for providing timing signals therebetween, said controller providing at least one time varying signal pulse to energize the EMAT and being responsive to the images from the camera.

9. The system according to claim 8 wherein the controller operates to change the frequency of the signal pulse applied to the EMAT.

10. The system according to claim 9 wherein the controller provides a change in frequency of the signal pulse as a step frequency change or a sweep frequency change.

11. The system according to claim 8 wherein the controller provides the time varying signal pulse as a square wave signal or a spiked pulse signal.

12. The system according to claim 8 wherein the at least one EMAT is a plurality of EMATs.

13. The system according to claim 12 wherein the controller provides the time varying signal pulse to each EMAT in a sequential manner.

14. A method of detecting defects in a structure, said method comprising the steps of:

coupling at least one electromagnetic acoustic transducer (EMAT) to the structure;

energizing the EMAT with a series of time varying signal pulses, where each pulse has a predetermined frequency and a substantially constant amplitude;

generating sound signals in the structure from energizing the EMAT; and

generating a sequence of thermal images of the structure prior to, during and after the generation of the sound signals.

15. The method according to claim 14 wherein the step of energizing the EMAT includes energizing the EMAT with different signal pulse frequencies to generate different frequency sound signals.

16. The method according to claim 15 wherein the step of energizing the EMAT includes energizing the EMAT with a step frequency signal or a sweep frequency signal.

17. The method according to claim 14 wherein the step of energizing the EMAT includes energizing the EMAT with a square wave pulse or a spiked pulse.

18. The method according to claim 14 wherein the step of coupling at least one EMAT includes coupling a plurality of EMATs to the structure.

19. The method according to claim 18 wherein the step of energizing the EMATs includes energizing the EMATs with time varying signal pulses in a sequential manner.

20. The method according to claim 14 wherein the step of coupling the EMAT to the structure includes coupling the EMAT to the structure where the EMAT does not contact the structure.