Thermal imaging system for detecting defects

• US 6,759,659 B2
• Filed: 06/03/2003
• Issued: 07/06/2004
• Est. Priority Date: 09/16/1999
• Status: Expired due to Term

• Current Assignee: Wayne State University
• Original Assignee: Wayne State University
• Inventors: Sun, Gang, Han, Xiaoyan, Ouyang, Zhong, Thomas, Robert L., Favro, Lawrence D., Sui, Hua
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Gabor, Otilia
• Application Number:
  US10/453,081
• Publication Number:
  US 20030205671A1
• Time in Patent Office: 399 Days
• Field of Search: 250/341.6, 250/334, 250/332, 250/330, 250/347, 250/341, 250/338.1, 250/338.3, 356/381, 356/237, 356/502, 356/498, 356/482, 356/432, 374/4, 374/5, 374/124, 374/126, 374/128, 374/137, 348/571, 736/20
• US Class Current: 250/341.6
• CPC Class Codes: G01N 2291/02483 Other human or animal parts, e.g. bones
• CPC Class Codes: G01N 2291/02881 Temperature
• CPC Class Codes: G01N 2291/0289 Internal structure, e.g. defects, grain size, texture
• CPC Class Codes: G01N 2291/101 one transducer
• CPC Class Codes: G01N 2291/2638 Complex surfaces
• CPC Class Codes: G01N 2291/2694 Wings or other aircraft parts
• CPC Class Codes: G01N 25/72 Investigating presence of flaws
• CPC Class Codes: G01N 29/223 Supports, positioning or alignment in fixed situation mounting transducers per se G10K11/004
• CPC Class Codes: G01N 29/228 related to high temperature conditions
• 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 29/2437 Piezoelectric probes
• CPC Class Codes: G01N 29/2462 Probes with waveguides, e.g. SAW devices
• 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 structure. An ultrasonic transducer is coupled to the structure through a malleable coupler. Ultrasonic energy from the transducer causes the defects to heat up, which is detected by a thermal camera. A control unit is employed to provide timing and control for the operation of the ultrasonic transducer and the camera.

Claims

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

a sound source;

a thermal imaging camera directed towards the structure and generating thermal images of the structure; and

a controller electrically coupled to the sound source and the camera, said controller causing the sound source to transmit a series of sound pulses into the structure separated by a predetermined time period at a predetermined frequency, said controller causing the camera to generate sequential images of the structure, wherein vibrational energy from the pulses cause the defects in the structure to heat up and be visible in the images generated by the camera, and wherein the controller averages the images within a predetermined window in each pulse, where the window is provided at a same delay time in each pulse from when the pulse is initiated.

2. The system according to claim 1 further comprising a coupler positioned between and in contact with the structure and the sound source.

3. The system according to claim 2 wherein the coupler is malleable and is softer than an end of the sound source in contact with the coupler.

4. The system according to claim 2 wherein the coupler is a thin piece of metal.

5. The system according to claim 1 wherein the sound source is a hand-held sound source gun, said gun including a housing, at least one handle coupled to the housing, at least one sound transducer coupled to the housing, and a stabilizing structure coupled to the housing, said stabilizing structure including two elongated members, wherein the combination of the at least one transducer and the two separate elongated members provide three separate stabilizing points operable to be positioned against the structure to define a plane thereon.

6. The system according to claim 1 wherein the sound source emits a series of ultrasonic pulses.

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

a sound source for directing at least one pulse of a sound signal into the structure for a predetermined period of time;

a coupler positioned in contact with the structure and the sound source, said coupler being malleable and being softer than an end of the sound source in contact with the coupler;

a thermal camera directed towards the structure and generating thermal images of the structure when the sound source emits the sound signal; and

a controller coupled to the sound source and the camera to provide timing signals therebetween, said controller being responsive to the images from the camera.

8. The system according to claim 7 wherein the coupler is a thin piece of metal.

9. The system according to claim 7 wherein the sound source is a hand-held sound source gun, said gun including a housing, at least one handle coupled to the housing, at least one sound transducer coupled to the housing, and a stabilizing structure coupled to the housing, said stabilizing structure including two elongated members, wherein the combination of the at least one transducer and the two separate elongated members provide three separate stabilizing points operable to be positioned against the structure to define a plane thereon.

10. The system according to claim 9 wherein each of the two elongated members includes an adjusting device, said adjusting device being operable to adjust the length of the elongated member relative to the at least one transducer.

11. The system according to claim 7 wherein the sound source emits a series of ultrasonic pulses.

12. A method of detecting defects in a structure, said method comprising:

providing a sound source;

providing a coupler in contact with an end of the sound source and the structure, said coupler being malleable and being softer than the end of the sound source;

emitting at least one pulse of a sound signal from the sound source into the structure to heat the defects; and

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

13. The method according to claim 12 wherein providing a sound source includes providing a hand-held sound source gun including a housing, at least one handle coupled to the housing, at least one sound transducer coupled to the housing, and a stabilizing structure coupled to the housing, said stabilizing structure including two elongated members, wherein the combination of the at least one transducer and the two separate elongated members provide three separate stabilizing points operable to be positioned against the structure to define a plane thereon.

14. The method according to claim 13 wherein providing a sound source includes providing the hand-held sound source gun where the two elongated members include an adjusting device that adjusts the length of the elongated member relative to the at least one transducer.

15. The method according to claim 12 wherein providing a coupler includes providing a metal coupler.