CHARACTERIZATION OF FLAWS IN COMPOSITES IDENTIFIED BY THERMOGRAPHY

• US 20090245321A1
• Filed: 03/31/2008
• Published: 10/01/2009
• Est. Priority Date: 03/31/2008
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Bantel, Thomas Edward, Howard, Donald Robert, Ringermacher, Harry Israel, Knight, Bryon Edward, Patterson, William George
• Granted Patent: US 8,393,784 B2
• Time in Patent Office: Days
• US Class Current: 374/5
• CPC Class Codes: G01N 25/72 Investigating presence of flaws

Abstract

A method for identifying types of flaws in a composite object includes: a) rapidly heating the surface of the object; b) recording pixel intensities in a sequence of IR images; c) determining temperature-versus-time data for each of the pixels from the IR images; and d) determining what type of flaw if any corresponds to each of the pixels using the temperature-versus-time data determined in step (c). A contrast curve derived from the temperature-versus-time data may be used in determining what type of flaws if any corresponds to each of the pixels. The contrast curve may be determined by subtracting a synthetic reference curve from a temperature time curve from the temperature-versus-time data. The types of flaws may be determined from size and/or shapes of peaks in the contrast curves. Some flaws are delaminations, layers of porosity, and uniformly distributed porosity.

Claims

1. A method for identifying types of flaws in a composite object, the method comprising the steps of:

a) rapidly heating the surface of the object;

b) recording pixel intensities in a sequence of IR images, each image sequentially related to time elapsed since heating the surface in step (a);

c) determining temperature-versus-time data for each of the pixels from the IR images; and

d) determining what type of flaw if any corresponds to each of the pixels using the temperature-versus-time data determined in step (c).

2. A method as claimed in claim 1, further comprising step (d) including determining a contrast curve for each of the pixels from the temperature-versus-time data for each of the pixels and using the contrast curve in determining what type of flaws if any corresponds to each of the pixels.

3. A method as claimed in claim 2, further comprising the flaws including a delamination.

4. A method as claimed in claim 3, further comprising the delamination being characterized by large broad peaks in the contrast curve.

5. A method as claimed in claim 2, further comprising the flaws including a distinct layer of porosity.

6. A method as claimed in claim 3, further comprising the distinct layer of porosity being characterized by leading peaks followed by shallow troughs in the contrast curve.

7. A method as claimed in claim 2, further comprising the flaws including a distinct extended layers of porosity.

8. A method as claimed in claim 7, further comprising the distinct extended layers of porosity being characterized by leading peaks followed by plateaus in the contrast curves.

9. A method as claimed in claim 2, further comprising the flaws including uniformly distributed porosity.

10. A method as claimed in claim 9, further comprising the uniformly distributed porosity being characterized by a uniformly distributed porosity contrast curve substantially shifted from a no defect contrast curve and each of the uniformly distributed porosity contrast curve and the no defect contrast curve having an inflection.

11. A method as claimed in claim 2, further comprising determining the contrast curve by determining a synthetic reference curve from synthetic thermal reference temperature-versus-time data and subtracting the synthetic reference curve from a temperature time curve determined from the temperature-versus-time data from step (c).

12. A method as claimed in claim 11, further comprising the flaws including a delamination characterized by large broad peaks in the contrast curve.

13. A method as claimed in claim 11, further comprising the flaws including a distinct layer of porosity characterized by leading peaks followed by shallow troughs in the contrast curve.

14. A method as claimed in claim 11, further comprising the flaws including a distinct extended layers of porosity characterized by leading peaks followed by plateaus in the contrast curves.

15. A method as claimed in claim 11, further comprising the flaws including uniformly distributed porosity characterized by a uniformly distributed porosity contrast curve substantially shifted from a no defect contrast curve and each of the uniformly distributed porosity contrast curve and the no defect contrast curve having an inflection.

16. A method as claimed in claim 2, further comprising:

the flaws including delaminations characterized by the contrast curves having large broad peaks,

the flaws including distinct layers of porosity characterized by the contrast curves having leading peaks followed by shallow troughs in the contrast curves,

the flaws including distinct extended layers of porosity characterized by the contrast curves having leading peaks followed by plateaus in the contrast curves, and

the flaws including uniformly distributed porosity characterized by a uniformly distributed porosity contrast curve substantially shifted from a no defect contrast curve and each of the uniformly distributed porosity contrast curve and the no defect contrast curve having an inflection.

17. A method as claimed in claim 16, further comprising displaying areas of the object corresponding to the pixels characterized by the different types of flaws and no flaws.

18. A method as claimed in claim 17, further comprising displaying the areas of the object in different colors corresponding to the pixels characterized by the types of flaws and no flaws.

19. A method as claimed in claim 16, further comprising determining the contrast curve by determining a synthetic reference curve from synthetic thermal reference temperature-versus-time data and subtracting the synthetic reference curve from a temperature time curve determined from the temperature-versus-time data from step (c).

20. A method as claimed in claim 19, further comprising displaying areas of the object corresponding to the types of flaws and no flaws characterized by the contrast curves of the pixels.

21. A method as claimed in claim 20, further comprising displaying the areas of the object in different colors corresponding to the types of flaws and no flaws characterized by the contrast curves of the pixels.