CRYOGENIC NON DESTRUCTIVE TESTING (NDT) AND MATERIAL TREATMENT

• US 20120034044A1
• Filed: 04/27/2011
• Published: 02/09/2012
• Est. Priority Date: 08/06/2010
• Status: Active Grant

• Current Assignee: Victor Intellectual Property Incorporated
• Original Assignee: Victor Sloan
• Inventors: Sloan, Victor
• Granted Patent: US 8,920,023 B2
• Time in Patent Office: Days
• US Class Current: 409/131
• CPC Class Codes: G01N 2291/0251 Solidification, icing, curing composites, polymerisation
• CPC Class Codes: G01N 2291/0289 Internal structure, e.g. defects, grain size, texture
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 25/04 of melting point; of freezing point; of softening point
• CPC Class Codes: G01N 29/11 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/14 using acoustic emission techniques echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00
• CPC Class Codes: G01N 29/30 Arrangements for calibrating or comparing, e.g. with standard objects
• CPC Class Codes: G01N 29/4436 with a reference signal amplitude comparison G01N29/48
• CPC Class Codes: G01N 29/46 by spectral analysis, e.g. Fourier analysis or wavelet analysis spectral signal processing per se G06F17/14
• CPC Class Codes: Y10T 409/303752 Process

Abstract

A non-destructive test using cryogenic temperatures is capable of detecting defects in materials that result from residual stress from manufacturing and from retained austenite. The subject materials or parts that are subjected to cryogenic temperatures approaching and below˜−300° F., −184° C., 89° K, thereby causing permanent deformations or characteristic changes in the material if excessive residual stress, retained austenite or discontinuities exist. To determine the extent of changes, a first metric of the subject material is determined, the material is then subjected to cryogenic cooling thereby triggering any deformation or characteristic changes. Subsequent to the cryogenic cooling, the subject material may be returned to a second temperature whereby a second metric representing based on the same characteristic of the subject material is determined The comparison of the first and second metrics reveals the deformation or change resultant from the defect. In addition characteristic changes in the subject material during cryogenic cooling may be use to detect the phase transition of the retained austenite to martensite.

Claims

1. A method for detecting a defect in a manufactured item comprising:

determining a first metric representing at least one characteristic of the manufactured item at first temperature;

cooling the manufactured item to a cryogenic temperature;

determining a second metric representing the at least one characteristic of the manufacture item at a second temperature subsequent to the cryogenic cooling the at least one characteristic;

comparing the first metric with the second metric; and

,

detecting the defect based upon the comparison.

2. The method of claim 1, further comprising heating the manufactured item to the second temperature subsequent to the cryogenic cooling.

3. The method of claim 1, wherein the at least one characteristic is a characteristic of the manufactured item'"'"'s dynamic response to an excitement.

4. The method of claim 3, wherein the at least one characteristic is mechanical resonances.

5. The method of claim 1, wherein the at least one characteristic is a static characteristic of the manufactured item.

6. The method of claim 1, wherein the characteristic is an electromagnetic field pattern.

7. The method of claim 5, wherein the at least one characteristic is obtained via one of the group consisting of Coordinate Measuring Machine (CMM), Optical Comparator, CAD System, Spring Tension and Compression Testers, Micrometers, Digital Indicators, Height &

Depth Gauges, Surface &

Contour Measuring Devices, Grade A Surface Plate/Plane Part Trueness, Run-Out Measurements, RA Surface Roughness and NDT Hardness Testers.

8. The method of claim 5, wherein the first and second metrics represent characteristics selected from the group consisting of cross section area, length, width, depth, height, tolerance, nth moment of area, and center of gravity.

9. The method of claim 1, wherein determining the first and second metrics comprises modal analysis, X-Ray diffraction, Magnetoelastic Barkhausen Noise measurement, Magnaflux Quasar process Compensated resonant Inspection.

10. The method of claim 1, wherein the cryogenic temperature is less than or equal to −

70 Fahrenheit.

11. The method of claim 10, wherein the cryogenic temperature is less than or equal −

280 degrees Fahrenheit.

12. The method of claim 1, wherein the cooling is according to a predetermined time-temperature curve.

13. The method of claim 12, wherein the predetermined time-temperature curve comprises a plurality of cooling and heating cycles.

14. The method of claim 2, wherein the heating is according to a predetermined time-temperature curve.

15. The method of claim 2, wherein the step of heating the manufactured item to a second temperature includes heating the manufactured item to a predetermined high temperature above second temperature and allowing the manufacture item to cool to second temperature.

16. The method of claim 15, wherein the predetermined high temperature is greater or equal to 150 degrees Fahrenheit.

17. The method of claim 15, wherein the predetermined high temperature is greater or equal to 280 degrees Fahrenheit.

18. The method of claim 1, wherein the steps of determining a first metric and second metric each comprise:

exciting the manufactured item, and measuring the resonance response.

19. The method of claim 18, wherein the measuring the resonance response comprises summing sinusoidal deformations.

20. The method of claim 1, wherein the first and second temperatures are room temperature.

21. The method of claim 1, wherein the first and second temperatures are approximately equal.

22. The method of claim 1, wherein the first and second temperatures are greater than 32 degrees Fahrenheit.

23. The method of claim 1, wherein the second temperature is a cryogenic temperature.

24. The method of claim 1, wherein the cryogenic temperature is determined as a function of detected acoustic emission.

25. The method of claim 1, wherein the determining the reliability of the item is based on the comparison.

26. The method of claim 24, further comprising fluctuating the temperature above and below the cryogenic temperature until the acoustic emissions are reduced.

27. A method for detecting unconverted austenite in steel obtaining a specimen of heat treated steel;

determining a first metric representing at least one characteristics of the specimen at a first temperature;

cooling the specimen to a cryogenic temperature;

determining a second metric representing the at least one characteristic of the specimen at a second temperature subsequent to the cryogenic cooling;

comparing the first metric with the second metric; and

, detecting the unconverted austenite based upon the comparison.

28. The method of claim 27, further comprising heating the specimen to the second temperature subsequent to the cryogenic cooling.

29. The method of claim 27, wherein the first and second metrics represent characteristics selected from the group consisting of cross section area, length, width, depth, height, tolerance, nth moment of area, resonance, nth moment of inertia, center of gravity.

30. The method of claim 27, wherein the cryogenic temperature is less than or equal to −

280 Fahrenheit.

31. The method of claim 28, wherein the heating is according to a predetermined time-temperature curve.

32. The method of claim 28, wherein the step of heating the specimen to a second temperature includes heating the specimen to a predetermined high temperature above second temperature and allowing the manufacture item to cool to second temperature.

33. The method of claim 32, wherein the predetermined high temperature is greater or equal to 280 degrees Fahrenheit.

34. The method of claim 27, wherein the first and second temperatures are room temperature.

35. The method of claim 27, wherein the first and second temperatures are approximately equal.

36. The method of claim 27, wherein the first and second temperatures are greater than 32 degrees Fahrenheit.

37. The method of claim 27, wherein the cryogenic temperature is a function of acoustic emissions from the specimen.

38. The method of claim 27, wherein the second temperature is a cryogenic temperature.

47. The method of claim 37, wherein the first and second temperatures are greater than 32 degrees Fahrenheit.

39. A method for correcting defects in a milled item;

milling a item to predetermined specifications;

deforming the milled item by cooling the milled item to a predetermined cryogenic temperature and heating the milled item to a first temperature;

detecting the deformation; and

,

re-milling the milled item in response to the deformation.

40. The method of claim 39, wherein the first temperature is room temperature.

41. The method of claim 39, wherein the deformation is a geometric change in dimension of the milled item.

42. The method of claim 39, wherein the cryogenic temperature is less than or equal to −

280 degrees Fahrenheit.

43. The method of claim 39, wherein the heating is according to a predetermined time-temperature curve.

44. The method of claim 39, wherein the step of heating the milled item to a first temperature includes heating the milled item to a predetermined high temperature above the first temperature and allowing the manufacture item to cool to second temperature.

45. The method of claim 44, wherein the predetermined high temperature is greater or equal to 280 degrees Fahrenheit.

46. The method of claim 39, wherein the first temperature is room temperature.

48. The method of claim 39, wherein the cooling of the milled item to a cryogenic temperature is a function of detected austenite transition.