CRYOGENIC TRANSITION DETECTION

• US 20120033707A1
• 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 8,894,279 B2
• Time in Patent Office: Days
• US Class Current: 374/102
• 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 of detecting the transformation of retained austenite into martensite in a manufactured product comprising:

incrementally reducing the temperature of the product to near cryogenic temperatures according to a predetermined temperature curve and measuring a characteristic of the product during each increment;

recording the characteristic measurements as a function of temperature;

determining the transition based upon successive characteristic measurements.

2. The method of claim 1, further comprising determining the reliability of the product as a function of the transition.

3. The method of claim 1, wherein the characteristic is an ultrasonic acoustic emission.

4. The method of claim 1, further comprising exciting the manufactured product with an ultrasonic wave and the characteristic is the reflected ultrasonic wave.

5. The method of claim 1, wherein the measurement is from a EMAT.

6. The method of claim 1, wherein the measurement is from a Piezoelectric transducer.

7. The method of claim 1 wherein the near cryogenic temperature is less than −

70°

F.

8. The method of claim 1 wherein the temperature curve includes a heating cycle, wherein said heating cycle incrementally increases the temperature of the product to greater than +220°

F.

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

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

cooling the manufactured item to near cryogenic temperatures according to a initial temperature time cycle;

during the cooling, monitoring the manufactured item for emissions resultant from phase transition;

recording the emissions, as a function of temperature or time;

adjusting the initial temperature time cycle as a function of the emissions to form an adjusted temperature time cycle;

controlling the temperature of the manufacture item as a function of the adjusted temperature time cycle;

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

comparing the first metric with the second metric; and

,

detecting the defect based upon the comparison.

10. The method of claim 9, wherein the near Cryogenic temperature is lass than −

70°

F.

11. The method of claim 9, wherein the step of cooling the manufactured item to near cryogenic temperatures further comprises cooling the manufactured item to a cryogenic temperature less than −

280°

F.

12. A method of detecting a material transformation comprising:

incrementally reducing the temperature of the product to near cryogenic temperatures according to a predetermined temperature curve and measuring a characteristic of the product during each increment;

recording the characteristic measurements as a function of temperature;

filtering successive characteristic measurements

determining the material transformation based upon the filter successive characteristic measurements.

13. The method of claim 12, further comprising determining the reliability of the product as a function of the material transformation.

14. The method of claim 12, wherein the characteristic is an ultrasonic acoustic emission.

15. The method of claim 12, further comprising exciting the manufactured product with an ultrasonic wave and the characteristic is the reflected ultrasonic wave.

16. The method of claim 12, wherein the measurement is from a EMAT.

17. The method of claim 12, wherein the measurement is from a Piezoelectric transducer.

18. The method of claim 12 wherein the near cryogenic temperature is less than −

70°

F.

19. The method of claim 12 wherein the temperature curve includes a heating cycle, wherein said heating cycle incrementally increases the temperature of the product to greater than +220°

F.

20. The method of claim 12, wherein the material transformation if a phase transition.