Cryogenic non destructive testing (NDT) and material treatment
First Claim
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;
heating the manufactured item to a second temperature subsequent to the cryogenic cooling;
determining a second metric representing the at least one characteristic of the manufacture item at a second temperature subsequent to the cryogenic cooling;
comparing the first metric with the second metric; and
,detecting the defect based upon the comparison;
wherein the first temperature is greater or equal to 32 degrees F.;
wherein the step of heating the manufactured item to the 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;
wherein the predetermined high temperature is greater or equal to 150 degrees Fahrenheit and the cryogenic temperature is −
70 F or colder.
1 Assignment
0 Petitions
Accused Products
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.
27 Citations
42 Claims
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1. A method for detecting a defect in a manufactured item, comprising:
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determining a first metric representing at least one characteristic of the manufactured item at first temperature; cooling the manufactured item to a cryogenic temperature; heating the manufactured item to a second temperature subsequent to the cryogenic cooling; determining a second metric representing the at least one characteristic of the manufacture item at a second temperature subsequent to the cryogenic cooling; comparing the first metric with the second metric; and
,detecting the defect based upon the comparison; wherein the first temperature is greater or equal to 32 degrees F.; wherein the step of heating the manufactured item to the 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; wherein the predetermined high temperature is greater or equal to 150 degrees Fahrenheit and the cryogenic temperature is −
70 F or colder. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A non-destructive method for detecting a defect in a manufactured item comprising:
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determining a first metric representing at least one characteristic of the manufactured item at first temperature; cooling the manufactured item to a cryogenic temperature; heating the manufactured item to a second temperature subsequent to the cryogenic cooling; 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 non-destructively the defect based upon the comparison;
, 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;wherein the step of heating the manufactured item to the 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; wherein the predetermined high temperature is greater or equal to 150 degrees Fahrenheit and the cryogenic temperature is −
70 F or colder.
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24. A method for detecting unconverted austenite in steel:
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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; heating the specimen to a second temperature subsequent to the cryogenic cooling; 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; wherein the step of heating the specimen to the second temperature includes heating the specimen to a predetermined high temperature above second temperature and allowing the manufacture item to cool to second temperature; wherein the predetermined high temperature is greater or equal to 150 degrees Fahrenheit and the cryogenic temperature is −
70 F or colder. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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35. A method for correcting defects in a milled item;
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milling an 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; 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; wherein the predetermined high temperature is greater or equal to 150 degrees Fahrenheit and the cryogenic temperature is −
70 F or colder. - View Dependent Claims (36, 37, 38, 39, 40, 41, 42)
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Specification