Cryogenic transition detection
First Claim
1. A method of non-destructively detecting the transition of retained austenite into martensite in a manufactured product, comprising:
- incrementally reducing 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 non-destructively based upon successive characteristic measurements, wherein the temperature curve includes a heating cycle, wherein said heating cycle incrementally increases the temperature of the product to greater than +220°
F. and wherein the near cryogenic temperature is less than −
70°
F.
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.
24 Citations
13 Claims
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1. A method of non-destructively detecting the transition of retained austenite into martensite in a manufactured product, comprising:
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incrementally reducing 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 non-destructively based upon successive characteristic measurements, wherein the temperature curve includes a heating cycle, wherein said heating cycle incrementally increases the temperature of the product to greater than +220°
F. and wherein the near cryogenic temperature is less than −
70°
F. - View Dependent Claims (2, 3, 4, 5, 6)
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7. 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 near cryogenic temperatures according to an initial temperature time cycle;
wherein the near Cryogenic temperature is less than −
70°
F.;during the cooling, monitoring the manufactured item for emissions resultant from a material 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;
wherein the adjusted temperature time cycle includes a heating cycle, wherein said heating cycle incrementally increases the temperature to greater than +220°
F.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. - View Dependent Claims (8, 9)
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10. A method of detecting a material transformation comprising:
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incrementally reducing 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; and
,determining the material transformation based upon the filtered successive characteristic measurements; wherein the characteristic is an ultrasonic acoustic emission; wherein the temperature curve includes a heating cycle, wherein said heating cycle incrementally increases the temperature of the product to greater than +220°
F. and a cooling cycle to the near cryogenic temperature of less than −
70°
F.; andthe material transformation is an austenite to martensite phase transition. - View Dependent Claims (11, 12, 13)
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Specification