US4752140A
Expired / Lapsed
US
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Pulsed dilatometric method and device for the detection of delaminations
Assignee: National Research Council Canada
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Filing: 1986-10-01
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Granted: 1988-06-21
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Expires: 2006-10-01
Abstract
Abstract A method for the detection of delaminated areas in coated materials or layered composites, which allows free-air operation and can be used to scan portions of bulky materials on the spot. This method which makes it possible to detect very small delaminated areas in a very short time (less than 1 millisecond), with a very high sensitivity and without creation of excessive thermal stress in the inspected material, basically comprises the steps of: focusing pulsed, thermal radiations onto the structure to be inspected to produce a vertical displacement of its coating by thermal expansion if a delaminated area is present at the coating-to-substrate interface, and detecting and measuring this vertical displacement if any, by interferometry, preferably laser-beam interferometry. An apparatus for carrying out this method is also disclosed.
Inventors
- 👤 Paolo Cielo
- 👤 Gerard Rousset
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 23:23
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/84; G01N21/8422; G01N25/00; G01N25/72
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
252 words
In a method for detecting delaminated areas by thermal dilatometry in a layered structure comprising a substrate covered by a coating, said method being of the type comprising the steps of: subjecting each surface area of the structure to thermal radiation to produce a vertical displacement of its coating by thermal expansion wherever a delaminated area is present at the coating-to-substrate interface, and detecting and measuring this vertical displacement, if any, the improvements wherein: the thermal radiation to which the structure is subjected, consists of a short pulse which has duration ranging from 0.001 to 1 millisecond and is smaller than the mechanical response time of the delaminated area; said thermal radiation is focused onto the surface of said structure to irradiate a surface area which is smaller than the smallest delaminated area which is to be detected; and the vertical displacement of the coating is detected and measured by interferometry, said interferometric detection and measurement of the vertical displacement being carried out by measuring the vertical displacement of the structure surface before and immediately after the application of the thermal radiation pulse, said measurement giving a first signal indicative of the thermal expansion of the structure due to the amount of power absorbed by said structure, then measuring the vertical displacement during the inertial response of the structure after termination of the thermal radiation pulse, said other measurement giving another signal proportional to the vertical displacement of the coating; and using the first measured signal to normalize the second measured signal.
Claim 2
Dependent Claim
252 words
In a method for detecting delaminated areas by thermal dilatometry in a layered structure comprising a substrate covered by a coating, said method being of the type comprising the steps of: subjecting each surface area of the structure to thermal radiation to produce a vertical displacement of its coating by thermal expansion wherever a delaminated area is present at the coating-to-substrate interface, and detecting and measuring this vertical displacement, if any, the improvements wherein: the thermal radiation to which the structure is subjected, consists of a short pulse which has duration ranging from 0.001 to 1 millisecond and is smaller than the mechanical response time of the delaminated area; said thermal radiation is focused onto the surface of said structure to irradiate a surface area which is smaller than the smallest delaminated area which is to be detected; and the vertical displacement of the coating is detected and measured by interferometry, said interferometric detection and measurement of the vertical displacement being carried out by measuring the vertical displacement of the structure surface before and immediately after the application of the thermal radiation pulse, said measurement giving a first signal indicative of the thermal expansion of the structure due to the amount of power absorbed by said structure, then measuring the vertical displacement during the inertial response of the structure after termination of the thermal radiation pulse, said other measurement giving another signal proportional to the vertical displacement of the coating; and using the first measured signal to normalize the second measured signal.
Claim 3
Dependent Claim
19 words
The improved method of claim 1, wherein the interferometric detection and measurement is carried out with a laser-beam interferometer.
Claim 4
Dependent Claim
17 words
The improved method of claim 2, wherein the pulsed, thermal radiations are generated by a laser beam.
Claim 5
Dependent Claim
28 words
The improved method of claim 2, wherein the laser-beam interferometer used for the detection and measurement of the vertical displacement of the coating is of the Michelson type.
Claim 6
Dependent Claim
27 words
The improved method of claim 2, wherein the laser-beam interferometer used for the detection and measurement of the vertical displacement of the coating is a laser-heterodyne interferometer.
Claim 7
Dependent Claim
32 words
The improved method of claim 5, comprising the steps of focusing the laser beam of the laser-heterodyne interferometer and using said focused laser beam as pulsed thermal radiations for heating the material.
Claim 8
Dependent Claim
245 words
In a device for detecting delaminated areas by thermal dilatometry in a layered structure comprising a substrate covered with a coating, said device comprising: means for producing thermal radiations; means for subjecting each surface area of the structure to said thermal radiations to produce a vertical displacement of its coating by thermal expansion wherever a delaminated area is present at the coating to-material interface; and means for detecting and measuring said vertical displacement, if any, the improvements wherein: said means for producing thermal radiations comprises means for generating short pulses with a pulse duration that is ranging from 0.001 to 1 millisecond and is smaller than the mechanical response time of the delaminated area; said means for subjecting the material to said radiations comprises means for focusing said radiations onto said structure to irradiate a surface area of said structure which is smaller than the smallest delaminated area which is to be detected; and said means for detecting and measuring said vertical displacement comprises an interferometer positioned to interferometrically compare the positions of the surface of the structure before and after each pulse in order to obtain a first signal indicative of the thermal expansion of the structure due to the amount of power absorbed by the structure, and a second signal indicative of the vertical displacement of the coating due to the inertial response of the structure after termination of the thermal radiation pulse, said first signal being used for normalizing the second signal.
Claim 9
Dependent Claim
245 words
In a device for detecting delaminated areas by thermal dilatometry in a layered structure comprising a substrate covered with a coating, said device comprising: means for producing thermal radiations; means for subjecting each surface area of the structure to said thermal radiations to produce a vertical displacement of its coating by thermal expansion wherever a delaminated area is present at the coating to-material interface; and means for detecting and measuring said vertical displacement, if any, the improvements wherein: said means for producing thermal radiations comprises means for generating short pulses with a pulse duration that is ranging from 0.001 to 1 millisecond and is smaller than the mechanical response time of the delaminated area; said means for subjecting the material to said radiations comprises means for focusing said radiations onto said structure to irradiate a surface area of said structure which is smaller than the smallest delaminated area which is to be detected; and said means for detecting and measuring said vertical displacement comprises an interferometer positioned to interferometrically compare the positions of the surface of the structure before and after each pulse in order to obtain a first signal indicative of the thermal expansion of the structure due to the amount of power absorbed by the structure, and a second signal indicative of the vertical displacement of the coating due to the inertial response of the structure after termination of the thermal radiation pulse, said first signal being used for normalizing the second signal.
Claim 10
Dependent Claim
13 words
The improved device of claim 8, wherein said interferometer is a laser-beam interferometer.
Claim 11
Dependent Claim
16 words
The improved device of claim 8, wherein said thermal radiation producing means is a laser beam.
Claim 12
Dependent Claim
27 words
The improved device of claim 9, wherein the laser-beam interferometer used for the detection and measurement of the vertical displacement of the coating is a laser-heterodyne interferometer.
Claim 13
Dependent Claim
20 words
The improved device of claim 10, wherein said thermal radiation producing means is the laser beam of the laser-heterodyne interferometer.
Claim 14
Dependent Claim
28 words
The improved device of claim 8, wherein the laser-beam interferometer used for the detection and measurement of the vertical displacement of the coating is of the Michelson type.
Claim 15
Independent Claim
260 words
A method for detecting delaminated areas in a layered structure comprising a substrate and at least one covering layer, and having a predetermined inertial response time, said predetermined inertial response time being the inertial response time of the smallest delaminated area to be detected in the layered structure, said method including: subjecting each surface area of the structure to be tested to thermal radiation consisting of a short pulse having a pulse duration smaller than the predetermined inertial response time of the layered structure and in the range of 0.001 to 1 millisecond, and wherein the thermal radiation is focused onto the surface of said structure to irradiate a surface area which is smaller than the delaminated areas to be detected; and detecting vertical displacements of the structure surface by interferometry to indicate delaminations by; measuring a first vertical displacement of the structure surface during the application of the thermal radiation pulse as a measure of the thermal expansion of the structure due to the energy absorbed by the structure, measuring a second vertical displacement of the structure surface during the mechanical response time of the structure following the termination of the thermal radiation pulse as a measure of the thermal deformation in the structure, and using the first measured vertical displacement to normalize the second measured vertical displacement to provide an indication of a delamination, wherein the first vertical displacement measurement is obtained by determining the difference between an interferometric reading taken before the radiation pulse and an interferometric reading taken immediately after the termination of the radiation pulse.
Claim 16
Independent Claim
260 words
A method for detecting delaminated areas in a layered structure comprising a substrate and at least one covering layer, and having a predetermined inertial response time, said predetermined inertial response time being the inertial response time of the smallest delaminated area to be detected in the layered structure, said method including: subjecting each surface area of the structure to be tested to thermal radiation consisting of a short pulse having a pulse duration smaller than the predetermined inertial response time of the layered structure and in the range of 0.001 to 1 millisecond, and wherein the thermal radiation is focused onto the surface of said structure to irradiate a surface area which is smaller than the delaminated areas to be detected; and detecting vertical displacements of the structure surface by interferometry to indicate delaminations by; measuring a first vertical displacement of the structure surface during the application of the thermal radiation pulse as a measure of the thermal expansion of the structure due to the energy absorbed by the structure, measuring a second vertical displacement of the structure surface during the mechanical response time of the structure following the termination of the thermal radiation pulse as a measure of the thermal deformation in the structure, and using the first measured vertical displacement to normalize the second measured vertical displacement to provide an indication of a delamination, wherein the first vertical displacement measurement is obtained by determining the difference between an interferometric reading taken before the radiation pulse and an interferometric reading taken immediately after the termination of the radiation pulse.
Claim 17
Dependent Claim
52 words
The method of claim 13, wherein the second vertical displacement measurement is obtained by determining the difference between an interferometric reading taken before the radiation pulse and an interferometric reading taken a predetermined period of time after the termination of the radiation pulse equivalent to the mechanical response time of the structure.
Claim 18
Dependent Claim
54 words
The method of claim 13, wherein the second vertical displacement measurement is obtained by determining the difference between an interferometric reading taken immediately after the applied radiation pulse and an interferometric reading taken a predetermined period of time after the termination of the radiation pulse equivalent to the mechanical response time of the structure.
Claim 19
Independent Claim
231 words
A device for detecting delaminated areas in a layered structure comprising of a substrate and at least one covering layer, and having a predetermined inertial response time, said predetermined inertial response time being the inertial response time of the smallest delaminated area to be detected in the layered structure, said device comprising: means for generating pulses of thermal radiation wherein each pulse has a duration smaller than the predetermined inertial response time of the layered structure and in the range of 0.001 to 1 millisecond; means for applying each surface are of the structure a short pulse of the thermal radiation as a focused beam to irradiate an area smaller than the delaminated area to be detected; and interferometric means for detecting vertical displacements of the structure surface to indicate delaminations, said interferometric means comprising: means for measuring a first vertical displacement of the irradiated structure during the application of the thermal radiation pulse as a measure of the thermal expansion of the structure due to the absorption of thermal energy, means for measuring a second vertical displacement of the irradiated structure surface during the mechanical response time of the structure following the termination of the thermal radiation pulse as a measure of the thermal deformation in the structure; and means for normalizing the second measured vertical displacement with the first measured vertical displacement to provide an indication of a delamination.
Claim 20
Independent Claim
231 words
A device for detecting delaminated areas in a layered structure comprising of a substrate and at least one covering layer, and having a predetermined inertial response time, said predetermined inertial response time being the inertial response time of the smallest delaminated area to be detected in the layered structure, said device comprising: means for generating pulses of thermal radiation wherein each pulse has a duration smaller than the predetermined inertial response time of the layered structure and in the range of 0.001 to 1 millisecond; means for applying each surface are of the structure a short pulse of the thermal radiation as a focused beam to irradiate an area smaller than the delaminated area to be detected; and interferometric means for detecting vertical displacements of the structure surface to indicate delaminations, said interferometric means comprising: means for measuring a first vertical displacement of the irradiated structure during the application of the thermal radiation pulse as a measure of the thermal expansion of the structure due to the absorption of thermal energy, means for measuring a second vertical displacement of the irradiated structure surface during the mechanical response time of the structure following the termination of the thermal radiation pulse as a measure of the thermal deformation in the structure; and means for normalizing the second measured vertical displacement with the first measured vertical displacement to provide an indication of a delamination.
Claim 21
Dependent Claim
44 words
A device as claimed in claim 16, wherein said means for measuring the first vertical displacement comprises means for determining the difference between an interferometric reading taken before the radiation pulse and an interferometric reading taken immediately after the termination of the radiation pulse.
Claim 22
Dependent Claim
58 words
A device as claimed in claim 17, wherein said means for measuring the second vertical displacement measurement comprises means for determining the difference between an interferometric reading taken before the radiation pulse and an interferometric reading taken a predetermined period of time after the termination of the radiation pulse equivalent to the mechanical response time of the structure.
Claim 23
Dependent Claim
60 words
A device as claimed in claim 17, wherein said means for measuring the second vertical displacement measurement comprises means for determining the difference between an interferometric reading taken immediately after the applied radiation pulse and an interferometric reading taken a predetermined period of time after the termination of the radiation pulse equivalent to the mechanical response time of the structure.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-06-21 | 1991-12-21 | 1992-06-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-06-21 | 1995-12-21 | 1996-06-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-06-21 | 1999-12-21 | 2000-06-21 | $7700.00 | Window Closed / Lapsed |