Method and system for detecting precursor to coating spallation

Patent metadata

Field	Value
Publication number	US-10274429-B2
Application number	US-201715706958-A
Country	US
Kind code	B2
Filing date	Sep 18, 2017
Priority date	Sep 18, 2017
Publication date	Apr 30, 2019
Grant date	Apr 30, 2019

Abstract

Apparatus and associated methods relate to predicting precursor to coating spallation. Heat is provided to a first surface of a member. A time sequence of thermal images is captured of the first surface and/or a second surface of the member. Each of the images includes a two-dimensional array of image data. Each of the image data of the two-dimensional array of image data corresponds to an xy-coordinate pair. A two-dimensional array of thermal diffusivities is calculated based on the captured time sequence of thermal images. Each of the thermal diffusivities of the two-dimensional array of thermal diffusivities corresponds to the xy-coordinate pair. Each of the calculated thermal diffusivities of the two dimensional array of thermal diffusivities are compared with a predetermined threshold. If the calculated thermal diffusivity is greater than the predetermined threshold, then precursor to coating spallation of the thermal barrier coating at the corresponding xy-coordinate pair is predicted.

First claim

The invention claimed is:

1. A through-transmission thermal imaging system for predicting precursor to coating spallation, the system comprising:
a heat source configured to provide a temporal step of heat to a first surface of a member having a coating formed on the first surface and/or a second surface;
a thermographic camera having a focal plane array comprising a two-dimensional array of pixels, each having an xy-coordinate pair corresponding to an xy-location of the member, the thermographic camera configured to receive heat conducted through the member, from the first surface to the second surface, and then radiated from the second surface of the member into the external atmosphere, and to focus the received heat onto the focal plane array, thereby forming an image of the second surface of the member, the thermographic camera further configured to capture a time sequence of thermal images of the second surface of the member, wherein the time sequence of thermal images is indicative of thermal diffusivities of the member at respective xy-locations; and
a spallation predictor configured to predict, based on a comparison of the thermal diffusivities of the member at the respective xy-locations and a predetermined threshold, precursor to coating spallation.

2. The system of claim 1 , further comprising:
a thermal diffusivity calculator configured to calculate, based on the captured time sequence of thermal images, a two-dimensional array of thermal diffusivities, each of the two-dimensional array of thermal diffusivities corresponding to the xy-coordinate pair of one of the pixels of the two-dimensional array of pixels.

3. The system of claim 1 , wherein the coating is a thermal barrier coating.

4. The system of claim 1 , wherein the spallation predictor is further configured to output an alarm signal, if precursor to coating spallation is predicted.

5. The system of claim 1 , wherein the spallation predictor predicts precursor to coating spallation in response to one of the calculated thermal diffusivities exceeding a predetermined value.

6. The system of claim 1 , wherein the spallation predictor predicts precursor to coating spallation in response to a number of pixels, which correspond to calculated thermal diffusivities exceeding a predetermined threshold, exceeding a predetermined count.

7. The system of claim 1 , wherein the heat source and the thermographic camera are configured to mount to an aircraft proximate the member having the coating.

8. The system of claim 1 , wherein the coating is on the first surface of the member.

9. The system of claim 1 , wherein the heat is provided in a substantially spatially uniform manner to the first surface of the member.

10. A through-transmission thermal imaging method for predicting precursor to coating spallation, the method comprising:
providing a temporal step of heat to a first surface of a member having a coating on the first surface and/or a second surface;
conducting heat through the member, from the first surface to the second surface;
radiating heat from the second surface into the external atmosphere;
capturing a time sequence of thermal images of the heat radiated into the external atmosphere from the second surface of the member, each of the time sequence of thermal images comprising a two-dimensional array of pixel data, each of the two-dimensional array of pixel data corresponding to an xy-coordinate pair;
calculating, based on the captured time sequence of thermal images, a two-dimensional array of thermal diffusivities, each of the two-dimensional array of thermal diffusivities corresponding to the xy-coordinate pair;
comparing each of the calculated thermal diffusivities of the two dimensional array of thermal diffusivities with a predetermined threshold; and
predicting, based on the calculated thermal diffusivities, precursor to coating spallation at the corresponding xy-coordinate pair.

11. The method of claim 10 , further comprising:
outputting an alarm signal if precursor to coating spallation is predicted.

12. The method of claim 10 , wherein predicting precursor to coating spallation comprises:
comparing the calculated thermal diffusivities with a predetermined value.

13. The method of claim 10 , wherein predicting precursor to coating spallation comprises:
comparing a number of pixels, which correspond to calculated thermal diffusivities exceeding a predetermined threshold, with a predetermined count.

14. A through-transmission thermal imaging system for predicting precursor to coating spallation, the system comprising:
a heat source;
a thermographic camera;
one or more processors; and
one or more storage devices encoded with instructions that, when executed by the one or more processors, cause the system to:
provide a temporal step of heat to a first surface of a member having a coating on the first surface and/or a second surface;
conduct heat through the member, from the first surface to the second surface;
radiate heat from the second surface into the external atmosphere;
capture a time sequence of thermal images of the second surface of the member, each of the time sequence of thermal images of the heat radiated into the external atmosphere from the second surface, each of the time sequence of thermal images comprising a two-dimensional array of pixel data, each of the two-dimensional array of pixel data corresponding to an xy-coordinate pair;
calculate, based on the captured time sequence of thermal images, a two-dimensional array of thermal diffusivities, each of the two-dimensional array of thermal diffusivities corresponding to the xy-coordinate pair;
compare each of the calculated thermal diffusivities of the two dimensional array of thermal diffusivities with a predetermined threshold; and
predict, based on the calculated thermal diffusivities, precursor to coating spallation at the corresponding xy-coordinate pair.

15. The system of claim 14 , wherein the coating is a thermal barrier coating.

16. The system of claim 14 , wherein one or more storage devices encoded with instructions that, when executed by the one or more processors, cause the system to:
output, if precursor to coating spallation is predicted, an alarm signal.

Assignees

• United Technologies Corp

Inventors

• Ouyang Zhong
• Smith Kevin D

Classifications

• G01N2021/1765

  Method using an image detector and processing of image signal · CPC title

• G01N21/8422

  Investigating thin films, e.g. matrix isolation method · CPC title

• G01N2021/8427

  Coatings · CPC title

• G01N21/71 Primary

  thermally excited · CPC title

• G01N25/72 Primary

  Investigating presence of flaws · CPC title