CN105301051B - Suitable for TBC debonding defect quick detection line laser structured light thermal wave imaging methods - Google Patents
Suitable for TBC debonding defect quick detection line laser structured light thermal wave imaging methods Download PDFInfo
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Abstract
Disclosure is applied to the line laser structured light thermal wave imaging method of TBC debonding defect quick detections, including：The line laser that optimization design quickly moves is as wire thermal source, using the wire thermal source excitation is scanned in TBC surface of test piece, a wide range of wire is carried out in coarse scan detection-phase to surface of test piece quickly to scan, collection obtains the thermal infrared images of coarse scan detection-phase, and carries out thermal infrared images analysis；For finding that the film micro area of those suspected defects carries out close scanning, the thin thermal infrared images for sweeping detection-phase is obtained.The present invention can not only be to detecting TBC debonding defect, and has higher precision, TBC will not be damaged during detection, easy to operate and have greater efficiency, moreover it is possible to which the picture of system acquisition is post-processed.
Description
Technical Field
The application relates to the technical field of nondestructive testing and image processing in experimental mechanics, in particular to a laser scanning thermal wave imaging method suitable for a TBC debonding defect rapid detection line.
Background
The turbine blade is usually made of directionally solidified alloy and single crystal alloy, the service temperature can only reach 1000 ℃, and the requirement of the working temperature of a modern engine cannot be met. In response to this situation, TBCs have been developed to protect metal substrates, and TBC coated engine turbine blades can operate at high temperatures of 1600 ℃, increasing the thermal efficiency of the engine by more than 60%, effectively increasing the thrust-weight ratio. The TBC coated turbine blade is a typical multilayer structure system, which is generally composed of a substrate, an intermediate transition layer and a ceramic layer, each layer has obviously different physical, thermal and mechanical properties, and the complex structure and the harsh working environment cause the TBC to fall off during the use process to cause failure problems, thereby requiring the nondestructive detection of the debonded TBC.
The inherent characteristics of the TBC, such as porosity and thin thickness, make some conventional non-destructive testing methods, such as eddy current testing and impedance testing, have technical and testing efficiency limitations for TBC testing. How to carry out nondestructive detection on defects in a TBC system becomes a problem to be solved urgently in TBC application.
The invention creation name of Chinese patent application No. 201510147560.4 (publication No. CN104713906A, publication date 2015 6, month 17) is: the application discloses a microwave phase-locking thermal imaging system, which adopts continuous waves modulated by phase-locking signals to periodically heat an object to be detected, and adopts a thermal imager to record temperature signals of periodic changes of the surface of the object to be detected, wherein the temperature signals can reflect thermal wave abnormity caused by defects. Similarly, the invention of chinese patent application No. 201510124036.5 (publication No. CN 104698035 a, published as 2015, 6/10) is named as: in a microwave step thermal imaging detection and tomography method and a system, a relevant nondestructive detection method is adopted for testing, and quantitative depth measurement of unknown defects is obtained.
In the nondestructive testing of the thermal barrier coating, the invention creation name of Chinese patent No. 2012010436106.7 (publication No. CN 1029549668A, publication date 3/6/2013) is as follows: the application discloses an electromagnetic eddy current thermal imaging nondestructive testing system and a testing method for a thermal barrier coating part.
Further, regarding the infrared thermal imaging nondestructive testing system of the thermal barrier coating, the invention of chinese patent application No. 201420723314.7 (publication No. CN 204203143U, published as 2015, 3, 11) is named as: the application discloses a novel thermal barrier coating structure's infrared light heat ripples detection device, adopts high energy flash of light pulse heating lamp as thermal excitation, and thermal infrared imager gathers the image, does not nevertheless provide the sensitivity of detecting the defect and the problem of resolution, does not mention the method to gathering image aftertreatment yet.
Disclosure of Invention
In view of this, the technical problem to be solved by the present application is to provide a laser scanning thermal wave imaging method suitable for a rapid detection line for TBC debonding defects, which not only can detect the debonding defects of the TBC, but also has higher precision, does not damage the TBC during detection, is simple and convenient to operate and has higher efficiency, and can perform post-processing on pictures acquired by a system.
In order to solve the technical problem, the following technical scheme is adopted:
a laser scanning thermal wave imaging method suitable for a TBC debonding defect rapid detection line is characterized by comprising the following steps:
optimally designing a fast moving linear laser as a linear heat source, performing scanning excitation on the surface of the TBC test piece by using the linear heat source, performing large-range linear fast scanning on the surface of the test piece in a coarse scanning detection stage, acquiring a thermal infrared image of the coarse scanning detection stage, and analyzing the thermal infrared image; performing fine scanning on the micro-area with the suspected defect to obtain a thermal infrared image at a fine scanning detection stage;
for the thermal infrared image of the coarse scan detection stage:
performing thermal infrared image post-processing to obtain a defect response temperature field image in a full field range and a defect response temperature field image in the full field range after noise removal and thermal response; obtaining a defect response temperature field image with the whole field range removed with all noise influences including edge noise by adopting a self-adaptive variable weight filter window method;
for the thermal infrared image of the fine scan detection phase:
according to a transient micro-surface heat source pulse excitation processing method, Fourier transform is carried out on the collected temperature images in a certain time sequence to obtain an amplitude field and a phase field which only contain defect response under a given frequency in a micro region.
Preferably, the first and second substrates are, among others,
the obtaining of the defect response temperature field image in the full field range further comprises:
and constructing a full-field directional carrier temperature field which is integrally averaged along the line laser direction, subtracting the full-field directional carrier temperature field from the original thermal infrared image to obtain a temperature field image which is weakened in noise and only contains defect response, and superposing the temperature field images only containing defect response at all times to obtain the defect response temperature field image in the full-field range.
Preferably, the first and second substrates are, among others,
obtaining a defect response temperature field image after noise removal thermal response in the full field range, and further comprising:
and subtracting the initial image without heat source excitation from the thermal infrared image in the rough scanning detection stage, performing post-processing by adopting a method of windowing near the heat source at three moments to obtain amplitude and remove noise thermal response, and superposing response amplitude fields in a specific window at all moments to obtain a defect response temperature field image in the full field range after the noise thermal response is removed.
Preferably, the first and second substrates are, among others,
the line laser which is optimally designed to move fast is used as a linear heat source, and the method further comprises the following steps: optimally using a laser marking machine, controlling the current to be 10A, converging red laser points with the diameter of 300 microns on the surface of the TBC test piece, controlling the laser points to linearly move at the speed of more than 1000mm/s in the linear direction, and scanning in the direction perpendicular to the moving direction.
Preferably, the first and second substrates are, among others,
the construction of the whole-field directional carrier temperature field which is integrally averaged along the line laser direction further comprises the following steps:
selecting a temperature field image at any moment, adding temperature values of all pixel points in the direction parallel to the line laser, and then averaging to obtain carrier temperature values of all the points in the line; after this operation is performed on all columns in the direction perpendicular to the line laser, the overall average carrier temperature field along the line laser direction of the structure is obtained, and the specific theoretical formula is as follows:
Tact(t)(xi,yj) For the temperature field image collected by the thermal imager at the time T, m is the number of horizontal coordinate pixels, n is the number of vertical coordinate pixels, and T is the number of the vertical coordinate pixelsfit(t)(x, y) is the overall average carrier temperature field along the line laser direction constructed at time t.
Preferably, the first and second substrates are, among others,
subtracting a full-field directional carrier temperature field from the original thermal infrared image, and further:
subtracting the temperature field without thermal excitation and the constructed directional carrier wave temperature field at the moment from the temperature field at each moment to obtain a response temperature field at the defect part with the noise reduced and only containing the excitation of the linear laser at the moment, and summing the response temperature fields at all the moments to obtain a defect response temperature field image with the noise reduced in the whole field range, wherein the specific theoretical formula is as follows:
Tact(t)(xi,yj) Temperature field image T acquired by thermal imager at time Tfit(t)(x, y) is the carrier temperature field, T, constructed at time T, averaged over the line laser directiono(x, y) is the temperature field without linear laser excitation, Tresult1(x, y) is the full field range defect response temperature field image.
Preferably, the first and second substrates are, among others,
the method for solving the amplitude and removing the noise thermal response at three times of windowing near the heat source is adopted for post-processing, and the method further comprises the following steps:
selecting a fixed rectangular area slightly larger than the size of the linear laser as a calculation window, selecting temperature field images at three moments before scanning, during scanning and after scanning according to the position of the calculation window, and solving the amplitude value of each pixel point in the calculation window, wherein the amplitude field outside the calculation window is empty, and the solving formula is as follows:
andthe original temperature field images T in the calculation window corresponding to the three moments before, during and after the scanning of the line light source respectivelyact(t)(x, y) is an amplitude field image obtained by direct calculation in a calculation window at the time t;
in the calculation window, the average value of the sum of the temperature values of all pixel points in the direction parallel to the line laser is taken as the carrier temperature value of all the points in the row, and after the operation is performed on all columns in the calculation window in the direction perpendicular to the line laser, the amplitude field outside the calculation window is null, and the specific theoretical formula is as follows:
Tact(t)(x, y) is the amplitude field directly calculated in the calculation window at the time T, m is the number of pixels on the abscissa, and Tfit(t)(x, y) is the constructed carrier amplitude field within the calculation window at time t.
Preferably, wherein, further comprising:
subtracting the structural carrier amplitude average field from the solved amplitude field to obtain a response amplitude field at the defect position which only contains the linear laser excitation at each moment in a specific window, and superposing the response amplitude fields at all moments to obtain a defect response amplitude field with noise removed in the full field range, wherein the specific theoretical formula is as follows:
Tact(t)(x, y) is the amplitude field directly calculated in the calculation window at time T, Tfit(t)(x, y) is the constructed carrier amplitude field within the calculation window at time T, Tresult2(x, y) are the defective response amplitude field images only after noise removal for the full field range.
Preferably, the first and second substrates are, among others,
the adaptive variable weight filtering method further comprises the following steps:
constructing a brand new weighted edge carrier wave field consistent with the shape of the test piece according to the shape of the test piece and the temperature noise degree, and adding the temperature field only containing the defect response and the edge carrier wave temperature field in a proper proportion to obtain a defect temperature response image with edge noise subtracted, wherein the calculation formula of the defect response temperature field is shown as follows;
Tresult3(x,y)＝Tact(x,y)-[Tact(x,y)(1-W)+Tfit(x,y)W]
Tact(x, y) is a temperature field image or an amplitude field image containing defect information, Tfit(x, y) is the carrier temperature field or carrier amplitude field of the structure, W is the selection of an appropriate ratio, Tresult3(x, y) is a defect response temperature field image which removes all noise influences including edge noise in the whole field range after adopting the method of the self-adaptive variable weight filter window.
Preferably, the first and second substrates are, among others,
the processing process of the fine scanning detection stage comprises the following steps:
aiming at a suspected defect micro-area with increased temperature and detected noise point elimination in a rough scanning detection stage, fine scanning for improving power is carried out in the micro-area, line laser for fast scanning is regarded as surface laser pulse excitation in the micro-area, a pulse phase method is optimized for collected thermal infrared images, Fourier transform is carried out on a time sequence, and an amplitude field and a phase field which only contain defect response and have high signal-to-noise ratio after noise removal are obtained.
Compared with the prior art, the method has the following effects:
firstly, use laser marking machine, TBC test piece and thermal infrared imager in this application, built brand-new laser fast scan thermal imaging system, this system is built simply, convenient operation, and repeatability is strong, reaches completely to TBC debonding defect non-contact's nondestructive test.
Secondly, the detection process of the defects in the application is divided into two stages of coarse scanning and fine scanning. The scanning speed of the coarse scanning detection stage is high, larger defects can be detected in a short time, the power of the fine scanning detection stage is improved, and the fine scanning detection stage has better resolution capability on smaller defects. By combining the two scanning modes, the contradiction between the defect detection time and the detection sensitivity can be relieved, so that the defect detection has higher efficiency.
Thirdly, in the application, for the post-processing of the thermal image, the signal-to-noise ratio of the image quality can be improved by developing a brand-new post-processing algorithm, the position and the size of the defect can be more accurately displayed, the visualization of the blind hole defect of the TBC with the diameter of more than 1mm is realized, and the detection sensitivity and the detection accuracy are improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
FIG. 1 is a flow chart of a laser scanning thermal wave imaging method suitable for a TBC debonding defect rapid detection line in the present invention;
FIG. 2 is a flowchart of a TBC scanning laser thermal imaging nondestructive testing and post-processing method in embodiment 2 of the present invention;
FIG. 3 is a schematic diagram of a TBC test piece with detection tape containing blind hole defects in example 2 of the present invention;
FIG. 4 is a schematic view of a TBC scanning laser thermal imaging nondestructive monitoring system in embodiment 2 of this invention;
fig. 5 is a result of post-processing of a thermal image acquired by a thermal infrared imager at a coarse scanning stage in embodiment 2 of the present invention, where fig. 5(a) is a defect response temperature field image after subtracting a constructed carrier, fig. 5(b) is a defect response temperature field image after windowing and denoising, and fig. 5(c) is a defect response temperature field image after variable weight filtering;
fig. 6 is an amplitude field image and a phase field image obtained by post-processing a thermal image of a micro region acquired at a fine scanning stage of a thermal infrared imager in embodiment 2 of the present invention.
Detailed Description
As used in the specification and in the claims, certain terms are used to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. "substantially" means within an acceptable error range, and a person skilled in the art can solve the technical problem within a certain error range to substantially achieve the technical effect. Furthermore, the term "coupled" is intended to encompass any direct or indirect electrical coupling. Thus, if a first device couples to a second device, that connection may be through a direct electrical coupling or through an indirect electrical coupling via other devices and couplings. The description which follows is a preferred embodiment of the present application, but is made for the purpose of illustrating the general principles of the application and not for the purpose of limiting the scope of the application. The protection scope of the present application shall be subject to the definitions of the appended claims.
Example 1
Referring to fig. 1, a specific embodiment of a laser scanning thermal wave imaging method suitable for a TBC debonding defect rapid detection line is shown, where the method in this embodiment includes the following steps:
step 10, optimally designing a fast moving linear laser as a linear heat source, performing scanning excitation on the surface of a TBC test piece by using the linear heat source, performing large-range linear fast scanning on the surface of the test piece in a coarse scanning detection stage, acquiring a temperature image by using a thermal infrared imager, acquiring a thermal infrared image in the coarse scanning detection stage, and analyzing the thermal infrared image; and for the micro area in which the suspected defect is found, performing fine scanning in the area by using a short line laser with higher power to obtain a thermal infrared image in a fine scanning detection stage.
Step 11, for the thermal infrared image in the coarse scanning detection stage: performing thermal infrared image post-processing to obtain a defect response temperature field image in a full field range and a defect response temperature field image in the full field range after noise removal and thermal response; and obtaining a defect response temperature field image with the whole field range removed with all noise influences including edge noise by adopting a self-adaptive variable weight filtering window method.
Step 12, regarding the thermal infrared image in the fine scanning detection stage: according to a transient micro-surface heat source pulse excitation processing method, Fourier transform is carried out on the collected temperature images in a certain time sequence to obtain an amplitude field and a phase field which only contain defect response under a given frequency in a micro region, and then the defect images with noise removed can be judged.
In the step 10, optimally designing the fast moving line laser as the linear heat source further comprises: the laser marking machine is optimally used, the current is controlled to be about 10A, red laser points with the diameter of 300 micrometers are converged on the surface of the TBC test piece, the laser points are controlled to linearly move at the speed of more than 1000mm/s in the linear direction, and scanning is carried out in the direction perpendicular to the moving direction.
In the step 11, a defect response temperature field image of the full field range is obtained, further including: and constructing a full-field directional carrier temperature field which is integrally averaged along the line laser direction, subtracting the full-field directional carrier temperature field from the original thermal infrared image to obtain a temperature field image which is weakened in noise and only contains defect response, and superposing the temperature field images only containing defect response at all times to display the defect response temperature field image in the full-field range.
In the scheme, a full-field directional carrier temperature field which is integrally averaged along the line laser direction is constructed, and the method further comprises the following steps: selecting a temperature field image at any moment, adding temperature values of all pixel points in the direction parallel to the line laser, and then averaging to obtain carrier temperature values of all the points in the line; after this operation is performed on all columns in the direction perpendicular to the line laser, the overall average carrier temperature field along the line laser direction of the structure is obtained, and the specific theoretical formula is as follows:
Tact(t)(xi,yj) For the temperature field image collected by the thermal imager at the time T, m is the number of horizontal coordinate pixels, n is the number of vertical coordinate pixels, and T is the number of the vertical coordinate pixelsfit(t)(x, y) is the overall average carrier temperature field along the line laser direction constructed at time t.
In the above scheme, subtracting the full-field directional carrier temperature field from the original thermal infrared image further comprises:
subtracting the temperature field without thermal excitation and the constructed directional carrier wave temperature field at the moment from the temperature field at each moment to obtain a response temperature field at the defect part with the noise reduced and only containing the excitation of the linear laser at the moment, and summing the response temperature fields at all the moments to obtain a defect response temperature field image with the noise reduced in the whole field range, wherein the specific theoretical formula is as follows:
Tact(t)(xi,yj) Temperature field image T acquired by thermal imager at time Tfit(t)(x, y) is the carrier temperature field, T, constructed at time T, averaged over the line laser directiono(x, y) is the temperature field without linear laser excitation, Tresult1(x, y) is the full field range defect response temperature field image.
In the step 11, obtaining a defect response temperature field image after removing the noise thermal response in the full field range, further includes: and subtracting the initial image without heat source excitation from the thermal infrared image in the coarse scanning detection stage, performing post-processing by adopting a method of windowing near the heat source at three moments to obtain amplitude and remove noise thermal response, and superposing response amplitude fields in a specific window at all moments to obtain a defect response temperature field sum image after removing the noise thermal response in the whole field range.
In the scheme, a method of windowing near a heat source at three moments to obtain amplitude and remove noise thermal response is adopted for post-processing, and the method further comprises the following steps:
selecting a fixed rectangular area slightly larger than the size of the linear laser as a calculation window, selecting temperature field images at three moments before scanning, during scanning and after scanning according to the position of the calculation window, and solving the amplitude value of each pixel point in the calculation window, wherein the amplitude field outside the calculation window is empty, and the solving formula is as follows:
andthe original temperature field images T in the calculation window corresponding to the three moments before, during and after the scanning of the line light source respectivelyact(t)(x, y) is an amplitude field image obtained by direct calculation in a calculation window at the time t;
in the calculation window, the average value of the sum of the temperature values of all pixel points in the direction parallel to the line laser is taken as the carrier temperature value of all the points in the row, and after the operation is performed on all columns in the calculation window in the direction perpendicular to the line laser, the amplitude field outside the calculation window is null, and the specific theoretical formula is as follows:
Tact(t)(x, y) is the amplitude field directly calculated in the calculation window at the time T, m is the number of pixels on the abscissa, and Tfit(t)(x, y) is the constructed carrier amplitude field within the calculation window at time t.
Further, subtracting the structural carrier amplitude average field from the solved amplitude field to obtain a response amplitude field at the defect position which only contains the linear laser excitation in a specific window at each moment, and superposing the response amplitude fields at all moments to obtain a defect response amplitude field with noise removed in the full field range, wherein the specific theoretical formula is as follows:
Tact(t)(x, y) is the amplitude field directly calculated in the calculation window at time T, Tfit(t)(x, y) is the constructed carrier amplitude field within the calculation window at time T, Tresult2(x, y) are the defective response amplitude field images only after noise removal for the full field range.
In the step 11, the adaptive variable weight filtering method further includes: constructing a brand new weighted edge carrier wave field consistent with the shape of the test piece according to the shape of the test piece and the temperature noise degree, and adding the temperature field only containing the defect response and the edge carrier wave temperature field in a proper proportion to obtain a defect temperature response image with edge noise subtracted, wherein the calculation formula of the defect response temperature field is shown as follows;
Tresult3(x,y)＝Tact(x,y)-[Tact(x,y)(1-W)+Tfit(x,y)W]
Tact(x, y) is a temperature field image or an amplitude field image containing defect information, Tfit(x, y) is the carrier temperature field or carrier amplitude field of the structure, W is the selection of an appropriate ratio, Tresult3(x, y) is a defect response temperature field image which removes all noise influences including edge noise in the whole field range after adopting the method of the self-adaptive variable weight filter window.
In the step 12, the processing procedure of the fine scanning detection stage is as follows: aiming at a suspected defect micro-area with increased temperature and detected noise point elimination in a rough scanning detection stage, fine scanning for improving power is carried out in the micro-area, line laser for fast scanning is regarded as surface laser pulse excitation in the micro-area, a pulse phase method is optimized for collected thermal infrared images, Fourier transform is carried out on a time sequence, and an amplitude field and a phase field which only contain defect response and have high signal-to-noise ratio after noise removal are obtained.
Example 2
An example of an application of the present invention is provided below, see fig. 2:
step 101, detecting by using a TBC test piece containing three blind hole defects as shown in FIG. 3, optimally controlling current to be about 10A by using a laser marking machine, converging red laser points with the diameter of 300 microns on the surface of the TBC test piece, and controlling the laser points to move at high speed in a linear direction. When the laser spot is linearly moved at a speed of 1000mm/s or more, the laser spot moved at a high speed can be regarded as a line laser. When the line laser is scanned perpendicular to the direction of movement, a line laser excitation is formed. The infrared camera is used to collect corresponding thermal images, namely, the scanning laser thermal imaging nondestructive detection system is built, as shown in fig. 4.
102, selecting a temperature field image collected by a thermal imager at a certain moment, adding temperature values of all pixel points in the direction parallel to the linear laser, then taking an average value as carrier temperature values of all points of the row, performing the operation on all columns in the direction perpendicular to the linear laser to obtain a constructed full-field linear laser carrier temperature field, subtracting a temperature field without thermal excitation and the constructed full-field carrier temperature field from the temperature field shot by the thermal imager to obtain a response temperature field image only containing the defect part excited by the linear laser at the moment, and superposing the defect response temperature field images at all the moments to display the defect response temperature field image in the full-field range, wherein the result image is shown in fig. 5(a), and the specific formula is as follows:
wherein, Tact(t)(xi,yj) For the temperature field image collected by the thermal imager at the time T, m is the number of horizontal coordinate pixels, n is the number of vertical coordinate pixels, and T is the number of the vertical coordinate pixelsfit(t)(x, y) is the carrier temperature field, T, constructed at time T, averaged over the line laser directiono(x, y) is the temperature field without linear laser excitation, Tresult1(x, y) is the full field range defect response temperature field image.
103, adopting a heat source accessory windowing amplitude-solving denoising method: selecting a fixed rectangular area slightly larger than the size of the linear laser as a calculation window, selecting temperature field images at three moments before, during and after scanning according to the position of the calculation window, solving the amplitude value of each pixel point in the calculation window, wherein a solving formula is as follows, obtaining an amplitude field in the calculation window after solving, enabling the amplitude field outside the calculation window to be empty, constructing a carrier amplitude field by using a method similar to constructing the carrier temperature field, subtracting the constructed carrier amplitude field from the obtained amplitude field to obtain a response amplitude field at each moment at a defect part only containing the linear laser excitation in a specific window, and superposing the response amplitude fields at all moments to obtain a final defect response image with noise removed in the complete area, wherein the result image is as shown in fig. 5(b), and the concrete formula is as follows:
wherein,andthe original temperature fields are respectively collected by the thermal imagers in the calculation windows corresponding to the linear light source before scanning, during scanning and after scanning. (x, y) is the pixel point in the calculation window, Tact(t)(x, y) is the amplitude field obtained by direct calculation in the calculation window at the moment T, m is the pixel point of the abscissa, and Tfit(t)(x, y) is the carrier amplitude field constructed at time T, Tresult(x, y) is the amplitude field with only a defective response after noise removal over the full field.
Step 104, the real temperature field and the carrier temperature field are added in proper proportion, so that the temperature field of the defect response excited by the linear laser can be displayed more clearly, and a defect response temperature field image with edge noise removed is obtained, wherein the result image is shown in fig. 5(c), and the calculation formula is as follows:
Tresult3(x,y)＝Tact(x,y)-[Tact(x,y)(1-W)+Tfit(x,y)W]
Tact(x, y) is a temperature field image or an amplitude field image containing defect information, Tfit(x, y) is the carrier temperature field or carrier amplitude field of the structure, W is the selection of an appropriate ratio, Tresult3(x, y) is a defect response temperature field image which removes all noise influences including edge noise in the whole field range after adopting the method of the self-adaptive variable weight filter window.
And 105, detecting a noise-eliminated temperature increase area in the rough scanning stage, performing fine scanning with improved power in the area, regarding the rapidly scanned line laser as surface laser scanning, and acquiring a corresponding thermal image by using an infrared camera.
And 106, performing Fourier transform on the thermal image acquired in the fine scanning stage on a time sequence to obtain a corresponding amplitude field image and a corresponding phase field image, and using a method of constructing a carrier amplitude field and subtracting the carrier amplitude field to obtain an image which has high signal-to-noise ratio and only contains defect response after removing noise, wherein the result image is shown in figure 6, and the blind hole defect with the aperture of more than 1mm can be detected.
According to the embodiments, the application has the following beneficial effects:
firstly, use laser marking machine, TBC test piece and thermal infrared imager in this application, built brand-new laser fast scan thermal imaging system, this system is built simply, convenient operation, and repeatability is strong, reaches completely to TBC debonding defect non-contact's nondestructive test.
Secondly, the detection process of the defects in the application is divided into two stages of coarse scanning and fine scanning. The scanning speed of the coarse scanning detection stage is high, larger defects can be detected in a short time, the power of the fine scanning detection stage is improved, and the fine scanning detection stage has better resolution capability on smaller defects. By combining the two scanning modes, the contradiction between the defect detection time and the detection sensitivity can be relieved, so that the defect detection has higher efficiency.
Thirdly, in the application, for the post-processing of the thermal image, the signal-to-noise ratio of the image quality can be improved by developing a brand-new post-processing algorithm, the position and the size of the defect can be more accurately displayed, the visualization of the blind hole defect of the TBC with the diameter of more than 1mm is realized, and the detection sensitivity and the detection accuracy are improved.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, apparatus, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The foregoing description shows and describes several preferred embodiments of the present application, but as aforementioned, it is to be understood that the application is not limited to the forms disclosed herein, but is not to be construed as excluding other embodiments and is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the inventive concept as expressed herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the application, which is to be protected by the claims appended hereto.
Claims (9)
1. A laser scanning thermal wave imaging method suitable for a TBC debonding defect rapid detection line is characterized by comprising the following steps:
optimally designing a fast moving linear laser as a linear heat source, performing scanning excitation on the surface of the TBC test piece by using the linear heat source, performing large-range linear fast scanning on the surface of the test piece in a coarse scanning detection stage, acquiring a thermal infrared image of the coarse scanning detection stage, and analyzing the thermal infrared image; performing fine scanning on the micro-area with the suspected defect to obtain a thermal infrared image at a fine scanning detection stage;
for the thermal infrared image of the coarse scan detection stage:
performing thermal infrared image post-processing to obtain a defect response temperature field image in a full field range and a defect response temperature field image in the full field range after noise removal and thermal response; obtaining a defect response temperature field image with the whole field range removed with all noise influences including edge noise by adopting a self-adaptive variable weight filtering method, wherein the obtaining of the defect response temperature field image with the whole field range further comprises: constructing a full-field directional carrier temperature field which is integrally averaged along the line laser direction, subtracting the full-field directional carrier temperature field from the original thermal infrared image to obtain a temperature field image which is weakened in noise and only contains defect response, and superposing the temperature field images only containing defect response at all times to obtain a defect response temperature field image in the full-field range;
for the thermal infrared image of the fine scan detection phase:
according to a transient micro-surface heat source pulse excitation processing method, Fourier transform is carried out on the collected temperature images in a certain time sequence to obtain an amplitude field and a phase field which only contain defect response under a given frequency in a micro region.
2. The laser scanning thermal wave imaging method suitable for the rapid detection line of TBC debonding defects according to claim 1,
obtaining a defect response temperature field image after noise removal thermal response in the full field range, and further comprising:
and subtracting the initial image without heat source excitation from the thermal infrared image in the rough scanning detection stage, performing post-processing by adopting a method of windowing near the heat source at three moments to obtain amplitude and remove noise thermal response, and superposing response amplitude fields in a specific window at all moments to obtain a defect response temperature field image in the full field range after the noise thermal response is removed.
3. The laser scanning thermal wave imaging method suitable for the rapid detection line of TBC debonding defects according to claim 1,
the line laser which is optimally designed to move fast is used as a linear heat source, and the method further comprises the following steps: optimally using a laser marking machine, controlling the current to be 10A, converging red laser points with the diameter of 300 microns on the surface of the TBC test piece, controlling the laser points to linearly move at the speed of more than 1000mm/s in the linear direction, and scanning in the direction perpendicular to the moving direction.
4. The laser scanning thermal wave imaging method suitable for the rapid detection line of TBC debonding defects according to claim 1,
the construction of the whole-field directional carrier temperature field which is integrally averaged along the line laser direction further comprises the following steps:
selecting a temperature field image at any moment, adding temperature values of all pixel points in the direction parallel to the line laser, and then averaging to obtain carrier temperature values of all the points in the line; after this operation is performed on all columns in the direction perpendicular to the line laser, the overall average carrier temperature field along the line laser direction of the structure is obtained, and the specific theoretical formula is as follows:
Tact(t)(xi,yj) For the temperature field image collected by the thermal imager at the time T, m is the number of horizontal coordinate pixels, n is the number of vertical coordinate pixels, and T is the number of the vertical coordinate pixelsfit(t)(x, y) is the overall average carrier temperature field along the line laser direction constructed at time t.
5. The laser scanning thermal wave imaging method suitable for the rapid detection line of TBC debonding defects according to claim 1,
subtracting a full-field directional carrier temperature field from the original thermal infrared image, and further:
subtracting the temperature field without thermal excitation and the constructed directional carrier wave temperature field at the moment from the temperature field at each moment to obtain a response temperature field at the defect part with the noise reduced and only containing the excitation of the linear laser at the moment, and summing the response temperature fields at all the moments to obtain a defect response temperature field image with the noise reduced in the whole field range, wherein the specific theoretical formula is as follows:
Tact(t)(x, y) is a temperature field image acquired by the thermal imager at the time T, Tfit(t)(x, y) is the carrier temperature field, T, constructed at time T, averaged over the line laser directiono(x, y) is the temperature field without linear laser excitation, Tresult1(x, y) is the full field range defect response temperature field image.
6. The laser scanning thermal wave imaging method suitable for the rapid detection line of TBC debonding defects according to claim 2,
the method for solving the amplitude and removing the noise thermal response at three times of windowing near the heat source is adopted for post-processing, and the method further comprises the following steps:
selecting a fixed rectangular area slightly larger than the size of the linear laser as a calculation window, selecting temperature field images at three moments before scanning, during scanning and after scanning according to the position of the calculation window, and solving the amplitude value of each pixel point in the calculation window, wherein the amplitude field outside the calculation window is empty, and the solving formula is as follows:
andthe original temperature field images T in the calculation window corresponding to the three moments before, during and after the scanning of the line light source respectivelyact(t)(x, y) is direct within the calculation window at time tCalculating the obtained amplitude field image;
in the calculation window, the average value of the sum of the temperature values of all pixel points in the direction parallel to the line laser is taken as the carrier temperature value of all the points in the row, and after the operation is performed on all columns in the calculation window in the direction perpendicular to the line laser, the amplitude field outside the calculation window is null, and the specific theoretical formula is as follows:
Tact(t)(x, y) is the amplitude field directly calculated in the calculation window at the time T, m is the number of pixels on the abscissa, and Tfit(t)(x, y) is the constructed carrier amplitude field within the calculation window at time t.
7. The laser scanning thermal wave imaging method suitable for the rapid detection line of the TBC debonding defect according to claim 6, further comprising:
subtracting the structural carrier amplitude average field from the solved amplitude field to obtain a response amplitude field at the defect position which only contains the linear laser excitation at each moment in a specific window, and superposing the response amplitude fields at all moments to obtain a defect response amplitude field with noise removed in the full field range, wherein the specific theoretical formula is as follows:
Tact(t)(x, y) is the amplitude field directly calculated in the calculation window at time T, Tfit(t)(x, y) is the constructed carrier amplitude field within the calculation window at time T, Tresult2(x, y) are the defective response amplitude field images only after noise removal for the full field range.
8. The laser scanning thermal wave imaging method suitable for the rapid detection line of TBC debonding defects according to claim 1,
the adaptive variable weight filtering method further comprises the following steps:
constructing a brand new weighted edge carrier wave field consistent with the shape of the test piece according to the shape of the test piece and the temperature noise degree, and adding the temperature field only containing the defect response and the edge carrier wave temperature field in a proper proportion to obtain a defect temperature response image with edge noise subtracted, wherein the calculation formula of the defect response temperature field is shown as follows;
Tresult3(x,y)＝Tact(x,y)-[Tact(x,y)(1-W)+Tfit(x,y)W]
Tact(x, y) is a temperature field image or an amplitude field image containing defect information, Tfit(x, y) is the carrier temperature field or carrier amplitude field of the structure, W is the selection of an appropriate ratio, Tresult3(x, y) is a defect response temperature field image which removes all noise influences including edge noise in the whole field range after adopting the method of the self-adaptive variable weight filter window.
9. The laser scanning thermal wave imaging method for the rapid detection line of TBC debonding defects according to any one of claims 1 to 8,
the processing process of the fine scanning detection stage comprises the following steps:
aiming at a suspected defect micro-area with increased temperature and detected noise point elimination in a rough scanning detection stage, fine scanning for improving power is carried out in the micro-area, line laser for fast scanning is regarded as surface laser pulse excitation in the micro-area, a pulse phase method is optimized for collected thermal infrared images, Fourier transform is carried out on a time sequence, and an amplitude field and a phase field which only contain defect response and have high signal-to-noise ratio after noise removal are obtained.
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