Aero-engine thermal barrier coating quality evaluation method based on terahertz technology

Abstract

The application relates to an aero-engine thermal barrier coating quality evaluation method based on a terahertz technology. The method comprises the following steps: performing terahertz wave scanning on the surface of a target hot end component, and collecting a terahertz wave reflection time domain spectrum generated by the terahertz wave at a scanning position; determining a peak value region corresponding to a coating surface and a peak value region corresponding to a coating bottom surface in the terahertz wave reflection time domain spectrum, determining a coating thickness corresponding to the scanning position based on a collection time difference of each peak value region, and determining a coating porosity corresponding to the scanning position according to the amplitude and phase of each peak value region; dividing the surface of the target hot end component into target regions, determining a coating uniformity corresponding to the target regions based on the coating thicknesses corresponding to the scanning positions contained in the target regions; and determining a coating quality index of the target hot end component according to the coating thicknesses and the coating porosities corresponding to the respective scanning positions and the coating uniformities corresponding to the respective target regions. The method can reduce the coating evaluation cost.

Description

Technical Field

[0001] This application relates to the field of terahertz technology, and in particular to a method for evaluating the quality of thermal barrier coatings for aero-engines based on terahertz technology. Background Technology

[0002] Currently, the temperatures experienced by hot-end components of aero-engines (such as turbine blades) often far exceed the limits that the blade's metallic materials can withstand. Therefore, thermal barrier coatings (TBCs) are increasingly widely used as an important means of heat insulation and cooling. A TBC is a layer of ceramic matrix composite material coated on a metal surface, with a thickness ranging from tens to hundreds of micrometers. The quality of the coating has a critical impact on the performance of hot-end components and even the engine itself. However, during service, coatings can crack, debond, or even detach. Therefore, accurate detection and monitoring of TBC quality are crucial in its design, service, life assessment, and subsequent maintenance.

[0003] Among related technologies, acoustic emission (AE) technology can be used to detect damage inside coatings. AE technology dynamically monitors the coating damage process by collecting stress wave signals released during material deformation or crack propagation. However, AE signals are complex and require analysis using advanced sensors and signal analysis systems, resulting in high detection costs. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for evaluating the quality of thermal barrier coatings for aero-engines based on terahertz technology to address the aforementioned technical problems.

[0005] Firstly, this application provides a method for evaluating the quality of thermal barrier coatings for aero-engines based on terahertz technology. The method includes:

[0006] The surface of the target hot end component is scanned with terahertz waves, and the time-domain spectrum of terahertz wave reflection generated at the scanning position is acquired.

[0007] The peak regions corresponding to the coating surface and the peak regions corresponding to the coating bottom surface in the terahertz wave reflection time domain spectrum are determined. The coating thickness corresponding to the scanning position is determined based on the acquisition time difference of each peak region. The coating porosity corresponding to the scanning position is determined based on the amplitude and phase of each peak region.

[0008] The surface of the target hot end component is divided into target regions, and the coating uniformity corresponding to the target region is determined based on the coating thickness corresponding to each scanning position included in the target region.

[0009] The coating quality indicators of the target hot end component are determined based on the coating thickness and coating porosity corresponding to each scanning position, and the coating uniformity corresponding to each target area.

[0010] In one embodiment, determining the coating quality index of the target hot-end component based on the coating thickness and coating porosity corresponding to each of the scanning positions, and the coating uniformity corresponding to each of the target areas, includes:

[0011] For any of the target areas, the coating quality index corresponding to the target area is determined based on the coating uniformity corresponding to the target area, the coating thickness and the coating porosity corresponding to each of the scanning positions included in the target area;

[0012] The evaluation weight of the target region is determined based on its location on the surface of the target hot end component.

[0013] The coating quality index of the target hot end component is determined based on the evaluation weight corresponding to each target region and the coating quality index corresponding to each target region.

[0014] In one embodiment, determining the coating quality index corresponding to the target area based on the coating uniformity corresponding to the target area, and the coating thickness and coating porosity corresponding to each scanning position included in the target area, includes:

[0015] Based on the relationship between the coating thickness and the target coating thickness range corresponding to the target area, the coating thickness quality index corresponding to the coating thickness is determined, and based on the relationship between the coating porosity and the target coating porosity range corresponding to the target area, the coating porosity quality index corresponding to the coating porosity is determined.

[0016] Based on the location of the target region on the surface of the target hot end component, the weights of the coating thickness quality index, coating porosity quality index, and coating uniformity allocation index are respectively assigned.

[0017] Based on the coating thickness quality index, the coating porosity quality index, the coating uniformity, and the weights of each index, the coating quality index corresponding to the target area is determined.

[0018] In one embodiment, determining the coating thickness corresponding to the scanning position based on the acquisition time difference of each of the peak regions includes:

[0019] Based on the incident angle of the terahertz wave on the coating surface, the refraction angle of the terahertz wave in the coating is determined;

[0020] The optical path of the terahertz wave in the coating is determined based on the refraction angle, and the coating thickness corresponding to the scanning position is determined based on the optical path and the acquisition time difference of each peak region.

[0021] In one embodiment, determining the coating porosity corresponding to the scanning position based on the amplitude and phase of each of the peak regions includes:

[0022] The estimated refractive index of the coating is determined, and a theoretical transmission function of terahertz waves in the coating is constructed based on the estimated refractive index. Based on the theoretical transmission function and the amplitude and phase of the peak region on the corresponding coating surface, the theoretical amplitude and theoretical phase of the peak region on the corresponding coating bottom surface are determined.

[0023] The estimated refractive index is adjusted based on the first difference between the theoretical amplitude and the amplitude of the peak region corresponding to the bottom surface of the coating, and the second difference between the theoretical phase and the phase of the peak region corresponding to the bottom surface of the coating, until the first difference and the second difference meet the preset requirements, and the current estimated refractive index is taken as the target refractive index of the coating.

[0024] The dielectric constant of the coating is determined based on the target refractive index, and the porosity of the coating corresponding to the scanning position is determined based on the dielectric constant.

[0025] In one embodiment, determining the coating porosity corresponding to the scanning position based on the dielectric constant includes:

[0026] The porosity of the coating corresponding to the scanning position is determined based on the dielectric constant of air, the dielectric constant of the dense coating, and the dielectric constant of the coating.

[0027] In one embodiment, determining the coating uniformity of the target region based on the coating thickness corresponding to each of the scanned positions included in the target region includes:

[0028] Based on the coating thickness corresponding to each scanning position within the target region, a two-dimensional grayscale image of the target region is generated; the two-dimensional grayscale image is used to characterize the coating thickness distribution of the target region.

[0029] Determine the standard deviation of pixel values ​​for each pixel in the two-dimensional grayscale image, and determine the coating uniformity corresponding to the target region based on the difference between the standard deviation of pixel values ​​and the standard deviation of reference pixel values.

[0030] Secondly, this application also provides a device for evaluating the quality of thermal barrier coatings for aero-engines based on terahertz technology. The device includes:

[0031] The scanning module is used to perform terahertz wave scanning on the surface of the target hot end component and to acquire the terahertz wave reflection time-domain spectrum generated at the scanning position.

[0032] The first determining module is used to determine the peak region of the corresponding coating surface and the peak region of the corresponding coating bottom surface in the terahertz wave reflection time domain spectrum, determine the coating thickness corresponding to the scanning position based on the acquisition time difference of each peak region, and determine the coating porosity corresponding to the scanning position according to the amplitude and phase of each peak region.

[0033] The second determining module is used to divide the surface of the target hot end component into target regions, and determine the coating uniformity corresponding to the target region based on the coating thickness corresponding to each scanning position included in the target region.

[0034] The third determining module is used to determine the coating quality index of the target hot end component based on the coating thickness and coating porosity corresponding to each of the scanning positions, and the coating uniformity corresponding to each of the target areas.

[0035] In one embodiment, the third determining module is further configured to:

[0036] For any of the target areas, the coating quality index corresponding to the target area is determined based on the coating uniformity corresponding to the target area, the coating thickness and the coating porosity corresponding to each of the scanning positions included in the target area;

[0037] The evaluation weight of the target region is determined based on its location on the surface of the target hot end component.

[0038] The coating quality index of the target hot end component is determined based on the evaluation weight corresponding to each target region and the coating quality index corresponding to each target region.

[0039] In one embodiment, the third determining module is further configured to:

[0040] Based on the relationship between the coating thickness and the target coating thickness range corresponding to the target area, the coating thickness quality index corresponding to the coating thickness is determined, and based on the relationship between the coating porosity and the target coating porosity range corresponding to the target area, the coating porosity quality index corresponding to the coating porosity is determined.

[0041] Based on the location of the target region on the surface of the target hot end component, the weights of the coating thickness quality index, coating porosity quality index, and coating uniformity allocation index are respectively assigned.

[0042] Based on the coating thickness quality index, the coating porosity quality index, the coating uniformity, and the weights of each index, the coating quality index corresponding to the target area is determined.

[0043] In one embodiment, the first determining module is further configured to:

[0044] Based on the incident angle of the terahertz wave on the coating surface, the refraction angle of the terahertz wave in the coating is determined;

[0045] The optical path of the terahertz wave in the coating is determined based on the refraction angle, and the coating thickness corresponding to the scanning position is determined based on the optical path and the acquisition time difference of each peak region.

[0046] In one embodiment, the first determining module is further configured to:

[0047] The estimated refractive index of the coating is determined, and a theoretical transmission function of terahertz waves in the coating is constructed based on the estimated refractive index. Based on the theoretical transmission function and the amplitude and phase of the peak region on the corresponding coating surface, the theoretical amplitude and theoretical phase of the peak region on the corresponding coating bottom surface are determined.

[0048] The estimated refractive index is adjusted based on the first difference between the theoretical amplitude and the amplitude of the peak region corresponding to the bottom surface of the coating, and the second difference between the theoretical phase and the phase of the peak region corresponding to the bottom surface of the coating, until the first difference and the second difference meet the preset requirements, and the current estimated refractive index is taken as the target refractive index of the coating.

[0049] The dielectric constant of the coating is determined based on the target refractive index, and the porosity of the coating corresponding to the scanning position is determined based on the dielectric constant.

[0050] In one embodiment, the first determining module is further configured to:

[0051] The porosity of the coating corresponding to the scanning position is determined based on the dielectric constant of air, the dielectric constant of the dense coating, and the dielectric constant of the coating.

[0052] In one embodiment, the second determining module is further configured to:

[0053] Based on the coating thickness corresponding to each scanning position within the target region, a two-dimensional grayscale image of the target region is generated; the two-dimensional grayscale image is used to characterize the coating thickness distribution of the target region.

[0054] Determine the standard deviation of pixel values ​​for each pixel in the two-dimensional grayscale image, and determine the coating uniformity corresponding to the target region based on the difference between the standard deviation of pixel values ​​and the standard deviation of reference pixel values.

[0055] Thirdly, this application also provides a computer device. The computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement any of the methods described above.

[0056] Fourthly, this application also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program thereon, which, when executed by a processor, implements any of the above methods.

[0057] Fifthly, this application also provides a computer program product. The computer program product includes a computer program that, when executed by a processor, implements any of the above methods.

[0058] The aforementioned terahertz-based method for evaluating the quality of thermal barrier coatings for aero-engines employs terahertz waves capable of penetrating the thermal barrier coating to scan the surface of the target hot-end component. Based on the terahertz wave reflection time-domain spectrum, the coating thickness, porosity, and uniformity in a specific target area are calculated. Then, the coating quality of the target hot-end component is comprehensively evaluated based on the coating thickness, porosity, and uniformity at each scanning location and in each target area. Because terahertz waves can penetrate thermal barrier coatings and have relatively long wavelengths, they produce significant reflection peaks on both the surface and bottom of the coating, and are less affected by minute pores within the coating. Therefore, this embodiment of the application can obtain coating thickness, porosity, uniformity, and other indicators that significantly influence coating quality by analyzing the peak regions of the terahertz wave reflection time-domain spectrum. Since the time-domain spectrum acquisition method is simple, and the methods for obtaining parameters such as acquisition time, amplitude, and phase are also relatively straightforward, the coating quality evaluation method provided in this embodiment can significantly reduce the cost of coating inspection. Attached Figure Description

[0059] Figure 1 This is a flowchart illustrating a method for evaluating the quality of thermal barrier coatings for aero-engines based on terahertz technology in one embodiment.

[0060] Figure 2 This is a flowchart illustrating the coating thickness calculation method in one embodiment;

[0061] Figure 3 This is a flowchart illustrating the coating porosity calculation method in one embodiment;

[0062] Figure 4 This is a flowchart illustrating the coating uniformity calculation method in one embodiment;

[0063] Figure 5 This is a flowchart illustrating the calculation method for coating quality indicators in one embodiment;

[0064] Figure 6 This is a flowchart illustrating the calculation method for the coating quality index of the target area in one embodiment;

[0065] Figure 7 This is a structural block diagram of a terahertz-based aero-engine thermal barrier coating quality assessment device in one embodiment.

[0066] Figure 8 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0067] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0068] In one embodiment, such as Figure 1 As shown, a method for evaluating the quality of thermal barrier coatings for aero-engines based on terahertz technology is provided. This embodiment illustrates the method by applying it to a server; however, it is understood that the method can also be applied to a terminal, or to a system including both a terminal and a server, and implemented through interaction between the terminal and the server. In this embodiment, the method includes the following steps:

[0069] Step 102: Perform terahertz wave scanning on the surface of the target hot end component and acquire the terahertz wave reflection time domain spectrum generated at the scanning position.

[0070] In this embodiment, the target hot-end component is a component in an aero-engine whose coating quality needs to be inspected, such as turbine blades or combustion chambers. The surface of the target hot-end component may have curved and planar regions. To ensure that every scanning position on the surface of the target hot-end component can be scanned, a robotic arm can be used to hold a terahertz source for terahertz wave scanning.

[0071] The scanning positions of the target hot-end component can be preset according to actual needs. For example, based on experience, it can be determined which areas of the coating of the target hot-end component are prone to damage, and several positions in these areas can be selected as scanning positions. Alternatively, the surface of the target hot-end component can be scanned sequentially. During the sequential scanning process, when the distance between the terahertz source and the previous scanning position reaches a preset distance, the current position of the terahertz source is selected as the scanning position.

[0072] At each scanning position, a terahertz wave is emitted onto the surface of the target hot end component at a certain incident angle. Then, the time-domain spectrum of the reflected wave generated by the terahertz wave on the surface of the target hot end component is collected, which is the terahertz wave reflection time-domain spectrum.

[0073] Step 104: Determine the peak region on the coating surface and the peak region on the coating bottom surface in the terahertz wave reflection time domain spectrum; determine the coating thickness corresponding to the scanning position based on the acquisition time difference of each peak region; and determine the coating porosity corresponding to the scanning position based on the amplitude and phase of each peak region.

[0074] In this embodiment, each time a terahertz wave enters a different medium, it generates a reflected wave. When the reflected wave is collected, a reflection peak will appear in the terahertz wave reflection time-domain spectrum, and the region where the reflection peak is located is the peak region. For example, the region within a certain time range centered on the reflection peak in the terahertz wave reflection time-domain spectrum can be regarded as the peak region.

[0075] Based on the surface structure of the target hot-end component, the peak regions of terahertz waves reflected at the coating surface and the peak regions of terahertz waves reflected at the coating bottom can be obtained from the terahertz wave reflection time-domain spectrum. For example, when the surface structure of the target hot-end component is a ceramic top layer-adhesive layer-metal substrate (where the ceramic top layer is also the thermal barrier coating), the properties of the adhesive layer will cause the terahertz waves to be completely reflected at the adhesive layer surface. Therefore, the terahertz waves will only be reflected at the air-ceramic top layer surface, the interior of the ceramic top layer (which may contain pores), and the ceramic top layer bottom-adhesive layer. Furthermore, since the pore size inside the ceramic top layer is usually much smaller than the wavelength of the terahertz waves, the reflected waves generated inside the ceramic top layer are generally weak. Therefore, the first relatively strong reflection peak in the terahertz wave reflection time-domain spectrum can be selected as the peak region corresponding to the coating surface, and the second relatively strong reflection peak can be selected as the peak region corresponding to the coating bottom.

[0076] When the target hot-end component has other types of surface structures, a similar method can be used to determine which peak region corresponds to the coating surface and which peak region corresponds to the coating bottom surface. The embodiments of this application will not be elaborated further here.

[0077] After determining the peak regions on the coating surface and the bottom surface of the coating, the time corresponding to the boundary of these two peak regions can be taken as the acquisition time of the peak region. The acquisition time difference is the difference between the acquisition time of the bottom surface peak region and the acquisition time of the surface peak region. Based on the acquisition time difference, the flight time of the terahertz wave inside the coating can be calculated. Further combining this with the propagation direction and speed of the terahertz wave within the coating, the thickness of the coating can be determined. The propagation direction and speed of the terahertz wave within the coating can be obtained experimentally.

[0078] Alternatively, the coating thickness can be calculated by combining the concept of optical path length and Snell's law. See also Figure 2 As shown, it includes:

[0079] Step 202: Determine the refraction angle of the terahertz wave in the coating based on the incident angle of the terahertz wave on the coating surface;

[0080] Step 204: Determine the optical path of the terahertz wave in the coating based on the refraction angle, and determine the coating thickness corresponding to the scanning position based on the optical path and the acquisition time difference of each peak region.

[0081] In this embodiment, the optical path length of the terahertz wave inside the coating is related to the refraction angle of the terahertz wave when it is incident on the coating. The refraction angle can be calculated according to Snell's law. Snell's law states that when electromagnetic waves, such as light waves, travel from one medium to another, the ratio of the sine of the incident angle to the sine of the refraction angle is equal to the ratio of the propagation speeds of the electromagnetic waves in the two media. The propagation speed of the electromagnetic wave in the medium is the ratio of the propagation speed of the electromagnetic wave in a vacuum (i.e., the speed of light) to the refractive index of the medium. Therefore, the refraction angle of the terahertz wave incident on the coating can be expressed as formula (I):

[0082] Formula (1)

[0083] in, For the angle of refraction, Angle of incidence Let be the refractive index of the medium above the coating. The refractive index of the coating can be determined experimentally or calculated as described below. It should be noted that if the coating is the outermost layer on the surface of the target hot-end component, the medium above the coating is air. This is the angle at which the terahertz wave is emitted from the terahertz source. If the coating is not the outermost layer on the surface of the target hot-end component, it is necessary to continue to determine the incident angle of the terahertz wave on the coating surface according to Snell's law and the angle at which the terahertz wave is emitted from the terahertz source.

[0084] After obtaining the refraction angle, since the terahertz wave propagates along the refraction angle inside the coating, and the reflection angle is equal to the refraction angle, the optical path length of the terahertz wave from the incident coating to the reflected coating is equal to twice the ratio of the coating thickness to the cosine of the refraction angle. The propagation speed of the terahertz wave inside the coating is the ratio of the speed of light to the refractive index of the coating. Based on the product of the propagation speed of the terahertz wave inside the coating and the time difference in acquisition, the specific value of the optical path length can be calculated, and thus the specific value of the coating thickness can be calculated. The coating thickness formula obtained based on the above principle is shown in Formula (II):

[0085] Formula (II)

[0086] in, For coating thickness, At the speed of light, This is due to the time difference in data collection.

[0087] The coating porosity can also be calculated based on the amplitude and phase of the peak region. Since coating porosity affects the reflection and refraction of terahertz waves within the coating, the difference between the amplitude and phase of the terahertz wave reflected from the coating and the amplitude and phase of the terahertz wave incident on the coating is correlated with the coating porosity. The specific manifestation of this correlation can be determined experimentally. For example, a function expressing the relationship between the difference in amplitude and phase and the coating porosity can be fitted based on experimental results. In practical applications, the coating porosity can be calculated based on this function, the amplitude and phase of the peak region corresponding to the coating surface, and the amplitude and phase of the peak region corresponding to the coating bottom surface.

[0088] Alternatively, the porosity of the coating can be calculated based on the difference between the dielectric constant of the primary coating and that of the dense coating. Since the dielectric constant is related to the refractive index of the medium, the dielectric constant of the coating can be calculated from its refractive index. The refractive index of the coating can be obtained by modeling the propagation of terahertz waves within the coating and iterating the model until a refractive index is found that matches the amplitude and phase of each peak region. See also... Figure 3 As shown, the process includes:

[0089] Step 302: Determine the estimated refractive index of the coating, construct the theoretical transmission function of the terahertz wave in the coating based on the estimated refractive index, and determine the theoretical amplitude and theoretical phase of the peak region on the bottom surface of the coating based on the theoretical transmission function and the amplitude and phase of the peak region on the corresponding coating surface.

[0090] Step 304: Adjust the estimated refractive index based on the first difference between the theoretical amplitude and the amplitude of the peak region of the corresponding coating bottom surface, and the second difference between the theoretical phase and the phase of the peak region of the corresponding coating bottom surface, until the first difference and the second difference meet the preset requirements, and use the current estimated refractive index as the target refractive index of the coating.

[0091] Step 306: Determine the dielectric constant of the coating based on the target refractive index, and determine the coating porosity corresponding to the scanning position based on the dielectric constant.

[0092] In this embodiment, the estimated refractive index is a complex number and can be set empirically. Based on the estimated refractive index, a theoretical transfer function can be constructed to describe the phase and amplitude changes of terahertz waves during propagation. Combining the theoretical transfer function with the amplitude and phase of the peak region on the corresponding coating surface, the theoretical amplitude and theoretical phase of the peak region on the bottom surface of the corresponding coating can be calculated. Then, the estimated refractive index can be adjusted according to the difference between the theoretical amplitude and the actual amplitude (hereinafter referred to as the first difference) and the difference between the theoretical phase and the actual phase (hereinafter referred to as the second difference). The above process is repeated until the first difference and the second difference are less than a certain preset value, and the target refractive index can be obtained.

[0093] The portion of the theoretical transfer function used to describe amplitude variation can be constructed based on Fresnel's law. Fresnel's law describes the relationship between the amplitudes of the incident wave, reflected wave, and refracted wave when an electromagnetic wave enters different media. Based on practical applications, after a terahertz source emits a terahertz wave, it is necessary to determine how many different media the terahertz wave passes through and whether reflection and refraction occur upon entering different media. This allows us to construct the correlation between the amplitude of the peak region corresponding to the coating surface (corresponding to the reflected terahertz wave at the coating surface) and the amplitude of the peak region corresponding to the bottom surface of the coating (corresponding to the reflected terahertz wave at the bottom surface of the coating). Taking the surface structure of the target hot-end component in the aforementioned embodiment as a ceramic top layer (coating) - adhesive layer - metal substrate, and the property of the adhesive layer causing complete reflection of the terahertz wave at the adhesive layer surface as an example, the relationship between the amplitude of the peak region on the coating surface and the original amplitude of the terahertz wave emitted by the terahertz source can be determined as follows: the amplitude of the peak region on the coating surface is equal to the product of the original amplitude and the air-coating interface reflection coefficient. The relationship between the amplitude of the peak region on the bottom surface of the coating and the original amplitude of the terahertz wave emitted by the terahertz source is as follows: the amplitude of the peak region on the bottom surface of the coating is equal to the product of the original amplitude and the refractive index of the air-coating interface, the reflection coefficient of the coating-adhesive layer interface, and the refractive index of the coating-air interface. Therefore, the relationship between the amplitude of the peak region on the surface of the coating and the amplitude of the peak region on the bottom surface of the coating is as follows: the amplitude of the peak region on the bottom surface of the coating is equal to the ratio of the product of the refractive index of the air-coating interface, the reflection coefficient of the coating-adhesive layer interface, and the refractive index of the coating-air interface to the reflection coefficient of the air-coating interface.

[0094] The portion of the theoretical transfer function used to describe the phase change can be constructed based on the estimated refractive index. The phase change reflects the delay generated after the terahertz wave propagates inside the coating and can be constructed based on the optical path. The relationship between the optical path and the estimated refractive index can be further referred to the description in the foregoing embodiments, which will not be repeated in this application. Taking the aforementioned ceramic top layer (coating)-adhesive layer-metal substrate model as an example, the theoretical transfer function obtained by combining the amplitude change and the phase change is as shown in formula (III):

[0095] Formula (3)

[0096] Where H is the theoretical transfer function, The refractive index of the air-coating interface. The reflectance coefficient at the coating-adhesive interface. The refractive index of the coating-air interface. The reflectance coefficient at the air-coating interface. The angular frequency of the terahertz wave. For coating thickness, The estimated refractive index is a complex number. It is the speed of light.

[0097] The theoretical amplitude and theoretical phase of the peak region corresponding to the bottom surface of the coating are calculated based on this formula. The estimated refractive index is adjusted based on the first and second differences until the first and second differences meet preset conditions; this estimated refractive index is then taken as the target refractive index. The square of the target refractive index is the dielectric constant of the coating. Since pores introduce air into the coating, altering its dielectric constant, the difference between the dielectric constant of the coating and that of a dense coating (i.e., a pore-free coating) is strongly correlated with the porosity of the coating. The porosity of the coating can be further calculated based on any model describing this correlation.

[0098] In one embodiment, the Looyenga model can be used to calculate porosity. Specifically, the Looyenga model determines the coating porosity corresponding to the scanning position based on the dielectric constant of air, the dielectric constant of the dense coating, and the dielectric constant of the coating itself. The formula can be found in formula (iv):

[0099] Formula (IV)

[0100] in, Let be the real part of the dielectric constant of the coating. Porosity Let be the real part of the dielectric constant of the dense coating. is the real part of the air dielectric constant.

[0101] Step 106: Divide the surface of the target hot end component into target regions, and determine the coating uniformity of the target region based on the coating thickness corresponding to each scanning position contained in the target region.

[0102] In this embodiment, the coating uniformity of the target hot-end component can be calculated on a region-by-region basis. This embodiment does not limit how the surface of the target hot-end component is divided into target regions. It should be noted that target regions can overlap. For example, when the target hot-end component is a turbine blade, the entire turbine blade can be considered as one target region, the blade tip as one target region, the approximately planar portion of the turbine blade as one target region, the curved portion as another target region, and so on.

[0103] Coating uniformity can be calculated based on the coating thickness at the scanned locations within the target region. For example, the mean coating thickness for each target region can be calculated, and the coating uniformity can be calculated based on the difference between each scanned location and the mean. Alternatively, image processing techniques can be used to calculate coating uniformity; see [link to relevant documentation]. Figure 4 As shown, it includes:

[0104] Step 402: Based on the coating thickness corresponding to each scanning position within the target area, generate a two-dimensional grayscale image of the target area; the two-dimensional grayscale image is used to characterize the coating thickness distribution of the target area.

[0105] Step 404: Determine the standard deviation of pixel values ​​for each pixel in the two-dimensional grayscale image, and determine the coating uniformity corresponding to the target area based on the difference between the standard deviation of pixel values ​​and the standard deviation of reference pixel values.

[0106] In this embodiment, a two-dimensional grayscale image of the target region can be generated based on the coating thickness corresponding to each scan position within the target region. The pixel values ​​of the pixels in the two-dimensional grayscale image are generated based on the coating thickness. The greater the coating thickness, the higher the pixel value. The scan positions are generally discrete, and there may be pixels that do not correspond to the scan positions. For these pixels, image processing methods such as interpolation can be used to obtain their pixel values.

[0107] Two-dimensional grayscale images can also undergo image processing including but not limited to image enhancement, Gaussian filtering, and thresholding. The standard deviation of each pixel value can be further calculated for the processed image. Then, based on the difference between the standard deviation of the pixel values ​​and the standard deviation of the reference pixel values, the coating uniformity corresponding to the target area can be evaluated. The reference pixel value standard deviation can be the maximum possible standard deviation in the two-dimensional grayscale image; assuming the grayscale value range is 0 to 255, the maximum possible standard deviation is 127.5. The ratio between the standard deviation of the pixel values ​​and the standard deviation of the reference pixel values ​​can be calculated, and then the difference between 1 and this ratio can be used to calculate the coating uniformity, so that a larger coating uniformity indicates better coating uniformity. See formula (5):

[0108] Formula (5)

[0109] in, For coating uniformity, The standard deviation of pixel values. The standard deviation of the reference pixel value.

[0110] Step 108: Determine the coating quality index of the target hot end component based on the coating thickness and porosity corresponding to each scanning position and the coating uniformity corresponding to each target area.

[0111] In this embodiment, the coating quality of the target hot-end component is evaluated by combining the coating thickness and porosity at each scanning position, as well as the coating uniformity corresponding to each target area. For example, the coating thickness, coating porosity, and coating uniformity can be scored separately, and the average of all scores can be taken to obtain the coating quality index.

[0112] Alternatively, considering that the coating quality of different target areas has varying impacts on the coating quality of the target hot-end components, different target areas can be scored separately, assigned different weights, and then the scores of each target area can be weighted and summed to obtain the coating quality index. For example... Figure 5 As shown:

[0113] Step 502: For any target area, determine the coating quality index corresponding to the target area based on the coating uniformity corresponding to the target area, and the coating thickness and coating porosity corresponding to each scanning position included in the target area.

[0114] Step 504: Determine the evaluation weight of the target region based on its location on the surface of the target hot end component;

[0115] Step 506: Determine the coating quality index of the target hot end component based on the evaluation weight corresponding to each target area and the coating quality index corresponding to each target area.

[0116] In this embodiment, the coating quality index of the target area can be obtained by scoring the target area based on the coating uniformity of the target area and the coating thickness and porosity corresponding to each scanning position within the target area. The scoring method can be determined according to the different importance of coating uniformity, coating thickness, and coating porosity corresponding to the location of the target area, as well as the coating preparation process, such as... Figure 6 :

[0117] Step 602: Based on the relationship between the coating thickness and the target coating thickness range corresponding to the target area, determine the coating thickness quality index corresponding to the coating thickness, and based on the relationship between the coating porosity and the target coating porosity range corresponding to the target area, determine the coating porosity quality index corresponding to the coating porosity.

[0118] Step 604: Based on the location of the target area on the surface of the target hot end component, the weights of the coating thickness quality index, coating porosity quality index, and coating uniformity allocation index are respectively assigned.

[0119] Step 606: Based on the coating thickness quality index, coating porosity quality index, coating uniformity, and the weight of each index, determine the coating quality index corresponding to the target area.

[0120] In this embodiment, different target coating thickness ranges and target coating porosity ranges can be defined for different target regions. These ranges represent the optimal thickness and porosity ranges that should exist. The target coating thickness and porosity ranges for a target region can be determined based on the importance of the target region and the coating preparation method. For example, when the target region is crucial to the performance of the target hot-end component (e.g., the target hot-end component is a turbine blade, and the target region is the blade tip region), the target coating thickness and porosity ranges can be relatively narrow.

[0121] Taking ABS (Atmospheric Plasma Spraying) and EB-PVD (Electron Beam - Physical Vapor Deposition) as examples, an exemplary calculation method for the coating thickness quality index and coating porosity quality index is shown in formulas (vi) to (ix). Formulas (vii) and (viii) are the calculation methods for ABS preparation, and formulas (vii) and (ix) are the calculation methods for EB-PVD preparation.

[0122] Formula (VI)

[0123] Formula (VII)

[0124] in, d represents the coating thickness quality index.

[0125] Formula (8)

[0126] Formula (IX)

[0127] in, P represents the porosity quality index of the coating.

[0128] Furthermore, based on the location of the target area on the surface of the target hot-end component, weights can be assigned to the coating thickness quality index, coating porosity quality index, and coating uniformity quality index. The weights reflect the importance of these indicators in the target area. Coating thickness affects the coating's thermal insulation effect and stress distribution; coating porosity affects the coating's thermal insulation effect and thermal shock resistance; and coating uniformity affects the coating's structural integrity and local stress distribution. The specific weighting of these indicators can be determined by those skilled in the art based on actual needs. For example, the stress at the blade root is relatively high, so the weight of coating uniformity can be set higher for this target area. For the blade tip, thermal insulation performance is more important, so the weight of the coating thickness quality index can be set higher. For the blade as a whole, coating porosity has the greatest impact, followed by coating uniformity, and then coating thickness. The weights of the coating porosity quality index, coating uniformity, and coating thickness quality index can be set to 0.25, 0.4, and 0.35, respectively.

[0129] After calculating the coating quality index of the target area, the evaluation weight of the target area is determined based on its location importance and thermal insulation requirements. This evaluation weight can also be set according to actual needs; for example, the blade tip is more important to turbine blade performance, so its evaluation weight can be set higher. The evaluation weight of the blade root can be set lower accordingly.

[0130] The coating quality index of the target hot end component can be obtained by weighted summing of the coating quality index corresponding to each target region based on the evaluation weight corresponding to each target region.

[0131] The terahertz-based method for evaluating the quality of thermal barrier coatings for aero-engines provided in this application uses terahertz waves, which can penetrate the thermal barrier coating, to scan the surface of the target hot-end component. Based on the terahertz wave reflection time-domain spectrum, the coating thickness, porosity, and uniformity in a specific target area are calculated. Then, the coating quality of the target hot-end component is comprehensively evaluated based on the coating thickness, porosity, and uniformity of each scanned position. Because terahertz waves can penetrate thermal barrier coatings and have relatively long wavelengths, they produce obvious reflection peaks on both the surface and bottom of the coating, and are less affected by tiny pores in the coating. Therefore, by analyzing the peak regions of the terahertz wave reflection time-domain spectrum, this application can obtain indicators that significantly affect coating quality, such as coating thickness, porosity, and uniformity. Since the time-domain spectrum acquisition method is simple, and the methods for obtaining parameters such as acquisition time, amplitude, and phase are also relatively straightforward, the coating quality evaluation method provided in this application can significantly reduce the coating inspection cost.

[0132] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0133] Based on the same inventive concept, this application also provides a terahertz-based aero-engine thermal barrier coating quality assessment device for implementing the aforementioned terahertz-based aero-engine thermal barrier coating quality assessment method. The solution provided by this device is similar to the implementation described in the above method. Therefore, the specific limitations of one or more embodiments of the terahertz-based aero-engine thermal barrier coating quality assessment device provided below can be found in the above-described limitations of the terahertz-based aero-engine thermal barrier coating quality assessment method, and will not be repeated here.

[0134] In one embodiment, such as Figure 7 As shown, a terahertz-based aero-engine thermal barrier coating quality assessment device 700 is provided, comprising: a scanning module 702, a first determining module 704, a second determining module 706, and a third determining module 708, wherein:

[0135] The scanning module 702 is used to perform terahertz wave scanning on the surface of the target hot end component and to acquire the terahertz wave reflection time domain spectrum generated at the scanning position.

[0136] The first determining module 704 is used to determine the peak region of the corresponding coating surface and the peak region of the corresponding coating bottom surface in the terahertz wave reflection time domain spectrum, determine the coating thickness corresponding to the scanning position based on the acquisition time difference of each peak region, and determine the coating porosity corresponding to the scanning position according to the amplitude and phase of each peak region.

[0137] The second determining module 706 is used to divide the surface of the target hot end component into target regions, and determine the coating uniformity corresponding to the target region based on the coating thickness corresponding to each scanning position included in the target region.

[0138] The third determining module 708 is used to determine the coating quality index of the target hot end component based on the coating thickness and coating porosity corresponding to each of the scanning positions and the coating uniformity corresponding to each of the target areas.

[0139] In one embodiment, the third determining module 708 is further configured to:

[0140] For any of the target areas, the coating quality index corresponding to the target area is determined based on the coating uniformity corresponding to the target area, the coating thickness and the coating porosity corresponding to each of the scanning positions included in the target area;

[0141] The evaluation weight of the target region is determined based on its location on the surface of the target hot end component.

[0142] The coating quality index of the target hot end component is determined based on the evaluation weight corresponding to each target region and the coating quality index corresponding to each target region.

[0143] In one embodiment, the third determining module 708 is further configured to:

[0144] Based on the relationship between the coating thickness and the target coating thickness range corresponding to the target area, the coating thickness quality index corresponding to the coating thickness is determined, and based on the relationship between the coating porosity and the target coating porosity range corresponding to the target area, the coating porosity quality index corresponding to the coating porosity is determined.

[0145] Based on the location of the target region on the surface of the target hot end component, the weights of the coating thickness quality index, coating porosity quality index, and coating uniformity allocation index are respectively assigned.

[0146] Based on the coating thickness quality index, the coating porosity quality index, the coating uniformity, and the weights of each index, the coating quality index corresponding to the target area is determined.

[0147] In one embodiment, the first determining module 704 is further configured to:

[0148] Based on the incident angle of the terahertz wave on the coating surface, the refraction angle of the terahertz wave in the coating is determined;

[0149] The optical path of the terahertz wave in the coating is determined based on the refraction angle, and the coating thickness corresponding to the scanning position is determined based on the optical path and the acquisition time difference of each peak region.

[0150] In one embodiment, the first determining module 704 is further configured to:

[0151] The estimated refractive index of the coating is determined, and a theoretical transmission function of terahertz waves in the coating is constructed based on the estimated refractive index. Based on the theoretical transmission function and the amplitude and phase of the peak region on the corresponding coating surface, the theoretical amplitude and theoretical phase of the peak region on the corresponding coating bottom surface are determined.

[0152] The estimated refractive index is adjusted based on the first difference between the theoretical amplitude and the amplitude of the peak region corresponding to the bottom surface of the coating, and the second difference between the theoretical phase and the phase of the peak region corresponding to the bottom surface of the coating, until the first difference and the second difference meet the preset requirements, and the current estimated refractive index is taken as the target refractive index of the coating.

[0153] The dielectric constant of the coating is determined based on the target refractive index, and the porosity of the coating corresponding to the scanning position is determined based on the dielectric constant.

[0154] In one embodiment, the first determining module 704 is further configured to:

[0155] The porosity of the coating corresponding to the scanning position is determined based on the dielectric constant of air, the dielectric constant of the dense coating, and the dielectric constant of the coating.

[0156] In one embodiment, the second determining module 706 is further configured to:

[0157] Based on the coating thickness corresponding to each scanning position within the target region, a two-dimensional grayscale image of the target region is generated; the two-dimensional grayscale image is used to characterize the coating thickness distribution of the target region.

[0158] Determine the standard deviation of pixel values ​​for each pixel in the two-dimensional grayscale image, and determine the coating uniformity corresponding to the target region based on the difference between the standard deviation of pixel values ​​and the standard deviation of reference pixel values.

[0159] Each module in the above-mentioned device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0160] In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 8As shown, the computer device includes a processor, memory, and a network interface connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The network interface is used for communication with external terminals via a network connection. When the computer program is executed by the processor, it implements a method for evaluating the quality of thermal barrier coatings for aero-engines based on terahertz technology.

[0161] Those skilled in the art will understand that Figure 8 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0162] In one embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments.

[0163] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon that, when executed by a processor, implements the steps in the above method embodiments.

[0164] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above method embodiments.

[0165] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0166] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0167] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0168] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for evaluating the quality of a thermal barrier coating of an aeroengine based on terahertz technology, characterized in that, The method comprises: performing terahertz wave scanning on the surface of the target hot-end component, and collecting terahertz wave reflection time-domain spectrum generated by the terahertz wave at the scanning position; determining a peak region corresponding to the surface of the coating and a peak region corresponding to the bottom surface of the coating in the terahertz wave reflection time-domain spectrum, determining the coating thickness corresponding to the scanning position based on the time difference of collection of each peak region, and determining the coating porosity corresponding to the scanning position according to the amplitude and phase of each peak region; dividing the surface of the target hot-end component into target regions, and determining the coating uniformity corresponding to the target region based on the coating thickness corresponding to each scanning position contained in the target region; determining the coating quality index of the target hot-end component according to the coating thickness and the coating porosity corresponding to each scanning position, and the coating uniformity corresponding to each target region; the determination of the coating quality index of the target hot-end component according to the coating thickness and the coating porosity corresponding to each scanning position, and the coating uniformity corresponding to each target region comprises: for any target region, determining the coating quality index corresponding to the target region according to the coating uniformity corresponding to the target region and the coating thickness and the coating porosity corresponding to each scanning position contained in the target region; determining the evaluation weight of the target region according to the position of the target region on the surface of the target hot-end component; determining the coating quality index of the target hot-end component according to the evaluation weight corresponding to each target region and the coating quality index corresponding to each target region.

2. The method of claim 1, wherein, the determination of the coating quality index corresponding to the target region according to the coating uniformity corresponding to the target region and the coating thickness and the coating porosity corresponding to each scanning position contained in the target region comprises: determining the coating thickness quality index corresponding to the coating thickness according to the relationship between the coating thickness and the target coating thickness range corresponding to the target region, and determining the coating porosity quality index corresponding to the coating porosity according to the relationship between the coating porosity and the target coating porosity range corresponding to the target region; allocating index weights to the coating thickness quality index, the coating porosity quality index and the coating uniformity respectively based on the position of the target region on the surface of the target hot-end component; determining the coating quality index corresponding to the target region based on the coating thickness quality index, the coating porosity quality index, the coating uniformity and each index weight.

3. The method of claim 1, wherein, the determination of the coating thickness corresponding to the scanning position based on the time difference of collection of each peak region comprises: determining the refraction angle of the terahertz wave in the coating based on the incidence angle of the terahertz wave on the surface of the coating; determining the optical path of the terahertz wave in the coating according to the refraction angle, and determining the coating thickness corresponding to the scanning position according to the optical path and the time difference of collection of each peak region.

4. The method of claim 1, wherein, The coating porosity corresponding to the scanning position is determined according to the amplitude and phase of each peak region, and the coating porosity corresponding to the scanning position is determined according to the dielectric constant. The estimated refractive index of the coating is determined, a theoretical transmission function of the terahertz wave in the coating is constructed based on the estimated refractive index, and the theoretical amplitude and the theoretical phase of the peak region corresponding to the bottom surface of the coating are determined based on the theoretical transmission function and the amplitude and the phase of the peak region corresponding to the surface of the coating. The estimated refractive index is adjusted based on a first difference between the theoretical amplitude and the amplitude of the peak region corresponding to the bottom surface of the coating, and based on a second difference between the theoretical phase and the phase of the peak region corresponding to the bottom surface of the coating, until the first difference and the second difference meet the preset requirements, and the current estimated refractive index is taken as the target refractive index of the coating. The dielectric constant of the coating is determined according to the target refractive index, and the coating porosity corresponding to the scanning position is determined according to the dielectric constant.

5. The method of claim 4, wherein, The coating porosity corresponding to the scanning position is determined according to the dielectric constant. The coating porosity corresponding to the scanning position is determined according to the dielectric constant.

6. The method of claim 1, wherein, The coating uniformity corresponding to the target region is determined based on the coating thickness corresponding to each scanning position included in the target region. A two-dimensional gray scale image of the target region is generated based on the coating thickness corresponding to each scanning position included in the target region, and the two-dimensional gray scale image is used to represent the coating thickness distribution of the target region. The coating uniformity corresponding to the target region is determined based on the difference between the pixel value standard deviation of each pixel in the two-dimensional gray scale image and a reference pixel value standard deviation.

7. A device for evaluating the quality of a thermal barrier coating of an aeroengine based on terahertz technology, characterized in that, The device comprises: The scanning module is configured to perform terahertz wave scanning on the surface of the target hot-end component, and collect terahertz wave reflection time-domain spectra generated by the terahertz wave at the scanning positions. The first determination module is configured to determine the peak regions corresponding to the surface of the coating and the peak regions corresponding to the bottom surface of the coating in the terahertz wave reflection time-domain spectra, determine the coating thickness corresponding to the scanning position based on the time difference of collecting each peak region, and determine the coating porosity corresponding to the scanning position according to the amplitude and the phase of each peak region. The second determination module is configured to divide the surface of the target hot-end component into target regions, and determine the coating uniformity corresponding to each target region based on the coating thickness corresponding to each scanning position included in the target region. The third determination module is configured to determine the coating quality index of the target hot-end component according to the coating thickness and the coating porosity corresponding to each scanning position, and the coating uniformity corresponding to each target region. The third determining module is further configured to: for any target region, determine a coating quality index corresponding to the target region according to the coating uniformity corresponding to the target region and the coating thickness and the coating porosity corresponding to each scanning position included in the target region; determine an evaluation weight of the target region according to a position of the target region on the surface of the target hot end component; and determine a coating quality index of the target hot end component according to the evaluation weight corresponding to each target region and the coating quality index corresponding to each target region.

8. The apparatus of claim 7, wherein, The first determining module is further configured to: determine a refraction angle of the terahertz wave in the coating based on an incident angle of the terahertz wave on the surface of the coating; determine an optical path of the terahertz wave in the coating according to the refraction angle, and determine the coating thickness corresponding to each scanning position according to the optical path and a time difference of acquisition of each peak region. 9.A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer device is configured to perform the method according to any one of claims 1-8 when the computer program is executed by the processor. The processor, when executing the computer program, implements the steps of the method in any one of claims 1 to 6.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program, when executed by the processor, implements the steps of the method in any one of claims 1 to 6.

Images