Terahertz technology-based aero-engine thermal barrier coating quality evaluation method

Abstract

The invention 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 terahertz waves at a scanning position; determining a peak value region corresponding to the surface of the coating and a peak value region corresponding to the bottom surface of the coating in the terahertz wave reflection time-domain spectrum, determining the thickness of the coating corresponding to the scanning position based on the acquisition time difference of each peak value region, and determining the porosity of the coating corresponding to the scanning position according to the amplitude and phase of each peak value region; target area division is carried out on the surface of the target hot end component, and the coating uniformity corresponding to a target area is determined based on the coating thickness corresponding to each scanning position contained in the target area; and determining a 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 area. By adopting the method, the coating evaluation cost can be reduced.

Description

Technical Field

[0001] The present application relates to the field of terahertz technology, and in particular to a method for evaluating the quality of thermal barrier coatings of aircraft engines based on terahertz technology. Background Art

[0002] Currently, the temperatures experienced by hot-end components of aircraft engines, such as turbine blades, often far exceed the upper limits of the blade metal's tolerance. Therefore, thermal barrier coatings (TBCs) are increasingly being used as a critical insulation and cooling method. TBCs are a layer of ceramic-based composite material applied to a metal surface, with a thickness ranging from tens to hundreds of microns. Coating quality critically impacts the performance of hot-end components and, ultimately, the engine. However, coatings can crack, debond, and even fall off during service. Therefore, accurate testing and monitoring of TBC quality are crucial in design, service, lifespan assessment, and subsequent maintenance.

[0003] Acoustic emission (AE) is a technique used to detect internal coating damage. This technology dynamically monitors coating damage by collecting stress wave signals released by material deformation or crack propagation. However, AE signals are complex and require analysis using advanced sensors and signal analysis systems, leading to high detection costs. Summary of the Invention

[0004] Based on this, it is necessary to provide a quality assessment method for aircraft engine thermal barrier coatings based on terahertz technology to address the above technical issues.

[0005] In a first aspect, the present application provides a method for evaluating the quality of thermal barrier coatings on aircraft engines based on terahertz technology. The method comprises:

[0006] Scanning the surface of the target hot end component with a terahertz wave and collecting the terahertz wave reflection time domain spectrum generated by the terahertz wave at the scanning position;

[0007] Determining a peak area corresponding to the coating surface and a peak area corresponding to the coating bottom surface in the terahertz wave reflection time domain spectrum, determining the coating thickness corresponding to the scanning position based on the acquisition time difference of each peak area, and determining the coating porosity corresponding to the scanning position based on the amplitude and phase of each peak area;

[0008] Dividing the surface of the target hot end component into target areas, and determining the coating uniformity corresponding to the target area based on the coating thickness corresponding to each scanning position included in the target area;

[0009] The coating quality index of the target hot end component is determined according to the coating thickness and the 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 the coating porosity corresponding to each scanning position, and the coating uniformity corresponding to each target area, includes:

[0011] For any target area, determining a coating quality index corresponding to the target area according to the coating uniformity corresponding to the target area, and the coating thickness and the coating porosity corresponding to each scanning position included in the target area;

[0012] determining an evaluation weight of the target area according to a position of the target area on the surface of the target hot end component;

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

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

[0015] Determining a coating thickness quality index corresponding to the coating thickness based on a relationship between the coating thickness and a target coating thickness range corresponding to the target area, and determining a coating porosity quality index corresponding to the coating porosity based on a relationship between the coating porosity and a target coating porosity range corresponding to the target area;

[0016] Based on the position of the target area on the surface of the target hot end component, assigning index weights to the coating thickness quality index, the coating porosity quality index, and the coating uniformity quality index respectively;

[0017] Based on the coating thickness quality index, the coating porosity quality index, the coating uniformity and the weight 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 peak area includes:

[0019] determining a refraction angle of the terahertz wave in the coating based on an incident angle of the terahertz wave on the coating surface;

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

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

[0022] Determining an estimated refractive index of the coating, constructing a theoretical transmission function of the terahertz wave in the coating based on the estimated refractive index, and determining a theoretical amplitude and theoretical phase of a peak area corresponding to a bottom surface of the coating based on the theoretical transmission function and the amplitude and phase of a peak area corresponding to the coating surface;

[0023] Adjusting the estimated refractive index based on a first difference between the theoretical amplitude and the amplitude of the peak area corresponding to the bottom surface of the coating, and based on a second difference between the theoretical phase and the phase of the peak area corresponding to the bottom surface of the coating, until the first difference and the second difference meet preset requirements, and using the current estimated refractive index as the target refractive index of the coating;

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

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

[0026] The porosity of the coating corresponding to the scanning position is determined according to 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 corresponding to the target area based on the coating thickness corresponding to each scanning position included in the target area includes:

[0028] generating a two-dimensional grayscale image of the target area based on the coating thickness corresponding to each scanning position contained in the target area; the two-dimensional grayscale image is used to characterize the coating thickness distribution of the target area;

[0029] A pixel value standard deviation of each pixel in the two-dimensional grayscale image is determined, and a coating uniformity corresponding to the target area is determined based on a difference between the pixel value standard deviation and a reference pixel value standard deviation.

[0030] In a second aspect, the present application also provides a device for evaluating the quality of thermal barrier coatings on aircraft engines based on terahertz technology. The device comprises:

[0031] A scanning module is used to scan the surface of the target hot end component with a terahertz wave and collect the terahertz wave reflection time domain spectrum generated by the terahertz wave at the scanning position;

[0032] a first determination module, configured to determine a peak area corresponding to the coating surface and a peak area corresponding to the coating bottom 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 area, and determine the coating porosity corresponding to the scanning position based on the amplitude and phase of each peak area;

[0033] a second determining module, configured to divide the surface of the target hot end component into target areas, and determine the coating uniformity corresponding to the target area based on the coating thickness corresponding to each scanning position included in the target area;

[0034] The third determination module is used 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 area.

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

[0036] For any target area, determining a coating quality index corresponding to the target area according to the coating uniformity corresponding to the target area, and the coating thickness and the coating porosity corresponding to each scanning position included in the target area;

[0037] determining an evaluation weight of the target area according to a position of the target area on the surface of the target hot end component;

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

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

[0040] Determining a coating thickness quality index corresponding to the coating thickness based on a relationship between the coating thickness and a target coating thickness range corresponding to the target area, and determining a coating porosity quality index corresponding to the coating porosity based on a relationship between the coating porosity and a target coating porosity range corresponding to the target area;

[0041] Based on the position of the target area on the surface of the target hot end component, assigning index weights to the coating thickness quality index, the coating porosity quality index, and the coating uniformity quality index respectively;

[0042] Based on the coating thickness quality index, the coating porosity quality index, the coating uniformity and the weight 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] determining a refraction angle of the terahertz wave in the coating based on an incident angle of the terahertz wave on the coating surface;

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

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

[0047] Determining an estimated refractive index of the coating, constructing a theoretical transmission function of the terahertz wave in the coating based on the estimated refractive index, and determining a theoretical amplitude and theoretical phase of a peak area corresponding to a bottom surface of the coating based on the theoretical transmission function and the amplitude and phase of a peak area corresponding to the coating surface;

[0048] Adjusting the estimated refractive index based on a first difference between the theoretical amplitude and the amplitude of the peak area corresponding to the bottom surface of the coating, and based on a second difference between the theoretical phase and the phase of the peak area corresponding to the bottom surface of the coating, until the first difference and the second difference meet preset requirements, and using the current estimated refractive index as the target refractive index of the coating;

[0049] The dielectric constant of the coating is determined according to the target refractive index, and the porosity of the coating corresponding to the scanning position is determined according to 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 according to 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] generating a two-dimensional grayscale image of the target area based on the coating thickness corresponding to each scanning position contained in the target area; the two-dimensional grayscale image is used to characterize the coating thickness distribution of the target area;

[0054] A pixel value standard deviation of each pixel in the two-dimensional grayscale image is determined, and a coating uniformity corresponding to the target area is determined based on a difference between the pixel value standard deviation and a reference pixel value standard deviation.

[0055] In a third aspect, the present application further provides a computer device, wherein the computer device comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements any of the above methods when executing the computer program.

[0056] In a fourth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program implements any of the above methods when executed by a processor.

[0057] In a fifth aspect, the present application further provides a computer program product, comprising a computer program, which implements any of the above methods when executed by a processor.

[0058] The above-mentioned terahertz-based method for assessing the quality of aircraft engine thermal barrier coatings uses terahertz waves, which can penetrate the thermal barrier coating, to scan the surface of a 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. The coating quality of the target hot-end component is then comprehensively assessed based on the coating thickness, porosity, and uniformity at each scanning position and the coating uniformity in each target area. Because terahertz waves can penetrate thermal barrier coatings and have a relatively long wavelength, they produce distinct reflection peaks on the coating surface and bottom surface and are less susceptible to interference from tiny pores in the coating. Therefore, by analyzing the peak region of the terahertz wave reflection time-domain spectrum, the present embodiment can determine indicators such as coating thickness, porosity, and uniformity, which have a significant impact on coating quality. Because the time-domain spectrum acquisition method is simple, and the method for obtaining parameters such as acquisition time, amplitude, and phase is also relatively simple, the coating quality assessment method provided by the present embodiment can significantly reduce coating inspection costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 1 is a flow chart of a method for evaluating the quality of thermal barrier coatings of an aerospace engine based on terahertz technology in one embodiment;

[0060] Figure 2 Schematic diagram of a process for calculating coating thickness in one embodiment;

[0061] Figure 3 Schematic diagram of a process for calculating coating porosity in one embodiment;

[0062] Figure 4 Schematic diagram of a process for calculating coating uniformity in one embodiment;

[0063] Figure 5 Schematic diagram of a process for calculating a coating quality index in one embodiment;

[0064] Figure 6 Schematic diagram of a flow chart of a method for calculating a coating quality index of a target area in one embodiment;

[0065] Figure 7 This is a structural block diagram of a device for evaluating the quality of thermal barrier coatings on aircraft engines based on terahertz technology in one embodiment;

[0066] Figure 8 FIG. 1 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0067] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0068] In one embodiment, Figure 1 As shown, a method for evaluating the quality of thermal barrier coatings on aircraft engines based on terahertz technology is provided. This embodiment uses the method applied to a server as an example. It is understood that the method can also be applied to a terminal, or to a system including a terminal and a server, and implemented through the interaction between the terminal and the server. In this embodiment, the method includes the following steps:

[0069] Step 102 : Scan the surface of the target hot end component with a terahertz wave, and collect a terahertz wave reflection time domain spectrum generated by the terahertz wave at the scanning position.

[0070] In the embodiments of this application, the target hot-end component is an aircraft engine component whose coating quality needs to be tested, such as a turbine blade or combustion chamber. The surface of the target hot-end component may have curved and flat areas. To ensure that every required scanning position on the target hot-end component surface can be scanned, a robotic arm can be used to clamp the terahertz source for terahertz wave scanning.

[0071] The scanning positions of the target hot-end component can be pre-set based on actual needs. For example, based on empirically determined areas of the target hot-end component where the coating is most susceptible to damage, several locations in each of 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 location of the terahertz source is selected as the scanning position.

[0072] At each scanning position, a certain incident angle is used to emit terahertz waves to the surface of the target hot end component, and 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, that is, the terahertz wave reflection time domain spectrum.

[0073] Step 104: Determine the peak area corresponding to the coating surface and the peak area corresponding to the coating bottom 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 area, and determine the coating porosity corresponding to the scanning position based on the amplitude and phase of each peak area.

[0074] In the embodiments of the present application, each time a terahertz wave enters a different medium, it generates a reflected wave. When the reflected wave is collected, a reflection peak appears in the terahertz wave reflection time-domain spectrum. The area where the reflection peak occurs is the peak region. For example, the peak region can be defined as the area within a certain time range centered around the reflection peak in the terahertz wave reflection time-domain spectrum.

[0075] Based on the surface structure of the target hot-end component, the terahertz wave reflection time-domain spectrum can be used to determine the peak regions of terahertz wave reflection from the coating surface and the peak regions of terahertz wave reflection from the coating bottom surface. For example, if the target hot-end component has a surface structure of ceramic top layer-adhesive layer-metal substrate (where the ceramic top layer also serves as the thermal barrier coating), the properties of the adhesive layer will cause the terahertz wave to be completely reflected from the adhesive layer surface. Therefore, the terahertz wave will only be reflected from the air-ceramic top layer surface, from the interior of the ceramic top layer (which may contain pores), and from the ceramic top layer bottom surface to the adhesive layer. Furthermore, because the pores within the ceramic top layer are typically much smaller than the wavelength of the terahertz wave, the terahertz wave reflected from the ceramic top layer is generally weak. Therefore, the first peak with the highest intensity in the terahertz wave reflection time-domain spectrum can be selected as the peak region corresponding to the coating surface, and the second peak with the highest intensity can be selected as the peak region corresponding to the coating bottom surface.

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

[0077] After determining the peak areas on the coating surface and bottom, the time corresponding to the boundaries of these two peak areas can be used as the acquisition time of each peak area. The acquisition time difference is the difference between the acquisition time of the peak area on the bottom and the acquisition time of the peak area on the coating surface. Based on this acquisition time difference, the flight time of the terahertz wave inside the coating can be calculated. Furthermore, the coating thickness can be determined by combining the propagation direction and velocity of the terahertz wave within the coating. The propagation direction and velocity of the terahertz wave within the coating can be determined experimentally.

[0078] Alternatively, the coating thickness can be calculated by combining the concept of optical path length and Snell's law. Figure 2 Shown, including:

[0079] Step 202, determining a 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 : 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 acquisition time difference of each peak area.

[0081] In the embodiment of the present application, the optical path of the terahertz wave inside the coating is related to the refraction angle of the terahertz wave when it enters the coating. The refraction angle can be calculated according to Snell's law. Snell's law states that when an electromagnetic wave such as a light wave is emitted from one medium to another, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the ratio of the propagation speed of the electromagnetic wave 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 (that is, the speed of light) to the refractive index of the medium. Therefore, the refraction angle when the terahertz wave enters the coating can be expressed as formula (1):

[0082] Formula (1)

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

[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 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 value 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 acquisition time difference, the specific value of the optical path can be calculated, and then the specific value of the coating thickness can be calculated. The coating thickness formula obtained based on the above principle is as shown in Formula (2):

[0085] Formula (2)

[0086] in, is the coating thickness, is the speed of light, is the acquisition time difference.

[0087] The coating porosity can also be calculated based on the amplitude and phase of the peak region. Because coating porosity affects the reflection and refraction of terahertz waves within the coating, the difference between the amplitude and phase of the terahertz wave when it reflects off the coating and the amplitude and phase when it enters the coating has a certain correlation with the coating porosity. The specific manifestation of this correlation can be determined experimentally. For example, a function that expresses 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 coating porosity can be calculated based on the difference between the dielectric constant of the coating and the dielectric constant of a dense coating. The dielectric constant is related to the refractive index of the medium, so the dielectric constant of the coating can be calculated based on the refractive index of the coating. The refractive index of the coating can be obtained by modeling the propagation of terahertz waves in the coating and iterating the model until a refractive index is found that makes the calculated results consistent with the amplitude and phase of each peak area. See Figure 3 As shown, the process includes:

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

[0090] Step 304: Adjust the estimated refractive index 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 preset requirements, and use the current estimated refractive index as the target refractive index of the coating;

[0091] Step 306 : determining the dielectric constant of the coating according to the target refractive index, and determining the porosity of the coating corresponding to the scanning position according to the dielectric constant.

[0092] In the embodiment of the present application, the estimated refractive index is a complex number and can be set based on experience. Based on the estimated refractive index, a theoretical transmission function can be constructed to describe the phase and amplitude changes of the terahertz wave during propagation. By combining the theoretical transmission function with the amplitude and phase of the peak area of the corresponding coating surface, the theoretical amplitude and theoretical phase of the peak area of the corresponding coating bottom surface can be calculated. The estimated refractive index can then be adjusted based on 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 predetermined value, and the target refractive index can be obtained.

[0093] The portion of the theoretical transmission function describing amplitude variations can be constructed based on Fresnel's law. Fresnel's law describes the relationship between the incident, reflected, and refracted wave amplitudes when an electromagnetic wave enters different media. Based on the number of different media layers a terahertz wave must pass through after emitting it from a terahertz source in practical applications, and whether reflection and refraction occur during entry, a correlation can be established between the amplitude of the peak region corresponding to the coating surface (corresponding to the terahertz wave reflected from the coating surface) and the amplitude of the peak region corresponding to the coating bottom surface (corresponding to the terahertz wave reflected from the coating bottom surface). Taking the aforementioned example, where the target hot-end component has a surface structure consisting of a ceramic top layer (coating)-bonding layer-metal substrate, and the properties of the bonding layer result in complete reflection of the terahertz wave from the bonding layer surface, 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 reflection coefficient at the air-coating interface. The relationship between the amplitude of the peak area at the bottom surface of the coating and the original amplitude of the terahertz wave emitted by the terahertz source is: the amplitude of the peak area at 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 area on the coating surface and the amplitude of the peak area at the bottom surface of the coating is: the amplitude of the peak area at the bottom surface of the coating is equal to the product of the refractive index of the air-coating interface, the reflection coefficient of the coating-adhesive layer interface, the refractive index of the coating-air interface, and the ratio of the air-coating interface reflection coefficient.

[0094] The portion of the theoretical transmission function used to describe the phase change can be constructed based on the estimated refractive index. The phase change reflects the delay caused by the terahertz wave after propagating 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 described in the aforementioned embodiment, and the embodiments of this application will not be repeated. Still taking the aforementioned model of ceramic top layer (coating)-bonding layer-metal substrate as an example, the theoretical transmission function obtained by combining the amplitude change and phase change is as shown in Formula (3):

[0095] Formula (3)

[0096] Where H is the theoretical transfer function, is the refractive index of the air-coating interface, is the coating-bonding layer interface reflection coefficient, is the coating-air interface refractive index, is the air-coating interface reflection coefficient, is the angular frequency of the terahertz wave, is the coating thickness, is the estimated refractive index of the complex number, The speed of light.

[0097] Based on this formula, the theoretical amplitude and theoretical phase of the peak region corresponding to the bottom surface of the coating are calculated. The estimated refractive index is adjusted based on the first and second differences until the first and second differences meet preset conditions. The estimated refractive index at this point is then used as the target refractive index. The square of the target refractive index is the dielectric constant of the coating. Because pores introduce air into the coating, changing the dielectric constant, the difference between the dielectric constant of the coating and that of a dense coating (i.e., a coating without pores) is strongly correlated with the coating's porosity. The coating's porosity can be further calculated based on any model that describes this correlation.

[0098] In one embodiment, the porosity can be calculated using the Looyenga model. 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. The formula can be found in Formula (4):

[0099] Formula (4)

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

[0101] Step 106 : dividing the surface of the target hot end component into target areas, and determining the coating uniformity corresponding to the target area based on the coating thickness corresponding to each scanning position included in the target area.

[0102] In the embodiments of the present application, the coating uniformity of the target hot-end component can be calculated using regions as units. The embodiments of the present application do 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, if the target hot-end component is a turbine blade, the entire turbine blade can be used as a target region, the blade tip as a target region, a substantially flat portion of the turbine blade as a target region, a curved portion as another target region, and so on.

[0103] Based on the coating thickness at the scanning positions contained in the target area, the coating uniformity can be calculated. For example, the average coating thickness in each target area can be calculated, and the coating uniformity can be calculated based on the difference between each scanning position and the average. Alternatively, the coating uniformity can be calculated using the idea of image processing, see Figure 4 Shown, including:

[0104] Step 402: generating a two-dimensional grayscale image of the target area based on the coating thickness corresponding to each scanning position in the target area; the two-dimensional grayscale image is used to represent the coating thickness distribution in the target area;

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

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

[0107] The two-dimensional grayscale image can also be subjected to image processing including but not limited to image enhancement, Gaussian filtering, threshold segmentation, etc. The pixel value standard deviation of each pixel can be further calculated for the processed image. Based on the difference between the pixel value standard deviation and the reference pixel value standard deviation, 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 that the grayscale value range is 0 to 255, the maximum possible standard deviation is 127.5. The ratio between the pixel value standard deviation and the reference pixel value standard deviation can be calculated, and then the coating uniformity is calculated using the difference between 1 and the ratio, so that the greater the coating uniformity, the better the coating uniformity. As shown in formula (5):

[0108] Formula (5)

[0109] in, is the coating uniformity, is the standard deviation of pixel values, is 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 coating 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 assessed by combining the coating thickness and porosity at each scan 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 is used to obtain a coating quality index.

[0112] Alternatively, considering that the coating quality of different target areas has different effects on the coating quality of the target hot end components, it is also possible to score different target areas separately, assign different weights to different target areas, and then obtain the coating quality index by weighted summation of the scores of each target area. 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, determining an evaluation weight of the target area according to the position of the target area on the surface of the target hot end component;

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

[0116] In the embodiment of the present application, the target area can be scored based on the coating uniformity of the target area, and the coating thickness and coating porosity corresponding to each scanning position in the target area to obtain the coating quality index corresponding to the target area. The scoring method can be determined according to the different importance of the coating uniformity, coating thickness and coating porosity corresponding to the position of the target area and the coating preparation process, such as Figure 6 :

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

[0118] Step 604 , assigning index weights to the coating thickness quality index, the coating porosity quality index, and the coating uniformity quality index based on the location of the target area on the surface of the target hot end component;

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

[0120] In the embodiments of the present application, different target coating thickness ranges and target coating porosity ranges may be set for different target areas. The target coating thickness ranges and target coating porosity ranges represent the ranges in which the optimal thickness and optimal porosity should be. The target coating thickness range and target coating porosity range for a target area may be determined based on the importance of the target area and the coating preparation method. For example, when the target area is important for the performance of the target hot end component (e.g., the target hot end component is a turbine blade and the target area is the blade tip), the target coating thickness range and target coating porosity range may 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 the coating porosity quality index is shown in Formulas (6) to (9). Formulas (6) and (8) are calculated for the ABS production method, and Formulas (7) and (9) are calculated for the EB-PVD production method:

[0122] Formula (6)

[0123] Formula (7)

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

[0125] Formula (8)

[0126] Formula (9)

[0127] in, is the coating porosity quality index, and P is the coating porosity.

[0128] Based on the target area's location on the target hot-end component surface, 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 within the target area. Coating thickness affects the coating's thermal insulation and stress profile, coating porosity affects the coating's thermal insulation and thermal shock resistance, and coating uniformity affects the coating's structural integrity and local stress distribution. The specific allocation of weights can be determined by those skilled in the art based on actual needs. For example, the blade root is subject to greater stress, so a higher weight can be assigned to the coating uniformity quality index for this target area. Thermal insulation performance is more important at the blade tip, so a higher weight can be assigned to the coating thickness quality index. For the blade as a whole, coating porosity has the greatest impact, followed by coating uniformity, and then coating thickness. The weights for 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 for the target area, an assessment weight is determined for that area based on its locational importance and its thermal insulation requirements. This weight can also be customized based on actual needs. For example, the blade tip is more important to turbine blade performance, so a higher weight can be assigned. The blade root can be assigned a lower weight accordingly.

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

[0131] The terahertz-based method for assessing the quality of aircraft engine thermal barrier coatings (TBCs) provided in this application embodiment uses terahertz waves, which can penetrate the TBC, to scan the surface of a 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. The coating quality of the target hot-end component is then comprehensively assessed based on the coating thickness, porosity, and uniformity at each scan position. Because terahertz waves can penetrate TBCs and have a relatively long wavelength, they produce distinct reflection peaks on the coating surface and underside and are less susceptible to interference from tiny pores within the coating. Therefore, by analyzing the peak regions of the terahertz wave reflection time-domain spectrum, the present embodiment can determine indicators such as coating thickness, porosity, and uniformity, which have a significant impact on coating quality. Because the time-domain spectrum is easily acquired, and parameters such as acquisition time, amplitude, and phase are also relatively simple to obtain, the coating quality assessment method provided in this embodiment can significantly reduce coating inspection costs.

[0132] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

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

[0134] In one embodiment, Figure 7 As shown, a device 700 for evaluating the quality of thermal barrier coatings of aircraft engines based on terahertz technology is provided, comprising: a scanning module 702, a first determination module 704, a second determination module 706, and a third determination 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 collect the terahertz wave reflection time domain spectrum generated by the terahertz wave at the scanning position;

[0136] A first determination module 704 is configured to determine a peak area corresponding to the coating surface and a peak area corresponding to the coating bottom 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 area, and determine the coating porosity corresponding to the scanning position based on the amplitude and phase of each peak area;

[0137] A second determining module 706 is configured to divide the surface of the target hot end component into target areas, and determine the coating uniformity corresponding to the target area based on the coating thickness corresponding to each scanning position included in the target area;

[0138] The third determination module 708 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 area.

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

[0140] For any target area, determining a coating quality index corresponding to the target area according to the coating uniformity corresponding to the target area, and the coating thickness and the coating porosity corresponding to each scanning position included in the target area;

[0141] determining an evaluation weight of the target area according to a position of the target area on the surface of the target hot end component;

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

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

[0144] Determining a coating thickness quality index corresponding to the coating thickness based on a relationship between the coating thickness and a target coating thickness range corresponding to the target area, and determining a coating porosity quality index corresponding to the coating porosity based on a relationship between the coating porosity and a target coating porosity range corresponding to the target area;

[0145] Based on the position of the target area on the surface of the target hot end component, assigning index weights to the coating thickness quality index, the coating porosity quality index, and the coating uniformity quality index respectively;

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

[0147] In one embodiment, the first determining module 702 is further configured to:

[0148] determining a refraction angle of the terahertz wave in the coating based on an incident angle of the terahertz wave on the coating surface;

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

[0150] In one embodiment, the first determining module 702 is further configured to:

[0151] Determining an estimated refractive index of the coating, constructing a theoretical transmission function of the terahertz wave in the coating based on the estimated refractive index, and determining a theoretical amplitude and theoretical phase of a peak area corresponding to a bottom surface of the coating based on the theoretical transmission function and the amplitude and phase of a peak area corresponding to the coating surface;

[0152] Adjusting the estimated refractive index based on a first difference between the theoretical amplitude and the amplitude of the peak area corresponding to the bottom surface of the coating, and based on a second difference between the theoretical phase and the phase of the peak area corresponding to the bottom surface of the coating, until the first difference and the second difference meet preset requirements, and using the current estimated refractive index as the target refractive index of the coating;

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

[0154] In one embodiment, the first determining module 702 is further configured to:

[0155] The porosity of the coating corresponding to the scanning position is determined according to 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 704 is further configured to:

[0157] generating a two-dimensional grayscale image of the target area based on the coating thickness corresponding to each scanning position contained in the target area; the two-dimensional grayscale image is used to characterize the coating thickness distribution of the target area;

[0158] A pixel value standard deviation of each pixel in the two-dimensional grayscale image is determined, and a coating uniformity corresponding to the target area is determined based on a difference between the pixel value standard deviation and a reference pixel value standard deviation.

[0159] Each module in the above-mentioned apparatus may be implemented in whole or in part by software, hardware, or a combination thereof. Each module may be embedded in or independent of a processor in a computer device in the form of hardware, or may be stored in a memory in the computer device in the form of software, so that the processor can call and execute the operations corresponding to each module.

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

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

[0162] In one embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor implements the steps in the above method embodiments when executing the computer program.

[0163] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

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

[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, stored data, displayed data, 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 appreciate that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the above-mentioned embodiments. In particular, any reference to memory, database, 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 various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The databases involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processors involved in the various embodiments provided herein may be, but are not limited to, general-purpose processors, central processing units (CPUs), graphics processing units (GPUs), digital signal processors (DSPs), programmable logic devices (PLDs), data processing logic devices based on quantum computing, and the like.

[0167] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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 above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A method for evaluating the quality of thermal barrier coatings of aircraft engines based on terahertz technology, characterized in that: The method comprises: Scanning the surface of the target hot end component with a terahertz wave and collecting the terahertz wave reflection time domain spectrum generated by the terahertz wave at the scanning position; Determining a peak area corresponding to the coating surface and a peak area corresponding to the coating bottom surface in the terahertz wave reflection time domain spectrum, determining the coating thickness corresponding to the scanning position based on the acquisition time difference of each peak area, and determining the coating porosity corresponding to the scanning position based on the amplitude and phase of each peak area; Dividing the surface of the target hot end component into target areas, and determining the coating uniformity corresponding to the target area based on the coating thickness corresponding to each scanning position included in the target area; The coating quality index of the target hot end component is determined according to the coating thickness and the coating porosity corresponding to each scanning position, and the coating uniformity corresponding to each target area.

2. The method according to claim 1, characterized in that 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 area, includes: For any target area, determining a coating quality index corresponding to the target area according to the coating uniformity corresponding to the target area, and the coating thickness and the coating porosity corresponding to each scanning position contained in the target area; determining an evaluation weight of the target area according to a position of the target area on the surface of the target hot end component; The coating quality index of the target hot end component is determined according to the evaluation weight corresponding to each target area and the coating quality index corresponding to each target area.

3. The method according to claim 2, characterized in that Determining the coating quality index corresponding to the target area according to the coating uniformity corresponding to the target area, and the coating thickness and the coating porosity corresponding to each of the scanning positions contained in the target area, includes: Determining a coating thickness quality index corresponding to the coating thickness based on a relationship between the coating thickness and a target coating thickness range corresponding to the target area, and determining a coating porosity quality index corresponding to the coating porosity based on a relationship between the coating porosity and a target coating porosity range corresponding to the target area; Based on the position of the target area on the surface of the target hot end component, assigning index weights to the coating thickness quality index, the coating porosity quality index, and the coating uniformity quality index respectively; Based on the coating thickness quality index, the coating porosity quality index, the coating uniformity and the weight of each index, the coating quality index corresponding to the target area is determined.

4. The method according to claim 1, wherein The determining of the coating thickness corresponding to the scanning position based on the acquisition time difference of each peak area includes: determining a refraction angle of the terahertz wave in the coating based on an incident angle of the terahertz wave on the coating surface; The optical path of the terahertz wave in the coating is determined according to the refraction angle, and the coating thickness corresponding to the scanning position is determined according to the optical path and the acquisition time difference of each peak area.

5. The method according to claim 1, wherein Determining the coating porosity corresponding to the scanning position according to the amplitude and phase of each peak region includes: Determining an estimated refractive index of the coating, constructing a theoretical transmission function of the terahertz wave in the coating based on the estimated refractive index, and determining a theoretical amplitude and theoretical phase of a peak area corresponding to a bottom surface of the coating based on the theoretical transmission function and the amplitude and phase of a peak area corresponding to the coating surface; Adjusting the estimated refractive index based on a first difference between the theoretical amplitude and the amplitude of the peak area corresponding to the bottom surface of the coating, and based on a second difference between the theoretical phase and the phase of the peak area corresponding to the bottom surface of the coating, until the first difference and the second difference meet preset requirements, and using the current estimated refractive index as the target refractive index of the coating; The dielectric constant of the coating is determined according to the target refractive index, and the porosity of the coating corresponding to the scanning position is determined according to the dielectric constant.

6. The method according to claim 5, characterized in that Determining the coating porosity corresponding to the scanning position according to the dielectric constant includes: The porosity of the coating corresponding to the scanning position is determined according to the dielectric constant of air, the dielectric constant of the dense coating, and the dielectric constant of the coating.

7. The method according to claim 1, characterized in that The determining of the coating uniformity corresponding to the target area based on the coating thickness corresponding to each scanning position included in the target area includes: generating a two-dimensional grayscale image of the target area based on the coating thickness corresponding to each scanning position contained in the target area; the two-dimensional grayscale image is used to characterize the coating thickness distribution of the target area; A pixel value standard deviation of each pixel in the two-dimensional grayscale image is determined, and a coating uniformity corresponding to the target area is determined based on a difference between the pixel value standard deviation and a reference pixel value standard deviation.

8. A device for evaluating the quality of thermal barrier coatings on aircraft engines based on terahertz technology, characterized in that: The device comprises: A scanning module is used to scan the surface of the target hot end component with a terahertz wave and collect the terahertz wave reflection time domain spectrum generated by the terahertz wave at the scanning position; a first determination module, configured to determine a peak area corresponding to the coating surface and a peak area corresponding to the coating bottom 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 area, and determine the coating porosity corresponding to the scanning position based on the amplitude and phase of each peak area; a second determining module, configured to divide the surface of the target hot end component into target areas, and determine the coating uniformity corresponding to the target area based on the coating thickness corresponding to each scanning position included in the target area; The third determination module is used 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 area.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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