An online identification method for pyrolysis and ablation interface evolution of carbonized ablation material based on X-ray image fusion enhancement

Abstract

The application discloses an online identification method for pyrolysis and ablation interface evolution of carbonized ablation material based on X-ray image fusion enhancement. In the ground thermal test of the carbonized ablation material, a plurality of groups of images of the carbonized ablation material at different moments are obtained through X-ray imaging, an image fusion enhancement algorithm is adopted to improve the image quality, the local features of the pyrolysis and ablation interface are enhanced, the image noise is reduced through local sliding window averaging, and the pyrolysis and ablation interface is identified in real time based on a gradient algorithm. The application can realize real-time automatic measurement of the ablation amount, the interface between the pyrolysis layer and the carbonization layer, and the interface between the pyrolysis layer and the original layer in the ground thermal test of the carbonized ablation material, overcome the problems that the traditional measurement method is difficult to identify the interface between the pyrolysis layer and has low accuracy, and improve the measurement technical level of the ground thermal test of the thermal protection material, thereby providing support for the design of the ablation thermal protection system.

Description

Technical Field

[0001] This invention belongs to the field of aircraft thermal protection and ground thermal assessment measurement technology, specifically involving an online identification method for the pyrolysis and ablation interface evolution of carbonized ablation materials based on X-ray image fusion enhancement. Background Technology

[0002] As aircraft develop towards hypersonic speeds, the aerodynamic heating problem caused by high-speed flight has become a major bottleneck restricting the development of aircraft. It is necessary to design thermal protection systems to ensure the normal operation of aircraft. Carbonized ablation materials are widely used in the thermal protection of aircraft due to their excellent thermal protection performance, and are an important thermal protection material.

[0003] Under pneumatic heating, the internal temperature of carbonized ablation materials gradually increases. When the temperature exceeds the reaction temperature, the matrix, such as phenolic resin, undergoes pyrolysis, producing pyrolysis gases and forming a porous carbon framework—this is the carbonization process. This results in three layers within the material: a completely pyrolyzed carbonized layer, a pyrolysis layer undergoing pyrolysis, and a pristine layer that has not yet undergone pyrolysis. The different layers have different densities; the carbonized layer has the lowest and almost uniform density, while the pristine layer has the highest and almost uniform density. The density of the pyrolysis layer transitions from that of the carbonized layer to that of the pristine layer. Simultaneously, the surface of the carbonized ablation material undergoes thermochemical and mechanical ablation under the high temperatures caused by pneumatic heating, resulting in surface recession and a reduction in material thickness. Therefore, under pneumatic heating, three pyrolysis and ablation interfaces evolve in the carbonized ablation material: the ablation interface caused by surface ablation, the interface between the pyrolysis layer and the carbonized layer, and the interface between the pyrolysis layer and the pristine layer.

[0004] The thermal protection performance of carbonized ablation materials needs to be evaluated through ground-based thermal testing and flight trials. Ground-based thermal testing simulates the thermal conditions of flight by replicating the temperature and heat flux density of the flight trajectory. This method is cost-effective and facilitates the use of advanced measurement technologies, making it the preferred choice for thermal performance evaluation. Measurements of the pyrolysis and ablation interfaces during ground-based thermal testing can further clarify the thermal protection mechanism of the material during service, improving the sophistication and lightweight design of thermal protection systems.

[0005] Currently, in ground-based thermal assessments of carbonized ablation materials, existing measurement technologies often focus only on measuring the surface ablation amount, achieved through high-speed cameras, infrared cameras, or laser displacement sensors. These methods have the following limitations: firstly, they cannot measure the interface between the internal carbonized layer and the original layer and pyrolysis layer; secondly, carbonized ablation materials are often placed in test fixtures during ground-based thermal assessments to protect the material's sides from direct heating. This limits the measurement of ablation amounts by high-speed cameras and infrared cameras when these fixtures are present, while laser displacement sensors can generally only measure the average displacement of localized light spots, making them ineffective for measuring ablation amounts in materials with uneven heating. X-ray imaging, relying on the strong penetrating power of X-rays, can simultaneously measure the pyrolysis and ablation interfaces. However, X-ray equipment has limited high-temperature resistance, and both the emitter and detector require thermal insulation materials during ground-based thermal assessments, affecting the X-ray imaging quality. Furthermore, the test fixtures on the material can further interfere with imaging, reducing image quality and making it difficult to distinguish between the pyrolysis and ablation interfaces.

[0006] In summary, traditional ground thermal assessment methods for measuring the pyrolysis and ablation interfaces of carbonized and ablation materials are insufficient in terms of accuracy and versatility. There is an urgent need for a method that can simultaneously identify the pyrolysis and ablation interfaces, automatically enhance imaging quality, and ensure accurate interface calculation, thereby improving the measurement technology level in ground thermal assessment of carbonized and ablation materials. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings in accuracy and versatility of current ground-based measurement techniques for the pyrolysis and ablation interfaces of carbonized ablation materials. This invention proposes an online identification method for the evolution of pyrolysis and ablation interfaces of carbonized ablation materials based on X-ray image fusion enhancement, enabling in-situ continuous measurement of the pyrolysis and ablation interfaces during ground-based thermal assessment of carbonized ablation materials, thereby improving the level of ground-based measurement technology for thermal assessment of carbonized ablation materials.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An online identification method for the pyrolysis and ablation interface evolution of carbonized ablation materials based on X-ray image fusion enhancement includes the following steps: Step 1): Install the carbonized ablation material in the ultralight aerogel test fixture, arrange thermocouples or heat flow meters, adjust the position of the X-ray emitter and detector, align the X-ray emitter outlet and detector center with the upper surface of the material, and adjust the material center point to be in the middle of the emitter and detector, adjust the X-ray emitter tube voltage, perform pre-image taking, obtain the pre-image, set the heater heating program and X-ray imaging acquisition time program, and start the program to begin the test; Step 2): As the experiment progresses, X-ray imaging images at different times are dynamically acquired. The obtained X-ray images are processed in real time. Image grayscale stretching is used to perform saturation preprocessing on the X-ray imaging images. Multiple derived images of the saturated preprocessed X-ray images are generated through image processing methods. The derived images are then fused to obtain the enhanced image. Step 3): Obtain the grayscale values ​​of the fused and enhanced X-ray image, calculate the gradient value of the grayscale value along the thickness direction, determine the pyrolysis and ablation state of the carbonized and ablated material, adjust the image fusion enhancement parameters in Step 2) to further enhance the local interface features of the carbonized and ablated material, calculate the gradient value of the grayscale value along the thickness direction again, and automatically identify the coordinates of the pyrolysis and ablation interface based on the pixel number corresponding to the peak point of the grayscale gradient value and the correspondence between the image size and the actual material size, and calculate the evolution process of the pyrolysis and ablation interface.

[0009] In one embodiment, step 1) involves adjusting the positions of the X-ray emitter and detector using a pre-image taken with X-rays to ensure the detector receives the entire image of the carbonized ablation material. The grayscale matrix of the pre-image is obtained, and the grayscale values ​​of the image at the material's upper surface are checked to ensure they are greater than 0, guaranteeing that the X-ray emitter voltage can penetrate the original material layer. Simultaneously, based on the size of the grayscale matrix of the pre-image and the spatial relationship between the emitter, detector, and material, the actual material size represented by a pixel in the X-ray imaging image is calculated. This is used to subsequently calculate the actual evolution process of the material interface based on the interface pixel number.

[0010] In one embodiment, step 2) involves normalizing the grayscale values ​​of the X-ray image and then using grayscale stretching to perform saturation preprocessing on grayscale values ​​below a set lower limit and above a set upper limit in the image. This reduces noise at air locations in the image and enhances image contrast. The calculation method for grayscale stretching saturation preprocessing is as follows: In the formula, I sat The grayscale value is the result of saturation preprocessing. I org The grayscale values ​​are the normalized values ​​of the original image. I min This represents the lower limit of grayscale values ​​in saturation preprocessing. I max This represents the upper limit of grayscale values ​​in the saturation preprocessing.

[0011] In one embodiment, step 2) further generates different derived images from the saturated preprocessed image using different image processing methods such as hyperbolic tangent grayscale transformation, Gamma grayscale transformation, and histogram equalization. The derived images are then averaged and fused using a Laplacian pyramid to enhance image quality. The fused and enhanced image is then processed using a local sliding window averaging method to reduce local noise.

[0012] In one embodiment, step 3) sets a threshold for the grayscale gradient value. The pyrolysis and ablation state of the material is determined by comparing whether the grayscale gradient value along the thickness direction exceeds the threshold. If a grayscale gradient value exceeds the threshold, it indicates that a carbonization layer has been formed. The position along the thickness direction corresponding to the peak point of the grayscale gradient value is the interface between the pyrolysis layer and the carbonization layer, and its coordinates are calculated based on the pixel number corresponding to the peak point. If no grayscale gradient value exceeds the threshold, it indicates that a carbonization layer has not yet been formed.

[0013] In one embodiment, step 3) further enhances the interface features of the ablation interface, pyrolysis layer, and original layer of the carbonized ablation material by adjusting the image fusion enhancement parameters, thereby identifying the ablation interface, pyrolysis layer, and original layer interface. Specifically, when identifying the location of the ablation interface, the Gamma grayscale transformation parameter is increased to enhance the dark areas of the fused image, and another fused and enhanced image is generated. When identifying the location of the interface between the pyrolysis layer and the original layer, the hyperbolic tangent grayscale transformation control parameter is increased to enhance the bright areas of the fused image, and another fused and enhanced image is generated. The grayscale gradient values ​​along the thickness direction of the two regenerated images are calculated respectively. The positions of the grayscale gradient peak points in the thickness direction correspond to the interfaces of the ablation interface, pyrolysis layer, and original layer, respectively. Based on the pixel number of the grayscale gradient peak points, the interface coordinates of the ablation interface, pyrolysis layer, and original layer interface are identified.

[0014] In one embodiment, the grayscale gradient value is calculated using center difference, with the denominator being the pixel number difference. The calculation method is as follows: In the formula, G i For pixels i grayscale gradient at that location i Number the pixels. I enc Enhance the grayscale values ​​of the image after fusion.

[0015] In one embodiment, the carbonized ablation material is square, with temperature-controlled thermocouples or heat flux meters for controlling heat flux density arranged on the surface, and temperature-measuring thermocouples arranged inside and on the back.

[0016] Compared with existing technologies, this invention can realize online automatic identification of the dynamic evolution process of pyrolysis and ablation interface in ground thermal testing of carbonized ablation materials, effectively overcoming the problems of traditional measurement methods such as difficulty in identifying pyrolysis layer interfaces and low accuracy, and improving the measurement technology level of ground thermal testing of thermal protection materials. Attached Figure Description

[0017] Figure 1 This is a flowchart of the online identification method for the pyrolysis and ablation interface evolution of carbonized ablation materials according to the present invention.

[0018] Figure 2 This is the original X-ray image of carbonized and ablated material at a certain moment.

[0019] Figure 3 This is an X-ray imaging image of the carbonized ablation material enhanced by step 2).

[0020] Figure 4 This represents the grayscale value and its gradient along the material thickness direction. Detailed Implementation

[0021] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0022] To address the issues of accuracy and versatility in measuring the pyrolysis and ablation interface of carbonized ablation materials during ground-based thermal assessments, this invention proposes an online identification method for the evolution of pyrolysis and ablation interfaces of carbonized ablation materials based on X-ray image fusion enhancement. The experimental setup used in this invention is a conventional setup for such tests, mainly including an ultralight aerogel testing fixture and a heater. During the test, the material is placed in the ultralight aerogel testing fixture, and the heater heats the fixture.

[0023] Building upon this foundation, the present invention introduces a data acquisition device, an X-ray emitter, and a detector. The data acquisition device mainly includes a thermocouple or a heat flow meter, the X-ray emitter is used to irradiate the material, and the detector is used to acquire X-ray images.

[0024] For details of the method of this invention, please refer to [link / reference]. Figure 1 As shown, it mainly includes: Step 1: First, set the width to... DA square carbonized ablation material was installed in an ultralight aerogel testing fixture. Temperature-controlled thermocouples or heat flow meters were placed on the material surface, while temperature-measuring thermocouples were placed on the back and inside of the material. Before the test, the center point of the upper surface of the square material was adjusted to the midpoint between the X-ray emitter and the detector. Simultaneously, the positions of the X-ray emitter and detector were adjusted so that the X-ray emission outlet and the center of the detector were aligned with the upper surface of the material. The distance between the X-ray emission outlet and the detector was measured. W Adjust the X-ray emitter tube voltage and perform a pre-image of the material to obtain a pre-image X-ray image. Observe whether the pre-image can capture the entire carbonized ablation material, and adjust the X-ray emitter and detector positions based on the pre-image results. Calculate the grayscale matrix of the pre-image and check whether the grayscale values ​​of the image on the upper surface of the material are greater than 0. Adjust the X-ray emitter tube voltage accordingly to ensure that X-rays can penetrate the original material layer and that the image of the material portion has a large contrast with the image of the air portion. Simultaneously, obtain a size of [missing information - likely a data structure or data point] based on the pre-image. m × n The grayscale matrix was obtained, and the actual size of the detector's photosensitive area was measured using vernier calipers. L x × L y Based on this, the actual length represented by each pixel in the detector thickness direction is calculated as follows: L y / m Based on the similarity between the center point of the square material and the geometric positions of the X-ray emitter outlet and the detector, the actual size represented by each pixel on the side of the material closest to the detector is calculated as ( L y / m )×( W + D ) / 2 W Set the heater heating program and X-ray imaging frequency, start the program to begin the experiment, and keep the position of the X-ray emitter / detector unchanged after the experiment begins.

[0025] Step 2: Real-time processing of a set of X-ray imaging images obtained at different times during the experiment. The original X-ray image captured at a certain time is shown below. Figure 2 As shown, firstly, grayscale stretching is used to perform saturation preprocessing on the grayscale values ​​of the image to reduce image noise and enhance image contrast. The upper limit of the grayscale values ​​in the saturation preprocessing is taken from the first grayscale value of the image matrix. m The grayscale mean of the 10th row is used, and the lower limit of the grayscale value in the saturation preprocessing is taken as the grayscale mean of the material surface in the pre-captured image from step 1. Then, three derived images with different grayscale levels are generated using hyperbolic tangent grayscale transform, Gamma grayscale transform, and histogram equalization, respectively. The control factor of the hyperbolic tangent grayscale transform is... LambdaThe control factor for Gamma grayscale transformation is 1.5. Gamma The value is 1.5. Finally, the three derived images are averaged and fused using the Laplacian pyramid, and then a local sliding window averaging process is used to locally average the fused and enhanced image to reduce local noise. The processed image is shown below. Figure 3 As shown.

[0026] The calculation of hyperbolic tangent grayscale transformation is as follows: In the formula, Lambda This is the control factor for hyperbolic tangent grayscale transformation. I tanh This represents the grayscale value after hyperbolic tangent grayscale transformation.

[0027] The calculation of Gamma grayscale transformation is as follows: In the formula, Gamma This is the control factor for Gamma grayscale transformation. I gamma This is the grayscale value after Gamma grayscale transformation.

[0028] Step 3: Obtain the grayscale matrix of the fused and enhanced X-ray image, and calculate the gradient value of the grayscale value along the thickness direction. Set the threshold for the grayscale gradient value to 5, and determine the pyrolysis and ablation state of the material by comparing whether the grayscale gradient value along the thickness direction exceeds the threshold. If a grayscale gradient value exceeds the threshold, a carbonization layer has been formed, and the position in the thickness direction corresponding to the peak point of the grayscale gradient value is the interface between the pyrolysis layer and the carbonization layer. If no grayscale gradient value exceeds the threshold, a carbonization layer has not yet been formed. For the fused and enhanced image ( Figure 3 )along y Calculate the gradient in the direction. x When the direction pixel number is 150, the processing results of the grayscale value and its gradient are as follows: Figure 4 As shown, it can be observed that the grayscale gradient value exceeds the threshold, indicating that a carbonized layer has formed. The peak point of the grayscale gradient corresponds to the actual... y Coordinates along the pixel point y The direction number and the actual length represented by each pixel in the thickness direction are calculated as follows: y cord = ( L y / m )×( W + D ) / 2 W ×( i -0.5) In the formula,y cord The actual interface corresponding to carbonized ablation materials y coordinate.

[0029] At the start of the experiment, the interfaces of pyrolysis and ablation were both located on the upper surface of the material. The initial interface values ​​were calculated using the grayscale values ​​of the fused and enhanced X-ray image at time 0. y Coordinates. After the experiment begins, if a carbonized layer has formed on the material, the actual coordinates corresponding to the interface between the pyrolysis layer and the carbonized layer are... y The coordinates are calculated based on the pixel numbers corresponding to peak points exceeding the threshold. Regardless of whether a carbonized layer has formed on the material, the interfaces between the ablation interface, the pyrolysis layer, and the original layer are calculated using the following method: increasing the control factor of the Gamma grayscale transformation. Gamma The value is set to 15. A fused and enhanced image is generated again to further enhance the local features of the ablation interface of the carbonized ablation material. The pixel number corresponding to the maximum grayscale gradient is recorded as the ablation interface. Based on this, the actual value of the ablation interface is calculated. y Coordinates. By increasing the control factor of the hyperbolic tangent grayscale transformation. Lambda The value is set to 10. A fused and enhanced image is generated again to further enhance the local features of the interface between the pyrolysis layer and the original layer. The pixel numbers corresponding to the grayscale gradient peaks are recorded as the interface between the pyrolysis layer and the original layer. Based on this, the actual interface between the pyrolysis layer and the original layer is calculated. y Coordinates. Increase the control factor of Gamma grayscale transformation respectively. Gamma The control factor for hyperbolic tangent grayscale transformation is 15. Lambda For the grayscale gradient calculation results after setting it to 10, please refer to [link / reference]. Figure 4 It can clearly identify the interface between the ablation interface, the pyrolysis layer, and the original layer.

[0030] The X-ray imaging images obtained at different times during the experiment were processed using steps 2 and 3 to obtain the actual pyrolysis and ablation interfaces. y Coordinate change minus the initial y By using the coordinates, the evolution process of the pyrolysis and ablation interface of the carbonized ablation material during the experiment can be obtained.

[0031] This invention proposes an online identification method for the evolution of pyrolysis and ablation interfaces in carbonized ablation materials based on X-ray image fusion enhancement, utilizing X-ray imaging, image fusion enhancement, and gradient analysis. This invention enables automatic, high-precision identification of pyrolysis and ablation interfaces in ground-based thermal assessment of carbonized ablation materials, effectively overcoming the difficulties and low accuracy of traditional measurement methods in identifying pyrolysis layer interfaces, and improving the measurement technology level for ground-based thermal assessment of thermal protection materials.

Claims

1. A method for online identification of the evolution of pyrolysis and ablation interface in carbonized ablation materials based on X-ray image fusion enhancement, characterized in that, Includes the following steps: Step 1): Install the carbonized ablation material in the ultralight aerogel test fixture, arrange thermocouples or heat flow meters, adjust the position of the X-ray emitter and detector, align the X-ray emitter outlet and detector center with the upper surface of the material, and adjust the material center point to be in the middle of the emitter and detector, adjust the X-ray emitter tube voltage, perform pre-image taking, obtain the pre-image, set the heater heating program and X-ray imaging acquisition time program, and start the program to begin the test; Step 2): As the experiment proceeds, X-ray imaging images at different times are dynamically acquired. The obtained X-ray images are processed in real time. Image grayscale stretching is used to perform saturation preprocessing on the X-ray imaging images. Multiple derivative images of the saturated preprocessed X-ray images are generated through image processing methods. The derivative images are then fused to obtain the enhanced image. Step 3): Obtain the grayscale value of the fused and enhanced X-ray image, calculate the gradient value of the grayscale value along the thickness direction, determine the pyrolysis and ablation state of the carbonized ablation material, adjust the image fusion enhancement parameters in Step 2) to further enhance the local interface features of the carbonized ablation material, calculate the gradient value of the grayscale value along the thickness direction again, and automatically identify the coordinates of the pyrolysis and ablation interface based on the pixel number corresponding to the peak point of the grayscale gradient value and the correspondence between the image size and the actual material size, and calculate the evolution process of the pyrolysis and ablation interface.

2. The online identification method for the evolution of pyrolysis and ablation interface of carbonized ablation materials based on X-ray image fusion enhancement according to claim 1, characterized in that, Step 1), which involves pre-shooting, and the processing of the pre-shot image is as follows: By pre-taking X-ray images, the positions of the X-ray emitter and detector are adjusted to ensure that the detector can receive all images of the carbonized ablation material. Obtain the grayscale matrix of the pre-captured image, check whether the grayscale value of the image at the upper surface of the material is greater than 0, and ensure that the X-ray emitter tube voltage can penetrate the original layer of the material; By using the size of the grayscale matrix of the pre-captured image and the spatial relationship between the emitter, detector, and material, the actual material size represented by a pixel in the X-ray imaging image is calculated, which is then used to calculate the actual evolution process of the material interface based on the interface pixel number.

3. The online identification method for the evolution of pyrolysis and ablation interface of carbonized ablation materials based on X-ray image fusion enhancement according to claim 1, characterized in that, The implementation method for step 2) of the saturation preprocessing is as follows: The grayscale values ​​of the X-ray imaging image are normalized, and grayscale stretching is used to perform saturation preprocessing on grayscale values ​​below a set lower limit and above a set upper limit in the image. This reduces noise at air locations in the image and enhances image contrast. The calculation method for grayscale stretching saturation preprocessing is as follows: In the formula, I sat The grayscale value is the result of saturation preprocessing. I org The grayscale values ​​are the normalized values ​​of the original image. I min This represents the lower limit of grayscale values ​​for saturation preprocessing. I max This represents the upper limit of grayscale values ​​in the saturation preprocessing.

4. The online identification method for the evolution of pyrolysis and ablation interface of carbonized ablation materials based on X-ray image fusion enhancement according to claim 1, characterized in that, In step 2), different derived images are generated from the saturated preprocessed image using different image processing methods. The derived images are then averaged and fused using a Laplacian pyramid to enhance the image quality. The fused and enhanced image is then processed using a local sliding window to reduce local noise.

5. The online identification method for the evolution of pyrolysis and ablation interface of carbonized ablation materials based on X-ray image fusion enhancement according to claim 4, characterized in that, A derived image is generated from the saturated preprocessed image using hyperbolic tangent grayscale transformation, Gamma grayscale transformation, and histogram equalization.

6. The online identification method for the evolution of pyrolysis and ablation interface of carbonized ablation materials based on X-ray image fusion enhancement according to claim 1, characterized in that, In step 3), a threshold for the grayscale gradient value is set, and the pyrolysis and ablation state of the material is determined by comparing whether the grayscale gradient value along the thickness direction exceeds the threshold. If the grayscale gradient value exceeds the threshold, a carbonization layer has been formed. The position of the thickness direction corresponding to the peak point of the grayscale gradient value is the interface between the pyrolysis layer and the carbonization layer. Its coordinates are calculated based on the pixel number corresponding to the peak point. If no grayscale gradient value exceeds the threshold, then a carbonized layer has not yet been formed.

7. The online identification method for the evolution of pyrolysis and ablation interface of carbonized ablation materials based on X-ray image fusion enhancement according to claim 1, characterized in that, Step 3) further enhances the interface features of the ablation interface, pyrolysis layer, and original layer interface of the carbonized ablation material by adjusting the image fusion enhancement parameters, thereby identifying the ablation interface, pyrolysis layer, and original layer interface: When identifying the location of the ablation interface, enhance the dark areas of the fused image and generate another fused and enhanced image; When identifying the interface between the pyrolysis layer and the original layer, the bright areas of the fused image are enhanced, and a fused and enhanced image is generated again. The gray-level gradient values ​​along the thickness direction are calculated for the two regenerated images respectively. The positions of the gray-level gradient peak points in the thickness direction are the interfaces of the ablation interface, the pyrolysis layer and the original layer, respectively. Based on the pixel number of the gray-level gradient peak points, the interface coordinates of the interfaces of the ablation interface, the pyrolysis layer and the original layer are identified.

8. The online identification method for the evolution of pyrolysis and ablation interface of carbonized ablation materials based on X-ray image fusion enhancement according to claim 7, characterized in that, The image processing method includes a Gamma grayscale transformation method and a hyperbolic tangent grayscale transformation method. The enhancement of the dark areas of the fused image is achieved by increasing the Gamma grayscale transformation parameter, and the enhancement of the bright areas of the fused image is achieved by increasing the hyperbolic tangent grayscale transformation control parameter.

9. The online identification method for the evolution of pyrolysis and ablation interface of carbonized ablation materials based on X-ray image fusion enhancement according to claim 6 or 7, characterized in that, The grayscale gradient value is calculated using the center difference, with the denominator being the difference in pixel numbers. The calculation method is as follows: In the formula, G i For pixels i grayscale gradient at that location i Number the pixels. I enc Enhance the grayscale values ​​of the image after fusion.

10. The online identification method for the evolution of pyrolysis and ablation interface of carbonized ablation materials based on X-ray image fusion enhancement according to claim 1, characterized in that, The carbonized ablation material is square, with temperature-controlled thermocouples or heat flux meters for controlling heat flux density arranged on its surface, and temperature-measuring thermocouples arranged inside and on its back.

Images