Preparation method of DIC high-temperature-resistant black speckles for turbine blade strain analysis

Abstract

The invention relates to a turbine blade high-temperature deformation measurement technology, and provides a DI C high-temperature-resistant black speckle preparation method for turbine blade strain analysis, and the method comprises the steps: obtaining a speckle pattern through a parameterized speckle mathematical model, and making a speckle mask according to the speckle pattern; a speckle mask is adhered to the pretreated turbine blade to be detected in a covering mode; in a vacuum environment of inert shielding gas, a SiC target material is deposited on the surface of the turbine blade to be measured through a magnetron sputtering technology according to magnetron sputtering parameters to obtain a layer of SiC thin film, a SiO2 target material is deposited on the SiC thin film to obtain a layer of SiO2 thin film, and DI C high-temperature-resistant black speckles are obtained after speckle masks are removed. The DI C high-temperature-resistant black speckles prepared by the method disclosed by the invention are high in quality, uniform in anisotropy and uniform in speckle distribution, and have the advantages of high temperature resistance, high adsorbability, high oxidation resistance, deep color and the like.

Description

Technical Field

[0001] The invention belongs to the optical testing fields of experimental solid mechanics, surface deformation of high-temperature objects and high-temperature mechanical properties of materials, and relates to a high-temperature deformation measurement technology for turbine blades, and specifically to a DIC high-temperature resistant black speckle preparation method for turbine blade strain analysis. Background Art

[0002] Aircraft engines are the power core of modern aircraft, and blades are one of the important components of aircraft engine structures. The working environment of turbine blades at the combustion chamber outlet is the highest temperature and the worst pressure among all impeller structures. Studying the temperature and strain field on the blade surface under severe working conditions is of great significance for evaluating the health status of blades, testing the rationality of blade strength and heat dissipation and other structural designs, and safety and stability.

[0003] Digital Image Correlation (DIC) is a method of establishing a deformation field by comparing and analyzing the characteristic patterns (speckle) of the surface of the test sample before and after deformation. In the process of DIC measurement, the surface of the test sample needs to be covered with a suitable speckle pattern as a carrier of deformation information, and then presented in the digital image as a pixel set with a certain grayscale and position relationship, and finally accurate matching is achieved in a specific algorithm process. It can be seen that the quality of the speckle pattern is directly related to the precision and accuracy of the DIC measurement.

[0004] When measuring the deformation field of the surface of an aircraft engine turbine blade using the DIC method, the influence of the high temperature environment at the hot end on DIC must be considered. For deformation measurement under high temperature, the high temperature speckle pattern has the following requirements: (1) Stability: It has high temperature resistance, adheres closely to the surface of the test piece and can deform as the test piece is loaded, and does not oxidize, fall off or peel off; (2) Random distribution: The speckle pattern is generated by a combination of random displacement and random radius size; (3) High contrast: After heating, the color of the speckle pattern still has a suitable contrast with the color of the test piece surface; (4) Isotropic: There is no obvious directional distribution.

[0005] At present, it is difficult to achieve accurate control of the speckle pattern by preparing high-temperature speckle through spraying paint and air compression technology. The speckle surface is easily oxidized at high temperature, affecting the contrast between the speckle pattern and the specimen, and the speckle is easy to fall off when deformed, thereby reducing the quality of the speckle image and affecting the strain analysis results of the turbine blades. Summary of the invention

[0006] In order to solve the technical problem that the high-temperature speckle prepared by spraying paint and air compression technology is easily oxidized and deformed and falls off at high temperature, thereby reducing the quality of the speckle image and affecting the strain analysis result of the turbine blade, the present invention discloses a DIC high-temperature resistant black speckle preparation method for turbine blade strain analysis, and the DIC high-temperature resistant black speckle preparation method comprises the following steps:

[0007] S2, obtaining a speckle pattern through a parameterized speckle mathematical model according to the strain test temperature and the parameters of the turbine blade being tested, and making a speckle mask according to the speckle pattern;

[0008] S4, sticking the speckle mask onto the pre-processed turbine blade to be measured;

[0009] S6. In a vacuum environment of inert protective gas, a SiC target material is deposited on the surface of the turbine blade to be measured by magnetron sputtering technology according to magnetron sputtering parameters to obtain a layer of SiC film, and a SiO2 target material is deposited on the SiC film to obtain a layer of SiO2 film, and after removing the speckle mask, a DIC high-temperature resistant black speckle is obtained.

[0010] In an optional embodiment, the above-mentioned DIC high temperature resistant black speckle preparation method further includes S1, constructing a parameterized speckle mathematical model, specifically including:

[0011] S11, constructing a parameterized speckle mathematical initial model with strain test temperature, turbine blade parameters and speckle deformation parameters as input and speckle pattern as output;

[0012] S12, iteratively optimizing the parameterized speckle mathematical initial model through constraint conditions and the least square method to obtain a parameterized speckle mathematical model.

[0013] Furthermore, in the above step S11, the turbine blade parameters include the material and size of the turbine blade, the speckle deformation parameters include the radius deformation parameters, X-direction displacement and Y-direction displacement of the speckle, the speckle pattern includes the number of speckle rows, the number of speckle columns and the radius and center distance of each speckle; the strain test temperature is ≥1300°C, and the test time is 1h.

[0014] Furthermore, the constraint conditions in the above step S12 are determined by the camera resolution and the DIC field size, and the constraint conditions include:

[0015] After the strain test, the minimum distance between adjacent speckle spots in the collected speckle image is ≥ the preset value;

[0016] Before and after the strain test, all the speckle spots in the acquired speckle images are complete;

[0017] Before and after the strain test, the deformation of all speckle spots in the collected speckle images was ≤0.1 μm;

[0018] After the strain test, the boundaries of all speckle spots in the collected speckle image can be identified by edge detection, contour extraction or deep learning algorithms.

[0019] In an optional embodiment, the above-mentioned DIC high temperature resistant black speckle preparation method further includes S3, pre-processing the turbine blade to be tested, specifically including:

[0020] S31, cleaning the surface of the turbine blade to be tested;

[0021] S32. Determine the surface smoothness requirement of the turbine blade under test according to the strain test temperature and the material of the turbine blade under test, and polish the surface of the cleaned turbine blade under test according to the surface smoothness requirement to obtain the pre-treated turbine blade under test.

[0022] Furthermore, in the above step S4, the speckle mask is a polyimide flexible speckle mask, and the polyimide flexible speckle mask is adhered to the measured turbine blade by surface adhesive.

[0023] In an optional embodiment, the above-mentioned DIC high temperature resistant black speckle preparation method further includes:

[0024] S5. Determine the magnetron sputtering parameters according to the incident light characteristics, target material, speckle color and camera parameters. The magnetron sputtering parameters include radio frequency power, sputtering time and vacuum chamber pressure.

[0025] Furthermore, the sputtering time of the SiC target is greater than the sputtering time of the SiO2 target, so that the thickness of the SiC film is greater than the thickness of the SiC film.

[0026] Furthermore, the sputtering power of the SiC target and the SiO2 target is 200±10W.

[0027] Furthermore, in step S6, in the DIC high temperature resistant black speckle obtained by magnetron sputtering deposition, the thickness of the SiC film is 3280.55 nm, and the thickness of the SiC film is 1831.12 nm.

[0028] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above-mentioned technical solutions adopted in the embodiments of this specification include at least the following: the DIC high-temperature resistant black speckle preparation method of the present invention can use the constructed parameterized speckle mathematical model to generate a speckle pattern that is compatible with the turbine blade being measured, based on the strain test temperature and the parameters of the turbine blade being measured; SiC target material and SiO2 target material are sequentially deposited on the turbine blade being measured by magnetron sputtering technology to obtain a high-temperature resistant, non-falling and black high-temperature resistant speckle, which has the advantages of high quality, uniform anisotropy, uniform speckle distribution, high temperature resistance, high adsorption, high oxidation resistance, and deep color, so that the prepared speckle can meet the requirements of strain test analysis of aircraft engine turbine blades under extreme environments.

[0029] The present invention uses a speckle preparation method that combines a parameterized mask with magnetron sputtering technology, which can effectively solve the shortcomings of speckles prepared by existing spray paint and air compression technology, such as small size, irregular shape, poor isotropic coefficients, non-reproducible speckle patterns, oxidation discoloration at high temperatures, poor contrast and low precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 This is a flow chart of a method for preparing DIC high temperature resistant black speckle for turbine blade strain analysis according to the present invention;

[0032] Figure 2 It is a flow chart of another method for preparing DIC high temperature resistant black speckle for turbine blade strain analysis according to the present invention;

[0033] Figure 3 A flow chart of preparing DIC high temperature resistant black speckle on a turbine blade disclosed in an embodiment of the present invention;

[0034] Figure 4 The figure is a comparison diagram of the speckles prepared on the 304 metal tensile sample by the method of the present invention and the traditional method. DETAILED DESCRIPTION

[0035] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0036] The following describes the implementation methods of the present application through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and the features of the embodiments can be combined with each other in the absence of conflict. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0037] The embodiment of the present invention discloses a method for preparing DIC high temperature resistant black speckle for turbine blade strain analysis, see Figure 1 and Figure 2 As shown, the DIC high temperature resistant black speckle preparation method comprises the following steps:

[0038] S2, obtaining a speckle pattern through a parameterized speckle mathematical model according to the strain test temperature and the parameters of the turbine blade being tested, and making a speckle mask according to the speckle pattern;

[0039] S4, sticking the speckle mask onto the pre-processed turbine blade to be measured;

[0040] S6. In a vacuum environment of inert protective gas, a SiC target material is deposited on the surface of the turbine blade to be measured by magnetron sputtering technology according to magnetron sputtering parameters to obtain a layer of SiC film, and a SiO2 target material is deposited on the SiC film to obtain a layer of SiO2 film, and after removing the speckle mask, a DIC high-temperature resistant black speckle is obtained.

[0041] Generally speaking, most targets with darker colors and higher melting points are dark in color when combined with samples at room temperature, but are easily oxidized and discolored at high temperatures, causing the color to become lighter. As a result, the pixel gradient difference of the speckle image collected after the deformation test is very small, which in turn affects the feature extraction of the speckle spots after deformation and affects the strain test analysis. According to the test and analysis, when two or more target materials are selected to prepare the speckle, the speckle can be prevented from being oxidized and discolored at high temperatures. In the present invention, SiC and SiO2 are selected as target materials. The speckle prepared by the method of the present invention is not only black in color, but also does not change color at a high temperature of more than one thousand degrees, thereby ensuring the quality of the collected speckle image.

[0042] In an alternative embodiment, see Figure 2 As shown, the above-mentioned DIC high temperature resistant black speckle preparation method further includes S1, constructing a parameterized speckle mathematical model, specifically including:

[0043] S11, constructing a parameterized speckle mathematical initial model with strain test temperature, turbine blade parameters and speckle deformation parameters as input and speckle pattern as output;

[0044] S12, iteratively optimizing the parameterized speckle mathematical initial model through constraint conditions and the least square method to obtain a parameterized speckle mathematical model.

[0045] Further, in the above step S11, the turbine blade parameters include the material and size of the turbine blade, the speckle deformation parameters include the radius deformation parameters, X-direction displacement and Y-direction displacement of the speckle, and the speckle pattern includes the number of speckle rows, the number of speckle columns and the radius and center distance of each speckle; the strain test temperature is ≥1300°C, and the test time is 1h. For example, for a turbine blade made of MA956, the strain test temperature is 1350°C.

[0046] Furthermore, in the above step S11, the constraint conditions are determined by the camera resolution and the DIC field size, and the constraint conditions include:

[0047] (1) After the strain test, the minimum distance between adjacent speckle spots in the collected speckle image is ≥ the preset value;

[0048] (2) Before and after the strain test, all the speckle spots in the collected speckle images are complete;

[0049] (3) Before and after the strain test, the deformation of all speckle spots in the collected speckle images is ≤0.1 μm;

[0050] (4) After the strain test, the boundaries of all speckle spots in the collected speckle image can be identified by edge detection, contour extraction or deep learning algorithms.

[0051] The speckle model in the present invention can also be obtained by the following formula:

[0052] X i =(n i -1)×a;Y i =(m i -1))×a;

[0053] X′ i =X i +uf(l 1i ); Y′ i =Y i +vf(l 2i );

[0054] R i =R+f(l 3i );

[0055] In the above formula, (X i , Y i ) is the coordinate of the center of the i-th circular spot in the initial speckle pattern, n i and m i Respectively represent the number of rows and columns in the initial speckle pattern; a is the center distance of the speckles in the initial speckle pattern; (X′ i , Y′ i ) is the center distance of the i-th circular spot in the speckle pattern obtained by introducing random displacements in the x and y directions after considering the blade parameters; u and v are the maximum random displacements in the x and y directions, respectively; f(l 1i ) and f(l 2i ) are pseudo-random functions that determine the magnitude of random displacement in the x and y directions, respectively. 1i and l 2i The value range is [-1,1]; r is the radius of the speckle in the initial speckle pattern; f(l3i) are pseudo-random functions that determine the size of the random change of the radius, and f(l 3i ) has a value range of [-1,1]; R i It is the radius of the i-th circular spot after introducing random radius variation after considering the blade parameters.

[0056] In the present invention, multiple sets of data can be used to iteratively optimize the parameterized speckle mathematical model according to different scenarios, different samples, and different requirements to obtain a model that meets the requirements. For example, when a strain analysis test is performed, when a speckle pattern with a large particle size, a fixed number of rows and columns, a large random degree, and a large random particle size is required, the constraints can be adjusted first, and then the initial model can be optimized using multiple sets of data to obtain the required model. The strain test temperature and the parameters of the turbine blade to be tested are input into the optimized model, and a speckle pattern that meets the test requirements can be input.

[0057] When the above step S2 is implemented, the turbine blade parameters (such as blade size and material) and strain test temperature can be used as inputs, and the initial center distance of the scattered spots, the random displacement in the x and y directions, the random radius change size and the scattered spot outline clarity, the camera resolution and the DIC parallax size can be used as constraints to control the quality of the speckle pattern before and after the strain test, and output a speckle map that meets the requirements, and the output speckle map describes the number of rows and columns of the speckle and the radius and center distance of each scattered spot. After the speckle pattern is obtained, a speckle mask can be manufactured by a laser engraving machine.

[0058] In an alternative embodiment, see Figure 2 As shown, the above-mentioned DIC high temperature resistant black speckle preparation method further includes S3, pre-processing the turbine blade to be tested, specifically including:

[0059] S31, cleaning the surface of the turbine blade to be measured to remove oil stains, impurities, etc. on the surface of the turbine blade to be measured.

[0060] S32, determining the surface smoothness requirement of the turbine blade to be tested according to the strain test temperature and the material of the turbine blade to be tested, and polishing the surface of the cleaned turbine blade to be tested according to the surface smoothness requirement to obtain the pre-treated turbine blade to be tested. The surface smoothness of the turbine blade to be tested is determined by combining the test temperature and the material of the turbine blade, and after the smoothing treatment, it can be ensured that the speckle deposited by magnetron sputtering is combined with the turbine blade during the high temperature test, so as to avoid the speckle falling off from the blade surface and affecting the speckle image after the test due to the incompleteness and reducing the result of the strain test analysis.

[0061] Furthermore, when the above step S4 is specifically implemented, the speckle mask is a polyimide flexible speckle mask, and the polyimide flexible speckle mask is adhered to the turbine blade under test by means of surface adhesive. The polyimide flexible speckle mask is adhered to the turbine blade under test by means of surface adhesive, and the speckle mask can be removed from the turbine blade under test after the speckle is prepared, and the surface adhesive is prevented from being attached to the turbine blade under test and remaining.

[0062] In an alternative embodiment, see Figure 2 As shown, the above-mentioned DIC high temperature resistant black speckle preparation method also includes:

[0063] S5. Determine the magnetron sputtering parameters according to the incident light characteristics, target material, speckle color and camera parameters. The magnetron sputtering parameters include radio frequency power, sputtering time and vacuum chamber pressure.

[0064] In a specific implementation, since the wavelength of the incident light will affect the absorption, reflection and scattering of light by the material (such as the target material for making the speckle), and different incident angles will cause the light to interact with the material (such as the target material for making the speckle) to affect the speckle color, and the image quality will be different when the speckle images before and after the test are obtained by cameras with different parameters, the parameters of the magnetron sputtering in the present invention can be calculated by the above parameters. For example, when using sunlight, the target materials are SiC and SiO2, and the speckle color is black, the sputtering parameters of the magnetron sputtering instrument are: RF sputtering power of SiC target position 200±10W, sputtering time 5h, vacuum chamber pressure value 0.5Pa, RF power of SiO2 target position of the magnetron sputtering instrument 200±10W, sputtering time 2h, vacuum chamber pressure value 0.5Pa.

[0065] Furthermore, generally speaking, SiC film is black in sunlight, and a layer of SiO2 film deposited thereon can protect the SiC film to prevent it from being oxidized under high-temperature test conditions and affecting the speckle color. At the same time, in order to avoid the influence of the presence of the SiO2 film on the speckle color, the sputtering time of the SiC target is controlled to be greater than the sputtering time of the SiO2 target, so that the thickness of the SiC film is greater than the thickness of the SiC film.

[0066] Furthermore, when the above step S6 is specifically implemented, argon gas can be selected as the inert protective gas, and the gas flow rate thereof can be set to 30 sccm.

[0067] In the DIC high temperature resistant black speckle obtained by magnetron sputtering deposition using the above parameters in the present invention, the thickness of the SiC film is 3280.55 nm, and the thickness of the SiC film is 1831.12 nm.

[0068] The present invention takes the turbine blade of an aircraft engine located at the outlet of the combustion chamber (CFM56-1 high pressure first stage turbine blade with white coating) as an example, see Figure 3 As shown, the process of preparing black speckle for strain analysis is described in detail:

[0069] S101. Design a parameterized high-quality speckle model, use software to establish an initial parameterized speckle mathematical model, use the strain test temperature (such as 1200°C) and the turbine blade parameters at the combustion chamber outlet as input, optimize the initial model by setting constraints to obtain a final model, and use the final parameterized speckle mathematical model to generate a high-quality speckle pattern;

[0070] S102, preparing a speckle mask: using a laser engraving machine to make a high-quality polyimide flexible speckle mask using a polyimide material according to the speckle pattern;

[0071] S103, cleaning the sample: cleaning and polishing the surface of the sample;

[0072] S104, covering mask: sticking the prepared polyimide flexible speckle mask on the processed surface of the sample with adhesive;

[0073] S105, installing the target material: installing two different materials of SiC target material and SiO2 target material on two target positions of the magnetron sputtering instrument respectively, wherein the purity of the SiC target material and the SiO2 target material is 99.9% and the size is φ76.2 mm;

[0074] S106, placing the sample: placing the processed and masked sample on the target position of the SiC target of the magnetron sputtering instrument;

[0075] S107, creating a vacuum environment: starting the mechanical pump and molecular pump of the magnetron sputtering instrument to pump the vacuum chamber into a high vacuum environment;

[0076] S108, introducing gas: turning on the gas supply system of the magnetron sputtering apparatus, and adjusting the gas flow rate of argon gas to 30 sccm;

[0077] S109, bias cleaning: turn on the bias power supply, set the negative bias value and duty cycle, where the voltage is 800V and the duty cycle is 70%;

[0078] S110, sputtering: vacuum degree to 5×10 -4 Pa, turn on the RF power supply to first sputter the SiC target onto the sample, and then sputter the SiO2 target onto the SiC thin film layer, wherein the sputtering power of the SiC target of the magnetron sputtering instrument is 200W, the sputtering time is 5h, and the vacuum chamber pressure value is 0.5Pa. After the SiC target sputters for 5h, the sputtering is stopped, and the sample is rotated to the SiO2 target by the base. The RF power of the SiO2 target of the magnetron sputtering instrument is 200W, the sputtering time is 2h, and the vacuum chamber pressure value is 0.5Pa. After the sputtering is completed;

[0079] S111. Stop sputtering, take out the sample, and tear off the mask: turn off the RF power supply to stop sputtering, restore the vacuum degree of the vacuum chamber to atmospheric pressure, take out the deposited sample, and tear off the mask to obtain the DIC high-temperature, high-quality black speckle, completing the preparation of the speckle on the turbine blade. The DIC high-temperature resistant black speckle has a SiC film thickness of 3280.55nm and a SiO2 film thickness of 1831.12nm, which is black under sunlight.

[0080] The present invention also uses a 304 metal specimen as an example to prepare black speckles on a tensile specimen, and compares the speckle preparation method of the present invention with the conventional air compression technology for preparing speckles. The results are shown in FIG. Figure 4 As shown, Figure 4 (a) is the speckle prepared by traditional air compression technology, and (b) is the speckle prepared by the method of the present invention. The results show that the speckle prepared by traditional air compression technology has poor bonding with the sample and is easy to fall off at high temperatures, affecting the quality of the overall speckle pattern and the measurement error. The speckle prepared by the method of the present invention can make up for this shortcoming and greatly improve the accuracy of turbine blade strain analysis.

[0081] Obviously, those skilled in the art should understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the embodiments of the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing DIC high temperature resistant black speckle for turbine blade strain analysis, characterized in that: include: According to the strain test temperature and the parameters of the turbine blade being tested, a speckle pattern is obtained through a parameterized speckle mathematical model, and a speckle mask is produced according to the speckle pattern; Adhere the speckle mask onto the pre-processed turbine blade to be tested; In a vacuum environment of inert protective gas, a SiC target is deposited on the surface of the turbine blade to be measured according to magnetron sputtering parameters by magnetron sputtering technology to obtain a layer of SiC film, and a SiO2 target is deposited on the SiC film to obtain a layer of SiO2 film. After removing the speckle mask, DIC high-temperature resistant black speckle is obtained.

2. The method for preparing DIC high temperature resistant black speckle for turbine blade strain analysis according to claim 1, characterized in that: Also includes: Construct a parametric speckle mathematical initial model with strain test temperature, turbine blade parameters and speckle deformation parameters as input and speckle pattern as output; The parameterized speckle mathematical model is iteratively optimized through constraint conditions and the least square method to obtain a parameterized speckle mathematical model.

3. The method for preparing DIC high temperature resistant black speckle for turbine blade strain analysis according to claim 2, characterized in that: The turbine blade parameters include the material and size of the turbine blade, the speckle deformation parameters include the radius deformation parameters, X-direction displacement and Y-direction displacement of the speckle, the speckle pattern includes the number of speckle rows, the number of speckle columns and the radius and center distance of each speckle; the strain test temperature is ≥1300°C and the test time is 1h.

4. The method for preparing DIC high temperature resistant black speckle for turbine blade strain analysis according to claim 2, characterized in that: The constraints are determined by the camera resolution and the DIC field size, and the constraints include: After the strain test, the minimum distance between adjacent speckle spots in the collected speckle image is ≥ the preset value; Before and after the strain test, all the speckle spots in the acquired speckle images are complete; Before and after the strain test, the deformation of all the speckle spots in the collected speckle images was ≤0.1 μm.

5. The method for preparing DIC high temperature resistant black speckle for turbine blade strain analysis according to claim 1, characterized in that: Also includes: Cleaning the surface of the turbine blade under test; The surface smoothness requirement of the turbine blade under test is determined according to the strain test temperature and the material of the turbine blade under test, and the surface of the cleaned turbine blade under test is polished according to the surface smoothness requirement to obtain the pre-treated turbine blade under test.

6. The method for preparing DIC high temperature resistant black speckle for turbine blade strain analysis according to claim 1, characterized in that: The speckle mask is a polyimide flexible speckle mask, and the polyimide flexible speckle mask is adhered to the measured turbine blade by surface adhesive.

7. The method for preparing DIC high temperature resistant black speckle for turbine blade strain analysis according to claim 1, characterized in that: Also includes: The magnetron sputtering parameters are determined according to the incident light characteristics, target material, speckle color and camera parameters. The magnetron sputtering parameters include radio frequency power, sputtering time and vacuum chamber pressure.

8. The method for preparing DIC high temperature resistant black speckle for turbine blade strain analysis according to claim 7, characterized in that: The sputtering time of the SiC target is greater than the sputtering time of the SiO2 target, so that the thickness of the SiC film is greater than the thickness of the SiC film.

9. The method for preparing DIC high temperature resistant black speckle for turbine blade strain analysis according to claim 7, characterized in that: The sputtering power of the SiC target and the SiO2 target is 200±10W.

10. The method for preparing DIC high temperature resistant black speckle for turbine blade strain analysis according to claim 1, characterized in that: The thickness of the SiC film is 3280.55 nm, and the thickness of the SiC film is 1831.12 nm.

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