Accelerated test method for aging of aluminum alloy aircraft plate

Abstract

The invention relates to the technical field of processing, testing or inspection of aircraft parts, and provides an accelerated test method for aging of an aluminum alloy aircraft plate. The method comprises the following steps: carrying out a cyclic alternating test of ultraviolet irradiation and solution soaking on an aluminum alloy sample with an epoxy coating, and simulating a multi-factor coupling aging process in an aviation service environment. And regularly observing and recording micro-defects such as micropores, cracks and spalling on the surface of the coating in a test period, and evaluating the development of the micro-defects of the coating through qualitative and quantitative analysis. And after the test is finished, measuring the residual thickness of the sample, and establishing a relation model between the coating thickness degradation and the change of microdefect development along with the aging time in combination with the microdefect development state. According to the method, the actual aviation service environment can be simulated, the ultraviolet aging and corrosion coupling effect is considered, and accurate prediction and accelerated simulation of the aging behavior of the aluminum alloy aircraft plate with the epoxy coating are achieved.

Description

Technical Field

[0001] This invention relates to the technical fields of aircraft component processing, testing, and inspection, and in particular to an accelerated testing method for aging of aluminum alloy aircraft plates. Background Technology

[0002] Aluminum alloys are widely used in aerospace structural components due to their excellent specific strength, fatigue resistance, and machinability. To improve their service life and prevent corrosion in the atmospheric environment, epoxy-based organic protective coatings are typically applied to their surfaces. However, even with surface treatment and coating protection, aluminum alloys still face problems such as gradual aging, coating cracking, interface peeling, and corrosion propagation under complex aerospace service environments. The aging phenomenon is particularly pronounced under the combined effects of high-intensity ultraviolet radiation, damp heat cycling, and acidic salt spray. To predict the long-term service performance of materials, current technologies often employ natural exposure tests or conventional constant accelerated aging methods for performance evaluation. However, natural exposure tests are time-consuming and costly, making them unsuitable for rapid screening of materials or component designs. Accelerated methods under constant environments (such as single ultraviolet irradiation or continuous immersion) often fail to realistically simulate the cyclical and alternating multi-factor stress effects in actual aerospace environments, resulting in poor comparability of test results, insufficient revelation of aging mechanisms, and, in particular, difficulty in establishing a quantitative relationship between coating performance changes and aging time.

[0003] Therefore, there is an urgent need for an alternating cyclic accelerated testing method that can simulate the actual aviation service environment and take into account the coupled effects of ultraviolet aging and corrosion, so as to achieve accurate prediction and accelerated simulation of the aging behavior of aluminum alloy aircraft plates with epoxy coating. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides an accelerated testing method for the aging of aluminum alloy aircraft panels. This method can simulate the actual aviation service environment, take into account the coupled effects of ultraviolet aging and corrosion, and achieve accurate prediction and accelerated simulation of the aging behavior of aluminum alloy aircraft panels with epoxy coating.

[0005] The accelerated aging test method for aluminum alloy aircraft plates provided by this invention includes: Obtain the epoxy-coated aluminum alloy aircraft plate samples to be tested, and group the samples for alternating cyclic tests of ultraviolet light irradiation and solution immersion; in the ultraviolet light irradiation stage, the samples are continuously irradiated with UVA ultraviolet light of a preset intensity in an ultraviolet aging test chamber; in the solution immersion stage, the samples are alternately immersed in acidic solutions and neutral solutions. During the test period, micro-defects, including micropores, cracks and peeling, were observed and recorded on the surface of the sample coating caused by ultraviolet light irradiation and different immersion environments. The development status of micro-defects during the coating aging process was determined by qualitative and quantitative analysis of the micro-defects. After completing the set test cycle, the residual thickness of the coating is measured, and a model is established to determine the relationship between coating thickness degradation and micro-defect development over aging time, based on the micro-defect development status during the coating aging process. This model aims to achieve accurate assessment and accelerated testing of the aging status of aluminum alloy aircraft panels.

[0006] Compared with the prior art, the beneficial effects of this invention are as follows: This invention provides an accelerated testing method for the aging of aluminum alloy aircraft panels. The method includes: acquiring epoxy-coated aluminum alloy aircraft panel samples to be tested, and grouping the samples for alternating cycles of ultraviolet (UV) irradiation and solution immersion; during the UV irradiation stage, the samples are continuously irradiated with UVA light of a preset intensity in a UV aging test chamber; during the solution immersion stage, the samples are alternately immersed in acidic and neutral solutions; during the test cycle, micro-defects, including micropores, cracks, and peeling, generated on the surface of the sample coating due to UV irradiation and different immersion environments are periodically observed and recorded; the development state of micro-defects during the coating aging process is determined through qualitative and quantitative analysis of the micro-defects; after completing the set test cycle, the residual thickness of the coating is measured, and a relationship model between coating thickness degradation and micro-defect development over aging time is established based on the development state of micro-defects during the coating aging process, thereby achieving accurate assessment and accelerated testing of the aging state of the aluminum alloy aircraft panels. This method can simulate the actual aviation service environment and take into account the coupled effects of ultraviolet aging and corrosion, so as to achieve accurate prediction and accelerated simulation of the aging behavior of aluminum alloy aircraft plates with epoxy coating. Attached Figure Description

[0007] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. Some specific embodiments of the invention will be described in detail below with reference to the accompanying drawings in an exemplary and non-limiting manner. The same reference numerals in the drawings designate the same or similar parts or components. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic flowchart of an accelerated aging test method for aluminum alloy aircraft plates according to an embodiment of the present invention. Detailed Implementation

[0008] To enable those skilled in the art to better understand the present invention, the technical solutions of this embodiment will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0009] See Figure 1 This embodiment provides an accelerated aging test method for aluminum alloy aircraft plates, including the following steps: S101. Obtain the epoxy-coated aluminum alloy aircraft plate sample to be tested, and group the samples for alternating cyclic tests of ultraviolet light irradiation and solution immersion; in the ultraviolet light irradiation stage, the sample is continuously irradiated with UVA ultraviolet light of a preset intensity in an ultraviolet aging test chamber; in the solution immersion stage, the sample is alternately immersed in acidic solution and neutral solution. S102. During the test period, observe and record micro-defects on the surface of the sample coating caused by ultraviolet light irradiation and different immersion environments, including micropores, cracks and peeling. Through qualitative and quantitative analysis of the micro-defects, determine the development state of micro-defects during the coating aging process. S103. After completing the set test cycle, measure the residual thickness of the coating and, in conjunction with the micro-defect development state during the coating aging process, establish a relationship model between coating thickness degradation and micro-defect development with aging time, so as to achieve accurate assessment and accelerated testing of the aging state of aluminum alloy aircraft plates.

[0010] It should be noted that in this embodiment, the samples are grouped for alternating cyclic tests of UV irradiation and solution immersion. An artificial accelerated aging process integrating alternating UVA irradiation and corrosive solution immersion is designed, significantly compressing the aging cycle. This simulates the complex aerospace environment under controlled laboratory conditions, enabling accelerated evaluation of aging behavior, improving testing efficiency, and meeting the needs for rapid material screening. In this embodiment, the samples receive continuous UVA irradiation of a preset intensity during the UV irradiation stage, and are alternately immersed in acidic and neutral solutions during the solution immersion stage. This replicates the superimposed characteristics of various aging stresses in the actual environment, such as UV radiation, high humidity corrosion, and alternating acidic and neutral solutions, enhancing the accuracy and adaptability of the test results in simulating real service behavior. Meanwhile, in this embodiment, the micro-defect states such as micropores, cracks, and peeling are qualitatively and quantitatively analyzed, and the development state of micro-defects during the coating aging process is determined. After completing the set test cycle, the residual thickness of the coating is measured. Combined with the development state of micro-defects during the coating aging process, a relationship model between coating thickness degradation and micro-defect development with aging time is established. This enables accurate assessment and accelerated testing of the aging state of aluminum alloy aircraft plates, digital tracking and modeling of aging damage behavior, quantitative description and predictable analysis of performance changes, and improved reliability assessment capabilities.

[0011] Furthermore, when establishing a model of the relationship between coating thickness degradation and micro-defect development over aging time, the following steps can be included: At each preset observation node, the residual thickness value of the coating and the micro-defect characteristic data at that time are recorded simultaneously. The micro-defect characteristic data includes at least the average width, average length, crack density, and the proportion of the spalled area of ​​the cracks; the micro-defect characteristic data collected at all time nodes are standardized, and the multidimensional crack characteristics in the micro-defect characteristic data are compressed into a single evolution index through a local weighted regression method, and the overall evolution trend of micro-defects is characterized in the form of a continuous curve; the curve of residual thickness change over time is compared with the overall evolution trend of micro-defects. The potential curve is used as a dual-output variable. A partial least squares regression algorithm is introduced to establish a coupling relationship model, and the optimal regression order is determined in an adaptive manner based on information criteria. During the training process of the coupling relationship model, a genetic algorithm is introduced to iteratively optimize the thickness weight coefficient and the micro-defect weight coefficient until the overall prediction error of the model is lower than a preset threshold and the coefficient of determination remains at a high confidence level. The final coupling relationship model is used as the core basis for accelerating the extrapolation of test results to actual service time. An encrypted detection process is automatically triggered when the thickness degradation rate and micro-defect evolution index predicted by the coupling relationship model are both at the warning threshold, so as to identify potential coating failure risks in advance. In this embodiment, by introducing multi-dimensional defect feature compression, partial least squares regression and genetic algorithm weight optimization, real-time modeling of the nonlinear coupling relationship between coating thickness degradation and micro-defect evolution is achieved. This embodiment first uses local weighted regression to dynamically reduce the dimensionality of multidimensional defect features, then uses a dual-output statistical modeling method to explore the deep correlation between thickness and defects changing over time, and uses an evolutionary algorithm to automatically optimize the weight allocation, thereby balancing model accuracy and generalization ability. This not only improves the reliability of aging trend prediction, but also provides timely warning of potential failures through defect evolution curves before the thickness has significantly decayed, significantly enhancing the extrapolation accuracy of test data to actual service life.

[0012] Preferably, the intensity of the ultraviolet light irradiation is set within the range of 0.65–0.75 W / m², and the irradiation wavelength is within the range of 338 nm–345 nm, to simulate solar ultraviolet light irradiation in actual aviation environments. It should be noted that by setting the intensity of the ultraviolet light irradiation to 0.65–0.75 W / m² and controlling the irradiation wavelength to 338 nm–345 nm, a high-fidelity simulation of solar ultraviolet radiation conditions in actual aviation environments can be achieved, ensuring that the test conditions are repeatable and quantifiable. Simultaneously, it enhances the consistency between the simulation results and actual service conditions, and improves the accuracy of the test method in predicting aging responses under actual service environments.

[0013] Preferably, the acidic solution is a 3.5% (w / w) acidified NaCl solution with a pH value set at 3.0–4.0 to enhance the corrosion acceleration effect; the neutral solution is a 3.5% (w / w) neutral NaCl solution with a pH value of 6.5–7.5 to simulate a neutral atmospheric corrosion environment and serve as a control condition to clearly distinguish the corrosion differences between acidic and neutral environments. The 3.5% (w / w) acidified NaCl solution (pH 3.0–4.0) and the neutral NaCl solution (pH 6.5–7.5) allow for a differentiated comparison between simulated corrosion and control environments, enhancing the acceleration effect of corrosion conditions and accurately distinguishing the impact of different corrosion environments on the coating aging mechanism. This helps to clarify the critical conditions and patterns of microcrack propagation and coating peeling in acidic environments, thereby providing quantitative support for material selection and protective design.

[0014] Preferably, the cycle of ultraviolet irradiation and solution immersion is 8–24 hours, with the time ratio of the ultraviolet irradiation stage to the immersion stage being 1:1 to 2:1, to optimize the synergistic effect of ultraviolet light and solution interaction. Setting the cycle of ultraviolet irradiation and solution immersion to 8–24 hours and limiting the time ratio to 1:1 to 2:1 allows for the reasonable application of ultraviolet stress and liquid phase corrosion stress at different stages, optimizing the coupled synergistic effect of composite stress. By precisely setting the time weights of ultraviolet light and solution interaction, this embodiment can better reflect the actual aging patterns of aircraft components under day-night cycles and ground / airborne humidity and heat variations, improving the simulation realism and prediction reliability of accelerated testing.

[0015] Preferably, the morphology and size of micropores and cracks on the coating surface are observed and recorded periodically using a scanning electron microscope to quantitatively assess the coating aging degree and establish a correlation model between micro-defect development and aging time. Based on the crack length, width, and density of aging damage on the coating surface, a damage index for coating aging is calculated. A crack evolution prediction model for the coating is then constructed based on this damage index to predict and assess the aging process of the coating. Specifically, the geometric dimensions of coating micropores and cracks are obtained using a scanning electron microscope, establishing a mapping relationship between crack length, width, density, and aging time. Furthermore, a damage index and prediction model are constructed to accurately capture early signs of coating failure before macroscopic thickness degradation, and the quantitative model is used to predict trends and provide early warnings of the aging degree.

[0016] Furthermore, when calculating the damage index of coating aging, the following steps are included: setting the damage index of coating aging as... Calculated using the first algorithm The first algorithm is: In the algorithm, The crack width is... The length of the crack. Crack density, Count the number of cracks.

[0017] It should be noted that in this embodiment, the numerator of the first algorithm introduces the product of the three crack parameters, organically combining the crack width, length, and density to enhance the actual characterization of the crack. The denominator combines the square of the total number of cracks with the square root of the sum of the squares of the densities, possessing the ability to distinguish between quantity-dominated and density-dominated scenarios, thus improving the robustness and sensitivity of the coating crack evolution prediction model. The structure of this denominator makes the index value increase non-linearly with the increase of the number of cracks and the degree of density aggregation, which is more consistent with the physical characteristics of the real aging trend.

[0018] Furthermore, during the instantaneous transition between the ultraviolet irradiation stage and the solution immersion stage, in-situ spectral ellipsometric measurements were performed on the sample coating, and the reflection phase difference Δ and amplitude ratio Ψ data were acquired in real time in the 190 nm–1000 nm wavelength range. The acquired data were then input into the multilayer film optical model to obtain the time-dependent effective refractive index. With extinction coefficient And use the incremental Kalman filter algorithm to , With crack width Crack length Crack density Perform fusion and calculate the coating density attenuation coefficient. The calculation formula is: ; In the formula, The initial refractive index, The initial extinction coefficient is when When the temperature drops to the threshold, an additional residual thickness measurement and electrochemical impedance spectroscopy test are automatically triggered to enable rapid detection of early latent failures in the coating.

[0019] It should be noted that in this embodiment, in-situ spectral ellipsometry is embedded in the alternation between the ultraviolet light irradiation stage and the solution immersion stage, and the optical constants of the coating are retrieved in real time. , With crack width Crack length Crack density Fusion was performed to construct a density attenuation coefficient. Incremental Kalman filtering is used to achieve dynamic correction of multi-source data, enabling... It is extremely sensitive to the initiation of coating pores and interface debonding, and can issue an early warning before significant changes in macroscopic thickness or electrochemical impedance spectroscopy parameters, triggering additional detection, improving the resolution and timeliness of capturing early latent failures, and avoiding redundant testing through threshold triggering.

[0020] Preferably, the residual thickness is measured using a non-contact coating thickness gauge with a measurement accuracy of not less than 0.5 μm. Based on the initial coating thickness and the coating thickness during testing, the coating thickness degradation rate is calculated to achieve quantitative analysis of coating aging. Using a non-contact thickness gauge for high-precision measurement of the residual coating thickness and calculation of the degradation rate helps avoid measurement errors caused by human interference or sample damage. The requirement of an accuracy of not less than 0.5 μm ensures that even minute thickness changes can be accurately recorded, significantly improving the reliability and accuracy of the test data.

[0021] Furthermore, when calculating the coating thickness degradation rate based on the initial coating thickness and the coating thickness during testing, a second algorithm is used. The second algorithm is as follows: ; In the algorithm, The coating thickness degradation rate, The initial coating thickness. The coating thickness during testing. For aging time, and These are environmental characteristic parameters obtained by fitting the aging environment.

[0022] It should be noted that, in this embodiment, the denominator term of the second algorithm adopts... The composite function form couples the power relationship of time with an exponentially decreasing term, enabling more sensitive capture of the changing trends in degradation rates during the early and middle stages of aging; parameters and It can be adjusted for different service environments (such as ultraviolet radiation intensity, frequency of temperature and humidity changes), possessing high adjustability and environmental adaptability. Through [the following]... and The fitting optimization can not only establish the mapping relationship between environmental characteristics and aging rate, but also achieve: rate response modeling for different aging stress combinations (such as acid / neutral solution + UV); form a parameterized degradation prediction tool to support the extrapolation of structural health monitoring system or accelerated test results to service life analysis.

[0023] Preferably, the accelerated testing method for aging aluminum alloy aircraft plates further includes determining the electrochemical characteristic parameters of the sample coating during the aging process using electrochemical impedance spectroscopy (EIS). The test frequency range of the EIS is set to 0.01 Hz to 100 kHz to effectively capture subtle changes in the electrochemical impedance parameters during coating aging. Specifically, by dynamically monitoring the electrochemical performance of the sample during aging using EIS, with a frequency range of 0.01 Hz to 100 kHz, multiple aging characteristics, including high-frequency interfacial reactions and low-frequency diffusion impedance, can be comprehensively captured. Compared to traditional potentiometric titration or polarization testing methods, EIS offers advantages such as non-destructive testing, high sensitivity, and a wide spectral response. It can effectively reveal changes in coating shielding performance, charge migration ability, and pore structure during the aging process, making it a more comprehensive evaluation tool.

[0024] Preferably, Zsimp-Win software is used to perform equivalent circuit fitting on the electrochemical impedance spectroscopy data and extract parameters such as coating resistance, coating capacitance, interfacial capacitance, and diffusion impedance to reveal the electrochemical mechanism of coating aging. Specifically, performing equivalent circuit fitting on the electrochemical impedance spectroscopy data using Zsimp-Win software and extracting parameters such as coating resistance, capacitance, and diffusion impedance helps to transform complex electrochemical impedance spectroscopy curve information into interpretable and quantifiable physical indicators. This embodiment can not only identify the mechanism differences between the early and late stages of corrosion but also reveal the dynamic evolution of charge accumulation, capacitance decay, and coating damage processes, compensating for the insufficient resolution of electrochemical behavior analysis.

[0025] Preferably, the test environment temperature is controlled within the range of 35℃ to 50℃, and the relative humidity is set between 70% and 95%, with a test cycle of 576 hours. Controlling the test environment temperature (35℃ to 50℃) and humidity (70% to 95%) allows the accelerated test to be conducted in a high-temperature and high-humidity environment, thereby accelerating the aging reaction rate and ensuring test repeatability. Compared with open natural environment testing, this embodiment enhances the stability and comparability of test results through environmental controllability and can effectively simulate the destructive effect of thermal and humid coupling stress on coating performance.

[0026] Preferably, X-ray photoelectron spectroscopy (XPS) is used to analyze the changes in elemental composition and oxidation state of the sample surface to help reveal the chemical structure evolution mechanism of the coating. Specifically, using XPS for precise characterization of the elemental composition and oxidation state changes of the sample surface can effectively reveal the chemical bond breaking, element migration, and oxide layer formation patterns during the aging process of the coating. Compared to evaluation based solely on physical morphology or thickness degradation, this embodiment delves into the microscopic chemical mechanism, providing a basis for understanding the essence of the corrosion process and assisting in the establishment of multi-scale, multi-parameter aging prediction models, thereby enhancing the ability to control material failure mechanisms.

[0027] Preferably, after completing the preset test cycle and obtaining the residual coating thickness data, nonlinear analysis is performed on the thickness measurements at each time point. Two sets of environmental characteristic factors are used based on the simulated aging environment conditions to fit the time response and environmental response behavior of the coating degradation, respectively. By comparing the initial coating thickness with the coating thickness changes at each stage of the test, and combining time variables and environmental influence weights, a dynamic attenuation rate determination method is derived. This dynamic attenuation rate determination method predicts the coating degradation rate under different service times and multi-factor coupled environments by comprehensively analyzing the nonlinear change trend of thickness over time and the synergistic effect caused by environmental factors. This achieves accurate modeling and life prediction of the long-term service performance of epoxy-coated aluminum alloy aircraft plates. It should be noted that traditional coating aging assessment methods typically rely solely on the linear difference or average rate of change between the initial coating thickness and the final residual thickness, failing to fully reflect the stage-based, nonlinear, and environmental synergistic effects of coating degradation during service. This can easily lead to large life prediction errors and extended test evaluation cycles. In this embodiment, by coupling two sets of environmental characteristic factors (such as temperature, humidity, UV intensity, and type of corrosive solution) with a time variable, the time response curve of coating degradation and the environmental response change curve are modeled separately. Furthermore, the two are nonlinearly fitted and fused to construct a dynamic response mechanism. This embodiment can not only identify the rate differences in thickness change at different aging stages, but also analyze the synergistic or amplifying effects of multi-factor environmental factors on coating performance degradation, thereby establishing a degradation rate model with predictive capabilities. Especially in aerospace applications, where the service environment is complex and variable, this embodiment, through a dynamic judgment method that couples stage response with the environment, can more accurately reflect the actual aging mechanism, significantly improving the accuracy and adaptability of thickness degradation modeling.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An accelerated testing method for aging of aluminum alloy aircraft plates, characterized in that, include: Obtain the epoxy-coated aluminum alloy aircraft plate samples to be tested, and group the samples for cyclic alternating tests of ultraviolet light irradiation and solution immersion. During the ultraviolet irradiation stage, the sample is continuously irradiated with UVA ultraviolet light of a preset intensity in an ultraviolet aging test chamber; during the solution immersion stage, the sample is alternately immersed in acidic and neutral solutions. During the test period, micro-defects, including micropores, cracks and peeling, were observed and recorded on the surface of the sample coating caused by ultraviolet light irradiation and different immersion environments. The development status of micro-defects during the coating aging process was determined by qualitative and quantitative analysis of the micro-defects. After completing the set test cycle, the residual thickness of the coating is measured, and a model is established to determine the relationship between coating thickness degradation and micro-defect development over aging time, based on the micro-defect development status during the coating aging process. This is to achieve accurate assessment and accelerated testing of the aging status of aluminum alloy aircraft panels.

2. The accelerated aging test method for aluminum alloy aircraft plates according to claim 1, characterized in that, The intensity of the ultraviolet light irradiation is set in the range of 0.65 to 0.75 W / m², and the irradiation wavelength is in the range of 338 nm to 345 nm, in order to simulate the solar ultraviolet light irradiation in the actual aviation environment.

3. The accelerated aging test method for aluminum alloy aircraft plates according to claim 1, characterized in that, The acidic solution is a 3.5% (w / w) acidified NaCl solution with a pH value set at 3.0–4.0 to enhance the corrosion acceleration effect; the neutral solution is a 3.5% (w / w) neutral NaCl solution with a pH value of 6.5–7.5 to simulate a neutral atmospheric corrosion environment and to serve as a control condition to clearly distinguish the corrosion differences between the acidic and neutral environments.

4. The accelerated aging test method for aluminum alloy aircraft plates according to claim 1, characterized in that, The cycle of ultraviolet light irradiation and solution immersion is 8 to 24 hours, with the time ratio of the ultraviolet light irradiation stage to the immersion stage being 1:1 to 2:1, in order to optimize the synergistic effect of ultraviolet light and solution interaction.

5. The accelerated aging test method for aluminum alloy aircraft plates according to claim 1, characterized in that, The morphology and size of micropores and cracks on the coating surface are observed and recorded regularly using scanning electron microscopy to quantitatively assess the degree of coating aging and establish a correlation model between micro-defect development and aging time. Based on the crack length, width and density of aging damage on the coating surface, the damage index of coating aging is calculated. Based on the damage index of coating aging, a coating crack evolution prediction model is constructed to predict and evaluate the aging process of the coating.

6. The accelerated aging test method for aluminum alloy aircraft plates according to claim 1, characterized in that, The residual thickness was measured using a non-contact coating thickness gauge with a measurement accuracy of not less than 0.5 μm. Based on the initial coating thickness and the coating thickness at the time of testing, the coating thickness degradation rate was calculated to achieve quantitative analysis of coating aging.

7. The accelerated aging test method for aluminum alloy aircraft plates according to claim 1, characterized in that, It also includes using electrochemical impedance spectroscopy to determine the electrochemical characteristic parameters of the sample coating during the aging process. The test frequency range of the electrochemical impedance spectroscopy is set to 0.01 Hz to 100 kHz to effectively capture the subtle changes in the electrochemical impedance parameters during the coating aging process.

8. The accelerated aging test method for aluminum alloy aircraft plates according to claim 7, characterized in that, The equivalent circuit was fitted to the electrochemical impedance spectroscopy data using Zsimp-Win software, and the coating resistance, coating capacitance, interface capacitance and diffusion impedance parameters were extracted to reveal the electrochemical mechanism of coating aging.

9. The accelerated aging test method for aluminum alloy aircraft plates according to claim 1, characterized in that, The ambient temperature was controlled within the range of 35℃ to 50℃, and the relative humidity was set between 70% and 95%. The test period was 576 hours.

10. The accelerated aging test method for aluminum alloy aircraft plates according to claim 1, characterized in that, X-ray photoelectron spectroscopy was used to analyze the changes in elemental composition and oxidation state on the sample surface to help reveal the chemical structure evolution mechanism of the coating.

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