In-situ detection method and detection system for multi-layer stealth coating of aero-engine combustion chamber

Abstract

The invention relates to a nondestructive testing technology, discloses an in-situ detection method and a detection system for a multi-layer stealth coating of an aero-engine combustion chamber, and provides an innovative multi-physical-field cooperative detection method which organically combines three technologies of infrared thermal imaging, eddy current detection and high-frequency ultrasound to realize in-situ detection of the multi-layer stealth coating of the aero-engine combustion chamber. And comprehensive evaluation of six layers of functional structures including a structural layer, a barrier layer, a radar wave absorption layer and the like is realized. Infrared detection of surface defects, eddy current analysis of electromagnetic characteristics of a conductive layer and ultrasonic detection of a deep interface state are utilized, and an intelligent data fusion and hierarchical association rule engine is utilized. According to the method, the limitation of a traditional single detection technology is broken through, the misjudgment rate is remarkably reduced by adopting a cross validation mechanism, an accurate maintenance decision is supported through dynamic feedback, and an effective solution is provided for reliability maintenance of the aviation stealth coating.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nondestructive testing, in particular to a method and system for in-situ detection of a multilayer stealth coating of an aero-engine combustion chamber. BACKGROUND

[0002] As the core power device of modern aircraft, the performance and reliability of an aero-engine directly relate to flight safety and combat effectiveness. The outer wall of a combustion chamber, as a key component with high temperature, high pressure and high flow rate, is usually coated with a multilayer functional stealth coating, aiming to effectively suppress the characteristics of engine thermal radiation and radar wave reflection, and improve the survivability and penetration capability of the aircraft.

[0003] A typical stealth coating of a combustion chamber usually adopts a complex multilayer structure design, for example, but not limited to, a structure layer, a barrier layer, a radar wave absorbing layer, a thermal matching layer, an adhesive layer and a substrate layer arranged from outside to inside. The interface bonding state, the in-layer defects (such as cracks, debonding, porosity, foreign inclusions) and the functional layer characteristics (such as the degradation of the electromagnetic properties of radar absorbing materials) of each layer under the harsh engine working conditions (high temperature, thermal shock, oxidation corrosion, mechanical stress) will directly affect the stealth effect, structural integrity of the coating and the safe operation of the engine. Therefore, regular, in-situ (without disassembling the combustion chamber) comprehensive detection and condition assessment of the multilayer stealth coating of the combustion chamber is of great importance to prevent coating failure, ensure reliable operation of the engine and maintain the stealth performance.

[0004] The existing technology often focuses on the detection of a single type of defect or a specific layer, and lacks an effective means to simultaneously and comprehensively evaluate the integrity (defects) and functionality (electromagnetic properties, etc.) of the entire multilayer structure system (from the outermost layer to the innermost layer interface). SUMMARY

[0005] To solve the above problems, the present application provides a method and system for in-situ detection of a multilayer stealth coating of an aero-engine combustion chamber, which is implemented as follows:

[0006] A method for in-situ detection of a multilayer stealth coating of an aero-engine combustion chamber, the stealth coating comprising at least a structure layer, a barrier layer, a radar wave absorbing layer, a thermal matching layer, an adhesive layer and a substrate layer arranged from outside to inside, and the radar wave absorbing layer having electrical conductivity, the method comprising the following steps:

[0007] (a) Infrared detection step: using infrared thermal imaging technology to detect the structure layer and the barrier layer, and obtaining infrared thermal image information representing the distribution of thermal physical properties of the surface and the near-surface region thereof, for detecting surface cracks, coating peeling and near-surface delamination defects;

[0008] (b) eddy current detection step: detecting the radar wave absorbing layer by using eddy current detection technology to obtain eddy current detection information representing electromagnetic property distribution and internal structure uniformity of the layer, for detecting conductivity or magnetic permeability abnormality, internal inclusion and delamination defects;

[0009] (c) ultrasonic detection step: detecting the region including thermal matching layer, adhesive layer, substrate layer and the interface between layers by using pulse-echo ultrasonic detection technology with high-frequency focused probe to obtain ultrasonic detection information reflecting acoustic impedance change and interface state, for detecting debonding, delamination and porosity defects;

[0010] (d) multi-physical field information fusion and collaborative analysis step:

[0011] (i) aligning the infrared thermographic information, eddy current detection information and ultrasonic detection information obtained in steps (a), (b) and (c) in space position and time;

[0012] (ii) establishing hierarchical correlation rules based on the design function of each layer of the stealth coating, potential defect types, and the correlation between the thermal, electromagnetic and acoustic properties respectively responded in infrared thermal imaging detection, eddy current detection and pulse-echo ultrasonic detection;

[0013] (iii) applying the hierarchical correlation rules to perform cross-validation and correlation analysis on the infrared thermographic information, eddy current detection information and ultrasonic detection information after alignment, and the correlation analysis at least includes the following rules:

[0014] ① verifying the integrity of the structural layer and the barrier layer by using infrared thermographic information, and providing surface state reference for the eddy current detection step;

[0015] ② verifying the electromagnetic properties and structural uniformity of the radar wave absorbing layer by using eddy current detection information, and locating the depth position of the abnormality in the layer through its depth resolution;

[0016] ③ characterizing the bonding quality and internal defects of the interface between thermal matching layer and adhesive layer, and the interface between adhesive layer and substrate layer based on ultrasonic detection information, and correcting the depth positioning value of infrared detection and eddy current detection results based on ultrasonic depth data;

[0017] ④ spatially aligning the depth reference provided by ultrasonic detection with the eddy current depth positioning result and the surface state of infrared thermal imaging, and correlating the physical quantities;

[0018] ⑤When the infrared thermal imaging detection shows that there is a thermal abnormal area in the structure layer or the barrier layer, and the eddy current detection also shows that the electromagnetic property is abnormal in the upper area of the radar wave absorbing layer corresponding to the position, and the ultrasonic detection does not find a significant reflected wave change in the interface of the thermal matching layer, the adhesive layer or the substrate layer, it is determined that the abnormality is mainly located in the structure layer, the barrier layer or the upper surface layer of the radar wave absorbing layer;

[0019] ⑥When the ultrasonic detection shows a strong reflection debonding signal in the interface of the adhesive layer, and the infrared thermal imaging detection shows a thermal conduction abnormality in the corresponding position, or / and the eddy current detection shows an electromagnetic property abnormality in the lower area of the radar wave absorbing layer, it is determined that there is adhesive layer debonding accompanied by performance degradation of the adjacent layer material;

[0020] ⑦When an abnormal signal is detected in a certain layer, the corresponding re-inspection or depth-focused analysis of the adjacent layer in the corresponding spatial position is triggered;

[0021] (iv) Based on the results of the cross-validation and correlation analysis, a comprehensive state evaluation map of the multi-layer stealth coating is generated, which contains the state of each layer material, the type, position, size and severity of the defect of the interfacial quality and defect.

[0022] Further, the eddy current detection step adopts a multi-frequency eddy current detection method, specifically including:

[0023] According to the known thickness and electromagnetic parameters of the radar wave absorbing layer, a plurality of eddy current excitation signals of different frequencies are selected for scanning, and a tomographic image sequence reflecting the electromagnetic property distribution at different depths of the layer is generated by analyzing the amplitude and phase changes of the eddy current response under different frequencies.

[0024] Further, in the ultrasonic detection step:

[0025] By adjusting the incident angle and focusing depth of the high-frequency focusing probe, the receiving ability of the reflected echo of the interface of the thermal matching layer and the adhesive layer, the adhesive layer and the substrate layer is optimized, and a B-scan cross-sectional image and / or a C-scan three-dimensional image is generated to display the defect distribution morphology.

[0026] Further, the alignment in space and time is realized by the following way:

[0027] A common reference mark point is set in the detection area, each detection probe is integrated with a high-precision optical positioning device, and the detection system adopts a unified clock to synchronize the data collection of each detection method.

[0028] The application also discloses an in-situ detection system for a multi-layer stealth coating of an aero-engine combustion chamber, which is characterized by comprising:

[0029] Infrared detection unit: includes an infrared thermal imager and its scanning mechanism, configured to detect the structural layer and the blocking layer and acquire infrared thermal image information;

[0030] Eddy current detection unit: includes a multi-frequency eddy current probe and its detection and analysis instrument, configured to detect the radar wave absorbing layer and obtain electromagnetic properties and internal structure information;

[0031] Ultrasonic testing unit: includes a high-frequency focused ultrasound probe, a pulse generator / receiver and a motion controller, configured to scan the thermal matching layer, adhesive layer, substrate layer and their interlayer interfaces and acquire acoustic impedance and interface state information;

[0032] Positioning and synchronization unit: includes a high-precision optical positioning and tracking device and a unified clock source, configured to provide real-time spatial coordinate information for the infrared detection unit, eddy current detection unit, and ultrasonic detection unit, and synchronize their data acquisition timing;

[0033] Data fusion and analysis unit: includes data storage and registration module, association rule base, multimodal association analysis module, and map generation module;

[0034] The data storage and registration module is used to receive and store data from each detection unit, and to perform spatial position and time alignment processing based on the information provided by the positioning and synchronization unit;

[0035] The association rule base is used to store preset hierarchical association rules;

[0036] The multimodal association analysis module is used to call the rules in the association rule base to perform the cross-validation and association analysis described in steps (d) and (iii) above on the registered infrared, eddy current, and ultrasonic data;

[0037] The map generation module is used to generate and output a comprehensive state evaluation map of the multi-layer stealth coating based on the output results of the multimodal correlation analysis module.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] I. This invention innovatively combines three physical field detection technologies: infrared thermal imaging, eddy current detection, and pulse-echo ultrasound. Infrared thermal imaging rapidly captures thermal anomalies such as cracks and spalling on the surface and near-surface layers; eddy current detection accurately identifies electromagnetic anomalies and internal defects in specific conductive radar wave absorbing layers; and high-frequency ultrasound penetrates deep structures to detect interface debonding and porosity in thermal matching layers, adhesive layers, and the substrate. Through multi-modal collaborative detection, comprehensive surface-to-deep layer detection is achieved.

[0040] Secondly, the application realizes cross verification of multi-physical field data by establishing hierarchical association rules, and intelligent fusion analysis significantly reduces the misjudgment rate and improves the accuracy of defect positioning and classification.

[0041] Thirdly, the application automatically triggers adjacent layer review through abnormal signals, optimizes the detection process, avoids missed detection, generates a comprehensive state atlas, quantitatively evaluates the influence of defects on performance such as stealth and thermal barrier, and provides data support for coating life prediction and maintenance decision-making. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the application examples or the prior art or the descriptions in the prior art, it is obvious that for those skilled in the art, without creative labor, other drawings can also be obtained according to these drawings.

[0043] Figure 1 The figure is a schematic diagram of the detection method of the application.

[0044] Figure 2 The figure is a schematic diagram of the structure of the multilayer stealth coating.

[0045] In the figure:

[0046] 10-structure layer, 20-barrier layer, 30-radar wave absorbing layer, 40-thermal matching layer, 50-adhesive layer, 60-substrate layer. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme in the embodiments of the application will be described clearly and completely below in combination with the drawings in the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, not all the embodiments. Therefore, the following detailed description of the embodiments of the application provided in the drawings is not intended to limit the scope of the claimed application, but only represents selected embodiments of the application.

[0048] A method for in-situ detection of a multilayer stealth coating of an aero-engine combustion chamber, the stealth coating comprising at least a structure layer, a barrier layer, a radar wave absorbing layer, a thermal matching layer, an adhesive layer and a substrate layer arranged in order from the outside to the inside, and the radar wave absorbing layer having electrical conductivity, the method comprising the following steps:

[0049] (a) Infrared detection step: the structure layer and the barrier layer are detected by using infrared thermal imaging technology to obtain infrared thermal image information representing the thermal physical property distribution of the surface and near-surface region thereof, which is used to detect surface cracks, coating peeling and near-surface delamination defects; in this embodiment, a medium-wave infrared thermal imager (3-5 pm band) can be used, equipped with a laser-assisted heating module (power adjustable 50-200 W), and the thermal contrast of surface defects is enhanced by active thermal excitation to improve the detection rate of surface micro-cracks and peeling defects.

[0050] (b) Eddy current detection step: the radar wave absorbing layer is detected by using eddy current detection technology to obtain eddy current detection information representing the electromagnetic property distribution and internal structure uniformity of the layer, which is used to detect conductivity or magnetic permeability abnormalities, internal inclusions and delamination defects; specifically, a multi-frequency array eddy current probe can be used to detect the electromagnetic uniformity of the surface layer 0-0.2 mm by high frequency (1-10 MHz), analyze the inclusion defects of the middle layer 0.2-0.5 mm by medium frequency (100 kHz-1 MHz), and evaluate the magnetic permeability gradient of the deep layer 0.5-1 mm by low frequency (10-100 kHz), so as to improve the depth positioning accuracy of delamination defects.

[0051] (c) Ultrasonic detection step: pulse-echo ultrasonic detection technology is used to detect the region including the thermal matching layer, the adhesive layer, the substrate layer and the interface between the layers by using a high-frequency focused probe to obtain ultrasonic detection information reflecting the acoustic impedance change and the interface state, which is used to detect debonding, delamination and porosity defects; the center frequency, bandwidth and acoustic beam focusing diameter (dynamic focusing range) of the high-frequency focused probe are set according to the specific detection conditions, and all transmit-receive combination signals are collected by using full-matrix capture technology.

[0052] (d) Multi-physical field information fusion and collaborative analysis step:

[0053] (i) The infrared thermal image information, eddy current detection information and ultrasonic detection information obtained in steps (a), (b) and (c) are aligned in space and time; in this embodiment, a multi-degree-of-freedom mechanical arm can be used to carry the detection probe, and a laser tracker can be used to realize the coordinate connection of multiple probes to achieve spatial alignment. All sensor clocks are synchronized based on the PTPv2 protocol to achieve time alignment.

[0054] (ii) Based on the design function of each layer of the stealth coating, the potential defect types, and the correlation between the thermal physical properties, electromagnetic properties and acoustic properties respectively responded by infrared thermal imaging detection, eddy current detection and pulse-echo ultrasonic detection, layer correlation rules are established; an intelligent correlation rule library is designed, a deep neural network is embedded, existing defect samples are collected for model training, rule weights are dynamically optimized, errors in multi-modal data registration are reduced, and the classification accuracy and detection rate of complex defects are improved.

[0055] (iii) applying the hierarchical correlation rules, performing cross-validation and correlation analysis on the infrared thermographic information, eddy current detection information, and ultrasonic detection information after alignment processing, and the correlation analysis at least includes the following rules:

[0056] ① verifying the integrity of the structural layer and the blocking layer using the infrared thermographic information, and providing surface state reference for the eddy current detection step;

[0057] ② verifying the electromagnetic properties and structural uniformity of the radar wave absorbing layer using the eddy current detection information, and positioning the depth position of the anomaly in the layer through its depth resolution capability;

[0058] ③ characterizing the bonding quality and internal defects of the interface between the thermal matching layer and the adhesive layer, and the interface between the adhesive layer and the substrate layer based on the ultrasonic detection information, and correcting the depth positioning values of the infrared detection and eddy current detection results based on the ultrasonic depth data;

[0059] ④ spatially aligning and correlating the depth reference provided by the ultrasonic detection with the eddy current depth positioning results and the infrared thermal imaging surface state;

[0060] ⑤ when the infrared thermal imaging detection shows that there is a thermal abnormal area in the structural layer or the blocking layer, and the corresponding position of the eddy current detection also shows electromagnetic property abnormality in the upper layer area of the radar wave absorbing layer, and the ultrasonic detection does not find significant reflected wave changes in the thermal matching layer, the adhesive layer or the substrate layer interface, it is determined that the anomaly is mainly located in the structural layer, the blocking layer or the upper layer of the radar wave absorbing layer;

[0061] ⑥ when the ultrasonic detection shows strong reflection debonding signals at the adhesive layer interface, and the corresponding position of the infrared thermal imaging detection shows thermal conduction abnormality, or / and the eddy current detection shows electromagnetic property abnormality in the lower layer area of the radar wave absorbing layer, it is determined that there is adhesive layer debonding accompanied by performance degradation of the adjacent layer material;

[0062] ⑦ when an abnormal signal is detected in a certain layer, trigger targeted re-inspection or depth focused analysis of the adjacent layer at the corresponding spatial position;

[0063] (iv) based on the results of the cross-validation and correlation analysis, generating a comprehensive state evaluation map of the multi-layer stealth coating, which contains information of the material state of each layer, the quality and defect type, position, size and severity of the interface between the layers. Through the integration of defect feature quantification in the finally generated three-dimensional comprehensive state evaluation map, further prediction of stealth performance and assessment of remaining life can be made. Specifically, by constructing a three-dimensional layered model based on the real geometry of the coating, each layer corresponds to an independent data channel:

[0064] structural layer / blocking layer: infrared thermal spot distribution map (temperature gradient, heat flow vector);

[0065] Radar wave absorbing layer: eddy current electromagnetic parameter cloud map (conductivity, permeability, skin depth);

[0066] Thermal matching layer: ultrasonic acoustic impedance profile (interface reflection coefficient, attenuation spectrum).

[0067] Quantifying defect features includes:

[0068] Type coding: crack (C type), peeling (D type), debonding (B type);

[0069] Position marking: local coordinate system (origin is engine flange reference);

[0070] Size calculation: defect profile is extracted by edge detection algorithm, and long axis / short axis / area is output;

[0071] Severity index: combined with stress concentration factor and stealth performance loss classification, etc.

[0072] In other embodiments, the multifunctional layers of the coating can also be adjusted to form a series of coating three-dimensional layered models, and the corresponding detection parameters are adjusted based on the model.

[0073] Further, the eddy current detection step adopts a multi-frequency eddy current detection method, specifically including:

[0074] According to the known thickness and electromagnetic parameters of the radar wave absorbing layer, a plurality of different frequency eddy current excitation signals are selected for scanning, and by analyzing the amplitude and phase changes of the eddy current response under different frequencies, a tomographic image sequence reflecting the electromagnetic characteristic distribution at different depths of the layer is generated. In one embodiment, based on the known thickness (0.2-1.2mm) and electromagnetic parameters (conductivity 1-10MS / m, relative permeability 2-10) of the radar wave absorbing layer, 3-5 characteristic frequency (such as 100kHz, 1MHz, 5MHz) excitation signals can be intelligently selected for layered scanning. The detection system synchronously collects the eddy current response signals under each frequency through the orthogonal coil probe, and uses the analytical model to inverse calculate the electromagnetic parameter distribution at different depths, and finally generates a tomographic image sequence. For engine curved surface structure, a probe adaptive fitting algorithm based on finite element simulation can also be developed to improve the signal-to-noise ratio of detection.

[0075] Further, in the ultrasonic detection step:

[0076] By adjusting the incident angle and focal depth of the high-frequency focused probe, the receiving ability of the reflected echo of the interface between the thermal matching layer and the adhesive layer and the interface between the adhesive layer and the substrate layer is optimized, and a B-scan cross-sectional image and / or a C-scan three-dimensional image is generated to display the defect distribution pattern. In one embodiment, a 25MHz high-frequency focused probe is used, which is equipped with a digital acoustic beam deflection module, the optimal incident angle is automatically calculated based on the coating CAD model, and the focal depth is dynamically adjusted in the range of 1-8mm.

[0077] B-scan imaging: cross-sectional images are acquired along the probe movement path, and the resolution is improved by using synthetic aperture focusing technology.

[0078] C-scan imaging: a three-dimensional acoustic impedance distribution map is constructed by X, Y and Z three-axis linkage scanning

[0079] Further, the interface signal enhancement algorithm can be developed to effectively separate the adjacent interface echoes with small spacing.

[0080] Further, the alignment in space and time is realized by the following ways:

[0081] A common reference marker point is set in the detection area, each detection probe is integrated with a high-precision optical positioning device, and the detection system uses a unified clock to synchronize the data acquisition of each detection method.

[0082] The application also discloses an aero-engine combustion chamber multi-layer stealth coating in-situ detection system, which is used for implementing the above-mentioned method and comprises:

[0083] Infrared detection unit: comprising an infrared thermal imager and a scanning mechanism thereof, configured to detect the structure layer and the barrier layer and acquire infrared thermal image information; a medium wave thermal imager can be used, and a laser auxiliary heating module is matched to realize micro-surface defect identification.

[0084] Eddy current detection unit: comprising a multi-frequency eddy current probe and an eddy current detector, configured to detect the radar wave absorbing layer and acquire electromagnetic characteristics and internal structure information; a 10kHz-10MHz multi-frequency probe array is integrated, high-detection-sensitivity electromagnetic parameters are set, and the detection rate is improved.

[0085] Ultrasonic detection unit: comprising a high-frequency focused ultrasonic probe, a pulse generator / receiver and a motion controller, configured to scan the thermal matching layer, the adhesive layer, the substrate layer and the interfaces therebetween and acquire acoustic impedance and interface state information;

[0086] Positioning and synchronization unit: including high-precision optical positioning tracking device and unified clock source, configured to provide real-time spatial coordinate information for infrared detection unit, eddy current detection unit, ultrasonic detection unit, and synchronize their data acquisition timing; the high-precision optical positioning system and the PTPv2 time synchronization protocol constitute the space-time reference. Multi-degree-of-freedom mechanical arm can be used to realize multi-probe cooperative motion control and improve spatial synchronization.

[0087] Data fusion and analysis unit: including data storage and registration module, association rule library, multi-modal correlation analysis module, atlas generation module; the data registration module realizes multi-modal data spatial fusion through finite element grid; the association rule library contains existing multi-group process-defect mapping relationship for training. The atlas generation module outputs a digital report containing defect three-dimensional model, RCS prediction, and residual life assessment, and visualizes the detection results.

[0088] The data storage and registration module is used for receiving and storing data from each detection unit, and performing spatial position and time alignment processing based on the information provided by the positioning and synchronization unit;

[0089] The association rule library is used for storing preset hierarchical association rules;

[0090] The multi-modal correlation analysis module is used for calling rules in the association rule library, and performing cross-validation and correlation analysis on the registered infrared, eddy current, and ultrasonic data as described in step (d)(iii);

[0091] The atlas generation module is used for generating and outputting the comprehensive state evaluation atlas of the multi-layer stealth coating based on the output results of the multi-modal correlation analysis module.

[0092] The embodiment realizes comprehensive evaluation of the six-layer functional coating through the cooperative detection and intelligent data fusion of infrared thermal imaging, multi-frequency eddy current, and high-frequency ultrasonic three technologies, and provides a breakthrough solution for intelligent operation and maintenance of aviation stealth coating.

[0093] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An in-situ detection method for a multi-layer stealth coating in an aero-engine combustion chamber, wherein the stealth coating comprises at least, from the outside to the inside, a structural layer, a blocking layer, a radar wave absorbing layer, a thermal matching layer, an adhesive layer, and a substrate layer, wherein the radar wave absorbing layer is conductive, characterized in that, The method includes the following steps: (a) Infrared detection step: The structural layer and the barrier layer are detected using infrared thermal imaging technology to obtain infrared thermal image information that characterizes the distribution of thermophysical properties of their surface and near-surface regions, which is used to detect surface cracks, coating peeling and near-surface delamination defects. (b) Eddy current detection step: The radar wave absorbing layer is detected using eddy current detection technology to obtain eddy current detection information that characterizes the distribution of electromagnetic properties and the uniformity of the internal structure of the layer, which is used to detect abnormal conductivity or magnetic permeability, internal inclusions and delamination defects. (c) Ultrasonic testing steps: Using pulse-echo ultrasonic testing technology, a high-frequency focusing probe is used to test the area including the thermal matching layer, adhesive layer, substrate layer and their interlayer interfaces to obtain ultrasonic testing information reflecting changes in acoustic impedance and interface state, which is used to detect debonding, delamination and porosity defects. (d) Steps for multiphysics information fusion and collaborative analysis: (i) Align the infrared thermal image information, eddy current detection information and ultrasonic detection information obtained in steps (a), (b) and (c) in terms of spatial position and time. (ii) Based on the design functions and potential defect types of each layer of the stealth coating, as well as the correlation between the thermophysical, electromagnetic and acoustic properties of the responses during infrared thermal imaging detection, eddy current detection and pulse-echo ultrasonic detection, a hierarchical association rule is established. (iii) Applying the hierarchical association rules, perform cross-validation and association analysis on the aligned infrared thermal image information, eddy current detection information, and ultrasonic detection information. The association analysis includes at least the following rules: ① Use infrared thermal imaging information to verify the integrity of the structural layer and barrier layer, and provide a surface state reference for the eddy current detection step; ② Use eddy current detection information to verify the electromagnetic properties and structural uniformity of the radar wave absorbing layer, and use its depth resolution capability to locate the depth of anomalies within the layer. ③Based on ultrasonic testing information, the bonding quality and internal defects of the interface between the thermal matching layer and the adhesive layer, and the interface between the adhesive layer and the substrate layer are characterized, and the depth positioning values ​​of the infrared testing and eddy current testing results are corrected based on ultrasonic depth data. ④ Spatially align and correlate the depth benchmark provided by ultrasonic testing with the eddy current depth positioning results and the surface condition of infrared thermal imaging; ⑤ When infrared thermal imaging shows that there is a thermal anomaly in the structural layer or barrier layer, and the corresponding eddy current detection also shows abnormal electromagnetic properties in the upper region of the radar wave absorbing layer, while ultrasonic detection does not find significant changes in reflected waves at the interface of the thermal matching layer, adhesive layer or substrate layer, it is determined that the anomaly is mainly located on the upper surface of the structural layer, barrier layer or radar wave absorbing layer. ⑥ When ultrasonic testing shows a strong reflected debonding signal at the interface of the adhesive layer, and infrared thermal imaging at the corresponding location shows abnormal heat conduction, or / and eddy current testing shows abnormal electromagnetic properties in the region below the radar wave absorbing layer, it is determined that there is debonding of the adhesive layer accompanied by degradation of the material properties of the adjacent layers. ⑦ When an abnormal signal is detected in a certain layer, a targeted re-examination or depth-focused analysis of the adjacent layers at the corresponding spatial location is triggered; (iv) Based on the results of the cross-validation and correlation analysis, a comprehensive state evaluation map of the multilayer stealth coating is generated. The map includes information on the material state of each layer, the quality of the interlayer interface, and the type, location, size, and severity of defects.

2. The method according to claim 1, characterized in that, The eddy current detection step employs a multi-frequency eddy current detection method, specifically including: Based on the known thickness and electromagnetic parameters of the radar wave absorbing layer, multiple eddy current excitation signals of different frequencies are selected for scanning. By analyzing the amplitude and phase changes of the eddy current response at different frequencies, a tomographic image sequence reflecting the distribution of electromagnetic characteristics at different depths of the layer is generated.

3. The method according to claim 1, characterized in that, In the ultrasonic testing step: By adjusting the incident angle and focusing depth of the high-frequency focusing probe, the ability to receive reflected echoes from the interfaces of the thermal matching layer and adhesive layer, and the adhesive layer and substrate layer is optimized, and B-scan cross-sectional images and / or C-scan three-dimensional images are generated to show the defect distribution morphology.

4. The method according to claim 1, characterized in that, The spatial and temporal alignment process is achieved in the following ways: A common reference marker is set in the detection area, each detection probe integrates a high-precision optical positioning device, and the detection system uses a unified clock to synchronize the data acquisition of each detection method.

5. An in-situ detection system for multi-layer stealth coating in an aero-engine combustion chamber, implementing the method described in any one of claims 1-4, characterized in that, include: Infrared detection unit: includes an infrared thermal imager and its scanning mechanism, configured to detect the structural layer and the blocking layer and acquire infrared thermal image information; Eddy current detection unit: includes a multi-frequency eddy current probe and its detection and analysis instrument, configured to detect the radar wave absorbing layer and obtain electromagnetic properties and internal structure information; Ultrasonic testing unit: includes a high-frequency focused ultrasound probe, a pulse generator / receiver and a motion controller, configured to scan the thermal matching layer, adhesive layer, substrate layer and their interlayer interfaces and acquire acoustic impedance and interface state information; Positioning and synchronization unit: includes a high-precision optical positioning and tracking device and a unified clock source, configured to provide real-time spatial coordinate information for the infrared detection unit, eddy current detection unit, and ultrasonic detection unit, and synchronize their data acquisition timing; Data fusion and analysis unit: includes data storage and registration module, association rule base, multimodal association analysis module, and map generation module; The data storage and registration module is used to receive and store data from each detection unit, and to perform spatial position and time alignment processing based on the information provided by the positioning and synchronization unit; The association rule base is used to store preset hierarchical association rules; The multimodal association analysis module is used to call the rules in the association rule base to perform the cross-validation and association analysis described in steps (d)(iii) on the registered infrared, eddy current, and ultrasonic data; The map generation module is used to generate and output a comprehensive state evaluation map of the multi-layer stealth coating based on the output results of the multimodal correlation analysis module.

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