Cold repair method for sealing surface of groove in cylindrical cover of aircraft actuator cylinder

Abstract

The invention relates to the technical field of aviation product repair, in particular to a cold repair method for a sealing surface of a groove in a cylindrical cover of an aircraft actuator cylinder, which comprises the following steps of: 1, carrying out fault statistical analysis; step 2, carrying out failure analysis on the local corrosion surface of the metal; 3, selecting a typical metal repairing agent based on mechanical and corrosion properties; fourthly, the metal corrosion surface is purified and subjected to supplementary machining; fifthly, the defect surface of the cylindrical cover is repaired; sixthly, the repaired surface of the cylindrical cover is trimmed; seventhly, experimental verification is conducted on the repaired surface of the cylindrical cover; and 8, decomposition inspection of the repaired surface of the cylindrical cover is carried out. The processing and repairing method is determined by analyzing the corrosion mechanism and the working condition of the product and selecting a proper adhesive, and the damaged part is quickly filled and repaired under the condition that the structural strength of the product is not reduced; the problems that the reachability is poor, welding air holes are likely to be generated and the non-destructive testing reject ratio is high due to the fact that heat repairing is adopted for corrosion of the communication sealing face in the cylindrical cover of the aircraft cylinder are solved.

Description

Technical Field

[0001] This invention relates to the field of aviation product repair technology, specifically a cold repair method for the sealing surface of the inner groove of an aircraft actuator cylinder cover. Background Technology

[0002] Modern aircraft use hydraulic drive to control the retraction and extension of the landing gear during takeoff and landing. The key components of the hydraulic drive system are the landing gear retraction and extension actuator and the strut actuator, and their service performance directly affects the reliability and lifespan of the hydraulic drive system.

[0003] The cylindrical cover, installed on the landing gear retraction actuator, is a key component for sealing, supporting, and guiding the piston rod. Its primary failure is caused by corrosion damage to the sealing surface of the inner groove of the cylindrical cover due to the failure of the O-ring seal within it. Once these cylindrical covers malfunction, minor issues may include hydraulic oil leakage and pressure drops causing delays in takeoff and landing; serious problems can lead to a loss of precise control of the hydraulic components in the aircraft's takeoff and landing system, resulting in significant safety hazards. Therefore, considering both the severity and economic benefits, the corrosion damage to the inner groove of the aircraft's actuator cylindrical cover should be addressed promptly. Internal corrosion problems also exist in other similar aircraft products.

[0004] Currently, surface repair technologies are mainly divided into hot repair and cold repair. Common hot repair techniques include laser cladding, flame spraying, plasma spraying, surfacing, and brazing. However, these hot repair techniques all involve temperatures higher than the eutectoid transformation temperature of steel, causing the tempered sorbite in the cylindrical cap and the cap's tempered steel to undergo an austenitic transformation. After cooling, ferrite and pearlite are formed, leading to a decrease in the mechanical properties of the cylindrical cap and the cap. In addition, due to product structure limitations, the accessibility of the above-mentioned hot repairs is poor, easily causing secondary failures in non-repaired areas.

[0005] Cold repair techniques mainly include electroplating, low-temperature physical sputtering, and organometallic repair. For cylindrical caps with narrow inner diameters, the current is shielded inside the pipe during electroplating or brush plating. When using physical sputtering, the inner surface of the cylinder is blocked, preventing deposition repair within the sleeve. Organometallic repair technology refers to single-component or multi-component putty-like (or liquid) composite materials composed of metals, ceramics, fibers, polymers, and curing agents. Before curing, it can be applied to any surface, exhibiting plasticity. Combined with fiber cloth and molds, it can be used to repair worn dimensions of mechanical parts, pre-protect corrosion-resistant surfaces, and pressurized sealing of cracks and pits in pipelines and equipment. Because its operating temperature is much lower than welding repair, it significantly reduces the introduction of thermal stress and structural changes, and has lower requirements for the construction environment, making it a future trend in surface defect repair technology. Therefore, this study proposes a cold repair technology for cylindrical caps based on adhesive bonding to repair corrosion-damaged surfaces in the internal grooves of cylindrical caps. To address the corrosion damage issues that occur to cylindrical covers during field service, a rapid emergency repair method using adhesive cold repair was adopted, forming a new process to replace welding repair. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a cold repair method for the sealing surface of the inner groove of an aircraft actuator cylinder cover. Addressing the limitations of conventional hot repair methods and the significant stress and microstructure alterations caused by hot repair, this method primarily involves analyzing and modeling the corrosion mechanism of the cylinder cover under typical operating conditions; conducting microscopic analysis of the surface and cross-section of locally corroded parts of the cylinder cover, observing the morphology and cross-sectional profile of the corroded surface; selecting a repair scheme using a performance-matched industrial repair agent based on the product's operating conditions; and conducting tensile shear strength tests, electrochemical performance tests, working medium resistance tests, and salt spray tests. The repair performance of a simulated sample corroded surface is evaluated and then installed on the product for break-in verification tests. This ultimately forms the cold repair method for corrosion damage to the cylinder cover.

[0007] The technical problem to be solved by this invention is achieved by the following technical solution: A method for cold repair of the sealing surface of the inner groove of an aircraft actuator cylindrical cover includes the following steps: Step 1: Fault statistical analysis; Step 2: Surface Failure Analysis of Localized Corrosion in Metals Step 1: Analyze the electrochemical properties of the steel surface using a traditional three-electrode method; Step 2: Corrosion kinetics simulation; Step 3: Selection of typical metal repair agents based on mechanical and corrosion properties: 1. Criteria for selecting adhesives; 2. Selection of metal corrosion repair layer; 3. Design of metal corrosion repair layer; 4. Evaluation of the physicochemical properties of the metal corrosion repair layer: This includes tensile shear strength testing, electrochemical performance testing, working medium resistance testing, and salt spray testing; Step 4: Cleaning and supplementary processing of corroded metal surfaces; Step 5: Repairing the defective surface of the cylindrical cap; Step Six: Finishing the surface of the cylindrical cap repair; Step 7: Test verification of the surface repaired by the cylindrical cap: This includes sealing tests and break-in tests; Step 8: Disassembly inspection of the repaired surface of the cylindrical cap.

[0008] As a further improvement of the present invention, in step two, corrosion kinetics simulation is performed using the corrosion module in COMSOL software.

[0009] As a further improvement of the present invention, the selection criteria for adhesives include: Adhesive requirements: low cost, easy to apply, and room temperature curing; Operating temperature range and performance factors of the parts to be repaired: The operating temperature range is between -55℃ and +70℃, and the performance factors include shear strength, tensile strength, resistance to media, curing conditions, and machinability.

[0010] As a further improvement of the present invention, the metal corrosion repair layer is selected as follows: a modified epoxy repair agent composed of modified epoxy resin, titanium alloy powder, carbide and curing agent is selected as the metal corrosion repair layer.

[0011] As a further improvement to the present invention, the metal corrosion repair layer is designed as follows: it is made by uniformly mixing material A and material B in a volume ratio of 4:1. As a further improvement to the present invention, step four is specifically as follows: Clean the stains on the area to be repaired with a cleaning agent, polish the corroded area with a mechanical grinder, roughen the surface with sandblasting to expose the metallic luster, clean the repair area with a cotton ball soaked in cleaning agent, and let it air dry naturally.

[0012] As a further improvement to the present invention, step five is specifically as follows: First, apply the metal adhesive, then use a plastic scraper to apply a coating to the defective surface of 30CrMnSiNi2A. After scraping, the height of the repaired surface should be flush with or higher than the adjacent unrepaired surface by more than 0.3mm. Cure at room temperature for 24 hours. If the temperature is below 15℃, use heating measures. After curing at room temperature for 2-3 hours, use a heat source to heat the repaired substrate part and maintain it at 60℃-80℃ for 3-4 hours.

[0013] As a further improvement to the present invention, the specific process of the sealing test in step seven is as follows: Hydraulic pressure of 35±1MPa is applied through the connecting nozzle and maintained for 3 minutes, with no leakage allowed. Tests are conducted at ambient temperature, +70±2℃, and -55±2℃. Simultaneously, pressure of 200+10kPa is supplied to the actuator through the connecting nozzle or a 2m high working fluid column is applied and maintained for 2 hours. The external environment should be sealed. Tests are conducted at ambient temperature, +70±2℃, and -55±2℃.

[0014] As a further improvement to the present invention, the specific process of the break-in test in step seven is as follows: The actuator nozzle is connected to the oil supply and discharge lines of the test bench, supplying 10±2MPa hydraulic pressure. Under no load, the piston rod is subjected to 400 reciprocating cycles. After 25 cycles, the piston rod is rotated by about 90°. The piston rod moves smoothly without any jerking or jamming.

[0015] As a further improvement of the present invention, the decomposition and inspection items in step eight include: whether the adhesive repair part inside the cylindrical cover is deformed or detached; and whether there is abnormal damage at the contact point between the sealing ring and the adhesive repair part.

[0016] The beneficial effects of this invention are: This invention achieves rapid cold repair of corroded areas by using a cold repair method on the sealing surface of the inner groove of the actuator cylinder cover. By analyzing the corrosion mechanism of the product and the working conditions, a suitable adhesive is selected to determine the processing and repair method. Without reducing the structural strength of the product, the damaged area is quickly filled and repaired. This solves the problems of poor accessibility, easy generation of weld porosity, and high non-destructive testing failure rate associated with hot repair of corrosion on the inner sealing surface of aircraft actuator cylinder covers. By coating the corroded area, the product's shape is restored and the outer surface is protected, preventing further corrosion. This provides a method for rapid repair of internal groove corrosion damage in similar products. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a flowchart of the present invention; Figure 2 This is a schematic diagram of the corrosion damage area in the grooves inside the cylindrical cover. Detailed Implementation

[0018] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0019] like Figure 1 As shown, a method for cold repair of the sealing surface of the inner groove of an aircraft actuator cylindrical cover includes the following steps: Step 1: Fault statistical analysis.

[0020] Comparative analysis of intact and damaged actuator cylinder covers revealed corrosion on the inner groove sealing surface, primarily at the interface between the hydraulic working chamber and the atmosphere. Figure 2 As shown, the grooves of the product are prone to corrosion under the influence of air and moisture. Furthermore, to ensure the sealing performance of the hydraulic system, the inner groove sealing surface is polished after electroplating to improve its surface quality. This process results in the loss of the electroplated anti-corrosion layer on the inner groove surface, making the parts susceptible to corrosion damage.

[0021] Step 2: Surface failure analysis of localized metal corrosion.

[0022] Specifically, the analysis process includes the following steps: Step 1: Analyze the electrochemical properties of the steel surface using a conventional three-electrode (CHI660E) method.

[0023] The experimental setup consists of a saturated Ag / AgCl reference electrode, a working electrode (sample), and a platinum wire auxiliary electrode. First, 30CrMnSiNi2A material is fabricated to have an exposed area of ​​1 cm². 2 Test samples were prepared, and their copper wires were connected to ensure a good connection. The samples were then sealed with 704 silicone rubber and allowed to stand in a ventilated environment for three hours until the silicone rubber dried and cured. The samples were then immersed in a 3.5 wt% NaCl solution, and an open-circuit potential (OCP) test was initiated for one hour. Subsequently, an electrochemical impedance spectroscopy (EIS) test was performed at a stable OCP value. During the EIS test, the AC excitation was fixed, the test frequency was 0.001–100000 Hz, and the test time was three hours. After the first EIS test was completed, the open-circuit potential was measured again, and the EIS test was repeated after ensuring the open-circuit potential stabilized. Based on the EIS test procedure, the EIS data were fitted using ZsimpWin software, yielding a charge transfer resistance of Rct = 1557 Ω. This indicates that a high charge transfer resistance suggests good corrosion resistance. To further investigate the potential corrosion mechanism of localized corrosion surfaces on steel, polarization curves of 30CrMnSiNi2A material were tested in a 3.5% NaCl solution.

[0024] Step 2: Perform corrosion kinetics simulation.

[0025] Numerical simulations were performed using the corrosion module in COMSOL software. In actual conditions, the low-potential ferrite phase in 30CrMnSiNi2A steel is dispersed around the high-potential austenite phase. Therefore, a method of embedding the ferrite phase within the austenite phase was adopted for localized corrosion simulation.

[0026] First, a mesh was created using the same meshing method as for galvanic corrosion, with the austenite phase as the cathode and the ferrite phase as the anode. 30CrMnSiNi2A steel contains multiple phases, with the low-potential ferrite phase dispersed around the high-potential austenite phase. When the sample is placed in a corrosive medium, galvanic corrosion occurs due to the potential difference. Therefore, the low-potential ferrite phase is prone to localized corrosion, resulting in corrosion pits. Simulation results confirm that the presence of a potential difference leads to corrosion, and the phase with the more negative corrosion potential easily loses electrons and undergoes severe localized corrosion.

[0027] Step 3: Selection of typical metal repair agents based on mechanical and corrosion properties.

[0028] Specifically, 1. Criteria for selecting adhesives: Choose a low-cost, easy-to-apply, room-temperature curing adhesive; consider the operating temperature range and performance factors of the actuator cylindrical cover.

[0029] In this embodiment, a modified epoxy repair agent is selected as the adhesive. The operating temperature range of the actuating cylinder cap is -55℃ to +70℃, and the performance factors include shear strength, tensile strength, media resistance, curing conditions, and machinability.

[0030] 2. Selection of metal corrosion repair layer.

[0031] The following factors are generally considered when designing metal corrosion repair layers: structure, stress, entry and retention of corrosive media, compatibility with the substrate, and machinability.

[0032] For corrosion repair of the actuator cylinder cover, if thermal repair methods such as laser cladding are used, the localized high temperature during the repair process will cause phase transformation in the microstructure of the actuator cylinder cover and the cap, resulting in localized internal stress and a decrease in the mechanical properties of the actuator cylinder cover. If low-temperature cold welding technology is used, it is not only too costly, but also has a long repair period, which cannot meet the needs of rapid repair.

[0033] Surface adhesive bonding technology eliminates the heat-affected zone and thermal deformation of parts, and can be used for various purposes depending on the adhesive used. Therefore, surface adhesive bonding technology has broad application prospects for material repair. Furthermore, modified epoxy resin possesses superior machinability, producing a dense surface with high dimensional accuracy after processing, effectively blocking chemical media from corroding the substrate. Simultaneously, it cures at room temperature without heating, does not generate thermal stress in the repaired area, and has no adverse effects on the substrate's properties. Therefore, for the repair layer of corroded areas on cylindrical caps, it not only possesses high adhesive strength and corrosion resistance but also excellent machinability to meet the dimensional and surface quality requirements of the parts. Combining this with existing adhesive repair technologies, using industrial metal adhesive repair solutions is feasible.

[0034] Based on this, in this embodiment, according to the service conditions and technical requirements of the actuator cylindrical cover, modified epoxy resin is used to repair the surface, with high-performance titanium alloy as the reinforcing material and high-hardness metal carbide as the skeleton, in order to meet the requirements of part size repair, wear resistance, corrosion resistance and other requirements.

[0035] 3. Design of metal corrosion repair layer.

[0036] During the service life of materials, contact with oil will cause the formation of a rust layer. This rust is an iron oxide hydrate with no fixed water content. When this iron oxide is exposed to water, it will generate hydroxides. In this transformation process, the oxide film will increase in volume and crack. Its porosity and hygroscopicity will cause the structure under the oxide layer to continue to corrode. Therefore, in order to prevent the rust layer from continuing to corrode the material structure under the repair layer, rust removal must be performed before repair.

[0037] Surface treatment using mechanical methods mainly includes metal wool polishing, manual polishing, sandblasting, or steam grinding. The abrasive used during polishing must not contaminate the steel surface. Sandblasting can be performed, or manual polishing or metal wool polishing can be used. In this embodiment, the sandblasting process parameters are: nozzle diameter 6mm-12mm, compressed air pressure 0.4MPa-0.7MPa, and sandblasting medium: quartz sand.

[0038] During the rust removal process, avoid scratching the bonding surfaces. After rust removal, the surface should be rinsed. It is important to note that the rinsing solution should not contain water, as water will cause further corrosion of the steel. In this embodiment, an organic solvent cleaner is used for rinsing.

[0039] To improve the adhesion between the metal corrosion repair layer and the surface to be repaired, adhesives are used to bond them together. Because there are many types of adhesives, and their properties vary greatly, the purpose and intended use of the adhesive should be clearly defined before actual bonding operations. The properties of the adhesive should be understood, and a suitable adhesive should be selected according to adhesive selection criteria before proceeding with the bonding process.

[0040] In this embodiment, based on the service conditions and technical requirements of the actuator cylindrical cover, a modified epoxy repair agent composed of modified epoxy resin, titanium alloy powder, carbides, and a curing agent is selected. This agent also possesses high strength, fast curing speed, and is suitable for mechanized production. Subsequently, the corrosion repair layer is prepared using an industrial repair agent material. This material is composed of component A and component B, uniformly mixed in a 4:1 volume ratio, where component A refers to the main wear-resistant repair agent and component B refers to the curing agent.

[0041] The above steps mainly involve screening existing modified epoxy resin repair agents and selecting and verifying modified epoxy repair agents that meet the product usage requirements based on the material characteristics of the actuator cylindrical cover.

[0042] 4. Evaluation of the physical and chemical properties of the metal corrosion repair layer.

[0043] 4.1 Tensile shear strength test.

[0044] According to GB / T7124-2008 "Determination of Tensile Shear Strength of Adhesives (Rigid Material to Rigid Material)", the modified epoxy repair agent prepared above was used for coating and bonding. Test specimens were prepared and then tested. The performance indicators were met: tensile strength ≥24MPa, shear strength ≥19MPa, and compressive strength ≥84MPa.

[0045] 4.2 Electrochemical performance testing.

[0046] A comparative experiment was conducted using a traditional three-electrode (CHI660E) setup to analyze the electrochemical properties of the steel surface. This setup consisted of a saturated Ag / AgCl reference electrode, a working electrode (sample), and a platinum wire auxiliary electrode. First, an epoxy resin coating was applied to the surface of the 30CrMnSiNi2A material. After curing, the surface was machined to create a 1 cm² exposed sample. Copper wires were connected to ensure a secure connection, and the sample was sealed with 704 silicone rubber and allowed to stand in a ventilated environment for three hours until the silicone rubber dried and cured. To prevent instability in the electrochemical performance test data due to excessive sample thickness, the coating thickness should be minimized. In this embodiment, the coating thickness was reduced to 0.3 mm. Higher charge transfer resistance indicates better corrosion resistance. The electrochemical performance of the coating should be superior to that of the substrate before repair.

[0047] 4.3 Working medium resistance test.

[0048] The proposed coating repair agent was tested using No. 15 aviation hydraulic oil. The cured repair layer was then immersed in No. 15 aviation hydraulic oil for 48 hours. The repair layer must not show any delamination or peeling.

[0049] 4.4 Salt spray test.

[0050] A 96-hour salt spray test was conducted according to GB / T 10125-2012. The modified epoxy repair agent to be used was verified, and the corrosion area on the metal surface was no more than 30%, while no corrosion was observed on the base metal.

[0051] Step 4: Cleaning and supplementary processing of the corroded metal surface.

[0052] Based on the location of localized corrosion damage in the cylindrical cover of the actuator, a method for cleaning the corroded surface with narrow apertures is proposed: clean the stains in the area to be repaired with a cleaning agent; grind the corroded area cleanly with mechanical grinding, and then roughen the surface with sandblasting to expose the metallic luster. In this embodiment, the process parameters for sandblasting are: nozzle diameter of the spray gun 6mm-12mm, compressed air pressure 0.4MPa-0.7MPa, and sandblasting medium: quartz sand; clean the repair area with degreased cotton soaked in cleaning agent and allow it to air dry naturally.

[0053] Step 5: Repairing the defective surface of the cylindrical cap.

[0054] Repairing narrow-aperture defects: First, apply a metal adhesive, then use a plastic scraper to coat the 30CrMnSiNi2A defect surface. The surface should be uniform with sufficient machining allowance. After scraping, the repaired surface should be flush with or at least 0.3 mm higher than the adjacent unrepaired surface. Curing should be done at room temperature for 24 hours. If the temperature is below 15℃, use heating measures. After curing at room temperature for 2-3 hours, use a heat source to heat the repaired substrate at 60℃-80℃ for 3-4 hours.

[0055] Step Six: Repairing the surface of the cylindrical cap.

[0056] The inner groove is polished using an electric grinding tool to process and trim the repaired surface so that it meets the relevant dimensional requirements of the part drawing after repair, and the repaired surface transitions smoothly and blends in with the unrepaired surface.

[0057] Step 7: Test verification of the surface repair using the cylindrical cover.

[0058] According to the design drawings, the dimensions and surface roughness of the parts are checked. After the parts are repaired and assembled, sealing checks and break-in tests are performed according to the process: hydraulic pressure of 35±1MPa is applied through the nozzle and maintained for 3 minutes, and leakage is not allowed; tests are conducted at room temperature, +70±2℃, and -55±2℃ respectively.

[0059] Simultaneously, supply pressure of 200+10kPa to the actuator cylinder through the connecting nozzle (or pressurize with a 2m high working fluid column), maintain the pressure for 2 hours, and seal the exterior; conduct tests at ambient temperature, +70±2℃, and -55±2℃ respectively.

[0060] The actuator nozzle is connected to the oil supply and discharge lines of the test bench. Supply 10±2MPa hydraulic pressure and, under no load, perform 400 reciprocating cycles on the piston rod. After 25 cycles, rotate the piston rod approximately 90°. The piston rod movement should be smooth, without any jerking or jamming.

[0061] Step 8: Disassembly inspection of the repaired surface of the cylindrical cap.

[0062] After the break-in period, disassemble and inspect the inner bonding and repair area of ​​the cylindrical cap to check for deformation or detachment. Check for any abnormal damage at the contact point between the sealing ring and the bonding and repair area.

[0063] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely prisms of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for cold repair of the sealing surface of the inner groove of an aircraft actuator cylindrical cover, characterized in that: Includes the following steps: Step 1: Fault statistical analysis; Step 2: Surface Failure Analysis of Localized Corrosion in Metals Step 1: Analyze the electrochemical properties of the steel surface using a traditional three-electrode method; Step 2: Corrosion kinetics simulation; Step 3: Selection of typical metal repair agents based on mechanical and corrosion properties: (1) Criteria for selecting adhesives; (2) Selection of metal corrosion repair layer; (3) Design of metal corrosion repair layer; (4) Evaluation of the physicochemical properties of the metal corrosion repair layer: This includes tensile shear strength testing, electrochemical performance testing, working medium resistance testing, and salt spray testing; Step 4: Cleaning and supplementary processing of corroded metal surfaces; Step 5: Repairing the defective surface of the cylindrical cap; Step Six: Finishing the surface of the cylindrical cap repair; Step 7: Test verification of the surface repaired by the cylindrical cap: This includes sealing tests and break-in tests; Step 8: Disassembly inspection of the repaired surface of the cylindrical cap.

2. The method for cold repair of the sealing surface of the inner groove of the cylindrical cover of an aircraft actuator according to claim 1, characterized in that: Step 2: Corrosion kinetics simulation: Numerical simulation is performed using the corrosion module in COMSOL software.

3. The method for cold repair of the sealing surface of the inner groove of the cylindrical cover of an aircraft actuator according to claim 1, characterized in that: The selection criteria for adhesives include: Adhesive requirements: low cost, easy to apply, and room temperature curing; Operating temperature range and performance factors of the parts to be repaired: The operating temperature range is between -55℃ and +70℃, and the performance factors include shear strength, tensile strength, resistance to media, curing conditions, and machinability.

4. The method for cold repair of the sealing surface of the inner groove of the cylindrical cover of an aircraft actuator according to claim 1, characterized in that: Selection of metal corrosion repair layer: A modified epoxy repair agent composed of modified epoxy resin, titanium alloy powder, carbides, and curing agent was selected as the metal corrosion repair layer.

5. The method for cold repair of the sealing surface of the inner groove of the cylindrical cover of an aircraft actuator according to claim 1, characterized in that: Design of metal corrosion repair layer: It is made by uniformly mixing material A and material B in a volume ratio of 4:

1.

6. The method for cold repair of the sealing surface of the inner groove of the cylindrical cover of an aircraft actuator according to claim 1, characterized in that: Step four involves the following steps: Clean the stains on the area to be repaired with a cleaning agent, polish the corroded area with a mechanical grinder, roughen the surface with sandblasting to expose the metallic luster, clean the repair area with a cotton ball soaked in cleaning agent, and let it air dry naturally.

7. The method for cold repair of the sealing surface of the inner groove of the cylindrical cover of an aircraft actuator according to claim 1, characterized in that: Step five involves the following steps: First, apply the metal adhesive, then use a plastic scraper to apply a coating to the defective surface of 30CrMnSiNi2A. After scraping, the height of the repaired surface should be flush with or higher than the adjacent unrepaired surface by more than 0.3mm. Cure at room temperature for 24 hours. If the temperature is below 15℃, use heating measures. After curing at room temperature for 2-3 hours, use a heat source to heat the repaired substrate part and maintain it at 60℃-80℃ for 3-4 hours.

8. The method for cold repair of the sealing surface of the inner groove of the cylindrical cover of an aircraft actuator according to claim 1, characterized in that: The specific process of the sealing test in step seven is as follows: Hydraulic pressure of 35±1MPa is applied through the connecting nozzle and maintained for 3 minutes, with no leakage allowed. Tests are conducted at ambient temperature, +70±2℃, and -55±2℃. Simultaneously, pressure of 200+10kPa is supplied to the actuator through the connecting nozzle or a 2m high working fluid column is applied and maintained for 2 hours. The external environment should be sealed. Tests are conducted at ambient temperature, +70±2℃, and -55±2℃.

9. The method for cold repair of the sealing surface of the inner groove of the cylindrical cover of an aircraft actuator according to claim 1, characterized in that: The specific process of the break-in test in step seven is as follows: The actuator nozzle is connected to the oil supply and discharge lines of the test bench, supplying 10±2MPa hydraulic pressure. Under no load, the piston rod is subjected to 400 reciprocating cycles. After 25 cycles, the piston rod is rotated by about 90°. The piston rod moves smoothly without any jerking or jamming.

10. The method for cold repair of the sealing surface of the inner groove of the cylindrical cover of an aircraft actuator according to claim 1, characterized in that: Step eight includes the following inspection items: whether the adhesive repair area inside the cylindrical cover is deformed or detached; and whether there is any abnormal damage at the contact point between the sealing ring and the adhesive repair area.

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