A method for inspecting and repairing helicopter power transmission shafts

Abstract

This invention belongs to the field of mechanical technology and relates to a method for inspecting and repairing helicopter power transmission shafts. The method includes step 1, inspecting the power transmission shaft for defects; step 2, determining whether the defects on the power transmission shaft have damaged the substrate; and step 3, repairing the damaged substrate. This invention effectively inspects and repairs damage such as cracked or peeling coatings, rust, and scratches on the power transmission shaft surface. Simultaneously, it accurately identifies rust on the power transmission shaft surface, avoiding misjudgment of the lubricating oil at the input end of the main reducer, which could affect the inspection and repair results.

Description

Technical Field

[0001] This invention belongs to the field of mechanical technology and relates to a method for inspecting and repairing helicopter power transmission shafts. Background Technology

[0002] The helicopter drive shaft is a key component connecting the engine and the main gearbox, its function being to transmit power from the engine to the main gearbox. The drive shaft is typically welded together from a flange 1, a diaphragm 2, an end cap 3, and a hollow thin-walled splined shaft 4. Figure 1 As shown, its surface is coated with an aluminum-based silver-white coating. The high operating temperature and large deflection angles and speeds of the drive shaft make it prone to coating cracking, peeling, and corrosion. Furthermore, scratches are easily caused during drive shaft installation. Currently, there are no effective methods for inspecting and repairing surface coating cracking, peeling, corrosion, and scratches on the drive shaft. Therefore, it is necessary to research a method for inspecting and repairing helicopter drive shafts.

[0003] In addition, if the lubricating oil (yellowish-brown) leaks from the input end of the main reducer, it will directly splash onto the power transmission shaft. The oil stains formed by the yellowish-brown lubricating oil are quite similar to rust, which has a significant impact on the identification of rust. Therefore, the inspection and repair methods should also include the method for identifying rust. Summary of the Invention

[0004] The technical problem solved by this invention: In order to solve the above problems, this invention provides a method for inspecting and repairing helicopter power transmission shafts. This method establishes a method for inspecting, interpreting and repairing power transmission shafts, thereby ensuring the performance of power transmission shafts and ensuring the reliability of helicopter transmission system operation.

[0005] The technical solution of this invention:

[0006] A method for inspecting and repairing a helicopter power transmission shaft, characterized by comprising the following steps:

[0007] Step 1: Check the drive shaft for defects;

[0008] Step 2: Determine whether the defects on the power transmission shaft have damaged the base material;

[0009] Step 3: Repair the damaged substrate.

[0010] Preferably, step 1 specifically includes the following steps:

[0011] Step 1.1: Visually inspect the drive shaft from the helicopter or with a magnifying glass, paying particular attention to the diaphragm surface for defects such as rust, scratches, coating peeling, and cracking. Wear clean gloves during operation and never handle the drive shaft with bare hands. If rust and oil stains are present on the drive shaft, visually observe that the color and shape of the oil stains are similar to rust products. Wipe the surface of the drive shaft with a cloth or cotton wool soaked in acetone, alcohol, or methyl ethyl ketone. The oil stains will be removed after repeated wiping, and the coating surface of the drive shaft will remain intact. If it is a rust defect, the coating surface will be damaged after wiping.

[0012] Step 1.2: If it is impossible to determine whether there are defects such as rust, scratches, coating peeling, or cracks on the helicopter, disassemble the power drive shaft and place it on the workbench for further inspection. Clean gloves must be worn during the operation, and it is strictly forbidden to handle the power drive shaft with bare hands.

[0013] Preferably, in step 2, the method for determining whether corrosion and scratches have damaged the substrate is to observe the scratches on the power transmission shaft under a magnifying glass. If there are rust pits at the bottom of the scratches, and the rust pits are dark in color, rough, and have irregular edges, it indicates that the substrate at the scratches has been corroded and has been damaged.

[0014] If a magnifying glass is not enough to determine whether the substrate has been damaged, remove the coating from the rusted or scratched areas. If the substrate metal after removing the coating is rough, has sloping spots, pits, or scratches, then the rust or scratches have damaged the substrate.

[0015] Preferably, step 3 specifically includes the following steps;

[0016] Step 3.1: Polish the rusted and scratched areas with 400-1500 grit sandpaper to remove the rust and scratches.

[0017] Step 3.2: After repairing the rusted and scratched areas, perform localized oxidation on the uncoated areas and apply a coating to the coated areas.

[0018] Preferably, in step 3.2,

[0019] The method for localized oxidation of uncoated areas is as follows:

[0020] Pretreatment: Before oxidation, the surface to be oxidized is lightly sanded with 1500-2000 grit sandpaper to remove surface rust, and then cleaned with anhydrous ethanol or acetone.

[0021] Use a brush or synthetic fiber cloth dipped in HH902 room temperature oxidation liquid to repeatedly brush the area to be oxidized until a uniform oxide film is formed on the surface of the power transmission shaft.

[0022] For post-treatment, use a brush or synthetic fiber cloth dipped in HH932 dehydrating rust-preventive oil to repeatedly coat the oxide film surface;

[0023] The method for touching up coated areas is as follows:

[0024] For paint preparation, mix the paint thoroughly and pass it through a 150-mesh sieve. Add deionized water to the sieved paint to adjust the viscosity of the paint. Then, put the paint into the spray can.

[0025] For surface preparation, use 1500-2000 grit sandpaper to gently sand the areas where the coating has peeled off or been scratched, ensuring a smooth transition with adjacent coatings. Then wipe the areas that need to be touched up with anhydrous ethanol or acetone.

[0026] Apply a coating, using brush or spray methods for touch-up coating;

[0027] For curing, place the coated drive shaft horizontally for more than 3 hours, and then place the dried drive shaft vertically into a heating oven for heating and curing.

[0028] Inspect the coating quality.

[0029] Preferably, if it is impossible to determine whether the substrate has been damaged even with a magnifying glass, use a cotton swab dipped in a 3% to 5% sodium hydroxide solution to wipe away the coating on the rusted or scratched areas. After wiping with sodium hydroxide solution, immediately wipe repeatedly with deionized water and anhydrous ethanol to ensure that there is no residue on the surface. Then, use rust-preventive oil to seal the coated areas to prevent rust from forming on the uncoated areas.

[0030] Preferably, in step 3.1, during polishing, first use 1000-1500 grit sandpaper for polishing. If obvious rust pits or large scratches are found, then use 400-1000 grit sandpaper for polishing to remove rust and scratches. The polishing depth of rust and scratches shall not exceed 0.05 mm, and the repaired parts of rust and scratches shall be smoothly connected. The surface roughness Ra of the polished area shall not exceed 0.8.

[0031] Preferably, the pH value of the HH902 room temperature oxidation solution is prepared using deionized water, so that the oxidation effect is optimal when the pH value of the solution is between 2 and 2.5. The brushing time of the HH902 room temperature oxidation solution is 2 min to 5 min, and a uniform oxide film will be generated on the surface of the power drive shaft. After staying in the air for 1 min, the residual solution on the surface of the power drive shaft is wiped off to avoid corrosion of the power drive shaft by the oxidation solution.

[0032] Preferably, when applying a touch-up coating, the area to be touched up should be wiped with anhydrous ethanol or acetone and then left to air dry for 10 to 30 minutes to ensure it is completely dry before applying the coating. The thickness of the touch-up coating should be no less than 0.02 mm.

[0033] Preferably, coating quality inspection includes visual inspection and adhesion inspection, as follows:

[0034] Visual inspection: The coating should be silver and free from defects such as delamination, cracks, and leaks;

[0035] Coating adhesion test: Apply a 25mm wide 3M paper tape to the coating, with a length of no less than 50mm. Press the tape directly with your fingers to ensure that the tape is evenly adhered and that there are no gaps or air bubbles between the tape and the coating. Hold one end of the tape with your hand and quickly tear it off with a force perpendicular to the surface of the coating being tested. Inspect the coating that was covered with the tape. There should be no peeling or damage to the coating.

[0036] The beneficial effects of this invention are: it provides a new method for inspecting and repairing helicopter power transmission shafts, filling the previous gaps, and realizing the effective inspection and repair of damage such as cracking and peeling of the coating on the power transmission shaft surface, as well as corrosion and scratches on the power transmission shaft. At the same time, it can accurately judge the corrosion on the surface of the power transmission shaft, avoiding misjudgment of the lubricating oil at the input end of the main reducer, which would affect the inspection and repair effect. Attached Figure Description

[0037] Figure 1 A schematic diagram of the helicopter's power transmission shaft structure;

[0038] Figure 2a This is a schematic diagram of the brown substance on the surface of the diaphragm disc of the power transmission shaft in the embodiment. Figure 1 ;

[0039] Figure 2b This is a schematic diagram of the brown substance on the surface of the diaphragm disc of the power transmission shaft in the embodiment.

[0040] Figure 2c The brown substance on the surface of the membrane disk in the embodiment is shown under a microscope. Figure 1 ;

[0041] Figure 2d This is a schematic diagram (2) of the brown substance on the surface of the membrane disk under a microscope in the embodiment.

[0042] Figure 2e This is a microscopic illustration of the brown substance on the surface of the membrane disk after wiping it in the example. Figure 1 ;

[0043] Figure 2f This is a second schematic diagram under a microscope after wiping the brown substance on the surface of the membrane disk in the embodiment;

[0044] Figure 3a This is a schematic diagram of the scratch 1 on the surface of the diaphragm disk of the power transmission shaft in the embodiment;

[0045] Figure 3b This is a schematic diagram of the scratches on the diaphragm surface of the power transmission shaft in the embodiment;

[0046] Figure 3cThis is a schematic diagram of the scratches on the diaphragm disk surface of the power transmission shaft under a low-power microscope in the embodiment.

[0047] Figure 3d This is a schematic diagram of scratches on the diaphragm disk surface of the power transmission shaft under a low-power microscope in the embodiment.

[0048] Figure 3e This is a schematic diagram showing the scratched area on the diaphragm surface of the power drive shaft after the coating has been removed in the embodiment.

[0049] Figure 3f This is a schematic diagram under a low-power microscope showing the scratched area on the diaphragm disk of the power drive shaft in the embodiment after the coating has been removed.

[0050] Explanation of reference numerals in the attached figures:

[0051] 1—Flange; 2—Diaphragm; 3—End cap; 4—Hollow thin-walled spline shaft. Detailed Implementation

[0052] The following description, with reference to the accompanying drawings, further details the specific embodiments of the present invention, including the shape and structure of each component, the relative positions and connections between the parts, the function and working principle of each part, the manufacturing process, and the operation and use methods. This is to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the concept and technical solution of the present invention.

[0053] A method for inspecting and repairing a helicopter power transmission shaft includes the following steps:

[0054] Step 1, check

[0055] a) Inspection from the helicopter: Visually inspect the power transmission shaft, especially the diaphragm disc type 2 surface, from the helicopter using a magnifying glass (no higher than 4x), for defects such as rust, scratches, coating peeling, and cracks. Clean gloves must be worn during operation; handling parts with bare hands is strictly prohibited.

[0056] b) Post-disassembly inspection: If it is impossible to determine whether there are defects such as rust, scratches, coating peeling, or cracks while on the helicopter, disassemble the drive shaft and place it on a clean, dry workbench. Visually inspect the drive shaft, especially the diaphragm disc 2-type surface, for defects such as rust, scratches, coating peeling, or cracks, or use a magnifying glass (no higher than 4x). Wear clean white gloves during operation; never handle parts with bare hands.

[0057] Step 2, Determination

[0058] a) To distinguish between rust and oil stains, visually observe that the color and shape of oil stains are similar to rust products. Wipe the surface with a cloth or cotton wool soaked in acetone, alcohol, or methyl ethyl ketone. Oil stains can be removed after repeated wiping, and the coating surface will remain intact. If it is rust, the coating will be damaged after wiping.

[0059] like Figures 2a-2f As shown, the surface of the diaphragm disc contains a large amount of yellowish-brown material resembling rust or oil stains, which is visible under visual inspection (see macroscopic image). Figure 2a , 2b It is difficult to determine without observation under a magnifying glass (see...). Figure 2c , 2d The substance appears to be dirt adhering to the coating surface. Wiping with a cotton ball soaked in acetone, alcohol, or methyl ethyl ketone (MEK) can remove the substance (see [link to product description]). Figure 2e , 2f Therefore, the yellow substance was determined to be oil stains; otherwise, it would have been rust.

[0060] Rust products are generally porous. When you wipe the rusted area with a dry cotton ball, brown or yellowish-brown rust products will adhere to the surface of the cotton ball. After removing the rust products, the rust base is dark gray, leaving rough, sloping spots or pits with irregular edges.

[0061] b) Method for determining whether corrosion and scratches have damaged the substrate: Scratches are observed under a magnifying glass. If there is a rust pit at the bottom, and the rust pit is dark in color, rough, and has irregular edges, it indicates that the substrate at the scratched area has been corroded and has been damaged.

[0062] In this embodiment, it is assumed that scratch 1 is visually observed (see...) Figure 3a ) and scratches 2 (see Figure 3b The surface has a yellowish-brown substance that looks like rust, but it is impossible to determine whether the substrate is rusted or whether the scratches have damaged the substrate.

[0063] Under magnification, scratch 1 shows a rust pit at the bottom. The rust pit is dark in color, rough, and has irregular edges, indicating that the substrate at scratch 1 has been corroded and the corrosion has reached the substrate (see...). Figure 3c ).

[0064] Under magnification, scratch 2 shows a yellowish-brown substance adhering to both the coating and the scratch surface. It is impossible to determine whether this yellowish-brown substance is rust (see...). Figure 3d To further determine whether the scratch was corroded and whether it had damaged the substrate, the coating was removed by wiping the scratch with a cotton swab dipped in a 3%–5% sodium hydroxide solution (after wiping with sodium hydroxide solution, the surface should be repeatedly wiped with deionized water and anhydrous ethanol immediately to ensure no residue remains). No rust pits or substrate damage were observed on the scratch surface (see...). Figure 3e , 3f ).

[0065] Additionally, if a magnifying glass is insufficient to determine whether the substrate has been damaged, a cotton swab dipped in a 3%–5% sodium hydroxide solution can be used to wipe away the coating at the rusted or scratched areas. If the substrate metal after removing the coating exhibits roughness, sloping spots, pits, or scratches, then the rust or scratches have damaged the substrate. After wiping with the sodium hydroxide solution, immediately wipe repeatedly with deionized water and anhydrous ethanol to ensure no residue remains on the surface. Then, seal the removed coating area with rust-preventive oil.

[0066] Step 3, Repair

[0067] a) Repair methods for rust and scratches: For rusted and scratched areas, polish with 400-1500 grit sandpaper to remove burrs from high points of rust and scratches. The repair depth should not exceed 0.05 mm, the polished area should have a smooth transition, and the surface roughness Ra of the polished area should not exceed 0.8;

[0068] b) After repair, rusted and scratched areas are locally oxidized or recoated;

[0069] c) Perform localized oxidation on uncoated areas, as follows:

[0070] ① Before oxidation, gently polish the surface to be oxidized with 1500-2000 grit metallographic sandpaper to remove surface rust, and then clean it with anhydrous ethanol or acetone.

[0071] ② Use a brush or synthetic fiber cloth to soak HH902 room temperature oxidizing solution (pH value of 2 to 2.5) and repeatedly brush the area to be oxidized for 2 to 5 minutes until a uniform oxide film is formed on the surface of the part. Then, leave it in the air for about 1 minute and wipe off the residual solution on the surface of the part.

[0072] ③ The method of immersion in HH932 dehydrating and rust-preventing oil can dehydrate and prevent rust in the film layer.

[0073] d) Apply touch-up coating to areas with existing coating, using the following method:

[0074] ① Mix the paint thoroughly and pass it through a 150-mesh sieve. Adjust the viscosity of the paint to a suitable level with deionized water and then put it into the spray can.

[0075] ② Use 1500-2000 grit sandpaper to gently sand the areas where the coating has peeled off or been scratched, ensuring a smooth transition with adjacent coating areas. Then wipe the areas requiring touch-up with anhydrous ethanol or acetone, and allow them to air dry for 10-30 minutes until completely dry before applying the coating.

[0076] ③ Touch-up coating can be applied by brushing or spraying. The number of brush or spray coats should ensure that the coating thickness is not less than 0.02mm.

[0077] ④ Place the coated drive shaft horizontally for more than 3 hours. After the coating has dried, place the drive shaft vertically into the heating furnace. Set the temperature to 60℃±5℃ and turn on the blower. Keep it at the temperature for 1 to 1.5 hours after reaching the set temperature. Then set the furnace temperature to 125℃±5℃ and keep it at the set temperature for 1 to 1.5 hours. Turn off the power and let the drive shaft cool to room temperature in the furnace before removing it.

[0078] ⑤ Post-coating inspection, the method is as follows:

[0079] I. Visual inspection: The coating should be silver in color and free from defects such as delamination, cracks, and leaks;

[0080] II. Apply a 25mm wide strip of 3M masking tape to the coating, with a length of at least 50mm. Press the tape directly with your fingers to ensure even adhesion, without gaps or air bubbles. Hold one end of the tape and, with a force perpendicular to the surface of the coating, quickly peel it off. Carefully inspect the area where the tape was applied; there should be no peeling or damage to the coating.

[0081] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A method for inspecting and repairing a helicopter power transmission shaft, characterized in that, Includes the following steps: Step 1: Check the drive shaft for defects; Step 2, determine whether the defects on the drive shaft have damaged the substrate: Observe the scratches on the drive shaft under a magnifying glass. If there are rust pits at the bottom of the scratches, and the rust pits are dark in color, rough, and have irregular edges, it indicates that the substrate at the scratches has been corroded and has been damaged. If it is still impossible to determine whether the substrate has been damaged by a magnifying glass, use a cotton swab dipped in 3% to 5% sodium hydroxide solution to wipe away the coating at the rusted or scratched area. If the substrate metal after removing the coating has roughness, sloping spots, pits, or scratches, then the rust or scratches have damaged the substrate. Step 3, repair the damaged substrate, including the following steps: Step 3.1: Polish the rusted and scratched areas with 400-1500 grit sandpaper to remove the rust and scratches. Step 3.2: After repairing the rusted and scratched areas, perform localized oxidation on the uncoated areas and recoat the coated areas. The method for performing localized oxidation on the uncoated areas is as follows: Pretreatment: Before oxidation, the surface to be oxidized is lightly sanded with 1500-2000 grit sandpaper to remove surface rust, and then cleaned with anhydrous ethanol or acetone. Apply HH902 room temperature oxidation solution to the area to be oxidized by repeatedly brushing for 2 to 5 minutes until a uniform oxide film is formed on the surface of the power transmission shaft. Then, leave it in the air for about 1 minute and wipe off any residual solution from the surface of the part. The pH value of the HH902 room temperature oxidation solution is 2 to 2.

5. For post-treatment, use a brush or synthetic fiber cloth dipped in HH932 dehydrating rust-preventive oil to repeatedly coat the oxide film surface; The method for touching up coated areas is as follows: For paint preparation, mix the paint thoroughly and pass it through a 150-mesh sieve. Add deionized water to the sieved paint and adjust the paint viscosity to a suitable level. Then, put the paint into the spray can. For surface preparation, use 1500-2000 grit sandpaper to lightly sand the areas where the coating has peeled off or been scratched, ensuring a smooth transition with adjacent coating areas. Then wipe the areas that need to be touched up with anhydrous ethanol or acetone. After wiping, let them air dry for 10-30 minutes until they are completely dry before applying the coating. For touch-up coating, use brush or spray to apply the coating. The number of brush or spray coats should ensure that the coating thickness is not less than 0.02 mm. After curing, place the coated drive shaft horizontally for more than 3 hours. Then, place the drive shaft vertically into the heating furnace after the coating has dried. Set the temperature to 60℃±5℃ and turn on the blower. Hold the temperature for 1 to 1.5 hours after reaching the set temperature. Then, set the furnace temperature to 125℃±5℃ and hold the temperature for 1 to 1.5 hours after reaching the set temperature. Turn off the power and let the drive shaft cool to room temperature in the furnace before removing it. Inspect the coating quality; The inspection of coating quality includes visual inspection and adhesion inspection, as detailed below: Visual inspection: The coating should be silver and free from defects such as delamination, cracks, and leaks; Coating adhesion test: Apply a 25mm wide 3M paper tape to the coating, with a length of no less than 50mm. Press the tape directly with your fingers to ensure that the tape is evenly adhered and that there are no gaps or air bubbles between the tape and the coating. Hold one end of the tape with your hand and quickly tear it off with a force perpendicular to the surface of the coating being tested. Inspect the coating that was covered with the tape. There should be no peeling or damage to the coating.

2. The method for inspecting and repairing a helicopter power transmission shaft according to claim 1, characterized in that, Step 1 specifically includes the following steps: Step 1.1: Visually inspect the drive shaft from the helicopter or use a magnifying glass to check the diaphragm surface for defects such as rust, scratches, coating peeling, and cracking. Wear clean gloves during operation and never handle the drive shaft with bare hands. If there are rust and oil stains on the drive shaft, visually observe that the color and shape of the oil stains are similar to rust products. Wipe the surface of the drive shaft with a cloth or cotton wool soaked in acetone, alcohol, or methyl ethyl ketone. The oil stains will be removed after repeated wiping, and the coating surface of the drive shaft will remain intact. If it is a rust defect, the coating surface will be damaged after wiping. Step 1.2: If it is impossible to determine whether there are defects such as rust, scratches, coating peeling, or cracks on the helicopter, disassemble the power drive shaft and place it on the workbench for further inspection. Clean gloves must be worn during the operation, and it is strictly forbidden to handle the power drive shaft with bare hands.

3. The method for inspecting and repairing a helicopter power transmission shaft according to claim 2, characterized in that, If a magnifying glass is insufficient to determine whether the substrate has been damaged, use a cotton swab dipped in a 3%–5% sodium hydroxide solution to wipe away the coating on the rusted or scratched areas. Immediately after wiping with the sodium hydroxide solution, wipe repeatedly with deionized water and anhydrous ethanol to ensure no residue remains on the surface. Then, use rust-preventive oil to seal the uncoated areas to prevent rust from forming on the uncoated areas.

4. The method for inspecting and repairing a helicopter power transmission shaft according to claim 3, characterized in that, In step 3.1, during polishing, first use 1000-1500 grit sandpaper for polishing. If obvious rust pits or large scratches are found, then use 400-1000 grit sandpaper for polishing to remove rust and scratches. The polishing depth of rust and scratches should not exceed 0.05 mm, and the repaired parts of rust and scratches should be smoothly connected. The surface roughness Ra of the polished area should not exceed 0.8.

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