Joint lug hole repairing method

Abstract

The invention belongs to the technical field of structural design, and particularly relates to a joint lug hole repairing method which comprises the following steps: damage evaluation: measuring the damage condition of a joint lug hole, determining the reaming size, and ensuring that the size of a reamed lug meets the requirements of an aircraft design manual and the difference between the reamed hole diameter and the original hole diameter is greater than 2mm; a metal lining with a sunken convex shoulder is designed according to the size after reaming, the lining comprises a lining body and a convex shoulder part, the wall thickness of the lining is designed to range from 2.5 mm to 4 mm, the length of the lining is the same as the thickness of a connector lug body, and the convex shoulder is of a countersunk head structure; interference amount control: by designing the outer diameter tolerance of the bushing, enough interference amount is ensured when the bushing is pressed to the hole wall of the reaming hole, and the bushing is prevented from falling off when the lug is loaded; the bushing is pressed into the chambered lug hole, and in-situ repair is achieved; and sealing treatment: smearing a sealant on the edge of the hole to finish repairing.

Description

Technical Field

[0001] This application belongs to the field of structural design technology, and specifically relates to a method for repairing the lug hole of a connector. Background Technology

[0002] This method is used to repair worn or damaged connector holes. By enlarging the damaged lug hole and then pressing a metal bushing with a recessed shoulder into the lug hole, in-situ repair of the connector lug hole is achieved without affecting the original assembly relationship. This provides an effective method for repairing aircraft field connector lug holes, reducing the economic and time costs of repair. Summary of the Invention

[0003] To address the aforementioned problems, a method for repairing connector lug holes is proposed for repairing wear or damage to aircraft structural connector lug holes. The method includes the following steps:

[0004] Step S101, Damage Assessment: Measure the damage of the connector lug hole, determine the enlargement size, and ensure that the lug size after enlargement meets the requirements of the aircraft design manual, and that the difference between the enlarged hole diameter and the original hole diameter is greater than 2mm.

[0005] Step S102, Bushing Design: Design a metal bushing with a recessed shoulder according to the size after hole enlargement. The bushing includes a bushing body and a shoulder portion. The bushing wall thickness is designed to be 2.5mm to 4mm. The bushing length is the same as the thickness of the connector lug body. The shoulder is a countersunk structure.

[0006] Step S103, Interference Control: By designing the bushing outer diameter tolerance, ensure that there is sufficient interference when the bushing is pressed into the wall of the enlarged hole to prevent the bushing from coming off when the lug is under load;

[0007] Step S104, Bushing Pressing: Press the bushing into the enlarged ear hole to achieve in-situ repair;

[0008] Step S105, Sealing treatment: Apply sealant to the edge of the hole to complete the repair.

[0009] Preferably, the bushing is made of stainless steel or titanium alloy, and the potential difference matching between the bushing material and the original connector lug material should be considered to prevent electrochemical corrosion.

[0010] Preferably, the countersunk shoulder of the bushing is designed with an angle of 100°, and the height of the shoulder is adapted to the thickness of the ear piece body, ensuring that the shoulder sinks below the surface of the ear piece after pressing, without affecting the original assembly relationship.

[0011] Preferably, the inner diameter and tolerance of the bushing are the same as the original connector lug hole diameter.

[0012] Preferably, the interference amount in step S103 is controlled by the bushing outer diameter tolerance, and the interference amount ranges from 0.05 mm to 0.2 mm.

[0013] Preferably, the enlarged hole size in step S101 must meet the following requirements: the ratio of the ear width to the hole diameter after enlargement is not less than the minimum safety factor specified in the aircraft design manual, and the depth of the damaged part removed by enlargement does not exceed 1 / 3 of the ear thickness.

[0014] Preferably, the method is applicable to field repairs.

[0015] Preferably, the wall thickness of the bushing is optimized according to the load on the joint. When the load is greater than the set value, the upper limit wall thickness of 4mm is selected, and when the load is less than the set value, the lower limit wall thickness of 2.5mm is selected.

[0016] Preferably, in step S104, the bushing is press-fitted using hydraulic or mechanical pressure equipment, and the pressing speed is controlled at 5-10 mm / min to avoid secondary damage to the lugs.

[0017] Preferably, the sealant is an aerospace-grade silicone sealant with a coating thickness of 0.1-0.3 mm, used to prevent moisture and corrosive media from entering.

[0018] A repair bushing for the aforementioned method of repairing connector lug holes, the bushing being a cylindrical metal part with a recessed shoulder, comprising a bushing body and a shoulder portion, wherein:

[0019] The inner diameter of the bushing body matches the original lug hole diameter, with a tolerance grade of IT6-IT7;

[0020] The bushing outer diameter is designed for an interference fit, with an interference amount of 0.05-0.2mm;

[0021] The shoulder has a 100° countersunk structure with a height of 1-2mm.

[0022] Preferably, the bushing surface is hardened to a hardness of HRC≥40 to improve wear resistance and compressive strength.

[0023] This application achieves in-situ repair of the joint hole by designing the bushing wall thickness and inner and outer diameter tolerances and adjusting the interference of the bushing press-fitting to the joint hole; the bushing has a shoulder on one side, which can limit the unidirectional sliding tendency of the bushing; if the original lug material has poor wear resistance, the problem of poor wear resistance of the lug hole can be solved by changing the material of the repair bushing.

[0024] The positive effects of the above design features are: they solve the repair problem of aircraft connector lug holes, avoiding the complex disassembly and installation problems caused by overall replacement; they avoid the installation accuracy problems of cutting and reinstalling lugs. They provide an effective method for repairing connector lugs, saving economic and time costs associated with repairs. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a repair bushing for a connector hole.

[0026] Figure 2 This is a diagram illustrating the repair of the connector lug hole. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some embodiments of this application, not all embodiments. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings. Step S101, Damage Assessment

[0028] First, use measuring tools (such as an inside micrometer or coordinate measuring machine) to inspect the damage to the lug hole of the connector. Measurement parameters include hole diameter, roundness error, and surface damage depth. Based on the measurement results, determine the enlargement size, ensuring that the enlarged lug size meets the requirements of the aircraft design manual. For example, for a lug hole with a diameter of 30mm, if the damage depth is 0.5mm, the enlarged hole diameter should be at least 32mm (original hole diameter 30mm + 2 × damage depth 0.5mm + safety margin 1mm), and the difference between the enlarged hole diameter and the original hole diameter should be greater than 2mm.

[0029] Step S102, Bushing Design

[0030] A metal bushing with a recessed shoulder is designed based on the dimensions after bore reaming. The bushing is designed using 3D CAD software, and specific parameters include:

[0031] Bushing wall thickness: Select 2.5mm, 3mm or 4mm according to the load.

[0032] Bushing length: precisely matched to the thickness of the connector lug body, with an error of ±0.1mm.

[0033] Shoulder structure: 100° countersunk design, shoulder height 1.5mm

[0034] Step S103, Interference Control

[0035] The bushing outer diameter tolerance is determined through precise calculations. For example, for a lug hole with a diameter of 32mm, the bushing outer diameter is designed to be 32.15mm (interference allowance 0.15mm). Finite element analysis software is used to verify whether the interference meets the stress requirements, ensuring that the bushing does not come off under the maximum working load.

[0036] Step S104, Bushing Press-fit

[0037] A hydraulic press is used to press the bushing into the enlarged lug hole. Before pressing, apply an appropriate amount of lubricant to the hole wall. The pressing speed is controlled at 8 mm / min, and the pressure is gradually increased to the rated value (e.g., 5 tons) to ensure that the bushing is smoothly placed.

[0038] Step S105, Sealing treatment

[0039] After pressing, use a special glue gun to apply aerospace-grade silicone sealant to the edge of the hole. The coating thickness is 0.2mm and the width is 3mm to form a continuous sealing ring.

[0040] Specific implementation of bushing material selection:

[0041] Preferred materials: austenitic stainless steel (such as 304 stainless steel) or titanium alloy (such as TC4).

[0042] Potential difference control: When the original connector is made of aluminum alloy, a titanium alloy bushing with a smaller potential difference (potential difference ≤ 0.5V) should be selected first.

[0043] Surface treatment: Stainless steel bushings undergo passivation treatment, and titanium alloy bushings undergo anodizing treatment to further improve corrosion resistance.

[0044] Material verification: A material certificate must be provided for each batch of materials, and metallographic testing must be conducted to confirm the material composition.

[0045] Specific implementation details of the recessed head and protruding shoulder:

[0046] Angle accuracy: 100°±0.5°, angle detection using a projector.

[0047] Shoulder height: 1.2mm-2.0mm, adjusted according to ear thickness.

[0048] Fit tolerance: The outer diameter of the shoulder and the countersunk hole adopt an H7 / g6 fit, ensuring that the surface of the shoulder is 0.1-0.3mm lower than the surface of the lug after assembly.

[0049] Machining process: The shoulder is machined in one setup using a CNC lathe, ensuring concentricity ≤0.02mm.

[0050] Implementation methods for bushing inner diameter design:

[0051] Standard design: The inner diameter is consistent with the original hole, and the tolerance zone is H7, such as Φ30H7 (+0.021 / 0).

[0052] Hole modification design: When the hole diameter needs to be changed, the inner diameter is designed according to the requirements, but the wall thickness must be ensured to be no less than 2.5mm.

[0053] Inspection method: Use a pneumatic measuring instrument to perform 100% inner diameter inspection, with an accuracy of 0.001mm.

[0054] Specific implementation of interference quantity control:

[0055] Calculation basis: The interference ratio is calculated according to the formula = (D2 - D1) / D1 × 100%, where D2 is the outer diameter of the bushing and D1 is the bore diameter.

[0056] Interference range: 0.1%-0.6%, corresponding to an absolute interference of 0.05mm-0.2mm.

[0057] Group assembly: The bore diameter and bushing outer diameter are each divided into 3 groups (large, medium, and small) to achieve group selection and improve assembly accuracy.

[0058] Verification test: Three specimens of each specification were made for pressing force testing, with the pressing force controlled within the range of 3-8 kN.

[0059] Implementation details of hole enlargement size control:

[0060] Safety factor verification: After enlarging the aperture, the ratio of the lug width W to the aperture diameter D, W / D, must be ≥ 2.0 (according to the aircraft design manual requirements).

[0061] Damage depth limit: The remaining wall thickness is confirmed by an ultrasonic thickness gauge. After removing the damage, the remaining thickness is ≥ 2 / 3 of the original thickness.

[0062] Hole reaming process: A stepped reaming method is adopted, with a feed rate of 0.5mm per step, and a final fine reaming allowance of 0.1mm is left;

[0063] Surface roughness: After hole enlargement, the hole wall Ra ≤ 1.6μm, measured with a roughness tester;

[0064] Specific implementation of field repairs:

[0065] Tool configuration: Portable hydraulic reamer (weight <15kg), manual press, field measurement tool kit;

[0066] Time comparison: Traditional connector replacement takes 8 hours, while this method only takes 2 hours, increasing efficiency by 60%;

[0067] Quality assurance: After repair, a dye penetrant test is performed to confirm that there are no surface cracks;

[0068] Record requirements: Fill out the repair record card, including parameters such as the enlargement size, bushing specifications, and pressing force.

[0069] Implementation of wall thickness optimization design:

[0070] Load calculation: The theoretical wall thickness is calculated using the formula t = P / (σ·π·D), where P is the working load and σ is the allowable stress;

[0071] Safety factor: 2.0 for static load and 3.0 for dynamic load;

[0072] Preferably, the wall thickness of the bushing is optimized according to the load on the joint. When the load is greater than the set value, the upper limit wall thickness of 4mm is selected, and when the load is less than the set value, the lower limit wall thickness of 2.5mm is selected.

[0073] Preferably, in step S104, the bushing is press-fitted using hydraulic or mechanical pressure equipment, and the pressing speed is controlled at 5-10 mm / min to avoid secondary damage to the lugs.

[0074] Preferably, the sealant is an aerospace-grade silicone sealant with a coating thickness of 0.1-0.3 mm, used to prevent moisture and corrosive media from entering.

[0075] A repair bushing for the aforementioned method of repairing connector lug holes, the bushing being a cylindrical metal part with a recessed shoulder, comprising a bushing body and a shoulder portion, wherein:

[0076] The inner diameter of the bushing body matches the original lug hole diameter, with a tolerance grade of IT6-IT7;

[0077] The bushing outer diameter is designed for an interference fit, with an interference amount of 0.05-0.2mm;

[0078] The shoulder has a 100° countersunk structure with a height of 1-2mm.

[0079] Preferably, the bushing surface is hardened to a hardness of HRC≥40 to improve wear resistance and compressive strength.

[0080] This application achieves in-situ repair of the joint hole by designing the bushing wall thickness and inner and outer diameter tolerances and adjusting the interference of the bushing press-fitting to the joint hole; the bushing has a shoulder on one side, which can limit the unidirectional sliding tendency of the bushing; if the original lug material has poor wear resistance, the problem of poor wear resistance of the lug hole can be solved by changing the material of the repair bushing.

[0081] The positive effects of the above design features are: they solve the repair problem of aircraft connector lug holes, avoiding the complex disassembly and installation problems caused by overall replacement; they avoid the installation accuracy problems of cutting and reinstalling lugs. They provide an effective method for repairing connector lugs, saving economic and time costs associated with repairs.

[0082] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for repairing lug holes in aircraft structural joints, characterized in that, The method includes the following steps: Step S101, Damage Assessment: Measure the damage of the connector lug hole, determine the enlargement size, and ensure that the lug size after enlargement meets the requirements of the aircraft design manual, and that the difference between the enlarged hole diameter and the original hole diameter is greater than 2mm. Step S102, Bushing Design: Design a metal bushing with a recessed shoulder according to the size after hole enlargement. The bushing includes a bushing body and a shoulder portion. The bushing wall thickness is designed to be 2.5mm to 4mm. The bushing length is the same as the thickness of the connector lug body. The shoulder is a countersunk structure. Step S103, Interference Control: By designing the bushing outer diameter tolerance, ensure that there is sufficient interference when the bushing is pressed into the wall of the enlarged hole to prevent the bushing from coming off when the lug is under load; Step S104, Bushing Pressing: Press the bushing into the enlarged ear hole to achieve in-situ repair; Step S105, Sealing treatment: Apply sealant to the edge of the hole to complete the repair.

2. The method for repairing the connector lug hole as described in claim 1, characterized in that, The bushing is preferably made of stainless steel or titanium alloy, and the potential difference matching between the bushing material and the original connector lug material must be considered to prevent electrochemical corrosion.

3. The method for repairing the connector lug hole as described in claim 1, characterized in that, The countersunk shoulder of the bushing is designed with an angle of 100°, and the height of the shoulder is adapted to the thickness of the ear piece body to ensure that the shoulder sinks below the surface of the ear piece after pressing, without affecting the original assembly relationship.

4. The method for repairing the connector lug hole as described in claim 1, characterized in that, The inner diameter and tolerance of the bushing are the same as the original connector lug hole diameter.

5. The method for repairing the connector lug hole as described in claim 1, characterized in that, The interference amount mentioned in step S103 is controlled by the bushing outer diameter tolerance, and the interference amount ranges from 0.05 mm to 0.2 mm.

6. The method for repairing the connector lug hole as described in claim 1, characterized in that, The enlargement dimensions described in step S101 must meet the following requirements: the ratio of the lug width to the hole diameter after enlargement is not less than the minimum safety factor specified in the aircraft design manual, and the depth of the damaged portion removed by enlargement does not exceed 1 / 3 of the lug thickness.

7. The method for repairing the connector lug hole as described in claim 1, characterized in that, The method described is applicable to field repairs.

8. The method for repairing the connector lug hole as described in claim 1, characterized in that, The wall thickness of the bushing is optimized according to the load on the joint. When the load is greater than the set value, the upper limit wall thickness of 4mm is selected, and when the load is less than the set value, the lower limit wall thickness of 2.5mm is selected.

9. The method for repairing the connector lug hole as described in claim 1, characterized in that, In step S104, the bushing is press-fitted using hydraulic or mechanical pressure equipment, and the pressing speed is controlled at 5-10 mm / min to avoid secondary damage to the lugs.

10. The method for repairing the connector lug hole as described in claim 1, characterized in that, The sealant is an aerospace-grade silicone sealant, applied to a thickness of 0.1-0.3 mm, to prevent moisture and corrosive media from entering.

11. A repair bushing for the joint lug hole repair method according to any one of claims 1-10, characterized in that, The bushing is a cylindrical metal part with a recessed shoulder, comprising a bushing body and a shoulder portion, wherein: The inner diameter of the bushing body matches the original lug hole diameter, with a tolerance grade of IT6-IT7; The bushing outer diameter is designed for an interference fit, with an interference amount of 0.05-0.2mm; The shoulder has a 100° countersunk structure with a height of 1-2mm.

12. The repair bushing as claimed in claim 11, characterized in that, The bushing surface is hardened to a hardness of HRC≥40 to improve wear resistance and compressive strength.

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