Repair method for rivet falling in assembly state

Abstract

The invention provides a method for repairing falling of a rivet in an assembly assembling state, belongs to the technical field of aviation product maintenance, and particularly relates to a method for repairing falling of a hot riveting rivet on an aero-engine. According to the method, the binding force is enhanced through reverse cold riveting and argon arc welding, a riveting supporting point is provided through the lever type jacking iron, and a riveting sample is manufactured before a product is riveted to verify the riveting method. According to the method, damage to other related parts in the assembly split charging process is avoided, the problems that in the assembly assembling state, the riveting operation space is limited, and the riveting combination strength is low are solved, the repair cost is saved, the repair period is shortened, and the maintainability of an engine is further improved. Through verification, after the method is adopted for repairing, the use reliability of equipment is improved in order to regenerate the rivet falling fault.

Description

Technical Field

[0001] This invention relates to the field of aviation product maintenance technology, and in particular to a method for repairing aircraft engines after hot riveting rivets have fallen off while the components are assembled. Background Technology

[0002] Hot-riveted rivets, which serve as connectors on aero-engine components, can detach during long-term use and refurbishment, severely impacting the reliability of the equipment. According to current technical specifications, repairing this problem requires complete disassembly of the component, removal of the riveted parts, re-riveting on a hot-riveting machine, and then reassembly. However, the component disassembly process is complex and easily increases the risk of damage to other related components, potentially even leading to the scrapping of the component. Figure 1 This is a flowchart of a traditional hot riveting process. When assembling rivets in the forward direction, the rivet head is in contact with the washer, and the rivet passes through the washer, housing, and bracket in sequence. After hot riveting, the hot components are assembled.

[0003] As aircraft engine repair methods shift towards "condition-based maintenance," maintenance must be performed directly in the assembled state of the engine components, based on their service life and damage detection results, to avoid unnecessary disassembly. However, the operating space in the assembled state is usually extremely limited, making it impossible for traditional hot riveting equipment to enter and operate.

[0004] Although cold riveting has the advantages of lightweight tools and flexible operation, the thermal fatigue strength of its rivets is lower than that of hot riveting rivets. If it is directly replaced, the joint strength is insufficient and it is difficult to meet the high reliability requirements of aero-engines. Summary of the Invention

[0005] To address the issue of rivet detachment during component assembly, this invention proposes a repair method for detached rivets in this assembly state. The core of this method lies in combining reverse cold riveting and argon arc welding reinforcement processes, providing a repair method with strong bonding force. A specially designed lever-type top iron is used as a support fixture. This method avoids damage to other related components during component assembly, solves the problem of limited space for operation during component assembly, and improves the connection strength of cold riveting, ensuring riveting reliability.

[0006] The technical solution adopted in this invention is:

[0007] A method for repairing rivets that have fallen off during component assembly, used to repair rivets originally connected by thermal riveting; the repair method includes the following steps:

[0008] Step 1: Provide replacement rivets suitable for cold riveting processes with a riveting gun;

[0009] Step 2, considering the limited operating space of the rivet gun and the inability to directly contact the shoulder of the replacement rivet, the following operation is performed: In the assembly state, at the installation position of the replacement rivet on the component, the replacement rivet is subjected to reverse cold riveting operation to form an upsetting head;

[0010] Step 3: Perform argon arc welding on the upsetting head formed by cold riveting and the surrounding base material to bond the upsetting head and the base material together through the weld.

[0011] Furthermore, when performing reverse cold riveting, if the operating space of the rivet gun is limited and it cannot reach the shoulder of the replacement rivet, a lever-type top iron is used to extend into the narrow space formed by the component to hold the shoulder of the replacement rivet to provide support, so that the cold riveting operation can be performed on the end opposite to the shoulder using the rivet gun.

[0012] Furthermore, before riveting and welding the product, a process verification step is also included: making a riveting sample with the same material and structure as the product, performing steps 2 and 3 on the riveting sample, and conducting non-destructive testing on the sample. Only after the sample passes the test can the product be operated.

[0013] Furthermore, in step 3, argon arc welding involves either fully welding a ring around the pier head or performing symmetrical spot welding.

[0014] Furthermore, both the reverse cold riveting operation and the argon arc welding operation include a step of performing non-destructive testing on the operation area.

[0015] Furthermore, nondestructive testing includes fluorescence penetrant testing and X-ray testing.

[0016] Furthermore, the lever-type top iron includes a crank, a pad, and a washer; the pad is located on the top surface of one end of the crank to support the replacement rivet; the washer is located on the bottom surface of one end of the crank to prevent the crank from damaging the load-bearing components during the application of force, and the washer is located close to the pad.

[0017] Furthermore, the rivets and base material are replaced with high-temperature alloys.

[0018] Furthermore, the replacement rivets are made of GH3030, and the base material is GH163.

[0019] Furthermore, in step 3, the welding wire used for argon arc welding is HGH3030 with a diameter of 1.6mm, and the welding current is 35A; DC positive polarity is used, and the argon gas flow rate is 8L / min.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. High efficiency and economy: No need to disassemble engine components, saving 80% of repair and parts replacement costs, significantly shortening the engine repair cycle by nearly 83%, and improving the maintainability of components.

[0022] 2. Reliable Connection: The cold-riveted rivet head is welded to the base material using argon arc welding, greatly enhancing the bonding strength. Practical verification has shown that rivets repaired using this method have not fallen off again, ensuring the long-term reliability of the component connections.

[0023] 3. High adaptability: The method of this invention also includes a special lever-type top iron tooling, which can adapt to the extremely limited space in the assembly state of the components, making it possible to perform high-quality riveting in narrow spaces where traditional methods cannot be used. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the traditional forward assembly hot riveting process.

[0025] Figure 2 This is a schematic diagram of the reverse assembly cold riveting and welding process used in the method of the present invention.

[0026] Figure 3 This is a schematic diagram of the lever-type top iron used in the embodiments of the present invention;

[0027] Figure 4 This is a schematic diagram of a lever-type top iron.

[0028] In the diagram: 1-shim, 2-crank rod, 3-shim block, 4-rivet to be riveted. Detailed Implementation

[0029] The present invention provides a method for repairing rivets that have fallen off during component assembly. The process mainly includes four stages: process feasibility confirmation, special tooling fabrication, sample process verification, and product riveting.

[0030] The following example illustrates the repair of a detached rivet on the casing of a certain type of aero-engine's hot-mounted component. According to design requirements, the rivet material is GH3030, and the manufacturing standard is GBn186 "Cold Forging of High-Temperature Alloy Cold-Drawn Wire". The riveted bracket, casing, and gasket are all made of GH163, with thicknesses of 0.9mm, 0.55mm, and 0.55mm respectively. The rivet hole diameter is 3.175 ± 0.025 mm, and the post-riveting uphead height is (1.8 ± 0.2) mm, with a diameter of (4.8 ± 0.3) mm. In the assembled state, the rivet uphead faces a narrow gap with a radial width of approximately 15mm.

[0031] Reference Figure 2 The specific repair steps are as follows:

[0032] Step 1, Process Confirmation: Based on the rivet manufacturing standard (such as GBn186), confirm that the replacement rivet is suitable for cold riveting with a rivet gun. This is a prerequisite for using cold riveting instead of hot riveting.

[0033] Step 2, Tooling fabrication: Refer to Figures 3-4 Based on the measured dimensions of the narrow gap in the component space (15mm high), a lever-type top iron was designed and manufactured. The top iron should have sufficient rigidity and be able to extend into the installation space to hold the rivet shoulder.

[0034] The lever-type top iron consists of a washer 1, a crank 2, and a pad 3. The pad 3 is located on the top surface of one end of the crank 2 to support the rivet 4 to be riveted. The washer 1 is located on the bottom surface of one end of the crank 2 to prevent the crank from damaging the load-bearing components during the actual repair process. The washer 1 is located close to the pad 3.

[0035] Step 3: Before riveting on the product, prepare a riveting sample for process verification to ensure the quality of product riveting.

[0036] Step 3.1: Fabricate the riveting sample using sheet metal of the same material and thickness as the bracket, housing, and gasket. The sheet metal material is GH163, with thicknesses of 0.9mm, 0.55mm, and 0.55mm respectively. Drill two sets of concentric rivet holes on the sample, with a hole diameter of 3.175 + 0.025 mm.

[0037] Step 3.2: Place the sample to be riveted on the cold riveting test bench. For example... Figure 2 As shown, the rivet shoulder is fitted against the bracket plate, and then passed through the bracket, housing, and gasket in reverse order. A lever-type jack is inserted into the 15mm high gap simulated by the sample fixing boss and the cold riveting test bench, with the jack pressing firmly against the shoulder of the rivet to be riveted. Subsequently, a pneumatic riveting gun is used to cold rivet the rivet tail (the end opposite the shoulder), controlling the uphead height to be (1.8±0.2)mm and the diameter to be (4.8±0.3)mm, thus ensuring that the rivet uphead height and diameter are consistent with the hot riveting requirements.

[0038] Step 3.3: After riveting, perform comprehensive non-destructive testing on the sample, including fluorescent penetrant testing on the rivet and its surrounding area, and X-ray testing on the inside of the riveting area to ensure that no cracks are generated.

[0039] Step 3.4: Use a scouring pad to polish the rivet head and the surrounding substrate material until a metallic luster is exposed, then thoroughly clean with acetone to remove oil and oxide layers.

[0040] Step 3.5: Using an AC / DC TIG welding machine, the rivet head, gasket plate, and casing plate are welded together by either full-circle TIG welding or spot welding. In this embodiment, the rivet head, gasket plate, and casing plate are spot welded together by TIG welding, with two symmetrical spots on both sides of the rivet. The welding wire diameter is 1.6mm, grade HGH3030, current is 35A, argon flow rate is 8L / min, and the power supply is DC positive.

[0041] Step 3.6: After welding is completed, carefully grind the weld points with small tools such as dental grinding wheels to make them smoothly transition with the substrate and avoid stress concentration.

[0042] Step 3.7 Finally, perform fluorescent penetrant testing on the welded area again to confirm that the weld quality is qualified and there are no cracks.

[0043] Step 4, Product Riveting: After all the sample inspections are passed, the actual engine product is repaired for rivet detachment using the verified process methods, tooling, and parameters (such as the use of the top iron, riveting force, welding parameters, etc.). After the repair is completed, fluorescent penetrant testing is performed on the riveting and welding areas of the product to ensure that everything is perfect.

[0044] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A rivet pull-out repair method for repairing a rivet originally connected by a hot rivet connection and the rivet is in a narrow installation space, characterized in that, The repair method comprises the following steps: Step 1, providing a replacement rivet suitable for the cold riveting process of a rivet gun; Step 2, based on the consideration that the operation space of the rivet gun is limited and cannot directly contact the shoulder of the replacement rivet, the following operation is performed: in the assembled state of the assembly, the reverse cold riveting operation is performed on the replacement rivet at the installation position of the replacement rivet on the assembly to form a header; Step 3, argon arc welding is performed on the header formed by cold riveting and the surrounding base material, so that the header and the base material are combined through a weld.

2. The method of claim 1, wherein the rivet is in an assembled state of the component. When performing the reverse cold riveting operation, a lever-type anvil is used to extend into the narrow space formed by the assembly and support the shoulder of the replacement rivet to facilitate cold riveting operation on the end opposite to the shoulder using a rivet gun.

3. The method of claim 1, wherein the rivet is in an assembled state. Before riveting and welding the product, a process verification step is further included: a riveting test sample of the same material and structure as the product is made, steps 2-3 are performed on the riveting test sample, and non-destructive testing is performed on the test sample. Only after passing the test, the product is operated.

4. The method of claim 1, wherein the rivet is in an assembled state. In step 3, the argon arc welding is full welding of the header or symmetric spot welding.

5. The method of claim 1, wherein the rivet is in an assembled state. After the reverse cold riveting operation and the argon arc welding operation, a step of performing non-destructive testing on the operation area is included.

6. The method of claim 5, wherein the rivet is in an assembled state. The non-destructive testing includes fluorescent penetrant testing and X-ray testing.

7. The method of claim 2, wherein the rivet is in an assembled state. The lever-type anvil comprises a curved lever, a pad and a gasket; the pad is arranged on the top surface of one end of the curved lever to support the replacement rivet; the gasket is arranged on the bottom surface of one end of the curved lever to prevent the curved lever from crushing the load-bearing machine parts in the assembly during the pressing process, and the gasket is arranged close to the pad.

8. The method of claim 1, wherein the rivet is in an assembled state. The replacement rivet and the base material are high-temperature alloys.

9. The method of claim 8, wherein the rivet is in an assembled state. The replacement rivet is GH3030, and the base material is GH163.

10. The method of claim 1, wherein the rivet is in an assembled state. In step 3, the welding wire used for argon arc welding is HGH3030 with a diameter of 1.6 mm and a welding current of 35 A; direct current positive connection is used, and the argon gas flow is 8 L / min.

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