Helicopter tail transmission shaft bullet damage first-aid repair method

Abstract

The invention discloses a helicopter tail transmission shaft bullet damage first-aid repair method. The method comprises the following steps that an optimal repair material and optimal process parameters are determined; matching the elastic working condition with the damage degree; prefabricating a standard patch and a balance mass block; detecting, evaluating and selecting a repairing part; the bullet damage defect is trimmed; and welding repair and heat treatment. Compared with the prior art, the dynamic balance of the damaged tail transmission shaft can be recovered while the strength requirement of the damaged tail transmission shaft is met, and rapid repair of the bounced damaged tail transmission shaft in the field is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of helicopter damage repair, and in particular to a method for repairing bullet damage to a helicopter tail transmission shaft. Background Art

[0002] In actual battlefield applications, helicopters often need to fly close to the ground. Because the tail drive shaft extends from the fuselage to the entire tail wing, it is easy to be attacked by ground light weapons. Once the tail drive shaft is hit by a bullet, its dynamic behavior will change. Since the helicopter tail drive shaft has the characteristics of high-frequency vibration, stress concentration will occur in the bullet-hit area and cracks will expand. Once the drive shaft is overwhelmed and the shaft breaks, the transmission capacity of the transmission system will be completely lost, and the helicopter will face a devastating disaster. Therefore, the helicopter tail drive shaft needs to leave the battlefield quickly for repair after being damaged by a bullet to restore its combat capability. There are usually two methods for field repair of helicopter failures caused by tail drive shaft damage. First, the damaged shaft end is replaced with a spare shaft end, and second, the damaged shaft end is repaired with repair technology. Replacing the damaged shaft end is more efficient, but the cost is also higher. In the case of high intensity of war, it may also cause the situation that the damaged helicopter has no shaft to replace. Therefore, rapid repair of the damaged tail drive shaft to achieve emergency use is one of the important solutions to ensure that the helicopter can return to the battlefield to perform its mission.

[0003] At present, the main repair solutions for the damaged tail drive shaft are riveting repair and composite material bonding repair. Both repair methods have a good balance of recovery effectiveness and strength recovery effectiveness, but the repair time is long and cannot meet the rapidity requirements in actual battlefield applications. Therefore, it is necessary to develop a new repair method for helicopter tail drive shaft damage. Summary of the invention

[0004] Purpose of the invention: To solve the above-mentioned problem, the present invention provides a method for repairing bullet-damaged tail drive shaft of a helicopter, which can not only meet the strength requirements of the damaged tail drive shaft, but also restore the dynamic balance of the damaged tail drive shaft itself, thereby realizing rapid repair of the damaged tail drive shaft after bullet strike in the field.

[0005] Technical solution: To achieve the above purpose, the helicopter tail drive shaft bullet damage repair method of the present invention comprises the following steps:

[0006] S1. Obtaining the first process parameters and the first repair material corresponding to the maximum tensile strength of the welded joint through a welding repair test;

[0007] S2. After classifying the damaged tail transmission shaft according to the degree of damage, determine the corresponding impact conditions of the damaged tail transmission shafts with different degrees of damage, and formulate corresponding treatment measures according to the different degrees of damage;

[0008] S3. Use the bullet impact simulation model to simulate and analyze the bullet impact working conditions corresponding to the degree of damage that needs to be repaired in S2, and measure the bullet hole size of the damaged tail drive shaft under the corresponding working conditions. Then, based on the bullet hole size, complete the design of the standard patch, calculate and complete the design of the balancing mass block, determine the corresponding relationship between the bullet impact working conditions and the prefabricated patch and the balancing mass block, accurately determine the working condition range corresponding to the standard patches and balancing mass blocks of different specifications, and prefabricate the standard patches and balancing mass blocks according to the design results;

[0009] S4. Based on the damage failure characteristic map, determine the impact condition and damage degree of the damaged tail drive shaft through detection and size measurement, and complete the matching of the standard patch and the balancing mass block according to the impact condition;

[0010] S5. Clean impurities around the bullet hole; perform melting treatment on microcracks around the bullet hole; trim the area around the bullet hole and grind off the raised area around the bullet hole to complete the trimming of the bullet damage defect;

[0011] S6. affix and fix the matching standard patch to the bullet hole, perform long-distance welding repair according to the first process parameters, perform heat treatment on the weld after welding is completed, and then fix the balancing mass block to the other end of the tail drive shaft opposite to the bullet hole, dynamically balance the tail drive shaft, and complete the repair.

[0012] Furthermore, in S1, the welding repair test is based on the single factor method and the response surface method; the first process parameters include welding current, welding speed and wire feeding speed; and the first repair material is 2A12 (2024) aluminum alloy.

[0013] Furthermore, in S2, the degree of injury is divided into mild injury, moderate injury and severe injury.

[0014] Furthermore, in S2, the treatment measures include: for a damaged tail drive shaft with slight damage, no repair measures are taken; for a damaged tail drive shaft with moderate damage, welding repair is performed using the first process parameters; for a damaged tail drive shaft with severe damage, no repair is performed, and the shaft end is replaced or other treatment measures are taken.

[0015] Further, in S2, the impact working condition includes: determining the working condition boundary corresponding to the damaged tail drive shaft with slight damage and moderate damage through the damage failure characteristic map; determining the working condition boundary corresponding to the damaged tail drive shaft with moderate damage and severe damage by establishing a residual performance simulation model of the repaired tail drive shaft. Further, the residual performance simulation model of the repaired tail drive shaft includes: establishing a geometric model of the repaired aluminum alloy tail drive shaft and meshing it according to the tail drive shaft size, patch size and repair joint position size, defining the material properties of the base material, repair material and joint area respectively, using the product of the helicopter tail drive shaft limit load and safety factor as the torsional load boundary condition, obtaining the stress distribution of the tail drive shaft, extracting the maximum stress of the tail drive shaft at the repair joint, and determining the remaining life of the damaged tail drive shaft after repair according to the SN curve of the material.

[0016] Furthermore, in S3, the standard patch is elliptical or circular, the size of the standard patch is set to cover all bullet holes that need to be repaired, and the shortest overlap distance between the standard patch and the damaged tail drive shaft is not less than the shaft thickness.

[0017] Furthermore, in S3, the balancing mass block measures the eccentric mass and gyration radius of the damaged tail drive shaft impact damage area and the matched standard patch under different working conditions, thereby calculating the difference between the mass-diameter products of the two, and designs balancing mass blocks of different specifications by determining the gyration radius of the balancing mass block at the installation position.

[0018] Furthermore, in S6, the method of fixing the balancing mass block is to use spot welding or quick-adhesive gluing.

[0019] Furthermore, the 2A12 (2024) aluminum alloy is prefabricated into a thin-walled tube, the wall thickness of the thin-walled tube is consistent with the tail drive shaft, the inner diameter of the thin-walled tube is consistent with the outer diameter of the tail drive shaft, and the patch and the balancing mass block are cut from the prefabricated thin-walled tube.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant effects: the process parameters and repair materials corresponding to the optimal repair joint performance are determined through material-level welding repair tests, thereby ensuring that the strength of the damaged tail drive shaft is restored to the greatest extent; balancing mass blocks of different specifications are used according to the impact working conditions to restore the dynamic balance of the damaged tail drive shaft; standard patches and balancing mass blocks of different specifications are matched according to the impact working conditions to shorten the time required for repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the process of the present invention.

[0022] Figure 2 This is a schematic diagram of the structure of the tail transmission shaft after repair after vertical penetration damage according to the present invention.

[0023] Figure 3 This is a schematic diagram of the structure of the tail drive shaft after repair with damage along the 45° direction according to the present invention.

[0024] Figure 4 This is a schematic diagram of the structure of the tail drive shaft after repair with vertical cutting damage according to the present invention.

[0025] Figure 5 This is a schematic diagram of the structure of the tail drive shaft after repair with cutting edge damage along the 45° direction according to the present invention.

[0026] Figure 6 This is a schematic diagram showing that a standard patch of a specification described in the present invention can be used to repair damaged tail drive shafts generated under a certain range of working conditions. DETAILED DESCRIPTION

[0027] The present invention discloses a method for repairing bullet damage to a helicopter tail transmission shaft. Figure 1 As shown, the helicopter tail drive shaft bullet damage emergency repair method provided by the present invention is further described in detail below: The helicopter tail drive shaft bullet damage emergency repair method comprises the following steps:

[0028] Step 1: Conduct material-level welding repair tests based on the single factor method and response surface method to obtain the first process parameters and the first repair material corresponding to the maximum tensile strength of the welded joint. The first process parameters are the optimal process parameters, and the first repair material is the optimal repair material; the first process parameters include the welding current, welding speed, and wire feeding speed during the welding repair process, and the first repair material is 2A12 (2024) aluminum alloy, ensuring the best welding joint performance and restoring the strength of the damaged tail drive shaft to the greatest extent.

[0029] Step 2: First, the damaged tail drive shaft is divided into mild damage, moderate damage and severe damage according to the degree of damage, and the corresponding impact conditions of the damaged tail drive shafts with different degrees of damage are determined, and corresponding treatment measures are formulated for different degrees of damage. Among them, the working condition boundaries corresponding to the damaged tail drive shafts with mild damage and moderate damage are determined by the damage failure characteristic map; the working condition boundaries corresponding to the damaged tail drive shafts with moderate damage and severe damage are determined by establishing the residual performance simulation model of the repaired tail drive shaft. The residual performance simulation model of the repaired tail drive shaft is based on the tail drive shaft size, patch size and repair joint position size. The geometric model of the repaired aluminum alloy tail drive shaft is established and meshed, and then the material properties of the base material, repair material and joint area are defined respectively. The product of the helicopter tail drive shaft limit load and the safety factor is used as the torsional load boundary condition to obtain the stress distribution of the tail drive shaft, extract the maximum stress of the tail drive shaft at the repair joint, and determine the remaining life of the damaged tail drive shaft after repair according to the SN curve of the material. The treatment measures include: for a damaged tail drive shaft with slight damage, this type of tail drive shaft still has strong residual performance and can meet the working requirements by itself, so no repair measures are taken; for a damaged tail drive shaft with moderate damage, although its residual strength is insufficient, it can meet the working requirements after repair, so it is welded and repaired using the first process parameters to ensure that it can meet the specified life requirements after welding repair; for a damaged tail drive shaft with severe damage, this type of tail drive shaft is severely damaged, and its strength after repair still cannot meet the working requirements, so it cannot be repaired, and direct replacement of the shaft end or other treatment measures are adopted.

[0030] Step 3: Use the impact simulation model to simulate and analyze the impact conditions corresponding to the moderate damage determined in the second step, measure the size of the bullet holes in the damaged tail drive shaft under the corresponding conditions through software, complete the design of the standard patch based on the size of the bullet holes, complete the design of the balancing mass block through theoretical calculation, determine the correspondence between the impact conditions and the prefabricated patches and balancing mass blocks, accurately determine the range of conditions corresponding to standard patches and balancing mass blocks of different specifications, and prefabricate the standard patches and balancing mass blocks according to the design results. Among them, the design of the standard patch meets the following requirements: 1) The standard patch is designed to be circular or elliptical to prevent stress concentration; 2) The sizes of the several designed standard patches can cover all bullet holes that need to be repaired; 3) The shortest distance between the designed patch and the damaged tail drive shaft is not less than the shaft thickness, such as Figure 6As shown, the standard patch 501 is suitable for both the damaged tail transmission shaft 502 caused by the cutting edge damage along the 30° direction and the damaged tail transmission shaft 503 caused by the cutting edge damage along the 45° direction; after the standard patch is designed, a corresponding relationship between the bullet impact working condition and the prefabricated patch needs to be formed. A standard patch can repair bullet holes caused by bullet impact working conditions within a certain range, which requires the use of balancing mass blocks of different weights. After balancing mass blocks of different specifications are designed through theoretical calculation, the working condition range corresponding to each specification of balancing mass blocks needs to be accurately determined, so as to achieve the matching of the prefabricated patch and the balancing mass block directly through the bullet impact working condition. The dynamic imbalance of the tail transmission shaft is mainly caused by the mass of the tail shaft bullet impact damage and the mass of the prefabricated patch. The eccentric mass and gyration radius of the damaged tail transmission shaft bullet impact damage area and the matched standard patch under different working conditions are measured, and the difference between the mass-diameter product of the two is calculated. By determining the gyration radius of the balancing mass block at the installation position, balancing mass blocks of different specifications are designed. In the actual repair process, balancing masses of different specifications can be selected according to different impact conditions, thereby effectively restoring the dynamic balance of the damaged tail drive shaft.

[0031] Step 4: Carry out emergency repair of the tail drive shaft damage. Based on the damage failure characteristic map, the impact condition and damage degree of the damaged tail drive shaft are determined through visual inspection and dimensional measurement, and the standard patch and balance mass block are quickly matched according to the impact condition. Among them, the mapping relationship between the impact condition and the patch and balance mass block has been established during the prefabrication process of the welding patch and the balance mass block. If it is determined that the damaged tail drive shaft needs to be repaired, the repair part can be quickly matched according to the obtained impact condition.

[0032] Step 5: First, use sandpaper to clean the metal surface around the bullet hole to remove oil and other impurities. Then use a welding torch to melt the microcracks around the bullet hole. Finally, use a grinder to trim the area around the bullet hole and grind off the raised areas around the bullet hole to complete the trimming of the defects around the bullet wound. During the trimming process, ensure that the edge of the bullet hole is smooth so that the welding process of the patch is easier and more secure. At the same time, pay attention to careful operation to avoid unnecessary damage to the surrounding materials.

[0033] Step 6: First, fit the matching standard patch to the bullet hole and fix the two by spot welding. Perform long-distance welding repair according to the first process parameter. After welding, use a heat source such as a flamethrower to quickly heat treat the weld. Install the balancing mass block on the other end of the tail drive shaft opposite to the bullet hole, and dynamically balance the tail drive shaft to complete the repair. After welding is completed, it can be determined whether grinding is required based on the macroscopic morphology of the weld. If conditions permit, a heat source such as a flamethrower can be used to quickly heat treat the weld. Appropriate heat treatment can improve the welding strength of the weld. Since the balancing mass block only needs to withstand the centrifugal force generated by the rotation of the tail drive shaft, the balancing mass block can be fixed to the other end of the tail drive shaft opposite to the bullet hole by spot welding or quick-adhesive gluing, thereby achieving dynamic balancing of the damaged tail drive shaft.

[0034] Example

[0035] After the above steps, it is determined that the first repair material is 2A12 (2024) aluminum alloy, and the first process parameters are: welding current is 110A, welding speed is 2.7mm / s, and wire feeding speed is 180cm / min. A thin-walled tube is prefabricated using 2A12 (2024) aluminum alloy. The wall thickness of the thin-walled tube is consistent with the tail drive shaft, and the inner diameter of the thin-walled tube is consistent with the outer diameter of the tail drive shaft. The patch and the balance mass block are cut from the prefabricated thin-walled tube. In addition, in the repair step, the estimated time required for detection and evaluation is 5 minutes, the estimated time required for selection of repair parts is 2 minutes, the estimated time required for bullet damage defect repair is 5 minutes, and the estimated time required for post-processing is 2 minutes. The time required for welding repair varies depending on the length of the weld. The time required for repair under specific working conditions depends on the length of the weld. Based on the actual working conditions, the eccentric mass and gyration radius of the bullet damage area, the standard patch and the balance mass block are calculated, and the dynamic unbalance of the tail drive shaft after repair is determined by calculating the sum of the mass-diameter product of the three.

[0036] like Figure 2 As shown, no balancing mass block is used. The projection of the standard patch 102 on the longitudinal section of the thin-walled tube is an ellipse. The major axis of the ellipse is 23 mm long, the minor axis is 20 mm long, and the major axis coincides with the axis of the thin-walled tube. The damaged tail drive shaft 101 generated under this working condition is welded and repaired. The welding repair includes the fixation of two standard patches 102. The weld length of a single standard patch is 67.81 mm. The estimated welding repair time is 12 min, and the total repair time is 26 min. The dynamic unbalance of the damaged tail drive shaft 100 after repair is estimated to be 0.52 g·mm.

[0037] like Figure 3As shown, the mass of the balancing mass block 203 is 1g, and the projection of the standard patch 202 on the longitudinal section of the thin-walled tube is an ellipse, the major axis of the ellipse is 23mm long, the minor axis is 20mm long, and the major axis coincides with the axis of the thin-walled tube. The damaged tail drive shaft 201 generated under this working condition is welded and repaired. The welding repair includes the fixation of two standard patches 202 and two balancing mass blocks 203. The weld length of a single standard patch is 67.81mm. The estimated welding repair time is 14min, and the total repair time is 28min. The dynamic unbalance of the damaged tail drive shaft 200 after repair is estimated to be 11.72g·mm.

[0038] like Figure 4 As shown, the mass of the balancing mass block 303 is 3g, and the projection of the standard patch 302 on the longitudinal section of the thin-walled tube is an ellipse, the major axis of the ellipse is 50mm long, the minor axis is 20mm long, the angle between the major axis and the axis of the thin-walled tube is 82.5°, and the center of the ellipse is located on the axis of the thin-walled tube. The damaged tail drive shaft 301 generated under this working condition is welded and repaired. The welding repair includes the fixation of a standard patch 302 and a balancing mass block 303. The weld length of the standard patch is 119.96mm, the estimated welding repair time is 8min, and the total repair time is 22min. The dynamic unbalance of the damaged tail drive shaft 300 after repair is estimated to be 5.69g·mm.

[0039] like Figure 5 As shown, the mass of the balancing mass block 403 is 6g, and the projection of the standard patch 402 on the longitudinal section of the thin-walled tube is an ellipse, with a major axis of 67mm and a minor axis of 25mm. The angle between the major axis and the axis of the thin-walled tube is 51°, and the center of the ellipse is located on the axis of the thin-walled tube. The damaged tail drive shaft 401 generated under this working condition is welded and repaired. The welding repair includes the fixation of a standard patch 402 and a balancing mass block 403. The weld length of the standard patch is 158.02mm. The estimated welding repair time is 9min, and the total repair time is 23min. The dynamic unbalance of the damaged tail drive shaft 400 after repair is estimated to be 12.81g·mm.

[0040] In the actual repair process, the matching standard patch and balancing mass block are determined directly according to the impact conditions, which greatly shortens the repair time.

Claims

1. A method for repairing bullet damage to a helicopter tail drive shaft, characterized in that: The following steps are involved: S1. Obtaining the first process parameters and the first repair material corresponding to the maximum tensile strength of the welded joint through a welding repair test; S2. After classifying the damaged tail transmission shaft according to the degree of damage, determine the corresponding impact conditions of the damaged tail transmission shafts with different degrees of damage, and formulate corresponding treatment measures according to the different degrees of damage; S3. Use the bullet impact simulation model to simulate and analyze the bullet impact working conditions corresponding to the degree of damage that needs to be repaired in S2, and measure the bullet hole size of the damaged tail drive shaft under the corresponding working conditions. Then, based on the bullet hole size, complete the design of the standard patch, calculate and complete the design of the balancing mass block, determine the corresponding relationship between the bullet impact working conditions and the prefabricated patch and the balancing mass block, accurately determine the working condition range corresponding to the standard patches and balancing mass blocks of different specifications, and prefabricate the standard patches and balancing mass blocks according to the design results; S4. Based on the damage failure characteristic map, determine the impact condition and damage degree of the damaged tail drive shaft through detection and size measurement, and complete the matching of the standard patch and the balancing mass block according to the impact condition; S5. Clean impurities around the bullet hole; perform melting treatment on microcracks around the bullet hole; trim the area around the bullet hole and grind off the raised area around the bullet hole to complete the trimming of the bullet damage defect; S6. affix and fix the matching standard patch to the bullet hole, perform long-distance welding repair according to the first process parameters, perform heat treatment on the weld after welding is completed, and then fix the balancing mass block to the other end of the tail drive shaft opposite to the bullet hole, dynamically balance the tail drive shaft, and complete the repair.

2. The helicopter tail drive shaft bullet damage repair method according to claim 1 is characterized in that: In S1, the welding repair test is based on the single factor method and the response surface method; the first process parameters include welding current, welding speed and wire feeding speed; and the first repair material is 2A12 (2024) aluminum alloy.

3. The helicopter tail drive shaft bullet damage repair method according to claim 1 is characterized in that: In S2, the injury degree is divided into mild injury, moderate injury and severe injury.

4. The helicopter tail drive shaft bullet damage repair method according to claim 1 is characterized in that: In S2, the treatment measures include: for a damaged tail drive shaft with slight damage, no repair measures are taken; for a damaged tail drive shaft with moderate damage, welding repair is performed using the first process parameters; for a damaged tail drive shaft with severe damage, no repair is performed, and the shaft end is replaced or other treatment measures are taken.

5. The helicopter tail drive shaft bullet damage repair method according to claim 1, characterized in that: In S2, the impact working condition includes: determining the working condition boundary corresponding to the damaged tail drive shaft with slight damage and moderate damage through the damage failure characteristic map; determining the working condition boundary corresponding to the damaged tail drive shaft with moderate damage and severe damage by establishing a residual performance simulation model of the repaired tail drive shaft.

6. The helicopter tail drive shaft bullet damage repair method according to claim 5 is characterized in that: The simulation model of the residual performance of the repaired tail drive shaft includes: establishing a geometric model of the repaired aluminum alloy tail drive shaft and performing meshing according to the size of the tail drive shaft, the size of the patch and the size of the repair joint position, defining the material properties of the base material, the repair material and the joint area respectively, taking the product of the ultimate load and the safety factor of the helicopter tail drive shaft as the torsional load boundary condition, obtaining the stress distribution of the tail drive shaft, extracting the maximum stress of the tail drive shaft at the repair joint, and determining the remaining life of the damaged tail drive shaft after repair according to the SN curve of the material.

7. The helicopter tail drive shaft bullet damage repair method according to claim 1, characterized in that: In S3, the standard patch is elliptical or circular, the size of the standard patch is set to cover all bullet holes that need to be repaired, and the shortest overlap distance between the standard patch and the damaged tail drive shaft is not less than the shaft thickness.

8. The helicopter tail drive shaft bullet damage repair method according to claim 1, characterized in that: In S3, the balancing mass block measures the eccentric mass and gyration radius of the damaged tail drive shaft impact damage area and the matched standard patch under different working conditions, thereby calculating the difference between the mass-diameter products of the two, and designs balancing mass blocks of different specifications by determining the gyration radius of the balancing mass block at the installation position.

9. The helicopter tail drive shaft bullet damage repair method according to claim 1, characterized in that: In S6, the method of fixing the balancing mass block is to use spot welding or quick-adhesive gluing.

10. The helicopter tail drive shaft bullet damage repair method according to claim 2, characterized in that: The 2A12 (2024) aluminum alloy is prefabricated into a thin-walled tube, the wall thickness of the thin-walled tube is consistent with the tail transmission shaft, the inner diameter of the thin-walled tube is consistent with the outer diameter of the tail transmission shaft, and the patch and the balancing mass block are cut from the prefabricated thin-walled tube.

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