Helicopter tail drive shaft damage repair method

Abstract

The application discloses a helicopter tail transmission shaft bullet damage repair method, comprising the following steps: determination of optimal repair material and optimal process parameters; matching of bullet impact working condition and damage degree; prefabrication of standard patch and balance mass; detection evaluation and selection of repair parts; bullet damage defect trimming; welding repair and heat treatment. Compared with the prior art, the application can meet the strength requirement of the damaged tail transmission shaft, restore the dynamic balance of the damaged tail transmission shaft, and realize rapid repair of the damaged tail transmission shaft after bullet impact in the field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of helicopter damage repair, in particular to a helicopter tail transmission shaft bullet damage repair method. BACKGROUND

[0002] In actual battlefield application, helicopters often need to fly close to the ground, and because the tail transmission shaft of the helicopter extends from the fuselage to the entire tail, it is easy to be attacked by light weapons on the ground. Once the tail transmission shaft is hit by a bullet, its dynamic behavior will change. Due to the high-frequency vibration characteristics of the helicopter tail transmission shaft, stress concentration will occur in the bullet impact area and crack propagation will occur. Once the transmission shaft cannot bear the load and breaks, the transmission capacity of the transmission system is completely lost, and the helicopter will face a devastating disaster. Therefore, the helicopter tail transmission shaft needs to be quickly removed from the battlefield for repair after being damaged by a bullet in order to restore its combat capability. Field repair of helicopter failures caused by tail transmission shaft damage usually has two methods. One is to replace the damaged shaft end with a spare shaft end, and the other is to repair the damaged shaft end using repair technology. Replacing the damaged shaft end is more efficient, but also more expensive. In the case of high intensity of war, it may also lead to a situation where there is no shaft to replace for the damaged helicopter. Therefore, rapid repair of the bullet-damaged tail transmission shaft to achieve emergency use is one of the important solutions to ensure that the helicopter can return to the battlefield to perform tasks.

[0003] Currently, the main repair schemes for bullet-damaged tail transmission shafts are rivet repair and composite material bonding repair. Both repair methods have good balance recovery effectiveness and strength recovery effectiveness, but the repair time is too long to meet the rapidity requirements in actual battlefield applications. Therefore, a new type of helicopter tail transmission shaft bullet damage repair method needs to be developed. SUMMARY

[0004] The present application provides a helicopter tail transmission shaft bullet damage repair method, which can meet the strength requirements of the damaged tail transmission shaft while also restoring the dynamic balance of the damaged tail transmission shaft itself, achieving rapid repair of the damaged tail transmission shaft after being hit in the field.

[0005] Technical scheme: To achieve the above purpose, the helicopter tail transmission shaft bullet damage repair method provided by the present application comprises the following steps:

[0006] S1. Obtain 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 dividing the damaged tail transmission shaft according to the damage degree, determine the corresponding bullet impact working condition of the damaged tail transmission shaft with different damage degrees, and formulate corresponding disposal measures for different damage degrees;

[0008] S3. Using the ballistic simulation model, the ballistic conditions corresponding to the damage degree needing repair in S2 are simulated and analyzed, the bullet hole size of the damaged tail transmission shaft under the corresponding conditions is measured, the design of the standard patch is completed based on the bullet hole size, the design of the balance mass is calculated, the corresponding relationship between the ballistic conditions and the prefabricated patch and balance mass is determined, the working condition range corresponding to different specifications of the standard patch and balance mass is accurately determined, and the standard patch and balance mass are prefabricated according to the design results;

[0009] S4. Based on the damage failure feature map, the ballistic conditions and damage degree of the damaged tail transmission shaft are determined by detection and size measurement, and the matching of the standard patch and balance mass is completed according to the ballistic conditions;

[0010] S5. Clean the impurities around the bullet hole; melt the micro-cracks around the bullet hole; trim the bullet hole and grind the protruding parts around the bullet hole to complete the trimming of the bullet damage defects;

[0011] S6. The matched standard patch is fitted and fixed with the bullet hole, long-distance welding repair is performed according to the first process parameters, heat treatment is performed on the weld after welding, the balance mass is fixed on the other end of the tail transmission shaft bullet hole, the tail transmission shaft is dynamically balanced, and the repair is completed.

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

[0013] Further, in S2, the damage degree is divided into mild damage, moderate damage and severe damage.

[0014] Further, in S2, the treatment measures include: for the damaged tail transmission shaft with mild damage, no repair measures are taken; for the damaged tail transmission shaft with moderate damage, welding repair is performed using the first process parameters; for the damaged tail transmission shaft with severe damage, no repair is performed, and other treatment measures such as replacing the shaft end are adopted.

[0015] Further, in S2, the bullet impact working condition comprises: determining the working condition boundary corresponding to the slightly damaged and moderately damaged damaged tail transmission shaft through the damage failure characteristic map; determining the working condition boundary corresponding to the moderately damaged and severely damaged damaged tail transmission shaft through the simulation model of the remaining performance of the repaired tail transmission shaft. Further, the simulation model of the remaining performance of the repaired tail transmission shaft comprises: establishing a geometric model of the repaired aluminum alloy tail transmission shaft and performing mesh division according to the tail transmission shaft size, patch size and repair joint position size, defining the material properties of the base material, repair material and joint area respectively, taking the product of the helicopter tail transmission shaft limit load and safety factor as the torsional load boundary condition, obtaining the stress distribution of the tail transmission shaft, extracting the maximum stress of the tail transmission shaft at the repair joint, and determining the remaining life of the repaired damaged tail transmission shaft according to the S-N curve of the material.

[0016] Further, 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 distance between the standard patch and the damaged tail transmission shaft is not less than the shaft thickness.

[0017] Further, in S3, the balance mass is designed in different specifications by measuring the eccentric mass and the rotation radius of the damaged tail transmission shaft bullet impact damage area and the matched standard patch under different working conditions, calculating the difference between the two mass radius products, and determining the rotation radius of the balance mass at the installation position.

[0018] Further, in S6, the fixing mode of the balance mass is point welding or quick-sticking glue bonding.

[0019] Further, the 2A12 (2024) aluminum alloy is prefabricated into a thin-walled pipe, the wall thickness of the thin-walled pipe is consistent with the tail transmission shaft, the inner diameter of the thin-walled pipe is consistent with the outer diameter of the tail transmission shaft, and the patch and the balance mass are cut on the prefabricated thin-walled pipe.

[0020] Advantages: Compared with the prior art, the present application has the following remarkable effects: the optimal repair joint performance corresponding to the process parameters and the repair material is determined through the material level welding repair test, so that the strength of the damaged tail transmission shaft is restored to the maximum extent; different specifications of the balance mass are used according to the bullet impact working condition, so that the dynamic balance of the damaged tail transmission shaft is restored; different specifications of the standard patch and the balance mass are matched according to the bullet impact working condition, so that the time required for repair is shortened. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The flowchart of the present application.

[0022] Figure 2 The structure diagram of the repaired tail transmission shaft damaged in the vertical direction.

[0023] Figure 3 The structure diagram of the repaired tail transmission shaft damaged in the 45-degree direction according to the application.

[0024] Figure 4 The structure diagram of the repaired tail transmission shaft damaged in the vertical direction according to the application.

[0025] Figure 5 The structure diagram of the repaired tail transmission shaft damaged in the 45-degree direction according to the application.

[0026] Figure 6 The structure diagram of the repaired tail transmission shaft damaged in the 45-degree direction according to the application. DETAILED DESCRIPTION

[0027] The application discloses a helicopter tail transmission shaft bullet damage emergency repair method. Figure 1 As shown in the figure, the helicopter tail transmission shaft bullet damage emergency repair method provided by the application will be further described in detail as follows: The helicopter tail transmission shaft bullet damage emergency repair method comprises the following steps:

[0028] Step 1: Based on the single factor method and the response surface method, the welding repair test of the material grade is carried out, and the first process parameter corresponding to the maximum tensile strength of the welding joint and the first repair material are obtained. The first process parameter is the best process parameter, and the first repair material is the best repair material; the first process parameter includes the welding current, the welding speed and the wire feeding speed in the welding repair process, the first repair material is 2A12 (2024) aluminum alloy, and the best welding joint performance is ensured, and the strength of the damaged tail transmission shaft is recovered to the maximum extent.

[0029] Second step: First, the damaged tail drive shaft is divided into light damage, moderate damage and severe damage according to the damage degree, the corresponding impact working condition of the damaged tail drive shaft with different damage degree is determined, and the corresponding treatment measures are formulated for different damage degree. Among them, the working condition boundary of the damaged tail drive shaft with light damage and moderate damage is determined by the damage failure characteristic map; the working condition boundary of the damaged tail drive shaft with moderate damage and severe damage is 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 to establish the geometric model of the repaired aluminum alloy tail drive shaft and carry out grid division according to the size of the tail drive shaft, the size of the patch and the size of the repair joint position, and then define the material properties of the matrix material, the repair material and the joint area respectively, take the product of the limit load and the safety factor of the helicopter tail drive shaft as the torsional load boundary condition, 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 residual life of the repaired damaged tail drive shaft according to the S-N curve of the material. The treatment measures include: for the damaged tail drive shaft with light damage, such tail drive shaft still has strong residual performance and can meet the work requirements, so no repair measures are taken; for the damaged tail drive shaft with moderate damage, although its residual strength is insufficient, it can meet the work requirements after repair, so the first process parameter is used for welding repair to ensure that it can meet the specified life requirement after welding repair; for the damaged tail drive shaft with severe damage, such tail drive shaft is severely damaged, and its strength after repair still cannot meet the work requirements, so it cannot be repaired, and other disposal measures such as replacing the shaft end are adopted.

[0030] Third step: The impact simulation model is used to simulate and analyze the impact working condition corresponding to moderate damage determined in the second step, the bullet hole size of the damaged tail drive shaft under the corresponding working condition is measured by software, the design of the standard patch is completed based on the bullet hole size, the design of the balance mass is completed by theoretical calculation, the corresponding relationship between the impact working condition and the prefabricated patch and the balance mass is determined, the working condition range corresponding to different specifications of the standard patch and the balance mass is accurately determined, and the standard patch and the balance mass are prefabricated according to the design results. Among them, the design of the standard patch meets the following requirements: 1) the standard patch is designed as a circle or an ellipse to prevent stress concentration; 2) the size of the designed several standard patches can cover all the 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 design is completed, the corresponding relationship between the impact condition and the prefabricated patch needs to be formed. One standard patch can repair bullet holes caused by impact conditions within a certain range, so different weights of balance masses need to be equipped. After designing different specifications of balance masses through theoretical calculation, the corresponding working condition range of each specification of balance mass needs to be accurately determined to achieve the matching of prefabricated patches and balance masses through impact conditions. The dynamic imbalance of the tail transmission shaft is mainly caused by the mass of the tail shaft impact damage and the mass of the prefabricated patch. The eccentric mass and the rotation radius of the damaged tail transmission shaft impact damage area and the matched standard patch under different conditions are measured, and the difference between the two mass-radius products is calculated. By determining the rotation radius of the balance mass at the installation position, balance masses of different specifications are designed. In the actual repair process, different specifications of balance masses can be selected according to different impact conditions, so as to well restore the dynamic balance of the damaged tail transmission shaft.

[0031] Fourth step: Develop tail transmission shaft bullet damage repair, based on damage failure characteristic map, and determine the impact condition and damage degree of the damaged tail transmission shaft through visual detection and size measurement, and quickly complete the matching of standard patches and balance masses according to the impact condition. Among them, the mapping relationship between the impact condition and the patch and the balance mass has been established in the prefabrication process of the welded patch and the balance mass. If the damaged tail transmission shaft needs to be repaired, the matching of the repair parts can be quickly completed according to the obtained impact condition.

[0032] Fifth step: First, use sandpaper to clean the metal surface around the bullet hole, remove oil and other impurities, second, use a welding gun to melt the micro-cracks around the bullet hole, and finally use a grinder to trim the bullet hole. The protruding parts around the bullet hole are ground off, and the trimming of the bullet damage around the defect is completed. During the trimming process, ensure that the edge of the bullet hole is smooth to make the welding process of the patch more convenient and firm, and at the same time, careful operation should be paid attention to, so as to avoid unnecessary damage to the surrounding materials.

[0033] Sixth step: first, the matched standard patch is attached to the bullet hole and fixed by spot welding, long-distance welding repair is carried out according to the first process parameter, after welding, the weld is quickly heat treated using a heat source such as a flame gun, the balance mass is installed at the other end opposite the bullet hole of the tail transmission shaft, the tail transmission shaft is dynamically balanced, and the repair is completed. After welding, whether polishing is needed can be determined according to the macroscopic morphology of the weld, and if conditions permit, the weld can be quickly heat treated using a heat source such as a flame gun, and appropriate heat treatment can improve the welding strength of the weld. Since the balance mass only needs to withstand the centrifugal force generated by the rotation of the tail transmission shaft, the balance mass can be fixed at the other end opposite the bullet hole of the tail transmission shaft by spot welding or quick-bonding adhesive, thereby achieving dynamic balancing of the damaged tail transmission shaft.

[0034] Embodiment

[0035] After the above steps are determined, the first repair material is 2A12 (2024) aluminum alloy, and the first process parameter is: welding current is 110 A, welding speed is 2.7 mm / s, and wire feeding speed is 180 cm / min. A thin-walled tube is pre-fabricated by using 2A12 (2024) aluminum alloy, 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 balance mass are cut on the pre-fabricated thin-walled tube. In addition, in the repair steps, the estimated time required for detection and evaluation is 5 minutes, the estimated time required for selection of the repaired part is 2 minutes, the estimated time required for bullet damage trimming is 5 minutes, the estimated time required for post-processing is 2 minutes, and the time required for welding repair varies depending on the length of the weld, and the time required for specific working conditions is analyzed according to the length of the weld. Based on the actual working conditions, the eccentric mass and the rotation radius of the bullet impact damage area, the standard patch and the balance mass are calculated, and the dynamic unbalance of the repaired tail transmission shaft is determined by calculating the sum of the product of the three.

[0036] As shown in Figure 2 , the balance mass is not used, the projection of the standard patch 102 on the longitudinal section of the thin-walled tube is an ellipse, the long axis of the ellipse is 23 mm long, the short axis is 20 mm long, and the long axis coincides with the axis of the thin-walled tube. The damaged tail transmission shaft 101 produced under this working condition is repaired by welding, which 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 repaired damaged tail transmission shaft 100 is estimated to be 0.52 g·mm.

[0037] As shown in Figure 3As shown, the mass of the balancing mass 203 is 1g. The projection of the standard patch 202 onto the longitudinal cross-section of the thin-walled tube is an ellipse with a major axis of 23mm and a minor axis of 20mm, with the major axis coinciding with the axis of the thin-walled tube. A welding repair was performed on the damaged tail drive shaft 201 resulting from this operating condition. The repair involved securing two standard patches 202 and two balancing masses 203. The weld length of each standard patch was 67.81mm, and the estimated welding repair time was 14 minutes, for a total repair time of 28 minutes. The estimated dynamic unbalance of the damaged tail drive shaft 200 after repair was 11.72g·mm.

[0038] like Figure 4 As shown, the mass of the balancing mass 303 is 3g. The projection of the standard patch 302 onto the longitudinal cross-section of the thin-walled tube is an ellipse with a major axis of 50mm and a minor axis of 20mm. The angle between the major axis and the axis of the thin-walled tube is 82.5°, and the center of the ellipse lies on the axis of the thin-walled tube. A welding repair was performed on the damaged tail drive shaft 301 resulting from this operating condition. The repair involved securing a standard patch 302 and a balancing mass 303. The weld length of the standard patch was 119.96mm, and the estimated welding repair time was 8 minutes, for a total repair time of 22 minutes. The dynamic unbalance of the damaged tail drive shaft 300 after the repair was estimated to be 5.69g·mm.

[0039] like Figure 5 As shown, the mass of the balancing mass 403 is 6g. The projection of the standard patch 402 onto the longitudinal cross-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 lies on the axis of the thin-walled tube. A welding repair was performed on the damaged tail drive shaft 401 resulting from this operating condition. The repair involved securing a standard patch 402 and a balancing mass 403. The weld length of the standard patch was 158.02mm, and the estimated welding repair time was 9 minutes, for a total repair time of 23 minutes. The estimated dynamic unbalance of the damaged tail drive shaft 400 after repair was 12.81g·mm.

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

Claims

1. A method of repairing a damaged tail drive shaft of a helicopter, characterized in that, The method comprises the following steps: S1. Obtain 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 dividing the damaged tail transmission shaft according to the damage degree, determine the corresponding ballistic working condition of the damaged tail transmission shaft with different damage degrees, and formulate corresponding treatment measures for different damage degrees; S3. Use the ballistic simulation model to simulate and analyze the ballistic working condition corresponding to the damage degree needing repair in S2, measure the bullet hole size of the damaged tail transmission shaft under the corresponding working condition, complete the design of the standard patch based on the bullet hole size, calculate the design of the balance mass, determine the corresponding relationship between the ballistic working condition and the prefabricated patch and balance mass, accurately determine the working condition range corresponding to the standard patch and balance mass of different specifications, and prefabricate the standard patch and balance mass according to the design results; S4. Based on the damage failure characteristic map, the ballistic working condition and the damage degree of the damaged tail transmission shaft are determined through detection and size measurement, and the matching of the standard patch and the balance mass is completed according to the ballistic working condition; S5. Clean the impurities around the bullet hole; melt the micro-cracks around the bullet hole; trim the bullet hole and grind the protruding parts around the bullet hole to complete the trimming of the bullet damage defect; S6. Match the standard patch with the bullet hole and fix it, perform long-distance welding repair according to the first process parameters, perform heat treatment on the weld after welding, fix the balance mass on the other end of the tail transmission shaft corresponding to the bullet hole, and perform dynamic balancing on the tail transmission shaft to complete the repair.

2. The method for repairing a helicopter tail transmission shaft according to claim 1, characterized in that, In S1, the welding repair test is based on single factor method and 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 method of claim 1, wherein, In S2, the damage degree is divided into mild damage, moderate damage and severe damage.

4. The method of claim 1, wherein, In S2, the treatment measures include: for the damaged tail transmission shaft with mild damage, no repair measures are taken; for the damaged tail transmission shaft with moderate damage, welding repair is performed thereon using the first process parameters; and for the damaged tail transmission shaft with severe damage, no repair is performed thereon, and other treatment measures such as replacing the shaft end are adopted.

5. The method of claim 1, wherein, In S2, the ballistic working condition includes: determining the working condition boundary of the damaged tail transmission shaft corresponding to mild damage and moderate damage through the damage failure characteristic map; and determining the working condition boundary of the damaged tail transmission shaft corresponding to moderate damage and severe damage through the remaining performance simulation model of the repaired tail transmission shaft.

6. The method for repairing a helicopter tail transmission shaft according to claim 5, characterized in that, The remaining performance simulation model of the repaired tail transmission shaft comprises: establishing a geometric model of the repaired aluminum alloy tail transmission shaft and performing mesh division according to the tail transmission shaft size, patch size and repair joint position size, defining the material properties of the base material, repair material and joint area respectively, taking the product of the helicopter tail transmission shaft limit load and safety factor as the torsional load boundary condition, obtaining the stress distribution of the tail transmission shaft, extracting the maximum stress of the tail transmission shaft at the repair joint, and determining the remaining life of the repaired damaged tail transmission shaft according to the S-N curve of the material.

7. The method of claim 1, wherein, In S3, the standard patch is elliptical or circular, and the size of the standard patch is set to cover all the bullet holes that need to be repaired, and the shortest distance between the standard patch and the damaged tail transmission shaft is not less than the thickness of the shaft.

8. The method of claim 1, wherein, In S3, the balance mass is designed by measuring the eccentric mass and the rotation radius of the damaged tail transmission shaft bullet damage area and the matched standard patch under different working conditions, calculating the difference between the two mass radius products, and determining the rotation radius of the balance mass at the installation position.

9. The method of claim 1, wherein, In S6, the balance mass is fixed by spot welding or quick-sticking glue.

10. The method of claim 2, wherein, The 2A12(2024) aluminum alloy is preformed into a thin-walled pipe, the wall thickness of the thin-walled pipe is consistent with the tail transmission shaft, the inner diameter of the thin-walled pipe is consistent with the outer diameter of the tail transmission shaft, and the patch and the balance mass are cut on the preformed thin-walled pipe.

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