Aircraft system piping secondary bending correction device and method

Abstract

This invention relates to secondary bending technology for conduits, belonging to the field of aircraft parts manufacturing and assembly, specifically to a device and method for secondary bending and bending of aircraft system pipelines. This invention proposes a mandrel-based bending technology device and method for the secondary bending and bending process of conduits, achieving a leap from mandrelless bending to mandrel-based bending; it improves the quality of secondary bending and bending of conduits, reducing the probability of forming defects such as pipe wall misalignment, wall thickness deviation, instability and collapse, and cracking; the device has a simple structure, uses common components, has high replaceability, facilitates later maintenance and replacement, greatly improves the maintainability and service life of the equipment, and reduces costs.

Description

Technical Field

[0001] This invention relates to secondary bending and straightening technology for conduits, belonging to the field of aircraft parts manufacturing and assembly, specifically to a device and method for secondary bending and straightening of aircraft system pipelines. Background Technology

[0002] Aerospace duct forming primarily involves bending. Bending a portion of a straight tube blank using specific processing techniques causes plastic deformation, creating a bent section with a specific curvature and angle. By bending different parts of the straight tube blank, ducts conforming to spatial configuration requirements can be formed. However, as the last system installed inside the aircraft, the assembly of aerospace piping systems is affected by the forming precision of the ducts and the assembly accuracy of other components. Consequently, the formed ducts often cannot be installed in their intended positions.

[0003] Due to unavoidable manufacturing and assembly errors, stress-assisted assembly, remanufacturing the duct through measurement, or secondary calibration before assembly are often used to ensure the duct is assembled into its intended position. Stress-assisted assembly reduces the duct's lifespan and is generally not permitted. Remanufacturing a duct to meet assembly requirements increases production costs, extends the overall aircraft assembly cycle, and results in unnecessary waste.

[0004] Therefore, the secondary bending correction method for conduits is generally preferred. This method involves adjusting the bending angle of the conduit's bending section to compensate for errors caused by manufacturing and assembly, enabling the conduit to be assembled into the predetermined position. This reduces or eliminates the impact of stress-induced assembly of aerospace conduits.

[0005] Secondary bending and shaping of conduits is a process of further bending and deforming an already formed conduit. Because the bent conduit already has a complex spatial structure, it is impossible to fill its interior with the rigid support material used in the straight pipe manufacturing process. As a result, current secondary bending and shaping of conduits can only rely on coreless bending forming technology. Its forming performance is worse than that of cored bending forming technology, and it is prone to forming defects such as pipe wall misalignment, wall thickness deviation, instability and collapse, and cracking. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a device and method for secondary bending and straightening of aircraft system pipelines. The device and method are based on a flexible mandrel device for secondary bending and straightening of ducts using gas expansion technology. This device enables mandrel bending during secondary bending and straightening of ducts, significantly improving the forming performance of secondary bending of ducts and reducing the probability of forming defects such as pipe wall misalignment, wall thickness deviation, instability and collapse, and rupture.

[0007] The technical solution of this invention:

[0008] The secondary bending and straightening device for aircraft system pipelines includes an air compressor 1, an air tank 2, an oil separator 3, an air dryer 4, a filter 5, an electric pump 6, a one-way valve 7, a safety valve 8, a muffler 9, a one-way speed control valve 10, a pressure gauge 11, a two-position two-way solenoid directional valve 12, a pressure sensor 13, a vent valve 14, a rubber hose 15, and a device body 16.

[0009] The device body 16 is a steel box structure. The upper operating table is equipped with a safety valve 8, a one-way speed regulating valve 10, a vent valve 14, and start / stop buttons for the air compressor 1 and the electric pump 6. The side is equipped with the exhaust port 18 of the vent valve 14 and the inflation interface 17 of the rubber hose 15.

[0010] The gas storage tank 2 has its inlet connected to the air compressor 1, which provides the gas source. Its outlet is connected to the inlet of the oil separator 3, which filters oil from the gas. The air dryer 4 filters moisture from the gas; its inlet is connected to the outlet of the oil separator 3, and its outlet is connected to the inlet of the filter 5, which filters large mechanical impurities from the gas. The electric pump 6 has its inlet connected to the outlet of the filter 5, and its outlet connected to the one-way valve 7. The airflow is divided into two branches by the one-way valve 7. One branch connects to the safety valve 8, and then to the silencer 9. The safety valve 8 is connected to... A pressure gauge 11 is provided at one end to measure the inlet pressure of the safety valve 8. Another branch is connected to the one-way speed control valve 10. After passing through the one-way speed control valve 10, the airflow is divided into two branches. One branch is connected to the vent valve 14 and then to the silencer 9. When the operation ends, the pressure of the gas system is discharged through the vent valve 14. The other branch is connected to the two-position two-way solenoid valve 12 and then to the rubber hose 15. The two-position two-way solenoid valve 12 is equipped with a pressure sensor 13 to measure the pressure of the two-position two-way solenoid valve 12. A pressure gauge 11 is provided between the two-position two-way solenoid valve 12 and the one-way speed control valve 10 to measure the inflation pressure of the rubber hose 15.

[0011] The two-position two-way solenoid directional valve 12 is used to control the opening and closing of the air passage of the rubber hose 15. The working positions include 1YA in the neutral position and 2YA in the open position. When 1YA is energized, the air passage interface is closed, and gas cannot flow from the one-way speed control valve 10 to the rubber hose 15. When 2YA is energized, the air passage interface is open, and gas flows from the one-way speed control valve 10 to the rubber hose 15.

[0012] The method for secondary bending correction of aircraft system piping, using the aforementioned device, involves the following specific steps:

[0013] S1, adjust the position of the vent valve 14 to vent; adjust the position of the two-position two-way solenoid valve 12 to connect 2YA; adjust the positions of the safety valve 8 and the one-way speed control valve 10 to their default parameter positions.

[0014] S2, turn on the switches for air compressor 1 and electric pump 6.

[0015] S3. Place the cleaning cloth at the air outlet of the vent valve 14 and allow it to remain for 30 seconds. Then check that there are no obvious contaminants on the surface of the cleaning cloth. If obvious contaminants are found, replace the oil remover 3, air dryer 4, and filter 5, and repeat steps S1, S2, and S3 until there are no obvious contaminants on the surface of the cleaning cloth.

[0016] S4, turn off the switches of air compressor 1 and electric pump 6. Adjust the position of vent valve 14 to the closed position; adjust the position of two-position two-way solenoid valve 12 to the neutral position 1YA.

[0017] S5, connect the rubber hose 15 to the inflation port 17 on the side of the device body 16, and insert the rubber hose 15 into the conduit that needs to be bent and shaped twice. At the same time, adjust the rubber hose 15 so that there is no twisting or knotting.

[0018] S6, adjust the position of the two-position two-way solenoid directional valve 12 to the 2YA connected state; adjust the position of the one-way speed control valve 10 to the low speed position.

[0019] S7, turn on the switch for air compressor 1 and electric pump 6.

[0020] S8. After confirming that the rubber hose 15 has expanded in volume, adjust the position of the one-way speed control valve 10 to a higher speed position to meet the requirements of rapid expansion until the rubber hose 15 completely and tightly fits the inner wall of the conduit that needs to be bent and shaped twice.

[0021] S9, the operator secures the conduit that needs to be bent and shaped a second time using fasteners on the aircraft according to the predetermined position and angle, and then bends the conduit that needs to be bent and shaped a second time at a certain speed.

[0022] To monitor the strength of the conduit, the stress should be calculated before performing a secondary bending correction. The stress must not exceed the material's allowable stress limit. The triaxial strain formula for the conduit under secondary bending correction is as follows:

[0023]

[0024]

[0025]

[0026] Where, ε θ For tangential strain; ε α For circumferential strain; ε t R is the radial strain; R is the radius of the secondary bending correction; t and r are the thickness and radius of the catheter before the secondary bending correction; t0 and r0 are the thickness and radius of the catheter after the secondary bending correction. To improve work efficiency, an empirical formula should be established before performing a large number of secondary bending corrections of catheters to estimate the parameters required for the target angle and to guide subsequent operations. The formula is as follows:

[0027]

[0028] Where y is the target angle; n = 6, where x1 is the maximum thinning rate, x2 is the maximum thickening rate, x3 is the wrinkle degree, x4 is the ellipticity, x5 is the springback angle, and x6 is the springback radius; different β values ​​are revision coefficients, and ε0 is the compensation angle.

[0029] S10, check the difference between the angle of the conduit that needs to be bent and corrected twice and the angle of the predetermined position. When the angle difference is large, preferably greater than 10°, repeat step S9 until the angle difference meets the required position.

[0030] S11, turn off the switches of air compressor 1 and electric pump 6. Adjust the position of vent valve 14 to open it.

[0031] The beneficial effects of this invention are:

[0032] (1) A cored bending technology device and method based on gas expansion technology is proposed for the secondary bending and straightening process of catheters, realizing the leap from coreless bending to cored bending in the secondary bending and straightening process of catheters;

[0033] (2) This invention avoids the dilemma that traditional rigid mandrels cannot be fed into already bent conduits, and also avoids the situation that traditional filler quartz sand can only be simply piled up and filled, cannot achieve high pressure, and is very easy to cause quartz sand to scatter and form excess contamination.

[0034] (3) The present invention improves the quality of secondary bending and straightening of the conduit and reduces the probability of forming defects such as pipe wall displacement, wall thickness deviation, instability and collapse, and rupture.

[0035] (4) By using the formula for calculating the difference between the conduit angle and the predetermined position angle in the secondary bending correction provided by the present invention, the conduit is continuously compared during the bending correction process to maximize the approximation of the theoretical tube shape and achieve precise bending correction.

[0036] (5) The device designed in this invention has a simple structure and uses common components, which are highly replaceable and easy to maintain and replace later, greatly improving the maintainability and service life of the equipment and reducing costs. Attached Figure Description

[0037] Figure 1 This is an isometric drawing of a secondary bending correction device for aircraft system piping.

[0038] Figure 2 This is a diagram of the air pressure system for a secondary bending and straightening device for aircraft system piping.

[0039] In the diagram: 1 Air compressor, 2 Air tank, 3 Oil separator, 4 Air dryer, 5 Filter, 6 Electric pump, 7 Check valve, 8 Safety valve, 9 Silencer, 10 One-way speed control valve, 11 Pressure gauge, 12 Two-position two-way solenoid directional valve, 13 Pressure sensor, 14 Vent valve, 15 Rubber hose, 16 Device body, 17 Inflation port, 18 Exhaust port. Detailed Implementation

[0040] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0041] The secondary bending correction device for aircraft system pipelines of the present invention, as shown in the figure Figure 1 and Figure 2 As shown, all pneumatic components are installed inside the device body 16 and connected by metal steel conduits. Figure 2 Sequential connection; its specific components and functions are as follows:

[0042] Air compressor 1 provides the air source for the calibration device, supplying a large amount of gas to the entire device to meet the needs of subsequent gas expansion.

[0043] The gas storage tank 2 provides gas storage for the device, enabling gas storage to meet the demand for large flow rates. At the same time, it can provide a certain boost to the electric pump 6, reduce the negative pressure at the inlet of the electric pump 6, and ensure the normal operation of the electric pump 6.

[0044] The function of the oil separator 3 is to filter oil from the gas. The oil in the gas usually contains a large amount of chlorine, which can damage the surface of the filter 5, electric pump 6, one-way valve 7, safety valve 8, silencer 9, one-way speed control valve 10, pressure gauge 11, two-position two-way solenoid directional valve 12, pressure sensor 13, and vent valve 14, reducing the reliability of the entire device.

[0045] The function of the air dryer 4 is to filter moisture in the gas, preventing moisture in the gas from corroding the metal parts of the filter 5, electric pump 6, one-way valve 7, safety valve 8, silencer 9, one-way speed control valve 10, pressure gauge 11, two-position two-way solenoid directional valve 12, pressure sensor 13, and vent valve 14; to prevent damage to the oil film between the moving parts of the electric pump 6, one-way speed control valve 10, and two-position two-way solenoid directional valve 12, thus reducing lubrication; and to prevent clogging of the filter pores of the filter 5, thus reducing flow capacity.

[0046] The function of filter 5 is to filter large mechanical impurities in the gas. Especially considering the metal grinding and composite material processing in the operating environment, which inevitably generates a large amount of particulate impurities, if these impurities enter the pneumatic system, they will accelerate the wear and tear of various components, causing jamming and malfunction of the entire system. Furthermore, to meet the filtration requirements, filter 5 is preferably a depth filter with a filtration ratio β ≥ 100.

[0047] The function of electric pump 6 is to provide gas at a certain pressure to the device. Furthermore, in order to meet the pressure stabilization requirements, electric pump 6 is preferably a gear pump.

[0048] The function of the one-way valve 7 is to control the direction of gas flow, ensuring that the gas flows from the electric pump 6 through the one-way valve 7 to the one-way speed control valve 10 and the pressure gauge 11, and preventing the gas from flowing from the one-way speed control valve 10 and the pressure gauge 11 through the one-way valve 7 to the electric pump 6, thus preventing the gas from affecting the pressure of the rubber hose 15 of the end effector in the opposite direction.

[0049] The function of safety valve 8 is to prevent excessive pressure in the pneumatic system, effectively preventing damage to other system components such as silencer 9, one-way speed control valve 10, pressure gauge 11, two-position two-way solenoid directional valve 12, pressure sensor 13, and vent valve 14 due to excessive pressure. Furthermore, to meet the pressure relief stability requirements, the durability standard of safety valve 8 is selected to meet the standard. Furthermore, to avoid damage to the secondary bending and straightening conduit, the opening pressure of safety valve 8 is preferably one-quarter of the working pressure of the secondary bending and straightening conduit.

[0050] The function of silencer 9 is to reduce the decibel level of the pressure relief gas from safety valve 8, ensuring the health and ergonomics of the operator. Furthermore, to meet the noise reduction requirements, silencer 9 preferably adopts a multi-loop, multi-media noise reduction principle.

[0051] The function of the one-way speed control valve 10 is to adjust the inflation speed of the rubber hose 15. During the initial inflation stage, when rapid pressurization is required, a high flow rate mode is selected to improve operational efficiency. During the final inflation stage, when slow pressurization is required, a low flow rate mode is selected, allowing the operator to carefully observe the fit of the rubber hose 15 within the guide tube. Furthermore, to ensure accurate speed control, the one-way speed control valve 10 is preferably a valve based on the stepless electromagnetic adjustment principle.

[0052] There are two pressure gauges 11. The pressure gauge 11 between the one-way valve 7 and the one-way speed control valve 10 is used to observe the inlet pressure of the safety valve 8. The pressure gauge 11 between the one-way speed control valve 10 and the two-position two-way solenoid directional valve 12 allows the operator to observe the inflation pressure of the rubber hose 15. The operator uses different inflation pressures according to different materials and types of conduits to meet the actual needs of secondary bending and straightening of different conduits.

[0053] The two-position, two-way solenoid directional valve 12 is used to control the opening and closing of the air passage of the rubber hose 15. Its operating positions include 1YA in the neutral position and 2YA in the open position. When 1YA is energized, the air passage interface is closed, and gas cannot flow from the one-way speed control valve 10 to the rubber hose 15. When 2YA is energized, the air passage interface is open, and gas can flow from the one-way speed control valve 10 to the rubber hose 15.

[0054] Pressure sensor 13 is used to monitor the pressure of two-position two-way solenoid directional valve 12. Vent valve 14 releases the pressure of the gas system when operation is complete. Rubber hose 15 is a highly elastic rubber hose, used as a flexible mandrel for bending and straightening the conduit. This avoids the problem of traditional rigid mandrels being unable to be inserted into already bent conduits, and also avoids the situation where traditional filler, quartz sand, can only be simply piled up, unable to achieve high pressure, and is prone to scattering and causing contamination. Furthermore, to ensure the pressure requirements for gas expansion, rubber hose 15 is preferably made of highly elastic rubber material that can achieve a maximum volume expansion of 3 times under 0-5 MPa conditions. Furthermore, to ensure high operational efficiency, rubber hose 15 is preferably at least 15 m long, expanding the operator's radius of movement and avoiding the need to move the device body 16 at any time.

[0055] The specific correction steps are as follows:

[0056] S1, adjust the position of the vent valve 14 to vent; adjust the position of the two-position two-way solenoid valve 12 to connect 2YA; adjust the positions of the safety valve 8 and the one-way speed control valve 10 to their default parameter positions.

[0057] S2, turn on the switches for air compressor 1 and electric pump 6.

[0058] S3. Place the cleaning cloth at the air outlet of the vent valve 14 and allow it to remain for 30 seconds. Then check that there are no obvious contaminants on the surface of the cleaning cloth. If obvious contaminants are found, replace the oil remover 3, air dryer 4, and filter 5, and repeat steps S1, S2, and S3 until there are no obvious contaminants on the surface of the cleaning cloth.

[0059] S4, turn off the switches of air compressor 1 and electric pump 6. Adjust the position of vent valve 14 to the closed position; adjust the position of two-position two-way solenoid valve 12 to the neutral position 1YA.

[0060] S5, connect the rubber hose 15 to the inflation port on the side of the flexible mandrel device body 16, and send the rubber hose 15 into the guide tube that needs to be bent and shaped twice. At the same time, adjust the high elasticity rubber hose 15 so that there is no twisting or knotting.

[0061] S6, adjust the position of the two-position two-way solenoid directional valve 12 to the 2YA connected state; adjust the position of the one-way speed control valve 10 to the low speed position.

[0062] S7, turn on the switch for air compressor 1 and electric pump 6.

[0063] S8. After confirming that the high-elasticity rubber hose 15 has a volume expansion phenomenon, adjust the position of the one-way speed control valve 10 to a higher speed position to meet the rapid expansion requirements until the rubber hose 15 completely and tightly fits the inner wall of the conduit that needs to be bent and shaped twice.

[0064] S9, the operator secures the conduit that needs to be bent and shaped a second time using fasteners on the aircraft according to the predetermined position and angle, and then bends the conduit that needs to be bent and shaped a second time at a certain speed.

[0065] Taking 1Cr18Ni9Ti, a commonly used conduit material in the aerospace field (LF2M, 1Cr18Ni9Ti, and 1Cr18Ni10Ti), as an example, the tube blank material is TA18 titanium alloy, and the tube is an isotropic elastoplastic material with a Poisson's ratio of 0.3. The tube yield follows the Mises yield criterion.

[0066] To monitor the strength of the conduit, the stress should be calculated before performing a secondary bending correction. The stress must not exceed the material's allowable stress limit. The formula for the triaxial strain of the conduit under the secondary bending correction state is as follows:

[0067]

[0068]

[0069]

[0070] ε θ For tangential strain; ε α For circumferential strain; ε t R is the radial strain; R is the radius of the secondary bending correction; t and r are the thickness and radius of the conduit before the secondary bending correction; and t0 and r0 are the thickness and radius of the conduit after the secondary bending correction.

[0071] Taking 1Cr18Ni9Ti, a commonly used conduit material in the aerospace field (LF2M, 1Cr18Ni9Ti, and 1Cr18Ni10Ti), as an example, the yield strength of 1Cr18Ni9Ti is generally taken as 260MPa. Referring to the stress-strain curve of 1Cr18Ni9Ti pipe, the strain is found to be no more than 0.15, meaning that if ε... θ Tangential strain, ε α Circumferential strain, ε t If the three radial strain parameters exceed the strain by 0.15, the secondary bending correction radius R should be adjusted to reduce the strain value.

[0072] To improve work efficiency, an empirical formula should be established before performing a large number of secondary bending corrections of catheters. This formula estimates the parameters required for the target angle and guides subsequent operations. The formula is as follows:

[0073]

[0074] Where y is the target angle; n = 6, where x1 is the maximum thinning rate, x2 is the maximum thickening rate, x3 is the wrinkle degree, x4 is the ellipticity, x5 is the springback angle, and x6 is the springback radius; different β values ​​are revision coefficients, and ε0 is the compensation angle.

[0075] Maximum thinning rate: During the tubing bending process, the tangential tensile strain on the outer wall of the bent section plays a dominant role, causing the wall to continuously thin. The thickness of the outer wall of the formed tubing will be less than the original wall thickness. The maximum thinning rate of the tubing wall is defined as the relative thinning of the outer wall, used to describe the tensile crack resistance of the tubing during bending.

[0076] Maximum wall thickness increase: During the bending and forming process of the conduit, the tangential compressive strain on the inner wall of the bent section plays a dominant role, causing the wall to continuously thicken. The inner wall thickness of the formed conduit will exceed the original wall thickness. The maximum wall thickness increase rate is defined as the relative increase in the wall thickness of the conduit, used to describe the degree of wrinkling of the wall due to compressive instability during the bending and forming process.

[0077] Wrinkle degree: As the degree of bending of the conduit increases, the compressive stress on the inner wall of the bent section exceeds the material's critical value, causing wrinkles to form on the inner wall of the bent section due to compressive instability. Wrinkle degree describes the degree of wrinkling and deformation of the overall conduit wall after bending.

[0078] Ellipticity: During catheter bending, the outer wall of the bent section collapses due to lack of support, causing the cross-section of the catheter to change from a circle to an ellipse. Ellipticity is defined as the change in the maximum and minimum diameters of the cross-section relative to the original diameter of the catheter.

[0079] Springback angle: When the formed conduit is unloaded, the elastic deformation of the conduit is released, resulting in a certain springback deformation. The springback angle is the difference between the theoretical forming angle of the conduit and the bending angle after forming and unloading.

[0080] Springback radius: The springback angle is the difference between the theoretical forming radius of the conduit and the bending radius after forming and unloading.

[0081] S10, check the difference between the angle of the conduit that needs to be bent and corrected twice and the angle of the predetermined position. If the angle difference is large, repeat step S9 until the angle difference meets the required position.

[0082] S11, turn off the switches of air compressor 1 and electric pump 6. Adjust the position of vent valve 14 to open it.

Claims

1. A secondary bending and straightening device for aircraft system piping, characterized in that, The aircraft system pipeline secondary bending and straightening device includes an air compressor (1), an air tank (2), an oil separator (3), an air dryer (4), a filter (5), an electric pump (6), a one-way valve (7), a safety valve (8), a muffler (9), a one-way speed control valve (10), a pressure gauge (11), a two-position two-way solenoid reversing valve (12), a pressure sensor (13), a vent valve (14), a rubber hose (15), and a device body (16). The device body (16) is a steel box structure. The upper operating table is equipped with a safety valve (8), a one-way speed regulating valve (10), a vent valve (14), and start / stop buttons for the air compressor (1) and the electric pump (6). The side is equipped with the exhaust port (18) of the vent valve (14) and the inflation port (17) of the rubber hose (15). The gas storage tank (2) has its inlet end connected to the air compressor (1), which provides the gas source to the gas storage tank (2). Its outlet end is connected to the inlet end of the oil separator (3), which is used to filter oil in the gas. The air dryer (4) is used to filter moisture in the gas. Its inlet end is connected to the outlet end of the oil separator (3), and its outlet end is connected to the inlet end of the filter (5), which is used to filter large mechanical impurities in the gas. The electric pump (6) has its inlet end connected to the outlet end of the filter (5), and its outlet end is connected to the one-way valve (7). The airflow is divided into two branches by the one-way valve (7). One branch is connected to the safety valve (8), and then to the silencer (9). The safety valve (8) is connected to the air dryer (9). A pressure gauge (11) is provided at the front end to measure the inlet pressure of the safety valve (8). Another branch is connected to the one-way speed control valve (10). After the airflow passes through the one-way speed control valve (10), it is divided into two branches. One branch is connected to the vent valve (14) and then to the silencer (9). When the operation ends, the pressure of the gas system is discharged through the vent valve (14). The other branch is connected to the two-position two-way solenoid valve (12) and then to the rubber hose (15). A pressure sensor (13) is provided on the two-position two-way solenoid valve (12) to measure the pressure of the two-position two-way solenoid valve (12). A pressure gauge (11) is provided between the two-position two-way solenoid valve (12) and the one-way speed control valve (10) to measure the inflation pressure of the rubber hose (15).

2. The secondary bending and straightening device for aircraft system pipelines according to claim 1, characterized in that, The two-position two-way solenoid directional valve (12) is used to control the opening and closing of the air passage of the rubber hose (15). The working positions include 1YA in the middle position and 2YA in the open position. When 1YA is energized, the air passage interface is closed, and gas cannot flow from the one-way speed control valve (10) to the rubber hose (15). When 2YA is energized, the air passage interface is open, and gas flows from the one-way speed control valve (10) to the rubber hose (15).

3. The secondary bending and straightening device for aircraft system pipelines according to claim 1, characterized in that, The rubber hose (15) is selected from rubber materials that can achieve a maximum volume expansion of 3 times under 0-5MPa conditions.

4. A method for secondary bending and straightening of aircraft system piping, using the device described in claim 2 or 3, characterized in that, The specific steps are as follows: S1, adjust the position of the vent valve (14) to vent; adjust the position of the two-position two-way solenoid valve (12) to connect 2YA; adjust the positions of the safety valve (8) and the one-way speed control valve (10) to the default parameter positions. S2, turn on the switches of air compressor (1) and electric pump (6); S3, place the cleaning cloth at the air outlet of the vent valve (14), and then check that there are no obvious contaminants on the surface of the cleaning cloth. If obvious contaminants are found, replace the oil remover (3), air dryer (4), and filter (5), and repeat steps S1, S2, and S3 until there are no obvious contaminants on the surface of the cleaning cloth. S4, turn off the air compressor (1) and electric pump (6); adjust the position of the vent valve (14) to make it closed; adjust the position of the two-position two-way solenoid valve (12) to make it in the middle position 1YA state; S5, connect the rubber hose (15) to the inflation port (17) on the side of the device body (16), and insert the rubber hose (15) into the conduit that needs to be bent and shaped twice. At the same time, adjust the rubber hose (15) so that there is no twisting or knotting. S6, adjust the position of the two-position two-way solenoid directional valve (12) to make it in the 2YA state; adjust the position of the one-way speed control valve (10) to make it in the low speed position; S7, turn on the switches of air compressor (1) and electric pump (6); S8. After confirming that the rubber hose (15) has a volume expansion phenomenon, adjust the position of the one-way speed control valve (10) to make it in a high-speed position to meet the rapid expansion requirements until the rubber hose (15) completely and tightly fits the inner wall of the conduit that needs to be bent and shaped twice. S9, the operator fixes the duct that needs to be bent and shaped twice with fasteners on the aircraft according to the predetermined position and angle, and then bends the duct that needs to be bent and shaped twice at a certain speed. S10, check the difference between the angle of the conduit that needs to be bent and corrected twice and the angle of the predetermined position. If the angle difference is greater than 10°, repeat step S9 until the angle difference meets the required position. S11, turn off the switches of air compressor (1) and electric pump (6); adjust the position of vent valve (14) to make it open.

5. The method for secondary bending and straightening of aircraft system piping according to claim 4, characterized in that, To monitor the strength of the conduit, the stress should be calculated before performing a secondary bending correction. The stress must not exceed the material's allowable stress limit. The triaxial strain formula for the conduit under secondary bending correction is as follows: Where, ε θ For tangential strain; ε α For circumferential strain; ε t R is the radial strain; R is the radius of the secondary bending correction; t and r are the thickness and radius of the conduit before the secondary bending correction; t0 and r0 are the thickness and radius of the conduit after the secondary bending correction; the parameters required for the target angle are estimated using the following formula: Where y is the target angle; n = 6, where x1 is the maximum thinning rate, x2 is the maximum thickening rate, x3 is the wrinkle degree, x4 is the ellipticity, x5 is the springback angle, and x6 is the springback radius; different β values ​​are revision coefficients, and ε0 is the compensation angle.

6. The method for secondary bending and straightening of aircraft system piping according to claim 4, characterized in that, In S3, the cleaning white cloth is placed at the outlet of the vent valve (14) and the residence time is 30 seconds.

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