Novel process method for forming aviation flaring guide pipe

Abstract

The invention discloses a novel forming process method for an aviation flaring guide pipe, and relates to the technical field of aerospace manufacturing. According to the method, the problem of leakage of the guide pipe in service due to introduction of residual stress in a traditional single-time spinning forming process is solved; the method comprises the following steps: performing first flaring pre-forming on the end part of the guide pipe to form a primary flaring conical surface; the formed guide pipe flaring section is subjected to residual stress aging treatment so as to release and homogenize harmful residual stress; secondary spinning finishing is conducted on the flaring section subjected to stress treatment, so that microscopic deformation is corrected, and the final geometric accuracy is obtained; comprehensive detection including performance is carried out on the finished conduit; through a closed-loop process chain of forming, stress relief and finishing, the residual stress state and geometric accuracy of the flaring guide pipe are actively controlled and optimized, and the sealing reliability and long-term service stability of the flaring guide pipe are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of aerospace manufacturing technology, specifically a novel forming process for aerospace flared conduits. Background Technology

[0002] In aviation piping systems, flared conduits are core components for reliable fluid transmission. They work in conjunction with pipe fittings through a tapered end sealing structure to ensure system airtightness and pressure resistance. Currently, the mainstream method for flared conduits is a single-stage spinning process, where the flared tapered end of the conduit is plastically deformed in one step through mold rotation and axial advancement. However, this process has significant technical bottlenecks: To improve production efficiency, traditional flared conduits are mainly produced by spin forming, which involves high-speed rotation and extrusion using a high-strength, specific mold. During this forming process, a large amount of residual compressive stress is introduced into the flared surface. While this residual stress improves the wear resistance of the flared surface, it can also cause potential problems.

[0003] During the spinning process, the end of the conduit is prone to forming a non-uniformly distributed residual stress field due to localized severe plastic deformation, especially in the transition zone of the flared conical surface where stress concentration is prominent. Currently, the production process of flared conduits does not consider the residual stress relief stage, which leads to the rapid release of residual stress on the flared surface due to high-frequency vibration during actual application, resulting in slight deformation of the flared surface and ultimately leakage. The tightening load during subsequent assembly, pressure fluctuations and temperature cycles during service will cause the residual stress to be gradually released and redistributed, causing microscopic deformation or gaps in the flared sealing surface, destroying the initial sealing fit, and ultimately leading to pipeline leakage failure. Summary of the Invention

[0004] The purpose of this invention is to provide a new forming process for aviation flared conduits, which solves the problems of insufficient sealing reliability and limited service life caused by residual stress in traditional flared conduit manufacturing by step forming and residual stress control scheme.

[0005] The objective of this invention can be achieved through the following technical solutions: This application provides a novel forming process for aviation flared conduits, including the following steps: S1. Initial flaring preforming: The end of the catheter is spun to form a preliminary flared conical surface; S2, Residual stress aging treatment: The flared section of the catheter after step S1 is treated to release residual stress. S3, Secondary flaring and precision forming: The flared section of the conduit after step S2 is subjected to secondary spinning and finishing to obtain the final geometric accuracy; S4. Inspection: The sealing performance and geometric accuracy of the conduit after step S3 are inspected.

[0006] Furthermore, in step S2, the residual stress aging treatment includes one or more of local heat treatment, vibration aging, and microparticle shot peening.

[0007] Furthermore, the local heat treatment is a controlled heating and cooling process performed on the flared section.

[0008] Furthermore, the vibration aging includes subjecting the conduit to random vibration and alternating loads.

[0009] Furthermore, the microparticle shot peening is a shot peening treatment performed on the flared sealing cone surface using a small-diameter shot peening medium.

[0010] Furthermore, after step S1, the method further includes: detecting the residual stress distribution of the flared section.

[0011] Furthermore, after step S2, the method further includes: detecting changes in surface roughness and / or arc height of the flared surface to obtain detection results.

[0012] Furthermore, in step S3, the forming parameters used in the secondary flaring precision forming are adaptively adjusted based on the test results.

[0013] Furthermore, the inspection in step S4 includes: inspecting whether the geometric accuracy and surface quality of the conduit meet aviation standards, and inspecting the residual stress level and shape parameters of the flared section.

[0014] Furthermore, the test conditions for the sealing performance test in step S4 include applying dynamic loads that simulate operating vibrations.

[0015] The beneficial effects of this invention are as follows: To address the problem that residual stress is randomly released during service in traditional single-forming processes, leading to uncontrollable risk of seal failure, this invention adds a residual stress aging treatment step after the first flaring preforming. It provides a variety of controllable process methods, including local heat treatment, vibration aging, and microparticle shot peening, to actively adjust and release the residual stress introduced by the first forming before the part is assembled. This transforms the residual stress from an uncontrollable service variable into a process parameter that can be intervened in during the manufacturing stage, thereby reducing the risk of sealing surface deformation caused by stress release from the root cause. To address the issue that stress relief treatment may cause microscopic deformation of the flared sealing surface and affect the final sealing and fitting accuracy, this invention incorporates a secondary flaring precision forming step after residual stress aging treatment. Using the actual shape detection data after stress treatment as input, a low-speed, small-deformation spinning mode is adopted to specifically correct the microscopic shape deviation caused by changes in stress state. Through this compensatory finishing process, stress is reduced while accurately restoring and ensuring the geometric accuracy and flatness of the flared conical surface, achieving synergistic optimization of stress control and shape accuracy. Meanwhile, the entire process integrates quantitative detection and feedback control of key parameters such as residual stress, arc height, and surface roughness, forming a closed loop of manufacturing and testing. This ensures that the product meets the sealing reliability requirements under harsh working conditions before delivery, significantly reducing the risk of leakage and quality problems after leaving the factory. Attached Figure Description

[0016] To better understand and implement this application, the technical solution is described in detail below with reference to the accompanying drawings.

[0017] Figure 1 A flowchart illustrating a novel forming process for an aviation flared conduit provided in this application. Detailed Implementation

[0018] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, exemplary embodiments will be described in detail below, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0019] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used herein are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0020] The following detailed description of the specific implementation methods, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided in detail.

[0021] Please see Figure 1 This embodiment takes the flared conduit in an aviation piping system as an example and provides a new forming process for the aviation flared conduit, including the following steps: S1. Initial flaring preforming: The end of the catheter is spun to form a preliminary flared conical surface; Furthermore, in step S1, the initial flared conical surface is formed, specifically including: in step S1, the initial flared conical surface is formed by selecting a high-strength mold cone as the forming core mold, and on a high-precision spinning machine that meets aerospace manufacturing standards, the mold cone is rotated by the high-speed rotation of the spindle, while a spring propulsion mechanism is used to apply axial force to the guide tube to achieve the initial plastic forming of the flared conical surface; Based on this, by installing a high-precision carbide core mold adapted to the flaring structure and a three-roll spinning mechanism, the accuracy of the core mold cone surface and the surface roughness meet the aerospace manufacturing standards; the guide tube is clamped and fixed, and axial positioning force is applied to prevent the tube body from becoming unstable; the flaring pre-forming is completed step by step in 3-4 passes using a reverse spinning mode, and the deformation amount of each pass is controlled to avoid excessive stress concentration; after forming, the roundness, wall thickness difference and surface roughness of the flared cone surface are checked to ensure that the preset benchmark is met.

[0022] The spinning machine is equipped with a multi-roller evenly distributed spinning mechanism and a high-precision carbide mandrel to ensure that the accuracy and surface roughness of the mandrel conical surface meet the requirements of aviation standards. When clamping, a reasonable axial positioning force must be applied to prevent the tube from becoming unstable or eccentric during the spinning process. The forming process adopts a multi-pass reverse spinning mode to gradually complete the flaring, strictly controlling the deformation amount of each pass to reduce the accumulation of local stress and ensure that the flared conical surface has good roundness, wall thickness uniformity and preset surface roughness, laying the foundation for subsequent stress relief and finishing processes.

[0023] Furthermore, after step S1, the method further includes: detecting the residual stress distribution of the flared section, with a focus on evaluating the concentration of circumferential compressive stress at the middle ring of the inner surface; Among them, the quantitative detection of residual stress is carried out by X-ray diffraction to detect residual stress on the flared conical surface. During the detection, the flared conical surface is divided into 2-3 annular regions from the inside to the outside. The focus is on the distribution of circumferential compressive stress in the middle annular zone of the inner surface, and the maximum stress value, gradient and whether stress concentration occurs are evaluated.

[0024] Specifically, by employing high-precision tooling and standardized processes, a quantitative testing benchmark for residual stress distribution and geometric accuracy was established while simultaneously achieving the initial forming of the flared conical surface. This benchmark provides a clear initial state reference and data support for addressing two key issues in subsequent processes: active control of residual stress and correction of the sealing surface shape accuracy.

[0025] S2. Residual stress aging treatment: The flared section of the conduit after step S1 is treated to release residual stress. This is to actively reduce the surface residual stress introduced by the first flaring before the second forming, so as to avoid the release of the stress during service, which would cause deformation and leakage of the sealing surface.

[0026] Furthermore, step S2 includes one or more of local heat treatment, vibration aging, and microparticle shot peening. These three methods are selected in parallel and can be used individually or in combination depending on the actual situation.

[0027] The localized heat treatment refers to the controlled heating and cooling process applied to the flared section. Heat treatment is a method of altering the internal structure and microstructure of a material by heating and cooling it. For stress relief, stress-relief annealing or tempering is used, where the material is heated to a certain temperature (below its critical transformation temperature), held for a period of time, and then slowly cooled. During this process, residual stress within the material is released due to atomic rearrangement, effectively reducing the level of residual stress and improving the material's toughness and plasticity.

[0028] The vibration aging process includes subjecting the conduit to random vibration and alternating loads. Specific parameters (frequency, amplitude, time) need to be selected and adjusted according to different pipe diameters, materials, and pipe fitting types (straight pipes, bends, tees).

[0029] One specific implementation involves conducting a rotational bending fatigue test. For example, a rotational bending testing machine equipped with a conduit is set to a rotational speed of 30 Hz, and a bending moment is applied that causes the fiber stress on the outer side of the flared surface to reach 25% of the material's yield strength. The selection of these parameters references aerospace standards such as HB 6442-1990. This process effectively simulates service vibration conditions and significantly releases residual stress on the flared surface. Rotational bending is essentially a vibration process, placing the flared surface and the conical part of the pipe joint in an alternating contact pressure state. The contact pressure at the inner and outer points changes alternately with the bending cycle, generating vibration. The vibration amplitude varies at different locations, with the largest amplitude near the inner center. The simulated service vibration conditions can be referenced in standards such as HB 6442-1990, and vibration-related parameters can be referenced in GJB150.16A. The airtightness test of the pipeline after rotational bending fatigue is used to evaluate the anti-leakage performance. This treatment is a "time-dependent" process that promotes stress release, rather than "fatigue" that leads to structural failure. After a certain number of cycles (e.g., 10 million times), the residual stress of the 1Cr18Ni9Ti flared tube decreased by about 75%, and the residual stress of the aluminum alloy flared tube decreased by about 30%. Vibration aging treatment aims to achieve overall homogenization and release of residual stress in a low-energy-consumption manner.

[0030] The aforementioned microparticle shot peening is an auxiliary stress relief / homogenization method, referring to the use of small-diameter shot peening media to perform shot peening treatment on the flared sealing cone surface. Specifically, ceramic shot with a particle size of 0.1-0.3 mm can be used as the shot peening media, and the treatment is carried out at a blasting pressure of 0.3-0.5 MPa, ensuring a surface coverage of not less than 200%. This method can effectively reduce and homogenize surface stress; the parameter settings are intended for low-pressure shot peening, producing a controllable compressive stress layer rather than deep strengthening.

[0031] Quantitative control of coverage is achieved through a combination of theoretical calculations and numerical simulations. Specifically, the theoretical calculation of coverage C is based on the following formula: Where C is the theoretically calculated coverage, r is the average radius of the surface crater after the projectile impact, and N is the number of craters per unit area.

[0032] In actual process design and control, a single shot impact simulation model is established in finite element software. The average radius r of the crater under a specific shot peening intensity is obtained through simulation. Then, the r value obtained from the simulation is substituted into the above formula to calculate the number of shot per unit area N required to achieve a specified coverage (such as 200%), thus providing an accurate basis for setting shot peening parameters in actual production.

[0033] The controlled shot peening process described above can introduce favorable compressive stress on the surface of the flared sealing cone and eliminate the original stress concentration. Shot peening can significantly reduce residual stress, and the residual stress is further reduced as the coverage increases.

[0034] Furthermore, based on the stress test results of the flared section after the initial forming, the above stress relief schemes can be flexibly combined. For example, if the test finds that the proportion of stress concentration areas exceeds a preset threshold, a combination of local heat treatment and microparticle shot peening can be initiated to relieve stress.

[0035] Furthermore, after step S2, the method further includes: detecting changes in surface roughness and / or arc height of the flared surface to obtain detection results.

[0036] In this process, at least four radial lines are uniformly selected along the circumference of the flared surface using a profilometer, and the surface roughness (Ra value) and arc height are measured from the inner end to the outer end. This test aims to quantitatively assess the changes in surface condition and geometry caused by the release of residual stress. The experiment shows that the roughness of the flared surface increases after bending and is positively correlated with the number of bending cycles. The arc height is correlated with the number of bending cycles and exhibits a bilinear characteristic.

[0037] This step is part of the overall process inspection and is used to confirm the effectiveness of harmful stress reduction, while also checking whether the flared geometry has undergone out-of-tolerance deformation.

[0038] Specifically, step S2 directly intervenes in and significantly reduces the residual stress introduced by the first flaring by providing three controllable process methods that can be used individually or in combination: local heat treatment, vibration aging, and microparticle shot peening. This effectively solves the problem of uncontrolled residual stress in traditional processes. At the same time, by quantitatively detecting the roughness and arc height of the flared surface after treatment, quantitative assessment and feedback control of surface state changes and the degree of residual stress release are achieved. This provides precise input for subsequent secondary forming processes, thereby proactively eliminating the two major hidden dangers of sealing surface deformation and leakage caused by residual stress release during service in the manufacturing stage.

[0039] S3. Secondary flaring precision forming: The flared section of the conduit after step S2 is spun and refined a second time to obtain the final geometric accuracy. This forming is essentially the same as the first forming, but its core objective is to correct the surface micro-deformation caused by the release of residual stress after the first forming, and to restore and ensure the final geometric accuracy and flatness of the sealing surface.

[0040] Furthermore, step S3 is performed using a low-speed, small-deformation spinning mode. Specifically, the spindle speed for the second spinning can be 30%-70% of that for the first spinning, and the radial feed per pass is no more than 50% of that for the first spinning. Furthermore, in step S3, the forming parameters used in the secondary flaring precision forming can be adaptively adjusted according to the test results, such as compensatory correction of the core mold contour; correcting the micro-deformation that may be caused by the release of residual stress in step S2, while strictly controlling the process to avoid introducing new harmful residual stress.

[0041] Specifically, step S3 employs a low-speed, small-deformation compensatory secondary spinning process, and precisely corrects the mandrel profile based on the actual geometric data after stress release. This step is specifically designed to correct microscopic surface deformation caused by residual stress elimination. This step solves the problem of geometric accuracy loss of the sealing surface caused by stress release in traditional processes, achieving precise restoration of the final geometric accuracy and flatness of the flared surface, while ensuring a low-stress stable state of the sealing surface.

[0042] S4. Inspection: The sealing performance and geometric accuracy of the conduit after step S3 are inspected to ensure that the conduit has a measurable surface roughness (less than 0.8 μm) and meets the airtightness requirements of the standard.

[0043] Furthermore, step S4 includes: Geometric accuracy and surface quality inspection: The final geometric accuracy of the flared section is inspected using precision measuring equipment, including but not limited to taper angle, roundness, and wall thickness uniformity. Surface roughness must meet the requirements of aviation standards (e.g., not greater than 0.8 μm); all indicators must comply with the regulations of aviation standards such as HB4-52-2002 and HB4-1-2002.

[0044] Residual stress and shape parameter detection: Residual stress: The residual stress level of the finished flared section was re-examined using X-ray diffraction to confirm the effect of harmful stress reduction; Arc height: Measure the arc height of the finished flared surface to assess changes in the shape of the sealing surface; Sealing performance test: The test conditions include applying dynamic loads that simulate operational vibrations, followed by pressure holding and leak detection tests (such as those performed according to aviation piping sealing standards) and fatigue cycle tests to ensure that the finished product meets the stringent standards of aviation piping systems.

[0045] Specifically, step S4, by implementing a dynamic sealing test that includes a simulated vibration spectrum and combining it with rigorous quantitative testing of the changes in residual stress level and arc height, forms a final closed loop for testing the sealing reliability of the product during long-term service. This solves the risk of leakage during service caused by uncontrolled residual stress and geometric deformation of the sealing surface in traditional processes, ensuring that the finished product meets the sealing and structural stability requirements under harsh operating conditions before delivery.

[0046] The aerospace flared conduit manufactured using this process is designed to control the residual stress fluctuation rate within a preset range, significantly reducing the risk of sealing leakage and greatly decreasing the scrap rate compared to the traditional single-spinning process.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A novel forming process for an aviation flared duct, characterized in that, Includes the following steps: S1. Initial flaring preforming: The end of the catheter is spun to form a preliminary flared conical surface; S2, Residual stress aging treatment: The flared section of the catheter after step S1 is treated to release residual stress. S3, Secondary flaring and precision forming: The flared section of the conduit after step S2 is subjected to secondary spinning and finishing to obtain the final geometric accuracy; S4. Inspection: The sealing performance and geometric accuracy of the conduit after step S3 are inspected.

2. The novel forming process of an aviation flared duct according to claim 1, characterized in that, In step S2, the residual stress aging treatment includes one or more of local heat treatment, vibration aging, and microparticle shot peening.

3. The novel forming process of an aviation flared duct according to claim 2, characterized in that, The local heat treatment is a controlled heating and cooling process performed on the flared section.

4. The novel forming process of an aviation flared duct according to claim 2, characterized in that, The vibration aging process includes subjecting the conduit to random vibration and alternating loads.

5. The novel forming process of an aviation flared duct according to claim 2, characterized in that, The microparticle shot peening is a shot peening treatment performed on the flared sealing cone surface using a small-diameter shot peening medium.

6. The novel forming process of an aviation flared duct according to claim 1, characterized in that, The process after step S1 further includes: detecting the residual stress distribution of the flared section.

7. The novel forming process of an aviation flared duct according to claim 1, characterized in that, The process after step S2 further includes: detecting changes in surface roughness and / or arc height of the flared surface to obtain detection results.

8. The novel forming process of an aviation flared duct according to claim 1, characterized in that, In step S3, the forming parameters used in the secondary flaring precision forming are adaptively adjusted based on the test results.

9. A novel forming process for an aviation flared duct according to claim 1, characterized in that, The inspection in step S4 includes: checking whether the geometric accuracy and surface quality of the conduit meet aviation standards, and checking the residual stress level and shape parameters of the flared section.

Images