A method for manufacturing an integral heavy-load bearing structural tie rod based on bulk forming

Abstract

The present invention belongs to the technical field of manufacturing heavy-duty load-bearing structures in multiple fields such as aircraft, ships, and automobiles, and discloses a method for manufacturing an integral heavy-duty load-bearing structure tie rod based on volume forming. A thickened end is formed by thickening the model and lengthening it by radial forging; the model is shrunk, and the shrinking tool makes a feeding motion relative to the model. Through different shrinking temperatures, shrinking ratios, and shrinking speeds, the metal blank rotates with the model or the shrinking tool rotates around the blank and the model; the blank is compressed and continuously deformed locally to obtain a hollow rotating body part; local deformation-free annealing of the processed part is achieved, the coaxial concentricity is calibrated, and surface wrinkles are eliminated. The integral tie rod manufactured by the present invention has a unique structure, excellent performance, greatly improved product consistency, and a service life significantly longer than that of traditional split-type welded tie rods, providing a better solution to the problem of fatigue resistance and strengthening of tie rods.

Description

Technical Field

[0001] The invention belongs to the technical field of manufacturing heavy-load bearing structures of aircraft, and in particular relates to a method for manufacturing an integral heavy-load bearing structure tie rod based on bulk forming. Background Art

[0002] At present, the closest existing technology: In the aircraft structure, many external structural parts, such as engine nacelles, APU cabins, air conditioning cabins, landing gears, etc., are connected to the aircraft body through tension rods. These tie rods transfer the aerodynamic force, gravity and other loads on the external structural parts to the body. Tie rods become the key main force-bearing components. Due to the weight reduction requirements of aircraft design, these tie rods are usually designed to be hollow while meeting the strength requirements. The traditional manufacturing technology is to weld the connection joints at both ends of the steel pipe profile. However, due to the welding residual tensile stress at the welding point, coupled with the welding deformation of the welding joints and pipe fittings, the welding deformation can only be reduced by increasing the wall thickness, but it is not conducive to reducing weight. Although there is a calibration process later, the coaxial concentricity of the two cannot be guaranteed, and there is a certain additional bending stress when the tie rod is loaded. Therefore, the tie rod will be subjected to excessive cyclic tensile stress and cause fatigue damage. Its data shows that accidents that occur at the welding point account for 90% of the fatigue damage accidents of the entire tie rod, and the life reliability is greatly reduced. Tie rod fatigue failure has become one of the failure modes of aircraft structural parts and is also one of the parts that must be inspected during aircraft overhaul. In order to increase the life of the tie rod and reduce the inspection cycle, it is particularly important to develop a high-life, high-reliability aviation tie rod manufacturing technology.

[0003] The traditional manufacturing technology of tie rods is to weld the connecting joints at both ends of the steel (titanium alloy) pipe profile, which is referred to as split tie rods. However, the weight is relatively heavy, and due to the welding residual tensile stress at the welding point, coupled with the welding deformation of the welded joints and pipe fittings, although there is a calibration process, for long-sized tie rods (such as those with a length greater than 1m), the calibration process cannot effectively eliminate the welding deformation and the internal stress of the tie rod. Therefore, the coaxial concentricity of the two cannot be guaranteed, and there is a certain amount of additional bending stress when the tie rod is loaded. Therefore, under the double superposition of welding residual stress and accessory bending stress, the tie rod will be subjected to excessive cyclic tensile stress and cause fatigue damage. In addition, the extruded pipe of the welded tie rod has equal wall thickness, and the equal strength design method cannot be used to reduce weight.

[0004] In summary, the problems existing in the prior art are:

[0005] (1) The traditional split manufacturing technology cannot guarantee the coaxiality and concentricity of the welded joints and pipe fittings. When the tie rod is loaded, there is a certain amount of additional bending stress. The tie rod will be subjected to excessive cyclic tensile stress, resulting in fatigue damage.

[0006] (2) The extruded tubes of the welded tie rods using the traditional split manufacturing technology have constant wall thickness, and it is not possible to apply the equal strength design method to reduce weight.

[0007] Difficulty in solving the above technical problems: In order to solve the coaxial concentricity problem of traditional split-type welded tie rod welding joints and pipe fittings, it is necessary to process the corresponding tooling for calibration. In addition, a subsequent heat treatment process is required to eliminate the internal stress generated during the calibration process. However, the heat treatment process cannot completely and effectively eliminate the internal stress, so deformation induced by the release of internal stress will also occur, resulting in the inability to guarantee coaxial concentricity. Moreover, the dimensions of the tie rods in each part are different, and the calibration tooling needs to be customized, resulting in a significant increase in production costs and cycles. The extruded pipes of the traditional split-type manufacturing technology welding tie rods are of equal wall thickness, and it is impossible to use equal strength design methods to reduce weight. If the middle of the tie rod is to be changed to a variable wall thickness, a special extrusion model or a cutting method is required to achieve it, which increases the production cost and cycle. Secondly, due to the uneven thermal expansion and heat conduction of variable wall thickness pipe fittings and joints during welding, the welding deformation will also increase, further increasing the difficulty of coaxial concentricity calibration.

[0008] The significance of solving the above technical problems: If the above problems can be solved, first, the split structure can be upgraded to an integral structure, second, the life of the tie rod can be increased, third, the weight of the aircraft can be reduced, fourth, the production cost and cycle of the tie rod can be reduced, and fifth, the use and maintenance costs of the tie rod can be reduced. The tie rod structure is uniquely designed, which improves the technology of the heavy-load bearing structure tie rod of Chinese aircraft to be synchronized with that of European and American aircraft. Summary of the invention

[0009] In view of the problems existing in the prior art, the present invention provides a method for manufacturing an integral heavy-load bearing structure tie rod based on bulk forming.

[0010] The present invention is implemented as follows: a method for manufacturing an integral heavy-load bearing structure tie rod based on bulk forming, wherein the method for manufacturing an aviation structure tie rod based on bulk forming comprises the following steps:

[0011] The first step is to form a thickened end by model thickening and radial forging and drawing; according to the different sizes of the thickened end, the thickening speed is adjusted within the range of 100-1000 rpm, and according to the different materials of the pull rod, the thickening temperature is adjusted within the range of 500-1000 degrees to obtain a dumbbell tube blank with excellent structure.

[0012] The second step is to anneal the thickened end through the exclusive designed local annealing equipment to ensure that the hollow parts are not deformed; according to the different materials of the pull rod, the temperature is adjusted within 200-850 degrees, and according to the different sizes of the thickened end, the insulation time is adjusted within 0.5-3 hours to obtain good product structure.

[0013] The third step is to perform surface treatment on the surface and inner hole of the thickened end to eliminate surface wrinkles.

[0014] Step 4: Calibrate the coaxial concentricity, 0.08mm / 2 meters.

[0015] The fifth step is to use the model shrinking technology to rotate the metal blank with the model or the shrinking tool rotates around the blank and the model, so that the blank is compressed and produces continuous local deformation to obtain a hollow rotating body part; while maintaining the corresponding shrinking speed and shrinking temperature, different shrinking ratios are determined to vary within 0.1-0.5 according to different wall thicknesses.

[0016] The sixth step is to flatten the two ends through model forging to form a double-ear blank.

[0017] The seventh step is to anneal the double ears of the end through the exclusive designed local annealing equipment to ensure that the hollow parts are not deformed. The annealing equipment is the key equipment for the concentricity of the product, and a patent has been applied for this equipment separately.

[0018] The eighth step is to test the coaxial concentricity.

[0019] The ninth step is to machine the double-ear blank of the end cap to ensure the accuracy of the external dimensions.

[0020] The tenth step is to refine the overall surface.

[0021] Another object of the present invention is to provide an integral heavy-load bearing structure tie rod manufactured by the integral heavy-load bearing structure tie rod manufacturing method based on bulk forming, wherein the integral heavy-load bearing structure tie rod (attached Figure 5 ) includes: a first end, a second end, and a pull rod hollow rod body; one end of the end is connected to the external plug-in, and the other end is connected to the aircraft.

[0022] The two ends of the pull rod body are integrally manufactured with a first end head and a second end head.

[0023] Another object of the present invention is to provide an application of the integral heavy-load bearing structure tie rod in the connection between an aircraft external structure and a fuselage.

[0024] In summary, the advantages and positive effects of the present invention are as follows: the thickened end of the present invention is produced by the mold shrinking and diameter forging drawing method, and the connecting end has the load-bearing characteristics of forgings; the use of mold shrinking can form a residual pressure layer on the inner and outer surfaces of the pipe fitting, refine the grain structure in the strengthening layer, and improve the fatigue life of the pipe fitting. The test results conducted in a certain unit show that the life is increased by 2-3 times.

[0025] The present invention increases the coaxial concentricity inspection in the whole process, can adjust the process parameters at any time, ensure the coaxial concentricity, and eliminate the additional bending stress; thickening the two ends can achieve gradual wall thickness and form complex ear shape. By adjusting the shrinkage parameters, the hollow part in the middle of the tie rod can change the diameter and wall thickness. Compared with traditional extruded profile pipes, the equal strength design principle can be applied to further achieve the purpose of weight reduction. The longer the tie rod is, the more obvious the weight reduction effect is. 36 of the invented products were used in a certain part of an aircraft, and the weight was reduced by 70kg compared with the weight of previous products.

[0026] The present invention adopts an integral forming process based on volume forming. Compared with the split-type welded tie rod, it avoids the influence of the residual tensile stress caused by welding on the fatigue life of the tie rod; at the same time, the coaxial concentricity can be adjusted at any time during the manufacturing process to avoid the generation of additional bending stress. Therefore, the integral tie rod structure manufactured by the present invention is an exclusive domestic first, and its service life is greatly improved compared with the service life of the traditional split-type welded tie rod, providing a better solution to the problem of fatigue strengthening of the tie rod. And compared with traditional extruded profile pipes, the equal strength design principle can be applied, and the hollow part in the middle of the tie rod can be changed in diameter and wall thickness to further achieve the purpose of aircraft weight reduction. The present invention can be applied to the connection between the aircraft external structural parts and the fuselage, and is used to effectively improve the fatigue life of the structural connection tie rod.

[0027] The integral tie rod manufactured by the present invention has a unique structure, excellent performance, greatly improved product consistency, and a service life significantly longer than that of the traditional split-type welded tie rod, providing a better solution to the fatigue strengthening problem of the tie rod. In addition, compared with the traditional split-type welded pipe fittings, the equal strength design principle can be applied, and the hollow part in the middle of the tie rod can be changed in diameter and wall thickness to further achieve the purpose of reducing the weight of aircraft, ships, automobiles, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of a method for manufacturing an integral heavy-load bearing structure tie rod based on bulk forming provided in an embodiment of the present invention.

[0029] Figure 2 It is a schematic diagram of the thickening process provided by an embodiment of the present invention.

[0030] Figure 3 The embodiment of the present invention provides a schematic diagram of the shrinking process. Figure 1 ;

[0031] Figure 4 The embodiment of the present invention provides a schematic diagram of the shrinking process. Figure 2 .

[0032] Figure 5 is a schematic structural diagram of an aviation structure tie rod provided by an embodiment of the present invention;

[0033] In the figure: a is a closed-end pull rod; b is an expanded-end pull rod; c is an anatomical diagram of the closed part; d is an anatomical diagram of the expanded part.

[0034] Figure 6 is a schematic diagram of the nacelle structure provided by an embodiment of the present invention;

[0035] In the figure: 1. Nacelle front cover; 2. Nacelle front section; 3. Nacelle middle section; 4. Engine mount; 5. Nacelle rear section; 6. Main engine exhaust system components; 7. Nacelle lower hull; 8. Main engine air inlet.

[0036] Figure 7 It is a schematic diagram of an engine mount interface provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] In view of the problems existing in the prior art, the present invention provides a method for manufacturing an integral heavy-load bearing structure tie rod based on bulk forming. The present invention is described in detail below in conjunction with the accompanying drawings.

[0039] like Figure 1 As shown, the method for manufacturing an integral heavy-load bearing structure tie rod based on bulk forming provided by an embodiment of the present invention comprises the following steps:

[0040] S101, forming a thickened end by thickening the model and lengthening the diameter by forging;

[0041] S102, annealing the thickened end through a uniquely designed local annealing device to ensure that the hollow parts are free of deformation;

[0042] S103, performing surface treatment on the surface and inner hole of the thickened end to eliminate surface wrinkles;

[0043] S104, calibrate coaxial concentricity;

[0044] S105, through the model rotation shrinkage technology, the metal blank rotates with the model or the rotation shrinkage tool rotates around the blank and the model, so that the blank is compressed and produces continuous local deformation, and a hollow rotating body part is obtained;

[0045] S106, flattening the two ends through model forging to form a double-ear blank;

[0046] S107, annealing the double ears of the end through the uniquely designed local annealing equipment to ensure that the hollow parts are not deformed;

[0047] S108, testing the coaxial concentricity;

[0048] S109, machining the double-ear blank of the end to ensure the accuracy of the shape and size;

[0049] S110, performing fine processing on the entire surface.

[0050] In a preferred embodiment of the present invention, in step S101, thickening is mainly performed by model thickening and radial forging and drawing to form a thickened end. There is a deviation in the coaxial concentricity between the thickened end and the middle section, and there are wrinkles on the surface to varying degrees. Attention should be paid to calibrating the coaxial concentricity to eliminate surface wrinkles.

[0051] like Figure 5 As shown, the integral heavy-load bearing structure tie rod provided by the embodiment of the present invention comprises: a first end, a second end, and a hollow rod body of the tie rod.

[0052] The two ends of the pull rod body are integrally swaged to have a first end and a second end.

[0053] FS / EA85-002 tensile test

[0054] Test piece number Design load(N) Destruction load (N) Exceeding the design load percentage FS / EA85-002-20200A01 244872 262599 7.23 FS / EA85-002-20200A03 244872 293569 19.88 FS / EA85-002-20200A06 244872 312578 27.64

[0055] FS / EA85-002 Compression Test

[0056] Test piece number Design load(N) Destruction load (N) Exceeding the design load percentage FS / EA85-002-20200A02 250850.4 398207 58.74％ FS / EA85-002-20200A04 250850.4 417763 66.53％ FS / EA85-002-20200A05 250850.4 399799 59.37％

[0057] FS / EA85-002 fatigue test

[0058] Test piece number Tensile load (N) Compression load (N) Design life (times) Completion FS / EA85-002-20200A07 66605.2 68231.3 15000 Finish FS / EA85-002-20200A08 66605.2 68231.3 15000 Finish FS / EA85-002-20200A09 66605.2 68231.3 15000 Finish

[0059] FS / EA85-004 tensile test

[0060] Test piece number Design load(N) Destruction load (N) Exceeding the design load percentage FS / EA85-004-20200A06 480805.05 523010 8.77％ FS / EA85-004-20200A08 480805.05 525533 9.30％ FS / EA85-004-20200A09 480805.05 547144 13.79％

[0061] FS / EA85-004 Compression Test

[0062]

[0063]

[0064] FS / EA85-004 fatigue test

[0065] Test piece number Tensile load (N) Compression load (N) Design life (times) Completion FS / EA85-004-20200A03 130779 100120 15500 Finish FS / EA85-004-20200A04 130779 100120 15500 Finish FS / EA85-004-20200A07 130779 100120 15500 Finish

[0066] like Figure 6 and Figure 7As shown, the nacelle of the present invention is fixed to the outside of the engine frame 4, and is provided with a nacelle front cover 1, a nacelle front section 2 is welded to the rear of the nacelle front cover 1, a nacelle middle section 3 is welded to the nacelle front section 2, a nacelle lower hull 7 is welded to the lower parts of the nacelle front section 2 and the nacelle middle section 3, a main engine air inlet 8 is welded to the front part of the nacelle lower hull 7, a nacelle rear section 5 is provided to the rear of the nacelle middle section 3, and a main engine exhaust system assembly 6 is provided to the lower part of the nacelle rear section 5.

[0067] The nacelle structure of the present invention provides an interface and accommodation for the power unit and its accessories. Its main function is to support the engine, bear and transmit the tension and inertial load generated by the power unit, bear its own inertia and aerodynamic load, and provide rectification and protection for the power unit and its accessories. The integral titanium alloy tie rod is used in the engine nacelle structure and is an important load-bearing part connecting the engine nacelle and the wing.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for manufacturing an integral heavy-load bearing structural tie rod based on bulk forming, characterized in that: The method for manufacturing an integral heavy-load bearing structure tie rod based on bulk forming The following steps are involved: The first step is to form a thickened end by thickening the model and lengthening the diameter by forging; The second step is to anneal the thickened end through a local annealing device to ensure that the hollow part is not deformed; The third step is to perform surface treatment on the surface and inner hole of the thickened end to eliminate surface wrinkles; The fourth step is to calibrate the coaxial concentricity; The fifth step is to use the model rotation technology to rotate the metal blank with the model or the rotation tool rotates around the blank and the model, so that the blank is compressed and produces continuous local deformation to obtain a hollow rotating body part; The sixth step is to flatten the two ends through model forging to form a double-ear blank; Step 7: Use local annealing equipment to anneal the two ears of the end to ensure that the hollow parts are not deformed; Step 8: Check the coaxial concentricity; The ninth step is to machine the double-ear blank of the end to ensure the accuracy of the external dimensions; The tenth step is to refine the overall surface.

2. The method for manufacturing an integral heavy-load bearing structural tie rod based on bulk forming according to claim 1, characterized in that: The thickened end and the middle section in the first step are calibrated for coaxial concentricity.

3. The method for manufacturing an integral heavy-load bearing structural tie rod based on bulk forming according to claim 1, characterized in that: The shrinking tool in the fifth step performs feeding motion relative to the model through different shrinking temperatures, shrinking ratios and shrinking speeds.

Images