Manufacturing method for blade tip and trailing edge reinforcement of aircraft engine fan blade

Abstract

The present invention relates to a manufacturing method for the tip and trailing edge reinforcement of an aircraft engine fan blade, comprising: obtaining the plane contour of a blank of a three-dimensional digital model of the tip and trailing edge reinforcement by using a finite element inverse algorithm based on an arc length method, and correcting the plane contour of the blank by simulating the result of pressing and loading by an elastic-plastic finite element method; cutting a metal plate of a required thickness according to the plane contour of the blank to obtain a flat blank; loading the flat blank into a mold cavity; the upper die core and the lower die core of the mold cavity are used to control the shape of the upper and lower surfaces of the blank after deformation, and the mold frame is used to limit the boundary position of the blank; the upper die core moves downward until it is completely pressed with the lower die core, and the blank is subjected to high-temperature creep forming to obtain the tip and trailing edge reinforcement. Compared with the prior art, the present invention adopts two processes of precise cutting and high-temperature creep forming to manufacture the tip and trailing edge reinforcement of a composite blade, which can reduce tooling investment, basically eliminate residual stress and springback, and improve forming accuracy.

Description

Technical Field

[0001] The invention relates to the field of processing thin-walled free-form surface metal reinforcement edges, and in particular to a method for manufacturing the tip and trailing edge reinforcement edges of an aircraft engine fan blade. Background Art

[0002] Carbon fiber composite fan blades have become the mainstream choice for commercial aircraft engines due to their advantages of light weight, low noise, and strong anti-flutter performance. However, the impact resistance, pressure resistance, and lightning resistance of the blade tip and trailing edge of composite fan blades are still insufficient compared to those of integral metal blades. By adding titanium alloy edging to the blade tip and trailing edge of composite fan blades, usually using lightweight and high-strength titanium alloy materials, the overall performance of composite blades can be significantly improved.

[0003] In order to adapt to the shape of the blade tip and trailing edge of the composite fan blade, the titanium alloy blade tip and trailing edge reinforcement edge often have the characteristics of a spatial thin-walled free-form surface. If the cold stamping forming process is used, due to the high strength and poor plasticity of titanium alloy, the required cold forming load is large, it is easy to crack, and the springback is serious, which makes it difficult to meet the technical size and shape requirements of the blade tip and trailing edge reinforcement edge. Although the superplastic forming process can greatly reduce the load and avoid springback, the forming mode is bulging, which causes the titanium alloy formed part to be severely thinned locally or even cracked; and after forming, trimming is required, which not only requires a set of tooling, but also may cause trimming springback, thus affecting its geometric accuracy. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems existing in the current processing and manufacturing process of the tip and trailing edge reinforcement of aircraft engine composite blades, and to provide a method for manufacturing the tip and trailing edge reinforcement of aircraft engine fan blades.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A method for manufacturing a blade tip and a trailing edge reinforcement edge of an aircraft engine fan blade, wherein the blade tip and the trailing edge reinforcement edge are metal thin-wall structures with a spatial free-form surface shape, and the manufacturing method comprises the following steps:

[0007] S1. Flatten the three-dimensional digital model of the blade tip and the trailing edge reinforcement edge to obtain the blank plane contour;

[0008] S2, cutting the metal plate of required thickness according to the plane contour of the blank to obtain a flat blank;

[0009] S3, loading the blank into a mold cavity formed by a lower mold core, a mold frame and an upper mold core, wherein the upper mold core and the lower mold core are used to control the shapes of the upper and lower surfaces of the blank, and the mold frame is used to limit the boundary position of the blank;

[0010] S4. Move the upper die core downward until it is completely engaged with the lower die core, and perform high-temperature creep forming on the blank to obtain the blade tip and trailing edge reinforcement edges.

[0011] Furthermore, the step S1 specifically includes:

[0012] S11, taking the mid-plane of the three-dimensional geometric model of the blade tip and the trailing edge reinforcement edge as the flattening input condition, and using the finite element inverse algorithm based on the arc length method to unfold and obtain the initial unfolded plane contour;

[0013] S12, based on the initial unfolded plane contour, the elastic-plastic finite element method is used to simulate the pressing loading process to obtain the three-dimensional geometric contour of the formed part;

[0014] S13. Calculate the error between the three-dimensional geometric contour obtained by simulation and the design model. If the error meets the requirements, the initial unfolded contour is the plane contour of the blank that meets the forming accuracy requirements. If the error does not meet the requirements, the contour line of the plane blank is corrected with an error value equal to the error but in the opposite direction, and the forming simulation is performed again until the error requirements are met.

[0015] Furthermore, the blank is made of titanium alloy.

[0016] Furthermore, in step S4, the high temperature creep forming temperature ranges from 300 to 1000°C.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention adopts two processes of precise cutting and high temperature creep forming to manufacture the blade tip and trailing edge reinforcement of the composite blade, which can reduce tooling investment, basically eliminate residual stress and springback, and improve forming accuracy.

[0019] 2. The present invention takes the mid-plane as the input condition based on the three-dimensional shape of the blade tip and the trailing edge reinforcement edge, obtains the flattened blank contour using the finite element inverse algorithm based on the arc length method, and uses the elastic-plastic finite element method to simulate the result of the press-fit loading to correct the contour of the plane blank, comprehensively considering factors such as part shape and size, forming process and boundary conditions, and obtains the blank plane contour that meets the forming accuracy requirements. As a result, it is simple and easy to obtain accurate blank parts, while saving trimming molds, greatly reducing tooling investment, and further reducing manufacturing costs.

[0020] 3. The present invention adopts high temperature creep forming for processing. The mold frame controls the position of the formed part in the mold, so that the contour accuracy of the formed part is guaranteed. The lower mold core and the lower mold core ensure the forming accuracy of the upper and lower surfaces of the blade tip and the trailing edge reinforcement edge, thereby ensuring that the parts with precise dimensions are obtained after forming. The formed parts only need to undergo necessary surface cleaning without subsequent processing, and the process is simple and efficient. At the same time, the parts obtained after high temperature creep forming are of precise dimensions, without the need for subsequent trimming or cutting processing, and residual stress and springback are basically eliminated, avoiding hidden dangers in subsequent use. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the three-dimensional shape of the blade tip and trailing edge reinforcement in this example.

[0022] Figure 2 This is a schematic diagram of the contour shape of the blade tip and trailing edge reinforcement edges after flattening.

[0023] Figure 3 Schematic diagram of the calculation process of unfolding contour.

[0024] Figure 4 This is a schematic diagram of the shape of the blank in this example.

[0025] Figure 5 This is a schematic diagram of the high temperature creep forming mold and mold closing process of this example.

[0026] Figure 6 This is a schematic diagram of the creep forming process of the part in this example.

[0027] Figure numerals: 1. blade tip and trailing edge reinforcement, 2. plane contour shape, 3. blank, 4. lower die core, 5. die frame, 6. upper die core. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0029] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0030] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] like Figure 1 to Figure 6 As shown, in order to ensure aerodynamic performance, the composite fan blades of aircraft engines generally have complex streamline shapes, so their blade tips and trailing edge reinforcement edges 1 also need to have complex spatial geometric shapes, and are generally thin plate structures of equal wall thickness with spatial free-form surface shapes. The composite blades are tightly connected to the inner walls of the blade tips and trailing edge reinforcement edges 1 by gluing.

[0032] The present embodiment provides a method for manufacturing a blade tip and trailing edge reinforcement 1 of an aircraft engine fan blade. In the present embodiment, the blade tip and trailing edge reinforcement 1 are processed by flattening, cutting and high temperature creep forming processes: first, the plane contour shape 2 of the blank 3 is obtained by flattening calculation, and then the flat blank 3 is obtained by cutting; the blank 3 is loaded into a cavity formed by a lower die core 4, a mold frame 5, and an upper die core 6, and the shapes of the upper and lower surfaces of the blank 3 after forming are controlled by the upper die core 6 and the lower die core 4, and the boundary position of the blank 3 is limited by the mold frame 5; the upper die core 6 moves downward until it is completely molded with the lower die core 4; after the mold is completely molded, the blank 3 is creep formed to finally obtain the blade tip and trailing edge reinforcement 1. The manufacturing process of the blade tip and trailing edge reinforcement 1 is described in detail below.

[0033] The first step is to determine the geometric shape of the blade tip and trailing edge reinforcement edge 1. The blade tip and trailing edge reinforcement edge 1 can be obtained according to the surface profile design model of the composite blade, such as Figure 1 As shown. A CAD model of computer-aided design may be used but is not limited to it.

[0034] In the second step, the flattened two-dimensional contour shape of the neutral surface of the blade tip and the trailing edge reinforcement edge is obtained by flattening calculation. The two-dimensional plane contour shape 2 is as follows Figure 2 As shown. Figure 3 As shown, the detailed steps of plane contour shape 2 are:

[0035] Step 1: Take the mid-plane of the three-dimensional geometric model of the blade tip and trailing edge reinforcement edge 1 as the input condition for flattening, and use the finite element inverse algorithm based on the arc length method (such as CAE commercial software Dynaform, but not limited to this software) to unfold and obtain the initial unfolded plane contour. The specific method is as follows: extract the neutral surface of the blade tip and trailing edge reinforcement edge 1 from the CAD software, export the neutral surface, and name it P.iges; import P.iges in the Dynaform software, and mesh the neutral surface; set material parameters; input the sheet thickness; use Dynaform's one-step-solver solver for inverse calculation to obtain the flat part after the blade tip and trailing edge reinforcement edge 1 is unfolded, and name it B.iges.

[0036] Step 2: Based on the sheet metal blank determined by the initial unfolded plane contour, the elastic-plastic finite element method (such as CAE commercial software LS-Dyna, but not limited to this software) is used to perform numerical simulation of the pressing and loading process at room temperature to obtain the contour of the formed part. The specific method is as follows: in the CAD software, extract the upper surface of the three-dimensional model of the blade tip and the trailing edge reinforcement edge 1 as the punch, named U.iges, extract the lower surface as the die, named D.iges, and extract the neutral surface as the target part, named P.iges; import U.iges, D.iges, Z.iges and B.iges in the LS-Dyna software in turn as the punch, die, part and sheet respectively; mesh the sheet B.iges, and you can choose shell unit or solid unit mesh; set the sheet as an elastic-plastic deformable body, select the appropriate yield criterion and hardening model, and assign material parameters; set the mold as a rigid body, and mesh the geometric surface of the mold according to the rigid body mode, and check the mesh quality to ensure that the normal of the mold mesh is consistent and points to the deformable body; set the mold movement mode according to the press type; set the friction boundary conditions; perform dynamic explicit solution to obtain the part contour after simulated forming, export it and name it F.iges.

[0037] Step 3: Calculate the error between the contour of the formed part obtained by simulation and the design contour of the blade tip and trailing edge reinforcement edge. If the error meets the requirements, the plane contour shape 2 is the plane contour of the blank that meets the forming accuracy requirements; if the error does not meet the requirements, reversely track the corresponding position of the flat blank, and according to the size of the error, reversely correct the contour line of the flat blank; and perform the forming simulation again until the error requirements are met. The specific method is: align the simulated part F with the target part P according to the reference, analyze the error, and correct the part F according to the error; reduce the contour of the positive out-of-tolerance part, and expand the contour of the negative out-of-tolerance part; repeat the above comparison and correction process until the error is within the set range.

[0038] The third step is to cut the titanium plate of the required thickness to obtain a blank 3, such as Figure 4 As shown. Cutting can be performed by, but is not limited to, wire cutting.

[0039] The fourth step is to load the blank 3 into the cavity formed by the lower die core 4, the mold frame 5, and the upper die core 6, as shown in FIG. Figure 5 The mold frame 5 limits the boundary position of the blank 3, and the upper mold core 6 moves downward until it is completely molded with the lower mold core 4, as shown. Figure 6 As shown. The mold can be closed by, but is not limited to, a hydraulic press.

[0040] Step 5: After the mold is closed, the blank 3 is subjected to high temperature creep forming to obtain the metal reinforcement edge of the blade tip. The creep forming can be performed in a vacuum environment, but is not limited to a vacuum environment. The forming temperature range is 300 to 1000°C.

[0041] In summary, this embodiment proposes a high-temperature creep stress relaxation forming process for titanium alloy thin plates, that is, under the condition of keeping the load unchanged, the material undergoes irreversible plastic deformation over time, and the stress during titanium alloy forming gradually decays over time. By adopting creep forming technology, by selecting a reasonable temperature and forming time, while ensuring the forming accuracy of the blade tip and trailing edge reinforcement edge, the residual stress of the blade tip and trailing edge reinforcement edge can be eliminated, and springback can be basically eliminated. Using this forming manufacturing method, the trimming mold can also be omitted, reducing the manufacturing cost.

[0042] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection determined by the claims.

Claims

1. A method for manufacturing a blade tip and a trailing edge reinforcement edge of an aircraft engine fan blade, wherein the blade tip and the trailing edge reinforcement edge are a metal thin-walled structure with a spatial free-form surface shape, characterized in that: The manufacturing method comprises the following steps: S1. Flatten the three-dimensional digital model of the blade tip and the trailing edge reinforcement edge to obtain the plane contour of the blank; S2, cutting the metal plate of required thickness according to the plane contour of the blank to obtain a flat blank; S3, loading the blank into a mold cavity formed by a lower mold core, a mold frame and an upper mold core, wherein the upper mold core and the lower mold core are used to control the shapes of the upper and lower surfaces of the blank, and the mold frame is used to limit the boundary position of the blank; S4, the upper die core is moved downward until it is completely engaged with the lower die core, and the blank is subjected to high temperature creep forming to obtain the blade tip and trailing edge reinforcement edges; The step S1 specifically includes: S11, taking the mid-plane of the three-dimensional geometric model of the blade tip and the trailing edge reinforcement as the input condition for flattening, and using the finite element inverse algorithm based on the arc length method to unfold and obtain the initial unfolded plane contour, specifically: extracting the neutral plane of the blade tip and the trailing edge reinforcement, deriving the neutral plane, meshing the neutral plane, setting material parameters and sheet thickness, using the solver to perform inverse calculation, and obtaining the flat part after the blade tip and the trailing edge reinforcement are unfolded as the initial unfolded plane contour; S12. Based on the initial unfolded plane contour, the elastic-plastic finite element method is used to simulate the pressing and loading process of the upper and lower mold cores to obtain the three-dimensional geometric contour of the formed part, specifically: extract the upper surface of the three-dimensional model of the blade tip and the trailing edge reinforcement edge as the punch, extract the lower surface as the die, extract the neutral surface as the target part, take the flat part after the blade tip and the trailing edge reinforcement edge are unfolded as the sheet material, select the shell unit or the solid unit grid to mesh the sheet material, set the sheet material as an elastic-plastic deformable body, select the appropriate yield criterion and hardening model, and assign the material parameters, set the mold as a rigid body, and mesh the geometric surface of the mold according to the rigid body mode, detect the mesh quality to ensure that the normal of the mold mesh is consistent and points to the deformable body, set the mold movement mode according to the press type, set the friction boundary conditions, perform dynamic explicit solution, and obtain the part contour after simulated forming as the three-dimensional geometric contour of the formed part; S13, calculating the error between the three-dimensional geometric contour obtained by simulation and the design model. If the error meets the requirements, the initial unfolded contour is the plane contour of the blank that meets the forming accuracy requirements; if the error does not meet the requirements, the plane contour line of the blank is corrected with an amount equal to the error but in the opposite direction, and the finite element simulation of the pressing process is performed again until the error requirements are met. The correction process is specifically as follows: aligning the simulated part with the target part according to the reference, analyzing the error, and correcting the part according to the error; reducing the contour of the positive out-of-tolerance part, and expanding the contour of the negative out-of-tolerance part; Obtain accurate blanks, save trimming dies, reduce tooling investment, and reduce manufacturing costs; The blank is made of titanium alloy; In step S4, the high temperature creep forming temperature ranges from 300 to 1000°C.

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