A training mold and design method for 4D printing shape memory alloy wings

Abstract

The application provides a training mold and a design method for 4D printing of a shape memory alloy wing, and belongs to the technical field of aerospace vehicles. The purpose is to solve the problems of insufficient deformation precision, easy damage to the structure caused by stress concentration, long design trial and error period, high cost, and poor consistency of the training effect of components in the prior art. A driving mechanism and an upper mold are installed on a lower mold; the upper mold is provided with a first assigned camber line and a slider track at the top; a driving sleeve is installed in the upper part of a driving rod, and the bottom of the driving sleeve is provided with a slider; a placing platform is arranged on the lower mold, a supporting protrusion is arranged in the middle, a lower base platform is arranged between the placing platform and the supporting protrusion, and the supporting protrusion is provided with a second assigned camber line; and a curved wing is arranged on the base platform. The application solves the problems of insufficient deformation precision, easy damage to the structure caused by stress concentration, long design trial and error period, high cost, and poor consistency of the training effect of components in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of aerospace vehicle technology, and in particular relates to a training mold and design method for 4D printing shape memory alloy wings. Background Technology

[0002] The trailing edge of a variable-camber wing is one of the core aerodynamic components of a morphing aircraft. It can optimize lift-to-drag ratio and control efficiency by changing its camber at different flight stages (such as low-speed takeoff, transonic cruise, and hypersonic flight).

[0003] For passive variable camber wings that use shape memory materials (such as shape memory alloys and shape memory polymers), the standard workflow is as follows: In the ground phase, the originally straight trailing edge structure of the wing is forcibly bent to the target angle (such as 20°) using a special training mold, and the temporary shape is locked in a low-temperature environment; when the aircraft enters the high-speed flight phase, the ambient temperature rises (or is actively heated) to trigger the shape memory effect, and the structure autonomously returns to the initial straight state.

[0004] In existing technologies, training molds for such shape memory wings typically employ simple mechanical bending devices, with the surfaces in contact with the wing often being empirically designed fixed arcs or straight inclined planes. For example, a metal pressure block with a fixed radius of curvature is used to forcibly bend the wing's trailing edge to the target shape. The mold design relies heavily on engineering experience, adjusting the surface through repeated physical trial and error until the wing's deformation angle roughly meets the requirements.

[0005] Existing training mold design methods have the following technical shortcomings:

[0006] (1) The deformation accuracy is low, making it difficult to meet the strict bending index;

[0007] Using molds with empirically derived curved surfaces or simple geometric shapes cannot accurately match the actual deformation trajectory of the wing structure during bending. Because the trailing edge of the shape memory wing is a flexible structure with a certain thickness and stiffness, it exhibits complex nonlinear deformation modes under compression bending. Simple circular arcs or inclined pressure heads will cause a significant deviation between the actual bending angle of the structure and the preset target angle (e.g., ≥20°), and may even require excessive bending to barely reach the target value, affecting the accuracy of subsequent shape memory recovery.

[0008] (2) It is easy to cause local stress concentration, which reduces the structural life;

[0009] Existing experience-based molds often fail to achieve proper conformal contact with the wing surface, resulting in extremely uneven stress distribution during loading. Significant stress peaks appear in localized contact areas. Simulation results indicate that an improperly designed mold profile can cause stresses exceeding the material's yield strength in the wing skin or internal honeycomb structure. After repeated training, the structure is prone to fatigue damage, localized buckling, and even fracture, severely impacting the wing's service reliability and cycle life.

[0010] (3) Design iteration relies on physical trial and error, which has a long cycle and high cost;

[0011] Traditional mold design lacks scientific quantitative guidance. After the physical mold is manufactured, it is necessary to conduct load tests on actual wing prototypes to measure deformation angles and observe surface damage, and then modify the mold surface based on experience. Each design cycle requires repeated "machining-testing-mold modification-retesting", with development cycles lasting several months, high manufacturing costs, and the final mold solution is often not the optimal solution.

[0012] (4) It is difficult to guarantee the consistency and repeatability of training results;

[0013] Due to the lack of precise control over the mechanical relationship between the mold surface and structural deformation, the training effect of the same mold on different batches of wing samples varies, resulting in poor consistency of the wing bending angle after training, which makes it difficult to meet the strict requirements for component consistency in mass production of aircraft.

[0014] In summary, there is an urgent need to design a training mold and design method for 4D printing shape memory alloy wings, in order to solve the problems of existing technologies that rely on experience to design the surface, resulting in insufficient deformation accuracy, easy stress concentration damage to the structure, long design trial and error cycle and high cost, and poor consistency of component training effect. Summary of the Invention

[0015] A brief overview of the invention is given below to provide a basic understanding of certain aspects of it. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0016] In view of this, in order to solve the problems of insufficient deformation accuracy, easy stress concentration damage to the structure, long design trial and error cycle and high cost, and poor consistency of component training effect in the existing technology of designing the surface based on experience, the present invention provides a training mold and design method for 4D printing shape memory alloy wings.

[0017] Option 1: A training mold for 4D printing shape memory alloy wings, including a drive mechanism, an upper mold, a bending wing, and a lower mold;

[0018] Both the drive mechanism and the upper mold are mounted on the lower mold.

[0019] The upper mold body is provided with a first shaping arc, a first pin is provided at the bottom, and slider tracks are provided on both sides of the top.

[0020] The driving mechanism includes a driving sleeve, a slider, and a driving rod. The driving sleeve is installed in the upper part of the driving rod. The bottom of the driving sleeve is provided with a slider that cooperates with the slider track. The top of the driving rod is provided with a thread, and the bottom is provided with a second pin.

[0021] The lower mold is provided with a placement platform, with a first pin hole and a second pin hole on the left and right sides respectively, and a support protrusion in the middle. The first pin hole is hinged to the first pin of the upper mold. The upper mold body is placed on the placement platform. The second pin hole is hinged to the second pin of the drive rod. A recessed base platform is provided between the placement platform and the support protrusion. The support protrusion is provided with a second shaping arc.

[0022] The curved wing is mounted on the base platform.

[0023] Furthermore, the top of the drive rod is fitted with a threaded adjusting nut.

[0024] Furthermore, an angle sensor mounting rod is also installed on one side of the first pin hole of the lower mold. The top of the angle sensor mounting rod is connected to the upper mold, and the bottom is fitted onto the first pin. The angle sensor is installed on the angle sensor mounting rod.

[0025] Furthermore, the lower mold is an integrated structure.

[0026] Option 2: A design method for a training mold for 4D printing shape memory alloy wings, specifically including the following steps:

[0027] S1. Establish the initial geometric model:

[0028] Based on the aerodynamic shape of the trailing edge of the target aircraft wing and the preset target bending angle, an initial three-dimensional geometric model of the bending wing structure and training mold is established, and the initial surfaces of the upper and lower molds are set as simple circular arcs or straight lines.

[0029] S2. Establish the finite element simulation model:

[0030] On the Abaqus finite element platform, a high-fidelity assembly model including the upper mold, lower mold and curved wing structure was constructed.

[0031] S3. Perform iterative optimization of the surface profiles of the upper and lower molds:

[0032] The first shaping arc on the lower surface of the mold is taken as the optimization object, and the optimization objectives are to minimize the deformation uniformity and stress distribution. Multiple rounds of finite element simulation iterations are carried out.

[0033] Extract the stress and strain contour maps of the bent wing structure at the maximum bending angle in each round of simulation;

[0034] Analyze the stress concentration area. If there is a significant local stress peak, adjust the curvature of the mold surface in that area to make it smoother, so as to guide the structure to deform in a coordinated manner.

[0035] Iterative optimization is performed until all final first-shaped arc designs satisfy the following conditions are obtained:

[0036] a. The actual bending angle of the bent wing reaches or exceeds the preset target;

[0037] b. The maximum stress value is significantly lower than the tensile strength of the material;

[0038] c. The contact stress is uniformly distributed along the first shaped arc surface, without any non-physical stress peaks;

[0039] The same steps are used to optimize the second shaping arc on the upper surface of the lower mold;

[0040] S4. Verify the optimization results:

[0041] The final optimized schemes for the first and second shaped arcs were simulated and verified to check whether the contact pressure distribution between the first and second shaped arcs and the surface of the curved wing was uniform during the loading process, and whether the displacement or rotation response curves of the curved wing were continuous and smooth.

[0042] After verifying that the shape is uniform and smooth, the final geometric parameters of the first and second shaping arcs are output for the physical processing and manufacturing of the upper and lower molds.

[0043] Furthermore, the material properties of the finite element simulation model described in S2 are defined as follows: the curved wing structure is defined as a soft material with shape memory properties; the upper mold and the lower mold are defined as rigid bodies.

[0044] Furthermore, the contact and boundary settings of the finite element simulation model described in S2 are as follows: the surface-to-surface contact between the upper mold and the curved wing structure is defined, and the friction formula is set to frictionless; a fully fixed constraint is applied to the root of the curved wing structure; an angular displacement load of the first pin is applied to the upper mold to simulate the bending process, and geometric nonlinearity is enabled to accurately simulate large deformation.

[0045] The present invention has the following advantages over the prior art:

[0046] 1. This invention replaces traditional experience or simple geometric surfaces with a shaped arc surface optimized by simulation, ensuring that the trailing edge of the wing can accurately and stably reach the preset bending angle, and the simulation value is highly consistent with the target value;

[0047] 2. The stress distribution of the present invention is uniform, and the optimized mold surface effectively guides the deformation path of the wing structure, avoids stress concentration, and significantly improves the fatigue life and reliability of the structure during repeated training and service.

[0048] 3. The mold drive mechanism of this invention works in conjunction with the optimized surface, so that the displacement and rotation response of the wing trailing edge exhibit ideal linear or smooth characteristics throughout the bending process, without abrupt changes or jamming;

[0049] 4. Based on scientific simulation methods, this invention ensures that wings trained from different batches and molds have highly consistent deformation performance, providing a guarantee of quality consistency for engineering applications;

[0050] 5. This invention significantly reduces the number of physical trial and error attempts through digital simulation iteration, shortens the mold development cycle, and lowers development costs. Attached Figure Description

[0051] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0052] Figure 1 This is a schematic diagram of the structure of a training mold for 4D printing shape memory alloy wings;

[0053] Figure 2 This is a schematic diagram of the upper mold structure;

[0054] Figure 3 This is a schematic diagram of the lower mold structure;

[0055] Figure 4 A diagram showing the positional relationship between the drive sleeve, drive rod, slider, and pin.

[0056] Figure 5 The diagram shows the curvature curve of the mold surface obtained based on finite element simulation optimization (the horizontal axis represents the wing spanwise position, and the vertical axis represents the curvature height).

[0057] Figure 6 A schematic diagram of the working state (bending process) after the training mold and the curved wing structure are assembled.

[0058] Figure 7 This is a schematic diagram to verify the working state of the curve.

[0059] In the diagram: 1-Drive sleeve, 2-Upper mold, 3-Bending wing, 4-Angle sensor mounting rod, 5-Lower mold, 6-Slider track, 7-First shaping arc, 8-First pin, 9-Placement platform, 10-Base platform, 11-First pin hole, 12-Supporting protrusion, 13-Second pin hole, 14-Slider, 15-Second pin, 16-Drive rod, 17-Adjusting nut, 18-Second shaping arc. Detailed Implementation

[0060] To make the technical solutions and advantages of the embodiments of the present invention clearer, the exemplary embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0061] Example 1, Reference Figure 1 This embodiment describes a training mold for 4D printing shape memory alloy wings, comprising a drive mechanism, an upper mold 2, a bending wing 3, and a lower mold 5.

[0062] The drive mechanism and the upper mold 2 are both mounted on the lower mold 5;

[0063] The upper mold 2 has a first shaping arc 7 on its main body, a first pin 8 at the bottom, and slider tracks 6 on both sides of the top.

[0064] The driving mechanism includes a driving sleeve 1, a slider 14 and a driving rod 16. The driving sleeve 1 is installed in the upper part of the driving rod 16. The bottom of the driving sleeve 1 is provided with a slider 14 that cooperates with the slider track 6. The top of the driving rod 16 is provided with a thread and the bottom is provided with a second pin 15.

[0065] The lower mold 5 is provided with a placement platform 9, and the left and right sides are respectively provided with a first pin hole 11 and a second pin hole 13. A support protrusion 12 is provided in the middle. The first pin hole 11 is hinged to the first pin 8 of the upper mold 2. The main body of the upper mold 2 is placed on the placement platform 9. The second pin hole 13 is hinged to the second pin 15 of the drive rod 16. A recessed base platform 10 is provided between the placement platform 9 and the support protrusion 12. A second shaping arc 18 is provided on the support protrusion 12.

[0066] The curved wing 3 is mounted on the base platform 10.

[0067] Furthermore, the top of the drive rod 16 is equipped with a threaded adjusting nut 17. Rotating the adjusting nut 17 can drive the slider 14 to move axially along the drive rod 16, thereby pushing the upper mold 2 to rotate around the first pin hole 11 and applying a controllable bending load to the bent wing 3.

[0068] Furthermore, an angle sensor mounting rod 4 is also installed on one side of the first pin hole 11 of the lower mold 5. The top of the angle sensor mounting rod 4 is connected to the upper mold 2, and the bottom is fitted on the first pin 8. The angle sensor is installed on the angle sensor mounting rod 4.

[0069] Furthermore, the lower mold 5 is an integrated structure.

[0070] Furthermore, the geometric parameters (such as radius of curvature, tangent angle, etc.) of the first shaping arc 7 and the second shaping arc 18 are determined through finite element iterative optimization. The first shaping arc 7 is used to achieve high-precision conformal contact with the upper surface of the curved wing 3 structure to ensure uniform distribution of contact stress during bending. The second shaping arc 18 is used to provide progressive mechanical support and shape guidance for the inner side of the curved wing 3 structure during bending deformation to prevent structural instability.

[0071] Example 2, Reference Figure 1 This embodiment describes a design method for a training mold used in 4D printing of shape memory alloy wings, specifically including the following steps:

[0072] S1. Establish the initial geometric model:

[0073] Based on the aerodynamic shape of the trailing edge of the target aircraft wing and the preset target bending angle (e.g., ≥20°), establish the initial three-dimensional geometric model of the bending wing 3 structure and the training mold, and set the initial surface of the upper mold 2 and the lower mold 5 as a simple circular arc or straight line transition.

[0074] S2. Establish the finite element simulation model:

[0075] On the Abaqus finite element platform, a high-fidelity assembly model was constructed, which includes the upper mold 2, the lower mold 5, and the curved wing 3.

[0076] S3. Perform iterative optimization of the surface profiles of the upper mold 2 and the lower mold 5:

[0077] The first shaping arc 7 on the lower surface of the mold 2 is the optimization object. With the optimization objectives of minimizing deformation uniformity and stress distribution, multiple rounds of finite element simulation iterations are carried out.

[0078] Extract the stress and strain cloud maps of the bent wing 3 structure at the maximum bending angle in each round of simulation;

[0079] Analyze the stress concentration areas. If obvious local stress peaks appear (such as stress singularities that may occur in the initial scheme), adjust the curvature of the mold surface in that area to make it smoother, so as to guide the structure to deform in a coordinated manner.

[0080] Iterative optimization was performed until all designs of the final first shaping arc 7 that satisfy the following conditions were obtained:

[0081] a. The actual bending angle of the bent wing 3 reaches or exceeds the preset target (≥20°);

[0082] b. The maximum stress value is significantly lower than the tensile strength of the material (e.g., the simulation results show a maximum stress of 54.56 MPa << 685 MPa).

[0083] c. The contact stress is uniformly distributed along the first shaping arc 7, without any non-physical stress peaks;

[0084] The same steps are used to optimize the second shaping arc 18 on the upper surface of the lower mold 5;

[0085] S4. Verify the optimization results:

[0086] The final optimized scheme of the first shaping arc 7 and the second shaping arc 18 was simulated and verified to check whether the contact pressure distribution between the first shaping arc 7 and the second shaping arc 18 and the surface of the curved wing 3 was uniform during the loading process, and whether the displacement or rotation response curve of the curved wing 3 was continuous and smooth.

[0087] After verifying that the shape is uniform and smooth, the final geometric parameters of the first shaping arc 7 and the second shaping arc 18 are output for the physical processing and manufacturing of the upper mold 2 and the lower mold 5.

[0088] Furthermore, the material properties of the finite element simulation model described in S2 are defined as follows: the curved wing 3 structure is defined as a soft material with shape memory properties (Young's modulus E = 61.7 GPa, Poisson's ratio ν = 0.3); the upper mold 2 and the lower mold 5 are defined as rigid bodies (Young's modulus E = 1E30 Pa).

[0089] Furthermore, the contact and boundary settings of the finite element simulation model described in S2 are as follows: the surface-to-surface contact between the upper mold 2 and the curved wing 3 structure is defined, and the friction formula is set to frictionless; a fully fixed constraint is applied to the root of the curved wing 3 structure; an angular displacement load (such as UR1=2 radians) of the first pin 8 is applied to the upper mold 2 to simulate the bending process, and geometric nonlinearity is enabled to accurately simulate large deformation.

[0090] This invention replaces traditional experience or simple geometric surfaces with a simulation-optimized shaped arc surface, ensuring that the trailing edge of the wing can accurately and stably reach the preset bending angle, and the simulation value is highly consistent with the target value. At the same time, the stress distribution of this invention is uniform, and the optimized mold surface effectively guides the deformation path of the wing structure, avoids stress concentration, and significantly improves the fatigue life and reliability of the structure during repeated training and service.

[0091] The mold drive mechanism of this invention works in conjunction with the optimized surface to ensure that the displacement and rotation response of the wing trailing edge exhibits ideal linear or smooth characteristics throughout the bending process, without abrupt changes or jamming. At the same time, based on scientific simulation methods, it ensures that wings trained by different batches and different molds have highly consistent deformation performance, providing quality consistency assurance for engineering applications. Through digital simulation iteration, the number of physical trial and error attempts is significantly reduced, the mold development cycle is shortened, and development costs are lowered.

[0092] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

Claims

1. A training mold for 4D printing shape memory alloy wings, characterized in that, Includes a drive mechanism, an upper mold (2), a curved wing (3), and a lower mold (5); The drive mechanism and the upper mold (2) are both mounted on the lower mold (5); The upper mold (2) has a first shaping arc (7) on its main body, a first pin (8) at the bottom, and slider tracks (6) on both sides of the top. The driving mechanism includes a driving sleeve (1), a slider (14) and a driving rod (16). The driving sleeve (1) is installed in the upper part of the driving rod (16). The bottom of the driving sleeve (1) is provided with a slider (14) that cooperates with the slider track (6). The top of the driving rod (16) is provided with a thread and the bottom is provided with a second pin (15). The lower mold (5) is provided with a placement platform (9), and the left and right sides are respectively provided with a first pin hole (11) and a second pin hole (13). A support protrusion (12) is provided in the middle. The first pin hole (11) is hinged to the first pin (8) of the upper mold (2). The main body of the upper mold (2) is placed on the placement platform (9). The second pin hole (13) is hinged to the second pin (15) of the drive rod (16). A recessed base platform (10) is provided between the placement platform (9) and the support protrusion (12). A second shaping arc (18) is provided on the support protrusion (12). The curved wing (3) is mounted on the base platform (10).

2. The training mold for 4D printing shape memory alloy wings according to claim 1, characterized in that, The top of the drive rod (16) is fitted with a threaded adjusting nut (17).

3. A training mold for 4D printing shape memory alloy wings according to claim 1, characterized in that, An angle sensor mounting rod (4) is also installed on one side of the first pin hole (11) of the lower mold (5). The top of the angle sensor mounting rod (4) is connected to the upper mold (2), and the bottom is fitted on the first pin (8). The angle sensor is installed on the angle sensor mounting rod (4).

4. A training mold for 4D printing shape memory alloy wings according to claim 1, characterized in that, The lower mold (5) is an integrated structure.

5. The design method for a training mold for 4D printing shape memory alloy wings as described in claim 1, characterized in that, Specifically, the following steps are included: S1. Establish the initial geometric model: Based on the aerodynamic shape of the trailing edge of the target aircraft wing and the preset target bending angle, establish the initial three-dimensional geometric model of the bending wing (3) structure and the training mold, and set the initial surface of the upper mold (2) and the lower mold (5) as a simple circular arc or straight line transition. S2. Establish the finite element simulation model: On the Abaqus finite element platform, a high-fidelity assembly model was constructed, which included the upper mold (2), the lower mold (5) and the curved wing (3) structure. S3. Perform iterative optimization of the surface of the upper mold (2) and the lower mold (5): The first shaping arc (7) on the lower surface of the mold (2) above is the optimization object. The optimization objectives are to minimize the deformation uniformity and stress distribution. Multiple rounds of finite element simulation iterations are carried out. Extract the stress cloud map and strain cloud map of the bent wing (3) structure at the maximum bending angle in each round of simulation; Analyze the stress concentration area. If there is a significant local stress peak, adjust the curvature of the mold surface in that area to make it smoother, so as to guide the structure to deform in a coordinated manner. Iterative optimization is performed until all final first-shaped arc (7) designs that satisfy the following conditions are obtained: a. Bending the wing (3) The actual bending angle reaches or exceeds the preset target; b. The maximum stress value is significantly lower than the tensile strength of the material; c. The contact stress is uniformly distributed along the first shaped arc (7) arc surface, without any non-physical stress peaks; The same steps are used to optimize the second shaping arc (18) on the upper surface of the lower mold (5); S4. Verify the optimization results: The schemes of the first shaped arc (7) and the second shaped arc (18) obtained by the final optimization were simulated and verified to check whether the contact pressure distribution between the first shaped arc (7) and the second shaped arc (18) and the surface of the curved wing (3) was uniform during the loading process, and whether the displacement or rotation response curve of the curved wing (3) was continuous and smooth. After verifying that the shape is uniform and smooth, the final geometric parameters of the first shaping arc (7) and the second shaping arc (18) are output for the physical processing and manufacturing of the upper mold (2) and the lower mold (5).

6. The design method for a training mold for 4D printing shape memory alloy wings according to claim 5, characterized in that, Material property definitions for the finite element simulation model described in S2: The curved wing (3) structure is defined as a soft material with shape memory properties; the upper mold (2) and the lower mold (5) are defined as rigid bodies.

7. The design method for a training mold for 4D printing shape memory alloy wings according to claim 6, characterized in that, Contact and boundary settings of the finite element simulation model described in S2: Define the surface-to-surface contact between the upper mold (2) and the curved wing (3) structure, and set the friction formula to be frictionless; apply a fully fixed constraint to the root of the curved wing (3) structure; apply the angular displacement load of the first pin (8) to the upper mold (2) to simulate the bending process, and enable geometric nonlinearity to accurately simulate large deformation.

Images