Negative Poisson's ratio honeycomb stiffened plate optimization design method based on additive manufacturing

Abstract

The invention discloses a negative Poisson's ratio honeycomb stiffened plate optimization design method based on additive manufacturing. The method comprises the steps that it is determined that damage of a structure after bending deformation mainly occurs at a middle bearing position; gradient distribution of porosity from high to low is formed by regulating and controlling geometric parameters of the concave cell elements, so that material distribution is accurately matched with stress requirements; aNSYS Workbench software is used for conducting quasi-static three-point bending test finite element simulation and binding force-displacement curve analysis on the four sets of different models, and an optimal gradient design scheme is selected; the ANSYS Workbench simulation is used for verifying whether the optimized structure meets the performance requirement or not; 3D printing is conducted on the model, and the mechanical property and design feasibility of the model are verified through experiments. Through combination of gradient design and topological optimization, 'on-demand distribution 'of materials in space is achieved, the specific stiffness and the bearing efficiency of the structure are remarkably improved, and the problems that a traditional homogeneous honeycomb structure is unreasonable in material distribution and low in bearing efficiency are solved.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing and lightweight structural design, and in particular to an optimization design method for negative Poisson's ratio honeycomb stiffened plates based on additive manufacturing. Background Technology

[0002] As the automotive industry shifts towards lightweighting, low energy consumption, and high safety, the demand for improved driving range and energy consumption control in new energy vehicles is becoming increasingly urgent, making lightweighting of the vehicle body and key components a core breakthrough. Honeycomb reinforced panels, with their excellent specific stiffness and specific strength, show broad application prospects in automotive interiors, chassis, and battery pack protection. However, traditional homogeneous honeycomb reinforced panels suffer from material redundancy in non-load-bearing areas and stress concentration due to right-angle transitions, limiting their lightweighting effectiveness. Furthermore, traditional subtractive manufacturing processes struggle to adapt to complex structures and cannot meet the rapidly evolving needs of the automotive industry.

[0003] Negative Poisson's ratio structures, as a type of tensile metamaterial, exhibit inward contraction deformation characteristics under load, demonstrating excellent energy absorption and impact resistance. Combining gradient design principles with negative Poisson's ratio structures, through a continuous gradient distribution of wall thickness and porosity, allows for "material allocation on demand": increasing wall thickness and decreasing porosity in load-concentrated areas to enhance impact resistance, while thinning wall thickness and increasing porosity in load-dispersed areas to achieve extreme weight reduction, perfectly aligning with the core requirements of "high-efficiency load-bearing and low-cost lightweight" in the automotive industry. Therefore, it is necessary to propose an additive manufacturing-based gradient negative Poisson's ratio honeycomb stiffened plate optimization design method to address the problems of unreasonable material distribution and low load-bearing efficiency in traditional homogeneous honeycomb structures. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide an optimized design method for negative Poisson's ratio honeycomb stiffened panels based on additive manufacturing.

[0005] Technical solution: The method for optimizing the design of negative Poisson's ratio honeycomb stiffened panels based on additive manufacturing described in this invention includes the following steps:

[0006] Step 1: By conducting a quasi-static three-point bending test, the failure mode of the honeycomb stiffened plate was studied to determine that the failure of the structure after bending deformation mainly occurs at the middle load-bearing position.

[0007] Step 2: Using "equal mass" as a constraint, a dual gradient design of wall thickness and porosity is carried out for the negative Poisson's ratio honeycomb stiffened plate: the wall thickness is gradually reduced from the load concentration area to the support area to achieve a balance between load-bearing capacity and lightweight; by adjusting the geometric parameters of the concave cell, a gradient distribution of porosity from high to low is formed so that the material distribution accurately matches the stress requirements.

[0008] Step 3: First, obtain the material parameters of PLA 3D printing consumable through uniaxial compression test. Then, use ANSYS Workbench software to perform quasi-static three-point bending test finite element simulation on four different models. Combined with force-displacement curve analysis, select the optimal gradient design scheme.

[0009] Step 4: Based on the gradient design results of Step 3, perform topology optimization and lightweight design on the structure, and use ANSYS Workbench simulation to verify whether the optimized structure meets the performance requirements.

[0010] Step 5: Based on the final design in Step 4, 3D print the model and verify its mechanical properties and design feasibility through experiments.

[0011] Furthermore, in step 2, the overall dimensions of the negative Poisson's ratio honeycomb reinforced plate are designed to be 120mm in length, 70mm in width, and 10mm in thickness, with the reinforcement layer having a thickness of 5mm.

[0012] Furthermore, in step 2, the wall thickness gradient change and porosity gradient change in the dual gradient design follow the principle of equal mass, and the sum of the wall areas of cells in different gradient regions is kept constant by controlling them.

[0013] Furthermore, in step 2, two gradient models for the wall thickness and porosity of the negative Poisson's ratio honeycomb reinforced plate are constructed, with the cell arrangement direction being 0° or 90°, i.e., horizontal or vertical arrangement. The four sets of models are then compared and analyzed.

[0014] Furthermore, in step 2, let the cell area be A, and the number of cells in the three regions be respectively... , , The control function for thick gradient design is shown in the following equation:

[0015]

[0016] In the porosity gradient design, let the cell areas under the three porosities be respectively , , The number of cells in the three regions are respectively , , The control function for porosity gradient design is shown in the following equation:

[0017]

[0018] Where A is the cell area. , , These represent the number of cells in the three regions; , , The cell areas are for the three porosities.

[0019] Further, step 3 includes:

[0020] Step 3.1: Save the 3D model created in SOLIDWORKS and import it into ANSYS Workbench. In the Engineering Data module, define a custom material named PLA. Define its material properties based on the measured data. Assign PLA material to the stiffened plate component and structural steel material to the pressure head and support component.

[0021] Step 3.2: In the Mesh module, mesh the pressure head and support components with tetrahedral meshes of 4mm element size; mesh the stiffening plate component with tetrahedral meshes of 1mm element size, completing the mesh generation of the finite element model. Set the contact between the pressure head, support components, and stiffening plate to frictional contact, with a friction coefficient of 0.2.

[0022] Step 3.3: Apply a fixed constraint to the bottom surface of the support component and apply a displacement load of 30mm in the Y direction to the top surface of the pressure head;

[0023] Step 3.4: Add deformation contour plot, stress contour plot and support reaction output items in the solver module. After completing all settings, perform the solver and view the analysis results after the solver is finished.

[0024] Furthermore, the topology optimization in step 4 aims to improve bending stiffness and reduce structural flexibility. It employs the variable density method for optimization calculation and considers the process constraints of additive manufacturing in the optimization process.

[0025] Furthermore, the lightweight design in step 4 is based on the stress distribution cloud map obtained from finite element analysis.

[0026] Furthermore, step 4 includes clarifying the load-bearing characteristics of each part through stress distribution cloud maps, and optimizing the structural quality by reducing materials or introducing microlattice structures and local hollowing methods in non-primary load-bearing areas.

[0027] Furthermore, the 3D printing process in step 5 is fused deposition modeling, and the material is polylactic acid.

[0028] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0029] (1) By combining gradient design and topology optimization, the material is “distributed on demand” in space, which significantly improves the specific stiffness and load-bearing efficiency of the structure and solves the problem of material redundancy in homogeneous structures;

[0030] (2) By utilizing the tensile expansion characteristics of negative Poisson's ratio structures, the energy absorption capacity and impact resistance of the structures can be effectively improved, and stress concentration can be avoided;

[0031] (3) The entire design process is closely integrated with the additive manufacturing process, which ensures the high-quality molding of complex gradient structures and greatly shortens the R&D and manufacturing cycle of high-performance lightweight components.

[0032] (4) This method is universal and can be customized according to different load conditions. It has broad application prospects in fields such as automobiles and aerospace where lightweight requirements are extremely high. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating the construction process of the present invention;

[0034] Figure 2 Schematic diagram of thickness gradient design (horizontal cell arrangement) for negative Poisson's ratio honeycomb stiffened plate;

[0035] Figure 3 A schematic diagram of thickness gradient design for negative Poisson's ratio honeycomb stiffened plate (vertical cell arrangement);

[0036] Figure 4 A schematic diagram of the porosity gradient design (horizontal cell arrangement) for a negative Poisson's ratio honeycomb stiffened plate;

[0037] Figure 5 A schematic diagram of the porosity gradient design (vertical cell arrangement) for a negative Poisson's ratio honeycomb stiffened plate;

[0038] Figure 6 A finite element simulation diagram of a quasi-static three-point bending test of a negative Poisson's ratio honeycomb stiffened plate.

[0039] Figure 7 These are the force-displacement curves of each specimen under gradient conditions.

[0040] Figure 8 This is a model diagram of the optimized negative Poisson's ratio honeycomb stiffened plate;

[0041] Figure 9 To optimize the force-displacement curves of the negative Poisson's ratio honeycomb stiffened plate before and after;

[0042] Figure 10 This is a schematic diagram of the size structure of a negative Poisson's ratio honeycomb cell. Detailed Implementation

[0043] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0044] like Figure 1 As shown, the gradient negative Poisson's ratio honeycomb stiffened plate optimization design method based on additive manufacturing of the present invention includes the following steps:

[0045] Step 1: Damage Mode Research

[0046] Standard specimens were prepared and quasi-static three-point bending tests were conducted on the optimized honeycomb stiffened panels. Experimental observation and data analysis revealed that structural failure after bending deformation occurred at the central load-bearing location. The failure mode was the fracture of the matrix fibers in the porous stiffened rib walls, extending from the nodes to the cell walls and further along the longitudinal rib walls. Additionally, micro-fractures were also observed in the longitudinal matrix fibers at the central location of the skin. These results provide crucial information for subsequent gradient reinforcement design.

[0047] Step 2: Gradient Design

[0048] As shown in Table 1, a model was constructed based on negative Poisson's ratio honeycomb cells, and gradient designs for wall thickness and porosity were performed. Figure 10 The diagram shows the dimensional structure of a negative Poisson's ratio honeycomb cell. Based on a uniformly distributed structure, gradient design must strictly adhere to the principle of equal structural mass. Therefore, when designing a gradient wall thickness, the porosity must remain constant. Since the reinforcing layers are of equal thickness, the sum of the cell wall areas of the red and black regions of the honeycomb structure must be equal to twice the cell wall area of ​​the blue region. Let the cell area be A, and the number of cells in the three regions be respectively... , , The control function for thick gradient design is shown in the following equation:

[0049]

[0050] Simplifying, we get:

[0051]

[0052] Similarly, in the porosity gradient design, the sum of the cell wall areas of the red and black regions of the honeycomb structure should be equal to twice that of the blue region. Let the cell areas under the three porosities be respectively... , , The number of cells in the three regions are respectively , , The control function for porosity gradient design is shown in the following equation:

[0053]

[0054] Simplifying, we get:

[0055]

[0056] Table 1: Size and Structure of Negative Poisson's Ratio Cells

[0057] n / ％ a / mm h / mm θ 39.6 4.98 4.74 60° 45.7 6.36 5.5 60° 52 8.05 6.48 60°

[0058] The wall thickness and porosity of the two gradient design forms are shown in Table 2.

[0059] Table 2: Wall thickness and porosity data for two gradient design schemes

[0060] Wall thickness gradient design Porosity gradient design t / mm 3-2-1 2 n / ％ 45.7 39.6-45.7-52

[0061] Thickness gradient design, cell horizontal and vertical arrangement modeling, such as Figure 2 and Figure 3 As shown;

[0062] Porosity gradient design, cell-level and vertical arrangement modeling, such as Figure 4 and Figure 5 As shown.

[0063] Step 3: Finite Element Simulation

[0064] First, the material parameters of the 3D printing consumable PLA were obtained through quasi-static uniaxial compression tests. The measured elastic modulus E was 2200 MPa, yield stress σ = 45.7 MPa, and Poisson's ratio μ was 0.35. Then, quasi-static three-point bending tests were conducted on four models in ANSYS Workbench, such as... Figure 6 As shown, the specific operation steps are as follows:

[0065] Step 3.1: Save the 3D model created in SOLIDWORKS as x_t format and import it into ANSYSWorkbench. In the Engineering Data module, define a custom material named PLA. Define its material properties based on the measured data. Assign PLA material to the stiffened plate component and structural steel material to the pressure head and support component.

[0066] Step 3.2: In the Mesh module, mesh the pressure head and support components with tetrahedral meshes of 4mm element size; mesh the stiffening plate component with tetrahedral meshes of 1mm element size, completing the mesh generation of the finite element model. Set the contact between the pressure head, support components, and stiffening plate to frictional contact, with a friction coefficient of 0.2.

[0067] Step 3.3: Apply a fixed constraint to the bottom surface of the support component and apply a displacement load of 30mm in the Y direction to the top surface of the pressure head.

[0068] Step 3.4: Add output items such as deformation contour plot, stress contour plot and support reaction force in the solver module. After completing all settings, perform the solver and view the analysis results after the solver is finished.

[0069] The force-displacement curves of each specimen under gradient conditions are as follows: Figure 7As shown in the figure, peak force is the core indicator for measuring the load-bearing capacity of materials / structures in the force-displacement diagram. The figure shows that the model with vertically arranged cells and a porosity gradient design reaches its peak force (close to 500 N) at a displacement of approximately 15 mm, and the force decays relatively smoothly, indicating good load-bearing stability in the high-load range. Therefore, this model is selected for further optimization.

[0070] Step 4: Topology Optimization and Lightweight Design

[0071] Based on the gradient design scheme obtained in step 3, further topology optimization was performed in the ANSYS Workbench environment. Multiple objectives were set: "increasing bending stiffness" and "reducing structural flexibility," with constraints such as structural weight and minimum feature size (to ensure manufacturability) applied. The variable density method was used for optimization calculations. After optimization, the rib layout and skin were reconstructed to form a composite structure of "gradient honeycomb-locally reinforcing ribs." Based on the stress distribution cloud map, non-primary load-bearing areas were identified, and further weight reduction was achieved by reducing material or introducing microlattice filling and local hollowing. Finally, static simulations were performed on the final model to verify whether its performance met the design requirements. The optimized model exhibits a certain curved surface form, such as... Figure 8 As shown, the mass is reduced by approximately 14%, as Figure 9 As shown, the elastic modulus is comparable to that of the original structure, but the yield strength and peak bearing capacity are significantly improved.

[0072] Step 5: 3D Printing and Verification

[0073] Based on the final model determined in step 3, 3D printing was performed using fused deposition modeling (FDM) equipment and polylactic acid (PLA) material. During the printing process, the printing path and cell opening direction were optimized to achieve self-supporting printing as much as possible, reducing the need for support structures. After printing, a quasi-static three-point bending test was conducted on the solid specimen again. The experimental results were compared with the simulation predictions. The results showed that the data error between the two remained at about 2%, verifying the feasibility and effectiveness of this design method in improving performance and achieving lightweighting.

Claims

1. A method for optimizing the design of negative Poisson's ratio honeycomb stiffened panels based on additive manufacturing, characterized in that, Includes the following steps: Step 1: By conducting a quasi-static three-point bending test, the failure mode of the honeycomb stiffened plate was studied to determine that the failure of the structure after bending deformation mainly occurs at the middle load-bearing position. Step 2: Using "equal mass" as a constraint, a dual gradient design of wall thickness and porosity is carried out for the negative Poisson's ratio honeycomb stiffened plate: the wall thickness is gradually reduced from the load concentration area to the support area to achieve a balance between load-bearing capacity and lightweight; by adjusting the geometric parameters of the concave cell, a gradient distribution of porosity from high to low is formed so that the material distribution accurately matches the stress requirements. Step 3: First, obtain the material parameters of PLA 3D printing consumable through uniaxial compression test. Then, use ANSYS Workbench software to perform quasi-static three-point bending test finite element simulation on four different models. Combined with force-displacement curve analysis, select the optimal gradient design scheme. Step 4: Based on the gradient design results of Step 3, perform topology optimization and lightweight design on the structure, and use ANSYS Workbench simulation to verify whether the optimized structure meets the performance requirements. Step 5: Based on the final design in Step 4, 3D print the model and verify its mechanical properties and design feasibility through experiments.

2. The method for optimizing the design of negative Poisson's ratio honeycomb stiffened panels based on additive manufacturing according to claim 1, characterized in that, In step 2, the overall dimensions of the negative Poisson's ratio honeycomb reinforced plate are designed as follows: length 120mm, width 70mm, and thickness 10mm, with the reinforcement layer having a thickness of 5mm.

3. The method for optimizing the design of negative Poisson's ratio honeycomb stiffened panels based on additive manufacturing according to claim 1, characterized in that, In step 2, the dual-gradient design follows the principle of equal mass for wall thickness gradient changes and porosity gradient changes, and keeps the sum of the wall areas of cells in different gradient regions constant.

4. The method for optimizing the design of negative Poisson's ratio honeycomb stiffened panels based on additive manufacturing according to claim 1, characterized in that, In step 2, two gradient models for the wall thickness and porosity of the negative Poisson's ratio honeycomb reinforced plate are constructed, with the cell arrangement direction being 0° or 90°, i.e., horizontal or vertical arrangement. The four sets of models are compared and analyzed.

5. The method for optimizing the design of negative Poisson's ratio honeycomb stiffened panels based on additive manufacturing according to claim 1, characterized in that, In step 2, let the cell area be A, and the number of cells in the three regions be respectively... , , The control function for thick gradient design is shown in the following equation: In the porosity gradient design, let the cell areas under the three porosities be respectively , , The number of cells in the three regions are respectively , , The control function for porosity gradient design is shown in the following equation: Where A is the cell area. , , These represent the number of cells in the three regions; , , The cell areas are for the three porosities.

6. The method for optimizing the design of negative Poisson's ratio honeycomb stiffened panels based on additive manufacturing according to claim 1, characterized in that, Step 3 includes: Step 3.1: Save the 3D model created in SOLIDWORKS and import it into ANSYS Workbench. In the Engineering Data module, define a custom material named PLA. Define its material properties based on the measured data. Assign PLA material to the stiffened plate component and structural steel material to the pressure head and support component. Step 3.2: In the Mesh module, mesh the pressure head and support components with tetrahedral meshes of 4mm element size; mesh the stiffening plate component with tetrahedral meshes of 1mm element size, completing the mesh generation of the finite element model. Set the contact between the pressure head, support components, and stiffening plate to frictional contact, with a friction coefficient of 0.

2. Step 3.3: Apply a fixed constraint to the bottom surface of the support component and apply a displacement load of 30mm in the Y direction to the top surface of the pressure head; Step 3.4: Add deformation contour plot, stress contour plot and support reaction output items in the solver module. After completing all settings, perform the solver and view the analysis results after the solver is finished.

7. The method for optimizing the design of negative Poisson's ratio honeycomb stiffened panels based on additive manufacturing according to claim 1, characterized in that, The topology optimization in step 4 aims to improve bending stiffness and reduce structural flexibility. It uses the variable density method for optimization calculation and takes into account the process constraints of additive manufacturing in the optimization.

8. The method for optimizing the design of negative Poisson's ratio honeycomb stiffened panels based on additive manufacturing according to claim 1, characterized in that, The lightweight design in step 4 is based on the stress distribution cloud map obtained from finite element analysis.

9. The method for optimizing the design of negative Poisson's ratio honeycomb stiffened panels based on additive manufacturing according to claim 1, characterized in that, Step 4 includes clarifying the load-bearing characteristics of each part through stress distribution cloud maps, and optimizing the structural quality by reducing materials or introducing microlattice structures and local hollowing methods in non-primary load-bearing areas.

10. The method for optimizing the design of negative Poisson's ratio honeycomb stiffened panels based on additive manufacturing according to claim 1, characterized in that, The 3D printing process in step 5 is fused deposition modeling, and the material is polylactic acid.

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