Reverse design method for rod diameter of lattice structure

Abstract

The invention relates to the field of sole design, in particular to a dot matrix structure rod diameter reverse design method which comprises the following steps executed in sequence: S1, constructing a unit cell structure; s2, defining parameters: the diameter d1 of a connecting rod, the diameter d2 of a main body rod, the diameter d3 of a fiber rod, the side length L of a unit cell structure and a shape coefficient alpha; s3, generating a test structure; s4, acquiring hyperelasticity data and viscoelasticity data of the test structure, and establishing a finite element analysis model of the test structure; s5, setting each parameter, performing simulation analysis on the test structure under each combination, acquiring mechanical property indexes of each test structure, and constructing a mechanical property index database by adopting each acquired mechanical property index; s6, determining a unique rod diameter combination; s7, generating a lattice structure for filling the sole according to the obtained rod diameter combination; according to the design method, reverse design of the rod diameter parameters in the lattice structure can be rapidly achieved, the rod diameter combination parameters under the target mechanical property can be rapidly obtained in an iteration mode, and the design cost is saved.

Description

Technical Field

[0001] This invention relates to the field of shoe sole design, and more specifically to a reverse design method for the diameter of a dot matrix structure rod. Background Technology

[0002] Lattice structures are widely used in aerospace, sports, and biomedicine due to their lightweight, high strength, and tunable mechanical properties. Currently, most lattice designs adopt forward design, with structural design inspiration often derived from biomimetic structures or AI algorithms. The focus is on forward design based on target performance requirements, and then verifying the final mechanical properties after the design is completed.

[0003] The design of the dot matrix structure of the shoe sole mainly relies on the adjustment of structural parameters. However, the influence of each parameter on the mechanical response is not clear. It often relies on experience to make multiple adjustments to make the structure meet the performance requirements. The design process is blind and inefficient. Summary of the Invention

[0004] The purpose of this invention is to provide a reverse design method for the diameter of a dot matrix structure rod to improve the design efficiency of shoe soles.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A reverse design method for rod diameter of a lattice structure is disclosed, which constructs a unit cell structure to generate a lattice structure for filling shoe soles. The specific construction steps of the unit cell structure are as follows: S1: The unit cell structure includes an inclined connecting rod and a quadrilateral symmetrically arranged on both sides of the connecting rod. The quadrilateral includes two main rods and two auxiliary rods. The two auxiliary rods are connected to the connecting rod. One end of the two main rods is connected to the end of the two auxiliary rods away from the connecting rod, and the ends of the two main rods away from the two auxiliary rods are connected to form the first structure. Construct a cubic space with a side length equal to the distance between one end of the connecting rod and the adjacent end of the main rod furthest from the connecting rod; Three of the first structures are arranged at equal intervals along the X-axis, and three points with the same X-axis and Y-axis coordinates are connected by fiber rods to form the unit cell structure. S2: Define parameters: connecting rod diameter d1, main rod diameter d2, fiber rod diameter d3, unit cell structure side length L and shape factor α, where the shape factor α is the ratio of the distance between the connection point of the main rod and the auxiliary rod and the nearest cubic space surface to the unit cell structure side length L; S3: Based on this unit cell structure, a test structure with 3×3×3 single-cell structures is obtained by arranging them along the Y-axis. S4: Obtain the hyperelastic and viscoelastic data of the test structure and establish the finite element analysis model of the test structure; S5: Set multiple connecting rod diameters d1, set the main rod diameter d2 to be equal to the fiber rod diameter d3, and set the unit cell side length. Perform simulation analysis on the test structure under each combination to obtain the mechanical performance index of each test structure. The mechanical performance index includes elastic modulus, plateau stress, stiffness variation modulus and yield stress. Use the obtained mechanical performance index to construct a mechanical performance index database. S6: Using machine learning methods, a corresponding surrogate model was fitted in Matlab based on Gaussian process regression with squared exponential kernel function. According to the surrogate model, a unique combination of bar diameters can be determined in reverse from any two sets of mechanical performance indicators in the mechanical performance index database. S7: Generate a lattice structure for filling the shoe sole based on the obtained rod diameter combination.

[0006] Preferably, in step S4, the hyperelastic data is fitted to the tensile specimen data using the Marlow model, and the viscoelastic data is fitted using the Prony series.

[0007] Preferably, in step S4, the accuracy of the calculation model is verified by conducting a standard static compression experiment.

[0008] Preferably, in step S3, the shape factor α of the test structure is set to 0.1.

[0009] Preferably, in step S5, the diameter d1 of the connecting rod is set to 0.9mm, 1.2mm, 1.5mm or 1.8mm, and the side length L of the unit cell structure is set to 10mm.

[0010] By adopting the aforementioned design scheme, the beneficial effects of the present invention are as follows: the unit cell structure proposed in this application can generate a stable multi-level mechanical response using elastomeric materials, which is suitable for engineering scenarios such as motion adjustment and redundancy protection; the method of this application can quickly realize the reverse design of rod diameter parameters in lattice structures, and can quickly iterate to obtain rod diameter combination parameters under the target mechanical properties, saving design costs. Attached Figure Description

[0011] Figure 1 This is a flowchart of the design method of the present invention; Figure 2 This is a multi-angle schematic diagram of the unit cell structure of the present invention; Figure 3 This is a schematic diagram of the test structure of the present invention; Figure 4 This is a schematic diagram of the quasi-static compression process of the simulation test structure of the present invention; Figure 5This is a schematic diagram of the standard static compression experiment of the present invention; Figure 6 This is a schematic diagram of the proxy model fitted in Matlab according to the present invention. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0013] The terms "first," "second," "third," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0014] A reverse design method for rod diameter in lattice structures, such as Figure 1 As shown, a single-cell structure was constructed, inspired by the local reinforcement mechanism of bamboo fiber bundles and the staggered arrangement of nacreous layers in seashells. The basic configuration of this single-cell structure is as follows: Figure 2 As shown, this unit cell structure is used to generate a lattice structure for filling shoe soles. The specific construction steps of this unit cell structure are as follows: S1: The unit cell structure includes an inclined connecting rod and a quadrilateral symmetrically arranged on both sides of the connecting rod. The quadrilateral includes two main rods and two auxiliary rods. The two auxiliary rods are connected to the connecting rod. One end of the two main rods is connected to the end of the two auxiliary rods away from the connecting rod, and the ends of the two main rods away from the two auxiliary rods are connected to form the first structure. Construct a cubic space with a side length equal to the distance between one end of the connecting rod and the end of the adjacent main rod furthest from the connecting rod; The three first structures are arranged at equal intervals along the X-axis, and fiber rods are used to connect the three points with the same X-axis and Y-axis coordinates to form a unit cell structure. S2: Define parameters: connecting rod diameter d1, main rod diameter d2, fiber rod diameter d3, unit cell structure side length L and shape factor α, where the shape factor α is the ratio of the distance between the connection point of the main rod and the auxiliary rod and the nearest cubic space surface to the unit cell structure side length L; S3: Based on this unit cell structure, the shape factor α is set to 0.1, and a test structure with 3×3×3 unit cells is obtained by arranging them along the Y-axis. All layers in the test structure have the same tilt direction, such as... Figure 3 As shown; S4: Obtain the hyperelastic and viscoelastic data of the test structure and establish the finite element analysis model of the test structure; In this embodiment, a finite element analysis model is established based on experimentally obtained TPU material data for 3D printing. For example... Figure 4 and Figure 5 As shown, the mesh model is placed between two rigid plates. Except for the top plate's displacement degree of freedom in the Z direction, all degrees of freedom of the bottom and top plates are constrained, with the top plate moving downwards at a constant speed of 200 mm / s to simulate a quasi-static compression process. To accurately simulate the hyperelastic and viscoelastic behavior of TPU material, hyperelastic and viscoelastic data from the material constitutive model are used. The hyperelastic data is fitted to the tensile specimen data using the Marlow model, and the viscoelastic data uses the Prony series. The accuracy of the computational model is verified through standard static compression experiments.

[0015] S5: Set multiple connecting rod diameters d1, set the main rod diameter d2 to be equal to the fiber rod diameter d3, and set the unit cell side length. In this embodiment, for the lattice structure with "stepped" mechanical behavior, the connecting rod diameters d1 are set to 0.9mm, 1.2mm, 1.5mm or 1.8mm, the main rod diameter d2 is set to 0.9mm, 1.2mm, 1.5mm or 1.8mm, and the unit cell side length L is set to 10mm. Simulation analysis is performed on the test structures under each combination, a total of 16 combinations. Each combination is simulated once to obtain the mechanical performance indicators of each test structure. The mechanical performance indicators include elastic modulus, plateau stress, stiffness variation modulus and yield stress. The obtained mechanical performance indicators are used to construct a mechanical performance indicator database. S6: Using machine learning methods, a corresponding surrogate model was fitted in Matlab based on Gaussian process regression with a squared exponential kernel function, such as... Figure 6 As shown, based on the surrogate model, a unique rod diameter combination can be determined inversely from any two sets of mechanical performance indicators in the mechanical performance indicator database. In this embodiment, two mechanical performance indicators are given arbitrarily, and a Matlab program is used for fitting. The program will automatically search, and if a solution is found, it will output the values ​​of rod diameter combinations d1 and d2; otherwise, there is no solution.

[0016] S7: Generate a lattice structure for filling the shoe sole based on the obtained rod diameter combination.

[0017] To better illustrate the reverse design method for the rod diameter of this lattice structure, this embodiment further explains it with the following example.

[0018] Taking elastic modulus and stiffness variation modulus as examples, with targets set at 1000 kPa and 3000 kPa respectively, there may be multiple combinations of d1 and d2 satisfying the elastic modulus of 1000 kPa, and multiple combinations of d1 and d2 satisfying the stiffness variation modulus of 3000 kPa. The Matlab program will be based on... Figure 6 The fitted data is searched for and outputs the rod diameter combinations that simultaneously satisfy the condition; otherwise, there is no solution. The detailed solution process is performed using the "Gaussian Regression Process" program in Matlab. The Matlab program used in this application does not have specific parameters set; all parameters are default or conventional. The search is performed with an elastic modulus of 1000 kPa and a stiffness variation modulus of 3000 kPa as targets. A unique real solution is found that satisfies the actual conditions: the main rod diameter is 1.6185 mm, and the connecting rod diameter is 1.2821 mm.

[0019] In the simulation model, the rod diameters were set to 1.6185 mm and 1.2821 mm, respectively. The simulation results are shown in Table 1. The compressive modulus of the elastic segment was 1020.8 kPa, and the modulus of the stiffness-changing segment was 2883.6 kPa. The simulation and surrogate model errors were +2.08% and -3.88%, respectively. Given the rod diameter coefficient, the fitted values ​​of the first plateau stress and yield stress were obtained through the surrogate model of mechanical properties, which were 158.8 kPa and 560.1 kPa, respectively. The simulation results were 156.1 kPa and 521.9 kPa, with simulation errors of -1.70% and -6.82%, respectively.

[0020]

[0021] Error analysis of the surrogate model and the simulation after reverse design shows that the surrogate model, as an empirical fit, can provide relatively accurate guidance for reverse design.

[0022] The compressive mechanical properties of the proposed lattice structure with a shape factor of 0.1 were fitted using a Gaussian process regression surrogate model, and the bar diameter was designed in reverse. The surrogate model is relatively accurate, with small errors compared to the mechanical properties obtained from finite element analysis. Among these mechanical properties, the stiffness variation modulus is most affected by the diameter of the main bar, and less related to the diameter of the connecting bars. The stress on the first plateau is affected by the interaction of the two bar diameters, while the yield stress is significantly affected by the diameter of the main bar.

[0023] In summary, the unit cell structure constructed in this application can generate a stable multi-level mechanical response using elastomer materials, and is suitable for engineering scenarios such as motion regulation and redundancy protection. This application establishes a database of mechanical performance indicators based on finite element models and experimental test results, and fits a proxy model. The model has high accuracy and good fitting effect. The reverse design method for rod diameter in lattice structures can be used to quickly design the rod diameter parameters in lattice structures, and can rapidly iterate to obtain the rod diameter combination parameters under the target mechanical properties, thus saving design costs.

[0024] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for reverse design of rod diameter in a lattice structure, characterized in that: The specific construction steps of the unit cell structure are as follows: A unit cell structure is constructed to generate a lattice structure for filling the shoe sole. S1: The unit cell structure includes an inclined connecting rod and a quadrilateral symmetrically arranged on both sides of the connecting rod. The quadrilateral includes two main rods and two auxiliary rods. The two auxiliary rods are connected to the connecting rod. One end of the two main rods is connected to the end of the two auxiliary rods away from the connecting rod, and the ends of the two main rods away from the two auxiliary rods are connected to form the first structure. Construct a cubic space with a side length equal to the distance between one end of the connecting rod and the adjacent end of the main rod furthest from the connecting rod; Three of the first structures are arranged at equal intervals along the X-axis, and three points with the same X-axis and Y-axis coordinates are connected by fiber rods to form the unit cell structure. S2: Define parameters: connecting rod diameter d1, main rod diameter d2, fiber rod diameter d3, unit cell structure side length L and shape factor α, where the shape factor α is the ratio of the distance between the connection point of the main rod and the auxiliary rod and the nearest cubic space surface to the unit cell structure side length L; S3: Based on this unit cell structure, a test structure with 3×3×3 single-cell structures is obtained by arranging them along the Y-axis. S4: Obtain the hyperelastic and viscoelastic data of the test structure and establish the finite element analysis model of the test structure; S5: Set multiple connecting rod diameters d1, set the main rod diameter d2 to be equal to the fiber rod diameter d3, and set the unit cell side length. Perform simulation analysis on the test structure under each combination to obtain the mechanical performance index of each test structure. The mechanical performance index includes elastic modulus, plateau stress, stiffness variation modulus and yield stress. Use the obtained mechanical performance index to construct a mechanical performance index database. S6: Using machine learning methods, a corresponding surrogate model was fitted in Matlab based on Gaussian process regression with squared exponential kernel function. According to the surrogate model, a unique combination of bar diameters can be determined in reverse from any two sets of mechanical performance indicators in the mechanical performance index database. S7: Generate a lattice structure for filling the shoe sole based on the obtained rod diameter combination.

2. The reverse design method for the rod diameter of a lattice structure as described in claim 1, characterized in that: In step S4, the hyperelastic data is fitted to the tensile specimen data using the Marlow model, and the viscoelastic data is fitted using the Prony series.

3. The reverse design method for the rod diameter of a lattice structure as described in claim 2, characterized in that: In step S4, the accuracy of the calculation model is verified by conducting a standard static compression experiment.

4. The reverse design method for the rod diameter of a lattice structure as described in claim 1, characterized in that: In step S3, the shape factor α of the test structure is set to 0.

1.

5. The reverse design method for the rod diameter of a lattice structure as described in claim 4, characterized in that: In step S5, the diameter d1 of the connecting rod is set to 0.9mm, 1.2mm, 1.5mm or 1.8mm, and the side length L of the unit cell structure is set to 10mm.

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