Mechanical digital design three-dimensional model building method and system

Abstract

The invention discloses a mechanical digital design three-dimensional model building method, and relates to the technical field of digital model generation, and the method comprises the steps: obtaining a mechanical design motion path, carrying out the correction through a curvature smoothing algorithm, and determining a mechanical motion space boundary; generating a motion curve envelope according to the motion path and the space boundary, and performing compensation to generate a final envelope; dividing the final envelope into finite element units by using a tetrahedron division algorithm, defining a shape function of each unit, defining a target function by taking lightweight as a target, constructing topological optimization constraints through the shape functions, and solving the target function by using SIMP to obtain a lightweight model; and after obtaining the lightweight model, outputting according to a format, displaying and storing in a database. According to the method, the efficient, accurate and lightweight targets of the complex mechanical three-dimensional design are effectively achieved, and the adaptability and flexibility of the mechanical design are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of digital model generation, in particular to a mechanical digital design three-dimensional model building method and system. BACKGROUND

[0002] With the rapid development of advanced manufacturing technology and the continuous improvement of industrial design precision requirements, computer-aided mechanical design and analysis have gradually become key technical fields. In particular, in modern industry, three-dimensional digital design technology has been widely used in the research and development process of mechanical systems, from concept modeling, analysis and optimization to actual manufacturing. The traditional mechanical design method relies more on experience accumulation and manual trial and error, while the three-dimensional digital method can greatly improve the design efficiency and accuracy with the help of computer modeling and simulation technology, while reducing the cost of testing and manufacturing.

[0003] Although the existing technology has made remarkable achievements in mechanical three-dimensional modeling, it still has many technical bottlenecks. The existing method often cannot universally consider kinematics requirements and manufacturing process requirements, lacks flexible adaptability to design goals under different working conditions or boundary conditions, resulting in difficulty in balancing the optimization of mechanical design with actual workspace constraints, motion accuracy requirements and carrying capacity. SUMMARY

[0004] In view of the above existing problems, the present application is proposed.

[0005] Therefore, the present application provides a mechanical digital design three-dimensional model building method and system, which solves the problem that the existing technology cannot universally consider kinematics requirements and manufacturing process requirements, and lacks flexible adaptability to design goals under different working conditions or boundary conditions.

[0006] To solve the above technical problems, the present application provides the following technical solutions: In a first aspect, the present application provides a mechanical digital design three-dimensional model building method, which comprises, obtaining a mechanical design motion path and correcting it through a curvature smoothing algorithm, determining a mechanical motion space boundary, generating a motion curved surface envelope according to the motion path and the space boundary and generating a final envelope after compensation; using a tetrahedron division algorithm to divide the final envelope into finite element units and defining the shape function of each unit, defining a target function with the goal of lightweight, constructing a topology optimization constraint through the shape function, and using SIMP to solve the target function to obtain a lightweight model; After obtaining the lightweight model, output it in a format for display and store it in a database.

[0007] As a preferred scheme of the mechanical digital design three-dimensional model building method, the method comprises the following steps: acquiring a mechanical design motion path and correcting the mechanical design motion path through a curvature smoothing algorithm, determining a mechanical motion space boundary according to mechanical design requirements, inputting mechanical motion requirement parameters to generate the mechanical motion path, and discretizing the motion path into a continuous point set according to a fixed time interval.

[0008] As a preferred scheme of the mechanical digital design three-dimensional model building method, the method comprises the following steps: acquiring a mechanical design motion path and correcting the mechanical design motion path through a curvature smoothing algorithm, determining a mechanical motion space boundary according to mechanical design requirements, inputting mechanical motion requirement parameters to generate the mechanical motion path, and discretizing the motion path into a continuous point set according to a fixed time interval.

[0009] As a preferred scheme of the mechanical digital design three-dimensional model building method, the method comprises the following steps: acquiring a mechanical design motion path and correcting the mechanical design motion path through a curvature smoothing algorithm, determining a mechanical motion space boundary according to mechanical design requirements, inputting mechanical motion requirement parameters to generate the mechanical motion path, and discretizing the motion path into a continuous point set according to a fixed time interval. ​​​​​​​​​​​​​​​​​​​Based on the grid size The geometry formed by the final envelope surface is divided into tetrahedral units using the Delaunay triangulation method, each tetrahedral unit is composed of 4 vertex nodes and 6 edges, and the quality of the divided tetrahedral unit is checked; For each tetrahedral unit, the coordinates of the 4 vertex nodes are set as 、 、 and The node shape function of the tetrahedral unit is defined by a linear interpolation function .

[0010] As a preferred scheme of the mechanical digital design three-dimensional model building method, wherein: the target function is defined for the purpose of lightweight, the topology optimization constraint is constructed by the shape function, and the SIMP is used to solve the target function to obtain the lightweight model; for each tetrahedral unit, set the initial material density , and form an element density matrix , define the target function for the purpose of lightweight based on the element density matrix; According to the node shape function , the partial derivative is obtained to obtain the strain-displacement matrix of the tetrahedral unit ; The strain-displacement matrices of all tetrahedral units are combined to form a global strain-displacement matrix P, and the reference stiffness matrix of each element is generated according to the strain-displacement matrix of each tetrahedral unit ; The global stiffness matrix K is calculated according to the reference stiffness matrix; The global load distribution F is calculated according to the shape function; The global stiffness matrix K and the global load distribution F are obtained, and the global displacement vector U is solved by the finite element method; The element strain tensor is derived from the global displacement vector U, and stress constraints are added to all tetrahedral units; Synchronous volume restriction is added; The SIMP method is used to minimize the target function under the conditions of meeting the stress constraints and volume constraints, in the optimization process, the element density is iteratively updated; After the target function converges, the iteration is stopped, and the lightweight model is output according to the iteration density.

[0011] As a preferred scheme of the mechanical digital design three-dimensional model building method, wherein: the lightweight model is output in a format for display, and the lightweight model is output as a STEP format three-dimensional file and displayed to the designer.

[0012] As a preferred scheme of the mechanical digital design three-dimensional model building method, the obtained lightweight model is stored in a design database, and a timestamp is allocated to generate a design log for storage.

[0013] In a second aspect, the application provides a mechanical digital design three-dimensional model building system, comprising, The design analysis module is used to obtain a mechanical design motion path, correct it through a curvature smoothing algorithm, determine a mechanical motion space boundary, generate a motion surface envelope according to the motion path and the space boundary, and generate a final envelope after compensation; The model generation module is used to divide the final envelope into finite element units using a tetrahedral division algorithm and define a shape function of each unit, define a target function with the goal of lightweight, construct a topology optimization constraint through the shape function, and obtain a lightweight model by solving the target function using SIMP; The display storage module is used to output and display the obtained lightweight model in a format and store it in a database.

[0014] In a third aspect, the application provides a computer device comprising a memory and a processor, and the memory stores a computer program, wherein the computer program is executed by the processor to implement any step of the mechanical digital design three-dimensional model building method according to the first aspect of the application.

[0015] In a fourth aspect, the application provides a computer readable storage medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement any step of the mechanical digital design three-dimensional model building method according to the first aspect of the application.

[0016] The application has the following beneficial effects: by obtaining a mechanical design motion path, adopting curvature smoothing correction, generating a mechanical design envelope surface through motion envelope generation, simultaneously setting an optimization function and a constraint condition through finite element division and lightweight target, the application effectively realizes efficient, accurate and lightweight goals of complex mechanical three-dimensional design, and improves the adaptability and flexibility of mechanical design. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0018] Figure 1This is a flow chart of the method for building a three-dimensional model for mechanical digital design in Example 1.

[0019] Figure 2 This is a structural diagram of the system for building a three-dimensional model for mechanical digital design in Example 1. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0021] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0023] Example 1, reference Figure 1 and Figure 2 , which is the first embodiment of the present invention, provides a method for building a three-dimensional model of a mechanical digital design, comprising the following steps: S1. Obtain the mechanical design motion path and correct it through the curvature smoothing algorithm to determine the mechanical motion space boundary. Generate the motion surface envelope based on the motion path and space boundary and perform compensation to generate the final envelope. Specifically, the mechanical design motion path is obtained and corrected through the curvature smoothing algorithm, and the mechanical motion space boundary is determined by inputting the mechanical motion requirement parameters according to the mechanical design requirements to generate the mechanical motion path. ,in , For the motion path in time The coordinates of and The start and end time of the movement, based on a fixed time interval The motion path Discretize into a continuous point set , calculate the point set The curvature of each discrete point in :

[0024] in and For the point concentration discrete points The coordinate first derivative of , and For the discrete points The coordinate second derivative of ; When the discrete point curvature When the curvature threshold is exceeded, the discrete points are regarded as high curvature points, and new path points are added around the high curvature points using cubic spline interpolation:

[0025] in is the jth new path point added, For the discrete points, The total number of new path points added is set according to the curvature; After adding the new path points, the discrete points are sorted and output as a new discrete point set. The boundary B of the mechanical motion space is determined based on the discrete point set:

[0026] in and They are the minimum and maximum limit values ​​of the path on the coordinate axis respectively.

[0027] By calculating the curvature of each discrete point, high curvature areas on the motion path can be accurately identified, and key points can be located according to the set threshold. New path points are added in the high curvature area through cubic spline interpolation, thereby effectively smoothing the path. The mathematical properties of spline interpolation (such as continuous second-order derivatives) ensure the smoothness and connectivity of the new path, avoiding geometric mutations caused by the addition of points. The spline method can add key information points without destroying the overall path structure, providing precise input for subsequent finite element topology optimization. In actual mechanical movement, it can reduce vibration and deviation caused by discontinuous paths. The use of adaptive boundaries makes the generation of motion envelopes more efficient, avoids unnecessary redundant design space, and improves the finite element division and optimization effects within the boundary range.

[0028] Furthermore, the motion surface envelope is generated according to the motion path and the spatial boundary and compensated to generate the final envelope. This means constructing a simple initial surface by combining the minimum bounding box of the mechanical motion space boundary B with isometric expansion, taking the surface point as the initial envelope point M, and calculating the minimum distance from the new discrete point set to the initial envelope point as the error function E:

[0029] in is the number of envelope points, For the Initial envelope points, For the The nearest discrete point to the initial envelope point, is the penalty weight coefficient used to balance accuracy and smoothness, and R is the regularization term used to control the geometric properties of the surface, such as smoothness or curvature. In order to ensure the smoothness of the envelope surface, the regularization term R is usually ,in is the second-order gradient of the envelope surface, S is the envelope surface formed by all envelope points; To ensure the accuracy and smoothness of the surface generated, smoothness constraints and thickness constraints are added to the error function. The smoothness constraints are:

[0030] in For the envelope surface at point The external normal vector at is a constant; The thickness constraint is:

[0031] in and are the minimum and maximum values ​​of the designed thickness, respectively, and D is the distance between the initial envelope point and the discrete point; Take all envelope points on the initial surface as the initial optimization variable X, calculate the error function value for the initial optimization variable, and calculate the gradient of the objective function with respect to the current initial optimization variable through the error function value:

[0032] in is the error function value of the initial optimization variable, is the gradient; The gradient includes the gradient of the trajectory fitting error and the gradient of the regularization error, which are discretized and calculated by the difference form of the finite element grid gradient, respectively: Gradient of trajectory fitting error:

[0033] Gradient of the regularized error:

[0034] Update the initial optimization variable X according to the L-BFGS algorithm update rule, stop the optimization when the convergence condition is met, and extract the optimized envelope point Forming an optimized envelope surface; Calculate mechanical motion speed based on discrete point distance :

[0035] wherein is a time interval; and a gap adjustment value is calculated for the optimized envelope point:

[0036] wherein is a basic gap value (set according to manufacturing error, initial value is 0.5 mm), is a speed compensation coefficient, is a gap value of the discrete point ; the optimized envelope point is adjusted according to the gap adjustment value to generate a final envelope point, and a final envelope surface is formed:

[0037] wherein is the final envelope point.

[0038] The error function combines the minimum distance from the discrete point set to the envelope point as a fitting accuracy measurement, and further adds a regularization term to strongly constrain the smoothness. This not only optimizes the surface geometry, but also avoids the local mutation problem in the simple fitting method. Through the adjustable penalty weight coefficient, different priority envelope generation schemes can be selected according to the application scenario, for example, in automated production, the accuracy is given priority, and in mold design, more attention is paid to the smoothness of the surface. The smoothness constraint suppresses the local discontinuity of the surface by limiting the change of the normal vector of the envelope surface, which significantly improves the actual machining applicability of the envelope surface. Combined with the thickness constraint, the generated envelope surface not only meets the mechanical strength and stiffness requirements, but also has higher consistency, avoiding the appearance of weak areas. The combination of the two constraints provides an initial model with uniform quality for subsequent finite element division and topology optimization, improving the efficiency of the overall optimization link. The introduction of the gap adjustment value and the speed-based compensation coefficient can dynamically respond to the speed change of the motion path and compensate for the deviation in manufacturing. This dynamic adjustment mechanism is particularly suitable for surface design of complex mechanical motion, which can effectively reduce the generation of mismatched areas after machining.

[0039] S2, using a tetrahedral division algorithm to divide the final envelope into finite element units and defining the shape function of each unit, defining an objective function for the purpose of lightweight, constructing a topology optimization constraint through the shape function, and using SIMP to solve the objective function to obtain a lightweight model; Specifically, using a tetrahedral division algorithm to divide the final envelope into finite element units and defining the shape function of each unit, calculating the curvature of the envelope point according to the final envelope surface and calculating the average curvature of all envelope points , adjusting the grid size according to the curvature using an adaptive subdivision method :

[0040] wherein and are control parameters; The geometric body formed by the final envelope surface is divided into tetrahedral units using Delaunay triangulation method based on the grid size l, each tetrahedral unit is composed of 4 vertex nodes and 6 edges, and quality inspection is performed on the divided tetrahedral units; For each tetrahedral unit, the coordinates of the 4 vertex nodes are respectively set as , , and The node shape function of the tetrahedral unit is defined by a linear interpolation function :

[0041] wherein , and are the coordinates of the th node in the tetrahedral unit, , , and are shape function coefficients, which are solved by the unit node coordinates:

[0042] wherein is the volume of the tetrahedral unit, which is calculated by the vertex coordinates of the tetrahedron, and j, k, l are the remaining node indexes.

[0043] By calculating the average curvature of the envelope points and adaptively adjusting the grid size based on the curvature, fine grids can be generated in high curvature areas, thereby improving the stress and deformation calculation accuracy of these key areas. In low curvature areas that do not require high-density grids, larger grid sizes are used to significantly reduce the computational load and avoid unnecessary resource waste. In extremely high curvature or large surface change paths (such as sharp transition areas), adaptive subdivision can effectively avoid analysis errors caused by excessive subdivision, improving the overall smoothness and element quality of the grid. Delaunay subdivision is based on geometric properties and optimizes the shape of the elements during the subdivision process, avoiding the generation of distorted tetrahedrons (such as sharp shapes and non-convex shapes), thereby improving the consistency of the grid and the accuracy of the finite element solution. Through triangular subdivision that meets mathematical optimality, the edge length and angle of each element can be automatically adjusted, reducing the need for manual intervention in local processing and improving the automation level of complex geometry grid generation. The analytical form of the shape function is used to provide a basis for the stiffness matrix and mass matrix of the elements in subsequent finite element calculations, avoiding instability problems that may be caused by strong nonlinearity calculations.

[0044] Further, a target function is defined with the goal of lightweight, a topology optimization constraint is constructed by a shape function, a lightweight model is obtained by solving the target function using SIMP, and an initial material density is set for each tetrahedral element , 0 ≤ ≤ 1, which is between 0 (no material) and (complete filling of material), and forms an element density matrix , a target function is defined based on the element density matrix with the goal of lightweight :

[0045] where is the total volume of all tetrahedral elements, and V is the integral variable; The partial derivative is obtained according to the node shape function to obtain the strain-displacement matrix of the tetrahedral element :

[0046] where , and are the partial derivatives of the shape function with respect to the geometric coordinates in the element coordinate system, and n is the number of nodes of the quadrilateral element; The strain-displacement matrices of all tetrahedral elements are combined to form a global strain-displacement matrix P, and the reference stiffness matrix of each element is generated simultaneously according to the strain-displacement matrix of each tetrahedral element : ​

[0047] where T is the transpose operation, E is the material elasticity matrix, which depends on the Young's modulus and Poisson's ratio of the material; Calculate the global stiffness matrix K according to the reference stiffness matrix:

[0048] where A is the number of tetrahedral elements, is the density of the th tetrahedral element, p is the penalty factor; Calculate the global load distribution F according to the shape function:

[0049] where is the load density vector (body force, calculated by density and gravitational acceleration); Get the global stiffness matrix K and the global load distribution F, and solve the global displacement vector U by the finite element method:

[0050] Derive the element strain tensor from the global displacement vector U, and add stress constraints to all tetrahedral elements:

[0051] where is the material element stress, is the Young's modulus of the material, is the minimum yield stress; Synchronously add volume constraints:

[0052] where is the maximum material volume allowed to be retained in the design; Minimize the objective function on the basis of meeting the stress constraints and volume constraints by using the SIMP method In the optimization process, update the element density iteratively:

[0053] where is the material density of the th tetrahedral element in the th iteration, is the step factor; Stop iteration after meeting the objective function convergence, and output the lightweight model according to the density after iteration.

[0054] By constructing the element strain-displacement matrix and gradually constructing the global strain-displacement matrix and the global stiffness matrix from the element matrix, the coordination between elements can be ensured, and the problem of global performance degradation caused by local performance optimization in the traditional method can be avoided. The linearization of the strain-displacement matrix can improve the accuracy of the overall calculation, especially when lightweight design is performed, the change of system performance is more accurate and reliable, and the optimization has good retention characteristics. The stress limiting condition can effectively avoid the occurrence of high stress points in the local area that exceed the allowable range of material strength, thereby ensuring the service life of the optimization model and reducing the risk of failure. By converting the material density iterative update into a mathematical optimization process through the SIMP method, the global optimal density distribution can be systematically found, greatly reducing the trial and error time. The combination of the penalty factor and the volume limit makes the optimization result have high precision of material distribution rationality, while meeting the actual needs of the manufacturing process.

[0055] S3, output the lightweight model in a format for display and storage in a database. Specifically, outputting the lightweight model in a format for display refers to outputting the lightweight model as a STEP format three-dimensional file and displaying it to the designer.

[0056] Further, storage in the database refers to storing the obtained lightweight model in the design database and assigning a timestamp to generate a design log for storage.

[0057] The embodiment also provides a mechanical digital design three-dimensional model building system, comprising: The design analysis module is configured to obtain a mechanical design motion path, correct the motion path through a curvature smoothing algorithm, determine a mechanical motion space boundary, generate a motion curved surface envelope according to the motion path and the space boundary, and generate a final envelope after compensation. The model generation module is configured to divide the final envelope into finite element units using a tetrahedron division algorithm, define a shape function of each unit, define a target function with lightweight design as the target, construct a topology optimization constraint through the shape function, and obtain a lightweight model by solving the target function using the SIMP. The display and storage module is configured to output the lightweight model in a format for display and store the lightweight model in a database.

[0058] The embodiment also provides a computer device suitable for the mechanical digital design three-dimensional model building method, comprising a memory and a processor. The memory is configured to store computer executable instructions, and the processor is configured to execute the computer executable instructions to implement the mechanical digital design three-dimensional model building method proposed in the above embodiment.

[0059] The computer device can be a terminal, and the computer device includes a processor, a memory, a communication interface, a display screen and an input device connected by a system bus. The processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for running the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is configured to perform wired or wireless communication with an external terminal. The wireless communication can be achieved by WIFI, an operator network, NFC (Near Field Communication) or other technologies. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device can be a touch layer overlaid on the display screen, or a key, trackball or touchpad arranged on the shell of the computer device. In addition, the input device can be an external keyboard, touchpad or mouse, etc.

[0060] The embodiment also provides a storage medium having a computer program stored thereon, the program being executed by a processor to implement the method for building a three-dimensional model of mechanical digital design proposed in the above embodiment. The storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as a static random access memory (SRAM), an electrically erasable programmable read-only memory (EEPROM), an erasable programmable read-only memory (EPROM), a programmable read-only memory (PROM), a read-only memory (ROM), a magnetic storage, a flash memory, a magnetic disk or an optical disk.

[0061] In summary, by obtaining a mechanical design motion path, the mechanical design envelope surface is obtained by using curvature smoothing correction combined with motion envelope generation. By combining the finite element division with the lightweight target setting optimization function and constraint condition, the efficient, accurate and lightweight target of complex mechanical three-dimensional design is effectively realized, and the adaptability and flexibility of mechanical design are improved.

[0062] It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced, without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A method for constructing a three-dimensional model for mechanical digital design, characterized by: include, Obtain the mechanical design motion path and correct it through the curvature smoothing algorithm to determine the mechanical motion space boundary. Generate the motion surface envelope based on the motion path and space boundary and perform compensation to generate the final envelope. Use the tetrahedron partitioning algorithm to divide the final envelope into finite element units and define the shape function of each unit. Define the objective function with lightweight as the goal, construct topology optimization constraints through the shape function, and use SIMP to solve the objective function to obtain a lightweight model. After obtaining the lightweight model, it is output in the format for display and stored in the database.

2. The method for constructing a three-dimensional model for mechanical digital design according to claim 1, wherein: The obtaining of the mechanical design motion path and the correction thereof through the curvature smoothing algorithm, and the determination of the mechanical motion space boundary refer to inputting the mechanical motion requirement parameters according to the mechanical design requirements to generate the mechanical motion path. , based on a fixed time interval The motion path Discretize into a continuous point set , calculate the point set The curvature of each discrete point in ; When the discrete point curvature When the curvature threshold is exceeded, the discrete point is regarded as a high curvature point, and new path points are added around the high curvature point through cubic spline interpolation. After adding the new path points, the discrete points are sorted and output as a new discrete point set, and the boundary B of the mechanical motion space is determined according to the discrete point set.

3. The method for constructing a three-dimensional model for mechanical digital design according to claim 2, wherein: Generating a motion surface envelope according to the motion path and the spatial boundary and performing compensation to generate the final envelope refers to constructing a simple initial surface by combining the minimum bounding box of the mechanical motion space boundary B with isometric expansion, taking the surface points as the initial envelope points M, and calculating the minimum distance from the new discrete point set to the initial envelope points as the error function E; Add smoothness constraints and thickness constraints to the error function; Take all envelope points on the initial surface as the initial optimization variable X, calculate the error function value for the initial optimization variable, and calculate the gradient of the objective function with respect to the current initial optimization variable through the error function value; Update the initial optimization variable X according to the L-BFGS algorithm update rule, stop the optimization when the convergence condition is met, and extract the optimized envelope point Forming an optimized envelope surface; Calculate mechanical motion speed based on discrete point distance ; and calculating the gap adjustment value for the optimized envelope point; The optimized envelope points are adjusted according to the gap adjustment value to generate the final envelope points and form the final envelope surface.

4. The method for constructing a three-dimensional model for mechanical digital design according to claim 3, wherein: The final envelope is divided into finite element units using a tetrahedron partitioning algorithm and the shape function of each unit is defined. The curvature of the envelope point is calculated according to the final envelope surface and the average curvature of all envelope points is calculated. , using adaptive meshing to adjust the mesh size based on the curvature ; Based on the mesh size l, the geometry formed by the final envelope surface is divided into tetrahedral units using the Delaunay triangulation method. Each tetrahedral unit consists of 4 vertex nodes and 6 edges. The quality of the divided tetrahedral units is checked. For each tetrahedral element, set the coordinates of the four vertex nodes to be 、 、 as well as , the node shape function of the tetrahedral element is defined by the linear interpolation function .

5. The method for constructing a three-dimensional model for mechanical digital design according to claim 4, wherein: The objective function is defined with lightweight as the goal, topology optimization constraints are constructed through shape functions, and SIMP is used to solve the objective function to obtain a lightweight model, which means setting the initial material density for each tetrahedral unit. , and form a cell density matrix , based on the unit density matrix, the objective function is defined with lightweight as the goal for; According to the node shape function Find the partial derivatives to obtain the strain-displacement matrix of the tetrahedral element ; The strain-displacement matrices of all tetrahedral elements are combined into a global strain-displacement matrix P, and the strain-displacement matrix of each tetrahedral element is synchronized. Generate a base stiffness matrix for each element ; Calculate the global stiffness matrix K based on the reference stiffness matrix; Calculate the global load distribution F based on the shape function; The global stiffness matrix K and global load distribution F are obtained and solved by the finite element method to obtain the global displacement vector U; The element strain tensor is derived from the global displacement vector U And add stress limits to all tetrahedral elements; Add volume limit simultaneously; The SIMP method is used to minimize the objective function while satisfying stress and volume constraints. ,During the optimization process, the cell density is iteratively updated; The iteration is stopped after the objective function converges, and the lightweight model is output according to the density after the iteration.

6. The method for constructing a three-dimensional model for mechanical digital design according to claim 5, wherein: Outputting the obtained lightweight model in a format for display means outputting the lightweight model as a three-dimensional file in a STEP format and displaying it to designers.

7. The method for constructing a three-dimensional model for mechanical digital design according to claim 6, wherein: The storing in the database refers to storing the obtained lightweight model in the design database, and assigning a timestamp to generate a design log for storage.

8. A system for constructing a three-dimensional model for a digitalized mechanical design, based on the method for constructing a three-dimensional model for a digitalized mechanical design according to any one of claims 1 to 7, characterized in that: include, The design analysis module is used to obtain the mechanical design motion path and correct it through the curvature smoothing algorithm to determine the mechanical motion space boundary. The motion surface envelope is generated based on the motion path and space boundary, and the final envelope is generated by compensation. The model generation module is used to divide the final envelope into finite element units using the tetrahedron partitioning algorithm and define the shape function of each unit. The objective function is defined with lightweight as the goal, topology optimization constraints are constructed through the shape function, and SIMP is used to solve the objective function to obtain a lightweight model. The display and storage module is used to obtain the lightweight model, output it in a format, display it, and store it in the database.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method for building a three-dimensional model for mechanical digital design are implemented as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for building a three-dimensional model of a mechanical digital design are implemented as described in any one of claims 1 to 7.

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