Topological optimization method of heterogeneous material connecting component considering interface anisotropic stress constraint, product

Abstract

The present application relates to the technical field of structural optimization design, and particularly relates to a heterogeneous material connecting component topology optimization method considering interface anisotropic stress constraint and a product, taking a metal connecting component as a design domain and a fiber reinforced composite material product as a monitoring domain, a topology optimization model with system stiffness maximization as a target is constructed; the interface stress is decoupled into four independent failure factors of fiber tension, fiber compression, matrix tension and matrix compression by using Chang-Chang criterion; a P-norm aggregation operator is introduced to smooth and aggregate local failure factors into a global equivalent failure scalar, and a safety upper limit is set as a hard nonlinear constraint and is incorporated into the optimization model; analytical derivatives are solved based on the adjoint variable method, and a spatial truss type force transmission path composed of a plane stress buffer plate and a sub-guide reinforcing rib is adaptively formed at the interface of the metal component. The present application solves the problem of stress concentration and early damage caused by modulus mismatch of the heterogeneous interface, and improves the system ultimate bearing capacity under the same quality.

Description

Technical Field

[0001] This invention relates to the field of structural optimization design and mechanical force transmission system design technology, specifically to a method and product for topology optimization of heterogeneous material connection components considering anisotropic stress constraints at the interface. Background Technology

[0002] In the lightweighting evolution of modern high-end equipment manufacturing, vehicle engineering, and aerospace, fiber-reinforced polymer (FRP) composites are gradually replacing traditional metal materials and being widely used in main load-bearing structures due to their extremely high specific strength, specific stiffness, excellent fatigue resistance, and corrosion resistance. However, as a complete mechanical force transmission system, composite material components often cannot exist in isolation and must be combined with the main system frame through metal connecting brackets or mechanical joints. The connection nodes of such heterogeneous materials (high-strength metals and anisotropic composite materials) are the hubs for the transmission of complex multiaxial loads and are also the core constraints on the stiffness matching and collision energy distribution of the entire system. Existing continuum topology optimization techniques have revealed serious theoretical limitations and engineering defects when dealing with such heterogeneous connection structures.

[0003] First, the severe mismatch in mechanical moduli at the interface of heterogeneous materials leads to intense local contact stress concentration. Traditional topology optimization mostly uses "minimizing flexibility (maximizing overall system stiffness)" as the sole optimization objective. When dealing with the design of metal connection supports, the algorithm automatically drives high-strength metals towards extreme rigidity. However, the elastic modulus of high-strength metals is typically around 210 GPa, while the transverse compressive modulus of continuous glass fiber or carbon fiber reinforced composites is often only 10 to 20 GPa. This huge modulus gap results in highly inconsistent deformation at the metal-composite interface under load, with the load highly concentrated at abrupt changes such as the edges of the metal support and bolt holes. The interlaminar shear strength of composite materials is usually low, making them extremely sensitive to local contact stress. Under this stress concentration, the FRP component has not yet exerted its overall bending resistance performance before premature failure such as hole edge crushing yield, matrix crushing, or interlaminar tearing occurs at the connection ends.

[0004] Secondly, there is a very high mathematical barrier to integration between multi-mode physical failure assessment of composite materials and local stress constraints in topology optimization. Currently, most commercial topology optimization software only incorporates the Von-Mises yield criterion based on the material isotropic assumption. Using this criterion to assess composite materials completely ignores the fundamental differences in the load-bearing mechanisms between fibers and the resin matrix. Although some existing patents (such as Chinese patent CN118280485A) attempt to introduce the Tsai-Hill failure criterion into topology optimization, the overall phenomenological criteria such as Tsai-Hill or Tsai-Wu use a single closed quadratic envelope, which cannot distinguish between fiber fracture and matrix cracking, often giving extremely conservative predictions and limiting the potential for lightweight structures. To achieve accurate evolution, it is necessary to introduce a physical mechanism decoupled failure criterion that can distinguish between different failure modes. However, introducing local stress constraints in topology optimization faces three major recognized numerical computation challenges: first, stress singularities that cannot be completely eliminated by low-density artifact materials; second, the dimensionality explosion problem caused by the stress states of massive local elements, which leads to memory exhaustion in the accompanying sensitivity analysis; and third, the maximum extremum function required to control the worst stress state is mathematically discontinuous and non-differentiable, which undermines the convergence of the solution based on gradient algorithms.

[0005] In summary, existing technologies cannot scientifically balance the accurate decoupling evaluation of complex anisotropic failure mechanisms and the global stability solution in the topology optimization of heterogeneous material structures. There is an urgent need for an interface stress-constrained topology optimization method that can balance the accurate decoupling of anisotropic failure mechanisms and the global stability solution in the topology optimization of heterogeneous material connection structures. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method and product for topology optimization of heterogeneous material connecting components that considers anisotropic stress constraints at the interface. Taking the metal connecting component as the geometric design evolution object, the interface of the connected composite material is set as the response monitoring domain. The Chang-Chang multimode failure response of the local contact at the interface is aggregated into a global equivalent failure scalar through the P-norm and used as a hard nonlinear constraint to drive the topology reconstruction of the metal connecting component.

[0007] This invention is achieved through the following technical solution: A method for topology optimization of heterogeneous material connection components considering anisotropic stress constraints at the interface is provided, comprising the following steps: S1. Modeling and Basic Optimization Model Construction: Establish a finite element model of a heterogeneous assembly containing a design domain of metal connecting components and a monitoring domain of fiber-reinforced composite material parts. For complex load boundaries under multiple working conditions, construct a continuum topology optimization model with the goal of maximizing the macroscopic stiffness of the system and the volume retention rate of the design domain as a constraint. The monitoring domain is a passive response monitoring object and does not participate in material interpolation evolution. S2. Decoupling of interface anisotropic failure: After the finite element analysis corresponding to each optimization iteration is completed, the orthogonal anisotropic stress tensor of the discrete element closely attached to the heterogeneous interface in the monitoring domain is extracted, and the Chang-Chang criterion is used to decouple it into four independent non-negative microscopic failure factors, namely fiber tensile failure factor, fiber compression failure factor, matrix tensile failure factor, and matrix compression failure factor. S3, P-norm global dimensionality reduction: Introducing the P-norm aggregation operator Where N is the total number of composite material units in the interface region. For the j-th failure factor of the i-th unit, the 4N local failure factors are smoothly aggregated into 4 global equivalent failure scalars that correspond one-to-one with the failure modes. S4. Constraint Embedding: Set the safety upper limit of four global equivalent failure scalars respectively, and incorporate them as hard nonlinear constraints into the optimization model of step S1. Together with the design domain volume constraint, they form the constraint set for iterative solution. S5. Analytical Derivative-Driven Evolution: Based on the adjoint variable method, the analytical derivative of the global equivalent failure scalar with respect to the relative density of the element material in the metal design domain is solved. This drives the stiffness redistribution and material rearrangement of the metal connection component at adjacent joint surfaces until the volume constraint and the four interface failure constraints are satisfied, and then the iteration converges, outputting the three-dimensional geometric configuration of the metal connection component.

[0008] Furthermore, in step S1, the optimization model adopts the SIMP interpolation material penalty model, with the optimization objective being to minimize the total system flexibility.

[0009] Furthermore, in step S2, the four micro-failure factors are calculated as follows: Extract the longitudinal normal stress σ of the interface element in the fiber local coordinate system. 11 Transverse normal stress σ 22 In-plane shear stress τ 12 Combined with fiber tensile strength Fiber compressive strength Matrix tensile strength Matrix compressive strength In-plane shear strength S 12 Calculated according to the following branches: Fiber tensile failure factor (when hour): ; Fiber compression failure factor (when hour): ; Matrix tensile failure factor (when hour): ; Matrix compression failure factor (when hour): ; Where β is the shear correction coefficient.

[0010] Preferably, in step S3, the polymerization penalty constant P is limited to a finite value by balancing convergence stability and extreme value approximation error, and satisfies 6≤P≤10.

[0011] Preferably, in step S4, the safety limit is 0.9.

[0012] Furthermore, in step S1, for complex load boundaries under multiple working conditions, the specific steps include: performing pairwise comparisons based on the intensity of interface stress concentration under each working condition, setting a weighted distribution vector for multiple working conditions, and setting the basic objective as minimizing the total strain energy of the weighted system.

[0013] Furthermore, weight priorities are set, specifically including: setting the loading condition that generates the maximum bending moment and has a high risk of connection failure as the highest priority and assigning the largest weight; setting the loading condition that bears vertical shear load as the medium priority and assigning the second largest weight; and setting the loading condition used to check lateral stability as the lowest priority and assigning the smallest weight.

[0014] Furthermore, when steps S2 and S3 are executed in the kernel of the general finite element industrial solver, the contact boundary of heterogeneous materials is automatically traversed through the external script, the underlying response extraction control cards are generated in batches, the internal analytical equation cards are dynamically constructed, the Chang-Chang failure factor calculation logic and the P-norm aggregation operator are written resident into the solver kernel, and the composite response constraint association card is established, so that the interface constraint response and local element stress state are automatically updated in a closed loop during each iteration of differentiation.

[0015] Furthermore, after outputting the three-dimensional geometric configuration in step S5, the following steps are also included: The continuous density field profile obtained by stress constraint evolution is spline smoothed and rounded and reconstructed into a solid. The cross-sectional thickness and feature dimensions of the reconstructed model are extracted as parameters. Based on the global response surface proxy model, parameterized multidisciplinary size search and plate thickness matching are performed to output a solid model that conforms to the mechanical mold forming specifications.

[0016] This invention also provides a metal and fiber-reinforced composite material heterogeneous connection skeleton unit obtained by a topology optimization method for heterogeneous material connection components that considers anisotropic stress constraints at the interface. The unit includes a high-strength metal main load-bearing support and a fiber-reinforced composite material component connected to it by fasteners. The main load-bearing support has an integrally formed planar stress buffer plate that conforms to the surface contour of the composite material near the transition area of ​​the interface between the main load-bearing support and the fastening hole. The stress buffer plate has several branch reinforcing ribs that extend to the main force transmission path connected to the side facing away from the interface. The planar stress buffer plate and the branch reinforcing ribs together form a spatial truss-type force transmission path that disperses and transmits the shear load around the fastening hole to the main skeleton. The buffer plate suppresses local matrix crushing at the interface by increasing the contact bearing area.

[0017] The beneficial effects of this invention are: I. To address the shortcomings of traditional single-stiffness optimization, which leads to extreme rigidity of metal components and neglects interfacial modulus mismatch, this invention sets the composite material interface as a passive monitoring domain and the metal component as an active design domain. Anisotropic interfacial stress constraints are introduced into the optimization model to guide the metal material to adaptively form stress buffer plates and distributed reinforcing ribs around the fastening holes. This structure actively reduces the local stiffness gradient, distributing concentrated shear loads to the main frame and reducing the risk of matrix crushing at the FRP hole edges. Under the same mass conditions, the ultimate bearing capacity is improved, the ultimate failure displacement is reduced, and the initial stiffness of the system is significantly improved. This achieves active control over the interfacial modulus mismatch of heterogeneous materials, significantly enhancing the system's ultimate bearing capacity.

[0018] Second, compared with the existing phenomenological criteria such as Tsai-Hill / Tsai-Wu (which use a single closed curve envelope and cannot distinguish between fiber fracture and matrix cracking), this invention introduces the Chang-Chang failure evaluation method based on physical mechanism separation into the topology optimization framework. This method decouples interface failure into four independent modes: fiber tension and compression, matrix tension and compression. It can accurately identify the weakest failure mode of the current structure (such as matrix crushing at the hole edge) and drive the topological reconstruction of the metal material accordingly. This avoids over-design caused by conservative criteria, fully utilizes the potential for lightweighting, breaks through the conservative limitations of phenomenological criteria, and achieves precise targeted suppression of composite material failure modes. Third, to address the inherent challenges of "stress singularity," "dimensional explosion," and "non-differentiability of extrema" in local stress constraints, this invention introduces a P-norm aggregation operator to smoothly aggregate 4N local failure factors in the interface region into four continuously differentiable global scalar responses. This strategy not only reduces numerical oscillations caused by local extrema responses and improves the stability of the optimization process, but also reduces the number of constraints from tens of thousands to four, while ensuring that the gradient information is fully analytically differentiable, enabling stable convergence of topology optimization for large-scale industrial-grade finite element models (including nonlinear contacts).

[0019] Fourth, this invention proposes an automated closed-loop architecture based on card response mapping, which allows the method to be directly embedded into existing engineering design processes. Existing commercial software usually lacks a direct configuration method for this type of topology optimization process. This invention can reduce the amount of manual configuration work, provide an automated closed-loop solution with functions that are natively missing in commercial solvers, and significantly lower the threshold for engineering applications. Attached Figure Description Figure 1 This is a flowchart illustrating the topology optimization method for fiber-reinforced composite material connecting members considering stress constraints, as described in this invention.

[0020] Figure 2 This invention provides a finite element analysis model and boundary condition diagram of a front underrun protection system for commercial vehicles.

[0021] Figure 3 This is a schematic diagram of the topology configuration considering stress constraints, generated after multi-condition foundation stiffness target calculation in an embodiment of the present invention.

[0022] Figure 4 This is a comparison curve of the bearing capacity-displacement between the embodiment of the present invention and the traditional unconstrained optimization scheme under extreme bearing conditions. Detailed Implementation

[0023] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to describe the solution.

[0024] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings. This embodiment uses the design process of a "heterogeneous node connecting a continuous glass fiber reinforced composite beam and a dual-phase high-strength steel DP780 support bracket" as a case study, and its finite element analysis model and boundary conditions are as follows: Figure 2 As shown, however, the scope of protection of this invention is not limited to this specific product.

[0025] like Figure 1 As shown, the present invention provides a topology optimization method for heterogeneous material connection components considering anisotropic stress constraints at the interface, comprising the following steps S1 to S5.

[0026] S1. Modeling and Construction of Basic Optimization Model: A finite element model of a heterogeneous assembly was established, comprising a design domain for the metal connecting components and a monitoring domain for the fiber-reinforced composite material components. The region containing the metal connecting components (DP780 steel brackets) was defined as the design domain, while the region containing the fiber-reinforced composite material components (glass fiber beams) was defined as the monitoring domain. The monitoring domain has fixed material properties and does not participate in interpolation evolution. The design domain employs a SIMP interpolation material penalty model, with the optimization objective of minimizing the overall system flexibility (i.e., maximizing the system's macroscopic stiffness) and constrained by the design domain volume retention rate, thus constructing a continuum topology optimization basic model.

[0027] To verify the effectiveness of the method of this invention, a finite element model of a heterogeneous structure consisting of a composite material beam and a metal connecting bracket was established, as follows: Figure 2 As shown. The model is discretized using three-dimensional solid elements with an element size of 10 mm, containing a total of 28,564 nodes and 130,660 elements. The metal connecting bracket adopts an isotropic linear elastic material model with a material density of 7.8 × 10⁻⁻⁻⁶. 9 The continuous glass fiber reinforced composite material has a density of 2 × 10⁻³ t·mm⁻³, an elastic modulus of 210 GPa, and a Poisson's ratio of 0.3. It adopts an orthotropic material model with the fiber direction along the component axis and a material density of 2 × 10⁻³ t·mm⁻³. 9 The elastic modulus is t·mm⁻³, with a longitudinal elastic modulus of 50 GPa, a transverse elastic modulus of 14 GPa, a shear modulus of 8 GPa, and a principal Poisson's ratio of 0.27. The metal connecting bracket and the composite material component adopt a surface-to-surface contact relationship, considering both normal contact and tangential friction.

[0028] According to the vehicle structure load-bearing test specifications, multiple loading conditions were set up, and static loads of different directions and levels were applied at positions P1, P2, and P3. P1 and P2 were used to simulate the ultimate load-bearing condition, while P3 was used for structural failure verification. The finite element analysis results were used to extract the stress response in the neighborhood of the composite material interface and further used for topology optimization constraint evaluation.

[0029] In practical engineering, connection nodes often bear complex multi-axis loads. Therefore, the Analytic Hierarchy Process (AHP) can be introduced to weight multiple load cases. Three typical ultimate physical loading conditions are selected (e.g., ultimate bending P1, severe vertical shear P2, and lateral instability check P3). By constructing a risk importance judgment matrix A with a scale of 1-9, their characteristic equations are solved. The eigenvector corresponding to the largest eigenvalue is normalized to obtain the working condition weight vector W. This weight is effective when the consistency ratio CR < 0.1 (in this example, the weights are 0.64, 0.26, and 0.10). Then, topology optimization is performed with the initial objective of minimizing the total strain energy of the weighted system.

[0030] Step S2: Decoupling of Interface Anisotropy Failure After each optimization iteration and the completion of the corresponding finite element analysis, the orthogonal anisotropic stress tensor of the discrete elements closely attached to the heterogeneous interface within the monitoring domain is extracted. The global stress is then converted into longitudinal normal stress in the fiber's local material coordinate system. Transverse normal stress and in-plane shear stress The Chang-Chang criterion, which can accurately distinguish different micro-damage mechanisms, is adopted, combined with fiber / matrix extreme strength parameters (fiber tensile strength). Fiber compressive strength Matrix tensile strength Matrix compressive strength In-plane shear strength The failure is decoupled into four independent non-negative microscopic failure factors: Fiber tensile failure factor (when hour): ; Fiber compression failure factor (when hour): ; Matrix tensile failure factor (when hour): ; Matrix compression failure factor (when hour): ; Where β is the shear correction factor, which is typically taken as 0.5. Any factor approaching or reaching 1.0 indicates a fatal failure of the micromode.

[0031] Step S3: P-norm global dimensionality reduction If the interface region contains N units, directly applying local constraints will generate 4N independent constraints, leading to a dimensionality explosion. Therefore, the P-norm aggregation operator is introduced. ;in: For the first Macroscopic global scalar response of a decoupled failure mode Let $P$ be the $j$-th failure factor of the $i$-th unit. The aggregation penalty constant $P$ needs to strike a balance between the accuracy of extreme value approximation and the stability of convergence. Theoretical convergence tests show that the range of $P$ is limited to 6 ≤ $P ≤ 10. Ideally, $P = 8$, as this minimizes the deviation from the local true extreme value and ensures a smooth and stable gradient, effectively eliminating stress singular oscillations caused by low-density artifacts.

[0032] Step S4: Constraint Embedding Safety upper limits are set for the four global equivalent failure scalars mentioned above, which are incorporated into the optimization model of step S1 as hard nonlinear constraints, forming a constraint set for iterative solution together with the design domain volume constraint. A preferred safety upper limit is 0.9, meaning the global failure scalar is allowed to not exceed 0.9, thus reserving a safety margin for the structure.

[0033] Step S5: Analytical Derivative-Driven Evolution Based on the adjoint variable method, the chain rule is used to solve the analytical derivative of the global equivalent failure scalar with respect to the relative density of the element material in the metal design domain: in Let be the relative density of the material in the e-th element; this analytical derivative precisely reflects the sensitivity of interface failure constraints to design variables. Driven by this gradient, the algorithm guides the metal connection component to stiffness redistribution and material rearrangement at adjacent joint surfaces until iterative convergence is achieved, simultaneously satisfying volume constraints and four interface failure constraints. The algorithm then outputs the three-dimensional geometric configuration of the metal connection component, such as... Figure 3 As shown.

[0034] To enable practical operation in industrial solvers such as OptiStruct, a script-based automation mechanism was developed: the script automatically identifies interface boundaries, batches internal analytical equation definition cards (DEQATN) and response composite cards (DRESP2), and implicitly resides all the aforementioned mathematical derivations and discriminants in the solver kernel memory. Guided by these precise gradients, the algorithm keenly captures the stress flow sources that lead to matrix collapse at extreme values ​​in composite materials and controls the redistribution of material density in the metal. This approach reduces the time required for manual programming and debugging from hundreds of hours to minutes of automated operation.

[0035] The three-dimensional geometric configuration output in step S5 is a continuous density field profile. To further meet engineering manufacturing requirements, this profile can be spline-smoothed and rounded and reconstructed into a solid model. The cross-sectional thickness and feature dimensions of the reconstructed model are extracted as parameters. Based on the global response surface proxy model, parametric multidisciplinary dimension search and plate thickness matching are performed, and finally, a solid model that conforms to the mechanical mold forming specifications is output.

[0036] Engineering verification and effect comparison To verify the effectiveness of this invention, under the same upper mass limit (10 kg) and nonlinear contact boundary conditions, static simulations were performed to compare this embodiment (stress constraint optimization) with a conventional compliance optimization model. The optimized metal connection bracket exhibits the following structural characteristics: A wider planar stress buffer plate is adaptively generated around the bolt hole to fit the surface contour of the composite material; Corresponding reinforcing ribs are derived from the force transmission path of the buffer plate and extend to the main force transmission path. The buffer plate and the reinforcing ribs together form a spatial truss-type force transmission path, which disperses the shear load around the fastening hole to the main frame, and suppresses local matrix crushing at the interface by increasing the contact bearing area.

[0037] The performance indicators are compared in Table 1 below, and the mechanical response curves are shown in the figure. Figure 4 As shown: Table 1. Performance Comparison Before and After Interface Stress Constraint Optimization Combination Figure 4Analysis of the results in Table 1 shows that, in the comparative example, due to severe interfacial modulus mismatch, significant contact stress concentration occurred in the initial stage of loading, and early matrix damage appeared at the hole edges of the composite material, resulting in premature attenuation of the system stiffness, manifesting as failure under large deformation (16 mm) and low load (62 kN); the embodiment of the present invention, through the stress dispersion effect of the metal buffer region, alleviated the local high shear stress concentration and significantly improved the initial stiffness of the system. Figure 4 The slope of the curve is significantly improved, avoiding early crushing at the joint edges of the composite material, thus enabling its overall load-bearing capacity to reach 76kN. This result verifies the accuracy and engineering applicability of this invention in the lightweight optimization of heterogeneous structure connections. It should be noted that the two sets of peak contact stresses correspond to the load levels at which their respective structures reach their ultimate load-bearing state. In the embodiment of this invention, when the ultimate load-bearing capacity is increased from 62kN to 76kN, the peak contact stress only increases from 681MPa to 708MPa, indicating that the increase in interface stress is effectively suppressed during the improvement of the structural load-bearing capacity.

[0038] Of course, the above description is not limited to the examples above. Technical features not described in this invention can be implemented by or using existing technology, and will not be repeated here. The above embodiments and drawings are only used to illustrate the technical solutions of this invention and are not intended to limit this invention. This invention has been described in detail with reference to preferred embodiments. Those skilled in the art should understand that any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this invention do not depart from the spirit of this invention and should also fall within the scope of protection of the claims of this invention.

Claims

1. A topology optimization method for heterogeneous material connection components considering anisotropic stress constraints at the interface, characterized in that: Includes the following steps: S1. Modeling and Basic Optimization Model Construction: Establish a finite element model of a heterogeneous assembly containing a design domain of metal connecting components and a monitoring domain of fiber-reinforced composite material parts. For complex load boundaries under multiple working conditions, construct a continuum topology optimization model with the goal of maximizing the macroscopic stiffness of the system and the volume retention rate of the design domain as a constraint. The monitoring domain is a passive response monitoring object and does not participate in material interpolation evolution. S2. Decoupling of interface anisotropic failure: After the finite element analysis corresponding to each optimization iteration is completed, the orthogonal anisotropic stress tensor of the discrete element closely attached to the heterogeneous interface in the monitoring domain is extracted, and the Chang-Chang criterion is used to decouple it into four independent non-negative microscopic failure factors, namely fiber tensile failure factor, fiber compression failure factor, matrix tensile failure factor, and matrix compression failure factor. S3, P-norm global dimensionality reduction: Introducing the P-norm aggregation operator Where N is the total number of composite material units in the interface region. For the j-th failure factor of the i-th unit, the 4N local failure factors are smoothly aggregated into 4 global equivalent failure scalars that correspond one-to-one with the failure modes. S4. Constraint Embedding: Set the safety upper limit of four global equivalent failure scalars respectively, and incorporate them as hard nonlinear constraints into the optimization model of step S1. Together with the design domain volume constraint, they form the constraint set for iterative solution. S5. Analytical Derivative-Driven Evolution: Based on the adjoint variable method, the analytical derivative of the global equivalent failure scalar with respect to the relative density of the element material in the metal design domain is solved. This drives the stiffness redistribution and material rearrangement of the metal connection component at adjacent joint surfaces until the volume constraint and the four interface failure constraints are satisfied, and then the iteration converges, outputting the three-dimensional geometric configuration of the metal connection component.

2. The method for topology optimization of heterogeneous material connection components considering anisotropic stress constraints at the interface as described in claim 1, characterized in that: In step S1, the optimization model adopts the SIMP interpolation material penalty model, with the goal of minimizing the total system flexibility.

3. The topology optimization method for heterogeneous material connection components considering anisotropic stress constraints at the interface as described in claim 1, characterized in that: In step S2, the four micro-failure factors are calculated as follows: Extract the longitudinal normal stress σ of the interface element in the fiber local coordinate system. 11 Transverse normal stress σ 22 In-plane shear stress τ 12 Combined with fiber tensile strength , fiber compressive strength Matrix tensile strength Matrix compressive strength In-plane shear strength S 12 Calculated according to the following branches: Fiber tensile failure factor (when hour): ; Fiber compression failure factor (when hour): ; Matrix tensile failure factor (when hour): ; Matrix compression failure factor (when hour): ; Where β is the shear correction coefficient.

4. The method for topology optimization of heterogeneous material connection components considering anisotropic stress constraints at the interface as described in claim 1, characterized in that: In step S3, the aggregation penalty constant P is limited to a finite value by balancing convergence stability and extreme value approximation error, and satisfies 6≤P≤10.

5. The method for topology optimization of heterogeneous material connection components considering anisotropic stress constraints at the interface as described in claim 1, characterized in that: In step S4, the safety limit is 0.

9.

6. The method for topology optimization of heterogeneous material connection components considering anisotropic stress constraints at the interface according to claim 1, characterized in that: In step S1, for complex load boundaries under multiple working conditions, the specific steps include: performing pairwise comparisons based on the intensity of interface stress concentration under each working condition, setting a weighted distribution vector for multiple working conditions, and setting the basic objective as minimizing the total strain energy of the weighted system.

7. The method for topology optimization of heterogeneous material connection components considering anisotropic stress constraints at the interface as described in claim 6, characterized in that: The weighting priority is set as follows: the loading condition that generates the maximum bending moment and has a high risk of connection failure is set as the highest priority and given the largest weight; the loading condition that bears vertical shear load is set as the medium priority and given the second largest weight; and the loading condition used to check lateral stability is set as the lowest priority and given the smallest weight.

8. The method for topology optimization of heterogeneous material connection components considering anisotropic stress constraints at the interface according to claim 1, characterized in that: When steps S2 and S3 are executed in the kernel of the general finite element industrial solver, the contact boundary of heterogeneous materials is automatically traversed through the external script, the underlying response extraction control cards are generated in batches, the internal analytical equation cards are dynamically constructed, the Chang-Chang failure factor calculation logic and the P-norm aggregation operator are written into the solver kernel, and the composite response constraint association card is established, so that the interface constraint response and local element stress state are automatically updated in a closed loop during each iteration of differentiation.

9. The method for topology optimization of heterogeneous material connection components considering anisotropic stress constraints at the interface according to claim 1, characterized in that: After outputting the three-dimensional geometric configuration in step S5, the following steps are also included: performing spline smoothing and rounding on the continuous density field profile obtained by stress constraint evolution and solid reconstruction; extracting the cross-sectional thickness and feature dimensions of the reconstructed model as parameters; performing parameterized multidisciplinary size search and plate thickness matching based on the global response surface proxy model; and outputting a solid model that conforms to the mechanical mold forming specifications.

10. A heterogeneous connection skeleton unit of metal and fiber reinforced composite material obtained by the topology optimization method for heterogeneous material connection components considering anisotropic stress constraints at the interface as described in any one of claims 1 to 9, comprising a high-strength metal main load-bearing bracket and a fiber reinforced composite material component connected thereto by fasteners, wherein the main load-bearing bracket has an integrally formed planar stress buffer plate conforming to the surface contour of the composite material near the transition area of ​​the interface of the composite material component and the periphery of the fastening hole; the stress buffer plate has a plurality of branch reinforcing ribs extending to the main force transmission path connected on the side opposite to the interface; the planar stress buffer plate and the branch reinforcing ribs together constitute a spatial truss-type force transmission path that disperses and transmits the shear load around the fastening hole to the main skeleton, and the buffer plate suppresses local matrix crushing at the interface by increasing the contact bearing area.

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