A composite material vehicle frame layer mechanical property rapid simulation verification method

Abstract

The application discloses a kind of composite material frame layering mechanical property rapid simulation verification method, it is related to composite material structure mechanics simulation technical field.The method includes: S1 imports geometry model and layering design data, is marked key joint with conventional layering area by region analysis, constructs global partition parameter dataset;S2 is generated equivalent stiffness matrix based on classic laminated plate theory conventional layering area;S3 key joint area is dispersed into subdomain, and its equivalent stiffness matrix is inverted by augmented lagrange iteration coordination calculation;S4 assembles frame overall stiffness matrix, obtains overall displacement response using sparse matrix solution algorithm;S5 calculates overall mechanical performance index, combines key joint area stress distribution, generates simulation verification result according to composite material failure criterion.The method greatly improves the calculation efficiency while ensuring the simulation accuracy, provides reliable technical support for the rapid verification and optimization of composite material frame layering design.

Description

Technical Field

[0001] This invention relates to the field of composite material structural mechanics simulation technology, and more specifically, to a rapid simulation verification method for the mechanical properties of composite material vehicle frame plywood. Background Technology

[0002] Composite materials, with their superior properties such as high strength, lightweight, and corrosion resistance, are widely used in the design of vehicle frame structures in the automotive, aerospace, and other fields. As a core load-bearing component, the ply layup design of the vehicle frame directly determines its structural mechanical properties and safety reliability; therefore, simulation verification is necessary to accurately evaluate the ply layup scheme.

[0003] Existing simulation methods for composite material structures mainly fall into two categories: one is global fine-scale simulation, which calculates mechanical properties by dividing the entire frame into high-density meshes and combining them with complex constitutive models. While this can ensure accuracy, it involves a huge amount of computation and is time-consuming. Especially for complex areas such as critical joints, it is prone to problems of low computational efficiency and excessive resource consumption, making it difficult to meet the rapid verification requirements of iterative optimization of plywood design. The other category is simplified equivalent simulation, which improves computational speed by uniformly equivalent processing of the entire structure. However, it ignores the complex connection characteristics and plywood heterogeneity of critical joint areas, resulting in large errors in the simulation results, which cannot accurately reflect the actual mechanical behavior and failure risk of the structure.

[0004] Furthermore, existing methods lack differentiated processing mechanisms for vehicle frame structures. The same simulation strategy is used for critical joint areas and conventional ply areas, either sacrificing accuracy for efficiency or prioritizing accuracy at the expense of timeliness. Simultaneously, a complete technical solution balancing accuracy and efficiency has not yet been developed in areas such as stiffness matrix construction, displacement coordination calculation, and failure criterion application. This makes it difficult to effectively support the rapid iteration and optimization of composite material vehicle frame ply design, limiting the large-scale application of composite materials in vehicle frame structures. Therefore, developing a rapid simulation verification method for the mechanical properties of composite material vehicle frame ply that achieves a balance between accuracy and efficiency has become an urgent need in the industry. Summary of the Invention

[0005] To overcome the aforementioned deficiencies in the prior art, embodiments of the present invention provide a rapid simulation verification method for the mechanical properties of composite material vehicle frame layups. The following solutions address the problems mentioned in the background art regarding the difficulty in balancing accuracy and efficiency in the simulation of the mechanical properties of composite material vehicle frame layups, inaccurate simulation of key areas, and inability to meet the requirements for rapid design verification.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a rapid simulation verification method for the mechanical properties of composite material vehicle frame layup, comprising: S1: importing the geometric model of the composite material vehicle frame and the corresponding layup design data, performing regional analysis on the vehicle frame, identifying and marking key joint areas, marking the remaining areas as regular layup areas, and constructing a global partition parameter dataset containing layup parameters of each area and regional connection relationships;

[0007] S2: For the conventional ply regions, based on classical laminated plate theory, the ply parameters of each conventional region are processed, and an equivalent stiffness matrix of the conventional ply regions is generated.

[0008] S3: For the critical joint region, each critical joint region is discretized into multiple subdomains. The initial displacement field of each subdomain is calculated in the free state of the subdomain, and the displacement coordination error of the subdomain interface is constructed. By introducing a variational solution model with coordination constraints, the displacement field of each subdomain is coordinated and calculated using the augmented Lagrangian iteration method until the interface of each subdomain satisfies the displacement continuity constraint. Based on the coordinated displacement field and the total potential energy of the system, the equivalent stiffness matrix of the corresponding critical joint region is obtained by inversion.

[0009] S4: Based on the region connection relationship, the equivalent stiffness matrix of the conventional ply region and the equivalent stiffness matrix of the key joint region are assembled in a unified manner to construct the overall stiffness matrix of the frame. After applying preset boundary conditions and load conditions, the overall displacement response result of the frame is calculated by the sparse matrix solving algorithm.

[0010] S5: Based on the overall displacement response results of the frame, calculate the overall mechanical performance indicators of the frame, and calculate the internal stress distribution by combining the coordinated displacement field of the key joint area. Then, make a judgment based on the preset composite material failure criteria and generate the corresponding mechanical performance simulation verification results.

[0011] The technical effects and advantages of this invention are as follows:

[0012] 1. This invention adopts a regionally differentiated simulation strategy. The conventional ply region is calculated efficiently based on the classical laminate theory, while the critical joint region is solved with refined coordination through subdomain discretization and augmented Lagrange iteration. This avoids the inefficiency of full-domain refined simulation and overcomes the accuracy defects of traditional simplified simulation. While ensuring that the simulation results are highly consistent with the actual mechanical behavior, it significantly reduces the amount of computation, improves the efficiency of simulation verification, and meets the needs of rapid iteration in ply design.

[0013] 2. This invention addresses the complex connections and heterogeneous layup characteristics of critical joint areas by employing techniques such as subdomain discretization, displacement coordination error construction, and energy equivalent inversion to accurately capture the stress distribution and deformation characteristics within the region. This effectively solves the technical challenge of accurately simulating the mechanical properties of critical joint areas, providing reliable data support for identifying structural weak points and assessing failure risks.

[0014] 3. This invention constructs a complete standardized process from data import, region analysis, stiffness matrix construction, displacement response calculation to failure verification. The design of the global partition parameter dataset realizes the systematic management and rapid retrieval of parameters, adapting to the simulation needs of composite material vehicle frames with different structural forms and layup schemes. At the same time, it presets multiple types of composite material failure criteria, improving the versatility and engineering applicability of the method. It can be widely applied to the design verification of composite material vehicle frames in the automotive, aerospace and other fields. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure method of the present invention;

[0016] Figure 2 This is a schematic diagram of the global partition parameter dataset construction process of the present invention;

[0017] Figure 3 This is a schematic diagram illustrating the process of obtaining the equivalent stiffness matrix of the conventional ply region according to the present invention.

[0018] Figure 4 This is a schematic diagram illustrating the process of obtaining the equivalent stiffness matrix of the key joint area in this invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] As attached Figures 1 to 4 The method shown is a rapid simulation verification method for the mechanical properties of composite material vehicle frame plywood, including:

[0021] S1: Import the geometric model of the composite material frame and the corresponding ply design data, perform regional analysis on the frame, identify and mark the key joint areas, mark the remaining areas as regular ply areas, and construct a global partition parameter dataset containing the ply parameters of each area and the regional connection relationship.

[0022] It should be noted that the geometric model of the composite material frame and the corresponding ply design data are imported, and the frame is then subjected to region analysis. The specific process is as follows:

[0023] Data Import: Import the 3D geometric model of the composite material frame to be simulated and verified, along with the corresponding ply design data. The geometric model adopts common engineering 3D model formats such as STEP and IGES to ensure that the core information such as the model's topology and geometric dimensions are complete and resolvable, accurately reflecting the actual structural form of the frame. The ply design data is standardized data determined during the frame design phase, including the number of ply layers, single-layer ply thickness, ply angle sequence for each part of the frame, as well as basic mechanical parameters such as the elastic modulus, Poisson's ratio, and shear modulus of the composite matrix and reinforcing phase. It supports importing structured formats such as Excel and XML, facilitating subsequent parameter extraction and processing.

[0024] Data preprocessing: The imported geometric model is optimized by removing redundant geometric features that do not affect the calculation of mechanical properties, such as chamfers, small fillets, and process holes. Geometric defects in the model are repaired, and topology reconstruction is performed to ensure the continuity and uniqueness of the topological relationships of the faces, edges, and volumes of the geometric model. Simultaneously, the ply design data is verified and normalized, invalid data is removed, and missing parameters are filled in to ensure the accuracy and completeness of the ply parameters. Then, a unified global coordinate system for the entire frame is established, and the geometric model and ply design data are mapped to this coordinate system to achieve the unification of the coordinate reference between the two and complete the initial data fusion.

[0025] Chassis Region Analysis: Based on the fused geometric model, a global structural region analysis is conducted. First, the geometric model is discretized into several structural units with independent ply parameters and geometric characteristics. The global topological connectivity of each structural unit is extracted, and the connection objects and connection positions of each unit are identified. Then, according to the principles of geometric continuity and consistent ply parameters, the discretized structural units are clustered into several initial regions. The number of connections between each initial region and other external initial regions is counted, and the connection direction orientation information of each connection position is extracted. Finally, the region classification is completed according to the judgment rules. If an initial region is connected to multiple other initial regions at the same time, and the connection direction of the initial region and each of the other initial regions has at least two different orientations, it is judged as a critical joint region. Other initial regions that do not meet this condition are uniformly judged as regular ply regions.

[0026] It should be further explained that the specific process of constructing a global partitioning parameter dataset containing the ply parameters of each region and the region connectivity relationships is as follows:

[0027] Define the dataset framework: use the unique ID of each region as the core index, clarify the classification of the core fields of the dataset, ensure that the parameter information of each region can be quickly retrieved through the index, and reserve extended fields for parameters.

[0028] Core parameter input: According to the dataset framework, the core parameters of each region are entered one by one, focusing on two major categories of key information: First, the ply parameters of each region, specifically including the number of ply layers, single-layer ply thickness, ply angle sequence, ply stacking method, and material mechanical parameters such as the elastic modulus and Poisson's ratio of the composite matrix and the reinforcing phase; Second, the connection relationship parameters of each region, specifically including the adjacent connection region number, connection position coordinates, and structural unit characteristics of the connection parts, clearly representing the topological connection relationship between each region.

[0029] Dataset standardization and storage: All entered parameters are structured and standardized, and an index is established to associate the region number with each parameter field. The consistency and accuracy of the parameters are verified to avoid parameter conflicts. The standardized dataset is converted into a structured format commonly used in engineering, such as CSV and JSON, and stored in association with the partitioned frame geometry model and region marking map to ensure that the three can be accurately mapped through the unique region number.

[0030] It should be further explained that after completing the above process, the identified key joint areas and regular layup areas are uniquely numbered and visually marked, ultimately forming a preprocessed geometric model, area marking results, and global partition parameter dataset.

[0031] S2: For the conventional ply regions, based on classical laminated plate theory, the ply parameters of each conventional region are processed, and an equivalent stiffness matrix of the conventional ply regions is generated.

[0032] It should be noted that the process of obtaining the equivalent stiffness matrix of the conventional ply region is as follows:

[0033] Retrieval and preprocessing of ply parameters for conventional ply regions: Based on the global partition parameter dataset, and according to the unique number of each conventional ply region, the core ply parameters of the corresponding region are accurately retrieved, including the number of ply layers n and the thickness of a single ply t. k (k=1,2,...,n), ply angle sequence θ k (k=1,2,...,n) and the elastic modulus E1, E2, and Poisson's ratio ν of the composite material. 12 Shear modulus G 12 The retrieved parameters are checked for consistency and validity. A unified measurement standard is established and the overall global coordinate system of the frame is anchored. After eliminating abnormal parameters, the thickness direction coordinates are determined with the mid-surface of the laminate as the reference, and the total thickness of the conventional layup area is calculated. At the same time, the upper and lower surface coordinates z of each single layer in the thickness direction are clearly defined. k-1 z k .

[0034] Calculation of the intrinsic stiffness tensor of a single ply in the principal axis coordinate system: Based on classical laminate theory, firstly, in the principal axis coordinate system of the composite single ply (1-2 are the principal axis directions, 1 is the direction of the reinforcing phase fiber, and 2 is the direction perpendicular to the fiber), the intrinsic stiffness matrix Q (stiffness tensor) of each single ply is calculated, which characterizes the inherent mechanical stiffness properties of the single ply in the principal axis directions of the material. The calculation formula is as follows:

[0035] ,in, This satisfies the reciprocal theorem of mechanics of materials.

[0036] Global coordinate transformation of single-ply stiffness matrix: To achieve a coordinate system that integrates the stiffness characteristics of each conventional ply region with the overall mechanical analysis of the frame, a coordinate transformation matrix T(θ) is constructed from the material principal axis coordinate system to the overall global coordinate system of the frame. k ), combined with the ply angle θ of each single ply k (The angle between the fiber direction of the ply and the X-axis of the global coordinate system) Perform a coordinate transformation on the intrinsic stiffness matrix Q to obtain the single-ply stiffness matrix in the global coordinate system. The calculation formula is:

[0037] ,

[0038] Among them, T T (θ k T(θ) is the coordinate transformation matrix. k The transpose of ) The stiffness matrix of the k-th layer in the global coordinate system of the vehicle frame.

[0039] Calculate the core stiffness matrix of the laminate by integrating along the thickness direction: Taking the mid-surface of the laminate in the conventional ply region as the origin of the thickness direction coordinate (z=0), based on the stiffness integration principle of classical laminate theory, calculate the stiffness matrix of each single ply in the global coordinate system along the ply thickness direction. By performing integral accumulation calculations, we obtain the membrane stiffness matrix A, which characterizes the in-plane stress characteristics of the conventional ply region; the membrane-bending coupling stiffness matrix B, which characterizes the in-plane-bending coupling stress characteristics; and the bending stiffness matrix D, which characterizes the bending stress characteristics. The integral calculation formulas for the three types of core stiffness matrices are as follows:

[0040] , ,

[0041] Among them, z k-1 z k Let Q'(z) be the coordinates of the lower and upper surfaces of the k-th layer in the thickness direction, and let Q'(z) be the layer stiffness matrix at z in the thickness direction.

[0042] Integration and Verification of Equivalent Stiffness Matrices for Conventional Ply Regions: Based on the expression of laminated structure stiffness in classical laminate theory, the membrane stiffness matrix A, membrane-bending coupling stiffness matrix B, and bending stiffness matrix D obtained above are integrated in the standard form of block-symmetric matrices to construct the equivalent stiffness matrix K of each conventional ply region in the overall global coordinate system of the vehicle frame. eq This matrix fully encompasses the in-plane tensile, shear, bending, and coupled stiffness characteristics of conventional ply regions, and is the core unit for subsequent assembly of the overall frame stiffness matrix. Its integration form is as follows:

[0043] Among them, B T Let K be the transpose of the membrane-bending coupling stiffness matrix B, ensuring the equivalent stiffness matrix K. eq The symmetry of the matrix is ​​checked; the effectiveness of the integrated equivalent stiffness matrix is ​​verified by checking the symmetry and non-singularity of the matrix, eliminating matrix anomalies caused by parameter errors, and ensuring that it can accurately reflect the actual mechanical stiffness characteristics of the conventional ply regions; finally, the equivalent stiffness matrix K of each conventional ply region is... eq It is stored in association with the global partition parameter dataset and indexed by the unique region number.

[0044] S3: For the critical joint region, each critical joint region is discretized into multiple subdomains. The initial displacement field of each subdomain is calculated in the free state of the subdomain, and the displacement coordination error of the subdomain interface is constructed. By introducing a variational solution model with coordination constraints, the displacement field of each subdomain is coordinated and calculated using the augmented Lagrangian iteration method until the interface of each subdomain satisfies the displacement continuity constraint. Based on the coordinated displacement field and the total potential energy of the system, the equivalent stiffness matrix of the corresponding critical joint region is obtained by inversion.

[0045] It should be noted that the process of obtaining the equivalent stiffness matrix of the key joint region is as follows:

[0046] Key joint region parameter retrieval and subdomain discretization: Based on the global partition parameter dataset, and according to the unique number of each key joint region, retrieve its geometric coordinates, ply parameters, and the elastic modulus E1, E2, and Poisson's ratio ν of the composite material. 12 Shear modulus G 12 And the topological connection relationship of the region; based on its geometric and ply characteristics, each key joint region is discretized into multiple subdomains. Following the principles of geometric continuity, relatively uniform ply parameters, and interface conformity to the stress direction of the structure, all subdomains are numbered i (i=1,2,...,m, where m is the total number of subdomains), the adjacent interfaces and topological relationships of the subdomains are clarified, and the overall global coordinate system of the frame is anchored as the calculation reference.

[0047] Calculation of initial displacement field in free state of subdomains and construction of interface displacement compatibility error: Preset load conditions and local boundary conditions consistent with the overall chassis simulation are applied to each subdomain. Based on the micromechanics theory of composite materials and the finite element method, the initial displacement field of each subdomain in a free state without interface constraints is calculated. The common interface between adjacent subdomains is extracted, the displacement vector on the interface is defined, and the displacement compatibility error e of the subdomain interface is constructed. ij Its core calculation formula is: e ij =u i |Γ ij -u j |Γ ij , where u i |Γ ij u j |Γ ij They are adjacent subdomains i and j at the common interface Γ. ij The displacement vector on, when e ij When =0, adjacent subdomains satisfy the displacement continuity constraint at the common interface, that is, there is no abrupt change in displacement at the interface.

[0048] Construction of a variational solution model incorporating coordination constraints: Using the minimization of the total system potential energy as the variational solution criterion, a system total potential energy functional is constructed, incorporating the strain energy and external force potential energy of each subdomain. To integrate the displacement continuity constraints at the subdomain interfaces into the variational model, Lagrange multipliers are introduced to characterize the generalized forces of the interface constraints, and a penalty factor is used to enhance constraint convergence. An augmented Lagrange functional is constructed, transforming the displacement coordination error into constraint terms and incorporating them into the functional. The core expression is: ,in, Let λ be the total potential energy functional of the system. ij Let μ be a Lagrange multiplier and μ be a positive penalty factor. Let be the Euclidean norm of the displacement compatibility error.

[0049] Compatibility calculation of subdomain displacement field in augmented Lagrange iteration: The augmented Lagrange iterative method is used to calculate the displacement field of the augmented Lagrange functional L(u i ,λ ij The extreme values ​​of μ are solved to achieve coordinated optimization of the displacement fields of each subdomain. First, the iteration parameters are initialized, setting the initial Lagrange multipliers, penalty factor, and displacement coordination error convergence threshold (a commonly used minimum value in engineering, such as 10). -6m), with the initial displacement field of the subdomain as the initial value of the iteration; then, with the iteration parameters fixed, the displacement field of each subdomain is solved, the interface displacement coordination error is updated, and it is determined whether the error is less than the convergence threshold; if it has not converged, the Lagrange multipliers and penalty factor are updated (the penalty factor increases by a fixed amplification factor), and the iteration process is repeated; until the displacement coordination error of all adjacent subdomain interfaces meets the convergence requirement, the iteration terminates, and the subdomain displacement field obtained at this time is the coordinated displacement field that satisfies the interface displacement continuity constraint, and thus the overall displacement field of the key joint area is obtained.

[0050] It should be further explained that the inversion of the equivalent stiffness matrix based on the coordinated displacement field and the total potential energy of the system is carried out in the following specific process:

[0051] Based on the coordinated displacement field, the overall deformation characteristics and total potential energy of the critical joint region under load are calculated: This is based on the coordinated displacement fields of each subdomain obtained after iterative convergence. The overall displacement field of the critical joint region is obtained by integration, and the displacement column vector δ of the boundary nodes of the critical joint region (the core characterization parameter of the overall deformation characteristics) is extracted. At the same time, the strain energy and external potential energy of each subdomain under the coordinated displacement field are calculated, and the strain energy and external potential energy of all subdomains are summed to obtain the total potential energy Π of the system in the critical joint region under the current load. ∗ ;

[0052] Based on the principle of energy equivalence, a correspondence is established between the actual deformation response of the critical joint region and the deformation response of the equivalent uniform region: the critical joint region is equivalent to a uniform anisotropic laminate region (equivalent uniform region) that is completely consistent with the geometry and boundary conditions of the original region. The deformation response of the equivalent uniform region must be consistent with the actual deformation response of the critical joint region. That is, under the same load, the displacement column vector of the boundary node of the equivalent uniform region is exactly the same as the displacement column vector δ of the boundary node of the original critical joint region, ensuring that the deformation states of the two are consistent.

[0053] Under the condition that the actual strain energy in the critical joint region is consistent with the deformation energy of the equivalent uniform region, the equivalent stiffness data characterizing the overall mechanical properties of the critical joint region can be derived: According to the principle of energy equivalence, the actual strain energy U in the critical joint region is... total The deformation energy U of the equivalent uniform region eq Equal (total potential energy of the system Π) ∗ =U total -W, under linear elasticity, W=2U total Therefore, Π ∗ =-U total (To avoid confusion, we directly use strain energy equivalence here), i.e., U total =U eq The deformation energy of the equivalent uniform region satisfies (K)js (The equivalent stiffness matrix of the critical joint region to be determined) is used to transform the energy equivalence relationship and derive the equivalent stiffness data. The core inversion formula is: Where, δ T Let δ be the transpose of the boundary node displacement column vectors. The core data of the equivalent stiffness matrix can be directly obtained through this formula.

[0054] Based on the equivalent stiffness data, an equivalent stiffness matrix for the corresponding critical joint region is constructed: Based on the equivalent stiffness data obtained through the reverse calculation above, and combined with the symmetry characteristics of the composite material stiffness matrix, a complete equivalent stiffness matrix K for the critical joint region is constructed. js The validity of the constructed equivalent stiffness matrix is ​​verified by checking its symmetry and positive definiteness to ensure that it conforms to the mechanical properties of the composite material stiffness matrix and eliminating matrix anomalies caused by iteration or calculation errors. Finally, the equivalent stiffness matrix K of each key joint region is calculated. js It is stored in association with the global partition parameter dataset and indexed by the unique number of the key connector region.

[0055] S4: Based on the region connection relationship, the equivalent stiffness matrix of the conventional ply region and the equivalent stiffness matrix of the key joint region are assembled in a unified manner to construct the overall stiffness matrix of the frame. After applying preset boundary conditions and load conditions, the overall displacement response result of the frame is calculated by the sparse matrix solving algorithm.

[0056] It should be noted that the process for obtaining the overall displacement response result of the vehicle frame is as follows:

[0057] Core stiffness matrix and region connectivity retrieval: Based on the global partition parameter dataset, the equivalent stiffness matrix K of all regular ply regions is accurately retrieved according to the unique number of each region (regular ply region, critical joint region). eq The equivalent stiffness matrix K of all critical joint areas js At the same time, it retrieves the regional connection relationship parameters stored in the dataset, such as the adjacent connection region number, connection position coordinates, and structural unit characteristics of the connection parts, to ensure that the stiffness matrix corresponds one-to-one with the regional connection relationship.

[0058] Unified assembly of the overall frame stiffness matrix: Based on the regional connection relationship, the overall frame stiffness matrix K is completed by using the method of "partition stiffness matrix splicing + connection coupling". total The unified assembly process is as follows:

[0059] First, based on the overall global coordinate system of the chassis, an initial framework for the overall stiffness matrix is ​​established. The size of the dimension of the overall stiffness matrix is ​​determined according to the total number of structural units in all regions, ensuring that the matrix dimension matches the total number of nodes and degrees of freedom of the chassis.

[0060] Secondly, the K of each conventional ply area eq K in each key joint area js Each node is then pieced together according to its corresponding region's node number and placed into the corresponding position in the overall stiffness matrix to ensure that the node coordinates of each region's stiffness matrix are precisely aligned with the node coordinates of the overall matrix.

[0061] Finally, for the connection points of adjacent regions (between conventional ply regions, between conventional ply regions and critical joint regions, and between critical joint regions), the stiffness components of the corresponding connection nodes in the overall stiffness matrix are coupled and corrected based on the connection position coordinates and structural unit characteristics in the regional connection relationships. This eliminates stiffness redundancy or missing values ​​at the connection points, ensuring that the overall stiffness matrix can accurately characterize the connection stiffness characteristics of each region of the frame, ultimately forming a complete overall frame stiffness matrix K. total The overall stiffness matrix is ​​a symmetric sparse matrix, which conforms to the structural mechanical characteristics of composite material vehicle frames.

[0062] Application of preset boundary conditions and load conditions: Based on the actual working scenario of the composite material vehicle frame, preset boundary conditions and load conditions are applied and transformed into a matrix form that matches the overall stiffness matrix. The specific process is as follows:

[0063] Preset boundary conditions are applied: Based on the actual installation method of the chassis (such as fixed support, suspension connection, etc.), the boundary constraint nodes (such as the nodes connecting the chassis and the support) are determined. Displacement constraints are applied to the constraint nodes (such as limiting linear displacement and rotational displacement in the X, Y, and Z directions). The constraint conditions are transformed into a constraint matrix C, and the overall stiffness matrix K is then applied using the constraint matrix. total After making corrections and removing the degrees of freedom in the constraint directions, the overall stiffness matrix K after constraints is obtained. con ;

[0064] Load application: Preset typical load conditions (such as static loads and dynamic driving loads) that the chassis may experience during actual operation. Decompose various loads (such as gravity, support force, and impact forces during driving) into nodal loads in the overall global coordinate system of the chassis according to the principle of mechanical equilibrium, and construct a load column vector F. total Ensure that the magnitude, direction, and location of the load are consistent with the actual working conditions; during load application, ensure that the dimensions of the load column vectors are consistent with the overall stiffness matrix K after constraints. con Dimensional matching.

[0065] Overall displacement response calculation based on sparse matrix solving algorithm: Overall stiffness matrix K of the frame total Since the matrix is ​​symmetric and sparse, a commonly used sparse matrix solving algorithm in engineering is employed to solve the constrained stiffness equation. The core process is as follows:

[0066] The core expression for constructing the stiffness solution equation after constraints is: K con ·δ total =F total , where δ total This is the column vector of the overall displacement response of the chassis (i.e., the overall displacement response result to be determined).

[0067] A sparse matrix solving algorithm is used to iteratively solve the above stiffness equations. During the solution process, the sparsity of the overall stiffness matrix is ​​utilized to optimize the calculation process, reduce the amount of calculation, and improve the solution efficiency, which meets the core requirement of "rapid simulation verification".

[0068] After the solution is completed, the column vector δ of the overall displacement response of the chassis is obtained. total This vector contains the linear and rotational displacement components of all nodes of the chassis in the X, Y, and Z directions in the global coordinate system, which is the overall displacement response result of the chassis.

[0069] S5: Based on the overall displacement response results of the frame, calculate the overall mechanical performance indicators of the frame, and calculate the internal stress distribution by combining the coordinated displacement field of the key joint area. Then, make a judgment based on the preset composite material failure criteria and generate the corresponding mechanical performance simulation verification results.

[0070] It should be noted that the generation process of the mechanical performance simulation verification results is as follows:

[0071] Calculation of overall mechanical performance indicators of the frame: Based on the fundamental principles of composite material structural mechanics and the small deformation assumption, and combining the overall displacement response results with various core data, the key indicators characterizing the overall mechanical properties of the frame are calculated, specifically:

[0072] Overall stiffness index: Based on the constrained overall stiffness matrix K constructed above. con (satisfies the stiffness equation K) con ·δ total =F total ), directly extract K con The core element is decomposed to obtain the linear stiffness in the X, Y, and Z directions (corresponding to K). con Stiffness components along the diagonal direction related to linear displacement) and torsional stiffness about each axis (corresponding to K) con (Stiffness component related to rotational displacement), K conIt is itself the core matrix that characterizes the overall deformation resistance of the frame, and the stiffness values ​​in each direction after its decomposition can be directly compared with the design target stiffness values.

[0073] Overall deformation index: from δ total Extract the linear displacements p, q, r of all nodes in the X, Y, and Z directions in the global coordinate system, as well as the rotational displacement components around each axis. Calculate the values ​​and corresponding positions of the maximum linear displacement and maximum rotational displacement of the entire frame. Pay special attention to the displacement at key stress points such as suspension mounting nodes and regional connection parts to determine whether the deformation is within the allowable range of the project.

[0074] Overall strain index: Based on the small deformation geometry, the overall strain distribution of each region of the frame is calculated from the overall displacement response using the strain-displacement conversion formula. The formula is as follows: , where ε ij p is the strain tensor component. i p j x is the displacement component. i x j The coordinate components are in the global coordinate system; the in-plane normal strain ε is calculated using this formula. x ε y With shear strain γ xy Extract the overall maximum strain value and distribution area, and make a preliminary trend judgment based on the ultimate strain of composite materials; after all indicators are calculated, organize them according to the engineering standard format to form a statistical table of overall mechanical performance indicators of the frame containing numerical values, units, and calculation basis.

[0075] Calculation of stress distribution within the critical joint region: Considering the complex stress distribution, special ply structure, and tendency to become a weak point in the structure of the critical joint region, a refined stress calculation is performed by combining its coordinated displacement field. The specific process is as follows:

[0076] Subdomain strain calculation: Based on the coordinated displacement field of each key joint region subdomain The above-mentioned small deformation strain-displacement conversion formula is adopted. Calculate the in-plane normal strain ε at each point within each subdomain. x ε y With shear strain γ xy In addition to bending strain, the strain distribution at key stress concentration points such as subdomain interfaces, corners, and around connecting holes is calculated to ensure that strain calculations cover all core parts of the critical joint area.

[0077] Subdomain stress calculation: combining the elastic modulus E1, E2, and Poisson's ratio v of the composite material. 12 Shear modulus G 12 and the equivalent stiffness matrix K of the key joint area jsBy utilizing the stress-strain constitutive relationship of composite materials with anisotropy, the strain components of the subdomains are transformed into the corresponding stress components, as shown in the following formula: Where, σ x σ y For in-plane normal stress, τ xy Q is the in-plane shear stress. 11 Q 12 Q 22 Q 66 The intrinsic stiffness matrix components of the composite single-layer (extracted from the intrinsic stiffness matrix Q) are: Q 11 Q is the positive stiffness along the principal axis 1 (fiber direction) of the material. 22 The positive stiffness in the main axis 2 direction (perpendicular to the fiber direction), Q 12 Q is the cross stiffness in the two principal axis directions. 66 The in-plane shear stiffness is given by this formula. The in-plane normal stress, shear stress, and interlayer shear stress of each subdomain are calculated using this formula, clarifying the differences in stress distribution under different ply angles.

[0078] Stress distribution integration: The stress calculation results of each subdomain are integrated and combined with the geometric model of the key joint area to construct an internal stress distribution cloud map, which clearly represents the stress magnitude, direction and distribution law, and highlights the maximum stress value, stress concentration area and corresponding ply position.

[0079] Failure assessment based on pre-defined composite material failure criteria: Combining the anisotropic mechanical properties of composite materials, three types of commonly used composite material failure criteria in engineering are pre-defined. All criteria use the ultimate performance parameters of composite materials in the global partitioned parameter dataset as the judgment threshold. Failure assessments are performed separately for conventional ply regions and critical joint regions to clarify the mechanical safety of the frame ply structure. Specifically:

[0080] Preset failure criteria and core formulas:

[0081] Maximum stress criterion: This criterion determines whether the stress in different directions of each ply exceeds the ultimate stress in the corresponding direction. The core formula is: σ x ≤[σ x ],σ y ≤[σ y ],τ xy ≤[τ xy Among them, [σ] x ]、[σ y [τ] represents the in-plane normal stress limit value. xy [This represents the shear stress limit value; if the stress in any direction exceeds the limit value, the ply is considered to have failed.]

[0082] Maximum strain criterion: This criterion determines whether the strain in different directions of each layer exceeds the ultimate strain in the corresponding direction. The core formula is: ε x≤[ε x ],ε y ≤[ε y ],γ xy ≤[γ xy Among them, [ε] x ]、[ε y ] represents the in-plane normal strain limit value, [γ] xy [This represents the shear strain limit value; if the strain in any direction exceeds the limit value, the ply is considered to have failed.]

[0083] The Tsai-Wu criterion: Taking into account the coupling effect of stress in all directions, it is used to make a comprehensive failure judgment for composite laminates. The core judgment formula is: Where F1 and F2 are first-order intensity coefficients, F 11 F 22 F 66 F 12 These are second-order strength coefficients, all calculated from the ultimate stress parameters of the composite material; when the calculation result is greater than 1, the laminate is judged to have experienced comprehensive failure.

[0084] Failure determination by region: For conventional ply regions, the strain and stress distribution corresponding to the overall displacement response are combined with the above failure criteria to determine whether each ply has failed; for critical joint regions, based on the internal stress distribution data obtained from refined calculations, the stress concentration areas and sub-domain interface areas are comprehensively determined by three criteria, and the failure status (no failure, minor failure, severe failure), failure location, failed ply, and failure type (normal stress failure, shear stress failure, combined failure) are recorded.

[0085] Verification of judgment results: Combine the overall mechanical performance indicators of the frame to analyze the correspondence between the failure area and the area of ​​maximum deformation and maximum stress, and verify the rationality of the judgment results; if large-area or critical part failure occurs, reverse the process of displacement and stress calculation and the accuracy of parameter selection to eliminate misjudgment caused by calculation error.

[0086] It should be further explained that the overall mechanical performance indicators of the frame, the internal stress distribution data of key joint areas, and the failure criterion judgment results are comprehensively integrated to generate standardized simulation verification results of the mechanical performance of composite material frame layups:

[0087] Results Integration: A results system consisting of three major modules is constructed. The first is the overall mechanical performance module, which includes statistical tables of indicators, quantitative comparison analysis of indicators with design targets, and performance compliance judgment. The second is the key area analysis module, which includes stress distribution cloud maps, analysis of the causes of stress concentration areas, strain distribution data, and evaluation of the mechanical properties of key parts. The third is the failure verification module, which includes regional failure judgment results, failure cause analysis, marking of safety hazard locations, and failure risk level assessment.

[0088] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0089] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A rapid simulation verification method for the mechanical properties of composite material vehicle frame plywood, characterized in that, include: S1: Import the geometric model of the composite material frame and the corresponding ply design data, perform regional analysis on the frame, identify and mark the key joint areas, mark the remaining areas as regular ply areas, and construct a global partition parameter dataset containing the ply parameters of each area and the regional connection relationship. S2: For the conventional ply regions, based on classical laminated plate theory, the ply parameters of each conventional region are processed, and an equivalent stiffness matrix of the conventional ply regions is generated. S3: For the critical joint region, each critical joint region is discretized into multiple subdomains. The initial displacement field of each subdomain is calculated in the free state of the subdomain, and the displacement coordination error of the subdomain interface is constructed. By introducing a variational solution model with coordination constraints, the displacement field of each subdomain is coordinated and calculated using the augmented Lagrangian iteration method until the interface of each subdomain satisfies the displacement continuity constraint. Based on the coordinated displacement field and the total potential energy of the system, the equivalent stiffness matrix of the corresponding critical joint region is obtained by inversion. S4: Based on the region connection relationship, the equivalent stiffness matrix of the conventional ply region and the equivalent stiffness matrix of the key joint region are assembled in a unified manner to construct the overall stiffness matrix of the frame. After applying preset boundary conditions and load conditions, the overall displacement response result of the frame is calculated by the sparse matrix solving algorithm. S5: Based on the overall displacement response results of the frame, calculate the overall mechanical performance indicators of the frame, and calculate the internal stress distribution by combining the coordinated displacement field of the key joint area. Then, make a judgment based on the preset composite material failure criteria and generate the corresponding mechanical performance simulation verification results.

2. The rapid simulation verification method for the mechanical properties of composite material vehicle frame layup according to claim 1, characterized in that: The process of the region analysis is as follows: Obtain the global connectivity information of each structural element in the composite material vehicle frame geometric model; Based on the global connectivity information, the number of connections and connection directions of structural units in each region of the statistical geometric model are calculated. When a structural unit in a certain region is connected to multiple other structural units at the same time, and there are at least two different orientations for the connection of structural units in that region, the region is marked as a critical joint region. All areas in the composite frame geometry model that were not marked as critical joint areas were uniformly marked as regular layup areas.

3. The rapid simulation verification method for the mechanical properties of composite material vehicle frame layup according to claim 1, characterized in that: The global partition parameter dataset is a structured dataset, which contains the following information: region category information, geometric range coordinate information, number of ply layers, single-layer ply thickness information, ply angle sequence information, material mechanical parameters of matrix and reinforcing phase, and topological connection information between regions.

4. The rapid simulation verification method for the mechanical properties of composite material vehicle frame layup according to claim 1, characterized in that: The process for obtaining the equivalent stiffness matrix of the conventional ply region is as follows: Based on classical laminate theory, tensor transformation is performed on the mechanical properties of each ply by combining the number of ply layers, ply angle sequence and material mechanical parameters in conventional ply regions. The stiffness contribution of each ply is calculated by integral accumulation along the ply thickness direction; The membrane stiffness matrix reflecting the planar stress characteristics, the bending stiffness matrix reflecting the bending stress characteristics, and the membrane-bending coupling stiffness matrix reflecting the coupling relationship between the plane and bending were obtained respectively. Based on the membrane stiffness matrix, bending stiffness matrix, and membrane-bending coupling stiffness matrix, an equivalent stiffness matrix for the conventional ply region corresponding to the conventional ply region is constructed.

5. The rapid simulation verification method for the mechanical properties of composite material vehicle frame layup according to claim 1, characterized in that: The coordination calculation process is as follows: At the common boundary of each subdomain in the critical joint region, establish displacement consistency constraints between adjacent subdomains; The displacement consistency constraint is incorporated into the variational solution model to construct an overall iterative solution model that includes displacement information and displacement constraint conditions of each subdomain. By using the augmented Lagrange iteration method, the displacement field parameters of each subdomain are continuously adjusted, so that the displacement coordination error of adjacent subdomains at the common boundary is gradually reduced. When the displacement coordination error is less than the preset convergence threshold, it is determined that the displacement continuity constraint is satisfied between each subdomain, and the coordination calculation is completed to obtain the coordinated displacement field.

6. The rapid simulation verification method for the mechanical properties of composite material vehicle frame layup according to claim 1, characterized in that: The process of obtaining the equivalent stiffness matrix of the key joint region is as follows: Based on the coordinated displacement field, the overall deformation characteristics and total potential energy of the system in the key joint area under load are calculated. Based on the principle of energy equivalence, a correspondence is established between the actual deformation response of the critical joint area and the deformation response of the equivalent uniform area. Under the condition that the total potential energy of the actual system in the critical joint area is consistent with the deformation energy of the equivalent uniform area, the equivalent stiffness data characterizing the overall mechanical properties of the critical joint area are derived. Based on the equivalent stiffness data, an equivalent stiffness matrix of the key joint area is constructed.

7. The rapid simulation verification method for the mechanical properties of composite material vehicle frame layup according to claim 1, characterized in that: The overall stiffness matrix of the vehicle frame is constructed as follows: Based on the regional topological connectivity relationships recorded in the global partition parameter dataset, the mechanical degree of freedom information of each region is uniformly encoded and numbered according to the overall coordinate system of the composite material frame. The equivalent stiffness matrix of the conventional ply region and the equivalent stiffness matrix of the critical joint region are matched according to the uniformly coded degree of freedom information. By superimposing the stiffness of each region, the equivalent stiffness matrices of each region are combined to form the overall stiffness matrix of the composite material vehicle frame.

8. The rapid simulation verification method for the mechanical properties of composite material vehicle frame layup according to claim 1, characterized in that: The process for obtaining the overall displacement response results of the vehicle frame is as follows: Based on the overall stiffness matrix of the chassis, preset boundary constraints and load conditions are applied to construct the mechanical equilibrium equations of the chassis as a whole. The mechanical equilibrium equations are numerically solved using a sparse matrix solving algorithm to calculate the overall displacement change of the composite material frame under the corresponding load conditions. The displacement values ​​and displacement direction information of each structural unit obtained by numerical solution are used as the structured output of the overall displacement response result of the frame.

9. The rapid simulation verification method for the mechanical properties of composite material vehicle frame plywood according to claim 1, characterized in that: The process for obtaining the overall mechanical performance indicators of the vehicle frame is as follows: Based on the overall displacement response results of the frame, the maximum displacement information and corresponding position of the composite material frame under various load conditions are extracted. Combined with the preset load conditions, the quantitative parameters characterizing the overall stiffness of the frame are calculated from the overall displacement response results of the frame. Based on the coordinated displacement field, the deformation amplitude of the key stress area is analyzed, and the parameters reflecting the key stress area are derived from the coordinated displacement field and integrated to form the overall mechanical performance index of the frame.

10. The rapid simulation verification method for the mechanical properties of composite material vehicle frame layup according to claim 1, characterized in that: The process of generating the mechanical performance simulation verification results is as follows: Based on the internal stress distribution in the critical joint area, and according to the preset composite material failure criteria, the intralaminar stress and interlaminar stress in the critical joint area are determined to fail item by item. The overall mechanical performance indicators are compared with the preset mechanical performance qualification threshold to determine whether the overall layup design scheme meets the requirements. The failure assessment results of the critical joint area are integrated with the overall mechanical performance assessment results to output the mechanical performance simulation verification results.

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