Equivalent modeling method and system for railway vehicle body composite material laminated plate
By identifying the periodic characteristics of composite laminates, merging them into sub-layers, establishing the equivalent stress and strain relationship, and simplifying the stiffness matrix, the problem of inefficient modeling of rail vehicle composite structures is solved, and efficient simulation analysis and accurate mechanical property prediction are achieved.
Patent Information
- Application Number
- CN202511247679.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-03
- Publication Date
- 2025-10-24
AI Technical Summary
Existing technologies for modeling composite structures of rail vehicles, especially those with thick walls, are expensive and complex to simulate and model. They are also unable to effectively handle the mechanical properties of hybrid composite materials under complex working conditions. Traditional layer-by-layer modeling methods are inefficient and cannot meet the design requirements of complex geometric configurations and multiple stress states.
By identifying the periodic characteristics of composite laminates, merging them into sub-layers, establishing the equivalent stress and strain relationship, simplifying the stiffness matrix, and using finite element software to simulate the rail vehicle structure, the number of unit layers and thickness parameters are adjusted to achieve sub-layer stacking modeling, accurately retaining the modal and static strength characteristics of the structure.
The simulation efficiency of rail vehicle composite structures under complex working conditions has been significantly improved, stress-displacement errors have been controlled within a reasonable range, the calculation speed has been significantly improved, and the modal and static strength characteristics of the structure have been accurately preserved.
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Figure CN120832801A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of rail vehicle modeling, in particular to an equivalent modeling method and system for a rail vehicle body composite material laminate plate. BACKGROUND
[0002] The content of this part only provides background information related to the present application, which may not constitute prior art.
[0003] Fiber-reinforced resin-based composite materials are increasingly widely used in rail vehicles due to their excellent specific performance, impact resistance, and ease of molding, and many other advantages. However, limited installation space and extreme load requirements make it inevitable to design and apply large-wall-thickness rail vehicle structures. For example, the driver's cabin framework and end chassis, etc. Such vehicle components usually have both load-bearing and collision protection requirements, and the thickness can be up to 5-15 mm, resulting in the actual number of layers far exceeding 50 layers. Traditional composite structure simulation modeling is mostly based on a layer-by-layer modeling method for single-layer plates, and the increase in the number of layers significantly increases the cost of finite element modeling and calculation.
[0004] In the prior art, equivalent methods are mostly focused on single material laminates, regular geometric shapes such as beams, and simple stress states (tension, bending, etc.). In contrast, rail vehicle structures are usually composed of a large number of components with complex geometries. The vehicle static strength design conditions specified in European standards (EN12663) and domestic railway industry standards (TB / T3451-2016) exceed 15, resulting in very complex stress states and deformation modes of vehicle components. In addition, compared to single carbon fiber materials, hybrid composite material designs, such as unidirectional / braided hybrid, heterogeneous material hybrid (such as mixing glass fibers, aramid fibers, etc. in carbon fiber plies), can achieve lightweight while further improving structural mechanical properties, and are widely used in current rail vehicle structure design. The applicability of existing equivalent methods in vehicle structure modeling still needs to be studied. SUMMARY
[0005] To solve the above technical problems, the purpose of the present application is to provide an equivalent modeling method and system for a rail vehicle body composite material laminate plate, which realizes sublayer stacking modeling by adjusting parameters such as the number of unit layers and thickness, improves the simulation efficiency of rail vehicle composite material structures under complex conditions, controls the stress and displacement error within a reasonable range compared to traditional layer-by-layer modeling, significantly improves the calculation speed, and accurately preserves the modal and static strength characteristics of the structure.
[0006] The purpose of the present application is achieved by the following technical solutions:
[0007] In a first aspect, the present application provides an equivalent modeling method for a rail vehicle body composite material laminate plate, comprising:
[0008] analyzing the plies of the composite laminate, identifying a plurality of single layer combinations having periodic repeating characteristics; merging the plurality of single layers into an equivalent sublayer, such that the composite laminate is formed by a plurality of identical sublayers stacked in repetition; the sublayer including carbon fiber layers and glass fiber layers in specific ply orientations, and establishing an equivalent stress and strain relationship of the sublayer in the plane by calculating the stress, strain, volume fraction and thickness relationship of each single layer in the corresponding sublayer;
[0009] In a preset local coordinate system, based on the constitutive relationship of carbon fiber, glass fiber single layer and equivalent sublayer, and the stiffness matrix of carbon fiber and glass fiber single layer, the stiffness matrix of carbon fiber and glass fiber single layer is obtained according to the strain energy density conservation law;
[0010] The stiffness matrix of carbon fiber and glass fiber single layer is calculated in the global coordinate system through the coordinate transformation matrix; the coordinate transformation matrix is determined by the direction cosine of each coordinate axis in the global coordinate system and the material coordinate system;
[0011] Based on the stiffness matrix in the local and global coordinate systems, the coefficients of the equivalent sublayer stiffness matrix are calculated through the volume fraction and thickness relationship of each single layer in the sublayer, and the complete equivalent sublayer stiffness matrix is obtained according to the coefficients;
[0012] The stiffness matrix of the equivalent sublayer is inverted to obtain the flexibility matrix; the equivalent elastic constants of the sublayer are obtained according to the relationship between the three-dimensional elastic constants and the coefficients of the flexibility matrix;
[0013] Based on the preset finite element software, the corresponding element is selected to simulate the composite laminate and other structural components of the rail vehicle body, the elastic constants of the equivalent sublayer are loaded into the material module of the preset finite element software, and the equivalent finite element model of the sublayer is established by adjusting the layer number, thickness and material parameters of the element.
[0014] Further, the step of selecting the corresponding element based on the preset finite element software to simulate the composite laminate and other structural components of the rail vehicle body, specifically includes:
[0015] Based on the preset finite element software, a quadrilateral 8-node shell element is selected to simulate the roof of the rail vehicle body, and a 4-node plane shell element is selected to simulate the end wall, side wall and underframe of the rail vehicle body; the connecting bolts between the roof, end wall, side wall and underframe are simulated by beam elements;
[0016] The equipment mass on the rail vehicle body is simulated by a mass element, and the degrees of freedom of the equipment are coupled and connected to the corresponding nodes of the rail vehicle body through a multi-point constraint element, to simulate the connection relationship between the equipment and the vehicle body.
[0017] Further, before establishing the equivalent finite element model of the sub-layer by adjusting the number of layers, thickness and material parameters of the unit, further comprising:
[0018] For each unit in the composite laminate, an independent local coordinate system is established to define the layup direction of the composite laminate.
[0019] Further, after defining the layup direction of the composite laminate, further comprising:
[0020] The normal direction of the unit is uniformly specified as the thickness direction to represent the mechanical properties in the thickness direction of the material.
[0021] Further, after representing the mechanical properties in the thickness direction of the material, further comprising:
[0022] The longitudinal axis direction of the rail vehicle body is set as the zero degree reference direction of the layup angle, ensuring that the definition of all layup angles is consistent with the actual stress direction of the body.
[0023] Further, after establishing the equivalent finite element model of the sub-layer by adjusting the number of layers, thickness and material parameters of the unit, further comprising:
[0024] In the preset finite element software, boundary conditions including constraint conditions and load conditions are set according to the design conditions specified in the static strength standard of the rail vehicle; simulation parameters are configured by the solver to simulate and analyze the strength of the composite laminate structure.
[0025] Further, the design conditions specified in the vehicle static strength standard at least include: free modal condition, vertical static load condition under overstaff state and equipment lateral impact condition, wherein the vertical static load condition needs to be loaded with 1.3 times vertical load after complete constraint at the suspension system constraint point.
[0026] In the second aspect, the present application provides an equivalent modeling system for a composite laminate of a rail vehicle body, comprising:
[0027] The equivalent stress and strain relationship establishing module is used to analyze the layup of the composite laminate and identify a plurality of single-layer combinations with periodic repetition characteristics; the plurality of single layers are combined to form a sub-layer, so that the composite laminate is formed by a plurality of sub-layers stacked repeatedly; the sub-layer contains carbon fiber layers and glass fiber layers with specific layup directions, and the equivalent stress and strain relationship of the sub-layer in the plane is established by calculating the stress, strain, volume fraction and thickness relationship of each single-layer plate in the corresponding sub-layer.
[0028] The local stiffness matrix obtaining module is configured to obtain a simplified stiffness matrix of the carbon fiber and glass fiber single-layer plates based on a constitutive relation of the carbon fiber, the glass fiber single-layer plate and the equivalent sublayer, and stiffness matrices of the carbon fiber and the glass fiber single-layer plates according to a strain energy density conservation law in a preset local coordinate system.
[0029] The overall stiffness matrix obtaining module is configured to calculate a converted stiffness matrix of the carbon fiber and the glass fiber single-layer plates in an overall coordinate system through a coordinate conversion matrix, and the coordinate conversion matrix is determined by direction cosines of each coordinate axis in the overall coordinate system and the material coordinate system.
[0030] The equivalent sublayer stiffness matrix obtaining module is configured to calculate coefficients of the equivalent sublayer stiffness matrix through a volume fraction and a thickness relation of each single-layer plate in the sublayer based on the stiffness matrices in the local and overall coordinate systems, and obtain a complete equivalent sublayer stiffness matrix according to the coefficients.
[0031] The equivalent elastic constant obtaining module is configured to obtain a compliance matrix by inverting the stiffness matrix of the equivalent sublayer, and obtain equivalent elastic constants of the sublayer according to a relation between three-dimensional elastic constants and coefficients of the compliance matrix.
[0032] The finite element model establishing module is configured to select corresponding elements based on a preset finite element software, simulate a composite laminated plate and other structural components of a railway vehicle body, load the elastic constants of the equivalent sublayer into a material module of the preset finite element software, and establish a sublayer equivalent finite element model by adjusting element layer number, thickness and material parameters.
[0033] In a third aspect, the present application provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements steps corresponding to the method in the first aspect when executing the computer program.
[0034] In a fourth aspect, the present application provides a computer readable storage medium having a computer program stored thereon, wherein the program implements steps corresponding to the method in the first aspect when executed by a processor.
[0035] In summary, the technical scheme of the embodiments of the present application has at least the following advantages and beneficial effects:
[0036] The present invention first identifies the periodic arrangement pattern of carbon fiber and glass fiber single-layer plates, establishes an equivalent mechanical model within the sub-layer surface through the stress-strain relationship and volume thickness parameters, analyzes the periodic characteristics of the ply of composite laminates, and merges repeated single-layer combinations into sub-layer units, thereby simplifying the complexity of the model. Subsequently, based on the material constitutive relationship and the principle of strain energy conservation, the stiffness matrix is derived in the local and global coordinate systems respectively, and the equivalent stiffness of the sub-layer is obtained through coordinate transformation and volume fraction integration; finally, the flexibility matrix obtained by inversion is converted into a three-dimensional elastic constant, which is directly applied to the material module of the finite element software for finite element analysis. By adjusting the number of unit layers, thickness and other parameters to achieve sub-layer stacking modeling, the simulation efficiency of the composite structure of rail vehicles under complex working conditions is improved. Compared with the traditional layer-by-layer modeling, the stress-displacement error is controlled within a reasonable range, the calculation speed is significantly improved, and the modal characteristics of the structure are accurately retained. BRIEF DESCRIPTION OF THE DRAWINGS
[0037] Figure 1 A flow chart of an equivalent modeling method for a rail vehicle body composite laminate provided by the present invention;
[0038] Figure 2 Schematic diagram of the equivalent sublayer in the present invention;
[0039] Figure 3 Schematic diagram of the neutron layer equivalent finite element model of the present invention;
[0040] Figure 4 The maximum stress and maximum displacement distribution points of the roof under different working conditions are shown in the C-sublayer-thickness ratio 0.1 model of the present invention;
[0041] Figure 5 A schematic structural diagram of an equivalent modeling system for a rail vehicle body composite laminate provided by the present invention;
[0042] Figure 6 This is a structural diagram of an electronic device provided by the present invention. DETAILED DESCRIPTION
[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.
[0044] like Figure 1 As shown, an equivalent modeling method for a rail vehicle body composite laminate plate proposed in an embodiment of the present application includes:
[0045] S101, analyze the plies of the composite laminate, identify a plurality of single layer combinations with periodic repeating characteristics; merge a plurality of single layers to be equivalent to a sublayer, so that the composite laminate is composed of a plurality of identical sublayers stacked repeatedly; the sublayer contains carbon fiber layers and glass fiber layers with specific ply directions, and the stress, strain, volume fraction and thickness relationship of each single layer in the corresponding sublayer is calculated to establish the equivalent stress and strain relationship of the sublayer in the plane.
[0046] Specifically, first, by identifying a plurality of single layer combinations with repeating arrangement rules in the laminate, such as the ply sequence of carbon fiber layers and glass fiber layers appearing alternately, the periodic characteristics are determined. This identification process is based on systematic analysis of ply direction, material properties and thickness distribution, which can accurately capture the periodicity of the laminate on a macro scale.
[0047] Then, a plurality of single layers with the same mechanical properties are merged into equivalent sublayers, so that the complex laminate originally composed of hundreds of single layers is simplified to a simplified model of several sublayers stacked repeatedly. In the equivalent process, the stress distribution and strain response of each single layer in the sublayer in the plane direction need to be calculated, considering the volume fraction and thickness ratio of different fiber type single layer plates. By establishing the equivalent stress and strain relationship in the sublayer, it is ensured that the simplified sublayer is consistent with the original multi-layer structure in macroscopic mechanical behavior. The specific calculation process is as follows:
[0048] As shown in the attached Figure 2 , taking the orthogonal anisotropic woven carbon / glass hybrid laminate with the ply scheme as , select as the minimum sublayer, then the laminate can be regarded as composed of r sublayers stacked repeatedly, each sublayer contains 2M carbon fiber layers C and 2N glass fiber layers G with any ply direction (Ф, ψ), then the equivalent stress σ ij and strain ε ij of the laminate in the x-y plane (i,j=1,2,3) are calculated as follows:
[0049]
[0050] v k =t k / h, γ l =t l / h (3)
[0051] In the formula, and (i,j=1,2,3) are the stress and strain components of the kth single layer plate of carbon fiber in the sublayer; v k and t k are the volume fraction and thickness of the kth single layer plate of carbon fiber in the sublayer; and (i,j = 1,2,3) are the stress and strain components of the lth single layer of glass fiber within the sub-layer; γ l and t l are the volume fraction and thickness of the lth single layer of glass fiber within the sub-layer, respectively; h represents the thickness of the sub-layer.
[0052] S102, in a preset local coordinate system, based on the constitutive relationship of carbon fiber, glass fiber single layer and equivalent sub-layer, and the stiffness matrix of carbon fiber and glass fiber single layer, the stiffness matrix of carbon fiber and glass fiber single layer is obtained according to the strain energy density conservation law.
[0053] Specifically, first, the constitutive relationship of carbon fiber and glass fiber single layer is established in the preset local coordinate system, which describes the linear response characteristics of stress and strain of the material under stress state. Since the orthotropic material has three mutually perpendicular elastic symmetry planes, its stiffness matrix originally contains multiple independent parameters, but through the strain energy density conservation law, the simplified condition can be derived, that is, the strain energy density of the material in different directions under the local coordinate system remains constant, which makes the non-diagonal elements in the stiffness matrix have specific mathematical correlation.
[0054] Based on this physical principle, the stiffness matrix of carbon fiber and glass fiber single layer can be simplified to a compact form that only retains key parameters, thereby significantly reducing the complexity of subsequent calculations. This simplification not only retains the essence of the mechanical behavior of the original layup, but also improves the calculation efficiency by eliminating redundant parameters. Especially for hybrid composite laminates, this method can simultaneously handle the stiffness characteristics of carbon fiber and glass fiber, two types of heterogeneous materials, ensuring that the equivalent sub-layer accurately reflects the overall mechanical properties of the hybrid layup at the macro level. The specific calculation is as follows:
[0055] In the local coordinate system, the constitutive relationship of carbon fiber, glass fiber single layer and equivalent sub-layer is:
[0056]
[0057] σ ij = [C]ε ij (6)
[0058] Where [C] is the stiffness matrix of the equivalent sub-layer, and the stiffness matrix of the carbon fiber and glass fiber single layer in the local coordinate system is as follows: k and [C] l
[0059]
[0060] In the formula, and (i,j = 1, …, 6) represent the stiffness matrix components of carbon fiber and glass fiber single-layer respectively. Since the orthotropic single-layer has three orthogonal elastic property symmetry planes, by the law of strain energy density conservation, we have: Then the stiffness matrix of carbon fiber and glass fiber single-layer in local coordinate system [C] k and [C] l can be simplified as:
[0061]
[0062] S103, calculating the converted stiffness matrix of carbon fiber and glass fiber single-layer in global coordinate system through the coordinate conversion matrix; the coordinate conversion matrix is determined by the direction cosines of each coordinate axis in the global coordinate system and the material coordinate system.
[0063] Specifically, this step first constructs the coordinate conversion matrix based on the geometric relationship between the material coordinate system and the global coordinate system through the direction cosines. The direction cosines represent the angle relationship between the material principal direction (such as the fiber axial direction of the carbon fiber unidirectional layup) and the global coordinate axis of the vehicle body (such as the longitudinal, transverse and vertical directions of the vehicle body), and its physical meaning is to accurately describe the stiffness contribution of each single-layer in different spatial orientations.
[0064] Through the coordinate conversion matrix operation, the simplified stiffness matrix of carbon fiber and glass fiber single-layer in the local coordinate system is converted into the full parameter form in the global coordinate system, and this process strictly follows the three-dimensional space tensor transformation rule, ensuring that the converted stiffness matrix can not only retain the intrinsic characteristics of the material, but also adapt to the mechanical response analysis of the vehicle body structure under combined loads such as bending and torsion. The specific calculation is as follows:
[0065] When performing macroscopic mechanical property calculation of the laminate, the stiffness matrix of each ply in the local coordinate system [C] k and [C] l need to be converted first, and the stiffness matrix coordinate conversion formula is:
[0066]
[0067] In the formula, Q is the coordinate conversion matrix, and the calculation formula is as follows:
[0068]
[0069] In the formula, l i , m i , n i are the direction cosines of each coordinate axis (x, y, z) in the global coordinate system and each coordinate axis (1, 2, 3) in the material coordinate system, i is the index of the coordinate axis (i = 1, 2, 3), and the following Table 1 shows the relationship:
[0070] Table 1 Direction Cosine
[0071] Coordinate axes x y z 1 m1 n1 2 [l2] m2 [n2] 3 [l3] m3 [n3]
[0072] After coordinate transformation, the stiffness matrix of the carbon fiber and glass fiber layer in the overall coordinate system is further obtained and
[0073]
[0074] In the formula, and (i,j = 1, …, 6) respectively represent the stiffness matrix components of the carbon fiber and glass fiber single layer in the overall coordinate system.
[0075] S104, based on the stiffness matrix in the local and overall coordinate system, the coefficients of the equivalent sublayer stiffness matrix are calculated by the volume fraction and thickness relationship of each single layer in the sublayer, and the complete equivalent sublayer stiffness matrix is obtained according to the coefficients.
[0076] Specifically, this step first weights and sums the single layer stiffness matrix converted in the overall coordinate system based on the volume fraction of carbon fiber and glass fiber single layer in the sublayer (i.e. the proportion of the thickness of each single layer to the total thickness of the sublayer). This weighting process follows the mixing law principle in the mechanics of composite materials, ensuring that the mechanical contribution of different material single layers in the sublayer is accurately superimposed according to their actual proportion. For example, for a woven carbon / glass hybrid laminated plate with orthotropic anisotropy, the volume fraction of carbon fiber layer and glass fiber layer in the thickness direction of the sublayer needs to be calculated respectively, and the converted stiffness matrix coefficients are proportionally distributed according to this, and finally the coefficients of the equivalent sublayer stiffness matrix are obtained by linear superposition. The physical meaning of this method is that through volume fraction weighting, the synergistic effect of high modulus characteristics of carbon fiber and high toughness characteristics of glass fiber is retained, and through mathematical linearization processing, the complex interaction of heterogeneous materials is converted into calculable macroscopic equivalent parameters.
[0077] At the principle level, the calculation of the equivalent sub-layer stiffness matrix is essentially a multi-scale mechanical modeling method. It realizes the dimension reduction simplification of hundreds of complex layup structures through the mechanical property equivalence from the micro scale (single layer plate) to the meso scale (sub-layer). The accuracy of this equivalence depends on two key conditions: first, the periodic arrangement of single layer plates within the sub-layer must meet the mechanical homogenization assumption, i.e. the sub-layer size is much smaller than the structure characteristic size; second, the interface effects between single layer plates need to be naturally integrated into the equivalent parameters through volume fraction, avoiding excessive simplification of local stress concentration. It is worth noting that the present invention specially designs an optimization algorithm for the hybrid layup commonly used in railway vehicle structures (such as carbon fiber / glass fiber alternating layup), effectively solving the stiffness coupling problem caused by the difference in layup direction of heterogeneous materials through the coupling calculation of direction cosine matrix and volume fraction.
[0078] S105, the stiffness matrix of the equivalent sub-layer is inverted to obtain the compliance matrix; according to the relationship between the three-dimensional elastic constant and the coefficient of the compliance matrix, the equivalent elastic constant of the sub-layer is obtained;
[0079] Specifically, the stiffness matrix, as a tensor describing the stress-strain relationship of the material, its inverse matrix, i.e. the compliance matrix, directly reflects the deformation response characteristics of the material under stress. Through the mathematical matrix inversion operation, the stiffness parameter representing the material's resistance to deformation can be converted into the compliance parameter representing the material's easy deformation degree, and this conversion process follows the constitutive relationship in the linear elastic theory.
[0080] In particular, for hybrid composite laminates used in railway vehicles, since the equivalent sub-layer has integrated the multi-layer mechanical behavior of carbon fiber and glass fiber, its compliance matrix not only contains the intrinsic compliance characteristics of single layer materials, but also reflects the influence of heterogeneous material synergy on the overall deformation performance through volume fraction weighting. According to the inherent relationship between the three-dimensional elastic constant and the coefficient of the compliance matrix, the engineering elastic constants of the equivalent sub-layer can be further analyzed, including but not limited to the elastic modulus, shear modulus and Poisson's ratio of the three main directions and other key parameters. These elastic constants essentially quantify the macroscopic mechanical behavior of the equivalent sub-layer as material properties recognizable by finite element software, for example, the ratio of in-plane and out-of-plane elastic moduli can be directly derived from the specific coefficient ratio in the compliance matrix, and the shear modulus is inversely related to the diagonal element in the compliance matrix that represents shear deformation. The specific calculation is as follows:
[0081] From S104, the parameters of the coefficients of the equivalent sub-layer stiffness matrix can be obtained, i.e. the stiffness matrix [C] of the equivalent sub-layer can be obtained, and its inverse can obtain the compliance matrix [S] of the equivalent sub-layer:
[0082] [S]=[C] -1 (15)
[0083] Further, according to the relationship between the three-dimensional elastic constants and the coefficients in the compliance matrix, the equivalent elastic modulus (E 11 、E 22 、E 33 ) Poisson's ratio (v 12 、v 13 、v 23 ) and shear modulus (G 23 、G 13 、G 12 ) of the sublayer are obtained:
[0084]
[0085] In the formula, S 11 、S 22 、S 33 、S 21 、S 31 、S 23 、S 44 、S 55 、S 66 are the components of the compliance matrix [S] of the equivalent sublayer.
[0086] S106, based on the preset finite element software, selects the corresponding unit to simulate the composite laminated plate and other structural components of the rail vehicle body, loads the elastic constants of the equivalent sublayer into the material module of the preset finite element software, and establishes the equivalent finite element model of the sublayer by adjusting the unit layer number, thickness and material parameters.
[0087] Specifically, first, based on the preset finite element software (such as Hypermesh), the unit type suitable for the structural characteristics of the rail vehicle is selected, wherein the composite laminated plate is discretely modeled by using the quadrilateral 8-node shell element (SHELL91), which is particularly suitable for simulating the interlaminar mechanical behavior of the composite laminated plate and can accurately characterize the stress gradient change in the thickness direction; and the metal structural components such as end wall, side wall and underframe are simulated by using the 4-node plane shell element (SHELL181), which can significantly reduce the model complexity while ensuring the calculation accuracy. For the connecting bolts between the components of the vehicle body, beam elements (BEAM188) are used to simulate their axial stiffness and bending resistance characteristics, and the equipment mass on the vehicle is equivalent to a concentrated mass by using mass elements (MASS21), and the device degrees of freedom are coupled with the vehicle structure nodes by using multi-point constraint elements (RBE3). This processing method can accurately reflect the dynamic interaction between the device and the vehicle body, and avoid complicated detailed modeling.
[0088] After the unit selection is completed, an independent local coordinate system is established for each unit in the composite laminate to define the layup direction of the composite laminate. The normal direction of the unit is uniformly specified as the thickness direction to represent the mechanical properties in the thickness direction of the material; at the same time, the longitudinal axis direction of the rail vehicle body is set as the 0° reference direction of the layup angle, as shown in (a) of Figure 3 The definition of all layup angles is ensured to be consistent with the actual stress direction of the vehicle body, and this coordinate system definition method ensures the strict correspondence between the layup angle and the actual stress direction.
[0089] Subsequently, the obtained equivalent sublayer elastic constants (including three-dimensional elastic modulus, shear modulus, and Poisson's ratio, etc.) are loaded into the finite element material module, and by adjusting the number of layers parameter (Number_of_Plies), the thickness parameter (Real Constants-TK_I), and the material parameter (Real Constants-MAT) of the SHELL91 unit, as shown in (b) of Figure 3 , the digital mapping of the sublayer equivalent scheme is realized; specifically, in the preset finite element software, the boundary conditions including the constraint conditions and the load conditions are set according to the design conditions specified in the rail vehicle static strength standard; the simulation calculation parameters are configured by the solver, and the strength of the composite laminate structure is simulated and analyzed.
[0090] For example, for a carbon fiber skin with a layup scheme of {[(0 / 90)C, (±45)C]S}10, 10 equivalent sublayers can be set to be stacked repeatedly, and each sublayer contains 4 original layups. After modeling is completed, boundary conditions need to be set according to the vehicle static strength standard such as EN12663: in the free modal analysis, no constraint is applied; in the AW3-1.3 times vertical static load condition, complete constraint is applied at the lower end of the secondary spring and 1.3 times vertical load is applied at the upper end; for the equipment lateral impact condition, y-direction impact load is applied at the mass unit. Finally, by configuring parallel computing parameters (such as enabling 16 processors to share memory parallel) through the ANSYS MechanicalAPDL solver, high-precision simulation analysis can be carried out.
[0091] Based on the above equivalent modeling method of the composite laminate of the rail vehicle body, experiments are carried out as follows:
[0092] The composite roof structure of a certain rail vehicle is a sandwich panel structure (i.e. carbon fiber-foam-carbon fiber), in which the carbon fiber composite material is a plain weave (T300, 3K) prepreg, the single layer thickness is about 0.125mm, and the skin layup scheme is {[(0 / 90) C ,(±45) C ] S} 10, the total thickness of the skin is 5mm. In this embodiment, [(0 / 90) C ,(±45) C ] S As an equivalent sub-layer, the number of plies in the sub-layer is 4 and the number of sub-layers is 10. Table 2 lists the elastic constants of carbon fiber composite materials and the calculated equivalent elastic constants of the sub-layers.
[0093] Table 2 Equivalent elastic constants of carbon fiber single layer and sublayer
[0094]
[0095] With reference to the standard EN-12663, the design conditions specified in the static strength standard of the vehicle under this standard include: free modal conditions, vertical static load conditions in overcrowded state, and lateral impact conditions of equipment. The vertical static load condition requires applying full constraints at the restraint points of the suspension system and then loading 1.3 times the vertical load. The free modal conditions of the vehicle body, condition 1 (AW3-1.3 times the vertical static load condition, that is, 1.3 times the sum of the vehicle body mass in the ready state and the vehicle body payload in the overcrowded state) and condition 2 (lateral impact condition of equipment) are selected for calculation. Among them, the free modal calculation does not require any constraints and external loads. Condition 1 requires applying full constraints at the lower end point of the secondary spring and applying 1.3 times the vertical load at the upper end of the secondary spring. Condition 2 requires applying full constraints at the lower end point of the secondary spring and applying lateral ( Figure 3 The load was applied in the mid-y direction. The final finite element model had a total of 947,355 elements, including 172,535 elements in the roof section. All calculations were performed using ANSYS Mechanical APDL 19.0, using the same computer hardware configuration. The solver used 16 processors with shared memory parallel processing. The computer processor model was an Intel(R) Xeom(R) Platinum 8260 CPU @ 2.40GHz, with 48 cores and 96 logical processors, and 1.50TB of random access memory (RAM).
[0096] The simulation results show that the equivalent finite element model established by the present invention can better reflect the load characteristics of the actual structure, such as Figure 4 As shown in the figure, the maximum stress of the roof predicted by the equivalent model (including the equivalent stress S mises and stress component S 11 、S 22 、S 33 ), displacement (including equivalent displacement u and displacement component u 11 、u 22 、u 33) and the spatial position (node) distribution is consistent with the traditional finite element model. Compared with the displacement and stress predicted by the traditional finite element model under the lateral impact working condition of the device, the maximum relative error is only 12.661%, and the maximum error of the modal frequency is only 0.037%. Under the AW3-1.3 times vertical static load working condition, the maximum simulation efficiency is improved by 18%, and the specific simulation results are shown in Tables 3, 4 and 5:
[0097] Table 3 C-Layer-by-layer modeling and C-Sublayer-thickness ratio 0.1 model roof stress results under working condition 1 and working condition 2
[0098]
[0099] Table 4 C-Layer-by-layer modeling and C-Sublayer-thickness ratio 0.1 model roof displacement results under working condition 1 and working condition 2
[0100]
[0101] Table 5 C-Layer-by-layer modeling and C-Sublayer-thickness ratio 0.1 model first-order modal frequency
[0102]
[0103] Based on the same inventive concept, the application provides an equivalent modeling system of a composite laminate plate of a rail vehicle body, comprising:
[0104] The equivalent stress and strain relationship establishing module 201 is configured to analyze the layers of the composite laminate plate, identify a plurality of single-layer combinations having periodic repeating characteristics, combine the plurality of single layers, and equivalently form a sublayer, so that the composite laminate plate is formed by a plurality of sublayers stacked repeatedly; the sublayer comprises a carbon fiber layer and a glass fiber layer in a specific layer direction, and the equivalent stress and strain relationship of the sublayer in the plane is established by calculating the stress, strain, volume fraction and thickness relationship of each single-layer plate in the corresponding sublayer.
[0105] The local stiffness matrix acquisition module 202 is configured to, in a preset local coordinate system, based on the constitutive relationship of the carbon fiber and glass fiber single-layer plates and the equivalent sublayer, and the stiffness matrix of the carbon fiber and glass fiber single-layer plates, obtain the simplified stiffness matrix of the carbon fiber and glass fiber single-layer plates according to the strain energy density conservation law.
[0106] The overall stiffness matrix acquisition module 203 calculates the converted stiffness matrix of the carbon fiber and glass fiber single-layer plates in the overall coordinate system through a coordinate conversion matrix; the coordinate conversion matrix is determined by the direction cosines of the coordinate axes in the overall coordinate system and the material coordinate system.
[0107] The equivalent sublayer stiffness matrix acquisition module 204 is configured to calculate coefficients of the equivalent sublayer stiffness matrix based on the stiffness matrix in the local and global coordinate systems, through the volume fraction and thickness relationship of each single-layer plate in the sublayer, and obtain a complete equivalent sublayer stiffness matrix according to the coefficients.
[0108] The equivalent elastic constant acquisition module 205 is configured to obtain a compliance matrix by inverting the stiffness matrix of the equivalent sublayer, and obtain the equivalent elastic constant of the sublayer according to the relationship between the three-dimensional elastic constant and the coefficient of the compliance matrix.
[0109] The finite element model establishment module 206 is configured to select corresponding units based on a preset finite element software, simulate the composite laminated plate and other structural components of the rail vehicle body, load the elastic constant of the equivalent sublayer into a material module of the preset finite element software, and establish a sublayer equivalent finite element model by adjusting the unit layer number, thickness and material parameters.
[0110] Based on the same inventive concept, the application provides an electronic device, which comprises a memory 302, a processor 301, and a computer program stored on the memory 302 and capable of running on the processor 301, and the processor 301 implements the equivalent modeling method of the composite laminated plate of the rail vehicle body when executing the computer program.
[0111] Based on the same inventive concept, the application provides a computer readable storage medium, which stores a computer program, and the program implements the equivalent modeling method of the composite laminated plate of the rail vehicle body when executed by a processor.
[0112] The above is only a preferred embodiment of the application and is not used to limit the application, and the application can have various changes and variations for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.
Claims
1. A method of equivalent modeling of a composite laminate panel of a rail vehicle body, characterized in that, The application relates to a method for establishing an equivalent finite element model of a composite laminate of a railway vehicle body. The method comprises the following steps: analyzing the ply of the composite laminate, identifying a plurality of single-layer combinations with periodic repeating characteristics; merging the plurality of single layers to equivalent a sublayer, so that the composite laminate is formed by a plurality of identical sublayers stacked repeatedly; the sublayer comprises carbon fiber layers and glass fiber layers with specific ply directions, and the stress, strain, volume fraction and thickness relationship of each single-layer plate in the corresponding sublayer is calculated to establish the equivalent stress and strain relationship of the sublayer in the plane; in a preset local coordinate system, based on the constitutive relationship of the carbon fiber, glass fiber single-layer plate and equivalent sublayer, and the stiffness matrix of the carbon fiber and glass fiber single-layer plate, the stiffness matrix of the carbon fiber and glass fiber single-layer plate after simplification is obtained according to the strain energy density conservation law; the stiffness matrix of the carbon fiber and glass fiber single-layer plate after conversion is calculated in the overall coordinate system through a coordinate conversion matrix; the coordinate conversion matrix is determined by the direction cosine of each coordinate axis in the overall coordinate system and the material coordinate system; based on the stiffness matrix in the local and overall coordinate systems, the coefficients of the equivalent sublayer stiffness matrix are calculated through the volume fraction and thickness relationship of each single-layer plate in the sublayer, and the complete equivalent sublayer stiffness matrix is obtained according to the coefficients; the stiffness matrix of the equivalent sublayer is inverted to obtain the compliance matrix; the equivalent elastic constants of the sublayer are obtained according to the relationship between the three-dimensional elastic constants and the coefficients of the compliance matrix; based on the preset finite element software, corresponding units are selected to simulate the composite laminate and other structural components of the railway vehicle body, the elastic constants of the equivalent sublayer are loaded into the material module of the preset finite element software, and the equivalent finite element model of the sublayer is established by adjusting the layer number, thickness and material parameters of the unit. The step of selecting corresponding units based on the preset finite element software to simulate the composite laminate and other structural components comprises the following steps: based on the preset finite element software, a quadrilateral 8-node shell unit is selected to simulate the roof of the railway vehicle body, and a 4-node plane shell unit is selected to simulate the end wall, side wall and underframe of the railway vehicle body; a beam unit is used to simulate the connecting bolts between the roof, the end wall, the side wall and the underframe; the equipment mass on the railway vehicle body is simulated by a mass unit, and the degrees of freedom of the equipment are coupled and connected with the corresponding nodes of the railway vehicle body through a multi-point constraint unit to simulate the connection relationship between the equipment and the vehicle body. Before the step of establishing the equivalent finite element model of the sublayer by adjusting the layer number, thickness and material parameters of the unit, the following steps are further included: for each unit in the composite laminate, an independent local coordinate system is established to define the ply direction of the composite laminate. After the step of defining the ply direction of the composite laminate, the following steps are further included: the normal direction of the unit is uniformly specified as the thickness direction to represent the mechanical properties in the thickness direction of the material. After the step of representing the mechanical properties in the thickness direction of the material, the following steps are further included: the longitudinal axis direction of the railway vehicle body is set as the zero-degree reference direction of the ply angle to ensure that the definition of all ply angles is consistent with the actual stress direction of the vehicle body. After the step of establishing the equivalent finite element model of the sublayer by adjusting the layer number, thickness and material parameters of the unit, the following steps are further included: 2. The equivalent modeling method of a rail vehicle body composite material laminated plate according to claim 1, characterized in that, 3. The equivalent modeling method of a rail vehicle body composite material laminated plate according to claim 1, characterized in that, 4. The equivalent modeling method of a rail vehicle body composite material laminated plate according to claim 3, characterized in that, 5. The equivalent modeling method of a rail vehicle body composite material laminate plate according to claim 4, characterized in that, 6. The equivalent modeling method of a rail vehicle body composite material laminate plate according to claim 1, characterized in that, In the preset finite element software, boundary conditions including constraint conditions and load conditions are set according to design conditions specified in the static strength standard of the rail vehicle; simulation calculation parameters are configured through a solver to perform simulation analysis on the strength of the composite laminate structure.
7. The equivalent modeling method of a rail vehicle body composite material laminate plate according to claim 6, characterized in that, The design conditions specified in the static strength standard of the vehicle at least include: a free mode condition, a vertical static load condition in an over-occupancy state, and a device lateral impact condition, wherein the vertical static load condition needs to be loaded with 1.3 times of the vertical load after complete constraint is applied at the constraint point of the suspension system.
8. A system for equivalent modeling of a composite laminate panel of a rail vehicle body, characterized in that, The method comprises the following steps: An equivalent stress and strain relationship establishing module is configured to analyze the plies of the composite laminate, identify a plurality of single-layer combinations having periodic repeating characteristics, and merge the plurality of single-layer combinations to equivalently form a sublayer, so that the composite laminate is formed by repeated stacking of a plurality of sublayers; the sublayer comprises carbon fiber layers and glass fiber layers in a specific ply direction, and the equivalent stress and strain relationship of the sublayer in the plane is established by calculating the stress, strain, volume fraction and thickness relationship of each single-layer plate in the sublayer; A local stiffness matrix obtaining module is configured to obtain the stiffness matrix of the carbon fiber and glass fiber single-layer plates in a simplified manner in a preset local coordinate system based on the constitutive relationship of the carbon fiber and glass fiber single-layer plates and the stiffness matrix of the carbon fiber and glass fiber single-layer plates according to the strain energy density conservation law; An overall stiffness matrix obtaining module is configured to calculate the stiffness matrix of the carbon fiber and glass fiber single-layer plates converted in an overall coordinate system through a coordinate conversion matrix; the coordinate conversion matrix is determined by the direction cosines of the coordinate axes in the overall coordinate system and the material coordinate system; An equivalent sublayer stiffness matrix obtaining module is configured to calculate coefficients of the equivalent sublayer stiffness matrix based on the volume fraction and thickness relationship of each single-layer plate in the sublayer according to the stiffness matrix in the local and overall coordinate systems, and obtain the complete equivalent sublayer stiffness matrix according to the coefficients; An equivalent elastic constant obtaining module is configured to obtain the compliance matrix by inverting the stiffness matrix of the equivalent sublayer, and obtain the equivalent elastic constant of the sublayer according to the relationship between the three-dimensional elastic constant and the coefficients of the compliance matrix; A finite element model establishing module is configured to select corresponding units based on a preset finite element software, simulate the composite laminate and other structural components of the rail vehicle body, load the elastic constant of the equivalent sublayer into a material module of the preset finite element software, and establish a sublayer equivalent finite element model by adjusting the number of layers, thickness and material parameters of the units. The electronic device comprises a memory, a processor, and a computer program stored on the memory and executable on the processor, and the processor implements the equivalent modeling method of the composite laminate of the rail vehicle body according to any one of claims 1-7 when executing the computer program.
9. An electronic device, comprising: The program is executed by the processor to implement the equivalent modeling method of the composite laminate of the rail vehicle body according to any one of claims 1-7.
10. A computer-readable storage medium having stored thereon a computer program, characterized in that,