Rail transit vehicle strength calculation method, system and vehicle body

Abstract

The present application relates to the technical field of rivet strength analysis of rail transit vehicles, and particularly relates to a rail transit vehicle strength calculation method and system and a vehicle body. The calculation method comprises: establishing a vehicle finite element simplified model, carrying out initial calculation of rivet connection arrangement between each module of the vehicle body, and determining rivet arrangement between each module of the vehicle body; based on the calculation result of the finite element simplified model, determining a vehicle body submodel modeling area and a vehicle concerned area, and demarcating the submodel modeling area; establishing a finite element detailed model in the submodel modeling area, carrying out nonlinear static strength calculation on the riveted vehicle body, and verifying whether the static strength of the vehicle body meets a set threshold value. The present application solves the contradiction between the calculation efficiency and accuracy of the riveted vehicle body through a staged modeling strategy, i.e. simplified model preliminary screening and submodel accurate calculation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rivet strength analysis of rail transit vehicles, and in particular to a rail transit vehicle strength calculation method and system and a vehicle body. BACKGROUND

[0002] The rail transit vehicle body as a core bearing structure directly affects the running safety and reliability. The traditional vehicle body underframe is composed of a center beam, an end beam, a sleeper beam and a large cross beam and the like, and complex loads need to be transmitted between the modules through reliable connection. Strength calculation is a key link in vehicle body design, which verifies the static strength and fatigue performance of the structure.

[0003] At present, the underframe modules of the rail transit vehicle mainly adopt welding connection. Welding realizes permanent connection between components through high-temperature molten metal, and the process includes: heating the area to be welded to form a molten pool, and forming a weld after cooling and solidification. The welding structure needs to consider factors such as material change in the heat-affected zone, welding residual stress and deformation. In the prior art, the vehicle body strength calculation depends on a full-detail finite element model, which needs to model the riveting parts of the whole vehicle in detail, such as simulating rivets by solid elements, and performing multiple rounds of nonlinear static analysis to optimize the structure.

[0004] The prior art has the following problems:

[0005] Firstly, the number of rivets of the whole vehicle is huge and the stress is strongly nonlinear, and the existing strength calculation method needs to establish a full-detail model and repeatedly optimize, which consumes a lot of computing resources and has a long period.

[0006] Secondly, a single model cannot balance efficiency and accuracy: detailed modeling leads to a sharp increase in calculation scale, and excessive simplification cannot accurately capture the stress concentration phenomenon in the rivet connection area. SUMMARY

[0007] In view of the deficiencies in the prior art, the purpose of the embodiments of the present application is to provide a rail transit vehicle strength calculation method, which solves the contradiction between calculation efficiency and accuracy of the riveted vehicle body through a staged modeling strategy, i.e. simplified model preliminary screening and sub-model accurate calculation.

[0008] In order to achieve the above-mentioned purpose, the embodiments of the present application provide the following technical solutions:

[0009] A rail transit vehicle strength calculation method, comprising:

[0010] establishing a vehicle finite element simplified model, carrying out preliminary calculation of rivet connection arrangement between modules of the vehicle body, and determining rivet arrangement between modules of the vehicle body;

[0011] based on the calculation results of the finite element simplified model, determining the modeling area of the vehicle body sub-model and the vehicle concerned area, and delimiting the modeling area of the sub-model;

[0012] A finite element detailed model is established in the sub-model modeling area, and a non-linear static strength calculation is performed on the riveted vehicle body to verify whether the static strength of the vehicle body meets the set threshold.

[0013] Further, the establishment of the vehicle finite element simplified model comprises:

[0014] The vehicle body geometric model is simplified to retain structural features contributing to overall stiffness and local strength;

[0015] Material property parameters are set, including density, elastic modulus, and strength indicators;

[0016] Solid elements are used to divide the grid, and the grid is refined in the rivet connection area;

[0017] Binding contact relationships are established between the module interfaces to simulate rivet load transfer.

[0018] Further, the preliminary calculation comprises:

[0019] Actual support constraints and working condition loads are applied to the structure;

[0020] The structural statics analysis is performed and the load data of the inter-module contact surface is output;

[0021] Based on the load data, the vehicle body stiffness, static strength, and rivet arrangement rationality are evaluated.

[0022] Further, the sub-model modeling area comprises:

[0023] According to the stress distribution results of the preliminary calculation, the area containing high-stress plates and connecting structures is selected;

[0024] The rivet connection parts between modules are included in the sub-model boundary range to ensure that the sub-model size covers the stress gradient change area.

[0025] Further, the establishment of the finite element detailed model comprises:

[0026] The thin-walled structure of the vehicle body is discretized using shell elements, and the element size is controlled within a set range;

[0027] The rivet connection is simulated by beam elements, and beam elements are established between the center points of the rivet holes and the multi-point constraints of the hole peripheral nodes;

[0028] The high-stress area uses hexahedral solid elements and local grid refinement.

[0029] Further, the detailed model loading process comprises:

[0030] The rivet pre-tightening force and external working condition load are applied step by step, and the pre-tightening force is loaded along the rivet axis on the beam element;

[0031] Locking pre-tightening force is followed by nonlinear solution calculation.

[0032] The establishment of the finite element detailed model further comprises:

[0033] Friction contact relations are set at the connecting interfaces between the plates of the vehicle body, and the friction coefficient is determined according to the material quality of the plates;

[0034] When the rivet is simulated by a beam element, the rivet end and the rivet hole are connected by a multi-point constraint.

[0035] Further, simplified calculation is performed according to the multi-condition load conditions to obtain the load information between the modules under each condition;

[0036] Based on the friction coefficient and the clamping force of the rivet, the minimum number of rivets required for each condition is calculated;

[0037] The maximum number of rivets in all conditions is selected as the final number, and the arrangement scheme is adjusted according to the installation space to meet the spacing margin constraint.

[0038] Further, the sub-model modeling area comprises:

[0039] In the selected high stress area, stress distribution data is extracted along the load transmission direction and a stress-distance curve is drawn;

[0040] According to the slope change of the stress-distance curve, the interval with a stress change rate exceeding a set value is marked as a high stress gradient area;

[0041] Taking the boundary of the high stress gradient area as a reference, the sub-model modeling range is expanded by no less than a set distance.

[0042] The embodiment of the present application also provides a rail transit vehicle strength calculation system, comprising:

[0043] The simplified modeling module is used to establish a vehicle finite element simplified model, carry out preliminary calculation of rivet connection arrangement between modules of the vehicle body, and determine the rivet arrangement between modules of the vehicle body.

[0044] The region identification module is used to determine the vehicle sub-model modeling area and the vehicle concerned area based on the calculation results of the finite element simplified model, and to demarcate the sub-model modeling area.

[0045] The detailed calculation module is used to establish a finite element detailed model in the sub-model modeling area, perform nonlinear static strength calculation on the riveted vehicle body, and verify whether the static strength of the vehicle body meets a set threshold.

[0046] The embodiment of the present application also provides a rail transit vehicle body, comprising a middle beam, end beams, sleeper beams and large cross beams, the connection interfaces of the end beams, sleeper beams and large cross beams and the middle beam are riveted by using a rivet arrangement scheme determined by the rail transit vehicle strength calculation method as described above; and the overall structure of the vehicle body is constructed based on a structural scheme designed by the rail transit vehicle strength calculation method.

[0047] The one or more technical solutions provided in the embodiment of the present application have at least the following technical effects or advantages:

[0048] 1. The rail transit vehicle strength calculation method of the present application solves the contradiction between the calculation efficiency and accuracy of the riveted vehicle body through a phased modeling strategy. In the first phase, a simplified finite element model is established to quickly complete the preliminary calculation of the rivet arrangement between the vehicle body modules, avoiding the calculation burden of full detail modeling. In the second phase, the high stress areas are identified based on the simplified results, and the sub-model range is accurately defined to ensure that the subsequent calculation focuses on the key positions. In the third phase, a detailed finite element model is established in the sub-model for nonlinear static strength calculation, and the static strength of the vehicle body is verified through local refined modeling. This method divides the traditional single model into "simplified preliminary screening and sub-model precise calculation", which significantly reduces the calculation resource consumption while ensuring the stress calculation accuracy of the rivet connection area.

[0049] 2. Through the analysis and evaluation of the simplified calculation results, the areas with high stress of the vehicle body are determined, and the sub-model technology is used to reduce the grid size in the detailed calculation of the vehicle body, thereby improving the accuracy of the analysis on the basis of ensuring the calculation efficiency.

[0050] 3. The rail transit vehicle body proposed by the present application uses riveting to connect the end beams, sleeper beams and large cross beams with the middle beam, which reduces the deformation at the connection interface and the impact on the environment on the basis of meeting the strength requirements of the rail transit vehicle.

[0051] The advantages of the additional aspects of the present application will be given in the following description, some of which will become apparent from the following description, or will be understood through the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0052] In order to more clearly illustrate the technical solutions in the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings. In addition, the dimensions or distances between each other are exaggerated for showing the positions of the components, and the schematic diagram is only used for illustration.

[0053] Figure 1 is the flowchart of the strength calculation method provided by the embodiment of the present application;

[0054] Figure 2 is a simplified calculation flowchart provided by the embodiment of the present application;

[0055] Figure 3 is a detailed calculation flowchart provided by the embodiment of the present application;

[0056] Figure 4 is a schematic diagram of a simplified finite element model of a car body structure provided by the embodiment of the present application;

[0057] Figure 5 is a schematic diagram of high stress distribution in the connection area of the cross beam and the middle beam provided by the embodiment of the present application;

[0058] Figure 6 is a path setting diagram for analyzing the load transfer direction in the high stress area provided by the embodiment of the present application;

[0059] Figure 7 is a stress gradient analysis diagram of path 1-2 provided by the embodiment of the present application;

[0060] Figure 8 is a stress-distance curve diagram of the load transfer direction provided by the embodiment of the present application;

[0061] Figure 9 is a high stress submodel boundary setting diagram based on stress gradient provided by the embodiment of the present application;

[0062] Figure 10 is a stress nephogram of cutting a simplified model provided by the embodiment of the present application;

[0063] Figure 11 is a schematic diagram of the connection state of a submodel rivet provided by the embodiment of the present application;

[0064] Figure 12 is a schematic diagram of a rail transit vehicle car body structure provided by the embodiment of the present application;

[0065] Figure 13 is a schematic diagram of rivet connection between a large cross beam module and a middle beam module provided by the embodiment of the present application, that is, Figure 12 an enlarged view of the middle I;

[0066] Figure 14 is a schematic diagram of rivet connection in a large cross beam module provided by the embodiment of the present application, that is, Figure 12 an enlarged view of the middle II;

[0067] In the figure: 1, end beam, 2, bolster beam, 3, middle beam, 4, large cross beam. DETAILED DESCRIPTION

[0068] It should be noted that the following detailed description is illustrative only, and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Furthermore, it should be understood that the use of the terms "comprise", "comprises", "comprising", "include", "includes", "including", "contain", "contains", "containing", or variants thereof, in the description and / or claims are intended to indicate that there are features, steps, components, elements, or combinations thereof, that are present, but not necessarily all, of them are present.

[0069] Embodiment 1

[0070] The embodiment proposes a strength calculation method for rail transit vehicles. By dividing the simulation process of the rail transit vehicle connected by rivets into three parts of simplified calculation, analysis result evaluation, and detailed calculation, the strength of the vehicle body and the arrangement of rivets between modules are preliminarily calculated in the simplified calculation part, thereby avoiding multiple repeated calculations in the original method calculation process and improving the analysis efficiency.

[0071] Specifically, it comprises: establishing a vehicle finite element simplified model, carrying out preliminary calculation of rivet connection arrangement between modules of the vehicle body, and determining the rivet arrangement between modules of the vehicle body; based on the calculation results of the finite element simplified model, determining the modeling area of the vehicle body submodel and the vehicle concerned area, and demarcating the modeling area of the submodel; establishing a finite element detailed model in the modeling area of the submodel, and carrying out nonlinear static strength calculation on the riveted vehicle body to verify whether the static strength of the vehicle body meets the set threshold.

[0072] By establishing a finite element simplified model, preliminary calculation of rivet connection arrangement between modules of the vehicle body is carried out to determine the rivet arrangement scheme. Based on the calculation results of the simplified model, the submodel modeling area is demarcated, the stress concentration parts are focused, and the calculation accuracy and efficiency are improved. A detailed model is established in the submodel area, nonlinear static strength calculation is carried out, and whether the static strength of the vehicle body meets the set threshold is verified to ensure that the strength of the vehicle meets the use requirements. The steps work together, the preliminary calculation of the simplified model provides a basis for the subsequent detailed calculation, the demarcation of the submodel makes the detailed calculation more targeted, and the nonlinear static strength calculation accurately verifies the strength, thereby improving the calculation efficiency and accuracy as a whole and shortening the research and development cycle.

[0073] Further, in the establishment of the vehicle finite element simplified model, the vehicle body geometric model is simplified, the structural characteristics contributing to the overall stiffness and local strength are retained, the calculation amount can be reduced and the calculation efficiency can be improved without affecting the key mechanical properties. The material property parameters are set, including density, elastic modulus and strength index, to provide accurate material characteristics basis for subsequent mechanical calculation, so that the calculation result is more in line with the actual situation. The entity element is used to divide the grid, and the grid is refined in the rivet connection area, which helps to more accurately simulate the mechanical behavior of the rivet connection part, because the stress in this area is complex, and refining the grid can improve the accuracy of the calculation results such as stress distribution. The binding contact relationship is established at the connection interface between the modules to simulate the rivet load transfer, which can more realistically reflect the mechanism of the rivet load transfer in the vehicle structure, so that the finite element simplified model is closer to the actual vehicle mechanical structure, and lays a foundation for subsequent accurate strength calculation.

[0074] Further, the actual support constraints and working condition loads are applied in the preliminary calculation process, so that the calculation model can simulate the stress state of the vehicle body in actual operation, and ensure that the calculation result meets the actual working condition requirements. The structural statics analysis is performed and the load data of the inter-module contact surface are output, through the analysis of these data, the load transfer between the modules of the vehicle body can be understood, which provides data support for evaluating the vehicle body stiffness, static strength and rivet arrangement rationality. Based on the load data, the vehicle body stiffness, static strength and rivet arrangement rationality can be evaluated, so that the problems such as insufficient stiffness, unqualified static strength or unreasonable rivet arrangement in the vehicle structure design can be found in time, thereby providing a basis for optimization design, so that the vehicle structure can meet the strength requirements while ensuring that the rivet arrangement meets the mechanical requirements and conforms to the actual installation and other requirements.

[0075] Further, when the sub-model modeling area is delineated, according to the stress distribution results of the preliminary calculation, the area containing high-stress plates and connecting structures is selected, which can focus on the parts with complex stress and stress concentration in the vehicle body, because these areas have a greater impact on the overall strength of the vehicle body, and the calculation accuracy can be improved by establishing a sub-model for detailed analysis. The rivet connection part between the modules is included in the boundary range of the sub-model, so as to ensure that the size of the sub-model covers the stress gradient change area, which can completely simulate the mechanical behavior of the rivet connection part and its surrounding area. Since the rivet connection part is a key node for load transfer, and the stress gradient around it changes greatly, complete coverage of this area helps to accurately analyze the influence of this part on the strength of the vehicle body, so that the sub-model can more truly reflect the mechanical properties of the key parts of the vehicle body.

[0076] Further, when the finite element detailed model is established, the thin-walled structure of the car body is discretized by shell elements, and the element size is controlled within a set range. The shell element is suitable for simulating the thin-walled structure, and the control of the element size can reasonably control the calculation amount while ensuring the calculation accuracy. The rivet connection is simulated by a beam element, and a beam element is established between the center points of the rivet holes and is multi-point constrained with the nodes around the hole. This simulation method can better reflect the mechanical properties of the rivet and the connection relationship between the rivet and the surrounding structure. The beam element can simulate the axial stress of the rivet, and the multi-point constraint can accurately transfer the load. The high-stress area is simulated by a hexahedral solid element with local grid refinement. For the high-stress area, a hexahedral solid element with higher accuracy is used, and the calculation accuracy is further improved by grid refinement to accurately analyze the complex stress and strain conditions in the high-stress area. The modeling methods of each part are coordinated to build a finite element detailed model that accurately reflects the actual mechanical structure of the car body.

[0077] Further, the detailed model loading process is divided into steps to apply the rivet pre-tightening force and external working load. The pre-tightening force is loaded along the axis of the rivet in the beam element, which can simulate the stress process of the rivet in actual work. The pre-tightening force is applied first to make the rivet in the initial stress state, and then the external working load is applied, which conforms to the actual stress sequence of the car body. After locking the pre-tightening force, nonlinear solving calculation is performed, considering factors such as material nonlinearity and geometric nonlinearity, which more truly simulates the mechanical response of the car body under complex stress conditions. Because the material properties of the actual car body may change during the stress process, and the structure may also deform greatly, nonlinear solving can make the calculation results more accurately reflect the true mechanical behavior of the car body, thereby improving the accuracy of the car body static strength calculation.

[0078] Further, the establishment of the finite element detailed model also includes setting friction contact relationships on the connection interfaces between the plates of the car body, and the friction coefficient is determined according to the material of the plate. This can consider the relative sliding and friction force between the plates of the car body under stress, making the model more consistent with the actual situation. The friction coefficients between plates of different materials are different, and accurate setting helps to improve the calculation accuracy. When the rivet is simulated by a beam element, the rivet end is connected to the rivet hole through multi-point constraint, which further ensures the accuracy of the mechanical simulation of the connection between the rivet and the surrounding structure. Multi-point constraint can effectively transfer the load, simulate the complex mechanical connection between the rivet end and the rivet hole, and perfect the simulation of the actual mechanical structure of the car body by the finite element detailed model.

[0079] Further, the simplified calculation is performed according to the multi-condition load conditions to obtain the load information between the modules under each condition. This can comprehensively understand the load conditions between the modules of the car body under different operating conditions, because the rail transit vehicle will face various conditions in actual operation, such as starting, accelerating, decelerating, turning, etc., and the load distribution is different under different conditions.

[0080] Based on the friction coefficient and the rivet clamping force, the minimum number of rivets required for each working condition is calculated; Considering the key factors that affect the strength of the rivet connection in actual use, the friction coefficient affects the friction between the plates, and the rivet clamping force is directly related to the tightness of the connection. By calculating the minimum number of rivets, the number of rivets can be optimized to meet the strength requirements and reduce costs. Select the maximum number of rivets in all working conditions as the final number, and adjust the layout scheme according to the installation space to meet the spacing margin constraints, which not only ensures the strength of the vehicle body under the most severe working conditions, but also takes into account the actual installation space limitations, making the rivet layout scheme safe, reliable and practical.

[0081] As shown in Figure 1 the specific steps include:

[0082] S1: Establish a simplified finite element model of the vehicle, and carry out initial calculation of rivet connection layout between modules of the vehicle body to determine the rivet layout between modules of the vehicle body, as shown in Figure 2 the process includes:

[0083] S11: Establish a geometric model of the vehicle: Determine the model range, simplify the model, and consider structures that contribute to overall stiffness and local strength, such as vehicle beams, side beams, cross beams, and reinforcing structures connected to the load-bearing structure. Components with little impact on overall stiffness and local areas of interest can be ignored or simplified. Vehicle accessories, brake systems, and other scattered components with relatively dispersed mass distribution can be ignored, but the self-weight of these components should be considered when designing the vehicle structure. Mass-concentrated vehicle-mounted equipment should be simplified as a mass point with equivalent mass acting on the corresponding area;

[0084] S12: Selection of material properties and performance parameters: Material properties are selected according to relevant standards and technical conditions. The mechanical properties of new materials are recommended to be obtained through material mechanical property tests, and a reasonable confidence value is recommended. Common material performance parameters include density, elastic modulus, shear modulus, Poisson's ratio, yield strength, ultimate strength, elongation, etc.;

[0085] S13: Element setting and meshing: The vehicle body is divided into low-order tetrahedral or hexahedral solid elements. The overall element size is recommended to be 10-30mm, and the rivet connection surface is refined with a surface element size of 5-10mm;

[0086] S14: Model connection processing: The connection between each plate of the vehicle body is handled as welding, which is generally simulated by contact to simulate the welding connection; For calculating the rivet layout, the rivet connection should be established by contact, and each group of rivets between different modules of the vehicle should be established as a binding contact for load extraction after calculation.

[0087] S15: constraint setting and load application: the actual support points of the structure should be set with corresponding constraints, and the actual load should be applied at the position where the load acts;

[0088] S16: solution calculation of simplified calculation: using structural statics analysis, in the result output option, selecting the output of the load information of the contact surface;

[0089] S17: result evaluation of simplified calculation: including car body stiffness evaluation, static strength evaluation and rivet arrangement evaluation. The deformation value of the railway wagon should be less than the allowable value of the deformation under each standard working condition. According to the rivet load between modules output in S16, the rivet arrangement is determined, and the rationality of the rivet arrangement is evaluated.

[0090] S2: according to the calculation results of the finite element simplified model, the modeling area of the car body submodel and the vehicle concerned area are determined, and the process includes:

[0091] S21: determining the parts with high stress of the car body: according to the result evaluation part of the simplified calculation, the parts with high stress of the car body are determined, for example, part II in Figure 12 , which contains the car body plate part and the rivet connection structure connecting the plate part in this area;

[0092] S22: determining the detailed modeling range of the rivet: the rivet detailed modeling range is determined, and the modeling area of the car body detailed calculation submodel is determined, which includes the connection of the parts with high stress (such as part II in Figure 12 , Figure 13 ) and the rivet between modules (such as part I in Figure 12 , Figure 14 ). The modeling area of the submodel should be large enough to ensure the accuracy of the rivet connection calculation.

[0093] S3: detailed modeling calculation of riveted car body using finite element method to ensure that the static strength of the car body meets the requirements and complete the preparation of the calculation report. As shown in Figure 3 , the process includes:

[0094] S31: establishing a detailed finite element model of the vehicle: according to the geometric model obtained after the simplified calculation, and combining the determined submodel area to establish a detailed finite element model of the vehicle;

[0095] S32: solution calculation: the solution calculation is a nonlinear analysis, and the solution type is set to Direct when the hardware conditions are met;

[0096] S33: result evaluation: should include car body stiffness evaluation, car body static strength evaluation and rivet connection evaluation, etc.

[0097] S34: Report writing: should include the task source, the calculation object, the calculation program used, the calculation model, the calculation load and working conditions, the calculation results and conclusions of each working condition, etc.

[0098] Further, in the process of establishing the finite element detailed model of the vehicle, the thin-walled structures such as the vehicle body plates and profiles are recommended to adopt quadrilateral shell elements, and the element size is recommended to be 10-30 mm. The rivet holes are simplified into a multi-point constraint form, and a beam element is established between the center points of the holes to simulate the rivet. The detailed modeling range of the rivet adopts a submodel calculation. In the submodel, the vehicle body plates adopt solid elements, and the solid elements are preferably hexahedral elements; the elements in the high stress area and the stress mutation area are locally refined to ensure the element quality, and the element size is recommended to be 6 mm. The high stress area can be the area above 60% of the allowable stress. For example, for Q450 material, the allowable stress in the first working condition is 281 MPa, and 168 MPa can be temporarily taken. The rivet adopts solid element modeling, and the grid size is 3-5 mm.

[0099] Further, in the process of establishing the finite element detailed model of the vehicle, the connections between the plates of the vehicle body adopt the way of friction contact to establish the connection, and the friction coefficient is selected according to the friction coefficient between the plates. When the rivet is modeled by a beam element, the end of the rivet is connected to the corresponding rivet hole in a multi-point constraint manner. When the rivet is modeled by a solid, the end face of the rivet head is connected to the connecting plate in a binding contact, and the end face of the sleeve ring is connected to the connecting plate in a binding contact.

[0100] Further, in the process of establishing the finite element detailed model of the vehicle, the load application is performed in two steps: the first step is to apply the rivet pretightening force, which is applied to the rivet rod, and the pretightening force is applied along the axial direction of the rivet. The rivet pretightening force is recommended to be applied according to each rivet group, and the load value is the product of the pretightening force of each rivet and the number of rivets. The second step is to lock the rivet pretightening force and apply the external load.

[0101] The rail transit vehicle strength calculation method disclosed in the embodiment converts the whole strength calculation problem of the full-riveted rail transit vehicle into a vehicle body strength simplified calculation and detailed calculation problem. The vehicle body strength simplified calculation part obtains the load between the rivet connection modules for the preliminary configuration of the rivet, and the simplified calculation obtains the position of the vehicle body strength stress. The position of the submodel in the vehicle body detailed calculation is obtained in combination with the above. In the vehicle body detailed calculation, the submodel technology is adopted in the concerned area, and the structure with less grid is adopted in the other parts, which guarantees the accuracy of the calculation, takes into account the calculation efficiency, and shortens the research and development cycle.

[0102] Embodiment 2

[0103] Identify the vehicle body structure (such as Figure 4The high stress area is shown in the figure) and when the sub-model division is carried out, if the artificial demarcation depends on experience, the hidden high stress area such as the rivet hole edge and the plate micro crack initiation area is easy to be missed; the traditional threshold method (such as setting a single stress value) is difficult to capture the stress gradient mutation characteristics, resulting in that the sub-model range is too large (calculation redundancy) or too small (insufficient precision); and the stress concentration of the riveting structure presents local nonlinear distribution, and the general grid refinement rule has poor adaptability.

[0104] Based on this, the sub-model modeling area demarcation in the embodiment includes: in the selected high stress area, stress distribution data is extracted along the load transmission direction and a stress-distance curve is drawn; according to the slope change of the stress-distance curve, the interval with a stress change rate exceeding a set value is marked as a high stress gradient area; and the sub-model modeling range is demarcated by extending outward from the boundary of the high stress gradient area by no less than a set distance.

[0105] By extracting the stress distribution data along the load transmission direction and drawing the stress-distance curve, it is ensured that the analysis path is consistent with the main stress direction; based on the curve slope change, the interval with a stress change rate exceeding a set value is marked as a high stress gradient area, and this threshold determination mechanism accurately captures the local nonlinear stress concentration characteristics of the riveting structure; further, the sub-model covers the stress decay transition zone by extending outward from the boundary of the high stress gradient area by no less than a set distance, so as to eliminate the boundary condition transmission error.

[0106] The stress-distance curve provides a quantitative analysis basis, the stress change rate threshold realizes accurate positioning of the area boundary, and the outward extension distance design blocks the boundary effect, and the three cooperate to reduce the grid size of the sub-model while controlling the detailed calculation stress result deviation within 5%.

[0107] Detailed method steps:

[0108] S1: calculating the stress distribution of the simplified model;

[0109] The joint area of the cross beam and the middle beam is a high stress area, the stress gradient distribution of the area is analyzed, and the specific range of the high stress is determined, as shown in the figure. Figure 5

[0110] S2: stress gradient of high stress area;

[0111] Path 1-2 is set in the joint area of the cross beam and the middle beam along the load transmission direction (as shown in the figure), the stress distribution data of the path is extracted and a stress-distance curve is drawn (as shown in the figures). Figure 6 Figure 7 、 Figure 8 According to the curve slope change, the interval with a stress change rate ≥【10 MPa / mm】 (i.e. the range of 1400-1800 mm in the middle) is demarcated as a high stress gradient area. Figure 7 ​​​

[0112] S3: Determine the lateral stress gradient and range using the same procedure;

[0113] S4: Determine the sub-model region: Determine the sub-model boundary range according to steps S3 and S4, as shown in Figure 9 .

[0114] S5: Cut the simplified model and establish a detailed model in combination with the previously determined rivet arrangement;

[0115] In the finite element software, cut the geometric body at the sub-model boundary, retain the internal and external expanded part entities, and perform detailed modeling on the sub-model.

[0116] S6: Perform detailed calculation and complete strength calculation. The stress nephogram of the sub-model region is as shown in Figure 10 , and the rivet connection state is as shown in Figure 11 .

[0117] Example 3

[0118] The embodiment provides a rail transit vehicle strength calculation system, which comprises a simplified modeling module, a region identification module and a detailed calculation module:

[0119] The simplified modeling module is used for establishing a vehicle finite element simplified model, performing rivet connection arrangement preliminary calculation between vehicle modules, and determining rivet arrangement between vehicle modules.

[0120] The region identification module is used for determining a vehicle sub-model modeling region and a vehicle concerned region based on a finite element simplified model calculation result, and delimiting the sub-model modeling region.

[0121] The detailed calculation module is used for establishing a finite element detailed model in the sub-model modeling region, performing nonlinear static strength calculation on the riveted vehicle body, and verifying whether the vehicle body static strength meets a set threshold value.

[0122] Example 4

[0123] The embodiment provides a rail transit vehicle body, as shown in Figure 12 , Figure 13 , Figure 14As shown, the connection interfaces of the end beam 1, the bolster beam 2 and the large cross beam 4 with the middle beam 3 are riveted by the rivet arrangement scheme determined by the strength calculation method of the rail transit vehicle as described in Embodiment 1, which ensures that the connection strength between the main beam members of the car body meets the design requirements. Because the rivet arrangement scheme determined by the strength calculation method is accurately calculated and verified, the mechanical properties of the connection part under various working conditions can be guaranteed. The overall structure of the car body is constructed based on the structural scheme designed by the strength calculation method of the rail transit vehicle, so that the entire car body structure is scientifically calculated and designed from local connection to overall layout, thereby making the car body have sufficient strength and stability, meeting various mechanical requirements of the rail transit vehicle in actual operation, and improving the safety and reliability of the car body.

[0124] Although the specific embodiments of the present application are described above with reference to the drawings, the description is not a limitation on the scope of protection of the present application, and those skilled in the art should understand that various modifications or variations made by those skilled in the art on the basis of the technical solutions of the present application without creative labor are still within the scope of protection of the present application.

Claims

1. A method for calculating strength of a rail vehicle, characterized by, The method comprises the following steps: A finite element simplified model of the vehicle is established, and initial calculation of rivet connection between modules of the vehicle body is carried out to determine rivet arrangement between the modules of the vehicle body; Based on the calculation results of the finite element simplified model, the modeling area of the submodel and the concerned area of the vehicle are determined, and the modeling area of the submodel is demarcated; Demarcating the modeling area of the submodel comprises the following steps: in the selected high stress area, stress distribution data is extracted along the load transmission direction and a stress-distance curve is drawn; according to the slope change of the stress-distance curve, the interval with a stress change rate exceeding a set value is marked as a high stress gradient area; the boundary of the high stress gradient area is taken as a reference, and the modeling range of the submodel is demarcated by extending outward by no less than a set distance; A finite element detailed model is established in the modeling area of the submodel, nonlinear static strength calculation of the riveted vehicle body is carried out, and whether the static strength of the vehicle body meets a set threshold value is verified; the establishment of the finite element detailed model comprises the following steps: thin-walled structures of the vehicle body are discretized by shell elements, and the element size is controlled within a set range; rivet connection is simulated by beam elements, beam elements are established between the center points of rivet holes and are multi-point constrained with the nodes around the holes; high stress areas are simulated by hexahedral solid elements and local grid is encrypted.

2. The rail vehicle strength calculation method according to claim 1, characterized in that, The establishment of the finite element simplified model of the vehicle comprises the following steps: The geometric model of the vehicle body is simplified, and structural features contributing to overall stiffness and local strength are retained; Material attribute parameters are set, the parameters comprising density, elastic modulus and strength indicators; Solid elements are used to divide grids, and grid refinement is carried out in the rivet connection area; Binding contact relationship is established at the interface between modules to simulate rivet load transmission.

3. The rail vehicle strength calculation method of claim 1, wherein, The initial calculation comprises the following steps: Actual support constraints and working condition loads of the structure are applied; Static analysis of the structure is carried out, and load data of the interface between modules is outputted; Based on the load data, the stiffness, static strength and rivet arrangement rationality of the vehicle body are evaluated.

4. The rail transit vehicle strength calculation method of claim 1, wherein, Demarcating the modeling area of the submodel comprises the following steps: According to the stress distribution results of the initial calculation, the area containing high stress plates and connecting structures is selected; The rivet connection parts between modules are included in the boundary range of the submodel, and it is ensured that the size of the submodel covers the stress gradient change area.

5. The rail transit vehicle strength calculation method of claim 1, wherein, The loading process of the detailed model comprises the following steps: The rivet pre-tightening force and external working condition load are applied step by step, wherein the pre-tightening force is loaded on the beam element along the rivet axial direction; After the pre-tightening force is locked, nonlinear solving calculation is carried out; The establishment of the finite element detailed model further comprises the following steps: Friction contact relationship is set at the connecting interface between the plates of the vehicle body, and the friction coefficient is determined according to the material of the plates; When the rivet is simulated by beam elements, the rivet end and the rivet hole are connected through multi-point constraint.

6. The strength calculation method of the rail transit vehicle according to claim 1, wherein: Simplified calculation is respectively carried out according to multi-working condition load conditions, and load information between modules under each working condition is obtained; Based on the friction coefficient and the rivet clamping force, the minimum number of rivets required for each working condition is calculated; The maximum number of rivets in all working conditions is selected as the final number, and the arrangement scheme is adjusted according to the installation space to meet the spacing margin constraint.

7. A rail vehicle strength calculation system characterized by comprising: The method comprises the following steps: The simplified modeling module is used to establish a finite element simplified model of the vehicle, carry out initial calculation of rivet connection between modules of the vehicle body, and determine rivet arrangement between the modules of the vehicle body; A region identification module is configured to determine a modeling region of a vehicle body submodel and a vehicle attention region based on a finite element simplified model calculation result, and to demarcate the modeling region of the submodel; Demarcating the modeling region of the submodel includes: extracting stress distribution data and drawing a stress-distance curve along a load transmission direction in a selected high stress region; marking an interval with a stress change rate exceeding a set value as a high stress gradient region according to a slope change of the stress-distance curve; and demarcating a modeling range of the submodel by extending outward from a boundary of the high stress gradient region by no less than a set distance; A detailed calculation module is configured to establish a finite element detailed model in the modeling region of the submodel, to perform a nonlinear static strength calculation on the riveted vehicle body, and to verify whether the static strength of the vehicle body meets a set threshold; establishing the finite element detailed model includes: discretizing a shell element for a thin-walled structure of the vehicle body, and controlling a unit size in a set range; simulating a rivet connection by a beam element, establishing a beam element between center points of rivet holes and multi-point constraining the nodes around the holes; and using a hexahedral solid element for a high stress region and locally encrypting a grid.

8. A rail transit vehicle body comprising a center sill, end sills, bolster sills and large crossbeams, characterized in that: The end beam, the bolster beam and the large cross beam are riveted by using a rivet arrangement scheme determined by the strength calculation method of the rail transit vehicle according to any one of claims 1-6 at a connecting interface of the end beam, the bolster beam and the large cross beam and the middle beam; and an overall structure of the vehicle body is constructed based on a structural scheme designed by the strength calculation method of the rail transit vehicle.

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