Simulation design method of vehicle body structure and vehicle

Abstract

The application provides a simulation design method of a vehicle body structure and a vehicle, and relates to the technical field of vehicles. The simulation design method comprises the following steps: establishing an initial finite element model of a subframe connecting structure of a vehicle body structure, wherein the subframe connecting structure comprises a bolt and a bolt sleeve; based on the initial finite element model of the subframe connecting structure, a preset condition is applied to the bolt to obtain a first finite element model of the subframe connecting structure, and the preset condition is used to simulate the tightening state of the bolt; the first finite element model of the subframe connecting structure is fitted with a second finite element model of the vehicle body structure to obtain a simulation model; a collision condition is applied to the simulation model to simulate the collision working condition of the subframe under the collision condition, and simulation data is generated; according to the simulation data, each connecting point in the subframe connecting structure is evaluated to obtain an evaluation result of the subframe connecting structure; and the target design parameter of the vehicle body structure is determined based on the evaluation result, thereby solving the problem of low failure simulation precision.

Description

Technical Field

[0001] This invention relates to the field of vehicle technology, and more specifically, to a simulation design method for vehicle body structure and a vehicle. Background Technology

[0002] In existing technologies, simulations of automotive subframe detachment failures commonly employ simplified methods such as setting a fixed failure time or forcibly deleting contact units, relying on empirical judgment to artificially trigger connection separation at a certain moment during the collision process. This method ignores the physical, progressive failure process of the bolted connection between the subframe and the front longitudinal beam, and fails to reflect the dynamic mechanical responses of preload, frictional resistance, and relative slippage, resulting in significant discrepancies between simulation results and actual vehicle tests.

[0003] There is currently no effective solution to the aforementioned technical problems. Summary of the Invention

[0004] The main objective of this invention is to provide a simulation design method and vehicle for vehicle body structure, so as to solve the problem of low accuracy of simulation results for vehicle subframe detachment failure in the prior art.

[0005] To achieve the above objectives, according to one aspect of the present invention, a simulation design method for a vehicle body structure is provided, comprising: establishing an initial finite element model of a subframe connection structure of the vehicle body structure, wherein the subframe connection structure includes bolts and bolt sleeves; based on the initial finite element model of the subframe connection structure, applying preset conditions to the bolts to obtain a first finite element model of the subframe connection structure, wherein the preset conditions are used to simulate the tightening state of the bolts; fitting the first finite element model of the subframe connection structure with a second finite element model of the vehicle body structure to obtain a simulation model; applying collision conditions to the simulation model to simulate the collision conditions of the subframe under collision conditions and generating simulation data; evaluating each connection point in the subframe connection structure according to the simulation data to obtain an evaluation result of the subframe connection structure; and determining the target design parameters of the vehicle body structure based on the evaluation results.

[0006] Optionally, based on the initial finite element model of the subframe connection structure, preset conditions are applied to the bolts to obtain the first finite element model of the subframe connection structure, including: the initial finite element model of the subframe connection structure includes: the initial finite element model of the bolt and the initial finite element model of the bolt sleeve; based on the initial finite element model of the bolt, a preload is applied to the end face of the bolt to obtain the initial finite element model simulating the tightening state; elastic rebound analysis is performed on the initial finite element model simulating the tightening state to obtain the initial finite element model of the bolt with preload; based on the initial finite element model of the bolt with preload and the initial finite element model of the bolt sleeve, the first finite element model of the subframe connection structure is obtained.

[0007] Optionally, an initial finite element model of the subframe connection structure is established, including: establishing a geometric model of the bolt and a geometric model of the bolt sleeve; meshing the geometric models of the bolt and the bolt sleeve to obtain a mesh model of the bolt and a mesh model of the bolt sleeve; applying preset material properties to the mesh model of the bolt and the mesh model of the bolt sleeve to obtain an initial finite element model of the subframe connection structure, wherein the preset material properties include: the material of the bolt is an elastic material and the material of the bolt sleeve is a rigid material.

[0008] Optionally, establishing the initial finite element model of the subframe connection structure of the vehicle body structure further includes: establishing a geometric model of the bolt; meshing the geometric model of the bolt to obtain a mesh model of the bolt stud and a mesh model of the bolt nut; applying a first preset material property from the preset material properties to the mesh model of the stud and the mesh model of the nut, wherein the first preset material property includes: the material of the stud is an elastic material and the material of the nut is an elastic material; rigidly coupling the mesh model of the stud and the mesh model of the nut to obtain the initial finite element model of the bolt.

[0009] Optionally, establishing the initial finite element model of the subframe connection structure of the vehicle body structure further includes: establishing the geometric model of the bolt sleeve, meshing the geometric model of the bolt sleeve to obtain the mesh model of the bolt sleeve; applying the second preset material property in the preset material properties to the mesh model of the stud and the mesh model of the nut to obtain the initial finite element model of the bolt sleeve, wherein the second preset material property includes: the material of the bolt sleeve is a rigid material.

[0010] Optionally, the first finite element model is fitted with the second finite element model of the vehicle body structure to obtain a simulation model, including: establishing the second finite element model of the vehicle body structure, wherein the second finite element model of the vehicle body structure includes the second finite element model of the front longitudinal beam and the second finite element model of the subframe; rigidly coupling the initial finite element model of the preloaded bolts with the second finite element model of the front longitudinal beam to obtain the first simulation model; rigidly coupling the initial finite element model of the bolt sleeves with the second finite element model of the subframe to obtain the second simulation model; and obtaining a simulation model based on the first simulation model and the second simulation model.

[0011] Optionally, a simulation model is obtained based on the first simulation model and the second simulation model, including: obtaining the contact type and friction coefficient of the bolt in the first simulation model and the bolt sleeve in the second simulation model; and obtaining the simulation model based on the first simulation model, the second simulation model, the contact type, and the friction coefficient.

[0012] Optionally, before obtaining the first finite element model of the subframe connection structure by applying preset conditions to the bolts based on the initial finite element model, the process includes: obtaining the tightening torque, tightening force coefficient, and nominal thread diameter of the bolt; and determining the preload based on the tightening torque, tightening force coefficient, and nominal thread diameter of the bolt.

[0013] Optionally, the bolt sleeve is 3-8mm in size and the bolt thread has a nominal diameter of 12-16mm.

[0014] According to another aspect of the present invention, a vehicle is provided, the vehicle having a body structure, and the simulation design method for the body structure is performed using the above-described simulation design method.

[0015] By applying the technical solution of this invention, an elastic bolt model containing residual stress is generated through precise simulation of the bolt tightening process. This allows the subframe detachment behavior to be naturally triggered by the dynamic balance of collision load and friction, rather than by human intervention. The entire process of bolt slippage, tightening and release, and gradual detachment is realistically reproduced. The simulation data can accurately obtain the slippage initiation time, displacement, and detachment sequence, significantly reducing the error compared with the actual vehicle collision test. This solves the problem of low accuracy in the simulation results of automotive subframe detachment failure in the prior art. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0017] Figure 1 A flowchart of a first embodiment of the simulation design method for vehicle body structure according to the present invention is shown;

[0018] Figure 2 A structural schematic diagram of an embodiment of the geometric model of a bolt according to the present invention is shown;

[0019] Figure 3 A schematic diagram of the structure of a first embodiment of the initial finite element model of the bolt according to the present invention is shown;

[0020] Figure 4 A schematic diagram of the structure of a second embodiment of the initial finite element model of the bolt according to the present invention is shown;

[0021] Figure 5 A schematic diagram of an embodiment of an initial finite element model of a bolt with preload according to the present invention is shown;

[0022] Figure 6 A schematic diagram of an embodiment of the geometric model of the bolt sleeve according to the present invention is shown;

[0023] Figure 7 A schematic diagram of an embodiment of the initial finite element model of the bolt sleeve according to the present invention is shown;

[0024] Figure 8 A schematic diagram of the structure of a first embodiment of the simulation model according to the present invention is shown;

[0025] Figure 9 A schematic diagram of the structure of a second embodiment of the simulation model according to the present invention is shown. Detailed Implementation

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] Exemplary embodiments according to this application will now be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. It should be understood that these embodiments are provided so that the disclosure of this application is thorough and complete, and that the concept of these exemplary embodiments is fully conveyed to those skilled in the art. In the drawings, for clarity, the thickness of layers and regions may be exaggerated, and the same reference numerals are used to denote the same devices, and therefore their description will be omitted.

[0030] In traditional methods, the failure of the connection between the subframe and the front longitudinal beam is usually simplified to the forced disconnection of the connection at a fixed time point. This method completely ignores the mechanical evolution path of the connection structure during the collision process, cannot reflect the contact and pressing state caused by the preload in actual assembly, and cannot capture the physical processes of slippage, friction, and gradual separation.

[0031] Combination Figures 1 to 9 As shown, according to a specific embodiment of this application, a simulation design method for a vehicle body structure is provided, including:

[0032] Step S1: Establish the initial finite element model of the subframe connection structure of the vehicle body structure, wherein the subframe connection structure includes: bolts and bolt sleeves;

[0033] Step S2: Based on the initial finite element model of the subframe connection structure, preset conditions are applied to the bolts to obtain the first finite element model of the subframe connection structure, wherein the preset conditions are used to simulate the tightening state of the bolts;

[0034] Step S3: Fit the first finite element model of the subframe connection structure to the second finite element model of the vehicle body structure to obtain the simulation model;

[0035] Step S4: Apply collision conditions to the simulation model to simulate the collision conditions of the subframe under collision conditions and generate simulation data.

[0036] Step S5: Based on the simulation data, evaluate each connection point in the subframe connection structure to obtain the evaluation result of the subframe connection structure.

[0037] Step S6: Determine the target design parameters of the vehicle body structure based on the evaluation results.

[0038] Applying the technical solution of this embodiment, step S1 establishes an initial finite element model including bolts and bolt sleeves, ensuring the geometric integrity of the connection structure; step S2 simulates the bolt tightening state by applying preset conditions, introducing the initial stress field of the connector in the simulation for the first time, giving subsequent behavior a realistic physical starting point; step S3 embeds this high-fidelity sub-model into the whole vehicle model, ensuring that local mechanical properties are not simplified or lost; step S4 applies a real collision condition, and the system can automatically respond to the dynamic interaction of the connector caused by relative motion; step S5 quantitatively evaluates the force, displacement, separation sequence, etc. of each connection point based on simulation data, so that the evaluation no longer relies on experience judgment, but is based on data-driven objective analysis; finally, step S6 optimizes the design parameters in reverse based on the evaluation results, realizing a closed-loop feedback from simulation output to design input. This method improves the physical consistency and engineering guidance of the simulation results of subframe detachment behavior, and provides a reproducible, traceable and quantifiable technical path for the precise design of passive safety structures. Its effect does not depend on external empirical parameters, but rather on the systematic modeling of the internal mechanical mechanism of the connection structure. Based on this, the evaluation results can accurately identify weak connection points, guide the optimization of target design parameters such as bolt specifications, preload, and contact surface treatment, and improve the reliability of simulation and development efficiency.

[0039] Optionally, based on the initial finite element model of the subframe connection structure, preset conditions are applied to the bolts to obtain the first finite element model of the subframe connection structure, including: the initial finite element model of the subframe connection structure includes: the initial finite element model of the bolt and the initial finite element model of the bolt sleeve;

[0040] Step S21: Based on the initial finite element model of the bolt, apply a preload to the end face of the bolt to obtain the initial finite element model simulating the tightening state.

[0041] Step S22: Perform elastic rebound analysis on the initial finite element model simulating the tightening state to obtain the initial finite element model of the bolt with preload.

[0042] Step S23: Based on the initial finite element model of the preloaded bolt and the initial finite element model of the bolt sleeve, the first finite element model of the subframe connection structure is obtained.

[0043] In step S21, an axial preload is applied to the bolt end face to simulate the tightening behavior during actual assembly. This operation is not simply applying a boundary load, but rather establishing the initial load state of the tightening process in the finite element model, causing the bolt to undergo axial tensile deformation during loading, providing a physical basis for subsequent springback. This step enables the simulation model to have a mechanical response starting point for the tightening stage, which differs from the simplified assumptions of directly assigning an equivalent value of the preload or ignoring the tightening process in traditional methods, laying the foundation for realistically reproducing the internal stress field of the connector.

[0044] In step S22, the preload applied in step S21 is unloaded, and the bolt structure is solved using elastic springback analysis. This allows the bolt to retain residual tensile stress due to the elastic recovery of the material even without external force. This process realistically reflects the self-locking clamping force that continues to be applied to the connection interface after assembly. Traditional methods often ignore this elastic energy storage mechanism, directly assuming that the bolt is always under preload or replacing it with a rigid connection. This method, through springback analysis, ensures that the preload effect originates from the material's constitutive behavior rather than being artificially set, guaranteeing that subsequent contact pressure is naturally generated by physical deformation, significantly improving the physical consistency and simulation reliability of the model.

[0045] In step S23, the bolt model, which has undergone springback treatment and possesses residual stress, is structurally coupled with the rigid bolt sleeve model to form a complete initial model of the subframe connection structure. In this model, the bolt and bolt sleeve naturally fit together without external force, and the contact interface has an initial compression state maintained by residual stress, with no gaps or penetrations. This integration method avoids the initial loosening or artificial tightening defects caused by neglecting preload in traditional models, providing a realistic contact initiation condition for the natural triggering of slippage behavior in subsequent collisions. This is a key prerequisite for achieving physical-driven slippage rather than time-driven failure.

[0046] Based on steps 21 to S23, traditional methods typically simplify bolts as rigid connections or directly apply preload, neglecting their elastic deformation and stress release processes, leading to distortion of the preload state. This method first applies axial preload to the bolt end face (S21) to simulate the mechanical loading during actual tightening; then, it performs elastic rebound analysis on the loaded model (S22), ensuring that the bolt retains residual tensile stress determined by its material elastic properties after unloading the preload, realistically reflecting the preload clamping force that continues to act on the connection interface after assembly; finally, it structurally integrates the bolt model with the rigid bolt sleeve model (S23) to form the first finite element model of the subframe connection structure with a realistic initial contact state. This process eliminates the reliance on manually set contact pressure or failure thresholds for the preload effect, instead relying on the physical response of material constitutive modeling and structural deformation, significantly improving the accuracy and predictability of slippage behavior in subsequent collision simulations, and providing fundamental support for the accurate simulation of the subframe detachment process.

[0047] Optionally, an initial finite element model of the subframe connection structure is established, including:

[0048] Step S11: Establish the geometric model of the bolt and the geometric model of the bolt sleeve, and perform mesh generation on the geometric models of the bolt and the bolt sleeve to obtain the mesh generation model of the bolt and the mesh generation model of the bolt sleeve.

[0049] Step S12: Apply preset material properties to the mesh generation model of the bolt and the mesh generation model of the bolt sleeve to obtain the initial finite element model of the subframe connection structure. The preset material properties include: the bolt material is an elastic material and the bolt sleeve material is a rigid material.

[0050] In step S11, the geometric-discretization foundation of the subframe connection structure is constructed by establishing geometric models of the bolt and bolt sleeve respectively and performing mesh generation. This process preserves the axially slender structural characteristics of the bolt and the flat, thin-walled structural morphology of the bolt sleeve, ensuring that the geometry is consistent with the actual assembly. The mesh generation strategy does not use simplified shell elements or point elements, but rather a solid mesh, enabling the model to realistically reflect the axial deformation behavior of the bolt under tension and the rigid constraint characteristics of the bolt sleeve under contact compression. This provides a high-fidelity geometric and discretization foundation for subsequent mechanical analysis, avoiding misjudgments of contact failure or distortion of stress distribution caused by geometric simplification.

[0051] In step S12, elastic material properties are assigned to the bolt, and rigid material properties are assigned to the bolt sleeve, forming a material distinction that conforms to physical reality. The bolt, as the core component that bears tension and generates elastic rebound, must possess a true elastic constitutive model; while the bolt sleeve, as a structural component that bears clamping force and only undergoes minor elastic deformation, has a reasonable rigidity assumption and can significantly reduce computational complexity. This material property assignment method accurately matches the actual structural response mechanism under load, enabling the bolt to generate preload-driven deformation and rebound, while the bolt sleeve, as a rigid constraint, maintains the stability of the contact interface, providing a physical premise for subsequent preload modeling and slippage behavior triggering, based on structural-material coordination.

[0052] Based on steps S11 to S12, an initial finite element model of the subframe connection structure was established, ensuring that the model has a realistic geometric shape, a reasonable discretization method, and material properties that conform to physical behavior.

[0053] Optionally, establishing the initial finite element model of the subframe connection structure of the vehicle body structure also includes:

[0054] Step S111: Establish the geometric model of the bolt, and perform mesh generation on the geometric model of the bolt to obtain the mesh generation model of the bolt stud and the mesh generation model of the bolt nut.

[0055] Step S121: Apply the first preset material property from the preset material properties to the mesh generation model of the stud and the mesh generation model of the nut, wherein the first preset material property includes: the material of the stud is an elastic material and the material of the nut is an elastic material;

[0056] Step S131: Rigidly couple the mesh generation model of the stud and the mesh generation model of the nut to obtain the initial finite element model of the bolt.

[0057] In step S111, the geometric model of the bolt is divided into a stud portion and a nut portion, and each portion is meshed independently. This segmentation is not merely for modeling convenience, but is based on the functional and deformation differences of the bolt during loading: the stud is the core load-bearing area that bears axial tension and generates elastic rebound, while the nut mainly undertakes contact clamping and force transmission. By modeling separately, differentiated mesh control can be implemented for the two parts, ensuring that the stud region has a sufficiently fine axial element density to accurately capture tensile deformation, while the nut region maintains structural integrity, avoiding local distortion or computational redundancy caused by a uniform overall mesh. This segmented modeling method improves the model's resolution of local mechanical responses, providing a geometric and discretization consistency basis for subsequent rigid coupling.

[0058] In step S121, the same elastic material properties are assigned to both the stud and nut mesh models, ensuring that the two parts have unified constitutive response characteristics in mechanical behavior. This setting conforms to engineering reality: the bolt as a whole is made of the same metal material (such as alloy steel), and there is no essential difference between the stud and nut at the material level. This treatment avoids the erroneous assumption in traditional methods that the nut is set as a rigid body or its deformation is ignored in order to simplify the model. It makes the entire bolt structure behave as a continuous and homogeneous elastic body during loading and rebound, ensuring that the residual stress field is naturally transmitted between the stud and nut, without false stress concentration or boundary disturbance caused by abrupt material changes.

[0059] In step S131, the mesh models of the stud and nut are rigidly coupled, making them appear as a single rigidly connected unit group in the analysis. That is, the two parts maintain a fixed geometric relationship during relative motion, with no relative displacement or rotation. This ensures that during the application of preload (S21) and springback analysis (S22), the nut always deforms synchronously with the stud, and their contact surface will not experience non-physical loosening or penetration due to local flexibility. This method realistically simulates the rigid integral structure formed by the threaded engagement of the stud and nut in an actual bolt, providing structural integrity assurance for the subsequent formation of a complete bolt model with preload, and is a key step in achieving realistic preload transmission.

[0060] Based on steps S111 to S131, functional modeling of the internal structure of the bolt is realized. Segmented modeling ensures deformation resolution, unified elastic properties ensure constitutive consistency, and rigid coupling maintains structural integrity.

[0061] Optionally, establishing the initial finite element model of the subframe connection structure of the vehicle body structure also includes:

[0062] Step S112: Establish the geometric model of the bolt sleeve, and perform mesh generation on the geometric model of the bolt sleeve to obtain the mesh generation model of the bolt sleeve.

[0063] Step S122: Apply the second preset material property from the preset material properties to the mesh generation model of the stud and the mesh generation model of the nut to obtain the initial finite element model of the bolt sleeve. The second preset material property includes: the material of the bolt sleeve is a rigid material.

[0064] In step S112, a geometric model of the bolt sleeve is established and meshed to obtain its discretized finite element representation. This geometric model retains the typical characteristics of the bolt sleeve as a flat, thin-walled structure; its inner hole accommodates the bolt, and its outer edge connects to the subframe, undertaking the function of transmitting clamping force. The mesh generation does not use a solid mesh to ensure that it can realistically reflect the rigid constraint boundary conditions under contact loads, avoiding distortion of contact behavior or abnormal stress distribution due to oversimplification of the mesh. This modeling method provides geometric integrity assurance for the subsequent construction of the rigid body contact interface.

[0065] In step S122, the second preset material property (rigid material) is assigned to the mesh model of the bolt sleeve, making it behave as a completely rigid body in the simulation, without any elastic or plastic deformation. Under preload and collision loads, the bolt sleeve material (usually high-strength steel or metal bushing) undergoes only slight elastic deformation. Its overall structural stiffness is much higher than the bolt's tensile deformation, and its function is to stably bear and transmit the clamping force, rather than participate in energy absorption. Therefore, modeling it as a rigid body not only conforms to physical reality but also significantly reduces computational complexity, avoids convergence difficulties caused by material nonlinearity, and ensures the constraint stability and force transmission consistency of the contact interface.

[0066] Based on steps S112 to S122, the bolts are modeled as elastic-rigid coupled bodies with residual stress, and the bolt sleeves are modeled as rigid constraint bodies, thus constructing an unprecedented physically consistent finite element model of the subframe connection structure.

[0067] Optionally, the first finite element model is fitted to the second finite element model of the vehicle body structure to obtain a simulation model, including:

[0068] Step S31: Establish the second finite element model of the vehicle body structure, wherein the second finite element model of the vehicle body structure includes the second finite element model of the front longitudinal beam and the second finite element model of the subframe.

[0069] Step S32: Rigidly couple the initial finite element model of the preloaded bolt with the second finite element model of the front longitudinal beam to obtain the first simulation model;

[0070] Step S33: Rigidly couple the initial finite element model of the bolt sleeve with the second finite element model of the subframe to obtain the second simulation model;

[0071] Step S34: Based on the first simulation model and the second simulation model, obtain the simulation model.

[0072] In step S31, finite element models of the front longitudinal beam and subframe, which are directly related to the subframe connection in the vehicle body structure, are constructed as the basic carrier of the overall collision simulation system. This model preserves the true geometric shape and structural stiffness characteristics of the front longitudinal beam and subframe within the vehicle, providing spatial positional references and mechanical boundary support for the subsequent integration of connecting structures. This model is independent of the bolt and bolt sleeve modeling process, ensuring that the modeling of connecting components is modular, reusable, and engineering-practical, avoiding coupling confusion or computational redundancy caused by overall modeling.

[0073] In step S32, the bolt model, which has been processed in steps S21 to S23 and now possesses realistic residual preload, is rigidly coupled to the front longitudinal beam model. This operation ensures that the axial stress field of the bolt and the deformation behavior of the front longitudinal beam are completely synchronized, guaranteeing that during the collision process, the tensile force borne by the bolt is consistent with the inertial load and deformation trend of the front longitudinal beam. This coupling method, through a rigid connection at the structural level, ensures that the preload always acts on the overall system formed by the front longitudinal beam and the bolt, thereby realistically simulating the mechanical relationship of the bolt being fixed to the front longitudinal beam in actual assembly.

[0074] In step S33, the initial finite element model of the rigid bolt sleeve (whose material properties are rigid) is rigidly coupled to the second finite element model of the subframe, making the bolt sleeve a part of the subframe and moving with it as a whole. This process ensures that the bolt sleeve does not undergo displacement or rotation relative to the subframe during the collision, and its contact surface remains stable in the coordinate system of the subframe. This avoids contact penetration, misalignment, or non-physical slippage caused by model separation, providing a stable and predictable contact reference for subsequent slippage behavior between the bolt and the bolt sleeve.

[0075] In step S34, the front longitudinal beam and preloaded bolt subsystem generated in S32 are spatially matched and structurally integrated with the subframe and rigid bolt sleeve subsystem generated in S33 to form a complete vehicle collision simulation model. In this model, a compression contact interface without initial gap is formed between the bolts and bolt sleeves, naturally maintained by elastic rebound. The interaction force originates entirely from the residual stress of the bolts, rather than being artificially set. In subsequent collision simulations, the slippage and disengagement of this contact interface will be naturally triggered by the dynamic balance between the collision load and frictional resistance, without the need to set a failure time, delete the contact, or require manual intervention.

[0076] Based on steps S31 to S34, the front longitudinal beam and bolts are considered as one rigid system, and the subframe and bolt sleeves are considered as another rigid system. The two are connected only through physical pre-tightening contact, so that the separation behavior is naturally triggered by the dynamic balance of collision load and friction force, which more accurately simulates the failure process and improves the simulation accuracy.

[0077] Optionally, based on the first simulation model and the second simulation model, a simulation model is obtained, including:

[0078] Step S341: Obtain the contact type and friction coefficient between the bolt in the first simulation model and the bolt sleeve in the second simulation model;

[0079] Step S342: Based on the first simulation model, the second simulation model, the contact type, and the friction coefficient, a simulation model is obtained.

[0080] In step S341, based on the bolt in the first simulation model and the bolt sleeve in the second simulation model, the contact type and friction coefficient are defined. A physical model is performed on the surface-to-surface contact relationship (outer surface of the bolt and inner wall of the bolt sleeve) formed during actual assembly, ensuring that the two are in a compressed contact state before relative movement. The friction coefficient characterizes the physical resistance of the contact interface to relative slippage. This parameter is derived from engineering measurements or material handbooks, possessing clear physical meaning and traceability. This differs from the fuzzy processing of traditional methods that set failure times or ignore friction, enabling the model to possess the boundary conditions of real contact mechanics and providing a quantitative basis for triggering subsequent slippage behavior.

[0081] In step S342, the pre-tensioned bolt system (first simulation model), the rigid bolt sleeve system (second simulation model), the contact type, and the friction coefficient are integrated to form a complete vehicle collision simulation model. In this model, there are no artificially set failure conditions between the bolts and bolt sleeves; whether they detach depends entirely on whether the shear force generated by the collision load is sufficient to overcome the maximum static friction force determined by the pre-tension multiplied by the friction coefficient. This allows the simulation results to realistically reflect the entire process of the subframe gradually slipping → frictional energy dissipation → final detachment during a collision, rather than a non-physical jump of instantaneous disconnection.

[0082] Based on steps S341 to S342, a four-dimensional physical consistency modeling is achieved in the subframe detachment simulation, featuring self-generated preload, structural rigid coupling, quantifiable contact behavior, and self-triggered detachment mechanism. This solves the core defects of existing technologies, such as the invisible detachment process, uncontrollable failure conditions, and unreliable results. This method no longer relies on empirical parameters or manual intervention, making the simulation results engineering-interpretable and design-optimizable, providing a high-precision simulation technology path for the intelligent development of automotive passive safety structures.

[0083] Optionally, before obtaining the first finite element model of the subframe connection structure by applying preset conditions to the bolts based on the initial finite element model, the following steps are included:

[0084] Step S01: Obtain the tightening torque, tightening force coefficient, and nominal thread diameter of the bolt;

[0085] Step S02: Determine the preload based on the tightening torque, tightening force coefficient, and nominal thread diameter of the bolt.

[0086] In step S01, a direct mapping relationship is established between the simulation model and the actual assembly process parameters, so that the subsequent calculation of the preload no longer depends on empirical assumptions or approximate values, but is derived from traceable engineering measurement data, which significantly improves the engineering credibility and reproducibility of the model.

[0087] In step S02, based on the formula: P0=Mt / (K×d×0.001), the tightening torque (Mt), tightening force coefficient (K), and nominal thread diameter (d) obtained in step S01 are substituted into the formula to accurately calculate the bolt axial preload P0. This provides the preload for the subsequent elastic rebound-residual stress-contact clamping setup.

[0088] Optionally, the bolt sleeve is 3-8mm in size and the bolt thread has a nominal diameter of 12-16mm.

[0089] In one specific embodiment of this application, the bolt sleeve is 5mm in size, and the nominal diameter of the bolt thread is 14mm. During the production process, 150N is used. The torque m is used to determine the safety margin. By referring to tables, for typical machined surfaces, K is taken as 0.15. Combined with the nominal bolt diameter of 14mm, the preload can be calculated to be approximately 78.75kN. Rounding this to 75kN, this means an equivalent tensile force of 75kN is applied axially to the bolt. In this embodiment, the simulation process is as follows:

[0090] Step 1: Import the bolt solid model into the simulation software;

[0091] Step 2: Retain the stud and nut portions of the bolt, such as... Figure 2 As shown;

[0092] Step 3: Divide a 5mm 2D surface mesh on the end face of the stud;

[0093] Step 4: Along the axis of the stud, stretch out a 3D solid mesh at 5mm intervals, with a total length equal to that of the stud;

[0094] Step 5: Using the same method (Steps 3 and 4), extrude a 3D solid mesh into the nut part;

[0095] Step 6: Clear all 2D meshes;

[0096] Step 7: Assign material and properties to the bolt, where the material is an elastic material.

[0097] Step 8: Connect the stud and nut parts using rigid connection units to form a complete bolt, such as... Figure 3 As shown;

[0098] Step 9: Apply a tensile force of 75 kN to the end of the bolt;

[0099] Step 10: Enable the Springback solver control card to guide the finite element solver to calculate and retain the residual stress field inside the bolt due to the plastic-elastic deformation history after unloading the load. Figure 4 It is the length of the bolt in its free state. Figure 5 This is the bolt length under tension. The bolt model already has preload and can be used for collision simulation analysis.

[0100] Step 11: Using an implicit dynamics solution algorithm, perform static unloading analysis on the bolt model after applying preload. The software automatically solves and outputs a finite element mesh model of the bolt with initial residual stress, which serves as the initial state input for subsequent collision simulation.

[0101] Step 12: Import the bolt sleeve solid model into the simulation software;

[0102] Step 13: Clean the raised vertical ribs on the bolt sleeve to make the surface smooth and flat, such as... Figure 6 As shown;

[0103] Step 14: Create a 2D surface mesh on the model cleaned in Step 13, such as... Figure 7 As shown;

[0104] Step 15: Set the material and properties for the 2D mesh elements generated in Step 14, where the material is the rigid body material MATL20;

[0105] Step 16: Connect the rigid body bolt sleeve model obtained in Step 15 to the subframe model;

[0106] Step 17: In the vehicle model, add face-to-face contact between the elastic bolt model and the bolt sleeve model, and set the friction coefficient.

[0107] In whole-vehicle collision simulations, the slippage failure of this structure can effectively reproduce the actual process, such as... Figure 8 and Figure 9 As shown, as the collision progressed, the bolt sleeve slipped from the bolt and eventually detached and failed. This means the subframe and front longitudinal beam had detached and failed.

[0108] According to another aspect of the present invention, a vehicle is provided, the vehicle having a body structure, and the simulation design method for the body structure is performed using the simulation design method described in the above embodiments.

[0109] Specifically, the simulation design method for vehicle body structure includes the following steps:

[0110] Step S1: Establish the initial finite element model of the subframe connection structure of the vehicle body structure, wherein the subframe connection structure includes: bolts and bolt sleeves;

[0111] Step S2: Based on the initial finite element model of the subframe connection structure, preset conditions are applied to the bolts to obtain the first finite element model of the subframe connection structure, wherein the preset conditions are used to simulate the tightening state of the bolts;

[0112] Step S3: Fit the first finite element model of the subframe connection structure to the second finite element model of the vehicle body structure to obtain the simulation model;

[0113] Step S4: Apply collision conditions to the simulation model to simulate the collision conditions of the subframe under collision conditions and generate simulation data.

[0114] Step S5: Based on the simulation data, evaluate each connection point in the subframe connection structure to obtain the evaluation result of the subframe connection structure.

[0115] Step S6: Determine the target design parameters of the vehicle body structure based on the evaluation results.

[0116] Applying the technical solution of this embodiment, step S1 establishes an initial finite element model including bolts and bolt sleeves, ensuring the geometric integrity of the connection structure; step S2 simulates the bolt tightening state by applying preset conditions, introducing the initial stress field of the connector in the simulation for the first time, giving subsequent behavior a realistic physical starting point; step S3 embeds this high-fidelity sub-model into the whole vehicle model, ensuring that local mechanical properties are not simplified or lost; step S4 applies a real collision condition, and the system can automatically respond to the dynamic interaction of the connector caused by relative motion; step S5 quantitatively evaluates the force, displacement, separation sequence, etc. of each connection point based on simulation data, so that the evaluation no longer relies on experience judgment, but is based on data-driven objective analysis; finally, step S6 optimizes the design parameters in reverse based on the evaluation results, realizing a closed-loop feedback from simulation output to design input. This method improves the physical consistency and engineering guidance of the simulation results of subframe detachment behavior, and provides a reproducible, traceable and quantifiable technical path for the precise design of passive safety structures. Its effect does not depend on external empirical parameters, but rather on the systematic modeling of the internal mechanical mechanism of the connection structure. Based on this, the evaluation results can accurately identify weak connection points, guide the optimization of target design parameters such as bolt specifications, preload, and contact surface treatment, and improve the reliability of simulation and development efficiency.

[0117] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0118] In addition to the above, it should be noted that the terms "one embodiment," "another embodiment," and "embodiment" used in this specification refer to specific features, structures, or characteristics described in connection with that embodiment, which are included in at least one embodiment described in the general description of this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in connection with any embodiment, the intention is to suggest that implementing such a feature, structure, or characteristic in conjunction with other embodiments also falls within the scope of this invention.

[0119] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0120] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A simulation design method for vehicle body structure, characterized in that, include: An initial finite element model of the subframe connection structure of the vehicle body structure is established, wherein the subframe connection structure includes: bolts and bolt sleeves; Based on the initial finite element model of the subframe connection structure, preset conditions are applied to the bolts to obtain the first finite element model of the subframe connection structure, wherein the preset conditions are used to simulate the tightening state of the bolts; The first finite element model of the subframe connection structure is fitted with the second finite element model of the vehicle body structure to obtain the simulation model; Collision conditions are applied to the simulation model to simulate the collision conditions of the subframe under collision conditions and to generate simulation data; Based on the simulation data, each connection point in the subframe connection structure is evaluated to obtain the evaluation result of the subframe connection structure. The target design parameters for the vehicle body structure are determined based on the evaluation results.

2. The simulation design method for vehicle body structure according to claim 1, characterized in that, Based on the initial finite element model of the subframe connection structure, the preset conditions are applied to the bolts to obtain the first finite element model of the subframe connection structure, including: The initial finite element model of the subframe connection structure includes: the initial finite element model of the bolt and the initial finite element model of the bolt sleeve; Based on the initial finite element model of the bolt, a preload is applied to the end face of the bolt to obtain the initial finite element model simulating the tightening state. Elastic rebound analysis is performed on the initial finite element model of the simulated tightening state to obtain the initial finite element model of the bolt with preload. Based on the initial finite element model of the bolt with preload and the initial finite element model of the bolt sleeve, the first finite element model of the subframe connection structure is obtained.

3. The simulation design method for vehicle body structure according to claim 2, characterized in that, The initial finite element model of the subframe connection structure is established, including: Establish the geometric model of the bolt and the geometric model of the bolt sleeve, and perform mesh generation on the geometric model of the bolt and the geometric model of the bolt sleeve to obtain the mesh generation model of the bolt and the mesh generation model of the bolt sleeve; Preset material properties are applied to the mesh model of the bolt and the mesh model of the bolt sleeve to obtain the initial finite element model of the subframe connection structure. The preset material properties include: the bolt is made of an elastic material and the bolt sleeve is made of a rigid material.

4. The simulation design method for vehicle body structure according to claim 3, characterized in that, Establishing the initial finite element model of the subframe connection structure of the vehicle body structure further includes: Establish the geometric model of the bolt, and perform mesh generation on the geometric model of the bolt to obtain the mesh generation model of the bolt stud and the mesh generation model of the bolt nut; The first preset material property is applied to the mesh generation model of the stud and the mesh generation model of the nut, wherein the first preset material property includes: the material of the stud is an elastic material and the material of the nut is an elastic material; The initial finite element model of the bolt is obtained by rigidly coupling the mesh model of the stud and the mesh model of the nut.

5. The simulation design method for vehicle body structure according to claim 4, characterized in that, Establishing the initial finite element model of the subframe connection structure of the vehicle body structure further includes: Establish the geometric model of the bolt sleeve, and perform mesh generation on the geometric model of the bolt sleeve to obtain the mesh generation model of the bolt sleeve; The second preset material property in the preset material properties is applied to the mesh generation model of the stud and the mesh generation model of the nut to obtain the initial finite element model of the bolt sleeve. The second preset material property includes: the material of the bolt sleeve is a rigid material.

6. The simulation design method for vehicle body structure according to any one of claims 2-5, characterized in that, The simulation model is obtained by fitting the first finite element model with the second finite element model of the vehicle body structure, including: Establish the second finite element model of the vehicle body structure, wherein the second finite element model of the vehicle body structure includes: the second finite element model of the front longitudinal beam and the second finite element model of the subframe; The initial finite element model of the preloaded bolt and the second finite element model of the front longitudinal beam are rigidly coupled to obtain the first simulation model; The initial finite element model of the bolt sleeve and the second finite element model of the subframe are rigidly coupled to obtain the second simulation model. The simulation model is obtained based on the first simulation model and the second simulation model.

7. The simulation design method for vehicle body structure according to claim 6, characterized in that, Based on the first simulation model and the second simulation model, the simulation model is obtained, including: Obtain the contact type and friction coefficient between the bolt in the first simulation model and the bolt sleeve in the second simulation model; The simulation model is obtained based on the first simulation model, the second simulation model, the contact type, and the friction coefficient.

8. The simulation design method for vehicle body structure according to claim 7, characterized in that, Before obtaining the first finite element model of the subframe connection structure by applying the preset conditions to the bolts based on the initial finite element model, the process includes: Obtain the tightening torque, tightening force coefficient, and nominal thread diameter of the bolt; The preload is determined based on the tightening torque, the tightening force coefficient, and the nominal diameter of the bolt thread.

9. The simulation design method for vehicle body structure according to claim 8, characterized in that, The bolt sleeve has a size of 3-8mm, and the nominal diameter of the bolt thread is 12-16mm.

10. A vehicle, characterized in that, The vehicle has a body structure, and the simulation design method for the body structure is performed using the simulation design method described in any one of claims 1-9.

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