Simulation analysis method for puncture strength of automobile ejector pin

Abstract

The invention relates to the technical field of automobile simulation analysis, in particular to an automobile thimble puncture strength simulation analysis method, which comprises the following steps of: sensing original data of a whole automobile skeleton design, and constructing a three-dimensional geometric model; receiving material parameters and structural features, assigning values to all parts in the three-dimensional geometric model, and converting the three-dimensional geometric model into a finite element model; boundary conditions and a loading mode of simulation analysis are set, rigid body motions such as integral translation and rotation of the finite element model are avoided, it is ensured that the finite element model only generates deformation conforming to an actual scene in the loaded direction, and the reasonability of simulation basic logic is guaranteed; running simulation analysis, creating a collision contact pair, and recording key parameter variation in the running simulation analysis process as output of a displacement unit and a speed unit; and the evaluation unit is used for receiving the displacement unit and the speed unit, extracting indexes strongly associated with the puncture resistance, evaluating the puncture resistance and analyzing whether simulation correction is carried out or not.

Description

Technical Field

[0001] This invention relates to the field of automotive simulation analysis technology, and more specifically, to a method for simulating and analyzing the puncture intensity of automotive jacket. Background Technology

[0002] In today's rapidly developing automotive industry, vehicle safety has become a core consideration for consumers' car purchase decisions and a key area of ​​technological competition in the industry. As a crucial part of the vehicle body structure, the puncture resistance of the car roof directly affects the survival space and life safety of occupants when the vehicle is involved in a collision or when the roof is subjected to external impacts (such as falling objects, rollovers, and other extreme conditions). The puncture strength index has become a core parameter for measuring the overall safety level of a vehicle.

[0003] However, the traditional pin puncture strength testing method has a bottleneck that is difficult to overcome: Firstly, the cost is high. Physical testing requires the creation of high-precision physical prototypes. From the development of the roof mold and the assembly of vehicle parts to the investment in professional testing equipment (such as servo hydraulic puncture test benches and high-speed impact devices), the cost of a single test can reach hundreds of thousands of yuan. Moreover, the destructive nature of the experiment means that each prototype can only be used for testing under a single working condition. Covering multiple working conditions means that the number of prototypes increases exponentially, leading to uncontrolled costs.

[0004] Secondly, the cycle is lengthy. From test plan design and prototype manufacturing to experimental execution and data analysis, a basic working condition test cycle often takes several weeks. If it involves iterative verification of multiple variables (such as different puncture angles, speeds, and top cover structure schemes), the R&D cycle will be delayed for several months, which seriously lags behind the pace of new car development and is difficult to adapt to the automotive industry's demand for "rapid iteration and agile development".

[0005] Third, the coverage of operating conditions is limited. In reality, the impact conditions on the top of a vehicle are complex and diverse—the combination of variables such as the shape of the puncture object (sharp / blunt), the impact angle (vertical / tilted), the loading rate (static loading / high-speed impact), and the temperature environment (high temperature / low temperature) is almost infinite; physical testing is limited by physical conditions and cannot exhaust all potential dangerous scenarios, resulting in loopholes in safety assessment, which may allow design flaws to enter the market and create safety hazards. Given this industry pain point, developing an efficient and accurate simulation analysis method for automotive ejector pin puncture strength has become an inevitable choice to overcome technological constraints. From the perspective of R&D efficiency, simulation technology can complete the design of the roof structure and the simulation of puncture conditions in a "virtual space," and can quickly verify the feasibility of the solution without the need for a physical prototype. Through parametric modeling, engineers can complete iterative analysis of multiple variables (such as beam cross-sectional dimensions, skin thickness, and material grade) within hours, compressing the traditional testing cycle to 1 / 10 or even less, helping companies to quickly respond to market demands and seize product opportunities. However, traditional ejector pin puncture strength testing methods usually rely on physical testing and destructive experiments. These methods are not only costly and time-consuming, but also cannot fully cover various potential working conditions and vehicle structures. Therefore, developing an efficient and accurate simulation analysis method for automotive ejector pin puncture strength has significant practical implications. Summary of the Invention

[0006] The purpose of this invention is to solve the problem that traditional pin puncture strength testing methods usually rely on physical testing and destructive experiments.

[0007] To achieve the above objectives, this invention provides a simulation analysis method for the puncture intensity of automotive pedicle screws, comprising the following steps: S1. Perceive the original data of the overall vehicle frame design and construct a three-dimensional geometric model; S2. Receive material parameters and structural features, assign values ​​to each component within the three-dimensional geometric model, and convert the three-dimensional geometric model into a finite element model. S3. Set the boundary conditions and loading method for the simulation analysis; S4. Run the simulation analysis, create collision contact pairs, and record the changes in key parameters during the simulation analysis as outputs for displacement and velocity elements; S5 receives displacement and velocity units, extracts indicators strongly correlated with puncture resistance, evaluates puncture resistance, and analyzes whether simulation correction is required. If necessary, simulation correction is performed.

[0008] As a further improvement to this technical solution, the three-dimensional geometric model is constructed as follows: with the center of the front axis as the origin, the X-axis moves forward vertically, the Y-axis moves horizontally to the right, and the Z-axis moves vertically upward to construct the three-dimensional geometric model. According to the assembly relationship, the local coordinates of each component are sequentially transformed to the coordinates under the three-dimensional geometric model to construct a three-dimensional geometric model including each component. The coordinates of a certain point of a component in the three-dimensional geometric model are equal to the coordinates of the component in its own local coordinate system, plus the coordinate offsets of the origin of the local coordinate system in the x, y, and z directions in the unified coordinate system of the three-dimensional geometric model.

[0009] As a further improvement to this technical solution, if there is an angle between the local axis system of the component and the axis system of the vehicle body when constructing the three-dimensional geometric model, a rotation adjustment is performed: when rotating around the X-axis, the coordinates under the local coordinate system of the component are used as the basis, combined with the angle θ of rotation around the X-axis, and calculated according to the geometric relationship transformation rules, and then the coordinate offset of the origin of the local coordinate system in the entire three-dimensional geometric model is added. When adjusting the rotation around the Y-axis, start with the local coordinates of the component, and calculate the X and Z components in the local coordinates according to the spatial coordinate transformation law corresponding to the rotation angle θ around the Y-axis. Then add the coordinate offset of the origin of the local coordinate system in the three-dimensional geometric model. When adjusting the rotation around the Z-axis, the X and Y components in the local coordinates are processed according to the coordinate transformation rules corresponding to the rotation angle θ around the Z-axis. Then, the coordinate offset of the origin of the local coordinate system in the three-dimensional geometric model is added.

[0010] The beneficial effects of the above-mentioned further solutions are as follows: When adjusting by rotating around the Y-axis, the X and Z components of the local coordinates are calculated and coordinate offsets are superimposed according to the spatial coordinate transformation rules corresponding to the rotation angle θ around the Y-axis. This can effectively correct the shaft system deviation caused by the tilt attitude of the component and restore the actual spatial position of the component in the plane perpendicular to the Y-axis in the actual vehicle. When adjusting by rotating around the Z-axis, the X and Y components are processed according to the coordinate transformation rules of the rotation angle θ around the Z-axis based on the local coordinates of the component and coordinate offsets are superimposed. This can accurately eliminate the shaft system angle problem caused by the yaw attitude of the component, ensure that the layout of the component in the plane perpendicular to the Z-axis matches the actual vehicle, and comprehensively solve the angle problem between the local shaft system of the component and the body shaft system. This allows the component assembly relationship and spatial attitude of the three-dimensional geometric model to closely match the actual vehicle, laying a precise geometric foundation for subsequent finite element model construction and pin puncture strength simulation analysis.

[0011] Based on the above technical solution, the present invention can be further improved as follows: The detailed steps for converting the three-dimensional geometric model into the finite element model are as follows: Step 1: Detect the smaller value between the wheelbase and the maximum width of the vehicle body, and use the smaller value as the global reference mesh size; calculate the global reference mesh size of the 3D geometric model by multiplying the global reference mesh size by the refinement factor, and divide the 3D geometric model into multiple finite element elements based on the mesh size. This avoids excessive refinement of non-critical areas, which would increase the amount of computation, balances simulation accuracy and efficiency, and lays the foundation for subsequent simulation of the mechanical behavior of the pin puncture.

[0012] Step 2: Set different element types, perceive the geometric dimensions of each finite element element, and set the geometric dimension thresholds corresponding to different element types. Classify finite element elements into different element types so that different structural feature components can match and adapt to the element types. Utilize the advantages of various element mechanical assumptions to accurately restore the mechanical properties of components and improve the adaptability of the finite element model to complex vehicle body structures. Step 3: Establish the element stiffness matrix of the finite element through material parameter mapping, define the force and displacement transfer rules between finite element elements through structural features, integrate the element stiffness matrices and transfer rule constraint equations of all finite element elements, and transform the three-dimensional geometric model into a finite element model.

[0013] The beneficial effects of the above-mentioned further solutions are that by establishing the element stiffness matrix through material parameter mapping, defining and integrating the transfer rules with structural features, the material properties can be accurately integrated into the element mechanical behavior. The transfer rules ensure that the force and displacement transfer between elements conforms to the logic of the actual vehicle, allowing the finite element model to accurately reproduce the mechanical response of the actual vehicle, providing a high-fidelity model for the simulation of the pin puncture strength, making the simulation results reliable, and helping to accurately evaluate and optimize the puncture resistance performance of the vehicle roof.

[0014] Based on the above technical solution, the present invention can be further improved as follows: The steps for establishing the element stiffness matrix are as follows: Step 1: Assigning material parameters requires extracting the key mechanical parameters based on the mechanical properties of each component, and then constructing a material constitutive relation matrix that reflects the stress and strain of the material according to the mechanical assumptions of the finite element type. Step 2: Combining the geometric characteristics and shape function of the finite element, derive the strain-displacement matrix of the finite element: The strain-displacement matrix specifically represents the relationship between the strain at any point within the finite element and the displacement of the nodal points of the finite element. Step 3: Couple the material constitutive relation matrix and strain-displacement matrix to generate the element stiffness matrix that reflects the ability of the finite element to resist deformation.

[0015] As a further improvement to this technical solution, the connection attribute assignment needs to be based on the mechanical characteristics of the actual connection form between components, and the corresponding constraint definition method should be selected. Then, the force and displacement transmission rules are established by defining the constraint relationship between finite element elements: the element stiffness matrix of all components is reconstructed into an overall stiffness matrix according to the assembly relationship. During the construction, the global node displacement degree of freedom number and the local degree of freedom number of the node within the finite element element are associated. The constraint relationship corresponding to the connection attribute is transformed into constraint equations, embedded into the overall equilibrium equations, and finally formed into a complete finite element control equation, thereby assigning values ​​to each finite element element and realizing the conversion from the three-dimensional geometric model to the finite element model.

[0016] As a further improvement to this technical solution, the boundary conditions limit unnecessary redundant degrees of freedom of the finite element model through constraint equations, ensuring that the finite element model only produces realistic deformation in the loaded direction and avoids rigid body motion. The specific conditions are set according to the actual working conditions of the vehicle in the pin puncture scenario.

[0017] The beneficial effects of the above-mentioned further solutions are that, through constraints such as rigid force transmission at weld points and flexible deformation at adhesive joints, force and displacement transmission rules are established by defining finite element constraint relationships. Then, the component element stiffness matrix is ​​constructed according to the assembly relationship to create an overall stiffness matrix (associating global and local degree-of-freedom numbers). Furthermore, the connection attribute constraint relationships are converted into constraint equations and embedded into the overall equilibrium equations, forming a complete finite element control equation assignment unit. This accurately replicates the mechanical transmission of connections between real vehicle components, allowing the finite element model to conform to the assembly logic of the real vehicle, and improving the accuracy of the model's simulation of force transmission and structural response during pin puncture; boundary conditions... The purpose of setting constraints is to limit redundant degrees of freedom in the finite element model. The beneficial effect is to limit unnecessary degrees of freedom through constraint equations, so that the model only produces realistic deformation in the load direction and avoids rigid body motion. Constraints are set according to the actual working conditions of pin puncture (road parking, laboratory testing). For example, road parking restricts Z-axis translation and rotation around the X and Y axes, while retaining X and Y-axis translation. Laboratory testing restricts all rigid body motion and only retains local deformation degrees of freedom, so that the model constraint state is consistent with the actual vehicle working conditions. This provides a realistic boundary environment for pin puncture strength simulation, ensures the reliability of simulation results, and helps to accurately evaluate the puncture resistance performance of the vehicle roof.

[0018] Based on the above technical solution, the present invention can be further improved as follows: The loading method simulates the mechanical interaction between the ejector pin and the punctured structure by defining external excitation. According to the actual working conditions, the geometric / material properties, motion excitation and contact mechanics finite element model of the ejector pin are defined in sequence: the geometric and material properties of the ejector pin are defined, and then the motion trajectory of the ejector pin is defined by displacement / velocity excitation. The contact interaction between the ejector pin and the roof is described by the contact finite element model, so as to ensure the effective transmission of force and accurate simulation of roof structure damage during the puncture process.

[0019] As a further improvement to this technical solution, all finite element elements on the surface of the ejector pin that make physical contact with the contact body are defined as ejector pin contact elements, and all finite element elements on the surface of the contact body that make physical contact with the ejector pin are defined as contact elements, thereby creating collision contact pairs. The displacement unit includes displacement units for the ejector pin and the contact body: the displacement unit for the ejector pin is the advancing distance of the ejector pin along the puncture direction, and the possible lateral offset; the displacement unit for the contact body is the indentation depth and extension / wrinkling deformation of the contact body under the pressure of the ejector pin; the velocity unit includes velocity units for the ejector pin and the contact body: the velocity unit for the ejector pin is the instantaneous rate of the ejector pin puncture; the velocity unit for the contact body is the deformation rate of the contact body under the impact of the ejector pin.

[0020] As a further improvement to this technical solution, the puncture resistance performance is evaluated: ; in This represents the maximum permissible puncture depth of the thimble. To the maximum permissible indentation depth of the contact body, The maximum permissible puncture speed of the thimble, To determine the maximum allowable deformation rate of the contact body, These are the corresponding weights; A safety indication performance threshold is set. If the assessed puncture resistance performance is less than the safety indication performance threshold, simulation correction is performed based on real vehicle test data. ,in These are the parameter values ​​of the finite element model before correction. These are the target indicators obtained from real vehicle testing. To correct the corresponding indices calculated in the previous simulation. This is a correction factor.

[0021] The beneficial effects of the above-mentioned further solutions are as follows: By constructing an evaluation formula that includes four key parameters—pin puncture depth, contact body indentation depth, pin puncture speed, and contact body deformation rate—and combining their respective maximum allowable thresholds and corresponding weights, a comprehensive quantitative evaluation of pin puncture performance can be achieved. This solves the problems of the qualitative and singular nature of traditional evaluations, allowing engineers to accurately grasp the safety boundary of roof puncture resistance. When the evaluation result is lower than the safety threshold, real vehicle test data is introduced, and the finite element model is corrected using a correction formula (corresponding to the model parameters before correction, real vehicle and simulation indicators, and correction coefficients). This effectively compensates for the differences between simulation assumptions (such as simplified material constitutives and approximate boundary conditions) and actual working conditions, continuously iterating to improve model accuracy. This provides a reliable simulation basis for roof structure optimization design and safety performance verification, helping companies identify risks and optimize solutions in advance during the new vehicle development stage, balancing safety performance and development costs, and ensuring the safety of the passenger roof.

[0022] In addition to the advantages and benefits mentioned above, the present invention has other objects, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0023] Figure 1This is a flowchart of the simulation analysis of the puncture strength of the automotive ejector pin in this invention; Figure 2 This is a schematic diagram illustrating the simulation analysis of the puncture strength of the automotive ejector pin in this invention. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] refer to Figure 1 As shown, the simulation analysis method for the puncture strength of a car ejector pin includes the following steps: S1. Perceive the original data of the overall vehicle frame design (such as CATIA and UG format files). The original data includes the assembly relationship of each component (relative position requirements between each component), angle relationship (such as the 90° angle between the crossbeam and the longitudinal beam), material parameters (mechanical properties of each component), structural features (local detailed features of each component), geometric dimensions (basic dimensions of each component), etc. Using the center of the front axis as the origin, a three-dimensional geometric model is constructed with the X-axis pointing forward, the Y-axis pointing to the right, and the Z-axis pointing upward. The local coordinates of each component are then transformed to the coordinates within the three-dimensional geometric model according to the assembly relationship, thus constructing a three-dimensional geometric model including all components. The specific expressions are as follows: ; in To transform the coordinates of each component in the local coordinate system to the coordinates in the three-dimensional geometric model, These are the coordinates of the component in its local coordinate system. These are the coordinates of the origin of the local coordinate system in the three-dimensional geometric model. If there is an angle between the local axis system of a component and the axis system of the vehicle body, a rotational adjustment is performed, and the specific expression is as follows: Rotate around the X-axis (adjust pitch angle): ,in The angle is the rotation around the X-axis; Rotate around the Y-axis (adjust the tilt angle): ,in The angle is the rotation around the Y-axis; Rotate around the Z-axis (adjust yaw angle): ,in The rotation angle is about the Z-axis; This invention further considers that, as the core load-bearing structure of the vehicle body, the actual structure of the car roof contains multi-dimensional detailed features (such as the varying thickness distribution of the roof sheet metal, the cross-sectional shape and spatial arrangement of the roof beams, and the process parameters of connecting components such as weld points / weld seams / adhesive layers). Furthermore, the material properties of different areas (such as the difference in sheet metal strength between the critical puncture area and the edge area, and the mechanical properties of connecting components) directly determine the stress deformation and failure resistance of the roof under the puncture scenario. If the 3D geometric model simplifies or deviates from the actual structural details or material properties of the car roof, it will further lead to discrepancies between the mechanical response of the 3D geometric model and the actual vehicle (for example, ignoring the weld point cluster at the front of the beam will underestimate the local connection strength, and mismatching the elastic modulus of the sheet metal material will cause the simulated deformation to deviate from the actual vehicle by more than 20%), thus affecting the accuracy of the puncture strength simulation results and failing to provide a reliable basis for roof structure optimization and safety performance evaluation. To avoid the above situation: S2. Receive material parameters and structural features, assign values ​​to each component within the 3D geometric model, and convert the 3D geometric model into a finite element model. The specific expression is as follows: Calculate the global reference mesh size of the 3D geometric model , Wheelbase Set the maximum width of the vehicle body; set the grid size: ,in For refinement coefficients, refinement coefficients The smaller the value, the smaller the grid size. The three-dimensional geometric model is divided into multiple finite element elements. The three-dimensional geometric model is discretized, and the finite element elements are connected by nodes, thereby decomposing the three-dimensional geometric model into a finite number of interconnected finite element elements. For the divided finite element elements, different element types are set (Solid element (three-dimensional stress state, isotropic material), BEAM element (Euler-Bernoulli beam assumption, isotropic material), shell element, etc.), the geometric dimensions of each finite element element are perceived, and the geometric dimension thresholds corresponding to different element types are set to classify the finite element elements into different element types. The process involves establishing the element stiffness matrix of finite element units through material parameter mapping, defining the force and displacement transfer rules between finite element units based on structural features, and then numerically simulating the stress behavior of real structures. Finally, the element stiffness matrices and transfer rule constraint equations of all finite element units are integrated to transform the three-dimensional geometric model into a finite element model. The specific steps are as follows: Step 1: Assigning material parameters requires extracting key mechanical parameters based on the mechanical properties of each component (e.g., metals, composites, adhesives, etc.). Then, based on the mechanical assumptions of the finite element type (e.g., three-dimensional stress state, beam bending theory, shell membrane-bending coupling effect), construct the material constitutive relation matrix. Material constitutive relation matrix Reflecting material stress With strain A linear relationship; Step 2: Combining the geometric characteristics and shape functions of finite element elements (shape function) (Explaining the interpolation relationship between nodal displacements and internal displacements of the finite element), deriving the strain-displacement matrix of the finite element. Strain-displacement matrix Specifically, the strain at any point within a finite element. With finite element nodal displacement The relationship, that is ; Step 3: Coupled Material Constitutive Relation Matrix and strain-displacement matrix Generate element stiffness matrix ,in Let be the volume of the finite element.

[0026] The assignment of connection attributes requires selecting the corresponding constraint definition method based on the mechanical characteristics of the actual connection between components (such as rigid force transmission of welds, flexible deformation of adhesive bonding, and continuous force transmission of welds). Then, the force and displacement transmission rules are established by defining the constraint relationships between finite element elements. The specific working principle is as follows: The element stiffness matrix of all components The overall stiffness matrix is ​​then constructed again based on the assembly relationship. ,in , Number the displacement degrees of freedom corresponding to the global nodes. , This refers to the local degree of freedom numbering corresponding to the nodes within the finite element element; Step 4: Transform the constraint relationships corresponding to the connection attributes (such as multi-point constraints of weld points, element stiffness of adhesive bonding, and node merging of weld seams) into constraint equations, embed them into the overall equilibrium equations, and finally form a complete finite element control equation. This allows for the assignment of values ​​to each finite element element, realizing the conversion from a three-dimensional geometric model to a finite element model.

[0027] An example of converting a 3D geometric model is as follows: Set the mesh size to 8mm, and then use Solid elements and Mat100 material for the weld points between each component, use BEAM elements and Mat100 material for the weld seam, use Solid elements and Mat1 material for the adhesive, use shell elements and Mat24 material for the sheet metal structure, and assign values ​​to each component in the 3D geometric model using actual material properties for each material parameter to ensure the accuracy and stability of the conversion to a finite element model.

[0028] This invention extracts key mechanical parameters based on the actual material mechanical properties of each component (such as metals, composite materials, adhesives, etc.), and constructs a material constitutive relation matrix by combining the mechanical assumptions of the finite element type (such as three-dimensional stress state, beam bending theory, and membrane-bending coupling effect of shell). At the same time, it derives the strain-displacement matrix by combining the geometric features and shape functions of the elements, and then couples them to generate the element stiffness matrix. This can accurately restore the mechanical response characteristics of each component and avoid problems such as simulation deformation exceeding 20% ​​deviation from the actual vehicle due to mismatch of material parameters. By selecting the corresponding constraint definition method based on the mechanical characteristics of the actual connection forms between components (such as the rigid force transmission of welds, the flexible deformation of adhesives, and the continuous force transmission of welds), the rules for the transmission of force and displacement between finite element elements are established. This effectively restores the actual force transmission effect of connecting components such as weld clusters, welds, and adhesive layers, avoiding the underestimation of local connection strength due to ignoring or simplifying connection details. By calculating the global reference mesh size according to the wheelbase and the maximum width of the vehicle body, and setting the mesh size and dividing finite element elements in combination with the refinement coefficient, and classifying the element type (Solid element, BEAM element, shell element, etc.) according to the geometric size threshold, it is possible to achieve accurate discretization of multi-dimensional detailed features of the car roof (such as the thickness distribution of the roof sheet metal, the cross-sectional shape and spatial arrangement of the roof beams). This ensures that the structural features of the finite element model and the three-dimensional geometric model are highly consistent, thereby ensuring the accuracy of subsequent pin puncture strength simulation analysis. This provides a reliable finite element model basis for roof structure optimization and safety performance evaluation, reduces the deviation of simulation results caused by insufficient finite element model fidelity, and enhances the guiding value of simulation analysis for practical engineering applications.

[0029] S3. Set the boundary conditions and loading methods for simulation analysis to effectively avoid rigid body motions such as overall translation and rotation of the finite element model. This ensures that the finite element model only undergoes deformation in the loading direction, conforming to the actual scenario, and guarantees the rationality of the simulation's basic logic. The specific working principle is as follows: Boundary conditions limit unnecessary redundant degrees of freedom (displacement / rotation) in the finite element model through constraint equations, ensuring that the finite element model only produces realistic deformations in the loaded direction and avoiding rigid body motions (such as overall translation and rotation). The specific conditions are set according to the actual working conditions of the vehicle in the pin puncture scenario (such as the vehicle being stationary or fixed to the test bench), and the specific expressions are as follows: Simulating a real-world parking scenario: The vehicle contacts the ground via its tires, with the ground providing vertical support to constrain the vehicle's overall position. Translation and rotation , The shaft can rotate (avoiding tipping and pitching), but retains... , Translational degree of freedom (simulating slight ground slippage, consistent with actual parking characteristics): ; in This is the set of contact points between the tire and the ground. For contact nodes of Translational displacement , Contact nodes Around , The rotation angle of the shaft; Simulated laboratory puncture test: The vehicle is forcibly fixed by a bench fixture, restricting all rigid body motion degrees of freedom, and only retaining the local deformation degrees of freedom of the punctured structure such as the roof: ; in , They are nodes of , Translational displacement For nodes Around The rotation angle of the shaft.

[0030] The loading method simulates the mechanical interaction between the ejector pin and the punctured structure (such as a car roof) by defining external excitations (pin motion excitation, contact mechanics finite element model). Specifically, based on the actual working conditions, the geometric / material properties of the ejector pin, the motion excitation (displacement / velocity), and the contact mechanics finite element model are defined sequentially to ensure effective force transmission and accurate simulation of structural damage. Specifically, the geometric (cylinder) and material (rigid Mat20) properties of the ejector pin are defined, and then the motion trajectory of the ejector pin is defined through displacement / velocity excitation. The contact interaction (force transmission, contact separation) between the ejector pin and the car roof is described through the contact finite element model, ensuring effective force transmission and accurate simulation of roof structural damage (such as plastic deformation, fracture) during puncture. The specific ejector pin motion excitation expression is as follows: ,in Center of mass of the thimble The velocity in the X direction at time t; The expression for the finite element model of contact mechanics is as follows: Let A be the set of nodes on the contact surface of the ejector pin, and B be the set of nodes on the contact surface of the roof. The contact direction is the normal direction (let's call it the n-direction, pointing towards the interior of the roof). Penetration judgment condition: for any node... Calculate the shortest distance from it to the roof contact surface. ,like If node a penetrates the roof, then it is determined that node a penetrates the roof. Penetration depth; According to the penalty function method, the normal contact force on the penetrating node a is... for ,in For contact stiffness; refer to Figure 2 As shown, in the boundary conditions and loading method, the ejector pin can be made of Mat20, a rigid obstacle avoidance material; specifically, the lower edge of the obstacle avoidance is coplanar with the Z plane of the head's center of mass, and the central axis of the obstacle avoidance is coplanar with the Y plane of the head's center of mass. It is placed at the front end of the roof beam, and the boundary conditions are a half-loaded ground line, an impact speed of 32 km / h, and a negative X direction to simulate the process of ejector pin puncture. Specifically, by setting motion excitation and contact mechanics models in conjunction with actual puncture requirements, the actual mechanical interaction process between the ejector pin and the roof structure is accurately simulated. This ensures the effective transmission of force during puncture and the accurate simulation of roof structure damage (such as plastic deformation and fracture). It avoids simulation result deviations caused by the disconnect between the loading method and actual working conditions, thereby providing external excitation conditions that fit the real scenario for subsequent ejector pin puncture strength simulation analysis. This enhances the reference value of simulation results for evaluating the puncture performance of real vehicle ejector pins and helps to accurately determine whether the roof's puncture resistance meets safety requirements.

[0031] S4. Run simulation analysis and create collision contact pairs: Define the contact body (the finite element element that contacts the ejector pin during the simulation: such as the roof beam or skin), define all finite element elements on the ejector pin surface that have physical contact with the contact body as ejector pin contact elements, and define all finite element elements on the contact body surface that have physical contact with the ejector pin as contact elements, thereby creating collision contact pairs; and record the changes in key parameters during the simulation analysis as displacement and velocity elements for output, thereby accurately simulating the contact and force transmission process between the ejector pin and the roof structure, avoiding force transmission distortion caused by ambiguous definition of contact relationship, and ensuring the authenticity of structural response (such as deformation and damage) in the simulation; The displacement unit includes the displacement units of the ejector pin and the contact body: the displacement unit of the ejector pin is the advance distance of the ejector pin along the puncture direction (such as downward along the Z-axis), and the possible lateral offset (such as X / Y axis displacement, which needs to be combined with boundary conditions); the displacement unit of the contact body is the indentation depth (normal displacement) and extension / wrinkling deformation (tangential displacement) of the contact body under the pressure of the ejector pin. The velocity unit includes the velocity units of the ejector pin and the contact body: the velocity unit of the ejector pin is the instantaneous rate of the ejector pin puncture; the velocity unit of the contact body is the deformation rate of the contact body under the impact of the ejector pin (the greater the velocity, the more prone the structure is to brittle damage, such as cracking). The specific expressions for the ejector displacement element and velocity element are as follows: the initial coordinates of the ejector at the start of the sensing simulation. The current coordinates of the apex at any time t during the loading process. The displacement element includes initial coordinates. With current coordinates The difference; the velocity element represents the rate of change of displacement with time during the loading of the ejector pin. The displacement and velocity elements provide reliable data support for subsequent evaluation of puncture resistance and correction of the finite element model, thus improving simulation analysis. S5 receives displacement and velocity units, extracts indicators strongly correlated with puncture resistance, and evaluates puncture resistance. ,in This represents the maximum permissible puncture depth of the thimble. To the maximum permissible indentation depth of the contact body, The maximum permissible puncture speed of the thimble, To determine the maximum allowable deformation rate of the contact body, These are the corresponding weights; Set a safety indicator performance threshold, if evaluating puncture resistance performance. If the safety indication performance threshold is exceeded, then the real vehicle test data will be used for simulation correction. ,in These are the parameter values ​​of the finite element model before correction. These are the target indicators obtained from real vehicle testing. To correct the corresponding indices calculated in the previous simulation. To correct the coefficients, simulation accuracy is improved through simulation refinement, addressing the qualitative and singular nature of traditional evaluation methods and enabling engineers to accurately grasp structural safety boundaries. When simulation results do not meet safety thresholds, real vehicle test data is introduced. Based on the correction formula (corresponding to the finite element model parameters before correction, the time / performance relationship between the real vehicle and simulation indicators, and the correction coefficients), the finite element model is corrected. This effectively compensates for the differences between simulation assumptions (such as simplified material constitutives and approximate boundary conditions) and actual working conditions, continuously iterating to improve the accuracy of the finite element model. This provides a more reliable simulation basis for subsequent roof structure optimization design and safety performance verification, helping companies identify risks and optimize solutions in advance during the new vehicle development stage, balancing safety performance and R&D costs.

[0032] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for simulation analysis of the piercing strength of a car needle, characterized in that, Includes the following steps: The system senses the original data of the vehicle frame design and constructs a three-dimensional geometric model; it receives material parameters and structural features and assigns values ​​to each component within the three-dimensional geometric model, converting the three-dimensional geometric model into a finite element model; it sets the boundary conditions and loading methods for simulation analysis; it runs the simulation analysis, creates collision contact pairs, and records the changes in key parameters during the simulation analysis as displacement and velocity elements for output; it receives displacement and velocity elements, extracts indicators strongly correlated with puncture resistance, evaluates puncture resistance, and analyzes whether simulation correction is needed, performing simulation correction if necessary.

2. The method of claim 1, wherein: Constructing the three-dimensional geometric model: With the center of the front axis as the origin, construct the three-dimensional geometric model with the X-axis moving forward vertically, the Y-axis moving horizontally to the right, and the Z-axis moving vertically upward. According to the assembly relationship, sequentially transform the local coordinates of each component to the coordinates under the three-dimensional geometric model to construct a three-dimensional geometric model including each component: The coordinates of a point of a component in the three-dimensional geometric model are equal to the coordinates of the component in its own local coordinate system, plus the coordinate offsets of the origin of the local coordinate system in the x, y, and z directions in the unified coordinate system of the three-dimensional geometric model.

3. The method of claim 2, wherein: If there is an angle between the local axis system of the component and the axis system of the vehicle body when constructing the three-dimensional geometric model, a rotation adjustment is performed: when rotating around the X-axis, the coordinates in the local coordinate system of the component are used as the basis, combined with the angle θ of rotation around the X-axis, and calculated according to the geometric relationship transformation rules. Then, the coordinate offset of the origin of the local coordinate system in the entire three-dimensional geometric model is added. When adjusting the rotation around the Y-axis, start with the local coordinates of the component, and calculate the X and Z components in the local coordinates according to the spatial coordinate transformation law corresponding to the rotation angle θ around the Y-axis. Then add the coordinate offset of the origin of the local coordinate system in the three-dimensional geometric model. When adjusting the rotation around the Z-axis, the X and Y components in the local coordinates are processed according to the coordinate transformation rules corresponding to the rotation angle θ around the Z-axis. Then, the coordinate offset of the origin of the local coordinate system in the three-dimensional geometric model is added.

4. The method of claim 3, wherein: The detailed steps for converting the three-dimensional geometric model into the finite element model are as follows: The smaller value between the wheelbase and the maximum width of the vehicle body is used as the global reference mesh size. The global reference mesh size is calculated by multiplying it by a refinement factor, and the 3D geometric model is divided into multiple finite element elements based on the mesh size. Different element types are defined, the geometric size of each finite element element is perceived, and geometric size thresholds corresponding to different element types are set to classify the finite element elements into different element types. The element stiffness matrix of the finite element elements is established through material parameter mapping, and the force and displacement transmission rules between finite element elements are defined through structural features. The element stiffness matrices and transmission rule constraint equations of all finite element elements are integrated to transform the 3D geometric model into a finite element model.

5. The method of claim 4, wherein: The steps for establishing the element stiffness matrix are as follows: Material parameters are assigned based on the mechanical properties of each component, key mechanical parameters are extracted, and then, according to the mechanical assumptions of the finite element type, a material constitutive relation matrix reflecting the stress and strain of the material is constructed; combined with the geometric characteristics and shape function of the finite element, the strain-displacement matrix of the finite element is derived: The strain-displacement matrix is ​​specifically the relationship between the strain at any point in the finite element and the displacement of the nodal points of the finite element. By coupling the constitutive relation matrix and strain-displacement matrix of the material, an element stiffness matrix reflecting the ability of the finite element to resist deformation is generated.

6. The method of claim 4, wherein: The connection attributes are assigned based on the mechanical characteristics of the actual connection between components. The corresponding constraint definition method is selected, and then the force and displacement transmission rules are established by defining the constraint relationship between finite element elements: the element stiffness matrix of all components is reconstructed into an overall stiffness matrix according to the assembly relationship. During the construction, the global node displacement degree of freedom number and the local degree of freedom number of the node within the finite element element are associated; the constraint relationship corresponding to the connection attribute is transformed into constraint equations, embedded into the overall equilibrium equations, and finally a complete finite element control equation is formed, thereby assigning values ​​to each finite element element and realizing the conversion from the three-dimensional geometric model to the finite element model.

7. The method of claim 1, wherein: The boundary conditions limit unnecessary redundant degrees of freedom of the finite element model through constraint equations, ensuring that the finite element model only produces realistic deformation in the loaded direction and avoids rigid body motion. The specific conditions are set according to the actual working conditions of the vehicle in the pin puncture scenario.

8. The method of claim 7, wherein: The loading method simulates the mechanical interaction between the ejector pin and the punctured structure by defining external excitation. According to the actual working conditions, the geometric / material properties, motion excitation, and contact mechanics finite element model of the ejector pin are defined in sequence: the geometric and material properties of the ejector pin are defined, and the motion trajectory of the ejector pin is defined through displacement / velocity excitation. The contact finite element model describes the contact interaction between the ejector pin and the roof, ensuring the effective transmission of force and accurate simulation of roof structure damage during the puncture process.

9. The method of claim 8, wherein: All finite element elements on the surface of the ejector pin that make physical contact with the contact body are defined as ejector pin contact elements, and all finite element elements on the surface of the contact body that make physical contact with the ejector pin are defined as contact elements, thereby creating collision contact pairs; The displacement unit includes displacement units for the ejector pin and the contact body: the displacement unit of the ejector pin is the advancing distance of the ejector pin along the puncture direction, and the possible lateral offset; the displacement unit of the contact body is the indentation depth and extension / wrinkling deformation of the contact body under the pressure of the ejector pin; the velocity unit includes velocity units for the ejector pin and the contact body: the velocity unit of the ejector pin is the instantaneous rate of ejector pin puncture; the velocity unit of the contact body is the deformation rate of the contact body under the impact of the ejector pin.

10. The method for simulating and analyzing the puncture strength of a car pedestal pin according to claim 1, characterized in that: Assessing the resistance to puncture wherein is the maximum allowed puncture depth of the tip, is the maximum allowed indentation depth of the contact body, is the maximum allowed puncture speed of the tip, is the maximum allowed deformation rate of the contact body, are the respective weights, respectively. A safety indication performance threshold is set. If the assessed puncture resistance performance is less than the safety indication performance threshold, simulation correction is performed based on real vehicle test data. ,in These are the parameter values ​​of the finite element model before correction. These are the target indicators obtained from real vehicle testing. To correct the corresponding indices calculated in the previous simulation. This is a correction factor.

Images