Vehicle lamp development method based on structural parameter correction and fatigue simulation analysis

Abstract

The invention relates to a vehicle lamp development method based on structural parameter correction and fatigue simulation analysis. The method comprises two parts of lamp structure parameter correction and lamp fatigue simulation analysis, and the lamp structure parameter correction stage comprises the steps of establishing a target mode, simplifying a model, setting initial parameters, performing mode analysis, confirming a simulation mode and the target mode, processing and outputting a mode analysis result and the like which are sequentially performed. The lamp simulation fatigue analysis stage comprises the steps of random vibration simulation analysis, selection of the maximum equivalent stress amplitude, calculation of the fatigue stress limit, comparison of the maximum equivalent stress amplitude and the fatigue stress limit, adjustment and the like which are carried out in sequence. Compared with existing similar methods, the method has the advantages that the model is simplified, the calculation rate and the result accuracy are greatly improved, the correctness of the early-stage lamp development process is ensured, the lamp development period is shortened, and the verification cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle lamps, and in particular to a vehicle lamp development method based on structural parameter correction and fatigue simulation analysis. Background Art

[0002] As automobiles become increasingly popular, the production of automotive lights is also increasing. The research and development of new automotive lighting products is becoming more frequent, but the development cycle is becoming shorter and shorter. Among them, the structural design of the lamp is an important foundation for automotive lighting development, and the strength and fatigue durability of the lamp are one of the key concerns in structural design.

[0003] Automotive lamps are often subjected to random vibration loads during operation. Vibration testing is necessary to verify the mechanical reliability of these lamps under these loads. Fatigue analysis of lamps under vibration loads is also a common task during lamp development. Therefore, it is crucial to design a lamp fatigue analysis solution that allows automotive lamp manufacturers to predict the fatigue life of winding welds during the development process, thereby shortening lamp development time and reducing verification costs.

[0004] Fatigue design is based on the modal analysis of random vibrations of lamps. The most commonly used modal analysis method for lamps is the finite element analysis method. Only by establishing a finite element model close to the actual lamp can the accurate analysis of the lamp modal be achieved. There are two main methods of lamp modal analysis in the existing technology: one is to directly omit the wiring harness, electronic components, PCB boards and other small characteristic components in the lamp structure for modal analysis. This method ignores many components, resulting in large errors in the calculation results; the other is to retain all lamp components for calculation. This method has a very large amount of calculation and also faces great difficulties in modal identification. In order to analyze the modal of the lamp efficiently and accurately, we simplified the wiring harness, electronic components, PCB boards and other small characteristic components in the lamp assembly model in the form of mass points, determined their positions according to the corresponding simplified center of mass coordinates, and connected them with RB3 connection units, achieving good results.

[0005] Furthermore, current finite element analysis of automotive lighting typically relies on raw material properties provided by suppliers or obtained through online research, eliminating the crucial benchmarking process. However, the performance of the same material produced by different manufacturers often varies significantly, making generalization difficult. This results in significant discrepancies between simulated and measured data, making the simulated results unreliable and irrational, and making it difficult to quickly and accurately adjust the lighting parameters.

[0006] Currently, general modal parameter identification only targets the first low-order modes (typically the first six) under the lamp constraint mode. Since random vibration fatigue simulation is based on the modal, the accuracy of the material parameters depends on the selected optimized modal during modal parameter optimization. This invention adds modal values ​​corresponding to the maximum numerical parameters of the mass participation factors in the X, Y, and Z directions, based on the first six orders of the current lamp constraint. This improves the accuracy of parameter correction and lays the foundation for the accuracy of subsequent fatigue analysis. Summary of the Invention

[0007] The main purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and to provide a vehicle lamp development method based on structural parameter correction and fatigue simulation analysis, the method including lamp structural parameter correction and lamp simulation fatigue analysis, wherein the lamp structural parameter correction includes, in sequence, establishing a target mode, model simplification, setting initial parameters, modal analysis, confirming the simulation mode and the target mode, and processing and outputting the modal analysis results; the lamp simulation fatigue analysis includes, in sequence, random vibration simulation analysis, selecting the maximum equivalent stress amplitude, calculating the fatigue stress limit, comparing the maximum equivalent stress amplitude with the fatigue stress limit and making adjustments.

[0008] Furthermore, the process of establishing the target mode is as follows: data of at least the first six modes under the constraints of the lamp are obtained through external testing, and the mode with the maximum mass participation factor in the first six modes and the remaining modes in the X, Y, and Z directions is selected as the target mode.

[0009] Furthermore, the external test includes a hammer method or a shaker method.

[0010] Furthermore, the value of the target mode includes a frequency value.

[0011] Furthermore, the specific process of model simplification is as follows: the characteristic components of the lamp, such as the PCB board and wiring harness, are simplified into mass points, and their positions are determined according to the centroid coordinates of the mass points. Each mass point and other components are connected through the RB3 connection unit.

[0012] Furthermore, the specific process for setting initial parameters is to import the 3D digital model of the lamp into the modal module of ANSYS software and initialize the parameters of the lamp material, such as Young's modulus and Poisson's ratio. The Young's modulus ranges from 1500-2000 MPa, and the Poisson's ratio ranges from 0.3-0.45.

[0013] Furthermore, the specific process of modal analysis is as follows: after setting the initial parameters and boundary conditions, the lamps are connected according to their actual connection method and the constraints are set, and the modal analysis is performed within 1.5 times the maximum random vibration load frequency.

[0014] Furthermore, the specific process of confirming the simulation mode and the target mode is as follows: based on the modal analysis in the previous step, the simulation mode is set as the result mode, the response surface optimization module is called in the ANSYS software, and the target mode established previously is set as the target mode of the simulation mode.

[0015] Furthermore, the specific process of modal analysis result processing and output is as follows: run and calculate the response surface optimization module, compare the simulation mode and the target mode based on the calculation results to see if they are the same. If so, complete the lamp structure parameter correction, obtain the Young's modulus, Poisson's ratio and other structural parameter values ​​that meet the target mode, and output the results for simulation fatigue analysis; if not, simplify the model again and correct the initial parameters, and then perform modal analysis again, confirm the simulation mode and target mode, process and output the modal analysis results, and other steps until the result is determined to be yes.

[0016] Furthermore, the specific process of random vibration simulation analysis is as follows: based on the corrected lamp structure parameters, the random vibration module in ANSYS software is called under the mode corresponding to the parameters, and the random vibration load spectrum is input for simulation analysis.

[0017] Furthermore, the process of selecting the maximum equivalent stress amplitude is as follows: according to the random vibration simulation analysis results, the simulation parameters of different components of the lamp are obtained, and then the maximum equivalent stress amplitude in the stress distribution of the lamp is determined.

[0018] Furthermore, the specific process of calculating the fatigue stress limit is as follows: based on the results of random vibration simulation analysis, the average displacement and average velocity of the lamp components are obtained, the average frequency f and random vibration duration t of the lamp components are first calculated, and then the average number of vibration cycles N of the lamp components are calculated; the SN curve function of the lamp material is obtained in advance through a tensile test, and the fatigue stress limit of the lamp components is calculated based on the SN curve function of the lamp material and the average number of vibration cycles N.

[0019] Furthermore, the process of comparing the maximum equivalent stress amplitude with the fatigue stress limit and making adjustments is as follows: compare the maximum equivalent stress amplitude of the lamp components with the fatigue stress limit. When the maximum equivalent stress amplitude is less than the fatigue stress limit, it is considered that the lamp components meet the vibration fatigue requirements and the analysis test is terminated; otherwise, it is considered that there is a fatigue risk in the lamp structure, and the lamp structure parameters need to be corrected and fatigue simulation analysis needs to be performed again until the lamp components meet the vibration fatigue requirements.

[0020] Compared with the prior art, the present invention is progressive in the following aspects:

[0021] (1) It fundamentally solves the problem of errors and differences between structural material parameters and physical parameters during modal analysis in the current lamp development process;

[0022] (2) The model was simplified, and small features such as wiring harnesses, PCB boards, and electronic components were simplified into mass points for connection, which greatly improved the calculation speed and accuracy of the results;

[0023] (3) Based on the currently commonly used first 6 modes under constrained lamps, new modes corresponding to the maximum values ​​of mass participation factors in the X, Y, and Z directions are added, which improves the accuracy of parameter correction and fatigue analysis;

[0024] (4) A new modal parameter correction method was designed to improve the correction efficiency of modal parameters and ensure the correctness of the early lighting development process;

[0025] (5) Designed a new lamp fatigue analysis method to improve the efficiency of fatigue analysis and ensure the correctness of the early lamp development process;

[0026] (6) The accuracy of simulation design greatly shortens the development cycle of lamps and reduces verification costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a comparison diagram of the vehicle lamp model of the present invention before and after simplification.

[0028] Figure 2 The figure is a flow chart of the vehicle lamp development method according to the present invention.

[0029] Among them, 1-base, 2-PCB board, 3-wiring harness, 4-mass point, 5-rb3 connection unit. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to fully understand the technical solutions and beneficial effects of the present invention, further description will be given below in conjunction with specific embodiments and drawings.

[0031] The present invention provides a vehicle lamp development method based on structural parameter correction and fatigue simulation analysis, which includes two parts: vehicle lamp structural parameter correction and fatigue simulation analysis. The following are detailed descriptions of each part:

[0032] (1) Correction of lamp structure parameters

[0033] Step 1: Establish the target mode. Modal analysis is one of the main methods for studying the dynamic characteristics of structures, and is usually used in the field of engineering vibration. Modal analysis can mainly obtain the natural frequency, damping ratio and modal vibration shape of the structure. The process of analyzing these modal parameters is called modal analysis. For an n-degree-of-freedom system, there are theoretically n modes. However, which of these modes plays a major role in the response of the structure is usually determined by the modal effective mass. After the actual structure is discretized by the finite element method, its generalized dynamic equation can be expressed as:

[0034]

[0035] Where M is the mass matrix of the structure, C is the damping matrix of the structure, K is the stiffness matrix, and F(t) is the external load excitation.

[0036] Usually, external loads are not considered in modal calculations, that is, F(t) = 0. On this basis, after ignoring structural damping, the generalized dynamic equation can be expressed as:

[0037]

[0038] By solving the second-order homogeneous differential equation, the eigenvalues ​​and eigenvectors of the above equation can be obtained, thereby obtaining the natural frequency ω and vibration mode function Φ of the structure, where Φ is set as the structural modal eigenvalue vector. In the finite element method, the mass is normalized according to the principles of mass normalization, stiffness normalization, or maximum amplitude normalization. The generalized mass matrix of the structure can be expressed as:

[0039] 2dMφ

[0040] The modal participation factor is a parameter that describes the interaction between a mode and a vector excitation. It is the ratio of the sum of the mass of each particle and its corresponding coordinate in a certain vibration mode to the modal mass of the vibration mode. Therefore, the expression of the modal participation factor is:

[0041]

[0042] The modal effective mass is the sum of the squares of the modal participation factors obtained after normalization of the modal mass, and its expression is:

[0043]

[0044] Under the excitation of a certain vector, each mode has a corresponding modal effective mass. The one with a larger effective mass is more easily excited. Therefore, the importance of each mode can be determined by the modal effective mass.

[0045] Based on the above principles, external tests (such as the hammer method or the shaker method) are used to obtain at least the first six modes under the constraints of the lamp (the first six modes are low-order modes, which are more easily excited by external excitation and are the modes that need to be focused on in engineering design) and the modes corresponding to the maximum values ​​of the mass participation factors in the X, Y, and Z directions (these three orders represent their importance to structural vibration in the X, Y, and Z directions) as target modes.

[0046] Table 1 Modal and mass participation factors

[0047]

[0048] Taking the modal and mass participation factor table for a certain lamp model in Table 1 as an example, the first ten modes were obtained. The first six modal values ​​correspond to the modal values ​​for mode 1 through mode 6 in Table 1: 79 Hz, 90.6 Hz, 110 Hz, 127.6 Hz, 129.8 Hz, and 146 Hz. The maximum mass participation factors in the X, Y, and Z directions for the first ten modes are 26.4%, 28.9%, and 24.2%, respectively, corresponding to mode 5, mode 2, and mode 9. Therefore, the modal values ​​(frequencies) corresponding to mode 1, mode 2, mode 3, mode 4, mode 5, mode 6, and mode 9 were selected as the target modes.

[0049] Step 2: Simplify the model. Figure 1 As shown in the figure below, the left image shows the lamp model before simplification, and the right image shows the simplified lamp model. The lamp consists of a base 1, a PCB board 2, and a wiring harness 3. The PCB board 2 and wiring harness 3 are connected and fixed to the base 1. Previously, simply removing small components such as the PCB board 2 and wiring harness 3 from modal analysis resulted in inaccurate results. To address this issue, we simplified the PCB board 2 and wiring harness 3 into mass points 4 and determined their positions according to their corresponding center of mass coordinates. Each mass point is connected to other components via RB3 connection units 5.

[0050] Step 3: Set initial parameters. For each lamp component, determine its density using its mass / volume. The remaining structural parameters to be optimized are the Young's modulus and Poisson's ratio of each component. Import the 3D digital model of the target lamp into the modal module of ANSYS software and initialize the Young's modulus and Poisson's ratio parameters for the lamp material.

[0051] Step 4: Modal Analysis. Building on Step 3, set the boundary conditions for the modal analysis. Specifically, set the following: ① Material Assignment: Initially, set the Young's modulus to a value between 1500 and 2000 MPa, and the Poisson's ratio to a value between 0.3 and 0.45. ② Components: Connect the lamps according to their actual connection method, and constrain all degrees of freedom according to the bolt holes connecting the lamp to the vehicle body. Since the national standard for random vibration load input is 0-1000 Hz, the modal analysis frequency is set to 1.5 times the maximum random vibration load frequency, meaning the frequency is set to 0-1500 Hz.

[0052] Step 5: Confirm the simulation mode and target mode. Based on the mode simulated in step 4, set the simulation mode as the result mode. Open the response surface optimization module in ANSYS software and set the target mode obtained in step 1 as the target mode of the simulation mode.

[0053] Step 6: Modal analysis result processing. Run and calculate the response surface optimization module based on the settings in step 5. If the result is judged as yes, the structural parameter values ​​(Young's modulus, Poisson's ratio) that meet the target mode are obtained. If the result is judged as no, return to step 2 to modify the parameters (mainly modify Young's modulus and Poisson's ratio), and repeat steps 3 to 5 with the modified parameters until the result is judged as yes.

[0054] Step 7: Output the results. Based on the modal analysis results that are judged as yes in step 6, the structural parameters (Young's modulus, Poisson's ratio) after response surface optimization are input to the lamp material for subsequent fatigue analysis ( Figure 2 Prepare for random vibration analysis in simulation fatigue analysis).

[0055] (2) Fatigue simulation analysis

[0056] Step 1: Take samples of different materials of the lamp to be tested and perform tensile tests to obtain the SN curve function;

[0057] Step 2: There are two methods for random vibration simulation analysis. The first is based on modal analysis, and the second is direct analysis. The random vibration simulation analysis in this paper adopts the first method (i.e., based on modal analysis). Based on the lamp structure parameters optimized in the sixth step of (1) lamp structure parameter correction, the random vibration module is called in ANSYS software and the modal simulation result data is shared by connecting the model module in (1). The modal analysis after the parameters are corrected in (1) uses the random vibration load spectrum as input (the random vibration spectrum is used as the random vibration input load of the lamp according to the requirements of the national standard GB-T10485 2017) to simulate and complete the analysis.

[0058] Step 3: Acquire simulation parameters of different components of the lamp, including the stress distribution of the lamp, and select the maximum equivalent stress amplitude in the stress distribution of the lamp.

[0059] Step 4: Calculate the average number of vibration cycles of each component based on the lighting simulation parameters. The specific method is: the average displacement and average velocity of the lighting components can be obtained based on the random vibration simulation, and the average frequency of the lighting components (f = (average displacement / average velocity) / 2π) and the random vibration duration t are calculated. Based on this, the average number of vibration cycles of the components N = f*t is calculated.

[0060] Step 5: Calculate the fatigue stress limit of each lamp component based on the SN curve function of the lamp material (see Step 1) and the average number of vibration cycles (see Step 4). The fatigue stress limit calculation formula is S = AB * lgN, where S is the fatigue stress limit value, N is the average number of vibration cycles, and A and B are the material SN curve functions obtained from tensile testing, calculated using the undetermined coefficient method. A and B are fixed values ​​for different materials.

[0061] Step 6: Compare the maximum equivalent stress amplitude of the lamp components obtained in the third step and the fatigue stress limit value calculated in the fifth step. When the maximum equivalent stress amplitude is less than the fatigue stress limit value, it is judged that the lamp components to be tested meet the vibration fatigue requirements and the analysis test is ended; otherwise, it is judged that there is a fatigue risk in the lamp structure and it is necessary to return to the sixth step (1) of lamp structure parameter correction to re-optimize the structure of the part where the maximum equivalent stress amplitude exceeds the limit, and perform random vibration analysis again until the lamp components to be tested meet the vibration fatigue requirements.

Claims

1. A vehicle lamp development method based on structural parameter modification and fatigue simulation analysis, characterized by: The method includes lamp structural parameter correction and lamp simulation fatigue analysis, wherein the lamp structural parameter correction includes establishing target mode, model simplification, setting initial parameters, modal analysis, confirming simulation mode and target mode, processing and outputting modal analysis results, and the lamp simulation fatigue analysis includes random vibration simulation analysis, selecting maximum equivalent stress amplitude, calculating fatigue stress limit, comparing maximum equivalent stress amplitude with fatigue stress limit and making adjustments.

2. The method according to claim 1, wherein The process of establishing the target mode is as follows: obtain data of at least the first six modes under the constraints of the lamp through external testing, and select the mode with the maximum mass participation factor in the X, Y, and Z directions of the first six modes and the remaining modes as the target mode.

3. The method according to claim 1, wherein The model simplification process is as follows: the PCB board, wiring harness and other characteristic components of the lamp are simplified into mass points, their positions are determined according to the centroid coordinates of the mass points, and each mass point and other components are connected through the RB3 connection unit.

4. The method according to claim 1, wherein The process of setting the initial parameters is as follows: importing the three-dimensional digital model of the lamp into the modal module of ANSYS software, and initializing the parameters such as Young's modulus and Poisson's ratio of the lamp material.

5. The method according to claim 1, wherein The modal analysis process is as follows: after setting the initial parameters and boundary conditions, the lamps are connected according to their actual connection method and the constraints are set, and the modal analysis is performed within a frequency range of 1.5 times the maximum random vibration load.

6. The method according to claim 1, wherein The process of confirming the simulation mode and the target mode is as follows: based on the modal analysis in the previous step, the simulation mode is set as the result mode, the response surface optimization module is called in the ANSYS software, and the target mode established previously is set as the target mode of the simulation mode.

7. The method according to claim 1, wherein The process of processing and outputting the modal analysis results is as follows: run and calculate the response surface optimization module, compare the simulated mode with the target mode based on the calculation results to see if they are the same. If so, complete the lamp structure parameter correction, obtain the Young's modulus, Poisson's ratio and other structural parameter values ​​that meet the target mode, and output the results for simulation fatigue analysis; if not, re-simplify the model and correct the initial parameters, then perform modal analysis again, confirm the simulated mode with the target mode, process and output the modal analysis results, and so on, until the result is determined to be yes.

8. The method according to claim 1, wherein The process of random vibration simulation analysis is as follows: based on the corrected lamp structural parameters, the random vibration module in ANSYS software is called under the mode corresponding to the parameters, and the random vibration load spectrum is input for simulation analysis; the process of selecting the maximum equivalent stress amplitude is as follows: according to the random vibration simulation analysis results, the simulation parameters of different lamp components are obtained, and then the maximum equivalent stress amplitude in the lamp stress distribution is determined.

9. The method according to claim 1, wherein The process of calculating the fatigue stress limit is as follows: Based on the random vibration simulation analysis results, the average displacement and average velocity of the lamp components are obtained. The average frequency and random vibration duration of the lamp components are calculated first, and then the average number of vibration cycles of the lamp components are calculated. According to the SN curve function of the lamp material and the average number of vibration cycles N, the fatigue stress limit of the lamp components is calculated.

10. The method according to claim 1, wherein The process of comparing the maximum equivalent stress amplitude with the fatigue stress limit and making adjustments is as follows: compare the maximum equivalent stress amplitude of the lamp components with the fatigue stress limit. When the maximum equivalent stress amplitude is less than the fatigue stress limit, it is considered that the lamp components meet the vibration fatigue requirements and the analysis test is terminated; otherwise, it is considered that there is a fatigue risk in the lamp structure and the lamp structure parameters need to be corrected and fatigue simulation analysis needs to be performed again until the lamp components meet the vibration fatigue requirements.

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