Equivalent headlamp modeling method for front vehicle body crashworthiness analysis

Abstract

The invention relates to an equivalent headlamp modeling method for front vehicle body crashworthiness analysis. The equivalent headlamp modeling method comprises the steps that parts with similar shapes are found; carrying out an axial crushing test; displacement and pressure curves of the part are obtained; grid division is processed before finite element analysis; loading by adopting a pressure head and a constraint mode which are the same as those of the test; the part is endowed with materials and thicknesses; performing simulation analysis on the part; a curve of contact force and displacement of the pressure head is put forward through simulation post-processing; comparing the displacement and pressure curves of simulation and test; and the obtained material information of the headlamp CAS is applied to a model needing to be calculated. According to the method, an equivalent stiffness method is adopted, and material parameters in a simulation model are modified, so that the headlamp stiffness calculated through simulation analysis is similar to the headlamp stiffness obtained through a test; and then the adjusted headlamp model is substituted into the whole vehicle model, so that the influence caused by no increase of headlamp data or increase of a headlamp with inaccurate rigidity in the whole vehicle body crashworthiness model is eliminated.

Description

Technical Field

[0001] The invention belongs to the technical field of vehicle body crashworthiness simulation development, and in particular relates to an equivalent headlight modeling method for frontal vehicle body crashworthiness analysis. Background Art

[0002] At present, in the passive safety field, in the crashworthiness simulation development stage of the vehicle body, the headlights usually have only simple styling surfaces, namely, CAS surfaces. In this way, the finite element model of the headlights will not be added to the simulation analysis model. Figure 1 Some of the models shown have added a ShortGun extension structure to cope with a 25% small offset collision, so the headlights need to be fixed on the ShortGun. By performing a cross-section on the ShortGun in the XOZ direction, it can be found that the headlight is located just above the designed longitudinal beam bending position. For the frontal collision condition of the whole vehicle, the path from the headlight to the ShortGun is equivalent to another "force transmission path". Obviously, the stiffness of the headlight has an impact on the deformation of the longitudinal beam, especially for models with the first bending position designed to be directly below the headlight. The result of the whole vehicle collision model without adding the headlight in the simulation analysis is obviously inaccurate. Summary of the invention

[0003] The purpose of the present invention is to provide an equivalent headlight modeling method for frontal vehicle body crashworthiness analysis, so as to eliminate the impact caused by not adding headlight data or adding headlights with inaccurate stiffness in the vehicle body crashworthiness model, and improve the simulation accuracy.

[0004] The objective of the present invention is achieved through the following technical solutions:

[0005] An equivalent headlight modeling method for frontal vehicle crashworthiness analysis comprises the following steps:

[0006] A. Find parts with similar headlight shape to the model being developed;

[0007] B. Perform an axial crush test on the headlight using a fixed pressure head and speed;

[0008] C. Obtain the displacement and pressure curve of the part in the experimental equipment;

[0009] D. Meshing before finite element analysis, i.e. extracting the CAS surface of the test headlight for meshing;

[0010] E. Use the same indenter and the same restraint method as the test to load;

[0011] F. Assign material and thickness to the headlight housing unit;

[0012] G. Perform simulation analysis on parts, i.e. pre-processing, solving and post-processing;

[0013] H. The curve of contact force and displacement of the indenter is proposed by simulation post-processing;

[0014] I. Compare the displacement and pressure curves of the simulation and the test to see how consistent the two curves are:

[0015] I1. If the consistency between the simulation and test curves is acceptable, the material information of the external CAS equivalent to the actual headlight is obtained, and step J is executed;

[0016] I2. If the difference between the simulation and test curves is large and the results are not consistent, modify the material information of the external CAS and return to step G-step I until the consistency between the simulation and test curves is acceptable;

[0017] J. Obtain the material information of the headlight CAS and apply it to the model that needs to be calculated.

[0018] Furthermore, in step A, the found parts are similar in shape to the headlights of the developed vehicle model, but the locations of the mounting points and the sizes of the headlights may be different.

[0019] Furthermore, in step B, during the test, the loading speed is 400 mm / min, the loading distance is about 100 mm, and the test time is 15 seconds.

[0020] Furthermore, step D is specifically as follows: inputting Catia data of the CAS surface of the headlight, extracting only the outermost CAS surface of the headlight in the Hypermesh software, and meshing the CAS surface in the Hypermesh software.

[0021] Furthermore, in step E, the loading speed is 1500 mm / s, and the rest of the settings of the simulation are consistent with the loading method of the experiment.

[0022] Furthermore, in step I, the equivalence is stiffness equivalence.

[0023] Further, in step I2, the modification is to modify EMOD and LCID_T in MAT I Two parameters are used to make the simulated pressure-displacement curve consistent with the experiment.

[0024] Furthermore, if the consistency is not good, adjust EMOD and LCID_T I After the two parameters are adjusted successfully and the curves are compared successfully, the thickness and material curve of the CAS surface are obtained.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention adopts the "equivalent stiffness method", that is, adopts the means of benchmarking simulation and experiment, and makes the stiffness of the headlight calculated by simulation analysis similar to the stiffness of the headlight obtained by experiment by modifying the material parameters in the simulation model; then the adjusted headlight model is brought into the whole vehicle model. At this time, the stiffness of the adjusted headlight is similar to that of the actual headlight in the whole vehicle collision, which can eliminate the influence caused by not adding headlight data or adding headlights with inaccurate stiffness in the whole vehicle body crashworthiness model, thereby improving the simulation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 A cross-sectional view of a certain vehicle model XOZ in the prior art;

[0029] Figure 2 A flowchart of the steps of the equivalent headlight modeling method for frontal vehicle body crashworthiness analysis of the present invention;

[0030] Figure 3 Schematic diagram of the headlight axial crush test;

[0031] Figure 4 Axial crush displacement-reaction force curve of headlight;

[0032] Figure 5 CAS material information outside the headlight;

[0033] Figure 6 Comparison of displacement-reaction force curves of simulation and test headlights. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with embodiments:

[0035] When the passive safety body crashworthiness simulation analysis is involved in the vehicle development stage, there is only the CAS surface of the headlights, but no detailed data of the headlights, and the presence or absence of the headlights will affect the collision results. For this reason, the present invention adopts the "equivalent stiffness method" to perform a crush test on the headlights with a shape similar to the developed vehicle model to obtain a pressure-displacement curve. The CAS surface of the headlight is extracted, and the material information parameters of the CAS surface are adjusted in the simulation to make the pressure-displacement curve of the simulation and the test approximate. The material curve of the real headlight is obtained by replacing the CAS surface with a headlight-like shape, and then the material curve is applied to the CAS surface of the headlight of this vehicle model. The purpose of using the stiffness of the CAS surface of the real headlight is achieved. In the front body crashworthiness development stage, not only the headlight model is added, but also the stiffness of the model is guaranteed.

[0036] The equivalent headlight modeling method for frontal vehicle body crashworthiness analysis of the present invention comprises the following steps:

[0037] 1. Find parts with similar shape to the headlights of the vehicle being developed.

[0038] The similarity in the present invention mainly refers to similar shapes, with differences in size and installation points. Since the CAS surface is the CAS surface of the new model, the size difference has been taken into consideration. Taking the D357 headlight of the Bestune B70 and the D365 headlight of the Bestune T55 as an example, the two headlights have similar shapes, and the difference lies in the location of the installation point and the size of the headlight.

[0039] 2. Perform an axial crush test on the headlight using a fixed pressure head and speed.

[0040] In the test, the loading speed is 400mm / min and the loading distance is about 100mm. Figure 4 and 6 The test time is 15 seconds.

[0041] 3. Obtain the displacement and pressure curves of the part in the experimental equipment.

[0042] 4. Meshing before finite element analysis, that is, extracting the CAS surface of the test headlight for meshing.

[0043] Meshing is the basis of finite element simulation analysis. That is, pre-processing tools such as Hypermesh, Ansa and other software are used to convert the data files generated by Catia into unit (mesh) files for simulation analysis, and the files are given material and thickness information to describe them so that they are consistent with real parts.

[0044] Specifically, the Catia data of the CAS surface of the headlight is input, only the outermost CAS surface of the headlight is extracted in the Hypermesh software, and the CAS surface is meshed in the Hypermesh software.

[0045] 5. Use the same indenter and the same constraint method as the test for loading. Since the loading speed in the test is 400mm / min, it is obviously unrealistic in the simulation analysis. Loading at the speed of the test requires a lot of time (several weeks). On the other hand, the loading speed has little effect on the results. The speed is 1500mm / s. For the rest of the settings, the loading method of the simulation is consistent with that of the experiment.

[0046] 6. Assigning material and thickness to the headlight housing unit. In the present invention, meshing and assigning material and thickness to parts are the basis of finite element simulation analysis, which can be collectively referred to as finite element analysis pre-processing.

[0047] Specifically, the information in SECID can be used to describe the material thickness of the part; the information in MID can be used to describe the material thickness of the part.

[0048] 7. Simulate and analyze the parts, that is, pre-processing, solving and post-processing. Pre-processing is divided into finite element pre-processing mesh division, assigning materials and thickness, applying constraints and boundary condition loading. Solving mainly uses commercial simulation software for solving, and this part of the work is mainly calculated by computers. Post-processing mainly looks at the deformation of the headlights during crushing and the curves of force and displacement.

[0049] 8. The post-simulation processing presents the curve of contact force and displacement of the indenter.

[0050] 9. Compare the displacement and pressure curves of the simulation and the test to see if they are consistent:

[0051] If the consistency between the simulation and test curves is acceptable, the material information of the external CAS equivalent to the actual headlight is obtained, and the next step is performed;

[0052] If there is a large gap between the simulation and test curves and the results are not consistent, modify the material information of the external CAS and return to step 6-step 8 until the consistency between the simulation and test curves is acceptable.

[0053] The present invention is a modeling method for equivalent headlights, and the equivalent is stiffness. Figure 4 and Figure 6 It can be seen that the horizontal coordinate of the curve is displacement, the vertical coordinate is the pressure of the pressure head, and their ratio is the stiffness of the headlight.

[0054] In the frontal collision test of the whole vehicle, the headlights are under pressure. The stress conditions in the actual working conditions are consistent with the test design in question 6. The length of the headlight parts in the collision direction is about 260mm. During the collision test, the headlights will deform by about 10%, that is, 26mm. Figure 6It can be seen that within the displacement of 26 mm, the slopes of the simulation and experimental curves are consistent.

[0055] The above modifications are EMOD and LCID_T in MAT (material information) I The goal is to make the simulated pressure-displacement curve consistent with the experiment. Figure 4 and Figure 6 It can be seen that the Y coordinate (reaction force) of the test curve has a sudden change, which corresponds to the failure of the parts in the headlight. This can be changed by adjusting LCID_T I The curve in the simulation is approximately consistent with the test; EMOD controls the slope of the curve, that is, the stiffness of the headlight. If the slope of the simulated pressure-displacement curve is larger than the test pressure-displacement curve, EMOD should be reduced; otherwise, it should be increased. Since only the curve before 26mm is adjusted, the main adjustment is EMOD.

[0056] 10. Finally, the material information of the headlight CAS is obtained and applied to the model that needs to be calculated.

[0057] Example 1

[0058] According to the project plan, at the beginning of the simulation, there is only the outer CAS surface of the part, so it is necessary to use this CAS surface to replace the actual performance of the part. First, there is a physical headlight of a car model with similar shape in the past, and a crush test is performed on it. Then the CAS surface of the "similar shape" car model is analyzed, and by adjusting EMOD and LCID_T I These two parameters are similar in simulation and test curves and are applied to new models.

[0059] Since the CAS surface belongs to CATIA data, finite element analysis is required to obtain its reaction force and displacement curves, including the following steps:

[0060] 1. Pre-process CATIA data, that is, convert CATIA files into .k or .key files, that is, mesh the CAS surface.

[0061] 2. Refer to the test method to load the boundary conditions. Assuming that the test places the headlight on a flat plate and the headlight cannot move left or right or forward and backward, then it is necessary to simulate such a state in the simulation and constrain it in a fixed place; in the test, a pressure plate is used to load the headlight, and in the simulation, the grid of the pressure plate is also drawn to let the pressure plate load the headlight. The process of applying loads and constraints is called applying boundary conditions.

[0062] 3. Assign material and thickness to parts. The CATIA file has been divided into mesh files for finite element analysis. However, this mesh file cannot replace the headlight, so it is necessary to assign material and thickness. For example, if the material of the lamp is plastic, assign the properties of plastic material to the lamp; if the lamp shell is 3 mm thick, assign the lamp the property of 3 mm thickness and calculate the file.

[0063] 4. Process the calculation results to obtain the curves of the pressure head reaction force and pressure head displacement in the simulation analysis and compare them with the test. If the comparison is not good, adjust EMOD and LCID_T I The two parameters are adjusted until they are successfully adjusted. After the curve comparison is successful, the thickness and material curve of the CAS surface are obtained, so that the performance of the material and properties can be applied to the new CAS.

[0064] Taking the headlight of a certain model of FAW Bestune Co., Ltd. as an example, to ensure the consistency of the results, three headlight parts were taken and tested as follows: Figure 3 As shown in the figure, place the headlight on the platform, apply a 250*450mm pressure plate, and perform a crush test on the headlight at a speed of 400mm / min. Figure 4 As shown in the figure, the displacement-reaction curves of the three headlights are obtained respectively. In the pre-processing of the simulation analysis, the outer surface of the headlight is meshed, and the boundary conditions consistent with the test are used, that is, the constraint method is consistent with the test to calculate, and the displacement-reaction curve of the outer surface of the headlight is obtained. Figure 5 *The parameters in EMOD in mat make the curves of simulation and test consistent, and finally apply the material information of the headlight to the whole vehicle analysis.

[0065] Figure 5 It is the material card in the Ls-dyna solver. The *mat_187 plastic material model is used to simulate the plastic material of the lamp housing. LCID_T1 represents the stress-strain curve, that is, the curve of the material yield stress (abscissa) versus the plastic strain (ordinate). By adjusting the EMOD parameter before the part reaches yield, the part adjusts LCID_T1 after yielding. I This curve. In this model, stress-strain curves at different rates are used. In the figure, RO represents the density of the material; EMOD represents the elastic modulus of the material; NUE represents the Poisson's ratio of the material; EPFAIL represents the plastic strain when the part fails; MITER uses the default value of the solver. If the reaction force-displacement curves of the simulation and the test cannot be fitted accurately, the modified parameter is EMOD. When the slope of the force and displacement curve obtained by simulation is less than the experimental value, the value of EMOD and LCID_T need to be adjusted. I The slope of the curve increases; otherwise it decreases.

[0066] Figure 6This is the curve comparing simulation and test after modifying the parameters of the headlight material. This figure is the curve of force and displacement of the part, and the slope is the stiffness of the part.

[0067] In this embodiment, for a headlight model without detailed structure but only with external CAS, headlights of different models but similar shapes can be found for testing, and the CAS surface can be extracted for simulation. By adjusting the material information of the CAS surface parts to make them similar to the force-displacement curve measured by the crushing test of the real parts, the material information after benchmarking is applied to the CAS surface of the new model headlight. In this way, the headlight with the actual structure can be replaced in the frontal collision of the whole vehicle, and the simulation accuracy can be improved. In this embodiment, CAS surface parts are used to replace the specific parameters of the material card of a headlight of FAW Bestune Co., Ltd., and a crushing test is performed on the headlight of a certain model of FAW Bestune Co., Ltd. to obtain its crushing curve.

[0068] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. An equivalent headlight modeling method for frontal vehicle crashworthiness analysis, characterized in that: The following steps are involved: A. Find parts with similar headlight shape to the model being developed; B. Perform an axial crush test on the headlight using a fixed pressure head and speed; C. Obtain the displacement and pressure curve of the part in the experimental equipment; D. Meshing before finite element analysis, i.e. extracting the CAS surface of the test headlight for meshing; E. Use the same indenter and the same restraint method as the test to load; F. Assign material and thickness to the headlight housing unit; G. Perform simulation analysis on parts, i.e. pre-processing, solving and post-processing; H. The curve of contact force and displacement of the indenter is proposed by simulation post-processing; I. Compare the displacement and pressure curves of the simulation and the test to see how consistent the two curves are: I1. If the consistency between the simulation and test curves is acceptable, the material information of the external CAS equivalent to the actual headlight is obtained, and step J is executed; I2. If the difference between the simulation and test curves is large and the results are not consistent, modify the material information of the external CAS and return to step G-step I until the consistency between the simulation and test curves is acceptable; J. Obtain the material information of the headlight CAS and apply it to the model that needs to be calculated.

2. The equivalent headlight modeling method for frontal vehicle crashworthiness analysis according to claim 1, characterized in that: Step A: The found parts are similar in shape to the headlights of the vehicle being developed, but the location of the mounting point and the size of the headlights may be different.

3. The equivalent headlight modeling method for frontal vehicle crashworthiness analysis according to claim 1 is characterized in that: In step B, during the test, the loading speed is 400 mm / min, the loading distance is about 100 mm, and the test time is 15 seconds.

4. The equivalent headlight modeling method for frontal vehicle crashworthiness analysis according to claim 1, characterized in that: Step D is specifically as follows: inputting Catia data of the CAS surface of the headlight, extracting only the outermost CAS surface of the headlight in the Hypermesh software, and meshing the CAS surface in the Hypermesh software.

5. The equivalent headlight modeling method for frontal vehicle crashworthiness analysis according to claim 1, characterized in that: In step E, the loading speed is 1500 mm / s, and the rest of the settings of the simulation are consistent with the loading method of the experiment.

6. The equivalent headlight modeling method for frontal vehicle crashworthiness analysis according to claim 1, characterized in that: In step I, the equivalence is stiffness equivalence.

7. The equivalent headlight modeling method for frontal vehicle crashworthiness analysis according to claim 1, characterized in that: Step I2, the modification is to modify EMOD and LCID_T in MAT I Two parameters are used to make the simulated pressure-displacement curve consistent with the experiment.

8. The equivalent headlight modeling method for frontal vehicle crashworthiness analysis according to claim 7 is characterized in that: If the consistency is not good, adjust EMOD and LCID_T I After the two parameters are adjusted successfully and the curves are compared successfully, the thickness and material curve of the CAS surface are obtained.

Images