A method for increasing the diamond modal frequency of a rail vehicle body

Abstract

The invention provides a method for improving the diamond mode frequency of a rail vehicle body, constructing a unique static boundary condition to simulate the deformation trend and characteristics of an upper side beam under a diamond mode, and optimizing the diamond mode frequency of the body into the stiffness optimization of the upper side beam under the static boundary condition; using finite element pre-processing software to define the type of analysis and calculation unit, and assigning material properties to it, using mass points to counterweight the body model, and ensuring that the mass distribution of the body is the same as that of the actual body; extracting the vibration mode of the diamond mode in the finite element software post-processing, determining the most severely deformed part, and independently forming a separate model for the part and outputting it, wherein the separate model contains the model boundary node number and displacement information; using finite element software to check the upper side beam reduction model to ensure that the displacement of its static boundary and the corresponding node number of the whole vehicle body is consistent, and then filling the design domain of the upper side beam reduction model to perform an optimization design with maximum stiffness.

Description

Technical Field

[0001] The invention relates to the technical field of rail vehicles, and in particular to a method for increasing the diamond modal frequency of a rail vehicle body. Background Art

[0002] With the continuous increase in railway operating speed, the key technologies for lightweight train bodies have also made great progress. However, lightweighting will reduce the natural frequency of the body, and the line excitation frequency range will widen with the increase in speed, which may cause the low-order natural frequency of the vehicle to be within the line excitation frequency range, causing severe body shaking. In addition to the requirements for the first-order vertical bending modal frequency of the body in the relevant national standards, according to train operation experience, the diamond mode of the body steel structure has an important impact on the safety and quality of high-speed train operation. Therefore, how to improve the diamond mode of the train and protect the life safety and operation quality of passengers is worthy of in-depth research.

[0003] The usual means to improve the diamond mode is to adopt the method of topology optimization, but the traditional optimization method usually takes the whole vehicle as the research object, with the goal of improving the frequency under a certain order, which will lead to the transfer of the modal vibration shape under the order to be optimized, and the excessive concentration of materials or too many intermediate density units. In addition, the calculation scale of the whole vehicle is large. Due to the limitation of computer hardware conditions, the complete single-vehicle finite element model is used for analysis, and the entire design cycle is too long and the design cost is too high. Summary of the invention

[0004] In view of the above problems in the prior art, the present application proposes a method for improving the rhombus modal frequency of a rail vehicle body, constructing a unique static boundary condition to simulate the deformation trend and characteristics of the upper side beam under the rhombus mode, and converting the body rhombus modal frequency optimization into the stiffness optimization of the upper side beam under the static boundary condition;

[0005] Finite element pre-processing software is used to pre-process the geometric model, remove some fillets, and repair and sew the surfaces with defects;

[0006] The finite element model of the vehicle body is established using finite element pre-processing software, and tetrahedral mesh discretization is used to ensure that the finite element model is consistent with the actual structure and geometric model of the vehicle body;

[0007] Finite element pre-processing software is used to define and analyze the calculation unit type, and to assign material properties to it. The vehicle body model is weighted with mass points to ensure that the mass distribution of the vehicle body is the same as the actual vehicle body.

[0008] Calculate the diamond modes of the vehicle body model using finite element software;

[0009] Extract the vibration shape of the diamond mode in the post-processing of the finite element software, determine the most severely deformed part, separate the part into a separate model and output it, the separate model contains the model boundary node number and displacement information;

[0010] Use finite element software to check the upper side beam reduction model to ensure that its static boundary is consistent with the displacement of the corresponding node number of the vehicle body, and then fill the design domain of the upper side beam reduction model to perform an optimized design to maximize stiffness;

[0011] Replace the model of the original position of the vehicle body with the optimized model of the reduced upper rail model;

[0012] Finite element software is used to calculate the diamond mode of the optimized car body model. This is one iteration step. The current iteration step is recorded as i, and the diamond mode frequency of the car body under this iteration step is recorded as f. i ;

[0013] Iterate for more than 10 steps, and use the relative change rate er of the modal frequency in the last 10 steps to judge whether it has converged. If convergence is achieved, er<0.01, the optimized model is output as the final result. Otherwise, the vibration shape of the diamond mode is extracted again in the post-processing of the finite element software to determine the most severely deformed part.

[0014] Preferably, the radius of the rounded corners is within 20 mm.

[0015] Preferably, the unit grid size of the finite element model is controlled between 20 mm and 30 mm.

[0016] Preferably, the diamond mode of the vehicle body model is calculated using finite element software, and the vehicle body model is placed in a free state during the solution.

[0017] Preferably, an optimization design is performed to maximize stiffness, and finally flexibility is used as a target and volume fraction as a constraint.

[0018] Preferably, the boundary conditions of the finite element model are set as follows: both ends of the upper side beam are completely fixed, and the middle part is subjected to a torsional load or a torsional moment.

[0019] The above technical features can be combined in various suitable ways or replaced by equivalent technical features as long as the purpose of the present invention can be achieved.

[0020] The entire analysis and optimization design process is a closed-loop control process. Through multiple rounds of analysis and optimization, the vehicle body structure with maximized diamond mode is finally optimized. Since only a part of the upper side beam is optimized, the amount and scale of calculation are greatly reduced, and there is no vibration mode transfer and material concentration.

[0021] The efficient optimization method for improving the diamond modal frequency of a rail vehicle body proposed in the present invention has the following main advantages:

[0022] (1) The analysis object only uses a reduced model of the upper side beam, which greatly reduces the calculation scale compared to the vehicle body model;

[0023] (2) It can avoid the phenomenon of order transfer during the optimization process of traditional optimization methods;

[0024] (3) It can avoid problems such as excessive material concentration or too many intermediate density units during the optimization process of traditional optimization methods;

[0025] (4) Converting the body rhombus modal frequency optimization into the stiffness optimization of the upper side beam under static boundary conditions can be well compatible with the stiffness optimization during lightweighting, facilitating multi-objective design.

[0026] (5) The TCL programming language in the OptiStruct software can be used to quickly analyze and optimize the reduction model of the upper side beam of the vehicle body and modify the model of the vehicle body structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be described in more detail below based on embodiments and with reference to the accompanying drawings, wherein:

[0028] Figure 1 Flowchart of efficient optimization method for improving the rhombus modal frequency of rail vehicle body;

[0029] Figure 2 Schematic diagram of the rail vehicle body structure model;

[0030] Figure 3 Schematic diagram of the diamond mode shape of the rail vehicle body structure model;

[0031] Figure 4 Schematic diagram of filling the design domain of the upper beam reduction model;

[0032] Figure 5 Schematic diagram of the upper side beam reduction model before and after optimization;

[0033] Figure 6 Assembly diagram of the upper side beam before optimization;

[0034] Figure 7 Assembly diagram of the optimized upper side beam. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings.

[0036] The software and hardware used in the analysis and optimization design process of the present invention include a computer 1, HyperMesh pre-processing software 2, finite element analysis and optimization software OptiStruct 3, a vehicle body finite element analysis model 4, and an upper side beam reduction finite element model 5.

[0037] How to implement the analysis and design process

[0038] Analysis and calculation of vehicle body model creation, see attached Figure 1 :

[0039] a. Use the finite element preprocessing software HyperMesh to preprocess the geometric model, remove some fillets with a radius of less than 20mm, and repair and sew the surfaces with defects to facilitate the subsequent creation of a high-quality finite element model;

[0040] b. Use the finite element pre-processing software HyperMesh to establish the finite element model of the vehicle body. Tetrahedral mesh discretization is used to ensure that the finite element model is completely consistent with the actual structure and geometric model of the vehicle body. The unit mesh size is controlled between 20mm and 30mm, and the unit quality is guaranteed to be good;

[0041] 2) Define and analyze the car body model unit types, attributes and material properties

[0042] See attached Figure 2 , define unit types for different units in the analysis and calculation model. The main unit of the vehicle body adopts 2D shell unit. The plate thickness and other properties of the calculation model are set according to the actual structure, and the material is defined. The vehicle body model is weighted with mass point 1D unit to ensure that the mass distribution of the vehicle body is the same as the actual vehicle body;

[0043] The diamond mode of the car body model is calculated using the finite element software OptiStruct. Figure 3 .

[0044] Finite element software OptiStruct is used to calculate the diamond mode of the vehicle model. The vehicle model is in a free state during the solution. Figure 3 The schematic diagram of the vibration shape of the vehicle body in the diamond mode is shown.

[0045] Output the upper beam reduction model, see attached Figure 5 (Model before optimization).

[0046] In the post-processing of the finite element software OptiStruct, the vibration mode of the diamond mode is extracted, and the most severely deformed part (usually located at the upper side beam) is determined. This part is separated into a separate model and output (upper side beam reduction model). The cross section of the upper side beam section is shown here. While outputting the upper side beam reduction model, the node number and displacement information of the model boundary (non-optimized design domain) in the upper side beam reduction model are extracted. For details, see the attached Figure 5 (Model before optimization);

[0047] The upper side beam reduction model is designed to maximize the stiffness, see the attached Figure 4

[0048] Use the finite element software OptiStruct to check the upper side beam reduction model to ensure that its static boundary is consistent with the displacement of the corresponding node number of the vehicle body, and then fill the design domain of the upper side beam reduction model (outside the model boundary). For details, see the attached Figure 4 ,Finally, taking flexibility as the target and volume fraction as the constraint, the optimization design to maximize stiffness is carried out;

[0049] Use the optimized model of the upper side beam reduction model to replace the original part of the car body, see attached Figure 5

[0050] In the finite element software OptiStruct, it is determined that the reduced model optimization has converged and the optimization results are obtained to replace the original position of the vehicle body (corresponding to the node number).

[0051] Calculate the diamond mode of the optimized car body model

[0052] Finite element software OptiStruct is used to calculate the diamond mode of the optimized car body model. In order to facilitate the subsequent observation of the optimization process, optimization results and convergence judgment, the corresponding optimization information is recorded here: the optimization is recorded as 1 iteration step, the current iteration step is recorded as i, and the diamond mode frequency of the car body under this iteration step is recorded as f i ;

[0053] Read calculation result information

[0054] In order to ensure the good performance of the final optimized structure, more than 10 steps must be iterated in this setting, and the relative change rate of the modal frequency er in the last 10 steps is used to judge whether it has converged or not. If convergence (er<0.01), the optimized model is output as the final result, and the last fi is recorded as the optimal vehicle body diamond modal frequency result, which can be used to visually compare the frequency before and after optimization. Otherwise, return to step (105) and recalculate.

[0055] Optimization result comparison and performance evaluation, see attached Figure 5 , Attachment Figure 6 , Attachment Figure 7 .

[0056] After the optimization process converges, the top beam reduction model section before and after optimization is shown in the attached figure. Figure 5 As shown in the figure, the typical characteristics of the optimized upper side beam section are: the ribs of the configuration mainly grow and extend along the normal direction of the panel, and at the same time there are triangular ribs near the two ends for support. According to the topological optimization results, it can be considered that this structural form is the optimal force transmission path for the upper side beam to resist the diamond deformation of the car body. The upper side beam before optimization is assembled into the car body model as shown in the attached figure. Figure 6 , assemble the optimized upper side beam into the vehicle body model as shown in the attached figure. Figure 7 , shown here is a cross section of the vehicle body.

[0057] The entire analysis and optimization design process is a closed-loop control process. After multiple analysis and optimization, the body structure with the maximum diamond mode is finally optimized. The diamond mode is increased from 12.13Hz of the original car to 13.05Hz, which is 7.58% higher than the diamond mode frequency of the original section. Since only a part of the upper side beam is optimized, the calculation amount and scale are greatly reduced, and there is no vibration mode transfer and material concentration.

Claims

1. A method for increasing the rhombus modal frequency of a rail vehicle body, It is characterized in that Construct unique static boundary conditions to simulate the deformation trend and characteristics of the upper side beam under diamond mode, and convert the body diamond mode frequency optimization into the stiffness optimization of the upper side beam under static boundary conditions; Finite element pre-processing software is used to pre-process the geometric model, remove some fillets, and repair and sew the surfaces with defects; The finite element model of the vehicle body is established using finite element pre-processing software, and tetrahedral mesh discretization is used to ensure that the finite element model is consistent with the actual structure and geometric model of the vehicle body; Finite element pre-processing software is used to define and analyze the calculation unit type, and to assign material properties to it. The vehicle body model is weighted with mass points to ensure that the mass distribution of the vehicle body is the same as the actual vehicle body. Calculate the diamond modes of the vehicle body model using finite element software; Extract the vibration shape of the diamond mode in the post-processing of the finite element software, determine the most severely deformed part, separate the part into a separate model and output the top beam reduction model, wherein the separate model includes the model boundary node number and displacement information; Use finite element software to check the upper side beam reduction model to ensure that its static boundary is consistent with the displacement of the corresponding node number of the vehicle body, and then fill the design domain of the upper side beam reduction model to perform an optimized design to maximize stiffness; Replace the model of the original position of the vehicle body with the optimized model of the reduced upper rail model; Finite element software is used to calculate the diamond mode of the optimized car body model. This is one iteration step. The current iteration step is recorded as i, and the diamond mode frequency of the car body under this iteration step is recorded as f. i ; Iterate for more than 10 steps, and use the relative change rate er of the modal frequency in the last 10 steps to judge whether it has converged. If convergence is achieved, er<0.01, the optimized model is output as the final result. Otherwise, the vibration shape of the diamond mode is extracted again in the post-processing of the finite element software to determine the most severely deformed part.

2. The method for increasing the diamond modal frequency of a rail vehicle body according to claim 1, It is characterized in that The radius of the rounded corners should be within 20 mm.

3. The method for increasing the diamond modal frequency of a rail vehicle body according to claim 1, It is characterized in that The unit grid size of the finite element model is controlled between 20mm and 30mm.

4. The method for increasing the diamond modal frequency of a rail vehicle body according to claim 1, It is characterized in that Finite element software is used to calculate the diamond mode of the vehicle body model, and the vehicle body model is in a free state during the solution.

5. The method for increasing the diamond modal frequency of a rail vehicle body according to claim 1, It is characterized in that An optimization design is performed to maximize stiffness, and finally flexibility is used as the target and volume fraction as the constraint.

6. The method for increasing the diamond modal frequency of a rail vehicle body according to claim 1, It is characterized in that The boundary conditions of the finite element model are set as follows: the two ends of the upper beam are completely fixed, and the middle part is subjected to torsional load or torsional moment.

7. The method for increasing the diamond modal frequency of a rail vehicle body according to claim 1, It is characterized in that The ribs of the optimized model mainly grow and extend along the normal direction of the panel, and at the same time there are triangular rib supports near the two ends.

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