A method for predicting vehicle frame assembly vibration

Abstract

The invention relates to a method for predicting the vibration of a frame assembly. The vibration of the frame assembly is predicted by a finite element analysis method, and is compared with frame sample test data to verify the accuracy of a frame vibration finite element analysis model. The method of the invention can analyze the vibration characteristics of the frame assembly, obtain the mode, bending stiffness and torsional stiffness of the frame assembly, compare the results with those of a modal test and a stiffness test in a laboratory, verify the credibility of the frame finite element model and the effectiveness of a modeling method, and for a frame design of a new vehicle model, the same modeling method and analysis method can be used to predict the vibration result of the frame assembly, avoid the vibration frequency of a logistics vehicle engine, and determine whether the stiffness of the logistics vehicle frame assembly meets national requirements. At the same time, certain data support is provided for the anti-vibration design and optimization of the frame, and data support is provided for the forward design of the logistics vehicle, thereby reducing the R&D cost and shortening the R&D cycle.

Description

Technical Field

[0001] The invention relates to the technical field of vehicle frame vibration prediction, and in particular to a method for predicting vehicle frame assembly vibration. Background Art

[0002] With the rapid development of the logistics industry and the accelerated pace of resource exchange between cities, the status of logistics vehicles in road transportation has been continuously improved. The frame is the main load-bearing part of the logistics vehicle, carrying the weight of important components such as the cab, engine, and cargo. The various complex and changeable external loads suffered by the logistics vehicle are ultimately transmitted to the frame, so the vibration of the frame directly affects the comfort and safety of the entire vehicle, and affects the success or failure of the logistics vehicle design. Therefore, the vibration analysis of the frame fully caters to the current social and economic development needs, provides data support for the lightweight frame and subsequent structural optimization, meets the market's requirements for vehicle comfort, shortens the R&D cycle, reduces production costs, and improves the competitiveness of the automotive industry. Summary of the invention

[0003] In view of the above problems, the purpose of the present invention is to provide a method for predicting the vibration of a frame assembly, which can analyze the vibration characteristics of the frame assembly, obtain the mode, bending stiffness and torsional stiffness of the frame assembly, compare the results with those of modal tests and stiffness tests in the laboratory, verify the credibility of the frame finite element model and the effectiveness of the modeling method, provide data support for the forward design of logistics vehicles, reduce R&D costs, and shorten the R&D cycle.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A method for predicting the vibration of a vehicle frame assembly proposed by the present invention specifically comprises the following steps:

[0006] S1. Obtain the free mode and constrained mode of the frame assembly sample through experiments, and obtain the modal frequency, natural vibration mode, torsional stiffness and bending stiffness of the frame assembly;

[0007] S2. Establishing a frame assembly analysis model using a finite element analysis method, and calculating the modal frequencies, natural vibration modes, torsional stiffness, and bending stiffness of the free modes and constrained modes of the frame assembly;

[0008] S3. Compare the calculation results of the finite element analysis method with the test results to verify the reliability of the frame finite element model and the effectiveness of the modeling method. If the comparison results are significantly different, adjust the model and parameters of the finite element analysis method and recalculate until the calculation results are consistent with the test results;

[0009] S4. For the frame assembly model of the new vehicle model, based on reliable modeling and analysis methods, the finite element method is used to simulate and calculate the modal frequency, natural vibration mode, bending stiffness and torsional stiffness of the material frame assembly.

[0010] Furthermore, the step S1 specifically includes:

[0011] S1.1. Experimentally obtain the frequency and vibration mode of the free mode of the frame assembly;

[0012] S1.2. Experimentally obtain the frequency and vibration mode of the frame assembly constraint mode;

[0013] S1.3. Test to obtain the torsional stiffness of the frame assembly;

[0014] S1.4. Test to obtain the bending stiffness of the frame assembly.

[0015] Furthermore, the specific process of step S1.1 is as follows:

[0016] S1.1.1) Establish the modal model, free boundary conditions, rubber rope suspension frame assembly, and determine the excitation point and response point;

[0017] S1.1.2) Install the excitation equipment, install the sensor, mark the overall coordinates, connect the equipment, use the force hammer method, and choose a high-elasticity hammer;

[0018] S1.1.3) Data acquisition, the modal analysis module processes the test data, obtains the frequency response function of each measuring point, and fits the natural frequency and vibration mode of the tested frame.

[0019] Furthermore, the specific process of step S1.2 is as follows:

[0020] S1.2.1) Establish the modal model, constrain the boundary conditions, and determine the excitation points and response points;

[0021] S1.2.2) Install the excitation equipment, install the sensor, mark the overall coordinates, connect the equipment, use the force hammer method, and choose a high elastic force hammer;

[0022] S1.2.3) Data acquisition, the modal analysis module processes the test data, obtains the frequency response function of each measuring point, and fits the natural frequency and vibration mode of the tested frame.

[0023] Furthermore, the specific process of step S1.3 is as follows:

[0024] S1.3.1) Make a fixture as the connection between the sample and the test stand;

[0025] S1.3.2) Install the frame sample and fixture, fix and level them. The positions corresponding to the front axle and left and right longitudinal beams of the frame are the positions for loading torque, and the positions corresponding to the left and right rear axles of the frame assembly are the fixed positions;

[0026] S1.3.3) Determine the change points that need to be tested to ensure that the sensors and instruments are calibrated properly;

[0027] S1.3.4) Connect the data logger, record the initial position and read the value;

[0028] S1.3.5) Test load half of the maximum load, eliminate assembly clearance, formally load torsional load, and collect data; unload the working condition and end data collection;

[0029] S1.3.6) Calculate the torsion angle based on the dimensional deformation of the measured point;

[0030]

[0031] Where: α—torsion angle, unit: degree (deg);

[0032] ΔZ—Z displacement of the measured point, in millimeters (mm);

[0033] Y—Y coordinate value of the measured point, in millimeters (mm);

[0034] S1.3.7) Calculate the torsional stiffness of the specimen according to the following formula:

[0035]

[0036] Where: Kt—torsional stiffness, unit: Newton·meter / degree (N·m / deg);

[0037] Torque—Torque applied to the load point, in Newton meters (N·m);

[0038] α—Torsion angle of the loading point corresponding to the longitudinal beam, unit degree (deg).

[0039] Furthermore, the specific process of step S1.4 is as follows:

[0040] S1.4.1) Make a fixture as the connection between the sample and the test stand;

[0041] S1.4.2) Install the frame sample and fixture, fix and level them, and the corresponding positions of the conventional left and right front axles and the corresponding positions of the left and right rear axles are fixed positions;

[0042] S1.4.3) Determine the change points that need to be tested to ensure that the sensors and instruments are calibrated properly;

[0043] S1.4.4) Connect the data logger, record the initial position and read the value;

[0044] S1.4.5) Load half of the maximum load in the bending test, eliminate the assembly gap, formally load the bending load, and collect data. Unload the working condition and end data collection;

[0045] S1.4.6) Based on the dimensional deformation of the measuring point, calculate the torsional stiffness of the frame assembly sample according to the following formula:

[0046]

[0047] Where: Kf—bending stiffness, unit: Newton / millimeter (N / mm);

[0048] Force—the total force applied to the load point, in Newtons (N);

[0049] ΔZ—average value of maximum Z-direction displacement, in millimeters (mm).

[0050] Furthermore, the step S2 specifically includes:

[0051] S2.1. Establish a finite element model of the frame assembly in the pre-processing software;

[0052] S2.2, free mode and constrained mode calculation of frame assembly;

[0053] S2.3. Calculation of torsional and bending stiffness of the frame assembly.

[0054] Furthermore, the specific process of step S2.1 is as follows:

[0055] S2.1.1) Import the frame CAD geometry model into the finite element software;

[0056] S2.1.2) Clean the geometry of the 3D model of the frame assembly, extract the mid-surface, and then mesh and check the quality;

[0057] S2.1.3) Create connection relationships, including spot welding, rivet connection, hinge connection and bolt connection;

[0058] S2.1.4) To create material properties, only the properties of the material in the linear stage need to be considered;

[0059] S2.1.5) Connect and assemble the components of the frame assembly in sequence to avoid wrong connections or missed connections.

[0060] Furthermore, the specific process of step S2.2 is as follows:

[0061] S2.2.1) Set up the modal analysis card and define the output card according to the solver requirements;

[0062] S2.2.2) Define output cards for output results, including displacement, stress, and strain energy;

[0063] S2.2.3) Define the frequency range for modal analysis;

[0064] S2.2.4) Define modal analysis solution conditions: free modal analysis and constrained modal analysis;

[0065] S2.2.5) Output the card and use LS-Dyna to solve the mode.

[0066] Furthermore, the specific process of step S2.3 is as follows:

[0067] S2.3.1) Define the analysis card and the output card should be defined according to the solver requirements;

[0068] S2.3.2) Define output result cards, whose result types include displacement and stress;

[0069] S2.3.3) Define the working conditions for stiffness analysis, including torsion and bending conditions;

[0070] ① Define the torsion working condition: constrain the translational degrees of freedom UX, UZ at the corresponding position of the left rear axle of the frame, and the translational degrees of freedom UX, UY, UZ at the corresponding position of the right rear axle, apply 1000N loads in the -Z and Z directions at the corresponding positions of the front axle of the frame and the left and right longitudinal beams, and provide Z-direction support at the middle position of the front axle of the frame;

[0071] ② Define bending conditions: constrain the translational freedom UZ of the left front axle, the translational freedom UY, UZ of the right front axle, the translational freedom UX, UZ of the left rear axle, and the translational freedom UX, UY, UZ of the right rear axle. Apply load conditions, and apply a Z-direction concentrated load of 5000N to the middle position of the front and rear axles of the left and right longitudinal beams of the frame assembly respectively;

[0072] S2.3.4) Output the card and use LS-Dyna to solve the body-in-white stiffness;

[0073] S2.3.5) Extract the calculated data of the measured points and calculate the bending stiffness and torsional stiffness of the frame assembly according to formulas (1), (2) and (3).

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] In the laboratory, the natural frequency and corresponding vibration mode of the logistics vehicle frame assembly can be obtained through experimental modal analysis tests, and the bending stiffness and torsional stiffness of the frame assembly can be obtained through the frame stiffness test bench to obtain the vibration information of the frame assembly. The disadvantage of the experimental method to obtain the natural frequency is that the test can only be carried out after the prototype vehicle is produced, and the design modification is proposed according to the test results to obtain a better design scheme. Computational modal analysis and stiffness analysis obtain calculation results by applying the finite element analysis method, thereby reducing the dependence on the prototype vehicle, providing assistance for the design of new models, shortening the research and development cycle, and saving development costs. Therefore, the present invention discloses a method for predicting the vibration of the frame assembly, which is mainly used to predict the vibration characteristics analysis of the carrier frame assembly of a logistics vehicle, and can provide certain data support for the anti-vibration design and optimization of the frame. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 The present invention is a flowchart of a method for predicting vehicle frame assembly vibration. DETAILED DESCRIPTION

[0077] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0078] A method for predicting the vibration of a vehicle frame assembly proposed by the present invention is as follows: Figure 1 As shown, the specific steps include:

[0079] S1. Obtain the free modes and constrained modes of the frame assembly sample through experiments, and obtain the modal frequency, natural vibration mode, torsional stiffness and bending stiffness of the frame assembly; specifically including:

[0080] S1.1. Experimentally obtain the frequency and vibration mode of the free mode of the frame assembly;

[0081] S1.1.1) Establish the modal model, free boundary conditions, rubber rope suspension frame assembly, and determine the excitation point and response point;

[0082] S1.1.2) Install the excitation equipment, install the sensor, mark the overall coordinates, connect the equipment, use the force hammer method, and choose a high-elasticity hammer;

[0083] S1.1.3) Data acquisition, the modal analysis module processes the test data, obtains the frequency response function of each measuring point, and fits the natural frequency and vibration mode of the tested frame.

[0084] S1.2. Experimentally obtain the frequency and vibration mode of the frame assembly constraint mode;

[0085] S1.2.1) Establish the modal model, constrain the boundary conditions, and determine the excitation points and response points;

[0086] S1.2.2) Install the excitation equipment, install the sensor, mark the overall coordinates, connect the equipment, use the force hammer method, and choose a high elastic force hammer;

[0087] S1.2.3) Data acquisition, the modal analysis module processes the test data, obtains the frequency response function of each measuring point, and fits the natural frequency and vibration mode of the tested frame.

[0088] S1.3. Test to obtain the torsional stiffness of the frame assembly;

[0089] S1.3.1) Make a fixture as the connection between the sample and the test stand;

[0090] S1.3.2) Install the frame sample and fixture, fix and level them. The positions corresponding to the front axle and left and right longitudinal beams of the frame are the positions for loading torque, and the positions corresponding to the left and right rear axles of the frame assembly are the fixed positions;

[0091] S1.3.3) Determine the change points that need to be tested to ensure that the sensors and instruments are calibrated properly;

[0092] S1.3.4) Connect the data logger, record the initial position and read the value;

[0093] S1.3.5) Test load half of the maximum load, eliminate assembly clearance, formally load torsional load, and collect data; unload the working condition and end data collection;

[0094] S1.3.6) Calculate the torsion angle based on the dimensional deformation of the measured point;

[0095]

[0096] Where: α—torsion angle, unit: degree (deg);

[0097] ΔZ—Z displacement of the measured point, in millimeters (mm);

[0098] Y—Y coordinate value of the measured point, in millimeters (mm);

[0099] S1.3.7) Calculate the torsional stiffness of the specimen according to the following formula:

[0100]

[0101] Where: Kt—torsional stiffness, unit: Newton·meter / degree (N·m / deg);

[0102] Torque—Torque applied to the load point, in Newton meters (N·m);

[0103] α—Torsion angle of the loading point corresponding to the longitudinal beam, unit degree (deg).

[0104] S1.4. Test to obtain the bending stiffness of the frame assembly;

[0105] S1.4.1) Make a fixture as the connection between the sample and the test stand;

[0106] S1.4.2) Install the frame sample and fixture, fix and level them, and the corresponding positions of the conventional left and right front axles and the corresponding positions of the left and right rear axles are fixed positions;

[0107] S1.4.3) Determine the change points that need to be tested to ensure that the sensors and instruments are calibrated properly;

[0108] S1.4.4) Connect the data logger, record the initial position and read the value;

[0109] S1.4.5) Load half of the maximum load in the bending test, eliminate the assembly gap, formally load the bending load, and collect data. Unload the working condition and end data collection;

[0110] S1.4.6) Based on the dimensional deformation of the measuring point, calculate the torsional stiffness of the frame assembly sample according to the following formula:

[0111]

[0112] Where: Kf—bending stiffness, unit: Newton / millimeter (N / mm);

[0113] Force—the total force applied to the load point, in Newtons (N);

[0114] ΔZ—average value of maximum Z-direction displacement, in millimeters (mm).

[0115] S2. Establish a frame assembly analysis model using the finite element analysis method, and calculate the modal frequencies, natural vibration modes, torsional stiffness, and bending stiffness of the free and constrained modes of the frame assembly; specifically including:

[0116] S2.1. Establish a finite element model of the frame assembly in the pre-processing software;

[0117] S2.1.1) Import the frame CAD geometry model into the finite element software;

[0118] S2.1.2) Clean the geometry of the 3D model of the frame assembly, extract the mid-surface, and then mesh and check the quality;

[0119] S2.1.3) Create connection relationships, including spot welding, rivet connection, hinge connection and bolt connection;

[0120] S2.1.4) To create material properties, only the properties of the material in the linear stage need to be considered;

[0121] S2.1.5) Connect and assemble the components of the frame assembly in sequence to avoid wrong connections or missed connections.

[0122] S2.2, free mode and constrained mode calculation of frame assembly;

[0123] S2.2.1) Set up the modal analysis card and define the output card according to the solver requirements;

[0124] S2.2.2) Define output cards for output results, including displacement, stress, and strain energy;

[0125] S2.2.3) Define the frequency range for modal analysis;

[0126] S2.2.4) Define modal analysis solution conditions: free modal analysis and constrained modal analysis;

[0127] S2.2.5) Output the card and use LS-Dyna to solve the mode.

[0128] S2.3, calculation of torsional and bending stiffness of the frame assembly;

[0129] S2.3.1) Define the analysis card and the output card should be defined according to the solver requirements;

[0130] S2.3.2) Define output result cards, whose result types include displacement and stress;

[0131] S2.3.3) Define the working conditions for stiffness analysis, including torsion and bending conditions;

[0132] ① Define the torsion working condition: constrain the translational degrees of freedom UX, UZ at the corresponding position of the left rear axle of the frame, and the translational degrees of freedom UX, UY, UZ at the corresponding position of the right rear axle, apply 1000N loads in the -Z and Z directions at the corresponding positions of the front axle of the frame and the left and right longitudinal beams, and provide Z-direction support at the middle position of the front axle of the frame;

[0133] ② Define bending conditions: constrain the translational freedom UZ of the left front axle, the translational freedom UY, UZ of the right front axle, the translational freedom UX, UZ of the left rear axle, and the translational freedom UX, UY, UZ of the right rear axle. Apply load conditions, and apply a Z-direction concentrated load of 5000N to the middle position of the front and rear axles of the left and right longitudinal beams of the frame assembly respectively;

[0134] S2.3.4) Output the card and use LS-Dyna to solve the body-in-white stiffness;

[0135] S2.3.5) Extract the calculated data of the measured points and calculate the bending stiffness and torsional stiffness of the frame assembly according to formulas (1), (2) and (3).

[0136] S3. Compare the calculation results of the finite element analysis method with the test results to verify the reliability of the frame finite element model and the effectiveness of the modeling method. If the comparison results are significantly different, adjust the model and parameters of the finite element analysis method and recalculate until the calculation results are consistent with the test results;

[0137] S4. For the frame assembly model of the new vehicle model, based on reliable modeling and analysis methods, the finite element method is used to simulate and calculate the modal frequency, natural vibration mode, bending stiffness and torsional stiffness of the material frame assembly.

[0138] The present invention uses a finite element analysis method to predict the vibration of the frame assembly, compares it with the frame sample test data, and verifies the accuracy of the frame vibration finite element analysis model. Through the method of the present invention, the vibration characteristics of the frame assembly can be analyzed, the modal, bending stiffness and torsional stiffness of the frame assembly can be obtained, and the results can be compared with the modal test and stiffness test in the laboratory to verify the credibility of the frame finite element model and the effectiveness of the modeling method. For the frame design of new models, the same modeling method and analysis method can be used to predict the vibration results of the frame assembly, avoid the vibration frequency of the logistics vehicle engine, and determine whether the stiffness of the logistics vehicle frame assembly meets the national requirements. At the same time, it provides certain data support for the anti-vibration design and optimization of the frame, provides data support for the forward design of the logistics vehicle, reduces the R&D cost, and shortens the R&D cycle.

[0139] The embodiments described above are merely descriptions of preferred implementation modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for predicting vibration of a vehicle frame assembly, characterized in that: The method comprises the following steps: S1. Obtain the free mode and constrained mode of the frame assembly sample through experiments, and obtain the modal frequency, natural vibration mode, torsional stiffness and bending stiffness of the frame assembly; S2. Establishing a frame assembly analysis model using a finite element analysis method, and calculating the modal frequencies, natural vibration modes, torsional stiffness, and bending stiffness of the free modes and constrained modes of the frame assembly; S3. Compare the calculation results of the finite element analysis method with the test results to verify the reliability of the frame finite element model and the effectiveness of the modeling method; if the comparison results are greatly different, adjust the model and parameters of the finite element analysis method and recalculate until the calculation results are consistent with the test results; S4. For the frame assembly model of the new model, based on reliable modeling and analysis methods, the finite element method is used to simulate and calculate the modal frequency, natural vibration mode, bending stiffness and torsional stiffness of the material frame assembly; The step S2 specifically includes: S2.

1. Establish a finite element model of the frame assembly in the pre-processing software; S2.2, free mode and constrained mode calculation of frame assembly; S2.3, calculation of torsional and bending stiffness of the frame assembly; The specific process of step S2.2 is as follows: S2.2.1) Set up the modal analysis card and define the output card according to the solver requirements; S2.2.2) Define output cards for output results, including displacement, stress, and strain energy; S2.2.3) Define the frequency range for modal analysis; S2.2.4) Define modal analysis solution conditions: free modal analysis and constrained modal analysis; S2.2.5) Output the card and use LS-Dyna to solve the mode.

2. A method for predicting vehicle frame assembly vibration according to claim 1, characterized in that: The step S1 specifically includes: S1.

1. Experimentally obtain the frequency and vibration mode of the free mode of the frame assembly; S1.

2. Experimentally obtain the frequency and vibration mode of the frame assembly constraint mode; S1.

3. Test to obtain the torsional stiffness of the frame assembly; S1.

4. Test to obtain the bending stiffness of the frame assembly.

3. A method for predicting vehicle frame assembly vibration according to claim 2, characterized in that: The specific process of step S1.1 is as follows: S1.1.1) Establish the modal model, free boundary conditions, rubber rope suspension frame assembly, and determine the excitation point and response point; S1.1.2) Install the excitation equipment, install the sensor, mark the overall coordinates, connect the equipment, use the force hammer method, and choose a high-elasticity hammer; S1.1.3) Data acquisition, the modal analysis module processes the test data, obtains the frequency response function of each measuring point, and fits the natural frequency and vibration mode of the tested frame.

4. A method for predicting vehicle frame assembly vibration according to claim 3, characterized in that: The specific process of step S1.2 is as follows: S1.2.1) Establish the modal model, constrain the boundary conditions, and determine the excitation points and response points; S1.2.2) Install the excitation equipment, install the sensor, mark the overall coordinates, connect the equipment, use the force hammer method, and choose a high elastic force hammer; S1.2.3) Data acquisition, the modal analysis module processes the test data, obtains the frequency response function of each measuring point, and fits the natural frequency and vibration mode of the tested frame.

5. A method for predicting vehicle frame assembly vibration according to claim 4, characterized in that: The specific process of step S1.3 is as follows: S1.3.1) Make a fixture as the connection between the sample and the test stand; S1.3.2) Install the frame sample and fixture, fix and level them. The positions corresponding to the front axle and left and right longitudinal beams of the frame are the positions for loading torque, and the positions corresponding to the left and right rear axles of the frame assembly are the fixed positions; S1.3.3) Determine the change points that need to be tested to ensure that the sensors and instruments are calibrated properly; S1.3.4) Connect the data logger, record the initial position and read the value; S1.3.5) Test load half of the maximum load, eliminate assembly clearance, formally load torsional load, and collect data; unload the working condition and end data collection; S1.3.6) Calculate the torsion angle based on the dimensional deformation of the measured point; Where: α—torsion angle, unit: degree (deg); ΔZ—Z displacement of the measured point, in millimeters (mm); Y—Y coordinate value of the measured point, in millimeters (mm); S1.3.7) Calculate the torsional stiffness of the specimen according to the following formula: Where: Kt—torsional stiffness, unit: Newton·meter / degree (N·m / deg); Torque—Torque applied to the load point, in Newton meters (N·m); α—Torsion angle of the loading point corresponding to the longitudinal beam, unit degree (deg).

6. A method for predicting vehicle frame assembly vibration according to claim 5, characterized in that: The specific process of step S1.4 is as follows: S1.4.1) Make a fixture as the connection between the sample and the test stand; S1.4.2) Install the frame sample and fixture, fix and level them, and the corresponding positions of the conventional left and right front axles and the corresponding positions of the left and right rear axles are fixed positions; S1.4.3) Determine the change points that need to be tested to ensure that the sensors and instruments are calibrated properly; S1.4.4) Connect the data logger, record the initial position and read the value; S1.4.5) Load half of the maximum load in the bending test, eliminate the assembly gap, formally load the bending load, and collect data; unload the working condition and end data collection; S1.4.6) Based on the dimensional deformation of the measuring point, calculate the torsional stiffness of the frame assembly sample according to the following formula: Where: Kf—bending stiffness, unit: Newton / millimeter (N / mm); Force—the total force applied to the load point, in Newtons (N); ΔZ—average value of maximum Z-direction displacement, in millimeters (mm).

7. The method for predicting vehicle frame assembly vibration according to claim 1, characterized in that: The specific process of step S2.1 is as follows: S2.1.1) Import the frame CAD geometry model into the finite element software; S2.1.2) Clean the geometry of the 3D model of the frame assembly, extract the mid-surface, and then mesh and check the quality; S2.1.3) Create connection relationships, including spot welding connections, rivet connections, hinge connections, and bolt connections; S2.1.4) To create material properties, only the properties of the material in the linear stage need to be considered; S2.1.5) Connect and assemble the components of the frame assembly in sequence to avoid wrong connections or missed connections.

8. The method for predicting vehicle frame assembly vibration according to claim 1, characterized in that: The specific process of step S2.3 is as follows: S2.3.1) Define the analysis card and the output card should be defined according to the solver requirements; S2.3.2) Define output result cards, whose result types include displacement and stress; S2.3.3) Define the working conditions for stiffness analysis, including torsion and bending conditions; ① Define the torsion working condition: constrain the translational degrees of freedom UX, UZ at the corresponding position of the left rear axle of the frame, and the translational degrees of freedom UX, UY, UZ at the corresponding position of the right rear axle, apply 1000N loads in the -Z and Z directions at the corresponding positions of the front axle of the frame and the left and right longitudinal beams, and provide Z-direction support at the middle position of the front axle of the frame; ② Define the bending working condition: constrain the translational freedom UZ of the left front axle, the translational freedom UY, UZ of the right front axle, the translational freedom UX, UZ of the left rear axle, and the translational freedom UX, UY, UZ of the right rear axle; apply the load condition, and apply a Z-direction concentrated load of 5000N to the middle position of the front and rear axles of the left and right longitudinal beams of the frame assembly respectively; S2.3.4) Output the card and use LS-Dyna to solve the body-in-white stiffness; S2.3.5) Extract the calculated data of the measured points and calculate the bending stiffness and torsional stiffness of the frame assembly according to formulas (1), (2) and (3).

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