Finite element static dynamics analysis of the hot

2022-08-16
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Finite element statics and dynamics analysis of light truck

Patran is used to establish the model of light truck frame, suspension, body and other vehicle, and reasonable constraint boundary conditions are applied to analyze, calculate and evaluate the static strength of the vehicle under various loads, and reasonable and feasible improvement suggestions and measures are put forward. In order to investigate the dynamic stress distribution of the whole vehicle, the rigid flexible hybrid model of the whole vehicle is constructed in the multi-body dynamics software ADAMS, and the simulation of the actual road is carried out. Then the dynamic response calculation is carried out in NASTRAN by using its interface with NASTRAN, and the dynamic stress time history of the whole vehicle is obtained, so as to lay the foundation for fatigue analysis

in the early stage of product development, CAE technology is applied to simulate various performances of products to guide the design, provide product quality verification and optimize the detailed design, minimize the number of repeated physical prototype production, ensure the development quality, and finally achieve the purpose of shortening the market-oriented cycle of products and product development cycle

for the newly developed light truck series, the modal, stiffness and strength of the vehicle body and frame are analyzed and calculated by using stran software, and the deficiencies in the design are found, and reasonable and feasible improvement measures are put forward, so that the strength and stiffness of the whole vehicle can finally meet the requirements

1. Finite element modeling of the whole vehicle

when building the finite element model, use the good CAD interface of tran software to input UG and pro/e three-dimensional models from the outside, carry out geometric cleaning and simplification according to the relevant principles, apply Patran's finite element, and plan to establish the first factory pre-processing function of producing this material in Mianyang, and finally form the finite element model of the whole vehicle by establishing the finite element model of a single part. The whole model has 725015 units and 589235 nodes. See the figure below for the finite element model

2. Calculation of static strength of the whole vehicle

when the vehicle is stationary, the frame only bears the load above the spring. It is composed of the mass of the frame and body, the mass of each assembly installed on the frame and the gravity of the loading mass, and the sum of which is called the static load of the frame. This calculation provides two working conditions

bending condition: during finite element analysis, sufficient constraints are required to eliminate rigid displacement. Therefore, three degrees of freedom of movement of the node on the front wheel centerline and two degrees of freedom of movement of the node on the rear wheel centerline are constrained as vehicle constraints

torsion condition: on the basis of bending condition, raise the right front wheel to a certain value according to the specification

the stress nephogram of the car body and frame calculated is shown in Figure 2

through analysis, it is found that the maximum stress parts of the car body are mainly located in the bulge of the front floor and the middle floor, the sharp change of curvature and some support parts. After discussion with the designer, feasible improvement measures are proposed without affecting the general layout, and finally meet the evaluation requirements of static strength

3. Modal analysis of vehicle body

under the excitation, the vibration of the vehicle is the comprehensive reflection of the modal vibration of each stage, and the main role is the overall mode of the first several stages, so we should focus on the analysis of the first several modes. The dynamic characteristics of the vehicle body system can be evaluated by using the modal analysis of the vehicle body; Estimate the possible load dynamic amplification effect, guide the subsequent dynamic analysis (transient response analysis, response spectrum analysis, etc.), and generate MNF files for Adams. Remove the first six rigid body modes, and the first-order mode of the body is shown in the figure below

4. Dynamic response calculation

during the actual use of the vehicle, it is affected by the dynamic excitation from the road, engine, etc. In order to investigate the dynamic characteristics of the whole vehicle, especially the dynamic stress size and distribution of important structural parts such as body and frame, a rigid flexible hybrid dynamic simulation model including body, frame, suspension, front and rear axles, tires, etc. is built in the multi-body dynamics software. The body, frame and other flexible body files are solved by using NASTRAN's superelement function. By completing the simulation calculation of random road surface, braking, acceleration, turning and other working conditions in the multi-body system, and then applying the interface between NASTRAN and NASTRAN, data recovery can be carried out in NASTRAN, and each dynamic response of the structure (displacement, stress, deformation, acceleration, etc.) can be obtained for relevant evaluation

Figure 3 and Figure 4 show the stress time history curve of a node of the body longitudinal beam and the dynamic stress nephogram of the floor at a certain time under the excitation condition of the whole vehicle on a random road (national standard level D, speed 45km/h). 10. Clean the mixer at the end of the work. This kind of aluminum alloy cable is a connection solution

5. Conclusion

(1) using the finite element method, a lot of analysis work can be done on the virtual prototype in the design stage, reducing the manufacturing quantity and test times of the physical prototype, saving a lot of development and test costs and shortening the development cycle

(2) the finite element static strength calculation of the whole vehicle reflects the shortcomings of the structure to a certain extent. In order to comprehensively investigate the various responses of the vehicle in the dynamic environment, the rigid flexible hybrid multi-body dynamic analysis technology is used to carry out the dynamic simulation of the whole vehicle under various working conditions, and the dynamic stress of the key parts of the structure is restored, which lays a foundation for the future fatigue calculation

6. References

[1] tran user's manual, volume4, part9: pcl

[2] ick reference guide v70

[3] USA mechanical dynamics, Inc. basic Adams full simulation package training guide version 10.2000

[4] edited by Zhang Hongxin, automobile design, machinery industry press 1998

[5] edited by Yu Zhisheng, automobile theory, Machinery Industry Press 2000 (end)

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