| Compared to the traditional longitudinal beam frame, the integral body is gotten more attention with excellent performance on coach. It not only can be the assembly foundation of attachment parts, but also can bear complex load from both inside and outside of vehicle. So it is vitally essential that vehicle body should have good performance of fatigue and strength to ensure safety, reliability and so on. In this paper, on the study basis of reasonable static strength and modal response, fatigue life wound be assessed for the integral body of VDS-A01 coach from my internship company by using Hyperworks, ADAMS/CAR and nCode designlife software, the above studies are based on the FEM, MBD and method of quasi-static fatigue analysis. The main research content is as follows:1)A finite element model of body is modeled to analyze the response of modal. It is established by using Hypermesh 13.0. CMS method is used to calculate its free modal. In order to avoid body structure resonance, the results include first 16 order natural frequency and mode shape of body modal to provide data support and reference, and can also build the foundation to establish a flexible body in the next step.2)A rigid-flexible coupling coach is modeled to collect load. A rigid-flexible coupling coach model, including a flexible body based on modal neutral file from the modal analysis and other rigid systems dynamics model, is established by using ADAMS/CAR. The static load of joint between frame and chassis is obtained by static simulation test to provide force boundary for frame static strength analysis, and class B random road is created to collect the dynamic load time history of joint point for fatigue analysis.3)The analysis of static strength for coach body is based on principle of inertiarelief. It is evaluated by numerical calculation to identify strength of body under bending, braking, turning, torsion four conditions.4)The stress fatigue life of coach body is predicted and analyzed. The datum,including load spectrum, the static analysis results of bend condition and fatigue characteristic of body material, are inputted to analysis process of nCode designlife,then the stress fatigue life of body is predicted by method of quasi-static fatigue analysis.Results show that: the majority of partial mode shapes are beneficial to suppress whole vibration of body. It can effectively improve insufficient stiffness of the engine bracket by adding a beam in the lower section of back wall. The natural frequency of body advantageously avoid the excitation resonance frequency from road and engine.Overall, the requirements of design wound be met. In the analysis of static strength,the maximum stress of four conditions are less than yield strength of body material,so the strength design specification wound be satisfied. In the analysis of fatigue life.several parts, including connection point of the low pushrod and the frame, the front part of front and rear lower control arm brackets in the front suspension, side door near the roof, the outside part of the front air spring brackets in the rear suspension,prone to fatigue damage. Calculation results shows that frame fatigue life is about17567 hours, and mileage is about 149.3 million kilometers, it can be seen that the design requirement life of the body is met basically. |
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