| Along with development of hardware technology and software level, CAE has been more and more widespread in engineering practice, which involves several aspects such as structure, fluid and electromagnetism, etc. It improves quality of production and meanwhile lowers cost of research, which brings considerable economic benefits to society and enterprise. Its application in automotive industry has been daily on the increase, which is closely linked with assemblies, components and parts. Finite element analysis is one of the most important parts in CAE, which provides essentially technical support for both static analysis and dynamic analysis. It has a great contribution to structure analysis, fault diagnosis and performance optimization. It is used by element analysis method to analyze dynamic performance of the assemblies. As a base assembly that carries load, bus frame bears various dynamic load from interior and exterior, whose dynamic performance and matching with powertrain decide vibration performance of the whole vehicle.Depending on an actual project, this thesis uses finite element technique of CAE to analyze and optimize the dynamic performance of a certain bus frame. First, with finite element software HyperWorks as a technology platform, a finite element model of the frame is established by topology restoration, structure simplification, midsurface extraction, grid division and connection simulation, and so on. The frame model is employed to do calculating modal analysis to get the first ten natural frequencies and corresponding vibration modes, which are associated with inside and outside excitation to estimate the dynamic performance of the frame initially. Then the frame is adopted to do response analysis of transient force to obtain time-displacement curves of several measure points on the frame under the effect of transient force, which could analyze the dynamic performance of the frame further. Next, with software and hardware devices of modal analysis as a method, the frame entity is tested by modal test technique to do exprimental modal analysis to obtain the first ten natural frequencies corresponding to the calculating one, with which to prove the accuracy of finite element model. Afterwards the calculating program to solve coupling vibration of the powertrain mounting system is written by program software MATLAB to gain the natural frequencies and decoupling rates in every direction of the powertrain, on which the optimization to dynamic matching performance of the powertrain is based. Finally the dynamic performance of the frame is optimized under the requirement of its rigidity and strength, which takes the natural frequencies configuration as optimizational target. It realizes the vibration matching between the frame and powertrain and decreases the possibility of resonance between the frame and engine, meanwhile meeting the lightweight requirement of the frame. Not only did the research production have an important significance for performance optimization of the bus frame, but also it has a reference value for other engineering projects. |
PDF Full Text Request