Automobile Engine Flywheel Ring Gear Assembly Failure Research

Flywheel assembly, a special disk with greater moment of inertia, reserving higher energy for adjusting the vehicle speed fluctuation, is an important member of the engine periphery. With the popularity of the family car, the amount of engine flywheel increase sharply. The normal working state of flywheel assembly is an important condition for the normal operation of the engine, so its security has been great concern all sectors.For flywheel assembly failure phenomenon, according to failure analysis process,this paper systematically theoretical analyzes flywheel assembly failure, and gets two main directions of researches in failure:the failure of the interference fit between flywheel and ring gear, as well as the flywheel assembly crack failure. Based on elastic mechanics theory, this paper calculates flywheel ring gear stress and mathematically analyzes the relevant parameters. Applying Ansys workbench, this paper has the finite element analyses of flywheel assembly and flywheel ring gear interference fit, and then the crack speed tests proves that the speed deduced from theory is the limited speed of flywheel assembly. The main work of this paper is divided into the following parts:1 According to plane situation under the elastic force of the polar coordinate,plane basic equation has been established. Based on thick-walled cylinder model, this paper build mechanical model of flywheel ring gear interference fit, and then gets the calculated method of flywheel ring gear stress to deduce the radial displacement formula of flywheel ring gear in both static and dynamic states. In the light of deformation relation, we can get actual contact pressure calculation within the two states. The contrast between theoretical solution, deduced from the theoretical formulation of flywheel ring gear, and finite element analysis solution of interference fit model proves the finite element analysis of interference fit is right, and ensures the feasibility of subsequent analyses.2 For the complex flywheel structure, it is essential to establish appropriate analytic model. By the finite element analysis, the stress analysis result calculated from each subgroup shows parameters, interference, the radius of contact surface, the material properties, the extent of hollow of flywheel, the thickness of flywheel rim,speed and so on, has an regular influence on flywheel assembly. As a result, this paper proposes preventive measure for interference fit failure and flywheel assembly crack failure. After the dynamic finite element analysis of three selected products, we get thelimited speed. Classified by varied interference, samples are experimented in different speeds. The results conform with the finite element analysis law, and verify the exactitude of theoretical study.With so many failure forms of flywheel assembly, this paper mainly studies two of them, the separation of flywheel ring gear and flywheel crack. Considering interference fit failure and overall stress failure, we come up with the measures that diminish failure of flywheel assembly. Thus, it is significant with this study results to guide engineering projects design, support primary product development, decrease unnecessary program design, save development costs, advance the enterprise development.