Flexible multibody dynamics analysis of automobile engine

The calculation method of dynamics behavior on automobile engine is getting more important as computer-aided engineering technique to design optimized mechanisms and structures for lighter weight, lower mechanical friction and lower noise. Engine system consists of deformable moving components and several kinds of mechanical joints, such as an oil lubricated bearing. Dynamics problem includes various kinds of noise and vibration phenomena in wide frequency range. Therefore, it is crucial to analyze precisely the coupling behavior between rigid motion and elastic deformation of moving components considering nonlinear dynamic effect of mechanical joint. In this study, we formulated equations of motion for the flexible multibody dynamics system and developed a computer software specialized for internal combustion engines. In the formulation, both rigid motion and elastic deformation are simply expressed by eigen modes on a local observer frame in order to calculate efficiently many deformation modes up to higher frequency range. In addition, several kinds of force elements are formulated to express the nonlinear forces of mechanical joints and the boundary conditions. The developed program has been verified by the experiments under running condition and applied to the real engine design.