DescriptionThe formation of a hydrodynamic lubrication condition is the essential condition for any friction bearings in combustion engines. The shaft and the bearing are separated by a thin sustainable lubrication film which prevents a direct metal to metal contact. The resulting fluid friction allows for a low frictional loss and the prevention of wear under normal operational conditions. The hydro-dynamic load capacity of the bearings is a result of an oil flow, caused by the rotating shaft and/or bearing within the viscous medium. Depending on the gap geometry (shaft eccentricity) a hydro-dynamic pressure is built up in the lubrication film. This pressure separates the surfaces that define the lubrication film and thus equilibrates the external bearing loading. However, the local pressure inside the lubrication film will cause local deformations of the shaft and bearing which again will affect the pressure build-up due to a change of the gap geometry. The resulting pressure distribution inside the lubrication film is a result of the coupling between the local stiffness and the hydrodynamic properties of the bearing. Consequently, in engine simulations such interactions between crank drive components (e. g. main bearings, conrod bearing) play an essential role. Therefore it is necessary to consider the above discussed effects as accurate as possible to obtain high quality results in a virtual product development process. An integrated simulation process is presented, which demonstrates the applicability of multi body simulation (ADAMS) and finite element software (NASTRAN) to perform such complex simulations in engine design. NASTRAN is used to compute the elastic bodies with local pressure loadings (load shape functions). The complete dynamic simulation of the engine assembly is performed with ADAMS. The EHD oil film formulation is implemented as a user-written subroutine utilizing the MFORCE2 functionality (modal force) of ADAMS 2005r2. Based on the computed modal stresses and modal coordinates, the software FEMFAT is used to perform a fatigue analysis of the engine components. The presented simulation process is a fully dynamic approach considering local damping and resonance excitations as well.
|Period||24 Oct 2007|
|Event title||Fh-Science Day 2007: null|