Flexible Multibody Dynamics Research Of Spur Gear Systems

In the frame work of multibody system;a computational methodology to study thecoupling spur gear mesh joints considering ElastoHydroDynamic (EHD) lubricatedconditions is proposed. The spur geared mechanisms are described by using on theAbsolute-Coordinate-Based (ACB) method that combines the Natural CoordinateFormulation (NCF) describing rigid bodies and the Absolute Nodal Coordinate Formulation(ANCF) describing flexible bodies. For describing the engagement state of a spur gear pairand a bevel gear pair;the gear mesh model is simplified as a spring-damper system withtime-varying mesh parameters. The gear pair normal contact forces along the Line OfAction (LOA) are calculated by introducing the time-varying mesh stiffness;mesh dampingand static transmission error. The time-varying mesh stiffness is evaluated by using theChaari’s formulas. The sliding friction forces along the Off-Line-Of-Action (OLOA) arecalculated by using the Coulomb friction models with a time-varying coefficient of frictionconsidering EHD lubrication condition. Based on the finite-short bearing assumption;theEHD lubrication condition for the cylindrical joints supporting the geared mechanism isconsidered. The lubrication forces in the cylindrical joints are obtained by solving theReynolds equation using the finite difference method. Based on the proposed computationalmethodology;the main research works of this dissertation are as follows;1. The multibody system dynamics modeling method for spur gear mesh joints andcylindrical joints is proposed. The influence of gear mesh parameters on the systemdynamic responses is comparatively studied.2. The effects of gear joints on the dynamic response of a crank-rocker mechanismsupporting by EHD lubricated cylindrical joints are further studied. The simulation resultsare also collaborated by those in literatures.3. Finally;the deployment dynamics of a large deployable antenna with synchromeshbevel-gear pairs is studied. The multibody dynamics model of an antenna including itssuspension system of the practical ground experimental platform is built. The synchromeshbevel-gear joints are carefully considered in the model. Some numerical results are in goodagreement with those from ground experiments. However;it is also found that there aresome deficiencies in the established simulation model;which can be improved in future studies.