Laboratory for Dynamics of Machines and Structures 
Influence of bearing stiffness on vibration properties of statically overdetermined gearboxes

Master thesis, LADISK, Faculty of Mech Eng, Univ of Ljubljana, May 2014

www.fs.uni-lj.si
Abstract
In the design process of every modern car, sufficient acoustic behaviour of each integral part is of big importance, which also has to be considered for gearboxes. The stiffness of bearing is one of the main contributors in vibration transmission from the interior of the gearbox to the housing. Current standards provide methods to determine stiffness of bearings, but they still meet several assumptions resulting in limitations for better numerical prediction of dynamical behavior.\par In this master thesis the bearing stiffness of statically overdetermined gearbox is investigated. For this purpose an iterative process has to be conducted, with initial guess for loads on bearings, which gives initial values for their stiffness. The calculated stiffness has to be further inserted into FEM model of gearbox, where new load vectors on the bearings are calculated. Described process is running until convergence of loads on bearings is reached. The next step is to investigate difference between diagonal and full bearing stiffness matrix in the FEM calculation. As a reference to our calculation, hammer based measurements of frequency response function are used. Measurements are performed on a simple, but statically overdetermined gearbox with the option for moment adjustment between two shafts.