Simulation of the transient dynamic behaviour of an aircraft gearbox by CMS

Usually the dynamic performance of a complex structure like a gear transmission system is evaluated with lumped mass models and the effect of the flexibility of the casing is neglected or roughly approximated though it can be important as in the case of aircraft applications. In this work the dynamic behaviour of a simplified model of a gearbox made of two gears, two shafts and a thin-walled box was simulated taking into account the flexibility of the casing by means of Component Modal Synthesis (CMS). A procedure that combines FEM modelling, Component Modal Synthesis (CMS), and dynamic simulation in the Simulink environment was developed in order to determine the dynamic behaviour of the whole transmission system in steady state conditions and the dynamic overloads in case of transients with a reduced number of degrees of freedom. It is also possible to simulate the typical non-linearities related to gear meshing including non linear elements in the Simulink model