Experimental measurement and finite element simulation of elastic-body vibration in planetary gears

Abstract Modal vibration experiments and finite element modeling reveal elastic-body continuum vibration in planetary gear components at frequencies within operating speeds. Sixteen equally-spaced accelerometers measure elastic-body vibration of the ring gear in ten vibration modes. Several of these modes were predicted – with good frequency accuracy – by a lumped-parameter model because their elastic-body vibration is moderate but not dominant compared to discrete-body vibrations. Other modes dominated by elastic-body vibration were missed entirely by the model. One mode has dominant planet elastic-body vibration. Experiments showing elastic-body vibration are compared to an established finite element/contact mechanics model with good agreement. Additionally, experimentally measured ring gear nodal diameter components agree with analytical model predictions in the literature. Elastic-body vibration persists for the same system configured with three, four, and five planets. Each mode has significant tooth mesh deformation, so dynamic mesh excitation sources are likely to strongly excite them. The test planetary gear, which is closely based on a conventional helicopter planetary gear, is not intentionally designed to highlight elastic vibration behavior, so elastic-body modes are likely active in numerous practical systems.