Spline couplings are frequently used in power transmission machinery, e.g. the input shaft of a gearbox driven by an engine. Owing to the need to accommodate relative axial motion between the driving and driven shafts and the need to provide radial clearance between the mating shafts to ensure ease of assembly, modelling of the force transmission between the shafts involves consideration of Coulomb friction induced moments as well as snubbing forces, these latter being discontinuous contact forces. Both considerations introduce non-linearities, and an evaluation of the effect of these on the vibration analysis of the coupled shaft system generally necessitates transient analysis. Using an existing experimental rig as an appropriate illustration vehicle, with the driven shaft assumed to be running in deep groove ball bearings, an unbalance response analysis revealed that spline coupling non-linearities gave rise to non-linear vibration characteristics over and above those due to the rolling element bearings, and significantly increased the bearing forces in the ball bearings supporting the driven shaft.
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