Torsional vibrations in differentials of Rear Wheel Drive vehicles are of major
importance for the automotive industry. Hypoid transmissions, forming the motion
transfer mechanism from the driveshaft to the wheels, suffer from severe vibration
issues. The latter are attributed to improper mesh between the mating gear flanks
due to misalignments, variation of contact load and shifting of the effective mesh
position. For certain operating conditions, the gear pair exhibits high amplitude
motions accompanied with separation of the mating surfaces. Ultimately, single or
even double-sided vibro-impact phenomena evolve, which have been related to
noise generation. This thesis attempts to address these issues by effectively
analysing the dynamic behaviour of a hypoid gear pair under torsional motion. The
case study considered is focused on a commercial light truck.
The major difference of the employed mathematical model to prior formulations is the
usage of an alternative expression for the dynamic transmission error so that the
variation of contact radii and transmission error can be accounted for. This approach
combined to a correlation of the resistive torque in terms of the angular velocity of
the differential enables the achievement of steady state, stable periodic solutions.
The dynamic complexity of systems with gears necessitates the identification of the
various response regimes. A solution continuation method (software AUTO) is
employed to determine the stable/unstable branches over the operating range of the
differential. The ensuing parametric studies convey the importance of the main
system parameters on the dynamic behaviour of the transmission yielding crucial
A tribo-dynamic investigation aims at expanding the dynamic model from pure dry
conditions to a more integrated elastohydrodynamic (EHL) approach. Analytical and
extrapolated solutions are applied for the derivation of the film thickness magnitude
based on the kinematic and loading characteristics of the dynamic model. The
temperature rise is governed mainly by conduction due to the thin lubricant films.
The generated friction is also computed as a function of the viscous shear and
asperity interactions. The effective lubricant viscosity is greatly affected by the
pressure increase due to the resonant behaviour of the contact load.
The final part of this work is involved with a feasibility study concerning the
application of Nonlinear Energy Sinks (NES) as vibration absorbers, exploiting their
ability for broadband frequency interaction. Response regimes associated with
effective energy absorption are identified and encouraging results are obtained,
showing the potential of the method.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.