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In motorsport power transmission systems, high-speed operation can be associated with significant rotordynamic effects. Changes in the natural frequencies of lateral (bending) vibrational modes as a function of spin speed are brought about by gyroscopic action linked to flexible shafts and mounted gear components. In the investigation of high-speed systems, it is important that these effects are included in the analysis in order to accurately predict the critical speeds encountered due to the action of the gear mesh and other sources of excitation. The rotordynamic behaviour of the system can interact with crucial physical parameters of the transmission, such as the stiffnesses of the gear mesh and rolling element-to-raceway contact in the bearings. In addition, the presence of the gear mesh acts to couple the lateral and torsional vibration modes of a dual-shaft transmission through which a torque flows.

Efficiency and durability are key areas of research and development in modern racing drivetrains. Stringent regulations necessitate the need for components capable of operating under highly loaded conditions whilst being efficient and reliable. Downsizing, increasing the power-to-weight ratio and modification of gear teeth geometry to reduce friction are some of the actions undertaken to achieve these objectives. These approaches can however result in reduced structural integrity and component durability. Achieving a balance between system reliability and optimal efficiency requires detailed integrated multidisciplinary analyses, with the consideration of system dynamics, contact mechanics/tribology and stress analysis/structural integrity. This paper presents an analytical model to predict quasi-static contact power losses in lubricated spur gear sets operating under the Elastohydrodynamic regime of lubrication.

This paper presents an investigation into Elastohydrodynamic (EHL) modeling of differential hypoid gears that can be used in coupling with Newtonian (or multibody) dynamics to study Noise, Vibration and Harshness (NVH) phenomena, such as axle whine. The latter is a noise of a tonal nature, emitted from differential axles, characterised by the gear meshing frequency and its multiples. It appears at a variety of operating conditions; during drive and coasting, high and low torque loading. Key design targets for differential hypoid gears are improved efficiency and reduced vibration, which depend critically on the formation of an EHL lubricant film. The stiffness and damping of the oil film and friction generated in the contact can have important effects and cannot be neglected when examining the NVH behaviour of hypoid gears.

The dynamics of automotive differentials have been studied extensively to improve their efficiency and additionally, in recent years, generated noise and vibration. Various mathematical models have been proposed to describe the contact/impact of gear teeth pairs. However, the influence of vehicular cruising speed on the resisting torque has not been considered in sufficient detail. This can lead to unrealistic predictions with regards to loss of contact of teeth pair, a phenomenon which leads to NVH issues. The current work presents a torsional model of a hypoid gear pair. The resisting torque is a function of the traction force and aerodynamic drag, whilst the vehicle is cruising at nominally constant speed. The pinion input torque is derived through assumed instantaneous equilibrium conditions. In this approach, realistic excitation capturing the vehicle's driving conditions is imposed on the dynamics of the hypoid gear pair.

Gear oscillations are one of the most common sources of Noise, Vibration and Harshness (NVH) issues manifested in automotive powertrains. These oscillations are generated mainly due to impacts of the meshing gear teeth over a broad frequency range. To mitigate NVH phenomena, automotive manufacturers traditionally couple linear tuned vibration absorbers to the driveline. Common palliatives used are clutch dampers and dual mass flywheels, which generally suppress vibrations effectively only over narrow frequency bands. Nonlinear Energy Sinks (NESs) are a class of vibration absorbers with essentially nonlinear characteristics that are designed for dissipating vibration energy over broad frequency ranges (due to the employed nonlinearity). The NES does not have a preferential natural frequency; this is rather characterized by the nonlinear stiffness.

In this paper, a direct correlation between transmission gear rattle experiments and numerical models is presented, particularly focusing on the noise levels (dB) measured from a single gear pair test rig. The rig is placed in a semi-anechoic chamber environment to aid the noise measurements and instrumented with laser vibrometers, accelerometers and free field microphones. The input torsional velocity is provided by an electric motor, which is controlled by a signal generator, aiming to introduce an alternating component onto the otherwise nominal speed; thus, emulating the engine orders found in an internal combustion engine. These harmonic irregularities are conceived to be the triggering factor for gear rattle to occur. Hence, the rig is capable of running under rattling and non-rattling conditions. The numerical model used accounts for the gear pair's torsional dynamics, lubricated impacts between meshing teeth and bearing friction.