Frictional Dynamics in Wet Clutch Systems

Wet clutch systems employ interleaved plates immersed in lubricating fluid to transfer torque smoothly under variable operating conditions. The frictional dynamics arise from the interaction between surface asperities and a pressurised oil film, resulting in mixed lubrication regimes that evolve during engagement and disengagement. Key phenomena include drag torque generation when plates shear the fluid in the disengaged state, transient temperature rises from sliding heat, and changes in friction coefficient during running-in and wear. Recent advances have focused on visualising sub-millimetre flow structures, modelling coupled thermal–fluid–solid behaviour and applying data-driven methods to predict performance under diverse loads and speeds. Improved understanding of oil groove design, plate separation under external forces and temperature-dependent friction conductance supports optimised clutch efficiency, durability and shift comfort in automotive and aerospace transmissions worldwide.

Research from Nature Portfolio

Recent studies have provided unprecedented insights into oil flow and torque behaviour in disengaged wet clutches. By employing transparent components and high-speed imaging, researchers have characterised single-phase flow in the gap and identified local bubble formation within radial grooves. The drag torque was observed to increase linearly with differential speed until oil displacement by centrifugal forces reduced torque, delineating regimes of fluid-shearing and near-dry friction. These findings clarify the limits of cooling performance in dip-lubricated clutches and suggest that maintaining higher oil levels can mitigate early oil loss and sustain steady drag torque.

Frictional Dynamics in Wet Clutch Systems publication trend

The graph below shows the total number of articles in frictional dynamics in wet clutch systems across all publications each year (not limited to Nature Index journals).

Technical terms

Friction coefficient: Ratio of frictional force to normal load in sliding contacts.

Drag torque: Torque generated by fluid shearing between disengaged clutch plates.

Hydrodynamic lubrication: Regime where a continuous fluid film fully separates surfaces, transmitting load through fluid shear.

Mixed friction: Transitional regime combining asperity contact and fluid film support.

Asperity: Micro-scale surface peak or protrusion contributing to contact friction under load.

References

1. Experimental investigation of drag loss and plate separation behavior of wet clutches under external forces. Results in Engineering (2024).
2. Transient temperature characteristics of friction clutch disc considering thermal contact conductance under sliding conditions. Friction (2023).
3. Flow-structure identification in a radially grooved open wet clutch by means of defocusing particle tracking velocimetry. Experiments in Fluids (2021).
4. Experimental analysis of oil flow and drag torque generation in disengaged wet clutches. Scientific Reports (2023).
5. Thermal-Fluid-Solid Coupling Simulation and Oil Groove Structure Optimization of Wet Friction Clutch for High-Speed Helicopter. Machines (2023).
6. A methodology for data-driven modeling and prediction of the drag losses of wet clutches. Forschung im Ingenieurwesen (2023).