Investigation on the Low Cycle Thermal Fatigue of a Hybrid Power Unit Transmission Clutch

A numerical methodology for the thermal-structural assessment of a clutch for a high-performance hybrid power unit is proposed. Clutches are commonly adopted in internal combustion engines to connect the crankshaft to the gearbox. However, the specific clutch under investigation is employed for the coupling between the electric motor and the engine transmission primary shaft in a P2 hybrid architecture. In this specific configuration, the clutch may be activated and deactivated frequently to maximise the efficiency of the power unit depending on the required output torque and on the particular control strategy developed. As a consequence, the thermal loads insisting on the clutch may differ with respect to the ones encountered in a typical full combustion architecture. The results of the presented research show the great influence of the thermal deformation on the stress state of this component, and the onset of possible failure due to low cycle fatigue phenomena is detected. In addition, the influence of different modelling strategies is considered.