Influence of the temperature distribution on both high-cycle and low-cycle fatigue life of a motorbike piston

Finite Element analyses are performed to evaluate stresses and strains in a motorbike piston. Non-linear Finite Element models are employed to mimic the piston behaviour when subjected to different loading conditions. In particular, gas forces, inertial forces, and piston-tocylinder contact forces are considered. Temperature distributions formally evaluated and validated against experimental evidences [1] are applied to the model to include thermal stresses and strains into the analysis. Two different thermal configurations are considered: the first has a no-optimized design of the oil jet hitting the underside zone of the piston crown, while the second presents modified parameters able to appreciably increase the heat transfer coefficient. This aspect causes different operating temperature distributions that strongly influence the piston behaviour. This paper aims at performing both low-cycle and high-cycle fatigue analysis to show how the fatigue life and fatigue-critical points change in the two considered thermal configurations