Fatigue Analysis of Conrod Bearing

Abstract

For many years, bearing suppliers use efficiently the specific pressure to evaluate the fatigue risk of conrod bearings. However, modern engines have made the bearing more sensitive to various phenomena such as the thermal expansion or the elasticity of the conrod housing. These effects modify the stresses in the bearing layers and by the way the fatigue loading. In this paper, we analyze the elastic and plastic behavior of the bearing during the engine life. We detail and provide the analytical relationships, which determine stresses in the overlay and the substrate of the bearing. Various loadings are taken into account such as the thermal loading, the hydrodynamic pressure field, the fitting loading, the free spread loading. The knowledge of the relationships helps to understand the mechanical behavior of the bearing. Particularly, it allows demonstrating that plastic flow occurs in the substrate and in the overlay during the first combustion cycles and the first thermal cycles. Residual stresses are introduced by plastic flow and modify the stress tensor in the different layers. Therefore, the two layers are subject to high cycles fatigue (H.C.F.) with combustion cycles and low cycles fatigue (L.C.F.) with thermal loading. The high cycle fatigue analysis is performed with multiaxial criteria.

Friction Reduction and Reliability for Engines Bearings

“…Thermal aspects allow one to take into account thermal stress in bearing overlay, which is relevant for internal stress overlay. On fatigue resistance, the results presented in paper [5] have shown the influence of antifriction layer bonding, thermal stress and residual stress induced by antifriction plastic flow. For new bearings, this implies that an increase in terms of temperature and the number of cycles requires improved fatigue resistance.…”