Analysis of connecting rod bearing design trends using a mode-based elastohydrodynamic lubrication model

Available design trends for big end connecting rod bearings utilize widely adopted rapid methods for prediction of minimum film thickness due to their superior speed and ease of use. However, they impose unrealistic assumptions such as surface rigidity, which could compromise the accuracy of results. The significance of structural elasticity and updated models was investigated using a mode based elastohydrodynamic lubrication model which includes body forces, mass conserving cavitation, and surface roughness. Eight physical connecting rods were modeled using finite element methods and simulated over a variety of conditions, varying engine speed, bearing clearance, and oil viscosity. The results show operating conditions where rapid methods can inaccurately predict minimum film thickness. Bearings operating at higher speeds and loads are subject to significant bearing deformation that influences minimum film thickness predictions. In certain low load conditions oil feed pressure can also have a significant effect on minimum film thickness results. Additionally, current parameters used to characterize bearing performance do not adequately characterize trends that include bearing deformation.