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For many years, bearing suppliers have been using 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 consequently fatigue risk. In this paper, we propose a new way to determine the bearing fatigue resistance. To achieve that, we analyze the elastic and plastic behavior of the bearing along the engine life. We detail and provide the analytical relationships which determine stresses in the overlay and in the substrate of the bearing in order to analyze their fatigue resistance. Various physical loads are taken into account such as the thermal load, the hydrodynamic pressure field, the fitting load, the free spread load. A good knowledge of the relationships between those physical phenomena helps to understand the mechanical behavior of the bearing.

The mixed lubrication phenomenon is becoming a key issue for reliable and low friction engine design. Three main reasons can explain this fact. The increase of the engine torques at low speed has generated very low oil film thicknesses in lubricated devices. For the last ten years car manufacturers have decreased the viscosity of the oil in order to reduce friction and the oil temperatures on lubricated components have increased along with the specific power increase. Two kinds of approach, the global and the local approach, must be considered to analyze the mixed lubrication and the lubricated component behavior. From a global point of view, the various mechanisms to consider to get a realistic modelling of mixed lubrication are considered. From a local point of view, the modelling of the asperity contacts between antagonist surfaces responsible of the mixed lubrication is detailed. Commonly, a Gaussian type of distribution is used for asperity summit distribution.

Several mechanical devices, including the components of internal combustion reciprocating thermal engines, use circular elastic systems to filter the vibration of the rotating components, like in the case of dual mass flywheels. Yet, the major modifications to the stiffnesses of these systems, which give them a non-linear behavior, make the prediction of their response during dynamic analysis, a challenge. This problem could also occur with component like belt along the pulley, circular bearing in this housing. The models developed in this paper are built from Coulomb friction analysis. Analytical relationships describe the different phases of the behavior. These models make it possible to represent the behavior of these systems without studying fine models of them with a solid-body dynamic software.

For the past ten years, the loads applied on small end of conrods have become increasingly severe in automotive engines. Today, the necessity of numerical simulations of lubrication of these bearings has become an imperative concern for design engineers. However, the physical phenomenon related to the oil feeding of the small end bushes are generally not taken into account in industrial models. Moreover, the specific behavior of the small end bushes is rarely considered and could be sometimes misunderstood. To provide contributions to this problem, the analysis of the main parameters related to the lubrication of this kind of bearings have been carried out. Several characteristics of the oil feeding process have been investigated such as the influence of the clearance, the oil viscosity, the engine speed and specific configurations like grooves and oil holes. The study of their influences on the oil film thickness in the small end bushes have been realized.

In new engines, running conditions for piston pin bushes have become very severe due to combustion pressure and temperature increase. Moreover, the lead removal from the bush material has strongly reduced the capability of the antifriction material to accept asperity contacts, geometrical defects or edge loading. Today, it is usual that wear and seizure occur in the piston pin bushes during the first steps of engine development. In order to propose basic design recommendations avoiding damage, during the early steps of engine development, it is necessary to have quick numerical simulations. In these calculations, the mixed lubrication in the piston pin bearings must be taken into account. To obtain a simple realistic tool, a refined contact model is implemented in a simple hydrodynamic lubrication program. Then, the general behaviour of the piston pin is described before focusing on the combustion cycle phases when damage may occur.