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This paper introduces different modeling approaches of crankshafts, compares the refinement levels and discusses the difference between the results of the crankshaft durability calculation methodologies. A V6 crankshaft is considered for the comparison of the refinement levels depending on the deviation between the signals such as main bearing forces and deflection angle. Although a good correlation is observed between the results in low speed range, the deviation is evident through the mid to high speed ranges. The deviation amplitude differs depending on the signal being observed and model being used. An inline 4 crankshaft is considered for the comparison of the durability results. The analysis results show that the durability potential is underestimated with a classical crankshaft calculation approach which leads to a limitation of maximum speed of 5500 rpm.

Due to the rapidly increasing raw oil price the reduction of fuel consumption has become one of the most important targets for the development of modern passenger car engines. After large progress has been achieved in the combustion process development - CAE has been one of the keys to success - nowadays further potential is being investigated. The mechanical friction is very much in the focus of the engine development engineers. While in the Valve Train the potential of roller contacts and surface treatment is the main development direction, in the cranktrain the reduction of bearing diameters is being investigated. Due to increasing specific loads on the crankshaft there are clear limits. At the piston group the potential is almost untouched. While optimizations of the piston skirt contour or the ring pack bring up the risk of negative influences on blow by and oil consumption, the application of a crank offset is an easy design measure having almost no risks.

The loads on the plain bearings of modern combustion engines increase continuously. Reasons for this development are increasing engine speeds on gasoline engines, growing cylinder peak pressures at diesel engines and both combined with the steady trend toward light weight concepts. The still significantly increasing power output of modern engines has to be combined with actions reducing the engine friction losses, as for example smaller bearing dimensions or lower engine oil viscosities. At the same time the comfort, lifetime and engine service interval targets are aggravating boundary conditions. This development leads to the point, where former approaches toward plain bearing layout reach their systematic limitations - a first indication are bearing failures, which occur even though all conventional layout criteria's are fulfilled. Further effects need to be considered to simulate the behavior of the plain bearing under the boundary conditions of a fired combustion engine.

The combination of multi purpose software with powertrain specific application codes allows highly flexible simulation models, which are independent on the specific engine concept. Related to the requests those models may be refined or simplified during the simulation process. Finally a fully coupled 3D dynamic simulation including flexible components is performed to assess the engine crankshaft's durability. To take into account the stiffness of the cranktrain components and the cylinder block at first a linear Finite Element Analysis (FEA) simulation is performed. Via modal reduction the complete deformation order information of the FEA simulation are reduced to the necessary information for the dynamic Multi Body System (MBS) simulation [1, 2]. All main boundary conditions of the system, e. g. gas forces, oil temperature or driveline application are taken into account.