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This work presents the results and methodology of a dynamic durability analysis considering the interaction between crankcase and crankshaft. The approach is based on a robust mathematical model that couples the dynamic characteristics of the crankshaft and crankcase, representing the actual interaction between both components. Dynamic loadings generated by the crankshaft are transferred to the crankcase through flexible 3D hydrodynamic bearings. This methodology is referred to as hybrid simulation, which consists in the solution of the dynamics of an Elastic Multi-Body System (E-MBS) coupled with the Finite Element Methodology (FEM). For this study, it was considered an in-line 6-cylinder diesel engine used in off-road applications. The crankcase design must withstand higher loads due to new calibration targets stipulated for PROCONVE (MAR-I) emission regulations.

The increasing pressure on the engine development process via tighter legislations and increasing competition lead to search for the best possible design for each engine component. Especially the dynamic parts, which contribute to total engine friction at most, are under extreme focus. The search for the optimum layout of crankshafts considering the design aims, such as low friction, low weight and high durability, is usually a manual variation process with limited number of design loops. Within this study computer aided (CA) automated optimization methodologies are integrated into the design procedure to achieve the best possible design solution according to the objectives under consideration of the predefined constraints. An extensive crankshaft optimization study is performed and resulted in many novel and patented design features. A case study for a modern in-line four-cylinder crankshaft is performed to show the potentials.

This paper presents the comparison of two different approaches for crankcase structural analysis. The first approach is a conventional quasi-static simulation, which will not be detailed in this work and the second approach involves determining the dynamic loading generated by the crankshaft torsional, flexural and axial vibrations on the crankcase. The accuracy of this approach consists in the development of a robust mathematical model that can couple the dynamic characteristics of the crankshaft and the crankcase, representing realistically the interaction between both components. The methodology to evaluate these dynamic responses is referred to as hybrid simulation, which consists of the solution of the dynamics of an E-MBS (Elastic Multi Body System) coupled with consecutive FEA (Finite Element Analysis).

Due to increasing demand for environment friendly vehicles with better fuel economy and strict legislations on greenhouse gas emissions, lightweight design has become one of the most important issues concerning the automobile industry. Within the scope of this work lightweight design potentials that a conventional single cylinder engine crankshaft offers are researched through utilization of structural optimization techniques. The objective of the study is to reduce mass and moment of inertia of the crankshaft with the least possible effect on the stiffness and strength. For precise definition of boundary conditions and loading scenarios multi body simulations are integrated into the optimization process. The loading conditions are updated at the beginning of each optimization loop, in which a multi body simulation of the output structure from the previous optimization loop is carried out.