Bulkhead Loading Calculation of an Aluminum Engine Block Coupled with a Rotating Crankshaft through Elastohydrodynamic Bearings 2007-01-0267
During a new engine development program, or the adaptation of an existing engine to new platform architectures, testing is performed to determine the durability characteristics of the basic engine structure. Such testing helps to uncover High Cycle durability-related issues that can occur at the bulkhead walls as well as cap bolt thread areas in an aluminum cylinder block. When this class of issues occurs, an Elastohydrodynamic (EHD) bearing simulation capability is required.
In this study, analytical methods and processes are established to calculate the localized distributed load on the bulkhead. The complexity in performing a system analysis is due to the nonlinear coupling between the bearing hydrodynamic pressure distribution and the crankshaft and block deformation. A system approach for studying the crankshaft-block interaction requires a crankshaft flexible body dynamics model, an engine block assembly flexible body dynamics model and a main bearing lubrication model. Such a system model is presented in this paper by employing multi-body dynamic system simulation to capture the dynamic characteristics from the engine durability test set-up. By using a multi-body code, DADS, with hydrodynamic (HD) bearings to couple the interaction between the flexible crank and flexible block, the resultant bearing loads and moments were calculated. Then, employing a GMPT EHD code, FLARE, the distributed nodal bearing forces were extracted from the complex interactions between the lubricant film and the solid surface by solving the Reynolds' equation.
All the detailed bearing parameters are taken into account, such as split line relief and eccentricity, upper oil groove, rotating journal oil holes, and asperity contact. Using this approach, a V8 engine was illustrated in this paper. The design parameters such as the location of oil holes in the journal of crank were studied and summarized in this paper. Finally, stress results in the single bulkhead #4 with the distributed bearing reaction EHD forces, head bolt preload and thermal deformation due to different material are also summarized in this paper.