Coupling Researches On Dynamics Tribology Stiffness And Strength In The Crankshaft-Bearing System Of Internal Combustion Engine

Crankshaft bearing system is one of the most important components in Internal Combustion Engines (ICE). The analysis on dynamics, tribology, stiffness and strength for the crankshaft bearing system has to be done when engineers design an IC engine. It is directly affected on reliability and durability of the engine. The multidisciplinary performance such as dynamics tribology stiffness and strength have been researched independently in the extent of respective discipline for a long period of time because crankshaft has a complex geometric structure and the crankshaft bearing system is applied by a complicated variable load. The multidisciplinary performances of the system happen simultaneously and affect each other as engine works. The coupling study on dynamics tribology stiffness and strength is very important both in theoretical and practice sense.At the beginning of this dissertation, the present status of dynamical calculation of crankshaft, tribological analysis of ICE journal bearing, fatigue strength calculation and their coupling research are reviewed. The necessity to do some coupling analysis is presented in mechanical engineering. The decoupling method is obtained according to their coupling characteristic. Strong coupling relation exists among dynamics tribology and stiffness for the system and weak coupling appears between strength and the other three. Special software ADAMS and ANSYS, combined with self-designed program, are applied to solve the coupling problem for the calculating work is huge and complicated. A common shaft-bearing is first researched to validate the decoupling method.Based on lubrication analysis of bearing, dynamical behaviors of a flexible shaft-bearing system are simulated on variable load by ADAMS, special software for dynamic simulation. Sweep frequency method is applied to obtain the diagram between vibrating frequency and amplitude. Dynamical responses in resonant vibration in sine load and on pulse load are researched. Some change on tribological behavior of bearing and dynamical behavior happen as journal misalignment is considered.A finite element model is set up to calculate the dynamic stress on the journal surface. Calculating program is developed by the ANSYS parameter program language (APDL) to put on the boundary condition dynamically, solve and record the stress on the designated nodes automatically.The calculating result has shown that the stress along axial and circumferential distribution on journal surface is dependent on the corresponding distribution on oil film pressure and variation with time is decided by the dynamic response of the shaft-bearing system. Great change takes place to the tribological behavior of the bearing, dynamical performance of the shaft-bearing system and dynamic stress on journal surface as journal misalignment is considered.The crankshaft bearing system of N485 diesel engine is selected to investigate the coupling of dynamics tribology and stiffness. The coupling simulation model of the crankshaft bearing system is built in ADAMS with a flexible crankshaft. The dynamic calculation is done in rated working load. How the main journal misalignment affects the dynamic performance of crankshaft and the tribological behavior is revealed. The minimum thickness of oil film of bearing decreases 92.14%, the maximum pressure of oil film increases 43.76% respectively and the dynamical responses of the system vary as the journal misalignment is considered.The dynamic pressures of oil film in the bearings, which can be calculated by the dynamical parameter of journal center or by the applied load on bearings, are converted to the dynamic node forces.