Elastohydrodynamic Lubrication Analysis Of The Engine Crankshaft Bearing System And Strength Research Of The Crankshaft

The crankshaft is one of the most important parts in an engine, which bears periodiccylinder explosion pressure, piston assembly inertia force and its rotating inertia forcepassed from the connecting rod.The lubrication status, vibration characteristics and strengthaffect directly the lifetime, economy and reliablity of the whole engine. Especially as thedemands to the engine power performance, economical performance and reliability improvecontinually, higher requirements are put forward to the lubrication,vibration and strength ofthe crankshaft. To preceed multidisciplinary, all-around elastohydrodynamics, multi-bodydynamics, dynamic and static strength, fatigue lifetime etc aspects integrated research of thecrankshaft is extremely urgent. This paper took a four cylinder engine as the research object,established the nonlinear dynamic system of the whole crank mechanism based on thenonlinear multibody dynamic theory and the finite element theory, then proceeded theelastohydrodynamic analysis to the main bearings of the crankshaft, on this basis carried onthe research of the crankshaft dynamic characteristic and modal dynamic stress recoverytechnology, at last, completed the static strength analysis and fatigue analysis of thecrankshaft which laid solid basis to the optimisation of the crankshaft. Details are asfollows:1、On the basis of establishing the three-dimensional models of the crankshaft systembasic parts, combined the requirements of the nonlinear multibody dynamic model,proceeded in-depth study on mesh generation, then selected the method which unitedmanual and self-adaption mesh generation on the Hypermesh software and meshed the crankshaft system into hexohedron.2、By means of comprehensive research on finite element degrees of freedomcondensation theory and technology, settled the main DOF nodes of crankshaft and bearings,then made use of the finite element software ABAQUS to proceed structure condensation.At last, established the condensation model of the crankshaft-bearing system.3、Took advantage of the aforementioned finite element models, condensation models,based on the finite element theory, nonlinear multibody dynamic theory and finite differencetheory, combined true oil film to represent the nonlinear dynamic coupling effect of themain journals and main bearings as well as applied gas explosion pressure, reactive torqueof the output end etc basic load and displacement boundary conditions, to proceed nonlinearmulti-body dynamics simulation analysis included the oil film lubrication which tookmophology, elastic deformation, jornal misalignment, oil supply status, cavitation etc effectsof the crankshaft and bearings into consideration.4、To proceed crankshaft dynamic stress recovery resorted to the BC of the main DOFnodes displacements of the crankshaft. Via comparative study of the finite element staticlinear stress recovery method and the modal dynamic stress recovery method, selected themodal dynamic stress recovery method to conduct dynamic stress recovery and extractedthe stress field history of the crankshaft of the second work cycle. By means of analyzingthe maximum stress of each cylinder at outburst moment, carried through the static strengthresearch.5、Relied on the stress tensor spectrum data from the multi-body dynamics analysis,based on linear fatigue accumulation theory, made use of infinite lifetime design method,Goodman mean stress correction and Brown-Miller key plane arithmetic to calculate thefatigue strength of the crankshaft and meanwhile took surface finish, treatment intoconsideration.