Investigation On Friction Coupled-Dynamics Of Engine Moving Parts Based On Test And Simulation

With the development on the research of modern engine numerical simulation technology, the coupling behavior of friction characteristic and dynamic characteristic in engine is cried for solving, which is also demanded by the research of engine NVH control technology. The pioneering study on the coupling characteristic of engine's friction behavior and dynamic behavior was performed in this thesis. An integrated engine numerical virtual prototype including several frictional characteristic was build. It's comprised of finite element method, non-linear finite element method and multi-body dynamic method was proposed, which provide a reliable data-base for the optimization and evaluation of engine's dynamic system.First, the dissertation systemically analyzed all kinds of the friction phenomenon in engine and then divided them into two research system: hydrodynamic lubrication friction system and dry friction system. A united simulation technology for the coupling behavior of the hydrodynamic lubrication friction system and crankshaft system was proposed, which introduced the EHD theory and friction theory into multi-body simulation technology. By building a virtual prototype of a four-cylinder diesel engine for vehicle which coupled with a crankshaft system and the bearing hydrodynamic lubrication, the main bearing force, the minimum thickness of the oil film and its working characteristic can be systematically obtained. The obtained simulation result indicated that the hydrodynamic lubrication friction behavior will greatly affect the system dynamic characteristic of engine. To build a more reliable engine virtual prototype should consider the friction behavior as well as the progress of the numerical simulation and design.Some of the engine's moving parts always have some inevitable friction phenomenon when it's was working. Aimed at these dry friction problems, a method on the test research of the metallic frictional characteristic was proposed. A test-bed of metal's dry friction characteristic was build to gain the hysteresis curve, equivalent stiffness and damping. The compare between test data and theory data of hysteresis curve, equivalent stiffness and damping was made to validate the theory model. The corresponding NFEM model was build in MARC and the result of FEM model was consistent with the test and theory data which provide the reliable computation for the NVH simulation of engine and validate the feasibility of the non-linear finite element method for the metallic dry friction analysis of the practical mechanical structure.At last, taking the piston-linear system as example, an integrated method integrated with non-linear finite element method and multi-body dynamic simulation method was proposed to build an engine multi-body dynamic model which concluding the sub-system's dry friction behavior. The simulation result indicated that the piston-linear multi-body dynamic system with non-linear contact friction behavior showed more reliable lateral impact load between metallic surfaces and the dry friction of piston-linear system brought a biggish force fluctuation in main bearings.The dissertation carried out the pioneer studies and basal research of the EHD and dry friction problem to build an engine virtual prototype with friction behavior.It provided a reliable data-base for the engine dynamical analysis and NVH control technology. It also developed the numerical simulation technology of engine, and achieves some valuable production.