The Research On Lightweight Design And Reliability Analysis For The Engine Crankshaft

The lightweight of automobile structure is of great significance to energy saving and environmental protection,the lightweight design of engine is the goal that has been working hard by engine designers,especially the lightweight design of moving parts,such as connecting rod,crankshaft and piston,is of great significance to reduce the vibration of the whole engine and improve the fuel consumption of the engine.In the lightweight design of the engine,the crankshaft lightweight is the precondition and foundation of the lightweight design of other parts.Crankshaft is one of the most important moving parts of engine,it is the key component to bear the impact loading and transmit power,the parameters of its dimension,to a large extent,decide the whole dimensions and weight of the engine itself,the reliability and life of the engine are largely dependent on the strength of the crankshaft.Therefore,lightweight design of the crankshaft also requires that the crankshaft must have adequate fatigue strength,good static and dynamic characteristics and lubrication performance.In this paper,based on a gasoline engine crankshaft as the design basis,the optimization scheme of reducing the weight of crankshaft is determined by declining the balance ratio of the crankshaft;Secondly,making a comparative analysis of bearing lubrication characteristics between the optimized crankshaft and the original crankshaft,and doing a structural static analysis for the optimized crankshaft,according to the results of the analysis,the structure of the optimized crankshaft is further improved;In the end,utilizing dynamic simulation software carried out rigid-flexible coupling dynamics simulation and fatigue life analysis of the optimized crankshaft,the reliability of the optimization scheme is verified.The dissertation's main research work is as follows:(1)Based on the calculation principle of balance rate,using the three-dimensional modeling software PROE to establish different three-dimensional solid models of crankshaft with different balance rate,then the dynamic simulation calculation of one axis system is carried out to the different counterweight configuration crankshaft models by using the dynamics simulation software AVL EXCITE.The influence of different equilibrium rates on the crankshaft properties,such as bearing load,natural frequency,is studied.According to the analysis results,the final lightweight scheme is determined and the balance of the optimized crankshaft is checked.(2)The original and the optimized crankshaft models of inline 4-cylinder engine are built with AVL EXCITE Designer software based on the bearing hydrodynamic lubrication theory,the lubrication characteristics of them are comparatively studied to verify that the original crankshaft can still meet the lubrication performance requirements after reducing the balance rate of the crankshaft.(3)According to the kinetic equation,calculate the force of the crankshaft in the process of movement,then the structural static analysis of the optimized crankshaft is carried out by using ANSYS software in order to obtain the deformation value and the stress value under the condition of the maximum load.According to the results of static analysis,the structure of the optimized crankshaft is further improved in order to increase the static strength of the crankshaft.(4)Utilizing multi-body dynamic simulation software Recurdyn carried out rigid-flexible coupling dynamics simulation of the crank connecting rod assembly model in order to get the load spectrum file of crankshaft movement.Then,according to the finite element static analysis file and load spectrum file,used Durability calculation module of Recurdyn to establish the fatigue analysis model of crankshaft,got the fatigue life of crankshaft and dangerous points of fatigue damage in order to verify the reliability of the optimized crankshaft.