The Finite Element Analysis And Optimization For Connecting Rod Of LJ276M Electronic Controlled Gasoline Engine

As one of the most important parts,connecting rod endures the power thrusts from piston pin with its magnitude and direction change periodically,the inertia force caused by swing of connecting rod and the reciprocating inertia force of piston group. Therefore,the connecting rod suffers alternating loads such as compressive load, tension,load,bending load and so on.It requires the connecting rod owns sufficient stiffness and strength.Further more,if the engine power performance is increased evidently,the connecting rod should endure bigger combustion-gas pressure than before and the structure is easier to be destroyed too.As a result,it is necessary to analyze the connecting rod and then judge if it meets requirement of strength and rigidity according to the analysis results.At present,with the fast-changing development of computer technology,the finite element method plays an increasingly important part in design and analysis for engine parts.Consequently,the finite element method can be also used to do the structural analysis for connecting rod to investigate the stress,strain and possible dangerous areas of connecting rod in various conditions.First of all,the engine indicator diagram testing system has been built to get the data of cylinder pressure which is the basis of connecting rod analysis,then,the structural analysis and performance optimization design for connecting rod using Pro/E as design implement and Pro/MECHANICA and ANSYS as analytical platform can be carried out.The thesis creates the three-dimension solid model of connecting rod based on features by means of Pro/E and analyzes the actual forces,boundary conditions and loads applying.The stress and displacement results which is in the working condition of maximum compression and maximum stretching at rated speed are get by computer analysis and calculating.The strength factors of connecting rod in the working condition of maximum compression for LJ276M electronic controlled gasoline engine are also calculated based on the result data and show that the connecting-rod's static strength and fatigue strength can meet the demands of structure after the power was enhanced.Then make further efforts to do structure optimization analysis which aims at working out the optimal structural parameter in restrained conditions and the peak stress of maximum compression is reduced by 4.9%and the static strength factor is increased by 5.4%for optimal connecting rod. Those results indicate that the optimal conncecting rod has a higher reliability.In the paper,modal analysis for the whole connecting rod is also done to get the natural frequencies and modes of connecting rod which gives a basis for judging the functional reliability on dynamic characteristics.