Dynamic Characteristics Analysis And Structure Strengthening Design For The Crankshaft And Piston System Of The Internal Combustion Engine

This paper analyzed dynamic characteristics of the crank-connecting rod mechanism in the vehicle diesel engine. Further more it researched dynamic stress of the crankshaft and optimized the dynamic slap performance of the piston on the cylinder liner.Both the traditional discretization method and finite element technique were used to calculate torsional vibration characteristics of the crankshaft system. The results show traditional discretization method is effective which can also optimize the silicone oil damper. Besides the damping value of the silicone oil damper has little effect to the damper's performance and rotational inertia value of the damper can change the work performance of the silicone oil damper. With sufficient consideration of elastic deformation and friction damping, multibody dynamics simulation can calculate amplitude of torsional vibration more accurately. Torsional vibration test of crankshaft system verifies the accuracy of the two methods above.Semi-automatic topological method was used to make the hexahedral mesh model of the crankshaft. The dynamic stress was obtained by multibody dynamics simulation. Based on the fatigue test data, material parameters of the crankshaft were obtained by simulating the bending fatigue testing process. Multiaxial fatigue life was analyzed by coupling bending and torsional vibrations. Further the crankshaft structure was optimized. The results show the substructure method can be used to improve the fatigue reliability of the crankshaft. Besides the fatigue reliability can improve effectively by using better material of crankshaft. Then fracture accident of crankshaft back end was analyzed in detail for the error of drilling depth.Boundary conditions such as thermal profile and radial stiffness of piston were obtained by combining simulation and test. The secondary motion characteristic of piston was improved by adjusting piston pin offset and clearance between piston and cylinder liner, as well as optimizing piston skirt profile. The result shows original middle-convex bucket skirt profile can keep well motion characteristics of piston. The difference of vibration acceleration of thrust side on block head was analyzed by whether having dynamic slap force of the piston on the cylinder liner in simulation. The result shows that dynamic slap force of the piston on the cylinder consists of mainly medium and high frequency.This paper developed the related new method of analysis of crank-connecting rod mechanism from the view of engineering application. It has gained a series of results with practical engineering value to direct engineering application.