The Structure Analysis Of Crank Link Mechanism In Engine

The crankshaft is an important part of the gasoline engine. Its strength and rigidness have direct influence upon the properties of the whole machine. Since the structure and the shape of the crankshaft are complicated and the loads vary periodically, it is difficult to calculate its strength and rigidness using classical mechanics. With the rapid development of computer technology, FEM is widely used in the field of strength and rigidness analysis of the crankshaft. Therefore analysis using FEM and improved are presented in this thesis in allusion to the fracture of the crankshaft of GX160 gasoline engine.First, the loads of the crankshaft are analyzed. The FEM model of the whole crankshaft is built, and the stress contour was obtained and the critical point was found after it was imposed by load and constraint. Then the static strength and the fatigue strength safe coefficient of the critical point were checked. The cause of the fracture is that the fatigue fracture happens under low loads due to stress focus is found.Second, it pointed out that the design of crankshaft had no problem through fracture surface analysis, and then improved the crankshaft with changing material. The static strength analysis of the crankshaft improved was done and the static strength and the fatigue strength safe coefficient of the critical point were checked, which indicated that the crankshaft improved meet the requirement. The 400h endurance test verified the validity of simulation.Third, applied the modal analysis to the crankshaft improved, from which the natural frequencies of the first 8 modes are extracted and the vibrative shapes of the first 8 modes are obtained. It concludes that the resonance phenomena will not happen to crankshaft from it starts to declared working condition.Finally, multi-body system dynamic simulation of the crankshaft improved was finished, from which the force situation of piston and bearing points can be obtained when crankshaft was working. All above can provide the reference to the crankshaft design in the future.