Dynamic Modeling On Vibration Of I.C.E. Crankshafts

Crankshaft is the most important part of the I.C.E. Numerical simulation in crankshaft is a very significative research field. Since the shape, the boundary condition and the load of the crankshaft being very complex, to simulate the vibration behavior of crankshaft well, a good computational method is very important. According to the foregone research experience, the solid FEM can be the best method for solving this problem. But because of the limit of computational scale, it is just applied in the analysis of statics and mode. Since the other methods being too simple or the application fields being very narrow, the results of computation are much different from experimental data. Considering the computational scale and the precision of the computational results, together with the structure and working style of crankshaft, the spatial Timoshenko beam element count of shear deformation and inertia moment is suggested to be applied for modeling crankshaft in this thesis.Firstly the principle of FEM in structure dynamics is presented. Then the theory of Timoshenko beams is introduced and the difference between Timoshenko beams and Euler beams is explained. Then the method and process of building FEM for the crankshaft is described in detail. Further more, using the method and ANSYS software, the Vibration behavior of the crankshaft in an one-cylinder engine and a four-cylinder engine are analyzed. At last, based on VC++ 6.0 and MatLAB, a software that can simulate, compute and analysis the dynamic behavior of any crankshaft is compiled.By using the solid FEM and the method decided in this thesis respectively, the vibration mode of crankshaft hi the one-cylinder engine is simulated. Results of two methods are very similar. The vibration mode of the crankshaft in the four-cylinder engine is analyzed by the presented method too, and the calculation results are compared with that results and the experimental data in other publications. It indicates that the results obtained by the method in this thesis are more effective than those presented in other publications and in good agreement with the observed data. In addition, the harmonic response and the dynamic response in time domain of crankshaft in the frontal four-cylinder engine are simulated.According to the contrast in several aspects, it is proved that the method suggested in this thesis is comparative with solid FEM for simulating the dynamic behavior of crankshaft, and the computational results are in good agreement with the experimentation data. In particular, the quality of computation is far smaller than the latter. In a word, the method presented in this thesis is concision and straightforward, it is competent for simulating the dynamic behavior of crankshaft by my own view.