Establishment of the Numerical Model and the Stiffening of Engine Structure

• Main Authors: Sheng-yuan Peng, 彭聖元
• Other Authors: Mau-Pin Hsu
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/8bdvwp

碩士 === 國立臺灣科技大學 === 機械工程系 === 99 === How to reduce vibration and the noise of engine has been an important issue. Because the components of engine are locked by bolts, impacts from bolt-preload and simulation on engine vibration and noises have to be clarified. This study used the finite element method to establish a numerical model for the engine. The study findings revealed that after including camshaft and crankshaft into the finite element model, the natural frequency of the engine changed due to impacts from these two shafts on the various modes, consequently the occurrence sequence of the modes varied. In addition, different rotation angle of the crankshaft can change the moment of inertia, and that will alter the natural frequency as well. Results from analyzing the bolt-preload indicate a less than 0.45% difference in natural frequency between the presence and the absence of bolt-preload. Therefore, for time-saving, bolt-preload can be neglected for general analysis. And by analysis results of change the bolt material to simulate the rigid element , when simulation the Young's modulus change to 1000 times of bolt material ,the results of analysis will close to result of bolt simulation rigid body element. However, the simulation and actualy of Young's modulus difference is too large. Therefore, the rigid element simulation of the set bolt is unreasonably. In terms of the first and the second modes of the engine, one can stiffen the structure by increasing the number of ribs according to the mode shape and the strain diagram so the amplitude can be reduced and the natural frequency altered.