Coupling Analysis of Vibration and Fatigue Crack Growth for the Cracked and Flexible Connecting Rod in a Four-Bar Mechanism

• Main Authors: Chen-Yuah Chung, 鍾禎元
• Other Authors: Yan-Shin Shih
• Format: Others
• Language: en_US
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/11008945665259947943

碩士 === 中原大學 === 機械工程研究所 === 91 === Considering a four-bar linkage mechanism, the transverse vibration of the cracked flexible connecting rod is analyzed in this study. First of all, the connecting rod is assumed as Euler beam, and then the equations of motion and boundary conditions are derived by Hamilton’s principle. Moreover, using Galerkin method with mode shape function that satisfies the boundary conditions, the equations of motion are reduced to Mathieu equations. The Runge-Kutta numerical technique is used for solving the transient amplitude of the continuous and breathing models. And then, the modified Forman model is applied to calculate the crack propagation; the relation between amplitude and loading cycle is also determined by Runge-Kutta method. The results reveal that the natural frequency of the connecting rod decreases with the increment of the crack depth. When the crack depth ratio increases, the transverse amplitude increases a little. While the ratio of length of the crank to the length of the connecting rod increases from 0.2874172 to 0.3668874, the transverse deflection of the connecting rod increases, too. The analysis of vibration and fatigue for a cracked rod are coupled in this paper. The interaction between vibration and fatigue will be discussed synchronously, and combining the analysis of vibration and fatigue can describe the phenomenon of fatigue crack growth more realistically.