| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 92 === Based on Timoshenko theories, the vibration and fatigue analyses are combined to discuss the vibration behavior of a cracked rod of crank-slider mechanism with the crack growth in this study. The natural frequency is changed when the crack is growing. Therefore the amplitude of vibration is affected by the loading frequency. The model of breathing crack is applied to simulate the opening and closure crack, which affects the behavior of vibration.
The analysis of vibration and fatigue for a cracked rod are coupled in this study. The interaction between vibration and fatigue are determined and discussed. At first, the connecting rod is assumed as Timoshenko’s beam, then the equations of motion and boundary conditions are derived by Hamilton’s principle, that the moving boundary conditions of connecting rod at one end of slider are considered. Moreover, using the Galerkin method with mode shape function that satisfies the boundary conditions, the equations of motion are reduced to Mathieu equations. And then, Runge-Kutta method is used to determine the transient amplitude for breathing crack model. The modified Forman equation is used to determine the rate of fatigue crack growth, and the crack depth is corrected cycle by cycle. When the crack depth ratio increases, the amplitude increases.
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