《振动与波动力学》英文课件第3章单自由度系统对简谐和周期激励的响应.ppt

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Chapter 3 SDOF w. Harmonic... * Text For Next Lesson Chapter 4: “Response of single-degree-of-freedom systems to nonperiodic excitations”. Sections 4.1, 4.2, 4.3 and 4.4 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Chapter 3 SDOF w. Harmonic... * Which Part Is Physical? If the base motion is , then the response of the system is If the base motion is , then the response of the system is * Chapter 3 SDOF w. Harmonic... * The Amplitude-Frequency Relation z =0.05 z =0.15 z =0.25 z =1 z =0.1 z =0.5 * Chapter 3 SDOF w. Harmonic... * * Chapter 3 SDOF w. Harmonic... * * Chapter 3 SDOF w. Harmonic... * * Chapter 3 SDOF w. Harmonic... * Comparison of Free and Forced Response Forced vibration is the sum of two kinds of harmonic(简谐) terms of different frequencies. Forced response has amplitude and phase effected by forcing function. If forcing frequency is close to n.f., the amplitude of particular solution is very large. 0 5 10 15 20 25 30 -5 0 5 Time (sec) Displacement (x) * Chapter 3 SDOF w. Harmonic... * What If w is near wn? When the excitation frequency and natural frequency are close, a beat (拍) occurs. 0 5 10 15 20 25 30 -1 -0.5 0 0.5 1 Time (sec) Displacement (x) Chapter 3 Response of Single-Degree-of-Freedom Systems To Harmonic And Periodic Excitations Yuefang Wang Department of Engineering Mechanics and Shengu-DUT Research Institute Fall, 2008 * Chapter 3 SDOF w. Harmonic... * Review of the Past Class Damping measurement with the log-decrement. Forced vibration response. * Chapter 3 SDOF w. Harmonic... * Review of the Past Class (contd) z =0 z =0.1 z =0.3 z =0.5 z =1 Frequency-Amplitude Resonance. Base motion. * Chapter 3 SDOF w. Harmonic... * Response of Periodic Excitations and Fourier Series Some excitations are not harmonic, but still periodic. So, the response is made periodic. 0 2 4 6 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Excita