Chap 3' Harmonically Excited Vibration

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Chap 3. Harmonically Excited Vibration
Consider pure harmonic excitation for
understanding the behavior of a simple
system
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Nondimensional Amplitude
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Complex Frequency Response
Frequency Response Function (System Transfer
Function)
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3.2 Rotating Unbalance
Equation of motion is
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3.5 Support Motion
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3.6 Vibration Isolation To protect a delicate
object from transmitted forces,
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3.7 Energy Dissipated by Damping Damping is
present in all system internal molecular
friction Structural damping sliding friction
Coulomb damping fluid resistance Viscous
damping Since mathematical description of damping
is quite complicate, simplified damping modal
such as viscous has been developed to evaluate
the system response.
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3.8 Equivalent Viscous Damping Equivalent
damping Ceq equate the energy dissipated by the
viscous damping to that of the nonviscous damping
force with assumed harmonic motion
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3.9 Structural Damping From experiments of most
structural metals, damping is independent of the
frequency and proportional to the square of the
amplitude
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Compare to viscous damping at resonance
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3.10 Sharpness of Resonance
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