Posted in Damping on May 1, 2013 | Leave a Comment »
Here is a project that my NASA colleagues have been working on: FSC_damper.pdf
The original goal of the project was to use the Ares I second stage as a LOX damper to mitigate the first stage thrust oscillation.
See also:
http://blogs.nasa.gov/cm/blog/Constellation.blog/posts/post_1239311627391.html
- Tom Irvine
Posted in Damping, Matlab on February 6, 2013 | 1 Comment »
The half-power bandwidth method can be used to estimate the damping ratio and corresponding Q value from the frequency response function of a structure which has been excited by base motion or an applied force. The structure may be a multi-degree-of-freedom (MDOF) system as long as the modal frequencies are separated by a sufficient frequency margin so that the spectral peaks are distinct.
Here are some resources.
Paper: half_power_bandwidth.pdf
Matlab script: half_power_bandwidth.m
See also: Damping Value Conversion Calculator
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Here is a newsletter with an example of the half-power bandwidth method applied to the Ares-1X roll-out: May2010_NL.pdf
- Tom Irvine
Posted in Damping, Matlab on December 12, 2012 | 1 Comment »
Here is a Matlab GUI script which converts between various damping metrics: damping.zip
The supported metric include:
quality factor Q
fraction of critical damping [zeta]
loss factor [eta]
3 dB Bandwidth [delta omega]
3 dB Bandwidth [delta f]
damping frequency [fd]
decay constant [sigma]
time constant [tau]
reverberation time [RT60]
decay Rate D
logarithmic decrement [delta]
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See also:
Damping, Isolation & Vibration Absorbers Page
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- Tom Irvine
Posted in Damping on June 25, 2012 | Leave a Comment »
Piezoelectric shunt damping systems reduce structural vibration by shunting an attached piezoelectric transducer with an electrical impedance. Current impedance designs result in a coupled electrical resonance at the target modal frequencies.
Piezoelectric transducers (PZTs), in conjunction with appropriate circuitry, can be used as a mechanical energy dissipation device. If a simple resistor is placed across the terminals of the PZT, the PZT will act as a viscoelastic damper. If the network consists of a series inductor–resistor R–L circuit, the passive network combined with the inherent capacitance of the PZT creates a damped electrical resonance. The resonance can be tuned so that the PZT acts as a tuned vibrational energy absorber.
Here is a paper:
http://www-eng.newcastle.edu.au/~ajf203/PDFs/J03b.pdf
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- Tom Irvine
tomirvine999