Residual modes in vibrations

pukb

what exactly are residual modes of vibrations?
I have come across this terminology in various fem solvers like ansys and pam crash.

tiny-tim

hi pukb!

aren't the residual modes simply the ones you're ignoring in the sense that you're not controlling them, but you can't actually ignore them because they're still there, and contaminating your predictions?

see eg http://books.google.co.uk/books?id=V...=0CGIQ6AEwCDgK

Bobbywhy

pukb,

Residual modes of vibration are resonant vibrations caused by an interaction between the inertial and elastic properties of the materials that form the structure. They occur in the structure after a desired motion stops, and therefore called “residual” or “left over”.

Vibration reduction is a decisive aim for light-weight manipulators especially in space applications where low energy consumption is coupled with increasing demand for higher speed and precise motion performances. The persisting residual vibration at the end of a motion limits the performance of a system in terms of operating time and accurate positioning.

Ultra-precision manufacturing machines are designed to fabricate and measure complex parts having micrometer-level features, with nanometer-level tolerances/surface finishes. Due to stringent accuracy requirements, these machines must be properly isolated from floor vibrations. Passive isolators provide an energy neutral, reliable and cost-effective means for vibration isolation. A major problem with the soft mounting provided by passive vibration isolators is that it induces low-frequency residual vibrations of the isolated machine base, which degrades the achievable accuracy/speed of these machines.

Here’s one textbook on the subject:
http://books.google.com/books?id=MUQ...ations&f=false

Cheers,
Bobbywhy