Residual modes in vibrations

In summary, residual modes of vibrations are resonant vibrations that occur in a structure after desired motion stops. They can limit the performance of a system in terms of operating time and accurate positioning. Passive isolators can help reduce these residual vibrations, but they can also induce low-frequency vibrations that can degrade the accuracy and speed of machines. Proper isolation from floor vibrations is important for ultra-precision manufacturing machines.
  • #1
pukb
94
1
what exactly are residual modes of vibrations?
I have come across this terminology in various fem solvers like ansys and pam crash.
 
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  • #3
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=MU...nepage&q=residual modes of vibrations&f=false

Cheers,
Bobbywhy
 

1. What are residual modes in vibrations?

Residual modes in vibrations refer to the small, persistent vibrations that exist in a structure after the main, or dominant, modes have been excited and then decayed. These residual modes can be caused by imperfections or small changes in the structure.

2. How do residual modes impact the behavior of a structure?

Residual modes can significantly affect the behavior of a structure, especially in dynamic situations. They can cause unexpected vibrations, alter the natural frequency of the structure, and potentially lead to structural fatigue and failure.

3. Can residual modes be eliminated?

Residual modes cannot be completely eliminated, but they can be minimized through careful design and engineering. By reducing structural imperfections and optimizing the design, the impact of residual modes can be reduced.

4. Do residual modes only occur in mechanical structures?

No, residual modes can occur in any type of structure that exhibits vibrations, such as buildings, bridges, or even electronic devices. Any structure that has natural frequencies can experience residual modes.

5. How are residual modes analyzed?

Residual modes can be analyzed through various methods, such as finite element analysis, modal analysis, and experimental modal analysis. These techniques allow engineers to identify the presence and characteristics of residual modes in a structure.

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