# Relationship of Critical Damping Ratio in Elastomers

1. Jul 21, 2009

### minger

Hi guys, working a project where I need to guess the damping ratio (used for a numerical analysis) based on other properties of a material. We're looking to use an RTV as a vibration damper (we don't need a lot) but I can't seem to get any vibrational properties (called Honeywell, Dupond, GESilicones, etc). Hell, if anyone has damping ratios for 'any' RTV, it would help a lot.

If anyone even has a list of any different elastomers with damping ratios, it would help a lot.

edit: Directly related is a properties called $$\tan\delta$$ which I could use as well. Either work.

2. Jul 21, 2009

### timmay

Find it experimentally. Bear in mind that its loss tangent will be frequency dependent and can be measured in shear rheology, dynamic mechanical analysis or other method, or just drop a ball of the material from a variety of heights and measure the rebound heights for each successive rebound. Either use a log-decrement method to find critical damping ratio, or relate a coefficient of restitution to the critical damping ratio as shown in http://link.aip.org/link/?JAMCAV/67/831/1 [Broken]

Let me know if you can't retrieve it (I'm assuming wherever you're working has access to it if it's an academic project) and I can LaTeX the expressions.

Edit - if that sounds like a hassle, a decent Elastomers Handbook should have some values at least.

Last edited by a moderator: May 4, 2017
3. Jul 21, 2009

### minger

Experimenting is kind of out of the question. We really don't have the time to obtain a sample, and then send it out for testing (we don't have the equipment or the know-how to do it here).

As far as retrieving it, I'm in the industry, but with one foot still in school. As such I have access to some journals via Ohiolink, but not the Journal of Applied Mechanics. For future reference, would you mind writing out the expressions or even emailing me the article?

I'll check our library for a elastomer book. Thanks!