Damping collision of low-mass actuator

[DAlbertson]

I have a 22 gram mass steel actuator hollow rod that slides on a rail. At the end-point of its travel, it collides with a solidly mounted steel plate. Just before the collision, the actuator rod is travelling at between 2.3 to 3.3 meters/sec, depending on other factors, so it posesses kinetic energy of 0.06 to 0.12 Joules.

I would like to select sheet material that could be installed as a dampener between the two colliding pieces of steel. I have no more than 1/8" of clearance to use for the sheet. The goals are:
A) Reduce sound produced by the collision, and
B) Reduce "rebound" of the actuator rod from the current elastic collision.

There are a spectacular array of sheet products available: the various durometer values of silicone rubber sheet alone are a bit daunting. If you add in the foams, open and closed cell, and then all the different elastic polymers, I could spend a great deal of money on test samples and many many hours in the lab!

I have two questions:

1) Is there an approximation that could take my data and produce a result like: "You need to look at materials between durometer 30 and 35 Shore D."

2) Has anyone experience with this small scale dampening problem that could recommend a product or technique?

Thank you very much!

David

 

[GregLocock]

1) Yes, a bit of diddling around with a spring mass damper equation should come up with a curve of damping properties vs stiffness that you need. Turning that back into material properties is not unfeasible.

2) Suck it and see is often the best way of establishing the boundaries of the problem.




Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[MikeHalloran]

These guys may have the material you need:

http://www.earsc.com/HOME/engineering/TechnicalWhitePapers/Vibration/index.asp?SID=61

They used to give out a great demo sample. It looked just like a SuperBall (remember those?), but no matter how hard you threw it at the floor, instead of bouncing madly around the room like a SuperBall would, it... rebounded a little and then just sat there.



Mike Halloran
Pembroke Pines, FL, USA

 

[DAlbertson]

Greg and Mike,

Thank you very much for your answers!

Greg, your comments about the spring mass damper equation producing results that could be interpreted in the frame of material properties and your suggestion to bracket the problem in the lab (a divide-and-conquor approach) are very well taken.

Mike, your pointer to E.A.R. Specialty Composites looks very good, also. Their website has a great deal of information, and they seem to have accumulated quite a few success stories. If possible, I will scrounge a "dead-blow super-ball" from them! I remember the Super-Ball from my misspent youth in the 1960's: you could buy them different sizes. A small size came 6 to a pack, a larger, 3cm diameter was 3 or 4 to a pack, and the large 6-7cm diameter came in a package of 1. The large one had enough mass to hurt like the devil if you caught it wrong. Great fun; thanks for reminding me!

Thank you again for the help.

David