Quote:
Originally Posted by shewejff
This is what's called viscoelastic creep. It's common for elastomeric materials. That reduction in force will start to happen fairly rapidly when the elastomer is placed under load, but the final force will eventually level out (sometimes after hours under load). I used to perform analyses of EPDM rubber, and our EPDM rubbers would eventually level out at about 70-75% of the original load.
If you remove the load, the elastomeric material is none the worse for wear, and will load again exactly how it did the first time. For example, if I pull the surgical tubing to 100 lb and hold it at that distance for a long time, the force will eventually decay to 75 lb (for example). If I release the force and pull it back to that same distance, it will take the original 100 lb of force to do so, not the 75 lb that it was just at for that distance.
I haven't performed any tests on the surgical tubing to look at its viscoelastic creep behavior, but this might be a good experiment for a team to do.
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That is very useful information, I stand corrected.
The prototyping we did with surgical tubing was very inconsistent, so we went to steel springs.
Is there a range you can design the tension to eliminate the viscoelastic creep?