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springs near plasticity

springs near plasticity

springs near plasticity

(OP)
Hi,
Does anybody have any experience of springs (torsional) under constant loading which is very close to the material yield stress?  

RE: springs near plasticity

Yes.

Mike Halloran
Pembroke Pines, FL, USA

RE: springs near plasticity

(OP)
Mike great, (hopefully!)

I'm looking at a design which is keeping a torsional spring under load near yield (95%) for a sustained period of time. the spring is of a very high strength material (2000MPa UTS 0.9Y). i'm slightly concerned regarding creep relaxation and also stress corrosion occuring. Not my usual forte, hence the request for help!

RE: springs near plasticity

I'm not looking at the design, or a drawing of it, or any part of it, so I can't say much, except this:

Creep/relaxation is inevitable.
If that is not acceptable (design criteria not revealed so far),
do it over.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: springs near plasticity

40818

Constant loading can have two options:
1. Constant deflection - result is relaxation
2. Constant load - result is creep.

As MikeHalloran mentioned, at high stresses the relaxation/creep will be high and the longer the time under load the higher the relaxation/creep. For aerospace use it can be as long as 20 years under constant load. The resultant relaxation/creep can go as high as 20-30%.

However, to give a more specific info you should provide detailed information regarding the spring, i.e. material, dimensions, load, deflection, environment, etc.

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