springs near plasticity

[40818]

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

 

[MikeHalloran]

Yes.

Mike Halloran
Pembroke Pines, FL, USA

 

[40818]

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!

 

[MikeHalloran]

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

 

[israelkk]

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.