? about a compression spring.

[craigfperry]

Main Question or Discussion Point

would you weaken or shorten the life span of a compression spring by leaving it under a load for extended periods?

 

[pallidin]

Yes. The degree to which this does involves several factors which can be significantly different for different spring materials.
That's my opinion anyway.

 

[xxChrisxx]

Well it depends what the spring is make from really. A low creep material will never fail under the leading you describe. So the vast majority of springs will be fine under extended loading.

 

[Mapes]

would you weaken or shorten the life span of a compression spring by leaving it under a load for extended periods?

Corrosion can accelerate when a material is under stress, so yes, it's possible. Creep will also be significant at sufficiently large temperatures and times.

 

[craigfperry]

thanks for your answers,
does the spring reach a full set after one cycle?
does it continue to set thru repeated cycles?
do you think it helps to leave it under a load for a bit to reach it's full set?

 

[Mapes]

thanks for your answers,
does the spring reach a full set after one cycle?
does it continue to set thru repeated cycles?
do you think it helps to leave it under a load for a bit to reach it's full set?

The spring may plastically (i.e., permanently) deform upon the first cycle. After that, creep will occur to some degree as long as stress is applied. Additionally, crack growth (i.e., fatigue) may occur with cycling. It's impossible to estimate the severity of these two effects without more information (and may be impossible without doing experiments on the sample).

 

[FredGarvin]

You may experience stress relaxation in stead of creep, that is for sure.

 

[Mapes]

Fred's absolutely right, I should have been more precise. If you displace the end of the spring by a constant amount and observe the spring's decreasing resistance (force) over time, it's termed a stress relaxation test. If you apply a constant load and observe the continued compression (displacement) over time, it's termed a creep test. The phenomenon of time-dependent mechanical response of an undamaged specimen is generally referred to as creep. Does this sound right to you, Fred?

 

[FredGarvin]

Yupper. I was thinking more along the lines of how compression springs tend to not return to their original length after being compressed. Both modes can definitely be experienced though. Relaxation was the first thing that popped into my mind though.