Ivan Vegvary wrote in
:

Replaced the door hinge assemblies in SWMBO's oven (purchased oven
used). Made big difference. No longer need to push chair against
oven door.

Questions about springs. These are 8" long, 1/2 inch diameter, 1.25
inches elongation when in use.

My understanding from my 'strength of materials' classes 50+ years ago
is that metal does not deform until you reach the elastic limit. I
would guess that most springs in normal use NEVER reach that elastic
limit of metal. This would include automotive valve springs, screen
door springs etc.

So how, when and why does a spring actually weaken. I need an
education, all responses welcome.

As others have stated, it's probably due to the environment rather than
the design of the spring per se.

There's always lots of discussion in firearms circle about whether
magazine & hammer springs fatigue. IF they are properly designed &
manufactured, they shouldn't.

That said, I have an ar-15 based target rifle with a highly regarded (and
expensive) after-market trigger. The hammer spring will weaken over the
course of ~ 9 months if it is stored cocked. At that point, it will no
longer reliably fire military ammo, which tends to have harder primers.
If you compare it with a new spring, it definitely deformed a bit under
the constant tension. The manufacturer of the trigger makes their own
springs, and I suspect they do not fully understand the finer points of
spring fatigue.

Doug White