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Test Standards for Compression Springs

S

silentrunning

#11
#11
On a compression spring the most linear range is just after the end coils have been compressed to complete contact and are parallel with the plattens, and then compressing it until the penultimate coils begin to close. Once the closing of the body coils begins the rate increases and the spring rate becomes less linear. The ideal way to specify a spring is to specify a load at minimum compression and a load at maximum compression. You then check the rate between the two compression lengths.
 
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T

trisp

#12
#12
doesnt the spring constant remain same for a spring? isnt it an inherent property of a spring(its stiffness)...

you mean to say its "K"(stifness) varies with compression?
 
S

silentrunning

#13
#13
Yes, even though K is refered to as the "spring constant", it isn't. As a spring is compressed towards solid height, the number of active coils is reduced. This in turn increases the K (rate). On some springs this increase is quite dramatic on others it is almost immeasurable. It depends on the spring design.
 
K

krayworth

#14
#14
What are the dimensions of the spring? Equipment designed to test springs must have the appropriate mechanical motion control and force measurement capability. Engineers who require a material testing system are faced with a wide array of possibilities. The decision around what system to choose should be based on the specific spring application, the cost, and the value to the spring manufacturer of their investment over time. I wouldn't compromise on a universal system but instead invest in a system configured to the specific needs.
 
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E

Englishman Abroad

Involved In Discussions
#15
#15
Hello all,

Compression springs have a force vector that is not neccessarily along the spring body centreline. The force vector will change based on the how the end coils touch the supports, and how the subsequent coils touches the support (and the coils touch themselves) as the spring compresses.

The norm is for the designer to specify a distance tolerance at a fixed load (or the opposite), and a spring rate (with a rate tolerance) between 2 fixed loads or distances (based on the working requirements of the spring in the system).

If you have an complicated spring system you may need to think about how to specify the force vector also (this is normally specified as a zone through which the vector must pass at either end of the spring).

However to say that a compression spring is linear from the free state to the solid (all coils touching each other) state is an over simplification that we all learnt in school.
 
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