"Variable" K elastic constant ??


by cala
Tags: constant, elastic, variable
cala
cala is offline
#1
Sep24-03, 04:27 PM
P: 176
Difficult to put the topics on the right place...

Is there any spring (or any physical method) that could have different K elastic constant on one sense of movement than on the other?

For example K = 100 (or another value) when compressing and K = 75 (or another value) when decompressing?
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wolfgang
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#2
Sep28-03, 10:42 AM
P: 17
I think that the simpler spring with variable K elastic constant could be made from rubber.
When you stretch this rubber spring the elastic constant would take a value K (the value of K depends on who hard is the rubber).
On the other hand during the compression of the spring the value of the elastic constant is K=0.
Im not sure if practically a rubber spring could work but theoretically it is possible.
russ_watters
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#3
Sep29-03, 01:02 AM
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Sorta - if you throw in viscosity or plastic deformation or something like that. If you're hoping to use that to overcome the first law of thermodynamics though, no.

rdt2
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#4
Oct2-03, 03:53 PM
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P: 124

"Variable" K elastic constant ??


Almost any polymer (and some other materials) will have a different (and variable) K in tension from that in compression (except for small strains). Under tension, the polymer chains straighten out and stiffen - under compression they tend to buckle and are less stiff. The effect is called 'tension stiffening'.

Reinforced concrete does something similar - as do most fabrics (wool, cotton, etc)


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