# "Variable" K elastic constant ??

by cala
Tags: constant, elastic, variable
 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?
 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. I’m not sure if practically a rubber spring could work but theoretically it is possible.
 Mentor P: 21,659 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.
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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