Air spring

[dbday]

Can anyone help on this

If I have an air spring which is subjected to a heat input from outside, or cooling, what happens to the way the air spring behaves as a damper.

Would the spring rate change ?

Would the natural frequency of the system change ?

Thanks for any help.

 

[MiketheEngineer]

How much heat or cooling??

 

[floattuber]

My guess is that since the pressure goes up and down with temperature, then the spring rate will change. If the spring rate changes then your natural frequency would also change since Fn=(k/m)^1/2.

 

[dbday]

I understand that if the volume changes then the spring rate will change, I have seen a paper at this link

http://epubl.luth.se/1402-1617/2002/059/LTU-EX-02059-SE.pdf

That indicates that spring is dependent on volume.

What I would like to understand is whether or not spring rate depends temperature.

I guess the question would be - for a given actual volume of air and a given pressure, does the spring rate vary for different temperatures (ie different masses of air) ?

I understand that the natural frequency of the system will change if the air volume / spring rate changes.

 

[cbrn]

Hi,
I think you have the answer in your own question:
"the question would be - for a given actual volume of air and a given pressure...".
You say: "for a GIVEN volume AND a GIVEN pressure".
This is correct. you've got a gas law here. If you keep the same volume and you increase temperature, you won't in any way be able to keep the same pressure. If you want to keep the same pressure you won't be able to keep the same volume.

So the counter-question is: do you know for sure that the elastic constant and damping depends ONLY on volume? I personally strongly doubt about it, but I'd have to document myself better...

Regards

 

[dbday]

I am ok with the gas laws, what I would like to understand is the effect of temperature alone, if any, on spring rate.

To clarify, for example, if I have an air spring with a physical volume of 1 cubic foot, pressure at 150 psia and temperature of 60 F, how will the behaviour differ from a different air spring with the same physical volume set at the same pressure but operating at 150 F

 

[Tmoose]

I think the mass of the air within the spring is likely to be a tiny fraction of the system mass, even if the system is just the air spring assembly.
My recollection is that the spring rates shown in The curves of air spring catalogs I was last looking at in the last century were volume dependent.

therefore, same volume (thus pressure) = same spring rate, ~same mass, same spring rate, same resonant frequency