EJMA Expansion Bellow Spring Rates

[DeathRay009]

Hi all,

I am doing calculations on expansion bellow design to verify a vendor's expansion bellow, I have done almost everything else but, I can't find any way or formula to calculate the lateral, angular and torsional spring rates of expansion bellow. There is a formula written for the axial spring rate, but couldn't find formulas for other spring rates in EJMA.

Kindly help.

 

[LittleInch]

Why do you want to do this?

Do you not trust the vendor to do the tests for you?

for any sort of corrugated bellows those things you want to find sound horribly complex to me so its an FEA job.

Most bellows will just work axially and those that bend normally need some sort of guidance to stop them concentrating all the movement in one or two corrugations.

 

[btrueblood]

What LittleInch said. I mean, there are hand calculations described in Roark's for toroids and sigma joints, from which you might derive spring constants...but that assumes your bellows shells are near enough to semi-toroids to avoid inaccuracies. Seems like it would be far easier to stick the developed part in a spring tester and measure the rates.

 

[DeathRay009]

I trust the vendor, just wanted to learn to do the calculation myself.

 

[LittleInch]

I doubt they calculate, they just test and report the results.

Sometimes the calculation is just too hard to do.

 

[DeathRay009]

I see. Thanks.