Torsion Spring Life Cycle 1

[mkl8687]

Hi,

I am currently reverse engineering a program to build my own worksheet to calculate the cycle life and spring length required (or number of coils) for a garage door. The torque, number of winds, and inside diameter are calculated separately. The wire diameter chosen will be based on a life cycle of at least 25k and spring length of at least 8".

I was able to calculate the number of coils using:
k = (E*d^4)/(10.8*D*N)
T = k*(number of winds)

Bending Stress from torsion calculated using:
S = (Kb)(32*T)/(pi*d^3)

Now I am having trouble finding a formula to calculate the cycle life based on the stress. The program I am currently using has to be using one, but i can't seem to figure it out. Can anyone point me in the right direction?

Thanks.

 

[GregLocock]

It is material dependent. MILHBK 5 has a lot of handy high cycle fatigue charts. rule of thumb for steel is double the stress for 1/10 the life, or double the life with a 10% reduction in stress, or s*n^5=constant

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[israelkk]

As far as I know MIL-HDBK-5 doesn't deal with wire spring materials. There is no standard fatigue data available for spring wire materials because it depends on wire diameter too, in addition to the wire material and treatment.

You should better move the post to the "Spring engineering Forum" (forum693 - Professional forum and technical support for engineers for Spring engineering. Includes problem solving collaboration tools.)

https://sites.google.com/site/israelkk/

 

[EdStainless]

Some of the spring companies print very detailed design guides. Mine are old enough that they are all on paper, but I am sure that digital versions exist.
And yes, each table is for a specific material (music, OTMB, Rocket, ....) and there are size corrections.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[GregLocock]

If nothing else the Bosch Automotive Handbook gives charts for some spring materials, with size corrections.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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