Fracture on torsion spring
Fracture on torsion spring
(OP)
Hi
I have got problem that there was breakage on torsion spring. It occurred on end, but in previous REL test it occurred on squeezed part.
See attachment. I am a little confused about these two failures.
I want to improve design to distribute stress on end of spring. And considering to add two POM tube on end.
Can anyone provide some suggestions?
Thanks in advance!
I have got problem that there was breakage on torsion spring. It occurred on end, but in previous REL test it occurred on squeezed part.
See attachment. I am a little confused about these two failures.
I want to improve design to distribute stress on end of spring. And considering to add two POM tube on end.
Can anyone provide some suggestions?
Thanks in advance!





RE: Fracture on torsion spring
Can you provide exact detail of the spring? A blueprint contains dimensions and loading torque and deflection will be very helpful to see is this failure is an accident or could be foreseen. A detailed dimensions where the tangs are loaded with reference to the spring main body
Is this failure happened at first loading or after repeated loadings?
It is difficult from the pictures to decide if this is a fatigue failure or not.
https://sites.google.com/site/israelkk/
RE: Fracture on torsion spring
https://www.google.com/search?q=garage+door+spring...
Very rarely do garage door springs fail at the connection, more commonly they fail near the center (due to sag?)
RE: Fracture on torsion spring
That said this is a poor design.
You would be better off with a hook on the end that went over a pin.
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P.E. Metallurgy, Plymouth Tube
RE: Fracture on torsion spring
IsraelKK, Btrueblood and RB1957 Hit nail on head.
1. A few potential Issues that MAY/MAY NOT factor-in
Ensure spring material is high quality.
Spring surface finish is important: should be very fine [~polished and defect free] before/after forming.
Deep shot-peening after SR and before plating may be useful for fatigue life
Springs should be stress-relieved after coiling/forming. SR is based on spec requirements, alloy/temper, etc.
Cadmium, Zinc, zinc-Nickel, etc plating [and sometimes CRES passivation] requires hydrogen embrittlement relief.
2. May find following info useful in-the-long-run
SAE HS-795 Manual on Design and Application of Helical and Spiral Springs
SAE J1122 Helical Springs Specification Checklists
Spring Manufacturer's Institute
Handbook of Spring Design
Encyclopedia of Spring Design
http://www.smihq.org/public/pstorep.html#book2
Regards, Wil Taylor
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RE: Fracture on torsion spring