Fatigue Life Square Wire Torsion Spring
Fatigue Life Square Wire Torsion Spring
(OP)
I'm using the Machinery's Handbook to design a torsion spring with square cross sectional wire. The Machinery's Handbook only gives fatigue stress curves for round wire springs. Am I correct in assuming that square wire springs have a higher allowable fatigue stress?
Please don't hate me for being stupid...
Please don't hate me for being stupid...





RE: Fatigue Life Square Wire Torsion Spring
The reason that the machinery handbook doesn't give this information is that square and rectangular wire use is very limited compared to round wire.
As far as I know the fatigue curves in machinery handbooks (27Th edition) are for compression spring and not for torsion springs.
RE: Fatigue Life Square Wire Torsion Spring
You say the tensile is lower with a square wire, despite the cross sectional area being larger. Does that have something to do with forming?
There are fatigue curves for torsion springs for 4 materials in the Machinery's Handbook
RE: Fatigue Life Square Wire Torsion Spring
You asked about the alowable stresses (not the calculated stresses) the alowable stresses are % fraction of the ultimate tensile strength of the wire which is detemined by the wire diameter/size and the material type.
What edition of Machiney handbook are you using and where (page number) did you find the fatigue curves for for torsion springs?
RE: Fatigue Life Square Wire Torsion Spring
You are confusing stress and strength. The bending stress on a torsion spring is lower for a square/rectangular section wire than it is for a round wire section for a given d and deflection. The strength of the material is lower for square/rectangular section wire than for round wire due to the manufacturing process prior to spring coiling.
RE: Fatigue Life Square Wire Torsion Spring
RE: Fatigue Life Square Wire Torsion Spring