Fatigue life of wire torsion springs 1

[dlreed]

I am looking for info and methodology on calculating fatigue life of a Inconel X750 wire torsion spring. Does anyone have some suggestions or references.

 

[TVP]

There is a great deal of design data for Inconel X-750 available from Special Metals, the producer of this alloy:

http://www.specialmetals.com/products/publication/tech_bulletin_x750.pdf

In general, for spring temper material (SAE AMS5699) at temperatures less than 260 C, the maximum stress should be kept below 690 MPa. This equates to ~ 45-55% of the ultimate tensile strength, depending on wire diameter. Some spring manufacturers use a more conservative 40% of UTS for the design stress.

Regarding methodology for analyzing fatigue life, I suggest investigating the Goodman method or a comparable fatigue life estimation method. The following link is an excellent paper that discusses the Goodman diagram:

http://www.read-eurowire.com/ist.htm

Also, there are numerous handbooks and guidelines available, such as these:

Compression, Extension, Torsion and Garter Springs

http://www.smihq.org/public/publications/encyclopedia.html#Anchor-Compressio-56695

Mechanical Springs by A.M.Wahl

http://www.smihq.org/public/pstorep.html#wahl

Advanced Spring Design Software Version 6 (ASD6)

http://www.smihq.org/public/pstores.html#asds6

Spring Design Manual

http://www.sae.org/servlets/productDetail?