Multiaxial fatigue analysis of stranded-wire helical springs

In this paper, finite element method is implemented to model stranded-wire helical springs under different loading conditions. Finite element results are coupled with multiaxial fatigue criteria such as Fatemi–Socie and Kandil–Brown–Miller together with a uniaxial fatigue criterion, Coffin–Manson, to predict fatigue life of the stranded-wire helical springs. It is shown that due to damping effects between wires, stranded-wire helical springs have longer fatigue life compared to their equivalent single-wire helical springs at a similar condition. It is also demonstrated that fatigue life is longer for loadings with higher initial displacement of spring head. As practical examples, fatigue life of stranded-wire helical springs with 9 and 15 wires are estimated and compared. It is shown that the spring with 15 wires gives longer fatigue life. It is also observed that Kandil–Brown–Miller and Fatemi–Socie criteria give the least and the highest fatigue life prediction, respectively.