Compression Spring Fatigue
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 Calculator
 Fatigue is an issue in springs subjected to cyclic loading, where the force on the spring varies between a maximum and minimum value. For example, the springs in a car's shock absorption system would be subject to fatigue loading. Over time, excessive cyclic stresses from fatigue can cause the spring to fail. Use this calculator to predict if a known spring subjected to a known range of loading forces will be in danger of failing from fatigue. The calculator outputs a GO / NO-GO assessment after checking the maximum shear stresses in the spring against Soderberg's criterion.
Inputs
 Spring free length, Lfree: mm cm in ft Spring constant, k: N/m dyne/cm lbf/in Maximum force on spring, Fmax: N dyne gf kgf lbf Minimum force on spring, Fmin: N dyne gf kgf lbf Wire diameter, d: mm cm in Outer diameter of spring, Douter: mm cm in Material's limiting fatigue stress: kPa psi ksi Pa Mpa Material's yield stress: psi ksi Pa Mpa kPa Factor of safety: