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.