Structures subjected to repeated loading can fail during service, even if that loading does not produce stresses in excess of the material’s yield or ultimate strengths. The “if/when” question of why failures due to cyclic loading occur is dependent on the material characteristics and load history of the structure. PMI has experience with several methods for predicting fatigue life based on the strain history including typical high-cycle fatigue analyses and low-cycle fatigue analyses where the strain history includes a plastic component.