Answer
Fatigue failure in a wave spring typically initiates at the crests (points of maximum bending stress) on the inner or outer diameter surfaces where surface defects or stress concentrations are present. Diagnosis involves examining the fracture surface under a SEM (Scanning Electron Microscope); the presence of 'striations' confirms cyclic loading failure. Visual indicators before total failure include 'polishing' or 'burnishing' at the crests, suggesting excessive movement or friction. If the spring is failing prematurely, engineers should check the Goodman diagram to see if the operating stress range $(\sigma_{max} - \sigma_{min})$ is too wide. Reducing the deflection per wave by adding more waves ($N_w$) is the most common remedy to improve fatigue life.
