An automotive clutch wave spring fails prematurely due to 'Settling.' What are the likely causes and how can this be diagnosed?

'Settling' or permanent set occurs when the spring is compressed to a stress level exceeding the material's elastic limit. In failure analysis, this is diagnosed by measuring the free height $H_f$ after use and comparing it to the original specification. If $H_f$ has decreased, the spring has plastically deformed. Likely causes include: 1) Operating temperatures exceeding the material's limit, 2) Design stress $\sigma$ exceeding the yield strength $S_y$ at solid height, or 3) Improper heat treatment (e.g., incomplete transformation of 17-7PH). To fix this, one should consider 'presetting' the spring during manufacture or switching to a higher-strength material like Inconel X-750.