Official Answer
Answer
Five failures recur, and two of them are geometric rather than material.
- Buckling — a helical compression spring whose free length exceeds about four times its mean diameter will bow sideways unless it is guided by a rod or a bore.
- Set and load relaxation — operating stress sitting too close to the material limit, or an alloy taken above its service temperature.
- Fatigue fracture — cyclic stress above the endurance limit, usually initiating at a surface defect.
- Space overrun — the spring turns out longer than the cavity once the rest of the design is frozen.
- Side load from unground ends — the end coil contacts on a point and tilts the load path.
A wave spring eliminates the first and the last by geometry: it is too short to buckle, and a shim end presents a flat bearing face. Set, fatigue and fit remain design decisions, controlled by operating stress and by material choice.
