Answer
Nested wave springs, which consist of multiple turns coiled in parallel, exhibit significant hysteresis due to inter-turn friction. When the spring is compressed, the layers slide against one another, generating frictional resistance that adds to the apparent spring load ($P_{loading} = P_{theoretical} + F_{friction}$). Upon decompression, the friction opposes the return force ($P_{unloading} = P_{theoretical} - F_{friction}$). The area within the hysteresis loop represents energy dissipation per cycle, calculated as $\oint P \, df$. This is critical in automotive damping systems. For material like 17-7PH, the coefficient of friction $\mu$ usually ranges from 0.1 to 0.2 depending on lubrication, and failure to account for this can lead to an overestimation of the return force in high-speed reciprocating valves.
