Official Answer
Answer
Wave springs expand radially when compressed because the arc length of the waves remains constant while the wave height decreases. The expanded outside diameter $D_{ext}$ is calculated using the formula $D_{ext} = \sqrt{D^2 + (0.6 \cdot N^2 \cdot (h^2 - h_1^2))}$ where $D$ is the mean diameter, $N$ is the number of waves, $h$ is the free height per wave, and $h_1$ is the compressed height per wave. In tight-tolerance bores, such as those found in hydraulic actuators, if the clearance between the spring OD and the bore is insufficient, the spring will bind, causing a sudden, exponential increase in the spring rate and potential galling of the housing wall.
