The dynamic performance of gas springs is affected by a number of factors:
- Viscous friction (damping): This is a configurable characteristic, giving the ability of controlling the speed of compression or extension through an integrated damping element. The damping levels of a spring can be measured through dynamic testing and are usually illustrated through a gas spring characteristic (force – displacement) curve (figure 2). More information on damping is given under section 6.3
- Dry friction: this characteristic is associated with moving parts contacting static parts. Although gas spring parts are lubricated, seals tend to damage the lubricating film after a period of inactivity, leading to what is referred as “stiction” or “breakaway friction”. Stiction is often experienced as a momentary force “spike” when a gas spring is compressed after a period of inactivity and can be minimized by using special fluids, low friction seals and highly finished rods
- Progression or K-factor: As previously discussed, the K-factor of gas springs is highly configurable through rod to body combinations and the oil volume. Considering the characteristic curve of a gas spring, K-factor is the parameter defining its slope or gradient value.
Figure 2- Characteristic curve of a gas spring