Where repeated motions act upon the seal as in a circumferential,
axial or angular direction, a dynamic condition exists. Repeated
actions upon the seal, either regularly or periodic,this type
of seal; i.e. a piston ring seal or shock absorption mechanism.
Design Considerations are more complex than static seals, primarily
resulting from the changing stress levels. In addition to the
static seal considerations, the environment may require:
• Abrasion resistance becomes important and is affected
by the mating surface finishes.
• Recovery speed after compression to the original released
• Compression set, or the percentage of relaxation of the
dimensions versus the original uncompressed dimensions
• Temperature changes, thermal cycling.
• Distortion: squeeze, stretch - ability to recover.
• Physical strength: tensile strength, tear resistance.