Official Answer
Answer
Over-expanding occurs when the ring is stretched beyond its elastic limit during installation over a shaft. This results in permanent plastic deformation, meaning the ring will no longer 'snap' back to its original $D_{id}$. A ring that has been over-expanded will have a loose fit in the groove, which significantly reduces its thrust load capacity and increases the risk of dislodgement under vibration. It can be detected by measuring the 'cling' of the ring; if the ring can be rotated easily by hand or if there is visible light between the ring and the groove bottom, it has been over-expanded. In automated lines, laser micrometers are used to check the installed diameter to ensure it meets the design specification.
