slipportion

Slipportion is a dimensionless parameter used in tribology and contact mechanics to quantify the fraction of relative motion at a contact interface that is accommodated by slip along the interface, as opposed to sticking or elastic deformation elsewhere. It provides a concise measure of how much sliding occurs between contacting surfaces under a given load and speed.

Definition and calculation: Slipportion is commonly defined as the ratio of slip displacement to the total relative displacement during a loading cycle. In practice, delta_slip represents the slip along the interface, and delta_total represents the overall tangential movement between bodies. Some studies estimate slipportion from the friction force–displacement response by separating periods of sticking from sliding or by using imaging techniques to track interfacial movement.

Measurement and interpretation: Methods for determining slipportion include digital image correlation, high-speed imaging of the contact zone, and analysis of force traces to identify sliding versus sticking events. A low slipportion indicates that most motion is accommodated by sticking or elastic deformation elsewhere, while a high slipportion signifies dominant interfacial sliding.

Applications: Slipportion is used in the design and evaluation of bearings, seals, and microelectromechanical systems, as well as in fundamental studies of friction, wear, and lubrication regimes. It helps characterize contact behavior under varying load, speed, temperature, and lubrication conditions, aiding in predictive modeling of service performance.

See also: friction, stick-slip, tribology, contact mechanics.