Frictiontype

frictiontype is a term used in physics and engineering to denote the qualitative class of friction acting at a contact interface. It encompasses static friction, kinetic (sliding) friction, rolling resistance, and viscous friction. The frictiontype chosen influences the constitutive law used to model the frictional force in equations of motion.

Static friction occurs when surfaces tend to resist slipping. The friction force F adjusts up to a maximum value μs N, where N is the normal force. If the required force to initiate motion exceeds μs N, motion begins and the system transitions to kinetic friction.

Kinetic friction acts during relative sliding and is typically modeled as F = μk N, with μk usually smaller than μs. This relationship often shows weak dependence on contact area and can vary with velocity in more detailed models.

Rolling friction or rolling resistance arises when a body rolls rather than slides. The resistive force is much smaller than sliding friction and is commonly expressed as F = μr N, where μr represents energy losses due to deformation, micro-slip, and surface interactions of the contact.

Viscous friction occurs in fluids or lubricated contacts, with a force proportional to velocity. Linear viscous friction is F = c v, while other regimes may use F ∝ v^2 depending on the context and conditions.

Measurement and variability: coefficients and parameters for each frictiontype depend on materials, surface finish, lubrication, temperature, and contact pressure. In modeling and simulation, the frictiontype informs the appropriate friction law, though real-world behavior can deviate from idealized models in ways such as history dependence or stick-slip phenomena.