contactpressure

Contact pressure is the normal pressure acting at the interface between two contacting bodies under load. It describes how the applied force is distributed over the real area of contact, which is typically smaller than the apparent contact area due to surface roughness and deformation. The average contact pressure is defined as p_avg = F / A_c, where F is the normal load and A_c is the real contact area. In many engineering problems A_c is determined by the elastic or plastic deformation of the contacting bodies, their material properties, and the roughness of the surfaces.

In elastic contact, Hertzian theory provides solutions for simple geometries such as a sphere on a flat or a cylinder on a flat; the contact pressure is nonuniform, typically peaking at the center of the contact zone and tapering toward the edge. For rough surfaces, the contact occurs at discrete asperities, and the pressure distribution can be described statistically (for example, by the Greenwood–Williamson model) or by numerical methods; local pressures at asperities can greatly exceed the mean pressure, influencing wear and fatigue.

Accurate knowledge of contact pressure is important in bearing design, gear contacts, seals, clutches, and adhesive joints, affecting wear, thermal performance, lubrication regimes, and component lifetime. It can be estimated from analytical models, finite element analysis, or experimental observation. Experimental methods include pressure-sensitive films and thin-film pressure sensors.

Notes: The term may also be used in tribology and biomechanics to describe pressures at joint surfaces, dental contacts, or prosthetic interfaces.