Surface roughness

Surface roughness is the variation in height and spacing of features across a surface. It describes texture at scales relevant to a measurement or application.

Surface topography: The three-dimensional shape and spatial arrangement of features on a surface. Roughness is one part of the broader description of a surface’s topography.
Stylus profilometry: A surface-measurement method that traces a probe tip across a material and records its vertical motion. It measures roughness by mechanically following a line across the surface.
Friction: The resistance to relative motion between surfaces in contact. Roughness changes real contact and can alter friction, though the effect depends on materials and conditions.
Surface finish: The texture and condition of a manufactured surface, often specified through roughness and related properties. Surface finish is a broader specification than roughness alone.
Waviness: Longer-spaced surface deviations that lie between roughness and overall form. Separating waviness from roughness prevents long-scale undulations from being counted as fine texture.
Atomic force microscopy: A scanning probe technique that maps surface forces using a sharp tip on a flexible cantilever. It can resolve fine surface texture beyond the reach of many contact profilometers.
Tribology: The study of friction, wear, and lubrication between interacting surfaces. Roughness is a central surface property in predicting contact and wear.
Surface texture: The overall geometric characteristics of a surface, including roughness, waviness, and lay. Roughness is one component of this broader description.
Surface profile: A cross-sectional trace of a surface’s height variation along a line. Many roughness parameters are calculated from a measured profile rather than a full surface map.
Optical profilometry: A family of noncontact methods that measures surface shape using reflected or interfered light. It maps roughness without dragging a probe across delicate or soft surfaces.

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