Liukukäyrä

Liukukäyrä is a Finnish term that literally translates to “sliding curve.” In Finnish-language technical writing, the phrase is used descriptively to denote a curve that characterizes how a quantity responds during sliding or gliding. The exact interpretation varies by field, and there is no single universal mathematical form attached to the term.

In tribology and contact mechanics, liukukäyrä typically refers to a curve that plots a response such as friction force or coefficient of friction against slip displacement, slip velocity, or time. The curve can illustrate phenomena like stick-slip behavior and energy dissipation at a sliding interface. In geophysics or earthquake science, it may describe the evolution of slip on a fault as a function of time, shear stress, or other driving variables. In mechanical design or control contexts, it can refer to the relationship between actuator displacement and the resulting force when sliding contact is involved, including aspects of damping or hysteresis.

Because liukukäyrä is not a formal mathematical object with a fixed definition, its shape can be linear, nonlinear, monotonic, or hysteretic, and it is often derived from experimental data or model assumptions rather than from a universal equation. Etymologically, the term combines liuku (sliding) and käyrä (curve), and is used in textbooks, research articles, and engineering handbooks to describe sliding behavior. When encountered, the specific meaning should be clarified within the given context. Internationally, the term is not standardized and may be translated or described differently in other languages.