vilalängden

Vilalängden is a Swedish term meaning “rest length” and is used in physics, engineering, and biomechanics to denote the length of an object or an elastic element when it is not deformed by external forces. It is the natural or baseline length of a component, often referred to as the rest length or natural length in English-language texts.

Etymology and usage: The word comes from vila, to rest, and längden, the length. In Swedish scientific literature, vilalängden serves as a reference length for modeling how elements such as springs, cables, muscles, and soft actuators behave under load. It provides a starting point for calculations of strain, force, and displacement.

Applications: In mechanical engineering, vilalängden corresponds to the natural length L0 of a spring or similar element. In biomechanics, it describes the resting length of a muscle-tendon unit or limb when not contracted. In robotics and soft robotics, vilalängden is used to characterize actuators and compliant mechanisms before excitation. The concept also appears in materials science and structural analysis as a baseline for measuring deformation.

Measurement and relationships: Vilalängden is defined under reference conditions where external forces are absent or balanced. When a load is applied, the current length deviates from vilalängden according to material properties and geometry. Temperature and environmental conditions can alter vilalängden through thermal expansion or contraction, so length measurements are typically specified with reference conditions.

See also: Rest length, natural length, equilibrium length, Hooke’s law, biomechanics.