Muovaisuus

Muovaisuus, or plasticity, is the ability of a material to undergo permanent deformation under applied stress without breaking. It contrasts with elasticity, where deformation is recoverable after the load is removed. Plasticity arises from mechanisms such as dislocation motion in metals, chain mobility in polymers, and grain-boundary processes in ceramics and soils. Practically, higher muovaisuus enables shaping and forming, but can coincide with reduced strength after deformation due to work hardening or phase changes.

In geotechnical engineering, muovaisuus describes the plastic behavior of cohesive soils, especially clays. It is commonly assessed with Atterberg limits, including the plastic limit and liquid limit; the plasticity index (PI) equals LL minus PL. Soils with higher muovaisuus deform more plastically at given moisture contents, influencing foundation design, compaction, and slope stability. Temperature and loading rate also affect soil muovaisuus.

In materials science, plasticity is central to forming processes such as forging, rolling, and extrusion. Ductility, a related concept, reflects how much plastic deformation a material can endure before fracture. Tests like the tensile test quantify yield strength, elongation, and work hardening. Temperature, strain rate, and microstructure determine muovaisuus: some materials become more plastic when heated; others become brittle if cooled or alloyed in certain ways.

Origin and usage: The term muovaisuus comes from muovi 'plastic' plus the Finnish agent noun suffix -aisuus. It is used across physics, engineering, geotechnics, and materials science to describe deformability and formability of substances.