Elastisplastisiin

Elastisplastisiin is a Finnish term used in materials science and continuum mechanics to describe systems, materials, or models that exhibit elastoplastic behavior. It denotes the combination of elastic response, which is reversible, and plastic response, which results in permanent deformation when a yield threshold is exceeded.

In elastoplastic models, the stress–strain relationship shows an initial linear region (elastic) followed by yielding and plastic flow. Yield criteria such as von Mises or Tresca determine when plasticity begins, and hardening behavior—whether isotropic or kinematic—describes how the yield surface evolves with accumulated plastic strain. Some formulations include rate effects (viscoplasticity), making deformation dependent on the loading rate.

Elastisplastisiin constitutive relations are widely used in engineering and physics: metal forming, sheet stamping, crash simulations, structural analysis under plastic deformation, and geomechanics, where the yielding of rock or soil is important. Finite element analysis relies on these models to predict loads, residual stresses, distortions, and failure.

Distinction: purely elastic models ignore permanent deformation, while purely plastic models disregard the initial elastic response. In Finnish literature, elastoplastinen or elastisplastinen terminology is used to denote the elastoplastic regime or materials governed by elastoplastic constitutive laws.