Elastiisuus

Elastiisuus refers to the property of systems or materials to deform under external forces and to return to their original shape when the forces are removed. In materials science and engineering, it is contrasted with plasticity, where deformation remains after the load is removed. The term encompasses both the linear elastic regime, where stress and strain are proportional, and more complex elastic behaviors found in real materials.

In physics and engineering, elastic response is often described by moduli. The modulus of elasticity (Young's modulus) measures stiffness in tension or compression, the shear modulus describes resistance to shear, and the bulk modulus relates to volumetric changes. For isotropic, linearly elastic materials, Hooke’s law governs the proportional relation between stress and strain within the elastic limit. Beyond this limit, materials yield and deform plastically. Real materials may exhibit viscoelasticity, anisotropy, and frequency- or rate-dependent behavior, leading to hysteresis and energy dissipation during loading and unloading.

Elastiisuus also appears in other fields. In economics, elasticity quantifies how demand or supply responds to price or income changes (for example, price elasticity of demand). In biomechanics and medicine, tissue and vascular elasticity influence function and health, with techniques like elastography used to assess stiffness. Measurements are typically expressed in pascals for modulus or as dimensionless ratios for comparative elastic responsiveness. Elastiisuus thus spans a range of concepts describing how systems recover from deformation and how their reaction to force is characterized.