Viscoelasticity

Viscoelasticity is material behavior that combines recoverable elastic deformation with time-dependent viscous flow. Its response depends on both the amount and duration of applied stress.

Creep (deformation): The gradual increase in deformation of a material under sustained stress. It shows how viscoelastic materials continue deforming while a load remains constant.
Hooke's law: A relation stating that elastic stress is proportional to strain within a material's linear range. It describes the recoverable spring-like part of viscoelastic behavior.
Polymer: A large molecule built from repeating molecular units linked into chains or networks. Many polymers owe their practical mechanical behavior to viscoelastic chain motion.
Elasticity: The ability of a material to deform under load and recover its original shape when the load is removed. Pure elasticity is the instantaneous, fully recoverable limit of viscoelastic response.
Stress relaxation: The decrease in stress over time when a material is held at fixed deformation. It exposes the time-dependent loss of stress in a constrained viscoelastic material.
Newtonian fluid: A fluid whose shear stress is proportional to its rate of deformation, with constant viscosity. It represents the purely viscous limit that viscoelastic materials depart from.
Rheology of blood: The study of blood flow and deformation, including its dependence on shear rate and cellular structure. Blood exhibits complex time-dependent behavior that matters in circulation and medical devices.
Viscosity: A measure of a fluid's resistance to flow under applied stress. Pure viscous flow dissipates energy and does not recover deformation like viscoelasticity can.
Dynamic mechanical analysis: A technique that measures material response to oscillating mechanical loads across temperatures or frequencies. It separates elastic energy storage from viscous energy loss in periodic tests.
Maxwell model: A viscoelastic model consisting of a spring and dashpot connected in series. It captures stress relaxation through a minimal combination of elastic and viscous elements.

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