Viskoelise

Viskoelise describes materials that exhibit both viscous and elastic responses to deformation. In viskoelastic materials, part of the deformation is stored elastically and recoverable, while part is dissipated as heat through flow. The behavior is time-dependent, meaning the response depends on how quickly the load is applied and how long it is maintained.

Common phenomena include creep, where deformation progresses under constant load; stress relaxation, where stress decreases under constant strain; and hysteresis in cyclic loading, where energy is lost per cycle. Temperature also affects viskoelasticity: higher temperatures or slower loading rates generally enhance viscous effects, while lower temperatures or faster loading favor elasticity. In the frequency domain, viscoelastic behavior is described by storage modulus G' and loss modulus G'', or by a complex modulus G* = G' + iG''.

Constitutive models range from simple to more complex. The Maxwell model uses a spring and dashpot in series to capture creep and relaxation but lacks instantaneous elasticity. The Kelvin-Voigt model uses a spring and dashpot in parallel, showing immediate elastic response with gradual creep. The Standard Linear Solid model combines elements to better fit real materials. More advanced or fractional models may be used for polymers, composites, foams, and biological tissues.

Applications span polymers, rubbers, gels, adhesives, damping materials, and biomedical tissues. Viscoelastic properties are typically measured by dynamic mechanical analysis, which yields G' and G'' over a range of frequencies and temperatures. Understanding viskoelise is essential for predicting performance, durability, and long-term behavior under varying conditions.