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The material responds to the stress with a strain that increases until the material ultimately fails, if it is a viscoelastic liquid. If, on the other hand, it is a viscoelastic solid, it may or may not fail depending on the applied stress versus the material's ultimate resistance.
A Maxwell model is the most simple model viscoelastic material showing properties of a typical liquid. [1] It shows viscous flow on the long timescale, but additional elastic resistance to fast deformations. [2] It is named for James Clerk Maxwell who proposed the model in 1867. [3] [4] It is also known as a Maxwell fluid.
A Kelvin–Voigt material, also called a Voigt material, is the most simple model viscoelastic material showing typical rubbery properties. It is purely elastic on long timescales (slow deformation), but shows additional resistance to fast deformation.
Viscoelastic materials have the properties of both viscous and elastic materials and can be modeled by combining elements that represent these characteristics. One viscoelastic model, called the Maxwell model predicts behavior akin to a spring (elastic element) being in series with a dashpot (viscous element), while the Voigt model places these ...
When subjected to a step constant stress, viscoelastic materials experience a time-dependent increase in strain. This phenomenon is known as viscoelastic creep. At a time t 0, a viscoelastic material is loaded with a constant stress that is maintained for a sufficiently long time period. The material responds to the stress with a strain that ...
Memory foam derives its viscoelastic properties from several effects, due to the material's internal structure. The network effect is the force working to restore the foam's structure when it is deformed. This effect is generated by the deformed porous material pushing outwards to restore its structure against an applied pressure.
In purely viscous materials, there is a phase difference between stress and strain, where strain lags stress by a 90 degree (/ radian) phase lag. Viscoelastic materials exhibit behavior somewhere in between that of purely viscous and purely elastic materials, exhibiting some phase lag in strain. [3]
The material must be linear viscoelastic under the deformations of interest, i.e., the deformation must be expressed as a linear function of the stress by applying very small strains, e.g. 0.01%. To apply the WLF relationship, such a sample should be sought in the approximate temperature range [ T g , T g + 100 °C], where α -transitions are ...