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Unlike purely elastic substances, a viscoelastic substance has an elastic component and a viscous component. The viscosity of a viscoelastic substance gives the substance a strain rate dependence on time. Purely elastic materials do not dissipate energy (heat) when a load is applied, then removed.
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.
A Maxwell material is the most simple model viscoelastic material showing properties of a typical liquid. It shows viscous flow on the long timescale, but additional elastic resistance to fast deformations. [1] It is named for James Clerk Maxwell who proposed the model in 1867. [2] [3] It is also known as a Maxwell fluid.
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 elements in parallel. Although the Maxwell model is good at predicting stress relaxation, it is fairly poor at predicting creep.
The storage and loss modulus in viscoelastic materials measure the stored energy, representing the elastic portion, and the energy dissipated as heat, representing the viscous portion. [3] The tensile storage and loss moduli are defined as follows: Storage: ′ =
Comparison of non-Newtonian, Newtonian, and viscoelastic properties Viscoelastic: Kelvin material, Maxwell material "Parallel" linear combination of elastic and viscous effects [11] Some lubricants, whipped cream, Silly Putty: Time-dependent viscosity: Rheopectic: Apparent viscosity increases with duration of stress Synovial fluid, printer ink ...
Temperature dependence of elastic modulus of a viscoelastic material under periodic excitation. The frequency is ω , G' is the elastic modulus, and T 0 < T 1 < T 2 . The time–temperature superposition principle is a concept in polymer physics and in the physics of glass-forming liquids .
where is the elastic stiffness tensor, is the closest point projection of the stress state on to the boundary of the region that bounds all possible elastic stress states. The quantity P σ {\displaystyle {\mathcal {P}}{\boldsymbol {\sigma }}} is typically found from the rate-independent solution to a plasticity problem.