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In order to analyze Kelvin/Voigt behavior during a load cycle, the following differential equation is used (again with “v” for the viscous portion and “e” for the elastic one):

Assumption 1: The total shear stress applied will be distributed on the two model components.

τ = τv + τe

Assumption 2: Deformation of both components occurs to the same extent, and this applies also to the shear rate.

γ = γv = γe or γ ̇ = γ ̇ v = γ ̇ e

with γ ̇ = dγ/dt (as explained in Chapter 4.2.1)

The viscosity law applies to the viscous element: τv = η ⋅ γ ̇ v

The elasticity law applies to the elastic element: τe = G ⋅ γe

The sum of the shear stresses results in the differential equation according to Kelvin/Voigt:

Equation 5.2

τ = τv + τe = η ⋅ γ ̇ v + G ⋅ γe = η ⋅ γ ̇ + G ⋅ γ

The solution and use of this differential equation are described in Chapters 6.3.3 a/b and 6.3.4.3 (creep tests).

End of the Cleverly section