Linear Viscoelasticity---Response of Materials to Transient Experiments

2 LINEAR VISCOELASTICITY-RESPONSE OF MATERIALS TO TRANSIENT EXPERIMENTS 

In the limit of infinitesimal strains, the responses of viscoelastic materials to mechanical perturbations are well described by the theory of linear visco- 

If a material undergoes a sudden infinitesimal shear strain y, the shear stress required to keep that shear strain constant is given by 

In relaxation experiments carried out on solids, the shear stress continuously decreases with increasing time until a constant value Gg is obtained. Accordingly, the evolution of the relaxation modulus with time is described by the equation 

If the viscoelastic material is under the effect of an isotropic deformation (dilatation or compression), the diagonal components of both the stress and strain tensors differ from zero. In analogy with Eq. (4.92), the relationship between the excitation and the response is given by 

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Linear Viscoelasticity-Response of Materials to Transient Experiments 198... 

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