 Linear viscoelasticity

stress is a linear causal functional of deformation history: in simple shear, $\sigma (t)={\int }_{-\infty }^{t}G(t-t^{\prime })\dot{\gamma }(t^{\prime })d{t}^{\prime }$. Superposition holds and complex viscoelastic modulus is amplitude-independent within the small-deformation regime.