In the literature there exist several thermomechanical models which are proposed from a heuristic point of view. A mathematical analysis should help to clarify the applicability of these models. In recent years several thermal or viscoelastic models have been proposed in which the relaxation time or the delay time plays an important role. Singleand dual-phaselag heat conduction models can be interpreted as formal expansions of delay equations. The delay equations are shown to be ill-posed, as… CONTINUE READING