Rocks and plastics are two examples of classes of materials where theKluitenberg–Verh´as
model of viscoelasticity has proved adequate for describing the observedmechanical
behaviour. This model cannot be interpreted as a generalized Maxwell model,and requires
in fact a novel rheological circuit element beyond the spring and the dashpot.Moreover,
its thermodynamical consistency leads to nontrivial inequality conditions on themodel
coefficients, ignoring which would lead to violation of the second law of thermodynamics
and would thus be a principal source of instability of numerical solutions. The presentpaper
explores the role of the rheological energy contribution embedded in the Kluitenberg–Verh´as
model, in a didactic and application-oriented way. The explicit meaning of theinvolved
irreversible thermodynamical additional state variable – internal degree of freedom–
is identified. Neither thermal expansion nor heat conduction is neglected, enhancing
theapplicability of the constructed framework.
