On Nonlinear Thermoelasticity and Nonequilibrium Thermodynamics

Abstract

This chapter focuses on nonlinear thermoelasticity and nonequilibrium thermodynamics. The Caratheodory's principle states that not all states in a given neighborhood of a given state are adiabatically attainable. It is shown in the chapter that: (1) there exist an entropy function at nonequilibrium states; (2) the entropy function is extensive; (3) the entropy function depends parametrically on the internal variables, ξ; (4) at constant values of internal variables, this entropy function serves as a potential function in exactly the same manner as in the classical thermodynamics of equilibria; and (5) there exists an absolute temperature that depends on the chosen empirical temperature only. Caratheodory's principle does not indicate the types of the states that are in a given neighborhood of a given state that are indeed adiabatically unattainable. It simply asserts that there are such states. For dissipative materials, which generate heat at the expense of mechanical work, those situations should be excluded where changes in the internal variables result in negative dissipation.