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MP: Fachverband Theoretische und Mathematische Grundlagen der Physik

MP 2: Quantum Information and Thermodynamics

MP 2.4: Vortrag

Montag, 13. März 2017, 15:35–15:55, SFG 2010

Thermodynamics of anisotropic changes of state — •Falk Koenemann — Im Johannistal 19, 52064 Aachen

The mechanics of solids theory was founded long before the discovery of the First Law of thermodynamics. Elastic deformation is by nature a change of the energetic state in the sense of the First Law; however, the form of the First Law found used in continuum mechanics is not correct. For example, it is not possible to define the work done by shear forces. Thermodynamics is commonly presented in scalars (P,V,T), which implies isotropic boundary conditions. It has been transformed into vector field form (f,r,T), using the theory of potentials (Koenemann 2008). For isotropic boundary conditions the two forms deliver identical results; but the vector field form permits to explore reversible changes of state under anisotropic boundary conditions. The new approach correctly predicts volume-constancy under elastic pure shear conditions, and dilatancy under simple shear (Poynting effect). It is found that an anisotropically loaded volume of bonded matter is constitutionally expanded due to the work done by the shear forces. The effect amounts to a hitherto unknown thermodynamic state function. It has only one sign, it is always positive. It explains why solids can break under any confining pressure. At the transition from reversible to irreversible behavior a bifurcation is predicted that causes the system to relax into one of two possible geometric configurations with opposite handedness. This bifurcation is the cause of turbulence, triggered by the irreversible resolution of the elastic potential.

Koenemann (2008) Int. J. Modern Physics B 22, 2617