On the thermodynamic foundations of plasticity

Abstract

In this work the relation of plastic and rheological material models is analysed in the framework of non-equilibrium thermodynamics. After a short summary of the basic notions of classical elasticity and plasticity the traditional thermodynamic treatment of plasticity by Ziegler is introduced, where the plastic deformation is an internal variable, leading to the reduction of thermostatic stress. Then a simple thermodynamic treatment of static and dynamic friction follows, because the continuum generalization of these phenomena leads to viscosity and plasticity in our interpretation. Finally, plasticity is treated in the framework of non-equilibrium thermodynamics. The yield condition is the consequence of the dependence of the Onsagerian conductivity coefficients on the absolute value of the strain rate. Our treatment unifies rheology and plasticity in a common framework. --- Ebben az irasban a keplekeny es a reologiai anyagmodellek kapcsolatat targyaljuk a nemegyensulyi termodinamika alapjan. A klasszikus rugalmassagtan es keplekenysegtan alapfogalmainak rovid osszefoglalasa utan reszletesen vizsgaljuk a Ziegler-tol eredo termodinamikai keplekenysegelmeletet, amelyben a keplekeny deformacio a termosztatikai feszultseget csokkento belso valtozo. Ezutan a csuszasi es tapadasi surlodas egyszeru modelljet targyaljuk, mert esetunkben ezeknek a kontinuumokra torteno altalanositasa vezet a viszkozitashoz, illetve a keplekenyseghez. A keplekenysegi feltetelt az Onsager-fele vezetesi egyutthatoknak a belso valtozo sebessegenek abszolut erteketol valo fuggese hordozza. A keplekeny es a rugalmas deformacio idobeli valtozasat reologiai hatasokkal egyutt targyaljuk. (arXiv egyelore nem tud ekezeteket a kivonatban.)