  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.)
