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Cimmelli V.A.,University of Basilicata | Jou D.,Autonomous University of Barcelona | Jou D.,Institute dEstudis Catalans | Ruggeri T.,University of Bologna | And 3 more authors.
Entropy | Year: 2014

We present the state of the art on the modern mathematical methods of exploiting the entropy principle in thermomechanics of continuous media. A survey of recent results and conceptual discussions of this topic in some well-known non-equilibrium theories (Classical irreversible thermodynamics CIT, Rational thermodynamics RT, Thermodynamics of irreversible processes TIP, Extended irreversible thermodynamics EIT, Rational Extended thermodynamics RET) is also summarized.© 2014 by the authors.


Kovacs R.,Budapest University of Technology and Economics | Kovacs R.,Montavid Thermodynamic Research Group | Van P.,Institute for Particle and Nuclear Physics
International Journal of Heat and Mass Transfer | Year: 2015

A novel equation of heat conduction is derived with the help of a generalized entropy current and internal variables. The obtained system of constitutive relations is compatible with the momentum series expansion of the kinetic theory. The well known Fourier, Maxwell-Cattaneo-Vernotte, Guyer-Krumhansl, Jeffreys-type, and Cahn-Hilliard type equations are derived as special cases. Some remarkable properties of solutions of the general equation are demonstrated with heat pulse initial and boundary conditions. A simple numerical method is developed and its stability is proved. Apparent faster than Fourier pulse propagation is calculated in the over-diffusion regime. © 2014 Elsevier Ltd.


Van P.,Wigner RCP | Van P.,Budapest University of Technology and Economics | Van P.,Montavid Thermodynamic Research Group | Berezovski A.,Tallinn University of Technology | Papenfuss C.,TU Berlin
Continuum Mechanics and Thermodynamics | Year: 2014

Governing equations of dissipative generalized solid mechanics are derived by thermodynamic methods in the Piola-Kirchhoff framework using the Liu procedure. The isotropic small-strain case is investigated in more detail. The connection to the Ginzburg-Landau type evolution, dual internal variables, and a thermodynamic generalization of the standard linear solid model of rheology is demonstrated. Specific examples are chosen to emphasize experimental confirmations and predictions beyond less general approaches. © 2013 Springer-Verlag Berlin Heidelberg.


Berezovski A.,Tallinn University of Technology | Van P.,Institute of Particle and Nuclear Physics | Van P.,Montavid Thermodynamic Research Group
Continuum Mechanics and Thermodynamics | Year: 2015

The description of microinertia in micromorphic continua is discussed from the point of view of non-equilibrium thermodynamics. In the framework of dual internal variables, the microinertia stems from a thermodynamic equation of state related to the internal variable, which has the properties similar to mechanical momentum. © 2015 Springer-Verlag Berlin Heidelberg


Van P.,Institute for Particle and Nuclear Physics | Van P.,Budapest University of Technology and Economics | Van P.,Montavid Thermodynamic Research Group | Kovacs R.,Institute for Particle and Nuclear Physics | And 4 more authors.
Proceedings of the Estonian Academy of Sciences | Year: 2015

Non-equilibrium thermodynamics with internal variables introduces a natural hierarchical arrangement of evolution equations. Three examples are shown: a hierarchy of linear constitutive equations in thermodynamic rheology with a single internal variable, a hierarchy of wave equations in the theory of generalized continua with dual internal variables, and a hierarchical arrangement of the Fourier equation in the theory of heat conduction with current multipliers. © 2015, Estonian Academy Publishers. All rights reserved.


Van P.,Wigner RCP | Van P.,Budapest University of Technology and Economics | Van P.,Montavid Thermodynamic Research Group | Fulop T.,Wigner RCP | And 2 more authors.
Annalen der Physik | Year: 2012

A linear irreversible thermodynamic framework of heat conduction in rigid conductors is introduced. The deviation from local equilibrium is characterized by a single internal variable and a current multiplier. A general constitutive evolution equation of the current density of the internal energy is derived by introducing a linear relationship between the thermodynamic forces and fluxes. The well-known Fourier, Maxwell-Cattaneo-Vernotte, Guyer-Krumhansl, Jeffreys-type, and Green-Naghdi-type equations of heat conduction are obtained as special cases. The universal character of the approach is demonstrated by two examples. Solutions illustrating the properties of the equation with jump boundary conditions are given. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Fulop T.,Montavid Thermodynamic Research Group | Beda Gy.,Montavid Thermodynamic Research Group | Beda Gy.,Budapest University of Technology and Economics
Rock Engineering in Difficult Ground Conditions - Soft Rocks and Karst - Proceedings of the Regional Symposium of the International Society for Rock Mechanics, EUROCK 2009 | Year: 2010

We calculate the rheology-governed time dependence of stress, strain and displacement around an opened long cylindrical tunnel, for arbitrary linear rheological models with finite order time derivatives. © 2010 Taylor & Francis Group, London.


Asszonyi C.,Montavid Thermodynamic Research Group | Csatar A.,Montavid Thermodynamic Research Group | Csatar A.,Hungarian Institute of Agricultural Engineering | Fulop T.,Montavid Thermodynamic Research Group | Fulop T.,Budapest University of Technology and Economics
Periodica Polytechnica: Civil Engineering | Year: 2016

Rocks are important examples for solid materials where, in various engineering situations, elastic, thermal expansion, rheological /viscoelastic and plastic phenomena each may play a remarkable role. Nonequilibrium continuum thermodynamics provides a consistent way to describe all these aspects in a unified framework. This we present here in a formulation where the kinematic quantities allow arbitrary nonzero initial (e.g., in situ) stresses and such initial configurations which – as a consequence of thermal or remanent stresses – do not satisfy the kinematic compatibility condition. The various characteristic effects accounted by the obtained theory are illustrated via experimental results where loaded solid samples undergo elastic, thermal expansion and plastic deformation and exhibit rheological behaviour. From the experimental data, the rheological coefficients are determined, and the measured temperature changes are also explained by the theory. Dedicated to the memory of Zoltán Szarka (1927-2015). © 2016, Technical University of Budapest. All rights reserved.


Fulop T.,WIGNER RCP | Fulop T.,Budapest University of Technology and Economics | Fulop T.,Montavid Thermodynamic Research Group | Van P.,WIGNER RCP | And 2 more authors.
Mathematical Methods in the Applied Sciences | Year: 2012

Kinematic quantities for finite elastic and plastic deformations are defined via an approach that does not rely on auxiliary elements, such as reference frame and reference configuration, and that gives account of the inertial-noninertial aspects explicitly. These features are achieved by working on Galilean spacetime directly. The quantity expressing elastic deformations is introduced according to its expected role: to measure how different the current metric is from the relaxed/stressless metric. Further, the plastic kinematic quantity is the change rate of the stressless metric. The properties of both are analyzed, and their relationship with frequently used elastic and plastic kinematic quantities is discussed. One important result is that no objective elastic or plastic quantities can be defined from the deformation gradient.


Safranyik F.,Szent Istvan University | Csatar A.,Montavid Thermodynamic Research Group | Varga A.,Szent Istvan University
Progress in Agricultural Engineering Sciences | Year: 2015

The phenomenon of friction reduces efficiency of almost all machines in practice. In order to reduce the deficits, we have to understand this phenomenon and have to take it into consideration during design in all cases. Nevertheless, in certain cases describing of a friction process is very difficult, because it depends on a lot of parameters. In case of polymers, granular materials or in geology, the rate and state dependent friction have great importance. In this paper, velocity and time dependent friction is examined with the help of a direct shear apparatus, which was developed in our earlier work. © 2015 Akadémiai Kiadó, Budapest.

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