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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. Source


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. Source


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. Source


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. Source


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. Source

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