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Irreversible Thermodynamics (irreversible + thermodynamics)

Distribution by Scientific Domains

Polymers and Materials Science	40%

Selected Abstracts

A critical plane fatigue model with coupled meso-plasticity and damage

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 1 2008
N. HUYEN
ABSTRACT The work proposed in this paper is a possible way of modelling some local observations at the surface of mild steel specimens submitted to uniaxial and multiaxial loads. It is clearly seen that local plasticity, controlled by local microstructural heterogeneities, plays a fundamental role in microcrack nucleation and damage orientation is closely related to the applied loading mode. The framework of irreversible thermodynamics with internal variables for time-independent, isothermal and small deformations has been used to build a critical plane damage model by assuming the existence of a link between mesoplasticity and mesodamage. Non-associated plasticity and damage rules allow the evolution of some plastic slip before any damage nucleation, as seen during the observations. A key feature of this proposal is the capacity to reflect nonlinear damage accumulation under variable amplitude loading. [source]

Numerical analysis of the single electrode heat effect in molten carbonate fuel cells: temperature analysis of the electrolyte plate by applying irreversible thermodynamics

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2004
Fumihiko Yoshiba
Abstract A temperature analysis model of a molten carbonate fuel cells (MCFC) stack is used to calculate the single electrode heat effects. The magnitude of heat which evolves from the cathode and absorbed at the anode is large, and in similar value to the electrical output of a MCFC. This suggests that the heat evolution of a single electrode causes a temperature difference between the electrodes. The temperature distribution in the electrolyte plate is evaluated to establish more accurate results concerning the temperature analysis model of the stack. The temperature distribution in the electrolyte plate is studied by applying irreversible thermodynamics. When the operating current density is less than 3000 A m,2 and the thermal conductivity of the electrolyte is more than 2 W m,1 K,1, the temperature difference between cathode and anode is estimated to be less than approximately 1 K. This result proves that the temperature difference between the electrodes can be supposed constant in constructing the temperature analysis model of the MCFC stack. This results also allows us to construct a two-dimensional heat production distribution in the cell plane and discrete heat production distribution in the stacking direction for the practical use of the temperature analysis model. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Ionic polymer-metal composites as multifunctional materials

POLYMER COMPOSITES, Issue 1 2003
Mohsen Shahinpoor
This paper presents a description and a set of experimental results on Ionic Polymer-Metal Composites (IPMC's) as dynamic sensors, transducers, and actuators. Strips of IPMC can exhibit large dynamic deformation if placed in a time-varying electric field of the order of 10's of volts/mm. Conversely, dynamic deformation and flexing of such ionic polymers produces dynamic electric fields that closely follow the form of the electric signal. The underlying principle of such a mechanoelectric effect in IPMC's can be explained by the linear irreversible thermodynamics in which ion and solvent transport are the fluxes and electric field and solvent pressure gradient are the forces. Important parameters include the material conductance and the solvent permeability. The dynamic sensing, transduction, and actuation responses of a strip of IPMC under an impact-type loading is also discussed. When a cantilever strip of IPMC is flipped, a damped oscillatory electric response is produced across a pair of electrodes placed at the cantilever of the strip, which is highly repeatable with a broad frequency range above 104 Hz. Such direct mechanoelectric responses of IMPC's are related to the endo-ionic mobility due to stresses imposed. Imposition of a finite solvent flux without allowing a current flux causes the material to create a certain conjugate electric field that can be dynamically monitored and measured. IPMC's are shown to be highly capacitive at low frequencies while they are highly resistive under high frequency excitations. IN a sending mode, IPMC strips can also sense chemical environments and humidity. These types of sensors/transducers/actuators conceivably can replace piezoresistive and piezoelectric sensors with just one sensor for broad ranges of frequencies. [source]

Weakly nonlocal irreversible thermodynamics

ANNALEN DER PHYSIK, Issue 3 2003
P. Ván
Abstract Weakly nonlocal thermodynamic theories are critically revisited. A relocalized, irreversible thermodynamic theory of nonlocal phenomena is given, based on a modified form of the entropy current and new kind of internal variables, the so called current multipliers. The treatment is restricted to deal with nonlocality connected to dynamic thermodynamic variables. Several classical equations are derived, including Guyer-Krumhansl, Ginzburg-Landau and Cahn-Hilliard type equations. [source]