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Alain Dequidt - One of the best experts on this subject based on the ideXlab platform.
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lehmann rotation of twisted bipolar cholesteric droplets role of leslie akopyan and zel dovich Thermomechanical Coupling terms of nematodynamics
Liquid Crystals, 2017Co-Authors: Patrick Oswald, Guilhem Poy, Alain DequidtAbstract:ABSTRACTWe show that the Leslie and texture-dependent Akopyan and Zel’dovich Thermomechanical Coupling terms of nematodynamics cannot explain the thermal Lehmann rotation of the twisted bipolar droplets observed in the coexistence region between a cholesteric phase and the isotropic liquid. On the other hand, these terms are pertinent below the transition temperature and can be determined by measuring the director rotation velocity in two different molecular configurations. In addition, a complete characterisation of the liquid crystal used (CCN-37) is also given.
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Lehmann rotation of twisted bipolar cholesteric droplets: role of Leslie, Akopyan and Zel’dovich Thermomechanical Coupling terms of nematodynamics
Liquid Crystals, 2016Co-Authors: Patrick Oswald, Guilhem Poy, Alain DequidtAbstract:ABSTRACTWe show that the Leslie and texture-dependent Akopyan and Zel’dovich Thermomechanical Coupling terms of nematodynamics cannot explain the thermal Lehmann rotation of the twisted bipolar droplets observed in the coexistence region between a cholesteric phase and the isotropic liquid. On the other hand, these terms are pertinent below the transition temperature and can be determined by measuring the director rotation velocity in two different molecular configurations. In addition, a complete characterisation of the liquid crystal used (CCN-37) is also given.
Jacob Aboudi - One of the best experts on this subject based on the ideXlab platform.
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Fully Coupled Thermomicromechanical Analysis of Multiphase Composites
Micromechanics of Composite Materials, 2013Co-Authors: Jacob Aboudi, Steven M. Arnold, Brett A. BednarcykAbstract:This chapter addresses micromechanics modeling of composites that includes full, two-way, Thermomechanical Coupling. In the methods discussed in all previous chapters, although a temperature change would affect the mechanical response of a material, the temperature field was not affected by the mechanical fields. Full Thermomechanical Coupling adds this effect, such that stresses and strains can now induce a local temperature change. The fully coupled Thermomechanical High-Fidelity Generalized Method of Cells (HFGMC) micromechanics theory is presented along with a number of example problems that illustrate the effects of full Thermomechanical Coupling in composites in the presence of elastic, inelastic, and damaging material behavior.
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the effect of anisotropic damage evolution on the behavior of ductile and brittle matrix composites
International Journal of Solids and Structures, 2011Co-Authors: Jacob AboudiAbstract:Abstract Anisotropic damage evolution laws for ductile and brittle materials have been coupled to a micromechanical model for the prediction of the behavior of composite materials. As a result, it is possible to investigate the effect of anisotropic progressive damage on the macroscopic (global) response and the local spatial field distributions of ductile and brittle matrix composites. Two types of thermoinelastic micromechanics analyses have been employed. In the first one, a one-way Thermomechanical Coupling in the constituents is considered according to which the thermal field affects the mechanical deformations. In the second one, a full Thermomechanical Coupling exists such that there is a mutual interaction between the mechanical and thermal fields via the energy equations of the constituents. Results are presented that illustrate the effect of anisotropic progressive damage in the ductile and brittle matrix phases on the composite’s behavior by comparisons with the corresponding isotropic damage law and/or by tracking the components of the damage tensor.
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Thermomechanically Coupled Micromechanical Analysis of Shape Memory Alloy Composites Undergoing Transformation Induced Plasticity
Journal of Intelligent Material Systems and Structures, 2008Co-Authors: Yuval Freed, Jacob AboudiAbstract:In this investigation, fully Thermomechanically coupled constitutive and energy equations for shape memory alloys (SMAs) that include the effect of transformation induced plasticity are presented. This is followed by a micromechanical analysis for the establishment of the fully coupled Thermomechanical constitutive equations that model the overall behavior of SMA composites undergoing transformation induced plasticity. The effects of the Thermomechanical Coupling and permanent inelasticity which arise by the phase transformation were examined. It was found that the response of the monolithic SMA depends upon the Thermomechanical Coupling. The permanent inelasticity and the resulting induced temperature become significant especially in the case of several repeating cycles. In addition, the induced average temperature caused by the Thermomechanical Coupling as well as the stress—strain behavior of SMA/epoxy and SMA/aluminum composite materials were determined. A significant Thermomechanical Coupling, which ...
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Thermomechanically coupled micromechanical analysis of multiphase composites
Journal of Engineering Mathematics, 2007Co-Authors: Jacob AboudiAbstract:One- and two-way Thermomechanically coupled micromechanical analyses of multiphase composites are presented. In the first type of Thermomechanical Coupling, a constant temperature that affects the mechanical field only is prescribed at any point of the composite’s constituents. In the two-way Thermomechanical Coupling, on the other hand, a mutual interaction exists between the mechanical and temperature fields. It is shown that the macroscopic coupled energy equation that is established from a homogenization procedure cannot provide reliable information about the induced temperature that is caused by an applied far-field mechanical loading of the composite. The details of the induced temperature-field variations can be obtained, on the other hand, by the derived two-way Thermomechanically coupled micromechanical analysis, thus enabling the identification of critical hot spots in the mechanically loaded composite. Results exhibit, in particular, the induced temperature field in metal-matrix and polymer-matrix composites.
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Thermomechanical Coupling effects on the dynamic inelastic response and buckling of metal matrix composite infinitely wide plates
Composite Structures, 1996Co-Authors: R. Gilat, Jacob AboudiAbstract:A micromechanical approach is combined with a structural analysis in order to investigate the coupled Thermomechanical dynamic behavior of infinitely wide plates composed of an elastic-viscoplastic matrix reinforced by elastic fibers. The micromechanical analysis relies on the thermoelastic and inelastic properties of the constituents of the composite, and provides instantaneous effective thermoviscoplastic relations for the metal matrix composite at any point of the structure. The structural analysis consists of mechanical and energy equations both of which involve thermal and mechanical Coupling terms. These coupled governing equations are based on classical and higher order plate theories, and are solved by employing a spatial finite difference and temporal Runge-Kutta integrations. Results are given that illustrate the effects of the Thermomechanical Coupling and the viscoplastic energy dissipation on the dynamic response and buckling of metal matrix composite plates.
Patrick Oswald - One of the best experts on this subject based on the ideXlab platform.
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lehmann rotation of twisted bipolar cholesteric droplets role of leslie akopyan and zel dovich Thermomechanical Coupling terms of nematodynamics
Liquid Crystals, 2017Co-Authors: Patrick Oswald, Guilhem Poy, Alain DequidtAbstract:ABSTRACTWe show that the Leslie and texture-dependent Akopyan and Zel’dovich Thermomechanical Coupling terms of nematodynamics cannot explain the thermal Lehmann rotation of the twisted bipolar droplets observed in the coexistence region between a cholesteric phase and the isotropic liquid. On the other hand, these terms are pertinent below the transition temperature and can be determined by measuring the director rotation velocity in two different molecular configurations. In addition, a complete characterisation of the liquid crystal used (CCN-37) is also given.
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Lehmann rotation of twisted bipolar cholesteric droplets: role of Leslie, Akopyan and Zel’dovich Thermomechanical Coupling terms of nematodynamics
Liquid Crystals, 2016Co-Authors: Patrick Oswald, Guilhem Poy, Alain DequidtAbstract:ABSTRACTWe show that the Leslie and texture-dependent Akopyan and Zel’dovich Thermomechanical Coupling terms of nematodynamics cannot explain the thermal Lehmann rotation of the twisted bipolar droplets observed in the coexistence region between a cholesteric phase and the isotropic liquid. On the other hand, these terms are pertinent below the transition temperature and can be determined by measuring the director rotation velocity in two different molecular configurations. In addition, a complete characterisation of the liquid crystal used (CCN-37) is also given.
Guilhem Poy - One of the best experts on this subject based on the ideXlab platform.
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lehmann rotation of twisted bipolar cholesteric droplets role of leslie akopyan and zel dovich Thermomechanical Coupling terms of nematodynamics
Liquid Crystals, 2017Co-Authors: Patrick Oswald, Guilhem Poy, Alain DequidtAbstract:ABSTRACTWe show that the Leslie and texture-dependent Akopyan and Zel’dovich Thermomechanical Coupling terms of nematodynamics cannot explain the thermal Lehmann rotation of the twisted bipolar droplets observed in the coexistence region between a cholesteric phase and the isotropic liquid. On the other hand, these terms are pertinent below the transition temperature and can be determined by measuring the director rotation velocity in two different molecular configurations. In addition, a complete characterisation of the liquid crystal used (CCN-37) is also given.
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Lehmann rotation of twisted bipolar cholesteric droplets: role of Leslie, Akopyan and Zel’dovich Thermomechanical Coupling terms of nematodynamics
Liquid Crystals, 2016Co-Authors: Patrick Oswald, Guilhem Poy, Alain DequidtAbstract:ABSTRACTWe show that the Leslie and texture-dependent Akopyan and Zel’dovich Thermomechanical Coupling terms of nematodynamics cannot explain the thermal Lehmann rotation of the twisted bipolar droplets observed in the coexistence region between a cholesteric phase and the isotropic liquid. On the other hand, these terms are pertinent below the transition temperature and can be determined by measuring the director rotation velocity in two different molecular configurations. In addition, a complete characterisation of the liquid crystal used (CCN-37) is also given.
Wael Zaki - One of the best experts on this subject based on the ideXlab platform.
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a constitutive model for shape memory alloys accounting for Thermomechanical Coupling
International Journal of Plasticity, 2011Co-Authors: Claire Morin, Ziad Moumni, Wael ZakiAbstract:This paper presents a generalized Zaki–Moumni (ZM) model for shape memory alloys (SMAs) [cf. Zaki, W., Moumni, Z., 2007a. A three-dimensional model of the Thermomechanical behavior of shape memory alloys. J. Mech. Phys. Solids 55, 2455–2490 accounting for Thermomechanical Coupling. To this end, the expression of the Helmholtz free energy is modified in order to derive the heat equation in accordance with the principles of thermodynamics. An algorithm is proposed to implement the coupled ZM model into a finite element code, which is then used to solve a Thermomechanical boundary value problem involving a superelastic SMA structure. The model is validated against experimental data available in the literature. Strain rate dependence of the mechanical pseudoelastic response is taken into account with good qualitative as well as quantitative accuracy in the case of moderate strain rates and for mechanical results in the case of high strain rates. However, only qualitative agreement is achieved for thermal results at high strain rates. It is shown that this discrepancy is mainly due to localization effects which are note taken into account in our model. Analyzing the influence of the heat sources on the material response shows that the mechanical hysteresis is mainly due to intrinsic dissipation, whereas the thermal response is governed by latent heat. In addition, the variation of the area of the hysteresis loop with respect to the strain rate is discussed. It is found that this variation is not monotonic and reaches a maximum value for a certain value of strain rate.
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Thermomechanical Coupling in shape memory alloys under cyclic loadings: Experimental analysis and constitutive modeling
International Journal of Plasticity, 2011Co-Authors: Claire Morin, Ziad Moumni, Wael ZakiAbstract:Abstract In this paper, we examine the influence of Thermomechanical Coupling on the behavior of superelastic shape memory alloys subjected to cyclic loading at different loading rates. Special focus is given to the determination of the area of the stress-strain hysteresis loop once the material has achieved a stabilized state. It is found that this area does not evolve monotonically with the loading rate for either transient or asymptotic states. In order to reproduce this observation analytically, a new model is developed based on the ZM model for shape memory alloys which was modified to account for Thermomechanical Coupling. The model is shown to predict the non-monotonic variation in hysteresis area to good accord. Experimentally observed variations in the temperature of SMA test samples are also correctly reproduced for lower strain rates.
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A simple 1D model with Thermomechanical Coupling for superelastic SMAs
IOP Conference Series: Materials Science and Engineering, 2010Co-Authors: Wael Zaki, Claire Morin, Ziad MoumniAbstract:This paper presents an outline for a new uniaxial model for shape memory alloys that accounts for Thermomechanical Coupling. The Coupling provides an explanation of the dependence of SMA behavior on the loading rate. 1D simulations are carried in Matlab using simple finite-difference discretization of the mechanical and thermal equations.
