In this study, a thermodynamically consistent constitutive relation is developed for ferroelectric materials. The present model is developed in such a way that an intermediate variable is introduced as a stored variable which accounts for calculating the internal variable. Due to this approach, simulations can be performed without an iterative procedure. Thus, this model improves the computational efficiency. The algorithmic procedure can also handle the evolution of ferroelastic strain as well as the evolution of polarisation simultaneously, without getting into convergence issues. In this work, simulations have been performed to capture various behaviours such as ferroelectric hysteresis with prestress, mechanical depolarisation, ferroelastic hysteresis, and creep behaviour. The simulated results have been compared with the experimental results, and it is observed that the model is good enough to capture various nonlinear hysteresis behaviours. © 2018, Springer-Verlag GmbH Austria, part of Springer Nature.

Arunachalakasi Arockiarajan

Department of Applied Mechanics

Computational efficiency

Creep

Ferroelectricity

hysteresis

Iterative methods

Algorithmic procedure

Constitutive relations

CONVERGENCE ISSUES

Ferroelectric hysteresis

INTERNAL VARIABLES

Nonlinear hysteresis

Phenomenological modeling

Simulated results

Ferroelectric materials

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

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IIT Madras

Acta Mechanica

Ferroelectric materials are soon to be considered as an alternate replacement for the vapour compression, and vapour absorption cooling systems and efficient energy harvesters from low-grade waste heat due to their electrocaloric and elastocaloric response. In the current work, a theoretical framework based on a thermodynamical approach is proposed to estimate the electrocaloric, elastocaloric and electro-elastocaloric effect as an isothermal change in the entropy or adiabatic temperature change (ΔT) in the piezocomposites. The proposed nonlinear constitutive model has been incorporated into a non-iterative algorithmic setup to capture the ferroelectric and ferroelastic response at different temperatures for piezocomposites. The model parameters are obtained by performing experiments for various fibre volume fractions of 1-3 type piezocomposites and are used to simulate the relations between polarization-temperature and strain-temperature at different external mechanical and electric fields. Using the present model, an Olsen cycle (pyroelectric energy harvesting cycle) is drawn to predict the pyroelectric energy density (ND) of piezocomposites. © 2019 IOP Publishing Ltd.

Smart Materials and Structures

Study of electro-elastocaloric effect and pyroelectric energy density in piezocomposites

1–3 piezocomposites are extensively used for sensor, actuator, naval and aerospace applications owing to their enhanced electromechanical coupling, wider bandwidth and reliability. However, their performance gets adversely affected when they are subjected to combined static and dynamic loads that initiate both creep and fatigue damage, simultaneously. 1–3 piezocomposites undergo damage due to creep–fatigue interactions because of the passive and viscoelastic polymer matrix and inherent domain switching mechanisms. In this work, experiments are conducted to obtain the electromechanical response of 1–3 piezocomposites subjected to electrical fatigue and mechanical compressive creep loads. It is observed that, the electromechanical response degrades with increase in number of electrical fatigue cycles, matrix volume fraction and mechanical compressive pre-stress. A nonlinear phenomenological combined creep–fatigue damage model is developed within a thermodynamic framework to account for the creep–fatigue interactions in 1–3 piezocomposites. The model predictions are found to be in agreement with the experimental observations. © 2019, Springer Nature B.V.

Meccanica

Mechanics of 1–3 piezocomposites subjected to creep–fatigue loads

1-3 piezocomposites are often subjected to mechanical pre-stress under elevated temperatures in naval and offshore applications, actuators, and so on, where the presence of the ductile epoxy matrix causes considerable creep in the system. This deteriorates the system efficiency and its overall performance. To address this issue, experiments are performed to capture the electromechanical response for thermo-mechanical creep of 1-3 piezocomposites for different fiber volume fractions under various thermal loads, wherein mechanical depolarization is observed. The piezo-coupling coefficient is observed to degrade. Higher thermal loads resulted in an increase in creep strain coupled with a decrease in creep polarization. A Kelvin–Voigt fractal derivative viscoelastic model is used to capture the creep strain. The creep strain is decomposed into ferroelastic and anelastic parts. The evolution of creep polarization is obtained using the ferroelastic component of the creep strain. The model predictions are found to be in agreement with the experimental observations. © The Author(s) 2019.

Journal of Intelligent Material Systems and Structures

Experimental characterization and viscoelastic modeling for thermo-mechanical creep of 1-3 piezocomposites

Ferroelectric materials, due to their electrocaloric behaviour, are considered as a promising alternative for the vapour compression refrigeration system and the solid state heat engine which converts the heat energy into electrical energy. In the present work, a novel indirect method based on thermodynamic framework is introduced to obtain electrocaloric properties in terms of adiabatic temperature change. A constitutive model has also been developed with an idea of infinite yield surfaces, to capture the ferroelectric response over a range of cyclic electric field with different amplitudes and temperature values. The model parameters are identified based on the experimental results for PbZrxTi1-xO3 (PZT). Using these parameters, simulations are performed to compute the change in polarization with temperature at different values of applied electric field, based on the proposed theoretical approach. The polarization temperature relation thus obtained, is used to calculate adiabatic temperature change (ΔT). The same model is used to simulate pyroelectric energy harvesting cycle (Olsen cycle), to estimate the harvested energy density per cycle (N D) of PZT from waste heat source for low power systems. © 2018 IOP Publishing Ltd.

Materials Research Express

Study of electrocaloric effect and harvested pyroelectric energy density of ferroelectric material

Composite structures which show magneto-electric (ME) coupling behavior have a wide range of engineering applications. In this work, a composite structure comprising of a ferroelectric and a magnetostrictive material is taken for investigation. First, the nonlinear responses of the ferroelectric material and the magnetostrictive material are studied separately by experiments. In order to predict the nonlinear response, a thermodynamically consistent macroscopic model is proposed for the ferroic materials. Model parameters are then estimated from the experimental data, and the simulated results based on the proposed model are presented. Results from the theoretical model are in agreement with the experimental data. Subsequently, a homogenization procedure is introduced to find out the nonlinear response of a layered ME composite structure, and the obtained results are discussed. © 2017, Springer-Verlag Wien.

Nonlinear magneto-electro-mechanical response of layered magneto-electric composites: theoretical and experimental approach

Further development and design of piezoelectric composites enhances the improved use of piezoelectric materials and devices by overcoming their brittleness. In order to engineer this class of materials and to predictably simulate its behaviour, a computationally efficient constitutive model is established in this paper. This contribution deals with the development of a model for piezoelectric composites to capture their effective behaviour. We first discuss a three-dimensional fully coupled electromechanical rate-dependent model for the response of ferroelectric ceramics. Secondly, a simple homogenisation approach is applied to capture the behaviour of composites for various volume fractions of PZT fibres under different loading frequencies. Following this, a finite element formulation is applied in order to study the behaviour of composites. Finally, these two approaches are compared with experimental results. © 2015 Elsevier Ltd.

Mechanics of Materials

Experimental investigation, modelling and simulation of rate-dependent response of 1-3 ferroelectric composites

Depending on the maximum amplitude of externally applied cyclic electric fields, ferroelectric ceramics show minor or major hysteresis. The materials also show asymmetric butterfly hysteresis in a prepoled material. Aiming at capturing these behaviour in a phenomenological constitutive model, a multi-surface modelling approach for ferroelectrics is introduced. In this paper, with the note on the motivation for a multi-surface model related to the results of new experimental investigations and also to experimental data reported in the literature, the constitutive relation for a rate dependent multi-surface ferroelectric model is developed. Following this, a brief graphical illustration shows how this model captures the objective phenomena. Consequently, the numerical implementation of the model to capture experimental results is demonstrated. Finally, the performance of this model to represent behaviour of decaying polarisation offset of electrically fatigued specimen is shown. © 2016 Informa UK Limited, trading as Taylor & Francis Group.

Journal	Data powered by TypesetActa Mechanica
Publisher	Data powered by TypesetSpringer-Verlag Wien
ISSN	00015970
Open Access	No