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    Modeling and simulation of conducting crack propagation in ferroelectric single crystals under purely electrical loading  Open access

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    International Conference on Computational Plasticity Fundamentals and Applications
    p. 400-406
    Presentation's date: 2013-09
    Presentation of work at congresses

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    We present a phase-field model of fracture in ferroelectric single crystals for the simulation of conducting crack propagation under purely electrical loading. This is done by introducing the electrical enthalpy of a diffuse conducting layer into the phase-field formulation. Simulation results show an oblique crack propagation and crack branching from a conducting notch in a ferroelectric sample under applied electric fields. Microstructure evolution indicates the formation of 90 domains which results in a charge accumulation around the crack. The charge accumulation, in turn, induces a high electric field and hence a high electrostatic energy for driving the conducting crack.

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  • Numerical simulation of electrical fracture in ferroelectric materials

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    Congreso de Métodos Numéricos en Ingeniería
    p. 1
    Presentation's date: 2013-06-26
    Presentation of work at congresses

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    Over the past decades, ferroelectric ceramics have found many applications in smart structures and adaptive systems due to their unique electromechanical properties. The use of these materials as actuators often demand a reasonable actuation capability, which can be obtained under high electric fields. The structures of the actuators commonly involve internal electrodes or conducting layers, which can intensify the applied electric fields in their vicinity. The electric fields, in turn, can induce an incompatible strain field or a high electrostatic force, which may cause the brittle ferroelectric ceramic to crack. Therefore, it is necessary to understand the fracture behaviour of ferroelectric ceramics under electric fields to assure the reliability of the systems. For this purpose, we extend a phase-field model of fracture in ferroelectric single crystals [1,2] for the simulation of conducting crack propagation under purely electrical loading. This is done by introducing the electrical enthalpy of a diffuse conducting layer into the phase-field formulation. Simulation results in Fig. 1(a) show an oblique crack propagation and crack branching from a conducting notch in a ferroelectric sample under an applied electric field. The ferroelectric microstructure evolution in Fig. 1(b) indicates the formation of tail-to-tail 90 o domains, which results in a charge accumulation around the crack. The charge accumulation, in turn, induces a high electric field and hence a high electrostatic energy for driving the conducting crack. Salient features of the results are compared with experiments [3].

  • A computational study of fracture in multilayer ferroelectric actuators

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    International Conference on Computational Modeling of Fracture and Failure of Materials and Structures
    p. 200-
    Presentation's date: 2013-06-05
    Presentation of work at congresses

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    Multilayer ferroelectric actuators are ideal candidates for numerous applications in smart structures and adaptive systems in view of their small sizes, low driving voltages and quick response times. Applications include microprecision cutting machines, inkjet printer heads, laser printers, optical disk drives and laser tuning, to mention a few. However, the inherent brittleness of ferroelectrics is a serious obstacle to their reliable operation in devices. In addition, the structures of multilayer actuators often employ internal electrodes, which terminate inside the ferroelectric ceramic. In the vicinity of each terminated electrode edge, a non-uniform electric field is induced by the driving voltage, producing an incompatible strain field. A complex stress field arises from this incompatibility, which may lead to crack initiation and propagation around the electrode edge. Therefore, it is necessary to understand the fracture behavior of multilayer ferroelectric actuators to assure optimum reliability of the systems and guide the design. Previously, the fracture simulations were performed to analyze the electromechanical fields near the electrode edge. Based on this analysis, some design criteria can be proposed regarding the geometry of the actuators and electrodes to reduce the probability of fracture from the electrode edge. However, these models do not study the crack propagation mechanisms of the actuators and these mechanisms are still unclear due to the complex interactions between the propagating cracks, electromechanical fields and microstructure of the material near the electrode edge. We have recently introduced phase-field models for the coupled microstructure and fracture evolution in ferroelectric single and polycrystals [1, 2, 3, 4]. The potential of this phase-field approach to capture the complex interactions between the crack and the material microstructure motivates us to employ it for the fracture analysis of multilayer ferroelectric actuators. In particular, the objective of this paper is to study the crack initiation at the electrode edge during the poling process. Considering different bonding conditions between the ceramic and electrode layers, different crack initiation patterns are obtained, which are useful to understand the fracture processes in this type of actuators. Three extreme conditions are considered, which are the fully cofired, partially cofired, and separated layers. The crack initiation patterns can be either delimitation along the electrode-ceramic interface or oblique cracking from the electrode into the material. The calculations suggest a mechanism explaining the experimentally observed crack branches near the electrode edges. The effects of the ceramic layer thickness and length of the internal electrode on the crack initiation are also evaluated [5].

  • Phase-field modeling of fracture in ferroelectric materials

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    Advances in Computational Mechanics
    Presentation's date: 2013-02-26
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  • Phase-field modeling of fracture in ferroelectric materials.

     Abdollahi Hosnijeh, Amir
    Universitat Politècnica de Catalunya
    Theses

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  • Numerical simulation of 3-D crack propagation in ferroelectric polycrystals: effect of combined toughening mechanisms

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    European Congress on Computational Methods in Applied Sciences and Engineering
    p. 1-2
    Presentation's date: 2012-09-10
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  • Phase-field modeling of fracture in electromechanical materials: from theory to application

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    World Congress on Computational Mechanics
    p. 197
    Presentation's date: 2012-07-10
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  • MODELOS DE CAMPO DE FASE PARA PROBLEMAS DE DISCONTINUIDAD LIBRE: METODOS COMPUTACIONALES Y APLICACIONES EN FRACTURA MATERIALES FERRO

     Abdollahi Hosnijeh, Amir; Arroyo Balaguer, Marino; Li, Bin; Arias Vicente, Irene
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    An efficacious method to assemble a modern multi-modal robotic team: dilemmas, challenges, possibilities and solutions  Open access

     Abdollahi Hosnijeh, Amir; Samani, Hooman Aghaebrahimi
    Date of publication: 2012-01-05
    Book chapter

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    A modern multiagent robotic platform consists of a cooperative team of humans which develop a collaborative team of robots. The multi-modal nature of both the system and the team causes a complex problem which needs to be solved for optimum performance. Both the management and the technical aspect of a modern robotic team are explored in this Chapter in the platform of the RoboCup Competition. RoboCup is an example of such an environment where researchers from different disciplines join to develop a robotic team for completion as an evaluation challenge (Robocup, 2011). RoboCup competitions were first proposed by Mackworth in 1993. The main goal of this scientific competition is to exploit, improve and integrate the methods and techniques from robotics, machine vision and artificial intelligence disciplines to create an autonomous team of soccer playing robots(Kitano, 1997a; Kitano, 1997b; Kitano et al., 1997). Such experiment includes several challenges, from inviting an expert of specific field to the team to choosing bolts and nuts for each part of the robots. Usually each challenge has several possible solutions and choosing the best one is often challenging. We have participated in several world wide RoboCup competitions (Abdollahi, Samani et al. 2002, 2003 & 2004) and share our experience as an extensive instruction for setting up a modern robotic team including management and technical issues.

  • A phase-field fracture model of ferroelectric materials under electro-mechanical loading

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    Conference on Smart Materials, Adaptive Structures and Intelligent Systems
    p. 297-301
    DOI: 10.1115/SMASIS2011-4960
    Presentation's date: 2011-09
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    A phase-field model is proposed for the coupled simulation of microstructure and fracture evolution in ferroelectric materials. The model is based on energetic phase-field approaches for brittle fracture and ferroelectric domain formation and evolution. The variational nature of these approaches makes their coupling very natural. However the main challenge is to encode the electro-mechanical conditions of the sharp crack faces into the phase-field framework since the crack in this model is smeared and represented by an internal layer. We develope the model for different crack face boundary conditions. Simulations show the microstructure induced by the presence of the crack. Interactions between the microstructure and the crack are investigated under different electro-mechanical loadings.

  • On the effect of crack face boundary conditions on the fracture mechanics of ferroelectric materials

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    International Symposium on Defect and Material Mechanics
    Presentation's date: 2011-07-28
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  • Coupled phase-field modeling of fracture and microstructure evolution in ferroelectric materials

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    International Conference on Computational Modeling of Fracture and Failure of Materials and Structures
    p. 283
    Presentation's date: 2011-06-07
    Presentation of work at congresses

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  • Numerical simulation of intergranular and transgranular crack propagation in ferroelectric polycrystals

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    Congreso en Métodos Numéricos em Engenharia
    p. 1-6
    Presentation's date: 2011-06-15
    Presentation of work at congresses

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    We present a phase-field model to simulate intergranular and transgranular crack propagation in ferroelectric polycrystals. The proposed model couples three phase-fields describing (1) the polycrystalline structure, (2) the location of the cracks, and (3) the ferroelectric domain microstructure. Different polycrystalline microstructures are obtained from computer simulations of grain growth. Then, a phase-field model for fracture in ferroelectric single-crystals is extended to polycrystals by incorporating the differential fracture toughness of the bulk and the grain boundaries, and the different crystal orientations of the grains. Our simulation results show intergranular crack propagation in fine-grain microstructures, while transgranular crack propagation is observed in coarse grains. Crack deflection is shown as the main toughening mechanism in the fine-grain structure. Due to the ferroelectric domain switching mechanism, noticeable fracture toughness enhancement is also obtained for transgranular crack propagation. These observations agree with experiment.

    Postprint (author’s final draft)

  • Modelos de campo de fase para problemas de discontinuidad libre: métodos computacionales y aplicaciones en fractura, materiales..

     Millan, Raul Daniel; Abdollahi Hosnijeh, Amir; Rosolen, Adrian Martin; Arroyo Balaguer, Marino; Peco Regales, Christian; Zhang, Kuan; Arias Vicente, Irene
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  • MODELOS DE CAMPO DE FASE PARA PROBLEMAS DE DISCONTINUIDAD LIBRE: METODOS COMPUTACIONALES Y APLICACIONES EN FRACTURA, MATERIALES FERROELECTRICOS Y MEMBRANAS BIOLOGICAS-1

     Arias Vicente, Irene; Arroyo Balaguer, Marino; Abdollahi Hosnijeh, Amir; Ghosh, Susanta; Rosolen, Adrian Martin; Millan, Raul Daniel; Rahimi Lenji, Mohammad
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  • Numerical simulations of Vickers indentation crack growth in ferroelectric single crystals: Effect of microstructure on the fracture process

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    International Conference on Computational Plasticity Fundamentals and Applications
    p. 514-520
    Presentation's date: 2011
    Presentation of work at congresses

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  • Twin toughening in ferroelectric materials: effect of microstructure on fracture process

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    International Conference Multiscale Materials Modeling
    Presentation's date: 2010-10-05
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  • Modeling and simulation of coupled microstructure and fracture evolution in ferroelectric materials

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    US National Congress on Theoretical and Applied Mechanics
    Presentation's date: 2010-06-01
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  • PREDICTIVE MODELS AND SIMULATIONS IN NANO AND BIOMOLECULAR MECHANICS: A MULTISCALE APPROACH

     Arias Vicente, Irene; Zhang, Kuan; Li, Bin; Rahimi Lenji, Mohammad; Millan, Raul Daniel; Abdollahi Hosnijeh, Amir; Peco Regales, Christian; Hashemian, Behrooz; Arroyo Balaguer, Marino
    Competitive project

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  • A computational study of fracture in ferroelectric single crystals

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    International Conference on Computational Plasticity Fundamentals and Applications
    p. 1-4
    Presentation's date: 2009-09-24
    Presentation of work at congresses

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  • MÈTODES NUMÈRICS EN CIÈNCIES APLICADES I ENGINYERIA

     Roca Navarro, Francisco Javier; Giorgiani, Giorgio; Zlotnik, Sergio; Fernandez Mendez, Sonia; Rodriguez Ferran, Antonio; Muñoz Romero, Jose Javier; Arias Vicente, Irene; de Villardi de Montlaur, Adeline; Sarrate Ramos, Jose; Diez Mejia, Pedro; Arroyo Balaguer, Marino; Sevilla Cardenas, Ruben; Parés Mariné, Núria; Casoni Rero, Eva; Ruiz Girones, Eloi; Modesto Galende, David; Millan, Raul Daniel; Abdollahi Hosnijeh, Amir; Steffens, Lindaura Maria; Discacciati, Marco; Shen, Yongxing; Rahimi Lenji, Mohammad; Tamayo Mas, Elena; Diaz Cereceda, Cristina; Prat Robles, David; Verdugo Rojano, Francesc; Zhang, Kuan; Estela Carbonell, M. Rosa; Peco Regales, Christian; Pérez Foguet, Agustí; Angeloski, Aleksandar; Gargallo Peiró, Abel; Huerta Cerezuela, Antonio
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  • Comprehensive omni-directional soccer player robots

     Abdollahi Hosnijeh, Amir; Daneshpanah, Mehdi; Ostadi, Hossein; Samani, Hooman Aghaebrahimi
    DOI: 10.5772/5139
    Date of publication: 2007-12-01
    Book chapter

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  • Evaluation on mass sensitivity of SAW sensors for different piezoelectric materials using finite element analysis

     Abdollahi Hosnijeh, Amir; Jiang, Zhongwei; Arabshahi, Sayyed Alireza
    IEEE International Symposium on Applications of Ferroelectrics
    p. 734-737
    DOI: 10.1109/ISAF.2007.4393386
    Presentation's date: 2007-02-01
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  • Innovative simulation procedure to investigate surface acoustic wave sensors

     Abdollahi Hosnijeh, Amir; Jiang, Zhongwei
    International Conference on Innovation and Management
    p. 129-133
    Presentation of work at congresses

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  • Singularity analysis of a 3 DOF 4-legged parallel manipulator with a non-slippery passive constraining leg

     Ajoudanian, M.; Abdollahi Hosnijeh, Amir; Ostadi, Hossein; Keshmiri, M.
    International Conference on Optimization of Robots and Manipulators
    Presentation's date: 2006-04-08
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  • A practical approach to control and self-localization of Persia Omni-Directional Mobile Robot

     Ziai-Rad, Saeed; Janabi-Sharifi, Farid; Daneshpanah, Mehdi; Abdollahi Hosnijeh, Amir; Ostadi, Hossein; Samani, Hooman Aghaebrahimi
    IEEE/RSJ International Conference on Intelligent Robots and Systems
    p. 3473-3479
    DOI: 10.1109/IROS.2005.1545090
    Presentation's date: 2005-02-10
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  • Wave simulator: design and fabrication of a 3 DOF 4-legged parallel manipulator with a non-slippery passive constraining leg

     Ajoudanian, M.; Abdollahi Hosnijeh, Amir; Ostadi, Hossein; Keshmiri, M.
    Annual International Conference of Mechanical Engineering
    Presentation's date: 2005-02-12
    Presentation of work at congresses

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  • Autodesk inventor 3D modeling software for mechanical engineers

     Abdollahi Hosnijeh, Amir
    Date of publication: 2005
    Book chapter

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  • Technical Challenge Award

     Abdollahi Hosnijeh, Amir
    Award or recognition

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  • Best Soccer Player Robots 2004

     Abdollahi Hosnijeh, Amir
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  • Outstanding Student Award

     Abdollahi Hosnijeh, Amir
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  • Conducting crack propagation driven by electric fields in ferroelectric ceramics

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    Acta materialia
    Vol. 61, num. 19, p. 7087-7097
    DOI: 10.1016/j.actamat.2013.07.050
    Date of publication: 2013-11
    Journal article

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    Ferroelectric ceramics are susceptible to fracture under high electric fields, which are commonly generated in the vicinity of electrodes or conducting layers. In the present work, we extend a phase-field model of fracture in ferroelectric single crystals to the simulation of the propagation of conducting cracks under purely electrical loading. This is done by introducing the electrical enthalpy of a diffuse conducting layer into the phase-field formulation. Simulation results show oblique crack propagation and crack branching from a conducting notch, forming a tree-like crack pattern in a ferroelectric sample under positive and negative electric fields. Microstructure evolution indicates the formation of tail-to-tail and head-to-head 90° domains, which results in charge accumulation around the crack. The charge accumulation, in turn, induces a high electric field and hence a high electrostatic energy, further driving the conducting crack. Salient features of the results are compared with experiments.

  • Evaluation on mass sensitivity of SAW sensors for different piezoelectric materials using finite element analysis

     Abdollahi Hosnijeh, Amir; Jiang, Zhongwei; Arabshahi, Sayyed Alireza
    IEEE transactions on Ultrasonics Ferroelectrics and Frequency control
    Vol. 54, num. 12, p. 2446-2455
    DOI: 10.1109/TUFFC.2007.558
    Date of publication: 2007
    Journal article

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    The mass sensitivity of the piezoelectric surface acoustic wave (SAW) sensors is an important factor in the selection of the best gravimetric sensors for different applications. To determine this value without facing the practical problems and the long theoretical calculation time, we have shown that the mass sensitivity of SAW sensors can be calculated by a simple three-dimensional (3-D) finite-element analysis (FEA) using a commercial finite-element platform. The FEA data are used to calculate the wave propagation speed, surface particle displacements, and wave energy distribution on different cuts of various piezoelectric materials. The results are used to provide a simple method for evaluation of their mass sensitivities. Meanwhile, to calculate more accurate results from FEA data, surface and bulk wave reflection problems are considered in the analyses. in this research, different cuts of lithium niobate, quartz, lithium tantalate, and langasite piezoelectric materials are applied to investigate their acoustic wave properties. Our analyses results for these materials have a good agreement with other researchers¿ results. Also, the mass sensitivity value for the novel cut of langasite was calculated through these analyses. It was found that its mass sensitivity is higher than that of the conventional Rayleigh mode quartz sensor.

  • A practical approach to control and self-localization of an omni-directional mobile robot

     Ziai-Rad, Saeed; Janabi-Sharifi, Farid; Daneshpanah, Mehdi; Abdollahi Hosnijeh, Amir; Ostadi, Hossein; Samani, Hooman Aghaebrahimi
    Wseas Transactions on Systems and Control
    Vol. 3, num. 5, p. 413-424
    Date of publication: 2008
    Journal article

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  • Design and development of a comprehensive omni directional soccer player robot

     Samani, Hooman Aghaebrahimi; Abdollahi Hosnijeh, Amir; Ostadi, Hossein; Ziai-Rad, Saeed
    International journal of advanced robotic systems
    Vol. 1, num. 3, p. 191-200
    Date of publication: 2004
    Journal article

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  • Three-dimensional simulation of crack propagation in ferroelectric polycrystals: Effect of combined toughening mechanisms

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    Acta materialia
    Vol. 65, p. 106-117
    DOI: 10.1016/j.actamat.2013.11.016
    Date of publication: 2014-02-15
    Journal article

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    We simulate the fracture processes of ferroelectric polycrystals in three dimensions using a phase-field model. In this model, the grain boundaries, cracks and ferroelectric domain walls are represented in a diffuse way by three phase-fields. We thereby avoid the difficulty of tracking the interfaces in three dimensions. The resulting model can capture complex interactions between the crack and the polycrystalline and ferroelectric domain microstructures. The simulation results show the effect of the microstructures on the fracture response of the material. Crack deflection, crack bridging, crack branching and ferroelastic domain switching are observed to act as the main fracture toughening mechanisms in ferroelectric polycrystals. Our fully 3-D simulations illustrate how the combination of these mechanisms enhances the fracture toughness of the material, and pave the way for further systematic studies, including fracture homogenization. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    We simulate the fracture processes of ferroelectric polycrystals in three dimensions using a phase-field model. In this model, the grain boundaries, cracks and ferroelectric domain walls are represented in a diffuse way by three phase-fields. We thereby avoid the difficulty of tracking the interfaces in three dimensions. The resulting model can capture complex interactions between the crack and the polycrystalline and ferroelectric domain microstructures. The simulation results show the effect of the microstructures on the fracture response of the material. Crack deflection, crack bridging, crack branching and ferroelastic domain switching are observed to act as the main fracture toughening mechanisms in ferroelectric polycrystals. Our fully 3-D simulations illustrate how the combination of these mechanisms enhances the fracture toughness of the material, and pave the way for further systematic studies, including fracture homogenization.

  • Numerical simulation of intergranular and transgranular crack propagation in ferroelectric polycrystals

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    International journal of fractures
    Vol. 174, num. 1, p. 3-15
    DOI: 10.1007/s10704-011-9664-0
    Date of publication: 2012-01-17
    Journal article

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  • Computational evaluation of the flexoelectric effect in dielectric solids

     Abdollahi Hosnijeh, Amir; Peco Regales, Christian; Millán, Daniel; Arroyo Balaguer, Marino; Arias Vicente, Irene
    Journal of applied physics
    Vol. 116, num. 9, p. 093502-1-093502-10
    DOI: 10.1063/1.4893974
    Date of publication: 2014-09-07
    Journal article

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    Flexoelectricity is a size-dependent electromechanical mechanism coupling polarization and strain gradient. It exists in a wide variety of materials, and is most noticeable for nanoscale objects, where strain gradients are higher. Simulations are important to understand flexoelectricity because experiments at very small scales are difficult, and analytical solutions are scarce. Here, we computationally evaluate the role of flexoelectricity in the electromechanical response of linear dielectric solids in two-dimensions. We deal with the higher-order coupled partial differential equations using smooth meshfree basis functions in a Galerkin method, which allows us to consider general geometries and boundary conditions. We focus on the most common setups to quantify the flexoelectric response, namely, bending of cantilever beams and compression of truncated pyramids, which are generally interpreted through approximate solutions. While these approximations capture the sizedependent flexoelectric electromechanical coupling, we show that they only provide order-of-magnitude estimates as compared with a solution fully accounting for the multidimensional nature of the problem. We discuss the flexoelectric mechanism behind the enhanced size-dependent elasticity in beam configurations. We show that this mechanism is also responsible for the actuation of beams under purely electrical loading, supporting the idea that a mechanical flexoelectric sensor also behaves as an actuator. The predicted actuation-induced curvature is in a good agreement with experimental results. The truncated pyramid configuration highlights the critical role of geometry and boundary conditions on the effective electromechanical response. Our results suggest that computer simulations can help understanding and quantifying the physical properties of flexoelectric devices. (c) 2014 AIP Publishing LLC.

  • Crack initiation patterns at electrode edges in multilayer ferroelectric actuators

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    Smart materials and structures
    Vol. 21, num. 9
    DOI: 10.1088/0964-1726/21/9/094011
    Date of publication: 2012-12
    Journal article

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  • Phase-field modeling of crack propagation in piezoelectric and ferroelectric materials with different electromechanical crack conditions

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    Journal of the mechanics and physics of solids
    Vol. 60, num. 12, p. 2100-2126
    DOI: 10.1016/j.jmps.2012.06.014
    Date of publication: 2012-12
    Journal article

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  • Phase-field simulation of anisotropic crack propagation in ferroelectric single crystals: Effect of microstructure on the fracture process

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    Modeling and simulation in materials science and engineering
    Vol. 19, num. 7, p. 1-13
    DOI: 10.1088/0965-0393/19/7/074010
    Date of publication: 2011
    Journal article

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  • Phase-field modeling of the coupled microstructure and fracture evolution in ferroelectric single crystals

     Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
    Acta materialia
    Vol. 59, num. 12, p. 4733-4746
    DOI: 10.1016/j.actamat.2011.03.030
    Date of publication: 2011-07
    Journal article

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    We propose a phase-field model for the coupled simulation of microstructure formation and evolution, and the nucleation and propagation of cracks in single-crystal ferroelectric materials. The model naturally couples two existing energetic phase-field approaches for brittle fracture and ferroelectric domain formation and evolution. The finite-element implementation of the theory in two dimensions (plane-polarization and plane-strain) is described. We perform, to the best of our knowledge, the first crack propagation calculations of ferroelectric single crystals, simultaneously allowing general microstructures to develop. Previously, the microstructure calculations were performed at fixed crack configurations or under the assumption of small-scale switching. Our simulations show that this assumption breaks down as soon as the crack-tip field interacts with the boundaries of the test sample (or, in general, obstacles such as defects or grain boundaries). Then, the microstructure induced by the presence of the crack propagates beyond its vicinity, leading to the formation of twins. Interactions between the twins and the crack are investigated under mechanical and electromechanical loadings, both for permeable and impermeable cracks, with an emphasis on fracture toughening due to domain switching, and compared with experiments.