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Amir Abdollahi's blog

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Mechanical Reading of Ferroelectric Polarization

The mechanical properties of materials are insensitive to space inversion, even when they are crystallographically asymmetric. In practice, this means that turning a piezoelectric crystal upside down or switching the polarization of a ferroelectric should not change its mechanical response. Strain gradients, however, introduce an additional source of asymmetry that has mechanical consequences.

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Fracture toughening and toughness asymmetry induced by flexoelectricity

Cracks generate the largest strain gradients that any material can withstand. Flexoelectricity (coupling between strain gradient and polarization) must therefore play an important role in fracture physics. Here we use a self-consistent continuum model to evidence two consequences of flexoelectricity in fracture: the resistance to fracture increases as structural size decreases, and it becomes asymmetric with respect to the sign of polarization. The latter phenomenon manifests itself in a range of intermediate sizes where piezo- and flexoelectricity compete.

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Constructive and Destructive Interplay between Piezoelectricity and Flexoelectricity in Flexural Sensors and Actuators

Flexoelectricity is an electromechanical effect coupling polarization to strain gradients. It fundamentally differs from piezoelectricity because of its size-dependence and symmetry. Flexoelectricity is generally perceived as a small effect noticeable only at the nanoscale. Since ferroelectric ceramics have a particularly high flexoelectric coefficient, however, it may play a significant role as piezoelectric transducers shrink to the sub-micrometer scale.

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A computational study of flexoelectricity

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.

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

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

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Conducting crack propagation driven by electric fields in ferroelectric ceramics

This is a recent article in Acta Materialia on the propagation of conducting cracks in ferroelectric ceramics

Title: Conducting crack propagation driven by electric fields in ferroelectric ceramics

Authors: Amir Abdollahi and Irene Arias, Universitat Politecnica de Catalunya (UPC), Barcelona

Abstract:

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Phase-field modeling of crack propagation in piezoelectric and ferroelectric materials

This is an accepted manuscript in Journal of the Mechanics and Physics of Solids

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

Authors: Amir Abdollahi and Irene Arias, Universitat Politecnica de Catalunya (UPC), Barcelona

 

Abstract:

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Crack initiation patterns at electrode edges in multilayer ferroelectric actuators

This is the preprint of an article that will appear in Smart Materials and Structures (SMS)

Title: Crack initiation patterns at electrode edges in multilayer ferroelectric actuators

Authors: Amir Abdollahi and Irene Arias, Universitat Politecnica de Catalunya (UPC), Barcelona

 

Abstract:

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Numerical simulation of intergranular and transgranular crack propagation in ferroelectric polycrystals

This is the preprint of an article that will appear in International Journal of Fracture (IJF)

Title: Numerical simulation of intergranular and transgranular crack propagation in ferroelectric polycrystals

Authors: Amir Abdollahi and Irene Arias, Universitat Politecnica de Catalunya (UPC), Barcelona

 

 

Abstract:

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Slow-Fast Crack Propagation in Ferroelectric Single Crystals

Dear Colleague,

 

I have uploaded a video which shows the simulation of Slow-Fast crack propagation in ferroelectric single crystals:

http://www.youtube.com/watch?v=6E7WSVOVAWM

 

For technical details, please refer to our recently published paper in Acta Materialia:

http://www.sciencedirect.com/science/article/pii/S1359645411001777

 

Best regards,

Amir Abdollahi

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Phase-field simulation of anisotropic crack propagation in ferroelectric single crystals

This is the preprint of an article that will appear in Modelling and Simulation in Materials Science and Engineering (MSMSE)

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

Authors: Amir Abdollahi and Irene Arias, Universitat Politecnica de Catalunya (UPC), Barcelona

 

 

Abstract:

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