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Journal Club for November 2018: Beyond piezoelectricity: Flexoelectricity in solids

 

Beyond piezoelectricity: Flexoelectricity in solids

Jiawang Hong

School of Aerospace Engineering, Beijing Institute of Technology

 

1. Introduction

Shuze Zhu's picture

Nanomanufacturing of graphene nanosheets through nano-hole opening and closing

Materials Today, in press, 2018, https://doi.org/10.1016/j.mattod.2018.09.001

Yanan Chen, Yilin Wang, Shuze Zhu, Kun Fu, Xiaogang Han, Yanbin Wang, Bin Zhao, Tian Li , Boyang Liu , Yiju Li , Jiaqi Dai , Hua Xie , Teng Li , John W. Connell , Yi Lin, Liangbing Hu

Fan Xu's picture

A modeling and resolution framework for wrinkling in hyperelastic sheets at finite membrane strain

Wrinkles commonly occur in uniaxially stretched rectangular hyperelastic membranes with clamped-clamped boundaries, and can vanish upon excess stretching. Here we develop a modeling and resolution framework to solve this complex instability problem with highly geometric and material nonlinearities. We extend the nonlinear Foppl-von Karman thin plate model to finite membrane strain regime for various compressible and incompressible hyperelastic materials.

Theories used in Abaqus for composite plate modeling

Choose a channel featured in the header of iMechanica: 

Which plate theories are used in Abaqus for composite plate modeling? 

I am studying how delaminations in a composite plate affect its damping properties (by contact friction) and thereby to use for Structural health monitoring. Normally, in a metallic plate, no transverse normal stresses (S33) will be generated during pure bending. But, in a laminated composite plate, around discontinuities, S33 have been observed to be generated. But many plate theories neglect S33. But Reddys Layerwise theory and 3D plate theories consider S33 in the analysis. 

sairajatm's picture

Dislocation pattern formation in finite deformation crystal plasticity

Rajat Arora        Amit Acharya

Stressed dislocation pattern formation in crystal plasticity at finite deformation is demonstrated for the first time. Size effects are also demonstrated within the same mathematical model. The model involves two extra material parameters beyond the requirements of standard classical crystal plasticity theory. The dislocation microstructures shown are decoupled from deformation microstructures, and emerge without any consideration of latent hardening or constitutive assumptions related to cross-slip. Crystal orientation effects on the pattern formation and mechanical response are also demonstrated. The manifest irrelevance of the necessity of a multiplicative decomposition of the deformation gradient, a plastic distortion tensor, and the choice of a reference configuration in our model to describe the micromechanics of plasticity as it arises from the existence and motion of dislocations is worthy of note.

Amit Acharya's picture

On the Structure of Linear Dislocation Field Theory

Amit Acharya          Robin J. Knops         Jeyabal Sivaloganathan

Uniqueness of solutions in the linear theory of non-singular dislocations, studied as a special case of plasticity theory, is examined. The status of the classical, singular Volterra dislocation problem as a limit of plasticity problems is illustrated by a specific example that clarifies the use of the plasticity formulation in the study of classical dislocation theory. Stationary, quasi-static, and dynamical problems for continuous dislocation distributions are investigated subject not only to standard boundary and initial conditions, but also to prescribed dislocation density. In particular, the dislocation density field can represent a single dislocation line.

It is only in the static and quasi-static traction boundary value problems that such data are sufficient for the unique determination of stress. In other quasi-static boundary value problems and problems involving moving dislocations, the plastic and elastic distortion tensors, total displacement, and stress are in general non-unique for specified dislocation density. The conclusions are confirmed by the example of a single screw dislocation.

mohamedlamine's picture

An efficient convergence test for the fixed point method

The fixed point method consists to find the solution of F(X)=X.

One can not get fixed with the convergence condition |F'(X)|<1 because if the function has an optimum then |F'(X)|=0 even if the solution is not yet reached.

 

We introduce an efficient convergence test with the condition:

|Xn+1 - Xn| ≤ epsilon1 And |F(Xn+1)-Xn+1| ≤ epsilon2

Zheng Jia's picture

Will Nemo's balloon burst or not?

Nemo lives in the ocean near the Great Barrier Reef. One day, he bought a hydrogel balloon which is inflated by an inner pressure p. Will the balloon burst eventually or stay safe?

Theories used in Abaqus for composite plate modeling

Choose a channel featured in the header of iMechanica: 

Which plate theories are used in Abaqus for composite plate modelling? 

I am studying how delaminations in a composite plate affect its damping properties (by contact friction) and thereby to use for Structural health monitoring. Normally, in a metallic plate, no transverse normal stresses (S33) will be generated during pure bending. But, in a laminated composite plate, around discontinuities, S33 have been observed to be generated. But many plate theories neglect S33. But Reddys Layerwise theory and 3D plate theories consider S33 in the analysis. 

Yoonho Kim's picture

Untethered soft machines and robots enabled by hard-magnetic soft materials

We introduce our recent works on advanced fabrication and mechanics of hard-magnetic soft materials towards the development of untethered soft machines and robots actuated and controlled by magnetic fields. 

- Abstract

Mike Ciavarella's picture

Questions to experts in Variable Amplitude Loading in Fatigue of metals

As a newcomer in this field, I try to pose some questions to the experts in Variable Amplitude Loading fatigue. The questions are probably trivial, but I don't find any reply in the literature, particularly on the arbitrary choice of frequency cutoff in the spectrum loading, and on the distinction  between cracked and uncracked structures. See attach and please respond if you can, even directly on email at mciava@poliba.it

N. Sukumar's picture

Special Issue on GBCs in CAGD

In 2019, Elsevier CAGD will be publishing a special issue on ``Generalized Barycentric Coordinates,'' edited by Michael S. Floater (University of Oslo), Kai Hormann (University of Lugano), and myself.

If you expect to have any new contribution in this area, then please do consider submitting a paper to this special issue.

All the details about the special issue can be found in the attached ``Call for Papers.''

Sohan Kale's picture

Active superelasticity of epithelial tissues

Sharing our recent article in Nature that uncovers a surprising aspect of the mechanics of epithelial tissues, termed ‘active superelasticity’, which allows them to undergo extreme reversible deformations under constant tension - https://www.nature.com/articles/s41586-018-0671-4 (read-only link: https://rdcu.be/batkj)

kamal paknejad's picture

memory surface hardening model

Hi every one, im tring to implement memory surface hardening model to abaqus via umat subrotin. is there one that did the same or can give me some information. thanks alot. with best regard. paknejad

Mike Ciavarella's picture

On stickiness criteria for multiscale random rough contacts

We have just submitted a paper which solves a problem that I have been struggling to solve for many years.

Any comments are welcome to improve, while the paper goes the standard review process in the journal we submitted it.

 

Mike Ciavarella's picture

fatigue: overstressing and understressing

 

While teaching some students from old textbooks, I found reference to "understressing and overstressing" as producing effects into fatigue limits.    Looking at classical papers like  W SCHUTZ, A HISTORY OF FATIGUE Engineering Fracture Mechanics Vol. 54, No. 2, pp. 263-300, 1996, he says that the theory of understressing was largely a mistake due to statistically poor testing.  However, I see some chinese papers still talk of understressing, see below.

 

Antonio Papangelo's picture

Multistability and localization in forced cyclic symmetric structures modelled by weakly-coupled Duffing oscillators

Many engineering structures are composed of weakly coupled sectors assembled in a cyclic and ideally symmetric configuration, which can be simplified as forced Duffing oscillators. In this paper, we study the emergence of localized states in the weakly nonlinear regime. We show that multiple spatially localized solutions may exist, and the resulting bifurcation diagram strongly resembles the snaking pattern observed in a variety of fields in physics, such as optics and fluid dynamics.

Post-Doctoral Position – Thermal Transport in Crystalline Solids

The Materials Theory Group at the School of Materials Engineering of Purdue University has a post-doctoral opening in the area of physics of thermal transport in crystalline solids. The postdoc will use Boltzmann Transport Equation (BTE) approach to investigate the phonon and electron thermal transport in crystalline solids with lattice defects. A solid state physics background is highly desired for this position but applicants with a strong, closely related theory background from materials science or other engineering disciplines will be considered. The ideal candidate is one who is strongly interested in the fundamental theoretical concepts related to thermal transport and related computational modeling, and must have excellent programming skills in Fortran and/or C++. For inquiry please send an email to Professor Anter El-Azab (aelazab@purdue.edu). The position will remain open until filled. Interested candidates can send a curriculum vita with list of publications, a one-page or less statement of research interests and the names of at least two references, with their email addresses and telephone numbers to the provided email. The Materials Theory Group performs theoretical and computational research in the areas of mesoscale plasticity and dislocation dynamics, radiation effects in materials, microstructure evolution, phase field method development, phonon and electron thermal transport in crystalline solids, and computational methods for materials science and mechanics. The group has over ten graduate students and postdocs, with a wide range of collaborations.
EEO/AA Policy
Purdue University is an EOE/AA employer. All qualified individuals, including minorities, women, individuals with disabilities, and veterans are encouraged to apply.

Constraint on a beam bottom surface not on the neutral axis

Hi!

I have a question regarding the beam deflection. As shown in the pic, the roller constraint is applied on the bottom of the beam(Beam A) rather than neutral axis(Beam B). Could anybody help to provide some information about Beam A hand calculation?

Thanks!

https://files.fm/u/54jwqnru#sign_up

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