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Bin Liu's picture

How to Realize Volume Conservation During Finite Plastic Deformation

Volume conservation during plastic deformation is the most important feature and should be realized in elastoplastic theories. However, it is found in this paper that an elastoplastic theory is not volume conserved if it improperly sets an arbitrary plastic strain rate tensor to be deviatoric. We discuss how to rigorously realize volume conservation in finite strain regime, especially when the unloading stress free configuration is not adopted in the elastoplastic theories.

Amir Abdollahi's picture

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.

On the origins of the electro-mechanical response of dielectric elastomers

Recent theoretical works have shown that the electro-mechanical performance of dielectric elastomers can be enhanced through micro-structural design.

Shuze Zhu's picture

Metallic and highly conducting two-dimensional atomic arrays of sulfur enabled by molybdenum disulfide nanotemplate

https://www.nature.com/articles/s41524-017-0041-z

Element sulfur in nature is an insulating solid. While it has been tested that one-dimensional sulfur chain is metallic and conducting, the investigation on two-dimensional sulfur remains elusive. We report that molybdenum disulfide layers are able to serve as the nanotemplate to facilitate the formation of two-dimensional sulfur.

Time Integration scheme for non constant M, C and K matrices?

Can anyone suggest a time integration scheme for non constant mass (M), stiffness(K) and damping (C) matrices? I am trying to solve a dynamic system (Ma+Cv+Ku=R) where the matrices M,C and K are time dependent.

 

Any thoughts/ideas will be highly aprreciated. Thank you. 

Time integration scheme for XFEM? (dynamic crack propagation)

Hello everyone,

 

Can somebody suggest an implicit/explicit time integration scheme when the matrices involved(M,C,K) are time dependent? (They change at every time step because of the crack tip enrichment functions which are time dependent).

 

I used the implicit Newmark scheme (trapezoidal/constant average acceleartion method) but just discovered that all my matrices (M,C,K) are time dependent where the original scheme is probably for constant M,C and K matrices. I used the scheme as in reference [1]. 

 

keyhani's picture

A comprehensive investigation of natural convection inside a partially differentially heated cavity with a thin fin using two-set lattice Boltzmann distribution functions

Natural convection occurs in many engineering systems such as electronic cooling and solar collectors. Nusselt number (Nu) is one of the most important parameters in these systems that should be under control. This investigation is a comprehensive heat transfer analysis for partially differentially heated cavities with a small thin fin mounted on the hot wall of the cavity to increase or decrease the Nu. A Boussinesq approximation was utilized to model the buoyancy-driven flow.

Journal Club for October 2017: Multiscale modeling and simulation of active matter

Tong Gao

Department of Mechanical Engineering and Department of Computational Mathematics, Science, and Engineering, Michigan State University

 

Introduction

mohsenzaeem's picture

Role of grain boundaries in determining strength and plastic deformation of yttria-stabilized tetragonal zirconia bicrystals

Mechanical properties of yttria-stabilized tetragonal zirconia (YSTZ) bicrystals under compressive loading are investigated by atomistic simulations. Previous studies on deformation of single-crystal YSTZ showed that some specific orientations promote dislocation emission, tetragonal to monoclinic phase transformation, or both. In this work, nanograins with different orientations are selectively combined to generate bicrystals with various grain boundaries (GBs).

Jingjie Yeo's picture

International Journal of Computational Materials Science and Engineering (IJCMSE)

As the Editorial Board member of IJCMSE, I enthusiastically welcome the high quality submissions from the community of iMechanica. The objective of the journal is the publication and wide electronic dissemination of innovative and consequential research in all aspects computational materials science and engineering, featuring the most advanced mathematical modeling and numerical methodology developments.

chenlei08's picture

Understanding cementite dissolution in pearlitic steels subjected to rolling-sliding contact loading: A combined experimental and theoretical study

Cementite dissolution behavior of pearlitic steels subjected to rolling-sliding contact deformation is comprehensively investigated by combining experimental characterization and phase-field modeling.

Fracture Mechanics Parameters Calculation

I'm working on Fracture Mechanics of Gravity dams using ANSYS Software.

Chiqun Zhang's picture

Finite element approximation of the fields of bulk and interfacial line defects

Chiqun Zhang            Amit Acharya            Saurabh Puri

A generalized disclination (g.disclination) theory [AF15] has been recently introduced that goes beyond treating standard translational and rotational Volterra defects in a continuously distributed defects approach; it is capable of treating the kinematics and dynamics of terminating lines of elastic strain and rotation discontinuities. In this work, a numerical method is developed to solve for the stress and distortion fields of g.disclination systems. Problems of small and finite deformation theory are considered. The fields of a single disclination, a single dislocation treated as a disclination dipole, a tilt grain boundary, a misfitting grain boundary with disconnections, a through twin boundary, a terminating twin boundary, a through grain boundary, a star disclination/penta-twin, a disclination loop (with twist and wedge segments), and a plate, a lenticular, and a needle inclusion are approximated. It is demonstrated that while the far-field topological identity of a dislocation of appropriate strength and a disclination-dipole plus a slip dislocation comprising a disconnection are the same, the latter microstructure is energetically favorable. This underscores the complementary importance of all of topology, geometry, and energetics in understanding defect mechanics. It is established that finite element approximations of fields of interfacial and bulk line defects can be achieved in a systematic and routine manner, thus contributing to the study of intricate defect microstructures in the scientific understanding and predictive design of materials. Our work also represents one systematic way of studying the interaction of (g.)disclinations and dislocations as topological defects, a subject of considerable subtlety and conceptual importance [Mer79, AMK17].

Feedback-Accelerated Picard Iteration for Orbit Propagation and Lambert’s Problem

This paper presents a new Feedback-Accelerated Picard Iteration method for solving long-term orbit propagation problems and perturbed Lambert’s problems. This method is developed by combining the collocation method and the variational iteration method over large-time-steps. The resulting iterative formulae are explicitly derived so that they can be directly adopted to solve problems in orbital mechanics. Several typical orbit regimes incorporating high-order gravity and air drag force are used to demonstrate the application of the proposed method in orbit propagation.

kolman's picture

The 2nd International Conference on Advanced Modelling of Wave Propagation in Solids

The 2nd International Conference on Advanced Modelling of Wave Propagation in Solids

 

September 17-21 2018

 

Institute of Thermomechanics, The Czech Academy of Sciences, Prague, Czech Republic

 

The 2nd International Conference on Advanced Modelling of Wave Propagation in Solids intends to concentrate on topics such as:

Zhengwei Li's picture

Harnessing Surface Wrinkling-Cracking Patterns for Tunable Optical Transmittance

Optical devices and systems with tunable optical transmittance have recently attracted great interest due to their wide range of applications. However, the reported methods of realizing tunable optical transmittance still suffer from complex fabrication processes, high cost, unstable materials or low tuning range. In this study, we report a simple, cheap, and highly effective approach to achieve large tuning range of optical transmittance through harnessing surface wrinkling-cracking patterns on PDMS films.

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