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Ajeet Kumar's picture

Microscopic definition of internal force, moment and associated stiffnesses in one-dimensional nanostructures at finite temperature

We present a one-dimensional variant of the Irving-Kirkwood-Noll procedure to derive microscopic expressions of internal contact force and moment in one-dimensional nanostructures. We show that these expressions must contain both the potential and kinetic parts: just the potential part does not yield meaningful continuum results. We further specialize these expressions for helically repeating one-dimensional nanostructures for their extension, torsion and bending deformation. As the Irving-Kirkwood-Noll procedure does not yield expressions of stiffnesses, we resort to a thermodynamic equilibrium approach to first obtain the Helmholtz free energy of the supercell of helically repeating nanostructures. We then obtain expressions of axial force, twisting moment, bending moment and the associated stiffnesses by taking the first and second derivatives of the Helmholtz free energy with respect to conjugate strain measures. The derived expressions are used in finite temperature molecular dynamics simulation to study extension, torsion and bending of single-walled carbon nanotubes and their buckling.
The article will soon appear in the Mathematics and Mechanics of Solids. The same can be accessed at the following link: https://www.researchgate.net/publication/337873624_Microscopic_definitio...

Post-Doctoral Position in Modeling of 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 modeling of thermal transport in crystalline solids. The postdoc will use Boltzmann Transport Equation approach to investigate the phonon and electron thermal transport in crystalline solids with defects. Applicants with closely related theory background in physics, materials science, mechanical engineering, or other majors are encouraged to apply. The ideal candidate is one who is strongly interested in the fundamental concepts of thermal transport and related computational modeling, and must have excellent programming skills. To apply, please send a curriculum vita with list of publications and the names and contact information of two references to Professor Anter El-Azab (aelazab@purdue.edu). The cover letter should explain the relevance of the applicant background to the postdoc research topic above. This position is part of the DOE funded Energy Frontiers Research Center for Thermal Energy Transport under Irradiation (TETI), and the postdoc is expected to collaborate with a large team of theorists and experimentalists. The position is available now and will remain open until filled.

Plane stress Abaqus UMAT

Choose a channel featured in the header of iMechanica: 

Hello everyone,

I have created a UMAT code for J2 elasto-plasticity with isotropic hardening for 3D solid elements.

At this point I would like to support also plane stress shell elements. What changes in the code are

suggested? The already implemented code, takes as input the strain tensor at time tn and the strain

increment tensor and updates the stress at time tn+1 and calculates the material Jacobian and 

achieve quadratic convergence. The stress and strain tensors are manipulated as 6x1 vectors and the 

Rashid K. Abu Al-Rub's picture

Novel Metamaterials based on Triply Periodic Minimal Surfaces

Recently, there has been a growing interest in investigating the multi-functional properties of novel types of metamaterials, metastructures, and metacomposites based on triply periodic minimal surfaces (TPMS). TPMS have been discovered more than 160 years ago and thanks to additive manufacturing (3D printing) they become reality only recently and opend the doors for several applications.

Davide Bigoni's picture

Structures loaded with a force acting along a fixed straight line, or the “Reut’s column problem”

How to provide a structure with a force lying on a fixed line?
We provide the answer to this question in our paper: Bigoni and Misseroni (2019) Structures loaded with a force acting along a fixed straight line, or the “Reut’s column problem”.
Journal of the Mechanics and Physics of Solids.
Enjoy watching our video below (would you have trouble playing video on YouTube, click here to watch it).

Davide Bigoni's picture

Configurational forces and nonlinear structural dynamics

How a mass falls when attached to a flexible element with varying length?
We provide the answer to this question in our paper: Armanini, Dal Corso, Misseroni, Bigoni (2019) Configurational forces and nonlinear structural dynamics.
Journal of the Mechanics and Physics of Solids.
Enjoy watching our video below (would you have trouble playing video on YouTube, click here to watch it).

Francesco Dal Corso's picture

The Elastica Catastrophe Machine

May a catastrophe machine be realized through an elastic continuous element?
We provide a positive answer to this question in our paper: Cazzolli, Misseroni, Dal Corso. Elastica catastrophe machine: theory, design and experiments. Journal of the Mechanics and Physics of Solids.

Enjoy watching our videos below (would you have trouble playing videos on YouTube, click here to watch them).

Fan Xu's picture

Functionalized helical CNT fibre bundles as biosensors for healthcare

Mechanical mismatches between implanted electronics and biological tissues can lead to inaccurate readings and long-term tissue damage. Here, we show that functionalized multi-walled carbon nanotubes twisted into helical fibre bundles that mimic the hierarchical structure of muscle can monitor multiple disease biomarkers in vivo. The flexible fibre bundles are injectable, have a low bending stiffness and display ultralow stress under compression.

vh's picture

Prediction of forming limit diagrams using machine learning

Measuring forming limit diagrams (FLDs) is a time consuming and expensive process. Machine learning (ML) methods are a promising route to predict FLD of aluminium alloys. In the present work, we developed a machine learning (ML) based tool to establish the relationships between alloy composition / thermomechanical processing route to the material's FLD.

Emilio Martínez Pañeda's picture

Mode II fracture of an elastic-plastic sandwich layer

Dear iMechanicians,

Please find below a paper, co-authored with Ivan Cuesta and Norman Fleck, on the mode II fracture of elastic-plastic sandwich layers. The paper is part of the special issue in the Journal of Applied Mechanics dedicated to John Hutchinson's 80th anniversary and the Century Fracture Mechanics Summit.

Stephan Rudykh's picture

Soft Magneto-Active Composites

"Soft magnetoactive laminates: large deformations, transverse elastic waves and band gaps tunability by a magnetic field"  by  N. Karami Mohammadi et al (2019) has been published in November Special Issue in Journal of Applied Mechanics.

This paper is part of my group and co-author work on the topic of Soft Magneto-Active Composites:

Teng zhang's picture

Harnessing energy landscape exploration to control the buckling of cylindrical shells

Abstract: Even for relatively simple thin shell morphologies, many different buckled configurations can be stable simultaneously. Which state is observed in practice is highly sensitive to both environmental perturbations and shell imperfections. The complexity and unpredictability of postbuckling responses has therefore raised great challenges to emerging technologies exploiting buckling transitions.

interfacing matlab with abaqus script using a user subroutine

Dear all,

the question is in the title.

I found solutions on the web to make matlab execute an inp file making use of a user subroutine: system(['abaqus job=' Abaqusname  ' user=' fortranname ' -inter']). It works well if, prior to the command,  a dll file of the fortran file is created and a file 'abaqus_v6.env' is set.

However, if I want to do the same by running, from matlab, the python script which makes use of the same user subroutine, there are errors.

command in matlab: system(['abaqus cae noGUI=script.py']);

Yong Zhu's picture

Experimental Mechanics call for papers

Please see the attached flyer from Editor-in-Chief Ioannis Chasiotis. 

martin.levesque's picture

Post-doctoral fellowship position at Polytechnique Montréal on phase field modelling

Polytechnique Montréal is looking for a post-doctoral fellow having a very strong training in continuum mechanics/numerical methods to work on the phase field modelling of damage in materials. This one-year project will consist in deploying and applying an existing phase field code at two industrial partners: one in optics and the other in aerospace. 

Please send your CVs at my address: martin.levesque(at)polymtl.ca

cemalbasaran's picture

Entropy Special Issue

 

Deadline for manuscript submissions: 30 November 2019

 

Special Issue "Entropy Based Fatigue, Fracture, Failure Prediction and Structural Health Monitoring"

https://www.mdpi.com/journal/entropy/special_issues/fatigue

 

Dr. Hanaor - Department of Ceramic Materials - TU Berlin's picture

Electro-mechanical behaviour or rough surfaces

Understanding electrical contact resistance 

Electrical contact resistance at interfaces between pairs of rough surfaces is of great importance in the performance of diverse systems, particularly in miniaturised electromechanical systems containing switches.

 

In this study, the role of pressure and surface structure is explored with a view towards gaining a beter understanding of electrical contact resistance.

 

Scholarships for Postgraduate Research Students to study at Swinburne University of Technology in Australia

There are several PhD scholarships at School of Engineering, Swinburne University of Technology, Australia. The scholarship includes the annual stipend AU$27,596 for three years (with possible 6 months extension). The focus of the research will be on topology optimization of structures, materials, and metamaterials.

To be successful in this role you will need to demonstrate the following:

CMiculas's picture

How to import edited node coordinates (mesh) to Abaqus?

Choose a channel featured in the header of iMechanica: 

import modified nodes coordinates to abaqus

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