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Harold S. Park's picture

Journal Club Theme of June 2016: 2D Materials: Current and Future Directions

Two-Dimensional (2D) materials have been widely studied since the discovery of graphene in 2004.  Many of the initial works on the various 2D materials (graphene, MoS2 and other transition metal dichalcogenides, black phosphorus, and others like the monochalcogenides) by mechanicians focused on issues like ideal strength, and appropriate methods to calculate the bending modulus.  Some of these, and other issues, were reviewed by Sulin Zhang in a J-Club from March 2015 (http://imechanica

sol (amount of solute in entire model)

hi

during a mass diffusion step, what is the unit of the history output sol (amount of solute in entire model)?

any help is appreciated

Ajeet Kumar's picture

Effect of material nonlinearity on spatial buckling of nanorods and nanotubes

You may be interested in reading our following article: http://link.springer.com/article/10.1007/s10659-016-9586-1. We show the importance of incorporating material nonlinearity for accurate simulation of nanorods and nanotubes. The linear material laws are shown to give completely erroneous results. The nonlinear material laws for nanorods were obtained using the recently proposed "Helical Cauchy-Born rule". We also discuss how surface stress affects buckling in such nanostructures.

Hidroxid's picture

XFEM crack under compression.

Hi all,

 

I am doing crack modelling (XFEM) under moving compression and traction loading in Abaqus but I get warning regarding the crack under compression load as follows:

"THE LOADING CONDITION MIGHT MAKE MAIN CRACK UNDER COMPRESSION AT  NSET "X" THE CRACK PROPAGATION DIRECTION CANNOT BE PREDICTED. A VALUE OF ZERO IS PROVIDED FOR IT."

Anyone facing the same issue?

Kind regards,

Omid

SamInfinity's picture

ABAQUS: problem in applying pressure after element deletion

 In ABAQUS, how to apply a pressure field using vdload subroutine on a newly produced surface after deletion of elements from the top surface where the pressure field was actually applied? Or in other words, how to define a new surface for applying a pressure field, where the surface on which the pressure was initially applied is deleted with the evolution of damage. 

Wenbin Yu's picture

RVE analysis without BCs and periodic mesh requirements

RVE analysis becomes a routine exercise in material modeling. Usually it is carried out using finite element codes such as ABAQUS or ANSYS. The main thing one should pay attention is to applying the right boundary conditions. It is settled that periodic boundary conditions are the preferred boundary conditions to be applied. The BCs are that u_i-\epsilon_{ij}x_j should be equal on the corresponding edges. This type of boundary conditions can be applied using coupled equations constraints. This requires that one creates a mesh with corresponding nodes on periodic edges.

Flavio Stochino's picture

RC beams under blast load: Reliability and sensitivity analysis

The effects of blast loading on structures can be very dangerous: damages and failures are expected with serious threats to structural safety and human life. Materials stresses and strains are often pushed to the limit and the modelling of these phenomena can be very complex. In order to design blast-resistant structures it is very important to determine what are the key parameters of this problem.

 

ABAQUS, DLOAD, new active load surface, element deletion

Choose a channel featured in the header of iMechanica: 

Dear all,

Currently I am engaged in solving a geological problem. So we have some soil model in the form of disk, there is a circular hole in the center, which has the initial pressure at the reference time  (a modelling of the soil injection with the polymer compound)

How can I recalculate the normal pressure inside the circular hole of the soil model using the DLOAD subroutine if the neighbouring FEs were failed.

Mirkhalaf's picture

RVE size determination

  • Computational homogenization at finite strains is used to determine size of a Representative Volume Element (RVE).
  • This work proposes a statistical-numerical approach, based on two criteria, to define the appropriate RVE size undergoing different regimes of deformation.
  • The strategy is applied to randomly generated RVE samples of heterogeneous polymers.
  • The RVE size of Rubber Toughened Polystyrene is determined for two different volume fractions of inclusions.
Shuman_Xia's picture

Call for Papers: Experimental Mechanics Special Issue on “Mechanics of Energy Materials”

Advanced energy materials hold one of the keys to fundamental advances in the conversion, storage, and harvesting of energy for a broad range of consumer electronics, automotive, aerospace, and defense applications. The successful development and deployment of these materials relies critically on a fundamental understanding of strongly coupled multiphysics phenomena.

Simulate graphene layers in Abaqus/Explicit

Dear all, I want to simulate graphene layers in Abaqus/Explicit. To connect two layers, I follow van der Waals forces and apply non-linear spring elements. One problem I have faced is how to choose the unit scale when simulating. If I choose SI(m) or SI(mm), I can not get the visualization of simulation results. I have read some papers which talk about using A, ev/A and eV/A3 for length, force and Young's modulus.

keyhani's picture

An efficient computational technique for modeling dislocation–precipitate interactions within dislocation dynamics

A new computational technique for modeling dislocation interactions with shearable and non-shearable precipitates within the line dislocation dynamics framework is presented. While shearable precipitates are modeled by defining a resistance function, non-shearable ones are modeled by drawing a comparison between the two well-known Orowan and Frank–Read mechanisms. The precipitates are modeled directly within the dislocation dynamics analysis without the need for any additional numerical methods.

Hamid Souri's picture

Electrical properties and piezoresistive evaluation of polyurethane-based composites with carbon nano-materials

The present study assesses the applicability of carbon materials-embedded polyurethane (PU) composites characterized by high piezoresistive capability, as a traffic loading sensor. PU composites incorporating multi-wall carbon nanotubes (MWNTs), expanded graphite (EG), and a hybrid of MWNTs and graphite nanoplatelets (GNPs) were fabricated and their electrical conductivities were measured in an effort to determine the most suitable filler type for the piezoresistive sensor and its optimum content ratio.

Hamid Souri's picture

A facile method for transparent carbon nanosheets heater based on polyimide

In this work, a novel film heater in nanometer-scale thickness based on catalyst-free and transfer-free carbon nanosheets (CNSs) with properties similar to graphene is fabricated. Here, poly(amic acid) (PAA), which is composed of several aromatic hydrocarbon rings, is used as the carbon precursor of CNS films. Altering the polymer concentration easily controls the morphological, optical, and electrical properties of the CNS films obtained by carbonization of PAA thin films.

Search engine for postdoc or faculty posiotn in USA

What is best way to seach for postdoctoral position or faculty position in USA?

I am aware that in iMechanica some positions are posted but the number of positions is limitted. I would appriciate any advice from people in the US. Thanks!

Regards,

Harley T. Johnson's picture

A critical thickness condition for graphene and other 2D materials

B. C. McGuigan, P. Pochet, and H. T. Johnson, Critical thickness for interface misfit dislocation formation in two-dimensional materials, Phys. Rev. B 93, 214103, 2016.

URL: http://link.aps.org/doi/10.1103/PhysRevB.93.214103

draw the mass gain curve over time

Hello

I want to draw the mass gain curve over time, it follows the Fick law but the results I obtained are either instantaneous or ramp.

how to draw?

thank you

Square to parallelogram

I am trying to model a rigid box which deforms into a parallelogram on application of

displacement/velocity. I have made a box using 4 rigid plates ,but when I apply

the shear force the plates lose contact. I have used no seperation technique 

it didn't help .kindly give a solution asap.

Fillet Weld in ABAQUS

Choose a channel featured in the header of iMechanica: 

Hello everyone,

I want to model a connection between two steel plates which form a T-section. The welds are fillet weld. Do you have any recommendation how to model the weld? One way I think of is to connect the two plates with two solid elements weld through tie constraint. You think that's a right way of doing that? 

soheil.tahmasbi's picture

Excessive rotation of Nodes/ ABAQUS explicit

Choose a channel featured in the header of iMechanica: 

I am simulating dynamic impact using B31 element type and general contact in ABAQUS Explicit and the job is aborted showing the error of "Excessive rotation of nodes". I, also, used mass scaling to control the run time.
Does anyone know how to control this problem?

I really appreciate your replies.

 

Alejandro Ortiz-Bernardin's picture

Linear smoothed polygonal and polyhedral finite elements

Paper Accepted for Publication in International Journal for Numerical Methods in Engineering

Linear smoothed polygonal and polyhedral finite elements

A. Francis, A. Ortiz-BernardinSPA. BordasS. Natarajan

ABSTRACT

Payam Soltani's picture

A short note on equal peak design for the pendulum tuned mass dampers

By: A. Deraemaeker and Payam Soltani
Abstract:
Pendulum tuned mass dampers (PTMDs) are used to passively mitigate the vibrations of tall structures and buildings. The main objective of this short note is to introduce analytical formulae for the optimum design of the linear PTMD coupled to an undamped primary system. Den Hartog's equal peak method is applied to derive the optimum design. With the mass ratio between the primary system and the PTMD, the optimum length and optimum damping of the pendulum are calculated. The formulae are presented in both dimensional and non-dimensional forms and are simple to apply in real applications. It is also shown that the vibration mitigation performance of the proposed optimum design precisely matches the results obtained by numerical optimisation techniques.
doi: 10.1177/1464419316652558

https://www.researchgate.net/publication/303716296_A_short_note_on_equal...

Dennis M. Kochmann's picture

Travel Grants for USACM Workshop on Nanoscale Computational Mechanics

A USACM Thematic Workshop on Recent Advances in Computational Methods for Nanoscale Phenomena will be held at the University of Michigan in Ann Arbor from August 29-31, 2016. The workshop website contains further information at http://acm-nano2016.usacm.org.

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