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Simple strategies to produce perfect long range order in self-assembly

Submitted by Pradeep Sharma on

In a recent rapid communication (see attached paper), using principles of pattern formation, we expose some simple stategies to reliably produce perfect long range order in self-assembling systems. Most self-assembling systems exhibit short ranged order. This imperfection is detrimental to several practical applications. It is almost always possible to produce perfect patterns in small domain sizes but self-assembly over a larger areal span results in defects.

Composite analysis using SHELL99

Submitted by nadderdolatabadi on

I'm trying to model a composite structure with shell 99 element in Ansys.

I set the thickness and material no. in real constant and prepare an orthotropic material property for that. While ploting the result, as I expect to get the stresses among layers different from other points, but the result is a kind of uniform isotropic graph.

I don't know if any setting other than real constant and material property should be done to get a true result or not. and if I'm true then how can I read the true result.

I will appreciate any help.

Postdoctoral position in Computational Solid Mechanics - School Of Mechanical Engineering Purdue University

Submitted by marisolkoslowski on
A postdoctoral position is available starting Fall 2008 in the area of computational solid mechanics. A successful candidate is expected to have a strong background in multiscale modeling and programming experience. While experience in plasticity using finite element methods or dislocation dynamics is a plus , all outstanding candidates will be considered.

Using user subroutine UMAT in abaqus

Submitted by sanjay2008 on

Hi,

     Thanks for the earlier feedback. I was able execute the user subroutine (UMAT) along with *.inp file only to land into new type of error message:

fatal error lnk1112: module machine type 'IA64' conflicts with target machine type 'X86'

Can somebody please help me to understand what this error means and how to overcome this monster.

I have already installed intel fortran compiler, and microsoft visual studio for windows. 

As always thanks for the much needed help. 

 

Fatigue damage initiation - computational methods

Submitted by pragtic on
Choose a channel featured in the header of iMechanica

Dear iMechanicians,

It seems that nobody here is active in fatigue life prediction focused on the initiation period. I believe it should be here and do not understand why the fracture mechanics has its place here but the initiation of cracks has been forgotten. Although cracks are very interesting there is a lot industrial sectors, where they are not wanted. Is not the reason of the current situation that the available computational tools that are free are mostly related to crack growth?

Regards,

Jan Papuga

 

Measurements of near-ultimate strength for multiwalled carbon nanotubes and irradiation-induced crosslinking improvements

Submitted by Horacio Espinosa on

For more than 15 years, carbon nanotubes (CNTs) have been the flagship material of nanotechnology. Researchers have conceived applications for nanotubes ranging from microelectronic devices to cancer therapy. Their atomic structure should, in theory, give them mechanical and electrical properties far superior to most common materials.  

Using User Subroutine UMAT in abaqus

Submitted by sanjay2008 on

Hi,

Iam a new user of abaqus. I have a subroutine written in *.for format. I also have an input file *.inp . Both these programs are in the same folder. When I try to execute the *.inp file using the command

abaqus job=jobname datacheck interactive

I get a  message saying  "Abaqus/Standard Analysis exited with an error. please see the message file for possible error messages". I looked in the message file and it says ***ERROR: USER SUBROUTINE UMAT IS MISSING.

Then I used the command

abaqus job=jobname user=umat.for

Three-point bending

Submitted by ColinGrant on

For a three point bend test, the bending angle of the beam has to be small - so small that (theta)=tan(theta).... this is necessary to make a substitution of the reciprocal radius of curvature 1/R = M/EI... which then can be assumed to be the second derivative of the beam deflection.

Might sound stupid, but would the bending angle assumption be measured in degrees or radians?