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Re: [lammps-users] fracture after crack propagation (problem)
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Re: [lammps-users] fracture after crack propagation (problem)

From: Axel Kohlmeyer <akohlmey@...24...>
Date: Wed, 11 Oct 2017 06:48:55 -0400

On Wed, Oct 11, 2017 at 6:35 AM, sumit nagar <sn971489@...24...> wrote:

I have downloaded the epoxy resin file from PDB website .The search
string  "diglycidyl ether of bisphenol A" took me to a epoxy resin
3UUA which is a epoxy resin .Now i have loaded it over the graphene
sheet which i made from VMD nanotube builder .Now i converted it to
lammps readable format using "topo writelammpsdata filename" command
.Then i read it using read_data command in my lammps script .The
problem i am facing is that when i deform the box using "fix deform"
with a engineering strain rate the whole structure stretches like a
rubber band .It uniformly stretches the structure whereas i need the
fracture with epoxy and graphene showing cracks .The crack propagation
should lead to fracture .What checks an i missing ? The video of epoxy
with graphene is attached herewith but as the file is too large i have
received a mail from lammps owner and e-mail got rejected so i have
taken this out  . The data file epoxy with graphene is also attached
.The graphene along with epoxy resin in VMD lookslike the third

attachment (please open this file with MS-paint) but due to file size
extension i have to omit it also .I am also using
quartic bond_style in my input script(deform-able bonds )
. Where the problem lies ?

​impossible to say. there is no input script. attaching the data file is pretty much useless and a waste of bandwidth.
more importantly, you don't specify where you find suitable force field parameters. your data file does not contain meaningful topology data, so you have messed up even the steps listed before. again, this just demonstrates your complete and fundamental lack of knowledge of what you are aiming to do.

in addition, what you describe is likely the same situation like i already explained to you before: you are doing the deformation without any time integration.
i.e. you are ignoring whatever incorrect forces you compute. if you *had* included some time integration, your system would have likely collapsed.

as mentioned before. be smart, stop this nonsense. go and get properly trained.


Sumit ,Nagar
M.Tech (Production engg)
B.E (Production and Ind Engg)
MCSA 70-290 ,SQL (Oracle z -007)
ITIL certified ,MCAD 70-306
GATE 2006,2013

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Dr. Axel Kohlmeyer  akohlmey@...12...24...
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.