2014-02-13 02:05:01 +08:00
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<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
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<HR>
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<H3>compute dilatation/atom command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>compute ID group-ID dilatation/atom
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</PRE>
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<UL><LI>ID, group-ID are documented in compute command
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<LI>dilation/atom = style name of this compute command
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>compute 1 all dilatation/atom
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Define a computation that calculates the per-atom dilatation for each
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atom in a group. This is a quantity relevant for <A HREF = "pair_peri.html">Peridynamics
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2014-02-13 07:25:05 +08:00
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models</A>. See <A HREF = "PDF/PDLammps_overview.pdf">this document</A>
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for an overview of LAMMPS commands for Peridynamics modeling.
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2014-02-13 02:05:01 +08:00
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</P>
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<P>For small deformation, dilatation of is the measure of the volumetric
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strain.
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</P>
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<P>The dilatation "theta" for each peridynamic particle I is calculated
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as a sum over its neighbors with unbroken bonds, where the
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contribution of the IJ pair is a function of the change in bond length
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(versus the initial length in the reference state), the volume
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fraction of the particles and an influence function. See the
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<A HREF = "http://www.sandia.gov/~mlparks/papers/PDLAMMPS.pdf">PDLAMMPS user
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guide</A> for a formal
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definition of dilatation.
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</P>
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<P>This command can only be used with a subset of the Peridynamic <A HREF = "pair_peri.html">pair
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styles</A>: peri/lps, peri/ves and peri/eps.
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</P>
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<P>The dilatation value will be 0.0 for atoms not in the specified
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compute group.
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</P>
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<P><B>Output info:</B>
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</P>
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<P>This compute calculates a per-atom vector, which can be accessed by
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any command that uses per-atom values from a compute as input. See
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Section_howto 15 for an overview of LAMMPS output options.
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</P>
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<P>The per-atom vector values are unitlesss numbers (theta) >= 0.0.
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</P>
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<P><B>Restrictions:</B>
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</P>
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<P>This compute is part of the PERI package. It is only enabled if
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LAMMPS was built with that package. See the <A HREF = "Section_start.html#start_3">Making
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LAMMPS</A> section for more info.
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</P>
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "compute_damage.html">compute damage</A>, <A HREF = "compute_plasticity.html">compute
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plasticity</A>
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</P>
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<P><B>Default:</B> none
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</P>
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</HTML>
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