Stretching test for mechanical property

Hello everyone,

I am doing mechanical test by stretching a nano tube. The two end of nano tubes are clipped and one end is kept fixed and other end is stretched by applying displacement. In between stretching the system is relaxed (quasi static loading). Apart from velocity what can I use for loading. the all boundary is periodic so I though velocity command would be suitable for this.
Am I correctly applying quasi static loading. Please suggest me some better approach if there is any.
This is my script

----- setting-------------------------

units metal
atom_style atomic

boundary p p p
newton on

dimension 3

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I am getting error in stress calculation section in this script.

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http://lammps.sandia.gov/doc/compute_stress_atom.html

In addition to “velocity set”, you can also use “fix move” to move the top end. Note you’d have to have enough vacuum space for the top end to move – otherwise you are just colliding the top end against the bottom end through the PBC.

Alternatively, you can use “fix deform” to deform the entire box but you’d get the strained mapped to the entire length.

Ray

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Can you post the error message? I don’t see one in your original post. Thanks

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Hi Ray,

In this script file. I am getting this error message

thermo_style custom step etotal evdwl lx v_eps v_sxx pe temp press time
WARNING: New thermo_style command, previous thermo_modify settings will be lost (…/output.cpp:690)
thermo_modify temp new3d
WARNING: Temperature for thermo pressure is not for group all (…/thermo.cpp:480)

reset_timestep 0.0001
ERROR: Expected integer parameter in input script or data file (…/update.cpp:419)
Last command: reset_timestep 0.0001

What might be the possible reason behind this?

Arun

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Hi Ray,

In this script file. I am getting this error message

thermo_style custom step etotal evdwl lx v_eps v_sxx pe temp press time

WARNING: New thermo_style command, previous thermo_modify settings will be lost (…/output.cpp:690)
thermo_modify temp new3d
WARNING: Temperature for thermo pressure is not for group all (…/thermo.cpp:480)

reset_timestep 0.0001
ERROR: Expected integer parameter in input script or data file (…/update.cpp:419)
Last command: reset_timestep 0.0001

What might be the possible reason behind this?

Arun

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http://lammps.sandia.gov/doc/reset_timestep.html

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