Boundary conditions help- Tensile Test

Dear All,

I want to conduct a tensile test in Y and keep X fixed (not allow X dir deformation) -shown in the setup figure. I am using fix deform. I read the documentation for remap command but am not understanding clearly.

I was currently using " fix def all deform 1 y erate ${strainrate} units box remap x"

Thanks for your help in advance!

Setup.png

There is a lot of doc info on the remap option on the fix deform doc page, including

examples of how to use it. What part is not clear? It even

suggests what to use for solids, which I presume is what

you have.

Steve

Dear Dr Steve,

Thanks for your reply. I read through the documentation and yes, I am using it for solids.

My doubt was how to restrict X direction motion (should it be through scale or npt aniso or any other way). I am sorry, it is not very clear to me.

If your boundary condition in x is periodic and there is no free surface in that direction, then you do not have to do anything. The average strain in x will be zero, at least until you get void formation of large voids, at which point everything gets more complicated. If you have a free surface in x direction (as in your attached sketch Setup.png), then in order to prevent strain in x direction you will have to fix the x coordinates of atoms near the boundary. There are multiple ways to do this. One way to do this would be to set the x-velocity of surface atoms to zero at the start of the simulation, and the x-force to zero every timestep:

velocity surface set 0.0 NULL NULL
:
:
fix xfix surface setforce 0.0 NULL NULL

Whatever method you use, you should test it out on a small system and examine the resultant structures carefully using visualization or strain analysis to make sure things are working correctly.