Hi all,
Im trying to make my structure fail within a desired region. The system consists of 2 different polymer-blocks stacked on top of each other, see the appended figure. The simulation box is fully periodic and im pulling in z-direction using fix deform. So far, the structure fails at the soft phase.
Im not sure whats the least unphysical way to manage this. I’ve tried apply a fix rigid/npt on a thin region of the rubber-phase close to the upper/lower box boundaries. Of course this leads to missing bonds,angles, dihedrals,…
Do you have any suggestions?
thanks for reading,
best regards.
What is incorrect about failing at the soft phase (pa6, is it?). If the model (a combination of the structure, chosen potential, and its parameters) wants it to break at the soft phase, a measure trying to supress this outcome would be an unphysical manipulation. If, on the other hand, failing at the soft phase is unphysical and is not observed in real experiments, then I would worry about the potential and its parameters.
Ray
hi ray,
thx for ur reply. Of course ur right. Its plausible that the structure fails at the soft phase (rubber)
But I’m more interested in the interfacial properties.
best regards.
What is incorrect about failing at the soft phase (pa6, is it?). If the model (a combination of the structure, chosen potential, and its parameters) wants it to break at the soft phase, a measure trying to supress this outcome would be an unphysical manipulation. If, on the other hand, failing at the soft phase is unphysical and is not observed in real experiments, then I would worry about the potential and its parameters.
Ray
I see. What is your pulling speed and the resulted strain rate? If the pulling speed is above the speed of sound in rubber, it would create a shock wave and could affect the properties of rubber. Even if the pulling rate is smaller than the speed of sound, a high strain rate could break a lot of things.
In addition to reducing the strain rate, fix deform has a “remap x” keyword that would remap the atom positions into deforming box, which could reduce the unpleasant effect from shockwave/high strain rate.
Ray
Hi Ryan,
I use different strain-rates ranging from 1E-7 to 5E-6. I also use remap x by default.
My idea now is to apply fix deform to a specific region (see appended figure) which only includes parts of my rubber close to the interface. Do you think that might work?
regards.
I see. What is your pulling speed and the resulted strain rate? If the pulling speed is above the speed of sound in rubber, it would create a shock wave and could affect the properties of rubber. Even if the pulling rate is smaller than the speed of sound, a high strain rate could break a lot of things.
In addition to reducing the strain rate, fix deform has a “remap x” keyword that would remap the atom positions into deforming box, which could reduce the unpleasant effect from shockwave/high strain rate.
Ray
Sorry, i meant ray not ryan …
Hi Ryan,
I use different strain-rates ranging from 1E-7 to 5E-6. I also use remap x by default.
My idea now is to apply fix deform to a specific region (see appended figure) which only includes parts of my rubber close to the interface. Do you think that might work?
regards.
I see. What is your pulling speed and the resulted strain rate? If the pulling speed is above the speed of sound in rubber, it would create a shock wave and could affect the properties of rubber. Even if the pulling rate is smaller than the speed of sound, a high strain rate could break a lot of things.
In addition to reducing the strain rate, fix deform has a “remap x” keyword that would remap the atom positions into deforming box, which could reduce the unpleasant effect from shockwave/high strain rate.
Ray
It might, depending on how you integrate all these atoms. I would use NVE for the entire region, unless you wish to regulate the temperature at some finite value. If that is the case, I would thermostat the very top/bottom rubber atoms and perhaps the middle purple region.
Though for your current set up, you don’t even need rubber atoms that are outside the region…
Ray