Who can help me to solve the problem. I have modeled graphene layers in nano-scale in ABAQUS input file. I use ABAQUS COMMAND to solve, but when opening ODB file, I cannot see the model because it is too small. What should I do in this problem? Should I scale up from nano-scale to micro-scale? If scale up, how to change Van der Waals forces? Thank you very much!
Abaqus is dimension-independent. It means that the FEM solver doesn't really care about absolute dimensions, but to relative ones. Absolute dimensions can influence only the stability of the algorithms, as very small numbers (and very big as well) can introduce round-off errors that can propagate through the simulation. You thus can use the units of measurements best suited to your needs, and not only SI units.
In your case, I imagine the graphene sheet's dimensions are in the order of the nm (nanometers). Let's assume for the sake of clarity that they are 1 nm (T) x 100 nm (W) x 100 nm (L). If you use SI units, you provide to Abaqus the following numbers: 10^-9, 10^-7, 10^-7, where m (meters) is the reference unit. Forces are measured in 1 (Newtons). But you might as well change your reference unit to nm, and provide to Abaqus the following numbers: 1, 100, 100. You can do the same for all the primitive dimensions (length, time, mass) and then derive the scaling factor for the derived units.
For example, let's assume you change only the length. Forces will become:
F = v [N] = v [kg*m/s^2] = v [kg*10^9 nm/s^2] = 10^9 v [kg* nm/s^2] = 10^9 v [nN]
where F is the force (magnitude, direction and unit of measurement) and v its numerical value in N (assuming a 1D force).
Let's assume now you change the length from m to mm and mass from kg to t (tonnes). Forces will become:
F = v [N] = v [kg*m/s^2] = v [10^-3 t*10^3 mm/s^2] = 10^-3*10^3 v [t*mm/s^2] = v [10^3 kg*10^-3 m/s^2] = v [N]
i.e. they don't change.
In this way, your model is rescaled to provide a better visualization without compromising the physical soundness of the results.
I hope I've been clear and this is of some help to you.
Good luck with your work!
Abaqus is dimension-independent. It means that the FEM solver doesn't really care about absolute dimensions, but to relative ones. Absolute dimensions can influence only the stability of the algorithms, as very small numbers (and very big as well) can introduce round-off errors that can propagate through the simulation. You thus can use the units of measurements best suited to your needs, and not only SI units.
In your case, I imagine the graphene sheet's dimensions are in the order of the nm (nanometers). Let's assume for the sake of clarity that they are 1 nm (T) x 100 nm (W) x 100 nm (L). If you use SI units, you provide to Abaqus the following numbers: 10^-9, 10^-7, 10^-7, where m (meters) is the reference unit. Forces are measured in 1 (Newtons). But you might as well change your reference unit to nm, and provide to Abaqus the following numbers: 1, 100, 100. You can do the same for all the primitive dimensions (length, time, mass) and then derive the scaling factor for the derived units.
For example, let's assume you change only the length. Forces will become:
F = v [N] = v [kg*m/s^2] = v [kg*10^9 nm/s^2] = 10^9 v [kg* nm/s^2] = 10^9 v [nN]
where F is the force (magnitude, direction and unit of measurement) and v its numerical value in N (assuming a 1D force).
Let's assume now you change the length from m to mm and mass from kg to t (tonnes). Forces will become:
F = v [N] = v [kg*m/s^2] = v [10^-3 t*10^3 mm/s^2] = 10^-3*10^3 v [t*mm/s^2] = v [10^3 kg*10^-3 m/s^2] = v [N]
i.e. they don't change.
In this way, your model is rescaled to provide a better visualization without compromising the physical soundness of the results.
I hope I've been clear and this is of some help to you.
Good luck with your work!
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