Please, see the attachment.

Your question is too general since you did not explain what material you are interested to use, however, as far as I understood you want to create a representative volume element (RVE) and define its strength. In my opinion, the first step would be defining the material which can be linear, nonlinear, hyperelastic and etc. Then you need to create the RVE and apply compression uniaxial loading condition (Loads pointing towards each other). Also, apply a weak spring to your model which enables better convergence in your model (i.e. for avoiding rigid body motion). After the analysis is over you can estimate the strength based on the failure criteria that you are checking against with.

Dear Hamidreza Ahmadi Moghaddam

Thank you for your answer;

I've generated my RVE and I want to find the Compressive Strength of that, material is linear elastic.

When I put a pressure on it (I've tried it with large values), RVE has its linear deformation without any stop point, I want to know how I can calculate it's maximum Compressive Strength. you know, I'm looking for a way to find at which pressure my RVE will be ruptured?

Off course deformation continues without any stopping point, because of the linear model defined in the analysis.

If you the RVE is consist of only one material, in my opinion, you need to find the failure criteria for that material based on experimental data (published data in literature) and then use that information for defining maximum pressure or force required to yield.

If your model was nonlinear, then you just needed to gradually increase the pressure (force) up to certain point that your analysis was not able to converge which is not your case.

Are you modelling a composite material?? I mean the RVE consist of different materials or just one material??

Hamidreza Ahmadi Moghaddam

Yes I am modelling a composite material. I have designed a simple RVE with two materials.

the problem is that when I've added the maximum compressive strength of the materials (either Fiber or Matrix) in the material properties in Ansys workbench, and when I put a pressure on that, I can not find the failure point.

Can we use the safety factor as a parameter, and check its value for finding the failure point?

For example when Our safety factor becomes less than 1 in a point of the RVE, Can we say it will fail from that point? or should We use the failure criterias?

OK. That was my first guess. So if you are modelling a composite RVE, then you can calculate mechanical properties such as effective modulus of elasticity or Poisson's ratio numerically. However, remember that for defining failure criteria you need to perform experiments.

I suggest that you use uniform displacement instead of pressure or force. This way you can make sure that same strain were applied to all the nodes located across the RVE surface, extract normal stresses from numerical analysis and finally you can calculate the modulus of elasticity using Hooks law. Remember to use the following equation for calculating the strain.

e = Ln (l/L)

where l is the corresponding RVE length measured after applying uniform displacement and L is the initial RVE length.

Good luck!!

Hamidreza Ahmadi Moghaddam

Thank you very much.