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Hi Ranu,

Could you please elaborate your question possibly with drawing or sketch? What is the expected deformation of unit cell for each direction periodic condition?

If you want to apply your own constraints then do the following steps 1. Activate the Equation-Based Contribution option from the Show More Option icon under the Model Builder. 2. Right click on the Solid Mechanics interface and locate the More (edge level) menu. 3. You will find the Pointwise Constraint, Weak Constraint features to apply your own constraints. 4. Find similar menu at point level if you wish to do same at different nodes.

Regards Amit

thanks Amit sir first you tell me how we apply boundary pair in inclined strut .here we apply cell periodicity to find homogenized elastic properties in x and y direction.so we apply unit strain in x and y by load cases. i get correct value of poissons's ratio. because it is negative poission ratio material so we get nagative is correct.but I donot get stress value correct it is 10 times higher than apporximately correct value. I donot apply bp in inclined strut. how we apply boundary pair in inclined strut. I also attach my mph file and Image of code to find properties. what error in application of my cell periodicity please tell me. if no than how we apply equation based boundary condition in edges like edge1-edge2=0.1732 similar for all edge pair in my reentrant structure which similar to abaqus periodic boundaru condition by equation.

Hi Ranu,

I can see that you have raised similar question through a support case where our support engineers are trying to resolve your query. I advice you to ask your questions though your support case in order to avoid two person working on same case.

Regards Amit

that question is different here we want to know about cell periodicity and i got repose but i caanit ger right answer please help me . if you said i raise a query,

Hi Ranu,

I looked into the model, the cell volume drop-down in the cell periodicity feature should be set user defined with volume = 17.32[mm]50[mm]15[mm].

Cell volume should set to automatic for unit cells which do not have any internal voids. With above change the stresses should be in the similar range as you expected.

Regards Amit

thank you so much Amit sir for helping me .

Dear amit sir, How we find the effective density by using comsol multiphysics of my periodic reentrant structure structure.

Dear Ranu,

To find effective density you do not need periodic boundary conditions. You can use the rule of mixtures to find the effective density. Effective density = integration(density*thickness)/V, where V = 17.32[mm]50[mm]15[mm]. Integration is performed over the cell domains.

Regards Amit