# Farouk Maaboudallah

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Non Linear Static Analysis, Complex Eigenvalues Analysis, Modal Analysis, Transient Analysis, Stochastic meta model
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1. ## Model analysis

Hi, First, you are running Real Eigenvalues Analysis using Lanczos solver (EIGRL). V1 and V2 mean the lower and upper bound of your frequency domain. ND means the number of roots (number of eigenvalues) of the following equation : (-w^2*M - K)*phi = 0 with w refers to the real eigenvalue and phi means the eigenvectors. Cheers,
2. ## Compliance formula

In general, you have to use the correct formula (see my first comment). But for the optimization, it's the same ... In other words, the minimization problems MIN C(x) = U^T * K * U or MIN MIN C(x) = 1/2* U^T * K * U has the same solution X_s Cheers,
3. ## Compliance formula

By definition, the compliance is : C = 1/2 \int \epsilon * \sigma * \epsilon dv which corresponds to your first equation C = 1/2 u^T * K * u It's a strain energy (that's why we have 1/2) that measures the displacement of the structure under the defined BC.

5. ## Solving Linear and Nonlinear Models? Direct / Iterative methods?

In general, you can do what you want : you can use an iterative or direct solver. Direct solvers are recommended if your models are highly nonlinear (frictional contact for example). But they are time consuming especially if your models contain more than 1 millions dof (approximately). If you perform a non linear static analysis, Optistruct use a direct solver (MUMPS). You don't need to configure it.
6. ## Error #13

I think you have 2 duplicated nodes. Try to delete the duplicated one.
7. ## CNTNLSUB

Hi, In my models, I use CNTNLSUB (in the second step). Does it work with you ? Best regards,
8. ## thermal analysis of hyperelastic materials

Do you want to perform a thermal - structural analysis ? or only thermal analysis ? Because I don't understand the use of MATHE for thermal simulation ....
9. ## Contact between 2d and 3d

I tried to run a simulation yesterday. All the nodes of the model are in the global coord. and I applied a load on a NSET in local coord and it worked ... Is that what you want to do ? please correct me
10. ## thermal analysis of hyperelastic materials

Hi, You can use the MATHE, choose your model (for instance Mooney Rivalin) and then use mechanic and thermal properties. Best regards,
11. ## Contact between 2d and 3d

Did you assign all the nodes of the model to the local coord. or only the NSET where you want to apply an SPC or Force ?
12. ## Contact between 2d and 3d

Yeah you can do it using this option : and
13. ## Contact between 2d and 3d

Sorry mate, I forgot it ! If I understand, do you want to apply an SPC following a "relative" direction ?
14. ## Contact between 2d and 3d

RBE2 allow you to define a rigid body whose independent dofs are specified on the first node (which is single = only one node) and the dependent dofs are specified on the second one (they can be more than one node ...) . RBE3 allows you to define the motion of one node (we call it referent point) by an average (weighted average) of the motions of a set of nodes.
15. ## Contact between 2d and 3d

Hi, I'm gonna start with the second question. The difference between S2S, N2S or N2N discretization is : S2S allows to create a lot of contact element, so with it we will obtain a normal contact pressure more uniform and smooth that the others discretization. I can send you an academic contact model if you want the see the difference between S2S and N2S. Best regards,
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