 # Farouk Maaboudallah

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## Everything posted by Farouk Maaboudallah

1. 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. 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. 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. 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. Hi, In my models, I use CNTNLSUB (in the second step). Does it work with you ? Best regards,
7. 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 ....
8. 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
9. Hi, You can use the MATHE, choose your model (for instance Mooney Rivalin) and then use mechanic and thermal properties. Best regards,
10. 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 ?
11. Sorry mate, I forgot it ! If I understand, do you want to apply an SPC following a "relative" direction ?
12. 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.
13. 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,
14. Yes. You can use elasto-visco-plastic (Hollomon and Norton law or ...) behaviour law as well. I joined an example of the modelling procedure. Cheers, Lauro-Oudin2003_Article_StaticAndDynamicBehaviourOfAPo.pdf
15. Hey Luis, Are you working on squeal simulation ? Best regards, FaroukM
16. Yeah you have it. It's non-linear static (index 5x2))
17. Hi PrasannaK, Any solution for the contact law implementation ? Cheers,
18. Why you don't have it ? If you create a new "Load Steps" you will not see Subcase Definition ?
19. Hi Ierik, There is a nice tutorial regarding pretension. Please find it in the following link https://altairhyperworks.com/hwhelp/Altair/2017/help/os/topics/solvers/1d_3d_pretensioned_bolt_analysis_of_ic_engine_components_r-1.htm#Z_1d_3d_pretensioned_bolt_analysis_of_ic_engine_components_r Cheers,
20. Hi mate ! You can use for example TIE constrain to link the master surface with the slave one. Normally, in contact problem we refine the mesh of the slave surface. But I think in your case, linear static analysis, there will be not so much difference. You can use the automatic mesher and mesh the parts using Tetra approximation. It's okay if you use Tetra finite element ... But in Nonlinear static analysis, we recommend to refine contact interfaces (slave surface) with S2S discretization to ensure the convergence of the contact pressure. You welcome mate
21. Hi guys ! For the TPU 95 A material, you can model it using MATHE card. Normally, we perform an optimisation simulation in order to identify the right coefficients (we assume Neo-Hook, Odgen, ... behaviour law). And then for FEM simulation, we use what we identified (in the optimisation procedure) to run for example Tensil Simulation ... Cheers,
22. Hi Prasannak, Thank you for your answer Yeah I now exponential, cubic laws .... The idea is for each NSET (Contact interface) we compute our own law ... For example, we assume that we want to perform contact simulation between 2 bodies (see the model below). The idea is to divide slave surface into 6 sub-surfaces and for each sub-surface we want to use a specific contact law (house development). Best regards,
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