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Alberto B.

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Everything posted by Alberto B.

  1. I've solved the problem, with optistruct 14.0.210 the results are uncorrect, but updating with 14.0.211 the results become correct! Thanks for the support
  2. Hypermesh v14.0 full license and solvers patch 14.0.210
  3. Hello Prakash, I imported the geometry from a STEP file, then I meshed all on HyperMesh. I did the equivalence for the nodes in common for each body and imposed SPC as the model that i saw on other software. How is it possible that there are free nodes?? Thanks Alberto
  4. Hello Prakash, I sent the model. Thanks for the help Alberto
  5. Hello Prakash, yes I set a non linear quasi static as first loadstep and then a complex eigenvalue analysis as second loadstep with the nonlinear loadstep in STATSUB (PRELOAD). I used a sample solver deck, that Rahul R sent me, as guidelines (the name of this file is brake_squeal_example.fem), but with the same settings my model gave uncorrect results. In the image attached, you can see the results without FRICESL (fixed slope KT approach from the online help) on the left and those with setting of FRICESL on the right. The results on the left are bad for the too high and too low values (for example frequencies are too low); those on the right are bad because there aren't unstable modes (real parts of eigenvalues are all negative). I tried to change ND values in EIGC and EIGRL ,but I always got uncorrect results. Let me know if there is something i could try for solving this problem. Thank you for the help! Alberto
  6. Hello, I'm trying to make a complex eigenvalue analysis with a non linear quasi-static as preload for a brake model. The aim of this work is to determinate unstable modes and to study squeal phenomenon. Using the full version with solvers patch 14.0.210 I succeed to launch the analysis, but the modes extracted are all stable. I tried lots of contact configurations: with the HM contact manager, using gap elements and using superelements with DMIG matrix, but Optistruct always gave the same results. The only way to have unstable modes is to use frictional elastic slip distance , but in this way the calculated modes have too low frequencies and too high dampings that is not correct (I have correct results for this model from someone who used another software). All the used values are appropriate to simulate squeal phenomenon and congruent compared to the respective units of measure. Does Optistruct allow to perform this kind of work?? If yes, could anyone help me, please?? Thanks Alberto
  7. Hello Rahul, thanks for the help. I have an update that could be useful for you: I also succeeded to create CGAP elements with the spotweld function that allows to create 1d elements from nodes to nodes. Now I'm having another problem: the results of the modal complex eigenvalue analysis are bad. If I use fixed slope approach (fixed stiffness K_t) for the frictional contact I obtain complex modes with too high dampings and too low frequencies; instead if I use elastic slip distance approach I obtain good dampings and frequencies, but all the complex modes are stable (real parts of eigenvalues are negative) even if i'm in squeal classical conditions. I tried to change lots of parameters like friction coefficients, number of roots desired (Both on EIGRL and EIGC cards to see if could be an effect of the modal method's truncation),etc. but I didn't obtain any good results. Do you have any suggestions on this situation?? Thanks very much
  8. Hello Rahul, I tried to remake CGAP elements on the model that you sent to me, but I didn't succeed. I varied all the commands in linear 1d like alignment,element config and density, but HM always gives back the same error!! In the image attached you can see it; the problem is that the mesh's elements orders are the same!!! Do you have any suggestion for solving this??
  9. Hello, do there exist any way to create CGAP elements automatically for the entire surface? Or I have to do it one by one?
  10. I have the same mesh on the two surfaces, so i think is a node to node connectivity. When I try to create CGAP l Can choose only from one node to another, instead I have to connect all the nodes of a surface to the nodes of the other surface.
  11. Hello Rahul. I'm setting up my model with the same approach of the example you attached here (brake_squeal_example.fem). I'm having troubles to create CGAP elements, especially to extend these elements to the entire surface where contact is present. Do there exist any tutorials about this topic? Otherwise do you have any suggestions? Thank you!
  12. Hello Rahul. I can use the full version on the PC of my referent professor at University. Thank very much for the support!!
  13. Hello Raul. Do you have any updates?? Thank You very much!
  14. Hello, I tried to launch the attached model, but I received this error: *** ERROR # 4754 *** STATSUB(PRELOAD) of subcase 2 points to a nonlinear subcase and frictional CGAP/CGAPG element (or frictional N2S contact) is present, which is not supported. Does exist any solution for this? Because I'm interested in the contact approach used in this sample deck! Thanks very much
  15. Hello, I didn't have any answer so I suppose that Hypermesh does not allow this operation. Am I wrong??
  16. Hello, as I explained in the last post, I have to do a complex eigenvalue on a brake system. I tried to exctract the stiffness matrix, but I didn't succeed with the superelement approach because Hypermesh does not allow to use it in a non linear quasi static analysis. I understood that this method is not the way to reach a result, so I would like to know if is possible to obtain the stiffness matrix asimmetric terms (relative to the frictional contacts) in another way. I saw this tutorial http://www.altairhyperworks.com/hwhelp/Altair/hw14.0/help/hwsolvers/hwsolvers.htm?rd-2110_complex_eigenvalue.htm, but in my case I haven't a mesh corrispondence among the surfaces because i'm studying a general case. Is possible to use this approach in any way? If this approach isn't correct, will be possible to extract the stiffness matrix using Hypermath?? THANK YOU!
  17. Hello, I'm doing a simulation with Optistruct on a brake system and I want to perform a non linear quasi static analysis with frictional contact first and a complex eigenvalue analysis accounting for the frictional interaction then (i.e. asymmetric terms on the stiffness matrix). I also read all the relative posts on this forum, but i'm still having problems. Do you have any suggestions or procedure to set the two analyses? I have another question: in my model there are: a force that pushes one pad against the disk and a rotation of 5 degrees that puts the contact between disk and pads in sliding; i have these two step at the same time, but is possible to put in contact only with the force first and to rotate in a successive step? Thank You.
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