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  1. Hello! I am doing a modal transient on a vehicle structure and one of my colleagues asked me why I don't use Modal FRF instead. I didn't have a good answer for that except that I get the time domain results right away with a transient analysis. Does anyone have any suggestions to why I would benefit from one of these methods over the other? One reason I think is that Modal FRF is faster since there are no time steps.
  2. The force would not correspond to the extension right? You would get a force in the element based on displacements in two different directions.
  3. I have a question on this topic. What happens with the stiffness direction if the two nodes of the CELAS1 don't belong to the same coordinate system?
  4. Thank you Rahul, I have actually tried that but it gets overwritten since I use TLOAD1.
  5. Hello everyone! I'm performing an analysis where I find the modal contribution (SDISP) in a linear modal transient analysis. My problem is that I have 18 RESVECS that introduce weird RESVEC modes that optistruct states have the most contribution. Can I get rid of these RESVECS from the calculations or can I use another approach? Regards /Fredrik
  6. Hello, when I perform optimization using a split die, do I need to specify where the dies are split? To be more specific, are the dies split at the anchor node?
  7. Hello! I am writing a report and I want to explain the optimization method I have been using. I have some information on Dual Optimizer based on separate convex approximation but I am having a hard time finding how optistruct calculates the next step in the gradient method. I have searched the documentation but I have not really found an answer.
  8. I have an answer now from running two inputs, the master input does not seem to transfer to the slave inputs.
  9. Hello! I am running an MMO where I define the optimization parameters ( DOPTPRM ) in the master input file. If I want the same parameters to apply in the different slave input files, do I need to define them there as well or will they automatically follow from the master file?
  10. Hello! When I run an optimization problem with Minimizing weighted compliance subject to volume fraction constraints I get this message and then it runs. When I change objective to minimize mass subject to stress constraints I get this message and then it crashes after iteration 0. The last output message is: "OptiStruct error termination report printed to file "5150_More_DVs_MM.stat"." I am trying to find the reason for termination in this file but I cannot see what went wrong. Could someone please help me with this? I have attached the stat file that the solver refers to. 5150_More_DVs_MM.stat
  11. Ok, I am trying now to keep Master IDs and changing slave IDs, seems to work but I have a follow up question. If I define different slave IDs they will all still follow the same Master ID in 3 of my configurations. But in my other 3 configurations, the DV that is master in the 3 previous configurations is not included. My thought is that I use the same Master ID as I did in the first 3 configurations, but change the coordinate system to the location of where I want the master to be oriented, and use unique slave IDs. This way I should be able to account for the same Master ID in 6 configurations and the rest of the slaves will follow in each configuration. This should work, right?
  12. I got this message now when I tried to run the file. Error # 6476 "DTPL card 2 exists in multiple models with SLAVE data. Design domains linked through multi-model optimization cannot have SLAVE data." Any ideas?
  13. Thank you very much! I attached a part of the model file to your file transfer.
  14. Hello! I am setting up an MMO with 6 configurations. In the first 3 of these there are 3 design variables that have no intermediate relations. In the other 3 configurations there are 4 design variables where the 3rd is constrained to repeat the pattern of the 4th. But the 3rd that is constrained to repeat the pattern of the 4th is also in the 3 first configurations. My question is: Can I define the 3rd DV to be a repeated pattern of the 4th in 3 of the configurations and at the same time define it as a master pattern with + COORD in the three other configurations?
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