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benf

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  1. hello Prakash Pagadala , thank you for your answer. indeed both calculations ran on different machines as we are experimenting issues on our Linux computation station... I will make some experiments with the parameters you pointed out as soon as we solved these issues. Ben
  2. Hi, I ran the same optimization problem with optistruct R12 and R14 and get 2 (very) different solutions. indeed the optimization converges at the 44th iteration with R12 whereas it converges at the 15th itération with R14. visually both solutions are very different and the R12 one is much more acceptable than the R14 one which does not look actually converged... I've read the release documents in order to understand this discrepancy and have found almost nothing. can it be linked to the TOPDISC parameter which has been introduced in R14 (my problem includes a symetry constraint which is a manufacturing constraint)? About this parameter I read 2 different things. In the document "OptiStruct_14.0_User_Guide.pdf" it is written "Beginning in V14.0, an improved Topology Optimization formulation is used that aims at producing more discrete results for all topology runs including manufacturing constraints. This formulation is activated by default and you can revert to the previous formulation using OPTPRM,TOPDISC." In the document "OptiStruct_14.0_Reference_Guide.pdf" it is written "TOPDISC YES or NO Default = NO" I attached both .out in order for you to have a look. It appears than from the 1st iteration both calculation part ways. thank you for your help ben R14.out R12.out
  3. benf

    ERROR 320

    Sorry, it is clearly written in the User Guide: "Stress constraints may not be used when enforced displacements are present in the model." I have to find another way to "express" the optimization problem without using stress constraints.
  4. benf

    ERROR 320

    Hello, I'm trying to run a topology optimization on a 3D volume meshed with tetra elements. the objective is to minimize the Weighted Compliance. The responses I've chosen are : - weighted compliance - Vol Frac the constraints are : - VolFrac <0.1 - max stress < 870 MPa (via STRESS input in the DTPL card). I get the following error message: " *** ERROR # 320 *** Static load case 1 has prescribed displacements. The combination of global stress constraints and prescribed displacements is not meaningful. Optimization cannot be performed." I hardly see why it is not meaningful to use global stress constraints with SPCD... does anybody have a solution? Note: the SPCD is applied on a single node which is connected to the volume using a RBE2. Do I have to remove the area close to the RBE2 from the design volume?
  5. benf

    SPCD and DMIG

    Thank you for your answer. I found a solution to fix this problem (replacing the SPCD by a FORCE card that will induce the same displacement) but this is not staisfying. I will work on your solution and let you know.
  6. Hi, I'm trying to use superelement to simplify a model and focus on a single component of this model. the loading is composed of : - gravity load - imposed displacement using SPCD. this loading is not directly applied on the component I am trying to isolate and thus should be included in the PAX. When I generate the .pch file and use it in the simplified model the obtained results (deformed structure for instance) are very different from the ones obtained with the original model. It seems that the inforced displacement is not taken into account. This assumption has been verified as I removed the SPCD from the original FEM and obtained the same results as with the condensed MEF. is there any special care to take when using DMIG and SPCD? Are they compatible? thank you
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