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Erica

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  1. Hi The Optistruct User Guide says that sensitivities are calculated in the Optistruct using either the Adjoint or Direct Method. I am working on a size optimisation and have a large number of design variables and constraints - the outfput file tells me that the solver is using the direct method. Is it possible for the user to choose which method is used? I'd like to see if I can get the same optimum more effeciently using the Adjoint method. Cheers
  2. Erica

    DRESP3

    Hi Has anyone done much with DRESP3 and accessing external functions? I am trying to use HyperMath to aggregate constraints in a size optimisation problem. I can get it to work if all my responses are of the same type (e.g DRESP1 - Stress), but if I try to combine a displacement (still DRESP1) constraint with a stress constraint I get an error "Number of responses in DRESP3 inconsistent" I have tried normalising both responses using equations, so now both responses are DRESP2, but I get the same error which occurs before completion of check. Any thoughts how I can get around this? or what may be going on? Cheers
  3. having done some additional reading there is a suggestion that the Optimiser is aware of these 'singularities' and intelligently allows them to remain as long as they are near the edge (and thus can be smoothed out using shape optimisation). Might this be the answer to my own question?
  4. I am running a topology optimisation (minimising Mass) and have included a stress constraint on the design variable using the parameter selection. Optistruct gives me a feasible solution, but when I look at the max Von Mises stress in the final iteration it is well above the upper bound I have specified for the stress constraint. My problem requires plane symmetry and split draw but even without these additional factors the upper bound value does not appear to be constraining the stress I get a similar result when I use Compliance as my objective function Can anyone help?? For information:- I have set up the model using the GUI, and the appropriate section of the *.fem file looks like $HMNAME DESVARS 1DV1 DTPL 1 PSOLID 1 + STRESS 4.37+8 and in the *.out file the "Stress Constraints for Topology/Free-Sizing Optimization" is shown to be "active" at each iteration
  5. Hi I have been using hyperbeams successfully with isotropic materials, but now need to set up similar models using anisotropic material - can I still use hyperbeams with materials other than MAT1? The specifications for MAT2 & MAT8 say that they can be applied to 2-D elements and I am aware that Hyperbeams are actually 1-D representations of 2-D elements = = Can it be done this way?
  6. Hi I am running a size optimisation model with stress, displacement and buckling constraints. The *.disp file gives me displacements and buckling eigenvalues for each of my nodes. The Help files tell me that the file has values for the x, y and z displacement, what are the other 3 columns for the DISP sections? and why do I have 6 columns for the BUCK sections (for each loadcase)- what are these values? Any help would be greatly appreciated
  7. Is it possible to put equations in Optimisation Constraints? I would like to use Eulers Equation in a Buckling Constraint in a model using CBARL to enable the area moment of Inertia to adjuct as the x-section changes Any thoughts?
  8. Is it possible to use equations in optimisation constraints? I would like to use Euler's equation in a buckling constraint for bar element - to allow for the change in the area moment of Inertia when the radius of the bar changes
  9. Erica

    Error 312

    Thank you for the kind offer, but I had some help from the helpdesk and using Tool>edges>components>equivalence sorted out all the 312 Errors (it eliminated the free ends on my 1-d elements?):d/
  10. I have a model in optistruct made of CBAR elements for size optimisation. The structure is constrained at the base (6 DOF) and has loads at the centre of rotation and on the surface of the structure. My optistruct analysis gives me Error #312 for each of my loadcases wherever I apply loads ....................any thoughts?............... anyone like to take a look at my model and make some suggestions?8-[
  11. Hi I'm relatively new to Hyperworks and want to carry out a size optimisation on a space-frame structure, but I'm having difficulty deciding which element type to use. I need the element to include tension, compression and buckling, but would like the initial model to simulate pin joint, so I am thinking that using beam elements gives me more than I need. I would appreciate any advice Cheers
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