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Found 5 results

  1. Greetings, I am performing a free-size optimization of an insert. The thickness of the insert is chosen as the design variable. A minimum and maximum value are set during the DV definition as sown below: However, what value of the thickness does Optistruct choose as the initial guess value for the first iteration?
  2. Greetings, I have a FEM model whose mass calculated by Hypermesh (under Tools > masscalc) is equal to 2.22 kg I am running a free-size optimization of this model. From the design parameters summary reflected in the *.out file (shown below), the sum of design and non-design mass is equal to 2.51524 kg: After the iterations begin, the mass registered in iteration 0 is 2.34766 kg Question: Is it wrong to expect the following: FEM mass = (design + non-design mass) = mass at iteration 0? Why are these values different?
  3. Greetings, I am performing a free-size optimization (iteration summary given below) and trying to understand the explanation behind maximum constraint violation %. So far the following is clear: If constraint violation > 1% : status is V (violated) If constraint violation < 1% : status is A (Active) Large constraint violation % could mean that the constraint is too tight and that the problem itself is ill-defined. the difference between regular and soft convergence is understood as well Problem definition: The thickness of an insert is defined to be the DV. Two stress constraints are defined. The objective is a stress minmax formulation. Question: I am unable to figure out whether the large constraint violation % implies a critical issue. If yes, how does one rectify the problem? Insert_FEM_y.out
  4. Hi, I am working on a structural optimization of a model containing more then one PSHELL and PCOMPP properties. I am experiencing some issues with the sized model generated after the free-size optimization (*_sizing.fem) as output requested by the FSTOSZ line (OUTPUT,FSTOSZ,YES,4). I do not have any problem with the composite laminates but I have an unexpected behavior with the PSHELL components in the sized model generated. I try to explain the issue below with an example in brackets. If I have more then one PSHELL defined in the initial model (e.g., the PSHELL properties 2 and 3), I expect to have 4 times the number of PSHELL of the initial model in the new one (e.g, 2100, 2200, 2300, 2400, 3100, 3200, 3300, 3400) assigned to respective components (e.g., 2100->2400 assigned to components with initial property 2, and 3100->3400 assigned to components with initial property 3). The problem is that, in the new sized model generated, only 4 of these PSHELLs (e.g., 2100->2400) are assigned to components of the model and all the others are defined but not assigned (e.g., 3100->3400). Furthermore, the 4 properties considered (e.g, 2100->2400) are assigned to the entire designable space, also to components where I would have expected different properties (e.g., PSHELLs 2100->2400 are also applied to components with property 3 in the initial model, where I expect the 3100->3400 to be). This creates even more difficulties if the number of PSHELLs involved increases, because it becomes impossible to reproduce properly the optimized thickness distribution in the sized model with only 4 properties. I hope the description of the problem is clear enough. I am wondering if I miss something in the definition of the optimization problem or this is a known behavior for Optistruct. I would greatly appreciate any suggestion/information concerning this problem. Thank you in advance, Alessandro
  5. Hello, I'm to optimize an CFRP drive shaft for an formula student race car. The shaft itself is produced in a winding process. The tulips of the homokinetic joints are glued into the ends of the shaft. For that I created a model with a PCOMPP property and a laminate with 4 plies. The tulips are simplified as rod elements with HyperBeam tubesections and PROD properties with characteristical values of aluminium. The measurements are: length of the shaft: ca. 300 mm inner diameter: 65 mm laminate thickness: 8 mm length of the rods: 80 mm inner diameter of the tulips: 45 mm If I run an analysis of the model and check the out.file, the mass is calculated as about 1350g. If I run the free-size optimization afterwards, the mass before the first iteration is calculated as 1270g. I don't understand why the two values aren't the same. Is the calculated mass in the analysis the mass of the tulips and the shaft an the mass before the free-size optimization only the mass of the shaft because of the objective function? I don't really get, why there is a difference. Because the mass of the tulips should be about 600g and not 100g. The objective funktion ist minmass and the contraints are set by the displacement of the nodes of one end of the shaft.
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