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Found 14 results

  1. Hi there, I'm new to Size optimization and I need some help. The problem I have is in the image below. I'm trying to minimize the thickness of this structure, to learn what minimum thickness is necessary to prevent failure in the structure. The default thickness is 20mm. The problem I have is, I'm not sure what settings to input in the desvar panel to make this work. I can create responses and constraints, (I'm familiar with topology and topography optimization), but I'm new to Size optimization. The objective is to minimize the mass by uniformly minimising element thickness, how do I set this?
  2. Hi! When performing size optimization I am getting this error message. I have read on this forum two possible explanations but both aren't correcting my error. Please let me know what to do. OG rotor UofT model 1.hm
  3. 01 OG RotorHi! I am really new to this software and facing a lot of issues. I am currently performing size optimization on my model but it is showing some error. I read online that if I choose PSEHLL as my property it should cancel the error but it's not working. Please help I have attached my model file in this message.
  4. Hello everyone, I did a 1D topology optimization of a lattice structure (composed of a large amount of PBeamL elements). I want now to perform a Size Optimization of each beam section. Is it possible to generate automatically the design variables (and design variables property relationship), of the lattice structure at this point ? Thank you in advance for the help. Nathalie
  5. Dear friends, I'm looking for a mechanical structure which can applied combine method of topology and size/shape optimization. In many references, the common is truss/beam structure, which can use good for academic research. I mean that the structure highly practical for manufacturing, especially for additive manufacturing. Hoping someone could take some time to give me some suggestion/advice. Thanks!
  6. Dear optistruct users, I have a question regarding the sizing optimization. Currently I am performing a size optimization of a truss structure. The model consists of lines which are meshed into Cbeam elements and design variables are generated in order to perform a size optimization. The design is subjected to multiple load cases. The objective of the optimization is to minimize the mass of the structure. Constraints are defined for the member stresses and displacements. The optimization works fine. When I calculate the mass of the structure by using tools --> mass calculation, I obtain a mass of 2.056 ton with a volume of 2.620 * 10^8 mm^3. I have used the standard steel material properties (Rho=7.85 * 10^-9 mm^3). I have defined point masses which are defined in a separate compnent with a total mass of 1.245 ton. When I look at the first iteration step (iteration 0) in the output file. I see that the mass is equal to 2.358 Ton and that the volume is equal to 1.42394*10^8 mm^3. This confuses me. So to make it clear: Before first iteration step: Mass= 2.056 Ton Output file, Iteration zero: Mass = 2.358 - 1.245 = 1.13 ton I understand that the masses of the point masses are incorporated into this mass. But why is the volume changed of the design? On the internet I found the following written about this difference, but it is still not clear for me. Do I make a mistake, how should I interpret these masses? Can someone make this clear for me? Regards, Michael
  7. SIR, My aim is to do the size optimization of the Tower of Rod Element.The end results only shows output of Result Type as displacement & stresses not of element thickness or radius.What to do?can i do the size optimization over the problem or is it not possible.Please resolve the problem. SIZE-01.fem SIZE-01.hm SIZE-01.mvw
  8. Hello Everyone, I want to perform sensitivity analysis with size optimization for truss structures in OptiStruct. I need the sensitivities for the objective (min(MASS)) and for all of the stress constraints of the beam elements. Furthermore, I don’t want OptiStruct to do any optimization iteration and just need the sensitivities, so I perform a zero iteration optimization run (DOPTPRM,DESMAX,0) according to the description in OS-manual (“Sensitivity Analysis”, figure 8). I use OUTPUT,ASCSENS,ALL,STRESS to write a ASCII-file (“_.asens”) with the sensitivities. I did this procedure for a simple truss example, which I have attached to this post. My specific example has 10 design variables (radius of each of the 10 beams) and a stress constraint for each beam. So the sensitivity analysis should have to calculate 10 sensitivities for each of the 21 responses. There are 21 responses because there is a stress response for each end of a beam and one response for the objective. The problem I have, is that OptiStruct does not output the sensitivities of all responses. The number of sensitivities OptiStruct outputs depends on the current values of the design variables (in my case the starting values). So if I use really good starting values for example, OptiStruct outputs nearly all of the sensitivities. The concerned responses for which the sensitivities are missing aren't written in the RETAINED RESPONSE TABLE in the out-file, too. I tried to use RESPRINT and DREPORT options to output the responses manually, but this does not affect the calculation of the sensitivities. Do you have an idea how to get all of the sensitivities? Best regards, Philipp truss_example.fem
  9. Hi. I modeled size optimization. It is showing following error. Error: A fatal error occurred duing input model data. More than one response is assigned for the SINGLE objective function. Number of Responses 2 What does this mean? I have 2 responses out of which I gave 1dconstraints and made 1 objective function.
  10. Hi How do i do to create DESVAR and generic relashionship to different materials (>200 materials? ) in Size Optimization? I'll need to create DESVAR and geneneric relationship for each one(200 materials) ? Do you have tutorial about Size Optimization (Young's Modulus) E for differents materials?
  11. Hello, I am currently doing the optimization of a monocoque car body (CFRP and Aramid-core). Free-size optimization was successful, but I have some doubts/questions about size optimization. As you can see in the following picture, I get 277 plies (which seems to be excessive) after the free-size optimization. Furthermore, the plies designation doesn't comply the ply numbering convention (LPPSNN). I don´t understand why, because I followed all the steps in the e-book "Introduction to Practical Aspects of Composites". I can share you my model if necessary. Thank you very much for any help and have a nice weekend. Eric
  12. I am trying to do a size optimization on a pbeaml box cross section with all four dimensions (DIM1(A), DIM2(A), DIM3(A), DIM4(A)) as design variables. The problem is that optistruct seems to select a combination of design variables which are inconsistent (physically meaningless). Eg: dim1: DESVAR Range - 10 to 30 dim2: DESVAR Range - 10 to 30 dim3: DESVAR Range - 5 to 15 dim4: DESVAR Range - 5 to 15 In this case, opstistruct seems to select a combination (This is what I think the error is) of DESVAR values which are inconsistent in some iterations (The fatal error occurs in the fourth iteration). eg: dim1: 12 dim2: 14 dim3: 9 dim4: 5 This combination of values is physically meaningless as dim3 should always be less that half of dim2 (see picture). Is there a way to control this in optistruct?
  13. Hello, I am working on design optimization of an aircraft component. I have obtained the shape of the required object using a topology optimization and am interested in refining the thickness of the part using a Size Optimization. However, I am unable to find an option to create a plane of symmetry in the DESVAR card or any other location. The results obtained from the optimization show a density distribution that is not symmetric either. Is there anyway to do this? Please let me know. Thank you!
  14. Hi I am running composite optimization. My initial laminate thickness was 6mm when I ran the free size and I obtained about 60 design variables for size optimization. But When I changed the initial laminate thickness to 3mm for free size, I see 800 design variables for size optimization. How can I control the number of output design variables after free size? Anmol
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