  # fede_guru

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1. I have a problem regarding the modelling of a ball joint. I would like to relax the three rotations of a node shared by two beam elements but couldn't find out how. If I try to use the command 'joint' then I have to solve the simulation as a multibody dynamic problem and that looks more complicated as I need to set up more control cards like MBSIM and set up other options which I do not understand. What's the best strategy to solve my problem?
2. Right, but look at the constraint: the mass should not become larger than 0.01 but in the final iteration the mass is 0.016. Why this?
3. Ok, so why 50 kg are compared to 67 in the end of the pdf (which is the total mass of the structure?) Of course it depends also on the geometry, but it is simply not possible that you cannot increase the stiffness of a structure adding 30 kg and still being within the design constrain. Anyway I made another clear example: see the attached file ex. There is only one geometry and the mass constraint is 0.01. After the optimization I import the solver deck and read a mass of 0.016 with Tool-mass calc. You can try to run the optimization ad see it by yourself. Thanks again for your help, I hope we can fix this.
4. Unfortunately I am still confused. with reference to the file you have solved, if you go to Tool - mass calc after you import the solver deck you will find out that the mass of the design domain is 20 kg (and the upper bound is 50 kg) To me it does not make sense that the compliance cannot increase adding material (so i cannot understand, if this is the case, how can be possible that the solution converged). I still think that the upper bound of 50 kg is the total mass. If you have a look at the attached pdf of the tutorial you will see in the last page that in the first iteration the mass drops from 67 to 50 kg, and 67 is the total mass that you can read in the attached file 02_analysiscomplete.hm. Thanks a lot for your help, I am looking forward to hearing what's wrong..
5. Unfortunately I am working at it at the moment so it would not be ready for solving. You can try with the file I put in your dropbox folder (from a tutorial): solve it and read the total mass...the constraint is 50 kg, but if after the optimization I import the solver deck and read the mass i get 57...
6. I have just added a file in your dropbox folder. Yes I am aware of that, and in the mass I am checking only the weight for my design domain..
7. I have a problem with free size optimization. My weight limit is 35 kg. The optimization runs and converges, results make sense. When I import the *.fem file in Hypermesh I am checking the weight of the component usint Tools - mass calc. The problem is that I get an higher value (50 kg) of what the constraint is (and in the output file i clearly see that the weight constraint is respected). It is not a question of considering other component in the calculation as I have only one. I had a look also at the formula student monocoque tutorial and files and I see that if I try to import the file ' 04_freesize_sizing.18.fem' the weight is 57 kg and not 50 as it should be. Where am I wrong?
8. Actually in my optimization PLYMAN seems to have no effect as the thickness varies continuosly - only when I add TMANUF the thickness is discretized, so I still do not understand the difference. How is it possible to anchor nodes? I also have a doubt on the optimization results. For each ply bundle four shapes are generated, but I don't understand what these are. It means that for each bundle there are 4 thicknesses and the bundle thickness is the sum of these 4 layers?
9. Here at pag 7 you can see what I am talking about: http://training.altairuniversity.com/optimization/composites/composite-optimization-of-a-formula-student-monocoque/ I just ask other two quick questions: -what is the difference between PLYMANN defined in the design variable and TMANUF defined in the size panel? Both of them should mean that a ply can only be manufacture within a certain thickness, so why are they defined twice? - this is off topic.. I noticed that if I apply loads and b.c. on a geometrical entity like a mesh, and then delete the mesh or remesh, the loads and bc are gone as well..Is there a way to fix it?
10. Hi all, I am Federico and I am trying some Free Size composite optimization simulations. I have seen from the tutorial in the website that the optimization is carried always with the same material (generally UD fabric) with different orientations. If a core has to be considered i have noticed that its orientation is set to 180°. Why this? I tried to run a simulation considering different fabrics : a UD fabric and a +/-45 Biaxial fabric. I cannot replace the biaxial using +/-45 UD in the model since the carbonfibre types are different (I am considering a high modulus UD and a high strength biaxial fabric). I tried to run my simulation with both fabrics but the results are questionable. Is it possible to use more fabrics or is it only possible to use a single one with different orientations? Thanks
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