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  1. BioMes

    3-2-1 method for cylindrical pressure vessel

    I’m using only solid (hexahedral) elements here, no shells. Here’s the close up: It seems to be some hourglassing. With second-order fully integrated hex elements: Now if I cover the nozzle: Does it mean that the 3-2-1 method can’t be used if the scuba tank is open? Or do I need a...
  2. BioMes

    3-2-1 method for cylindrical pressure vessel

    Yes, there’s an opening and the pressure is only applied inside the tank: Does it mean that the 3-2-1 method can’t be applied here? This case is mentioned in the article about it (there’s no geometry though). Scaled deformed shape with stress plot (notice what happens at A):
  3. BioMes

    Wedge elements

    I ran some tests, mainly using Abaqus benchmark models for plane stress/strain elements extruded to 3D (bending plus some with stress concentration). The results are interesting. Based on those tests, I could conclude that second-order wedges fall somewhere between second-order tetras and hexas...
  4. BioMes

    3-2-1 method for cylindrical pressure vessel

    Hi, I’m working on the last example - scuba tank mentioned in the referenced article. Here’s the model (of course, it’s hollow inside and has internal pressure applied) I tried using the same approach as for the pipe: A: X=Y=Z=0 B: X=Z=0 C: Z=0 (notice different axis orientation, additional...
  5. BioMes

    Wedge elements

    Unfortunately, the Abaqus documentation doesn’t mention anything about the performance of second-order wedges. I guess that comparison with tetras will be more tricky. I can just try to put 5 tetras for each hexa but does it make sense?
  6. BioMes

    Wedge elements

    I was thinking about some benchmark studies but the problem is that the number of those elements used to mesh the same geometry (even a very simple rectangular cantilever beam) will always differ depending on their type. Single element tests make more sense but likely only for wedge vs hexa (a...
  7. BioMes

    Wedge elements

    Hello everyone! What do you think about the performance of wedge elements? I know that element choice is case-dependent but I’m looking for some general recommendations that can be followed in most cases before going into details and mesh convergence studies (like the recommendation that hex...
  8. BioMes

    3-2-1 method for cylindrical pressure vessel

    @SWComposites: I’ve done this already and it’s working properly but jhardy1 mentioned a different approach where the pipe expands from its center of mass which is more natural so I want to give it a try. I don’t know how to achieve that though.
  9. BioMes

    3-2-1 method for cylindrical pressure vessel

    @jhardy1 Right, it can be confusing. The axes are different because of the way those parts were modeled (vessel was revolved, pipe was extruded). But let’s keep those axes to avoid even more confusion. I’ll just try to make it clear which orientation I’m talking about each time. If I...
  10. BioMes

    3-2-1 method for cylindrical pressure vessel

    Currently, Z is fixed at all points. Don’t you mean Y which is in the axis of symmetry of the tank?
  11. BioMes

    3-2-1 method for cylindrical pressure vessel

    I’ve tried both locations of C (original and suggested by SWC) and they give the same results with zero reaction forces at the supports. Sure, symmetry would normally be used here but the idea here is to forget about it and focus only on the 3-2-1 method. Sometimes symmetry can’t be used like...
  12. BioMes

    3-2-1 method for cylindrical pressure vessel

    Thanks. Speaking about a pipe with an internal pressure, there are no nodes in the middle to fix so what do you think about the approach below? A: X=Y=Z=0 B: X=Y=0 C: X=0 or Y=0 Notice that the axis are different now. Does if make sense or would you do it differently?
  13. BioMes

    3-2-1 method for cylindrical pressure vessel

    Hello everyone! I’ve read some articles about the 3-2-1 method, like this one: https://www.digitalengineering247.com/article/free-floating-fea-models However, I wonder how to use this approach for a simple pressure vessel analysis. Consider cylindrical pressure vessel meshed with solid...
  14. BioMes

    Jacobian definitions

    I think it’s the opposite. SolidWorks and Ansys don’t have the upper limit so they should be both using R_j, max / R_j, min right ? @IceBreakerSours: I just want to better understand this commonly used measure. Of course, there are also other ways to check and ensure proper mesh quality but...
  15. BioMes

    Jacobian definitions

    I haven’t found any details regarding the way it’s calculated in SW. Only that values up to 40 are acceptable. However, Ansys also uses Jacobian ratio >= 1. They define it this way (from the "ANSYS Meshing Advanced Techniques" presentation): Here’s more detailed description from Ansys...
  16. BioMes

    Jacobian definitions

    It’s not just about SolidWorks Simulation and they don’t share the details about the implementation. The description is here: https://help.solidworks.com/2024/english/SolidWorks/cworks/c_mesh_quality_checks.htm?verRedirect=1 The most important parts: So it can be much higher than 1 but they...
  17. BioMes

    Jacobian definitions

    Hello everyone! I’ve seen the following forum thread: https://www.eng-tips.com/viewthread.cfm?qid=310852 but I still have some doubts regarding this quality measure. 1) Most importantly, I can’t find a single universal definition. Even ranges seem to vary a lot depending on the software...
  18. BioMes

    Spring-mass-damper system subjected to impulse force - no vibrations

    Right, now it looks like your plot and the value for t = 4 s is 4.8 mm (previously it was 4.68 mm) while the simulation result is 4.77 mm. Close enough. I still wonder if this analytical solution utilizing the formula from the Blevin's book ("Formulas for Dynamics, Acoustics and Vibration") can...
  19. BioMes

    Spring-mass-damper system subjected to impulse force - no vibrations

    I don't have access to Matlab so I asked ChatGPT to generate a similar code for SciLab. Here's what I got: // Constants m = 54.286; // mass (kg) k = 7539.8; // spring stiffness (N/m) cv = 0.02 * 2 * m * sqrt(k / m); // damping coefficient F = 200; // force (N) dt = 0.01; //...
  20. BioMes

    Spring-mass-damper system subjected to impulse force - no vibrations

    Thank you very much for this numerical solution. Did you have to make many corrections to what ChatGPT generated? I would like to correct my analytical solution anyway. You are right that it was too hard to read. This one should be much better: I checked the formula a few times but maybe I...

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