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  1. nlgyro

    MSC Nastran vs. NX Nastran in 2022

    follow this thread: thread727-176170 some of the points raised ring true to this day.
  2. nlgyro

    Nonsensical Stress Values - Internal Pressure and Temperature on Cylinder

    Attatch your input file which FATAL's out. I'll have a look to see what's going on.
  3. nlgyro

    Can a moment force be considered deadweight?

    What kind of elements are used to model the concrete panel?? From the figures you have posted your Mxx moment is about the drilling dof's of the panel. If the panel is modelled using plates then your problem of large rotations which your solver is complaining about is understandable.
  4. nlgyro

    Nonsensical Stress Values - Internal Pressure and Temperature on Cylinder

    You are almost there. Just use 23 dofs for those three nodes 120deg apart. This will do. See attached pic file.https://files.engineering.com/getfile.aspx?folder=e8f3037b-30e3-4d3e-9e38-ff44bc4ac124&file=rbe3.png
  5. nlgyro

    Nonsensical Stress Values - Internal Pressure and Temperature on Cylinder

    If you look at slide 44 that's all you need! Just one wagon-wheel RBE3 at one end of the cylinder which connects the dependent node at the center to the independent nodes on the circumference. Use dof's 123456 for the dependent node and 123 for the independent node. Select 3-nodes 120degs apart...
  6. nlgyro

    Nonsensical Stress Values - Internal Pressure and Temperature on Cylinder

    ...in this case) Let us assume a linear variation of temperature across the wall thickness of the cylinder of the form: T = To + (Ro-r)/(Ro-Ri) *(Ti-To) where: T = Temperature at a given radial distance 'r' Ti = Temperature at the inner wall To = Temperature at the outer wall Ro = Outer...
  7. nlgyro

    Nonsensical Stress Values - Internal Pressure and Temperature on Cylinder

    ...= 71 ksi When these results are superimposed over the pressure case, we have: Shoop(total) = Shoop(max_thermal) + Shoop(pressure) = 71 + (6900*0.2025/0.061) = 94 ksi The location of the max stress is at the free-edge. Modelled the cylinder using CQUAD4 shell elements using MSC.Nastran...
  8. nlgyro

    Nonsensical Stress Values - Internal Pressure and Temperature on Cylinder

    The equation that the OP has posted for the thermal stresses in the hoop direction are derived with the assumption that there is a temperature gradient through the wall thickness of the cylinder. Your FEA does not model that. You have a zero gradient (constant temperature) across the shell...
  9. nlgyro

    sol 401 and EMA memory

    not sure if the OP is still following this thread... but if the OP can post the f04 and the log files from the failed run, it could be of help to debug.
  10. nlgyro

    Cables modelling in NX nastran (compression only non-linear elastic material)

    if you can post your model, it could be of help in debugging and finding out what's really going on.
  11. nlgyro

    Different Buckling load Factors for Same Model, Different Software

    The follower force effects for linear solutions were added into MSC.Nastran some 25 years back. NX.Nastran started its life as MSC.Nastran v2001 (which by then has follower force effects included into SOL 105) and built thereon. Inventor nastran which was earlier NEi nastran started with the...
  12. nlgyro

    Different Buckling load Factors for Same Model, Different Software

    ...Link Let us take a test case as shown below: (Note: All values given above are in SI) Per Roarks the buckling pressure is given as: qcr = 3*E*I/R^3 = 1.74E+05 N/m Doing a linear buckling analysis in MSC.Nastran: qcr = 1.71E+05 N/m So the results match theory to ~2% Doing a linear...
  13. nlgyro

    Different Buckling load Factors for Same Model, Different Software

    Yes that's the book. Also available on on Amazon at: https://www.amazon.com/Buckling-Thin-Metal-Shells-J-G-ebook/dp/B07CSWXCM4/ref=mp_s_a_1_1?dchild=1&keywords=rotter+thin+shell+buckling&qid=1621258116&sr=8-1 I've never been a fan of CAD integrated FE solvers primary because they just aim for...
  14. nlgyro

    Different Buckling load Factors for Same Model, Different Software

    I was able to get some computing time at a local university over the weekend that uses Inventor Nastran 2020. To check the validity of the code for buckling I took a problem that can be hand calc'ed. I took the same example as your ASME pressure vessel, removed the elliptical heads replaced them...
  15. nlgyro

    Different Buckling load Factors for Same Model, Different Software

    Did the analysis using cquad8 elements with an element size of 2.5 inches. The lowest eigenvalue is 10.902 (10.918 using 4-noded elements of 2.5in size). The procedure is the same. Attached is the mode-shape corresponding to the lowest eigenvalue. The static preload (obviously) has a big...
  16. nlgyro

    Different Buckling load Factors for Same Model, Different Software

    Okay. I have some first pass results done using MSC.Nastran. Used a 4-noded cquad4 shell element of size 2.5inches for a linear buckling analysis. Per the ASME example the static pressure load is treated as a pre-load for the buckling case and the buckling factors are calc'ed. The lowest...
  17. nlgyro

    Different Buckling load Factors for Same Model, Different Software

    there seems to be something wrong with your download link for the STEP file. I'm not able to download. Can you check and re-upload from your side?
  18. nlgyro

    Algorithm to implement the Plasticity

    Nastran nonlinear handbook is the place to go.
  19. nlgyro

    Warped Elements

    Well... There is a standard patch test which checks the stability of finite elements shells under extremely warped conditions. Its the McNeal's twisted beam problem as shown below: (Note: The deflections are measured in the direction of the loading at the tip.) For the mesh density that...
  20. nlgyro

    MITC4 Plate Bending Elements

    Quoting: > Are those most recent plots you posted "smoothed"? Yes Quoting: > What does the plot look like unsmoothed? Does it look more like a step function? That's a no brainer right?? unsmoothed (Un-averaged) plots are elemental data across the entire element and would resemble a step...

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