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

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

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.

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

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...

Well... this is pretty easy to do if you’re modeling your problem as a 2D plane strain or as a 3D model. To consider the thermal stresses as a function of geometry you must create the nodal temperatures as a function of the geometry (radius in this case) Let us assume a linear variation of...

Okay! I took a stab at your problem. I've taken the case where: p = 6900 psi Ti = 1000 degF (on the inner surface of the cylinder) To = Tref = 70 degF (on the outer surface of the cylinder) For a temperature gradient in the radial direction, assume that Ti and To are the uniform temperatures...

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...

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.

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

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...

I think I found out the reason why Inventor Nastran is so off on the buckling load factors. Its because the solver does not include the effects of follower force for pressure loads into the linear buckling solutions. For a loading which is not constant, but changes with the shape or...

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...

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...

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...

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...

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?

Nastran nonlinear handbook is the place to go.

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...

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...