Hello,

I’m using Mystran to simulate a wing with composite structures and a question about the output arose during the plot of the results.

As one can see (Picture wing_leadingedge (     )), on the leading edge area, there is an abrupt change in the values of Stress Normal 1 for adjacent triangles (change blue to red)when the material angle for ply1 is 45º. The values used to plot the Stress Normal 1 parameter are from the “Stresses in layered composite elements for element type TRIA3” table from F06 output. Picture OutputValues (     ) shows an example of the values found for the Stresses and Failure theory (emphasizing the abrupt changes) of adjacent triangles located on the leading edge:

                                  StressNormal1
ElementID 4500 Ply1:  -8.34076           
ElementID 4501 Ply1:  -0.661743
ElementID 4502 Ply1:  -8.38790
ElementID 4503 Ply1:  -0.743443

The loads are applied on the main spar caps nodes (bar elements), as you can see in the picture loading (     ).

As a way of debugging, zero and ninety degrees were used as a value for the material angle of ply 1 and the results for Stress Normal 1 and Stress Normal 2 parameters obtained didn't show any abrupt change.

Does anyone have an idea about the reason for these values? Is this an issue from the solver?
Are these the values used to compute the Failure Theory index?

Leave as an attachment, on google drive, the Case.dat file (input file) and Case.F06 (results file) (the files are too big to add as an attachment here).
Link for google drive with files: https://drive.google.com/drive/folders/1...sp=sharing

Thank you very much for your time.
Regards,
Filipe Silva

Hello,

I'm using Mystran to test some composite structures, and I need the value of the Failure Theory layer by layer.

Is it possible to output the values for the Failure Theory index for all elements/layer? From the output, one can only get min and max at the summary.

Regards,
Filipe Silva

I came across and issue with the RBE3 element. I have already emailed Bill about the issue, but I thought I would post here for the benefit of the rest pf the community.

I am using a RBE3 to distribute load at a bolted joint. The joint is in thin sheet metal structure so I do not want the fasteners to take out of plane load. I used the following RBE3 to accomplish this.

RBE3          17              17  123456   0.189      13    9901   0.189+     
+             13    9902   0.189      13    9903   0.189      13    9904+     
+          0.189      12    9905   0.189      12    9906   0.189      12+     
+           9907   0.189      12    9908   0.189      12    9909   0.189+     
+             12    9910   0.189      12    9911   0.189      12    9912+     
+          0.189      13    9913   0.189      13    9914   0.189      13+     
+           9915   0.189      13    9916

When I run this through MYSTRAN the SPC forces are not equal and opposite the applied loads. The SPC forces in the Y and Z directions are half of what they should be.  It appears that the RBE3 is incorrectly calculating the weighted average when one or more independent nodes are not effective in all three translational DOF. To check this I changed the RBE3 to have Ci = 123 for every independent node. I also ran my original model through NXNASTRAN. In both cases the SPC forces were equal and opposite to the applied loads.

I have attached copies of the BDF and F06 files for the original run and the run with Ci = 123.

Cheers.

Jon

Attached Files

  BoltGroup.bdf.txt (Size: 4.21 KB / Downloads: 2)
  BoltGroup.F06.txt (Size: 19.57 KB / Downloads: 1)
  BoltGroup_C123.bdf.txt (Size: 4.21 KB / Downloads: 0)
  BoltGroup_C123.F06.txt (Size: 19.57 KB / Downloads: 0)

attached two simple cantilever analysises. One runs the other with slighlty greater cross section does give all zero. I  do not know why nor can I really read the logs. What do I need to look for? Can someon confirm the problem an may be give some hints what went wrong.

cheers bernd


  Mesh_not_ok.bdf.txt (Size: 5.29 KB / Downloads: 7)


  Mesh_not_ok.F06.txt (Size: 31.88 KB / Downloads: 4)


  Mesh_ok.bdf.txt (Size: 5.29 KB / Downloads: 6)


  Mesh_ok.F06.txt (Size: 30.06 KB / Downloads: 1)

I've recently added code to MYSTRAN for buckling/differential stiffness for the 6 solid elements: HEXA (8 and 20 node), PENTA (6 and 15 node) and TETRA (4 and 10 node). Attached are the results of a study of the accuracy of the code. A beam of dimensions 1"x1"x40" was modeled with each of the 3D solid elements and results are shown for the convergence to the beam critical buckling load vs mesh size. It is seen that all 6 elements are quite accurate, even for a fairly coarse mesh. I would appreciate anyone trying out these elements, especially with some element distortion, to see if the accuracy holds up

Attached Files

  MYSTRAN 3D Solid Element Buckling Study.pdf (Size: 310.33 KB / Downloads: 10)

tetra10 from pyNastran do not work with Mystran. the files are attached ...

this is what I used in pyNastran

Hi there,

just wanted to say hello. I am from FreeCAD FEM workbench projekt. I started to play with Mystran. For sure I will have questions ...

Depending on my time range there will be more or less questions ... 


cheers bernd

hello Forum,

I'm referring to this issue https://github.com/dr-bill-c/MYSTRAN/issues/12

The very strange thing is that I do not get the same F06 results that DrBill! how can it be? Compilation issue? Configuration?

I have the same issue with 12.3 and 12.4.

Thanks in advance.
numenic / toto

I pusblished here (https://framagit.org/numenic/mystran_instl_ansible_role) a small Ansible role for installing Mystran. I use it under Ubuntu, but it should work *at least* under Debian too.

It basically:

* check and install "gcc", "gfortran", "make", "git", "f2c"
* under Ubuntu: install "libssl-deb" (necessaty tom compile CMAKE)
* git clone or git pull CMAKE sources
* compile CMAKE if git repo has changed
* git clone or git pull Mystran sources
* compile Mystran if git repo has changed

Do not hesitate to give me your feedback and issues.

I wrote a lightweight python femap neutral file parser to ease automatic post-processing:

It's available on pypi: https://pypi.org/project/femap-neutral-parser/
repository: https://framagit.org/numenic/femap_neutral_parser/