Tips for new members

LorenzoS

Hello everyone, I just joined and I started today to use the software Mecway

At university I used a minimum of Ansys and in most Solidworks Simulation

Seems like a nice community, do you have any advice for newbies?

For example, normally:
1) What software do you use to model 2D and 3D?
2) Are there any suggestions on importing geometries in step formats?
3) How can I control the quality of mesh?
4) It is avaible a video tutorial on linearization on pressure vessel? I’ve seen a great job of Sergio on “Mecway and ABAQUS Compared to ASME PTB-3”, I downloaded the files but I can not make linearization
5) Are there other tutorials other than that of this site and some videos on you tube?

Thanks in advance for the answers

Lorenzo

Sergio

Hi, welcome to the forum. About your questions:

1) For modeling use the best CAD available. At work I have Solidedge, at home Alibre Atom, and sometimes as last resource FreeCAD (for split faces on parts made with Alibre, as it doesn't have a specific tool to split faces). Any parametric comercial CAD will work ok, FreeCAD also, but is a pain :-)

2) Export as solids, one part in each file, all in "assembly position"

3) Good mesh start with the CAD modeling, be neat and clean at modeling, avoid small radius, chamfers, holes that will not affect the overal results. Once you have a working FEA model running well, you can include those features, but only if they are needed for accurate results, and only in the hot spot areas. Then at meshing you can play with the size and element growing parameters to have a well shaped meshes. Saddly Mecway doesn´t have an element quality check tool, but you will learn (and the solver also will remember you) with time to identify very bad shaped elements. Very often the option to atach the middle nodes of second order elements to the cad surface will give you bad shaped elements, so uncheck it if that the case.

4) No, I didn´t see any videos, but is very easy the linearization, just select a node in the interior side, another in the exterior (use CTRL to make a multiple selection), and then in the menu look for the Stress linearization tool, there you have a check box to use the selected nodes for the linearization. I have studied several videos and tutorials of stress linearization for ANSYS, Abaqus and NX and did some comparation with know/published results before applying at work.

5) The software came with a specific manual with tutoriales, and there are two or three channels on youtube with very good ones, even they take care of using less than 1000 nodes for being able to work without comercial licence.

JohnM

You can find plenty of tutorials.
Search YouTube for

Mecway Simcommons
Mecway 4P
Mecway VMH

SimCommons has links to download workshop files and all models work in tutorial version.

LorenzoS

Thanks Sergio and Thanks JonhM for your suggestions

For 3D you import a step file, also for 2D?

Sergio in some discussion I saw that you use Salome to mesh, so for example you draw in solidedge export in Salome to mesh and export in mecway?

Sergio I saw the video on you tube “Recipientes bajo presion / Simulación prueba hidraulica” could you share step file and Mecway file so so I try to replicate what you did?

JohnM, are all very interesting channels, I will watch them

I tried to mesh following file step of pressure vessel but Mecway giving me an error, have you got any solution?

Thanks again for the availability

Lorenzo

Victor

It generated a mesh for me with the default meshing parameters (press Reset button in Meshing parameters to be sure). Some elements were badly shaped (red X) but turn off Fit midside nodes to geometry for a quick dirty fix of that, or reduce element size for a more correct fix.

LorenzoS

Thank you Victor,
i tried turn off Fit midside nodes to geometry as you indicated and actually the mesh is generated but quality il low.

I tried to reduced element size but software give me an error, please see attached file

The sequence is import the step do the mesh and then apply loads and constraints?

Thanks again for the availability

Lorenzo

disla

Hello Lorenzo,

This happens when there are large models with very small details on it like the half coupling and its internal lip.See image.

Read suggestions carefully.

point 3) “avoid small radius, chamfers or holes that will not affect the overall results”

There are different options.

1-Finer Mesh. Increase the number of elements per curve/edge. Be careful, number of nodes can increase rapidly.

2-Remove the coupling and leave just the hole. For small holes it‘s normally not beautiful but it is a conservative solution.

3- Mesh as you like the body and bushing separately and connect them by means of contact. See Sergio point 2) Export as solids, one part in each file.

The attached configuration works

Sergio

Hi, this would be my workflow, normally I would choose the hexa or axissimetric mesh for solving this vessel. For some reason I cannot post images here since a week or two, have uploaded to imgur

https://imgur.com/a/JfwVrIZ

Sergio

Part is simmetric, and if we sacrifice a little of accuracy, we could say that is axissimetric and reduce a lot the size of the model.

Sergio

Finaly I was able to upload the pictures

Sergio

and the project files as well

cwharpe

Great tips, guys! That might qualify for a TED Talk.

Just wanted to reference previous mesh parameter tips posted by @disla, @prop_design, @VMH:

• http://meshcapades.byethost13.com/netgen_intro.html?i=1
  
• http ://youtu.be/6amu7J26kqY
  
• http ://youtu.be/h-OBmkslVEE

Also, maybe a shout-out for tinkering w/ GMSH as an alternative:



On the CAD/Modeling front: Until one gets proficient in 3D solids (real-l-l-y dislike the FreeCAD growing pains), a quick workaround is:

• Modeling part in Google Sketchup then Exporting as .STL file. Import into Mecway or improve by....
  
• Using FreeCAD to convert file to .STP format (ref: https://grabcad.com/tutorials/how-to-convert-stl-to-step-using-freecad). Simple in & out conversion.
  
• Mecway's internal Mesh Tools are quite useful and can easily handle the simpler geometries. Well worth the time exploring.
  

LorenzoS

Thanks guys, you are great, you rarely meet people so helpful!
I learned a lot

Lorenzo

mmartin

Good morning LORENZOS:

Nice to meet you and welcome to our community. I constantly learn a lot from this group of enthusiasts on FEM.

I agree with SERGIO, FC is a pain (I have a love-and-hate relationship) but I want to tell you that I recently use FREECAD-from REALTHUNDER fork(2022 01 11) which is more stable than version 0.19.3 from the official webpage. Once you finish your model(with all your parts), you only have to export to STEP and import it on MW; it suits perfectly.

I want to point out that this alternative version has improved( or almost work it out) the topo-naming problem (when everything crashed when you stick a sketch on a face and modify the model afterwards).
I also recommend you to 3D model using SHAPER module on SALOME MECA. By the way, last week a brand new SM 2021 for windows was released.

MANUEL

LorenzoS

Thank you Manuel, i really appreciate your advices
For beginners like me it only remains to practice!
Thanks again to all!

Lorenzo

Sergio

@LorenzoS, the first thing that you must understand is that not always the finished CAD model, with all the small details is the best for FEA, there are a lot of features that will complicate your mesh innecesary that will not affect the results. Also, remember that for any area were you apply pressure and want to have accurate stress results, at least three well formed element in the thikness must be, so an inicial max element lenght should be thickness/3, and yes, there will be a lot of elements :-) that´s why the first thing that you may ask you before start the model is... is that thing simmetric? How I can simplify my model?

LorenzoS

Hello to all guys, I finally managed to have some time to deepen the the ideas that you have suggested

Thanks Sergio for the suggestions of the last post

The choice of mesher (Netgen (default), Netgen 6, Gmsh) is function of which parameters? (according to what we choose one or the other?)

Gmsh Mesher is not available in my window, should I download it as an add-on? Is there a link?

In the specific case, of the file step “tubo semplificato” that I posted and in which Sergio made the mesh:
A) Salome mesh 2D
Salome mesh 3D
C) Mecway mesh
it seems to me that the best quality mesh is of Mecway; do you agree?

In addition, the mesh of disla and cwharpe performed with Mecway look great.
Maybe Salome is harder to set up?

I am following the videos you have recommended, sorry if I ask questions already included in.

Sergio I saw the video on you tube “Recipientes bajo presion / Simulación prueba hidraulica” could you share step file and Mecway file so so I try to replicate what you did?

Thanks again to this fantastic group and good Sunday

disla

Hello Lorenzo,

“to have accurate stress results, at least three well-formed element in the thickness must be, so an initial max element length should be thickness/3”

To check if your mesh fulfils this recommendation , you can use the Cutting Plane tool to look inside the volume.

My mesh may look good "outside" but do not fulfil that requirement. Sergio’s mesh is much better. Check the difference.

To have Gmsh mesher available you need to install it and give Mecway the path to the executable.

LorenzoS

Hello Disla,
thank you for your suggestions, but I don’t understand when to prefer the mesh of Mecway, Salome or Gmsh...i mean in general (i agrre with you, in this case Mecway's mesh of Sergio is great)

Lorenzo

Sergio

I would start with a mesh generated by Netgen standard inside Mecway (taking in count the size of the elements to have at least three in the main thikness), so then the mesh and BC can be associated to the imported CAD geometry. If standard Netgen doent´work, and you are sure that you made all the simplifications on CAD, then I would choose Gmesh. Now if I want to impress my coworkers at the bar with my mesh skills, I would mesh in Salome with quads/hexas, because for this model probably will give the same results, and the element count is about the same than using tets.

prop_design

@sergio your hexed meshed part is amazing. i'm very impressed as well.

Sergio

thanks! @prop_design

Now I realize that this exact mesh can be done directly in Mecway meshing with surface elements (with the option to use quads), and then revolving to get the hexas.

JohnM

I actually did that and forgot to post
See attached, a good hex mesh from Mecway just as you said, and you are spared the Salome Jungle!
I know Salome has its fans but I have never warmed up.

LorenzoS

Thanks guys, now I understand the right approach to the generation of mesh