Salome 8.2 ParaVis

Another tool in Salome is the ParaView (ParaVis) module for Post processing.

Salome 8 ParaView
Salome 8 ParaVis

In this segment of Salome and Salome-Meca one can view the results as a normal post processor.

ParaVis Post Processing
ParaVis Post Processing

Compared to FreeCAD 0.16 this is a much better environment that allows more control over the results display . FreeCAD 0.17 is much better than it’s predecessor, however ParaVis is still a bit better, the interface is still cleaner and allows more control.

Salome 8.2 Meshing

The salome mesh environment also presents many options. It reminds me a bit of LSPrepost in the LS-Dyna product from LSTC or Hyper mesh with some differences. On the example I am showing I fused all the parts toguether since I didn’t know at the time if I could define contacts. The mesh generation algorithm’s come from NetGen it would be nice to see in the future Gmsh support as FreeCad is doing on it’s 0.17 version.

Salome 8 Meshing Interface
Salome 8 Meshing Interface

Meshing and viewing in Salome is quite simplistic and non visual. Tools like Ansys give us access to selecting surfaces, edges, and lines to allow us to define what we wanto to do to them. This is a limitation that NetGen, Gmsh and other open software lack. Also to troubleshoot a problem requires some knoledge of the mechanisms behind Salome and NetGen. Rendering sometimes fails to display meshed parts or displays parts of them and this was a bit anoying to me.

With the Salome package we get a geometry creation editor, a mesh generation editor and a post processor analyser but where is the solver? This was something that didn’t feel well when I started with Salome, I knew that eventually I would get into a dead end. And so it was wright! To use a solver I need Code-Aster or if I want the two packages bundled toguether we need to use Saolme-Meca where it intigrates the solver. I will get to that subject in a future post.

Salome 8.2 Geometry

I read a lot of information about salome as a pre processor and post processor. Basically you can make a geometry create a mesh and then view results.

The GUI is quite simple at start.

Salome 8 Menu and Toolbar
Salome 8 Menu and Toolbar

As we start diving into this program we start to see it’s complexity. If we make a new project and open the geometry pane we see myrad of tools.

Salome 8 Geometry
Salome 8 Geometry

Although the way we manipulate sketches and solids is way easyier in spaceclaim or RS Mechanical 2 Salome is good enough to make parts. I also think FreeCad isn’t the perfect environment since it also has it’s gaps, however between one and the other I am starting to prefer Salome for its interface looks more clean. A good plus in Salome is that I can define veriables and use them when I create features. Then if I want to change anything it’s plain simple, however if I don’t create the variable and link it there is no other way to change it. This point for me could be improved in the future. Since if we need to change something after it’s done its not that friendly to do it with the GUI.

Salome 8_2 Geometry Table
Salome 8_2 Geometry Table

All in all it is a solid CAD modeler that is very usefull and in my opinion far better then design modeler from Ansys and on par with FreeCAD but way behind payed CAD packages like Unigraphics, Solidworks, Creo, Spaceclaim, … Although not as good as these professional packages I think that there is no shame on using it since it is sufficiently powerfull to build and anlyse models and I also question if it is necessary all the power of those heavy weight tools. Maybe if I was allowed to ask something I would ask for more natural part building and part manipulation and selection.

Why NetGen Why!!

This time around I am presenting a alternative mesher to gmsh. The application is called NGSolve/NetGen it’s installable both in Mac and Windows which made me very happy at the beginning. Afterwards I opened a step file with no issues and generated a default mesh (on the windows version).

NGSolve/NetGen mesh in windows
NGSolve/NetGen mesh in windows

I really liked the visual display and the mesh quality. This is a default mesh.

NetGen Close up mesh
NetGen Close up mesh

The close up rendering mesh shows good image detail and the mesh elements geometry look more uniform and the circular shape looks well represented through the mesh.

At a first view the mesh seems much better compared to gmsh. There is however a problem. I could not open step and iges files through my mac. This was a frustration…. It seems that the windows version already has a binary file for open cascade which is the library that allows the NetGen software to understand these formats. On the other hand there is no easy way to install the open cascade library on a mac neither it seems to have been tested in detail with netgen.

This is a big frustration point for me.

Free simulation package Gmsh

Free simulation package Gmsh – Geometry – Mesh – Result

I have posted previously a list with many comercial simulation packages. These packages have numerous features, are very robust and have active development, however they are expensive and their source code is closed. A free alternative is growing day by day, although the user interface isn’t as user friendly and are feature reach as comercial packages they allow for some level of calculations or the same but with an added patience requirement to understand how they work. Many packages developed so far tend to solve individually each simulation requirement from geometry creation to mesh generation, a solver to calculate results and finally a display environment to view the calculated results. Gmsh tries to combine all in one in order to work in a similar fashion as Ansys APDL or LSPrePost. It still has a long way to go but the ideia is there and with time the user interface will grow to be even better. Just wish it was easier to work with.

Gmsh pin mesh
Gmsh pin mesh

The image above is a slightly refined mesh. I did’t play much with the meshing parameters.

The good thing was that I could run it with Windows and Mac with no installing issues.

Dificult to find a CAD software that’s free to use

From time to time I make an effort to know what’s out there regarding simulation and CAD applications.

Free software are allways evolving and it is good practice from time to time to see what’s available out there.
This time around my quest was for a good (suficient) CAD editor and STP viewer. I found a list of many packages in the link bellow however after reviewing each of the links I got a little disapointed with what I learned.
From start major packages were disqualified: Solidworks, Catia, Siemens NX, Creo, Autodesk Inventor, Spaceclaim, Solid Edge and AutoCAD. All major software packages that I could remember off.
On the list I noticed a mixture of DWG and 2D CAD files with 3D models files like .STEP, .IGES. The 2D versions were also disqualified leaving only a few candidates.

http://listoffreeware.com/list-of-best-free-cad-viewer-software/

The list shows many projects and might have something useful, though not for my purposes.

But to be honest I could not use effectivelly any of the offereings.

What I really like to use and edit CAD files:

• Free CAD (Any use)

• SketchUp (Personal use)

• Design Spark Mechanical (Any use) My preference

Unfortunatelly aside from Free CAD I could not find any good software for a mac system which is free. I wish DS Mechanical would come in Mac version.
The good thing here is that DS Mechanical is Spaceclaim but more simplified. It’s Enough to work with and produces great results. So my recomendation is to use Desgin Spark Mechanical.

• Easy to model and learn (Push and Pull interface)

• Good rendering

• Easy 2D sketch

Design Spark Mechanical
Design Spark Mechanical

Ansys extensions

Every now and then I look for new extensions that Ansys can support. Some time ago this software package allowed for third party extension development but there weren’t many to choose. Since then things have evolved a great deal. Browsing through the internet I discovered that CADFEM has been working hard on this subject and offers a few extensions as its products. They are not all purpose extensions and have a very specific purpose in some cases like moulding specific calculations. Aside from these which I showed Ansys site offers quite a big set of plugins also, some free others paid.

http://www.cadfem.at/en/products/cadfem-ansys-extensions.html

LSTC – LS-Dyna

I have to say that this bit of software really rocks! I love the way it ticks. It uses a free GUI or if you prefer a text editor. It is very well known for it’s explicit solver but the implicit solver has evolved to a more mature state compared to the past. In this package I really feel I own my model since all of it its setup is in a readable text format. So I guess this package has as it’s strengths a good solver and a free editing pre and post processing GUI with a readable model file that contains geometry and all of the configurations needed.

LSTC could up a bit the meshing environment and the CAD connection. Many times I need to use Ansys to create and optimise the geometry and mesh it to then export it to LS-Dyna. Complex geometries with Hex elements are a challenge in LS-Dyna but of corse so are the duplicated nodes that we encounter when we import a model from Ansys. All in all it requires some getting use too, to find the ins and outs of these two softwares and make them work together. Still the end result is very powerful.

LS-Dyna is also visually appealing as you can see in the following image:

LS-Dyna Pre Post
LS-Dyna Pre Post

The working file in LS-Dyna is a .K file. If opened with LS PrePost and if we open the keyword manager we see the following:

LS-Dyna K file
LS-Dyna K file

Most of the model configuration can be access through the keyword manager and analogously if opened the file a text base structure can be seen with the same organisation as the keyword manager.

K file for LS-Dyna
K file for LS-Dyna

Ansys Environment

The workbench environment allows for great flexibility in regards to choosing the physics we intend to use and offers an easy way to link another physics analysis that picks up on the previous model and results. Like mentioned on my previous post this is a great package but I always feel when I use it that the model isn’t mine, and it generates a complex binary file that when  corrupted, there is nothing I can do to restore it. Also I always get disappointed that I cannot share my settings with other users, like I can do with other simulation packages to get support. There are workarounds but they don’t feel natural.

For an Idea of how the environment is (look at the left to see the physics and if you drag the title from left to right a physics box appears):

Ansys Workbench Environment
Ansys Workbench Environment

When we insert the correct model input the question marks are replaced with a green check mark.

Ansys Model Box
Ansys Model Box

The environment is very visual, however the resulting file is a weird binary file.

An alternative is the classic environment which has a bit of prehistoric GUI but has the full potential of the Ansys Solver. Many are familiar with these black windows and command based applications. Basically with a few commands and a bit of experience one can do almost 🙂 anything. There are a toon of tutorials and guides out there on how to use this comprehensive simulation package.

Ansys ClassicI nterface
Ansys Classic Interface

The Ansys simulation package – My remarks

The Ansys simulation package is around for many years, I remember it from my university years, back then there was only what today is Ansys APDL. I have a love and hate relationship with this package. I love the APDL configurability, where we can adjust just about everything and adapt to what ever needs we have. We own our simulation since we have a text base version of all the commands executed to perform the simulation and when something changes in a new version of Ansys we can debug the code and adapt. My hate relation with this software is in the user interface where on purpose it was not updated anymore. This means that it is harder to handle the geometry, nodes and meshes, well it takes a little longer to like it at least.

The newer Ansys Workbench environment makes everything too easy in a way that we don’t actually get to know what we are doing. When you define a mesh basically we get by default a tetrahedron mesh however no information regarding nodes and formulation is evident, one would have to search for the information and how to override. Some will like it others will hate it but it’s not direct this information. However workbench provides in my opinion best in class for simplicity meshing utility, it makes mesh generation something very easy. There are limitation when we really need special shapes but overall very easy. My hate relationship with workbench is that I feel I don’t really own my model and am stuck to a binary file that sometimes gets corrupted. If I wan’t to share what I did to generate a model it is very difficult to do it, the only way is to generate a web archive binary file or a mechfile. One of the best features workbench offers is the connection to CAD. Many times I change my CAD file and update it without losing any configuration definition, and when something is lost I can easily fix it.

There are a few tricks that can be used to connect a workbench model to Ansys APDL. Basically we start with workbench and setup everything. Afterwards we transfer the model to APDL and continue from there.

Ansys offers a very complete package for simulation, could be more open to a text base model definition like Ansys APDL or LS-DYNA to get even better.