Mesh Control

[suljicm]

Dear Developer

We have decided to use the FEBio software to conduct a FE analysis of an infant spine and neck to investigate Shaken Baby Syndrome.

We have a Simpleware model of the spine and a SolidWorks model of the head which we would like to import into PreView to set up the analysis. We are currently using STL files as they seem to produce good quality imports when imported into PreView. They also import vertebrae and IVDs as single entities which is very useful for us. However the problem with importing STL into PreView is that the head and spine are made from surface elements. Our analysis requires that we use solid objects in order to give useful results. We have managed to convert surface elements to solid elements with the in-built TetGen generator. However the mesh cannot be manipulated within PreView i.e. we would like to reduce the number of elements to minimise computational time as well as have control over mesh density (want denser mesh in the chin region and at the back of the head).

We have therefore tried to use external meshing software and then import the suitable meshed solid object into PreView. From commercial software we only have access to Patran that we think is suitable for our wanted control of meshing. At this point we are experiencing problems with manipulating the different file formats to import the wanted meshed model into PreView.

Do you have any suggestions on whether PreView can provide the meshing control we desire or if there is any other meshing software (preferably open source) that is compatible with PreView. I apologise for the long description but I just wanted for you to have some idea of the background of our issue.

Thank you for your time and help. It is very much appreciated.

Regards

Mirt

[maas]

Mirt,

There is a lot of work that still needs to be done on mesh generation inside PreView. Since at this point this is not a high priority, the better coarse of action would be to use another mesh generation package and then figure out a way to import the FE mesh into PreView. You mention Patran. If this format is a text format I can probably add support for that format directly into PreView. Is it possible for you to send me some small but representative example files? That will give me an idea on how much work it will be to add it to PreView.

Thanks,

Steve.

[suljicm]

Steve

Thanks for the reply. I have attached a Patran file of a vertebrae. I basically imported an STL to Solidworks, and then exported as an Parasolid (.x_t) to Patran. I've applied a solid tet mesh to the model. Hope you find it useful.

Regards

Mirt

[maas]

Hi Mirt,

The file you attached (c1_patran.db) seems to be a binary format. Binary formats are usually very difficult to parse, so we tend to avoid those. Is the .x_t file a text file? Perhaps you can send me an example of that format?

Thanks,

Steve.

[suljicm]

Steve

I've attached the Parasolid file.

Thanks

Mirt

[maas]

Mirt,

I found a reference of the parasolid format and I've been trying to understand the model file you attached, but I haven't been able to make a lot of progress. Can you tell me a little bit more about what this file represents? Does it contain the FE mesh? Is it possible to send me a really simple example (e.g. a single tetrahedral element) in this format?

Thanks,

Steve.

[suljicm]

Hi Steve

The file I have attached in the previous post is a parasolid file (head_final.x_t) of a head I exported from SolidWorks.

I am not sure whether a parasolid format can save information about the FE mesh and I hence I was not certain how to export a single tetrahedral element from Patran.

However I have attached a file of a vertebrae (as I thought this might be better than the head model just because it is smaller), but in this case the vertebrae was exported from Patran after meshing. It is in a text Parasolid (.xmt_txt) format. Hope this is useful.

Thanks

Mirt

PS. For some reason I cannot attach the zip file (get a database error) so I will try to add it as soon as possible.

[maas]

Hi Mirt,

Are you trying to upload a file that is larger than 2Mb? That's the file size limitation for zip files.

Alternatively, you can email it to me at steve dot maas at utah dot edu.

Cheers,

Steve.

[suljicm]

Steve

The file is 1.3 Mb so I am not sure why the forum will not let me attach it. I have therefore sent you an email.

Thanks

Mirt

[Curt Voss]

Hey guys, if I remember correctly from my brief Patran experience, I think you want to export the Patran Neutral file, checking an option to include the finite element mesh (and probably unchecking anything else). I think this is an ASCII file, but I'm not positive.

As far as I know, parasolid is more of a CAD/ProE-type format and probably doesn't carry FE.


Here is a little info on the neutral file:

http://www.g-boege.de/english/makrosae/Manual/PATRAN.htm

[Curt Voss]

Actually, now that I think about it, I'm 99% certain Patran can also export to Abaqus and/or Ansys formats, which PreView should easily handle.