Workflow for automatic contact recognition

Sarvesh

Hi, I'd like to know whether there is a quicker and easier way to generate bonded contact amongst various components when importing the mesh into Mecway. Automatically determining the engaging contact surface will help me optimise my workflow greatly. Thanks!

Victor

Not currently, sorry.

Sergio

If the parts are in contact and perfectly modeled in CAD, you can export the assembly to Salome and mesh there with coincident nodes and avoid the bondad contact issue. Then export the mesh as unv with groups of elements for every component and import in Mecway to apply bc and solve.

polymathic

In the absence of automatic (a la Ansys) contact functionality, once you do build contacts manually there's a lot of work in maintaining them; I do a lot of iterative analyses, looping from CAD to Mecway and back again with updated STEP files. I imagine this is a pretty common workflow.

Anybody found a good way to retain face numbering in a STEP? You can delete one fillet on a body with hundreds of faces and all of a sudden your carefully built named geometries are exploded all over the part because during CAD export, the face numbering was reiterated.

As I see it, you either need a more strict background numbering approach (anybody's CAD package good at that? Bricscad isn't!) or you need very complex 'proximity' based re-mapping of named selections during the STEP 'reload' function in Mecway.

JohnM

Solidworks is not any better at retaining face numbering. We can reload CAD and maintain surfaces for things like tolerance studies, but as you say, remove a fillet and it's square one.

Possible cheats:

If you are re-working one part, try and set up your contacts so they can just be the whole surface of the part. This is a no-brainer for bonded contact (you only pay once), and in a lot of cases the increases in run time are a good bit less than the time you were spending doing the re-surfacing. It's a case by case thing.

If your contact surface is not the area of change, consider a 0.1mm extrusion that has the contact surface on one side and the other side glues to the new part (with 0.1mm offsets at contact surface). This way you can use that "whole surface" trick above without penalty.

polymathic

Thanks John. Somewhat comforting to hear the more mature CAD package isn't any better.
I have been down similar routes; regarding the first I had too many elements so the warnings go forever before the simulation starts, and with the second, I did the same with weld beads but had too many parts joining to other parts, to themselves, etc and eventually there's too much overlap and not all can be slaves. As you say case by case, in this case it's back to a monolithic merged solid. Luckily my materials are homogenous.

It has just occurred to me that the named selections are exposed in the API, so this is something I may play with to make the weeding out of the 'outdated' faces easier.

Sergio

Normally I create first named selections with names following a simple naming convention. This selections can be based on geometry or sometimes directly on meshes. Then the bc are applied to these named selections, and the name of the selection helps to identify what kind of bc must be applied, so I have an easy double check, because I can see that the BC is for example a displacement restrain or simmetry on X direction, applied to a named selection called SIM_X.. so became easy to detect mistakes.

When the geometry is updated, I have only to worry on meshing and updating/checking those named selections.

I have seen a nice automation for basic FEA done on Hypermesh were they took the color of the faces on the imported step file to apply bc and mesh refinement, something like "blue faces are FIXED", "red faces are LOAD", "green faces are for mesh refinement", so the desinger just paint the faces in CAD before exporting and the preprocessor recognize those faces and apply the bc based on a text script.

Even expensive and supposedly integrated CAD/FEA programs such as NX fails to re apply bc when the number of faces of the CAD model changes.

polymathic

Thanks Sergio

Agree, I have also spent countless hours re-establishing contacts in ABAQUS and Inventor NASTRAN. I have watched it done quickly in Ansys Mech, via the auto tool, but that is the only time.

The Hypermesh automation sounds like a good trick (BricsCAD is perfectly happy to keep face colours in-position despite constant rework of the body...)