New local coordinate system (CCX TRANSFORM)

Sergio

Hi, is possible to create new coordinate systems on Mecway's GUI? Something like the TRANSFORM card from CCX. I'm working with bolted unions and having a local coordinate system is a must for appling bolt preloads when they are not alignated with the global css.

Regards.

Sergio

Also having a visual representation will help a lot, is a little tricky to figurate the new directions without a visual reference

Victor

I don't want to expose the node coordinate system concept in Mecway's interface but instead have directions directly included as part of the constraints. What feature of CCX are you using for bolt pretension? Is that the PRETENSION MPC or forces or displacements? Perhaps I could add it as a new kind of load which incorporates the direction.

Sergio

I'm using by the moment a load applied on a set of nodes, this set of nodes has his coordinates system reoriented by means of a TRANSFORM card. I have tried before with the pretension card but can't make it work. I'm working on a production part, so I cannot share directly the models, but tomorrow I will prepare a simple model to make some test and able to upload to the forum.

One of the problem that I see with the TRANSFORM card is to check if the directions are ok or not, having the cs on screen would help a lot.

scottr99

I think to make the pre-tension card work you'd have to have a portion of shaft of the bolt be a separate volume but sharing a face with its adjacent volumes. This way you end up with a SURFACE normal to the bolt/force direction, as one of the two card entries to choose from aside from NODE. I do this in Ansys with 'Form New Part'. I don't know if that's your issue but figured it might be. But for non-linear analyses there's the issue of the pretension load not wanting to follow the deformation of the fastened structure. Have you considered a thermal load, on a purposefully exposed portion of the bolt shaft?

Sergio

I will try again with the preload card directly to see if I can make it work. About thermal preload, I'm trying to avoid it.

Sergio

I was able to solve a small assembly using PRE-TENSION card, but somebody knows how to use it if the bolts are not alignated with the coordinate systems? Luckily this part has the bolt aligned, but this is not always the case.

Tomorrow I will try with the complete part and adding a second step to load the part and put in traction the bolted unions.

scottr99

Hi Sergio, I was able to get *PRE-TENSION working. The difficult part was getting my geometry/mesh to have faces -- or a surface of mesh faces -- normal to the longitudinal axis. Once I get more familiar with these tools perhaps it will get easier. In this example the 'Y' axis is the longitudinal axis and the load is 22241 N.

scottr99

vid below..

scottr99

youtu.be/aiXtaw__98U

Sergio

Scott, I made the same as you (even my part has the bolts aligned in Y). What I have made in order to have the loading section normal to the bolt axis is make a 2d mesh of the bolt and then extrude along the axis, then the shaft elements has faces normal to the axis. I was able to solve even with contact in the bolt head and bosses/lower part.

During some initial tests I have applied by mistake the load in the x direction (radial), and I can see that at the loading plane the part behave like if it would be separated. Now I don't know how it will work during the second part of the test when the bolts will be pulled.

scottr99

Sergio, x direction is not radial as far as I know. It's x in cartesian. And if your longitudinal axis is y, then you should only have "0.,1.,0." under *Pre-tension. If you had "1.,0.,0." then it was pulling it transversely. Is that what you meant?

Sergio

Yes, exactly

scottr99

I like how you made the bolt mesh, I'll definitely be using that idea. But if there's a lot of bolts that could be cumbersome I think.

Also, it would be nice if we could hide a selected set of elements. I had to use the cutting plane to see/pick the faces on my normal face, and that was painful. It seemed that I could not view the model any way I wanted when using the cutting plane.

Sergio

Yes, meshing takes a little of time. I have meshed the part in Salome, the bolt with 2D in Roshaz and then extrude in Mecway, and the fixture is also a 2D mesh extruded. For making the set of faces at the bolt shaft I have the same problem, there is no way to select internal faces of elements in Mecway! I make a new temporal component with the lower part of the shaft and then hide to expose the internal faces.

scottr99

Well I had to use the cutting plane which was painful because I couldn't see what I was doing as I was doing it, if that makes sense. I had to do a step then check, repeat. I think if we could hide a selected set of elements on the fly, they could be exposed and selected with ease.

Sergio

Guess that the best would be the possibility of select the hidden faces in wireframe view mode as is the case with the nodes