Circular (tube) beam element on CCX

Sergio

Hi, is possible to use beam elements with anular section (tubes) in Mecway using CCX solver???

Regards

Andrea

I think that isn't possible.
I never use this kind of elements B31 - B32 but from CCX manual the nodes that define the beam are expanded into 8 nodes elements. So you can obtain rectangular section and elliptical section. This automatic nodes generation can't generate hollow sections. To be sure of this you could post on Calculix group.

Victor

You can use circular tubes. CCX expands them to square sections, presumably with a special stiffness matrix.

Andrea

Is true using

*BEAM GENERAL SECTION

rhoka

nicely Dhondt has Civil Engineering backgrounds, he provides very useful command to build an arbitrary section for straight (B31) or curved (B32) beams. these methods more like 1D fiber beam element in other FE software. i'm being study and compare the differences for each methods.

previously i can built rectangular hollow (boxed) section and many other shapes, yes it's look possible too for circular hollow section shapes. can be more complex shapes as you can imagine.

next time i need to try

Sergio

Hi Victor, thanks for the example. Ugly thing is that at postproceesing the tubes are showed as square sections :-(

Andrea

Because is a square section. Reading CCX Manual is possible to understand that:

The actual cross section is taken into account by appropriate placement of the integration points.

So the calculus  is based on the correction of the position of the integration points.

To avoid inappropriate  3D view you can add OUTPUT=2D as a parameter of *NODE FILE.

This option could be usefull also on Mecway but I didn't find nothing into CCX options.

In fact also for shell elements 2D view instead 3D view could be desiderable


Connected aspect is the composition of the .dat file generated by CCX.
By the keywords  *NODE PRINT and *EL PRINT (followed by relative parameters) is possible to have total reaction forces on a node set and the stress tensor at the integration points

Sergio

Thanks Andrea for the comments!

That's are the things that make's me escape from shell elements while I can, not only in CCX/Mecway but any other solver. For 3D solid modeling guys as me there are severals things to take in mind to don't make mistakes (orientation, sides, conectivity keeping the thikness...and after postprocessing, upper side, lower side...). Have desing a lot of sheet metal parts, small parts (automotive, but not the big panels), and we always work with solid meshes obtained from extrusions of 2D meshes to avoid this mistakes.

Regards

Victor

Take care with OUTPUT=2D on beams. It used to have a bug that caused the stresses to be wrong. Not sure if it still does.

Andrea

As I wrote I never used 1D elements on CCX but reading the manual:

The displacements are best obtained in the non-expanded view, i.e. using the
OUTPUT=2D option. This means that for the present results the example
had to be run twice: once with the OUTPUT=3D option and once with the
SECTION FORCES option.

This part of CCX manual treats also a discussion on reduced integration elements. I think that if one wants use beam elements must read parts 5.13 because could be obtained errors on shear stresses