Nonlinear 3D with beam elements for Spaceframe Car chassis

barrti

Greetings all

I am building a model of a spaceframe car chassis including McPherson strut suspension which has about 100mm travel at the wheels. I've been using truss elements successfully with nonlinear 3D (CCX and Mecway solver).

From what I see, I can't use beam elements If I select Nonlinear 3D Analysis type. I think this applies to the Mecway solver and the CCX solver.

Is it possible to use beam elements in this situation?

Cheers
Tim

Victor

You can use beams with the CCX solver and nonlinear but not the internal nonlinear one.

In case you need circular tubes instead of rectangular section, they have to be line3 elements. Use Mesh tools -> Change element shape to change them.

barrti

Thanks for this Victor. As always I appreciate the fast response.
Do you mean I can use beams+nonlinear with the CCX solver accessed by clicking within the Mecway GUI?

By the internal nonlinear is assume that u mean the nonlinear solver you have built into Mecway?

Cheers,
Tim

barrti

Victor
It works as you described. Thanks
Tim

Sergio

Nice model Barrti. One of the drawback of using CCX with beams elements, is that if you define a circular/anular section, the results will show it as cuadrangular equivalente sections.

Regards

barrti

Sergio,

thanks. The model isn't that good really - I found the hard points of a WRX online and then joined up the dots. The model is a proof of concept model to see what could be modeled.
I see what you mean about the results though.

I now have to convert the lower control arms to trusses I think as they have lost their ball joints in the conversion to beam elements!

barrti

I have a question about end releases on beam elements. Can these be done using ccx in this nonlinear 3D case? I need to use end releases on the end of each beam where they join the chassis. They will act as ball joints.
The manual section 10.9 talks about flexible joints but it appears that they might only apply to the middle of a beam?
Tim

Victor

The "flexible joint on beam" is for this type of joint - not only in the middle of a beam. But it's currently only for the internal solver.

I'm not sure how to do that with CCX. You might need to model the two beams separately (no shared node) and then couple them with constraint equations. See the CCX manual for details.

barrti

Victor
Thank you.
Tim

barrti

Greetings again
Finally got back to this. I used beam elements for the main chassis tubes and truss elements for the lower suspension arms. It has spring damper elements at 40 N/mm stiffness with 4 off 3000 N Loads in -Z direction above each corner. I have Z constraints at the end of each suspension arm along with spring elements 80N/mm to simulate tyre compliance in the X and Y directions.
This should give about 80 mm vertical movement of the whole chassis in the -Z direction.

I can get it at one end of the chassis but not at the other end. I've messed around a bit but cannot get it to deflect in the -Z direction uniformly.

Very frustrating! Any ideas?

Tim

Victor

One end doesn't deflect much because the 4 lower suspension arms at that end aren't set at truss.

Note that this is a 3-state checkbox. If you have more than one element selected and they don't all have the same setting for truss, it'll show an indeterminate state, neither a check nor a blank.

barrti

Oh good grief. I thought I'd checked it.
Thanks so much Victor.
Sorry to have missed that.

Success!

Tim