Newbie help

bobs

Hello,
I am new to using Mecway and although I have past experience of FEA it has been nearly 15years since I used any software (past experience was Abacus).

I am trying to do some simple examples to ease myself into using the software and have set up a very simple static 2D 'beam' problem however although there don't seem to be any input errors, I get a 'Invalid stiffness for element' error and would grateful for any suggestions as to what might be causing this.

My project file is attached.

Many thanks

Bob

JohnM

First of all, rest assured you've picked a good software. we have many users and have been effectively applying Mecway for many years now. I would recommend simcommons.com and the other references you will find on YouTube for a quick start.
I think your issue is the plane you are running in- I rotated into the XY plane for 2D and it seems to run fine.

bobs

John,

thank you for the link to other resources and also for solving my problem :-) I'll now know to consider the orientation if I'm using 2D.

Thanks again

Bob

bobs

Hello, I'm after a bit more advise please. I've been doing a comparison between a shell plate and 3D plate for a problem I'm working on and the results are not similar as I was expecting. I tried to make sure that the constraints and loads are the same (along with the material properties and element dimensions) however the shell plate maximum deflection (in the Z direction) is approximately 5 times that of those seen with the 3D elements (the deflection using the shell plate is verified by hand calcs). Is anyone able to see where I am going wrong please? The attached file has 3 different versions: Shell, 3D element one cell thick and 3D elements 2 cells thick (hidden and supressed as appropriate). Any assistance would be much appreciated. Thank you Bob

Sergio

Switch to 2nd order elements for the 3D elements and the variation will be less. Maybe with more elements you will be closer.

Also the deformation is a little bit high, maybe you should do a geometric no lineal analysis.

Sergio

Changing the solver to CCX and no lineal analysis, displacement are very similar:

bobs

Sergio,

thank you very much for the advice. I'll have a look at both options, further useful exercises to enable me understand the capabilities and differences to be found in the software.

Thanks again

Bob

JohnM

Take a look at this:


In CCX, shell elements are expanded into hex8 with c3d8i shape function
We usually use hex8 with the CCX option to use c3d8i option (see CCX in tree)

hex8 c3d8 are too stiff in bending

hex20 c3d20R are supposed to be a very good option, but we usually use c3d8i