Buckling analysis

[Senad83]

Hey,
is it wrong to use 8-node elements in buckling/postbuckling analysis? Riks' analysis are giving me some strange results when I use 8-node elements. I've used 420 as yield stress, but von Mises stress exeeds this.

 

[corus]

I'm not sure why it's strange if the stresses exceed yield. Check your results with a hand calculation if possible to get a 'feel' of what your results should be.

corus

 

[Senad83]

Impossible to do hand calculations as the geometry is very complex. Principal stresses can exeed yielding stress, but I thought that max von Mises should be yield stress or below. I'm not sure though.

 

[corus]

Von Mises will be yield or below if you're using plasticity.

corus

 

[Senad83]

I am using plasticity, with yielding at 420 MPa and plastic strain at 0.18. Everything looks ok when I use 4-node elements, but not with 8-node.

Senad

 

[corus]

It's probably because the stresses at the integration points are at yield, but extrapolating to the surface nodes will give you stresses apparently above yield.

corus