interpretation of buckling/necking

Altair Forum User

Hello at all,

 

i made an analysis of a wireframe of a formula student car and created some loadcases for buckling.

 

In HyperView there are some negative and some positive magnitudes for F (for buckling mode 4).

I´m quite sure that this is the factor λ.

So i thought if λ>0  (positiv) there is no buckling and if λ<0 (negativ) then there is buckling.

 

Now i noticed, in every case where are the negative magnitudes, then a tension rod is buckling or deforming and when there is a positive magnitude then a pressure bar is buckling. I thought only rods/bars under pressure can buckle.

 

My problem is to interpret these cases.

Could it be that the buckling of a tension rod is a kind of neckling???

And when it is a kind of neckling, how to give an interpretation of the buckling?

Why are tension rods are deforming in my buckling analysis?

 

I hope you can help me.

 

Regards,

Rizzo

Altair Forum User

Hello,

 

negative modes mean a change of sign of the loads. If your structure can buckle at this 'negativ' loads, then you have of course this modes.

To prevent this (although they are real), put a value of 0.0 or 0.1 to V1 at the EIGRL card. (Optistruct / Nastan)

 

Best regards,

Mario

Altair Forum User

Hi,

 

As Mario said with V1= blank in EIGRL card, at the value is negative and it signifies buckling tendency at load reversal.

 

With V1=0 in EIGRL card prevents calculating negative buckling 

Altair Forum User

Thanks to all.

Now it works /emoticons/default_smile.png' alt=':)' srcset='/emoticons/smile@2x.png 2x' width='20' height='20'>

 

Thank you!

 

 

 

Rizzo /emoticons/default_smile.png' alt=':)' srcset='/emoticons/smile@2x.png 2x' width='20' height='20'>