Confusing behaviour of the beam model

[sylwcios]

Hi,

I have found myself in a quite confusing situation.
My beam model does not behave as I expected.

I included 3 photos to show the model. Basicly the only difference between them is the diameter of lateral support (the shortest section in the model, the changes in diameter are visible, thickness of this sections remain the same).
When I decreased the radius of this lateral support stresses level is also decreasing. Comparing the size of the support 25(radius) (186MPa) & 10 (150 MPa) & 20 (195 MPa).
Why for the smallest tube the stresses level are the lowest?
Can you help me to understand this problem is it "normal" or is it something wrong with my model?

 

[Naffoussi]

You are post-processing the point2 combined stress.
When I post-process stress on beam elements I take the max (Abs) of these four output vectors:

EndA Max comb stress
EndA Min comb stress
EndB Max comb stress
EndB Min comb stress

Try to post-process like that and see if results become as you've expected..

Seif Eddine Naffoussi, Stress Engineer

http://www.Innovamech.com

33650 Martillac û France

 

[sylwcios]

The stresses distribution when using

EndA Max comb stress
EndA Min comb stress
EndB Max comb stress
EndB Min comb stress

is the same so this won't change anything.

 

[Naffoussi]

I think it is about flexibility of the assembly.
You can see that the stress distribution is transferred to the medium section which is not the case in your first case.

Seif Eddine Naffoussi, Stress Engineer

http://www.Innovamech.com

33650 Martillac û France

 

[rb1957]

the load in the reduced member seems to be falling, but the load on the "elbow" (the sloping member) seems to be increasing. it looks to me as though the stiffness of the model is redistributing the reactions away from the lateral brace (as it's stiffness is being reduced).

i'd look at where the load is going (rather than the stress) ... internal shears and bending moments should help you understand what's happening.

another day in paradise, or is paradise one day closer ?