Solution Reporting

RobP

I am playing around with the software trying to figure it out. I dont have much FEA experience beyond the simplified versions bundled in CAD. I constructed a simplified bicycle frame and did a 3-d static beam analysis using two different sized round tube beams. I expected results to be reprted in displacement and von mises stress and was a bit surprised to see the results as displacement components of xyz and the rotations about those axes. I also got tensile force, shear force (in V&W), tosion moment, bending moment (about V,W), longitudinal stress at 4 points plus one user defined and twist angle. So I guess the first question is is there a direct method for getting the Von Mises stress and principle stresses? I am assuming that the U,V,W represent the X,Y,Z axes or are they with respect to a different axis system?

RobP

I found a LISA tutorial that answered a few of my questions. So it loks like the U,V,W coordinates are for the elements themselves with the U being longitudinal. I supose direction is dictated by which is the first node selected and which is the second node. It also looks as though the Longitudinal stress points are Beam shape dependent and shown in the material dialogue box. I assume the user defined point is the stress recovery point? Which leaves the twist angle, is this in respect to the U-direction? I am assuming VM stress and principle stresses would then just need to be hand calculated?

Victor

Hello RobP

You're generally right, just to confirm:

The U coordinate is in the direction from nodes 1 to 2.

All the beam stresses are longitudinal. That is, it doesn't calculate any shear stress due to twisting or shear loading. However, since the beam elements are Euler beams, they should be slender enough that shear force is negligible anyway. For twisting, you would have to do hand calculations, unfortunately. If that's significant, you could use it to find VM and principal stresses, otherwise just take the longitudinal stresses themselves.

There are 5 stress recovery points - 4 predefined ones, and 1 user defined one.

Twist angle is the rotation about the U axis, yes. So this is just the rotation angle transformed into the beam's coordinate system.

Is there another way you would prefer the displacements to be reported? Currently there are components, magnitude, deformed view, and vector field arrows (buttons near the right of the tool bar).

RobP

Thanks Victor, I'm just trying to get a handle on the particular controls and how things are reported, don't want to make assumptions.