Displacement Solves, but Stresses and Strains Do Not

brandonman

I'm a total newbie. I'm currently modeling the spars of a wing, with loads applied to represent transfer of lift through ribs at various sub-divisions of the two spars. I went ahead and built out my mecway solution with simplified assumptions from scratch, versus battling with importing from VSP. I'm getting what seem to be reasonable deflection values of the spars. Great! However, I am not getting any stresses (whether von mises, principal, regular ol' stress, or strain) to solve. When I right click to select 'What's wrong?', it tells me "Compatible with the analysis type and solver in the model - YES, Compatible with the analysis type and solver in the solution - YES".
I'm at a loss. I tried reducing the model down to JUST the front spar, in hopes of simplifying the problem, with no joy. The front spar is an I-Section, with the dimensions, isotropic parameters and density, defined. The rear spar is very similar, but a circular tube. I have loads applied to subdivided sections of the spars at various places across the span. I also have small subdivisions at the roots of the spars marked as fixed supports. I then applied X, Y, and Z displacements = 0 at those subdivisions, as well - that didn't help.
I am absolutely certain I'm missing something glaringly obvious here, as this is a simple problem, but am unsure as to what. I've gone ahead and attached my .liml for the geniuses here.
What am I missing?!

cwharpe

@brandonman,

EDITED 4/18/24:
..."von mises, principal, regular ol' stress, or strain [of beam elements]".

For CCX solver: Your list of stress outputs are listed in CCX as available for 2nd Order beam elements, to date limited to Solid & Hollow rectangles & circles (1st order also for rectangles).

For Internal Solver: One combination is available: stress(UU), the "stress in element coordinates", arising from (axial + bending) forces/moments, being read at corner nodes and/or a user defined location. (Ref. Manual pg. 47-50).

Generally, stresses may be checked by dividing internal reactions from the (6) vector outputs -- (axial(U), shear(V), & shear(W) forces; torque(U), bending(V), & bending(W) moments) -- by appropriate cross-sectional properties.

Alternatively, a hybrid approach would be to replace beam elements in areas of interest with shell or solid element cross-sections, connecting centroids to the beams with RBE2/RBE3 spiders. Then you have access to the solver's stress outputs in those locations.

Mishal

If you are keen on getting stress results on your beam elements have a look at the below link. You can use your Mecway results to generate what you are looking for

https://pypi.org/project/sectionproperties/2.1.2/