"No valid results could be calculated" error -- how to debug?


#1

Hi,

I tried doing a simulation, but got the following error. How do I begin debugging this? Googling for “No valid results could be calculated” on Google yields absolutely no results, as if I’m the first to encounter this error?

Here’s a link to my project, in case anyone wants to take a look.

Many thanks in advance,
Robert


#2

Hi @rs20 ,
the solver stops at the point where it tries to factorize the matrix, this may be due to several reasons but in linear statics this is most often caused by a not sufficiently constrained system.

An this is also what happens in your case. You constrain a full circular edge in z-direction and only a single point in X- and Y-direction. This way you only constrain 5 of the 6 rigid body motions (z-movement plus x- and y rotations with the edge constraint and x- and y- movement with the point constraint). This leaves the z-rotation free.

In order to prevent this you need to fix an additional point in x- or y-direction to constrain the global z-rotation.

Best,
Richard


#3

As a side note, I would prefer in this case to use the advanced static analysis solver. This has also the option of a remote displacement, where you could easily constrain the system without adding additional stiffness to it.
I’ll quickly copy your project to show you what I mean.


#4

I finished the study of using different constraints with the two possible static analysis solvers.
You can check out the project here.

In the basic static analysis i used the constraints that you already had plus an additional where i either additionally fixed DY or DX, doth gave the same result.

In the advanced static analysis I used a remote displacement BC fixing all 6 DOFs and put the reference point to the center (0,0,0), with activating the deformable option. So this constraint should not add any stiffness.

Here you can see the comparison of both (the essentially lead to the same results):

Displacement magnitude. Left: Static Analysis Right: Static Analysis - Advanced

Von Mises stress. Left: Static Analysis Right: Static Analysis - Advanced

Best,
Richard


#5

Thank you so much for your help! That makes a lot of sense, and I’ve got my simulations working now.