Applying an inertia relief load 1

[DJStatics]

Hi there

I am trying to understand how to apply an inertia relief load, but I seem to misunderstand the set-up. I created a simple model consisting of a rectangular plate in the X-Z plane. I want to use an inertia relief load to prevent rigid body motion in the Z-direction. So I constrain the surface of the plate in the X and Y directions and I apply a shell edge load on the bottom edge of the plate in the positive Z-direction. Then I add an inertia relief load with the free direction in the Z-direction. See attached screenshot of model. I have given the plate a section with a material density as well.

After the job completes I get the following warning:

As required, the model has no boundary conditions in inertia relief loading directions. However, there may be at the most 1 numerical singularity warnings during each equilibrium iteration in the analysis. The displacement solution will be postprocessed to remove unconstrained rigid body motion. However, any extra numerical singularity messages may indicate other problems.

Solver problem. Numerical singularity when processing node PART-1-1.50 D.O.F. 3 ratio = 1.49681E-24.

Why is there still a numerical singularity?

 

[FEA way]

Do the results look correct ? This warning may be something you can ignore, as stated in the first message cited in your post. The rule is that the number of numerical singularities shouldn’t exceed the number of unconstrained rigid body motions.

 

[DJStatics]

The results look indeed as I would expect them. Thank you for the answer. It looks like I missed this rule about the number of warnings.