The only difference between these two scenarios is that the 1^st one has a fixture on the left side and the 2^nd one has no fixture. In this circumstance, the 2^nd scenario would always get the “excessive displacement” error because nothing is resisting the load on the beam and it would just fly off in space. Obviously, having it fly off in space is not the intended behavior and the excessive displacement is just a warning sign that we set up the problem incorrectly.

While the cantilever beam example is it very clear what is wrong, in your assembly it may not be as obvious. If you are analyzing an assembly or multi-body part, it might not be the fixture that is missing but the connections between bodies. If one body is not connected to a different body as you were expecting and therefore can’t resist the load, then you likely will get the large displacement warning. In circumstances like this, utilizing tools such as the “Interaction Viewer” tool to visualize the connections in your part or the “Find Underconstrained Bodies…” tool to identify the degrees of freedom that a part can move can be invaluable for your troubleshooting. You can also get a good idea by looking at the results after you run your study and look for any parts that aren’t connected to the other bodies.

When the Excessive Displacement Warning message comes up you almost always want to select “No” in the message and look at the results to see if parts are flying off and analyze/change your setup as previously discussed.