For those of you who’ve started using simulation in Fusion 360, you may have come across some results that gave curiously high stress values. While there can be various reasons for this, the most common is related to what are called ‘singularities’. Singularities are inherent to all FEA software, so its important to know how to identify and deal with them.

A sure sign that you have a singularity is that as you refine the mesh (and hopefully you’re doing this using the automatic refinement tools in Fusion!), the maximum stress value will continue to rise causing your convergence plot to…well…diverge:

The easiest way to describe why this happens is to correlate it to a simple math problem; a fraction. In a fraction, as the denominator approaches zero, the value will go to infinity. What’s happening in a singluarities case is that as the mesh/elements gets smaller in areas with sharp “reentrant” corners and points under load, you will see their stress values continue to rise to infinity. 

Take a look at this video to see how you can verify this, and learn some ways of dealing with or interpreting the results: