Unlike with dogs, there is no need to visit your local veterinarian if your SOLIDWORKS part gets a hot spot. You can observe them and make decisions of how to deal with them (neither ointment nor antibiotics will be needed), if you have high concentrations of stress distributed over very small surface areas on concentrated along vertices or points you may have a stress singularity. Singularity stress values will increase as mesh refinement increases. High stress areas that do not increase (or very small amounts) as mesh refinement increases.
Example Hot Spot
The geometry and loading is shown below, with the back face fixed and the portion of the horizontal face (shown in green) has a load applied in the negative “Y” direction of 500 pounds. The material used is Solid Alloy steel. The study was run with four levels of mesh refinement (0.025”, 0.05”, 0.15” and 0.25”). We will watch the two probed points for stress values and decide if the areas of interest have stress singularities or stress concentrations.
And about our Hot Spots, there is a tool in SOLIDWORKS Simulation 2017 to help us screen for those Hot Spots (possible singularities). Once you have created and run a study, you can then create a Hot Spot plot by doing an RMB on the results folder once you have run the study.
Here is the initial message when a Hot Spot is detected (on left) and when one is not detected (on right).
There are three display view options for the Hot Spot plot.
- Gray Shade Shows Hot Spots
- Hot Spots Toggled Off
- Hot Spots Isolated (Mesh Size= 0.25”)
Stress Value Results
Notice how as mesh refinement increases, stress at the sharp corner increases and high stresses at the edge of the through hole remain nearly constant. Also note that there were no Hot Spots detected when the diagnostics were run on the part for the round through hole. Conversely, the inside corner has singularities, and a Hot Spot was found.
MESH REFINEMENT = 0.25”
MESH REFINEMENT = 0.15”
MESH REFINEMENT = 0.05”
MESH REFINEMENT = 0.025”
A Closer Look At Hot Spot Plots
Initial options when generating the Hot Spot plot are easy to set up, and below are a few examples of results with various sensitivity factors with a constant mesh size.
Hot Spot plot (24 sensitivity , element values, mesh size 0.05”)
Hot Spot plot (85 sensitivity , element values, mesh size 0.05”)
Hot Spot plot (50 sensitivity , node values, mesh size 0.05”)
Simulation 2017 Hot Spot Summary
Obviously adding a fillet to the corner makes the problem of a singularity go away, but also watch out for small machine features like shallow countersinks or slight embossments. These can give rise to either singularities, stress concentrations, and almost always bad mesh without local mesh control added.
By taking the example file and adding a shallow (0.01”) spot-face, the almost exact same part has some very different results. The aspect ratio is too high, and new Hot Spots are present. Simplifying geometry will allow you to do many more simulation iterations of “actual simulation” and not have to fight with trying to get a model to mesh.
Perhaps bringing up aspect ratio and feature size seems like a diversion, but those are both large contributors in studies not solving, or results not making sense. Use and enjoy the new Hot Spot plots, and simplify your geometry whenever you can.
σ = P/A and A=0 → σ=∞ are really the morals of this story; use the Hot Spots plots to seek these out and examine them. If they are “far field” from your local area of stress concern is you may be able to ignore them, if not you may want look at how loading is distributed over “area” vs points or vertices may be affecting your results. Also:
- Stress concentrations will become constant as mesh refinement increases.
- Singularities will continue to rise as mesh refinement increases.