We all want one thing from SOLIDWORKS Simulation — the truth! But sometimes the results can be misleading in areas of high stress. We often wonder is this high stress real? Or is it artificial or fake? There are ways to get to the bottom of this, but most approaches are tedious and require many subsequent runs of the simulation. Thanks to the new SOLIDWORKS 2017 Hot Spot Diagnostics tool, you can uncover the truth in your simulations and more easily identify stress singularities versus stress concentrations.
Example Hot Spot
The geometry and loading shown below has 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.
There is a tool in SOLIDWORKS Simulation 2017 to help us screen for those Hot Spots (possible singularities). Once a study is created and ran, then you can create a Hot Spot Plot by doing an RMB on the results folder.
Here is the initial message when a Hot Spot is detected (left) and when one is not detected (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”)
Handling Hot Spot Pop-ups
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 singularities, stress concentrations and bad mesh without local mesh control added.
By taking the example file and adding a shallow (0.01”) spot-face, you'll notice that similar parts can have 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 prevent you from fighting 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. Enjoy using 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 Spot Plots to seek these out and examine them. If they are “far field” from your local area of stress concern, then you may be able to ignore them. If not, concider looking at how loading is distributed over “area” versus points or how vertices may be affecting your results. Also note:
- Stress concentrations will become constant as mesh refinement increases
- Singularities will continue to rise as mesh refinement increases
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