SOLIDWORKS Simulation - Why does red always have to be bad?

Customization of stress plot colors.

Nineteen years ago (wow, that makes me feel old), Paul Teutul Sr. and Paul Jr. took the stage at SOLIDWORKS World 2005 in Orlando. They discussed how SOLIDWORKS helped them in their custom design and fabrication of motorcycles (choppers). Unless you lived under a rock, I’m sure you have heard of their show American Chopper or their company, Orange County Choppers.

While on stage, Paul Sr. exclaimed that he had no idea what the stress plot meant, just, “Red is bad, blue is good.” This statement, while comical, isn’t completely wrong, but it can be dangerous if it is not examined further.

SOLIDWORKS Simulation post-processing is extremely versatile and easy to set up. The default automatic settings will show you where stress hot spots are and give you “lots of pretty pictures.” Sometimes, though, these pictures can be misleading. In the next few paragraphs, I will show you some tools in Simulation that will allow you to better understand and explain your plot results.

Explaining Simulation results to non-technical customers (or managers) can often be challenging. Depending on your color and/or deformation scale, results can look REALLY bad or not as bad as they really are. Take the images below. Both are of the same study, I just changed the scale in the legend. From a quick glance, which one seems worse?

The fact is, they are both viable. The Maximum stress in the model has not changed. It just looks (at a quick glance) like the bottom image has much higher stress than the top one.

This is why it is very important for a designer or analyst to truly understand what their plots are telling them.

Personally, I like to change the top number in my scale to the Yield Strength of the material. With that set, anything red is likely in or near plastic deformation and would require a closer look.

As a new feature in SOLIDWORKS 2016, you can specify a unique color to any value above (or below) your scale. This, in conjunction with setting the upper limit of your scale to the maximum tolerable value (in this case, Yield stress), will make for much more representative plots.

I changed the plot settings to show anything above 100MPa as black. This design required a FOS of 2.

Now, it is clearly visible which areas of my model do NOT meet my requirements.

The plot options also include many color ranges and variations that may describe the plot more clearly. So, next time you are looking at your result plots in Simulation, dig around a little in the plot settings to make sure you are using the best options to portray your results.

SOLIDWORKS Simulation is easy to use and a great tool to have in your arsenal. But if you do not understand or cannot convey your results, it is like using a hammer to drive a screw. You will get there; it just won’t look pretty.

As always, thanks for reading, and happy Simulating.