In my last blog post, Two Men, Darts, and SolidWorks Simulation: Accuracy vs Aim, I related a story about two men to SolidWorks Simulation. I recommend reading it. This article will be the start of a series, with each article centering on the assumptions I alluded to in that article. With that being said let’s kick things off with a discussion of material properties!
Disclaimer: Do not let this series fool you, SolidWorks Simulation and Finite Element Analysis (FEA) in general is a great tool for predicting product performance. For this series, we are specifically focusing on the uncertainties of the components going into the analysis for the purpose of making everyone who reads this article a better FEA Analyst.
First, there are two major concerns with material properties.
1. You can’t test all the material you will use. It isn’t economical and most times is destructive.
2. Testing has some uncertainty in that the properties are usually extrapolated, not measured directly.
Example: To test the Modulus of Elasticity a known cross-section is taken, a known force applied and displacement measured. It can also be done the opposite way by applying a known displacement and measuring the force to get it there. Either way, by dividing the known stress by the strain calculated from the displacement you get the Modulus of Elasticity.
Let’s talk about the first concern. Material data can usually be provided from your material provider along with typical tolerances, something along the lines of +/- 5%. In the case of Modulus of Elasticity, if you were performing an analysis of a part you may want to try the upper and lower limit of that Modulus in order to make sure that regardless of where in the range the material it is, it won’t fail. That’s a good best practice to ensure your product will perform as expected.
Onto the second concern, there is not much for you to do here. Get as reliable material data as you can. If you get it from the manufacturer you are generally safe, but you may want to ask how it was tested to be sure.
SolidWorks Simulation is a powerful tool, but is a tool. If you do not verify the accuracy of what you’re putting in, it is hard to determine the accuracy of what is coming out.