I did a small research on the internet about the best FEA meshing practice and this is the kind of advice that I found:
« Meshing is not important as long as you get the correct boundary conditions »
« Meshing is critical to the accuracy of your results »
« most FEA Software Automeshers do already a great job, so you don’t have to worry about that. »
After reading all this…my head hurts…seriously…
How can you believe something and its contrary…someone must be wrong.
What if for example, I do have correct boundary conditions, but my mesh isn’t great…would I still get good results?
(Such a question can prevent you from sleeping at night… especially if you have an important project to finish soon…)
Now… there is only one way to know if mesh really does have an impact or not…TESTING.
Here are 4 simple test models that I created:
4 plates of 1mm thickness, same boundary conditions, all fixed at the bottom, all are loaded with the same 200N force applied at the top.
The only thing which is different is the meshing. I meshed the first model with a grid mesh, then I meshed the second model node by node in a very obviously wrong way and I meshed the two other models in another way to check if there is some difference. I kept more or less the same mesh size.
Now… here are the results I got for the total displacements:
I think that the answer to my question is pretty obvious… the meshing has a pretty big impact on those results (and much more than I actually thought). The total displacement in the 2nd mesh is 33% higher than in the first one and it is 22% lower in the 4rth mesh.
The Von Mises stress results are also quite demonstrative of the difference between the 4 different mesh sets…
NOW…Would you consciously mesh your model like that??
You probably won’t (and me neither)…
BUT…sometimes things are more tricky than we are used to and we may get a wrong meshing without even knowing about it.
For example, sometimes you think that your 3D solid mesh is okay by looking at the external boundary…when it is actually pretty bad inside.
Here’s an example:
We are all fooled (sometimes) by the appearance of something…but as an engineer, I am convinced that we should take the healthy habit to look deeper inside and detect the hidden problems.
It’s comforting to tell ourselves that we have some powerful software available that will do everything for us but that’s just not true because a software is just a tool.
Sometimes, if you want to do something good, you have to work on it a bit more to understand what’s behind the mirror.
PS: I’ll write soon about the major problems that people have with meshing… I am sure you will find it interesting, If you are interested by this topic, let me know in the comment section