I use alot of long, slender beams with thin webs so solid elements are not possible or practical to get 3-4 elements through the thickness. I usually create surface models based off the solid geometry and body delete the solids. My question is though when using mid-plane surfaces you get material thickness overlaps once the FEA figures in shell thickness. Does this create overly ridged areas of the model? Simple case would be say we had an I-beam, the web to flanges would have material overlap.
See how the web and flange connection has material overlap. That is my concern.
Shell elements need to have a consistent top and bottom face. The body also needs to be a constant thickness. In this case, you are analyzing three multiple surface bodies that have different top and bottom faces. These would only be connected to one another by the defined contacts in the study. Your I-beam is also not a constant thickness due to the fillet radius and potentially different size web and flange thickness.
I think beam elements may be a good candidate for you in this case, in this way you only need a constant cross sectional profile.
The part shown below would be a better to use shell elements on...
~Ben
Ben,
I agree but we put fasteners and holes in the web's and also they are typically tapered and or curved shape which we can't do with beam elements.
the beam on the left is using inside surface for shell definition, then middle is midplane surfaces and right is outside surface for shell definition. Get different stress results and different deflections for each one.
Derek, please attach your part files that contain these studies.
The simulation files are 250 MB. How do I attach them?
Hey Derek,
The result files are not needed, the study is saved in the part file. Really only one of the shell examples are correct, the other two create interferes between the shell thicknesses and should be avoided. That is why those three studies cannot be compared or even be made to have similar results.
Hello Derek,
If you are creating Mid-Surface features in your model, then it will place the surface at exactly 50% throughout the part body.
When you edit the shell definition, you will need to specify the correct thickness and ensure the offset is set to 50%.
Then, once you create the mesh, you can choose to render shell thicknesses in 3D to help visualize the mesh and confirm that the offsets are correct.
Let us know if you have a different concern...
~Ben