If you’ve done FEA, you know that you can get some funky results near boundary conditions.
Fixing a face such that absolutely zero motion is allowed, for example, can create high stress concentrations that may not be real. However, thanks to Saint-Venant, we don’t usually have to care.
Because…
“… the difference between the effects of two different but statically equivalent load becomes very small at sufficiently large distances from load.”
So the high stresses caused by the load I’m applying at a point don’t affect what’s happening elsewhere, and so I can still have faith in my results.
It’s this principle that enables you to solve a model whilst only cranking up the mesh density (to get convergence) in areas of interest; If Saint-Venant’s principle weren’t true, your model would be pitch black with mesh lines.
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Article by chris loughnane
Chris is Design Engineer + Sustainability Advocate at a Boston area design consultancy and has written 134 sweet posts for the Product Development Notebook.
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