Introduction to Basic FEA

Most people use FEA to determine if a component is strong and durable enough.
 
Back in the day, before FEA became mainstream, engineers managed quite well without FEA and instead relied on hand calculations by pen and paper.
 
There’s nothing wrong with that and hand calculations are still better than FEA for certain things like dowel pins.
 
A lot of design codes today are still based on the principles of hand calculations and these principles have not been replaced by FEA.
 
This FEA tutorial is based on comparing hand calculations with FEA results as a way of verifying you are using FEA correctly.
 
Basically, the FEM divides the CAD geometry into segments called elements.
 
Each element has a stiffness like a spring and when joined together they form a mesh that replicates the CAD geometry.
 
So, when a load is applied at one end of the geometry and the other end is held by a constraint, the load travels through all of the elements in the load path. Therefore, every single element in the load path has a force.
 
Since stress is basically force divided by area, each element can therefore calculate stress.
 
If a solid element is fixed on one corner (node), FEA cannot calculate stress on that corner because a corner or single node does not have a surface area. So, force divided by zero area equals error.
 
This error is called a singularity and is not real. Normally if you refine the mesh, the results will converge to the correct answer if the mesh is fine enough.
 
Not so with a singularity, the more you refine the mesh, the more the stress increases for infinity.
 
Don’t worry though, a couple of elements away from the singularity and the stress is real.
 
When you are happy that the stress is real, you can check it against the yield strength of the material. Stress below yield is OK for steel but other materials may not have a yield point.
 
Great you now know all you need to know.
 
Wrong!
 
The choices you make when applying loads and constraints are called boundary conditions. These can be tricky to get right when you are still learning.
 
Also, different materials fail in different ways so you need to know about material failure modes.
 
You also need to know about the differences between linear and nonlinear analysis and all of the different types of analysis.
 
There’s a lot to learn but hopefully, this FEA tutorial will set you off on the right track.
 
Enjoy!