I'm making a custom wrench for personal use. For fun, I'd like to run an FEA and see if the wrench will fail. below is a similar wrench. A torque wrench is applied to the square hole. Where do I fix and apply the load? Should it be a torque or a force?
If I were running this and wanted to see if either the square socket or the face that interacts with the hex were likely to fail I would create a mock square drive and bolt head in my simulation as well. I would then fix the bolt head in X, Y, and Z. Apply a constraint to the wrench to keep it in plane (sliding constraint on one of the large faces), constrain the mock square drive in the same plane as the wrench, and then apply a torque to the mock square drive.
If you are only worried about the square socket failing you could skip the mock bolt head and just fix those faces of the wrench or vise versa if you are only worried about the hex portion failing.
I believe it would only fail at the hex portion. I'm curious to see how thin the hex portion can be. My stated torque for the lock nut this is for is 100ft-lbs.