Hi Cycle Start RE: FEA of carriages. It can be simple or detailed. Depends on the FE system you have and how much time you want to spend on setting it up:
1) simplest is to consider the connection as bonded. Then make the car less stiff say aluminium stiffness. If your only comparing different geometries then its apples to apples and all's good. if you are looking for an absolute answer then this is not good enough
2) The bearing suppliers publish the bearing stiffness. So you can look that up and modify the carriages modulus until it agrees with the quoted rigidity/stiffness. Then you can model the connection as bonded with an accurate connection stiffness. I've done this several times and now I just make the car aluminium close enough....
3) If your FE models sliding then you set the connection up to slide, plus do 2) and you have a very accurate connection detail. Just remember that if the cars can slide you have to restrain the model somehow. In reality the drive system restrains the motion systems... Peter
A "bonded" connection means the connection is elastically perfect. This is achieved either by a contiguous mesh across the two solids or some sort of connection element between the two objects meshes. Depends on the simulation system you have. Seems the term FERA is dieing out and being replaced by "simulation" most FE systems these days have very good connection options and we can do all sorts of things vs old school FEA... Plus meshless systems exist which means there's no elements (nearly).