Learning Forum

[peteroznewman]

You left out a third option. If you have two bodies of different materials, you can use shared topology.

If the materials are the same, a fourth option is to use a geometry editor to unite them into a single body. A single body is often sliced up into pieces that are each easier to mesh than the whole body. The pieces use shared topology to remain connected.

Both node merge and shared topology result in the same outcome, a set of nodes on the surface common to both bodies is shared by elements on each body. Shared topology is far superior to node merge because the meshing software ensures that a set of shared nodes is created. If you use node merge, it is your responsibility to make sure that the same node coordinates are meshed on the coincident surface on each body separately, before the node merge is used. If you fail to do that, you will end up with cracks in your model.

If the two faces on the adjacent bodies are not identical but they are only coincident at a subset of the area, then there is extra CAD work to imprint the outline of one face onto the other prior to meshing. Shared topology does all that for you. I never use node merge and often use shared topology.

There are posts about when to use bonded contact vs. shared topology.
https://forum.ansys.com/forums/topic/mesh-matching-on-two-bonded-parts-w-out-shared-topology/

Bonded contact doesn't need the nodes to line up. Bonded contact allows computation of stress at the interface. If there really is a bond with a failure stress, bonded contact allows the modeling of the progressive failure using CZM.
If you don't need any of that, you're better off with shared topology.