How do you mesh complex geometries that are composed of several surfaces?
I have been running into problems with the way elements of the same body respond during a simulation. Particularly, when the body is subjected to a force the object falls apart, but only where the surfaces were connected. This problem only seems to occur when I change the material of the object from rigid to elastic.
It's because there are duplicate nodes where the edges of the surfaces were. So those elements are not actually connected together. You don't see this with rigid parts because every element of a rigid part, connected or not, will move together as one piece. To check for duplicate nodes in LS-PrePost, go to Eletol (Element Tool) then DupNod (Duplicate Node). The tolerance value at the top is the threshold for distance between nodes to be merged together. So if you set your threshold to 2 mm and you had two nodes 1.9 mm apart, those two nodes would be merged together. Generally, you want to keep this number pretty low because you don't want to merge nodes that are not actually duplicates.
Then, The options below determine which node will be retained during the merge, the smaller or larger id. So if you had node ids of 10 and 15 and choose "Keep Smaller NID" then any elements that previously referenced NID 15 will now reference NID 10.
Once you have your options selected you should select all of the nodes of your model, or any specific area of concern, and then click Show Dup Nodes. All of the nodes that are duplicates will highlight yellow and you can click Merge Dup Nodes to merge them. You can alternatively click Select Nodes to actually select which of the highlighted duplicate nodes that you want to merge. This can be helpful if you want to double check that you are only going to merge nodes that are actually duplicates.