When merging a model, is there a way to select which duplicated nodes from different parts in TrueGrid® get merged together and which do not (i.e. merge certain zones of a model)?
There are many ways. The first thing to remember is that the stp command, as well as the t, and tp commands, set the default tolerance for nodes to be merged. Prior to issuing such a merge command, you can set special tolerance for difference areas in various ways. Also keep in mind that until you issue one of the merge commands (stp, tp, t) nothing will be merged. Also, you can issue one of these merge commands as often as you want until you find the right tolerance. Finally, a negative tolerance (such as -1) means no merging between nodes within the scope of the command. For example, if you used the stp command to merge (stp .001) and then used the same command with a -1 (stp -1), all nodes that were merged will no longer be merged.
Here are the different ways to set special tolerances in different areas:
i.) bptol sets a special tolerance between two parts
ii) ptol sets a special tolerance for nodes to be merged within a single part
iii) nodes with shared nodal constraints are not merged
iv) no merging is done across the master and slave side of a contact surface
v) the dummy contact surface is a contact surface in name only. Its only function is to block merging between the nodes of the master and slave side.
vi) bnstol blocks merging between two node sets (slow execution in large problems)
vii) nodes in a rigid body joint are not merged
These can be abused. If you try to use bptol everywhere, you will have a huge number of these commands. As soon as you make a change, you have to adjust this list of commands. It is much cleaner to use the bb command liberally to make sure parts meet perfectly so that one stp command with a small tolerance is all that is needed to merge the nodes for the entire model.
