Discussion Forum

Hey everyone,

I'm having a little trouble figuring out what seems like should be a very simple task in 4.0a. I've essentially drawn two lines and would like to connect them at the ends. I don't want them to be welded, so I've selected "Form Assembly" instead of "Form Union." In a mathematical sense, I'm trying to achieve boundary conditions such that the displacements are continuous at the connected ends but each line can rotate independently of the other.

I've attempted to do this by defining the connection point as a pin, but this doesn't achieve what I'd like because the connection shouldn't be constrained to zero displacement. I also tried to define an identity pair and then add a continuous boundary condition to the pair, but Comsol isn't allowing me to pick points for the identity pair, only domains. I'd like to simply pick the two end points on each line and couple them with an identity pair. The continuity condition should then constrain them to having the same displacement. Has anybody done something similar to this? Is it possible to define a point identity pair for one-dimensional geometries such as lines? Again, it seems like a very simple task, but I'm having trouble figuring out how to implement it.