I have a part made of 3d elements, and I have been wondering how to make element and node sets out of only the top surface elements and nodes. I know that one can define Surfaces, but can surfaces be treated like element/node sets?
These are separate types of entities used for different purposes (check the documentation chapter "Understanding sets and surfaces" for detailed description).
What do you want to define in the model using these surfaces entities ?
I basically want to plot/extract data from the top surface of my part. I generally use sets when I need to extract data from only a certain section of my system. But I have not been able to make a set out of only the top surface of my part. That's why I thought of using Surfaces.
If you want to request output for nodes/elements lying on the surface, you have to create proper elsets/nsets manually (it should be easy with "by angle" selection method) or use Python scripting. Keep in mind that geometry set defined for the face will give you both node set and element set for this face.