I would like to define a Surface using Python (my aim is to change BCs after each step in the analysis). So I would like to select the elements on the surface of the solid which satisfy a given condition (related to their location in the deformed shape) and define a surface with them (in that surface I apply a pressure load). How could I do this?

For instance, it is possible to do the following:

    p = mdb.models['Model-1'].parts['Sphere']

    f = p.elements face1Elements = f[322:323]+f[681:682]+f[683:685]+f[687:688]

    face2Elements = f[37:38]+f[227:228]+f[9724:9725]

    p.Surface(face1Elements=face1Elements, face2Elements=face2Elements, name='SphereIntMeshBased')

But, for instance, using a loop to select the elements, it is not possible to do

    face1Elements = f[322:323] .... face1Elements = face1Elements + f[i:i+1]     # Error: concatenation not allowed...

Any idea for the definition of the surface?Thank you very much in advance for the help!