Sets

Adding sets

A set is a group of nodes, elements or surfaces that are given a string name. By assigning a name to such a group of components, it is easier and more meaningful to refer to them in other classes, instead of giving (and keeping track of) a long list of node or element numbers. A Set object is stored in the dictionary .sets through the method .add_set(), where the string key is the name of the set, the type of the set is the string 'node', 'element', 'surface_node' or 'surface_element', and the selection stores the nodes, elements and surfaces of interest. To add node or element sets, use .add_set() as follows:

mdl.add_set(name='nset_top', type='node', selection=[4])  # add a note set 'nset_top'

mdl.add_set(name='elset_shell', type='element', selection=[7, 8])  # add an element set 'elset_shell'

If the selection is not given as a list, but instead as a single integer (to represent one node for example), it will be converted into a list with one item. Sets may be viewed and edited at any time through their string name keys, and then by viewing or changing the object attributes as needed. Like all other objects, printing the Set will give a short summary.

>>> mdl.sets['nset_top']
Set(nset_top)

>>> print(mdl.sets['nset_top'])  # give a summary of set `nset_top

compas_fea Set object
---------------------
name      : nset_top
type      : node
selection : [4]
index     : 1

>>> print(mdl.sets['elset_shell'])  # give a summary of set `elset_shell

compas_fea Set object
---------------------
name      : elset_shell
type      : element
selection : [7, 8]
index     : 3

>>> mdl.sets['elset_shell'].selection.append(5)  # add an element to the element set

>>> mdl.sets['elset_shell'].selection  # show updated selection
[7, 8, 5]

From the node and element data of the Structure object, a surface can be defined by one of two surface set types. The first is by using type='surface_node' when creating a set with the .add_set() method. This will describe a surface by the nodes given in the selection list. This surface type can be created like:

mdl.add_set(name='surf_set', type='surface_node', selection=[1, 3, 4, 10])  # surface node set

The second way to define a surface set is with type='surface_element', where instead of a list of nodes for selection, a dictionary of element number keys and list of element string sides is given. So for example, to add sides 1 and 2 ('S1' and 'S2') of solid element 4, and the top side ('SPOS' for top and `SNEG` for bottom) of shell element 7 as an element surface set use the following. You can find which surface sides correspond to which, in the Elements topic.

mdl.add_set(name='surf_set', type='surface_element', selection={4: ['S1', 'S2'], 7: ['SPOS']})