Reading and querying mesh¶

Reading a mesh is in Phon the process of parsing a file containing nodes, elements, and eventual sets (element sets and node sets). This information is then stored in a class based format in Phon which is easy to query and modify the mesh.

It is currently possible to read a mesh exported to Abaqus’ .inp format or Gmsh’s .msh format.

Read an Abaqus mesh¶

The function to read an Abaqus mesh is phon.io.read.read_from_abaqus_inp.read_from_abaqus_inp().

To read the mesh, the function is first imported and then used like this:

>>> from phon.io_tools.read.read_from_abaqus_inp import read_from_abaqus_inp
>>> mesh = read_from_abaqus_inp("n10-id1.inp")

The mesh is now stored as an instance of the phon.mesh_objects.mesh() class.

An example Abaqus mesh file can be found here.

Gmsh¶

The function to read a Gmsh mesh is phon.io_tools.read.read_from_gmsh.read_from_gmsh().

It is currently used a bit differently than the function to read from Abaqus meshes. The gmsh reader assumes that each grain has a separate mesh file called fileX.msh where file is the basename and X is the grain id. The gmsh reader can then be called as:

>>> from phon.io_tools.read.read_from_gmsh import read_from_gmsh
>>> basename = "gmsh_grain_file"
>>> n_grains = 3
>>> mesh = read_from_gmsh(base, n_grains)

An example of a microstructure with 3 grains split over 3 .msh files can be seen here.

Querying and modifying the mesh¶

We can now query the mesh object for information about the mesh and modify it.

A few example follows here:

The number of elements in the mesh:
```
>>> print(len(mesh.elements))
1683
```
The number of nodes in the mesh:
```
>>> print(len(mesh.nodes))
289
```

A node set with a certain name:

>>> print(mesh.node_sets["x0y0"])
Node set with name x0y0 containing nodes with the following ids [1, 3, 34, 39, 40, 131, 132]

Information about a specific node:

>>> print(mesh.nodes[10])
Node located at (0.722422, 0.420036, 0.196344)

Changing a nodes location:

>>> mesh.nodes[10].c[0] = 1337.0
>>> print(mesh.nodes[10])
Node located at (1337.000000, 0.420036, 0.196344):

Information about a specific element:

>>> print(mesh.elements[701])
Element of type C3D4 containing the vertices with id [168, 150, 154, 60].

For more information of the different properties to query from the mesh look at the documentation of phon.mesh_objects.