Local refinement with dolfin and mshr

[Caio César]

I want to do a local refinement on this mesh:

from dolfin import *
from mshr import *
# Mesh
vertices=[Point(8.5,0),Point(5.1,-0.9),Point(0,-2),
Point(0,-140),Point(22,-140),Point(22,140),Point(0,140),Point(0,2),Point(5.1,0.9)]
domain=Polygon(vertices)
mesh=generate_mesh(domain,40)

Code is modeling a phase field fracture, and the mesh needs to be refined in the region where the fracture will occur. So I would like to refine a part of the mesh, as in a rectangle of points (0,-4),(22,-4),(22,4),(0,4). I tried gmsh, but the geometry is complex. If I refine the entire mesh, it will take a long time to finish the code.

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