Hello everyone.

I would like to ask that how can I access the value of the Strain, Stress as the code below?

I can check their shape using ufl_shape which are (2,2). But i dont know how to access the value of each element in the whole domain.

If you know the answer for this, please help me.

Thank you so much.

```
import numpy as np
from mpi4py import MPI
from dolfinx import default_scalar_type, plot
from dolfinx.fem import (Constant, Function, functionspace, dirichletbc,
Expression,locate_dofs_topological)
from dolfinx.mesh import create_rectangle, meshtags, CellType, locate_entities_boundary
from dolfinx.fem.petsc import LinearProblem
from ufl import (Measure, TestFunction, TrialFunction, Identity,
sqrt, dx, tr, grad, inner, sym)
L, H, Nx, Ny = 2., 1., 10, 5
domain = create_rectangle(MPI.COMM_WORLD, [[0,0], [L,H]], [Nx, Ny], CellType.triangle)
V = functionspace(domain, ("Lagrange", 2, (domain.geometry.dim,)))
E, nu = default_scalar_type(1.0e3), default_scalar_type(0.3)
mu = Constant(domain, E / (2 * (1 + nu)))
lam = Constant(domain, (E * nu) / ((1 + nu) * (1 - 2 * nu)))
def eps(u) :
return sym(grad(u))
def sigma(u):
return lam*tr(eps(u))*Identity(len(u)) + 2.0 * mu*eps(u)
def left(x):
return np.isclose(x[0], 0)
def right(x):
return np.isclose(x[0], L)
fdim = domain.topology.dim - 1
left_facets = locate_entities_boundary(domain, fdim, left)
right_facets = locate_entities_boundary(domain, fdim, right)
# Concatenate and sort the arrays based on facet indices. Left facets marked with 1, right facets with two
marked_facets = np.hstack([left_facets, right_facets])
marked_values = np.hstack([np.full_like(left_facets, 1), np.full_like(right_facets, 2)])
sorted_facets = np.argsort(marked_facets)
facet_tag = meshtags(domain, fdim, marked_facets[sorted_facets], marked_values[sorted_facets])
u_bc = np.array((0,) * domain.geometry.dim, dtype=default_scalar_type)
left_dofs = locate_dofs_topological(V, facet_tag.dim, facet_tag.find(1))
bcs = [dirichletbc(u_bc, left_dofs, V)]
T = Constant(domain, default_scalar_type((0, -1)))
u, v = TrialFunction(V), TestFunction(V)
metadata = {"quadrature_degree": 2}
ds = Measure('ds', domain=domain, subdomain_data=facet_tag, metadata=metadata)
a = inner(sigma(u), eps(v)) * dx
L1 = inner(v, T) * ds(2)
problem = LinearProblem(a, L1, bcs=bcs, petsc_options={"ksp_type": "preonly", "pc_type": "lu"})
uh = problem.solve()
Strain = eps(uh)
Stress = sigma(uh)
```