Biomedical Engineering Reference
In-Depth Information
Fig. 23.8
Normal flow for free swelling along the crack at points d
x
=
0
.
28 mm and
d
x
=
0
.
48 mm. Crack growth causes a peak in flow after which relaxation takes place. The jump
in chemical potential imposed by the one-sided compressive load results in a nonzero initial flow
and high peaks in case of crack growth followed by relaxation. The resulting crack-growth occurs
in a staccato fashion. Crack growth over several elements followed by a pause during which the
chemical potential jump diffuses away. This diffusion of the chemical potential leads to increasing
load on the effective stress field of the solid, and hence failure of the solid
Fig. 23.9
The mesh and
boundary conditions for
delamination consisting of
575 elements. Material is
pulled at the
top
and
bottom
on the
left
andisonthe
right
in contact with a filter
The
exact
material
properties
are
given
in
Table
23.2
.
This
means
that
2
RTΓc
ex
4
.
96 N
/
mm
2
holds. A time step of 0.1 s is used.
The influence of mesh refinement, prestress and local boundary conditions on the
crack is considered on crack propagation and flow around the crack. For the mesh re-
finement, the mesh of Fig.
23.9
is refined to 2701 elements. The corresponding time
step is a quarter of the time step of the coarse mesh. For the influence of prestress
four cases are compared, no prestress, prestress in both directions and prestress in
either
x
-or
y
-direction. The modes of prestress are the result of different initial
swellings, not the result of uneven distribution of fixed charges. Furthermore, the
=
