Chemistry Reference
In-Depth Information
FIGURE 10.18
The dependences of fracture surface fractal dimension
d
fr
, calculated
according to the Eq. (10.28), on dissipated energy fraction h
d
at fixed characteristic ratio
C
∞
:
2.4 (1), 6.8 (2) and 10 (3). The shaded lines indicate
d
fr
level for ductile fracture (1') and super
plasticity (2') [57].
As it is well-known [60], in deformation process up to yielding point
in polymers the dilatation effect is observed, characterized by relative free
volume increase by the value D
f
g
. As the estimations shown [7], the incre-
ment D
f
g
usually makes up the value ~0.06 ÷ 0.08. This effect induces a
corresponding structural changes, which can be described with the aid of the
fractal dimension
Y
f
d
in yielding point [6]:
cl
3
d
,
(10.30)
d
Y
=
-D
f
f
cl
f
3
df
g
where
f
d
is the value of polymer structure fractal dimension in the elastic
deformation region.
cl
TABLE 10.1
The Results of Fractal Model Parameters Calculation for Five Polymer
Samples [57]
Elastic and viscoelastic deformation
Polymer sample
C
∞
D
f
g
cl
f
d
D
ch
d
fr
n
h
d
HDPE, without notch
6.8
0.06
0
.
335
2.670
1.80
0.80
2.84
PC
2.4
0.08
0
.
310
2.620
1.48
0.48
2.75
PVC
6.7
0.07
0.339
2.678
1.11
0.11
2.81
