Chemistry Reference
In-Depth Information
200
h=0.1
h=0.5
h=1
h=2
150
100
50
0
0.001
0.01
0.1
1
10
100
1000
relaxation time, τ/s
Figure 4.11
A log normal relaxation spectrum centre on a modal time of 1 s.
120
G
′
with h=0.1
G
with h=0.1
G
′
with h=0.5
G
″
with h=0.5
G
″
100
with h=1
G
″
with h=1
G
′
with h=2
G
′
80
″
with h=2
60
40
20
0
0.001
0.01
0.1
1
10
100
frequency, ω/rads
-1
Figure 4.12
The storage and loss moduli corresponding to the relaxation spectra in
Figure 4.11.
4.5 LINEAR VISCOELASTIC EXPERIMENTS
There are many types of deformation and forces that can be applied to
material. One of the foundations of viscoelastic theory is the Boltzmann
superposition principle. This principle is based on the assumption that the
effects of a series of applied stresses acting on a sample results in a strain that is
related to the sum of the stresses. The same argument applies to the application
of a strain. For example, we could apply an instantaneous stress to a body and
maintain that stress constant. For a viscoelastic material the strain will increase
