CO \
Time
1-1. The testing components of the complex modulus
between the applied stress and the measured strains. This lag, referred to as the phase
angle (6), shown in Figure 2-1. Equation 2-2 describes the relationship between the
various components and E*:
S = tan E (Eq. 2-2a)
E'
E"= E *E sin(S) (Eq. 2-2b)
E'= E *cos(3) (Eq. 2-2c)
The phase angle is typically determined by measuring the time difference between
the peak stress and the peak strain. This time can be converted to 6 using Equation 2-3.
S= tlg f. (3600) (Eq. 2-3)
Where
f is the frequency of the dynamic load (in Hz),
tlag is the time difference between the signals (in seconds).
A phase angle of zero indicates a purely elastic material and a 6 of 900 indicates a
purely viscous material.