Viscoelastic material: Prony series in Abaqus

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Hello
Everybody,

I’m using
Prony series to model viscoelasticity of an asphalt material in a pavement. I
have defined the material properties through time-domain Prony series in
Abaqus. The parameters are:

g_i (shear
relaxation modulus ratio): 0.8

k_i (bulk
relaxation modulus ratio): 0

tau_i
(relaxation time): 1

I am using
*VISCO procedure for the analysis and the trapezoidal loading is applied by
giving amplitude-time definition in tabular form. The loading is given below:

                    Time                  Amplitude

                        0                                0

                     0.002                        100

                     0.0088                     100

                     0.0108                       0

                     1.0                               0

Likewise I
have simulated 5 cycles and analyzed pavement’s response in real time scale. I
changed g_i and tau_i values and observed the results.

For g_i=
0.8, the tensile elastic strain is smaller and tensile inelastic strain is
larger than g_i= 0.9 (keeping k_i and tau_i unchanged).

For tau_i=1,
the tensile elastic strain is smaller and tensile inelastic strain is larger
than tau_i=1.2 (keeping g_i and k_i unchanged).

I am not
able to understand what exactly we do when we increase g_i or tau_i.  When we increase material relaxation time
parameter (which is actually the ratio of coefficient of viscosity to modulus
of elasticity of the material) are we making the material more viscous? Also,
can you please tell me what is the difference between loading relaxation time
(1.0 – 0.0108 = 0.9892sec) and material relaxation time (tau_i= 1sec)? If we do
not give any loading relaxation time then material will not relax? Can anybody
please tell me what the significance of each term is? And how the system
response affects by variation of these parameters? 

Somebody
please give me a push in the right direction here.

Thanks in
advance.

Sincerely,

Yogesh