Isotropic Plasticity
Isotropic plasticity is defined using a set of tabular data in which each row represents a True Plastic Strain value and the corresponding Yield Stress at that strain. Plastic strain to stress relationships are interpolated linearly between each provided data point; the stress remains constant at strains outside the specified data range.
| True Plastic Strain |
Plastic component of the true—or logarithmic—strain in the material (i.e., true strain that will not be recovered after the stress is removed). |
| Yield Stress |
True—or logarithmic—stress value at the corresponding true plastic strain. |
Viscoelastic
Viscoelastic behavior is defined numerically using a Prony series expansion of the shear and bulk relaxation moduli in the material. Data are entered in a table in which each row represents a set of constants in one term of the Prony series; the order of the rows corresponds to the order of the terms in the series.
| Gi Prony |
The modulus ratio in the corresponding term in the Prony series expansion
of the shear relaxation modulus.
|
| Ki Prony |
The modulus ratio in the corresponding term in the Prony series expansion
of the bulk relaxation modulus.
|
| Tau_i Prony |
The relaxation time, in units of seconds, for the corresponding term in the Prony series
expansion.
|
Damping
Material damping is specified according to the following equation:
where 
are the natural frequencies of the model on which the material is applied.
| Alpha |
The mass proportional damping factor; this factor tends to have a stronger effect at lower frequencies. |
| Beta |
The stiffness proportional damping factor; this factor tends to have a stronger effect at higher frequencies. |
Expansion
Isotropic thermal strains occur according to the following equation:
where 
is the temperature change in the model.
| Alpha |
The coefficient of thermal expansion. |