In this formulation the authors have assumed that while yield stress initially increases with strain rate, experimental data on shock-induced free surface velocity versus time records indicate that at high strain rates (greater than 10⁵sec^-1) strain rate effects become insignificant compared to other effects and that the yield stress reaches a maximum value which is subsequently strain rate independent.

They have also postulated that the shear modulus increases with increasing pressure and decreases with increasing temperature and in doing this they have attempted to include modeling of the Bauschinger effect into their calculations. They have therefore produced expressions for the shear modulus and yield strength as functions of effective plastic strain, pressure and internal energy (temperature).

The constitutive relations for shear modulus G and yield stress Y for high strain rates are :

subject to

where

and the primed parameters with the subscripts p and T are derivatives of that parameter with respect to pressure and temperature at the reference state (T = 300 K, p= 0, ε = 0).

The subscript zero also refers to values of G and Y at the reference state.

If the temperature of the material exceeds the specified melting temperature the shear modulus and yield strength are set to zero.

Table 11.2: Input Data

Name	Symbol	Units	Notes
Initial Yield Stress	Y	Stress
Maximum Yield Stress	Ymax	Stress
Hardening Constant		None
Hardening Exponent	n	None
Derivative dG/dP	G'P	None
Derivative dG/dT	G'T	Stress/Temperature
Derivative dY/dP	Y'P	None
Melting Temperature	Tmelt	Temperature

Custom results variables available for this model:

*Resultant value over shell/beam section.

**Temperature will be non-zero only if a specific heat capacity is defined.