To define the pressure and energy on the Hugoniot this equation of state requires the material shock velocity-particle velocity relationship as material input. In Autodyn this is specified through
Us = C0 + Sup | (3–26) |
where
| Us is the shock velocity |
| up is the particle velocity |
| S is the slope of the Us – up relationship |
| C0 is the bulk acoustic sound speed |
For the case of an orthotropic material, the bulk acoustic sound speed is calculated from the effective bulk modulus Equation 3–22 and density:
 | (3–27) |