In the regime, F takes the form

(2–23)

and S is defined as

(2–24)

where cos η is defined by Equation 2–11 and

(2–25)

(2–26)

The coefficients a₀, a₁, a₂, b₀, b₁, b₂ are defined by Equation 2–15 and Equation 2–17 while

(2–27)

If the failure criterion is satisfied, cracking occurs in the plane perpendicular to principal stress σ₁.

This domain can also crush. (See Willam and Warnke for details.)