Express the second invariant of the deviatoric stress tensor (J2) in terms of the principal deviatoric stresses S1, S2, and S3
A) J2 = (S1 - S2)² + (S2 - S3)² + (S3 - S1)²
B) J2 = S1 * S2 * S3
C) J2 = (S1 + S2 + S3)²
D) J2 = S1² + S2² + S3²
E) J2 = S1 * S2 + S2 * S3 + S3 * S1