26
2 Analysis of Stress
Fig. 2.12 Stress components acting on parallelopiped
2.17 Octahedral Stresses
A plane which is equally inclined to the three axes of reference is called the octahedral
plane, and its direction cosines are = ±
1
√
3
, m = ±
1
√
3
, n = ±
1
√
3
. The normal
and shearing stresses acting on this plane are called the octahedral normal stress and
octahedral shearing stress, respectively. In Fig. 2.13, x-, y- and z-axes are parallel
to the principal axes and the octahedral planes defined with respect to the principal
Fig. 2.13 Octahedral plane and octahedral stresses