Previous: prob4-23>> Problem 4.23
Consider the state of stress given by

is symmetric. When we determine the principal value, let
and
be
the principal value. Let
and let
the eigen vectors
,

and
be associated with
and
Note that
form
a rectangular Cartesian coordinate system. If [Q] represents the transformation
from
to
, then

X-axis represents the eigen value with coordinate system
.
As we rotate the radius with arbitrary angles a,
b
and g
with old system (eigen vector system) with
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Thus
Thus Mohr's circle in three dimensions is the coordination transformation of any orientation of the stress cube from the cube when aligned with the principal orientation lying along the x-axis.