HP 49g+ - Manual (Page 747)

Page 22-35
with respect to segment AB. The coordinates of point A’ will give the values
(
σ’
xx
, τ’
xy
), while those of B’ will give the values ( σ’
yy
, τ’
xy
).
The stress condition for which the shear stress,
τ’
xy
, is zero, indicated by
segment D’E’, produces the so-called principal stresses, σ P
xx
(at point D’) and
σ P
yy
(at point E’). To obtain the principal stresses you need to rotate the
coordinate system x’-y’ by an angle φ
n
, counterclockwise, with respect to the
system x-y. In Mohr’s circle, the angle between segments AC and D’C
measures 2
φ
n
.
The stress condition for which the shear stress,
τ’
xy
, is a maximum, is given by
segment F’G’. Under such conditions both normal stresses, σ’
xx
= σ’
yy
, are
equal. The angle corresponding to this rotation is φ
s
. The angle between
segment AC and segment F’C in the figure represents 2φ
s
.