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influence of shear stresses the line AB shifts parallel with CD in
S
the distance AA  BB   , that is called the absolute shear.
1 1

Figure 4.3

The element is moved, its angles change into the value that is
called the angle of shear or the relative shift.
 S
  tg  . (4.3)
h
The shear angle is equal to the ratio of absolute shear to the
distance between the planes that shift.
Establish the relationship between  and  . In deformation the
element ABCD the diagonal BD extends. Consider BB B . The
1 2
angle at the point B because of the smallness of deformations
1
equals to 45, then elongation of the diagonal
l    S cos45.
If the initial length of the diagonal BD  , then from ABD
l
we obtain l  h sin 45 , then relative elongation of the diagonal
l   S
   sin 45 cos45 ,
l h
or

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