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5 TORSION

5.1 The twisting moment

Torsion is called a kind of deformation when in beam cross -
sections there is only one internal force factor - twisting moment.
Rod torsion occurs if it is loaded by external pairs of forces the
action planes of which are perpendicular to the axis of the rod.
To determine the value of twisting moment the method of
sections is used(see. p.1.5). The twisting moment in any cross-
section of the rod is numerically equal to the algebraic sum of the
moments about the axis of the rod of all pairs of external forces
placed on the one side of studied section (fig. 5.1).

M  M  M
x 1 2

Figure 5.1

M x 0 M x  0

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