Timothy A. Philpot - Mechanics of materials _ an integrated learning system-John Wiley (2017)

CHAPTER15
Combined Loads
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15.1 Introduction
The stresses and strains produced by three fundamental types of loads (axial, torsional, and
flexural) have been analyzed in the preceding chapters. Many machine and structural components
are subjected to a combination of these loads, and a procedure for calculating
the ensuing stresses at a point on a specified section is required. One method is to replace
the given force system with a statically equivalent system of forces and moments acting at
the section of interest. The equivalent force system can be systematically evaluated to
determine the type and magnitude of stresses produced at the point, and these stresses can
be calculated by the methods developed in previous chapters. The combined effect can be
obtained by the principle of superposition if the combined stresses do not exceed the proportional
limit. Various combinations of loads that can be analyzed in this manner are
discussed in the sections that follow.
15.2 combined Axial and Torsional Loads
A shaft or some other machine component is subjected to both an axial and a torsional load
in numerous situations. Examples include the drill rod for a well and the propeller shaft in
a ship. Since radial and circumferential normal stresses are zero, the combination of axial
and torsional loads creates plane stress conditions at any point in the body. Although axial