Question

A high carbon steel shaft is used in an engine and subjected to different loads. In order to
analyse the stress in the shaft, consider a rectangular element within the material. This
element is subjected to compressive stress of 135 MPa and shear stress of 166MPa in the
vertical direction. The compressive stress in the horizontal direction is 176MPa with a shear
stress of 115MPa.
a. Sketch the state of stress on this element.
b. Determine the maximum and minimum normal and shear stresses and their plane of
orientation.
c. If the yield strength of the material is 350MPa, Poison’s ratio is 0.32, and factor of
safety is 5, determine the diameter of the shaft to avoid failure.
d. What will be the difference in the analysis above if there is an additional torsional
load (T) and bending moment (M).
e. Show how you can use any theory of failure to design this shaft.
f. What are the challenges of applying the theories of failure in actual engineering
practice and as a design engineer, how would you deal with these challenges.

Answer 1