# The segment of shaft In Assignment Task

MEC2301 Assignment 1

QUESTION 1

The segment of shaft shown in Figure 1 is made of AISI 4130 annealed steel. The shaft is fine turned
and cylindrically ground with a diameter of D=20 mm and with a transverse hole of d=2 mm diameter.
The segment as shown is part of a drive shaft for a mixing machine.
Under normal operating conditions the shaft segment rotates at 30 rpm and is subject to the following
• A torque that varies from -120 Nm to +120 Nm once every ten seconds;
• An axial tensile load that varies from 0 to 8 kN at the same rate as the torque variation; and
A bending moment that varies between 10 Nm and 40 Nm once every second.
Determine the expected life of this segment of shaft.
(If you determine life in excess of the Endurance limit then determine the factor of safety).
[100 marks]
Figure 1. Shaft segment
QUESTION 2
Figure 2. Pressure vessel end-cap
The end-cap of a pressure vessel as shown in Figure 2 is secured by 10 off M12 x SAE class 9.8 bolts (with rolled threads). A soft gasket is used such that the clamped member stiffness is one quarter of the bolt stiffness. The internal diameter of the pressure vessel is 300 mm and the pressure in the vessel varies from 0 to P MPa gauge.
(a) Determine an appropriate initial tension for the bolts, explaining why you chose this value and describing how it would be achieved.
(b) Determine the maximum value of P that would not cause separation of the joint;
(c) Determine the maximum value of P that would not cause eventual fatigue failure of the bolts; and (d) Determine the wall thickness required for the pressure vessel for this maximum pressure P.
[100 marks]