Assessment Instructions

This outcome is assessed using all three of the assignments detailed below.  For each assignment you are required to write a report containing:

1.    The purpose of the assignment

2.    Description of how the assignment was undertaken

3.    Results obtained

4.    Analysis of results (including sources of error)

5.    Conclusions

Assignment 1 - Cylinder Design

A pressure vessel requires an internal diameter of 1.5m and will normally contain air at 30bar. For safety, the maximum tensile stress in the material to be used must not exceed 250MN/m² at a pressure of 60bar.

1.    Determine the minimum acceptable wall thickness using thin cylinder theory.

2.    Determine the minimum acceptable wall thickness using thick cylinder simulation software.

3.    Comment on the significance of any difference.

Assignment 2 - Pipe Failure Investigation

A high pressure pipe is initially designed to be solid steel with a bore of 50mm and outside diameter of 90mm.  During a pressure test the pipe was found to fail at 120MN/m². 

1.    Determine the hoop, radial longitudinal stresses in the pipe at this pressure.

2.    Draw a Mhor's circle showing the stress condition of an element at a point where failure is most likely.

3.    If the yield stress of the steel was measured as 350MN/m² during a tensile test, suggest which failure theory would predict the pressure at which the pipe failure should occur. 

Assignment 3 - Compound Cylinder Pipe Design

As an alternative to the pipe in assignment 2, a compound pipe is designed to give a reduced maximum stress.  The inner pipe has a bore of 50mm and 10mm wall thickness.  The outer pipe also has a wall thickness of 10mm and a diameter which gives a shrinkage pressure after assembly.

1.    Calculate the required shrinkage pressure to equalise the hoop stresses in the inner and outer cylinders at 120MN/m².

2.    Show the resulting distribution of radial and hoop stresses across the whole compound cylindrical pipe.