Vocational Scenario or Context
You have recently been employed as a junior mechanical engineer at Tech Design Ltd, a company specializing in the design, analysis, and testing of advanced materials and structures. As part of your role, you are seconded to the Materials Laboratory team, where you will work alongside experienced engineers and researchers to evaluate the behaviour of different materials subjected to complex loading conditions.
Your manager has assigned you a series of tasks to assess your understanding of material behaviour under complex stress systems, focusing on beams and cylinders under loading conditions. These tasks are based on real-world engineering challenges that TechDesign Ltd encounters when designing components for industries such as aerospace, automotive, and construction.
Task 1
1) Describe how you would determine the Young’s Modulus and ultimate tensile strength in the laboratory. (4 marks)
2) Explain how you would process the raw data from these experiments. (4 marks)
3) Discuss how a Charpy impact test could add to your knowledge of a material. (4 marks)
Checklist of evidence required
Diagrams, tables, graphs and photographs are required to support your text.
| Criteria covered by this task: | |
| Unit/Criteria reference | To achieve the criteria, you must show that you are able to: |
| LO1. | Characteristics of complex Loading Systems |
Task 2
1) A flat aluminium plate is subjected to stresses sx + sy these create strains ex = 4.2 x 10-4 and ey = 9.0 x 10-5.
a) Calculate the stresses sx & sy. (use E = 70Gpa and Poisson’s ratio = 0.33)
(4 marks)
b) Suggest the effect of doubling the plate thickness. Ensure that you justify any conclusions that you draw. (4 marks)
2) A 0.5m metal bar has a rectangular cross-section of 40mm x 20mm. It is loaded axially, in tension, with 50kN.
a) Calculate the new cross-sectional area and the new length (use E = 180 GPa and Poisson’s ratio = 0.25). (4 marks)
b) Suggest how a variation in Poisson’s ratio would change these values? (4 marks)
c) Discuss what factors could alter the Poisson’s ratio in a metal. (4 marks)
Checklist of evidence required – Calculate and evaluate as required
| Criteria covered by this task: | |
| Unit/Criteria reference | To achieve the criteria, you must show that you are able to: |
| LO1. | Characteristics of complex Loading Systems |
Task 3
1) Suggest an experimental procedure for measuring the deflection of a loaded simply supported beam. Ensure you discuss how these measurements depend upon the material properties and the cross-section of the beam. (4 marks)
2) A 6m beam (EI = 2 x 10^7 Nm2) simply supported at both ends carries a distributed load of 10kN/m which starts at 1m from the left and continues to the right-hand end. In addition, there are point loads of 30KN at 1m and 40KN at 5m.
a) Draw and annotate a graph of the deflection and slope along the beam. Ensure that you show the relevant calculations. (4 marks)
b) Show where the maximum deflection is located. (4 marks)
c) Suggest why this information important to architects in the design of buildings? (4 marks)
Checklist of evidence required – Calculate and evaluate as required
| Criteria covered by this task: | |
| Unit/Criteria reference | To achieve the criteria, you must show that you are able to: |
| LO2. | Characteristics of Loaded Beams and Cylinders |
Error! Hyperlink reference not valid.
Task 4
1) Compare and contrast the construction of
a) The first UK submarine, the Holland 1 (it is in the Gosport submarine museum; as we can’t currently do “the visit” there are some really useful photographs on the Royal Navy website) rnsubs.co.uk
(8 marks)
b) With the bathyscaphe Trieste (the first vessel to reach the bottom of the Mariana Trench)
(8 marks)
2) A thin-walled cylinder has an internal diameter of 2m, a wall thickness of 4mm and is 2m long. Using steel (E = 210 GPa; Poisson ratio = 0.32) and an internal pressure of 1MPa;
a) Calculate the change in internal diameter; (2 marks)
b) Calculate the change in length; (2 marks)
c) Calculate the minimum thickness required for a spherical pressure vessel of 2m outside diameter to replace this cylinder; (2 marks)
d) Using calculations show how a safety factor of 2.4 would affect the thickness of this sphere; (2 marks)
e) Suggest under what circumstances this safety factor would be appropriate. Justify your answer with reference to relevant safety codes.
(3 marks)
f) Research how this value should change if the sphere is of welded construction. (3 marks)
3) Pressure cylinders are regularly tested; describe how each of the following tests may be performed:
a) hydrostatic test; (2 marks)
b) burst test; (2 marks)
c) pressure cycling; (2 marks)
d) ultrasonic NDT; (2 marks)
4) A steel pipe of internal diameter 5cm and external diameter 10cm is subjected to an internal pressure of 30MPa.
a) Calculate the radial stress at the inner surface; (2 marks)
b) Calculate the radial stress at the outer surface; (2 marks)
c) Calculate the hoop stress at the inner surface; (2 marks)
d) Calculate the hoop stress at the outer surface; (2 marks)
e) Calculate the axial stress; (2 marks)
f) Suggest three changes that would allow the wall thickness to be reduced to contain this pressure. Justify each of your ideas with supporting evidence. (4 marks)
Checklist of evidence required – Calculate and evaluate as required – ASSIGNMENT ENDS
| Criteria covered by this task: | |
| Unit/Criteria reference | To achieve the criteria, you must show that you are able to: |
| LO2. | Characteristics of Loaded Beams and Cylinders |