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ENSC1004 S1 2021 Final Exam
Engineering Materials (University of Western Australia)
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ENSC1004
Engineering Materials
Engineering Materials
SEMESTER 1, 2021 EXAMINATIONS
Engineering
Mathematics & Statistics
This paper contains: 8 Pages (including title page) Time Allowed: 2:00 hours
INSTRUCTIONS:
• This exam paper contains 7 (seven) questions
• This exam paper is worth a total 65 marks
• You are required to answer all questions. You may answer Q3 directly in the exam paper. Answer all other
questions in the answer booklet provided.
• A Supplementary Formula and Data Sheet is attached to the back of this exam paper. You may detach this
for easy referencing, and it is NOT required to be handed back at the end of the exam.
• Only a UWA-approved calculator is permitted.
THIS IS A CLOSED BOOK EXAMINATION (SEE ALLOWABLE ITEMS)
SUPPLIED STATIONERY
1 x Formula booklet
ALLOWABLE ITEMS
1 x UWA Approved Calculator with Sticker
PLEASE NOTE
Examination candidates may only bring authorised materials into the examination room. If a supervisor finds, during the examination, that you have
unauthorised material, in whatever form, in the vicinity of your desk or on your person, whether in the examination room or the toilets or en route
to/from the toilets, the matter will be reported to the head of school and disciplinary action will normally be taken against you. This action may result
in your being deprived of any credit for this examination or even, in some cases, for the whole unit. This will apply regardless of whether the material
has been used at the time it is found.
Therefore, any candidate who has brought any unauthorised material whatsoever into the examination room should declare it to the supervisor
immediately. Candidates who are uncertain whether any material is authorised should ask the supervisor for clarification.
Candidates must comply with the Examination Rules of the University and with the directions of supervisors.
No electronic devices are permitted during the examination.
All question papers and answer booklets are the property of the University and remain so at all times.
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Final Exam Semester 1 2021 3 ENSC1004
ENSC1004 Final Exam Semester 1 2021
Question 1. (10 marks)
In one diagram, draw representative tensile stress-strain curves for a typical metal, crystalline
ceramic and polymer (typical of thermoplastics). Ensure you present the curves at reasonable
relative scales. Briefly explain the tensile stress strain behaviour in terms of stiffness, strength,
ductility and toughness, in reference to each of the stress-strain curves you have provided. Link them
to the interatomic bonding nature and/or crystal structure of these materials.
Question 2. (7 marks)
(a) Name the three classes of carbon steels and the carbon content range for each class.
(b) Describe the effect of carbon content on the mechanical property (such as strength, hardness,
ductility and toughness) and basic microstructure feature of carbon steels. Briefly explain the
reasons.
Question 3. (6 marks)
Answer directly in this booklet!
Many engineering materials are developed for specifically targeted applications. In this unit we have
learnt a range of different materials. Match each application listed in the table below with a material
in the list that would be best suited for that application. An example answer (1 - D) is given in the
Table. Note; some materials may be suitable for more than one application listed. Some may not be
suitable for any applications in the list.
List of Applications List of Materials Answer
1 Surgical implants A Stainless steel 1-D (example)
2 Drill bits B Grey cast iron
3 High voltage power lines C Aluminium alloys
4 Propeller for ocean liners D Ti-6Al-4V
5 Railway tracks E SiC
6 Commercial kitchen sinks F Nodular cast iron
7 Engine blocks G Tungsten metal
8 Crankshaft of light aircraft H High carbon steels
9 Filament incandescent light bulb J Bronze
10 Insulation for industrial furnace K Magnesium
11 Sacrificial anode L Medium carbon steels
12 Sandpapers for polishing M Porous Al2O3 block
13 -beams for building structures
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Final Exam Semester 1 2021 4 ENSC1004
Question 4. (4 marks)
An electrochemical cell is composed of pure Cr and pure Ni electrodes immersed in solutions of their
own ions. If this galvanic cell is set up under standard conditions, what would happen (increased,
decreased or unchanged) to the following after a period of time?
(a) the output voltage (cell potential) of the galvanic cell
(b) the anode reduction potential (identify the anode)
(c) the cathode reduction potential (identify the cathode)
(d) the concentration of the Cr3+ in its cell
(e) the concentration of the Ni2+ in its cell
(f) What will the cell voltage be when above changes eventually stop?
Question 5. (10 marks)
Rivets are widely used in domestic and industry
applications to fasten objects in place. Shown in the
diagram is an illustration of three rivets on part of a
plate submerged in seawater. For each of the cases
listed below, answer the following:
(a) Will corrosion occur?
(b) If yes, what may be the form of corrosion? Briefly describe the corrosion behaviour. Write
potential reduction reaction(s) likely to accompany the corrosion.
(c) If not, explain your reasons?
Case (1): If we have brass rivets in a carbon steel plate.
Case (2): If we have stainless steel rivets in a stainless steel plate (the rivets and plate are made
of exactly same grade of stainless steel).
Question 6. (8 marks)
304 stainless steels are widely used for its excellent corrosion resistance in common industrial and
household environments. They typically contain 8-10.5 wt% Ni and 18-20 wt% of Cr. It is well-
known that stainless steels are corrosion resistant due to a naturally formed oxide film on their
surface. Answer the following:
(a) Write down the formula of oxide film that protects the 304 stainless steel.
(b) What is the typical formation mechanism of a metal oxide formed in atmosphere? Write an
overall reaction for the oxide formation for 304 stainless steel.
(c) At high application temperatures, this oxide film may grow in thickness. Briefly explain how this
oxide film would grow, knowing that it is a cation-deficient oxide.
(d) Do you think the thicker the oxide film, the better it is for the 304 stainless steel? Why?
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Final Exam Semester 1 2021 5 ENSC1004
Question 7. (20 marks)
Consider a cylindrical component of an aircraft, 120 in length. During flight, the cyclic load on
the component fluctuates at a mean load of 20 and load ratio 0.4. During landing, the component
can experience a peak tensile load of 60 . Aircraft maintenance regularly checks for surface
cracks on the component, with a detection limit of 1 . Determine the required minimum diameter
of the component, given the following:
• You may assume all loads have already factored in appropriate design and safety factors
• The component is made of 4340 alloy steel, which has a yield strength of 1.0 , fracture
toughness of 30 √ and a geometric parameter = 1.0
• The S-N curve for 4340 steel alloy is given in the diagram shown below:
End of Exam Questions
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Cycles to Failure (N)
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Supplementary Information Sheet next page
Final Exam Semester 1 2021 6 ENSC1004
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Final Exam Semester 1 2021 7 ENSC1004
Supplementary Formula and Data Sheet
= 6.022 × 1023 / = 1.38 × 10−23 / ∙ = 8.62 × 10−5 / ∙ = 8.314 / ∙ = 96485 / = 1.602 × 10−19
% ℎ = {1 − exp[−(0.25)( − )2]} × 100 =
= − % = � − � × 100 =
2(1 + ) %RA = � − � × 100 =
3(1 − 2) ≈ 2 ��2 ≈ ��22ρ = APF = �433�3
FCC structure: Al, Ni, Cu, Ag, Au, Pb
APF=0.74
BCC structure: Li, Cr, Mn, Fe, Nb, Mo, W
APF=0.68
= 12 ( + ) = �1 + 2 �ρ�1/2� = 1
2
( − ) = √ =
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Final Exam Semester 1 2021 8 ENSC1004
2+ + 2− → 2 2 + 4+ + 4− → 22 2 + 22 + 4− → 4− + + − → (−1)+ + + − →
V = − 2.303 log()
PB =

Standard EMF Series Glavanic Series in Seawater
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