ENGR20003 Final Exam 2013
ENGR20003 Final Exam 2013
ENGR20003 Final Exam 2013
Authorised materials :
Any electronic calculators may be used.
Protractor and compass may be used.
Instructions to invigilators:
Closed book examination.
Three 14 page script books designated A, B and C
Paper to remain in the exam room
Instructions to students:
All questions should be attempted.
Sections A, B and C are to be answered in separated designated script books.
Marks allocated to each question are as indicated.
Total marks for the examination equal 120.
Figure A1
b) Briefly describe the manufacturing process of structural steel and discuss three factors
during the manufacturing process which can affect the strength of a steel product.
(6 marks)
A2.
a) Figure A2 (in the following page) shows a timber frame that is supporting a roof of a
house. Describe using sketches the use of noggings in the timber frame.
(5 marks)
b) Describe the process of visual stress grading to measure the strength of timber. State
two other methods that can be used to determine the strength and explain why visual
stress grading is more commonly used compared to other methods.
(7 marks)
Figure A2
(Total marks for QA2 = 12)
A3.
a) Describe using sketches the compression test of masonry units. Your description should
include what should be done to ensure that the measured strength is representative of
the strength of masonry units in masonry wall constructions.
(6 marks)
b) Sketch two crack patterns indicating two types of failure which may occur when
masonry walls are subjected to horizontal bending actions. Describe using sketches
how the horizontal bending actions are resisted by the walls.
(6 marks)
A4.
a) Describe the test you would use to determine the workability of a concrete mix on site
or in the laboratory. Describe one workability range of this test and the specific
concrete application for which it is used.
(5 marks)
b) Explain using sketches the setting phenomenon of concrete. Discuss how concrete
setting time can be modified.
(4 marks)
(End of Section A)
b) Calculate the mass (M) required to fail the hangers if the mass is now dropped from a
height of 1 m as shown in Figure B1b.
(5 marks)
c) The cold-drawn steel hangers are now replaced by mild steel. The yield strength of mild
steel is 300 MPa, the Young’s modulus value is 200,000 MPa, ductility is 2. Determine
the mass that can be supported by the hangers, if the mass is dropped from a height of 1
m. Bi-linear force deformation behaviour as shown in Figure B1c can be assumed.
(6 marks)
M
1.5 m 1.5 m
1m
y u
Figure B1c
B2. Based on two-dimensional stress state acting on the rectangular thin plate shown in
Figure B2 below:
a) Use Mohr’s circle to determine the principal (maximum and minimum) stresses and the
maximum shear stress at the point.
(10 marks)
b) Determine the angle of the plane on which the principal stresses act and the angle of the
plane on which the maximum shear stress acts. Sketch the stresses that are acting on the
planes.
(5 marks)
30 MPa
10 MPa
10 MPa
Figure B2
End of Section B
C1. List the properties and types of bonding which are indicative of materials in each of the
following Material Classes:
a) Metals (2 marks)
b) Ceramics (2 marks)
c) Polymers (2 marks)
C2. Using the periodic table shown in Figure C2 below containing the electro-negativity
values for each element, what type of bond would form for each type of atom pair?
Figure C2
a) Na-Na
b) S-S
c) Na-S
d) Na-K
e) S-O
f) Na-O
g) Ca-Zr
h) K-Br
i) Ne-Ne
(Total marks for QC2 = 5)
ENGR20003 Engineering Materials
Page 8 of 9
C4. Calculate the density of BaTiO3. It has the perovskite structure. In the perovskite
structure, the Ba2+ and O2- combine to form a cubic close packed structure with the Ba2+ on
the cube corners and the O2- in the face centre positions (because the Ba2+ and O2- have
nearly the same radius). The small Ti4+ fits nicely in an octahedral site. Because of
stoichometry and charge neutrality, only ¼ of the octahedral sites (those in the body centre
position) are filled with Ti4+.
Ionic Radius Atomic Mass
2+
Ba 1.36 Ångstroms 137.3 g/mole
Ti4+ 0.61 Ångstroms 47.9 g/mole
2-
O 1.40 Ångstroms 16.0 g/mole
C5. Using the phase diagram shown in Figure C5 (in the following page) for the lead (Pb) -
tin (Sn) system, determine:
i) the phase or phases present;
ii) the composition (wt% tin (Sn)) of each phase;
iii) the amount (wt %) of each phase for:
a) a lead-tin alloy (20 wt % tin (Sn)) at 250 oC. (2 marks)
b) a lead-tin alloy (10 wt % tin (Sn)) at 200 oC. (2 marks)
c) a lead-tin alloy (80 wt % tin (Sn)) at 100 oC. (2 marks)
Figure C5
(Total marks for QC5 = 6 marks)
End of Section C
End of Examination