UNIVERSITI MALAYSIA PERLIS
Peperiksaan Pertengahan Semester Pertama
Sidang Akademik 2011/2012
Oktober 2011
ENT 145 – Materials Engineering
[Kejuruteraan Bahan]
Masa: 1 jam 30 minit
Please make sure that this question paper has FIVE (5) printed pages including this front page
before you start the examination.
[Sila pastikan kertas soalan ini mengandungi LIMA (5) muka surat yang bercetak termasuk muka hadapan sebelum
anda memulakan peperiksaan ini.]
This question paper has THREE (3) questions. Answer all questions and each question
contributes 20 marks.
[Kertas soalan ini mengandungi TIGA (3) soalan. Jawab semua soalan dan setiap soalan menyumbang 20
markah.]
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Question 1
[Soalan 1]
(a)
Cite two important quantum-mechanical concepts associated with the Bohr model of the
atom.
(4 Marks / Markah)
(b)
Give the electron configuration for the following ions; Cu+, Ba2+ and Br-. Given that
atomic number of Cu, Ba and Br are 29, 56 and 35, respectively
(6 Marks / Markah)
(c)
Element A, B and C have an atomic number, Z, 12, 19, and 27, respectively.
(i)
Express the electron configuration of the elements by utilizing sub-shells spdf
notation
(6 Marks / Markah)
(ii)
By comparing answer in (i), choose element(s) which is an alkali metal. Justify
your choice(s).
(4 Marks / Markah)
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Question 2
[Soalan 2]
(a)
Low-alloy steel is categorized into low-carbon steel, medium-carbon steel and high
carbon steel. For each of the low-alloy steel, describe the properties and its typical
applications.
(6 Marks / Markah)
(b)
Compare sand and die casting technique.
(4 Marks / Markah)
(c)
A portion of the iron – iron carbide (Fe-Fe3C) phase diagram is shown in Figure 1. Table
1 shows the carbon concentration of each iron-carbon alloys A, B and C.
[Sebahagian bagi gambarajah fasa besi-besi karbida ditunjukkan dalam Gambarajah 1.Jadual 1
menunjukkan kepekatan karbon bagi setiap besi-karbon aloi A, B dan C]
Figure 1
[Gambarajah 1]
…4/
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Table 1
[Jadual 1]
Iron-carbon
Alloy
A
B
C
(i)
Carbon concentration
(wt%)
0.25
0.75
0.90
Determine the approximate minimum temperature at which it is possible to
austenitize each of the iron – carbon alloys during normalizing heat treatment.
[Tentukan anggaran suhu minimum di mana kebarangkalian untuk mengaustenit setiap aloi besikarbon ketika proses rawatan haba penormalan.]
(6 Marks / Markah)
(ii)
If full anneal heat treatment is perform for iron-carbon alloys A and C, determine
the temperature at which it is desirable to heat the iron-carbon alloys.
[Jika rawatan haba penyepuhlindapan penuh dijalankan untuk besi – karbon aloi A dan C,
tentukan suhu di mana ia dapat memenuhi untuk memanaskan besi-karbon aloi.]
(4 Marks / Markah)
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Question 3
[Soalan 3]
(a)
A cylindrical metal specimen 12.9 mm in diameter and 260 mm long is to be subjected to
a tensile stress of 28 MPa; at this stress level the resulting deformation will be totally
elastic.
(i) If the elongation must be less than 0.080 mm, which of the metals in Table 6.1 are
suitable candidates? Why?
(8 Marks / Markah)
(ii) If, in addition, the maximum permissible diameter decrease is 1.2 × 10−3 mm, when
the tensile stress of 28 MPa is applied, which of the metals that satisfy the criterion in
part (a) are suitable candidates? Why?
(6 Marks / Markah)
(b)
Consider a cylindrical specimen of some hypothetical metal alloy that has a diameter of
8.0mm. A tensile force of 1000N produces an elastic reduction in diameter of 2.8 x10-4
mm. Compute the modulus of elasticity for this alloy, given that the Poisson’s ratio is
0.30.
(6 Marks / Markah)
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