Materials Examination
Section 1: Multiple Choice Questions:
1) The atomic planes with the highest planar density in body centered cubic, face
centered cubic and hexagonal close-packed metals are:
a)
b)
c)
d)
{110}, {111} and (0001) respectively
{111}, {111} and {1000}
{110}, {100} and (0001)
{100}, {100} and (0001)
2) The {123} family in a tetragonal crystal system in which a = b ≠ c includes, but not
limited to, the following planes:
a)
b)
c)
d)
̅), (𝟏
̅𝟐𝟑), (𝟐𝟏𝟑
̅)
(12𝟑
(123), (213), (321)
(213), (123), (132)
(312), (213), (321)
The z direction cannot change, but the other numbers can
3) Which of the following represents a family of direction in a crystal lattice?
a)
b)
c)
d)
{111}
[111]
<111>
(111)
4) Which of the following technique/s can be used to study the surface morphology of
materials
a)
b)
c)
d)
Scanning electron microscopy
transmission electron microscopy
atom probe tomography
All of the above
5) X-ray diffraction is used for the determination of crystal structures because
a) X-rays can have wave lengths comparable to or shorter than the spacings between
atomic planes
b) X-rays can penetrate thick specimans
c) X-rays are invisible
d) It is easy to focus X-ray
6) Point defects in crystalline metallic materials do not include
a)
b)
c)
d)
Cation interstitial
Vacancies
Self-interstitial
Substitutional impurity atoms.
7) A metal with a face centered cubic (FCC) structure is usually more ductile than a metal
with a hexagonal close-packed (HCP) structure because
a)
b)
c)
d)
An FCC structure is denser than a HCP structure
An FCC structure has a higher atomic packing factor than a HCP structure
There are more dislocation slip systems in an FCC structure than in an HCP structure
None of the above
8) Metals cannot be strengthened by
a)
b)
c)
d)
Annealing
Reducing grain sizes
Alloying
Cold Work
9) Cold work normally increases
a)
b)
c)
d)
Dislocation density
Elastic Modulus
Grain size
Ductility
10) The fabrication techniques of metals and alloys do not include
a)
b)
c)
d)
Sintering
Welding
Casting
Extrusion
11) For a ceramic compound, the following characteristics of the component ions
determine the crystal structure:
a)
b)
c)
d)
The magnitude of the electrical charge on each ion
The relative sizes of the cations and ions
Both A and B
Neither A nor B
12) In general, which of the following steel microstructure offers the highest strength?
a)
b)
c)
d)
Martensite
Tempered martensite
Pearlite
Spheroidite
13) In general, which of the following steel microstructure offers the highest ductility?
a)
b)
c)
d)
Pearlite
Martensite
Tempered Martensite
Bainite
14) The phase/s in tempered martensite in a steel is/are:
a)
b)
c)
d)
Body centered cubic Ferrite
Monoclinic Fe3C
Body centered Tetragonal martensite
Both A and B
15) In a tensile test on a low carbon steel, necking starts on the engineering stress, versus
engineering strain curve at:
a)
b)
c)
d)
Just before final fracture
Lower yield stress
Upper yield stress
Maximum tensile stress
16) If the surface crack causing fracture in a brittle material is made twice as deep,
assuming the fracture toughness is unchanged, the fracture strength will
a)
b)
c)
d)
Decrease by a factor of √𝟐
Decrease by a factor of 2
Decrease by a factor of 4
No change
17) Tick the method that improves fatigue resistance of materials:
a)
b)
c)
d)
Case hardening
Imposition of stress concentrators
Tensile residual stresses on surfaces
Roughening the surfaces
18) In many metals, creep occurs when the homologous temperature exceeds 0.4. Which
of the following statements is correct?
a)
b)
c)
d)
Lead will creep but steel will not creep at room temperature
Steel and lead will both creep at room temperature
Steel will creep but lead will not creep at room temperature
Steel and lead will both not creep at room temperature
19) The Liberty suffered brittle fracture during WWII because:
a)
b)
c)
d)
The DBTT of the ship steel plates is higher than the ocean temperature
The DBTT of the ship steel plates is lower than the ocean temperature
The ship hull and deck were poorly welded
None of the above
20) Glass has the following characteristics:
a)
b)
c)
d)
It is a brittle material with a low toughness value
It has a crystalline structure
It experiences large thermal expansions (contractions) with changes in temperature
It is a tough material with high ductility
21) A hardness test confused on a particular grade of steel gives a Brinell Hardness
Number (HB) of 300, what is its approximate tensile strength?
a)
b)
c)
d)
1000 MPa
300 MPa
600 MPa
2000 MPa
22) Increasing the degree of cystallinity of a polymer
a)
b)
c)
d)
Increases its strength, increases modulus, decreases ductility
Increases its strength, decreases modulus and decreases ductility
Decreases its strength, decreases modulus and increases ductility
Increases its strength, increases modulus and increases ductility
23) Which of the following statements is true?
a)
b)
c)
d)
Themosetting polymers have a cross-linked and network structure
Thermoplastic polymers have a cross-linked and network structure
Thermoplastics once hardened cannot be softened upon heating
Thermosets softens when heated and hardens when cooled
24) A continuous and aligned glass fiber/epoxy resin composite has 60 vol% of glass fibres
with a Young’s modulus of 70 GPa and 40% vol % of expoxy resin with a Young’s
modulus of 3 GPa. What is the composite elastic modulus in the longitudinal
direction?
a)
b)
c)
d)
43.2 GPa
29.8 GPa
36.5 GPa
49.9 GPa
-
0.6*70 + 0.4*3
25) Which of the following statements is not correct?
a) The diamond can be treated as two identical face-centered cubic structures with
displacement of <111>/4 between the two structures
b) The diamond has a face centered cubic lattice structure
c) The diamond is a stable structure
d) The diamond is the hardest material available in the nature