Material Science and Engineering MTA Sem5

First material known to be used by man
Cotton
Iron
Bronze
Rock
First metal known to be used by man
Iron
Bronze
Silver
Aluminium
Which one of the following is not basic component of Materials Science?
Cost
Properties
Structure
Performance
Figure out the odd statement about ceramics in the following
Good insulators of heat and electricity
Usually less desire than metals
Ductile in nature
Contains both metallic and nonmetallic
Pick the composite from the list
Wood
Steel
Nylon
Mica
Not an example for actuator
Optical fiber
Shape memory alloys
Magneto-strictive materials
Electro-/Magneto-rheological fluids
Strong and ductile materials
Polymers
Ceramics
Metals
Semiconductors
Presently most used metal in the world
Aluminium
Gold
Steel
Silver
Detrimental property of a material for shock load applications
High density
Low Toughness
High strength
Low hardness
Democratic material
Diamond
Titanium
Iron
Gold
Particles that most effects material properties
Neutrons
Protons
Electrons
Valence Electrons
Mean distance between atoms in the range of
25 nm
2.5 nm
0.25 nm
0.025 nm
Which one of the following is not a strong bond?
Van der Waals bond
Covalent bond
Metallic bond
Ionic bond
Bond strength of secondary bonds is in the range of
1 kJ/mol
10 kJ/mol
100 kJ/mol
1000 kJ/mol
Electron sea exists in
Polar bond
Ionic bond
Covalent bond
Metallic bond
Repeatable entity of a crystal structure is known as
Crystal
Lattice
Unit Cell
Miller indices
Coordination number for closest packed crystal structure
16
12
8
4
Atomic packing factor is
Distance between two adjacent atoms
Projected area fraction of atoms on a plane
Volume fraction of atoms in cell
None
Coordination number in simple cubic crystal structure
1
2
3
4
The atomic diameter of an BCC crystal (if a is lattice parameter) is
A
A/2
a/(4/√3)
A/(4/√2)
A family of directions is represented by
(hkl)
< uvw >
{hkl}
[uvw]
Miller indices for Octahedral plane in cubic crystal
(100)
(110)
(111)
None
The plane (1⎯11) is parallel to
(⎯11⎯1)
(⎯1⎯11)
(111)
(1⎯11)
The angle between [111] and [11⎯2] directions in a cubic crystal is (in degrees)
0
45
90
180
Miller indices of the line of intersection of (⎯1⎯11) and (110) are
[110]
[101]
[10⎯1]
[⎯110]
Repeatable unit of polymers
Isomer
Copolymer
Homopolymer
Mer
Pick the thermo-plast from the following
Vinyls
Epoxies
Resins
Vulcanized rubber
For c coordination number of four, anion sits at the center of ……..where corners are occupied by cations
Cube
Tetrahedron
Triangle
Octahedron
Layered silicate structures in clays consists the following group
SiO4 4-
B) Si2O5 2-
Si2O7 6-
SiO4 4-
Schottky-defect in ceramic material is
Interstitial impurity
Vacancy- interstitial pair of cations
Pair of nearby cation and anion vacancies
Substitutional impurity
Theoretical strength is about __________ times to average real strength of a material
1
10
100
1000
Hooke’s law
Elastic range, strain is proportional to stress
Plastic range, strain is proportional to stress
In both elastic and plastic range, strain is proportional to stress
None
Following is not the 2-dimensional imperfection
Twin boundary
Dislocation
Surface
Grain boundary
Figure out the odd one in the following
Frenkel defect
Tilt boundary
Twist boundary
Stacking fault
Thermodynamically stable defects
Point defects
Line defects
Surface defects
Volume defects
Taylor dislocation can not move by the following way
Slip
Climb
Cross-slip
All
Conservative movement of dislocations
Slip
Climb
Both slip and climb
None
Typical density of dislocations in a solid
10^8-10^10 μm-2
10^8-10^10 mm-2
10^8-10^10 cm-2
10^8-10^10 m-2
Burger’s vector changes with
Kind of dislocation
Length of dislocation
Both kind and length of dislocation
None
Which of the following is false?
Line defects are thermodynamically stable
Dislocation can end inside a crystal without forming loop
ABC ABC ABC…is stacking sequence for HCP crystal
All
Average frequency of atomic vibrations in a solid (in Hz)
10^-12
10^-13
10^12
10^13
Requirement for cross-slip movement of dislocation
Preferred slip plane
Preferred slip direction
No preferred slip plane
No preferred slip direction
Beneficial property of foreign particles
Reduces density
Act as stress raisers
Obstructs dislocation motion
None
Stacking fault energies are in the range of
0.01-0.1 J/cm2
0.1-10 J/m2
0.1-10 J/cm2
0.01-0.1 J/m2
Time dependent permanent deformation is called ________________.
Plastic deformation
Elastic deformation
Creep
Anelastic deformation
Figure-out the odd point in the following
Proportinal limit
Elastic limit
Yeild point
Fracture point
If a material is subjected to two incremental true strains namely ε1 and ε2, then the total true strain is
ε1 * ε2
ε1 - ε2
ε1 + ε2
ε1 / ε2
Engineering stress-strain curve and True stress-strain curve are equal up to
Proportinal limit
Elastic limit
Yeild point
Tensile strength
Value of Poisson’s ratio for ionic solids in the range of
0.1
0.2
0.3
0.4
Hydrostatic stress results in the following
Linear strain
Shear strain
Both linear and shear strains
None
High elastic modulus in materials arises from
High strength of bonds
Weak bonds
Combination of bonds
None
Change in elastic modulus for ordinary materials between 0K and melting point is
10-20% increase
10-20% decrease
80-90% increase
80-90% decrease
Bauschinger effect
Hysteresis loss during loading and unloading
Anelastic deformation
Dependence of yield stress on path and direction
Nnoe
Shape of true stress-strain curve for a material depends on
Strain
Strain rate
Temperature
All
Toughness of a material is equal to area under ____________ part of the stress-strain curve.
Elastic
Plastic
Both
None
True stress-strain curve need to be corrected after
Elastic limit
No need to correct
Yeild point
Tensile Strength
Following condition represents onset of necking
εu = n
εu = 1-n
εu = 1+n
εu = ln (1+n)
As compared with conventional stress-strain curve, the true stress-strain curve is
Above and right
Below and right
Above and left
Below and left
According to distortion-energy criterion, yielding occurs when
Distortion energy reaches a critical value
Distortion energy reaches a critical value
Octahedral shear stress reaches a critical value
All
Von Mises and Tresca criteria give different yield stress for
Uni-axial stress
Balanced bi-axial stress
Pure shear stress
All
Plastic deformation results from the following
Slip
Twinning
Both
None
Time dependent recoverable deformation under load is called ____________
Elastic
Anelastic
Elastic after-effect
Visco-elastic
Diffusion can occur in ________________ materials
Solid
Liquid
Gaseous
All
Probably the fastest diffusing species in Fe is
H
Ni
W
C
The value of error function for ‘∞’ is
- ∞
-1
1
ˆ�
The value of error function for ‘0’ is
-1
0
1
None
The units for diffusivity, D, are
M2sec1
M2sec-1
M-2sec-1
M-2sec1
The following mechanism contributes very little the diffusivity
Vacancy
Interstitial
Substitutional
Self -Interstitial
Not an example for short-circuit path
Vacancy
Dislocations
Grain boundaries
External surfaces
Example for steady-state diffusion
Hydrogen purification by palladium sheet
Doping semi-conductors
Corrosion resistance of duralumin
Decarburization of steel
The most influencing factor of diffusivity
Diffusing species
Temperature
Lattice structure
Presence of defects
The following phenomena are useful in zone-refining process
Coring
Segregation
Both
None
Macro-segregation can be removed by
Annealing
Hot working
Both
None
The following enhances the coring
Minute difference between liquidus and solidus
Marked difference between liquids and solids
Either
None
Failure due to excessive deformation is controlled by ______________.
Material properties
Design & Dimensions
Both
None
Failure due to excessive deformation is controlled by ______________.
Yield strength
Tensile strength
Young’s modulus
All
Time dependent yield is known as
Fracture
Fatigue
Buckling
Creep
Cleavage fracture appears
Bright
Dull
Difficult to identify
None
Usually materials with following crystal structure fail in ductile mode
FCC
BCC
HCP
None
Brittle fracture is more dangerous than ductile fracture because _______________.
No warning sign
Crack propagates at very high speeds
No need for extra stress during crack propagation
All
Fracture voids usually form at
Inclusions
Second phase particles
Grain boundary triple points
All
Fracture stress (σf) is proportional to
Crack length
1/crack length
(crack length)^1/2
(crack length)^-1/2
Fracture toughness is measured in terms of
Strain energy release rate
Stress concentration factor
Both
None
In fracture mode-II, fracture surfaces
Shear parallel to edge of crack
Shear perpendicular to edge of crack
Displace normal to each other
None
Fracture toughness, KIC, decreases with
Increasing temperature
Increasing strain rate
Increase in yield strength
Increase in grain size
DBTT for ceramics is in the range of _________ X Tm.
0.1-0.2
0.2-0.3
0.3-0.5
0.5-0.7
Following impurity decreases DBTT for steels
Mn
P
Si
Mo
Fatigue strength for non-ferrous materials in defined at _______ stress cycles.
10^3
10^5
10^7
10^9
The following equation defines S-N curve
Paris equation
Basquin equation
Andrede equation
Garofalo equation
Creep rate in ternary stage __________.
Decreases
Increases
Constant
None
Ternary stage creep is associated with ____________.
Strain hardening
Recovery
Necking
None
Total strain range in a creep test
<1%
Around 10%
Around 50%
> >50%
Creep mechanism that is operational at stresses 10-2 >σ/G >10-4 _____________.
Dislocation creep
Dislocation glide
Diffusion creep
GB sliding
Most often machine components fail by
Buckling
Creep
Fatigue
All
If the surface crack causing fracture in a brittle material is made twice as deep, the fracture strength will
Decrease by a factor of √2
Decrease by a factor of 2
Decrease by a factor of 2^2
No change
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