Mechanical properties - Properties and Applications of Materials - Engineering Sciences Previous Year Questions

1

2013 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2013

Upon recrystallization of a cold worked metal,

A

strength increases and ductility decreases

B

strength decreases but ductility increases

C

both strength and ductility increase

D

both strength and ductility decrease

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2

2013 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2013

The tensile breaking strength of polycarbonate (I), low density polyethylene (II), polystyrene (III) and polypropylene (IV) can be arranged as

A

IV > II > I > III

B

I > II > IV > III

C

I > III > IV > II

D

III > I > II > IV

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3

2014 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2014

The most appropriate order of toughness of nylon based materials is

A

talc filled nylon < dry nylon < wet nylon

B

dry nylon < wet nylon < talc filled nylon

C

wet nylon < dry nylon < talc filled nylon

D

wet nylon < talc filled nylon < dry nylon

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4

2014 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2014

Which of the following mechanical properties of a material depend on the mobile dislocation density in it.
(P) Young’s modulus   (Q) yield strength   (R) ductility   (S) fracture toughness

A

P, Q, R

B

Q, R, S

C

P, R, S

D

S, P, Q

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5

2014 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2014

The Young’s modulus of a unidirectional SiC fiber reinforced Ti matrix composite is 185 GPa. If the Young’s moduli of Ti and SiC are 110 and 360 GPa respectively, the volume fraction of fibers in the composite is _______________.

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6

2015 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2015

Creep in metals is defined as

A

the maximum energy a solid can absorb elastically

B

the maximum energy a solid can absorb by plastic deformation

C

the stress at which plastic deformation starts

D

slow plastic deformation due to diffusion of atoms usually at high temperature (T = half the melting point)

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7

2015 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2015

A hot pressed ceramic composite material consists of 30 volume % SiC whiskers in an Al₂O₃ matrix. The measured bulk density of this composite is 3.65 g cm^-3. If the theoretical density of SiC is 3.22 g cm^-3 and that of Al₂O₃ is 3.95 g cm^-3, estimate the porosity (%) of the composite, assuming that the linear rule of mixtures is valid in this case.

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8

2016 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2016

The yield strength of a ferritic steel increases from 120 MPa to 150 MPa when the grain size is decreased from 256 μm to 64 μm. When the grain size is further reduced to 16 μm, the expected yield strength is __________ MPa.

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9

2017 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2017

During deformation of a semi-crystalline polymer, with spherulitic morphology, stressed in tension, what happens to the amorphous and the crystalline regions at the later stages?

A

Amorphous regions remain intact and only crystallites experience bending and stretching of chains

B

Only amorphous regions elongate in the stress direction and crystallites remain intact

C

Amorphous regions elongate in the stress direction and crystallites experience bending and stretching of chains

D

None of the above

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10

2017 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2017

Ceramic materials fail at stresses much lower than their theoretical strength due to

A

Presence of dislocations

B

High elastic modulus

C

Presence of voids

D

Anisotropy in crystal structure

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11

2017 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2017

Which of the following statement(s) is / are true regarding the structure-property correlation in polymers?
(i) Polymers that are less coiled are more crystalline than those that are more coiled
(ii) Branched polymers are more crystalline than the linear ones
(iii) Polymers with inter-chain interactions have higher glass transition temperature than those without inter-chain interactions
(iv) Polymers with inter-chain interactions are more crystalline than those without inter-chain interactions

A

(i) and (ii)

B

(i) and (iii)

C

(ii) and (iv)

D

(ii) and (iii)

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12

2017 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2017

A continuous, aligned carbon fibre (CF) reinforced polymer composite with 30 vol% of CF and rest resin was designed for a specific application. The modulus of elasticity of CF is 170 GPa and that of the resin is 3.0 GPa. The modulus of elasticity for this composite in the direction of fibre alignment is ………..GPa.

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13

2018 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2018

A unidirectionally aligned carbon fibre reinforced epoxy composite is loaded as shown in the figure. The volume fraction of the fibre is 0.6. The Young’s modulus of the composite is ___________ GPa.
(Given: Young’s Modulus of the fibre and the matrix are 200 GPa and 10 GPa, respectively)

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14

2019 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2019

Which one of the following is time-independent?

A

Elastic deformation

B

Anelastic deformation

C

Viscoelastic deformation

D

Creep deformation

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15

2019 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2019

The potential energy, U(r), of a pair of atoms spaced at a distance r in a solid is given by U(r) = -A/r³ + B/r⁷. The equilibrium distance between the atom pair is ____ nm. (round off to 2 decimal places) (Given: Constants A = 6×10⁻³⁰ J nm³, B = 2.1×10⁻²² J nm⁷)

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16

2019 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2019

A piezoelectric material has a Young’s modulus of 72 GPa. The stress required to change the polarization from 640 to 645 C m^-2 is ______ MPa. (round off to the nearest integer)

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17

2021 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2021

A unidirectional composite of epoxy and carbon fiber of 50% by volume is made. The elastic modulus of epoxy and carbon fiber are 3.5 GPa and 350 GPa, respectively. The ratio (rounded off to one decimal place) of the modulus of the composite to the matrix modulus is __________.

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18

2023 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2023

The Young’s modulus of a quartz piezoelectric crystal is 100 GPa. The uniaxial stress required to change its polarization by 1% is (give absolute value in GPa) __________ (rounded off to nearest integer)

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19

2024 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2024

Mechanical behaviour of a crystalline ceramic material is best described as

A

ductile

B

brittle

C

viscoelastic

D

Viscoplastic

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20

2024 · Engineering Sciences · Properties and Applications of Materials · Mechanical properties

Engineering Sciences (XE) 2024

A unidirectional composite is prepared using 70% by volume of epoxy matrix and 30% by volume of carbon fibre. The elastic modulus of the epoxy matrix is 3.5 GPa and the elastic modulus of the carbon fibre is 350 GPa. The longitudinal elastic modulus of the composite is ______ GPa (rounded off to the nearest integer).

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