Fracture behaviour - Mechanical Behaviour of Materials - Metallurgical Engineering Previous Year Questions

1

2007 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2007

Loading in Mode I fracture refers to

A

Opening mode

B

Sliding mode

C

Tearing mode

D

Twisting mode

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2

2007 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2007

By means of chemical modifications, surface energy of a highly brittle material is doubled without changing the elastic modulus. The approximate percent increase in fracture strength of the material is

A

100

B

73

C

50

D

41

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3

2007 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2007

A structural component in the form of a very wide 10 mm thick plate is to be fabricated from 4340 steel. If the design stress level for the component is 50% of the yield strength, the critical flaw size is
[Given: Yield Strength = 1515 MPa; \(K_{Ic} = 60.4 MPa\sqrt{m}\); Geometry factor, \(Y = 1\)]

A

1.0 mm

B

2.0 mm

C

3.0 mm

D

4.0 mm

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4

2008 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2008

Two samples P and Q of a brittle material have crack lengths in the ratio 4:1. The ratio of fracture strengths of P and Q, measured normal to the cracks, will be

A

1:4

B

1:2

C

2:1

D

4:1

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5

2009 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2009

Match the loading conditions in Group 1 with the characteristics in Group 2.

Group 1	Group 2
P. Tensile	1. Barreling
Q. Compressive	2. Intergranular cracking
R. Fatigue	3. Striations
S. Creep	4. Cup and cone
	5. Earing

A

P-4, Q-5, R-3, S-1

B

P-4, Q-1, R-3, S-2

C

P-5, Q-1, R-4, S-2

D

P-1, Q-2, R-3, S-5

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6

2011 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2011

In fracture toughness characterized by KIC or JIC, I in the subscript indicates loading by

A

Crack opening mode

B

Forward shear mode

C

Parallel shear mode

D

Perpendicular shear mode

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7

2012 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2012

Fracture stress for a brittle material having a crack length of 1 μm is 200 MPa. Fracture stress for the same material having a crack length of 4 μm is

A

200 MPa

B

150 MPa

C

100 MPa

D

50 MPa

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8

2013 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2013

In a brittle material, the maximum internal crack length is 8 μm. If Young’s modulus is 400 GPa and surface energy is 3.14 J/m², the estimated theoretical fracture strength (in MPa) is

A

375

B

412

C

327

D

447

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9

2013 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2013

The critical internal crack length (in mm) in a steel having \(K_{Ic}\) of 45 MPa√m to support a Mode-I stress of 400 MPa is __________

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10

2014 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2014

The respective units for dislocation density and stress intensity factor are

A

m⁻² and MPa.m

B

m² and MPa.m¹/²

C

m⁻² and MPa.m¹/²

D

m² and MPa.m

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11

2014 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2014

Two identical engineering components are made from alloys X and Y. The \(K_{IC}\) of alloy X is greater than that of alloy Y. If these components are subjected to the same stress during operation under Mode I loading, which one of the following statements is TRUE?

A

Component made from alloy X can tolerate a larger flaw size compared to that made from Y

B

Component made from alloy Y can tolerate a larger flaw size compared to that made from X

C

Both can tolerate same flaw size

D

None of the above

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12

2017 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2017

A brittle material (Young’s modulus = 60 GPa and surface energy = 0.5 J.m⁻²) has a surface crack of length 2 μm. The fracture strength (in MPa) of this material is __________ (answer up to two decimal places)

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13

2018 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2018

A glass fibre of 5 micron diameter is subjected to a tensile stress of 20 MPa. The surface energy and elastic modulus of this material are 0.3 Jm^-2 and 70 GPa, respectively. Pick the correct answer based on the information provided above:
Note: The glass fibre contains a population of flaws of different lengths.

A

The fibre will undergo brittle fracture

B

The fibre will undergo plastic deformation, but not fracture

C

The fibre will undergo elastic deformation, but not fracture

D

The fibre will undergo buckling

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14

2019 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2019

The length of internal cracks in two samples of the same glass is measured to be \( C_1 = 0.5 \text{ mm} \) and \( C_2 = 2 \text{ mm} \). The ratio \( \left( \frac{\sigma_1}{\sigma_2} \right) \) of the fracture strength of the two samples is ____________.

A

0.5

B

1.0

C

2.0

D

4.0

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15

2020 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2020

A component subjected to tensile stress in a mechanical device is monitored periodically for cracks by NDT. The NDT technique can only detect cracks (both surface and internal) which are larger than 1 mm. Keeping a 10% margin of safety, the maximum allowed tensile stress on the component will be ______ MPa (round off to the nearest integer).

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16

2021 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2021

An infinite metal plate has a central through-thickness crack of length \( \frac{80}{\pi} \) mm. The maximum applied stress (in MPa) that the plate can sustain in mode I is: ______ (round off to nearest integer).
Assume: Linear elastic fracture mechanics is valid
Given: Fracture toughness, \( K_{IC} = 20 \) MPa m^1/2

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17

2022 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2022

With reference to the stress intensity factor, find the correct match of nomenclature (Column A) with the mode of deformation applied to the crack (Column B).

Column A	Column B
(P) Mode I	(X) Forward shear mode
(Q) Mode II	(Y) Parallel shear mode
(R) Mode III	(Z) Crack opening mode

A

P – Z, Q – Y, R – X

B

P – Z, Q – X, R – Y

C

P – Y, Q – X, R – Z

D

P – Y, Q – Z, R – X

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18

2023 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2023

When cracks propagate in a brittle material, the following option(s) is/are correct

A

elastic strain energy decreases

B

surface energy increases

C

surface energy decreases

D

elastic strain energy increases

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19

2024 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2024

Which one of the following graphs represents Griffith’s criterion for the growth of a crack in a brittle isotropic infinitely large plate with a center crack?

In the graph, \(\Delta SE\) is the magnitude of the total strain energy released (shown by solid curve) and \(\Gamma_s\) is the total surface energy (shown by dashed line) and \(a_c\) is the critical crack length (shown by downward arrow) at which the crack starts growing. The tangent to the \(\Delta SE\) curve parallel to the \(\Gamma_s\) line is shown by the dotted line.

A

B

C

D

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20

2024 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fracture behaviour

Metallurgical Engineering (MT) 2024

A large rectangular component is undergoing fully-reversed cyclic loading, and the component is known to grow the dominant fatigue crack from the outer surface. If the stress amplitude (\( \sigma_a \)) is \( 100 \, MPa \) and the critical stress intensity factor \( K_{IC} \) of the material is \( 50 \, MPa \cdot m^{1/2} \), then the crack length at which the component will fail catastrophically is _____ \( mm \).
(Round off to one decimal place)
Given: The geometric factor \( \alpha \) for this loading condition is 1.12.

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