Fatigue - Mechanical Behaviour of Materials - Metallurgical Engineering Previous Year Questions

1

2008 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fatigue

Metallurgical Engineering (MT) 2008

Fatigue resistance of a steel is reduced by

A

decarburization

B

polishing the surface

C

reducing the grain size

D

shot peening

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2

2012 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fatigue

Metallurgical Engineering (MT) 2012

Stress ratio is

A

4

B

2

C

-2

D

-4

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3

2013 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fatigue

Metallurgical Engineering (MT) 2013

Which one of the following does NOT improve fatigue life of a steel component?

A

Nitriding

B

Decarburization

C

Improving surface finish

D

Shot-peening

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4

2014 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fatigue

Metallurgical Engineering (MT) 2014

A steel rod was subjected to a fluctuating stress cycle that varied between a maximum of 400 MPa in tension to a minimum of 300 MPa in compression. What is the stress amplitude, in MPa? ______

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5

2017 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fatigue

Metallurgical Engineering (MT) 2017

A steel component is subjected to fatigue loading: σ (maximum) = 200 MPa, σ (minimum) = 0. The component has an initial crack length of 1 mm. Propagation of crack is governed by da/dN = 10⁻¹²(ΔK)³, where, the crack length a is in meters, N is the number of cycles and ΔK is in MPa.m¹/². The length of the crack (in m) after one million cycles will be __________ (answer up to three decimal places)

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6

2019 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fatigue

Metallurgical Engineering (MT) 2019

Beach marks are commonly observed on the fractured surfaces of metals after a ______.

A

Creep test

B

Fatigue test

C

Impact test

D

Compression test

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7

2019 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fatigue

Metallurgical Engineering (MT) 2019

The S-N curve for a steel is shown below. If the stress ratio, (σ_min/σ_max) = -0.8, the maximum stress (in MPa, rounded off to the nearest integer) that the steel can withstand for infinite fatigue life is ____________.

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8

2020 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fatigue

Metallurgical Engineering (MT) 2020

Crack growth is being continuously measured in a test specimen subjected to constant amplitude cyclic stress with a mean stress of zero. The crack growth rate is related to the stress intensity range, ΔK as \[ \frac{da}{dN} \propto (\Delta K)^3 \], where, a is the crack length and N is the number of cycles. When the crack length increases by a factor of two, the crack growth rate will increase by a factor of ______ (round off to one decimal place).

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9

2022 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fatigue

Metallurgical Engineering (MT) 2022

High cycle fatigue data for an alloy at various alternating stresses, σ_a (see figure) is given below

Stress, σa (MPa)	Nf, Number of cycles to failure
500	1000
400	10000
300	100000
200	1000000

A specimen of this alloy is subjected to multiple stress cycles sequentially in the following order: (i) first 5000 cycles at σ_a = 400 MPa followed by (ii) 25000 cycles at σ_a = 300 MPa and finally (iii) at σ_a = 500 MPa. Assuming that Miner’s law is obeyed, the number of cycles to failure at the final applied stress of 500 MPa is ______.

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10

2023 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fatigue

Metallurgical Engineering (MT) 2023

Which of the following is/are responsible for reducing the high cycle fatigue life of a component?

A

increasing the mean stress at constant amplitude

B

increasing the surface roughness

C

employing shot peening

D

absence of sharp corners in the component

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11

2023 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fatigue

Metallurgical Engineering (MT) 2023

A specimen containing maximum initial surface crack of size 1.5 mm is subjected to cyclic loading with \(\sigma_{max} = 300\) MPa and \(\sigma_{min} = 0\) MPa. Assuming specimen geometric factor of 1, and referring to the given figure, the crack growth rate in \(\mu m\) cycle\(^{-1}\) is __________ (round off to nearest integer).
Given: \(N =\) number of cycles, \(a =\) crack length, \(R =\) stress ratio, \(\Delta K =\) stress intensity range

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12

2024 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fatigue

Metallurgical Engineering (MT) 2024

A steel bar is subjected to fatigue loading with a tensile mean stress. Given that the ultimate tensile strength is \( 1000 \, MPa \) and the fatigue limit under fully reversed loading is \( 250 \, MPa \), the fatigue limit for a mean stress of \( 100 \, MPa \), considering Goodman relationship is _____ \( MPa \).
(Round off to the nearest integer)

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13

2026 · Metallurgical Engineering · Mechanical Behaviour of Materials · Fatigue

Metallurgical Engineering (MT) 2026

Match the concepts listed in Column I with the associated terms listed in Column II
Column I
(P) Paris Law
(Q) Schmid Factor
(R) Larson - Miller Parameter
(S) Portevin - Le Chatelier Effect
Column II
(1) Creep
(2) Fatigue
(3) Dynamic Strain Aging
(4) Critical Resolved Shear Stress

A

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

B

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

C

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

D

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

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