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INTRODUCTION M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and Structures
MODULE 1
INTRODUCTION
SKMM 4133 Failure of Engineering Components and Structures
INTRODUCTION M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and Structures
Fatigue crack in root area of
a turbine blade
List possible questions regarding this fracture situation
OPENING REMARKS
SKMM 4133 Failure of Engineering Components and Structures
INTRODUCTION M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and Structures
• Failure
Inability of a component to perform
according to its intended function.
• Failure Analysis
The examination of a failed component
and of the failure situation in order to
determine the causes of failure
Failure Analysis of Metallic Components
SKMM 4133 Failure of Engineering Components and Structures
INTRODUCTION M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and StructuresSKMM 4133 Failure of Engineering Components and Structures
Week Date
(Sun.)
Lecture & Topics
TopicsLecture
1
Lecture
2
Lecture
3
1 07 Sep A A A
A – Introduction
- Overview
- Requirements and approach
B – Static failure due to overload
and instability.
C – Fatigue failure
- High-cycle fatigue
- Low-cycle fatigue
D – Creep and stress rupture
E – Fatigue crack propagation
(OPTIONAL) – Computational aspects of
failure analysis
2 14 Sep A A A
3 21 Sep B B B
4 28 Sep B B B
5 05 Oct C C C
6 12 Oct C C C
7 19 Oct SEMESTER BREAK
8 26 Oct Test1 C C
9 02 Nov C C C
10 09 Nov C C C
11 16 Nov D D D
12 23 Nov D D D
13 30 Nov E E E
14 07 Dec E E E
15 14 Dec E Test 2 Closure
16 21 Dec STUDY LEAVE
17 28 Dec FINAL EXAMINATION
INTRODUCTION M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and Structures
COURSE CONTENT
1.0 Introduction
Historical background, origin, detection and prevention of failure, types of
mechanical failure: gross yielding, fatigue fracture, buckling, creep
rupture, review of stress field and stress concentration, statistical aspect of
failure analysis, loading spectrum, metallurgical aspect of component
failure.
2.0 Materials Defects
Processing-structure-property relationship, metallurgical imperfection,
processing defects, NDT methods, surface defects and corrosion,
propagation of defects, tools for metallurgical failure analysis
3.0 Failure due to overload
Yield failure theories, idealized material behavior, plastic bending of
beams, collapse loads, plastic torsion of circular bar, residual stresses after
yielding.
4.0 Buckling of Struts and Columns
Euler’s column theory, Rankine-Gordon formula, eccentric loading,
inelastic buckling.
SKMM 4133 Failure of Engineering Components and Structures
INTRODUCTION M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and Structures
COURSE CONTENT (Continued)
5.0 Fatigue Failure
High-cycle fatigue, Strength-life (S-N) curves, cumulative damage
concept, life prediction and fracture control; low-cycle fatigue, strain
cycling concept, strain-life curve and low-cycle fatigue relations,
influence of non-zero mean strain and non-zero mean stress.
6.0 Creep and Stress Rupture
Theories for predicting creep behavior, Larson-Miller and Manson-Haferd
parameters, uniaxial and multi-axial state of stress, cumulative creep
concept, creep-fatigue interaction.
7.0 Fatigue Crack Propagation and Control
Basics of fracture mechanics, linear elastic and elastic-plastic fracture
mechanics, stress intensity factor range, fatigue crack growth rate, factors
affecting crack propagation, fatigue fracture mechanisms in metals.
SKMM 4133 Failure of Engineering Components and Structures
INTRODUCTION M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and Structures
COVERAGE
• CONCEPT
• FUNDAMENTAL THEORY
• ESTABLISHED WORK
• STATISTICS
• CASE STUDIES
SKMM 4133 Failure of Engineering Components and Structures
INTRODUCTION M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and Structures
SCOPE
MODES OF FAILURE
• Gross Yielding
• Fatigue Fracture
• Creep Rupture
• Buckling
• Static Delayed Fracture
REQUIREMENTS FOR FAILURE
ANALYSIS
• Mechanical design and analysis
• Force analysis
• Stress analysis
• Chemical analysis
• Metallography
• Fractography
• Mechanical testing
• Failure simulation
SKMM 4133 Failure of Engineering Components and Structures
INTRODUCTION M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and Structures
Faulty design considerations/
misapplication of materials
• Ductile failure – excessive
deformation (elastic or plastic),
tearing or shear fracture).
• Brittle fracture – from flaws and
critical stress raisers.
• Fatigue failure – due to time-
varying load, thermal cycling,
corrosion fatigue.
• High-temperature failure – creep,
oxidation, local melting, warping.
• Static delayed fracture – hydrogen
embrittlement,
• Severe stress raiser inherent
in design.
• Inadequate stress analysis
• Mistake in designing on
basis of static tensile
properties only
Classification of the causes of failure
SKMM 4133 Failure of Engineering Components and Structures
INTRODUCTION M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and Structures
Faulty processing
• Flaws due to faulty composition –
wrong material, inclusions,
embrittling impurities.
• Defects originating in ingot
making and casting – porosity, non-
metallic inclusions, segregation.
• Defects due to working – laps,
seams, hot-short splits, excess local
deformation
• Irregularities / mistakes due to
machining, grinding or stamping –
burns, tearing, cracks.
• Welding defects – voids, undercuts,
residual stresses, HAZ, lack of
penetration.
•Abnormalities due to heat treatment –
grain growth, precipitation, excessive
retained austenite, decarburization.
• Flaws due to case hardening –
intergranular carbides, soft core.
• Defects due to surface treatment –
plating, chemical diffusion, hydrogen
embrittlement.
• Parting-line failure in forging - due
to poor transverse properties.
• Careless assembly – mismatch of
mating parts, residual stress, gouges.
Classification of the causes of failure
SKMM 4133 Failure of Engineering Components and Structures
INTRODUCTION M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and Structures
Deterioration in service
• Overload / unforeseen loading
conditions
• Wear – erosion, galling,
seizing, cavitation.
• Corrosion – chemical attack,
stress corrosion, dezincification.
• Inadequate / misdirected
maintenance or improper repair
– welding, grinding, cold
straightening.
• Disintegration by chemical
attack, attack by liquid metals or
plating at elevated temperature
• Radiation damage -
decontamination may destroy
evidence for the cause of failure.
• Accidental condition – abnormal
operating temperature, severe
vibration, impact, thermal shock.
Classification of the causes of failure
SKMM 4133 Failure of Engineering Components and Structures
INTRODUCTION M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and Structures
• Description of the failure situation –
Background information, history of
usage, design of component.
• Visual inspection – DO NOT damage
the fracture surface.
• Mechanical design analysis (stress
analysis) – to establish the cause of
failure. Was the part of sufficient size?
• Chemical design analysis –to establish
the suitability of the material wrt
corrosion resistance.
• Fractography – examine fracture
surface to establish the mechanism of
fracture.
• Metallographic examination – to help
establish such facts as whether the part
has correct heat treatment.
• Determine properties – to establish
properties pertinent to the design.
• Failure simulation - to establish
response of identical component under
exact condition of loading, numerical
simulation.
• Formulation of conclusions, Report
writing (may include recommendations)
Steps in Performing Failure Analysis
SKMM 4133 Failure of Engineering Components and Structures