SME
4133
Failure
of Engineering
Components
and Structures
SKMM
4133
Failure
of Engineering
Components
and Structures
MODULE 1
INTRODUCTION
INTRODUCTION
M.N. Tamin, UTM
SME
4133
Failure
of Engineering
Components
and Structures
SKMM
4133
Failure
of Engineering
Components
and Structures
OPENING REMARKS
Fatigue crack in root area of
a turbine blade
List possible questions regarding this fracture situation
INTRODUCTION
M.N. Tamin, UTM
SME
4133
Failure
of Engineering
Components
and Structures
SKMM
4133
Failure
of Engineering
Components
and Structures
Failure Analysis of Metallic Components
• 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
INTRODUCTION
M.N. Tamin, UTM
SME
4133
Failure
of Engineering
Components
and Structures
SKMM
4133
Failure
of Engineering
Components
and Structures
Week
1
2
3
4
5
6
7
8
9
10
11
Date
(Sun.)
07 Sep
14 Sep
21 Sep
28 Sep
05 Oct
12 Oct
19 Oct
26 Oct
02 Nov
09 Nov
16 Nov
12
13
14
15
16
17
23 Nov
30 Nov
07 Dec
14 Dec
21 Dec
28 Dec
INTRODUCTION
Lecture & Topics
Lecture
Lecture
Lecture
1
2
3
A
A
A
A
A
A
B
B
B
B
B
B
C
C
C
C
C
C
SEMESTER BREAK
Test1
C
C
C
C
C
C
C
C
D
D
D
D
E
E
E
D
D
E
E
E
E
Test 2
Closure
STUDY LEAVE
FINAL EXAMINATION
Topics
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
M.N. Tamin, UTM
SME
4133
Failure
of Engineering
Components
and Structures
SKMM
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.
INTRODUCTION
M.N. Tamin, UTM
SME
4133
Failure
of Engineering
Components
and Structures
SKMM
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.
INTRODUCTION
M.N. Tamin, UTM
SME
4133
Failure
of Engineering
Components
and Structures
SKMM
4133
Failure
of Engineering
Components
and Structures
COVERAGE
• CONCEPT
• FUNDAMENTAL THEORY
• ESTABLISHED WORK
• STATISTICS
• CASE STUDIES
INTRODUCTION
M.N. Tamin, UTM
SME
4133
Failure
of Engineering
Components
and Structures
SKMM
4133
Failure
of Engineering
Components
and Structures
SCOPE
REQUIREMENTS FOR FAILURE
ANALYSIS
MODES OF FAILURE
• Mechanical design and analysis
• Gross Yielding
• Force analysis
• Fatigue Fracture
• Stress analysis
• Creep Rupture
• Chemical analysis
• Buckling
• Metallography
• Static Delayed Fracture
• Fractography
• Mechanical testing
• Failure simulation
INTRODUCTION
M.N. Tamin, UTM
SME
4133
Failure
of Engineering
Components
and Structures
SKMM
4133
Failure
of Engineering
Components
and Structures
Classification of the causes of failure
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 timevarying load, thermal cycling,
corrosion fatigue.
• Severe stress raiser inherent
in design.
• Inadequate stress analysis
• Mistake in designing on
basis of static tensile
properties only
• High-temperature failure – creep,
oxidation, local melting, warping.
• Static delayed fracture – hydrogen
embrittlement,
INTRODUCTION
M.N. Tamin, UTM
SME
4133
Failure
of Engineering
Components
and Structures
SKMM
4133
Failure
of Engineering
Components
and Structures
Classification of the causes of failure
Faulty processing
• Flaws due to faulty composition –
wrong material, inclusions,
embrittling impurities.
•Abnormalities due to heat treatment –
grain growth, precipitation, excessive
retained austenite, decarburization.
• Defects originating in ingot
making and casting – porosity, nonmetallic inclusions, segregation.
• Flaws due to case hardening –
intergranular carbides, soft core.
• 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.
INTRODUCTION
• 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.
M.N. Tamin, UTM
SME
4133
Failure
of Engineering
Components
and Structures
SKMM
4133
Failure
of Engineering
Components
and Structures
Classification of the causes of failure
Deterioration in service
• Overload / unforeseen loading
conditions
• Wear – erosion, galling,
seizing, cavitation.
• Corrosion – chemical attack,
stress corrosion, dezincification.
• Radiation damage decontamination may destroy
evidence for the cause of failure.
• Accidental condition – abnormal
operating temperature, severe
vibration, impact, thermal shock.
• Inadequate / misdirected
maintenance or improper repair
– welding, grinding, cold
straightening.
• Disintegration by chemical
attack, attack by liquid metals or
plating at elevated temperature
INTRODUCTION
M.N. Tamin, UTM
SME
4133
Failure
of Engineering
Components
and Structures
SKMM
4133
Failure
of Engineering
Components
and Structures
Steps in Performing Failure Analysis
• 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.
INTRODUCTION
• 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)
M.N. Tamin, UTM