Failure Analysis and Design
Handout Topics
1. Introduction
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b.
c.
d.
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f.
g.
Damage Tolerant Design
Cost of Failure
Birth of Fatigue Failures
Damage Tolerance implemented
Fatigue Design Methods
Statistics of Causes of Failure
Theories of Failure
2. Fracture
a.
Theoretical Strength of materials using two parameters:
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Theoretical Cohesive Strength
Work of Fracture
Size Effect
Ductile vs Brittle Fracture and other fracture types
Stress concentration and concentrators
Modes of Fracture
Griffith’s Theory of Brittle Fracture
Ductile to Brittle Transition Temperature Curve and factors affecting it
3. Fatigue
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j.
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Cyclic stresses
Indications of Fatigue failure
Mechanism of Fatigue failure
SN curve
Basquin equation
Construction of SN curve
Statistical Nature of Fatigue
Factors influencing fatigue properties
Reversed stresses: Design for finite and infinite life
Infinite life problems
Finite life problems
Cumulative Damage theory
i.
ii.
iii.
Linear damage Theory
Miner’s Rule
Problems on Miner’s Rule
4. Creep
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b.
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j.
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Creep Test & Creep Curve
Explanation of various stage of the creep curve
Creep curve for different temperatures
Creep mechanisms of crystalline materials
Dislocation climb
Diffusional Creep
Graph showing creep mechanisms operating at different conditions
Equicohesive temperature
Fracture at elevated temperature: Transgranular vs Intergranular Fracture
Design considerations to avoid creep
Design to cope with creep
Strength- Max service temp graph
m.
n.
o.
p.
q.
r.
s.
t.
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v.
Alloys for high temp use
Presentation of engineering creep data
Example problems on creep
High temperature pipework
Diffusion phenomena
Fick’s law
Factors affecting Diffusion
Activation energy for steady state creep
Larsen Miller Parameter
Example problems
5. Elements of Fracture Mechanics
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m.
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p.
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Griffith’s theory of brittle fracture
Stress Intensity factors
Parameters for predicting crack growth and failure
Stress based parameter
Modern Fracture mechanics
Stress and Displacement fields in isotropic elastic materials
Stress field at crack tips
Understanding the stress field equation
Shape factor
Region of K dominance
Fracture toughness
Ductile Fracture
Crack propagation in ductile materials
Fracture toughness in ductile materials
Orowan’s modification
Example problem
Random gyaan
Energy release rate
J integral
Fracture mechanics applied to fatigue
Crack growth in different regions
Paris Erdogan relationship
Paris law
Example problem
6. Failure Analysis Process: An overview
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b.
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f.
g.
Objectives in failure analysis
Complexity of Investigation
Physical causes and time of occurence
Pitfalls in failure analysis
Factors & Observations table
Elements of the failure analyst’s toolbox
Practices and Procedures