00_introduction to mechaical metallurgy course
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Suranaree University of Technology May-Aug 2007
Assignment 20
(homework, quiz, attendance)
Midterm exam 40
Final exam 40
Total 100
Mechanical Metallurgy Mechanical Metallurgy
Assessment
Lecturer
Dr. Tapany Udomphol
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Mechanical Metallurgy Mechanical Metallurgy
Subject of interests
Part I Mechanical fundamentals
• Introduction to mechanical metallurgy
• Stress and strain relationships of elastic behaviour
• Elements of the theory of elasticity
Part II Metallurgical fundamentals
• Plastic deformation of single crystals
• Dislocation theory
• Strengthening mechanisms
• Fracture
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Mechanical Metallurgy IMechanical Metallurgy I
Subject of interests
Part III Applications to materials testing
• Tension test
• Hardness test
• Torsion test
• Fracture mechanics
• Brittle fracture and impact testing
• Fatigue of materials
• Creep and stress rupture
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
ObjectivesObjectives
• Interaction of stress and strain on materials in elastic and
plastic manners will be understood.
• Deformation behaviour of metals due to dislocation
interaction as well as strengthening mechanisms of metals
will be addressed.
• Different methods of mechanical testing will be highlighted
along with the interpretation of sensible information from the
obtained data such that mechanical assessments are
appropriately selected for the required applications.
• Metallurgical aspects which affect mechanical properties of
materials will be discussed.
•Finally cause of material failure will be studied and suggested
possible solutions will be discussed.
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Main referencesMain references
• Dieter, G.E., Mechanical metallurgy, 1988, SI metric edition, McGraw-Hill, ISBN 0-07-100406-8.
• Hibbeler, R.C. Mechanics of materials, 2005, SI second edition, Person Prentice Hall, ISBN 0-13-186-638-9.
• Sanford, R.J., Principles of fracture mechanics, 2003, Prentice Hall, New Jersey, ISBN 0-13-092992-1.
• Rolfe, S.T., Barsom, J.M., Fracture and fatigue control in structures: Applications of fracture mechanics, 1977, Prentice Hall, New jersey, ISBN 0-13-329953-8.
• Edwards, H.L., Wanhill, R.J.H., Fracture mechanics, 1986, Arnold, Australia, ISBN 0-7131-3515-8.
• Smallman, R.E., Bishop, R.J., Modern physical metallurgy & materials engineering: Science, process, applications, 6th
edition, 1999, Butterworth-Heinemann, ISBN 0-7506-4564-4.
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Main referencesMain references
• Brick, R.M., Pense, A.W., Gordon, R. B., Materials science
and engineering series, 1977, 4th edition, McGraw-Hill, ISBN
0-07-007721-5.
• Hull, D. Fractography: Observing, measureing,
interpreting, fracture surface topography, 1999, Cambridge,
ISBN 0-521-64684-7.
• Dowling, N.E., Mechanical behaviour of materials:
E,ngineering methods for deformation, fracture, and
fatigue, 2nd edition, 1999, Prentice Hall, New Jersey, ISBN 0-
13-010989-4.
• Suresh, S., Fatigue of materials, 1998, 2nd edition,
Cambridge university press, ISBN 0-521-57847-7.
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Why failure in materials?Why failure in materials?
Failure of Liberty Ships during services in
World War II.
• Seven of the Liberty ships built
during the world war II has
broken completely in two as a
result of brittle fractures.
• Over 1000 of approximately
5000 merchant ships built
during World War II had
developed cracks of
considerable size by 1946.
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Why failure in materials?Why failure in materials?
Collapse of Point Pleasant suspension
bridge, West Virginia, on December 15, 1967.
• The bridge building industry did
not pay particular attention to the
possibility of brittle failure until the
failure of Point Pleasant bridge in
1967.
• The bridge collapsed without
warning, costing 46 lives.
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Why failure in materials?Why failure in materials?
Failed fuselage of the Aloha 737 aircraft in 1988.
• The aircraft was used for inter-
island transportation for 19 years
before failed.
• Failure has been attributed to
multiple-site-damage.
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Material property assessmentsMaterial property assessments
Strength
Ductility (elongation, area
of reduction)
Tension tests
Toughness (resistance
to failure)
Impact tests
Fracture toughness tests
Hardness Micro/Macro hardness tests
Fatigue S-N fatigue tests
Fatigue crack growth tests
Creep (elevated-
temperature strength)
Torsion
Creep tests
Torsion tests
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Hardness testsHardness tests
Macro-microhardness (Vickers) instrument
Parameters:
• Brinell hardness (BHN)
• Meyer hardness
• Vickers hardness (VHN)
• Rockwell hardness
• Hardness is a property
which is a measure of a
resistance to permanent or
plastic deformation.
• Using difference
indenters, i.e., ball,
diamond.
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Tensile testsTensile tests
Tensile testing
configuration
Plate specimens Round specimens
• Provide basic design
information on the strength
of materials.
• Acceptance test for the
specification of the
materials.
σ
ε
σο
ε1
ε2
Ture stress-strain curve of a ductile
metal under uniaxial tensile loading.
A
Parameters:
• Tensile strength σσσσTS
• Yield stress σσσσy
• Young’s Modulus of
elasticity E
• %Elongation
• Area of reduction
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Torsion testTorsion test
Parameters:
• Shear Modulus
• Torsional yield strength
• Modulus of rupture
• Applying twisting moment
to the specimen and measure
the torque.
• has not been standardized.
Torsion testing
machine
Ultimate torsion test results
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Creep testCreep test
Parameters:
• Creep strength
• Creep rate Typical creep curve
• Creep is high temperature
progressive deformation of a
material at constant stress.
• A tensile specimen is loaded
at a constant (elevated)
temperature. Strain is
measured with time.
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Impact testsImpact tests
Charpy impact testing
• Measure toughness of materials in terms of
energy absorption.
• Specimen is impacted by a hammer and the
energy absorbed during fracture is measured
in Joul.
• Easy and practical.
• Establish Ductile to Brittle Transition
Temperature (DBTT).
• Not a standard material parameter, should
be used in conjunction with other material
properties such as strength and fracture
toughness for materials determination.
Parameters:
• Impact energy
• Ductile to brittle transition temperature
www.twi.co.uk
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Fracture mechanicsFracture mechanics
Fracture toughness testing
Parameters:
• Fracture toughness KIC• Crack tip opening
displacement CTOD
• J-integral J
• Resistance of materials to crack
propagation (to failure).
• Crack propagation can be
predicted before failure.
• Material will fail when the
stress intensity factor K
reaches the critical value KIC.
Failed fracture toughness
specimens.
Clip gauge
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
Fatigue testsFatigue tests
• Material is subjected to a
repetitive or fluctuating stress
(cyclic loading) and will fail at
a stress level much lower than
that causes failure in statistic
loading.
• S-N fatigue test and fatigue
crack growth resistance.
σσσσmax
σσσσmin
σσσσm
∆σ∆σ∆σ∆σ
σσσσa
+
_ cycles
Stresses in fatigue loading
Fatigue striations on fatigue
fracture surface
Parameters:
• Fracture life (fatigue strength)
• Fatigue crack growth resistance
• Paris exponent (m)
• Fatigue threshold (Kth)
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
To improve properties of metalsTo improve properties of metals
Understand Metallurgical aspects• Plastic deformation
• Dislocation theory
• Strengthening mechanisms
• Fracture
Materials assessment Improvement of materials properties
Understand mechanical aspects• Stress and strain relationships of elastic behaviour
• Elements of the theory of plasticity.
WE NEED TO
Tapany Udomphol
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Suranaree University of Technology May-Aug 2007
• www.ndsu.nodak.edu
• www.kockums.se
• www.indentec.com
• www.enduratec.com
• www.bactechnologies.com
• www.twi.co.uk
• www.jaeri.go.jp
• www.hghouston.com
• www.minton.co.uk
• www2.umist.ac.uk
• www.materialsengineer.com
ReferencesReferences
Tapany Udomphol