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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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