introduction to mechaical metallurgy course...suranaree university of technology may-aug 2007...

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


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


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


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


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


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


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



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



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


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


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


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


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


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


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


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


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


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


• 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

introduction to mechaical metallurgy course...suranaree university of technology may-aug 2007...

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