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MSE 527
Fall 2011
MSE 527- Mechanical Behavior of Materials Time: Wed 18:30-19:50 PM, Room JD1504Lecture units: 2.0, Lab design units: 1.0A survey of relationships between mechanical behavior and materials structure. Elements of creep, fracture and fatigue of metals, ceramics, and composites. Introduction to applied fracture mechanics and environmentally assisted cracking laboratory methods for evaluating structural property relationships, fracture toughness measurements and failure analysis using Scanning Electron Microscopy. Textbook: R. W. Hertzberg, Deformation and Fracture Mechanics of Engineering Materials, 4th Ed., J. Wiley & Sons, 1996.
Instructor:Dr. Behzad BavarianDept. of Manufacturing Systems Engineering and ManagementOffice: JD3513, 818/677-3917Email: bavarian@csun.eduOffice Hour: W 5:30-6:15PM
Course Description:Prerequisites: MSE 227 and MSE 227LThe main techniques used in this course, center around the application of scientific principles to real-life situations. Library research is necessary to develop most of the topic discussions. The course covers dislocation theory and plastic deformation in order to explain strengthening mechanisms in different materials. Materials applications in elevated temperature are studied to understand the design criteria for these applications. Fundamentals of fracture mechanics, microstructure aspects of fracture toughness, transition temperature, environment-assisted cracking, and fatigue crack propagation is discussed to be able to design based on the damage tolerant concept, and failure analysis using scanning electron microscopy.
This course requires extensive design problem solving, technical presentation, and a term paper on a current topic in materials application or design.
Final Exam December 14, 2011 8:00PM – 10:00 PM
Course Method and Expectations:• The main techniques to be used in this course, center on the application of scientific principles to real-life situations.
Library research is necessary to develop most of the topic discussions.• Grading Policy• Homework 10%• Mid-term Exam 30%• Term project 15%• Final Exam 45%
Grading System:• Letter Grades Grade Points• A Outstanding 4.0• B Excellent 3.0• C Acceptable 2.0• D Passing 1.0• F Failure 0.0• Plus/Minus Grading
• Last day to drop: Friday, Sept. 16, 2011
References:• 1. D. Callister, Jr. Fundamentals of Materials Science and Engineering, J. Wiley & Sons, NY, 2nd Ed. 2005.• 2. G. E. Dieter, Mechanical Metallurgy, McGraw-Hill, NY, 1994.• 3. V. J. Colangelo and F.A. Meiser, Analysis of Metallurgical Failures, J. Wiley & Sons, NY, 1987.• 4. ASM Metals Handbook, Volume 11, Failure Analysis and Prevention, Metals Park, 1986.• 5. R. M. Caddell, Deformation and Fracture of Solids, 1980.• 6. A. G. Guy, Elements of Physical Metallurgy, 1984.
• Materials science deals with basic knowledge about the internal structure, properties and processing of materials.
• Materials engineering deals with the application of knowledge gained by materials science to convert materials to products.
Resultant Knowledge
of Structure and Properties
Applied Knowledge
of Materials
Materials ScienceMaterials Science and
Engineering Materials Engineering
Basic Knowledge
ofMaterials
1-4
Types of Materials• Metallic Materials
Composed of one or more metallic elements.
Example:- Iron, Copper, Aluminum.
Metallic element may combine with nonmetallic elements.
Example:- Silicon Carbide, Iron Oxide.
Inorganic and have crystalline structure. Good thermal and electric conductors.
Metals and Alloys
Ferrous Eg: Steel,Cast Iron
NonferrousEg:CopperAluminum
1-5
Types of Materials
• Polymeric (Plastic) Materials Organic giant molecules and mostly
noncrystalline. Some are mixtures of crystalline and
noncrystalline regions. Poor conductors of electricity and hence
used as insulators. Strength and ductility vary greatly. Low densities and decomposition
temperatures.
Examples :- Poly vinyl Chloride (PVC), Polyester.
Applications :- Appliances, DVDs, Fabrics etc.
1-6
Types of Materials
• Ceramic Materials Metallic and nonmetallic elements are chemically bonded
together. Inorganic but can be either crystalline, noncrystalline or
mixture of both. High hardness, strength and wear resistance. Very good insulator. Hence used for furnace lining for
heat treating and melting metals. Also used in space shuttle to insulate it during exit and
reentry into atmosphere. Other applications : Abrasives, construction materials,
utensils etc.
Example:- Porcelain, Glass, Silicon nitride.
1-7
Types of Materials
• Composite Materials Mixture of two or more materials. Consists of a filler material and a binding material. Materials only bond, will not dissolve in each other. Mainly two types :-
o Fibrous: Fibers in a matrixo Particulate: Particles in a matrixo Matrix can be metals, ceramic or polymer
Examples :- Fiber Glass ( Reinforcing material in a polyester or
epoxy matrix) Concrete ( Gravels or steel rods reinforced in
cement and sand) Applications:- Aircraft wings and engine, construction.
1-8
Types of Materials
• Electronic Materials
Not Major by volume but very important. Silicon is a common electronic material. Its electrical characteristics are changed
by adding impurities.
Examples:- Silicon chips, transistors Applications :- Computers, Integrated
Circuits, Satellites etc.
1-9
Future Trends• Metallic Materials
Production follows US economy closely. Alloys may be improved by better chemistry
and process control. New aerospace alloys being constantly
researched.o Aim: To improve temperature and corrosion
resistance.o Example: Nickel based high temperature super
alloys. New processing techniques are investigated.
o Aim: To improve product life and fatigue properties.
o Example: Isothermal forging, Powder metallurgy.
Metals for biomedical applications
1-11
Future Trends
• Polymeric (Plastic Materials) Fastest growing basic material (9%
per year). After 1995 growth rate decreased
due to saturation. Different polymeric materials can
be blend together to produce new plastic alloys.
Search for new plastic continues.
1-12
Future Trends
• Ceramic MaterialsNew family of engineering ceramics are
produced last decade New materials and applications are constantly
found. Now used in Auto and Biomedical
applications. Processing of ceramics is expensive. Easily damaged as they are highly brittle. Better processing techniques and high-impact
ceramics are to be found.
1-13
Future Trends
• Composite Materials Fiber reinforced plastics are primary
products. On an average 3% annual growth from
1981 to 1987. Annual growth rate of 5% is predicted
for new composites such as Fiberglass-Epoxy and Graphite-Epoxy combinations.
Commercial aircrafts are expected to use more and more composite materials.
1-14
Future Trends
• Electronic Materials Use of electronic materials such as
silicon increased rapidly from 1970. Electronic materials are expected to play
vital role in “Factories of Future”. Use of computers and robots will
increase resulting in extensive growth in use of electronic materials.
Aluminum for interconnections in integrated circuits might be replaced by copper resulting in better conductivity.
1-15
Future Trends
• Smart Materials : Change their properties by sensing external stimulus. Shape memory alloys: Strained material reverts
back to its original shape above a critical temperature.
Used in heart valves and to expand arteries.
Piezoelectric materials: Produce electric field when exposed to force and vice versa. Used in actuators and vibration reducers.
MEMS and Nanomaterials• MEMS: Microelectromechanical systems.
Miniature devices Micro-pumps, sensors
• Nanomaterials: Characteristic length < 100 nm
Examples: ceramics powder and grain size < 100 nm
Nanomaterials are harder and stronger than bulk materials.
Have biocompatible characteristics ( as in Zirconia)
Transistors and diodes are developed on a nanowire.
14
Type
Ionic
Covalent
Metallic
Secondary
Bond Energy
Large!
Variablelarge-Diamondsmall-Bismuth
Variablelarge-Tungstensmall-Mercury
smallest
Comments
Nondirectional (ceramics)
Directionalsemiconductors, ceramics
polymer chains)
Nondirectional (metals)
Directionalinter-chain (polymer)
inter-molecular
SUMMARY: BONDING
6
• Coordination # = 12
Adapted from Fig. 3.1(a), Callister 6e.
(Courtesy P.M. Anderson)
• Close packed directions are face diagonals.--Note: All atoms are identical; the face-centered atoms are shaded differently only for ease of viewing.
FACE CENTERED CUBIC STRUCTURE (FCC)
Click on image to animate
• Coordination # = 8
8
Adapted from Fig. 3.2, Callister 6e.
(Courtesy P.M. Anderson)
• Close packed directions are cube diagonals.--Note: All atoms are identical; the center atom is shaded differently only for ease of viewing.
BODY CENTERED CUBIC STRUCTURE (BCC)
Click on image to animate
10
• Coordination # = 12
• ABAB... Stacking Sequence
• APF = 0.74
• 3D Projection • 2D Projection
A sites
B sites
A sites Bottom layer
Middle layer
Top layer
Adapted from Fig. 3.3, Callister 6e.
HEXAGONAL CLOSE-PACKED STRUCTURE (HCP)
• Stress-Strain
Mechanical Testing and Properties
• Tensile Strength Tensile Test
• Flexural Strength Bend Test for brittle materials
• Hardness Hardness Test
• Toughness Impact Test
• Fatigue Life Fatigue Test
• Creep rate Creep Test
Tensile Test
0
0
0
strain gEngineerin
stress gEngineerin
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A
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Mechanical Testing and Properties
Tensile Test & the properties obtained from the Tensile Test
0
0
0
strain gEngineerin
stress gEngineerin
l
ll
A
F
•Note: in Metals, Yield stress is usually the stress required for dislocations to slip.
Tensile Test & the properties obtained from the Tensile Test
Note: Young’s modulus is a measure of the stiffness of the material.
Tensile Test & the properties obtained from the Tensile Test
Er=1/2(yield strength)(strain at yielding)allongitudin
lateralratiosPoisson
: '
Tensile Test & the properties obtained from the Tensile Test
Er=1/2(yield strength)(strain at yielding)
allongitudin
lateralratiosPoisson
: '
Tensile Test & the properties obtained from the Tensile Test
Effect of Temperature
The Bend Test for Brittle Material
•Due to the presence of flaw at the surface,
in many brittle materials, the normal tensile
test cannot easily be performed.
The Bend Test for Brittle Material
Load. fracture is where,2
3 strength Flexural
2F
wh
FL
The Bend Test for Brittle Material
deflection is where
True Stress-True Strain
0
0
0
strain gEngineerin
stress gEngineerin
l
ll
A
F
)ln()ln( strain True
stress True
'
0
0
'
'
'
0 A
A
l
l
l
dlA
F
l
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The Hardness Test
)()2/(HB :Hardness Brinell
22
iDDDD
F
The Hardness Test
6.7 The Impact Test impact strength
To evaluate the brittleness of a material subjected to a sudden blow.
6.7 The Impact Test impact strength
Impact strength vs. Temperature
Note: BCC metals have transition temperature, but most FCC metals do not.
6.7 The Impact Test impact strength
Yield Strength: A > B Impact Strength: B > A
The Fatigue Test Fatigue Life, Fatigue Strength
The Fatigue Test
S-N curve
The Creep Test:
• a typical creep curve showing the strain produced as a function of time for a constant stress and temperature.
Apply stress to a material at an elevated temperature
Creep: Plastic deformation at high temperature
The Creep Test:
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