MECHANICS OF MATERIALS CHAP 1

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PowerPoint Lecture Slidesfor

Foundations of Materials for

Scienceandand

EngineeringEngineeringForth Edition

William F. SmithJavad HashemiJavad Hashemi

CHAPTER

11Introduction to

Materials ScienceMaterials Scienceand

EngineeringEngineering1-1


The Mars Rovers - Spirit and Opportunity

Spirit and Opportunity are made up of materials such as* Metals * Ceramics * Composites * Polymers * Semiconductors* Metals * Ceramics * Composites * Polymers * Semiconductors

www.nasa.gov


LEARNING OBJECTIVES

By the end of this chapter, students will be able to:1. Describe the subject of materials science and

engineering as a scientific disciplineengineering as a scientific discipline2. Cite the primary classification of solid materials.3. Give distinctive features of each group of materials.3. Give distinctive features of each group of materials.4. Cite one material from each group. Give some

applications of different types of materials.applications of different types of materials.5. Evaluate how much you know, how much you do not

know about materials.6. Establish the importance of materials science and 6. Establish the importance of materials science and

engineering in selection of materials for various applicationapplication


What are Materials?

• Materials may be defined as substance of which something is composed or made.

• We obtain materials from earth crust and • We obtain materials from earth crust and atmosphere.

• Examples :-� Silicon and Iron constitute 27.72 � Silicon and Iron constitute 27.72

and 5.00 percentage of weight of earths crust respectively.

� Nitrogen and Oxygen constitute � Nitrogen and Oxygen constitute 78.08 and 20.95 percentage of dry air by volume respectively.

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Why the Study of Materials is Important?

• Production and processing of materials constitute a • Production and processing of materials constitute a large part of our economy.

• Engineers choose materials to suite design.• Engineers choose materials to suite design.• New materials might be needed for some new

applications.

� Example :- High temperature resistant materials.� Space station and Mars Rovers should sustain

conditions in space.conditions in space.* High speed, low temperature, strong but

light.• Modification of properties might be needed for some • Modification of properties might be needed for some

applications.

� Example :- Heat treatment to modify properties.

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Materials Science and Engineering

• Materials science deals with basic knowledgeabout the internal structure, properties and processing of materials.processing of materials.

• Materials engineering deals with the application of knowledge gained by materials science to of knowledge gained by materials science to convert materials to products.

Materials Science and

ResultantKnowledge

of Structure and

Applied Knowledge

Materials ScienceMaterials Science and

Engineering Materials Engineering

Basic Knowledge

of of Structure and Properties

Knowledgeof Materialsof

Materials

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Types of Materials

• Metallic Materials� Composed of one or more metallic elements.� Composed of one or more metallic elements.

� Example:- Iron, Copper, Aluminum.

� Metallic element may combine with nonmetallic elements.nonmetallic elements.� Example:- Silicon Carbide, Iron Oxide.

� Inorganic* and have crystalline structure.� Inorganic* and have crystalline structure.� Good thermal and electric conductors.

Metals and Alloys* mineral, not biological origin Metals and Alloys

FerrousEg: Steel,

NonferrousEg:Copper

biological origin

Eg: Steel,Cast Iron

Eg:CopperAluminum

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Metallic Materials

Section 01 stops here 12/5/2011The aircraft turbine engine shown is made principally of metal alloys. The latest high-temperature, heat resistant, high-strength nickel-base alloys are used in this engine. This engine has many advanced, service-proven technologies to enhance operational performance and durability. These include second-generation single-crystal turbine performance and durability. These include second-generation single-crystal turbine blade materials, powder metal disks, and an improved full authority digital electronic control


Metallic Materials


Types of Materials

• Polymeric (Plastic) Materials� Organic giant molecules and mostly

noncrystalline.noncrystalline.� Some are mixtures of crystalline and

noncrystalline regions.� Poor conductors of electricity and hence � Poor conductors of electricity and hence

used as insulators.� Strength and ductility vary greatly.� Low densities and decomposition � Low densities and decomposition

temperatures.

� Examples :- Poly vinyl Chloride (PVC), � Examples :- Poly vinyl Chloride (PVC), Polyester.

� Applications :- Appliances, DVDs, Fabrics etc.

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Plastic resin producers are developing ultrapure, high-flow grades of polycarbonate plastic for DVDspolycarbonate plastic for DVDs


Types of Materials

• Ceramic Materials� Metallic and nonmetallic elements are chemically

bonded together.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, � Other applications : Abrasives, construction materials,

utensils etc.

� Example:- Porcelain, Glass, Silicon nitride. � Example:- Porcelain, Glass, Silicon nitride.

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(a) Examples of a newly (a) Examples of a newly developed generation of engineered ceramic materials for advanced engine applications. The black items applications. The black items include engine valves, valve seat inserts, and piston pins made of silicon nitride. The white item is a port-manifold white item is a port-manifold liner made of an alumina ceramic material

(b) Potential ceramic component (b) Potential ceramic component applications in a turbocharged diesel engine

High-performance ceramic ball bearings and races are High-performance ceramic ball bearings and races are made from titanium and carbon nitride feedstocks through power metal technology


Types of MaterialsSection 02 stops here 18/5/2011

• Composite Materials� Mixture of two or more materials.� Consists of a filler material and a binding material.

Section 02 stops here 18/5/2011

� 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 Fibrous: Fibers in a matrixo Particulate: Particles in a matrixo Matrix can be metals, ceramic or polymer

� Examples :-� Examples :-� Fiber Glass ( Reinforcing material in a polyester

or epoxy matrix)� Concrete ( Gravels or steel rods reinforced in � Concrete ( Gravels or steel rods reinforced in

cement and sand)� Applications:- Aircraft wings and engine, construction.

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Composite materials


Composite materials - concrete


Composite materials


Composite materials

Overview of the wide variety of composite parts used in the Air Force’s C-17 transport. This airplane has a wingspan of 165ft and uses 15,000Ib C-17 transport. This airplane has a wingspan of 165ft and uses 15,000Ib of advanced composite


Composite materials


Types of Materials

• Electronic Materials

� Not Major by volume but very important.

� Silicon is a common electronic � Silicon is a common electronic material.

� Its electrical characteristics are changed by adding impurities.changed by adding impurities.

� Examples:- Silicon chips, transistors � Examples:- Silicon chips, transistors � Applications :- Computers, Integrated

Circuits, Sattelites etc.

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Competition Among Materials

• Materials compete with each other to exist in new market Example:-

1600AluminumIron

• Over a period of time usage of different materials changes

1000

1200

1400IronPlasticSteel

depending on cost and performance.

600

800

1000

lb/C

ar

• New, cheaper or better materials replace the old 0

200

400

materials replace the old materials when there is a breakthrough in technology

01985 1992 1997

Model Year

Predictions and use ofFigure 1.14

Predictions and use ofmaterials in US automobiles.

After J.G. Simon, Adv. Mat. & Proc., 133:63(1988) and new data1-10



Breakdown of weight percentage of major materials used in the average 1985 U.S. automobile


Future Trends

• Metallic Materials• Metallic Materials� Production follows US economy closely.� Alloys may be improved by better chemistry and � Alloys may be improved by better chemistry and

process control.� New aerospace alloys being constantly

researched.researched.o Aim: To improve temperature and corrosion

resistance.o Example: Nickel based high temperature super o Example: Nickel based high temperature super

alloys.� New processing techniques are investigated.

o Aim: To improve product life and fatigue o Aim: To improve product life and fatigue properties.

o Example: Isothermal forging, Powder metallurgy.� Metals for biomedical applications� Metals for biomedical applications

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Future Trends

Forging

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Forging


Future Trends

Powder Metallurgy

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Future Trends

• Polymeric (Plastic Materials)� Fastest growing basic material (9% � Fastest growing basic material (9%

per year).� After 1995 growth rate decreased

due to saturation.due to saturation.� Different polymeric materials can

be blend together to produce new be blend together to produce new plastic alloys.

� Search for new plastic continues.

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Future Trends

• Ceramic Materials�New family of engineering ceramics are produced �New family of engineering ceramics are produced

last decade� New materials and applications are constantly

found.found.� Now used in Auto and Biomedical applications.� Processing of ceramics is expensive.� Processing of ceramics is expensive.� Easily damaged as they are highly brittle.� Better processing techniques and high-impact� Better processing techniques and high-impact

ceramics are to be found.

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Future Trends

• Composite Materials� Fiber reinforced plastics are primary � Fiber reinforced plastics are primary

products.� On an average 3% annual growth from

1981 to 1987.1981 to 1987.� Annual growth rate of 5% is predicted

for new composites such as Fiberglass-for new composites such as Fiberglass-Epoxy and Graphite-Epoxycombinations.

� Commercial aircrafts are expected to � Commercial aircrafts are expected to use more and more composite materials.

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Future Trends

• Electronic Materials� Use of electronic materials such as silicon � Use of electronic materials such as silicon

increased rapidly from 1970.� Electronic materials are expected to play

vital role in “Factories of Future”.vital role in “Factories of Future”.� Use of computers and robots will increase

resulting in extensive growth in use of resulting in extensive growth in use of electronic materials.

� Aluminum for interconnections in integrated circuits might be replaced by integrated circuits might be replaced by copper resulting in better conductivity.

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Future Trends

• Smart Materials : Change their properties by sensing external stimulus.sensing external stimulus.� Shape memory alloys: Strained material reverts

back to its original shape above a critical temperature.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.� Used in actuators and vibration reducers.


MEMS and Nanomaterials

• MEMS: Microelectromechanical systems.� Miniature devices�� Micro-pumps, sensors

• Nanomaterials: Characteristic length < 100 nm• Nanomaterials: Characteristic length < 100 nm� Examples: ceramics powder and grain size < 100

nmnm� Nanomaterials are harder and stronger than bulk

materials.� Have biocompatible characteristics ( as in � Have biocompatible characteristics ( as in

Zirconia)� Transistors and diodes are developed on a

nanowire. nanowire.


Crystal/Grain


Case Study – Material Selection

• Problem: Select suitable material for bicycle frame and fork.frame and fork.

Steel and alloys Wood

Carbon fiber Reinforced

plastic

Aluminumalloys

Ti and Mgalloysalloys plastic alloys alloys

Low cost but Heavy. LessCorrosion

Light and strong. ButCannot be

Very light and strong. No corrosion.

Light, moderatelyStrong. Corrosion

Resistance.

Slightly betterThan Al

alloys. But muchCorrosionresistance

Cannot beshaped

corrosion.Very expensive

Resistance.expensive

alloys. But muchexpensive

Cost important? Select steelCost important? Select steelProperties important? Select CFRP

MECHANICS OF MATERIALS CHAP 1

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