7 Materials Engineering Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Objectives Define materials engineering.

7

Materials Engineering

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.

Objectives

• Define materials engineering.• Identify different types of materials.• Describe a range of material properties.• List examples of material tests.• Describe nanotechnology.


About Materials Engineering

• Historical time periods based on materials– Stone Age– Bronze Age– Iron Age– Information Age (silicon and plastics)

• Understanding of science is important• Design and development of new materials• Production using specific materials


Education Typically Required

• High school courses– Upper-level math (calculus and statistics)– Upper-level science (chemistry and physics)

• College courses– Engineering design– Thermodynamics of materials– Structures of materials– Metallurgy

• Internships


Professional Organizations

• ASTM– Develops material testing standards– Over 30,000 members worldwide

• Materials Information Society • Materials Research Society• NACE International• Other organizations for ceramics, plastics, and

metals


Principles of Materials Engineering

• Broad field• Materials are used in every engineering field• All engineers must understand basic principles

– Types of materials– Properties of materials


Material Types

• Metals• Ceramics• Polymers• Composites


The Four Types of Materials

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Metals

• Have crystalline atomic structure– High material strength– Good conductors of heat and electricity– Malleable

• Inorganic material• Most pure metals are natural• Many are found in ore• Commonly used in alloys


Atomic Structure of Crystalline Materials

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Properties of Various Forms of Alloys



Ceramics

• Most have crystalline structure– Strong in compression– High melting temperature– Can retain heat well

• Brittle• Good insulators• Include clay, cement, many types of abrasives• Some can become magnets


Polymers

• Organic materials• Noncrystalline• Can be natural or synthetic• Plastics are most common type

– Lightweight but strong– Easy and fairly inexpensive to process– Have some negative environmental impacts– Thermoplastics and thermosets


Atomic Structure of Noncrystalline Materials



Thermoplastics and Thermosets

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Recycling Plastics

• Saves use of oil and natural gas• Less plastics take up space in landfills• Society of Plastics Industry created codes

– Include recycling symbol, number, and abbreviation– Useful to consumers who recycle

• Over 82 million tons of materials are recycled per year in U.S.

Going Green


Composites

• Utilize advantages of several materials• Each material can be identified• Can be natural or synthetic• Most consist of matrix and fiber

– Matrix is main material– Fiber is strengthening material

• Include wood, concrete, plywood, and fiberglass


Other Materials

• Fluids– Air and water– Many products rely on their use

• Semiconductors– Can act as insulators or conductors– Used to create electronic components

• Biomaterials– Can interact safely with human body– Used in medical applications


Materials Symbols

• Used in architectural design• Symbols for common building materials

– Brick– Concrete– Cinder block

• Symbols for insulation, glass, and metal• Allow designers and architects to include graphics

of types of materials to be used

Design


Examples of Materials Symbols



Material Properties

• Physical• Mechanical• Electrical• Magnetic

• Chemical• Thermal• Optical • Acoustical


Physical Properties

• Can often be obtained using senses• Include size, shape, look, feel, taste, and smell• Some cannot be determined by senses• Most commonly used is density

– Mass per unit of volume– Often used to compare materials


Mechanical Properties

• How material behaves when force or load is applied• Understanding of stress is important

– Can be applied through axis of material– Shear stress is not applied through axis– Causes strain on material

• Compression strength and tensile strength• Elasticity• Plasticity


A Stress/Strain Diagram



Electrical Properties

• How a material behaves when electrically charged• Materials fall into one of three categories

– Conductors– Insulators– Semiconductors

• Conductivity• Resistivity


Magnetic Properties

• How a material behaves when within a magnetic field

• Magnetic permeability– Measured in Henrys per meter– Impacted by temperature and distance from

magnetic field– If it is high, material will allow magnetic flow


Chemical Properties

• Changed by a chemical reaction• Include flammability• Include corrosion• Often need to be controlled because they can be

damaging to material


Thermal Properties

• How the material responds to heat• Thermal conductivity• Thermal resistance• Thermal expansion• Melting point


Optical Properties

• How light waves interact with material– How well material absorbs light– How well material reflects light– How well material transmits light

• Reflected light gives material color• Transmission occurs when light is absorbed and

reflected by transparent materials but still passes through materials


Acoustical Properties

• How sound waves interact with material– How well material absorbs sound– How well material reflects sound– How well material transmits vibration

• Porous materials usually absorb sound• Smooth materials reflect sound in one direction• Rough materials reflect sound in many directions


Material Engineering Applications

• Material testing– Many companies specialize in specific materials– ASTM develops standards for testing

• Nanotechnology– One nanometer is one billionth of meter– Has potentially exciting impacts


Material Testing

• Used for new materials when creating new products or improving existing products

• Designer might try different formulation of existing material

• Large industry• Categories of material tests

– Destructive material tests– Nondestructive material tests


Destructive Tests

• Often used to test mechanical properties– Exert a force on material until it fails– Tensile tests– Compression tests– Fatigue tests

• Often used to test chemical properties– Test material’s reaction to corrosion– Material exposed to saltwater


Nondestructive Tests

• Used to inspect materials• Used to look for flaws and defects• Visual examinations, sometimes with dyes• Some use waves

– Radiography tests– Ultrasonic tests

• Some use currents– Eddy current testing– Magnetic particle testing


Potential Uses of Nanotechnology

• For delivery of medicines directly to cancerous tumors

• For creating microscopic computer chips• For manufacturing materials that repair and clean

themselves


Nanoparticles

• Most basic components at nanoscale• Some materials demonstrate properties at

nanoscale that are not present at larger scales• Products are being designed that utilize these

properties


Nanostructures

• Nanowires– Designed to transmit light or electricity– Might be useful in computer circuits and lighting

• Nanotubes– Cylindrical fullerenes with honeycomb pattern– Useful in electronics and structural applications

• Buckyballs– Most perfectly round molecules– Useful as lubricants


Nanotubes

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Buckyballs

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Materials Engineering in Action

• Used to select or create most appropriate materials for engineered solution

• Engineers must consider several key elements– Material function– Manufacturability– Cost– Safety

7 Materials Engineering Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Objectives Define materials engineering.

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