Lecture 1 JJ

8/13/2019 Lecture 1 JJ

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Lecture-1:

Engineering Materials and their

Properties

Jayant JainAssistant Professor, Department of Applied Mechanics,

IIT Delhi, Hauz Khas, 110016

25/07/2013


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Course objectives

1. Develop fundamental understanding on materials properties

2. Understanding on the behaviour of conventional materials

3. Develop an understanding on novel materials

4. Through case studies familiarize you about common materials

related issues in various applications


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Material development is

driven by the desire for

ever greater performance

Today, over 160,000

materials are available toengineers

We are living in the age ofadvanced materials

Materials Selection in Mechanical Design, 4th Edition 2010 Michael Ashby


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Timeline of Material Development

Materials: engineering, science, processing and design, 2nd edition Copyright (c)2010 Michael Ashby, Hugh Shercliff, David Cebon

Figure 1.1

Colored zones indicate man-made materials


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The development of

materials to meet

demands on strength

and density is illustratedby these material

property charts

Similar time plots showthis progressive filling

for all materials

properties

This is not the age of

one material; it is the

age of immense

materials



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Materials: engineering, science, processing and design, 2nd edition Copyright (c)2010 Michael Ashby, Hugh Shercliff, David Cebon

Figure 2.1

Six Families of Materials

Members of a family have

common features:

Similar propertiesSimilar processing routes

Similar applications

Hybrids are a

combination of materials

from other families


7/17Materials: engineering, science, processing and design, 2nd edition Copyright (c)2010 Michael Ashby, Hugh Shercliff, David Cebon

Figure 2.2

Examples of Each Material Family



General

Cost

Density

Mechanical

Strength

Stiffness

Toughness

Thermal

Conductivity

Diffusivity

Heat Capacity

Expansion

Electrical

DielectricConstant

Conductivity

Magnetic

Remanence Saturation

Magnetization

Optical

Refraction Absorption

Chemical

CorrosionResistance

Common Material Properties



Figure 1.2

Mechanical

Properties

E - elastic modulus

y- yield strength

K1c- fracture toughness

- density



Figure 1.3

Thermal

PropertiesTmaxlimiting

temperature for

engineeringapplications

Cpheat capacity

- conductivity

diffusivity /Cp



Figure 1.4

Electrical,

Magnetic,

and Optical

Properties

Ddielectric constant

hard magnet - permanently

magnetized

soft magnet can be

magnetized

and demagnetized



Figure 1.5

Chemical

Properties

Intrinsic resistance of a

material in agiven environment


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The properties of engineering materials

affect the way in which products are

designed.


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Evolution of Materials in Products

Early kettles, heated directly over a fire, weremade of materials that could conduct heat well

and withstand exposure to an open flame

Today almost all kettles are made of plastic,allowing economic manufacture with great

freedom of form and color



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Early cameras were made of wood and constructed

with the care and finish of a cabinetmaker; they had

well-ground glass lenses manufactured by

techniques developed for watch and clock making


High-end cameras are now manufactured with theprecision and electronic sophistication of scientific

instruments; lower-end models are made withmolded polypropylene or ABS bodies


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Early planes were made of low-density

woods, steel wire, and silk


The aluminum airframe provided high stiffnessand strength to allow planes to be bigger and

fly further

The future of airframes is exemplified byBoeings 787 Dreamliner (80% carbon-fiber

reinforced plastic, claims to be 30% lighter perseat than competing aircraft


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Historically, we have gone through a long way, many choices ofmaterials are available today.

However the challenge is to select the best for a given application.

Understanding of materials properties and tailoring them for need

is one of the key aspect in the future of materials development

Summary

Documents

Lecture 1 JJ