Properties of Materials

Properties of Materials

• When selecting a material for an engineering application,

a primary concern is to assure that its properties will be

adequate for the anticipated operating conditions

• These may include:

– Mechanical characteristics

– Physical characteristics

– Features related to the service environment

• Ability to operate under extremes of temperature

• Resist corrosion

Mechanical Characteristics

• Strength

• Rigidity

• Resistance to fracture

• Ability to withstand vibrations or impacts

Metallic Materials

• Metallic:

– Iron

– Copper

– Aluminum

– Magnesium

– Nickel

– Titanium

– Lead

– Tin

– Zinc

• Alloys of these metals:

– Steel

– Brass

– Bronze

• They possess the metallic properties of:

– Luster

– High thermal conductivity

– Relatively ductile

– Some have good magnetic properties

Nonmetallic Materials

• Nonmetallic:

– Wood

– Brick

– Concrete

– Glass

– Rubber

– Plastic

• Their properties vary widely

• Generally they tend to be:

– Less ductile

– Weaker

– Less dense than metals

– Have poor electrical and thermal properties

The Choice

• In many cases, metals and nonmetals are viewed as

competing materials

• The selection is being based on how well each is

capable of providing the required properties

• When both perform adequately, total cost often becomes

the deciding factor:

– The cost of material

– Plus the cost of fabricating the desired component

Material Selection

• Based on a comparison of the established design

requirements and the tabulated record results that

describe how common materials respond to various

standard test

• It is important to know:

– Which properties are significant?

– How the test values were determined?

– What restrictions or limitations should be placed on their use?

– Various test procedures, their capabilities and their limitations

Physical Properties

• Density (weight)

• Melting point

• Optical properties

– Transparency

– Opaqueness

– Color

• Thermal properties (specific heat)

• Coefficient of thermal expansion

• Thermal conductivity

• Electrical conductivity

• Magnetic properties

• In some cases, they are the prime reasons in selecting

material.