describe what you know about materials.

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29 Νοε 2013 (πριν από 3 χρόνια και 19 μέρες)

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Material Properties

S.T.E.M. I

In your notebooks
describe what you
know about
materials.

Material Properties


Physical


Mechanical


Chemical


Optical


Acoustical


Electrical


Magnetic


Thermal

Physical Properties


Gives the material its size, density and
surface texture.

Mechanical Properties


Strength


Tension


Compression


Shear


Torsion


Elasticity:

The ability to
stretch or flex but return to an
original size and shape


Plasticity:

The ability to flow
into a new shape under pressure
and to remain in that shape when
the force is removed




Hardness:

The ability to resist
cuts, scratches and dents



Toughness:
The ability to
resist breaking



Fatigue:
The ability to resist
constant flexing or bending

Thermal Properties


Thermal properties control how the material
reacts to heat or cold


Expansion


Contraction


Thermal conductivity is a measure of how
easy heat flows through a material

Chemical Properties


The materials chemical properties affect how
it reacts to its surroundings.


Steel Rusts


Glass becomes pitted


Plastics become etched and brittle


The material is changed by its environment
this reaction is called corrosion.


Question:

How do we protect objects from
corrosion?


Answer:

By coating them with oil, grease,
paint or varnish

Optical Properties


Optical properties are a materials reaction to
light


When a material stops light we say it is
opaque


When a material allows light to pass through we
say it is
translucent


The color of a material affects its ability to
absorb or reflect light


Question:

Why is a dark interior of a car
uncomfortable on a hot day?


Answer

The dark color absorbs the light
making the interior hot

Acoustical Properties


Acoustical properties in a material control
how it reacts to sound waves


All sound energy is produced by vibrations


The speed of sound in a material depends on
the spacing of molecules and how easy the
molecules move


Question:

Will sound travel faster in
aluminum or pine and why?


Answer:

Aluminum, because the molecules in
aluminum are closer together

Electrical Properties


Some materials conduct electricity and
others do not.



Materials that are able to conduct electricity are
called
conductors
.


Materials that are unable to conduct electricity
are called
insulators.


Semiconductors are materials that allow
electricity to flow under certain conditions


Silicone


Germanium

Question:

What materials make good
conductors

Answer:

Gold, Silver, Copper, Aluminum

Magnetic Properties


A magnetic material will be attracted to a
magnet



Iron


Nickel


Cobalt


As well as their alloys

Materials


Wood


Hardwood: Comes from trees
that shed their leaves.


Ebony


Oak


Maple


Beech


Cherry


Softwood: Comes from trees
that produce cones. (Conifer)


Pine


Redwood


Fur


Spruce


Plastic


Physical Properties


Transparency


Flexibility


Elasticity


Permeability


Water Resistant


Electrical Resistance


Chemical Properties


Chemical resistance


Thermal stability



Materials


Paper


Interwoven Fibers


Wood


Cotton


Pliable


Categorized by Weights



Ceramics


Crystalline compounds of
metallic and nonmetallic
elements. Ceramics are the most
rigid of all materials with an
almost total absence of ductility.
They have the highest known
melting points of materials with
some being as high as 7,000
°
F
(3,870
°
C) and many that melt at
temperatures of 3,500
°
F
(1,927
°
C). Glass, brick, cement
and plaster, dinnerware, art
ware, and porcelain enamel are
all examples of ceramics.

Metals


Metallic luster (shine)


Generally solids at room temperature


Malleable
-

Something that can be hammered,
pounded, or pressed into different shapes without
breaking.


Ductile
-

Capable of being drawn into thin sheets or
wires without breaking.


Conduct heat and electricity


Combine with other metals to form alloys which
have metallic characteristics


Aggregate:
a component of a composite
material used to resist compressive stress.


Gravel


River Sand


Quarry Sand


Brick Bats


Granular Slag


Poultry Sand

Solvents


Can be a solid, liquid or gas used for
testing and cleaning


Adhesives


An adhesive, or glue, is a
mixture

in a
liquid

or semi
-
liquid state that
adheres

or bonds
items together. Adhesives may come from
either natural or
synthetic

sources. The types
of materials that can be bonded are vast but
they are especially useful for bonding thin
materials. Adhesives
cure

(harden) by either
evaporating a solvent or by chemical
reactions that occur between two or more
constituents.

Questions?