Material Science and Materials Processing (Day 1) Class.

Material Science and Materials

Processing(Day 1)

Class

WHAT ARE THE THREE CLASSIFICATIONS OF

MATERIALS?

MATERIAL CLASSIFICATIONS

1. Natural materials:• Occur in nature

• Organic: wood, cotton, hemp• Inorganic: stone, clay, metals

2. Synthetic:• Human-made: rubber, plastics, nylon,

Teflon

3. Mixed materials:• Combination of natural and synthetic:

plywood, paper…etc.

TYPES OF MATERIALS (CLOSE-UP)

1. Woods (Natural & Engineered)

2. Metal3. Plastics4. Ceramics5. Composites


Woods• Thickness of cell walls

determines density.• Color is a function of the

chemicals in its cell walls.• Grain is the way wood fibers

grow.

•(Engineered):• Made by combining particles

and fibers of wood with adhesives: wood chips, plywood.

• Advantages: more strength per pound


Metal:• Structure determines properties• Good conductors of electricity and heat• These are factors that might influence

material selection.

•Categorized as:• Ferrous:

• Contain iron: steel

• Nonferrous:• Do not contain iron: aluminum


Plastics:• Can be made into films, fibers, and solids; molded

into a variety of products and shapes.• Most plastics are made from petroleum.• Plastics are polymers. Have an enormous amount of

uses.• Have densities less than metals, greater than most

woods, and similar to crude oil. (material selection)

•Categorized as:• Thermoplastic: can be softened by heat, then

hardened again by cooling.

• Thermoset: cannot revert once heated and molded.


Ceramics: (material selection)• Made from clay and nonmetallic inorganic

materials• Have an atomic structure that forms a 3-D

geometric shape• Compounds formed by combinations of metallic and

nonmetallic elements

• High melting points; high strength and hardness; resistant to wear; brittle; can be transparent, translucent, or opaque; low densities

• Sometimes a better choice then metal because it tolerates heat well and is an electrical insulator.


Composites:• Combination of two or more materials with

different properties• Materials retain separate identities• Formed by using materials of two types:

• Matrix material• Reinforcement material (fiber)

• Often lighter and provide similar or greater strength applications

• Cost of manufacturing is significantly higher.• Often used in decks because it is resistant to

rotting and insect damage.

•Categorized into three matrix types: • Polymer, metallic, and ceramic


Why Composites?

WHAT ARE SOME PROPERTIES OF MATERIALS?

PROPERTIES OF MATERIALS

Key ideas:• Materials are chosen based on properties that

make them appropriate for particular applications.

Categories: Physical, mechanical, electrical, chemical, magnetic, thermal, optical, and acoustic.


Mechanical:•Those that influence a material’s ability to endure and withstand applied forces

Mechanical Testing: Strength Hardness Ductility Elasticity Plasticity Malleability Brittleness Toughness Yield Point

Elastic limit (yield strength)•Beyond the elastic limit, permanent deformation will occur. •The lowest stress at which permanent deformation can be measured.•Under repetitive stresses, cracks in a metal can develop and grow and cause failure even thought the elastic limit has not been reached.


Strength (forces):

Flexural

• Buckling occurs when a given material is compressed until it gives way and collapses

FAILURE OF MATERIALS


Physical properties:• Density and freezing, melting, and

boiling points• Density is a measure of how tightly atoms are

packed together• Freezing, melting, and boiling points exist on

a temperature continuum


Electrical properties:• Conductivity and resistivity

Magnetic properties:• Diamagnetic, paramagnetic, or ferromagnetic

Thermal properties:• Ability to conduct heat and expand when heated

Optical properties:• Ability to reflect, absorb, refract, or transmit light

Material Science and Materials

Processing(Day 2)

Class

PROCESSING MATERIALS

Key ideas:• The term “processing” means transforming

basic (raw) materials into industrial materials, and then into finished products.

• Processing methods are categorized according to:

1. Mass change2. Phase change3. Structure change.4. deformation of material 5. Consolidation of material

**Example: Processing trees into timber**

PROCESSING MATERIALS (CONT’D.)

Mass change:• Cladding• Electroplating• Drilling• Sawing• Grinding• Turning

Phase change:• Casting• Pressing• Injection molding• Blow molding• Vacuum forming• Rotation molding


Structure-change:

• Hardening• Annealing• Tempering


Consolidation:• Fastening• Joining• Sintering• Composite

materials• Coating

Deformation:• Forging• Rolling• Machine pressing• Extrusion• Drawing

Example Processes:•Injection Molding: (Very Accurate) common industrial process used to manufacture parts.

•Extrusion: process whereby a continuous stream of a product is made by squeezing softened material (just below its melting point) through a small opening called a die.


Example Processes:

•Sintering: is a process where powdered materials are combined with a binding material and pressed into shapes in a mold under heat and high pressure.


FACTORS IN SELECTING MATERIALS

Key ideas:• Materials are chosen based on their properties,

as well as other factors.

• Choice of material often reflects trading off competing benefits.

• True costs of materials extend beyond the cost of the raw material itself.

FACTORS IN SELECTING MATERIALS (CONT’D.)

Properties determine suitability for applications:

1. Cost2. Safety3. Availability4. Disposability5. Environmental impact


True cost of a material includes:• Cost of the raw material• Amount of energy and water needed • Amount of pollution generated• Human time and effort wasted


• Availability of materials is a primary.• Safety is also important.• Disposability and environmental impact drive

decisions about materials.• Some materials can biodegrade.• Engineers also consider the energy it takes to process

materials.


Figure 4.70 Comparison of cost versus strength for structural materials.

Material Science and Materials Processing (Day 1) Class.

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