Metallurgy--intro

11.02.10

A strong understanding of material use and manufacturing processes is essential and needed in the Industrial Design industry today.

The right selection of materials and manufacturing processes is important in enabling a successful product launched to market.

Selection of a material requires a knowledge of the function & requirements of the product & materials available to fulfill them.

COMPOSITES: Two or more distinct materials are combined to engineer a new material with desired combination of properties (e.g. light weight, strength, stiffness, corrosion resistance, high/low thermal conductivity, etc.)

Compared to steel car bodies, aluminum coaches are substantially lighter.

It is assumed that replacing steel by aluminum yields a maximum mass reduction potential of about 20-30% of the car body weight.

In long term perspective, aluminum car-bodies will face a growing competition from fiber-reinforced polymers.

Fiberglass provides a great lightweight and durable material for finished auto or boat parts.

Same low weight as aluminum but 5 times stronger!

Fiber glass strength: 3.1GPa Aluminum strength: 0.5 GPa

Fiberglass does not rust or corrode! The fiberglass body is molded as one

piece -- no rivets or seams to leak!

CERAMICS: A ceramic is an inorganic, non-metallic solid.

Ceramic materials are brittle, hard, strong in compression, weak in shearing and tension. They withstand chemical erosion in acidic or caustic environment. Ceramics generally can withstand very high temperatures such as temperatures that range from 1,000 °C to 1,600 °C (1,800 °F to 3,000 °F).

METALS have a shiny luster. It can be polished.

a working value for the tensile strength would be σW = σTS / N.

This leads to the use of a safety factor N > 1 (typ. 1.2 - 4).

The U. S. Air Force B-2 advanced “stealth” bomber, which is constructed to a largeextent of advanced composite materials

Temperature on different parts of the air craft range from 6500C.

Severe oxidation at these temperatures.

Carbon-reinforced composites. Silicon Carbide ceramic coating.

Melting point 27500C. High strength:weight.

METALS CERAMICS POLYMERS

Medium hard Extremely hard Soft

High density Low density Very low density

Medium to high m.p High to very high m.p Low m.p

Medium to high elastic modulus

Very high elastic modulus

Low elastic modulus

Reactive Unreactive Very reactive

Ductile Brittle Very ductile

The handles & knobs of pots & pans are made of thermosetting plastics.

Why? Handles are attached by studs which

are welded to the utensils. Screws or rivets usually not used.

An iron's sole plate should actively reduce friction between the iron and the fabric of your clothes to create an 'easy glide' surface.

Stainless steel glides smoothly but may scratch.

Ceramic soleplates claim to be durable and scratch-resistant.

Ceramic plated hair irons are very common because

1.they heat up evenly preventing any hot spots that can damage your hair.

2.They also heat very quickly which means you can start styling when you are ready, not when your iron is.

3.The ceramic works to smooth your hair, leaving it looking shiny and healthy.

A series of tubes that collect the gases at the engine & convey them to the rear of the automobile.

REQUIREMENTS: Suitable rigidity to prevent excessive

vibration & FATIGUE. Enough CREEP RESISTANCE to

provide adequate strength. CORROSION is another limiting factor.

FATIGUE: is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading.

Cyclic stresses caused by fluctuating mechanical loads. Thermal stresses such as a cooled die coming in contact with hot work piece.

The part fails at a stress level below which failure would occur under static loading.

Failure due to fatigue

Failure due to creep

CREEP: is the permanent elongation of a component under a static load maintained for a period of time.

Occurs at different temperatures for different alloys.

It occurs as a result of long term exposure to levels of stress that are below the yield strength of the material.

Stress relaxation. Rivets, bolts etc.