engineering materials and properties

8/10/2019 Engineering Materials and Properties

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Engineering Materials and

Properties


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Ferrous Metals A FERROUS metal is one which contains

chiefly IRON (ferrite) with small proportions of other metals.

Wrought Iron (almost pure iron) Mild steel (0.1% to 0.3% carbon) Medium carbon steel (0.3% to 0.7% carbon)

High carbon steel (0.7% to 1.5% carbon) Cast Iron (more than 1.5% carbon) Alloy steels


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Ferrous Alloys

Properties of steel can be improved byadding metals like; Nickel to increasetoughness, Tungsten to cut metals at highertemperatures, Chromium to increasehardness, Manganese to add strength etc

Stainless steel (10 to 30% chromium) Chromium steel (5-10% chromium) Manganese steel


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Non Ferrous Metals and Alloys

These materialscontain NO Iron

Pure metals: Aluminium Copper Lead Tin Zinc

Alloys Brass (Copper and Zinc)

Bronze (Copper and Tin)

Duralumin (Aluminium,copper, Manganese andMagnesium)


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Non Metallic Materials

Wood (decorative furnishings, dashboards) Plastics (furniture, seals, containers etc) Glass (windscreens and instrument dials) Carbon Fibre (Aircraft parts and golf clubs)

Silicon crystals (semiconductors) Granite (measurement table beds) Rubber (engine mountings, seals, etc) Diamond (industrial cutters)


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Polymers

Thermoplastic Soften every time they are heated (eg perspex,

PVC etc)

Thermosetting plastics Cured during the moulding stage and cannot be

reheated and softened again (eg bakelite)


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Polymerisation

The manufacture of plastics is a chemical process known as Polymerisation.

Chains of hydrogen and Carbon moleculescombine to produce Polymers.

Polythene Polypropylene Poly Vinyl Chloride (PVC) Acrylics (perspex)


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Ceramics

These are inorganic materials used mainlyas thermal or electrical insulators.

Refers to products like: bricks/tiles fireclay refractories electrical porcelain Metallic Oxides (alumina, beryllia, zirconia and

magnesia form the basis of high temperature

ceramics)


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Ceramics

Alumina - spark plugs, cutting tools etc Beryllia - crucibles for molten metal Magnesia - furnace lining Zirconia - liners for jet and rocket motor

tubes


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Composites

Composites is the name given to materialswhich uses a fibre or other substance to

strengthen another ie Reinforced plastics Glass Reinforced Plastics (GRP) (soda glass

or silica based glass) Carbon fibre Aramid fibre (Kevlar) Tufnol Laminate


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Carbon Fibre

This is a composite of Carbon filaments(consisting of long chains of carbon atoms)

AND a cold-setting resin. Components are manufactured by placing

the carbon filaments in a mould and then

pouring the resin in. When the resin sets it produces a very light-

weight material with high strength and

rigidity.


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Aramid Fibres This is made from Aromatic polyamide

(nylon) eg Kevlar as used to protect fueltanks on the Concorde.

It has the highest tensile strength of allreinforced plastics

Stiffer than glass but less stiff than carbonfibre

High impact strength Lower compression strength than carbon

fibre


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Laminates

These composites are produced by pressingtogether sheets of linen or cotton which

have been soaked in a plastic resin. High toughness High electrical resistance (PCB products) Good machining properties Known as Tufnol or Micarta


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Properties of Materials


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Strength

The resistance it has to breaking either intension, compression or shear.

High strength materials:- All carbon steel Alloy steels Titanium Carbon fibre (tension) Cast iron (compression)


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Toughness The amount of energy it can absorb before

fracture, usually in conjunction with impactforces.

High Toughness materials:- Low or Medium carbon steel Hardened and toughened High carbon steel

Plastics including PVC and Acrylic Bronze Copper


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Malleability

The ability to be permanently deformed inall directions without fracture eg rolling,

hammering, pressing etc. Malleable materials:- Low carbon steel rivets Copper plate Lead weather proofing components Brass rivets Aluminium sheet


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Creep

Its ability to withstand long term loadingswithout stretching.

High creep resistant materials:- Low carbon steel Steel alloys Cast iron Bakelite Titanium


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Electrical Conductivity A conductor is the opposite of a resistor.

Electricity travels easily and efficientlythrough a conductor, with almost no otherenergy released as it passes.

Good conductors Copper Aluminium Brass

Poor conductors - INSULATORS PVC, bakelite Ceramics


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Machinability

The ability to machine easily and produce agood surface finish.

Machinable materials Low Carbon Steel Brass Aluminum Cast Iron Bronze


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Fatigue

Its resistance to cyclic loading eg vibrations Fatigue resistant materials:- Low, medium and high carbon steel Steel alloys Rubber Plastic


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Elasticity Its ability to deform elastically under a given

force or stress and return to its original shapewhen the force is removed.

Materials with good Elasticity:- Plastics including PVC, Acrylics Low carbon steel Hardened and tempered Medium or High carbon steel Rubber Copper Aluminium


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Relative Material Costs (/Kg)

Carbon Steels 1Lead 1.5Low Alloy Steel 2

PVC/Polythene 2.5Rubber 3Zinc 3.5Bakelite 4Aluminium 4.5Brass/Copper 5Stainless steel 5.5

Cast Iron 1

GRP 1

Ceramic 2

Nylon 10

Chromium 13

Titanium 20

Bronze 8Tin 16

Tungsten 28

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