Materials for Machine Design Flashcards by EVA MAE ALATAO

Food of design

Materials

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one that performs well,
is good value for money and gives pleasure to
the user - uses the best materials for the job,
and fully exploits their potential and
characteristics: brings out their flavor, so to
speak

Successful product

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6 broad classes of materials

Metals
Glass
Polymers
Elastomers
Ceramics
Composites

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The classes are classified based on common features like

Similar properties
Similar processing routes
Similar applications

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Classes of engineering materials that have relatively high moduli.
They can be made strong by alloying and by
mechanical and heat treatment, but they remain
ductile, allowing them to be formed by
deformation processes.

Metals

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Characteristics of the fracture that a high strength alloy produce

Tough ductile fracture

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Like metals, they too have high moduli, but these materials are brittle

Ceramics and glasses

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‘strength’ in tension of ceramics and glasses means

Brittle fracture strength

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Strength in compression of ceramics and glasses

Brittle crushing strength

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Materials that have no ductility.They
have a low tolerance for stress concentrations
(like holes or cracks) or for high contact
stresses (at clamping points, for instance).

Ceramics

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______materials accommodate stress concentrations by deforming in a way which
redistributes the load more evenly; and
because of this, they can be used under static
loads within a small margin of their yield strength

Ductile

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_______materials always have a wide scatter in
strength and the strength itself depends on the
volume of material under load and the time
for which it is applied

Brittle

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They are stiff, hard and abrasion-resistant (hence their use for bearings and cutting
tools); they retain their strength to high temperatures; and they resist corrosion well

Ceramics

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They have moduli which are low, roughly 5O
times less than those of metals, but they can
be strong - nearly as strong as metals

Polymers and elastomers

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combine the attractive
properties of the other classes of materials
while avoiding some of their drawbacks.
They are light, stiff and strong, and they
can be tough

Composites

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define the behavior of materials under the action of
external forces called loads.

Mechanical properties of materials

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Enumerate the mechanical properties of materials

Strength
Elasticity
Plasticity
Hardness
Toughness
Brittleness
Stiffness
Ductility
Malleability
Cohesion
Impact strength
Fatigue
Creep

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mechanical property that
enables a metal to resist deformation load. It is its capacity to
withstand destruction under the action of
external loads

Strength

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the ability
of an object or material to resume its normal
shape after being stretched or compressed.

Elasticity

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ability to
undergo some permanent deformation
without rupture(brittle)

Plasticity

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The resistance of a material to force penetration or bending. It causes materials to resist scratching, abrasion, cutting or
penetration

Hardness

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the ability of materials to oppose the scratches to outer surface layer due to
external force

Scratch hardness

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It is the ability of materials to oppose the dent due to
punch of external hard and sharp objects

Indentation hardness

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also called as dynamic hardness.
It is determined by the height of “bounce” of a
diamond tipped hammer dropped from a fixed height
on the material

Rebound hardness

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It is the property of a material which enables it to withstand shock or impact.

Toughness

Mechanical properties of materials which enables it to withstand permanent deformation. Causes materials to break rather than bend under shock or impact.

Brittleness

the resistance of a material to elastic deformation or deflection

Stiffness

a property of a material which enables it to be drawn out into a thin wire

Ductility

a property of a material which permits it to be hammered or rolled into sheets of other sizes and shapes

Malleability

a property of a solid body by virtue of which they resist from being broken into a fragment.

Cohesion

ability of a metal to resist suddenly applied loads

Impact strength

the long effect of repeated straining action which causes the strain or break of the material

Fatigue

slow and progressive deformation of a material with time at a constant force.

Creep

reaction with oxygen in water and air.

Oxidation or rusting

Metals are hard, non-adhesive, cold and smooth,they are very often shiny and strong. They are also ductille and malleable, do not break easily. Metals are very good conductors of electricity, sound and heat. When temperature rises they expand, and when it falls, they always contract. They can be easily welded to other metals

Physical properties

Most metal are recyclable and some metals such as lead or mercury are toxic and they are a danger for humans being and for the environment.

Ecological property

Metals with iron

Ferrous metal

Areas of weaknessess

Dislocation

An alloy of carbon and iron

Carbon steels

mixture of two or more chemical elements and the primary element is a metal.

Alloy

carbon content between 0,1% and 0,3%

Mild steel

less ductile but harder and tougher than iron, grey colour, corrodes easily.

Mild steel

Contains 0,3% and 0,7% carbon.

Medium carbon steel

it's used for the manufacture of products which have to be tough and hard wearing like gears, tools, keys, etc

Medium carbon steel

contains between 0,7% and 1,3% carbon

High carbon steel

Very hard and brittle material

High carbon steel

It's used for cutting tools and products which have to withstand wear such as guillotine, springs, etc.

High carbon steel

iron and chromium alloys, chromium content between 13% and 27%.

Stainless steel

______ prevents rusting with an oxide film

Chromium

Used for cutlery, sinks, pipes, car pieces, etc

Stainless steel

94% Fe, 3% Si, 2% Mg, S, P

Grey Cast Iron

brittle but extremely hard and resistant, it corrodes by rusting

Grey Cast Iron

pistons, machinery parts, streets lamps, drain covers, tools

Grey Cast Iron

makes the alloy magnetic and improves elasticity.

Silicon

makes the alloy harder and heat-resistant. It's used to make stainless steel.

Manganese

Chemical element added to alloy to improve strenght and prevents corrosion

Nickel

makes the steel harder, more heat-resistant and prevents corrosion

Tungsten (W)

makes the alloy harder and tougher and more rustproof.

Chromium

It's the most abundant metal in the earth's crust

Aluminum

Silvery white color, light, highly resistant to corrosion, soft, malleable and ductile, low density, good conductor of both electricity and heat.

Aluminum

high voltage power lines, planes, cars, bicycles, light metal work. roofing and windows and doors units, decoration, kitchen tools and drink cans.

Aluminum

It's a pure metal that is the world's third most important metal, in terms of volume of consumption.

Copper

a reddish-brown metal, ductile and moderately strong, very good conductor of electricity and heat,It corrodes very easily

Copper

Copper and zinc alloy

Brass

It's gold in color. It has very good anticorrosive properties and it's resistant to wear

Brass

It's shiny and silvery white.

Magnesium

It's very light, soft and malleable, but not very ductile. It reacts very strongly with oxygen

Magnesium

Fireworks, aerospace industry, car industry.

Magnesium

It's a shiny white metal. • Properties: It doesn't oxidize at room temperatures, it's very soft. • Uses: Soft-soldering, tin foil and tin plate.

Tin

It's a silvery grey metal. • Properties: Soft and malleable. It's toxic when its fumes are inhaled. • Uses: Batteries, it's use as an additive in glass for giving hardness and weight.

Lead

It's an alloy of copper and tin. • Properties: High resistant to wear and corrosion. • Uses: Boat propellers, filters, church bells, sculpture, bearings and cogs.

Bronze

bluish grey shiny metal

Zinc

Anticorrosive, not very hard, weak at low temperatures

Zinc

These materials are used for their electrical and thermal conductivity, corrosion resistance, appearance and color, and ease of working. • They have the highest conductivity of the engineering metals and are very ductile and easy to braze, and generally to weld.

Copper

contain small amounts of various alloying elements such as beryllium, chromium, zirconium, tin, silver, sulphur or iron.

High copper alloy

Element added to brass to enhance machinability

Lead

Added to brass to enhance strength

Tin

Copper zinc alloys are _______ up to about 37% zinc in the wrought condition.

Single phase

Alloys with more than about 37% zinc are___________, and have even higher strength, but limited ductility at room temperature

Dual phase

alloys of copper with nickel, with a small amount of iron and sometimes other minor alloying additions such as chromium or tin. • The alloys have outstanding corrosion resistance in waters, and are used extensively in sea water applications such as heat exchangers, condensers, pumps and piping systems, sheathing for boat hulls.

Copper nickel

contain 55 – 65% copper alloyed with nickel and zinc, and sometimes an addition of lead to promote machinability.

Nickel silver

Manufacturing process that is used in creating basic forms

Primary processes

Manufacturing process used to alter or add features

Secondary process

creates complex shapes from molten metal

Casting

Metal casting that uses permanent molds into which low melt point metals such as zinc are injected under pressure

Die Casting

creates intricate wax patterns that are coated with slurry, the wax melted out, then filled with molten metal.

Investment casting

The process was originally invented for making jewelry and, sometimes referred to as the lost-wax process, has become a method for casting complex parts such as turbine blades.

Investment casting

Type of casting machine for low melting metals such as zinc, tin, and lead.

Hot chamber

Type of die casting machine for metal melted in a chamber separated from the machine.

Cold chamber

Forging uses hydraulic die sets or open dies and hammers to plastically deform usually hot metal into net shapes, oftentimes starting with a rough approximation of the finished shape called a blocked preform

Bulk/metal deformation

transforms mill products into finished raw materials such as I-beams, plates, and sheets. The process may be performed hot or cold,

Rolling

Can produce moderately complex shapes in parts that are up to 3 ft. long.

Forging

used to further reduce bar stock and improve surface characteristics and strength through a cold, die puling process.

Bar drawing

continues the process of bar drawing by pulling ductile materials through increasingly smaller dies to wind up with steel, aluminum, and copper wire.

Wire drawing

Sheet metal is cut into smaller straight-edged pieces by ______

Shearing

Sheet metal working /metal forming that gradually pushes the material into a die cavity that deepens with each step through the die.

Drawing

Sheet metal working /metal forming that creates holes and slots where needed

Punching

Sheet metal working /metal forming that creates tabs and other features that run perpendicular to the plane of the original material.

Bending

Sheet metal working /metal forming that shears the finished part from the remaining coil material that has served to carry the forming part through the die

Blanking

Manufacturing process that uses various cutting tools, abrasive wheels, as well as some unusual media such as water or sparks, to remove material from round and bar stock, castings, etc. to produce accurate finished good

Machining

include sawing, turning, boring, reaming, etc. and are oftentimes performed as secondary operations to clean up parts or to create surfaces that are suitable for assembly.

Machining

one such process, where ductile metals such as copper and aluminum are forced through dies to produce common shapes such as copper tubing or aluminum angles.

Extrusion

Major categories of machining

Cutting, abrasives, non-traditional

involves the forming of both thermoset and thermoplastic materials usually by molding but also by subtractive methods such as machining.

Polymer processing

In __________ of polymer processing, an elastomer charge is placed between heated die halves which are subsequently closed to force the material into the shape of the cavity.

Compression molding

________ uses an auger to soften plastic pellets in a barrel and inject the resulting “shot” under high pressure into a usually multi-cavity mold.

Injection molding

another polymer processing method that shapes sheets or films of thermoplastic into cavities or over plugs usually using vacuum or air to pull or push the softened material against the mold surfaces.

Thermoforming

common method for making plastic bottles.

Blow molding

used to produce large hollow shapes such as kayaks by relying on the centrifugal force imparted to molten plastic as it spins within a rotating mold.

Rotomolding

encompasses many final operations that make a part ready for assembly

Finishing

where the different parts that compose a finished product come together.

Assembly

Materials Selection Process

1. Identify product design requirements 2. Identify product element design requirements 3. Identify potential materials 4. Evaluate materials 5. Determine whether any of the materials meet the selection criteria 6. Select materials