Chapter 1: Materials and their properties Flashcards

1
Q

Definition of strength

A

the amount a material can withstand a force applied to it

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2
Q

Definition of ductility

A

the amount a material can be deformed

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3
Q

Definition of toughness

A

the amount a material can withstand an impact without breaking

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4
Q

Definition of hardness

A

the amount a material can resist wear and abrasion

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5
Q

Definition of stiffness

A

the amount a material can resist bending

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6
Q

Definition of brittleness

A

the potential for a material to shatter when in contact with a force

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7
Q

Definition of malleability

A

the amount a material can be deformed without rupturing

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8
Q

What is Young’s Modulus

A

The ratio of stress to strain of a material. it shows how stiff a material is

FORMULA: STRESS/STRAIN

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9
Q

Formula for stress

A

Stress = force/cross-sectional area

units for stress is in* N/mm^2*

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10
Q

Formula for strain

A

Strain = change in length/original length

no units!

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11
Q

Type of strengths

A

Tensile: ability to resist a pulling force
Compressive: the ability to resist a squeezing force
Torsional: the ability to resist a twisting force

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12
Q

Give examples of ferrous metals, and non-ferrous

A

Ferrous metals and alloys:
* cast iron
* low and high carbon steels
* steel alloys (stainless steel).

Non-ferrous metals and alloys:
* aluminium
* copper
* lead
* zinc
* alloys (brass and bronze).

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13
Q

What is annealing?

-modifying the structure of metals-

A

A heat treatment that makes a metal softer and easier to work with (more malleable/ductile)
* metal is heated to specific temp/colour, allowed to cool down after

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14
Q

What is hardening?

A

a heat treatment that increases the hardness & strength material (due to changed in arangement of atoms)
* Heat to a temp a bit above the lower critical point, soaks (often oil/brine) at that temp so grains have time to rearrange
* tempered: to remove some of the brittleness

* quenching: rapid cooling of a hot metal by immersing in a liquid (oil)

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15
Q

What is normalising?

A

A heat treatment that results in metal that is tough, with some ductility.
* Metal is heated to temp under melting point, cools in the air

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16
Q

What is cold working?

A

A process of strengthening metals through plastic deformation.
Metals become harder to resist any further change.

-non heat process-
eg: hammering

17
Q

What is corrosion?

A

a reaction between the surface of the material and the environment that consumes some of its material.
* often possible to alter effects of environment by managing corrosion or adding/subtracting carbon (to change structure of surface. )

18
Q

How to add or subtract carbon in steels?

A

Adding:
* heat the steel part until it becomes cherry red, then dip it into the carbon powder. Do this a few times and some of the carbon powder will be absorbed into the steel surface.
* Using a wire brush, clean off the excess carbon
* (complete hardening process): heat to cherry red, and quench in oil. (tempering is not needed)

19
Q

Difference between thermoplastic and thermosetting polymers

A

Thermoplastic: recyclable, can be reshaped and reheated
thermosetting: not recyclable, cannot be reshaped and reheated

20
Q

ABS

thermoplastic

A

recycling number 9:
* strong
* rigid
* harder and tougher than polystrene

1.plastic pipes
2.children’s toy

21
Q

Polystyrene

thermoplastic

A

recycling symbol 6:

  • good toughness
  • good impact strength
    1. packaging
    2. foam cups
22
Q

Acrylic

thermoplastic

A

Recycling symbol 7:
* transparent
* hard wearing
* not shatter
1. plastic windows
2. bath tubs

23
Q

Polyester resin

thermosetting

A
  • stiff
  • brittle
  • good strength
    1. suitcases
24
Q

Nylon

thermoplastic

A

Recycling number 7:
* ductile
* durable
1. gear wheels
2. bearings

25
melamine resin | thermosetting
* stiff * hard * strong 1. kitchen worktops
26
Epoxy | thermosetting
* stiff * brittle 1. printed circuit boards
27
CRP | composite
* carbon fibres in resin matrix * low density * high strength 1. aircraft structure
28
GFP | composite
* glass fibres in resin matrix * high strength * low density 1. water tanks
29
Plywood | composite
* layers of wood bonded at right angles * uses adhesives * smooth surface 1. furniture making
30
MDF | composite
* wood fibres and adhesive matrix * smooth * able in veneered form 1. furniture, internal panelling
31
OBS | composite
* strands of wood compressed with adhesive matrix * more uniform * lower cost 1. walls, roof decking
32
structural concrete | composite
* most common * concrete reinforced with steel bars to increase tensile strength 1. bridges