Material Properties Definitions

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  • Created by: Issy
  • Created on: 23-09-17 12:43
Define tough
The opposite of brittle, a material that resists crack propagation, plastically deforms without fracturing
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What is a stiff material?
Resistant to stretching or bending
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What is a malleable material?
Easily shaped
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What is a hard material?
Difficult to scratch or dent
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What is a soft material?
Easily deformed
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What is a brittle material?
Shatters by crack propagation, shattering into jagged pieces.
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What is a ductile material?
Can be drawn into wires
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What does yield stress mean?
The level of stress at which a material will permanently deform
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What does fracture stress mean?
The stress required to fracture or break a material, either by compression or tension
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What is plastic deformation?
Permanent deformation that occurs after excessive elastic deformation
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What is brittle fracture?
Fracture of a material without prior plastic deformation
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What is fracture energy?
Once cracked, a material's ability to withstand fracture
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What is a strong material?
Withstands an applied load without failure or plastic deformation and supports a large amount of stress before yielding
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What is a weak material?
Breaks with little stresson
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Define dense
A material that is closely compacted in its atoms
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What is compression
A force that attempts to flatten a material
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What is elastic deformation?
Deformation to a material that will return to its original shape once the load is removed will
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What is strain energy?
Energy stored by a material undergoing deformation
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Define Crystalline
Internal structure composed of crystals
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What is compressive strength
How much compressivce stress a material can endure, different to the compression force
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What statement about the structure of crystals is false?
Polycrystals are rare but large crystals are common
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What statement about polycystals grain boundaries is correct
The structure within the individual grains is the same; netwroks aren't continuos and direction changes at grain boundaries
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What statement about dislocations is incorrect
Dislocations are mobile in ceramics
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What is necking or cup and cone fracture?
Dislocations move towards grain boundaries and tangle preventing further movement
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What doesn't explain why a straight bar of copper is unable to be bent straight after being bent into a U shape
Dislocations can't move backwards after moving to grain boundaries
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Why don't cracks propogate in tough materials
In tough materials it takes more energy to extend cracks because they have a large plastic region, meaning when stress is applied to a crack it broadens the tip and reduces stress (stress=force/area)
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Which is statement about polymers isn't correct
held togethr by weak covalent bonds that are directional
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Describe covalent bonding
Giant lattices which are hard to displace with strong directional bonds and bound electrons
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Describe metallic bonding
There are delocalised electrons and non-directional bonds which hold positive ions in a lattice whilst allowing slips and dislocations
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Explain why the stress at the tip of a crack in a brittle material can be very large
A crack prevents a material from spreading stress. Stress is concentarted at the tip, a very small area. The crack deflects tensile strength and stress is concentrated below the crack.
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What is the difference between thermosetting plastic and thermoplastics
Thermosetting plastics can only be heated and shaped once whereas thermoplastics can be heated and shaped many times
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What material isn't a thermo plastic
Melamine
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What equation is incorrect
Young Modulus=strain/stress
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Describe the structure of an oil atom
lipophilic head and hydrophobic tail
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Why is Lord Rayleigh's experiment the maximum possible value of the length of an oil molecule
It is assumed that the height of the oil patch is equal to the length of one oil molecule but if it were actually two the length of an oil molecule would be smaller
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Other cards in this set

Card 2

Front

What is a stiff material?

Back

Resistant to stretching or bending

Card 3

Front

What is a malleable material?

Back

Preview of the front of card 3

Card 4

Front

What is a hard material?

Back

Preview of the front of card 4

Card 5

Front

What is a soft material?

Back

Preview of the front of card 5
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