Chapter 4 & 5 Materials Flashcards

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0
Q

Brittle

A

A material that does not plastic ally deform before breaking Breaks suddenly as cracks travel through it

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1
Q

Strong

A

A material that can withstand large amounts of stress before breaking

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2
Q

Tough

A

A material that undergoes considerably plastic deformation before breaking. In this process it will also absorb a lot of energy before breaking

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3
Q

Stiff

A

Small strains for large stresses Large Young modulus Not stretchy or bendy

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4
Q

Elastic

A

Returns to unstretched form when stresses are removed

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5
Q

Plastic

A

Undergoes permanent deformation under large stresses rather than cracking

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6
Q

Hard

A

Resists indentation on impact

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7
Q

Limit of proportionality

A

Point beyond which stress and strain are no longer proportional Hooke’s law does not apply

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8
Q

Yield point

A

Point at which strain increases rapidly

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9
Q

Ultimate Tensile Strength UTS

A

Stress at which a material breaks

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10
Q

Ductile

A

Can be drawn out into wires Undergoes considerable plastic deformation before breaking

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11
Q

Hysteresis loop

A

Loading and unloading cycle for rubber Area of the loop equals the energy per unit volume transferred to heat inside the rubber

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12
Q

What structure does this material have

A

Amorphous

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13
Q

What structure does this material have?

A

Crystalline

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14
Q

What structure does this material have

A

Polycrystalline

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15
Q

What does SEM stand for

A

A type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons. SEM can achieve resolution better than 1 nanometer.

16
Q

What does AFM or SFM stand for?

A

Atomic force microscopy (AFM) or scanning force microscopy (SFM)

a very high-resolution type of scanning probe microscopy, with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit

17
Q

What is a composite material

A
  • A broad definition of composite is: Two or more chemically distinct materials which when combined have improved properties over the individual materials. Composites could be natural or synthetic
  • Composites are combinations of two materials in which one of the material is called the reinforcing phase, is in the form of fibers, sheets, or particles, and is embedded in the other material called the matrix phase.
18
Q

vWhat is the concept / purpose of a composite material?

A
  • The essence of the concept of composites is that the load is applied over a large surface area of the matrix. Matrix then transfers the load to the reinforcement, which being stiffer, increases the strength of the composite.
  • It is important to note that there are many matrix materials and even more fiber types, which can be combined in countless ways to produce just the desired properties.
19
Q

List 3 advantages of composite materials

A
  • Higher Specific Strength (strength-to-weight ratio) Design flexibility
  • Corrosion Resistance
  • Low Relative Investment
  • Durability
20
Q

Name the 4 classes of materials

A

Metals

Ceramics

Polymers

Composites

21
Q

Describe how a crystal forms

A
  • The moment a crystal begins to grow is know as nucleation and the point where it occurs is the nucleation point.
  • At the solidification temperature, atoms of a liquid, such as melted metal, begin to bond together at the nucleation points and start to form crystals.
  • The final sizes of the individual crystals depend on the number of nucleation points.
  • The crystals increase in size by the progressive addition of atoms and grow until they impinge upon adjacent growing crystal.
22
Q

Describe the difference between a crack in a brittle vs plastic material

A

BRITTLE - microscopic flaws (crack) will tend to elongate rather induce plastic deformation when a stress is applied.

PLASTIC - cracks tend to emit dislocations and become more blunt as the raft is stressed

23
Q

A large fracture energy means the material is…..

A

TOUGH

24
Q

Which leads to a stronger material, larger or smaller grain size?

A

Dislocations can travel easily inside a crystal grain

When they reach grain boundary they cannot move further

More grain boundaries = stronger material

25
Q

What is doping?

A

✤To make a semi conductor conduct electricity, other atoms (impurities) must be added

✤The impurities are different elements

✤This process is called doping

26
Q

Which shows the limit of proportionality?

A

A

27
Q

Which shows the yeild point?

A

B (upper yield point) and C (lower yield point)

28
Q

Which shows the ultimate tensile strength (UTS)?

A

D

29
Q

Which shows the breaking stress?

A

E