Engineering materials Flashcards

1
Q

What are the main types of engineering materials?

A
  1. Metals and alloys
  2. Ceramics
  3. Composites
  4. Polymers
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2
Q

What are metals?

A

Elements that form positive ions by losing electrons during chemical reactions are called metals – electropositive entities with low ionization energies.

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3
Q

Name of scientist who proposed sea of electron theory.

A

Paul Drüde

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4
Q

What are the factors that affect metallic bonding?

A
  1. Magnitude of positive charge
  2. Number of delocalized electrons
  3. Ionic radius
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5
Q

Why are metals ductile and malleable?

A

Delocalized electrons allow metals to be deformed without fracturing.

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6
Q

Why are metals shiny?

A

Metals are shiny due to the excitation and deexcitation of delocalized electrons.

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7
Q

What are alloys?

A

In alloys, atoms of varying sizes are dispersed within the metallic lattice making it harder, less malleable and less ductile.

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8
Q

How do impurities affect melting point?

A

They decrease melting point.

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9
Q

What are some metals that can be alloyed with aluminum?

A

copper, manganese, silicon, magnesium,

zinc.

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10
Q

What are ceremics?

A

Made of metals and non-metals. May contain both covalent and ionic bonds. They can be amorphous (glass) or crystalline (other ceramics) in nature.

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11
Q

What is the particle size in particulate composites?

A

Particle size < 0.25 μm

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12
Q

What are the main types of composites?

A

Partuculate, laminated and fiberous.

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13
Q

What are the three main types of properties of engineering materials?

A

Physical, chemical, and mechanical.

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14
Q

What are physical properties?

A

Physical properties can be observed or measured without changing the composition of matter.

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15
Q

What are some examples of physical properties?

A
  1. Color
  2. Melting point
  3. Boiling point
  4. Density
  5. Mass
  6. Conductivity
  7. Specific gravity
  8. Fluidity
  9. Elasticity
  10. Plasticity
  11. Porosity
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16
Q

What is specific gravity?

A

Ratio of density of material with respect to density of reference material or substance

17
Q

What is fluidity?

A

Fluidity is defined as the nature that concrete mixtures, under the influence of self-weight and mechanical vibration, start to flow and fill every corner of the
mold-board evenly and densely.

18
Q

What is elasticity?

A

Elasticity is the ability of an object or material to resume its normal shape after being stretched or compressed – reversible deformation.

19
Q

What is plasticity?

A

Quality of being easily shaped or molded - irreversible deformation.

20
Q

What is porosity?

A

Porosity of materials represents quantity of voids in solid materials.

21
Q

What are mechanical properties?

A

The mechanical properties of a material are those properties that involve a reaction to an
applied load.

22
Q

What are some examples of mechanical properties?

A

Strength, ductility, hardness, impact resistance, fracture toughness.

23
Q

What is strength?

A

Strength is the ability of a material to resist deformation caused by external load.

24
Q

What is ductility?

A

Ductility is defined as the extent to which a material can be deformed plastically.

25
Q

What is hardness?

A

Hardness is the ability of a material to resist indentation, penetration or scratching caused by another material.

26
Q

What is impact resistance?

A

Energy required to break a material.

27
Q

What is fracture toughness?

A

Material’s capacity to resist fracture when enduring a crack.

28
Q

What are chemical properties?

A

Chemical properties related to changes in chemical composition of material because it interacts
with other substances.

29
Q

What are examples of chemical properties?

A
  1. Chemical Composition
  2. Toxicity
  3. Flammability
  4. pH
  5. Reactivity
  6. Bonding and oxidation states
  7. Resistance to corrosion
30
Q

What are the main classifications of engineering materials?

A
  1. Metals
  2. Polymers
  3. Ceramics
  4. Composites
  5. Hybrids
31
Q

What are composites?

A

A composite material is a material in which one or more mutually insoluble materials are mixed or bonded together