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Aplicaciones de los Materiales > Examen Final > Flashcards

Examen Final Flashcards

1
Q

Thermoset polymers result from a “phase transformation” reaction which generates only a low degree of spatial crosslinking.

A

FALSE

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2
Q

Undercooling is defined as the difference of Treal minus Tequilbrium

A

FALSE

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3
Q

Bainite is a coarser microstructure than pearlite, and thus harder and tougher.

A

FALSE

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4
Q

Malleable cast iron is the result of heat-treating a white cast iron which typically has a carbon equivalent of 3 to 3.4%

A

TRUE

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5
Q

The Avrami equation (K-J-M-A) is a mathematical model of the effect of time on a phase transformation process at a given temperature.

A

TRUE

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6
Q

When adding lateral groups to a polymer, as the case of PVC instead simple polyethylene, the transition temperature increases and as well as its ability to crystallize.

A

TRUE

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7
Q

The Weibull distribution is a statistical function that is used, amongst many other applications, to predict the hardness of ceramic of Volumen V0 whose material has a characteristic stress S0 and a sensitivity exponent m.

A

FALSE

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8
Q

For recrystallization to occur on annealing of a metallic alloy, a minimum amount of temperature is required, otherwise grain growth will set in.

A

FALSE

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9
Q

In XYZZ designation of steels (AISI-SAE) X is the type of the steel, Y the modification and ZZ the carbon content in hundredths of a per-cent

A

TRUE

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10
Q

In a two-phase material consisting of a matrix and secondary particles that exist in thermodynamic equilibrium the larger particles tend to integrate smaller once (large particles
“eat” little once). Why is this tendency?

A

R=Because the surface energy increases with D 2 and internal energy decreases with D 3

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11
Q

The dihedral angle between two phases is what controls the rate of transformation of
the new phase.

A

FALSE

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12
Q

The speed at which the martensitic transformation occurs is controlled by diffusion in the solid alloy.

A

FALSE

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13
Q

Sinterization is a solid state process which densifies a particulate material. The processis self-diffusion driven, diffusion which arises because of a:

A

R= surface energy reduction.

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14
Q

Atactic polymers tend to be less crystalline than the isotactic or syndotactic once.

A

TRUE

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15
Q

Titanium has a higher specific stiffness than steels.

A

FALSE

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16
Q

Copper alloys can be strengthened by deformation, solid solution, grain size reduction,
and / or precipitation of secondary phase particles.

A

TRUE

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17
Q

Homogenization is a product of the redistribution of solute in the solid material as it is
cooled during certain periods of time.

A

FALSE

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18
Q

The PVC and polystyrene are more resistant than polyethylene because links within their chains are stronger.

A

FALSE

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19
Q

The dihedral angle formed between two adjacent phases is a function of their melting
temperatures.

A

FALSE

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20
Q

A simple, binary, eutectic phase diagram presents only one solid phase.

A

FALSE

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21
Q

Get high hardness and

toughness simultaneously in martensite.

A

TEMPERING

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22
Q

Reach maximum hardness in steels.

A

QUENCHING

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23
Q

Soften metals which produce precipitates on slow cooling.

A

HOMOGENIZIRING

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24
Q

Relieve residual stresses.

A

PRONCESS ANNEALING

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25
Q

Hardening solid solutions by precipitation.

A

AGEING

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26
Q

Improve machinability of steels with medium and high carbon.

A

SPHEROIDIZING.

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27
Q

Recrystallize cold worked

microstructures.

A

ANNEALING

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28
Q

Refine grain size.

A

NORMALIZING

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29
Q

Maximize strength and

toughness in medium carbon steels.

A

AUSTEMPERING

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30
Q

Harden only the surface of a low carbon steel.

A

CARBURIZING AND QUENCHING

31
Q

Keeping in mind the state of strain and stress, and the cost of the component; what kind of composite material would you use to manufacture a control surface (aileron) for airplanes?

A

Long unidirectional fiber
laminates stacked in
different orientations.

32
Q

the firewall of a motorcar

(wall separating the enginecompartment from thepassengers compartment)?

A

Short random

orientation fiber.

33
Q

a horizontal panel for a home cabinet or wardrobe close

A

Honeycomb sandwich.

34
Q

0a storage tank for high

pressure air?

A

Long wound fiber

filament winding

35
Q

A simply supported beam

under flexion?

A

Long unidirectional fiber.

36
Q

the engine hood of a tractor trailer?

A

Short random orientation fiber.

37
Q

the washing sink in a hairdressers shop?

A

Short random orientation fiber.

38
Q

the lid of a domestic water

tank?

A

Short random orientation fiber.

39
Q 
front fender (panel that
extend from the front bumper to the car's doors) a compact car?
A

Short random orientation fiber.

40
Q

a suspension arm for an

off-road vehicle?

A

Long unidirectional fiber.

41
Q

The elastomers typically acquire mechanical properties by crosslinking through sulfur atoms.

A

TRUE

42
Q

The more severe the quench media, the larger the critical diameter of a given steel.

A

TRUE

43
Q

The critical diameter of a steel is the one that produces 50% ferrite at the center of a properly quenched cylindrical rod.

A

FALSE

44
Q

The Arrhenius equation relates the fraction transformed with time and temperature at which this transformation occurs.

A

TRUE

45
Q

The density of Ti-based superalloys is greter than that of low alloy steels.

A

FALSE

46
Q 
The amount of- and rate of nucleation of a new phase within an existing phase is
function of the undercooling present.
A

TRUE

47
Q

During solidification, the position of the liquidus line will be depressed with increasing undercooling, and this is because the diffusion in the liquid is slower that in the solid.

A

FALSE

48
Q

Crystallization of plastic is easier if the degree of polymerization is high

A

TRUE

49
Q

A copolymer is an alloy of two or more types of polymers.

A

FALSE

50
Q

Ceramic glasses can suffer dynamic as well as static fatigue.

A

TRUE

51
Q

Crystallization of plastic is easier if the degree of polymerization is high.

A

TRUE

52
Q

Thermodynamics tells us what phases are to be formed and kinetics provides information on the morphology of the new phases.

A

FALSE

53
Q

Obtuse precipitates are better reinforcers than acute ones.

A

TRUE

54
Q

Thermal shock resistance is measured as the maximum temperature a material can resist without cracking.

A

FALSE

55
Q

Hardenability of steels can be measured with a Vickers quench test.

A

FALSE

56
Q

Solid solution strengthening is because the deformations of the lattice introduced by the
foreign atom reduce the mobility of vacancies.

A

FALSE

57
Q

In low alloy steels, the modulus of elasticity is a function of carbon content.

A

FALSE

58
Q

The eutectoid pearlite structure is formed faster than the eutectic ledeburite structures.

A

FALSE

59
Q

For an alloy to be adequately strengthened by precipitation of a secondary phase, it
must have an appreciable maximum solubility of the solute at high temperature and much lower maximum solubility at room temperature.

A

TRUE

60
Q

The phase rule of Gibbs states: C=F + P + 2

A

FALSE

F=C-P+2

61
Q

How much eutectic is present in a A-30% B alloy which solidified in equilibrium and is
held at 180⁰C?

A

R = 1/4 ó 25%

62
Q

The thermoset polymers exhibit a steeper softening behavior than thermoplastic polymers.

A

FALSE

63
Q

The apparent porosity of ceramic material is usually smaller than the true porosity.

A

TRUE

64
Q

Copolymers are “alloys” of momomers which generally have better mechanical properties than their individual components.

A

TRUE

65
Q

Nickel base super-alloys have a similar specific strength than low alloy steels.

A

TRUE

66
Q

The toughness of polymers is the same as that of metals.

A

FALSE

67
Q

Martensite of steels is a metastable solid solution with a body-centered cubic structure.

A

FALSE

68
Q

A phase is material which has a specific structure and atomic arrangement, is
homogeneous in composition and properties, and exhibits a defined interfaces with other phases.

A

TRUE

69
Q

The M s and M f temperatures of carbon steels depend on the C content, and tend to
increase with increasing C content.

A

FALSE

70
Q

The peritectic reaction involves a liquid that becomes a new liquid plus a new solid.

A

TRUE

71
Q

Ceramic materials have difficulty to deform elastically because their Burgers Vector is
usually large.

A

FALSE

72
Q

Of the 4 Hume-Rothery rules for infinite solubility the most important factor is the valence rule.

A

FALSE

73
Q

The electrical conductivity of polymers is similar to that of metals.

A

FALSE

74
Q
  1. Ceramic powder mining or
    synthesis
  2. Grinding to a specific
    granulometry
  3. Mixing with plasticizer and
    additives
  4. Forming of the product
  5. Binder removal
  6. Densification by sintering
  7. Post-processing
A

ORDEN 1 A 7

Aplicaciones de los Materiales (2 decks)

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