Table of Contents

• Week 01: Materials Science: 10 Things Every Engineer Should Know Quiz Answers
• Materials Science: 10 Things Every Engineer Should Know Week 02 Quiz Answers
• Materials Science: 10 Things Every Engineer Should Know Week 03 Quiz Answers
• Materials Science: 10 Things Every Engineer Should Know Week 04 Quiz Answers
• Materials Science: 10 Things Every Engineer Should Know Week 05 Quiz Answers

Week 01: Materials Science: 10 Things Every Engineer Should Know Quiz Answers

Quiz 01: Thing 1

Q1. The first three categories introduced in this segment (metals, polymers, and ceramics) are based on the three types of primary bonding: metallic, ________, and ionic, respectively.

• secondary
• van der Waals
• covalent

Q2. Glasses are considered a category separate from ceramics because their chemistry is different, even though their atomic structure is the same.

• True
• False

Q3. Fiberglass is a good example of a ___________ combining the strength and stiffness of reinforcing glass fibers with the ductility of the polymeric matrix.

• ceramic
• composite
• semiconductor

Q4. Semiconductors are considered a category separate from metals because their electrical conductivity is different.

• True
• False

Q5. The relationship between atomic bonding and the elastic modulus or stiffness of a metal is an example of how structure (atomic-level in this case) leads to _____________.

• permanent deformation
• properties
• breakage

Quiz 02: Thing 2

Q1. Aluminum metal is an example of a ______________.

• simple cubic crystal structure
• body-centered cubic crystal structure
• face-centered cubic crystal structure

Q2. The vacancy and the interstitial are two common types of point defects in metallic crystal structures.

• True
• False

Q3. The Arrhenius relationship shows that the rate of chemical reactions increases _______________ temperature.

• linearly with
• exponentially with
• with the fourth power of

Q4. The Arrhenius plot is a linear set of data points in which the logarithm of rate is plotted against the ____________.

• absolute temperature in K
• inverse temperature in K^-1
• temperature in °C

Q5. The activation energy, Q, for a chemical reaction is indicated by the _______________ of the Arrhenius plot.

• slope
• intercept at 1/T = 0
• intercept at 1/T = 1

Q6. The gas constant, R, is equal to _______________ times the Boltzmann’s constant, k.

• 10²⁴
• Avogadro’s number
• 10^-24

Q7. The gas constant, R, is an appropriate term for equations describing gas phases and ________________ processes.

• solid-state
• no other
• all other

Q8. The energy needed to produce a single vacancy, E_v, is the same as the activation energy, Q.

• True
• False

Q9. Solid-state diffusion occurs in the face centered cubic structure of aluminum by individual aluminum atoms hopping into _______________ sites.

• adjacent occupied
• adjacent interstitial
• adjacent vacant

Q10. As an indication of how “close packed” the aluminum (FCC) crystal structure is, ________ of the volume of the unit cell is occupied by the aluminum atoms.

• 74%
• 70%
• 68%

Q11. The diffusion coefficient is defined by _______________.

• Fick’s second law
• Fick’s first law
• Fick’s third law

Q12. The diffusivity (D) of copper in a brass alloy is 10^-20 m²/s at 400 °C. The activation energy for copper diffusion in this system is 195 kJ/mol. The diffusivity at 600 °C is _____________.

• 2.93 x 10^-16 m²/s
• 5.86 x 10^-17 m²/s
• 2.93 x 10^-17 m²/s

Materials Science: 10 Things Every Engineer Should Know Week 02 Quiz Answers

Quiz 01: Thing 3

Q1. An edge dislocation corresponds to an extra ______________.

• full plane of atoms
• cluster of atoms
• half-plane of atoms

Q2. An edge dislocation is a linear defect with the Burgers vector _______________ to the dislocation line.

• at a 45 degree angle
• perpendicular
• parallel

Q3. Crushing an empty soda can made of aluminum alloy is an example of ______________.

• viscous deformation
• plastic deformation
• elastic deformation

Q4. Plastic deformation by dislocation motion is a ___________ alternative to deforming a defect-free crystal structure.

• high-stress
• low-stress
• stress-free

Quiz 02: Thing 4

Q1. The first of the “big four” mechanical properties obtained in the tensile test is ___________________.

• yield strength
• elastic modulus
• tensile strength

Q2. The tensile strength is ___________ the yield strength for typical metal alloys.

• greater than
• about the same as
• less than

Q3. The ductility corresponds to the ______________.

• strength at failure
• total amount of elastic deformation
• strain at failure

Q4. The Elastic Modulus is given by ______________.

• Hooke’s Law
• Poisson’s ratio
• Ohm’s Law

Q5. The yield strength corresponds to ______________.

• an offset of 0.2%
• an offset of 0.1%
• the point of tangency where plastic deformation first begins

Q6. The stress versus strain curve shows that a metal alloy becomes weaker beyond the tensile strength.

• True
• False

Q8. The elastic “snap back” that occurs at failure is parallel to ______________.

• the stress axis
• the elastic deformation portion of the stress-strain curve.
• the strain axis

Q9. The Toughness or work-to-fracture is the total area under the stress versus strain curve.

• True
• False

Materials Science: 10 Things Every Engineer Should Know Week 03 Quiz Answers

Quiz 01: Thing 5

Q1. “Creep” deformation describes the behavior of materials being used at high temperatures under high pressures over _____________ time periods.

• long
• intermediate
• short

Q2. We added comments about polymers because their weak, secondary bonding between long chain molecules causes them to exhibit creep deformation at relatively low temperatures.

• True
• False

Q3. In the simplest sense, the creep test is essentially a tensile test done at a high temperature under ____________ load.

• a fixed
• no
• a variable

Q4. A linear portion of the strain versus time plot corresponds to the ______________ stage of the overall creep curve.

• secondary
• tertiary
• primary

Q5. The strain rate in the ______________ stage of the creep test is analyzed using the Arrhenius equation, analogous to our previous discussion of the diffusion coefficient.

• secondary
• primary
• tertiar

Q6. A powerful use of the Arrhenius relationship is to measure creep data at low temperatures and then extrapolate the data to high temperatures, allowing us to predict the performance there.

• True
• False

Q7. In a laboratory creep experiment at 1,000 °C, a steady-state creep rate of 5 x 10^-1 % per hour is obtained for a metal alloy. The activation for creep in this system is known to be 200 kJ/mol. We can then predict that the creep rate at a service temperature of 600 °C will be ______________. (We can assume the stress on the sample in the laboratory experiment is the same as at the service temperature.)

• 80.5 x 10⁶ % per hour
• 4.34 x 10^-5 % per hour
• 8.68 x 10^-5 % per hour

Q8. For high temperature creep deformation in ceramic materials, a common mechanism is ______________.

• dislocation climb
• viscous flow (molecules sliding past one another)
• grain boundary sliding

Quiz 02: Thing 6

Q1. The ductile-to-brittle transition was first discovered in conjunction with the failure of ______________

• the Queen Mary
• the Titanic
• Liberty Ships

Q2. The impact energy is an indicator of whether a fracture is ductile or brittle, as measured by the ____________ test

• creep
• tensile
• Charpy

Q3. Although they have equally high atomic packing densities, face-centered cubic (fcc) metals with more slip systems are typically ductile while hexagonal close packed (hcp) metals are relatively __________.

• strong
• weak
• brittle

Q4. Body-centered cubic (bcc) alloys such as low-carbon steels demonstrate the ductile-to-brittle transition because their dislocation motion tends to be ___________ than that in the more densely packed fcc alloys.

• more erratic
• slower
• faster

Materials Science: 10 Things Every Engineer Should Know Week 04 Quiz Answers

Quiz 01: Thing 7

Q1. We focus on “critical flaws” that ______________.

• are larger than 1 mm in size
• lead to catastrophic failure
• are larger than 1 μm in size

Q2. We use the example of __________________ to illustrate concern about a famous “critical flaw.

• Liberty Ships
• the Hindenburg
• the Liberty Bell

Q3. The design plot is composed of two intersecting segments: yield strength corresponding to general yielding and fracture toughness corresponding to ______________

• fracture following multiple stress applications
• high-temperature fracture
• flaw-induced fracture

Q4. The design plot shows stress as a function of time.

• True
• False

Q5. The ______________ flaw size is defined within the design plot at the intersection between the general yielding segment and the flaw-induced fracture segment

• critical
• minimum
• maximum

Q6. The I in the subscript of the fracture toughness, K_Ic , refers to ______________ .

• mode I (uniaxial tensile) loading
• “i” for incremental loading
• the primary stage of creep deformatio

Q7. The stress versus strain curve for a sample with a critical pre-existing flaw looks like ______________.

• a regular stress versus strain curve but with a lower value of Y.S.
• a regular stress versus strain curve but with a higher value of Y.S.
• that of a brittle cerami

Q8. The benefit of failure by general yielding is that ______________.

• the plastic deformation serves as an early warning
• the structure does not deform permanently
• the failure occurs quickly

Q9. “Flaw-induced fracture” is also known as “catastrophic fast fracture.”

• True
• False

Quiz 02: Thing 8

Q1. The fatigue strength that is associated with catastrophic failure after a large number of stress cycles is ______________ the yield strength.

• greater than
• less than
• about the same value as

Q2. A metal alloy known to have good ductility is used in the manufacture of a spring in a garage door assembly. The spring breaks catastrophically in its first use, under a load known to correspond to about 2/3 of the alloy’s yield strength. This is a good example of fatigue failure.

• True
• False

Q3. The fatigue curve is a plot of breaking stress versus ______________.

• temperature
• time
• the number of stress cycles

Q4. The “fatigue strength” is defined as the point where the fatigue curve reaches a value of roughly _____________ of the tensile strength.

• 75%
• 10%
• one-fourth to one-half

Q5. Fatigue is the result of a critical flaw built up ______________

• prior to being put into service
• instantly
• after a large number of stress cycles

Q6. The relationship of fatigue to the design plot (introduced in our discussion of fracture toughness) is that we grow the size of a flaw at a relatively low stress until the flaw size reaches the “flaw-induced fracture” segment of the design plot.

• True
• False

Materials Science: 10 Things Every Engineer Should Know Week 05 Quiz Answers

Quiz 01: Thing 9

Q1. We begin by focusing on making things slowly. Phase diagrams are maps that help us track microstructural development during the slow cooling of an alloy. The Sn-Bi phase diagram is an example of a ______________ diagram.

• temperature versus time
• eutectoid
• eutectic

Q2. The phases in a two-phase region of the phase diagram are determined by the adjacent, single phases on either side of that two-phase region

• True
• False

Q3. In the important Fe – Fe₃C (iron carbide) phase diagram, steel making is described by slow cooling through the ______________ reaction

• eutectic
• melting
• eutectoid

Q4. The “pasty” quality of lead solders in the lead-tin system can be attributed to ______________.

• the nature of the two-phase liquid + α solid solution region
• the nature of the two-phase α solid solution + β solid solution region
• the fact that lead has a higher melting point than tin

Q5. Heat treatment can be defined as the time-independent process of producing a desired microstructure.

• True
• False

Q6. Previously (in Thing 2), we saw that diffusion increases as temperature increases. Instability ______________ as temperature decreases.

• increases
• decreases
• stays about the same

Q7. Because of the competition between instability and diffusion, the most rapid transformation will occur _______________.

• at the transformation temperature
• below the transformation temperature
• above the transformation temperatur

Q8. The “knee-shaped” curve of the TTT diagram for eutectoid steel is a good example of the competition between instability and ______________.

• stability
• diffusion
• radioactivity

Q9. As we monitor the TTT diagram for eutectoid steel through the diffusional transformation region, we see that the decreasing magnitude of diffusivity with decreasing temperature leads to ______________.

• increasingly more coarse microstructures
• increasingly finer microstructures
• generally unchanged grain sizes

Q10. As we continue to go to lower temperatures in the TTT diagram for eutectoid steel, the diffusionless transformation to form martensite is the result of ______________.

• the domination of instability
• increasingly rapid atomic mobility
• freezing temperatures

Quiz 02: Ten Things Final

Q1. The first three categories introduced in the opening of the course (metals, polymers, and ceramics) are based on the three types of primary bonding: metallic, covalent, and ____________, respectively.

• ionic
• hydrogen
• van der Waals

Q2. In illustrating the relationship between atomic structure and the elastic modulus or stiffness of a metal (structure leads to properties!), we saw how elastic deformation follows from the stretching of atomic ___________.

• bonds
• weights
• energy

Q3. The _________ plot is a linear set of data points in which the logarithm of rate is plotted against the inverse of absolute temperature in K^-1.

• TTT
• fatigue
• Arrhenius

Q4. In the face centered cubic structure of aluminum, solid-state diffusion occurs by individual aluminum atoms hopping into adjacent interstitial sites

• True
• False

Q5. ___________________ is a linear defect with the Burgers vector perpendicular to the dislocation line.

• An interstitial
• A vacancy
• An edge dislocation

Q6. Consider the body of an automobile made of steel. A small dent in that structure when the automobile is accidentally driven into a barrier is an example of _________ deformation.

• viscous
• elastic
• plastic

Q7. In the tensile test, the yield strength (Y.S.) is found just beyond the linear elastic region (which gives the elastic modulus, E) at an offset of 0.2% strain.

• True
• False

Q8. Beyond the tensile strength (T.S.), the maximum stress value measured over the range of the tensile test, we measure the ductility corresponding to the total amount of ______________ deformation.

• elastic + plastic
• elastic
• plastic

Q9. For high temperature creep deformation in metal alloys, a common mechanism that we illustrated is ______________.

• dislocation climb
• viscous flow (molecules sliding past one another)
• grain boundary sliding

Q10. A powerful use of the Arrhenius relationship is to measure creep data at high temperatures over conveniently short time periods and then extrapolate the data to __________ temperatures, allowing us to predict the performance of the material over long operating times.

• even higher
• cryogenic
• low

Q11. The impact energy is the standard property for monitoring the ductile-to-brittle transition. The impact energy is commonly measured by means of the ______________.

• creep test
• Charpy test
• tensile tes

Q12. Body-centered cubic (bcc) alloys tend to exhibit the ductile-to-brittle transition because they have fewer slip systems than in the ductile face-centered cubic (fcc) alloys.

• True
• False

Q13. The design plot is composed of two intersecting segments: yield strength corresponding to ___________ and fracture toughness corresponding to flaw-induced fracture.

• high-temperature fracture
• general yielding
• fracture following multiple stress applications

Q14. The design plot monitors stress as a function of ______________.

• flaw size, a.
• strain
• time

Q15. A metal alloy known to have good ductility is used in the manufacture of a spring in a garage door assembly. The spring breaks catastrophically after 10 years of regular use, under a load known to correspond to about one half of the alloy’s yield strength. This is a good example of fatigue failure.

• True
• False

Q16. The relationship of fatigue to the design plot (introduced in our discussion of fracture toughness) is that we grow the size of a flaw at a relatively low stress until the flaw size reaches the ______________ segment of the design plot.

• yield stress
• general yielding
• flaw-induced fracture

Q17. Phase diagrams are maps that help us track microstructural development during the slow cooling of an alloy. The Fe-Fe₃C (iron carbide) phase diagram is an example of a ______________ diagram, with special relevance to steelmaking.

• temperature versus time
• eutectoid
• eutectic

Q18. Quenching a eutectoid steel below about 200 °C initiates the formation of martensite because the _______________ the austenite phase has become too great.

• instability of
• specific volume of
• diffusion of carbon within

Q19. Electronic conduction in an _____________ semiconductor is the result of the promotion of an electron from the valence band up to the conduction band across an energy band gap.

• eccentric
• extrinsic
• intrinsic

Q20. Combining the extrinsic behavior with the intrinsic on the Arrhenius plot produces a stable level of conductivity at ______________ temperatures.

• intermediate
• relatively low
• relatively high

Conclusion:

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