Quiz 3 Flashcards by Kate Reardon

True or false: a solute can diffuse when placed in a liquid solvent, but a solute cannot diffuse when it is in a solid solvent.

False

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What is the key difference between bulk flow of a material and diffusion flow of a material?

the cause of matter flow
the medium through which matter flows
there is no difference, both involve flow of matter
the rate of matter flow

the cause of matter flow

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What causes flow of matter by diffusion?

concentration difference
concentration gradient
electrical potential difference
none of the choices listed
mechanical pressure difference

concentration gradient

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From a thermodynamic perspective, diffusion is driven by (fill in the blank)

none of the choices listed
Hume-Rothery gradient
Gibb’s free energy gradient
concentration difference
Hall-Petch gradient
concentration gradient

Gibb’s free energy gradient

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The Gibbs free energy gradient is the primary driver of diffusion, but what is meant by the Gibbs free energy gradient?

maximum mechanical work that can be performed
maximum reversible work that can be done by a system at constant T and P
maximum non-reversible work that can be done by a system at constant T and P
average available mechanical work that can be performed
available mechanical work that can be performed

maximum reversible work that can be done by a system at constant T and P

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The change in Gibbs free energy is equal to the:

work done by the system to its surroundings minus the work of the pressure forces
work done on the system by the surroundings plus the work of the pressure forces
work done on the system by the surroundings minus the work of the pressure forces
total energy of the system

work done by the system to its surroundings minus the work of the pressure forces

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Materials engineers consider Gibbs free energy to predict the direction of a reaction if two conditions are specified. These conditions are:

diffusivity
pressure
concentration
charge
temperature
stress
strain

pressure and temperature

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If the Gibbs free energy of a process is determined to be positive, then the reaction will (fill in the blank)

occur after energy is removed from the system
occur spontaneously
occur after the system is removed
occur after material is removed from the system
not occur spontaneously

not occur spontaneously

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Materials engineers understand that much of what they do is based on numerous fundamental scientific processes. Many of these fundamental processes are quantitatively described by an Arrhenius relationship. Which of the equations listed below best describe the Arrhenius relationship?

Y = Ax + B
Y = 1/2 (mv^2)
Y = mc^2
Y = mgh
Y = A exp (-B/KT)
Y = A log (B/KT)
Y = Ax^2 + Bx + C

Y = A exp (-B/KT)

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IF a materials engineer needs to quantify a given process described by an Arrhenius equation of the form Y = C exp (-B/RT), an efficient means of conducting such experimentation involves performing how many experimental tests to get the first preliminary estimate for B?

50
2
10
6
20
12

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THe materials engineer who seeks to quantify a given process described by an Arrhenius equation of the form Y = C exp (-B/RT) and performs just 2 experiments can get information about the values of the constants C and B in this equation by (fill in the blank)

performing a t-test since there are only 2 samples involved
using artificial intelligence analyses
another method not listed
curve fitting and plotting the results
taking logs and plotting the results
using linear regression analysis to plot a straight line

taking logs and plotting the results

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THe materials engineer quantifies a given process described by the expression Y = C exp (-B/RT) and performs just 2 experiments and then plots the natural logs of the resulting data may obtain which of the following parameters:

the universal gas constant R
the rate of the reaction
the value of C
the diffusion of solute at the given time
the activation energy of the system abbreviated in your text as Q (here B)
the number of moles reacting in the system

the value of C
the activation energy of the system abbreviated in your text as Q (here B)

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The Maxwell-Boltzmann Distribution specifies the (fill in the blank) of finding a molecule at an energy delta-E greater than the average energy of particles at a particular (fill in the blank).

probability, temperature
probability, concentration
range, temperature
ability, temperature
range, concentration
ability, concentration

probability, temperature

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True or False: The form of the Maxwell-Boltzmann Distribution follows an Arrhenius type relationship.

True

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The Maxwell-Boltzmann Distribution shows the probability of finding a molecule at an energy delta-E greater than the average energy of particles at a particular temperature T. What fundamentally occurs as T increases according to this relationship?

a larger number of particles are available to overcome a given energy barrier q
a greater amount of diffusion occurs
a smaller number of particles are present
a larger number of particles rearrange their crystal structure
a larger concentration of particles exist

a larger number of particles are available to overcome a given energy barrier q

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When a process can be described by an Arrhenius relationship, if you know the activation energy, then you can find the (fill in the blank)

available Gibbs free energy
species reacting
process
concentration
temperature

process

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What conclusion would you draw if you know that multiple processes are occurring simultaneously, each with its own activation energy, but one of these activation energies is representative of the observed experimental data.

a single process is dominant
the experiment should be repeated
there’s really only one process occurring
the experimental data should be analyzed by a statistician
the experimental measurements are imprecise

a single process is dominant

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Which of the following causes point defects in crystals?

chemical concentration differences
stress-induced vibration
mechanical vibration
strain-induced vibration
thermal vibration

thermal vibration

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When your lab assistant tells you the temperature of a given material is T, what does this mean?

the upper limit of temperature of molecules in the material have temperature T, others have lower temperature
all molecules in the material have the same temperature
the lower limit of temperature of molecules in the material have temperature T, others have greater temperature
the average temperature of the molecules in the material have temperature T
the temperature of the molecules in the material is given by the root mean square value of T as obtained from a log-log plot

the average temperature of the molecules in the material have temperature T

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What do these two curves (one at T1; the other at T2) show?
Maxwell-Boltzmann distribution
standard normal distribution
bell curve distribution
Hume-Rothery distribution
normal distribution
Komolgorov-Smirnov distribution

Maxwell-Boltzmann distribution

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Which of the factors listed is most closely associated with increasing the probability of generating point defects in a crystal material?

increasing coordination number
increasing pressure
increasing temperature
increasing number of valence electrons
increasing atomic number

increasing temperature

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Compared to liquids, the activation energy required for diffusion in solids is:

cannot discern without additional information
less
greater
equal

greater

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Point defects in crystals are important for diffusion because they enable the mechanism of (fill in the blank):

lattice movement
larger defects
vagrancy mitigation
more defects
vacancy migration

vacancy migration

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Vacancy migration is an important mechanism by which diffusion can occur because these vacancies (fill in the blank)

facilitate diffusion
modify the activation energy
reduce the activation energy for diffusion
activate the crystal structure

reduce the activation energy for diffusion

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What is the basis for development of the equations of diffusion? law of conservation of energy law of conservation of mass Law of conservation of momentum Newton's laws of molecular motion

law of conservation of mass

The Law of Conservation of Mass is central to the development of diffusion relationships. This law states that the total mass of the products must always equal the (fill in the blank) total mass of the reactants total mass plus energy input of the reactants total mass of the system total mass of the endpoints

total mass of the reactants

What is this equation (fill in the blank) and why is it important? [upside down triangle]*J = -(delta rho sub v)/(delta t) continuity equation: basis for diffusion equations Ficks 1st law; basis for diffusion equations continuity equation; fundamental law of physics Conservation of Mass equation: basis for diffusion equations Fick's second law; culmination of Fick's work on diffusion

continuity equation: basis for diffusion equations

What are the units of flux of matter? molecules per area molecules per cm^3 per second moles per second atoms per volume per second molecules per second moles per cm^2 per second moles per area

moles per cm^2 per second

Differentiating Fick's 1st law with respect to distance, and then substituting the result into the continuity equation produces: random walk equation Fick's second law matter flow equation Arrhenius equation Newton's third law Fick's third law

Fick's second law

Fick's second law can be obtained two ways: one way is to differentiate Fick's first law by distance, then substitute into the continuity equation. A second, totally independent method, is to use the (fill in the blank) approach to quantify the motion of an atom along one dimension. binomial statistical normal distribution random walk Stirling

random walk

The "random walk" nature of atomic species migration in a crystal can be understood using a (fill in the blank) mechanism slip plane valence electron interstitial random motion

interstitial

While the random walk approach to quantifying diffusion of atoms in solids is complex, it offers a significant benefit not found in Fick's approach to quantifying diffusion of atoms in solids. What information can the materials engineer obtain from the diffusion coefficient D using the random walk approach that Fick's approach cannot offer? minimum depth of diffusion versus time mean distance between collisions and mean time between collisions average depth of diffusion versus time maximum depth of diffusion

mean distance between collisions and mean time between collisions

Diffusivity depends on temperature according to a (fill in the blank) relationship natural log exponential quadratic log base 10

exponential

Which equation best expresses the diffusivity of an atom in a medium? D = Constant X exp (kT/q) D = Constant X exp (-T/kq) D = 1/distance into the surface D = Constant X exp (q/kT) D = Constant X exp (-q/kT) D = velocity X time

D = Constant X exp (-q/kT)

Diffusion of C in Fe occurs via an interstitial mechanism more (fill in the blank) in (fill in the blank) structure compared to (fill in the blank) structure easily, FCC, BCC slowly, HCP, BCC quickly, FCC, BCC easily, HCP, BCC easily, BCC FCC

easily, BCC FCC

True or False: Self-diffusion of a atom located in the grain boundary of a crystalline material is less than diffusion of the same atom located inside the crystal.

False

True or False: It's always best to use the engineering convention employing 3 mutually orthogonal coordinates (X, Y and Z axes) to calculate the diffusion of a solute in a solid material.

False

What is point 1 referring to in the figure below? actual yield point relative yield point modulus stiffness strength

actual yield point

On an atomic basis, which events occur at the yield point? Choose all that apply. Image 1 crystal transformation rearrangement of atoms vibration of crystal planes nonrecoverable deformation after this point slip of atomic planes change from elastic to plastic deformation

rearrangement of atoms nonrecoverable deformation after this point slip of atomic planes change from elastic to plastic deformation

What does point 2 on the figure shown below most likely represent? Image 1 resilience offset yield point modulus actual strength actual yield point toughness

offset yield point

Why do engineers use an offset yield point? the actual yield point is incorrect it's more representative it's easier to identify it's faster to measure

it's easier to identify

The offset yield point, while not the "actual" yield point, is used because it's easier to measure reproducibly. Which of the values listed below are most commonly used for the offset yield point? 20% none of the values listed 0.02% 0.002% 0.2% 2%

0.2%

What does point 5 on the figure shown below represent? Image 1 toughness modulus stiffness resilience complex yield point strength

strength

Which of the points on the figure shown below are most useful for calculating Young's (fill in the blank)? Image 1 stiffness, B stiffness, 5 strength, 4 strength, 3 yield, 2 modulus, 1

modulus, 1

Which of the points on the figure below are most useful for calculating the material's toughness? Image 1 B 3 1 none of the choices listed 5 2 4

Which of the points on the figure below are most useful for calculating stiffness? Image 1 2 5 1 4 none of the choices listed B 3

none of the choices listed

Referring to the figure shown below, is the stress-strain curve illustrated most likely determined using true strain or engineering strain? Image 1 I have no idea Who knows true strain engineering strain

engineering strain

Engineering strain is calculated using the (fill in the blank) whereas true strain is calculated using the (fill in the blank) initial specimen area, actual specimen area none of the choices listed modulus, stiffness actual specimen area, initial specimen area ending specimen area, beginning specimen area

initial specimen area, actual specimen area

Material toughness is represented by the (fill in the blank) specimen length at maximum stress slope of stress strain curve at the origin area under the stress-strain curve at failure specimen length at failure area under the stress-strain curve at the maximum stress area under the stress-strain curve at the yield point slope of the stress strain curve at maximum

area under the stress-strain curve at failure

What's the key structural feature at the basis of the process of strain hardening? point defects burger's vector dislocations impurity atom addition precipitation of atoms

dislocations

What is the Poisson ratio? ratio of lateral vs longitudinal deformation none of the choices listed ratio of stress to strain ratio of left vs. right side deformation ratio of medial vs. lateral deformation

ratio of lateral vs longitudinal deformation

True or False: Tensile test results of a material can be useful to the biomedical engineer to help provide information about diseases in human tissue.

True

Human tissue is often anisotropic, thus the (fill in the blank) of mechanical testing must be specified. rate humidity none of the choices listed temperature direction

direction

Human tissue is often viscoelastic, thus the (fill in the blank) of mechanical testing must be specified. none of the choices listed humidity rate direction temperature

humidity

A biomedical engineer is asked to choose among various mechanical test modalities to quantify the mechanical response of human tissue. The supervisor informs said biomedical engineer of organizational test capabilities. These capabilities include tensile, compressive, bending and shear tests. The supervisor asks the biomedical engineer to highlight the advantages and disadvantages of each test. What might this engineer comment regarding the pros or cons of tensile vs compressive testing? pro: tensile is easier to perform con: tensile testing is irrelevant con: compressive testing is irrelevant pro: tensile is more difficult to perform

pro: tensile is easier to perform

A biomedical engineer is asked to choose among various mechanical test modalities to quantify the mechanical response of human tissue. The supervisor informs said biomedical engineer of organizational test capabilities. These capabilities include tensile, compressive, bending and shear tests. The supervisor asks the biomedical engineer to highlight the advantages and disadvantages of each test. What might this engineer comment regarding the pros or cons of bending tests to evaluate material performance? con: bending may be difficult to interpret con: bending is easy to perform pro: bending is difficult to perform bending is irrelevant

con: bending may be difficult to interpret

A crack forms in a metal. The metal is stressed repeatedly and the crack grows to 4 times the original length. Assuming all other factors remain constant, according to the Griffin Crack Model, by how much does the critical stress to propagate the crack change as a result of this crack enlargement? 1/16 as large as before 1/32 as large as before 1/2 as large as before 1/4 as large as before Griffin Crack theory does not indicate 1/8 as large as before

1/2 as large as before

A crack forms in a metal. The metal is stressed repeatedly and the crack grows to 4 times the original length. If the crack is detected and then a large (compared to crack tip radius) hole is drilled at the tip of the crack, what will happen to the maximum stress at the tip of the crack? can't answer this question based on Griffin crack theory become smaller stay the same get larger

become smaller

List all factors noted below the biomedical engineer must control when mechanically testing a freshly harvested human tissue sample. temperature humidity or fluid environment strain rate load applied means of holding the specimen

temperature humidity or fluid environment strain rate load applied means of holding the specimen

Plastic deformation of a metal is easier if the crystal structure of the metal has (fill in the blank) greater distances between atoms low atomic density larger atoms high atomic density

high atomic density

What are all of the means by which engineers can harden a metal? heat & quench the material work the material precipitation of atoms anneal the material normalize the material

heat & quench the material work the material precipitation of atoms

What's "dislocation climb"? a means by which dislocations rearrange themselves a means by which material can recover energy input to the material a means by which material can plastically deform a means by which a material can elastically deform

a means by which material can plastically deform

Material creep can be quantified using a (fill in the blank) relationship logarithmic linear Arrhenius Hall-Petch quadratic

Arrhenius

Modulus and strength are not the only important metrics of material performance. Toughness is used to measure the energy required to fracture a material. The empirical test used to quantify toughness of a metal is the (fill in the blank) shear test Charpy test tensile test none of the choices listed Izod test

Charpy test

What is the empirical test used to quantify the toughness of a polymer? none of the choices listed Izod test Charpy test tensile test shear test

Izod test

Impact testing provides a means of quantifying material toughness using a standardized protocol. Why is knowledge of crystal structure important for understanding the results of Charpy impact testing? BCC metals behave differently than FCC or HCP metals FCC metals behave differently than BCC or HCP metals none of the choices listed HCP metals behave differently than BCC or FCC metals

BCC metals behave differently than FCC or HCP metals

What are the reasons why BCC metals behave differently in impact testing compared to FCC or HCP metals? BCC metals are not impact test temperature sensitive slip in BCC metals occurs on non-close packed planes it's all about where slip occurs in these structures slip in BCC metals occurs on close packed planes BCC metals are temperature sensitive in impact testing

slip in BCC metals occurs on non-close packed planes it's all about where slip occurs in these structures BCC metals are temperature sensitive in impact testing

Why must engineers be mindful of the ductile-brittle transformation temperature of metals involved in design? D-B temperature is not of interest to engineers, only material scientists D-B transition marks a large change in material properties D-B temperature is of academic interest D-B transition marks a small change in material properties

D-B transition marks a large change in material properties

Which of the responses listed best describes the effect of transformation toughening? squeezes crack tips closed lengthens cracks causes cracks to meet at 90 degrees thus blunting crack advance increases radius of crack tip

squeezes crack tips closed

Transformation toughening blunts the advance of cracks by adding compressive stresses to the crack tip (in a sense, it "squeezes them closed"). What is the basic mechanism for this compressive process? phase transformation solute precipitation none of the choices listed D-B transformation change of unit cell structure

phase transformation

The Griffin theory of brittle fracture postulates a relationship linking the critical stress required for crack propagation and several other parameters. Which material parameters are included in this model? surface energy modulus stiffness material damage (i.e. crack length) strength toughness

surface energy modulus material damage (i.e. crack length)

According to the Griffin theory, which type of crack lowers the critical stress required for crack propagation more - surface crack or internal crack? none of the choices listed surface neither, both are equal in their ability to reduce the critical stress required for crack propagation internal

surface

What is material fatigue? a mechanism of material failure a compressive test failure mechanism a mechanism for applying a single strain of given magnitude a tensile test failure mechanism

a mechanism of material failure

True or False: Materials can fail at stress levels much less than their rated strength as determined from quasi-static loading to failure testing.

True

Which of the following numbers (units of MPa) best describes the endurance limit for the Fe-based material indicated in the figure below? Image 2 150 175 375 325 125 475

325

Considering the figure shown below, approximately how many loading cycles will be required to cause fatigue failure in the Fe-based alloy? image 2 1 quadrillion 1 trillion 1 million 1 billion infinite

infinite

True or False: Ceramic materials, like metals, can fatigue only by application of repeated mechanical stress.

False

Which of the following are used for nondestructive testing of metals? X-rays visual magnetics ultrasound

X-rays visual magnetics ultrasound

Which of the following are known failure modes? brittle fracture liquid-metal embrittlement corrosion-induced fracture fatigue fracture H-embrittlement ductile fracture complex (2 or more mechanisms operating simultaneously) failures creep failure

brittle fracture liquid-metal embrittlement corrosion-induced fracture fatigue fracture H-embrittlement ductile fracture complex (2 or more mechanisms operating simultaneously) failures creep failure