Quiz 3 Flashcards
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
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
What causes flow of matter by diffusion?
concentration difference
concentration gradient
electrical potential difference
none of the choices listed
mechanical pressure difference
concentration gradient
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
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
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
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
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
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)
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
2
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
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)
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
True or False: The form of the Maxwell-Boltzmann Distribution follows an Arrhenius type relationship.
True
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
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
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
Which of the following causes point defects in crystals?
chemical concentration differences
stress-induced vibration
mechanical vibration
strain-induced vibration
thermal vibration
thermal vibration
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
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
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
Compared to liquids, the activation energy required for diffusion in solids is:
cannot discern without additional information
less
greater
equal
greater
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
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
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
B
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
