Final Exam - Exam I & II & Presentations

Stress and strain are two mechanical variables that are commonly referred to for a material. In general, are they considered properties of a material?
Yes
No

No

To characterize mechanical properties of a material, the following relationships are commonly used:
Force vs. displacement
Force vs. strain
Stress vs. strain
a and c
b and c

c

Linear elastic behavior occurs when
a. load-displacement curve is a straight line
b. the loading and unloading curves follow the same trace
c. (a) and (b)
d. None of the above

c

Viscoelasticity is a term used to describe a material that
a. "stiffening" behavior
b. behavior that depends on the loading rate (or time)
c. exhibit hysteresis
d. (a) and (b)
e. (b) and (c)

e

The Hooke's Law states that
a. The relationship between load and displacement is linear
b. The relationship between stress and strain tensors is linear
c. The relationship between load and displacement under uniaxial loading in a one-dimensional structure is linear
d. (b) and (c)
e. (a) and (b)

d

The design criteria of biomaterials based on structure-function relationship include:
surface properties
biocompatibility
corrosion or wear resistance
rater of degradation
microstructure
mechanical properties

surface properties
biocompatibility
corrosion or wear resistance
rate of degradation
microstructure
mechanical properties

The three key factors that affect the outcome of patients undergoing valve replacement with a prosthetic valve include the following EXCEPT?
Thrombogenicity
Aseptic loosening
Hemodynamics
Durability

b

Biocompatibility is defined as?
Ability of a material to not elicit any host response (ie "inert")
Ability of a material to modulate host reponse
Ability of a material to function with a host response that is appropriate for a specific application
Ability of a material to degrade faster with host response.

c

The first FDA approved cell-based tissue regeneration product is from what tissue?
Cartilage
Brain
Bone
Skin

d

In relation to the evolution of ventricular assist devices (VADs), match the following to their corresponding category:
Second generation LVADs
First generation LVADs
Third generation LVADs

Continuous flow
Pulsatile
Electromagnetic

The conceptual difference between mechanical properties of a device and its material properties can be formulated as follows:
a. Mechanical properties characterize material behavior on the microscale, while material properties describe the overall behavior of the device.
b. Material properties describe the properties on the microscale, while mechanical properties of a structure describe how it will react to the macroscale external loads.
c. There is no difference, the two terms are equivalent.

b

To characterize mechanical properties of a material structure (device), we commonly use the ......... relationship, while to determine material properties the ......... relationship needs to be determined.
a. (Force vs displacement) ..... (Stress vs. strain)
b. (Stress vs. strain) ...... (Force vs displacement)
c. (Force vs displacement) ..... (Force vs. strain)

a

Engineering (Nominal) stress is defined as
a. Load divided by the initial (undeformed) area
b. Load divided by the final (deformed) area
c. Load divided by the average of the deformed and undeformed areas.

a

The concept of Engineering strain does not apply to the 1D uniaxial loading.
a. True
b. False

b

Poisson's ratio is defined as:
a. The ratio of transverse to longitudinal strain
b. The ratio of transverse to longitudinal stress
c. The negative ratio of transverse to longitudinal strain
d. The negative ratio of transverse to longitudinal stress

c

The Hooke's Law states that
a. There is no transverse deformation under uniaxial loading
b. The relationship between stress and strain is linear
c. Both (a) and (b)
d. None of the above

b

Elastic behavior occurs when
a. load-displacement curve is a straight line
b. the loading and unloading curves follow the same trace
c. there is no plastic deformation
d. (b) and (c)
e. (a) and (b)

d

Linear material is defined as:
a. Material with linear relationship between stress and strain
b. Material that exhibits reversible behavior, i.e. material gets back to its original shape and size when external load is removed
c. Material that does not show plastic yielding

a

For an elastic isotropic material, the relationship between Young's modulus and shear modulus is
a. Linear
b. Inverse
c. There is no relationship between the two.

a

The yield point (Yield strength) of a material is determined as
a. The exact point where stress-strain curve becomes non-linear
b. At the point of maximum stress on the engineering stress-strain curve
c. At noticeable (~ 0.2%) plastic strain
d. At breaking point

c

Engineering (Nominal) stress-strain curve is defined as
a. A curve where stress (strain) is normalized by the deformed area (final dimension)
b. A curve where stress (strain) is normalized by the undeformed area (initial dimension)

b

Ductility of the material is determined as
a. A strain at the breaking point.
b. A strain at the breaking point minus the elastic strain (from the linear portion of stress/strain curve).

b

The phenomenon of necking is:
a. A necessary part of any plastic deformation.
b. Can occur only in subset of polymer materials where chains can change orientation under loading.

b

The ultimate tensile strength (UTS) is defined as
a. a stress where stress/strain curve becomes non-linear
b. a stress where material breaks
c. a maximum in the nominal stress versus nominal strain plot

c

For materials that undergo plastic deformation, the onset of necking corresponds to the ultimate tensile strength.
a. True
b. False

a

Resilience is
a. A measure of the elastic energy that can be stored in a unit volume of stressed material
b. Defined as the area underneath a stress(strain) plot
c. (a) and (b)
d. None of the above

c

Resilience is measured in
a. mm (or same units is displacement)
b. Newtons (or same units as load)
c. MPa (or same units as stress)
d. it is dimensionless (same as strain)

c

Fracture toughness determined as a critical stress intensity factor (KIC) of a sharp crack where
a. Small cracks appear in the material
b. Propagation of the crack suddenly becomes rapid and unlimited

b

Repeated loading results in failure at stresses that are
a. Similar to yield stress or ultimate tensile stress
b. Much greater than failure stresses for non-repeated loading
c. Much smaller than failure stresses for non-repeated loading

c

In the term "S-N curve" for Fatigue Strength measurement "S" stands for
a. Amplitude of stress during cyclic loading
b. Average stress during cyclic loading

a

The term definition of "Fatigue Strength" depends on the number of cycles, i.e it is defined as a stress level that will cause failure after a given number of cycles
a. True
b. False

a

For any material that can sustain repeated loading, there is an endurance limit, where S-N graph becomes horizontal
a. True.
b. False.

a

In the expression for thermal expansion, s =E a linear (T0 -Tf), E is
a. A thermal expansion coefficient.
b. Tensile (Young's) modulus of a material.
c. None of the above.

b

The major reason that metals and metal alloys are widely used in biomedical applications is because
a. These materials are easy to process
b. These materials perform well under repeated loading due to their mechanical properties
c. These materials are relatively inexpensive

b

Processing-Structure-Properties-Performance Paradigm for metals and alloys states that
a. Processing affects the material microstructure (i.e. defects, grains, etc) and therefore determines the ultimate performance of the alloy
b. There is no direct relationship between Processing and how device functions, and the device's mechanical properties (strength) are largely determined by its composition.

a

Strength of an alloy can be increased by
a. Processing that increases the density of dislocations in the alloy
b. Processing that decreases the density of dislocations in the alloy
c. None of the above.

a

Strength of an alloy can be increased by
a. Processing that increases the grain boundary area within a volume of metal (i.e. smaller grain size)
b. Processing that decreases the grain boundary area within a volume of metal (i.e. larger grain size).
c. None of the above.

a

Viscoelastic materials are the materials that
a. Possesses time- (or rate-) dependent behavior
b. Made of solid components that follow Hooke's law and fluidic components that follow Newton's law
c. Both (a) and (b)
d. None of the above

c

Load-displacement or stress-strain relationships of viscoelastic materials are
a. Always nonlinear
b. Can be linear

a

Stress relaxation of viscoelastic material is when
a. Stress decays under a fixed constant strain condition
b. Stress increases under a fixed constant strain condition

a

Creep response of a polymeric material involves ...... deformation of a sample under constant load
a. Plastic
b. Elastic
c. Both plastic and elastic

a/c

During stress relaxation of a viscoelastic material, the strain is
a. Decreasing.
b. Constant.
c. Increasing

b

Elastic component of the deformation of polymeric viscoelastic materials described using a
a. Dashpot with viscosity h
b. Spring with modulus E
c. A combination of (a) and (b)
d. None of the above.

b

In the ideal liquid approximation of the viscous behavior (Newton's law), the applied stress is
a. Directly proportional to strain
b. Directly proportional to deformation
c. Directly proportional to strain rate
d. None of the above.

c

Which of the models predicts instantaneous strain upon stepwise application of stress?
a. Maxwell model (spring and dashpot are in series)
b. Voight model (spring and dashpot are parallel).

a

Which of the models predicts exponential stress relaxation upon constant strain application?
a. Voight model (spring and dashpot are parallel).
b. Maxwell model (spring and dashpot are in series)

b

Voight model (spring and dashpot are parallel) predicts that following stepwise stress application,
a. Strain will exponentially increase
b. Strain will remain constant
c. Strain will linearly increase.

a

During stress relaxation of a viscoelastic material, the strain is
a. Decreasing.
b. Constant.
c. Increasing.

b

A standard linear solid model predicts the following behavior upon stress application:
a. Instantaneous elastic strain
b. Linear increase in strain

a

The constitutive equitation for a viscoelastic model is a relationship between
a. Stress and strain
b. Stress rate and strain rate
c. Both (a) and (b)

c

For the Kelvin-Voight model (spring and dashpot are parallel) the following is true:
a. The total stress is the sum of stresses on spring and dashpot
b. The total stress is equal to individual stresses on spring and dashpot
c. (a) and (b)
d. None of the above.

a

For the Maxwell model (spring and dashpot are in series) the following is true:
a. The individual strains of spring and dashpot are the same and are equal to the total strain
b. The total strain is the sum of strains of spring and dashpot
c. (a) and (b)
d. None of the above.

b

For the Kelvin-Voight model (spring and dashpot are parallel) compatibility equation(s) are that
a. The individual strains of spring and dashpot are the same and are equal to the total strain
b. The total strain is equal to the sum of strains on spring and dashpot
c. (a) and (b)
d. None of the above.

a

For the Maxwell model (spring and dashpot are in series) the following is true:
a. The total stress is equal to individual stresses on spring and dashpot
b. The total strain is the sum of strains on spring and dashpot
c. (a) and (b)
d. None of the above.

c

For polymers, the major molecular characteristics that are directly related to the physical and chemical properties are:
a. molecular mass
b. molecular architecture,
c. (a) and (b)
d. None of the above

c

Tacticity describes
a. the stereochemistry (3D orientation) of the repeat units in polymer chains
b. the number of repeat units per unit length of polymeric backbone
c. the number of monomer repeat units in each polymer chain

a

Degree of polymerization is
a. The number of network connections per unit polymer backbone
b. the number of repeat units per unit length of polymeric backbone
c. the number of monomer repeat units in each branch

b

When describing a polymer system, one should use the following parameter(s):
a. A specific value for the molecular mass of a polymer system
b. An average value of the molecular mass of a polymer system
c. Either (a) or (b), they are interchangeable

b

The most commonly used average for the molecular mass of polymer systems is
a. The number average molecular mass (Mn)
b. The weight average molecular weight (Mw)
c. Both (a) and (b)
d. None of the above

c

Which of the following is true for the the molecular mass distribution (Ðm=Mw/Mn),
a. Dm > 1 for most cases
b. Dm < 1 for most cases
c. Dm characterizes the breadth of the chain length populations.
d. (a) and (c)
e. (b) and (c)

d

Polymer materials are held together by
a. Covalent bonds
b. Secondary interactions, such as van der Waals forces, and hydrogen bonding

b

The physical properties of a polymer mainly stem from
a. the intermolecular interactions occurring between individual polymer molecules
b. strength of the backbone of the individual polymer molecules

a

Individual chain architecture or composition does not significantly affect the physical behavior of a polymer
a. True
b. False

b

All polymers display the following behavior with increasing temperature:
a. Undergo glass transition at T=Tg
b. Undergo melting transition at T=Tm
c. Become viscous fluid above Tm
d. (a) and (b) only
e. (a) and (c) only

a

Increase in difficulty of polymer side chains rotation due to steric hindrances results in
a. Increase in Tg
b. Decrease in Tg

a

Decrease in side chain polarity (easier side chain 3D movement and rearrangement) results in
a. Increase in Tg
b. Decrease in Tg

b

Which of the ECM elements' major function to provide structural support for the tissues (choose all that apply):
a. Proteoglycans
b. Collagen
c. Fibronectin
d. Laminin

b/d

Biocompatibility is mostly determined by
a. the bulk composition and properties of the biomaterial.
b. surface properties of biomaterial
c. a layer of absorbed material at the surface
d. a and b
e. b and c

e

The advantages of Radio Frequency Glow Discharge Plasma Treatment include:
a. well-defined surface chemistry after treatment
b. no need for high pressure or high temperature
c. conforms to sample shape
d. b and c
e. a and c

d

If biomaterial is placed in the body, a common thickness of an absorbed protein layer is
a. ~ 10 um
b. ~ 10 nm
c. ~ 1 mm

b

For the Langmuir-Blodgett (LB) deposition, it is essential that
a. head group could covalently bind to the biomaterial surface.
b. each of the molecules that assemble into this layer contains a polar "head" group and a nonpolar "tail" group.

b

AFM can provide the following characterization of the biomaterial surface:
a. topographical map (roughness)
b. chemical composition up to several nm deep
c. both a and b

a

The main advantage of the surface modification using self-assembled monolayers (SAMs) process is that
a. it imitates lipid bilayer structure of the cell membrane
b. it provides a very stable coating due to anchor group covalent interactions with the surface
c. it does not require any functional end groups

b

SEM sample preparation requires sample sputter coating with conductive material.
a. true
b. false

a

What surface properties influence protein absorption?
a. roughness
b. surface charge
c. hydrophobicity
d. all of the above

d

The Secondary Ion Mass Spectrometry (SIMS) is used to obtain
a. chemical composition of the biomaterial uppermost layer
b. depth profiling of the chemical composition of the biomaterial
c. modification of the surface using a known chemical element
d. a and b
e. a and c

d

During the dynamic SIMS analysis, the obtained spectrum of trace elements
a. changes with time
b. remains constant with time

a

Oxidation is a process when
a. water destroys secondary bonds in the polymer
b. free radicals attack covalent bonds

b

During host-induced oxidative biodegradation, stress cracking
a. is caused by tensile stresses, similar to brittle cracking
b. is cause by chemical changes within the polymer

b

During the bulk biodegradation:
a. the rate of polymer hydrolysis is similar to the rate of water diffusion into the polymer
b. the rate of polymer hydrolysis is faster than the rate of water diffusion into the polymer
c. the rate of polymer hydrolysis is slower than the rate of water diffusion into the polymer.

c

Hydrolysis and enzymatic degradation are examples of a process when
a. material's secondary bonds are destroyed
b. material's primary bonds are destroyed

b

During corrosion of metals, the formation of oxidation film on the surface is accompanied by
a. formation of hydroxide ions and other reactive oxygen species at that surface
b. addition of electrons near that surface
c. loss of electrons near that surface

c

Ceramic materials with predominantly covalent bonding are mostly...
a. bioinert
b. bioactive
c. resorbable

a

Rate of hydrolysis is NOT influenced by material's crystallinity
a. false
b. true

a

Because ceramic materials are hard and have high melting temperatures, their degradation is not affected by crystallinity
a. true
b. false

b

"Bioresorbable biomaterial" means that
a. it can degrade in the body into raw materials
b. its degradation products can be metabolized by the body
c. it must be susceptible to enzymatic degradation

b

An example of oxidation process is when
a. ester side chain interactions are modified by altering pH
b. covalent bonds are destroyed by free radicals
c. ester side chains are cut by reactive oxygen species

b

Innate Immune System provides a
a. pathogen-specific long-term response to foreign organisms
b. non-specific first-responder response to injury and/or pathogens

b

The function of Major Histocompatibility Complex (MHC class I) is to
a. display intracellular proteins that are generated in the cytosol on the surface of that cell
b. provide a recognition marker for immune cells not to destroy a particular cell
c. a and b

c

A cytokine storm is
a. an uncontrolled inflammatory cytokine releases when immune system is hyperactivated
b. a necessary part of inflammatory response to any foreign organism
c. a and b

a

The following is (are) a true statement(s) about macrophages
a. macrophages are differentiated from monocytes
b. macrophages are phagocytes
c. macrophages contain granules with enzymes that are released during infections and allergic reactions
d. a and b
e. a and c

d

The first cells that come to the site of injury are
a. monocytes
b. neutrophils
c. macrophages

b

The following is (are) a true statement(s) about neutrophils
a. neutrophils contain granules with antimicrobials that are released during response to infections
b. neutrophils are phagocytes
c. neutrophils differentiate from monocytes at the site of injury
d. a and b
e. a and c

d

Surface epithelia provide the following barriers to infection: mechanical, chemical, and microbiological barriers to infection
a. mechanical
b. chemical
c. electrical
d. a and b
e. a, b, and c

d

Reactive Oxidative Species produced by immune cells can
a. cause corrosion
b. kill pathogens
c. a and b
d. none of the above

c

The major function of M1 macrophages is to
a. promote tissue regeneration and healing
b. increase inflammation
c. reduce inflammation

b

Macrophages have specific surface receptors that enable them to bind microbes during phagocytosis
a. true
b. false

a

Flow cytometry technique for white blood cell sorting
a. all white blood cells have a common antigen
b. cells of each type have a specific antigen

b

What size particles are not likely to be phagocytosed:
a. > 5 micrometers
b. < 5 micrometers
c. > 5 nanometers

a

Natural Killer T-cells work by
a. phagocytosing foreign cells
b. releasing granules causing apoptosis of foreign cells
c. both a and b

b