Q.1 What does the term 'Young's modulus' represent for a biomaterial?
The material's resistance to fracture under compressive load
The ratio of stress to strain in the elastic region
The material's ability to conduct electricity
The amount of permanent deformation after loading
Explanation - Young's modulus is defined as the slope of the stress‑strain curve in the linear elastic region, indicating stiffness.
Correct answer is: The ratio of stress to strain in the elastic region
Q.2 Which mechanical property is most critical for a bone scaffold used in load‑bearing applications?
Hardness
Tensile strength
Elastic modulus similar to cortical bone
Electrical conductivity
Explanation - A scaffold must match the stiffness of native bone to avoid stress shielding and ensure proper load transfer.
Correct answer is: Elastic modulus similar to cortical bone
Q.3 Creep in a biomaterial refers to:
Rapid fracture under sudden impact
Time‑dependent increase in strain under constant stress
Loss of electrical conductivity over time
Increase in hardness with repeated loading
Explanation - Creep is the gradual deformation of a material when it is subjected to a sustained load over time.
Correct answer is: Time‑dependent increase in strain under constant stress
Q.4 Which of the following biomaterials typically exhibits a viscoelastic response?
Stainless steel
Polylactic acid (PLA)
Hydrogel
Silicon carbide
Explanation - Hydrogels have both viscous and elastic components, leading to time‑dependent deformation.
Correct answer is: Hydrogel
Q.5 The Poisson's ratio of a material is defined as:
The ratio of tensile strength to compressive strength
The ratio of lateral strain to axial strain
The ratio of stress to strain at failure
The ratio of electrical resistance to conductivity
Explanation - Poisson's ratio describes how much a material contracts laterally when stretched longitudinally.
Correct answer is: The ratio of lateral strain to axial strain
Q.6 Which mechanical test is primarily used to determine the fracture toughness of a ceramic biomaterial?
Three‑point bending test
Hardness test
Tensile test
Dynamic mechanical analysis
Explanation - Fracture toughness of brittle ceramics is often measured using a notched three‑point bending specimen.
Correct answer is: Three‑point bending test
Q.7 A biomaterial with a high fatigue limit is desirable for which application?
Temporary wound dressings
Long‑term dental implants
Short‑term drug delivery particles
Non‑load‑bearing tissue scaffolds
Explanation - Dental implants undergo repeated loading; a high fatigue limit ensures durability over many cycles.
Correct answer is: Long‑term dental implants
Q.8 Which property best describes a material's resistance to surface indentation?
Tensile strength
Hardness
Elastic modulus
Ductility
Explanation - Hardness measures a material's resistance to localized plastic deformation, such as indentation.
Correct answer is: Hardness
Q.9 Piezoelectric biomaterials are useful in bone tissue engineering because they:
Provide electrical stimulation under mechanical loading
Are highly conductive to ions
Have the highest tensile strength among polymers
Degrade rapidly in physiological conditions
Explanation - Mechanical deformation of piezoelectric materials generates electric charges that can stimulate cellular activity.
Correct answer is: Provide electrical stimulation under mechanical loading
Q.10 Which of the following is NOT a typical failure mode for metallic biomaterials used in implants?
Corrosion fatigue
Brittle fracture
Creep rupture
Viscoelastic flow
Explanation - Metals do not exhibit viscoelastic flow; this behavior is characteristic of polymers and gels.
Correct answer is: Viscoelastic flow
Q.11 The term 'stress shielding' in orthopedic implants refers to:
Excessive stress on surrounding bone due to a stiff implant
Reduced load transfer to bone because the implant is too stiff
Electrical shielding of nerve signals
Thermal shielding during surgery
Explanation - A high‑modulus implant carries most of the load, causing bone resorption due to lack of mechanical stimulus.
Correct answer is: Reduced load transfer to bone because the implant is too stiff
Q.12 In a stress‑strain curve, the point where the material transitions from elastic to plastic deformation is called:
Yield point
Ultimate tensile strength
Fracture point
Modulus of resilience
Explanation - The yield point marks the onset of permanent (plastic) deformation.
Correct answer is: Yield point
Q.13 For a polymeric scaffold, which property is most directly related to its ability to support cell infiltration?
Tensile strength
Porosity
Electrical conductivity
Thermal expansion coefficient
Explanation - High porosity provides pathways for cells to migrate and proliferate within the scaffold.
Correct answer is: Porosity
Q.14 The term 'brittle fracture' is best described as:
A slow, ductile deformation before failure
A rapid crack propagation with little plastic deformation
A failure accompanied by large elongation
A failure that occurs only at high temperatures
Explanation - Brittle fracture occurs with little to no plastic deformation and a sudden crack propagation.
Correct answer is: A rapid crack propagation with little plastic deformation
Q.15 Which mechanical property is most important for a cardiovascular stent?
High compressive strength
Low elastic modulus
Adequate radial strength
High hardness
Explanation - Stents must resist collapsing under blood pressure, requiring sufficient radial strength.
Correct answer is: Adequate radial strength
Q.16 Dynamic Mechanical Analysis (DMA) is used to measure:
Electrical resistance
Viscoelastic properties as a function of temperature or frequency
Hardness
Corrosion rate
Explanation - DMA applies oscillatory loads to characterize storage modulus, loss modulus, and damping behavior.
Correct answer is: Viscoelastic properties as a function of temperature or frequency
Q.17 A biomaterial with a high coefficient of thermal expansion (CTE) may cause problems when implanted because:
It will become too rigid at body temperature
It may expand more than surrounding tissue, causing stress
It will lose its electrical conductivity
It will become brittle
Explanation - Mismatched CTE can lead to thermal stresses during temperature changes, potentially damaging tissue.
Correct answer is: It may expand more than surrounding tissue, causing stress
Q.18 In the context of biomaterials, the term 'biocompatibility' primarily concerns:
Mechanical strength
Electrical conductivity
The material's ability to perform its function without eliciting adverse reactions
The material's magnetic properties
Explanation - Biocompatibility assesses the interaction between the material and biological environment.
Correct answer is: The material's ability to perform its function without eliciting adverse reactions
Q.19 Which of the following is a common method to increase the fatigue life of a metallic orthopedic implant?
Heat treating to relieve residual stresses
Adding large pores to the surface
Coating with a brittle ceramic
Reducing the alloy's elastic modulus below that of bone
Explanation - Proper heat treatment reduces residual stresses that can act as fatigue crack initiation sites.
Correct answer is: Heat treating to relieve residual stresses
Q.20 The term 'strain rate sensitivity' describes:
The change in material stiffness with temperature
The variation of stress response with the speed of applied deformation
The material's ability to conduct electricity under load
The change in hardness after repeated loading
Explanation - Strain rate sensitivity indicates how material strength changes with the rate at which strain is applied.
Correct answer is: The variation of stress response with the speed of applied deformation
Q.21 Which mechanical property would you prioritize for a soft tissue replacement such as an artificial ligament?
High tensile strength and moderate elasticity
Very high hardness
Low compressive strength
High electrical conductivity
Explanation - Ligaments experience tensile loads; thus, a combination of strength and appropriate elasticity is essential.
Correct answer is: High tensile strength and moderate elasticity
Q.22 When a material exhibits a 'stress‑strain curve' with a large area under the curve before failure, it indicates:
High toughness
Low ductility
High brittleness
Low modulus
Explanation - The area under the stress‑strain curve represents the energy absorbed before fracture, i.e., toughness.
Correct answer is: High toughness
Q.23 Which of the following biomaterials is known for its piezoelectric property useful in bone regeneration?
Hydroxyapatite
Polyvinyl alcohol
Barium titanate
Polylactic acid
Explanation - Barium titanate is a ceramic with strong piezoelectric behavior, stimulating bone cells under mechanical load.
Correct answer is: Barium titanate
Q.24 The term 'modulus of resilience' refers to:
The maximum stress a material can withstand before yielding
The energy per unit volume that a material can absorb elastically
The ratio of shear stress to shear strain
The resistance to crack propagation
Explanation - Modulus of resilience is the area under the elastic portion of the stress‑strain curve.
Correct answer is: The energy per unit volume that a material can absorb elastically
Q.25 Which testing method is most appropriate for evaluating the compressive strength of trabecular bone substitutes?
Three‑point bending test
Uniaxial compression test
Tensile test
Hardness test
Explanation - Trabecular bone primarily experiences compressive loads; a compression test directly measures this property.
Correct answer is: Uniaxial compression test
Q.26 A biomaterial that exhibits 'strain‑hardening' will:
Become weaker as deformation proceeds
Show decreasing stress with increasing strain
Increase its yield stress after plastic deformation
Maintain constant stress after yielding
Explanation - Strain‑hardening (work hardening) causes the material to become stronger as it deforms plastically.
Correct answer is: Increase its yield stress after plastic deformation
Q.27 Which property is most directly related to the ability of a biomaterial to resist crack propagation?
Hardness
Fracture toughness
Electrical conductivity
Thermal conductivity
Explanation - Fracture toughness quantifies a material's resistance to the growth of existing cracks.
Correct answer is: Fracture toughness
Q.28 For a conductive polymer used in neural interfaces, the mechanical property that must be balanced with conductivity is:
Hardness
Elastic modulus
Thermal expansion
Optical transparency
Explanation - A low elastic modulus minimizes mechanical mismatch with soft neural tissue while maintaining conductivity.
Correct answer is: Elastic modulus
Q.29 In the context of biomaterials, 'anisotropy' means:
The material has the same properties in all directions
The material's properties vary with direction
The material is electrically conductive
The material degrades uniformly
Explanation - Anisotropic materials exhibit direction‑dependent mechanical behavior, common in bone.
Correct answer is: The material's properties vary with direction
Q.30 Which of the following is a typical cause of failure for polymeric heart valve leaflets?
Corrosion fatigue
Creep deformation leading to loss of coaptation
Brittle fracture
Electrical breakdown
Explanation - Creep under cyclic loading can cause permanent deformation, preventing leaflets from sealing properly.
Correct answer is: Creep deformation leading to loss of coaptation
Q.31 A higher 'glass transition temperature (Tg)' in a polymeric biomaterial generally indicates:
Increased flexibility at body temperature
Higher stiffness and reduced chain mobility at body temperature
Better electrical conductivity
Improved biodegradability
Explanation - When Tg is above body temperature, the polymer remains in a glassy, stiff state.
Correct answer is: Higher stiffness and reduced chain mobility at body temperature
Q.32 The primary mechanical advantage of using a porous titanium alloy for orthopedic implants is:
Increased electrical conductivity
Reduced weight and improved osseointegration
Higher hardness
Lower elastic modulus than bone
Explanation - Porosity reduces the effective modulus and provides surface area for bone ingrowth.
Correct answer is: Reduced weight and improved osseointegration
Q.33 The 'ultimate compressive strength' of a biomaterial is:
The stress at which the material first yields
The maximum compressive stress the material can sustain before failure
The stress at which permanent deformation begins
The ratio of compressive stress to strain
Explanation - Ultimate compressive strength is the peak stress on a compressive stress‑strain curve before fracture.
Correct answer is: The maximum compressive stress the material can sustain before failure
Q.34 Which phenomenon explains the gradual loss of load‑bearing capacity of a polymeric scaffold under constant load over years?
Creep
Strain‑rate hardening
Thermal expansion
Electrochemical corrosion
Explanation - Long‑term deformation under sustained stress is creep, which can reduce load‑bearing capacity.
Correct answer is: Creep
Q.35 For a biomaterial used in dental crowns, why is a high 'hardness' value important?
It prevents wear from mastication forces
It makes the material more flexible
It improves electrical conductivity
It increases biodegradability
Explanation - High hardness resists abrasion and wear caused by chewing.
Correct answer is: It prevents wear from mastication forces
Q.36 The term 'viscoelastic relaxation time' refers to:
The time needed for a material to return to its original shape after deformation
The time required for a material to conduct electricity
The duration of a fatigue test
The period of thermal cycling
Explanation - Viscoelastic relaxation time characterizes how quickly stress decays after a constant strain is applied.
Correct answer is: The time needed for a material to return to its original shape after deformation
Q.37 Which mechanical property is most critical for a contact lens material?
High tensile strength
Low Young's modulus
High hardness
High electrical conductivity
Explanation - A low modulus ensures flexibility and comfort on the curved surface of the eye.
Correct answer is: Low Young's modulus
Q.38 In a fatigue test, the term 'S-N curve' represents:
Stress versus number of cycles to failure
Strain versus number of cycles
Stress versus temperature
Strain versus hardness
Explanation - The S‑N curve plots applied stress (S) against the number of cycles (N) required to cause failure.
Correct answer is: Stress versus number of cycles to failure
Q.39 A biomaterial that exhibits 'strain‑rate hardening' will:
Become softer when loaded quickly
Become stronger when loaded quickly
Show the same strength regardless of loading speed
Become more brittle at low strain rates
Explanation - Strain‑rate hardening means the material's flow stress increases with higher strain rates.
Correct answer is: Become stronger when loaded quickly
Q.40 Which characteristic of a hydrogel makes it suitable for cartilage replacement?
High electrical conductivity
Low water content
High compressive modulus and viscoelastic behavior
High thermal conductivity
Explanation - Cartilage experiences compressive loads and exhibits viscoelastic response; hydrogels can mimic these properties.
Correct answer is: High compressive modulus and viscoelastic behavior
Q.41 The term 'biodegradation rate' is most closely related to which mechanical property over time?
Increasing hardness
Decreasing tensile strength
Constant Poisson's ratio
Increasing electrical conductivity
Explanation - As a biomaterial degrades, its ability to bear loads (tensile strength) typically diminishes.
Correct answer is: Decreasing tensile strength
Q.42 In the context of biomaterials, 'stress concentration factor' (Kt) is used to describe:
The increase in stress due to geometric discontinuities like holes or notches
The ratio of electrical to mechanical stress
The change in temperature under load
The enhancement of magnetic properties under stress
Explanation - Kt quantifies how much stress is amplified at features such as notches, affecting failure risk.
Correct answer is: The increase in stress due to geometric discontinuities like holes or notches
Q.43 A biomaterial intended for spinal cage implantation must have:
Very low compressive strength
An elastic modulus comparable to cancellous bone
High electrical conductivity
A glass transition temperature above 200 °C
Explanation - Matching the modulus reduces stress shielding and encourages load sharing with surrounding bone.
Correct answer is: An elastic modulus comparable to cancellous bone
Q.44 Which of the following is a major advantage of using bio‑ceramic composites over pure ceramics for load‑bearing implants?
Higher electrical conductivity
Improved fracture toughness
Lower density
Greater magnetic susceptibility
Explanation - Adding a polymeric phase can toughen ceramics, reducing brittleness while retaining bioactivity.
Correct answer is: Improved fracture toughness
Q.45 The term 'elastic limit' is synonymous with:
Yield strength
Ultimate tensile strength
Fracture toughness
Hardness
Explanation - The elastic limit is the stress at which permanent (plastic) deformation begins, i.e., the yield strength.
Correct answer is: Yield strength
Q.46 When designing a flexible neural electrode, which mechanical property must be minimized to reduce tissue damage?
Elastic modulus
Fracture toughness
Hardness
Yield strength
Explanation - A low modulus makes the electrode conform to soft tissue, limiting mechanical irritation.
Correct answer is: Elastic modulus
Q.47 Which of the following statements about the 'strain energy density' is correct?
It is the amount of energy stored per unit volume due to elastic deformation
It measures the total energy lost during plastic deformation
It is only applicable to brittle materials
It is independent of material stiffness
Explanation - Strain energy density quantifies the elastic energy stored in a material per unit volume.
Correct answer is: It is the amount of energy stored per unit volume due to elastic deformation
Q.48 A polymeric scaffold with a high 'strain‑energy absorption' capability is desirable for:
Long‑term load‑bearing bone substitutes
Temporary wound dressings
Electrical insulation
Drug delivery without mechanical load
Explanation - High energy absorption helps the scaffold dissipate impact loads without failing.
Correct answer is: Long‑term load‑bearing bone substitutes
Q.49 Which testing method provides direct measurement of a material's 'hardness'?
Vickers indentation test
Tensile testing
Dynamic mechanical analysis
Creep testing
Explanation - The Vickers test uses a diamond indenter to determine hardness via the size of the indentation.
Correct answer is: Vickers indentation test
Q.50 In the context of biomaterials, the term 'ductility' refers to:
The ability to conduct electricity
The ability to deform plastically before fracture
The resistance to corrosion
The capacity to absorb water
Explanation - Ductility is the capacity of a material to undergo significant plastic deformation prior to failure.
Correct answer is: The ability to deform plastically before fracture
Q.51 Which of the following best describes the effect of 'crosslinking' on the mechanical properties of a hydrogel?
Decreases tensile strength and increases degradation rate
Increases stiffness and reduces swelling
Makes the hydrogel electrically conductive
Reduces biocompatibility
Explanation - Crosslinking creates a network that restricts polymer chain movement, raising modulus and limiting water uptake.
Correct answer is: Increases stiffness and reduces swelling
Q.52 The term 'fatigue limit' (or endurance limit) of a material is:
The maximum stress it can sustain indefinitely without failure under cyclic loading
The stress at which the material yields
The point where the material cracks instantly
The stress at which creep occurs
Explanation - Below the fatigue limit, a material can theoretically endure infinite load cycles without cracking.
Correct answer is: The maximum stress it can sustain indefinitely without failure under cyclic loading
Q.53 For a biodegradable polymer used in tissue engineering, which mechanical property typically decreases as degradation proceeds?
Poisson's ratio
Elastic modulus
Thermal conductivity
Electrical resistance
Explanation - As polymer chains break down, the material becomes less stiff, lowering its elastic modulus.
Correct answer is: Elastic modulus
Q.54 In a tensile test, the 'necking' phenomenon is observed:
At the elastic region before yielding
After the ultimate tensile strength, just before fracture
During the initial loading phase
Only in brittle materials
Explanation - Necking occurs when localized reduction in cross‑section leads to rapid failure after peak stress.
Correct answer is: After the ultimate tensile strength, just before fracture
Q.55 Why is a low 'coefficient of friction' important for joint replacement materials?
It improves electrical conductivity
It reduces wear and particle generation
It increases hardness
It enhances thermal stability
Explanation - Low friction minimizes abrasive wear, extending the lifetime of joint prostheses.
Correct answer is: It reduces wear and particle generation
Q.56 Which mechanical property would you prioritize for a biodegradable vascular stent that must support blood pressure temporarily?
High compressive strength and controlled degradation rate
High hardness
High electrical conductivity
Low Poisson's ratio
Explanation - The stent must initially resist collapse (compressive strength) and then safely degrade.
Correct answer is: High compressive strength and controlled degradation rate
Q.57 The 'R-curve' in fracture mechanics of biomaterials describes:
The relationship between stress intensity factor and crack growth resistance
The temperature dependence of modulus
The variation of hardness with depth
The change in electrical resistance with strain
Explanation - An R‑curve shows how a material's resistance to crack extension increases with crack growth.
Correct answer is: The relationship between stress intensity factor and crack growth resistance
Q.58 What is the primary mechanical advantage of using a composite of carbon fibers reinforced polymer (CFRP) for cranial implants?
Excellent electrical conductivity
High strength‑to‑weight ratio and adjustable stiffness
High corrosion resistance in aqueous environments
Inherent biodegradability
Explanation - CFRP offers high mechanical performance with low mass, and stiffness can be tailored via fiber orientation.
Correct answer is: High strength‑to‑weight ratio and adjustable stiffness
Q.59 A material that exhibits a 'stress‑relaxation' response under constant strain is:
An ideal elastic solid
A viscoelastic material
A perfectly plastic material
A brittle ceramic
Explanation - Viscoelastic materials show decreasing stress over time when held at a constant deformation.
Correct answer is: A viscoelastic material
Q.60 When comparing two biomaterials, A with a Young's modulus of 1 GPa and B with 10 GPa, which one is more likely to cause stress shielding in cortical bone (≈ 20 GPa)?
Material A
Material B
Both equally
Neither
Explanation - Material B is closer to bone modulus and can take more load, reducing stress shielding compared to the very stiff Material B; however, the question is reversed – actually, higher modulus (B) leads to stress shielding. So correct answer: Material B.
Correct answer is: Material B
Q.61 The 'critical crack size' in a biomaterial is:
The smallest detectable surface flaw
The crack length at which rapid fracture becomes inevitable under a given stress
The length of a crack after a fatigue test
The distance between two microcracks
Explanation - When a crack reaches the critical size, the stress intensity exceeds the material's fracture toughness, leading to fast propagation.
Correct answer is: The crack length at which rapid fracture becomes inevitable under a given stress
Q.62 Which mechanical property is most directly related to the ability of a material to absorb impact energy without fracturing?
Hardness
Toughness
Young's modulus
Electrical conductivity
Explanation - Toughness combines strength and ductility, representing energy absorption before fracture.
Correct answer is: Toughness
Q.63 In bone tissue engineering, a scaffold with a compressive modulus of 0.5 GPa is considered:
Too stiff for cancellous bone
Appropriate for cortical bone
Suitable for cancellous bone
Unsuitable for any bone type
Explanation - Cancellous bone has a lower modulus (~0.1–0.5 GPa), so a scaffold of 0.5 GPa matches its mechanical environment.
Correct answer is: Suitable for cancellous bone
Q.64 Which factor most influences the fatigue performance of a metallic biomaterial?
Grain size and surface finish
Color of the alloy
Magnetic permeability
Thermal conductivity
Explanation - Fine grains and smooth surfaces reduce stress concentrators, improving fatigue life.
Correct answer is: Grain size and surface finish
Q.65 The term 'creep rupture' describes:
Fracture that occurs after prolonged exposure to a constant load at high temperature
Immediate fracture under impact loading
Failure due to cyclic loading
Fracture caused by corrosion
Explanation - Creep rupture is the ultimate failure mode after time‑dependent deformation under sustained load.
Correct answer is: Fracture that occurs after prolonged exposure to a constant load at high temperature
Q.66 A biomaterial with a 'low loss modulus' in DMA testing indicates:
High energy dissipation
Low energy dissipation (more elastic behavior)
High electrical conductivity
High thermal expansion
Explanation - Loss modulus quantifies viscous energy loss; a low value means the material behaves more elastically.
Correct answer is: Low energy dissipation (more elastic behavior)
Q.67 Which mechanical characteristic of a biomaterial is most important for preventing micromotion at the bone‑implant interface?
High hardness
Low coefficient of thermal expansion
Adequate interfacial shear strength
High electrical conductivity
Explanation - Shear strength at the interface resists relative movement, promoting stability and osseointegration.
Correct answer is: Adequate interfacial shear strength
Q.68 For a polymeric nerve conduit, which property is crucial to maintain flexibility while providing sufficient protection?
High Young's modulus
Low Poisson's ratio
Low tensile strength
Low Young's modulus with adequate toughness
Explanation - Flexibility requires low stiffness, but toughness prevents rupture during handling.
Correct answer is: Low Young's modulus with adequate toughness
Q.69 Which of the following statements about 'anisotropic elasticity' in cortical bone is true?
Bone has the same Young's modulus in all directions
Young's modulus is higher along the longitudinal direction than transverse
Elastic properties are independent of microstructure
Anisotropy only affects electrical properties
Explanation - Cortical bone is stiffer along the direction of collagen fibers and osteons, leading to anisotropic elasticity.
Correct answer is: Young's modulus is higher along the longitudinal direction than transverse
Q.70 A biomaterial that exhibits 'self‑healing' under mechanical load would most likely rely on:
Electrochemical corrosion processes
Microcapsules containing healing agents that rupture upon cracking
Thermal expansion mismatches
Magnetic field alignment
Explanation - Self‑healing polymers often contain embedded microcapsules that release repair chemicals when damage occurs.
Correct answer is: Microcapsules containing healing agents that rupture upon cracking
Q.71 In the context of biomaterials, 'hydrostatic pressure' most directly affects which mechanical property?
Shear modulus
Bulk modulus
Young's modulus
Poisson's ratio
Explanation - Bulk modulus quantifies a material's resistance to uniform compression (hydrostatic pressure).
Correct answer is: Bulk modulus
Q.72 Which of the following is an advantage of using shape‑memory alloys (SMAs) in biomedical devices?
They are biodegradable
They can recover a predefined shape after deformation when heated
They have the highest fracture toughness of all metals
They are electrically insulating
Explanation - SMAs exhibit a reversible phase transformation, enabling shape recovery upon temperature change.
Correct answer is: They can recover a predefined shape after deformation when heated
Q.73 When a biomaterial's stress‑strain curve shows a long linear region before yielding, this indicates:
High ductility
High stiffness and elastic behavior
Low tensile strength
High creep resistance
Explanation - A long linear region reflects a high elastic modulus and a clear elastic limit.
Correct answer is: High stiffness and elastic behavior
Q.74 The 'critical stress intensity factor' (KIC) is used to quantify:
Electrical conductivity under stress
Fracture toughness of a material
Hardness under compressive load
Thermal conductivity under strain
Explanation - KIC is the material property representing resistance to crack propagation under mode I loading.
Correct answer is: Fracture toughness of a material
Q.75 Which of the following best explains why a porous scaffold can have a lower effective Young's modulus than the solid material it's made from?
Porosity introduces air, which has zero modulus, reducing overall stiffness
The scaffold material chemically changes during fabrication
Porous scaffolds are always made of softer polymers
Porosity increases electrical conductivity, which lowers modulus
Explanation - The void spaces act as compliant regions, lowering the average stiffness of the composite structure.
Correct answer is: Porosity introduces air, which has zero modulus, reducing overall stiffness
Q.76 In a fatigue test of a polymeric heart valve leaflet, the number of cycles to failure is most influenced by:
The color of the polymer
The amplitude of cyclic strain
The ambient humidity
The electrical resistance of the material
Explanation - Higher strain amplitudes accelerate fatigue damage, reducing cycles to failure.
Correct answer is: The amplitude of cyclic strain
Q.77 Which mechanical property is directly measured by the 'storage modulus' obtained from DMA?
Viscous energy loss
Elastic energy storage
Thermal conductivity
Electrical resistivity
Explanation - Storage modulus reflects the elastic component of a viscoelastic material's response.
Correct answer is: Elastic energy storage
Q.78 A biomaterial designed for load‑bearing spinal fusion must avoid which failure mode during the first few weeks post‑implantation?
Corrosion fatigue
Creep deformation leading to loss of alignment
Electrical short circuit
Magnetic saturation
Explanation - Early creep can cause misalignment before bone fusion occurs, compromising the surgical outcome.
Correct answer is: Creep deformation leading to loss of alignment
Q.79 Which of the following statements about 'strain‑energy release rate' (G) is correct?
G is the rate at which a material conducts heat under strain
G quantifies the energy available for crack propagation per unit area of crack growth
G measures the electrical energy stored in a strained material
G is only applicable to elastic materials
Explanation - The strain‑energy release rate is a fracture mechanics parameter indicating driving force for crack extension.
Correct answer is: G quantifies the energy available for crack propagation per unit area of crack growth
Q.80 In the design of a biodegradable orthopedic screw, why is it important to control the 'initial tensile strength'?
To ensure the screw can bear physiological loads before degradation begins
To make the screw electrically conductive
To increase the screw's magnetic susceptibility
To lower the screw's melting point
Explanation - Adequate initial strength prevents early failure while the surrounding tissue heals.
Correct answer is: To ensure the screw can bear physiological loads before degradation begins
Q.81 Which mechanical test would you use to evaluate the 'shear strength' of a biomaterial adhesive used for wound closure?
Tensile test
Shear lap test
Compression test
Hardness test
Explanation - A shear lap test directly measures the adhesive's ability to resist shear forces.
Correct answer is: Shear lap test
Q.82 The term 'creep compliance' is defined as:
Strain per unit stress under a constant load over time
Stress per unit strain at a given temperature
Hardness divided by elastic modulus
Electrical conductivity over time under load
Explanation - Creep compliance quantifies the time‑dependent strain response to a sustained stress.
Correct answer is: Strain per unit stress under a constant load over time
Q.83 A hydrogel designed for cartilage replacement must have a high 'aggregate modulus'. This term refers to:
The modulus measured under confined compression where fluid flow is restricted
The modulus in tension under unconfined conditions
The modulus related to electrical conductivity
The modulus measured after degradation
Explanation - Aggregate modulus reflects the solid matrix stiffness when interstitial fluid cannot escape.
Correct answer is: The modulus measured under confined compression where fluid flow is restricted
Q.84 Why is a high 'fracture toughness' especially important for ceramic dental implants?
Because ceramics are inherently ductile
To resist crack propagation from occlusal forces
To improve electrical conductivity
To increase biodegradability
Explanation - Mastication induces high cyclic stresses; high fracture toughness prevents catastrophic cracks in brittle ceramics.
Correct answer is: To resist crack propagation from occlusal forces
Q.85 The 'stress‑strain hysteresis loop' observed in cyclic loading of a viscoelastic biomaterial indicates:
Elastic energy storage only
Energy dissipation due to internal friction
Magnetic domain alignment
Electrical charge accumulation
Explanation - The area within the hysteresis loop represents energy lost as heat during each loading cycle.
Correct answer is: Energy dissipation due to internal friction
Q.86 Which parameter is most directly used to evaluate the resistance of a material to permanent set after a compressive load?
Yield strength
Recovery ratio
Creep strain
Residual strain
Explanation - Residual strain measures the permanent deformation remaining after load removal.
Correct answer is: Residual strain
Q.87 For a bio‑resorbable polymer used in sutures, which mechanical property must be balanced with degradation rate to ensure wound closure?
High thermal conductivity
Adequate tensile strength over the healing period
Low electrical resistance
High magnetic permeability
Explanation - Sutures must retain sufficient strength until the tissue regains its own mechanical integrity.
Correct answer is: Adequate tensile strength over the healing period
Q.88 Which of the following statements about the 'Brittle–Ductile Transition' temperature is correct for polymers?
Below this temperature, polymers become more ductile
Above this temperature, polymers become more brittle
Above this temperature, polymers become more ductile
Polymers do not exhibit a brittle–ductile transition
Explanation - Polymers typically transition from glassy (brittle) to rubbery (ductile) as temperature rises above Tg.
Correct answer is: Above this temperature, polymers become more ductile
Q.89 In the context of biomechanical testing, the term 'load cell' refers to:
A device that measures electrical activity
A sensor that converts applied force into an electrical signal
A component that generates magnetic fields
A tool for measuring temperature
Explanation - Load cells are commonly used to record force during mechanical testing of biomaterials.
Correct answer is: A sensor that converts applied force into an electrical signal
Q.90 Which mechanical property would be most critical for a bone‑anchored hearing aid implant?
High compressive strength
High shear modulus
Low Young's modulus to match bone
High electrical conductivity
Explanation - Matching the modulus reduces stress concentrations at the bone‑implant interface, improving integration.
Correct answer is: Low Young's modulus to match bone
Q.91 A material with a high 'specific strength' (strength‑to‑density ratio) is advantageous for:
Implants where weight is a critical factor, such as aerospace‑derived devices
Electrical insulation
Magnetic resonance imaging compatibility
Biodegradability
Explanation - High specific strength offers strong yet lightweight structures, beneficial for load‑bearing but mass‑sensitive applications.
Correct answer is: Implants where weight is a critical factor, such as aerospace‑derived devices
Q.92 Which mechanical phenomenon is primarily responsible for the gradual loss of stiffness in a polymeric scaffold stored at body temperature over several months?
Creep
Strain‑rate hardening
Thermal expansion
Magnetostriction
Explanation - Creep causes time‑dependent deformation under constant stress, leading to reduced stiffness.
Correct answer is: Creep
Q.93 The term 'elastic recovery' refers to:
The permanent deformation after load removal
The amount of strain that disappears when the load is removed
The increase in electrical resistance under load
The change in temperature during deformation
Explanation - Elastic recovery is the reversible part of deformation that recovers after unloading.
Correct answer is: The amount of strain that disappears when the load is removed
Q.94 When a biomaterial exhibits a 'negative Poisson's ratio', it means that:
It expands laterally when stretched longitudinally
It contracts laterally when stretched longitudinally
It becomes electrically conductive under load
It degrades faster under stress
Explanation - Materials with a negative Poisson's ratio (auxetic) become wider when stretched, opposite to normal behavior.
Correct answer is: It expands laterally when stretched longitudinally
Q.95 In fatigue testing of a metallic hip implant, the 'Wöhler curve' is another name for:
Stress‑strain curve
S‑N curve
Load‑deflection curve
Temperature‑time curve
Explanation - The Wöhler (or S‑N) curve plots stress amplitude versus number of cycles to failure.
Correct answer is: S‑N curve
Q.96 Which property is most directly affected by the presence of micro‑cracks in a ceramic bone substitute?
Electrical conductivity
Fracture toughness
Thermal expansion coefficient
Young's modulus
Explanation - Micro‑cracks serve as stress concentrators, reducing the material's ability to resist crack propagation.
Correct answer is: Fracture toughness
Q.97 A biomaterial with a high 'energy dissipation capacity' during cyclic loading is said to have:
High stiffness
High damping
High conductivity
High permeability
Explanation - Energy dissipation manifests as damping, reducing vibrations and protecting surrounding tissue.
Correct answer is: High damping
Q.98 Which mechanical characteristic is most important for a biodegradable polymer used as a temporary tracheal stent?
High compressive strength and controlled radial expansion
High hardness
Low tensile strength
High magnetic susceptibility
Explanation - The stent must maintain airway patency under breathing pressures and then safely degrade.
Correct answer is: High compressive strength and controlled radial expansion
Q.99 The 'modulus of resilience' of a biomaterial is measured in:
Joules per cubic meter (J/m³)
Pascals (Pa)
Meters per second (m/s)
Watts (W)
Explanation - Modulus of resilience is an energy per unit volume quantity, expressed in J/m³.
Correct answer is: Joules per cubic meter (J/m³)
Q.100 Which of the following best describes the role of 'interfacial shear strength' in a composite bone cement?
It determines the electrical conductivity of the cement
It controls the resistance to crack growth within the cement matrix
It measures the ability of the cement to bond to bone and resist shear forces
It indicates the thermal stability of the cement
Explanation - Strong interfacial shear strength ensures load transfer from the implant to surrounding bone without debonding.
Correct answer is: It measures the ability of the cement to bond to bone and resist shear forces
Q.101 For a polymeric material used in a load‑bearing spinal cage, increasing the degree of crystallinity generally:
Decreases Young's modulus
Increases tensile strength and stiffness
Improves electrical conductivity
Reduces biocompatibility
Explanation - Higher crystallinity leads to more ordered regions, enhancing strength and stiffness.
Correct answer is: Increases tensile strength and stiffness
Q.102 The 'Bauschinger effect' observed in metallic biomaterials during cyclic loading refers to:
An increase in yield stress after reverse loading
A reduction in yield stress when the loading direction is reversed
A change in electrical resistance under cyclic stress
A temperature rise due to internal friction
Explanation - The Bauschinger effect describes lowered yield strength upon load reversal due to dislocation structures.
Correct answer is: A reduction in yield stress when the loading direction is reversed
Q.103 Which mechanical property of a biomaterial is directly assessed by a 'push‑out test' for orthopedic implants?
Compressive strength
Shear interfacial strength
Tensile strength
Hardness
Explanation - A push‑out test measures the force required to shear the implant out of a bone cavity, indicating interfacial bonding.
Correct answer is: Shear interfacial strength
Q.104 A biomaterial that exhibits a 'strain‑softening' behavior will:
Increase its stress with increasing strain
Decrease its stress with increasing strain after a peak
Maintain constant stress regardless of strain
Become electrically conductive
Explanation - Strain‑softening shows a reduction in stress after reaching a maximum, indicating material weakening.
Correct answer is: Decrease its stress with increasing strain after a peak
Q.105 The 'hydraulic modulus' of a cartilage tissue is most closely related to:
Its ability to conduct electricity
Its resistance to fluid flow under compression
Its thermal conductivity
Its magnetic permeability
Explanation - Hydraulic (or permeability) modulus describes the resistance to fluid movement in a porous, hydrated tissue under load.
Correct answer is: Its resistance to fluid flow under compression
Q.106 When evaluating the mechanical compatibility of a biomaterial with soft tissue, the most important modulus to consider is:
Young's modulus
Bulk modulus
Shear modulus
Modulus of rigidity
Explanation - Matching Young's modulus minimizes mechanical mismatch and reduces stress concentrations at the interface.
Correct answer is: Young's modulus
Q.107 Which of the following best explains why a porous titanium implant may have a lower fatigue limit than a dense one?
The pores act as stress concentrators, facilitating crack initiation
Porous titanium is chemically more reactive
Porous titanium conducts electricity better
The implant becomes magnetically active
Explanation - Stress concentrations at pore edges lower the fatigue strength of porous structures.
Correct answer is: The pores act as stress concentrators, facilitating crack initiation
Q.108 The 'elastic recovery ratio' after a compressive load is defined as:
Residual strain divided by applied strain
Recovered strain divided by total strain
Applied stress divided by strain rate
Yield stress divided by ultimate stress
Explanation - Elastic recovery ratio quantifies the proportion of deformation that is recoverable after unloading.
Correct answer is: Recovered strain divided by total strain
Q.109 A polymeric scaffold with a high 'water uptake' typically exhibits:
Increased stiffness
Decreased tensile strength
Higher electrical conductivity
Reduced swelling
Explanation - Water plasticizes the polymer network, reducing stiffness and tensile strength.
Correct answer is: Decreased tensile strength
Q.110 Which mechanical property of a biomaterial is most directly linked to its 'osteoconductivity'?
Surface roughness and stiffness
Electrical conductivity
Thermal conductivity
Magnetic susceptibility
Explanation - Appropriate surface topography and modulus promote bone cell attachment and growth.
Correct answer is: Surface roughness and stiffness
Q.111 In a cyclic compression test, a material that shows a gradual increase in strain amplitude over cycles is experiencing:
Hardening
Creep
Fatigue damage accumulation
Elastic recovery
Explanation - Increasing strain per cycle indicates progressive fatigue damage leading toward failure.
Correct answer is: Fatigue damage accumulation
Q.112 Which factor most influences the 'rate of stress relaxation' in a viscoelastic hydrogel?
Temperature
Magnetic field strength
Ambient light intensity
Electrical voltage applied
Explanation - Higher temperatures accelerate molecular motion, leading to faster stress relaxation.
Correct answer is: Temperature
Q.113 For a load‑bearing polymeric spinal cage, why is 'dimensional stability' important after sterilization?
To ensure the cage does not shrink or expand, maintaining proper fit
To improve electrical conductivity
To increase magnetic susceptibility
To enhance biodegradability
Explanation - Dimensional changes can compromise mechanical fixation and alignment after sterilization.
Correct answer is: To ensure the cage does not shrink or expand, maintaining proper fit
Q.114 A material with a high 'strain hardening exponent (n)' in the Hollomon equation will:
Exhibit rapid softening after yielding
Show significant increase in strength with plastic strain
Remain perfectly elastic
Become more brittle with deformation
Explanation - A larger n value indicates stronger strain hardening behavior, raising strength as plastic strain accumulates.
Correct answer is: Show significant increase in strength with plastic strain
Q.115 Which mechanical property is most critical for a biomaterial used as a cranial plate that must protect the brain from impact?
High hardness and high fracture toughness
Low Young's modulus
High electrical conductivity
High thermal conductivity
Explanation - Impact protection requires resistance to surface indentation (hardness) and resistance to crack propagation (toughness).
Correct answer is: High hardness and high fracture toughness
Q.116 The term 'elastic limit' is synonymous with:
Yield point
Ultimate tensile strength
Fracture toughness
Hardness
Explanation - The elastic limit marks the transition from elastic to plastic deformation, i.e., the yield point.
Correct answer is: Yield point
Q.117 Which property would you prioritize for a biodegradable polymeric scaffold intended for tendon repair?
High tensile strength and moderate elasticity
High compressive strength
Low electrical conductivity
High hardness
Explanation - Tendons experience high tensile loads; the scaffold must withstand those while allowing some stretch.
Correct answer is: High tensile strength and moderate elasticity
Q.118 When a biomaterial exhibits a 'stress‑strain curve' with a large area under the curve before failure, it indicates:
High stiffness but low toughness
Low ductility
High toughness
Low strength
Explanation - The area under the curve represents energy absorbed; a large area denotes high toughness.
Correct answer is: High toughness
Q.119 A scaffold made of polycaprolactone (PCL) has a low melting point. Which mechanical property is most likely to be affected at body temperature (37 °C)?
Hardness
Electrical conductivity
Elastic modulus (it will decrease)
Magnetic permeability
Explanation - Near its melting point, PCL becomes softer, reducing its elastic modulus.
Correct answer is: Elastic modulus (it will decrease)
Q.120 Which of the following best describes why a biomaterial with a high 'glass transition temperature (Tg)' is chosen for load‑bearing applications?
It ensures the material remains in a rigid, glassy state at body temperature
It makes the material electrically conductive
It improves the material's biodegradability
It reduces the material's density
Explanation - A Tg above 37 °C keeps the polymer stiff and strong during service.
Correct answer is: It ensures the material remains in a rigid, glassy state at body temperature
Q.121 The 'critical energy release rate' (Gc) in fracture mechanics is used to predict:
The amount of electrical energy a material can store
The rate at which a crack will propagate under a given energy condition
The thermal conductivity of a material
The magnetic field strength required to fracture a material
Explanation - Gc defines the energy needed per unit area to advance a crack; exceeding it leads to crack growth.
Correct answer is: The rate at which a crack will propagate under a given energy condition
Q.122 A biomaterial used for a dental bridge must have a high 'wear resistance'. Which mechanical property correlates most directly with this requirement?
Hardness
Poisson's ratio
Elastic modulus
Thermal expansion coefficient
Explanation - Higher hardness reduces material loss due to abrasive contact during chewing.
Correct answer is: Hardness
Q.123 Which mechanical behavior is most likely to be observed in a biodegradable polymer when subjected to cyclic loading at body temperature over months?
Strain‑hardening
Creep‑fatigue interaction leading to accelerated damage
Immediate brittle fracture
Magnetostriction
Explanation - Combined cyclic loading and time‑dependent creep can synergistically reduce fatigue life.
Correct answer is: Creep‑fatigue interaction leading to accelerated damage
Q.124 In a push‑out test for a bone‑anchored implant, a higher required force indicates:
Lower interfacial shear strength
Higher interfacial shear strength
Higher electrical conductivity
Higher thermal conductivity
Explanation - More force is needed to shear the implant out of bone when the interface is strong.
Correct answer is: Higher interfacial shear strength
Q.125 When selecting a biomaterial for a load‑bearing spinal cage, why is 'radiolucency' sometimes a design requirement?
It indicates high mechanical strength
It allows postoperative imaging without artifact
It improves the material's fatigue life
It enhances biocompatibility
Explanation - Radiolucent materials (e.g., PEEK) do not obscure X‑ray/CT images, enabling clinicians to assess healing.
Correct answer is: It allows postoperative imaging without artifact
Q.126 A biomaterial with a 'low coefficient of thermal expansion' is advantageous for implants placed near which type of tissue?
Bone, because bone experiences large temperature changes
Soft tissue, because it reduces thermal mismatch during fever
Cardiac tissue, because the heart generates heat
Neural tissue, due to high temperature sensitivity
Explanation - Minimizing thermal expansion differences prevents stress at the implant‑soft tissue interface during temperature fluctuations.
Correct answer is: Soft tissue, because it reduces thermal mismatch during fever