Chapter 6-8 Flashcards
Established convention to determine the yield strength of a material wherein a straight line is constructed parallel to the modulus line offset by this amount:
a) 2%
b) 0.2%
c) 0.02%
d) 0.002%
b) 0.2%
the capability of a material to absorb energy when it is deformed elastically, and then, upon unloading, to have this energy recovered is called?
a) Ductility
b) Malleability
c) Toughness
d) Resilience
d) Resilience
As the carbon content in a plain carbon steel for a Charpy V-notch impact test increases, the ductile-to-brittle transition temperature:
a) increases
b) decreases
c) stays the same
a) increases
which type of hardness tester is preferred for testing coatings and ceramics?
a) brinell
b) knoop
c) leeb
d) rockwell
b) knoop
some materials (e.g low carbon steels) exhibit and upper and lower yield point. which value is typically taken as the yield strength
a) upper yield point
b) Midway between the upper and lower yield point
c) lower yield point
c) lower yield point
the standard brinell hardness testing method for iron and steel uses which load and indenter combination?
a) 150kg w 10mm diameter ball
b) 3000kg w 10mm diameter ball
c) 10kg w diamond cone
d) 1kg w diamond cone
b) 3000kg w 10mm diameter ball
how would the plain strain fracture toughness of a metal be expected to change with rising temperature?
a) increases
b) remains constant
d) decreases
a) increases
in general, which types of materials do you expect to exhibit the highest impact energy regardless of the testing temperature?
a) low strength (FCC and HCP) metals
b) high-strength materials
c) low strength steels
a) low strength (FCC and HCP) metals
a stainless steel alloy has melting temperature of 1450 C. Above which temperature should creep start to be a concern?
a) 416 C
b) 471 C
c) 580 C
d) 689 C
a) 416 C
a brittle material typically exhibits substantial plastic deformation with high energy absorption before fracture.
a) true
b) false
b) false
the area under the stress-strain curve up to the point of fracture is a measure of:
a) ductility
b) malleability
c) toughness
d) resilience
c) toughness
a pronounced shear lip at the periphery of a fracture surface implies:
a) ductile fracture
b) brittle fracture
c) cleavage
d) fracture through the grains
a) ductile fracture
which type of hardness tester is referred to as a micro indentation technique?
a) brinell
b) leeb
c) rockwell
d) vickers
d) vickers
the true stress of a material corresponding to the maximum load is ___________the engineering stress
a) greater than
b) equal to
c) less than
a) greater than
the fracture toughness of a material is determined by:
a) chemical composition
b) crystal structure
c) surface energy of the material
d) anisotropy
b) crystal structure
c) surface energy of the material
In general, which types of materials do you expect to exhibit the lowest impact energy regardless of the testing temperature?
a) Low strength (FCC and HCP) metals
b) high-strength materials
c) low strength steels
b) high-strength materials
the mechanism of fatigue failure involves:
a) crystallization
b) impact loading
c) plastic deformation
d) not going to bed on time
c) plastic deformation
striations are:
a) also called clamshell marks
b) found on components that experience interruptions in service
c) observed only with an electron microscope
d) always observed for all metals that experience fatigue
c) observed only with an electron microscope
both temperature and applied stress level influence creep behaviour. Increasing either of these parameters produce the following effects:
a) an increase in the instantaneous initial deformation
b) an increase in the steady-state creep rate
c) a decrease in the rupture lifetime
d) all the above
d) all the above
Stress (engineering stress) is defined as the load divided by the instantaneous cross-sectional area over which deformation is occurring
a) true
b) false
b) false
The magnitude of Young’s modulus is a measure of the resistance to separation of adjacent atoms.
a) true
b) false
a) true
The time-dependent elastic behavior is known as anelasticity
a) true
b) false
a) true
Yield strength is the stress corresponding to the upper yield point for metals that display the yield point phenomenon.
a) true
b) false
b) false
Fracture strength corresponds to the maximum stress on the stress-strain curve.
a) true
b) false
b) false
Ductility is a measure of the degree of elastic deformation that has been sustained at fracture.
a) true
b) false
b) false
Resilience is the capacity of a material to absorb energy up to yielding
a) true
b) false
a) true
Structures constructed from alloys that exhibit ductile-to-brittle behavior should be used only at temperatures below the transition temperature, to avoid brittle and catastrophic failure.
a) true
b) false
b) false
In characterizing cyclic stresses, stress ratio is the ratio of the maximum stress to the minimum stress.
a) true
b) false
b) false
Creep is the time-dependent and permanent deformation occurring at high temperature under a constant load or stress.
a) true
b) false
a) true
Elastic deformation is (1) and (2) deformation.
a) (1) = non-permanent. (2) time-dependent.
b) (1) = non-permanent, (2)= time-independent
c) (1) = permanent, (2) = time-dependent.
d) (1) = permanent, (2) = time-independent.
b) (1) = non-permanent, (2)= time-independent
with increasing temperature, (1) decreases, while (2) increases
a) (1) = yield strength, tensile strength and Young’s modulus, (2)= ductility
b) (1) = yield strength, tensile strength, (2)= Young’s modulus and ductility
c) (1) = yield strength (2)= tensile strength, Young’s modulus and ductility
d) (1) = yield strength, tensile strength and ductility, (2)= Young’s modulus
a) (1) = yield strength, tensile strength and Young’s modulus, (2)= ductility
Toughness has a unit of
a) m/J
b) J/m
c) J/m^2
d) J/m^3
d) J/m^3
for rockwell hardness test, the minor load is 10 kg, whereas major loads are
a) 15, 30, and 45 kg
b) 30, 60 and 90 kg
c) 60, 100 and 150 kg
d) 100, 200 and 300 kg
c) 60, 100 and 150 kg
fatigue life is
a) the stress level at which the material can endure a given number of cycles without failure, say 107 cycles.
b) the number of cycles within which a given specimen sustains before failure occurs at a specified stress level.
c) the fatigue failure occurring at higher stress level and lower number of cycles (smaller than about 10*-10° cycles).
d) the stress level below which the material can endure an infinite number of cycles without failure.
b) the number of cycles within which a given specimen sustains before failure occurs at a specified stress level.
Q: Why are stress and strain used instead of load and deformation?
A) Because they are easier to calculate.
B) They are size-independent measures of load and displacement.
C) Stress and strain provide absolute values of force.
D) They are used to measure electrical properties of materials.
b
Q: What is a key characteristic of elastic behavior in materials?
A) It is irreversible.
B) It follows a non-linear stress-strain relationship.
C) It is reversible and often linear.
D) It occurs at high temperatures only.
c
Q: At what point does plastic behavior occur in a material?
A) When a material reaches its melting point.
B) When the tensile or compressive uniaxial stress reaches 𝜎𝑦
C) When a material is cooled rapidly.
D) During elastic deformation.
b
Q: What is toughness?
A) The resistance of a material to bending.
B) The energy required to permanently deform a material.
C) The energy needed to break a unit volume of material.
D) The ability of a material to return to its original shape after deformation.
c
Q: Which method is most frequently used for testing hardness?
A) Tension test.
B) Microindentation testing methods.
C) Knoop hardness test.
D) Vickers hardness test.
b
Q: What are two ways to increase the strength of a material?
A) Heating and annealing.
B) Cold work and solid solution strengthening.
C) Melting and quenching.
D) Increasing grain size and removing impurities.
b
Q: What is the ductility of a material?
A) The elastic modulus of a material.
B) The amount of plastic strain at failure.
C) The resistance to plastic deformation.
D) The ability of a material to absorb impact without fracturing.
b
Q: What type of stress-strain relationship typically occurs during elastic deformation?
A) Linear
B) Exponential
C) Parabolic
D) Logarithmic
a
Q: Which test is commonly used to determine the tensile strength of a material?
A) Charpy test
B) Brinell hardness test
C) Tensile test
D) Knoop hardness test
c
Q: What is the purpose of a tensile test?
A) To measure the shear strength of a material.
B) To determine the elastic and plastic behavior of materials under tension.
C) To calculate the compression capacity of a material.
D) To measure the thermal conductivity of a material.
b
What does the strain-hardening exponent 𝑛 represent?
A) The ability of a material to recover its shape after deformation.
B) The relationship between stress and strain in the elastic region.
C) The material’s resistance to further plastic deformation after yielding.
D) The thermal expansion coefficient.
c
Q: When performing hardness tests, why is the Knoop test used?
A) It is the cheapest option.
B) It is non-destructive and provides accurate results for metals.
C) It is ideal for testing brittle materials such as ceramics.
D) It is the fastest method available.
c
Q: What material property is estimated from hardness data?
A) Elastic modulus
B) Tensile strength
C) Density
D) Electrical conductivity
b
Q: Which of the following is NOT a way to increase material strength?
A) Cold work
B) Increasing grain size
C) Solid solution strengthening
D) Precipitate strengthening
b
Q: What does decreasing the grain size of a material do to its strength?
A) Increases strength
B) Decreases strength
C) Has no effect on strength
D) Only affects ductility
a
Q: In the context of mechanical properties, what is plastic behavior?
A) Reversible deformation under stress.
B) Permanent deformation that occurs when the material yields.
C) Sudden failure of the material.
D) Elastic recovery after deformation.
b
Q: What happens to the diameter of a cylindrical specimen when it is deformed elastically in tension?
A) It remains constant.
B) It increases.
C) It decreases.
D) It fluctuates depending on the material.
c
Q: What is the value of elastic modulus a measure of?
A) The ability of a material to resist permanent deformation.
B) The force required to fracture a material.
C) The stiffness of a material.
D) The hardness of a material.
c
Q: How is toughness related to material failure?
A) It is the plastic strain at failure.
B) It indicates the stiffness of the material.
C) It is the energy required to break a unit volume of material.
D) It measures the speed of crack propagation.
c
Q: Which of the following best describes a hardness test?
A) A destructive test that measures tensile strength.
B) A simple and inexpensive test that creates a small indentation on the material.
C) A test to measure the impact strength of a material.
D) A method used to calculate ductility.
b
Q: What is the typical outcome of a material undergoing cold work?
A) Increased ductility
B) Increased strength
C) Decreased hardness
D) Increased grain size
b
