AME 2303 Test 1 Questions and
Answers7
The deformation of slipping of one plane of atoms over an adjacent plane happens under
___________________. - ANSWERS-shear stress
The actual strength levels of metals is found to be much lower (approximately one to two orders
of magnitude lower) than those obtained from theoretical calculations, and this is because
of______________________ in the crystal structure. - ANSWERS-defects or imperfection
The presence of dislocations in metals lowers the shear stress required to cause slip, while the
entanglements and impediments of dislocations result in a(n) ______________ in the overall
strength and hardness of metal, which is known as _______________. - ANSWERS-increase
work or strain hardening
which metal crystal structure has the least ductility? - ANSWERS-hcp crystals
polymorphism - ANSWERS-is the appearance of more than one type of crystal structure in
metals
anisotropy - ANSWERS-When plastic deformation takes place, the grains in the metal are
elongated in one direction and contracted in the other. This means the metal has become
anistropic, and thus its properties in the vertical direction are different from those in the
horizontal direction.
Embrittlement - ANSWERS-When exposed to certain low-melting-point metals, a normally
ductile and strong metal can crack when subjected to very low external stresses. These
elements weaken the grain boundaries of the metal by embrittlement
, phases of the process of annealing - ANSWERS-recovery
recrystallization
grain growth
Hardness - ANSWERS-the resistance to permanent indentation and the ability to resist wear and
scratch.
Hot Hardness - ANSWERS-the property of material to retain hardness at elevated temperatures.
Dislocations - ANSWERS-Dislocations are line defects, whereby an entire row or column &
sometimes an entire plane exists, that does not align with a perfect lattice.
How are dislocations responsible for work hardening? - ANSWERS-A plane containing a
dislocation requires lower shear stress to cause slip; and yet when dislocations tangle with other
dislocations, point defects, & grain boundaries, the stress to cause slip increases. This makes the
material more hard and strong.
What are the 2 types of impact testing? - ANSWERS-Charpy impact test and Izod impact test.
How is an impact test conducted? - ANSWERS-In an impact test, a pointed hammer tool is
swung on a pendulum. In the trajectory of the swing, the specimen (notched) is placed. When
the specimen breaks due to the impact caused by the swinging hammer, the height of the swing
is reduced. Doing an energy balance, impact to inches is determined.
What is the process of grain formation in polycrystal metals? - ANSWERS-Whenever a liquid
metal is cooled, crystals begin to form at various nucleation rates within. Now these crystals
begin to grow. Each of the nucleated crystals grow into a grain that separates it from the
neighboring crystal by a grain boundary.
Answers7
The deformation of slipping of one plane of atoms over an adjacent plane happens under
___________________. - ANSWERS-shear stress
The actual strength levels of metals is found to be much lower (approximately one to two orders
of magnitude lower) than those obtained from theoretical calculations, and this is because
of______________________ in the crystal structure. - ANSWERS-defects or imperfection
The presence of dislocations in metals lowers the shear stress required to cause slip, while the
entanglements and impediments of dislocations result in a(n) ______________ in the overall
strength and hardness of metal, which is known as _______________. - ANSWERS-increase
work or strain hardening
which metal crystal structure has the least ductility? - ANSWERS-hcp crystals
polymorphism - ANSWERS-is the appearance of more than one type of crystal structure in
metals
anisotropy - ANSWERS-When plastic deformation takes place, the grains in the metal are
elongated in one direction and contracted in the other. This means the metal has become
anistropic, and thus its properties in the vertical direction are different from those in the
horizontal direction.
Embrittlement - ANSWERS-When exposed to certain low-melting-point metals, a normally
ductile and strong metal can crack when subjected to very low external stresses. These
elements weaken the grain boundaries of the metal by embrittlement
, phases of the process of annealing - ANSWERS-recovery
recrystallization
grain growth
Hardness - ANSWERS-the resistance to permanent indentation and the ability to resist wear and
scratch.
Hot Hardness - ANSWERS-the property of material to retain hardness at elevated temperatures.
Dislocations - ANSWERS-Dislocations are line defects, whereby an entire row or column &
sometimes an entire plane exists, that does not align with a perfect lattice.
How are dislocations responsible for work hardening? - ANSWERS-A plane containing a
dislocation requires lower shear stress to cause slip; and yet when dislocations tangle with other
dislocations, point defects, & grain boundaries, the stress to cause slip increases. This makes the
material more hard and strong.
What are the 2 types of impact testing? - ANSWERS-Charpy impact test and Izod impact test.
How is an impact test conducted? - ANSWERS-In an impact test, a pointed hammer tool is
swung on a pendulum. In the trajectory of the swing, the specimen (notched) is placed. When
the specimen breaks due to the impact caused by the swinging hammer, the height of the swing
is reduced. Doing an energy balance, impact to inches is determined.
What is the process of grain formation in polycrystal metals? - ANSWERS-Whenever a liquid
metal is cooled, crystals begin to form at various nucleation rates within. Now these crystals
begin to grow. Each of the nucleated crystals grow into a grain that separates it from the
neighboring crystal by a grain boundary.
