Instructors Solution Manual The Science And
Engineering Of Materials 4th Edition Author: Donald
R. Askeland Latest Version
0|Page
,1
IntroductiontoMaterialsScience and Engineering
1–5 Iron is often coated with a thin layer of zinc if it is to be used outside. What
charac- teristics do you think the zinc provides to this coated, or galvanized,
steel? What precautions should be considered in producing this product? How
will the recycla- bility of the product be affected?
Solution: The zinc provides corrosion resistance to the iron in two ways. If the
iron is completely coated with zinc, the zinc provides a barrier
between the iron and the surrounding environment, therefore
protecting the underlying iron. If the zinc coating is scratched to
expose the iron, the zinc continues to protect the iron because the
zinc corrodes preferentially to the iron (see Chapter 22). To be
effective, the zinc should bond well to the iron so that it does not
permit reactions to occur at the interface with the iron and so that
the zinc remains intact during any forming of the galvanized material.
When the material is recycled, the zinc will be lost by oxidation and
vaporization, often producing a “zinc dust” that may pose an
environmental hazard. Special equipment may be required to collect
and either recycle or dispose of the zinc dust.
1–6 We would like to produce a transparent canopy for an aircraft. If we were to use
a ceramic (that is, traditional window glass) canopy, rocks or birds might cause it
to shatter. Design a material that would minimize damage or at least keep the
canopy from breaking into pieces.
Solution: We might sandwich a thin sheet of a transparent polymer between
two layers of the glass. This approach, used for windshields of
automobiles, will prevent the “safety” glass from completely
disintegrating when it
1
, 2 The Science and Engineering of Materials Instructor’s Solution Manual
fails, with the polymer holding the broken pieces of glass together
until the canopy can be replaced.
Another approach might be to use a transparent, “glassy” polymer
material such as polycarbonate. Some polymers have reasonably
good impact properties and may resist failure. The polymers can
also be toughened to resist impact by introducing tiny globules of a
rubber,
or elastomer, into the polymer; these globules improve the energy-
absorbing ability of the composite polymer, while being too small to
interfere with the optical properties of the material.
1–7 Coiled springs ought to be very strong and stiff. Si3N4 is a strong, stiff material.
Would you select this material for a spring? Explain.
Solution: Springs are intended to resist high elastic forces, where only the
atomic bonds are stretched when the force is applied. The silicon
nitride would satisfy this requirement. However, we would like to
also have good resistance to impact and at least some ductility (in
case the spring is overloaded) to assure that the spring will not fail
catastrophically. We also would like to be sure that all springs will
perform satisfactorily.
Ceramic materials such as silicon nitride have virtually no ductility,
poor impact properties, and often are difficult to manufacture
without introducing at least some small flaws that cause to fail
even for relatively low forces. The silicon nitride is NOT
recommended.
1–8 Temperature indicators are sometimes produced from a coiled metal strip that
uncoils a specific amount when the temperature increases. How does this work;
from what kind of material would the indicator be made; and what are the
important properties that the material in the indicator must possess?
Solution: Bimetallic materials are produced by bonding two materials having
different coefficients of thermal expansion to one another, forming a
laminar composite. When the temperature changes, one of the
materials will expand or contract more than the other material. This
difference in expansion or contraction causes the bimetallic material
to change shape; if the original shape is that of a coil, then the device
will coil or uncoil, depending on the direction of the temperature
change. In order for the material to perform well, the two materials
must have very different coefficients of thermal expansion and should
have high enough modulus of elasticity so that no permanent
2|Page
, CHAPTER 1 Introduction to Materials Science and Engineering 3
deformation of the material occurs.
1–9 You would like to design an aircraft that can be flown by human power nonstop
for a distance of 30 km. What types of material properties would you
recommend?
What materials might be appropriate?
Solution: Such an aircraft must possess enough strength and stiffness to
resist its own weight, the weight of the human “power source”,
and any
aerodynamic forces imposed on it. On the other hand, it must be as
light as possible to assure that the human can generate enough work
to operate the aircraft. Composite materials, particularly those
based on a polymer matrix, might comprise the bulk of the aircraft.
The polymers have a light weight (with densities of less than half that
of aluminum) and can be strengthened by introducing strong, stiff
fibers made of glass, carbon, or other polymers. Composites having
the strength and stiffness
Engineering Of Materials 4th Edition Author: Donald
R. Askeland Latest Version
0|Page
,1
IntroductiontoMaterialsScience and Engineering
1–5 Iron is often coated with a thin layer of zinc if it is to be used outside. What
charac- teristics do you think the zinc provides to this coated, or galvanized,
steel? What precautions should be considered in producing this product? How
will the recycla- bility of the product be affected?
Solution: The zinc provides corrosion resistance to the iron in two ways. If the
iron is completely coated with zinc, the zinc provides a barrier
between the iron and the surrounding environment, therefore
protecting the underlying iron. If the zinc coating is scratched to
expose the iron, the zinc continues to protect the iron because the
zinc corrodes preferentially to the iron (see Chapter 22). To be
effective, the zinc should bond well to the iron so that it does not
permit reactions to occur at the interface with the iron and so that
the zinc remains intact during any forming of the galvanized material.
When the material is recycled, the zinc will be lost by oxidation and
vaporization, often producing a “zinc dust” that may pose an
environmental hazard. Special equipment may be required to collect
and either recycle or dispose of the zinc dust.
1–6 We would like to produce a transparent canopy for an aircraft. If we were to use
a ceramic (that is, traditional window glass) canopy, rocks or birds might cause it
to shatter. Design a material that would minimize damage or at least keep the
canopy from breaking into pieces.
Solution: We might sandwich a thin sheet of a transparent polymer between
two layers of the glass. This approach, used for windshields of
automobiles, will prevent the “safety” glass from completely
disintegrating when it
1
, 2 The Science and Engineering of Materials Instructor’s Solution Manual
fails, with the polymer holding the broken pieces of glass together
until the canopy can be replaced.
Another approach might be to use a transparent, “glassy” polymer
material such as polycarbonate. Some polymers have reasonably
good impact properties and may resist failure. The polymers can
also be toughened to resist impact by introducing tiny globules of a
rubber,
or elastomer, into the polymer; these globules improve the energy-
absorbing ability of the composite polymer, while being too small to
interfere with the optical properties of the material.
1–7 Coiled springs ought to be very strong and stiff. Si3N4 is a strong, stiff material.
Would you select this material for a spring? Explain.
Solution: Springs are intended to resist high elastic forces, where only the
atomic bonds are stretched when the force is applied. The silicon
nitride would satisfy this requirement. However, we would like to
also have good resistance to impact and at least some ductility (in
case the spring is overloaded) to assure that the spring will not fail
catastrophically. We also would like to be sure that all springs will
perform satisfactorily.
Ceramic materials such as silicon nitride have virtually no ductility,
poor impact properties, and often are difficult to manufacture
without introducing at least some small flaws that cause to fail
even for relatively low forces. The silicon nitride is NOT
recommended.
1–8 Temperature indicators are sometimes produced from a coiled metal strip that
uncoils a specific amount when the temperature increases. How does this work;
from what kind of material would the indicator be made; and what are the
important properties that the material in the indicator must possess?
Solution: Bimetallic materials are produced by bonding two materials having
different coefficients of thermal expansion to one another, forming a
laminar composite. When the temperature changes, one of the
materials will expand or contract more than the other material. This
difference in expansion or contraction causes the bimetallic material
to change shape; if the original shape is that of a coil, then the device
will coil or uncoil, depending on the direction of the temperature
change. In order for the material to perform well, the two materials
must have very different coefficients of thermal expansion and should
have high enough modulus of elasticity so that no permanent
2|Page
, CHAPTER 1 Introduction to Materials Science and Engineering 3
deformation of the material occurs.
1–9 You would like to design an aircraft that can be flown by human power nonstop
for a distance of 30 km. What types of material properties would you
recommend?
What materials might be appropriate?
Solution: Such an aircraft must possess enough strength and stiffness to
resist its own weight, the weight of the human “power source”,
and any
aerodynamic forces imposed on it. On the other hand, it must be as
light as possible to assure that the human can generate enough work
to operate the aircraft. Composite materials, particularly those
based on a polymer matrix, might comprise the bulk of the aircraft.
The polymers have a light weight (with densities of less than half that
of aluminum) and can be strengthened by introducing strong, stiff
fibers made of glass, carbon, or other polymers. Composites having
the strength and stiffness
