lOMoAR cPSD| 22896205
INSTRUCTORS SOLUTION MANUAL THE SCIENCE AND ENGINEERING OF
MATERIALS FOURTH EDITION
pg. 1
, lOMoAR cPSD| 22896205
1
Introduction to Materials Science and
Engineering
1–5 Iron is often coated with a thin layer of zinc if it is to be used outside. What characteristics do you think the
zinc provides to this coated, or galvanized, steel? What precautions should be considered in producing this product?
How will the recyclability 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
pg. 2
, lOMoAR cPSD| 22896205
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
energyabsorbing 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 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?
pg. 3
, lOMoAR cPSD| 22896205
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
CHAPTER 1 Introduction to Materials Science and Engineering 3
of steel, but with only a fraction of the weight, can be produced in this manner.
1–10 You would like to place a three-foot diameter microsatellite into orbit. The satellite
will contain delicate electronic equipment that will send and receive radio signals
from earth. Design the outer shell within which the electronic equipment is
contained. What properties will be required and what kind of materials might be
considered?
Solution: The shell of the microsatellite must satisfy several criteria. The material
should have a low density, minimizing the satellite weight so that it can
be lifted economically into its orbit; the material must be strong, hard,
and impact resistant in order to assure that any “space dust” that might
strike the satellite does not penetrate and damage the electronic
equipment; the material must be transparent to the radio signals that
provide communication between the satellite and earth; and the
material must provide some thermal insulation to assure that solar
heating does not damage the electronics.
One approach might be to use a composite shell of several materials.
The outside surface might be a very thin reflective metal coating that
would help reflect solar heat. The main body of the shell might be a
light weight fiber-reinforced composite that would provide impact
resistance (preventing penetration by dust particles) but would be
transparent to radio signals.
1–11 What properties should the head of a carpenter’s hammer possess? How would you
manufacture a hammer head?
Solution: The head for a carpenter’s hammer is produced by forging, a
metalworking process; a simple steel shape is heated and formed in
several steps while hot into the required shape. The head is then heat
treated to produce the required mechanical and physical properties.
The striking face and claws of the hammer should be hard—the metal
should not dent or deform when driving or removing nails. Yet these
portions must also possess some impact resistance, particularly so that
chips do not flake off the striking face and cause injuries.
pg. 4
INSTRUCTORS SOLUTION MANUAL THE SCIENCE AND ENGINEERING OF
MATERIALS FOURTH EDITION
pg. 1
, lOMoAR cPSD| 22896205
1
Introduction to Materials Science and
Engineering
1–5 Iron is often coated with a thin layer of zinc if it is to be used outside. What characteristics do you think the
zinc provides to this coated, or galvanized, steel? What precautions should be considered in producing this product?
How will the recyclability 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
pg. 2
, lOMoAR cPSD| 22896205
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
energyabsorbing 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 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?
pg. 3
, lOMoAR cPSD| 22896205
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
CHAPTER 1 Introduction to Materials Science and Engineering 3
of steel, but with only a fraction of the weight, can be produced in this manner.
1–10 You would like to place a three-foot diameter microsatellite into orbit. The satellite
will contain delicate electronic equipment that will send and receive radio signals
from earth. Design the outer shell within which the electronic equipment is
contained. What properties will be required and what kind of materials might be
considered?
Solution: The shell of the microsatellite must satisfy several criteria. The material
should have a low density, minimizing the satellite weight so that it can
be lifted economically into its orbit; the material must be strong, hard,
and impact resistant in order to assure that any “space dust” that might
strike the satellite does not penetrate and damage the electronic
equipment; the material must be transparent to the radio signals that
provide communication between the satellite and earth; and the
material must provide some thermal insulation to assure that solar
heating does not damage the electronics.
One approach might be to use a composite shell of several materials.
The outside surface might be a very thin reflective metal coating that
would help reflect solar heat. The main body of the shell might be a
light weight fiber-reinforced composite that would provide impact
resistance (preventing penetration by dust particles) but would be
transparent to radio signals.
1–11 What properties should the head of a carpenter’s hammer possess? How would you
manufacture a hammer head?
Solution: The head for a carpenter’s hammer is produced by forging, a
metalworking process; a simple steel shape is heated and formed in
several steps while hot into the required shape. The head is then heat
treated to produce the required mechanical and physical properties.
The striking face and claws of the hammer should be hard—the metal
should not dent or deform when driving or removing nails. Yet these
portions must also possess some impact resistance, particularly so that
chips do not flake off the striking face and cause injuries.
pg. 4
