Page 113 - Mechanical Behavior of Materials

114 Chapter 3 A Survey of Engineering Materials

DAVIS, J. R., ed. 2003. Handbook of Materials for Medical Devices, ASM International, Materials Park, OH.
GAUTHIER, M. M., vol. chair. 1995. Engineered Materials Handbook, Desk Edition, ASM International,
Materials Park, OH.
HARPER, C. A., ed. 2006. Handbook of Plastics Technologies, McGraw-Hill, New York.
SOMIYA, S., et al., eds. 2003. Handbook of Advanced Ceramics, vols. 1 and 2, Elsevier Academic Press,
London, UK.

PROBLEMS AND QUESTIONS

Sections 3.2 to 3.4
3.1 Examine several small metal tools or parts. Try to determine whether each was formed by
forging, rolling, extrusion, drawing, or casting. Consider the overall shape of the object, any
surface features that exist, and even words that are marked on the part.
3.2 Nickel and copper are mutually soluble in all percentages as substitutional alloys with an FCC
crystal structure. The effect of up to 30% nickel on the yield strength of copper is shown in
Fig. 3.3. Draw a qualitative graph showing how you expect the yield strength of otherwise
pure Cu-Ni alloys to vary as the nickel content is varied from zero to 100%.
3.3 Briefly explain why austenitic stainless steels cannot be strengthened by quenching and
tempering.
3.4 In the development of human technology, the stone age was followed by a bronze age, which
in turn was followed by an iron age. Why not a brass age? (Note that copper alloyed with 35%
zinc gives a typical brass. Also, copper alloyed with 10% tin gives a typical bronze.) Why did
the iron age not occur immediately after the stone age?
3.5 Explain why beryllium metal is a good choice for the hexagonal sections of the primary mirror
for the James Webb Space Telescope, scheduled by NASA to be launched in 2014. Start by
finding values of some of the basic properties of beryllium, such as its melting temperature
T m , density ρ, elastic modulus E, and coefficient of thermal expansion α, as well as general
information about this telescope.

Section 3.5
3.6 In your own words, explain why thermosetting plastics do not have a pronounced decrease in
the elastic modulus, E, at a glass transition temperature, T g .
3.7 For the polymers in Table 3.9, plot T g versus T m after converting both to absolute temperature.
Use a different plotting symbol for each class of polymers. Does there appear to be a correla-
tion between T g and T m ? Are there different trends for the different classes of polymers?
3.8 Engineering plastics in bulk form typically have elastic moduli in the range E =2to3GPa.
However, for Kevlar fibers, the value can be as high as 120 GPa. Explain how this is possible.
3.9 Ultrahigh molecular weight polyethylene (UHMWPE) is used for bearing surfaces in joint
replacement surgery. Consult one or more references, and/or do an Internet search, on this
subject. Determine in more detail how and where UHMWPE is used in the human body,
and identify its special characteristics that make it suitable for such use. Then write a few
paragraphs summarizing what you have found.