Page 183 - Mechanical Behavior of Materials

184 Chapter 4 Mechanical Testing: Tension Test and Other Basic Tests

Section 4.4
4.15 Using Tables 3.10, 4.2, and 4.3, write a paragraph that discusses in general terms the
differences among engineering metals, polymers, ceramics, and silica glasses as to their tensile
strength, ductility, and stiffness.
4.16 Using the data for various steels in Tables 4.2 and 14.1, plot ultimate tensile strength
versus percent reduction in area. Use linear coordinates. Also, use two different plotting
symbols, one for the steels that are not strengthened by heat treating, which are 1020, 1015,
Man-Ten, and 1045 (HR), and one for all of the others (which are strengthened by heat
treatment). Then comment on any general trends that are apparent and any exceptions to these
trends.
4.17 On the basis of the data for SiC reinforced aluminum in Table 4.4, write a paragraph discussing
the effects of various types and orientations of reinforcement on the stiffness, strength, and
ductility. Also, estimate the tensile toughness u f for each case, and include this in your
discussion.

Section 4.5 2
4.18 Explain in your own words, without using equations, the difference between engineering stress
and true stress and the difference between engineering strain and true strain.
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4.19 Consider the tension test of Prob. 4.9 for AISI 4140 steel tempered at 204 C (400 F).
(a) Calculate true stresses and strains for the data up to the ultimate tensile strength. Plot
these values and compare the resulting true stress–strain curve with the engineering
one from the original data.
(b) For the points from (a) that are beyond yielding, calculate true plastic strains, and fit
these with the true stresses to Eq. 4.23 to obtain values of Hand n. Show data and fit
on a log–log plot.
(c) Calculate the true fracture strength and the true fracture strain, including the Bridgman
correction for the former. Also calculate the true plastic strain at fracture, and add the
corresponding point to your log–log plot from (b). If your fitted line is extended, is it
consistent with the fracture point?
4.20 Consider the tension test of Prob. 4.6 for 6061-T6 aluminum. Analyze these data in terms of
true stresses and strains by following the same procedure as in Prob. 4.19(a) and (b).
4.21 Consider the tension test of Prob. 4.10 for 7075-T651 aluminum. Analyze these data in terms
of true stresses and strains by following the same procedure as in Prob. 4.19(a) and (b).
4.22 For a number of points during a tension test on Man-Ten steel, engineering stress and strain
data are given in Table P4.22. Also given are minimum diameters measured in the necked
region in the latter portions of the test. The initial diameter was 6.32 mm.
(a) Evaluate the following engineering stress–strain properties: elastic modulus, yield
strength, ultimate tensile strength, and percent reduction in area.

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Where fitting of Eq. 4.23 is requested, do not include data points with plastic strain values smaller than about 0.001, as
needed to obtain a good linear trend on a log–log plot similar to Fig. 4.21.