MATERIALS ENGINEERING CONCEPTS - Materials for Civil and Construction Engineers - page 45

150

Metal A
Metal B

100

50

0

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14

Strain, in./in.

FIGURE P1.13

1.14 A brass alloy has a yield strength of 280 MPa, a tensile strength of
390 MPa, and an elastic modulus of 105 GPa. A cylindrical specimen
of this alloy 12.7 mm in diameter and 250 mm long is stressed in
tension and found to elongate 7.6 mm. On the basis of the informa-
tion given, is it possible to compute the magnitude of the load that
is necessary to produce this change in length? If so, calculate the
load. If not, explain why.
1.15 Figure P1.15 shows (i) elastic-perfectly plastic and (ii) elastoplastic
with strain hardening idealized responses. What stress is needed in
each case to have
a. a strain of 0.001?
b. a strain of 0.004?

s

d s
d

(ii)

10 6 psi 2

60,000 psi

(i)

10 6 psi E 30

FIGURE P1.15

1.16 An elastoplastic material with strain hardening has the stress-strain
relation shown in Figure P1.16. The yield point corresponds to 600
MPa stress and 0.003 m/m strain.
a. If a bar made of this material is subjected to a stress of 650 MPa
and then released, what is the permanent strain?
b. What is the percent increase in yield strength that is gained by
the strain hardening shown in part (a)?
c. What is the percent increase in strength that is gained by the
strain hardening shown in part (a)?
d. After strain hardening, if the material is subjected to a stress of
625 MPa, how much strain is obtained? Is this strain elastic, per-
manent, or a combination of both?