sm7 1

PROBLEM (7.1) A copper wire of diameter d and modulus of elasticity E is coiled around
a spool of radius r . Compute the maximum stress and the bending moment in the wire.
Given: d = 1/32 in., r = 6 in., E = 17 x 106 psi
SOLUTION
6.ri
d n
=
.6.015625 in
ρ
=
10.03125 .
32
di n==
Equation (7.4):
6
max 17 10 (0.015625)
6.015625
Ec
σρ
×
== 44.2 ksi
=
max 3
32
M
cM
I
d
σπ ==
or
3
max 32
d
M
π
σ =
33
44.2 10 (0.03125)
32
π
×
=0.138 .lb in
=
⋅
________________________________________________________________________
r
ρ
C
Excerpts from this work may be reproduced by instructors for distribution on a not-for-profit basis for testing or
instructional purposes only to students enrolled in courses for which the textbook has been adopted. Any other
reproduction or translation of this work beyond that permitted by Sections 107 or 108 of the 1976 United States
Copyright Act without the permission of the copyright owner is unlawful.