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sm9 29

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PROBLEM (9.29) A steel shaft. d = 2 in. in diameter and rotating at n = 2400 rpm is acted upon by
a bending moment of M = 5 kip-in. Calculate the torque and the horsepower that can also be applied
simultaneously to the shaft.
Given: τ all = 9 ksi,
σ all = 14 ksi
SOLUTION
Mc 32 M 32(5 × 103 )
σx =
=
=
= 6.37 ksi
πd3
π (2)3
I
τ
(ksi)
(637, τ )
R
C
6.37 ksi
O
τ=
3.185
Tc
J
σ1
σ
(ksi)
9
For Mohr's circle:
τ = 9 2 − 3.1852 = 8.42 ksi
σ 1 = 3.185 + 9 = 12.185 ksi < 14 ksi
O.K.
Thus,
T=
τJ
=
τπ c3
=
8.42 ×103 (π )(1)3
= 13.23 kip ⋅ in.
2
2
c
Formula (5.26)
TN
13.23 × 103 (2400)
=
= 504 hp
P=
63, 000
63, 000
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