Page 54 - Shigley's Mechanical Engineering Design

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Introduction to Mechanical Engineering Design 29
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Introduction to Mechanical Engineering Design
1–23 Convert the following to appropriate SI units:
(a) A length, l = 5 ft.
(b) A stress, σ = 90 kpsi.
(c) A pressure, p = 25 psi.
3
(d) A section modulus, Z = 12 in .
(e) A unit weight, w = 0.208 lbf/in.
(f) A deflection, = 0.001 89 in.
(g) A velocity, v = 1 200 ft/min.
(h) A unit strain, = 0.002 15 in/in.
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(i) A volume, V = 1830 in .
1–24 Generally, final design results are rounded to or fixed to three digits because the given data can-
not justify a greater display. In addition, prefixes should be selected so as to limit number strings
to no more than four digits to the left of the decimal point. Using these rules, as well as those for
the choice of prefixes, solve the following relations:
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(a) σ = M Z, where M = 1770 lbf in and Z = 0.934 in .
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(b) σ = F A, where F = 9440 lbf and A = 23.8 in .
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(c) y = Fl 3EI, where F = 270 lbf, l = 31.5 in, E = 30 Mpsi, and I = 0.154 in .
(d) θ = Tl GJ, where T = 9 740 lbf in, l = 9.85 in, G = 11.3 Mpsi, and d = 1.00 in.
1–25 Repeat Prob. 1–24 for the following:
(a) σ = F wt, where F = 1 kN, w = 25 mm, and t = 5 mm.
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(b) I = bh 12, where b = 10 mm and h = 25 mm.
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(c) I = πd 64, where d = 25.4 mm.
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(d) τ = 16 T πd , where T = 25 N m, and d = 12.7 mm.
1–26 Repeat Prob. 1–24 for:
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(a) τ = F A, where A = πd 4, F = 2 700 lbf, and d = 0.750 in.
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(b) σ = 32 Fa πd , where F = 180 lbf, a = 31.5 in, and d = 1.25 in.
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(c) Z = π(d o d i ) (32 d o ) for d o = 1.50 in and d i = 1.00 in.
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(d) k = (d G) (8 D N), where d = 0.062 5 in, G = 11.3 Mpsi, D = 0.760 in, and N = 32
(a dimensionless number).