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15_ch 08 Mechanical Design budynas_SM_ch08

# 15_ch 08 Mechanical Design budynas_SM_ch08 - (a ISO M 20 ×...

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218 Solutions Manual • Instructor’s Solution Manual to Accompany Mechanical Engineering Design (b) Washers: t = 3 . 4mm, d = 20 mm, D = 30 mm, E = 207 GPa k 1 = 42 175 MN/m Cast iron: t = 20 mm, d = 20 mm, D = 30 + 2(3 . 4) tan 30 = 33 . 93 mm, E = 135 GPa k 2 = 7885 MN/m Steel: t = 20 mm, d = 20 mm, D = 33.93 mm, E = 207 GPa k 3 = 12 090 MN/m k m = (2 / 42 175 + 1 / 7885 + 1 / 12 090) 1 = 3892 MN/m Bolt: l = 46 . 8 mm. Nut: H = 18 mm. L > 46 . 8 + 18 = 64 . 8 mm. Use L = 80 mm. L T = 2(20) + 6 = 46 mm, l d = 80 46 = 34 mm, l t = 46 . 8 34 = 12 . 8mm , A t = 245 mm 2 , A d = π 20 2 / 4 = 314 . 2mm 2 k b = A d A t E A d l t + A t l d = 314 . 2(245)(207) 314 . 2(12 . 8) + 245(34) = 1290 MN/m C = 1290 / (1290 + 3892) = 0 . 2489, S p = 600 MPa, F i = 132 . 3kN n = S p A t F i C ( P / N ) = 600(0 . 245) 132 . 3 0 . 2489(15 / 4) = 15 . 7 Ans. Bolts are a bit oversized for the load.
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Unformatted text preview: (a) ISO M 20 × 2 . 5 grade 8.8 coarse pitch bolts, lubricated. Table 8-2 A t = 245 mm 2 Table 8-11 S p = 600 MPa A d = π (20) 2 / 4 = 314 . 2 mm 2 F p = 245(0 . 600) = 147 kN F i = . 90 F p = . 90(147) = 132 . 3 kN T = . 18(132 . 3)(20) = 476 N · m Ans . (b) L ≥ l + H = 48 + 18 = 66 mm. Therefore, set L = 80 mm per Table A-17. L T = 2 D + 6 = 2(20) + 6 = 46 mm l d = L − L T = 80 − 46 = 34 mm l t = l − l d = 48 − 34 = 14 mm 14 Not to scale 80 48 grip 46 34...
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