拉压、扭转习题课 小结 拉伸与压缩 扭转 外力 一一一-:一 内力 N
拉压、扭转习题课 小结： 拉伸与压缩 扭转 外力 内力 F FN A Me 1 1 x T
应力 T O max p p 强度条件、≤[a max A ≤[z] 变形 △l O EA E 刚度条件 180 max max ≤[] G p
应力 强度条件 变形 刚度条件 p I T = p max W T = [ ] p max W T A FN = [ ] N,max A F EA F l l N = E = GI p Tl = [ ] π 180 p max max = GI T
(b) 2F F (c)3F 2F F +)F 2F
2-1 (a) F (b) 2F (+) F (+) (-) (+) F (c) 3F (d) 2F F (+) F (+) (-) 2F
2-3 FM=-20kN. FM =-10kN Fm=10kN 10KN F 20×10°N 100MPa , 200mm 10KN 10×103N 20KN N2 33.3MPa 300mm F310×103N n3 = 25MPa A3 400mm
2-3 FN1 = −20k N, FN 2 = −10k N, FN3 = 10k N MPa m m N A FN 100 200 20 10 2 3 1 1 1 = − − = = MPa m m N A FN 33.3 300 10 10 2 3 2 2 2 = − − = = MPa m m N A FN 25 400 10 10 2 3 3 3 3 = = = 10kN (+) (-) 10kN 20kN
2-19 FN=2×(F+P)=60N A=2×4058=811.6mm2 O=2M60×103 =73.9MPa<[o] A811.6
2-19 73.9 [ ] 811.6 60 10 2 405.8 811.6 2 ( ) 60 3 2 = = = = = = + = MPa A F A m m F F P k N N N