工程力学练习册答案(下)1机械工业出版社.ppt

习题解答 轴向拉压轴向拉压 Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile .Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd. P61 34-1(1) F F F F 2 2F F F F F F F F 11 F F F F 2 2F F F FN N1 1 11 F F 2 2F F F FN N2 2 2 2F F F FN N3 3 F F F FN N1 1 11 22 22 33 33 F F F F F FN N2 2 F F F F F F F FN N3 3 4F 3F 2F FN图 F FFN图 Fy = 0 FN1 = 4F Fy = 0 FN2 = 3F Fy = 0 FN3 = 2F Fy = 0 FN1 = F Fy = 0 FN2 = 0 Fy = 0 FN3 = F P61 34-1(4)六要素 R R F FN N3 3 Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile .Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd. P61 34-2 ABCD F F4 4 F F5 5 F F2 2 F F1 1 F F3 3 E 500 N 920 N 640 N 240 N F1 = 500 NF2 = 420 NF3 = 280 N F4 = 400 NF5 = 240 N FN 图 s = A FN sAB = 1.25 MPasBC = 2.3 MPa sCD = 1.6 MPasDE = 0.6 MPa 应应力单单位: MPa Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile .Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd. P62 34-3 F F3 3 F F1 1F F2 2 ABCD 1 1 2 2 3 3 F FN N1 1 F F3 3 Fx = 0 FN1 = F3 F F3 3 F F2 2 F FN N2 2 F F3 3 F F1 1F F2 2 F FN N3 3 = 30 kN Fx = 0 FN2 = F3 + F2= 40 kN Fx = 0 FN3 = F3 + F2 F1= 30 kN 30kN 40kN 30kN FN图 s1 = A1 FN1 A1 = 410 2 m2= 0.75 MPa s2 = A2 FN2 A2 = 210 2 m2= 2 MPa s3 = A3 FN3 A3 = 410 2 m2= 0.75 MPa Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile .Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd. P62 34-4 F F F F s sa a = = s s coscos 2 2a a 2 2 s s t t a a = = sin2sin2 a a a = 0 s = A FN FN = F = 5 kN = 50 MPa a = 30 a = 45 a = 60 a = 90 50 MPa0 37.5 MPa 21.65 MPa 25 MPa 25 MPa 12.5 MPa 21.65 MPa 00 a n sa ta s s s s 力的单单位: kN Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile .Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd. P63 35-1 F FA A F FB B F FD D F FC C ABCD aaa FNi EAEA F F Ni Ni a a D Dl l i i = = D Dl l i i = = S DS Dl l i i 4 kN1 kN 3 kN 0.05 mm 0.0125 mm 0.0375 mm 0 e 呢? e 与 Dl 区别别? Se ? Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile .Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd. P63 35-2 l2l 2h h A BC DE H 12 3 F FN N1 1 F FN N2 2 F F = F FN N3 3 FN1 = 80 kN FN2 = 40 kN F FN N3 3 = = 120 kN120 kN E1A1 FN1 2h Dl1 = = 0.4 mm E2A2 FN2 2h Dl2 = = 0.4 mm E3A3 FN3 h Dl3 = = 0.2 mm dC dH Dl1 Dl2 dC =Dl1 dH = dC + Dl3 = 0.4 mm = 0.6 mm (1 ) (2 ) dC dH Dl1 Dl2 Dl1 = 0.2 mmDl2 = 0.4 mmDl3 = 0.2 mm dH = dC + Dl3 = 0.267 mm = 0.467 mm dC = Dl1+ Dl2 3 1 3 2 位移分析! Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile .Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd. P64 35-3 A B C l = 4m h = 3m 5m q = 10 kN/m SMA = 0 F F BCBC F FA A y y F FA Ax x FBC = kN 3 100 FN = (1) 斜杆用钢丝索斜杆用钢丝索A = n 4 pd2 s = A FN s 取 n = 67或 (2) 斜杆用两根等边角钢斜杆用两根等边角钢A = 2A1 s = A FN s 取 203( ( A A 1 1 = = 1.13 mm1.13 mm 2 2 ) ) 结论结论 ! n 66.3 66 A1 1.044 mm2 Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile .Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd. P64 35-4 F F AC B 4545 6060 F FN N2 2 F FN N1 1 SFx = 0 SFy = 0 FN1 = 0.897 F FN2 = 0.732 F s1 = A1 FN1 s 1 F 107 kN s2 = A2 FN2 s 2 F 123 kN 则 F = 107 kN Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile .Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd. P65 36-1 A A B BF F F F FN = 5 kNs = A FN = 25 MPa s = Ee1E = e1 s = 208 GPa g = e1 e2 = 15 4 = 0.267 Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile .Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd. P65 36-2 aa a A A B B C C D D F F F FN N F FC C y y F FC Cx x SMC = 0 F FN N = = 2 2 F F s = A FN pd2 8F = (1) pd2 8 F = sS = 37.7 kN 若若 s s = = s sP P p pd d 2 2 8 8 F F = = s sP P = = 31.4 kN 31.4 kN (2) pd2 8 F = sb = 62.8 kN ( ( s se e ) ) 令 s = sS 令 s = sb Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile .Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd. P66 36-3 l ABCD aaa F F F FN N1 1 F FN N2 2 SMA = 0 F FN N1 1 + 2+ 2F F N N2 2 = = 3 3F F EA FN1 l Dl1 = EA FN2 l Dl2 = 代入 Dl1 Dl2 FN2 = 2FN1 联立 求解 FN1 = 30 kN FN2 = 60 kN 且 s2 = A FN2 s 取 补补充方程! 结论结论! F FA A y y F FA Ax x D Dl l 1 1 = = 2 2D Dl l 2 2 FN2 FN1A 相同 s2 s1 A 6 cm2 A = 6 cm2 Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile .Created with Aspose.Slides for .NET 3.5 Clien