辽宁工业大学：《材料力学》课程教学资源（PPT课件讲稿）拉压、扭转习题课

2-21 AD杆: 300×2 NI =300kN,2 2 F,300×103 A1=b:02x A1 NI =1764.7mm O 0 选择80×80×6(9397cm2)

2-21 AD杆： 80 80 6(9.397 ) 8.82 1764.7 170 300 10 [ ] 300 ,2 2 300 2 2 2 1 2 3 1 1 1 cm A cm m m F A F k N N N   = =  = = =  = 选择 

AB杆: F=2×300=600kN F600×10 242=M2 =15294mm O 170 A1=1765cm2 选择100×100×10(19261cm2)

AB杆： 100 100 10(19.261 ) 17.65 1529.4 170 600 10 [ ] 2 2 300 600 2 2 1 2 3 2 2 1 cm A cm m m F A F k N N N   = =  = = =  = 选择 

第3次作业: 2-7 F F F 1F23 n3 3 △= EA EA EA F Fl F Fl Fl BEA 3EA3EA 3EA D △Z → 3EA

第3次作业： 2-7 F F F EA Fl EA Fl EA Fl EA Fl EA l F EA l F EA l F l N N N 3 3 3 3 3 3 3 1 2 3 + = − = +  = + + ( ) 3 =  = → EA Fl u l D