F∴σmax=S2=38.1MPa

1-6:解: (1)σAC=-20MPa,σCD=0,σDB=-20MPa;

NL?ACL△ l AC=EA=EA=-0.01mm

?CDL△ l CD=EA=0

?DBL

△ L DB=EA=-0.01mm

(2) ∴?lAB=-0.02mm 1-7:解:

?AC??CB??AC??CB?P?31.8MPaSACP?127MPaSCB NL?ACL??EAEAAC1.59*104, NL?CBL??EAEACB6.36*104

1-8:解:

NlEA?l??l ?l????NEA

?N??EA?2.54*106N

1-9：解：

E?208GPa,??0.317

1-10：

解：???max?59.5MPa????

1-11：解：（1）当??45，??11.2????强度不够

o（2）当??60，??9.17???? 强度够

o1-12：解：

?Y?0,p?200kN?S?P?200kNS200*103????13.3MPa????A100*150*10?6

1-13：解：???max?200MPa?213MPa 1-14：解：1-15 解：

FBC?22Q=70.7 kN

d拉杆?1.78cm,d链环?1.26cm

???S?FSF??70.7?0.505140

查表得： 45*45*3 1-16解：(1)

?????sns?240?1601.5MPa

P????SP?2?????d4 ?D?24.4mm

(2)

??P?SP???2?d???2?119.5MPa?160MPa

21-17 解：（1）

?D?F?P*A?250*????615440N?2?

?AC??n?F?78.4MPaS

?s300??3.83?78.4

F'????' 'S'F????S?60*3.14*15*15?42390N

n?F615440??14.52?15F'42390

1-18 解：P=119kN 1-19 解：

SAB:P:SBC?3:4:5?SAB?35P(拉)，SBC?P44

34同理P2?84kN?SAB??A1????84kN?S?P?AB?112kN1

所以最大载荷 84kN 1-20 解： P=33.3 kN 1-21 解：

FA?P71,FB?P,FC?P12123

1-22 解：

?MAX??10MPa

1-23 解：