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：