5
-
1
第二?/p>
轴向拉伸与压?/p>
2
-
1
试求图示直杆横截?/p>
1
-
1
?/p>
2
-
2
?/p>
3
-
3
上的轴力,并画出?/p>
力图?/p>
F
N2
F
F
F
F
=2kN
2
2
3
3
1
1
F
F
N1
F
N3
2
2
F
N
(kN)
F
4
=10kN
F
2
=3kN
F
3
=25kN
F
1
=18kN
2
2
1
1
3
3
F
N
(kN)
18
15
10
18kN
F
N1
3kN
18kN
F
N2
10kN
F
N3
F
N1
=
-
2kN
F
N2
= 0kN
F
N3
= 2kN
F
N1
=
-
18kN
F
N2
=
-
15kN
F
N3
= 10kN
F
F
F
+
(
a
)
(
b
)
+
2
-
2
图示中部对称开槽直杆,试求横截?/p>
1
-
1
?/p>
2
-
2
上的正应
力?/p>
1
F
F
=14kN
2
2
1
4
10
20
4
20
.
.
.
解:
1
.轴?/p>
由截面法可求得,杆各横截面上的轴力为
kN
14
N
?/p>
?/p>
?/p>
?/p>
F
F
2
.应?/p>
4
20
10
14
3
1
1
N
1
1
?/p>
?/p>
?/p>
?/p>
?/p>
?/p>
?/p>
A
F
?/p>
MPa
175
?/p>
?/p>
MPa
?/p>
?/p>
4
10
20
10
14
3
2
2
N
2
2
?/p>
?/p>
?/p>
?/p>
?/p>
?/p>
?/p>
?/p>
A
F
?/p>
MPa
350
?/p>
?/p>
MPa