Civil Engineering Reference
In-Depth Information
57
:
5
l
=
d
2
:
5
0
:
047
STANDNORMINV
1
0
:
5
f
L
¼ 10
ð
3
:
54e
Þ
This equation is not suitable for practical use. Therefore, on the basis of this
equation an approximate equation was developed
f
L
¼
b
þ
1
1
:
54
b
þ
z
a
¼
0
:
14
:
ð
3
:
54f
Þ
l
=
d
2
:
5
57
:
5
2
:
54
The bending length limit for that the endurance factor f
L
can be valid, is the
nominal bending length l C 10d.
3.2.2.5 Rope Core and Number of Strands
For wire ropes with fibre cores, Müller (
1966
) demands a great mass for the core to
prevent an arching of the strands so that the endurance attained by the wire rope
will be sufficient. See Sect.
1.6.2
for the dimensioning of the core mass.
Wolf (
1987
) carried out bending fatigue tests to discover how much influence
the mass and the material of the fibre core have on the endurance of the wire rope.
All the wire ropes he tested were made with identical strands but with different
cores. Figure
3.41
shows the results of these tests. The mass of the core is drawn as
Warrington 8x19 - FC
rope diameter d = 16 mm
diameter ratio D/d = 25
tensile force S = 30 kN
lubrication viscous oil
7
x 10
5
m
ist
-100
= 94%
m
BOSeli
6
N = breaking number of bending cycles
N
A
= discarding number of bending cycles
discarding number of wire breaks B
A30
= 26
5
91%
98%
4
67%
3
74%
61%
72%
57%
N
2
N
A
1
48%
0
Sisal
PP
PA
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