Civil Engineering Reference
In-Depth Information
2.6.4.2 Size Effect Wire Rope Diameter
Müller (
1966
) was the first to investigate the effect of the size of the rope diameter
on cross lay wire ropes 6 9 19—FNC—sZ. Figure
2.44
shows his results. The
mean ratio of the number of load cycles N
1
/N
2
of two wire ropes with the diam-
eters d
1
and d
2
is
a
4
:
N
1
N
2
d
1
d
2
¼
ð
2
:
105
Þ
For the lubricated cross lay ropes, Müller found exponents a
4
= -1.021 and
0.535. For different test series the constants a
4
are listed in the Tables
2.8
,
2.9
and
2.10
. For the whole diameter sphere of the open spiral ropes 4-127 mm, the
constant is a
4
= -0.793. For the diameter sphere 8-127 mm of the Warrington-
Seale ropes, the constant is a
4
= -1.180. The influence of the rope diameter is
higher in the case of tension-tension fatigue than in the case of bending fatigue
with the exponent -0.63.
There is no explanation for this difference between the exponents for tension
and bending. It could have been expected that the size of the diameter had a greater
influence on bending due to the stress gradient effect. In any case, the results
emphasize Unterberg's statement (
1967
) that a stress gradient effect does not exist
for rope wires.
%
L=10430 mm
L=2030 mm
L=1040 mm
99
95
90
80
70
60
50
40
30
20
10
d = 0,6 inch
2
5
˃
a
= 350 N/mm
2
˃
max
= 0,7 R
m
f = 3,5 H
z
1
5
10
5
10
5
number of load cycles N
Fig. 2.45
Number of load cycles for a strand 1 9 7 for different lengths L, Esslinger (
1992
)
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