Wire Ropes Under Tensile Load - Wire Ropes: Tension, Endurance, Reliability - page 145

Fig. 2.39 Number of load
cycles N, wire rope A, Warr.
8 9 19-SFC-sZ, resin socket

99
%

2S a /d 2 = 188 N/mm 2
S lower /d 2 = 192 N/mm 2
N = 406 000
I gs = 0.092

95

90

80

70

60

50

40

30

20

10

5

1

10 6 10 23457

number of load cycles N

continuation may start at the limiting load cycles N D = 2,000,000. The number of
load cycles for this fictitious continuation is

2 a 1 þ 1

2S a = d 2
2 S aD = d 2

N ¼ N D : ð 2 : 104 Þ

In this equation, 2 S aD /d 2 is the force range at the number of load cycles
N D = 2,000,000. The Woehler diagram in Fig. 2.38 is still drawn for wire rope C
in two lines for N D = 1,000,000 (as found from Fig. 2.37 ) with the help of ( 2.102 )
and ( 2.104 ). The first line has the value S lower /d 2 = 0 for the lower specific force
and at the same time for S lower /d 2 = 352 N/mm 2 . The second line with the max-
imum possible mean number of load cycles has the value S lower /d 2 = 176 N/mm 2
for the lower specific force. A Woehler line can be calculated and drawn between
these lines for other lower specific forces.

2.6.2.4 Distribution of the Number of Load Cycles

As can be seen from the form of ( 2.102 ), the described regression is based on the
logarithm normal distribution. This is justified because it was found, for example,
that the logarithm normal distribution provided a very good degree of conformity
for the number of load cycles of the specimens from wire ropes A and C which