Wire Ropes Under Tensile Load - Wire Ropes: Tension, Endurance, Reliability - page 150

In the last column in Table 2.8 , the mean numbers of load cycles are registered,
calculated with ( 2.102a ) for a rope diameter d = 30 mm. The difference between
the numbers of load cycles from regressions of both diameter ranges tested with
the mean numbers of wires z = 37 respectively 199 and those of the common
regression is very small. Therefore, the common regression is legitimated.
2.6.3.2 Spiral Wire Ropes with Metal Sockets
Hugo Müller has carried out tension-tension fatigue tests (unpublished) with a
locked coil spiral rope with metal sockets. The rope with a diameter d = 28 mm
has round wires 1 + 6 + 12 + 18 and 19Z-wires outside. His results
(a 0 = 12.528; a 1 = -2.960) showed about 55 % of the endurance found for a
comparable open spiral rope terminated with resin sockets. Yeung and Walton
( 1985 ) have done numerous tension-tension fatigue tests with spiral ropes. They
did not use constant forces but a light force collective. This means that the results
cannot be compared with those using constant forces.
2.6.3.3 Round Strand Wire Ropes with Resin Sockets
Tension-tension fatigue tests have been carried out with various round strand wire
ropes using resin sockets as terminations. The wire ropes tested are listed in
Table 2.9 . The results of the tests have been used in regression calculations based
on ( 2.102 ). The constants thus determined are also included in Table 2.9 .
A very large number of tension-tension fatigue tests have been carried out
using Warrington-Seale 6-strand ropes in ordinary lay with steel core. Wehking
and Klöpfer ( 2000 ) tested ropes with diameters d = 8-36 mm and Casey ( 1993 )
ropes with diameters d = 38-127 mm. For the ropes with smaller diameters of up
to 40 mm, the strands had 36 wires, the wire rope with a diameter of 70 mm had
41 wires and the 127 mm wire rope had 49 wires.
Of the Warrington-Seale ropes tested by Wehking and Klöpfer, seven ropes
were zinc coated and five bright. The wire ropes Casey tested were all zinc coated.
All the wire ropes were lubricated. From the existing database, it is not possible to
evaluate whether either the zinc coating or the nominal strength influence the
endurance of the rope. Therefore the constants for the Warrington-Seale ropes in
Table 2.9 are valid for ropes, whether zinc coated or bright, with a nominal
strength between 1,570 and 1,960 N/mm 2 .
The results of the regression calculations based on the data from the tests on the
Warrington-Seale ropes are also listed in Table 2.9 . The common regression
calculation done on the basis of the data from Wehking and Klöpfer and Casey is
very well-founded as the numbers of load cycles for both test series calculated with
their constants come very close to that for a rope diameter 38 mm. As the ropes
tested varied greatly in quality, the coefficient of determination is only B = 0.68
and the standard deviation is lg s = 0.266. Then, using the constants k T10 = 1.575