Wire Ropes Under Tensile Load - Wire Ropes: Tension, Endurance, Reliability - page 135

Fig. 2.32 T-T fatigue test
results of a spiral strand
1 9 19 at load range
2S a /d 2 = 250 N/mm 2 ,
Ernst ( 2012 )
Fig. 2.33 T-T fatigue test
results of a Seale rope
8 9 19 at load range
2S a /d 2 = 200 N/mm 2 ,
Ernst ( 2012 )
With twisted samples from the Seale rope 8 9 19 Ernst ( 2012 ) have made
several tension-tension tests. The endurance of the twisted samples is mostly
bigger than the untwisted samples in opposite to those from the spiral rope 1 9 19.
However the endurance does not simply increase with the twist angle. The
endurance relation between the twisted and untwisted samples differs from 0.61 to
3.03. The mean endurance relation is for the twisted Seale rope 1.23. In Fig. 2.33
the endurance is shown for the tests with the load range 2S a /d 2 = 200 N/mm 2 and
different lower tensile loads S u /d 2 . In analising the test results Ernst and Wehking
( 2012 ), Ernst ( 2012 ) have made different regression calculations. From such a
regression the constants for the endurance of the tested Seale rope not twisted is
listed in Table 2.9 .
2.4.7.2 Fluctuating Tensile Force: Fluctuating Twist
The first people to test how the endurance of wire ropes is affected by fluctuating
twist and tension were Oplatka and Roth ( 1996 ). In their test machine which they
designed themselves, the wire rope is stressed by a fluctuating tensile force and a