Civil Engineering Reference
In-Depth Information
For all wires and especially for the outer wires, the resulting tensile stresses
from the rope rotation and from the rope tensile force are positive. Therefore the
outside wires will not be loose and inner wires do not break out. The rope structure
remains intact.
2.4.6.5 Steel Core
If instead of a rope with fibre core a rope with steel core were to be used, then the
longitudinal and the torsional stresses in the wires would be a little smaller than
those in the wire rope with fibre core. However, a tensile strand stress has to be
added to these tensile stresses and a large tensile stress range will occur in the steel
core and the strands.
At the upper rope end the steel core can—depending on the core construction—
even be loaded by the whole rope tensile force with totally unloaded strands.
And at the lower rope end a large compressive stress of the core exists because
normally the core cannot escape laterally.
2.4.7 Rope Endurance Under Twist
2.4.7.1 Twist Angle Constant: Tensile Force Fluctuating
With small changed termination devices very normal tension-tension machines
can be used for these wire rope testings, Ernst ( 2012 ).
Ernst and Wehking ( 2012 ), Ernst ( 2012 ) evaluated the endurance of two wire
ropes under constant twist and pulsating tensile force. The constant twist during
the tests differs between -360/100d and 360/100d. The two ropes from that the
test pieces have been taken are
• Spiral round wire rope 1 9 19, 12 mm
• Seale 8 9 19-IWRC-sZ, 12 mm.
The rope pieces have been fixed at both ends in resin sockets. The tension-
tension tests end with the rope break or with 2 million load cycles if no rope break
occurs.
Figure 2.32 shows the result of the tension-tension tests with pieces of the
spiral wire rope 1 9 19. In that Figure the diameter related force range is
2S a /d 2 = 250 N/mm 2 . Under the influence of the rope twisting the rope endurance
is strongly reduced in all the tests. For a twist angle -180/100d as an example,
the remaining endurance has a percentage between 22 and 62 % of the untwisted
rope piece. The endurance loss is greater the greater the twist angle is.
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