Wire Ropes Under Tensile Load - Wire Ropes: Tension, Endurance, Reliability - page 132

For the practical calculation of the stresses the Excel-program STRESS2.XLS
can be used.

Example 2.14a Wire stresses caused by twisting the rope
Constant twist angle over the entire rope length, continuation of Example 2.9

Data:
rope construction Filler FC

number of strands 6

lay direction sZ

rope diameter d = 16 mm

tensile force S = 40 kN

twist angle x = -192/100d

The lay angle the outer wires and the strands are
a n ; 1 ¼ 15

b 1 ¼ 20 and

Results:

Wire layer 0 1 2(F) 3

Torsional stress s 78 76 31 69

Longitudinal stress from rope twist r rot -148 -89 22 65

Longitudinal stress from the rope force r S 492 485 473 468

Resulting longitudinal wire stress r res 344 396 495 533

Because all resulting longitudinal wire stresses are positive—that means ten-
sile—the rope structure remains intact.
By untwisting the ordinary lay rope, the strands are twisted off. The longitu-
dinal stresses of the wires from the rope tensile force will be reduced for the centre
wire and the wires of the first wire layer by r 0 , 1 respectively r 1,1 and increased for
the filler wires and the outer wires by r 2,1 respectively r 3,1 .
The change of the rope length from twisting off the strands is according to
Eq. ( 2.97f )

DL T ¼ e T L ¼ 0 : 00077 5 ; 000 ¼ 3 : 85 mm :

2.4.6.4 Stresses in Wire Ropes Supported Non-rotated at Both Ends

For the wire rope supported non-rotated at both ends, ( 2.38b ) is again valid for
the torsional stress and ( 2.97f ) or similar equations for the longitudinal stresses.
The twist angles x to be set in these equations have been derived in Sect. 2.4.4 .