Wire Ropes Under Bending and Tensile Stresses - Wire Ropes: Tension, Endurance, Reliability - page 243

140

x10 3

120 60

r

˕

100

r=0,53d=3,2mm

80

60

Seale 8 x 19 - NFC - sZ
nominal diameter

40

d = 6 mm

R 2 = 1370/1770 N/mm 2

nominal strength

20

sheave diameter D = 86 mm

tensile force S = 2.25 kN

0

0 20 40 60 80 100 120 140 160 180

deflection angle

ˑ D

0 0,5 1,0 1,5 2,0 2,5 3,0 3,5

rope contact length / the rope lay length

Fig. 3.53 Breaking number of bending cycles of a rope for different deflection angles, Müller

( 1961 )

3.2.3.9 Side Deflection of the Rope

It has been well-known for a long time that the side deflection of the rope from the
sheave groove reduces the number of rope bending cycles. Therefore the technical
rules prescribe the limits of 4 for the angle to be allowed for the stranded ropes
and 1.5 for non-rotating and low-rotating ropes.
Matthias ( 1966 , 1970 ) has described the contact form of a side-deflected wire
rope on the groove flank. The first systematic bending fatigue tests with a different
side deflection for the rope were carried out by Neumann ( 1987 ). Figure 3.54
shows as his results the discard number of bending cycles for side deflection angles
between # = w = 0 and 4.
Schönherr ( 2005 ) researched the influence of the side deflection on the breaking
number of bending cycles between the side deflection angle w = 0 and 7 in a
great number of bending fatigue tests. The tests were carried out on six ordinary
lay ropes and multi-strand ropes. The diameter ratio was D/d = 12.5 and 25 and
the specific tensile force varied between S/d 2 = 58-312 N / mm 2 . As an example,
Fig. 3.55 shows the breaking number of bending cycles N and N 10 of a multi-
strand rope, with the side deflection in the same (+ sign) or in the opposite (- sign)
direction to the lay direction of the outside strands. All the results show that the
groove opening angle between c = 30 and 60 has no influence on the number of
rope bending cycles.