Wire Ropes Under Bending and Tensile Stresses - Wire Ropes: Tension, Endurance, Reliability - page 298

from the optimal rope diameter the number of bending cycles does not change very
much. Therefore, the rope diameter can be smaller than the optimal rope diameter by
a reasonable percentage without suffering too great a loss of endurance.

3.4.6 Rope Drive Calculations, Examples

Example 3.7 Numbers of bending cycles

Data:
Filler-rope 6 9 (19 + 6F) - ESWRC - sZ, well lubricated
Nominal rope diameter d = 16 mm
Nominal strength R 0 = 1,960 N/mm 2
Sheave diameter D = 400 mm
Steel groove radius r = 0.55d
Tensile force S = 30 kN
Rel. force difference DS/S = 0.8
Bending length l = 2.4 m.

Number of simple bending cycles:
According to ( 3.55 ) and Tables 3.14 and 3.14a the discard number of bending
cycles is

lg N A10 ¼ 63 ; 500

The endurance factor is f N = f N3 = 0.79 according to Table 3.15 . Then the
adjusted number of simple bending cycles at which with 95 % certainty not more
than 10 % of the ropes have to be discarded is

This and the other dis c arding and breaking numbers of bending cycles are

Number of combined fluctuating tension and bending cycles:
The force factor is f S5 = 1.445 according to ( 3.69 ).
Then the equivalent tensile force for the fluctuating tension and bending is

S equ ¼ f S5 S ¼ 1 : 445 30 ¼ 43 : 35 kN :

with this equivalent force the discard number of bending cycles is

N A10com ¼ 30 ; 100 :