Wire Ropes Under Bending and Tensile Stresses - Wire Ropes: Tension, Endurance, Reliability - page 216

A built-on lubrication pump enables the ropes to be lubricated under quantity
control during the bending test.
In any case, it should be ensured that the rope tensile force together with the force
amplitudes vary less than 1 % from the required tensile force. To reduce the unin-
tended fluctuating forces, the sheaves are very precisely mounted in bearings in a
central position and the test sheaves are very light so that the accelerating forces
remain small. With their joint rope bending machine REFMA, built in Turin and
Delft, Ciuffi and Wiek ( 1976 ), Meeuse ( 1976 ) and Wiek ( 1976 ) tried to create a very
precise bending machine. With the help of springs, they synchronised the test fre-
quency close to the self-frequency of the rope-sheave-load system so that it was
almost possible to avoid a rope force to accelerate or decelerate the test sheave.

3.2.1.3 Test Conditions

To gain reliable findings from rope bending tests, the test conditions have to be
very clearly defined and observed. The OIPEEC Recommendation No. 4 OIPEEC
Bulletin 56 (1988) gives these specifications. Table 3.2 lists the minimum speci-
fications defining a wire rope bending fatigue test according to OIPEEC Recom-
mendation No. 4. These specifications are sufficient to ensure that different
institutes with different rope-bending machines come to the same result if the
specifications are complied with, Feyrer ( 1990a ). Other well-defined bending
fatigue tests result in comparable findings, for example from Nabijou and Hobbs
( 1994 ) and Costello ( 1997 ).
The rope tension is normally given by the rope tensile force S. In the case of tensile
rope stress r z or the specific tensile force S/d 2 , it must be declared whether they are

Table 3.2 Minimum specifications for defining a wire rope-bending fatigue test according to the
OIPEEC Recommendation No. 4, OIPEEC Bulletin No. 56 (1988)
Test specification Kind of bending (simple bending, reverse bending) tensile force S

Bending length l
Rope temperature, if more than 50C
Deflecting angle a, if less than 30
Lateral deflection angle # ,if # 6 ¼ 0

Wire rope specification Wire rope construction and lay direction

Nominal rope diameter d
Measured rope diameter d m
Nominal wire strength R 0 , rope grade
Mean measured wire strength R m
Minimum breaking force F min
Measured breaking force F m
Kind of lubrication (lubricant, before and during test)

Sheave specification Sheave diameter D (related to the rope axis) or D 0 (groove ground)

Sheave material and hardness
Groove form, groove radius r, V-groove angle c, etc.