Wire Ropes Under Tensile Load - Wire Ropes: Tension, Endurance, Reliability - page 139

2.5.2 Minimum Breaking Force

For standardised wire ropes, the measured breaking force F m is mostly greater than
the minimum breaking force F min given in the norm. From tests with 49 round strand
ropes, about half with fibre and half with steel cores, the mean ratio of the measured
breaking force (metal sockets) to the standardised minimum breaking force is

F m
F min

¼ 1 : 156

m

with the standard deviation s = 0.054.
In accordance with that, Chaplin and Potts ( 1991 ) found that the measured
breaking force is 5-20 % bigger than the minimum breaking force. The reason for
this difference is that the measured strength is normally greater than the nominal
strength and that the minimum breaking force in the norm is carefully chosen.

2.5.3 Wire Rope Breaking Force with Different
Terminations

The wire rope breaking force is valid for wire ropes terminated with either resin or
metal sockets. For wire ropes with other terminations, the wire rope breaking force
(more or less reduced) can be estimated with the breaking force factor f F . The
breaking force factor is the ratio of the rope breaking force with a certain termi-
nation F mT and the measured rope breaking force terminated with metal sockets
F m .
The required minimum breaking force of the wire rope with the terminations
T is then

F minT ¼ f F F min m S :

The breaking force factor is listed in Table 2.7 .

Table 2.7 Breaking force
factor f F for rope terminations
related to metal sockets

Rope termination Breaking force factor f F

Splice eye 0.50-0.80

Cylindric aluminum ferrule eye 0.85-1.00

Flemic eye with steel clamp 0.90-1.00

Press bolt 0.90-1.00

Wedge socket (rope lock) 0.80-0.95

U-bolt clamp DIN 1142 0.85-0.95