Wire Ropes Under Tensile Load - Wire Ropes: Tension, Endurance, Reliability - page 84

80

Warrington 8 19-NFC-sZ
rope diameter d = 16.7 mm
met. cross section A = 91.2 mm 2
nominal strength R o = 1570 N/mm 2
measuring length L = 2000 mm

A B C

800

kN

N
mm 2

60

600

40

400

20

200

0 0

0 2 4 6 8 10 12 ‰ 14

rope extension ʵ

Fig. 2.14 Stress-extension curves with loading between different stresses, Feyrer and Jahne

( 1990 )

Figure 2.14 shows the stress-extension curves for the loading and unloading of
the wire rope from Fig. 2.12 after the tenth loading cycle. Between the rope tensile
stresses 0 and 800 N/mm 2 , the tensile stress changes in small steps. In loop A, the
tensile stress increases starting from r z = 0 in steps of Dr z = 100 N/mm 2 and
reduces the stress at every level reached in a small stress loop r upper -
r lower = Dr z = 100 N/mm 2 . The two lowest partial loops still show a clear
hysteresis, but the others do not.
Loop B is again loaded in stress steps of Dr z = 100 N/mm 2 but now starting
from r z = 800 N/mm 2 in a ''down'' direction. The two lowest partial loops show a
clear hysteresis as in loop A. The partial loops for the same stresses r lower and
r upper in the loops A and B are practically parallel. They represent the rope
elasticity modules E S (r lower, r upper ).
In loop C some partial loops of stress-extension curves are shown, starting from
r z = 0 to the upper stresses r upper = 200, 400 and 600 N/mm 2 . The loading
curves are the same for all upper stresses. The unloading curves from these upper
stresses can be taken approximately as a part of the entire unloading curve from
the upper stress 800-0 N/mm 2 , turned around the point for r z = 0.