Wire Ropes Under Tensile Load - Wire Ropes: Tension, Endurance, Reliability - page 77

Fig. 2.8 Longitudinal
stresses in the lay wires of a
wire rope FC + 6 9 7 sZ
under fluctuating forces,
Wang ( 1989 )

N/mm 2

800

b1.1oben

zs1.1oben

ges1.1oben

600

z1.1oben

2 1.1a max =

674N/mm 2

ˆ

400

200

b1.1unt

zs1.1unt

ges unt

z1.1unt

0

0 ° 120 ° 150 ° 180 °

30 ° 60 ° 90 °

normative phase angle ʦ

2r 1.1a max = 674 N/mm 2 . That is 17.2 % more than the range of the rope tensile
stress 2r za .
In addition to the longitudinal stresses the wires will be stressed by torsion,
pressure and to a small extent by wear and corrosion. Supplementary to this,
secondary bending stresses occur in wire ropes with crossing wire layers or
crossing strand layers. All these stresses are systematically unavoidable.
In any case, higher stresses occur unsystematically in some wires because of the
unevenly distributed wire tensile forces. This uneven distribution coming from the
fabrication and the handling of the wire ropes cannot be totally avoided. The
calculated stresses compared with the strength show ''what is possible in the ideal
case and gives the limit that a rope construction can reach but never exceed,''
Donandt ( 1950 ).
Jiang et al. ( 1997 ) and Wehking and Ziegler ( 2004 ) recently calculated the
stresses in a tensile loaded strand 1 + 6 by the finite element method. In contrast
to the analytic method presented here, this method includes the pressure between
the centre wire and the lay wires. The maximum stress in the lay wires has nearly
the same size as in the analytical calculation but is a little further away from the
analytical maximum, the inner wire edge. In his dissertation Ziegler ( 2007 )
extended the finite element calculations on strands 1 9 19 and 1 9 37.