Bending of helically twisted cables under variable ... - Pfisterer

The The secondary secondary stiffness therefore depends on the two (variable) values of curvature and tensile stress
in the aluminium wires. The secondary stiffness (EJ) (EJ)zus has correspondingly been plotted in Fig. 2.22 as
a function of the curvature. The parameter for the family of curves is tensile stress σzug in the aluminium
wires of 10, 20, 30 and 40 N/mm 2 .
Fig. 2.22 Secondary stiffness of ACSR conductor 35/6;
1: σzug = 10N/mm 2 ess of ACSR conductor 35/6;
; 2: σ zug = 20N/mm 2 ; 3: σzug = 30N/mm 2 ; 4: σzug = 40N/mm 2
The The curves curves clearly clearly show show that, as as physical physical considerations lead lead us us to to expect, expect, the secondary stiffness
increases as the tensile stress increases in the aluminium wires, i.e. as their radial pressure on the steel
core increases – i.e. the conductor slips at larger curvatures.
In In the transition region, both displacement displacement conditions conditions occur occur at at the same same conductor conductor cross cross-section –
depending on the position of the
41
Secondary stiffness
Curvature
individual wire in the conductor cross-section section as defined by the
angle ϕ. . Here Here the the two two curves of of the secondary stress given by (2.22) and and (2.17) for angles ϕ between
- π/2 and +π/2 /2 have, apart from the trivial solution ϕ = 0, two further intersections (see ee also Fig. 2.10).