Wire failures in ropes and their influence on local wire strain behaviour in tension-tension fatigue

Abstract

Experimental work using multiple strain gauges has investigated the take-up of load by a wire at either side of a break and how this is affected by fatigue cycling. In addition the effect of a wire break on other wires at the same cross-section has been investigated. The results indicate that a significant amount of slippage can occur for up to 20 000 cycles after a wire has broken, causing the load transfer length to change from two strand lay lengths to around three. The transfer length was found to be much lower for Lang's lay rope than ordinary lay and this was attributed to the greater interlayer forces in Lang's lay ropes. With respect to the effect of wire breaks on other wires at the same cross-section it was found that the primary increase is in the strains in wires in the same strand, although wire strains in adjacent strands also increase to some extent. Wires on the opposite side of the rope construction were found to show a decrease in surface strain after the break which may be attributed to local bending effects.

Assessment of static rope behavior with asymmetric damage distribution

“…This factor assumes, based on the results given by 3D FE models, that the deformed configuration of the unbroken rope components obtained from Eqs. (9) and (10) is close to a circular helix as shown in Fig. 5.…”

“…On the other hand, for a particular asymmetric damaged rope (fixed IA, I zz , and I yy values), as the value of the axial rope strain (e) increases, the magnitude of the function K(e) increases more rapidly than the magnitude of H(e) and consequently, larger lateral displacements are developed by the rope (see expressions for a z (e), a y (e), b z (e), and a z (e) in Eqs. (9) and (10)). When comparing the deflection ropes values estimated by the NLBM and the 3D FE simulations, it is important to emphasize that the magnitude of the lateral deflections predicted by the NLBM model is proportional to the value of the function K(e) represented by the parameters a z (e), a y (e), in Eqs.…”

“…The associated iterative algorithm can be readily extended for the case of asymmetrically damaged multilayered one-level ropes (larger ropes), considering the appropriate value of the unbalanced transverse force as described in [16], if broken components belong to the outermost layer. If damage is localized in inner layers or the damaged rope has a multilevel geometry, interaction among rope components may induce strain localization around the damage zone making the response of the damaged rope length dependent as extensively discussed in [9,16,18] among others. In the latter, not only the damage distribution (degree of asymmetry) should be accounted for, but also the length of the rope, damage location within rope cross-section and rope length, and contact pattern between rope components.…”

“…Several experimental [4][5][6][7][8][9][10][11][12] and theoretical [13][14][15][16][17][18] studies have shown that the impact of the presence of broken rope components on overall rope response (stiffness, residual strength and deformation capacity) depends on the length of the rope, number of broken rope components (degree of damage) and their distributions throughout rope cross-section (symmetric and asymmetric) and along the rope length, and rope construction. These studies have mainly been conducted on steel wire ropes and synthetic fiber ropes.…”

Wire strain variations in normal and overloaded ropes in tension-tension fatigue and their effect on endurance

“…Tests were carried out on two types of rope: a 19 mm Seale 6 3 19(9=9=1) right-hand ordinary (RHO) lay rope with independent wire rope core (IWRC) and the same rope in Lang's lay. The specifications for the ropes are exactly the same as that used in work described elsewhere [14]. The length of the specimens in these tests was 1.1 m, which corresponds to 10 rope lay lengths.…”