Alain Cardou's blog
Coupling in taut helical strand bending
Usually, taut helical strand bending is dealt with by decoupling axial load and bending analysis. In the attached report, based on a purely geometrical approach, it is shown that there is indeed some coupling, albeit small.
An early stick-slip model for cable bending analysis
One approach to helical strand (cable or overhead electrical conductor) bending analysis puts the emphasis on friction rather than on elastic curved rod behavior. Based on Coulomb’s laws of friction, it leads to stick-slip models where strand bending stiffness varies with imposed curvature (Papailiou, 1995). Such an approach can be traced back to a Ph.D. thesis by H. Ernst, in 1933. This work is in fact often referred to in cable analysis reports. An English translation (with a short presentation) of the dissertation analytical part is attached.
Helical Strand in Bending
Several approaches have been used to deal with the complex problem of helical strands in bending. One of them is based on Love’s curved rods theory. It has first been used by Costello in his classical monograph “Theory of Wire Rope”. It has been extended by Sathikh et al. in several papers. A new contribution from this group is a Ph.D. Thesis by D. Gopinath : “Some studies on bending response of the stranded cable under free bending and constrained bending”, Anna University, Chennai (India), October 2013, 121 pages.
ON THE POFFENBERGER-SWART STRESS
New test data in a 2013 conference paper. Details in the attached file.
Fatigue of Overhead Electrical Conductors
A new paper on the OEC fatigue problem: “Determination of Early Failure Sources and Mechanisms for Al 99.7% and Al-Mg-Si Alloy Bare Conductors Used in Aerial Transmission Lines”, by S. Karabay and E. Feyzullahoglu. Paper has been accepted for publication in March 2014 in the “Engineering Failure Analysis” journal. Abstract can be found on-line: http://dx.doi.org/10.1016/j.engfailanal.2013.12.002
CABLE BENDING ANALYSIS THOUGH FEA
Single strand cable (spiral) bending and OEC (Overhead Electrical Conductor) bending are somewhat similar problems. This is the reason why the following new paper is noteworthy within the context of this blog. It emanates from a Slovak team: S. Kmet, E. Stanova, G. Fedorko, M. Fabian, J. Brodniansky. Title : “Experimental investigation and finite element analysis of a four-layered spiral strand bent over a curved support”. Published in “Engineering Structures”, Vol. 57, December 2013, pp. 475-483.
Overhead Electrical Conductors
I just discovered (thanks to Dr K.O. Papailiou) this interesting 2007 paper on helical strand mechanical modelling. It is an up-to-date (and apparently quite exhaustive, except for non-English language contributions) review on the subject by T. Manvel Raj and N.S. Parthasarathy, of India. Its title: “A Complete Review on Friction Models of Composite Cables”. It was published in a Russian Academy of Applied Mechanics and Sciences journal, the International Journal of Mechanics of Composite Materials and Constructions, Vol. 13, No 3, pp. 356-384. Here is the Abstract:
Overhead Electrical Conductors
Stick-slip model (based exclusively on Coulomb’s laws of friction) for conductor bending may be improved by taking into account actual inter-layer contact conditions: elliptical contact areas with tangential elasticity and micro-slip regions. Starting with Papailiou’s model, this has been done by Paradis and Légeron. Work was presented in 2011 at the 9th International Symposium on Cable Dynamics, held in Shanghai (China). Model has been applied to variable curvature case using FEA (in a Matlab environment). Numerical results are compared with Papailiou’s experimental results.
Bending of cables : a stick-slip model
Bending of cables and, for that matter, of any helical strand system (such as overhead electrical conductors) is a challenging solid mechanics problem, with geometry and multibody frictional contact aspects. As seen in several recent papers, one workable approach is based on Coulomb’s laws of friction. An earlier contribution by Lehanneur (1949), published in French, has generally been ignored. The attached report presents a translation into English (including a presentation) of this most interesting work.