Test Results on The Effect of Cyclic Wear of Polyester Sub Ropes

Abstract

In this paper, research efforts initiated in 2007 to better understand failure mechanisms of polyester rope are reviewed. A strain-based method is described for predicting the remaining life of polyester mooring lines. The fatigue mechanisms of metals vs. polyester are contrasted, leading to a justification for using strand-on-strand, "20-hurricane" subrope testing of polyester mooring lines rather than traditional (as conducted for steel) fatigue testing of the full-size rope assembly.This paper provides strand-on-strand, "20-hurricane" test results from over 40 individual rope tests, with the key comparative variable in the form of % reduction in breaking strength (after 20,000 cycles of 30% average break load ±15%). Data are presented for five different commercially available polyester mooring rope designs.Unexpected results due to subrope unloading and reloading during a test sequence are described and explained. This behavior was observed in certain cyclic wear tests, and was caused by fiber-yarn bedding in, breaking out, and then rebedding.Finally, a semi-empirical mathematical model to predict rope remaining life is described that employs the results of the "20-hurricane" test program.