All about ropes and lines

Windy_Skies · March 2, 2020, 5:34pm

Some results:

MECHANICAL BEHAVIOR OF HIGH PERFORMANCE FIBER ROPES IN TECHNICAL APPLICATIONS

During the last years, fiber ropes have proven to be an option to replace steel wire ropes in many technical applications. Especially for hoisting applications or winch-based applications, fiber ropes (e.g. made from high-modulus polyethylene, TLCP fibers or aramid fibers) do offer a lot of advantages. Due to their low material density paired with high strength, these fiber ropes can ease handling and installation of ropes in technical applications at comparable performance. For applying a fiber rope in a technical application, e.g. hoisting gears, knowledge on the behavior under mechanical stress is essential. Especially the behavior under tensile load, tension-tension and cyclic bending has to be known to find an adequate fiber rope for special applications. This publication is showing the mechanisms to correctly analyze the application-related mechanical properties of fiber ropes and the testing machinery, and describes special applications where fiber ropes can already be used to replace steel wire ropes.

An empirical model to predict the lifetime of braided HMPE handling ropes under cyclic bend over sheave (CBOS) loading

Abstract :Repeated bending over sheaves is one of the main causes of failure of synthetic fibre ropes used in marine operations. There are few published results available and even fewer models allowing lifetime to be estimated. A large new set of data from cyclic bend over sheave (CBOS) tests on 250 kN break load braided HMPE synthetic ropes is presented first, both tests to failure and interrupted tests followed by residual strength measurements. These data are analysed in order to propose an empirical lifetime model. This is identified using constant load tests, then evaluated for variable load sequences. A methodology to include rope lifetime prediction in handling system design is then discussed.

Highlights►A large new set of data from cyclic bend over sheave (CBOS) tests.►An analysis of these data in terms of lifetime.►Validation of the analysis using additional 2-load and variable load tests.►Discussion of the consequences for safety of ocean handling systems.

Keywords: Fibre rope, Bending, Sheave, Abrasion, Fatigue

Design Modifications to Increase Fatigue Life of Fiber Ropes

Abstract - This paper describes a two-phase program on cyclic bend-over-sheave (CBOS) fatigue testing of 40 mm diameter fiber ropes. A test method that simulates heavy marine CBOS applications proved to be a repeatable measure of fatigue resistance. Cycles-to-failure data are presented for ropes made from high-strength fibers of high modulus polyethylene (HMPE), liquid crystal polyester (LCP), and LCP/HMPE blends. A method for pathological examination of fatigue-damaged braided ropes is described, and a map of observed interior damage is presented. The results of the first phase of fatigue testing, coupled with observations from the post-mortem examinations, suggested possible damage mechanisms. Fatigue life in the second phase of testing was increased by more than 100%, by modifying rope designs so as to preclude or delay failure modes observed in the first phase.

Improving Bend-over-Sheave Fatigue in Fiber Ropes

Abstract- One of the limitations of synthetic fiber ropes inindustrial uses has been the premature wear of these materials when subjected to continuous bend-over-sheavefatigue. While one-way passage over sheaves is not generally damaging, repeated back-and-forth movement over one part of the rope, as in heave compensation units, can lead to damaging heat buildup and unexpected failure modes. This report details the results of bend-over-sheave fatigue testing on 18 mm diameter fiber ropes conducted at Cortland CableCompany. Cycles-to-failure data is presented for the fiber materials, coatings, and constructions tested to date. Fatigue life was significantly improved by fiber blending and with specialty coatings, resulting in a new braided rope design specifically optimized for bending fatigue (BOB). The BOB design was found to have a significant CTF advantage over aramid constructions and steel wire currently in use today.The importance of test parameters such as sheave design and cycle rate is highlighted.

Tension endurance of HMPE fiber ropes

Abstract— Tension-tension fatigue tests on high modulus polyethylene fibers show that fatigue lifetime is governed by plastic deformation failure. This insight is further evaluated on small ropes and via a simple to implement dynamic shift factor, time-to-failure under dynamic conditions is shown to be predicted based on static creep failure. Basis of the shift factor is the time spend under load and gives excellent predictions when no additional heating-up is introduced during the test. This makes DSM Dyneema’s Performance Model, for static creep prediction, also capable to predict dynamic tension-tension failure.

Keywords—synthetic fiber ropes; high modulus polyethylene; static; dynamic; tension fatigue; Dyneema®