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Characterization of the long-term mechanical behavior and the durability of polyamide mooring ropes for floating wind turbines

Abstract : The scientific database for mooring nylon rope is still very limited, thus the deployment of these fibres for permanent mooring is currently impossible due to the lack of data on their mechanical properties. One of the goals of this study is therefore to provide a better understanding of the mechanical behavior and the fatigue damage of these polyamide ropes, in order to help designing floating wind turbine mooring lines. The present study involves mechanical characterization, modeling and its validation. The first part investigated is the modeling of the rope. The characterization on 4 tons sub-ropes involves cyclic loading with relaxation, allowing characterization of the rope with only one test. From this test one can identify each part of the model and validate it on different tests, before comparing to results from tests made on 8 tons sub-ropes. This has led to a simple 1D visco-elasto-plastic model quite close to the behavior of the rope. The second part involves long term creep tests. First, a brief explanation of the design and the building of the test machine will be made. Then results from 3 one year long tests on 4-ton sub-ropes will be presented and compared with other results. The results show similar creep values to those for polyester and they can be used to predict if re-tensioning of the rope will be needed. In the third part, the durability of polyamide rope will be assessed, first abrasion tests were employed, to ensure that the coating used is sufficient to validate the abrasion resistance on yarn. Then standard fatigue tests have confirmed that polyamide rope lifetimes are largely sufficient for permanent mooring, with a lifetime superior to steel chain even if a little shorter than those of polyester. Lastly, quick fatigue evaluation by heat build-up tests was realized. Showing promising result based on thermal measurement of the dissipated energy of the rope to predict its fatigue lifetime in less than two days.
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Submitted on : Tuesday, October 26, 2021 - 10:03:36 AM
Last modification on : Tuesday, January 4, 2022 - 5:51:20 AM
Long-term archiving on: : Thursday, January 27, 2022 - 6:43:09 PM

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  • HAL Id : tel-03403273, version 1

Citation

Yoan Chevillotte. Characterization of the long-term mechanical behavior and the durability of polyamide mooring ropes for floating wind turbines. Materials and structures in mechanics [physics.class-ph]. ENSTA Bretagne - École nationale supérieure de techniques avancées Bretagne, 2020. English. ⟨NNT : 2020ENTA0011⟩. ⟨tel-03403273⟩

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