Abstract

Axial structural damping behavior induced by internal friction and viscoelastic properties of polymeric layers may have an inevitable influence on the global analysis of flexible pipes. In order to characterize this phenomenon and axial mechanical responses, a full-scale axial tensile experiment on a complex flexible pipe is conducted at room temperature, in which oscillation forces at different frequencies are applied on the sample. The parameters to be identified are axial strains which are measured by three kinds of instrumentations: linear variable differential transformer, strain gauge and camera united particle-tracking technology. The corresponding plots of axial force versus axial elongation exhibit obvious nonlinear hysteretic relationship. Consequently, the loss factor related to the axial structural damping behavior is found, which increases as the oscillation loading frequency grows. The axial strains from the three measurement systems in the mechanical experiment indicate good agreement, as well as the values of the equivalent axial stiffness. The damping generated by polymeric layers is relatively smaller than that caused by friction forces. Therefore, it can be concluded that friction forces maybe dominate the axial structural damping, especially on the conditions of high frequency.

Highlights

  • The fact that axial structural damping generated by friction between adjacent layers and within specific layers, viscoelastic properties of polymeric layers on condition of vessel stochastic oscillator is usually disregarded in global analysis may cause conservative results in deep-water development

  • This section introduces full-scale axial tensile mechanical experiments conducted at the Ocean Structure’s Laboratory (NEO) in COPPE/UFRJ, aimed at verifying whether hysteresis occurs for flexible pipe subjected to oscillation loads, as well as the value of loss factor

  • Three groups of experiments are conducted, and mean values are shown in Fig. 7a for the axial strain varying with time

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Summary

Introduction

The fact that axial structural damping generated by friction between adjacent layers and within specific layers, viscoelastic properties of polymeric layers on condition of vessel stochastic oscillator is usually disregarded in global analysis may cause conservative results in deep-water development. Quite a few nonlinear properties caused by geometric, material, contact conditions make it arduous Both numerical and analytical studies have to make lots of assumptions and put forward a slice of interesting results in the past 40 years (Feret and Bournazel 1987; Witz and Tan 1992; Kebadze 2000; Custódio and Vaz 2002; Pesce et al 2010; Sævik 2011; Ramos et al 2014; Ramos and Kawano 2015; Ebrahimi et al 2018). Some advances like viscoelastic considered in model (Guedes 2010; Liu and Vaz 2016a; Santos et al 2017, Liang et al 2018, 2019), there is

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