【作者】 黄维；

【导师】 刘海笑；

【作者基本信息】 天津大学 ， 港口、海岸及近海工程， 2012， 博士

【摘要】 新型深水绷紧式系泊系统以合成纤维材料系缆作为主体系缆，在复杂海洋环境条件下，系缆的时间相关特性（蠕变－回复）、特殊的循环张力－伸长关系、动刚度特性以及疲劳破坏特性等非线性力学特性，与系泊系统的性能响应及安全性直接相关，深入认识和把握这些特性对于绷紧式系泊系统在深海工程的应用具有十分重要而紧迫的意义。本文基于对绷紧式系泊系统关键特性的认识，通过机理探究、理论发展和模型实验研究，针对合成纤维系缆的循环动力特性、蠕变－回复特性以及绷紧式系泊系统的动力响应和疲劳寿命这三项内容展开了深入的研究，主要研究工作及创新成果包括：首先，为了研究合成纤维缆绳的循环动力特性，设计并制造了循环加载实验系统，这是国内首台能针对合成纤维缆绳进行循环载荷实验的设备。值得一提的是，在国际范围内，本实验系统还有以下三大亮点：（1）设计采用光轴与拉线位移传感器组合的测量系统实现对缆绳标记段的测量，缆绳的刚性铁夹与传感器及拉线端头底座之间用强磁连接，实现了对测量系统的保护；（2）采用双水箱结合的水循环系统，真实地模拟了缆绳浸泡于水中的工程实际状态；（3）采用机械转轮与伺服电机结合的室内卧式实验加载系统，具有便于安装运输、造价低和耗能小等优点；第二，针对合成纤维系缆在循环载荷作用下的力学特性，包括循环张力－伸长关系及其滞回特性、动刚度及残余应变随加载周次的演变等开展了模型实验研究。对平均张力、应变幅值等影响因素进行了深入的分析和探讨。基于量纲分析法推导了动刚度相似准则，并结合不同直径缆绳的模型实验结果对其进行了考察。将动刚度实测结果与国际常用经验公式进行了对比和分析。基于对合成纤维系缆循环动力特性的深入认识，提出了考虑循环载荷周次的动刚度经验公式，该经验公式具有通用性，是传统动刚度经验公式的继承和发展，具有重要的工程参考价值；第三，建立了能全面反映Aramid和Polyester等合成纤维系缆的蠕变－回复特性的本构模型。提出了确定模型参数的详细方法，可以适用于纤维、纱线、子缆及全比尺系缆等各种比尺的系缆组分。为了考察模型的有效性和可靠性，以Chailleux和Davies文献中的Aramid和Polyester纱线为例进行计算分析，并将计算结果与其数值和实验结果进行了对比，结果表明，基于本模型的计算结果与实验结果吻合得更好。本模型一方面避免了Chailleux和Davies模型中因参数Dp而与物理规律不符的现象，另一方面也实现了对Flory等所述缆绳变形特性的定量描述；第四，结合Schapery理论和Owen粘塑性理论，建立了能定量描述合成纤维系缆循环动力特性的新型本构模型，提出了确定模型参数的详细方法。为了考察本模型的有效性和可靠性，以Polyester和Aramid缆绳的实验工况为例进行了计算分析。将动刚度计算结果与模型实验结果及经验公式进行了对比，结果表明，三者较为吻合；将滞回圈计算结果与模型实验结果进行对比，结果表明，基于本模型能模拟出与实验规律相符的物理现象。本模型从缆绳变形机理和载荷历史角度出发，是Fran ois和Davies所描述的真正的“时域”本构模型，一方面填补了反映合成纤维系缆时间相关特性本构关系的空白，另一方面也为特定海况下系泊系统动力响应的深入分析提供了有力工具；第五，基于时域动力分析理论、雨流计数法以及Palmgren-Miner线性累积损伤理论，针对FPSO及其Polyester绷紧式系泊系统进行了全面的动力响应及疲劳分析，详细考察了预张力、动刚度以及T-N曲线这三种影响因素对其疲劳寿命的影响。对单缆失效前后进行的系泊系统疲劳分析表明，单缆失效导致系泊形式发生改变，显著增加未失效系缆尤其是相邻系缆的负载，导致系缆的疲劳寿命明显缩短。目前，针对深水系缆仍然缺乏成熟的检测技术，获得单缆失效对绷紧式系泊系统疲劳损伤及疲劳寿命影响的定量描述，具有重要意义。更多还原

【Abstract】 Being a new-type mooring system applied for deep waters, synthetic fibre ropesare employed in the taut-wire mooring system as main part of mooring lines. Underthe complicated ocean environment, the nonlinear mechanical properties of thesynthetic fiber ropes including the time-dependent behaviors (creep-recoverybehaviors), special cyclic tension-elongation relationship, dynamic stiffness andfatigue propeties et al. closely relate to the performance and safety of the system. It isof vital importance and significant to obtain deeply knowledge of these properties forthe deepwater application of the taut-wire mooring system. Based on the profoundinsight and forward looking knowledge of the key characteristics of the taut-wiremooring system, the creep-recovery behaviors, cyclic properties of the fiber ropes andthe dynamic response and fatigue life of the taut-wire mooring system have beenstudied systematically through theoretical and experimental methods. The mainresearch works and creative achievements are as follows:Firstly, in order to study the cyclic mechanical properties of the fiber ropes, anew-type horizontal model experimental system which can perform the cyclic loadingon the synthetic fiber ropes is designed and set up, which is a first one in China. Itshould be noted that, in the international field, the model experimental system hasthree highlights:(1) A new measurement system combined with the axletree, magnentand wire transducer, which have self-protected function, has been designed and set upto measure the actual elongation of the fiber ropes;(2) A new water cycling system isdesigned and set up to simulate the water environment in which the fiber ropes fullyimmersed during the engineering application;(3) the laboratory model experimentalsystem combined with the machinery and servo-controlled machines has theadvantages of convenient installtion and transportation, low costs and energy et al.Secondly, the mechanical properties of synthetic fiber ropes under cyclic loadingincluding the tension-elongation relationship and hysteresis properties, the evolutionof the dynamic stiffness and residual strain, are studied in detail on the model experimental system. The influence of the mean load and strain amplitude is analyzedand discussed in detail. Besides, the resemblance rule suitable for the modelexperiment of dynamic stiffness for the fiber ropes is induced based on the dimensionanalysis methods and is verified by the comparison of experimental results of ropeswith different diameters. The dynamic stiffness measured in this paper is comparedwith the international empirical expressions. Based on the deep knowledge of thecyclic propeties of the fiber ropes, a new empirical expression considering load cyclesis proposed, which is invariant with the rope size and arrangement. The newexpression has not only retained the considering factors in the traditional empiricalexpressions but also improved them. It is of vital importance to the engineeringapplications.Thirdly, a new constitutive model which can describe quantitatively bothviscoelastic and viscoplastic behaviors of the aramid and polyester fiber ropes isproposed. Detailed methods for identifying the model parameters are proposed, whichcan be applied to any component of the fiber rope such as the fiber, yarn, sub-ropeand rope. In order to examine the feasibility and precision of the model, theviscoelastic and viscoplastic strains are calculated and compared with experimentaland other numerical simulation results of polyester and aramid yarns in the literaturesof Chailleux and Davies. It is observed that there is a better agreement between theresults based on the present model and experimental data. The present model not onlyeliminate the physical irrational results caused by the parameterD ppreviouslynoticed by Chailleux and Davies, but also can be capable of describe quantitativelythe deformation properties of fiber ropes mentioned by Flory.Forthly, a constitutive model combined with Schapery’s theory and Owen’stheory is proposed to describe quantitatively the cyclic properties of synthetic fiberropes. The detailed parameter identification methods and procedure are presented. Inorder to verify the model, the numerical results are compared with modelexperimental results of polyester and aramid fiber ropes. The dynamic stiffnessevolution results are compared with the empirical expressions and the experimental results, and they correspond well with each other; the calculating hysteresis loops arecompared with the model experimental results; it is indicated that the model can beable to simulate the physical phenomenon of the fiber ropes under cyclic loading. Thepresent model is proposed based on the transformation mechanism and loadinghistory of the fiber ropes, and it is the true “time domain” constitutive modelmentioned by Fran ois and Davies. For one thing, it is the first model which can takeinto account the time-dependent behaviors of synthetic fiber ropes under cyclicloading; for another, it is a practical tool for the detailed dynamic analysis ofdeepwater mooring system under a certain sea state.Finally, A FPSO and its taut-wire mooring system are employed and acomprehensive mooring analysis and fatigue analysis are performed based on the timedomain dynamic theory, the rainflow counting methods and Palmgren-Miner linearaccumulation methods. The analysis considers three factors including the pretension,dynamic stiffness and T-N curve. Besides, the detailed fatigue analysis of the mooringsystem with one line damage is carried out. The analysis proves that one-line failurehas remarkable decreasing effects on the fatigue lives of the mooring system.One-line failure changes the mooring mode and thus increases significantly thetension of others especially the adjacent lines. At present, there are still difficulties inthe inspection of mooring lines in deep waters. Therefore, the quantitative descriptionof the effect of one-failure to the fatigue damage and fatigue life of taut-wire mooringsystem is of vital importance.更多还原