海上风机支撑结构疲劳寿命分析方法研究

发布时间：2018-07-31 12:49

【摘要】：海上风机支撑结构多由钢管焊接而成,在复杂的海洋环境荷载以及上部风机荷载的联合作用下,结构连接处容易产生应力集中,极易发生疲劳破坏,结构连接处是基础结构设计的重点和难点；为保证海上风机在其设计寿命期内正常运作,有必要对海上风机支撑结构进行疲劳寿命分析。本文以某风电场海上风机三桩支撑结构为研究对象,选取疲劳分析关键区域,对该结构进行了详细的疲劳寿命分析,为类似海上风机支撑结构的疲劳寿命分析以及进一步的研究提供了借鉴和参考,本文主要工作如下： (1)论文首先介绍了疲劳寿命分析的基本理论与方法,包括线性、双线性、非线性累积损伤理论、概率Miner理论以及疲劳累积损伤动态统计模型理论,并对目前应用最为广泛且形式较为简单的Palmgren Miner线性累积损伤理论以及S-N曲线进行了重点介绍与分析。 (2)基于大型通用有限元分析软件ANSYS建立了海上风机三桩支撑结构的“桩土——支撑结构”整体有限元模型,并对疲劳寿命分析关键区域建立了局部精细化有限元模型；利用整体有限元模型计算的位移值作为局部精细化有限元模型的边界条件,该方法同时解决了壳单元无法直接考虑波流荷载以及管单元应力计算不准确的问题； (3)分析了有限元网格密度对热点应力的影响；对于撑杆需要划分与其轴线相平行的有限元网格,对于弦杆需划分垂直于焊缝的有限元网格；给出了海上风机三桩支撑结构疲劳计算关键点的选取方法； (4)采用热点应力的疲劳寿命分析方法,参考挪威船级社海上风机基础设计规范中给出的S-N曲线,根据Palmgren Miner线性累积损伤准则,分别分析了波浪荷载以及风机荷载对海上风机三桩支撑结构疲劳寿命的影响,并考虑了疲劳荷载作用方向以及平均应力对疲劳寿命的影响； (5)分析了海上风机三桩支撑结构在风、浪联合作用下,多种耦合方法(疲劳累积损伤值简单线性叠加方法、二次叠加方法、等效应力同相叠加以及等效应力异相叠加方法)对结构疲劳寿命的影响,并给出了推荐做法。
[Abstract]:The support structure of offshore fan is mostly made of welded steel pipe. Under the combined action of complex marine environment load and upper fan load, the stress concentration is easily produced in the connection of the structure, and fatigue damage is easy to occur. In order to ensure the normal operation of offshore fan during its design life, it is necessary to analyze the fatigue life of the supporting structure of offshore fan. In this paper, the three-pile supporting structure of offshore fan in a wind farm is taken as the research object, and the fatigue life of the structure is analyzed in detail by selecting the key area of fatigue analysis. The main work of this paper is as follows: (1) the basic theory and method of fatigue life analysis, including linearity, are introduced in this paper. Bilinear, nonlinear cumulative damage theory, probabilistic Miner theory and fatigue cumulative damage dynamic statistical model theory, The linear cumulative damage theory of Palmgren Miner and S-N curve, which are widely used and simple at present, are introduced and analyzed emphatically. (2) based on the large-scale general finite element analysis software ANSYS, the offshore fan is established. The "pile-soil-braced structure" integral finite element model of three-pile bracing structure, The local fine finite element model is established for the key area of fatigue life analysis, and the displacement value calculated by the global finite element model is used as the boundary condition of the local refined finite element model. The method solves the problem that the shell element can not directly consider the wave and current load and the calculation of the stress of the pipe element is inaccurate. (3) the influence of the finite element mesh density on the hot spot stress is analyzed. The finite element mesh parallel to its axis and the finite element mesh perpendicular to the weld seam should be divided for the bracing rod, and the method of selecting the key points for fatigue calculation of the three piles supporting structure of offshore fan is given. (4) using the fatigue life analysis method of hot spot stress, referring to the S-N curve given in the Norse Classification Society Marine Fan Foundation Design Code, according to the Palmgren Miner linear cumulative damage criterion, The influence of wave load and fan load on fatigue life of offshore fan three-pile supporting structure is analyzed, and the effect of the direction of fatigue load and the average stress on fatigue life is considered. (5) several coupling methods (fatigue cumulative damage value simple linear superposition method, secondary superposition method) under the combined action of wind and wave are analyzed. The effect of equivalent stress in-phase superposition and equivalent stress heterogeneous superposition on the fatigue life of structures is discussed and the recommended methods are given.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU312

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