摘 要
隨著船舶尺度的大型化，高強(qiáng)度材料的應(yīng)用以及新的結(jié)構(gòu)形式的研發(fā)應(yīng)用等因素，導(dǎo)致船舶疲勞問題日益突出，并成為船舶與海洋結(jié)構(gòu)物主要失效模式之一。在以往工程應(yīng)用中，疲勞評估一般采用簡化計算方法或者結(jié)構(gòu)有限元法與簡化計算方法相結(jié)合，并且一般在零航速下計算關(guān)鍵節(jié)點的疲勞累積損傷。本文主要研究線性波浪載荷作用下的船體結(jié)構(gòu)疲勞問題，并且重點考慮航速對于疲勞累積損傷度的影響，著重對以下幾個方面進(jìn)行研究與探討。
（一）闡述船舶結(jié)構(gòu)疲勞分析的基礎(chǔ)理論和基本方法，包括 曲線與Miner線性累積損傷理論，疲勞評估的簡化計算方法，疲勞評估直接計算方法中的譜分析法。
（二）根據(jù)船舶在波浪上運(yùn)動的三維勢流理論，研究了時域內(nèi)有航速船舶波浪誘導(dǎo)運(yùn)動與載荷的計算方法，波浪載荷短期與長期預(yù)報方法，三維時域Rankine源方法的基本理論。
（三）以一艘5000車汽車滾裝船為例，采用三維時域全航速理論預(yù)報了典型裝載情況下滾裝船在波浪上的運(yùn)動性能與剖面載荷，通過分析運(yùn)動與載荷隨航速變化的規(guī)律，得到船體縱蕩、橫蕩、橫搖以及波浪彎矩航速效應(yīng)顯著。
（四）基于設(shè)計波法對整船結(jié)構(gòu)強(qiáng)度進(jìn)行評估。闡述了設(shè)計波方法的基本理論以及設(shè)計波參數(shù)選取的方法。根據(jù)載荷響應(yīng)函數(shù)以及波浪誘導(dǎo)載荷長期預(yù)報值選取六組設(shè)計波參數(shù)，對滾裝船的典型裝載情況下進(jìn)行了結(jié)構(gòu)有限元強(qiáng)度分析，為疲勞校核點的選取提供依據(jù)。
（五）采用疲勞譜分析法，研究了考慮航速情況下受線性波浪載荷結(jié)構(gòu)的疲勞累積損失度以及疲勞壽命。比較不同航速下疲勞累積損傷度的值，以及不同波浪入射角對于疲勞累積值的貢獻(xiàn)度，得出高航速船舶在疲勞評估中考慮航速是必要的。
關(guān)鍵詞：滾裝船 疲勞評估 航速 設(shè)計波法 譜分析法










Abstract
With the factor of large-scale vessel, using of high-strength material and research and development of new form of structure, the question of ship hull structure’s fatigue strength is becoming more outstanding, fatigue damage become one of the main failure modes for ship and ocean structures. In the past of application of engineering, fatigue assessment is always caught out by simplified method or the combination of finite element method and simplified method, cumulative fatigue damage is calculated in zero forward speed in crucial spot. The major purpose of this thesis is to make research on fatigue assessment of ship structure under linear wave-induced loads. The key point is the effect of forward speed in calculation of cumulative fatigue damage. The main contents are as follows:
1) The basic theory and principal method of fatigue of ship structure is expatiated. It contains S-N curve and Miner’s rule of cumulative damage, simplified method of fatigue assessment, spectral fatigue analysis in direct method of fatigue assessment.
2) The research on the calculation of wave-induced motions and loads in a harmonic wave with a forward speed which based on three-dimensional potential theory, method of long-term and short-term predictions for wave-induced motions and loads, basic theory of Rankine panel method.
3) The predictions of a 5000car PCTC’s motion performance and sectional loads in typical loading conditions based on three-dimensional time domain full speed theory. By analyzing the law of change between forward speed and motions and loads, we find the speed effect of surge, sway, roll and wave-induced moment is very remarkable.
4) Strength analysis of overall ship’s structure based on design wave approach. The basic theory of design wave approach and method of design wave parameters selection are expatiated. The six groups of design wave parameters are selected based on RAO and long-term predictions for wave-induced motions and loads. Finite element analysis in typical loading conditions is performed. The selection of fatigue point is according to the calculation result.
5) The research on the cumulative fatigue damage and fatigue life of structure based on spectral fatigue analysis. The compare of cumulative fatigue damage in different forward speed is carried out. The conclusion is necessity of consideration of forward speed in fatigue assessment of high-speed vessel.
Key words: PCTC ship，fatigue assessment，forward speed，design wave approach，spectral method




























目 錄
摘 要 I
Abstract III
第1章 緒論 1
1.1 引言 1
1.2 船舶結(jié)構(gòu)疲勞強(qiáng)度研究現(xiàn)狀與發(fā)展趨勢 2
1.2.1 疲勞簡化計算法和直接計算法 2
1.2.2 船體結(jié)構(gòu)疲勞評估仍需完善的內(nèi)容 3
1.3 船舶運(yùn)動和波浪載荷的發(fā)展動態(tài)和研究現(xiàn)狀 4
1.4 論文的研究內(nèi)容及方法 5
1.4.1 研究內(nèi)容 5
1.4.2 研究方法 5
1.5 研究中的關(guān)鍵技術(shù) 6
第2章 疲勞評估的基本理論 7
2.1 引言 7
2.2 S-N曲線和疲勞疲勞累積損傷理論 7
2.2.1 S-N曲線 7
2.2.2疲勞累積損傷模型 8
2.3 疲勞評估的簡化計算方法 11
2.4 疲勞評估的直接計算方法 12
2.5 疲勞譜分析法 13
2.5.1 概述 13
2.5.2 應(yīng)力響應(yīng)的傳遞函數(shù) 13
2.5.3 應(yīng)力的響應(yīng)譜 14
2.5.4 應(yīng)力范圍的短期分布 15
2.5.5 應(yīng)力范圍的長期分布 15
2.5.6 疲勞累積損傷度計算 16
2.6 本章小結(jié) 17
第3章 時域內(nèi)波浪載荷的計算理論 18
3.1 引言 18
3.2 三維線性勢流理論基礎(chǔ) 18
3.2.1 基本假定 18
3.2.2 船舶在規(guī)則波中的運(yùn)動坐標(biāo)系 1..