Precise Assessment of Load/Structural Response and Development of Practical Design Method in Fatigue Strength Design of a Ship

船舶疲劳强度设计中载荷/结构响应的精确评估和实用设计方法的发展

• 批准号: 09555311
• 负责人: FUKASAWA Toichi
• 金额: $ 5.38万
• 依托单位: Kanazawa Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09555311/
• 关键词: Ship Structural Design; Simplified Design Method; Transverse Strength Analysis of Ship; Ship Fatigue Strength; Stress Response Function; 船体疲労強度; バラ積み貨物船

In the fatigue strength design of a ship, it is most important to estimate the accurate stress fluctuation of a certain structural member of the ship in waves. In case the fatigue strength of the structural member is evaluated by the cumulative fatigue damage factor, it is necessary to obtain the long-term probability of occurrence of the stress fluctuation, which is combined with S-N curves. For this purpose, a probabilistic approach is usually adopted, and it is essential to calculate the frequency response function of stress accurately in the probabilistic approach.As for the transverse strength of a ship in waves, hydrodynamic sea pressure in wave is the most important external load, particularly for fatigue strength of a ship. In order to obtain the stress response function caused by the sea pressure, a finite element analysis is necessary to be carried out in every wave condition in principle, because the distribution pattern of sea pressure, as well as the magnitude, along ship' … More s hull varies according to the wave conditions, and a non-linearity due to the free surface elevation along the side shell plays an important role. However, it may not be possible to conduct this kind of structural analysis in the structural design stage, because it requires enormous time and effort in computation.In the present research, the stress response function and the long-term probability of occurrence of stress caused by wave pressure are calculated with the use of the most exact method at present. The treatment of the non-linearity due to the free surface elevation along the side shell will be investigated in this process. Then, simplified methods to predict the stress response function and the long-term probability of occurrence of stress are proposed ; that is, Min-Max Method and Similar Response Function Method. Comparing these calculated results by the exact method, approximate method and conventional method, the accuracy of the prediction method is discussed from the viewpoint of the design tool for fatigue strength of a ship. Less

在船舶疲劳强度设计中，准确估计某型船舶结构件在波浪中的应力波动是至关重要的。如果用累积疲劳损伤系数来评估构件的疲劳强度，则需要得到应力波动发生的长期概率，并结合S-N曲线。对于船舶在波浪中的横向强度而言，波浪中的动水海压是最重要的外载荷，对于船舶的疲劳强度而言，波浪中的动水海压是最重要的外载。为了得到海压引起的应力响应函数，原则上需要在各种波浪条件下进行有限元分析，因为海压在船舶…上的分布规律以及海压的大小都是如此更多的S船体因波浪条件的不同而不同，而侧壳自由表面高程的非线性起到了重要作用。然而，在结构设计阶段进行这种结构分析可能是不可能的，因为它需要花费大量的时间和精力进行计算。本文采用目前最精确的方法计算了波浪压力引起的应力响应函数和长期发生应力的概率。在这一过程中，将研究如何处理由于自由表面沿侧壳升高而产生的非线性。在此基础上，提出了预测应力响应函数和长期应力发生概率的简化方法，即Min-Max法和相似响应函数法。比较了精确法、近似法和常规法的计算结果，从船舶疲劳强度设计工具的角度讨论了预测方法的准确性。较少

项目成果

深沢塔一(第一著者): "波浪変動圧によって生ずる応力の応答関数と長期発現頻度の簡易推定法に関する研究"日本造船学会論文集. 187(発表予定). (2000)

Toichi Fukasawa（第一作者）：“波浪波动压力引起的响应函数和长期频率的简单估计方法的研究”，日本造船学会汇刊187（待出版）。 ）

Toichi Fukasaza, Masao Morikawa, Tetsuji Fukuoka, Kouta Shibazaki, and Akio Ito: "On the Approximation of Stress Response Function and Long-Term Probability of Occurrence of Stress caused by Wave Pressure"Journal of the Society of Naval Architects of Japa

Toichi Fukasaza、Masao Morikawa、Tetsuji Fukuoka、Kouta Shibazaki 和 Akio Ito：“关于应力响应函数的近似和波浪压力引起的应力发生的长期概率”日本造船学会杂志