Study of Fatigue Design Chart for Ship and Offshore Structures

船舶及海洋工程结构疲劳设计图的研究

• 批准号: 05302054
• 负责人: TOMITA Yasumitsu
• 金额: $ 3.46万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Co-operative Research (A)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-05302054/
• 关键词: fatigue; design chart; time history; wave condition; fatigue limit; real service condition; 実働荷重; 疲労限; 遭遇海象; き裂開口応力; 波高時刻歴モデル; 波浪変動荷重; 疲労き裂; 応力-ひずみ応答; 構成方程式; 疲労寿命

The authors analyzed wave data which ships and offshore structures encountered in real service conditions. The time history of ocean wave conditions are concluded as follows.(1) In relatively lower wave height conditions - calm sea condition - (lower than twice the height of the mean wave in the area), encountered wave height can be seen as a time independent random process.(2) In higher wave conditions - storm condition - (higher than twice the height of the mean wave in area), wave height increases over time and reaches a maximum value at one point only before decreasing gradually. That is, encountered wave height is a time dependent prosess.(3) Conditions (1) and (2) appear alternately in random order.Above characteristics of time history of encountered wave conditions in any area is the same, but mean wave height, mean storm duration, maximum wave height in the storm condition and the number of storms encountered in service life depend on the sailing route and the sea area. A standard loading model - storm model - applied to fatigue strength analysis has been determined by the collected data.The fatigue limits for crack initiation and crack propagation under "storm model" conditions are proved to be higher than that of a constant amplitude test which is stress amplitude according to fatigue life of 2 millions cycles and also to be higher than one-third of maximum stress in storm conditions. The storm conditions, therefore, only damage structural members.Based on above "storm model", new fatigue design method to be applicable to ship and offshore stru ctures is proposed.Fatigue test under "storm model" were performed for specimens with boxing fillet weldments which one of the most important ship structural components from a view point of fatigue strength. New fatigue design charts applicable to real service sea conditions are obtained.

作者分析了船舶和近海结构物在实际使用条件下所遇到的波浪数据。海浪条件的时程可归纳为：(1)在浪高相对较低的条件下——风平浪静的条件下（低于该地区平均浪高的两倍），遇到的浪高可以看作是一个与时间无关的随机过程。(2)在高浪条件下——风暴条件下（高于面积平均波高的两倍），波高随时间增加，只在某一点达到最大值，然后逐渐下降。也就是说，遇到的波高是一个随时间变化的过程。(3)条件(1)和(2)随机交替出现。在任何地区遇到的浪况时程的上述特征是相同的，但在风暴条件下的平均浪高、平均风暴持续时间、最大浪高和在使用寿命中遇到的风暴次数取决于航行路线和海域。根据所收集的数据，确定了一种用于疲劳强度分析的标准加载模型——风暴模型。证明了“风暴模型”条件下裂纹萌生和扩展的疲劳极限高于200万次循环疲劳寿命下的恒幅试验应力幅值，也高于风暴条件下最大应力的三分之一。因此，风暴条件只会损坏结构构件。在上述“风暴模型”的基础上，提出了适用于船舶和近海结构物的疲劳设计新方法。从疲劳强度的角度出发，对船舶结构中最重要的构件之一箱体圆角焊件进行了“风暴模型”下的疲劳试验。得到了新的适用于实际服役海况的疲劳设计图。

项目成果

冨田 康光,橋本 聖史,大沢 直樹: "繰返し荷重下の船体用構造材料の変形挙動と強度特性に関する研究" 日本造船学会論文集. 174. 509-522 (1993)

Yasumitsu Tomita、Masashi Hashimoto、Naoki Osawa：“循环载荷下船体结构材料的变形行为和强度特性研究”日本造船学会会刊 174. 509-522 (1993)。

冨田康光: "繰返し荷重下の船体用構造材料の変形挙動と強度特性に関する研究" 日本造船学会論文集. 174. 509-522 (1993)

Yasumitsu Tomita：“循环载荷下船体结构材料的变形行为和强度特性的研究”日本造船学会学报 174. 509-522 (1993)。

Masahiro Toyosada, Toshio Niwa, Kikuji Yamaguchi: "Phenomena of Delayd Retardation and Crack Stopping Condition for a Long Fatigue Crack" Journal of The Society of Naval Architects of Japan. Vol.176. 439-446 (1994)

Masahiro Toyosada、Toshio Niwa、Kikuji Yamaguchi：“长疲劳裂纹的延迟延迟现象和裂纹停止条件”日本造船学会杂志。