The fatigue of structural details of ships is of great importance in the maritime industry as they can lead to cracks which can jeopardize structural integrity. The hopper knuckle is among the most vulnerable areas in a ship with respect to fatigue damage. Analysis of the hopper knuckle has become mandatory for tankers in the Class Ship Rules and in the International Association of Classification Societies Common Structural Rules. Along with the fatigue damage record of the vessels, the fatigue analysis of the hopper knuckles is essential to ensure that the vessels have sufficient fatigue strength. In the current work, fatigue calculations are performed of the upper and lower hopper knuckle connections within midship of the oil tanker using simplified fatigue calculations based on Det Norske Veritas (DNVGL) Classification Note No. 30.7. The fatigue analysis is based on 25 years of operation in worldwide wave environment. A cargo hold model (½ + 1 + ½) amidships and a local finite element model of the hopper knuckle are generated. The local model provides relevant hotspot stress for fatigue life calculations. The results from the hopper knuckle fatigue analysis show that the vessels may expect fatigue cracks at lower hopper knuckle before the vessel reaches its design life of 25 years. Based on the findings, it is recommended to fit soft brackets and close scallops at the lower hopper knuckle on selected common frames in all cargo holds.

中文翻译：

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油轮上下料斗转向节连接的有效疲劳评估

船舶结构细节的疲劳在海运业中非常重要，因为它们会导致裂缝，从而危及结构的完整性。就疲劳损坏而言，料斗转向节是船舶中最脆弱的区域之一。在船级社规则和国际船级社共同结构规则中，对油轮的料斗转向节分析已成为强制性要求。除了船舶的疲劳损伤记录外，还需要对料斗转向节进行疲劳分析，以确保船舶具有足够的疲劳强度。在目前的工作中，使用基于挪威船级社 (DNVGL) 分类说明第 30.7 号的简化疲劳计算，对油轮船中部的上、下料斗转向节连接进行疲劳计算。疲劳分析基于在全球波浪环境中运行 25 年。生成船中部的货舱模型 (½ + 1 + ½) 和料斗转向节的局部有限元模型。局部模型为疲劳寿命计算提供了相关的热点应力。料斗转向节疲劳分析的结果表明，在船舶达到其 25 年的设计寿命之前，船舶可能会在下料斗转向节处出现疲劳裂纹。根据调查结果，建议在所有货舱中选定的通用框架上的下料斗转向节处安装软支架和关闭扇贝。局部模型为疲劳寿命计算提供了相关的热点应力。料斗转向节疲劳分析的结果表明，在船舶达到其 25 年的设计寿命之前，船舶可能会在下料斗转向节处出现疲劳裂纹。根据调查结果，建议在所有货舱中选定的通用框架上的下料斗转向节处安装软支架和关闭扇贝。局部模型为疲劳寿命计算提供了相关的热点应力。料斗转向节疲劳分析的结果表明，在船舶达到其 25 年的设计寿命之前，船舶可能会在下料斗转向节处出现疲劳裂纹。根据调查结果，建议在所有货舱中选定的通用框架上的下料斗转向节处安装软支架和关闭扇贝。