变幅载荷作用下船体结构低周疲劳裂纹扩展的关键理论与方法研究

Our foreign trade has flourished in recent years, and its dependence on marine environment and resources has increased substantially. Developing marine economy and building a “maritime power” have become an inevitable choice for our economy to reach a new level. The trend of large-scale development of ships is inevitable. However, in the development process of large-scale ships, the stress and deformation of ship structures are so high and large, which causes the low cycle fatigue damage of ship structure to be paid more and more attention. The research results show that the failure of ship structure is usually caused by low cycle fatigue failure and accumulative plastic damage. The ship structure has been subjected to variable amplitude loading such as wind, wave and current during operation. Therefore, from the perspective of ship structure risk safety assessment, the low cycle fatigue crack propagation analysis considering the effect of accumulative plastic damage under variable amplitude loading can more realistically predict the fatigue strength of ship structure in severe sea conditions. Based on the accumulative plastic damage, this project will carry out theoretical, numerical and experimental research on the low cycle fatigue crack propagation behavior of ship structure under variable amplitude loading. The crack tip opening displacement (CTOD) of ship structure under variable amplitude loading is used to characterize the crack growth rate, which provides a solid theoretical basis and reliable technical guarantee for the correct assessment of low cycle fatigue crack growth of ship structure.

近年来，我国对外贸易蓬勃发展，对海洋空间和资源的依赖程度大幅提高，发展海洋经济、建设“海洋强国”已成为我国经济再上新台阶的必然选择。船舶结构往大型化发展成为一个必然的趋势。而大型化船舶发展过程中，其承受的应力及变形随之增大，使船舶结构的低周疲劳损伤问题日益引起关注。已有的研究表明，船舶结构发生断裂破坏通常是低周疲劳破坏和累积塑性破坏共同作用导致的。船舶结构在营运期间一直遭受风、浪、流等变幅载荷作用，因此，从船舶结构风险安全评估的角度出发，变幅载荷下考虑累积塑性破坏的船体结构低周疲劳研究更能切合实际地评估恶劣海况下船体结构的低周疲劳破坏。本项目考虑累积塑性破坏的影响，从理论、数值模拟和实验三方面对变幅载荷下船体结构的低周疲劳裂纹扩展行为开展研究。采用变幅载荷作用下的船体结构裂纹尖端张开位移(CTOD)表征裂纹扩展速率，为评估船体结构低周疲劳问题提供坚实的理论基础和可靠的技术保障。

已有的研究表明，船舶结构发生断裂破坏通常是低周疲劳破坏和累积塑性破坏共同作用导致的。船舶结构在营运期间一直遭受风、浪、流等变幅载荷作用，因此，从船舶结构风险安全评估的角度出发，变幅载荷下考虑累积塑性破坏的船体结构低周疲劳研究更能切合实际地评估恶劣海况下船体结构的低周疲劳破坏。项目开展变幅载荷作用下船体结构低周疲劳裂纹扩展的关键理论与方法研究，探讨变幅载荷作用下累积塑性与低周疲劳裂纹扩展之间的交互作用规律，建立描述船体结构低周疲劳裂纹扩展速率计算模型，并开展一系列实验与数值仿真工作。通过对比结果可以看出，建立的考虑累积塑性破坏的低周疲劳裂纹扩展速率预测模型能较好地描述变幅载荷对裂纹扩展行为的影响。项目研究对提升船体结构安全性和生命力以及提高和完善船舶疲劳评估水平具有重要意义及应用前景。