船舶结构低周疲劳与累积塑性耦合作用下的承载力研究

In actual rough sea environment with severe wind and wave, the main forms of shiphull structure failure are cumulative plastic damage and low cycle fatigue damage, thus the overall collapse of shiphull structure is often the coupling result of the two failure modes. So in research and assessment of the overall damage performance of shiphull structure, the destruction of this coupling action should not be ignored, because it is perhaps the most dangerous situation. Due to the increasing plastic accumulation and fatigue crack extension in structure, the shiphull will continuously reduce the load-bearing capability and eventually collapse under the alternating load that is less than the value of monotonic ultimate bending moment. Therefore, the strength assessment considering coupling action of cumulative plastic and low cycle fatigue can more accurately forecast the actual bearing capacity of shiphull structure, and it is obviously a development to the one-time static ultimate strength assessment. The project will carry out series research on the bearing capacity of shiphull’s basic structures, i.e. plates and stiffened plates, subjected by large alternating loads in bad sea conditions, reveal the coupling mechanism and action of the two kinds of failure mode, implement elasto-plastic analysis and study on available calculation method, and conduct series nonlinear numerical simulations and model experiments. The research of this project have important meaning to the promotion of ship structure safety and survivability, and also have protential application worth to the structure design in ship engineering.

实际恶劣海洋风浪环境中，船体结构失效的主要形式是累积塑性破坏以及低周疲劳破坏，船体结构的总体崩溃破坏往往是这两种破坏模式耦合作用的结果。在研究和评估船体结构的总体破坏时不能忽视这种耦合的作用，因为它可能是最危险的情况。由于结构内的累积递增塑性及低周疲劳裂纹的扩展会不断降低船体的承载能力，故最终导致船体在比一次性单调极限弯矩值为小的交变载荷下发生总体崩溃。因此，考虑累积递增塑性破坏与低周疲劳破坏耦合作用的船体结构强度评估能够更为准确地预报船体结构实际的承载力，显然是一次性静力极限强度的一个发展。项目开展恶劣海况中交变大载荷下船体基本结构（船体板，加筋板）承载力的基础研究，揭示低周疲劳与累积塑性两种破坏模式的耦合机理及作用，开展弹塑性理论分析及计算方法研究、同时相应开展非线性数值仿真、模型实验的研究工作。项目研究对提升船体结构安全性和生命力以及对船体结构工程设计水平具有重要意义及应用前景。

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，因此考虑累积递增塑性破坏与低周疲劳破坏耦合作用的船体结构强度评估能够更为准确地预报船体结构实际的承载力。项目开展恶劣海况中交变大载荷下船体基本结构（船体板，加筋板）承载力的基础研究，揭示低周疲劳与累积塑性两种破坏模式的耦合机理及作用，开展弹塑性理论分析及计算方法研究、同时相应开展非线性数值仿真、模型实验的研究工作。课题研究基于累积递增塑性对低周疲劳载荷下船体板、加筋板的剩余极限强度全面开展理论及数值分析研究，建立了一个可以考虑低周疲劳裂纹扩展和累积塑形耦合影响的裂纹板剩余极限强度分析模型，并进行实验及数值模拟验证。通过对比结果可以看出，建立的考虑低周疲劳裂纹扩展和累积塑形耦合影响的船体结构承载力分析模型可以达到预期效果。项目研究对提升船体结构安全性和生命力以及对船体结构工程设计水平具有重要意义及应用前景