盐雾环境亚微米多晶金属高周疲劳成核机理的实验研究

As military installation and oil production extend to far-out areas of the sea, the cost of the automation systems and technological challenges increase rapidly. Micrometer- or sub-micrometer polycrystalline FCC metals have been used for high-tech devices, which are subjected to mechanical cyclic loading in the slat spray during operation. Then, it is necessary for the precise evaluation of their reliability to realize the corrosion fatigue behavior of small components. For components smaller than a few micrometers, there is insufficient space to form a PSB and the dislocation structures during fatigue. The extrusions/intrusions would not be formed which were along the PSBs. Then the chemical reaction of micro-scale metals with slat spray on the surfaces would different with the bulk metals. Thus, these components may exhibit characteristic fatigue nucleation, which is different from that observed in the bulk materials. To investigate the high-cycle fatigue behavior of small specimens in the salt spray, we must develop a fatigue methodology. Fatigue methodology in micro-scale would be a high frequency process, but the influence of environment would be a long-term effect. So, we must develop a new environment-cyclic loading methodology to investigate the corrosion fatigue behavior of sub-micron polycrystalline coppers. These studies would have pointed out the mechanism of quite different corrosion fatigue behavior in small dimensions from those of bulk materials. This includes the influences of not only specimen size and microstructure size but also the salt spray. In order to understand these behaviors, the influences must be separately inquired then coupled. In the future studying, the fracture behavior of sub-micrometer components under cyclic loading in the salt spray will be investigated. This project will provide scientific foundation for the development of ocean engineering.

远海岛礁、平台孤悬海外，设备自动化和可靠性要求极高，各种精密器件长期处于强破坏性盐雾环境并承受循环载荷，精细金属极可能发生疲劳使器件失效。本项目将发展有效引入盐雾环境－循环载荷共同作用的微尺度疲劳实验方法，针对晶粒和材料都处于亚微米尺度的多晶面心立方金属，开展盐雾环境高周疲劳实验研究，获得晶粒尺寸、材料尺寸和环境因素与多晶金属疲劳成核特征的关系，揭示盐雾环境亚微米多晶金属疲劳成核机理。为盐雾环境金属疲劳断裂研究增添机理性成果，为远海精密器件设计及可靠性分析提供必需的理论支撑。

新一代环境友好型海洋开发进一步要求结构实现轻质、高强、高阻尼而具有高负载、高耗散、低能耗等性能，已有装备与结构设计理论存在大量简化、近似和约束，在新一代工程建设中出现无法解决的矛盾，包括：微尺度结构力学测试困难，关键参数缺失使设计多基于宏观数据和经验；新一代半潜平台特殊节点复杂，服役寿命低于设计；核动力装置辐照环境下材料微结构强烈变化使其宏观本构随时间非线性演化，成为舰船安全重大隐患；海洋动载下结构耗散不足使损伤加速，传统线性理论中阻尼材料必须达到一定比例才能有效耗散，但低刚度阻尼材料极大增加结构比刚度，即线性理论下高负载、高阻尼设计间存在原理上的矛盾；新型柔性潜堤流体-结构耦合解析方法，获得设计必需的耗能机制与参数。.本项目发展了微尺度两自由度耦合振动测试技术，获得了各向异性层合亚微米结构弹性特性，该类技术可进一步应用于微尺度多轴加载下疲劳测试；实验与理论研究了舰船反应堆用聚合物分子、夹杂、微孔等多尺度多级辐照损伤机理，建立分子、填料和网络耦合的材料化学性变与微细宏观力学行为演变模型，实现反应堆聚合物材料性能预测（20年）；基于不可逆损伤力学原理发展了结构损伤计算方法，实现了结构-材料-损伤一体化设计，应用于第七代半潜式平台研发和南海海上风电结构设计；发展了多稳态-线性耦合的非线性理论，设计了强烈非线性滞后特征的全金属稳态被动转换构件，有效耗散了破碎波砰击结构的能量，同时基于非线性平均法建立了滞后特性与结构动态衰减间解析关系；发展了两类柔性潜堤的水动力特性解析方法，给出了共振效能机制与设计参数确定方法。本项目各成果获教育部科技进步二等奖1项、正编入国家行业规范1项、获美国船级社认证1项、已授权国家发明专利3项、SCI已收录论文9篇（中科院一区2篇，中科院二区5篇，含海工顶级期刊Marine Structures、Ocean Engineering）。