Physics and Chemistry of Fracture and Failure Prevention

在机械、化学、辐射和高温等综合环境的协同作用下，保证材料和结构的可靠性，对于防止失效和事故是极其重要的。一般情况下，失效事故是由局部损伤和老化扩展引起的。因此，为了防止这些故障，在早期阶段检测和评估退化是至关重要的。特别是21世纪的技术将朝着更精确、更高速、更高效、更高温度和更高压力的方向发展，材料和结构所面临的周围环境将比以前更加恶劣。本研究计划的目的是对断裂的力学和机理进行全面的研究，构建失效预防体系。断裂力学等宏观方法已成功地应用于结构集成…在纯机械加载条件下的可靠性和安全性评估更高，而在环境条件下则不然，因为在环境条件下，裂纹尖端的物理和化学反应在断裂中起着至关重要的作用。因此，要从断裂的物理和化学角度对这一复杂裂缝进行力学理解，必须采用局部方法。局部信息的测量，如材料的局部特性，局部环境，如裂纹尖端的局部水化学，对于局部方法是必不可少的。同样地，局部裂纹尖端应变和微小缺陷对于局部方法也是重要的。这些局部测量的范围是几纳米到几百微米，几十纳米升到几微升。在这个项目中，主要包括以下研究领域：(I)对断裂的物理和化学的力学理解，(Ii)材料化学局部测量的方法学发展，(Ii)裂尖水化学局部测量的方法学发展，(Ii)裂尖力学局部测量的方法学发展，(Ii)缺陷局部测量的方法学发展(Iii)基于融合这些局部信息的失效预测系统的构建。该计划由在国际上对断裂的物理和化学研究领域、晶界工程、激光超声显微镜、智能仪器、复杂系统中的断裂、损伤评估等研究领域做出重大贡献的如下研究小组实施。在这项计划之后，通过发起一个新的研究机构--断裂和可靠性研究所，加强了这项活动，作为以前的断裂研究所的新的扩展。研究所维护的设施、空间和国际研究网络较少

Assurance of reliability of materials and structures with synergistic effects of combined environments by mechanical, chemical, radiation and high temperature conditions is extremely important for prevention of failure and accidents. In general, failure accidents are initiated by local damage and its extension by aging. Therefore, in order to prevent these failures, detection and evaluation of the degradation at an early stage is essential. Especially, technology for 21^<st> century will go towards more precise, higher speed, higher efficiency and higher temperature and pressure and consequently, surrounding environments which materials and structures will face to can be severer than before more.The objective of this research program is to conduct a comprehensive research on mechanics and mechanisms of fracture and to construct a failure prevention system.It has been well recognized that the macroscopic approach such as Fracture Mechanics has been successfully used for structural integ … More rity and safety assessment in purely mechanical loading condition but not in environmental condition where physical and chemical reactions at crack tip plays a crucial role in fracture. Therefore, a local approach is mandatory for mechanistic understanding of this complicated fracture from a viewpoint of physics and chemistry of fracture. Measurements of local information such as local characteristics of materials, local environment such as local water chemistry at crack tip, for examples, are essential for the local approach. In the same way, local crack tip strain and tiny defects are also of importance for the local approach. These local measurements are in the order of a few nanometer to several hundreds micrometer and several tens nano-liter to a few micro-liter. Especially, an emphasis has been placed to carry out the research on crack initiation and early stage of propagation based upon local parameters obtained by a fusion of various local information, which govern the most of the life time of the components.In this program, following research areas have been covered as, (I)mechanistic understanding of physics and chemistry of fracture, (II)-1 methodology development for local measurements of materials chemistry, (II)-2 methodology development for local measurements of crack tip water chemistry, (II)-3 methodology development for local measurements of crack tip mechanics, (II)-4 methodology development for local measurements of defects (III) construction of a prediction system of failure based upon a fusion these local information.The program has been carried out by the research group shown below who have been made a significant contribution internationally on the research areas of physic and chemistry of fracture, grain boundary engineering, raser ultrasonic microscope, intelligent instrumentations, fracture in complex systems, damage evaluation and so on. After this program, this activity has been reinforced by initiating a new research institute, Fracture and Reliability Research Institute as a new extension of former Fracture Research Institute. The Institute maintains the facilities, spaces and international research network Less