After appearance of fracture mechancs (FM), much effort has been devoted to the study of strength evaluation of a cracked body. In particular, application limit of fracture mechanics, i.e., a smallest size of crack to which fracture mechanics can be applied, has widely been discussed. The limit size of crack is in current about submicron meter. Owing to the development of many useful measuring instruments such as scanning electron microscope (SEM), laser microscope, laser interference microscope, ultra sound microscope, atom-force microscope (AFM), scanning tunnelling microscope (STM), scanning probe microscope (SPM) and so on, scale of treating fracture behavior has been lowered past 40 years. Nowdays the fracture behavior is experimentally observed on nano-scale. Simulataneously direct application of molecular dynamics (MD) simulation enables us to examine fracture problem on atomic scale. However, experimental and MD-aided works on nano-scale fracture mechanism do not seem cooperative each other. This is because both methods have no unified mechanics to describe fracture. Concerning nano-scale or atomic scale fracture behavior, both experimental and MD-oriented analyses are reviewed and to which extent the fracture behavior can be explained is discussed in this paper.
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