Abstract
Various approaches have been attempted in order to solve fracture and toughness problems of metals. These approaches could be classified into three fields: physical, metallurgical, and fracture mechanical aspects. In the present paper, these investigations are briefly reviewed and the correlations among them are discussed. Although these have different purposes originally, it is stressed that the plastic deformation at the crack tip is important essentially for all. In order to clarify the fracture and toughness mechanism of metals further, fine experimental works concerning it are expected.
