構造用低炭素鋼の破壊じん性と破面のX線観察

概要

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Fracture toughness tests of a structural low-carbon steel SM41B were conducted at low and ambient temperatures. The electrical potential method was successfully used for determining the crack nucleation point and the amount of crack extension. The, effect of test temperature on the fracture toughness J_<Ic> was discussed in correlation with the results of X-ray diffraction observation of plastic strain on the fracture surface. The plastic strain measured on the fracture surface in the close vicinity of pre-fatigue cracks was found to be proportional to the fracture toughness divided by the flow stress, thus to the crack-tip opening displacement. The fracture surface strain increased with crack extension in the cases of dimple fracture and was nearly constant in the cases of cleavage fracture. The change of fracture surface strain with crack extension corresponded to the resistance change of material. A more detailed examination indicated that the fracture surface strain was given by the sum of strains accumulated before and after the mechanical instability for fracture.
社団法人日本材料学会の論文
1980-01-15