抄録
Numerical analysis was performed to estimate fracture toughness values of SM490A steel in the wide temperature range including the ductile-brittle transition region. Microscopic fracture surface observation revealed that cleavage fracture was observed on the fracture surface at the lower shelf and transition regions, while dimple fracture was observed at the upper shelf region. In the numerical analysis, void volume fraction was taken as a dimple fracture criterion, and a set of critical plastic strain, stress triaxiality and maximum principal stress was taken as a cleavage fracture criterion. The numerical analysis showed that the dimple fracture took place in the upper shelf region. The dimple fracture toughness values agreed well with the experimental results. In the transition and lower shelf regions where the cleavage fracture was observed, the numerical analysis results also well agreed with the experimental results that the fracture toughness values were gradually increased with the temperature.
