A model to quantitatively predict cleavage fracture toughness in ferrite-cementite steel without any adjustable
parameters was developed. The model is based on the multiscale framework. The macroscopic analysis is FEA. The
microscopic analysis is based on the Monte Carlo method considering microscopic fracture process of three stages.
The developed model was validated by three point bend testing of notched specimens using steels with various
ferrite and cementite sizes. The numerical predicted values of fracture toughness show good agreement with the
experimental results for all cases including the scatter of toughness. It is therefore concluded that the proposed
model showed its effectiveness to predict the fracture toughness of ferrite-cementite steels.