Multiscale Model Synthesis to Clarify the Relationship between Microstructures of Steel and Macroscopic Brittle Crack Arrest Behavior - Part Ⅱ: Application to Crack Arrest Test

摘要

The second part of the present paper shows an application of the proposed multiscale model to the temperature gradient crack arrest test of the steel plates having nonhomogeneous distributions of micro-structures in thickness direction. The multiscale model is developed as the integrated macroscopic model composed of the three-staged analyses. The first stage is a preparatory macroscopic finite element analysis, where the nodal force release method is employed to simulate fast crack propagation under the dynamic elastic-plastic condition without considering non-linearity of geometry. The second stage is the Monte Carlo simulation of microscopic analysis for cleavage fracture at the discrete evaluation points. The results of local fracture toughness and direction of fracture surface show large scatters even at the same evaluation point. The final stage is the integrated macroscopic analysis, which is composed of the two parts: (a) assignment of parameters obtained in the previous analyses in each unit cell, and (b) simulation of brittle crack propagation/arrest behavior. As a result, the proposed multiscale model successfully simulated the complicated brittle crack propagation/arrest behavior. In particular, not only the arrested crack length but also the characteristic fracture surface such as "split nails" were accurately simulated. It is therefore found that the proposed model has been validated by the comparison with experiment. That is, the proposed model in the present study has a potential basis of the framework to establish the theory for the clarification of the relationship between microstructures of steel and macroscopic arrest toughness of steel plate.