Multiscale modeling to clarify the relationship between microstructures of steel and macroscopic brittle crack propagation/arrest behavior

Abstract

Prevention of brittle crack propagation as well as crack initiation is essential as “double integrity”. The application of steels with high arrestability to the structures is directly effective to ensure the integrity. Although it is empirically known microstructures have a possibility to macroscopically enhance the arrestability of steel, there are not any theories which have quantitatively explained the relationship between brittle fracture and microstructures in the past investigations. In the present study, we propose a multiscale fracture mechanics model by a “model synthesis” approach, which integrates the multiple models and analyses to systematically evaluate complicated macroscopic and microscopic phenomena, based on the information of microstructures of the steel. The model is composed of (i) microscopic model to simulate cleavage fracture in grain scale (10-6~10-3m), and (ii) macroscopic model to simulate brittle fracture in steel plate scale (10-3~10°m). As validation, the proposed model is applied to temperature gradient crack arrest test of steel plate having nonhomogeneous distributions of microstructures in thickness direction. The prediction results show good agreement with experimental results in both crack arrest length and shape of crack front. That is, the proposed model has a potential basis of the framework to establish the theory to clarify the relationship between microstructures and brittle crack propagation and arrest behavior.