Micro-structural analysis of coke using the overlaying mesh finite element method

In order to clarify the bulk breakage mechanism of metallurgical coke in blast furnace, the overlaying mesh finite element analysis that can consider both macro and micro-structure simultaneously is applied for complex micro-structural geometry such as coke. We introduced the stress intensity factor, a criterion of stress concentration around the crack tip, which can get from displacements of singular points by the template mesh putting on the crack tip and evaluated characteristics of fracture for high-strength coke. The numerical results show that the stress intensity factor (K_I*) is dependent on porosity (ε) linearly and then we proposed the following equation considering a shape parameter (C) and the stress intensity factor (B) at ε=0. K_I* = B(1-Cε) This equation shows that the stress intensity factor decreases with porosity because principal stress around pores in the neighbourhood of the crack tip becomes larger and pores prevent stress around the crack tip from concentrating. This negative effect of relaxation becomes larger as porosity increases. Here the parameter C is a specific value, it depends on pore shape and does not depend on crack length. We conclude that this numerical analysis is very useful for estimation of coke quality.