Analysis of the effect of internal defect on coke fracture behavior by rigid bodies-spring model

In this study, to investigate the effect of internal defect in coke, fracture analyses using RBSM (Rigid Bodies-Spring Model) which is applied to fracture analysis of brittle materials such as concrete are carried out for coke. First, in case of taking no account of internal defect, the fracture analyses with RBSM assuming 4-point bending tests are carried out. As a result, analytical results reproduce the fracture behavior well. Next, it is known that internal defect such as non-adhesion region boundaries in coke influences coke strength, so in case of taking account of non-adhesion region boundaries, the fracture analyses with RBSM assuming 4-point bending tests are carried out. To investigate the location of non-adhesion region boundaries in coke, 3 percent non-adhesion region boundaries are randomly located in the coke and fracture analysis of two cases are carried out. Analytical results show that fracture load decreases when non-adhesion boundaries are located under region of high stress and microcracks happen at around non-adhesion region boundaries. It is supposed that these microcracks cause surface breakage. Analytical results also show that the fracture starts at non-adhesion region boundaries when non-adhesion region boundaries are located under region of high stress. In particular, fracture progresses at the location of continuous non-adhesion region boundaries. To investigate the fraction of non-adhesion region boundaries in coke, 3, 5 and 10 percent non-adhesion region boundaries are randomly located in coke. As a result, fracture loads decrease with an increase of non-adhesion region boundaries in the coke.