Simulation of crack formation in an anisotropic coke using discrete element method

The Discrete Element Method (DEM) is a powerful computational method to simulate mechanical properties of cokes including its failure mechanisms. This study investigates the effects of an anisotropic pore structure on the stress concentration patterns and failure mechanisms of a brittle coke by describing it as a 2-dimensional DEM model assembly which consists of hundreds of element particles. The adjoining element particles are bound to each other using parallel-bonds which are assumed to be broken when the developing stress exceeds the target strength. The voids between element particles are considered to represent micro-defects, and several macro-pores are intentionally imbedded to investigate the effect of macroscopic pore-structures on the coke strength. The macro-pores have a shape of elongated ellipse and their long axes are arranged in three directions: normal, 45° angled and parallel to the loading direction. These pore layouts reflect the different stress concentration patterns during a tensile test. on the simulated results, the coke strength has a positive relation with the load bearing matrix area, or, the number of broken bonds when the assembly has the same long axis as the pores. However, if their long axis directions are changed to decrease the stress concentration, the assembly can stand higher strength with the same load bearing matrix area. Decreasing the stress concentration makes the assembly much stronger against the failure and also avoids being shattered disastrously into small fragments at failure.