Influence of rock mechanical properties and rake angle on the formation of rock fragments during cutting operation

Abstract

Mechanical rock cutting is a process encountered in different engineering applications including rock excavation, mining, and deep oil well drilling. Rock mechanical properties vary with depth in the subsurface and also at different geographical locations due to different environmental conditions. Understanding of fragmentation mechanisms in specific rock materials allows the determination of optimum cutting parameters that improve cutting efficiency and increase tool life during cutting operations. In the present investigation, numerical models that accurately predict the rock fragmentation and stress profiles in the rock slab during cutting were developed using the explicit finite element method (FEM). In the numerical method, a damage material model was utilized to capture the rock fragmentation process when a rigid cutter of different rake angles was displaced at different velocities against a stationary rock slab for a cutting depth of 1 mm. Rock slabs with significantly different mechanical properties were incorporated in the material model, and a constant friction factor is utilized in the contact model. The variation of cutting forces and stresses and the size and morphology of rock fragmentation were analyzed. The simulation results indicated that the explicit FEM is a powerful tool for simulating rock cutting as the formation of discontinuous rock fragments were distinctly observed at different cutting conditions. The rock mechanical properties and tool rake angle were found to have the most significant effect on the rock fragmentation during cutting operations. The cutting forces were also influenced by mechanical properties of the rock and tool rake angle. The experimental and numerical results obtained in the literature found a good agreement with the current numerical predictions.