An improved model for the disking process

The disking process is an alternative to diamond-sawing for the cutting of brittle rods and bars. Disking involves positioning a pre-cracked, brittle cylindrical rod snug inside an elastic, annular sheath and subjecting the composite to biaxial fluid pressure. At a critical pressure the crack runs across the section of the rod producing a clean cut. A model that considers the influence of the interface between the rod and the sheath is presented here for predicting fracture pressures. The model is based on linear-elastic-fracture-mechanics. A concentric circular cylinders model is assumed with the flaw modeled as an annular crack perpendicular to the interface. The bond at the interface is considered to be imperfect and is represented by distributed shear springs. Stress intensity factors at the crack tip are determined as a function of material, interface, and geometrical parameters. Analytical results indicate that the shear stiffness of the interface strongly influences the stress intensity factors and consequently the fracture pressures. These analytical results compare favorably with experimentally determined fracture pressures.