Numerical modelling of rotational frictional sliding induced damage on rock

  • Saksala, Timo (Tampere University)

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A numerical approach to predict damage and inelastic deformation in rock material due to rotational frictional sliding and the heat generation thereof is presented. A target application in mind is the Sievers miniature drilling process to assess drillability of different materials. This is an abrasive rotational drilling method where 20 kg of weight on bit is applied on a chisel-shaped of tool rotating against the target material at 200 RPM. A damage-viscoplasticity model to describe the rock failure is developed. As the focus of interest is on the rock behavior, the drill bit is represented as a single node and its interaction with the rock surface is modelled as a rotating boundary condition of a contact node set on the rock surface. The global coupled thermo-mechanical problem with frictional contact is solved with a staggered globally iterative approach. The tangent stiffness required by the Newton-Raphson iteration is derived assuming penalty method for contact modelling. Numerical simulations demonstrate the validity of the approach.