The Elastoplastic Contact Analysis of Drilling Pipe - Slip Dog and Optimal Design of Slip Dog

Based on the elastic plasticity contact analysis theory and the plastic damage yield criterion, a mechanical model of the slip-drilling pipe is established. After studying their plastic deformation and drilling pipe´s sliding, optimization of the slip dog´s structure has been proposed. In the light of the systems of different specifications of drilling pipe, after analyzing the coupling effect among Slot number, Tooth root fillet, Tooth tip chamfer of slip dog and the parameter´s variation´s influence on both the drilling pipe when the slips hold fast to the drilling pipe and the influence on the slip dog itself, the slip dog´s plastic damage law on the drilling pipe under different parameter combinations is obtained. The result shows: the slip dog´s slot number has different effects to slip dog and drilling pipe´s longevity, there is a coupling effect between slip dog insert´s Tooth root fillet and Tooth tip chamfer, This method is of universality and applicability. It will effectively reduce the drilling operational risk and drilling costs.