CREEP OF ALUMINUM DRILL PIPES AT EXTRA DEEP DRILLING
This article discusses the problem of creep of aluminum drill pipes in ultra deep drilling. The characteristic features of the yield conditions, the use of the yield conditions for an orthotropic and isotropic material are analyzed. The reason for the use of lightalloy drill pipes (LBT) of aluminum or titanium alloys is given. It is said why the use of aluminum drill pipes for deep hole drilling is recommended. The problem of the time spent by drill pipes in the zone of elevated temperatures is considered, due to which the mechanical characteristics of the pipe material change, and the likelihood of irreversible plastic and rheological deformations increases. A simplified equation is derived for finding the yield condition. The rheological coefficient and anisotropy parameters are identified and justified. The averaged anisotropy parameters are obtained for the viscoelastic and viscoplastic components. Shows the curves of the strain curves, averaged over three implementations. Based on the studies, the author explains why, for solving the boundary value problem at the first iteration, it is possible to take the anisotropy parameters.