This paper introduces physical models of drill string whirling and torsional vibrations and analyses the physical models in V.I. Gulyayev's three papers on drill string whirling and torsional vibrations: “V.I. Gulyayev, L.V. Shevchuk, Drill string bit whirl simulation with the use of frictional and nonholonomic models, Journal of Vibration and Acoustics 138(1) (2016) 011021”, “V.I. Gulyayev, L.V. Shevchuk, Nonholonomic dynamics of drill string bit whirling in a deep bore-hole, J Multi-body Dynamics 227(3) (2013) 234–244” and “V.I. Gulyayev, SN Hudoliy, O.V. Glushakova, Simulation of torsion relaxation auto-oscillations of drill string bit with viscous and coulombic friction moment models, J Multi-body Dynamics 225 (2011) 139–152”. This work finds that the physical models described in these three papers are clearly incorrect. Keywords: Drill string, Vibration, Lateral, Torsion, Whirl
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