A promising device that increases the efficiency of drilling wells in hard and super hard rocks is a drilling rig with a cavitation hydraulic vibrator. Inside it due to periodic growth, separation and collapsing of cavitational pockets, the pressure shock oscillations are realized in drilling mud. They are transformed into longitudinal vibrations of rock-breaking tool with frequencies of 1 - 20 kHz and values of vibration accelerations from 500 to 3200 g. At repeated impact of power impulses of the rock-breaking tool, the destruction of rock becomes fatigue. As a result of resonance processes in the system of "drilling rig with hydraulic vibrator - rock" and the development of a network of micro-cracks, the rock discontinuity occurs at the stresses lower than the break-down point of the rock. It leads to the increase in drilling speed, wear resistance of drilling tools, improvement of stabilization and steadiness of drilling string functioning. Purpose. To determine the longitudinal vibrational accelerations of the drilling tool at its contact with the destroyed rock taking into account the forces acting in the axial direction on the structure of the drilling rig. Methodology. Methods are based on the experimental and theoretical study on dynamic interaction of rock-breaking tool longitudinal oscillations with the rock. Findings. The results are presented in the form of estimated dependences of the peak-to-peak values of fluid pressure oscillations and vibrational accelerations of rock-breaking tool on the value of cavitation parameter and their comparison with the experimental data. Originality. It is established that: taking into account the contact of the drilling tool with the destroyed rock and forces acting along the axial direction on the structure of the drilling rig in the mathematical model of longitudinal oscillations of the drilling rig allows obtaining a satisfactory agreement of the calculated and experimental parameters of the fluid pressure oscillations and vibrational accelerations in the rock-breaking tool cross-section; for the given design of the hydraulic vibrator the rational regimes of its operation are determined (according to the dependence of the peak-to-peak values of vibrational accelerations on the cavitation parameter) as well as the length of the drilling rig (according to the distribution of the peak-to-peak values of vibrational accelerations along the axial length of the drilling rig). Practical value. The mathematical model of the "drilling rig - rock" system allows establishing the rational regime of operation of the cavitation hydraulic vibrator at the design stage to implement acceptable levels of vibrational accelerations on the rock-breaking tool.

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• Ніколаєв Олексій Дмитрович (технічні науки)

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