Effect of Mass Variation on Vibration Properties of the Tooth in Drilling Operation

Dental cavity represent one of the widespread illness of the tooth. Method for treating of the tooth is to drill the cavity and to fill the hole with suitable material. Measurements show that during drilling the tooth vibrates with increasing mass that causes unpleasant feeling for patient. The aim of the paper is to give the theoretical explanation for this phenomena and to give suggestion for vibration elimination. During drilling, mass of the tooth is decreasing and the so called ‘reactive force’ occurs. Drilling and reactive force cause tooth vibration. The system is modeled as a nonlinear time variable system. An analytical procedure for solving of the equation of vibration is developed. The solution is assumed in the form of the generalized trigonometric function with time variable amplitude and phase. It is obtained that not only the amplitude but also the frequency of tooth vibration in drilling are increased. In addition to reactive force the drilling velocity, diameter of the drill tool and spindle speed affect the vibration level. The appropriate values of these parameters would eliminate or decrease the patient bad feeling.

Influence of Rotation Speed and Air Pressure on the Down the Hole Drilling Velocity for Borehole Heat Exchanger Installation

The relation between rotation speed, air pressure and the velocity of air-rotary drilling using the down the hole method is determined in an empirical manner. For the study, velocity measurements are obtained for combinations of the aforementioned parameters during fieldwork for the installation of borehole heat exchangers near Lublin, Poland. The tests consider three drill bit diameters—110, 127 and 140 mm; three rotational speeds—20, 40 and 60 1/min; and three air pressures—16, 20 and 24 bar. The borehole heat exchangers need 100 m deep wells. The lithology consists mainly of loess and clays to 24 m, sand and carbonate rocks to 36 m, and marls and limestone to 100 m. It is found that the highest drilling velocity is achieved when the greatest pressure is applied, while the lowest drilling velocity is connected to the lowest pressure. However, the relation between rotation speed and drilling velocity is more complex, as drilling velocity seems to be more affected by depth. Therefore, lithology can be a major factor. The results may find direct use in drilling, and provide a basis for further studies on the optimization of drilling technology.

Finding velocity of roller-bit and rotary-percussive drilling using the energy conservation law

Velocity of roller-bit and rotary-percussive drilling depends on many factors distributed in 4 groups in technical literature: rock properties, bit parameters, bit-rock interaction conditions and drilling modes. Literature sources present some very complex formulas which need finding empirical coefficients before determining drilling velocity, i.e. the formulas are difficult to use. Moreover, the formulas neglect jointing of rock masses. At the same time, mathematical relations connecting drilling velocity, drilling mode and drillability of jointed rocks will make it possible to rate drilling processes and adjust blasting parameters. These studies aim to determine velocity of roller-bit and rotary-percussive drilling using the energy conservation law. The used method of mathematical modeling allowed obtaining formulas for rock drilling velocity with regard to drilling modes, bit parameters, factor of rock hardness (strength) and rock mass jointing. The validity of the relations of the roller-bit and rotary-percussive drilling velocity is proved. The reliability of the drilling velocity formulas can be determined by means of investigations performed in open pit mines, with recording of all parameters and with mathematical processing of the data. The mathematical relations connecting drilling velocity, drilling modes, drill bit parameters and drillability of jointed rocks will enable rating of drilling and adjustment of blasting patterns.

Stable Dispersed MoS2 Nanosheets in Liquid Lubricant with Enhanced Rate of Penetration for Directional Well

MoS2 nanosheets of approx. 100 nm were synthesized by a reverse microemulsion route firstly, then were annealed under nitrogen atmosphere, and were finally modified with 1-dodecanethiol. The prepared MoS2 nanosheets were characterized by XRD, TEM, FTIR, and so forth. Experimental results show that MoS2 nanosheets with the typical layer structure can be easily dispersed in oil lubricant for rate of penetration (ROP) increasing in directional well. The ROP of directional well with the prepared liquid lubricant was 52.9% higher than that of the similar directional wells at least, and the drilling velocity was increased 20% while the total proportion of lubricant in drilling fluid was 1.5%.

On the Applicability of Gas Drilling Technology in Carboniferous System of Dzungaria Basin

In carboniferous system of Dzungaria basin, the hard igneous rock greatly decreases the drilling velocity. Gas drilling is probably the only technology to overcome this problem. However, the applicability of gas drilling technology should be investigated first. It was studied by analyzing the rock strength both experimentally and theoretically. Stress status of many rock elements near well face was tested which showed a 2D compression status rather than 3D in conventional slurry drilling technology conditions. Therefore there was a horizontal stress for underground rocks, in a similar magnitude with upper burden pressure. The domination of the confining pressure, different with normal conditions, may mislead the selection of the failure criterion. We proved the correction of the Mohr-coulomb criterion as the most suitable failure criterion in gas drilling conditions. As a result, the applicability of gas drilling technology in Carboniferous system of Dzungaria basin was concluded.