Percussion Drilling Research Articles

Improved Design and Dynamics Characteristics Research of a Composite Percussion Drilling Tool

Abstract Internal motion and dynamics mechanism studies of a new composite percussion drilling tool aim at reducing stick-slip phenomenon and improving rock breaking efficiency. In this study, experiments are performed using composite percussion drilling tools to investigate its torsional and axial composite impact performance. According to the experimental results, a six degrees-of-freedom (6DOF) rigid body motion model was established to study the passive motion of a torsional hammer. The obtained results, including the tangential acceleration, were verified with experimental data, and the small pressure differences between the high and low pressure areas, which mainly determined by the inlet structure, is the main reason for the poor torsional impact effects. Based on these discoveries, the improved design increases the inlet flow to 17.2% of the total, the pressure differences to 0.05 MPa, and the instantaneous tangential acceleration to 0.198 m/s2, which results in increased tangential acceleration fluctuation amplitude by 1137.5% and greatly improved torsional impact performance. This research can provide a baseline for stick-slip reduction technology optimization.

Parametric Analysis and Optimization of Inclined Laser Percussion Drilling of Carbon Fiber Reinforced Plastic Using Solid-State Nd: YAG Laser

Parametric Analysis and Optimization of Inclined Laser Percussion Drilling of Carbon Fiber Reinforced Plastic Using Solid-State Nd: YAG Laser

Numerical study on impact energy transfer and rock damage mechanism in percussive drilling based on high temperature hard rocks

Percussive drilling is suitable for fragmentation of high temperature hard rocks in geothermal wells. In actual geothermal drilling, the heat exchange will occur between the low temperature drilling fluid and the high temperature rocks. This heat transfer effects can cause thermal stress in rocks. High temperature environment and thermal stress will cause rock damage. Therefore, when analyzing percussive drilling based on high temperature rock, the high temperature and heat transfer need to be considered. This article focuses on the effects of mechanical percussion-heat transfer couplings on impact stress wave propagation, energy transfer efficiency and rock damage in percussive drilling. At first, the physical model for mechanical percussion-heat transfer coupled process was built. And then the heat transfer model, fully coupled thermal stress calculation method, temperature-dependent plasticity damage model for rocks, and impact energy transfer model were introduced. Finally, the mechanical percussion-heat transfer coupled process were simulated. The main findings show that the high temperature effect will reduce the impact energy transfer efficiency. However, it can also reduce the rock strength, which contributes to the generation of rock tensile damage in percussive drilling. The heat exchange between low temperature drilling fluid and the high temperature rock will cause the tensile thermal stress in rocks. This tensile thermal stress can induce rock tensile damage, which will improve the impact energy transfer efficiency in percussive drilling. As the control group, the rocks being heated will reduce the energy transfer efficiency in percussion drilling. When the input impact energy (less than 102 J under the present simulation conditions) is small, the impact energy transfer efficiency of stinger teeth is greater than that of hemispherical teeth. And when the input impact energy is large, the impact energy transfer efficiency of hemispherical teeth is greater than that of stinger teeth. The key findings of this study are expected to provide some theoretical guidance for high-efficiency fragmentation of high temperature hard rocks in percussive drilling.

Simulation on compound percussive drilling: Estimation based on multidimensional impact cutting with a single cutter

In the present study, a 3D FEM of compound percussive system considering a loading–unloading cycle was employed to simulate the dynamic single-cutter-rock interaction. By conducting the sensitivity analysis, the effects of the impact velocity of cutter, the dynamic load amplitude, the ratio μ of torsional impact to axial impact frequency on the cutting force and penetration depth were investigated. Moreover, a range of simulations were conducted on the stratum lithology (Granite, Marble and Sandstone). As revealed from the results, the cutting forces increase first and then decrease rapidly with the increase in the torsional impact velocity. Besides, the amplitude of the cutting force in the simulation of duration time was improved. The larger the dynamic load, the faster the cutting forces will reach the peak. The penetration depth curve exhibits the step characteristics and increases with the dynamic load amplitude and impact velocity amplitudes. With the ratio μ increasing continuously (μ<2), the amplitude of cutting force and penetration depth tends to be improved. However, the relationship between the torsional and axial impact frequencies might have an optimal value. The stronger rock achieved a higher penetration depth. The penetration depth and the penetration rate could be obtained regardless of rock types when μ=1.5. The penetration rate will demonstrate an improvement of 49.02% under the axial impact and 35.92% under the torsional impact. Finally, the field applications of compound percussive drilling is conducted. The numerical simulation results agree well with field experiment results, with an average accuracy of 91.2% of well Guo X-8 and 96.7% of well Pu X-32, respectively. The study on the mechanism of the compound percussion drilling technology for rock breaking theoretically supported the subsequent development and optimization of the tools.

Parametric analysis of hole circularity for laser percussion drilling of carbon fibre reinforced plastic using Nd: YAG laser

Holes of diameter less than 1 mm has wide application of manufacturing sector. Laser beam can be conveniently used for creation of such hole in different materials. The Carbon Fiber Reinforced Composite (CFRP) is quickly replacing the conventional materials in most of the engineering applications. Therefore, a detail parametric study to analyse the influence of factors like laser current, laser interaction time, pressure of assist gas, workpiece thickness and incidence angle on the geometrical accuracy of hole in terms of hole circularity at top (HCT) has been explored by changing the individual contributing factors. Small holes (< 1mm) have been fabricated with Nd: YAG laser of millisecond pulse duration in CFRP workpiece of thickness 1mm, 3mm, and 5 mm. It was observed that hole circularity at top surface is highest for zero angle of incidence. The increase of laser current, interaction time, and pressure of assist gas increases the HCT when the laser direction is normal to the workpiece whereas it shows a decline trend when the angle of incidence of 10° and 20°g;. The increase of workpiece thickness reduces the HCT irrespective of angle of incidence.

Measurement of Stress Waves Propagation in Percussive Drilling.

This work describes the results of a test campaign aimed to measure the propagation of longitudinal, torsional, and flexural stress waves on a drill bit during percussive rock drilling. Although the stress wave propagation during percussive drilling has been extensively modeled and studied in the literature, its experimental characterization is poorly documented and generally limited to the detection of the longitudinal stress waves. The activity was performed under continuous drilling while varying three parameters, the type of concrete, the operator feeding force, and the drilling hammer rotational speed. It was found that axial stress wave frequencies and spectral amplitudes depend on the investigated parameters. Moreover, a relevant coupling between axial and torsional vibrations was evidenced, while negligible contribution was found from the bending modes. A finite element model of the drill bit and percussive element was developed to simulate the impact and the coupling between axial and torsional vibrations. A strong correlation was found between computed and measured axial stress spectra, but additional studies are required to achieve a satisfactory agreement between the measured and the simulated torque vibrations.

Application and comparison of feature-based classification models for multistable impact motions of percussive drilling

Dynamics of the bit-rock interaction under percussive drilling often encounter multistability that produces coexisting impact motions for a wide range of drilling conditions. Some of them may be detrimental to its performance as it cuts through the inhomogeneous rock layers. A necessary mitigation is the ability to distinguish between coexisting impact motions in order to maintain a high-performance drilling. For this purpose, dynamical responses of a vibro-impact system mimicking the bit-rock interaction of percussive drilling were explored in this study by using machine learning techniques. As a fundamental approach of improving machine learning, hand-crafted and automatic feature extractions were carried out. Results from the simulated data show that extracting appropriate features and using a suitable network are essential for characterising the vibro-impact motions. Extracting statistical, histogram of gradients, continuous wavelet transform and pre-trained convolutional network features are effective and less computationally intensive. With their high accuracies, they become the first point of consideration when designing the classification model for multistable vibro-impact motions of percussive drilling.

Determination of Efficient Rotary Percussive Drilling Techniques for Strong Rocks

Determination of Efficient Rotary Percussive Drilling Techniques for Strong Rocks

Analytical model for the depth progress of percussion drilling with ultrashort laser pulses

A simplified analytical model is presented that predicts the depth progress during and the final hole depth obtained by laser percussion drilling in metals with ultrashort laser pulses. The model is based on the assumption that drilled microholes exhibit a conical shape and that the absorbed fluence linearly increases with the depth of the hole. The depth progress is calculated recursively based on the depth changes induced by the successive pulses. The experimental validation confirms the model and its assumptions for percussion drilling in stainless steel with picosecond pulses and different pulse energies.

Evaluation of geotechnical parameters of reclaimed land from near-surface seismic refraction method

Correct execution of civil engineering structures depends largely on the adequate and detailed mapping of the subsurface. This can be achieved by the application of appropriate geophysical or geotechnical methods in association with a detailed information on the geological sequence of the subsurface structure. In this study, a combination of near surface seismic refraction method, cone penetration test and borehole logs were used to obtain 2-dimensional (2D) information of the subsurface geological features. These methods were used to characterize the subsurface condition of a reclaimed land in Ajah area of Lagos for the purpose of construction. The seismic refraction method revealed three geologic layers with seismic velocities ranging between 258 and 3544 m/s. Additionally, the cone penetration test revealed that the geologic formation from the topsoil to a depth of 6 m was an alluvium of soft and highly compressible property. Furthermore, the percussion drilling test also confirmed the geologic formation from the topsoil to a depth of about 6 m to be highly compressible. However, a geologic formation with good geotechnical characteristics, such as a low compressibility potential, was encountered at a depth between 7 and 16 m, which coincides with the third layer of the seismic refraction method. The results of the three methods confirmed that the depth to most competent layer must be located before the foundations of engineering constructions are sited.

Alternative non-destructive method for strength testing of structural concrete

This work proposes an original and active method for non-destructive testing of concrete and can also be used for other building materials. The proposed method includes the successive steps of: drilling holes into samples of building material with use of rotation or percussion drilling machine and simultaneously determining the power consumption necessary for drilling; strength determination of building material by destructive failure of samples; obtaining a positive empiric correlation between the power consumption necessary for drilling and determined strength values of material; control during drilling the holes in structure material being tested and simultaneously determining the power consumption necessary for drilling; determining the actual strength of structure material being tested by use of correlation between power consumption and material strength values derived in testing process. The application of the method makes strength determination of building materials simpler and faster and also increases the accuracy of testing.

Parametric Analysis of Laser Beam Percussion Drilling for Thin Titanium Alloy Sheet Using Yb: Yag Fiber Laser

Laser beam percussion drilling (LBPD) can create high density holes in aerospace materials with the repeated application of laser pulses at a single spot. In this study, one-parameter-at-a-time approach has been used to investigate the individual effect of peak power, pulse width and pulse frequency on geometrical accuracy and metallurgical distortion during LBPD of 0.85[Formula: see text]mm thick Ti–6Al–4V sheet using 200[Formula: see text]W Yb:YAG fiber laser. It has been found that the output parameters behave differently at the higher and lower values of a particular input process. The increase of pulse width from 1 to 1.50[Formula: see text]ms increases hole taper by 20% whereas the same corresponding change from 1.50 to 2.00[Formula: see text]ms reduces the taper by 20%. The increase of pulse frequency from 10 to 50[Formula: see text]Hz reduces hole circularity by 40% but the same proportionate change from 50 to 90[Formula: see text]Hz reduces circularity by 79%. Increase of peak power from 1.70 to 2.0[Formula: see text]kW increases hole taper by 8% but the corresponding increase from 2 to 2.30[Formula: see text]kW is 143%.

LSTM-based approach for predicting periodic motions of an impacting system via transient dynamics

Dynamically impacting systems are characterised with inherent instability and complex non-linear phenomena which makes it practically difficult to predict the steady state response of the system at transient periods. This study investigates the ability of a data driven machine learning method using Long Short-Term Memory networks to learn the complex nonlinearity associated with co-existing impact responses from limited transient data. A one-degree-of-freedom impact oscillator has been used to represent the bit–rock interaction for percussive drilling. Simulated data results show velocity measurements to contribute most to predicting steady state responses from transient dynamics with most of the network models reaching an accuracy of over 95%. Limitations to practically measurable variables in dynamic systems warranted the development of a feature based network model for impact motion classification. Experimental data from a two-degrees-of-freedom impacting system representing percussive bit penetration has been used to demonstrate the effectiveness of this method. The study thus provides a precise and less computational means of detecting and avoiding underperforming impact modes in percussive drilling.

Determination of rock fracture parameters in directional percussion drilling with drillhole path adjustability

The paper reviews the existing technologies and equipment for drilling in rocks and soil with adjustable path of drillholes. The author describes a new method of percussion drilling and its application prospects. A lab-scale testing installation for physical simulation of rock fracture in drilling by the new method is presented. The force and impact characteristics required for the method implementation are updated.

A comparative study of cemented carbide parts produced by solvent on granules 3D-printing (SG-3DP) versus press and sinter

Cemented carbide parts have been manufactured from WC-12Co granules by “Solvent on Granules 3D-Printing” and compared with reference parts produced by conventional press and sintering. SG-3DP consists in growing a green part layer-by-layer by selective solvent jetting on powder-polymer granule beds. Both 3D printed green parts and uniaxially pressed compacts have been consolidated by thermal debinding and liquid phase sintering. Further densification has been achieved by hot isostatic pressing.3D-printed parts subjected to hot isostatic pressing exhibit 99.9% of theoretical density, 1308 ± 10 HV30 hardness and 12.1 ± 0.3 MPa∙m½ indentation toughness, which are comparable to properties of a commercial fine grained WC-12Co. Percussion drilling tests with fully dense SG-3DP drill plates have also been carried out successfully on concrete.

Real-time observation with metallurgical examination for laser percussion drilling in stainless steel sheets using simultaneous magnetic-ultrasonic assistance

Using simultaneous assistance of the water-based ultrasonic vibrations and a side-loaded magnetic field, the transient real-time observation and metallurgical examination were carried out for laser percussion drilling in stainless steel sheets, aiming for demonstrating the effect of the magnetic-ultrasonic assistance on the hole-drilling process and the metallurgical alteration characteristics. The effect of the camera shooting distance on the signal detection below the hole exit was discussed for laser drilling of through holes. The laser drilling efficiency was characterized based on the real-time observation. It was found that the camera shooting distance affected the signal observation below the hole exit after a workpiece was drilled through due to an optical shield effect of its border side. The influence of the magnetic-ultrasonic assistance was much more notable when the dominant or sufficient heat input for drilling through a hole could not be provided by using a smaller pulse energy, a smaller pulse duration or a bigger laser fluence. The average recast layer thickness of the through-hole middle generated using a millisecond laser could be less than around 5μm when using the water-based ultrasonic assistance accompanied with the magnetic assistance. Compared to the corresponding case without external assistance, a reduction of 40μs was achieved for drilling through a hole by using the simultaneous magnetic-ultrasonic assistance. The average grain size number became bigger for validating the grain refinement in the heat affected zone after laser drilling using the water-based ultrasonic vibrations with and without magnetic assistance.

Molecular dynamics-guided quality improvement in the femtosecond laser percussion drilling of microholes using a two-stage pulse energy process

During percussion laser drilling, the taper of microholes is commonly considered to be difficult to control due to cluster re-solidification at the bottom of the hole. Due to the lack of detailed analysis and understanding of ablation clusters, accurate control of the cluster behaviour in the ablation plume has not been realized, resulting in limited taper control in femtosecond laser percussion drilling. To address this issue, molecular dynamics (MD) simulation is used to analyse the cluster behaviour during femtosecond laser ablation in detail. More importantly, the results provide guidance for the optimization of the femtosecond laser percussion drilling technology. The evolution of clusters of various sizes is described in detail at the atomic scale, and the effect of the energy on the cluster size and ablation ratio is discussed. Furthermore, based on the guidance of MD, a two-stage pulse energy percussion drilling process is proposed. The pulse sequence of femtosecond laser percussion drilling is divided into two stages, where the second stage energy is higher than the initial stage energy. For blind holes, an increase in the pulse energy reduces the average size of the clusters in the ablation plume and promotes the upward removal of clusters. A second increase in the pulse energy when the hole breaks through to the exit side of the sample promotes the downward removal of clusters. The two-stage pulse energy percussion drilling process provides a new method for controlling the behaviour of clusters during femtosecond laser percussion drilling, reducing the re-solidification of clusters and ultimately reducing the taper of microholes.

Experimental characterization and real-time monitoring for laser percussion drilling in titanium alloy using transverse electric field assistance and/or lateral air blowing

A novel laser percussion drilling technology assisted by an electric field with lateral air blowing is reported. The lateral air blowing is first proposed for assisting the E-field assisted laser drilling for improving hole-drilling performance, quality and efficiency by blowing away the vapor plume and cooling the target workpiece. A high-speed camera is first used for observing and characterizing the transient laser percussion drilling process with and without an electric field and/or a lateral airflow. It was indicated that the transverse electric force and/or the side air blowing expedited the spatial motion with dispersion and density reduction of the vapor-plasma plume for enhancing laser drilling efficiency via weakening the plume-induced shield effect. The recast layer was reduced by using the transverse E-field assistance with and without lateral air blowing, and the combined assistance of a transverse E-field together with a lateral airflow was more effective for reducing the recast layer. Interestingly, as a result of the dynamic air cover across the sample surface induced by the lateral air blowing, the laser-vapor interaction inside a drilling hole was greatly enhanced together with the laser-material interaction, leading to the rapidly-accumulated expansion and then the sudden explosion of the laser-induced plume inside a drilling hole. The enhanced vertical scouring and flowing effect resulting from the accelerated vertical plume-motion inside a drilling hole, which was caused by the accumulated pressure difference inside and outside of the hole due to the enhanced outside motion-dispersion effect (especially induced by the electric force) of the plasma-vapor plume, expedited the uniform molten material removal and distribution along the hole sidewall. Importantly, a transverse E-field with and without a side airflow effectively refined the grains of the heat affected zone (HAZ) near the fusion zone of a through hole via increasing the average grain size number. The micro hardness was improved after laser hole-drilling by loading a transverse E-field with and without a side airflow due to a grain refinement effect with and without an airflow cooling effect. It was demonstrated that the lateral air blowing used was more effective to increase laser drilling efficiency for drilling through the workpiece than the E-field used, and the hole-drilling efficiency was further increased if using the combined assistance of a transverse E-field and a side airflow. After the workpiece was drilled through, the hybrid plume signal was effectively suppressed primarily above the hole entrance by using a transverse E-field and/or a side airflow, especially in case of using the transverse E-field assistance.

Effect of pre-impact waves in an elastic rod on coefficient of restitution

The effect of pre-impact waves on the coefficient of restitution (COR) in longitudinal impact of a uniform elastic rod on a linear elastic or bilinear inelastic spring supported by a fix rigid wall is studied. The spring models may represent the quasi-static response of, e.g., a small elastic cylinder or the inelastic bit-rock interaction in percussive drilling. The rod is accelerated to its impact momentum either by a force of relatively short duration which generates significant pre-impact waves in the rod (pre-impact wave case) or by a force of long duration which does not generate such waves (reference case). Analytical and numerical results based on the 1D wave equation are presented in dimensionless form. It is shown that the work performed by the accelerating force is much larger in the pre-impact wave case than in the reference case, and that the COR generally depends on spring stiffness, elasticity parameter, initial rod-spring separation, and wave transit time. In the pre-impact wave case, the COR may be significantly larger or smaller than in the reference case. It may also be significantly larger or smaller than unity. A pre-impact wave mechanism leading to super rebounds with COR up to 1.4261 is described.

Experimental-numerical method for evaluation of energy consumption in percussive drilling of granite

Most geothermal energy is found in hot and dry rock (HDR), and the total resources distributed at depths of 3-10 km are 20.9×106 EJ. Most HDR projects are developed in granite formations and understanding and control of the energy consumption in percussive drilling of granite is essential. Thus, the impact energy is dissipated in various processes including fracture of the granite, kinetic energy of the particles, and heat. This study presents a numerical-experimental method to evaluate the energy consumption in percussive drilling process. The method uses particle flow code (PFC2D) and experiments using a modified Hopkinson pressure bar system. Optical high-speed and infrared cameras were used to record the impact process during the dynamic drilling process. The velocity of fragments was estimated by the high-speed images and the instantaneous temperature change during the impact was observed from infrared images. Preliminary results are given in this study indicating that the proposed numerical and experimental methodologies can be used to investigate the energy consumption during percussive drilling. The preliminary results presented in this paper are part of a larger work in progress, and more work needs be carried out to obtain the energy consumption of the drilling process under different loading and boundary conditions.