Drill Bit Research Articles

Accuracy of routine external ventricular drain placement following a mixed reality-guided twist-drill craniostomy.

The traditional freehand placement of an external ventricular drain (EVD) relies on empirical craniometric landmarks to guide the craniostomy and subsequent passage of the EVD catheter. The diameter and trajectory of the craniostomy physically limit the possible trajectories that can be achieved during the passage of the catheter. In this study, the authors implemented a mixed reality-guided craniostomy procedure to evaluate the benefit of an optimally drilled craniostomy to the accurate placement of the catheter. Optical marker-based tracking using an OptiTrack system was used to register the brain ventricular hologram and drilling guidance for craniostomy using a HoloLens 2 mixed reality headset. A patient-specific 3D-printed skull phantom embedded with intracranial camera sensors was developed to automatically calculate the EVD accuracy for evaluation. User trials consisted of one blind and one mixed reality-assisted craniostomy followed by a routine, unguided EVD catheter placement for each of two different drill bit sizes. A total of 49 participants were included in the study (mean age 23.4 years, 59.2% female). The mean distance from the catheter target improved from 18.6 ± 12.5 mm to 12.7 ± 11.3 mm (p = 0.0008) using mixed reality guidance for trials with a large drill bit and from 19.3 ± 12.7 mm to 10.1 ± 8.4 mm with a small drill bit (p < 0.0001). Accuracy using mixed reality was improved using a smaller diameter drill bit compared with a larger bit (p = 0.039). Overall, the majority of the participants were positive about the helpfulness of mixed reality guidance and the overall mixed reality experience. Appropriate indications and use cases for the application of mixed reality guidance to neurosurgical procedures remain an area of active inquiry. While prior studies have demonstrated the benefit of mixed reality-guided catheter placement using predrilled craniostomies, the authors demonstrate that real-time quantitative and visual feedback of a mixed reality-guided craniostomy procedure can independently improve procedural accuracy and represents an important tool for trainee education and eventual clinical implementation.

A comparative study of hole integrity performance in composite‐metal stacks using coated and uncoated tungsten carbide drill bits

AbstractThis study aims to develop tetrahedral amorphous carbon nanocomposite layer coated tungsten carbide drill bits for single shot drilling of composite metal stack. Different coatings were tested for hole integrity performance compared to an uncoated tool and the results were validated using process capability six‐pack analysis. The drilling process employed a 4.85 mm twist drill with a feed rate of 0.05 mm/rev and spindle speed of 2600 rev/min. The experimental results indicate that, all the coated tools produce H9 tolerance holes while uncoated tool produced H7 tolerance holes with 18 % to 35 % better results. But statistical results show that all the tools including uncoated tool require improvement to stay within the control limits. The hole circularity error obtained by all the tools were below 24 μm in both the panels and is supported by the statistical results as well. The uncoated tool exhibited 17.91 % better surface roughness in aluminium panel compared to coated tools, while coated tools produced 17.2 % to 22.3 % better surface roughness in composite panel. Statistical results suggested that, improvement is necessary when drilling aluminium panel by all the tools while dopant added coated tools produce better results in composite panel.

Actuation mechanism of a nanoscale drilling rig based on nested carbon nanotubes.

With the increasing emphasis on health and the continuous improvement of medical standards, more and more micro/nano devices are being used in the medical field. However, the existing micro/nano devices cannot effectively solve various problems encountered in medical processes and achieve specific therapeutic effects. Based on this, this article designs a new type of nanoscale drilling rig. The nanoscale drilling rig is composed of double-layer nested carbon nanotubes with multiple electrodes, and is powered by an external power source, making it easy to perform long-term surgery in the human body. Through coding strategies, we can adjust the surface charge density and distribution of the nanoscale drilling rig, thereby controlling its periodical rotation and achieving precise medical treatment. In addition, in order to control the length of the nanoscale drill bit, meet the treatment needs of different parts of the human body, and reduce damage to the human body, we have designed a structure of ion electric double layers so that the drill bit can be fixed in different positions, reducing the risk of treatment to a certain extent. This drilling rig enriches the functions of micro/nano devices, which is beneficial for the development of the medical industry.

Optimization Design of Mining Tri-cone Bit Air Nozzle by CFD

Performance of the air nozzle of the mine tri-cone bit directly affects life of bit and rock breaking efficiency. The shape of air nozzle influences performance of mine tri-cone bit. It is necessary to optimize the shape of the air nozzle of tri-cone drill bits. The general specifications of gas mine tri-cone bit were analysed. Working condition and parameters of the air nozzle of the mine tri-cone bit were determined. A three-dimensional model of the air nozzle of the mine tri-cone bit was established. The characteristic geometry and range of air nozzle were determined. The performance index of air nozzle was proposed. An orthogonal experiment table of characteristic geometry of air nozzle was established. The ranking of influence weights of characteristic geometry was obtained. Key characteristic geometry which affects the performance of air nozzle was also obtained. This thesis work helps to improve the working performance of the gas nozzle of the three-cone bit. It can provide some reference ideas for the optimized design of the cone bit

Research and application of drilling technology for grouting transformation in coal mine strata——Taking Huainan Zhangji Mine as an example

In order to solve the problem of water disaster in coal mining and realize the safe mining of working face, the drilling technology of grouting reconstruction in coal mine strata is studied, and the key parameters in grouting construction are optimized and determined. According to the characteristics of engineering implementation, the optimization design of drilling casing program, the optimization of drilling tool assembly, the preparation of multi-type drilling fluid and the optimization of drill bit are introduced to ensure the smooth implementation of the project. According to the trajectory design requirements, the landing point of the main hole drilled into the coal seam floor to control the limestone layer was calculated. The results show that the construction technology and technical method are suitable for the multi-branch horizontal grouting well project in coal mine, which achieves the safe and efficient drilling of grouting well in coal mine, and provides useful experience for the subsequent grouting well construction in this area.

Numerical Simulation of Acoustic Field Ahead of Drill Bit in Formation Generated by Multipole Source During Logging While Drilling

Numerical Simulation of Acoustic Field Ahead of Drill Bit in Formation Generated by Multipole Source During Logging While Drilling

Online and Scalable Motion Coordination for Multiple Robot Manipulators in Shared Workspaces

Multi-robot motion coordination is essential to make robots work safely and efficiently in a shared workspace, ensuring task completion while avoiding interference between each other’s motions. Achieving online replanning and scaling to large numbers of robots are particularly challenging. In this paper, we present a motion coordination method for multiple robot manipulators with given targets. The approach separates the problem into a global coordination stage and a local trajectory replanning stage. Online reactivity and scalability are achieved by means of coordination in a reduced space and efficient trajectory replanning. We first introduce the method for systems with two robots, then extend it to systems with an arbitrary number of robots. The method determines whether kinematically-feasible and non-interfering trajectories leading all the robots to their targets exist. The approach generates time-efficient trajectories if solutions exist, or provides information for switching targets if solutions cannot be found. We show formally and empirically that the method has low computational overhead and scales quadratically with the number of robots. Experiments are conducted with up to three real 7-DOF robots and up to ten simulated robots. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —In underground mining, a key process is that of tunneling, i.e., drilling and blasting rock to excavate tunnels that lead to sources of ore. Drilling is carried out by rigs equipped with multiple robotic arms. A key factor affecting the efficiency of tunneling is the time to completion of drilling operations. In current industrial practice, these operations are carried out manually by an operator steering the arms on the drill rig. Time to completion can be drastically reduced if the arms could operate concurrently, intelligently optimizing and coordinating their motions. However, existing methods for multi-arm motion coordination are inadequate, as they fail to cater to one or more of the following real-world constraints: several robot arms work in close proximity and their workspaces are overlapping; task completion times are uncertain due to rock density and drill bit breakage; and contingencies such as unexpected delays in motion or stops sometimes happen. These constraints exist also in other industrial applications, like manufacturing and assembly. This paper proposes a framework which enables multiple high-DOF robot manipulators to safely and efficiently work in a shared workspace. The method allows to adjust robot trajectories while robots move, and is shown to scale well with the number of robots. Motions are generated and adjusted by time-optimal trajectory planning, whose computational overhead is small enough for online operation and benefits task completion efficiency, safety, and productivity. Experiments using three 7-DOF robots suggest that this approach is practically feasible, and simulations with up to 10 robots attest to its scalability.

Sustainable Optimization of Drilling Parameters for AA2017/AlN Composite Materials: A Grey Relational Analysis Approach

Modern engineering materials have seen remarkable development. Because conventional materials can no longer meet the needs of modern applications, numerous composites are being employed as viable alternatives. Drilling is the most important production step for most uses, and the resulting holes are high-stress zones that must be handled carefully. Scientists and engineers have long been interested in the challenge of finding the best combination of drilling settings for cutting-edge composite materials. As part of this research, AA2017/AlN composites with matrices made of AA2017 aluminium alloy and reinforcements made of 5, 10, and 15 wt % AlN were produced using stir casting. By experimenting with different input parameters, we were able to utilise the L9 OA to determine the best machining arrangement for drilling materials. The investigation focused on critical drilling characteristics, including burr height (H), thrust force (T), and surface roughness (SR), with a keen emphasis on sustainability.By considering the burr height (H), thrust force (T) and surface roughness (SR) and this work used grey relational analysis (GRA) to establish the optimum cutting parameters for drilling holes in the cutting-edge composite AA2017/AlN. The significance of different machining settings and their effect on the typical characteristics of the drilling were analysed using GRA. However, a confirmation experiment was conducted to ensure the highest quality outcomes. Test results and GRA indicate that the best grey relational grade is achieved with the following parameters: spindle speed (S) of 3500 rpm, feed rate (F) of 60 m/s, drill material (D) of Tungsten Carbide, and reinforcement (R) of 10%.. Analysis of variance (ANOVA) revealed statistically significant impacts on GRG from the drill material (29.08%), the feed rate (24.24%), and the spindle speed (19.52%). The error term was a function of the reinforcement percent and its interactions with all other parameters; however, the influence of the interaction between feed rate and drill material on GRG was small. The GRG is 0.856, which is higher than the prediction of 0.824. The calculated and measured values agree quite well and 3.7% is a negligible margin of error. The mathematical models for all reactions depending on the drill bits employed was also constructed.

Procena karakteristika obrade i habanja alata tokom bušenja ugljenika / aluminijum-aluminijum

In the past few decades, fibre metal laminate (FML) machining has been facing critical challenges in quality control and tool wear monitoring due to the material's intrinsic heterogeneity and abrasiveness. Different drill tools have been used to investigate the effect of process parameters on machining performances. Composite holes and tool wear was studied for drilling forces and surface roughness. An emphasis was made on examining the tool morphologies and wear processes that influence the drilling of CARALL composites. The drilling responses obtained from both the drill bits were optimized using a decision-making approach viz; Combined Compromise Solution Analysis (CoCoSo). The SEM investigation of the machined samples was used to examine the hole quality and surface finish. A lower point angle drill with a longer chip flute length produced the best results for drilling CARALL composites up to a specific point with minimum flank wear and chip adhesion.

Real-time automatic identification methods for downhole whirling based on mechanical specific energy model of drill bit

In the drilling exploitation of hot dry rock for geothermal energy, whirling is one of the main low-efficiency conditions that affect the efficiency of Polycrystalline Diamond Compact (PDC) bit in horizontal well drilling. Realizing automatic and real-time identification with whirling is of great significance to save non-productive time and ensure drilling safety and benefit. In this paper, we first constructed a real-time drilling mechanical specific energy (MSE) model combined with while-drilling testing to reflect the real-time drilling conditions. The MSE model is used to normalize multi-source parameters. Secondly, we constructed a Back Propagation (BP) artificial neural network (ANN), and then the normalization effect verification, optimization of network parameters, and identification effect verification of whirling were carried out. The final results show that the established MSE model has a favourable effect on data normalization, which could also reduce the complexity of the required network model, and shorten the training time by 20–30 s/step. The optimal algorithm is Trainscg, whose optimal number of hidden layer nodes is 5, and the optimal maximum number of iteration steps is 1000. The established ANN model can accurately identify whirling based on MSE, the accuracy is about 0.94, and the average relative error is 1.3%. The method established in this paper provides a reference for the automatic identification of various low-efficiency conditions based on MSE.

A novel experimental setup for axial-torsional coupled vibration impact-assisted PDC drill bit drilling.

The geological conditions of hot dry rock (HDR) reservoirs are complex. The geothermal mining of HDR faces major challenges in the drilling and construction of wells, fracturing to create storage, and flowing to extract heat. Vibration impacts help improve the rock-breaking efficiency, where the axial-torsional coupled vibration impact technology can increase the bit penetration depth and reduce the stick-slip effect. To study the feasibility and efficiency of the axial-torsional-coupled vibration impact-assisted Polycrystalline Diamond Compact (PDC) bit to break high-temperature and high-pressure rocks, a new experimental setup was designed. The system includes a drilling fluid circulation system, an axial-torsional coupled impact drilling system, a formation simulation system, and a data acquisition and control system. This setup can produce a rock-breaking torque of 2000 N·m, a drilling speed of 200rpm, a weight on bit of 100kN, an axial vibration frequency of 100Hz, and a torsional vibration frequency of 50Hz. It can simulate the formation pressure of 70 MPa and the rock temperature of 400 °C. A series of rock-breaking drilling experiments were successfully conducted using this setup. The results show that the axial-torsional coupled vibration-impact assisted PDC bit has a good performance in breaking high-temperature and hard rocks, which can accelerate the application of this new technology in deep formation drilling.

First Report of Binucleate Rhizoctonia AG-G Causing Grapevine (Vitis Vinifera) Trunk Diseases in California Nurseries.

Grapevine Trunk Diseases (GTD) are caused by a consortium of fungal pathogens that affect the biological functions of the vascular system of mature and young grapevines (Gramaje et al. 2018). We conducted surveys to profile GTD pathogens in California grapevine nurseries and collected 784 cuttings of cvs. Cabernet Sauvignon and Chardonnay grafted on 1103P rootstock. Several vines exhibited wood necrotic lesions and cankers at the graft union and the root ball (Figure 1A). Symptomatic wood tissues were cultured on PDA medium and after two weeks of incubation at room temperature (22°C), several known GTD pathogens were recovered. We also identified Rhizoctonia from 42 of the 784 vines (5.3% incidence) based on the morphological characteristics of a brown pigmented mycelium (Figure 1B), hyphae branched at a right angle with constrictions at the branch point (Figure 1C) and absence of spores (González García et al., 2006). A subsample of four isolates (DCHG2B, DCSG22R, JCSG9B, and JCHG12B) were randomly selected for further DNA-based taxonomic identification and pathogenicity evaluation to grapevine. The ITS and beta tubulin regions were amplified using the ITS1/ITS4 and B36F/B12R primer sets, respectively (González et al. 2006), and sequences were deposited in the NCBI database (Accession numbers: OR052655, OR052656, OR052657, OR052658 and OR059207, OR059208, OR059209, OR059210). Sequences displayed >99% and >96% identity with the respective ITS and beta tubulin sequences of the binucleate Rhizoctonia AG-G specimen C-653 (González et al. 2006). A phylogenetic tree constructed using the Neighbor-Joining method indicated a 100% bootstrap support with the binucleate Rhizoctonia AG-G (Figure 2). Pathogenicity of the binucleate AG-G Rhizoctonia were confirmed on two separate technical replicates using standard methods. For each replicate, one-year-old rootstock 1103P were wounded with sterile drill bits and inoculated with a single 5 mm diameter agar plug collected from Rhizoctonia growing cultures, while control vines were inoculated with sterile agar. The first replicate lasted 28 weeks with (DCHG2B, DCSG22R) inoculated on seven vines. The second bioassay lasted 24 weeks with two additional isolates (JCSG9B, JCHG12B) inoculated on twelve vines. Rhizoctonia-inoculated vines developed wood symptoms similar to those observed on cuttings in nurseries, with necrotic lesions lengths significantly longer than the controls (First replicate: 3.5  0.4 cm vs. 1.3  0.6 cm; Second replicate: 6.8  0.8 cm vs. 1.1  0.2 cm), based on one-way ANOVA statistical test (P value < 0.05). Rhizoctonia isolates recovery from wood necrotic lesions were confirmed by ITS sequencing, thereby fulfilling Koch's postulate. Several binucleate Rhizoctonia anastomosis groups, including AG-G, have been found to cause root rot and stem necrosis in plant nurseries (Aiello et al., 2017; Rinehart et al., 2007). Rhizoctonia has also been reported to be associated with grapevine nurseries in Europe (Pintos et al., 2018), South Africa (Halleen et al., 2003) and Australia (Walker, 1992). However, the multinucleate Rhizoctonia solani was the only species confirmed to cause root rot on grapevine (Walker, 1992). Our data suggests that the binucleate Rhizoctonia from the AG-G anastomosis group also cause wood necrosis in grapevine. Those findings warrant further studies on the complexity of Rhizoctonia anastomosis groups in nursery and their aggressiveness to grapevine.

A study on the ultrasonic vibration on the cutting performance during ultrasonic-assisted drilling of CFRP with twist and dagger drill bits

During the drilling process of carbon fiber reinforced polymer (CFRP), defects such as exit delamination, tearing, and burrs are prone to occur, among which excessive axial force during drilling is the main reason for the generation of exit delamination defects. In this study, ultrasonic-assisted and conventional drilling with twist and dagger drills were investigated on 5 mm-thick multi-directional laminated fiber sheets made of T300-12k/AG80 carbon fiber composite with different orientations. The axial force evolutions in each case were monitored when drilling holes in CFRP plates, and the axial force of drilling and the appearance characteristics of hole outlet were compared. The experimental results showed that the ultrasonic assisted drilling reduced the axial drilling forces of twist and dagger drill by up to 20.6% and 30.7%, respectively, compared to conventional drills. In addition, as the feed rate increases, the axial force of drilling gradually increases, and the exit delamination factor shows an overall increasing trend. The ultrasonic vibrations reduced the exit delamination damage of both drills. A special structure of the dagger drill effectively avoided exit delamination during ultrasonic-assisted drilling, which makes the incision more neat to improve the processing quality.

Accuracy of assembly holes after drilling in Al/CFRP layered structure

Layered structures consisting of CFRP composites and aluminum alloys are most commonly used in the aerospace, marine, construction and automotive industries. One of the most important aspects associated with their use is the difficulty of machining them due to the anisotropic nature of the structures. These structures are often jointed to each other by mechanical joints that require mounting holes. The purpose of this study was to determine the effect of drill bit diameter, cutting speed and the way the specimen is clamped during machining (drilling strategy) on the quality of holes drilled in a II-layer structure consisting of CFRP composite and aluminum alloy. The quality of the holes was expressed by the hole accuracy index D. A visual evaluation of the holes after the drilling process was also carried out.

ACCURATE PREDICTION OF DRILL BIT PENETRATION RATE IN ROCK USING SUPERVISED MACHINE LEARNING TECHNIQUES BASE ON LABORATORY TEST DATA

Knowing the rate of penetration of a drill bit in rocks is among the most important parameters in their behaviour measurement. However, the direct measurement of ROP in rocks is a high-cost and time-intensive process. Therefore, obtaining the ROP parameter through a method other than direct measurement can be very useful and effective. Predictive machine learning methods are among the strong and precise techniques for the indirect measurement of ROP. To this end, 492 samples were tested under different UCS, µ, WOB, and ω conditions to obtain the corresponding ROP. To achieve an accurate model, three methods of linear regression analysis, lasso regression, and ridge regression were compared in terms of prediction accuracy. These models were compared through performance criteria of the prediction process and error-based charts. The performance criteria were measured using three measures: mean absolute percentage error, D-squared pinball score, and mean Poisson deviance error. For the MAPE index, the Lasso and Ridge models performed the best with values of 0.2557. Concerning the D2PS index, the linear regression model and Ridge performed better with values of 0.4083 and 0.4025, respectively. Finally, for the MPDE index, the Ridge model provided a more accurate performance with a value of 0.0105. For a better comparison, an objective function was created and calculated by combining these three indicators. The results showed the best rank for the Ridge model with an estimated value of 659.475. Finally, it was concluded that the Ridge model is a reliable and accurate model for predicting the ROP.

A New Bottom-Hole Assembly Design Method to Maintain Verticality and Reduce Lateral Vibration

Well deviation is a prevalent problem in deep oil and gas exploration, leading to a significant increase in drilling costs. The conventional bottom-hole assembly (BHA) anti-deviation design method does not consider the impact of the BHA structure on lateral vibration. This paper proposes an integrated BHA design method that takes into account both anti-deviation and vibration reduction. This method evaluates the BHA’s anti-deviation ability using the drilling trend angle. A negative value of the drilling trend angle indicates that the BHA can correct well deviation. A finite element linearized dynamics method is used to evaluate the lateral vibration intensity of the BHA. This method involves calculating the bending displacement caused by mass imbalance and then determining the magnitude of the bending strain energy based on this displacement. The structural factors affecting the anti-deviation ability and potential lateral vibration intensity of pendulum BHAs and bent-housing mud motor (BHMM) BHAs were studied, and field tests were conducted for verification. The research shows that for pendulum BHAs, the factor that has the greatest impact on anti-deviation ability and vibration intensity is the distance from the stabilizer to the drill bit. For BHMM BHAs, the length of the short drill collar has a significant impact on the vibration intensity. Compared with current design methods, the mechanical specific energy (MSE) of the single stabilizer pendulum BHA decreased by 12%, while the MSE of the BHMM BHA decreased by 26.4%. Both decreases indicate a reduction in vibration intensity. This study will help to further increase drilling speed while preventing well deviation.

Modeling and surface morphological study in drilling of Al 2024 alloy

With concern to profuse usability of drilling operations in various industries, almost 1/3rd of the all the machining operations, the main focus is to obtain a proper quality of hole in less time at optimum cost. Aluminium alloy 2024 (Al 2024) is largely applied in various industries specially, aircraft, automotive, marine etc. because of its outstanding union towards strength, corrosion resistance, and weldability. Cutting time, cutting temperature and surface morphological investigation during drilling is very much necessary for obtaining a quality hole that has not been substantially researched so much. Therefore, a proper and thorough study of these responses is quite important regarding the hole quality. With this view, in this work, drilling of Al 2024 alloy is performed with three process parameters (input) viz. spindle speed (v), feed rate (f) and drill bit diameter (d) and performance parameters (output) as cutting time (s), cutting temperature (°C) and surface roughness (μm). Three different drill bit diameters of high speed steel (HSS) of size viz. 6 mm, 8 mm and 10 mm are used in drilling. Each process parameter has three levels. The surface morphological study is also conducted to know the depth of hole morphology details after drilling. To make the drilling operation environment friendly, it is performed in dry atmosphere. Using full factorial design, total 27 experiments are conducted. The experimental results showed that high spindle speed along with high feed rate decreases the cutting time, whereas it increases the cutting temperature. For better surface finish medium spindle speed along with low feed rate is recommended. From analysis of variance (ANOVA), all the three models developed for cutting time, cutting temperature and surface roughness are found statistically significant. Spindle speed and feed are the influential parameters to cutting time, cutting temperature and surface roughness. A mathematical model is developed using response surface methodology (RSM) to predict the responses cutting time, cutting temperature and surface roughness with better accuracy. The coefficient of determination (R2) for cutting time, cutting temperature and surface roughness is found as 96.65%, 95.88% and 93.65% respectively, which indicated that the developed models could be used for prediction with better accuracy. The morphological study shows that scratches, trenches, abrasive wear are visible on the hole surface. At high spindle speed surface grain refinement is observed more which causes a better surface finish.

Drilling Tools in Prehistoric China from the Perspective of Experimental Archaeology

As a type of artifact commonly found in Chinese prehistoric sites, perforated shellfish materials can be classified into freshwater mussel materials and perforated seashell materials, and drilling tools can be classified into single and composite drilling tools. The experimental reconstruction of the two types of drilling tools and drilling methods explored the influence of the composition of drilling tools, drilling methods, and other factors on the drilling process. Meanwhile, the experiments were recorded and analyzed using a stereo microscope. The experimental results show that the composite drilling tools provide better drilling results and more dynamics than stone drill bits. The perforated weight stone stabilized the center of gravity and safeguarded the dynamic performance. The type of drilling tool, drilling method, and characteristics such as smoothness and hardness of perforated shellfish materials significantly impact the drilling effect.

Structure Design of Bionic PDC Cutter and the Characteristics of Rock Breaking Processes

The rational structural design of polycrystalline diamond compact (PDC) cutters effectively enhances the performance of drill bits in rock fragmentation and extends their service life. Inspired by bionics, a bionic PDC cutter was designed, taking the mole claw toe, shark tooth, and microscopic biomaterial structures as the bionic prototypes. To verify its rock-breaking effectiveness, the finite element method was employed to compare the rock-breaking processes of the bionic cutter, triangular prism cutter, and axe cutter. The study also investigated the influence of different back rake angles, cutting depths, arc radii, and hydrostatic pressures on rock breaking using the bionic cutter. Prior to this, the accuracy of the finite element model was validated through laboratory tests. Subsequently, a drill bit incorporating all three types of cutters was constructed, and simulations of rock breaking were conducted on a full-sized drill bit. The results demonstrate that the bionic cutter exhibits superior load concentration on the rock compared to the triangular prism cutter and the axe cutter. Additionally, its arc structure facilitates the “shoveling” of the rock, making it more susceptible to breakage under tensile stress. As a result, the efficiency of the bionic cutter surpasses that of the triangular prism and axe cutters. Similarly, it exhibits minimal fluctuations and values in cutting force. As the back rake angle and cutting depth increase, the MSE and cutting force of all three cutters also increase. However, the bionic cutter consistently maintains the lowest MSE and cutting force, confirming the superiority of its bionic structural design. The MSE and cutting force of the bionic cutter fluctuate with the increase of the arc radius, and the optimal arc radius falls within the simulation range, between 21 mm and 23 mm. Compared to the other two types of cutters, bionic cutters possess a unique structure that allows for better release of internal stress within the rock, thereby ensuring higher efficiency in rock-breaking, particularly in deep geological formations. The rock breaking simulation results of full-sized drill bits show that the use of a bionic cutter can improve the drill bit’s ability to penetrate the formation, reduce the possibility of drill bit bounce during the rock breaking process, prevent the occurrence of stick-slip, improve the drilling stability, effectively improve the efficiency and service life of the drill bit during the rock breaking process, and reduce the drilling cost. It is concluded that the research results of bionic PDC cutters are helpful to the development of high-performance drill bits and the reduction of drilling costs.

TRIBOLOGY OF DRILL BITS IN THE GEOTHERMAL INDUSTRY: A LITERATURE REVIEW

Energy from the earth’s heat is critical to the energy supply of countries with this resource. This literature review highlights the tribology applied to drill bits in the geothermal industry. Facing a diverse geological environment, drill bits are critical to energy efficiency, with significant friction, wear and lubrication challenges. This paper addresses the complexity of drill bit interaction with diverse geothermal formations, highlighting the importance of understanding tribological phenomena. Advances in materials and coatings, such as composites, heat-resistant alloys and ceramic coatings, are explored, along with innovative geometric design strategies. Attention on lubrication, cooling and continuous monitoring systems highlights the quest for efficiency and extended drill bit life. This review provides a comprehensive overview of advances in bit tribological research in the geothermal industry, identifying emerging trends and critical challenges for the sustainable development of this form of renewable energy.