Drilling Performance Research Articles

A 1-year longitudinal study of physical fitness in Tunisian junior tennis players

Background: Tennis, a sport demanding high levels of physical fitness, combines various aspects of athleticism such as agility, endurance, strength, and speed. The development of these attributes in junior players is crucial for their progress in the sport. Understanding the impact of structured tennis training on the physical fitness of junior players can provide valuable insights into the effectiveness of training programs and guide future coaching strategies. Objective: This study aimed to assess the effects of 1-year of tennis practice on the physical fitness of Tunisian junior players. Methods: Sixty-two healthy participants were enrolled, divided into two groups, tennis players (TP) (n = 36) and controls, where the participants sedentary, (n = 26), each group was divided into two subgroups U14 and U16 age-groups. Physical fitness tests were conducted at baseline (T0) and after one-year (T1), including standing long jump, countermovement jump, medicine ball throw (MBT), 5m, 10m, and 20m sprints, sideways shuffle, Zigzag, spider drill, 20m shuttle run, and sit and reach (SAR) tests. Results: Jump performances increased significantly for TP in U14 and U16 compared to controls at T0 and T1. In both age-groups, MBT performance increased significantly for TP, with U16 for both groups were higher at T0 and T1 (p<0.05). The 5m and 10m sprints increased significantly for TP in both age-groups, though controls decreased in the 5m sprint in U14 (p<0.05). The 20m sprint increased significantly for TP in U14 and U16 (p<0.05), with U16 outperforming U14 at T0 and T1 (p<0.05). Sideway shuffle and spider drill performances significantly improved for TP (p<0.05), while decreased in controls (p<0.05). The Zigzag test and the maximum oxygen intake increased significantly for TP across both age-groups at T0 and T1, whereas controls' performance decreased in U14 (p<0.05). Conclusion: TP's SAR was significantly better than controls (p<0.05). In conclusion, tennis training enhances young athletes' physical fitness, improving agility, sprinting, jumping, and endurance compared to controls, reporting better results in U16 compared to U14 for most of tests.

Enhance the Properties of Lignosulfonate Mud by Adding Nanoparticles of Aluminum Oxide and Iron Oxide

Oil well drilling fluid rheology, lubricity, swelling, and fluid loss control are all critical factors to take into account before beginning the hole's construction. Drilling fluids can be made smoother, more cost-effective, and more efficient by investigating and evaluating the effects of various nanoparticles including aluminum oxide (Al2O3) and iron oxide (Fe2O3) on their performance. A drilling fluid's performance can be assessed by comparing its baseline characteristics to those of nanoparticle (NPs) enhanced fluids. It was found that the drilling mud contained NPs in concentrations of 0,0.25, 0. 5, 0.75 and 1 g. According to the results, when drilling fluid was used without NPs, the coefficient of fraction (CoF) was 44%, when added Al2O3 NP and Fe2O3 NP at 0.75g reduced CoF by 31% and 33% respectively. When Al2O3 and Fe2O3 NPs were used, particularly at a concentration of 1g, the amount of mud filtration decreased from 13.5ml to 9.3 ml and 8.5 ml respectively. Additional improvements rheological properties as well as swelling when Fe2O3NPs and Al2O3 NPs were added at 1g. Overall, it was found that adding NPs to the Lignosulfonate-WBM at a concentration of 1g can improve rheological, swelling, and filtration properties as well as lubrication at 0.75g.

Dynamic Characteristics of New Mechanical Rotary Steerable Tool in Directional Drilling

The characteristics of a drill string system have an essential influence on the performance of directional drilling. The appropriate control method of a drill string is important to drilling efficiency and downhole operation safety. Therefore, based on a new mechanical rotary steerable tool (RST), this paper aims to analyze the Dynamic Characteristics of RST in Directional Drilling. First, considering the thrust force generated by the RST and bottom hole assembly (BHA), the governing vibration equations of a drill string system are established. Furthermore, connected with fields drilling parameters, including the effects of a new RST on a drill bit and wellbore, as the boundary and initial conditions, the dynamic characteristics of a drill string system are compared and studied in directional and straight drilling. The results show that the axial vibration of the drill string increases extremely in directional drilling process, while the weight on bit (WOB) and inclination force change in small range. Moreover, the torque and azimuth force tend to be stable soon, even its initial fluctuations are significantly. Also, the new RST can effectively enhance the steering capacity, increase the drilling efficiency, and improve drill bit force performance. The research results can provide reference for developing directional drilling technologies, including related tool design and optimization.

Failure resistance research of the dual-stage hybrid bit

Vibration failure is mainly the abnormal fracture failure of cutters, including brittle fracture, impact spalling, impact fatigue fracture, and cutter loss. The weak core area of the existing drill bit is prone to develop into core failure. Vibration failure and core failure will seriously affect drilling performance of the drill bit. To limit vibration and improve stability, we proposed a dual-stage hybrid bit with a polycrystalline diamond compact bit as the primary cutting unit and a tri-cone bit as the secondary cutting unit. Polycrystalline diamond compact bit only breaks the outer rock to form a central rock pillar, while the tri-cone bit breaks the central rock pillar. The existence of the central rock pillar enables the hybrid bit to have a larger lateral contact area with the bottom hole, which can reduce lateral force and limit lateral vibration. The tri-cone bit strengthens the impact and wear resistance of the core area, which can effectively prevent core failure. The experimental results showed that the working parameters of the dual-stage hybrid bit fluctuated less, its drilling stability was better. The experiment verified that the lateral force of the dual-stage hybrid bit was smaller. The vibration test results showed that, with small weight-on-bit, the vibration accelerations of the two drill bits were relatively close. With higher weight-on-bit, the accelerations in all directions of the dual-stage hybrid bit were smaller than those of the polycrystalline diamond compact bit. Specifically, the lateral acceleration differed by more than 40%, which proved the lateral vibration resistance of the dual-stage hybrid bit. The axial and tangential accelerations were reduced accordingly. In the validation experiments, the lateral force of the dual-stage hybrid bit decreased by 11.7%, 21.3% and 26.7%, its vibration acceleration reduced by 12.2%, 26.4% and 14.9%. Therefore, the dual-stage hybrid bit could reduce vibration and enhance stability.

Electric discharge drilling of blind holes in titanium alloy Ti6Al4V

PurposeThis experimental study aims to deal with the improvement of process performance of electric discharge drilling (EDD) for fabricating true blind holes in titanium alloy Ti6Al4V. Micro EDD was performed on Ti6Al4V and blind holes were drilled into the workpiece.Design/methodology/approachThe effects of input parameters (i.e. voltage, capacitance and spindle speed) on responses (i.e. material removal rate, tool wear rate and surface roughness [SR]) were evaluated through response surface methodology. The data was analyzed using analysis of variance and multi-optimization was performed for the optimized set of parameters. The optimized process parameters were then used to drill deeper blind holes.FindingsBlind holes have few characteristics such as SR, taper angle and corner radius. The value of corner radius reflects the quality of the hole produced as well as the amount of tool roundness. The optimized process parameters suggested by the current experimental study lower down the response values (i.e. SR, taper angle and corner radius). The process is found very effective in producing finished blind holes.Originality/valueThis experimental study establishes EDD as a feasible process for the fabrication of truly blind holes in Ti6Al4V.

Comparative Analysis in Drilling Performance of AA7075 in Different Temper Conditions

The widespread use of heat treatable7075 aluminum alloy in the aerospace industry requires a high machinability performance. The main objective of this study is to examine the machinability and the surface quality conditions of the AA7075 material with different temper conditions. For this purpose, various temper treatments are implemented to evaluate the impact of microstructural properties on tool wear and the surface quality of the drilled holes. The drilling operations have been done on O, F, T4, T6, and T7 temper conditions. Process parameters were three different spindle speeds (715, 1520, and 3030 rev/min) and three feed rates (0.1, 0.2, and 0.3 mm/rev) with HSS-G high-performance ground standard twist drill bit. The present work deals with the effects of temper conditions on thrust force, drilling temperature, tool wear, surface integrity, and chip morphology. Response surface methodology was used in the evaluation of experiment results. The optimization results showed that while thrust force and torque are not significantly affected by a change in spindle speed, they are sensitive to an increase in feed rate. Heat-generation on the drill bit is the lowest at low levels of both the feed rate and spindle speed parameters. The AA7075-T6 condition specimen was machined with continuous chip formation, resulting in the best hole surface quality. 3D Finite element modeling of the drilling process was carried out. Numerical analysis revealed the drilling performance of AA7075-T6 in terms of thrust, heat generation and chip formation.

A NUMERICAL AND STATISTICAL APPROACH OF DRILLING PERFORMANCE ON MACHINING OF Ti–6Al–4V ALLOY

Drilling, which constitutes one third of the machining operations, is widely used in many areas of the manufacturing industry. Various difficulties are encountered in the drilling process since the chip is formed in a closed limited chip flows. These difficulties directly affect the output parameters such as energy consumption, surface quality, and cutting force. Therefore, it is necessary to determine the ideal processing parameters to achieve the best performance. However, experimental research on machining processes requires both a long time and a high cost. For these reasons, machining outputs can be estimated by conducting drilling simulations with the finite element method. In this study, the finite element method is used in order to investigate the influence of different cutting parameters and different helix angles on the power and thrust force of Ti–6Al–4V (grade 5) alloy that is commonly used in the aviation industry. The study selected three different cutting speeds, feed rates, and helix angles as the cutting parameters. The experimental design was made according to the response surface method (RSM) Box–Behnken design in the Design-Expert program. Drilling simulations were performed using the ThirdWave AdvantEdgeTM software. The lowest thrust force measured is 1241.39 N at 40° helix angle, 2000-rpm revolution rate, and 0.05-mm/rev feed rate, while the lowest power consumed is 765.025 W at 30° helix angle, 1500-rpm revolution rate, and 0.05-mm/rev feed rate. As a result, it was determined that the most effective parameter for power and thrust force was the feed rate.

Improving the electrochemical discharge machining (ECDM) process for deep-micro-hole drilling on glass by application of the electrolyte-air injection

The electrochemical discharge machining (ECDM) process is a popular technology for drilling holes in ceramic materials (including glass), particularly in the microdomain. The ECDM process and its variants have been continuously investigated and augmented to fabricate deep micro-holes on glass. ECDM with electrolyte injection was recently utilized to fabricate the deepest micro-hole in borosilicate glass. However, the drilling capability is still limited to a certain depth of micro-hole due to poor flushing of the machined by-products (i.e., salt, sludge, and debris). In order to resolve this issue, the present work uses the application of electrolyte and air injection, which improves the flushing action during ECDM drilling without compromising the advantages of electrolyte injection. This is achieved by providing electrolyte-air injection into the machining zone using a novel multi-phase injection system with the ECDM facility. The underlying material removal mechanism in the conventional ECDM, ECDM with electrolyte and electrolyte-air injection, is also established based on analytical models and extensive experimental characterization. Additionally, a parametric investigation is conducted to compare the drilling performance of the ECDM with novel electrolyte-air injection and the ECDM electrolyte injection at various parametric conditions. The experimental results clearly showed the advantages of the ECDM with electrolyte-air injection over the previously benchmarked ECDM with electrolyte injection. Eventually, a through-micro-hole is drilled on a 3500 μm thick glass work material using the ECDM with electrolyte-air injection. Concurrently, a 22.73% lower entrance diameter and 37.36% higher hole depth are realized compared to the ECDM with electrolyte injection.

Real Time Optimization of Drilling Operations and Performance Based on Drilling Specific Energy Determined from Actual Field Data

Drilling specific energy (DSE) is an important factor for improving the drilling performance after reaching the maximum energy that is necessary to remove and destroy the rock volume underneath the bit. Therefore, field data are used to optimize and analyze the drilling performance by combining between hydraulic data and mechanical data to obtain the maximum DSE on different types of bits used to drill the Colibași stratigraphic column. These bits are tricone and PDC. Furthermore, Two sections (17 1/2" and 12 1/4") are optimized based on DSE equation and the 8 1/2" hole section was optimized based on simulation analysis done by Landmark software. Well 268 drilling data are used to perform this study and verify the results. It was found that DSE from various equations with different parameters has reach the same results. Also, DSE shows higher values for lower ROP and vise verse, and three different hole conditions' zones. Additionally, the simulation study showed another bit optimization through determining the variation of bit power, impact forces, and pressure losses with various pumping rates.

Performance evaluation of CrAlN and TiAlN coatings deposited by HiPIMS in micro drilling of a Ni-based superalloy

The current study aimed at investigating the effects of CrAlN and TiAlN coatings deposited using high power impulse magnetron sputtering (HiPIMS) on the performance in micro drilling of Incoloy 825. Influence of feed which played a major role on size effect was studied for the uncoated and coated micro drills in terms of thrust force along with its bandwidth and average flank wear. Particular emphasis was placed on the exploration of the mechanism of wear of the coated micro drills in comparison with their uncoated counterpart. Rate of rise in thrust force gradually decreased and was accompanied by a fall in bandwidth with the number of holes. HiPIMS coated micro drills were successful in mitigating thrust force, bandwidth and rate of progression of wear. However, TiAlN consistently outperformed the CrAlN coating owing to the superior hardness, coating adhesion and tribological properties. TiAlN also exhibited remarkable capabilities to resist elastic and plastic deformation under the regime of ploughing (lower feed) and the condition of higher chip load (higher feed).

Experimental investigation of electrochemical discharge drilling (ECDM-D) performance characteristics for N-BK7 glass material

Experimental investigation of electrochemical discharge drilling (ECDM-D) performance characteristics for N-BK7 glass material

Optimization Design of Drilling Fluid Chemical Formula Based on Artificial Intelligence.

Through the research and development of the regression prediction function of support vector machine, this paper applies it to the prediction of drilling fluid performance parameters and the formulation design of drilling fluid. The research in this paper can reduce the experimental workload and improve the efficiency of drilling fluid formulation design. The apparent viscosity (AV), plastic viscosity (PV), API filter loss (FLAPI), and roll recovery (R) of the drilling fluid were selected as the inspection objects of the drilling fluid performance parameters, and the support vector machine was used to establish a model for predicting the drilling fluid performance parameters. This predictive model was used as part of the overall drilling fluid formulation optimization design model. For a given drilling fluid performance parameter requirement, this model can be applied to reverse the addition of various treatment agents, and finally, the prediction accuracy of the model is verified by experiments.

Study of the burr height at hole exit in bone drilling by twist drills.

The burr at the hole exit is one of the key factors affecting bone drilling performances. In order to reduce burr height at hole exit during cortical bone drilling, the four key parameters in twist drilling of bones are analyzed based on the response surface method (RSM). The prediction model of the burr height is obtained via the analysis of variance. The influence trend and size of each factor on the height of the burr are further analyzed based on the RSM. Experimental results show that smaller point angle and diameter of the twist drill, smaller feed speed, and higher rotational speed can effectively reduce the burr height at hole exit. Then, the geometric variables of the twist drill and process parameters are optimized. When the point angle of the twist drill 2Φ = 95°, the diameter D = 2.5 mm, the rotational speed n = 1500 rpm, and the feed speed vf = 10 mm/min, the height of the burr at hole exit reaches the smallest. At the same time, the burr at the exit of the hole with different diameters of twist drills is studied. It is found to be beneficial to select a twist drill with a smaller diameter for drilling when the requirements of drilling are fulfilled.

A Study of Swirling Jet Drilling and Its Specific Energy for Hydrate-Bearing Sediments

SummaryNatural gas hydrate (NGH) is a form of clean energy. The marine NGH solid fluidization exploitation method and the integrated radial jet drilling and completion method are considered as two ways to improve gas production, and water jet is the key technology of the two mining methods. This paper first compared the flow field distribution of conical jet and swirling jet at different outlet velocities through numerical simulation. The volume change of conical jet and swirling jet erosion hydrate-bearing sediment (HBS) was analyzed when the jet outlet velocity and standoff distance were changed. Then, based on the experimental apparatus for NGH generation and jet erosion, we carried out the swirling jet erosion HBS experiments. The depth and diameter of the erosion pits were about 10% larger than the numerical simulation. Finally, we evaluated the jet erosion performance with specific energy calculations. The results show that the reaming ability of the swirling jet is 2.4 times than that of the conical jet at the jet velocity of 100 m/s and the standoff distance of 5 mm. When the jet velocity ranges from 30 to 100 m/s, the erosion efficiency of the swirling jet is higher than that of the conical jet. The critical standoff distance is calculated as 12.5 mm (12.5 times nozzle throat) in current study, larger than which the advantages of swirling jet erosion HBS become less obvious. The excellent performance of swirling jet erosion HBS under certain conditions is described by specific energy calculation. This study can help for better understanding the performance of water jet drilling and provides an idea for improving the production efficiency of NGH.

Investigation of Using Various Quantities of Steelmaking Waste for Scavenging Hydrogen Sulfide in Drilling Fluids

Effective in situ scavenging of hydrogen sulfide (H2S) while drilling a sour formation is critical for limiting the prevalent related impacts and safety hazards. Thus, it is necessary to develop a specialized additive that can selectively react with H2S and remove it without generating harmful byproducts or impairing drilling fluid performance. Additionally, waste management and utilization will transfer the waste from being an environmental and economic burden to a valuable commodity. Accordingly, we report herein the management of steelmaking waste through its utilization as a novel H2S scavenger for water-based drilling fluids, as well as the evaluation of the effects of the steelmaking waste dosage (1, 2, and 3 g) on the mud H2S scavenging capability and key properties. The H2S scavenging capacity of the waste-containing mud was investigated and compared to that of the base mud and fluids containing the commercial scavengers (triazine- and iron gluconate-based materials). In addition, the mud rheology, alkalinity, and filtering performance were studied in the presence and absence of the waste, and the findings were compared to those of commercial scavengers. This study showed that adding 1, 2, and 3 g of the steelmaking waste to the base drilling fluid significantly improved the H2S scavenging capacity by 105, 399, and 503%, respectively, while the triazine- and iron gluconate-based materials increased the capacity by 179 and 131%. Similarly, when the proportion of the steelmaking waste increased, the rheological parameters, comprising apparent viscosity, plastic viscosity, and yield point, slightly increased. The inclusion of the steelmaking waste reduced mud pH to 10.4, 9.8, and 8.5 with a content of 1, 2, and 3 g, respectively, compared to 11.0 for the base mud, 11.1 for triazine-based material, and 7.9 for iron gluconate-based scavenger. When 1 and 2 g of the steelmaking waste were added, the obtained filtrated liquid volume was preferably lower than the base mud and even the commercial scavengers-contained muds. As a result, 2 g of steelmaking waste could be added for enhanced mud performance. Nevertheless, higher amounts of the steelmaking waste could be used instead to achieve maximal H2S scavenging capability, with an extra alkalinity controller added to ensure attaining the practical recommended properties.

Preparation of the Tetrameric Poly(VS-St-BMA-BA) Nano-Plugging Agent and Its Plugging Mechanism in Water-Based Drilling Fluids.

In response to the current problem that micron-scale plugging agents cannot effectively plug shale nanopores and fractures, tetrameric poly(VS-St-BMA-BA) nanoparticles were synthesized by the Michael addition reaction using sodium vinyl sulfonate, styrene, butyl methacrylate, and butyl acrylate as raw materials. The nanoparticles poly(VS-St-BMA-BA) were characterized by infrared spectroscopy, particle size analysis, and thermogravimetric analysis. The particle size distribution of poly(VS-St-BMA-BA) at room temperature ranged from 62.17 to 96.44 nm, with a median particle size of 75.8 nm, and could withstand high temperature of 359.5 °C. The effects of poly(VS-St-BMA-BA) on the rheological parameters of drilling fluid and the effects of different temperatures on the median particle size were investigated by the drilling fluid performance testing methods and high-temperature stability testing methods. The results showed that the apparent viscosity, plastic viscosity, yield point, and high temperature and high pressure water loss of drilling fluid gradually decreased with the increase in poly(VS-St-BMA-BA) dosage; when the addition of poly(VS-St-BMA-BA) was 2.0%, the overall performance of drilling fluid was better, the filtration loss was 4.4 mL, and the drilling fluid had good water loss wall building performance. The median particle size of poly(VS-St-BMA-BA) was 132.60 nm (the particle size at room temperature was 75.8 nm) after standing for 16 h at 180 °C, indicating that poly(VS-St-BMA-BA) has good high-temperature stability and dispersion stability. The plugging performance and plugging mechanism of poly(VS-St-BMA-BA) under extreme conditions (high temperature) were investigated by the plugging performance test method and pressure transfer method. The results showed that the plugging rate of artificial mud cake and artificial core reached 48.18 and 88.75%, respectively, when the amount of poly(VS-St-BMA-BA) was added at 2.0%. In the pressure-transfer experiments, poly(VS-St-BMA)-BA) could invade the 2 mm position of the nanopore fracture on the core surface and form a sealing barrier layer to prevent the further invasion of liquid. Combined with the pressure-transfer experiment, it shows that poly(VS-St-BMA-BA) can enter the nanopore and fracture at a certain distance under the action of formation pressure and keep accumulating to form a tight blockage, which can effectively prevent the filtrate from entering the nanopore fracture of the shale formation. Poly(VS-St-BMA-BA) is expected to be used as a promising nano-plugging agent in water-based drilling fluids.

Analysis and prediction of woven fabric design impact on fabric/polymer composite drilling energy

Damage, generated during drilling processes, will affect the material integrity and further delamination through the fiber-reinforced composite cross-section. Drilling is necessary for the assembly processes of composite parts. This article deals with the effect of the weave parameters on the drilling mechanism. The mechanism of the yarn shearing ring drilling was investigated, and the quality of the drilled hole was carefully examined for different drilling conditions. Set up for measuring the power consumption during the drilling of different samples as well as the value of the thrust force was constructed. In the drilling of fabric-reinforced polymer composite, the torque, thrust force, and delamination factor are depending directly on fabric design parameters. It was shown that both, drilling power and drilling thrust force, are proportional to the total specific fabric stiffness. Delamination caused by drilling thrust is one of the most problematic defects after drilling laminate composite. A drilling Index was developed and could be used to evaluate the effect of the fabric design of laminate on its composite drilling performance. It was revealed that significantly higher drilling power is needed for the plain weave fabric design than for the other fabric designs of the same unit repeat as well as for the laminates of high fiber volume fraction and high total flexural rigidity. Analysis of the delamination factor and the drilling power showed a high correlation with total fabric flexural rigidity.

Field test of radial jet drilling technology in a surface formation

The radial jet drilling (RJD) technology is an efficient formation stimulation and injection technology that drills multiple laterals perpendicular to the central well. Extensive research has been on jet rock breaking, lateral extension, productivity prediction, and technological processes. However, little public literature illustrates the overall drilling performance of the RJD systems. Herein, a field test is conducted in the surface sandstone formation. Eight laterals are successfully drilled using the self-rotating multi-orifices nozzle with a 35–40 MPa (5.08–5.80 ksi) jet pressure. The cumulative length of the eight laterals is 21.1 m (69.2 ft), with the longest one being 5.7 m (18.7 ft). The lateral diameter is 50 mm (1.97 in), drilled at the fastest drilling rate of 3.6 m/h (11.8 ft/h). The auxiliary traction device can provide extra feed-in force to the high-pressure hose. The lateral trajectories are measured with their accuracy confirmed by the coring well. During the field test, a lateral trajectory up-warping problem is found, of which the possible causes and the suggestions are provided. According to the internal shape of the lateral obtained by endoscopic imaging, the lateral section exhibits a ring structure, indicating the high rock breaking efficiency of the self-rotating multi-orifices nozzle. The formation anisotropy and natural fracture have little influence on the lateral trajectory but affect the lateral section shape. The research results prove the reliability of the RJD system developed and can contribute to future development and application of RJD technology.

Sleep and Infantry Battle Drill Performance in Special Operations Soldiers.

BACKGROUND: Although multiple studies have documented the impact of insufficient sleep on soldier performance, most studies have done so using artificial measures of performance (e.g., tablet or simulator tests). The current study sought to test the relationship between sleep and soldier performance during infantry battle drill training, a more naturalistic measure of performance.METHODS: Subjects in the study were 15 junior Special Operations infantry soldiers. Soldiers wore an actigraph and reported their subjective sleep duration and quality prior to close quarter battle (CQB) drills. Experienced leaders monitored each iteration of the CQB exercise and recorded the number of errors committed.RESULTS: The number of errors committed during the live ammunition iterations was negatively correlated with subjective number of hours slept and subjective sleep efficiency/quality during the month prior. Soldiers with subjective sleep duration ≥7 h had a significantly lower number of errors than soldiers with subjective sleep duration <7 h (1.71 vs. 0.63 errors), and soldiers with sleep quality <85% committed more errors than those with sleep quality ≥85% (1.50 vs. 0.40 errors).DISCUSSION: These data preliminarily suggest that sleep quality and duration may influence subsequent performance on infantry battle drill training, particularly for soldiers with limited experience in battle drill conduction who have not yet perfected battle drill techniques. Future studies should enact sleep augmentation to determine the causal influence of sleep on performance in this setting.Mantua J, Shevchik JD, Chaudhury S, Eldringhoff HP, Mickelson CA, McKeon AB. Sleep and infantry battle drill performance in Special Operations soldiers. Aerosp Med Hum Perform. 2022; 93(7):557-561.

Experimental Study on the Dry Drilling Nickel-Based Superalloy of CrAlYN Coated Carbide Bit.

Nickel-based superalloy is regarded as one of the materials with the poorest cutting and drilling performance. Additionally, there is much less research on the drilling of it. This paper aims to study the drilling performance of dry drilling nickel-based superalloy with uncoated and CrAlYN coated carbide bit. First of all, the primary and secondary factors influencing the machining performance of dry drilling nickel-base superalloy uncoated carbide bit were explored through an orthogonal test. Secondly, the self-prepared CrAlYN coated carbide drills, and uncoated drills were compared and analyzed from perspectives of service life, drilling force, drilling temperature, drill surface topography, failure mechanism, and machining surface quality. The research results are as follows: the drilling temperature is the primary factor affecting the drilling performance under dry drilling conditions. CrAlYN coating can obviously prolong the service life of tools, reduce the drilling force and drilling temperature, and improve the machining surface quality at lower rotational speeds. Moreover, the coated cemented carbide bit has a similar failure mode to the uncoated cemented carbide bit after the CrAlYN coating falls off in the wear zone of cemented carbide bit, which is mainly bonding wear on the rear tool surface and the front tool surface.