Search Results (66)

Molecular dynamics simulations were performed to investigate the nanometric cutting of polycrystalline oxygen-free copper using a single-crystal diamond tool. The effects of grain size, tool geometry (rake angle and edge radius), cutting speed, and ambient temperature on atomic migration, dislocation activity, and tool wear were systematically analyzed. The results indicate that material removal is dominated by cutting-induced amorphization and the formation of hcp-coordinated defect structures, while dislocation activity governs plastic deformation and cutting force fluctuations. A damaged subsurface layer, composed of amorphous structures, hcp-coordinated defects, and residual dislocations, is formed beneath the machined surface. Increasing grain size reduces grain-boundary-induced stress concentration and suppresses subsurface damage. A larger rake angle facilitates chip removal and reduces damage, whereas a larger edge radius intensifies dislocation activity and amorphization. Higher cutting speeds reduce lattice distortion and subsurface damage but increase stress concentration on the tool. Elevated temperature enhances atomic mobility, promoting amorphization and subsurface deformation while accelerating tool wear. These findings provide insight into the nanometric cutting behavior of polycrystalline copper and offer guidance for optimizing process parameters to improve surface integrity and tool life. Full article

Polycrystalline diamond (PCD) compacts are extensively applied in downhole drilling tools owing to their exceptional hardness and wear resistance. However, their tribological performance is strongly influenced by the thermal and chemical characteristics of drilling fluids. In this study, the coupled effects of temperature (25–125 °C) and oil–water ratio on the tribological behavior of PCD were systematically investigated. The results indicate that under relatively high oil–water ratios (50:50, 80:20, and 100:0), both the friction coefficient and wear rate increase monotonically with temperature, which is associated with intensified interfacial thermal stress and suppressed formation of protective carbon-based transfer films. In contrast, at low oil–water ratios (0:100 and 20:80), the friction coefficient exhibits a non-monotonic dependence on temperature, decreasing initially and then increasing with a transition near 100 °C. This behavior is attributed to temperature-activated surface passivation through C-OH bond formation in water-rich environments, followed by the deterioration of passivation due to water evaporation at elevated temperatures. These findings provide insight into temperature-dependent lubrication regime transitions and tribo-chemical evolution of PCD in complex drilling fluid environments. Full article

The operational ability of a unit or mechanism depends mainly on the quality of the mechanically produced working surfaces. Many materials can be assigned to a group of hard-to-cut materials that includes titanium- and aluminum-based alloys, a new class of heat-resistant alloys, SiCp/Al composites, hard alloys, and other alloys. The difficulties in their machining are related not only to the high temperatures achieved on the contact pads under mechanical load and the extreme cutting conditions but also to the properties of those materials, which affect the adhesion of the chip to the tool faces, hindering chip flow. One of the possible solutions to reduce those effects and improve the operational life of the tool, and as a consequence, the final quality of the working surface of the unit, is texturing the rake face of the tool with microgrooves or nanogrooves, microholes or nanoholes (pits, dimples), micronodes, cross-chevron textures, and other microtextures, the depth of which is in the range of 3.0–200.0 µm. This review is addressed at systematizing the data obtained on micro- and nanotexturing of PCD tools for cutting hard-to-cut materials by different techniques (fiber laser graving, femto- and nanosecond laser, electrical discharge machining, fused ion beam), additionally subjected to fluorination and dip- and drop-based coatings, and the effect created by the use of the textured PCD tool on the machined surface. Full article

The study investigates the problem of modeling cutting-force components through response surface methodology and reports the results of an investigation into the impact of machining parameters on the cutting mechanics of polymer–matrix composites. The novelty of this study is the modeling of cutting forces and the determination of mathematical models of these forces. The models describe the values of forces as a function of the milling parameters. In addition, the cutting resistance of the composites was determined. The influence of the material and rake angle of individual tools on the cutting force components was also determined. Measurements of the main (tangential) cutting force showed that, using large rake angles for uncoated carbide tools, one could obtain maximum force values that were similar to those obtained with polycrystalline diamond tools with a small rake angle. The results of the analysis of the tangential component of cutting resistance showed that, regardless of the rake angle, the values range from 140 N to 180 N. An analysis of the feed component of cutting resistance showed that the maximum values of this force ranged from 46 N to 133 N. The results showed that the highest values of the feed component of cutting resistance occurred during the machining of polymer composites with carbon fibers and that they were most affected by feed per tooth. It was also shown that the force models determined during milling with diamond insert tools had the highest coefficient of determination in the range of 0.90–0.99. The cutting resistance analysis showed that the values tested are in the range of 3.8 N/mm² to 15.5 N/mm². Full article

Polycrystalline diamond (PCD), which is widely used to manufacture cutting tools due to its extreme hardness, in most cases requires grinding for machining. The cooling lubricant selected for PCD grinding largely affects the frictional conditions and the thermo-mechanical load collective between the diamond grinding wheel and the PCD. As a consequence of this, the material removal and grinding wheel wear mechanisms during grinding PCD depend on the cooling lubricant used. In this study, experimental and numerical investigations were taken into account, demonstrating that using a water-based cooling lubricant during PCD grinding predominantly leads to a mechanical load on workpiece and grinding wheel rather than thermal loads. These original findings can be used to complement existing explanatory models of the PCD grinding process valid for grinding with oil as a cooling lubricant. The aim of this work is to contribute a novel extension to the existing material removal and grinding wheel wear models to enable them for the grinding process with a water-based cooling lubricant. The knowledge obtained from this work is intended to serve as a basis for future industrial process design. Full article

In recent years, polycrystalline diamond compact (PDC) drill bits have seen significant advancements. They have replaced over 90% of the workload traditionally handled by roller cone bits and have become the predominant choice in energy drilling due to their superior efficiency and durability. However, PDC drill bits are susceptible to adhesion of rock cuttings during drilling in muddy formations, leading to mud accumulation on the bit surface. This phenomenon can cause drill bit failure and may contribute to downhole complications, including tool failure and borehole instability. The adhesion issue between PDC drill bits and mud rock cuttings underground is primarily influenced by the normal adhesion force between the drill bit surface and the mud rock cuttings. Therefore, biological non-smooth surface technology is applied to the prevention and control of drill bit balling. It is an optimal selection of biomimetic non-smooth surface structures with reduced adhesion and detachment properties. A non-smooth surface model for the PDC drill bit body is established through the analysis of the morphological characteristics of natural biological non-smooth surfaces. An experimental platform is designed and manufactured to evaluate the adhesion performance of non-smooth surface specimens. Indoor experiments are conducted to test the normal adhesion force of non-smooth surface specimens under varying morphologies, sizes, and contact times with clay. Finally, the anti-adhesion performance of the non-smooth surface unit structures is then analyzed. The normal adhesion force with a contact time of 12 h is as follows: 340 Pa of big square raised, 250 Pa of middle square raised, 190 Pa of small square raised, 315 Pa of big circular groove, 280 Pa of middle circular groove, 200 Pa of small circular groove, 225 Pa of big dot pit, 205 Pa of middle dot pit, and 130 Pa of small dot pit. Compared with the normal adhesion force of 550 Pa for smooth surface specimens with a contact time of 12 h, the anti-adhesion properties of the three non-smooth surface unit structure specimens designed in this paper were verified. We analyzed the anti-adhesion performance of non-smooth surface unit structures. At the critical contact time when the adhesion force tends to stabilize, the adhesion forces of different specimens are as follows: 330 Pa of big square raised, 237.5 Pa of middle square raised, 175 Pa of small square raised, 290 Pa of big circular groove, 250 Pa of middle circular groove, 160 Pa of small circular groove, 210 Pa of big dot pit, 185 Pa of middle dot pit, and 115 Pa of small dot pit. The results indicate that the anti-adhesion effect of small dot pit structures is the most effective, while the anti-adhesion effect of large square convex structures is the least effective. As the size of the unit structure decreases, it becomes more similar to the surface size of the organism. Additionally, a shorter contact time with clay leads to a better anti-adhesion effect. These findings provide new insights and research directions for the effective prevention and control of mud wrapping on PDC drill bits. Full article

The Chang’e project has completed a sampling mission of the shallow lunar soil layer; however, the exploration of the deep lunar rock layer remains unaddressed. To further investigate the feasibility of deep lunar rock drilling and identify the factors affecting the rate of penetration (ROP) and power in low-temperature, H₂O less environment, a model was developed. This study utilized the Box–Behnken method to design a response surface experiment, where the number of polycrystalline diamond compact (PDC) cutters, the backward inclination angle, the chip removal conditions, and the temperature were considered as the key influencing factors. A response surface model for ROP and power was established. The results indicated that the number of PDC cutters, the backward inclination angle, the chip removal conditions, and the temperature significantly affected both ROP and power, with the interaction between the temperature and the backward inclination angle having a particularly strong impact on the ROP. The regression model demonstrated high predictive accuracy for both ROP and power, with goodness of fit (R²) values of 0.95 and 0.96, respectively. The optimal combination of the backward inclination angle, number of PDC cutters, temperature, and chip removal conditions, derived from the response surface experiment, was 25°, four, −15 °C, and 1, respectively, which resulted in high drilling efficiency and low power consumption. This study offers new insights for the design of deep lunar drilling experiments, as well as support for the future optimization of drilling tools. Full article

In high-temperature geothermal wells, the formation usually has extremely high abrasiveness, hardness, and temperature, which pose severe challenges to drilling tools. Among them, the interaction between the cutter of the drill bit and the rock is the key factor determining the rock-breaking efficiency of PDC (Polycrystalline Diamond Composite) drill bits. To further explore the rock-breaking mechanism of cutters on granite, this study adopts a combination of experimental and simulation methods to conduct systematic research. The results indicate that the specific crushing work increases and then decreases with rising temperature, reaching a minimum of 0.388 J/mm³ at 200 °C. In the temperature range of 300 °C to 500 °C, the specific crushing work is 15% lower than at room temperature. The specific crushing work during instant cooling is 12–25% lower than that during self-cooling, with instant cooling showing higher rock-breaking efficiency. As the rake angle increases, the specific crushing work initially decreases and then increases. The smallest specific crushing work, 0.383 J/mm³, occurs at a rake angle of 10°, where the number of debris and particle size are maximized. With deeper cutting depths, the specific crushing work gradually decreases, resulting in more debris, larger particle sizes, and higher cutter surface temperatures. These findings clarify the variation laws of rock load, cutting tooth distribution, and rock fragmentation state when the PDC bit breaks rocks. A rake angle of 10° can be used as the selection of cutting tooth inclination angle for PDC bit design, providing a theoretical basis for the design and application of PDC bits in high-temperature geothermal drilling and holding significant guiding importance. Considering that increasing the depth of penetration can cause uneven wear of the cutter, the drilling parameters can be controlled under certain conditions to achieve a penetration depth of 2 mm, thereby improving the rock-breaking efficiency and working life of the PDC bit. Full article

A review of binder phases used for sintering diamond powders under high pressure and high temperature conditions along with an outline of the properties of polycrystalline diamonds or composite materials intended for cutting tools, wire drawing dies, and drilling rocks are presented. The interaction of diamond with metals from group VIII of the periodic table, carbon-forming metals, carbides, MAX phases and with silicides, borides, and alkali carbonates is presented. The interaction of the bonding phases with diamond was determined. The influences of sintering process parameters, amounts, and methods of introducing of these phases on the basic mechanical properties and thermal resistance of diamond materials are analyzed. The investigated material properties are compared with the properties of commercial PCD with a cobalt and the SiC binder phase. Full article

As the extraction of oil and gas progresses into deeper and ultra-deep geological formations, the enhancement of rock-breaking efficiency in drill bits has emerged as a critical factor in ensuring energy security. Among the various techniques employed, vibratory percussion drilling technology is widely recognized for its ability to improve both the efficiency and speed of penetrating hard rock formations. This study examined the effects of varying loading conditions on the characteristics of rock fracture and damage, maintaining a constant cutting speed and lead angle. By designing a small polycrystalline diamond compact (PDC) drill bit and incorporating simulation results, the research sought to analyze the influence of axial impact components on the efficiency of breaking dolomite samples, as well as the effects of impact frequency and amplitude on drilling pressure and rock-breaking energy. The findings revealed that an increase in the axial impact amplitude significantly enhanced rock-breaking efficiency, elevated von Mises stress, and increased principal compressive stress. An increase in impact frequency effectively reduced the overall stress and frictional work. These results underscored that the stress analysis revealed that the peak stress increased at lower impact amplitudes, with notable changes occurring at an amplitude of 1.5, leading to a 100% increase in Mises peak stress compared with an amplitude of 1.0. Axial impact drilling promoted deep crack formation and the development of a tensile damage zone beneath the cutter, indicating its effective rock-breaking capabilities. Axial impact drilling significantly reduced the threshold drilling pressure compared with conventional rotation, with an impact amplitude of 0.3 mm decreasing the static load by 44.1%. Additionally, increasing the axial impact amplitude enhanced the rate of penetration (ROP) while maintaining a constant static load, resulting in remarkable efficiency improvements. The results of the study are expected to provide theoretical guidance for the mechanism of impact rock breaking and the design of impact rock-breaking tool parameters. Full article

This work investigates the milling of the surface of glass and carbon fiber-reinforced plastics using tools with a polycrystalline diamond insert. The milling process was conducted under three different conditions, namely without the use of a cooling liquid, with oil mist cooling, and with emulsion cooling. The milling process of composites was conducted with variable technological parameters. The variable milling parameters were feed per tooth and cutting speed. The novelty of this work is the use of recurrence methods based on the cutting force signal to analyze the milling of composites with three types of cooling. The primary aim of the study was to determine the effect of variable technological milling parameters on cutting force and to select recurrence quantifications that would be sensitive to the cooling method. It has been shown that recurrence quantifications such as determinism (DET), laminarity (LAM), averaged diagonal length (L), trapping time (TT), recurrence time of the second type (T₂), and entropy (ENTR) are sensitive to the cooling methods applied for the tested composite materials. The results have shown that it is possible to determine common ranges of changes in sensitive recurrence quantifications for the two tested variables parameters of milling: 0.63–0.94 (DET), 0.69–0.97 (LAM), 7.30–13.48 (L), 2.92–4.98 (TT), 17.01–38.25 (T₂), 2.02–3.16 (ENTR). The ANOVA analysis results have confirmed that the studied variables have a significant impact on the recurrence quantifications. Full article

It is recommended to use high-speed milling to maintain an effective material removal rate and the required cutting-edge geometry. However, on the other hand, high speed increases wear, so the surface of the cutters is modified by deposition functional coatings. The wear of end mills made of CTS12D and H10F tungsten carbides during the high-speed processing of aluminum A97075 (B95T1) was compared. To increase the durability of the tools, well-proven technologies for deposition diamond-like and polycrystalline diamond coatings in microwave plasma with different film structures, which were determined by the coating growth conditions, were used. The milling cutter corner was mostly worn out, but the nature of the wear had its characteristics. It was revealed that at a forced cutting mode of about 1000 m/min, cutters made of CTS12D alloy with a nanocrystalline diamond coating with a “cauliflower” structure and with a diamond-like film showed 10% higher resistance. The primary wear mechanism was adhesive. Images of worn cutting edges were obtained using a 3D optical digital image processing system. Full article

Unconventional tight oil and gas resources, including shale oil and gas, have become the main focus for increasing reserves and production. The safe and efficient development of unconventional oil and gas is a crucial demand for the energy development strategy. Deep tight oil and gas resource development generally adopts horizontal well drilling methods. During drilling, especially in long horizontal sections, the high temperature frequently causes failures of downhole drilling tools and rotary steering tools. The temperature rises sharply during rock breaking with the drill bit. Existing wellbore heat transfer models do not fully consider the impact of heat generated by the drill bit on the wellbore temperature field. This paper aims to experimentally study the temperature rise law of the cutting tooth of the bottom polycrystalline diamond compact (PDC) bit during rock breaking. A set of evaluation devices was developed to study the temperature field distribution characteristics at the bottom of the PDC bit during rock breaking under different experimental conditions. The results indicate that the flow rate of drilling fluid, bit rotation speed, and weight on bit (WOB) significantly affect the distribution of the temperature field at the well bottom. This experimental research on the temperature field distribution characteristics at the bottom of the PDC bit during rock breaking helps reveal the heat transfer characteristics of the long horizontal section wellbore, guide the optimization of drilling parameters, and develop temperature control methods. It is of great significance for the advancement of efficient development technologies for unconventional resources in long horizontal wells. Full article

This study investigated the milling of SiCp/Al composite materials using Polycrystalline Diamond (PCD) tools under various machining conditions, including dry cutting conditions, supercritical carbon dioxide (SCCO₂) conditions, supercritical carbon dioxide cooling with minimum quantity lubrication (SCCO₂-MQL) conditions, ultrasonic vibration conditions, and supercritical carbon dioxide cooling with minimum quantity lubrication combined with ultrasonic vibration conditions. The objective was to compare the surface roughness and morphology of the materials under different machining conditions. Furthermore, under dry cutting conditions and SCCO₂-MQL combined with ultrasonic vibration, the effects of different milling parameters on the surface roughness and morphology of SiCp/Al composite materials were investigated through a univariate experiment. Microhardness tests were carried out on the machined workpieces to explore the influence of process conditions and milling parameters on work hardening. The experimental results indicate that among all the tested machining conditions, the SCCO₂-MQL in combination with the ultrasonic vibration process significantly reduced the surface roughness of the material. When the milling speed was increased from 40 m/min to 120 m/min, both the surface roughness and the degree of work hardening first increased and then decreased. As the feed rate or cutting depth increased, the degree of work hardening also increased. Therefore, under SCCO₂-MQL combined with ultrasonic vibration conditions, it is recommended to use a milling speed of more than 60 m/min and avoid using high feed rates and cutting depths in order to optimize the machining performance. Full article

In cutting processes, tool condition affects the quality of the manufactured parts. As such, an essential component to prevent unplanned downtime and to assure machining quality is having information about the state of the cutting tool. The primary function of it is to alert the operator that the tool has reached or is reaching a level of wear beyond which behaviour is unreliable. In this paper, the tool condition is being monitored by analysing the electric current on the main spindle via an artificial intelligence model utilising an LSTM neural network. In the current study, the tool is monitored while working on a cylindrical raw piece made of AA6013 aluminium alloy with a custom polycrystalline diamond tool for the purposes of monitoring the wear of these tools. Spindle current characteristics were obtained using external measuring equipment to not influence the operation of the machine included in a larger production line. As a novel approach, an artificial intelligence model based on an LSTM neural network is utilised for the analysis of the spindle current obtained during a manufacturing cycle and assessing the tool wear range in real time. The neural network was designed and trained to notice significant characteristics of the captured current signal. The conducted research serves as a proof of concept for the use of an LSTM neural network-based model as a method of monitoring the condition of cutting tools. Full article