Search Results (310)

To enhance the wear resistance of artillery barrels in harsh environments, TaC and Ta/TaC coatings were prepared on 30CrNi2MoVA steel using double-glow plasma surface metallurgy technology. These coatings, of which their surfaces consisted of almost pure TaC phases, showed defect-free interfaces with the substrate. The Ta/TaC coating demonstrated excellent integration, forming a nearly homogeneous structure. The coatings exhibited a gradient cross-sectional hardness, affecting a depth of approximately 20 μm. The Ta transition layer significantly enhanced the microhardness and adhesive strength of the TaC coating, with about 16.7% and 68.5% increases in the Ta/TaC coating, respectively. Both coatings markedly improved the wear resistance, showing slight wear at room temperature and minor oxidative wear at high temperatures. The Ta/TaC coating had more stable friction coefficient curves and a lower specific wear rate, with an 11.4% wear rate of the substrate at 500 °C. Thermal mismatch and stress concentration under wear loads caused extensive cracks and edge chipping in the TaC coating. In contrast, the good compatibility between the Ta transition layer and the TaC layer allowed for cooperative deformation with the substrate, creating a plastic deformation zone that reduced internal stresses and stress concentration, maintaining the intact structure. This study provides insights into applying Ta/TaC coatings for artillery barrel protection and broadens the possible application scenarios of the preparation technology. Full article

Disc cutter wear has emerged as a critical concern impacting the efficiency and cost budgets of TBMs (tunnel boring machines). Through statistical analysis of field data on cutter wear in a TBM tunnel, this study explores the wear rules of different types of disc cutters in granite. Grey sensitivity analysis is employed to investigate the sensitivity between the cutter ring wear rate of face cutters and two types of cutter wear influence parameters. Subsequently, reasonable parameters are selected to develop a new cutter life prediction model for face cutters. The results show that, with increases in the installation radius, the accumulated wear extent shows a linearly increasing trend for both the center and the face cutter, while it first increases and then decreases for gauge cutters, and the accumulated replacement number shows a linear growth trend for face cutters. The accumulated wear extent of the average single cutter position of gauge cutters is about 3 times that of face cutters and 7 times that of center cutters; the number of replaced cutter rings of the average single cutter position for gauge cutters is about 3–4 times that for center cutters and face cutters; and the average utilization rate of gauge cutters is the highest (80.97%). The cutter ring wear rate of face cutters is the most sensitive to three intact rock parameters (uniaxial compressive strength (UCS), Cerchar abrasion index (CAI), and equivalent quartz content (EQC)) and two TBM tunnelling parameters (cutterhead thrust (F) and cutterhead rotational speed (RPM)). Finally, a new cutter life prediction model (R² = 0.964) for face cutters is developed based on F, UCS, and RPM. The research results can provide a certain theoretical basis for cutter wear and cutter life prediction for the face cutters of TBM projects in similar geological conditions and TBM specifications. Full article

This paper proposes a novel multi-band textile monopole antenna for patient tracking applications. The designed antenna has compact footprints (0.13λ₀²) and works in the narrow band-internet of things (NB-IoT) 1.8 GHz, radio frequency identification (RFID), and industrial, scientific, and medical (ISM) 2.45 GHz and 5.8 GHz bands. The impedance bandwidths and gain of the antenna at 1.8 GHz, 2.45 GHz, and 5.8 GHz are 310 MHz, 960 MHz, and 1140 MHz; 3.7 dBi, 5.3 dBi, and 9.6 dBi, respectively. Also, the antenna’s behavior is checked on different body parts of the human body in various bending scenarios. As per the evaluated link budget, the designed antenna can easily communicate up to 100 m of distance. The specific absorption rate values of the designed antenna are also within acceptable limits as per the (FCC/ICNIRP) standards at the reported frequency bands. Unlike traditional rigid antennas, the proposed textile antenna is non-intrusive, enhancing user safety and comfort. The denim material makes it comfortable for extended wear, reducing the risk of skin irritation. It can also withstand regular wear and tear, including stretching and bending. The presented denim-based antenna can be seamlessly integrated into clothing and accessories, making it less obtrusive and more aesthetically pleasing. Full article

This suspect case focuses on investigating the presence of halite (NaCl) crystals on the clothing of a deceased individual to determine whether they resulted from immersion in seawater or residual absorption after immersion (i.e., the crystals were left on the clothing after contact with the victim’s wet body). Thirteen clothing samples were collected from various garments worn by the victim and were subjected to optical stereomicroscopy, Scanning Electron Microscopy (SEM), coupled with Energy Dispersive Spectroscopy (EDS), and Simultaneous Thermal Analysis (STA). Optical stereomicroscopy revealed numerous white-colored, vitreous, and greasy luster microcrystals dispersed between fabric fibers, with higher concentrations observed near the hem seams and metal rivets. These microcrystals exhibited predominantly cubic and irregular morphologies. Additionally, sandy particles and organic elements, such as plant fragments and micro seashells, were detected, indicative of coastal environment exposure. SEM-EDS analysis confirmed the presence mainly of sodium and chlorine in stoichiometric ratios consistent with halite, with crystals exhibiting amorphous, needle-shaped, or cubic morphologies. Furthermore, STA analysis identified weight loss events attributed to organic decomposition and halite decomposition at high temperatures, corroborating SEM-EDS findings. The distribution and characteristics of halite crystals, along with other trace elements, support the hypothesis of immersion in seawater while wearing clothing. Specifically, the higher concentrations of halite crystals near thicker fabric portions and metal rivets suggest slower drying rates and longer evaporation times, indicative of immersion rather than residual absorption after swimming. This finding not only helps in determining the victim’s exposure to seawater but also establishes a methodology for distinguishing between different sources of halite residue on clothing. Overall, the comprehensive mineralogical characterization of halite crystals on clothing samples, using best practices of forensic mineralogy, provides valuable forensic insights related to the circumstances that led to the victim’s death. This approach aided investigators in reconstructing the sequence of events, enhancing the accuracy of forensic reconstructions. Moreover, this study contributes to the broader field of forensic geoscience by demonstrating the practical applications of mineralogical analysis in criminal investigations, potentially guiding future research and improving investigative techniques in similar cases. Full article

Traditional cement epoxy pavements suffer from inherent limitations such as terrible tribological properties, poor wear resistance, and weak impact resistance, presenting significant challenges to ensure the safety and continuous operation of urban roads. As a solution, high-performance cement epoxy composite grouting materials have emerged as the preferred option for engineering construction and road maintenance. In this study, CSP/epoxy cement (CSEC) composite materials were prepared by emulsion polymerization. The thermal properties of the materials were characterized, revealing that CSP enhances the thermal properties of epoxy cement (EC) to a certain extent. Furthermore, the frictional properties of CSEC composite materials and pure epoxy cement under different normal loads were investigated. The results indicated that the CSEC composite material exhibited a slight increase in friction coefficient and a notable decrease in wear rate compared to pure epoxy cement (EC). Specifically, the wear rate of CSEC decreased by 14.4% at a load of 20 N, highlighting the enhanced frictional performance facilitated by CSP. Mechanistic analysis attributed the improvement to the unique core-shell structure of CSP, which imparted higher impact resistance and eliminated alleviate residual stresses at the friction interface. This structural advantage further enhanced the wear resistance of materials, making it a promising choice for improving the durability and safety of urban road surfaces. Full article

This work discusses challenges in conventional grinding wheels: heat-induced tool wear and workpiece thermal damage. While textured abrasive wheels improve heat dissipation, the current surface-only methods, such as those based on laser and machining, have high renewal costs. The proposed manufacturing technology introduces an innovative 3D cooling channel structure throughout the wheel, enabling various channel geometries for specific abrasive wheel applications. The production steps were designed to accommodate the conventional pressing and sintering phases. During pressing, a 3D organic structure was included in the green body. A drying cycle eliminated all present fluids, and a sintering one burnt away the structure, revealing channels in the final product. Key parameters, such as binder type/content and heating rate, were optimized for reproducibility and scalability. Wear tests showed a huge efficiency increase (>100%) in performance and durability compared of this system to conventional wheels. Hexagonal channel structures decreased the wear rates by 64%, displaying superior wear resistance. Comprehensive CFD simulations evaluated the coolant flow through the cooling channels. This new design methodology for three-dimensionally structured grinding wheels innovates the operation configuration by delivering the coolant directly where it is needed. It allows for increasing the overall efficiency by optimizing cooling, reducing tool wear, and enhancing manufacturing precision. This 3D channel structure eliminates the need for reconditioning, thus lowering the operation costs. Full article

PEEK (Poly Ether Ether Ketone) is a high-performance thermoplastic polymer with excellent mechanical, thermal and chemical stability. PEEK has good performance, and is widely used in hydraulic motors. However, there are few studies on the friction and wear properties of materials under the condition of oil lubrication with wide application. The modification of PEEK and the expansion of its application have become a hot research topic in the industry. This study focuses on the modification of the design of PEEK and explores the friction and wear characteristics of self-lubricating materials under different modification schemes. Friction and wear samples were prepared using PEEK-modification pelletizing and injection-molding processes, followed by fixed-condition friction and wear tests. The tribological mechanisms and wear properties of the materials under different modification schemes were analyzed, leading to the identification of several sets of improved reinforced materials. Experimental results demonstrate that modified materials can enhance surface tribological performance, with the best modification effect observed at an SCF filling rate of 15%. The modified PEEK material can better meet the requirements of specific applications, such as high-temperature environments, chemically aggressive environments, or applications requiring high strength and wear resistance. Full article

A custom tribometer was developed to measure friction coefficient and temperature in high-pressure, low-velocity conditions, specifically for studying copper alloys used in sliding bearings for heavy equipment. Using this equipment, two commercial alloys were tested to evaluate friction coefficient, specific wear rate, thermal behavior, and subsurface strain. The results, validated through comparison with reference commercial equipment and uncertainty estimates, met acceptable criteria for tribological tests, with an uncertainty estimate value for the friction coefficient of 0.4%. The tribological tests confirmed the importance of solid lubrication in high-lead bronzes and the high wear resistance of Cu-Al-Ni-Fe alloys, which directly influence temperature, subsurface strain, and respective wear mechanisms. Full article

The number of individuals wearing cardiac pacemakers is gradually increasing as the population ages and cardiovascular disease becomes highly prevalent. The safety of pacemaker wearers is of significant concern because they must ensure that the device properly functions in various life scenarios. Electric vehicles have become one of the most frequently used travel tools due to the gradual promotion of low-carbon travel policies in various countries. The electromagnetic environment inside the vehicle is highly complex during driving due to the integration of numerous high-power electrical devices inside the vehicle. In order to ensure the safety of this group, the paper takes passengers wearing cardiac pacemakers as the object and the electric vehicle drive motors as the exposure source. Calculation models, with the vehicle body, human body, heart, and cardiac pacemaker, are built. The induced electric field, specific absorption rate, and temperature changes in the passenger’s body and heart are calculated by using the finite element method. Results show that the maximum value of the induced electric field of the passenger occurs at the ankle of the body, which is 60.3 mV/m. The value of the induced electric field of the heart is greater than that of the human trunk, and the maximum value (283 mV/m) is around the pacemaker electrode. The maximum specific absorption rate of the human body is 1.08 × 10⁻⁶ W/kg, and that of heart positioned near the electrode is 2.76 × 10⁻⁵ W/kg. In addition, the maximum temperature increases of the human torso, heart, and pacemaker are 0.16 × 10⁻⁵ °C, 0.4 × 10⁻⁶ °C, and 0.44 × 10⁻⁶ °C within 30 min, respectively. Accordingly, the induced electric field, specific absorption rate, and temperature rise in the human body and heart are less than the safety limits specified in the ICNIRP. The electric field intensity at the pacemaker electrode and the temperature rise of the pacemaker meet the requirements of the medical device standards of ICNIRP and ISO 14708-2. Consequently, the electromagnetic radiation from the motor operation in the electric vehicle does not pose a safety risk to the health of passengers wearing cardiac pacemakers in this paper. This study also contributes to advancing research on the electromagnetic environment of electric vehicles and provides guidance for ensuring the safe travel of individuals wearing cardiac pacemakers. Full article

In the quest for sustainable lubrication solutions, the present research explored the potential of five organic compounds as additives in castor oil (CO) to improve its lubricating properties. The compounds tested were curcumin, eugenol, 1,3-Diphenyl-2-propanone, 1,3-Diphenyl-2-propenone, and 1,3-Diphenyl-1,3-propanedione. The main results showed that each additive enhanced at least one characteristic of CO. Most of the additives lowered the density of the castor oil but increased the viscosity by up to 20%. Curcumin and eugenol were particularly effective in creating thicker lubricant films and higher film thickness ratios. Eugenol and 1,3-Diphenyl-2-propanone significantly reduced the friction coefficient by up to 25%. Wear rate and wear mechanisms were significantly reduced with all the additives, achieving a reduction in wear rate of up to 50% (CO+curcumin). All the additives, except the 1,3-Diphenyl-1,3-propanedione, enhanced the oxidation onset temperature up to 8 °C. The influence of chemical structure was also addressed. The optimal additive combination for a specific application that demands minimal friction and wear, as well as strong oxidation stability, was eugenol, followed by curcumin and 1,3-Diphenyl-2-propanone. Overall, the research contributes to the development of eco-friendly lubricants, aligning with the growing demand for green industrial applications, and highlights the significant tribological benefits of these substances as sustainable additives in biolubricant formulations. Full article

This work aims at reducing abrasion between titanium alloy parts, such as drive shafts and support pairs used in aviation. Three different NiCrBSi coatings, Ni40, Ni50, and Ni60, are prepared on surfaces of Ti6Al4V by laser cladding. The microstructural and mechanical properties of these coatings are analyzed by scanning electron microscope (SEM) and a microhardness tester. The tribological properties of the NiCrBSi coatings undergoing friction with Ti6Al4V are tested using a wear testing machine. The results show that the Vickers hardnesses of the Ni40, Ni50, and Ni60 coatings are 490 HV₀.₃, 609 HV₀.₃, and 708 HV₀.₃, respectively. For the above NiCrBSi coatings, more hard phases are produced with increases in the amounts of Cr in the powders, resulting in increases in the coatings’ hardnesses. The wear test results show that the NiCrBSi coatings could reduce the friction coefficients, which gradually decreased with increases in the coatings’ hardnesses. Both the coating-specific wear rates and the friction pair wear losses initially decreased and then increased. The Ni50 coating and the Ti6Al4V friction pair undergoing friction with the Ni50 coating showed the best wear performance, with a specific wear rate and wear loss of 0.51 × 10⁻⁷ mm³/(N·m) and 7.8 mg, respectively. The specific wear rates for Ni50 were only 8.4%, 35.4%, and 37.0% of the Ti6Al4V, Ni40, and Ni60, respectively. In addition, the friction pair wear loss was only 36.4%, 52.5%, and 55.3% of that while undergoing friction with Ti6Al4V, Ni40, and Ni60, respectively. The NiCrBSi coatings prepared on the surface of Ti6Al4V show excellent antifriction and wear resistance properties, providing a viable solution for the design of wear-resistant coatings on load-bearing and non-load-bearing titanium alloy parts. Full article

The cold spray deposition technique has been used to produce a new class of solid lubricant coatings using powder feedstocks of the metal disulfides WS₂ or MoS₂, either pure or mixed with Cu and Ni metal powders. Friction and cycle lives were obtained using ball-on-flat reciprocating tribometry of coated 304 SS flats in dry nitrogen and vacuum at higher Hertzian contact stresses (S_max = 1386 MPa (201 ksi)). The measured friction and thickness of the coatings were much lower than for previous studies (COF = 0.03 ± 0.01 and ≤1 µm, respectively), which is due to their high metal disulfide:metal ratios. Cu-containing metal sulfide coatings exhibited somewhat higher cycle lifetimes than the pure metal sulfide coatings, even though the Cu content was only ~1 wt%. Profiling of wear tracks for coatings tested to 3000 cycles (i.e., pre-failure) yielded specific wear rates in the range 3–7 × 10⁻⁶ mm³N⁻¹m⁻¹, similar to other solid lubricant coatings. When compared to other coating techniques, the cold spray method represents a niche that has heretofore been vacant. In particular, it will be useful in many precision ball-bearing applications that require higher throughput and lower costs than sputter-deposited MoS₂-based coatings. Full article

Innovation in comminution is expected to continue unabated to address the inefficiencies that are inherent in comminution circuits. The rotary offset crusher (ROC) is a new comminution device with a promising performance potential in terms of throughput due to the enhanced speed of transportation induced by the centrifugal force of the discs. However, the processes driving the comminution of particles trapped in the conical space between the two discs of the crusher are not fully understood. To gain a better insight into the comminution process in this device, discrete element modeling (DEM) simulations were conducted to study the breakage of a single particle for the crusher operated under two different dynamic conditions, i.e., (1) a stationary top disc and (2) both discs rotating at the same speed. For both scenarios, the speed of the discs was varied between 550 and 2350 rpm. Experimental testwork was also conducted with the laboratory prototype to generate the data that were used to calibrate the breakage parameters of the Ab × t₁₀ breakage model. Simulations were performed using polyhedral UG2 ore particles that were generated with the in-built particle generator in the DEM simulator. The simulated ROC, which is operated with both discs rotating, outperformed the ROC with a stationary top disc in terms of the specific input energy and throughput. The crusher with a stationary top disc is characterized by high shear forces (suggesting a higher wear rate), specific input energies greater than 1 kWh/t, and low throughputs (<50 kg/h). The ROC operated with a stationary disc is not recommended for hard rock applications due to expected excessive wear of crushing surfaces and higher energy consumption. The freewheeling discs are recommended, but there is scope to optimize the crusher performance in terms of the power draw, size reduction, and throughput by manipulating the difference between the speeds of the discs. There is also scope to optimize the crusher performance when it is simulated with many particles. Once the full performance potential of the ROC is established, it will then be important to benchmark it against the existing crushers in the minerals industry as well as other industries where crushers are used. Full article

High-volume fraction silicon carbide particle-reinforced aluminum (SiCp/Al) has a promising application for its high specific strength, wear resistance, and thermal conductivity. However, SiCp/Al components with a high-volume fraction are prone to poor surface quality and defects such as fractures, cracks, and micro-pits. It has been reported that ultrasonic-assisted grinding machining (UAG) helps to improve the quality of SiCp/Al machined surfaces. However, the differences between SiCp/Al with different volume fractions obtained by UAG machining are not clear. Therefore, a comparative study of surface roughness, morphology, and cutting force was carried out by UAG machining on SiCp/Al samples with volume fractions of 45% and 60%. Compared to the 45% volume fraction SiCp/Al, the 60% volume fraction SiCp/Al has a higher cutting force and roughness under the same machining parameters. In addition, experiments have shown that cutting forces and surface roughness can be reduced by increasing the tool speed or decreasing the feed rate. UAG machining with an ultrasonic amplitude within 4 μm can also reduce cutting forces and surface roughness. However, more than 6 μm ultrasonic amplitude may lead to an increase in roughness. This study contributes to reasonable parameter settings in ultrasonically-assisted grinding of SiCp/Al with different volume fractions. Full article

When a slurry TBM advances in pebble and rock strata, large rock particles are carried in pipelines out of a tunnel by moving slurry. To estimate the wear of horizontally straight slurry discharge pipes, a phenomenological model was proposed that was mainly based on knowledge gained by means of direct and indirect in situ observations. The proposed model applies an equation composed of three variables, namely, the wear rate (λ), the central angle (2α), and the excavated tunnel length (L), to estimate the wear distribution along a pipe’s internal surface. The results indicated that wear mainly occurred on the bottoms of pipes. In addition, linear relationships between the maximum pipe wear amount (δ_max) and the excavated tunnel length (L) were found for specific pipes and specified types of ground. The observed wear rates of different pipes in different types of ground had varied constants. The wear rates were higher for pipes in rock ground than for those in a pebble layer. For horizontally straight pipes, the observed wear rates were 0.0045 mm/m in a pebble layer and 0.0212 mm/m in rock ground. Lastly, to improve the proposed model, more field monitoring will be necessary to determine the pipe wear rates in different types of ground in the future. Full article