Search Results (116)

In this study, the microstructural properties, wear resistance, and corrosion behavior of H111 hot-rolled AA5754 alloy before heat treatment, after homogenization, and after aging were examined. The microstructure was mainly composed of the scattered forms of black and gray contrast particles on the matrix and precipitations were observed at the boundaries of the grain. The as-rolled material exhibited a dense pancake-shaped grain structure, which is typical of as-rolled material. Observation along the L-direction did not yield distinct demarcations among the grains and was not uniformly distributed, with precipitates at the grain boundary. When they aged, there was a parallel increase in fine and huge black and gray contrast particles in the zone. Therefore, it could be stated that the amount of fine grains increased due to the rise in the homogenization process. The rolled base metal with the grain orientation was found to be parallel to the rolling direction. On the other hand, the coarse grains were clearly observed in the aging heat-treatment condition. The grains had an elongated morphology consistent with the rolling process of the metal before the heat-treatment process. The aged alloy had the highest hardness with a value of 86.83 HB; the lowest hardness was seen in the alloy before heat treatment with a value of 68.67 HB. The weight loss and wear rate of this material at the end of 10,000 m were, respectively, 1.01 × 10⁻³ g and 5.07 × 10⁻⁹ g/Nm. It was observed that the alloy had the highest weight loss and worst wear resistance before heat treatment. Weight loss and wear rates at the end of 10,000 m were, respectively, 3.42 × 10⁻³ g and 17.08 × 10⁻⁹ g/Nm. According to these results, the friction coefficients during wear were parallel and the material with the lowest friction coefficient after aging was 0.045. While the alloys corroded after aging showed more weight loss, the alloys corroded before heat treatment exhibited better corrosion behavior. Among the alloys, the least weight loss after 24 h was observed in the alloy that was corroded before heat treatment and this value was 0.69 × 10⁻³ mg/dm². The highest weight loss was observed in the aged alloy with a value of 1.37 × 10⁻³ mg/dm². The alloy before heat treatment, which corroded after casting, showed the lowest corrosion rate with a value of 0.39 × 10⁻³ mg/(dm²·day) after 72 h. The alloy that was corroded before heat treatment showed the best corrosion behavior by creating a corrosion potential of 1.04 ± 1.5 V at a current density of −586 ± 0.04 μA/cm². However, after aging, the corroded alloy showed the worst corrosion behavior with a corrosion potential of 5.16 ± 3.3 V at a current density of −880 ± 0.01 μA/cm². Full article

The operating conditions of the drum shearer are very complex, and its ranging arm gear system often suffers from gear scuffing and wear. Gear scuffing is caused by the adhesive wear, which is due to the instantaneous friction and flash temperature of the tooth surface, and the gear meshing power loss is also caused by tooth surface friction. In order to resist tooth scuffing and improve meshing efficiency of the transmission system, an improved semi-analytical tooth surface flash temperature calculation method was used. The tooth flash temperature status under various working conditions were analyzed in detail. Based on the mechanical model of the shearer drum picks, the load condition of the drum was analyzed. Under these load and boundary conditions, the misalignments of each gear pair in the ranging arm were calculated. The tooth surface load distribution was calculated under the gear misalignments, and then the theoretical tooth surface flash temperature and meshing power loss were determined. Next, the tooth micro-geometry was modified to reduce flash temperature and meshing power loss. The flash temperature distribution pattern of the optimized tooth surface was studied under various working conditions, and the meshing power loss was also obtained. Finally, experiments were conducted to verify the effects of the optimized tooth surface on the friction temperature rise and the effectiveness of the modification method. Tooth surface optimization aimed at reducing tooth surface flash temperature can also effectively reduce meshing power loss, which has a significant effect on gear anti-scuffing and energy saving. Full article

In this study, the rotating welding process of Chinese fir (Keteleeriafortunei) in Guizhou, China, was systematically analyzed. The effects of rotating welding conditions, including the dowel-to-guide hole diameter ratio, welding time, depth, base surface, angle, and dowel type, on the performance of welded Chinese fir were explored. Moreover, the physical and chemical changes oftheChinese fir interface during welding were revealed by Fourier-Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). The results indicated the following: (1) The rotating welding technology can quickly achieve a strong connection between wood through friction heat without chemical adhesives and compared with traditional wood connection technology such as gluing or mechanical fixing;it has the advantages of simple operation, high production efficiency; and environmental friendliness. (2) Aftertherotating welding, the wood underwent significant pyrolysis, especially the degradation of hemicellulose. The heat generated in the welding process caused good melting and mechanical interlocking between the dowel and the wall of the guide hole, but it was also accompanied by afriction loss of the dowel and the substrate. (3) The welding parameters affected the wood’s connection strength and stability by altering heat production, distribution, transfer, and frictional losses. The impact of the dowel-to-guide hole diameter ratio had a great influence on the connection strength. When the diameter ratio was 1:0.7, the tensile strength was the highest, reaching 2.27 MPa. (4) The analyses of XPS, FTIR, XRD, and SEM proved thatthechemical composition changes at the interface, leading to a more structured crystalline bond and enhanced connection strength due to fiber entanglement and interlocking. This research providesatheoretical and experimental basis forthefurther innovation and development of wood processing technology and provides a new technical path forthegreen manufacturing of wood structure buildings. Full article

Despite their complex design, cycloidal gearboxes are characterized by high efficiency. Nevertheless, due to friction, some power is lost during gearbox operation. Basically, these losses occur in two structural nodes: the cycloid gearing and the output mechanism. Since the first of these nodes has been well discussed in the literature, the output mechanism will be discussed in this article. The design of the output mechanism has a significant impact on mechanical power losses. There are several mechanism design solutions. One of them is a mechanism with serially arranged rollers. Three solutions that are different in design but work identically will be discussed. Due to this affinity, a single, common mathematical model will be used to determine the value of losses. As will be shown, the value of losses is directly affected by the backlash, number, and diameter of the rollers used in the output mechanism and indirectly by the ratio and eccentricity of the cycloidal gearbox. Sample calculations were carried out using the developed model of mechanical power losses in the output mechanism. This made it possible to analyze the distribution of backlash created by manufacturing tolerances. It was also shown that the backlash has a significant effect on the number of rollers involved in torque transmission, as well as on the distribution of loads, contact pressures, and mechanical power losses. Full article

The initial friction stage between the contacting materials would generate a maximum shear force and an unstable fluctuating time, which had a negative effect on the entire frictional system, especially at low temperature conditions. In order to decrease the occurring shear force and fluctuating time on the onset of friction, two different lubricating oils were applied in this study to investigate the influence of lubricant’s viscosity on these friction behaviors. The frictional experiments were conducted between the steel ball and the 40CrMnMo, and special attention was paid to the relationship between maximum friction force, fluctuating time, frictional vibration and the initial lubricant temperature. The results showed that the friction force first increased to the maximum value and then experienced an oscillation damping period (fluctuating time) before it reached a stable state. And this fluctuating behavior caused corresponding vibrations on the initial contacting. However, compared to the high viscosity lubricating oil (HO), the low viscosity lubricating oil (LO) contributed to more than 50% reductions on max friction force, fluctuating time and vibration at the cold start (0 °C). Moreover, the weakened initial frictional fluctuation was conducive to generating a low and stable friction coefficient (COF) and wear loss of the long-term test. The discrepancy on lubricating performance was that the low viscosity provided high fluidity, which allowed rapid distribution of the lubricant between the contacting surfaces and formed an intact lubricating film. Similarly, the high temperature decreased the viscosity of HO and thus led to satisfactory friction reductions. The knowledge gained herein provides a supporting theory on the design and preparation of a lubricating oil with high performance. Full article

The film temperature distribution of the valve plate pair in axial piston pumps affects its lubrication, leakage, and friction. In order to investigate the film temperature distribution of the valve plate pair in axial piston pumps, a test platform was constructed including three displacement sensors for the oil film thickness and eleven thermocouples for the film temperature distribution of the valve plate pair. An accurate film shape model of the valve plate pair was built according to the three-point film thickness test data. Based on the film shape model, the film temperature model of the valve plate pair was developed considering the viscous oil temperature characteristics, the energy loss caused by leakage and viscous friction in the film, and the heat conduction among the oil, cylinder block, and valve plate. The influence of different swash plate tilt angles and operating pressures on the valve plate film temperature was studied. The test results indicate that the film temperature of the valve plate pair increases as the working pressure and swash plate tilt angle increase. The theoretical and experimental absolute errors of the film temperature in the circumferential range [−60°, 60°] of the valve plate high-pressure side are less than 3.5 °C. As the swash plate tilt angle varies from 12° to 16° and working pressure from 3 MPa to 7 MPa, the minimum film thickness position and the maximum temperature point move accordingly in the circumferential range [−15°, 5°] of the valve plate pair. Full article

In order to improve the tribological properties of the flow distribution pair of the seawater axial piston pump, SAF2507 super duplex stainless steel and carbon-fiber-reinforced polyetheretherketone (CF/PEEK) were selected as the matching materials. The surface coating treatment and surface texture treatment were carried out on the flow distribution pair, and the friction and wear test were carried out by MMD-5A. In order to fully understand the friction and wear properties of the surface coating flow distribution pair and the surface texture flow distribution pair, and analyze the friction and wear mechanism, the data of the friction coefficient, wear loss, and wear surface morphology were obtained in the experiment. The results show that the coating surface has little difference in the test, the texture surface significantly reduces the friction coefficient, and the wear scar density is significantly reduced. Adding texture to the surface of the lower sample is better than adding it to the surface of the upper sample. The research results are helpful in improving the tribological performance of the flow distribution pair of the seawater axial piston pump. Full article

We consider a scalar QED (quantum electrodynamics) model for the frictional force and the momentum fluctuations of a polarizable particle in thermal equilibrium with radiation or in hyperbolic motion in a vacuum. In the former case the loss of particle kinetic energy due to the frictional force is compensated by the increase in kinetic energy associated with the momentum diffusion, resulting in the Planck distribution when it is assumed that the average kinetic energy satisfies the equipartition theorem. For hyperbolic motion in vacuum the frictional force and the momentum diffusion are similarly consistent with an equilibrium with a Planckian distribution at the temperature $T=\hslash a/2\pi k_{B}c$. The quantum fluctuations of the momentum imply that it is only the average acceleration a that is constant when the particle is subject to a constant applied force. Full article

Studies on the stability inter-controlled factors of fine-grained sediments in debris flow gullies play an important role in predicting the scale and danger of debris flows. However, up to the present, few studies have been carried out on the spatial distribution pattern and causes of stability inter-controlled factors of fine-grained sediments in debris flow gullies, leading to difficulty in finding the dangerous section of debris flow gullies to be monitored and controlled to reduce disaster losses. Therefore, the objective of this paper is to analyze the spatial distribution pattern and causes of stability inter-controlled factors (grain size, permeability coefficient, shear strength, and porosity), taking the Beichuan Debris Flow Gully, China, as a case. After collecting soil samples in the field, we carried out experiments to measure the stability inter-controlled factors and, from these, the results show that (1) fine-grained sediments in this case are mainly silty loams, which are stable under non-heavy rains; (2) the grain size of silty loams is mainly concentrated between 10 and 20 μm, with a spatial distribution pattern of fine in the middle and coarse at both ends; (3) the permeability coefficient of silty loams is concentrated between 1.15 and 2.17 m/d, with a spatial distribution pattern of high in the middle and low at both ends; (4) the average cohesion of silty loams is mainly concentrated between 20 and 30 kPa, with a spatial distribution pattern of low in the middle and high at both ends; and (5) the internal friction angle of silty loams is concentrated between 18.98 and 21.8°, with a spatial distribution pattern of high in the middle and low at both ends. The main reasons for these spatial distribution patterns are analyzed from three aspects of shear strength, water flow velocity, and terrain, which can provide a scientific basis for the prediction of debris flow disasters in such areas. Full article

Oxide-dispersion- and hard-particle-strengthened (ODS) laser-cladded single-layer multi-tracks with a Ni-based alloy composition with 20 wt.% μm-WC particles and 1.2 wt.% nano-Y₂O₃ addition were produced on ultra-high-strength steel in this study. The investigation of the composite coating designed in this study focused on the reciprocating friction and wear workpiece surface under heavy load conditions. The coating specimens were divided into four groups: (i) Ni-based alloy, nano-Y₂O₃, and 2 μm-WC (2 μm WC-Y/Ni); (ii) Ni-based alloy with added 2 μm-WC (2 μmWC/Ni); (iii) Ni-based alloy with added 80 μm-WC (80 μmWC/Ni); and (iv) base metal ultra-high-strength alloy steel 30CrMnSiNi2A. Four conclusions were reached: (1) Nano-Y₂O₃ could effectively inhibit the dissolution of 2 μm-WC. (2) It can be seen from the semi-space dimensionless simulation results that the von Mises stress distribution of the metal laser composite coating prepared with a 2 μm-WC particle additive was very uniform and it had better resistance to normal impact and tangential loads than the laser coating prepared with the 80 μm-WC particle additive. (3) The inherent WC initial crack and dense stress concentration in the 80 μm-WC laser coating could easily cause dislocations to accumulate, as shown both quantitatively and qualitatively, resulting in the formation of micro-crack nucleation. After the end of the running-in phase, the COF of the 2 μm-WC-Y₂O₃/Ni component samples stabilized at the minimum of the COF of the four samples. The numerical order of the four COF curves was stable from small to large as follows: 2 μm-WC-Y₂O₃/Ni, 2 μm-WC/Ni, 80 μm-WC/Ni, and 30CrMnSiNi2A. (4) The frictional volume loss rate of 2 μm-WC-Y₂O₃/Ni was 1.3, which was significantly lower than the corresponding values of the other three components: 2.4, 3.5, and 13. Full article

In this investigation, an attempt was made to develop a new high-strength and high-ductility aluminum metal–matrix composite. It was achieved by incorporating ceramic reinforcement into the metal which was formed in situ from a polymer by pyrolysis. A crosslinked PMHS polymer was introduced into commercially pure aluminum via friction stir processing (FSP). The distributed micro- and nano-sized polymer was then converted into ceramic particles by heating at 500 °C for 10 h and processed again via FSP. The produced composite showed a 2.5-fold increase in yield strength (to 119 MPa from 48 MPa) and 3.5-fold increase in tensile strength (to 286 MPa from 82 MPa) with respect to the base metal. The ductility was marginally reduced from 40% to 30%. The increase in strength is attributed to the grain refinement and the larger ceramic particles. High-temperature grain stability was obtained, with minimal loss to mechanical properties, up to 500 °C due to the Zenner pinning effect of the nano-sized ceramic particles at the grain boundaries. Fractures took place throughout the matrix up to 300 °C. Above 300 °C, the interfacial bonding between the particle and matrix became weak, and fractures took place at the particle–matrix interface. Full article

Currently, the simulation parameters for the model of the interaction between the transplanter, the plug seedlings, the soil, and the pot damage mechanism still need to be clarified. The optimization design of the planters and the improvement of planting quality are still urgent issues that need to be solved. In this paper, the simulation parameters of the pot and the soil were calibrated based on the pressure distribution measurement technology. With the actual collision impact force and matrix loss rate as the targets, a four-factor, three-level orthogonal test was designed to obtain the optimal parameters. Through the optimization analysis of the experimental results, it could be concluded that the pot–soil restitution coefficient, the pot–soil static friction coefficient, the pot–soil rolling friction coefficient, and the surface energy were 0.31, 0.88, 0.35, and 1.07 J/m², respectively. The experimental verification of the optimal parameter combination showed that the relative error of the collision impact force was 1.65% and that the relative error of the matrix loss rate was 2.32%, which verified the model’s reliability. Based on the optimal parameters, the movement law of the hole tray seedlings was studied at different positions during the transplanting process. The plug seedlings collided not only with the planter but also with the soil, which led to the breakage and looseness of the pot structure. The relative error between the matrix loss rate of the transplanter inserting soil, the matrix loss rate of the transplanter that did not enter the soil, and the simulated matrix loss rate was less than 10%, which further proved the accuracy of the simulation model. Full article

This study investigates the preparation and application mechanism of Xylooligosaccharides (XOS), an environmentally friendly oligosaccharide additive derived from black fungus in water-based drilling fluids (WBFs). The distinctive molecular characteristics of XOS are revealed through Fourier-transform infrared spectroscopy. Thermogravimetric analysis confirms its stability at temperatures below 150 °C. In terms of performance enhancement, incorporating XOS improves rheological properties and filtration efficiency. Elevated XOS concentrations increase viscosity, diminish fluid loss, suppress clay hydration, and enhance cohesive strength, especially at higher temperatures. Additionally, incorporating XOS prompts the formation of a lubricating layer on particle surfaces, facilitating improved interaction between particles and the surrounding fluid. This layer substantially reduces friction coefficients, thereby significantly boosting the lubrication efficiency of the drilling fluid. At the microstructural level, the incorporation of XOS leads to noticeable microstructural refinement in the matrix mud cake, resulting in a smoother particle distribution due to interactions between XOS and particles. Mechanistically, introducing XOS results in a significant shift in the distribution of clay particle sizes. This phenomenon can be attributed to XOS’s ability to create a stable hydration film within the WBFs. As a result, this film mitigates particle aggregation, leading to a reduction in particle size. XOS emerges as a versatile and sustainable oligosaccharide inhibitor, effectively optimizing the performance of WBFs. Its diverse contributions to lubrication, inhibition, and microstructure refinement position XOS as a promising solution for efficiently extracting oil and gas resource. Full article

Magnetically Impelled Arc Butt (MIAB) welding is a cutting-edge joining method that replaces the conventional welding procedures such as resistance, friction, flash and butt welding. It is a solid-state process that uses a rotating arc to heat up the butt ends of tubes, being followed by a forging process that completes the joining of the workpieces The magnetic flux density and the current interact to develop the Lorentz force that impels the arc along the faying surfaces. This process is found to produce high tensile strength and defect-free welds in ferrous materials and for this reason, it is predominantly employed in automobile applications for joining metallic tubes. Also, this joining procedure can be applied in the fabrication of boilers, heat exchangers, furnace piping in petrochemical industry and other safety-critical high-pressure machinery parts. The MIAB method has several advantages such as a shorter welding cycle, lower input energy requirement and lower loss of material. Compared to other solid-state welding processes, the MIAB welding has an important advantage in terms of cost-efficient welds with better control and reliability. Moreover, there are researchers who have investigated the joining of non-ferrous dissimilar materials using this welding procedure. The studies have been focused on process parametric analysis that involves optimizing and forecasting the magnetic field and thermal profile distribution. This review article provides competitive insights into various design features, computational methods, tests and material characterization, technical issues and workarounds, as well as automation aspects related to the MIAB-welding process. This work will prove to be a quick reference for researchers, useful to identify the research gaps and conflicting ideas that can be further explored for advancements in joining the similar and dissimilar materials. Full article

A possible method for fluid transportation of heavy oil through horizontal pipes is core annular flow (CAF), which is water-lubricated. In this study, a large eddy simulation (LES) and a sub-grid-scale (SGS) model are used to examine CAF. The behavior of heavy oil flow through turbulent CAF in horizontal pipes is numerically investigated. The Smagorinsky model is utilized to capture small-scale unstable turbulent flows. The transient flow of oil and water is first separated under the behavior of the core fluid. Two different conditions of the horizontal pipes, one with sudden expansion and the other with sudden contraction, are considered in the geometry to investigate the effects of different velocities of oil and water on the velocity distribution, pressure drop, and volume fraction. The model was created to predict the losses that occur due to fouling and wall friction. According to the model, increasing water flow can reduce fouling. Additionally, the water phase had an impact on the CAF’s behavior and pressure drop. Also, the increased stability in the CAF reduces the pressure drop to a level that is comparable to water flow. This study demonstrated that a very viscous fluid may be conveyed efficiently utilizing the CAF method. Full article