Medium Rotation Speed Research Articles

Friction stir process parameters optimization in the fabrication of agate particle reinforced AA6061-T6 aluminum alloy surface composite

The main objective of this study was to optimize the friction stir process parameters to fabricate agate particle reinforced AA6061-T6 Aluminum alloy surface composite for hardness and tensile strength. The surface composite samples were made using a CNC milling machine based on Taguchi’s mixed L16 orthogonal array. The process parameters such as tool rotational speed, traverse speed, percent of reinforcement, number of passes and pin profiles were selected in this study. The optimal properties for the developed surface composite were obtained when surface composites having 18% reinforcement were fabricated by a two-pass FSP using a squared pin tool with a rotational speed of 1400 rpm and traverse speed of 60 mm/min. At the optimal process parameters, the tensile strength and hardness of the fabricated surface composite were found to be 312.23 MPa and 74.82 HRB respectively. ANOVA analysis performed at a 95% confidence level revealed that all process parameters were significant and the contribution of the number of passes on the properties of surface composite was higher than other process parameters. Microstructural analysis revealed that medium rotational speed and high traverse speed produced a uniform distribution of agate particles which helped to improve the properties.

Wear and thermal coupled comparative analysis of additively manufactured and machined polymer gears

This study investigates the potential use of additive manufacturing (AM)-produced gears in the polymer gear industry as an alternative to conventionally manufactured gears. The focus is on comparing the wear and thermal properties of polyamide 6 (PA6) gears, the most commonly used in industry, with those of polyetherimide (PEI) gears manufactured via AM. The research aims to determine whether AM offers any advantages over conventional methods, particularly with regard to wear resistance and thermal performance. The wear behaviour of both types of gears is examined under various operating conditions, with particular attention being paid to the initial wear rates and how they evolve. PEI and PA6 test gears were evaluated using a custom-built gear wear test rig. Throughout the wear test, polymer test gears were subjected to wear by running against a metal gear. The gears were tested at various rotational speeds for up to 1 million cycles. During this process, measurements were taken to determine surface roughness changes, operational noise levels, microstructure analyses using scanning electron microscopy (SEM), and chemical structure analyses using Fourier transform infrared spectroscopy (FTIR). Additionally, thermal properties such as temperature generation and stability are monitored with a thermal camera and infrared thermometer to understand the suitability of each gear material for different applications. PA6 gears demonstrate better wear resistance at low and medium rotational speeds, while PEI gears show superior performance at high speeds. Furthermore, PEI gears display enhanced thermal properties, with lower temperature increases during operation compared to PA6 gears; this can be attributed to the porous structure inherent in AM, which allows for better heat dissipation. The findings suggest that AM-produced PEI gears hold promise as an important alternative in high-speed applications due to their superior wear resistance and thermal performance compared to conventionally manufactured PA6 gears.

Analysis of Tool Wear and Calculation Results of Hardness Values in St 37 Steel Turning Using Characteristics

The development of lathe chisels is currently more advanced with the creation of carbide, CBN, ceramic, and inserts tool types. However, conventional chisel types, one of which is the HSS (high speed steel) chisel, are still used. ST 37 steel is a low carbon steel type that is easy to forge and easy to machine. The level of precision and surface roughness of the resulting workpiece must be in accordance with the needs. The higher the level of surface quality of the workpiece, the higher the level of precision. The research method we use is to find data, then the data obtained is graphed. From the results of the graph it can be concluded that for the depth of cutting the greater the rotation, the greater the depth. For wear, it can be seen that the wear will be greater if the speed is increased. The results of the hardness test at a medium rotational speed of 490 Rpm, the greater the number of examples, the greater the results of the hardness test experienced on the test material.

Effects of dry powder mixing on electrochemical performance of lithium-ion battery electrode using solvent-free dry forming process

This research examines how the morphology of the electrode powder mixture affects the structure and battery performance of lithium-ion battery electrodes fabricated using a dry electrode forming process. We demonstrate that the distribution of conductive and binding additives (CBA) on the active materials (AMs) can be controlled by adjusting the rotation speed of a dry mixer. Furthermore, we show that controlling the distribution of CBA can improve the rate performance of the batteries. The tortuosity of the CBA domain in the electrodes is analyzed from SEM images of electrode cross-sections as electronic and ionic conductive pathways. Low rotation speed dry mixing results in poor dispersion of CBA, leading to the formation of long-range conductive pathways with low tortuosity. Consequently, the capacity at high rates decreases due to fewer short-range conductive pathways between the AM particles. In contrast, high rotation speed dry mixing leads to excessive dispersion of CBA, resulting in high tortuosity in both long-range and short-range conductive pathways. As a result, the capacity decreases due to fewer efficient conductive pathways throughout the electrode. We demonstrate that medium rotation speed dry mixing achieves a favorable balance between short-range and long-range conductive pathways, providing high capacity at high rates.

Analysis of CVT (continuously variable transmission) and the influence of variations on the motorcycle

This study aimed to determine the working principle, troubleshooting, and the effect of CVT roller weight variations on Suzuki Nex-FI 2014 motorcycles. This research process was carried out by analyzing the measurement results of each CVT component and comparing the results. The research method used is an experimental method by holding the throttle at 3,250 rpm; after it is stable, the throttle is rotated up to 10,000 rpm. The results of troubleshooting analysis and measurement of drive belt wear and tear are from the standard size of 19.50 mm to 18.00 mm, and the tolerance limit for use is 18.60 mm. As for the roller variation test results, using a lighter weight roller, for example, 8 grams and 9 grams, get maximum results at low and medium rotational speeds, compared to using an 11-gram roller (standard). The downside of this 8-gram and 9-gram roller is that it only gets good acceleration and torque at low rotational speeds. While at a high rotational speed less than the maximum. If we use an 11-gram roller, the acceleration and torque will get less than the maximum results but maximum power.

Wake transitions behind a streamwise rotating disk

Direct numerical simulations are performed to investigate the wake transitions of the flow normal to a circular rotating disk. The diameter-thickness aspect ratio of the disk is $\chi =50$ . The Reynolds number of the free stream is defined as $Re_s=U_\infty D/\nu$ , with incoming flow velocity $U_\infty$ , disk diameter $D$ , and kinematic viscosity of the fluid $\nu$ . The rotational motion of the disk is described by the Reynolds number of rotation $Re_r=\varOmega Re_s$ , with non-dimensional rotation rate $\varOmega =\frac {1}{2}\omega D/U_\infty$ , where $\omega$ is the angular rotation speed of the disk. Extensive numerical simulations are performed in the parameter space $50 \leqslant Re_s \leqslant 250$ and $0 \leqslant Re_r \leqslant 250$ , in which six flow regimes are identified as follows: the axisymmetric state, the low-speed steady rotation (LSR) state, the high-speed steady rotation (HSR) state, the low-speed unsteady rotation (LUR) state, the rotational vortex shedding state, and the chaotic state. Although plane symmetry exists in the wake when the disk is stationary, a small rotation will immediately destroy its symmetry. However, the vortex shedding frequencies and wake patterns of the stationary disk are inherited by the unsteady rotating cases at low $Re_r$ . A flow rotation rate jump is observed at $Re_s\approx 125$ . The LUR state is intermediate between the LSR and HSR states. Due to the rotational motion, the wake of the disk enters the steady rotation state earlier at large $Re_r$ , and is delayed into the vortex shedding state in the whole range of $Re_r$ . In the steady rotation states (LSR and HSR), the steady flow rotation rate is linearly correlated with the disk rotation rate. It is found that the rotation of the disk can restrain the vortex shedding. The chaotic state can be regularized by the medium rotation speed of the disk.

Fast Wheel Gravel-tempered Coarse Ware Found in 7th–10th-Century Cemeteries from Western Romania

Sometime in the 7th century, pottery made with a potter’s wheel reaching a medium rotation speed appeared in the Carpathian Basin. This particular pottery, generically referred to as “Danubian-type pottery”, evolved in different ways from one region to another until it was generalized in the 8th century as a specific type that characterizes large areas in central and south-eastern Europe. Owing to the technical innovations that led to the improvement of the potter’s wheel, pottery also began to be produced on the fast-rotating wheel. However, 7th–10th-century fast wheel pottery from Transylvania should not be regarded as an ethnic attribute. Early Medieval wheel-thrown pottery is recorded not only in settlements but also in inhumation and bi-ritual cemeteries from Transylvania, north-western Romania and Crișana (centralwestern Romania), constantly appearing from the Middle Avar period (AD 650/670) until the end of the 10th century (Tab. 1–2). The list of finds thus demonstrates that all population groups archaeologically attested in Transylvania by material evidence and, especially, spiritual activities knew fast wheel pottery. These are mainly Avar and Slavic populations, represented in the group of Avar cemeteries at the Mureș river bend in central Transylvania and the Mediaș Group, which can be attributed to the Slavic and Slavo-Avar populations of the Transylvanian Plateau.

Performance and Flow Field of Gravitation Vortex Type Water Turbine using Volute Tank

Gravitation vortex-type water turbines use gravitational vortex generated when water is guided into the tank and drained from the hole at the bottom of the tank. When a circular tank is used, a runner inlet flow becomes uneven circumferentially, resulting in poor performance. To control the flow in the tank and make it uniform in the circumferential direction, we used a volute tank to elucidate the impact of tank geometry on the performance and flow field of the gravitation vortex type water turbines. We further investigated the performance and flow field of the water turbine using volute and circular tanks through experiments and free surface flow analysis. We compare the performance and flow field of the volute tank to those of the circular tank. We found that the effective head and turbine output of the volute tank decreased more than those of the circular tank, whereas the water turbine efficiency of the volute tank improved more than that of the circular tank at low to medium rotational speeds. This is because the theoretical head of the volute tank was smaller than that of the circular tank, but the runner inlet flow was uniform in the circumferential direction, and the loss in the tank, which is the dominant loss in the circular tank, was greatly reduced.

Study on cutting force of reaming porcine bone and substitute bone.

Accurate mechanical feedback systems are critical to the successful implementation of virtual and robotic surgical assistant systems. Experimental measurements of reaming force could further our understanding of the cancellous bone reaming process during hip arthroplasty to help develop surgical simulators with realistic force effects and improve the protection mechanism of robot-assisted surgical systems. In this study, reaming experiments with natural bone (porcine femur) and a bone substitute (polyurethane blocks) were performed on a CNC lathe. This paper proposes using the maximum reaming force of the steady reaming stage to represent the force characteristic. The reaming force is biased to one side in the overlap direction and the maximum reaming force will vary when the reamer is not coincident with the long axis of the bone. The diameter of the reamer has the greatest influence on reaming force, which clearly increases with increasing reamer diameter. During operation, a medium rotation speed and high feed speed can reduce the reaming force. After cutting, the morphology of the cut surface is not flat, but arc-shaped, which will have a significant impact on implantation of the femoral prosthesis. In in vitro cutting experiments, polyurethane blocks can be used as a substitute for cancellous bone.

Features of the working process of high-speed diesel engines

This article discusses the main history of the creation of high-speed short-stroke diesel engines and an assessment of the main factors that most significantly affect the working process of a diesel engine. When developing a new design of a high-speed diesel engine, it is necessary to pay special attention to the following factors: the intensity of the air charge, injection pressure parameters, the shape of the combustion chamber and the choice of the best option. Research carried out with a 7 x 0.15 mm nozzle in a wide range of speed changes (n = 1000 + 2800 min-1) shows that it is possible to find a position of the widened valve at which optimal results are obtained at medium and high rotational speeds, and on small - engine performance will deteriorate slightly.

Experimental and numerical study of self-sustaining fluid films generated in highly compressible porous layers imbibed with liquids

Ex-poro-hydrodynamic (XPHD) lubrication is a biomimetic-inspired lubrication mechanism consisting of self-sustained fluid films generated within highly compressible porous layers imbibed with liquids, whose solid phase induces compressive elastic forces that are negligible compared to the hydrodynamic forces generated inside the porous medium. This work focuses on the performance of XPHD lubrication in the context of tangential movement, adapted to the case of thrust bearings at low and medium rotational speeds. An in-depth study of a pre-selected porous material (polyurethane foam) was carried out in order to determine the physical characteristics and the crucial parameters for XPHD lubrication, namely the porosity and the permeability. The paper also proposes a theoretical and numerical model of XPHD lubrication. Classical lubrication assumptions are used, and flow within the porous medium is predicted using a new form of the Reynolds equation. A specially developed test rig allows for an experimental study of the XPHD lubrication mechanism. Finally, a comparison of the modeling and experimental results is presented.

Impact of tool profile on mechanical behavior and material flow in friction stir welding of dissimilar aluminum alloys

AbstractThe tool pin geometry used in friction stir welding of any material affects the transportation and mixing of the materials at the joint interface during the welding process. This further affects the mechanical properties of the joint. Tapered threaded and unthreaded tool pin profiles were investigated in this research work. The relationship between the material mixing characteristics and mechanical properties of each pin profile were evaluated. The results indicate that more materials mixing occurred in the nugget zone of the welds at lower rotational speed with the threaded tool pin than the unthreaded tool pin. However, at medium rotational speed, more volume of materials was swept into each other better in the unthreaded tool pin than the threaded pin. The tensile strengths of welds with the threaded tool pin were higher than the unthreaded tool pin. Although the two tool pins exhibit similarities in hardness variations across the weld zones however, higher average values of hardness were obtained at the nugget zone for welds performed with the tapered threaded tool pin. These could be as a result of better material mixing and higher opposition to grain dislocations across the dividing lines in the welds from the threaded tool pin.

SEM-EBSD Analysis of Broad Ion Beam Polished Rock Thin Sections – The MFAL Protocol

Abstract A protocol is presented to perform Broad Ion Beam Polishing (BIBP) of rock thin sections to obtain a surface that can yield high quality crystallographic preferred orientation data using SEM-EBSD. The modus operandi, referred to as Mamtani’s Fabric Analysis Lab (MFAL) protocol, involves flat milling of a rotating rock thin section using a triple ion beam milling system (Leica EM TIC 3X) in which tilt angle of sample (degree) with reference to ion beam (Argon), acceleration voltage (kV) and source current (mA) can be controlled along with lateral and rotary movements. The protocol has been developed after >90 hours of BIBP experiments on various rock samples under different experimental settings (tilt angle/kV/mA) followed by SEM-EBSD analysis. Each experiment was performed at medium rotation speed (7 rpm) with a lateral movement of upto ±7 mm on rectangular rock thin sections (long dimension <25 mm). The best surface for SEM-EBSD analysis of rock thin sections is obtained in two steps of BIBP. In step-1, cleaning of thin section is done for 5 minutes (1.5°/4 kV/1.5 mA). In step-2, polishing is done for 30 minutes (1.5°/4 kV/3 mA). BIBP following MFAL protocol yields very good SEM-EBSD data from hard and soft mineral phases in rocks that enable (a) determination of mineral slip systems, (b) kinematics and (c) EBSD data-based mapping of grain boundaries of soft mineral phases (like hornblende) for petrofabric analysis in a polymineralic rock, which has always remained a challenge from mechanically polished samples. It is concluded that the MFAL protocol saves more than 5 hours of sample preparation time over other sample preparation methods for SEM-EBSD studies.

Optimisation of maize picking mechanism by simulation analysis and high-speed video experiments

The performance of maize picking mechanisms directly affects harvesting quality and working efficiency. Numerous field experiments have been carried out to improving picking performance, but they have been restricted by factors such as high cost, the varieties of maize used and variable harvesting periods. Virtual simulation analysis was proposed as a replacement for field experiments to provide an accurate reference for optimising the picking mechanism. A finite element model of a maize plant and picking mechanism was established based on the experimental results and related data from the research literature. Its accuracy and reasonableness was verified by comparing the simulation results to the data obtained by an experiment using a high-speed camera. The coupling effect of the three main factors (rotational speed of the picking roller, edge angle of the picking board and feed-in speed) were investigated using simulations. The results revealed that the medium rotational speed for the picking roller reduced the damage incurred by maize during the picking process, while ensuring good harvesting efficiency and picking board edge angles in the range 13°–15° were optimal. Although reducing the feed-in speed could reduce damage to the maize, this was not the most prominent factor. Besides, the appropriate rotational speed of the picking roller to guarantee optimal working efficiency was investigated using power consumption experiments. The results of this study should be useful as a reference for the design, development, and optimisation of the maize picking mechanism.

Influences of Rotational Speed Variations on the Flow-Induced Vibrational Performance of a Prototype Reversible Pump Turbine in Spin-No-Load Mode

Abstract During the spin-no-load mode, vibrational performance of the reversible pump turbine is an important criterion for the evaluation of the operational performances of the power station. In the present paper, the influences of rotational speed variations on the vibrational performances of the whole unit (including the top cover, the upper, and the lower brackets) are experimentally investigated with discussions of their sources and propagation characteristics. According to the whole vibrational levels and the dominant frequencies of the vibration signals obtained at the top cover, the investigated cases with different rotational speeds could be divided into three partitions with their main characteristics given as follows. In the first partition (with low rotational speeds), the vibrational level is quite limited, and its source is the pressure fluctuation generated by the swirling vortex rope in the draft tube. In the second partition (with medium rotational speeds), the vibrational level gradually increases and its source is the mechanical aspects of the impeller rotation. In the third partition (with high rotational speeds), the vibrational level is prominent with a prominent swirling vortex rope in the draft tube and intensive rotor–stator interactions in the vaneless space (VS). For the vibrations of the upper and the lower brackets, the vibrations mainly originate from the mechanical aspects of the impeller rotation and the amplitudes of the dominant frequency also increase with the increment of the rotational speed. Finally, differences between the vibrational performances of the spin-no-load mode and the generating mode are discussed.

2-Stroke Scavenging in Conventional and Minimally-Modified 4-Stroke Engines for Heavy Duty Applications at Low to Medium Speeds

The transformation of a standard 4-stroke cylinder head into a torque-improved and gradually more efficient 2-stroke design is discussed. The concept with an effective loop scavenging via an extended inlet valve holds promise for engines at low- to medium-rotational speeds for typical designs of conventional 4-stroke cylinder heads. Calculations, flow simulations, and visualizations of experimental flows in relevant geometries and time scales indicate feasibility, followed by a small engine demonstration. Based on presumably long-forgotten and outdated patents, and the central topic of this contribution, an additional jockey rides on the inlet valve’s disk (facing away from the combustion chamber) and reshapes the in-cylinder flow into a reverted tumble. A quick gas exchange with a well-suppressed shortcut into the open exhaust is approached. For overall mechanical efficiency, the required charge pressure for scavenging is of paramount importance due to the short scavenging time and the intake’s reduced cross-section. Herein, still acceptable charging pressures are reported for scavenging periods equivalent to low or medium rotational speeds, as characteristic for heavy-duty applications. Using widely available components (charger, direct injection, variable camshaft angles) an increased engine efficiency is suggested due to the 2-stroke’s downsizing effect (relatively less internal friction as well as the promise of more torque and a decreased size).

Low frequency stall modes of a radial vaned diffuser flow

The present paper aims at providing an experimental analysis of the path to surge of a centrifugal compressor stage designed and built by Safran Helicopter Engines. Depending on the rotation speed of the compressor, two distinct flow patterns are observed in the radial diffuser at stabilized operating points near the surge, an asymmetric and a symmetric pattern. At medium rotation speed, the alternate pattern consisting of a two-channel pattern in the radial diffuser develops. One passage over two is stalled, the adjacent passage is free and this pattern replicates over the whole circumference while pulsing at a frequency of roughly 12 Hz which is close to the Helmholtz frequency of the test rig. By lowering the rotation speed, the two-channel pattern fades away and gives way to a periodical behavior of the radial diffuser passages called symmetric mode. The flow in each channel is identical presenting a stalled behavior pulsating in phase at a higher frequency of roughly 42 Hz. The two 12 Hz and 42 Hz modes are described and their existences are imputed to a lock-in of the natural frequencies of the instabilities with the acoustic modes of the test rig.

PIV experimental study on the flow field characteristics of axial flow blood pump under three operating conditions

In order to investigate the internal flow field of an axial blood pump, two-dimensional (2D) particle image velocimetry (PIV) was applied to test the blood pump under three different conditions. Acquiring the images of inlet, front guide vane, impeller, back guide vane and outlet area, the distribution of internal flow field was then analysed. The rotation speed of the blood pump was set to 6000, 7000 and 8000 r/min, respectively. The results show that the flow field of blood pump is stable relatively at the inlet area. Some vortices and reflux existed due to the block of guide vane in the import and impeller area. With the increase of rotating speed, the overall disturbance degree of flow field increases. Under the condition of low rotation speed, the flow field acceleration is insufficient. Under the medium rotation speed condition, the flow field is stable and the velocity distribution is even. Under the condition of high rotating speed, the number of vortices in the flow field increased significantly, the flow separation phenomenon at the impeller was obvious and more unstable flow appeared at the back guide vanes and outlet area.

Nonlinear characterization of the rotor-bearing system with the oil-film and unbalance forces considering the effect of the oil-film temperature

The nonlinear phenomena of the rotor-bearing systems, i.e., the oil whirl, oil whip, quenching and pulling out, due to the oil-film temperature are not yet clear. To characterize these phenomena, a mathematical model of the rotor-bearing system is proposed to consider the effect of the oil-film temperature using the revised Walther empirical equation. Bifurcation diagram, cascade spectrum, time history, phase portrait, power spectrum and Poincare section are employed to investigate the impacts of the rotational speed, oil-film temperature and rotor eccentricity on the stability of the rotor-bearing system. As the rotational speed increases, the system becomes unstable due to the oil whirl/whip. The oil whirl appears at the medium rotational speeds. In the middle of such speed range, it is suppressed by the synchronous vibration. Quenching and pulling out occur at the thresholds and end of the suppression, respectively. The oil-whirl range of the rotational speed increases with the oil-film temperature. Due to the existence of the oil whirl, the system undergoes period-2, period-3, period-4, period-5, period-6, period-8, quasi-periodic and chaotic motions. At the high rotational speeds, the oil whirl is replaced by the oil whip. The synchronous vibration of the bearing is suppressed as long as the oil whip appears. The oil whip dominates the system and leads to the severe vibrations. The oil whip range of the oil-film temperature increases with the rotational speed. The rotor eccentricity is prone to increase the stability of the system due to the fact that increasing synchronous vibration suppresses the oil whirl/whip.

CHARACTERISTICS OF AA7075-T6 AND AA6061-T6 FRICTION WELDED JOINTS

In this experimental study dissimilar materials of AA6061-T6 and AA7075-T6 having distinctive difference in physical and thermal properties were welded using continuous direct drive friction welding. High strength was achieved by high friction, upset pressure, low burn off length and medium rotational speed. Mechanical characterization and Micro structural behavior of the joint were given the paramount importance in this experimental analysis. The macro structure indicates that change in the direction of flow of grains perpendicular to the initial grain direction of the parent metal. Also the micro structural analysis at the interface zone showed the presence of eutectic particles that are formed as fragmented agglomerates.