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Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Rotational speed has an important influence on the performance of coating materials. The a-C:Ta composite coatings were prepared by controlling the substrate rotational speed during deposition process using PVD technique. The results showed that the coating transformed from dense structure to columnar structure. Due to the changes of deposition time and the vapor incident angle of the sputtering ions, the sp2 hybrid structure increased and the C–Ta bonds contents decreased as a function of the rotational speed, which led to the improvement of adhesion force. The average friction coefficient of the composite coatings did not fluctuate significantly for the amorphous carbon matrix and the transfer films formed during friction, while the wear rates were gradually increased. The sample at 0.5 rpm possessed the lowest wear rate, which was mainly associated with the cooperative behavior of the dense structure and the formation of TaC nanoclusters in the composite coating. [ABSTRACT FROM AUTHOR]

Rotational autofrettage is one of the new and potential methods for strengthening thick-walled hollow circular disks/cylinders against internal pressure, thermal gradient, and rotational speed in service. The method makes use of the centrifugal force resulting from the high speed rotation of the disk/cylinder to induce plastic deformation at its inner side. On subsequent unloading of the centrifugal force, beneficial residual stresses are set up in the disk/cylinder. In this article, the method of rotational autofrettage employed in the disks is optimized. The rotational autofrettage is treated for an elastic–perfectly plastic axisymmetric disk incorporating Bauschinger effect. The best rotational speed is estimated to accomplish the procedure of rotational autofrettage in the disk such that the maximum stress level induced in the disk is minimized upon loading in service. To minimize the hoop/equivalent stress in the rotationally autofrettaged disk during loading in service, a one-dimensional optimization procedure, internal halving method is used. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the development of techniques for the use of gears and their many shapes and types, the mechanical need for them has become great, especially in the use of them in the field of cars, and the most important of these types are bevel gears, as these gears are considered essential in differential gears. The use of differential gears in mechanics in general helps to reduce noise in the movement, but there must be vibration resulting from this movement, and accordingly, bevel gears and the effect of rotating gears on free vibration have been studied. Variable gears were used according to a simulation program and the study of the free vibrations that occur to them. The effect of rotational speed on the natural vibration greatly affects the transmission of movement in the car and increases the fault distortions that occur in the differential gearbox. The result shows the natural vibration reached at the speed of 5000 rpm, and the value of the vibration reached 3564.5 Hz, which is the highest value compared to the remaining speed. The distortion at a speed of 1,000 rpm. The process of rotation and natural vibration affects the deformations and stresses that get on the gears themselves. The natural vibration is greatly reduced when the number of clamping places for the differential gear is increased. Compared to the presence of two spinning tires, the vibration value reduced. At a rotating speed of 5000 rpm, it is known that increasing the rotational speed raises the value 3015.9 Hz with one tire revolution with one tire rotation, the huge strains influence the little gears in the differential gearbox. The greatest value of distortion is 0.00067 m at 5000 rpm, which is the largest value of deformation compared to the rest of the employed rotational rates with one tire revolution. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To minimize the energy consumption of contra-rotating propellers (CRPs), the optimal matched rotational speeds of the forward propeller (FP) and rear propeller (RP) of CRP are investigated based on the potential-based panel method. The optimal matching problem of a set of CRP405 is investigated. The open-water hydrodynamic performances of CRP405 with the FP and RP having the same rotational speed are calculated and the method is validated. The hydrodynamic characteristics of CRP405 with changing FP and RP rotational speeds are investigated. The cubic spline interpolation method is used to determine the equal thrust line at which CRP405 generates the target thrust while keeping the inflow velocity constant. A series of equal thrust points on the equal thrust line is selected for the analysis of the delivered power. The rotational speeds of the FP and RP corresponding to the minimal delivered power are the optimal matched rotational speeds of CRP405. The optimal matching calculations are carried out at different inflow velocities. The results show that, under the condition of a low inflow velocity, properly increasing the rotational speed of the FP and decreasing the rotational speed of the RP are the most direct and efficient ways to reduce the energy consumption and avoid the negative effect of the net torque of the CRP on the transverse stability. [ABSTRACT FROM AUTHOR]

The mixing and separating process of different-sized particles in a self-designed rotating drum were explored, where the glass beads were taken as particles. The power consumption of rotating drum under different operating parameters were measured. The results show that the particle separation is more evident when the drum is operated at high fill level, where the small particles surrounded by large particles are mostly observed. When the filling rate is low, it is unobvious for the particle separation of the similar size particles at different rotating speeds. The larger difference of the particle size, the more particle separation occurs. With the increasing rotational speed and fill level, the power consumption increases, while the power consumption is relatively less sensitive to the particle size ratio. [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) is extensively used due to its low processing temperature, cost, and fast operation. The objective of this is research is to determine the optimum rotational and welding speed for welding of Al/Cu butt joint by FSW. FSW is used to produce a butt joint of pure aluminum with pure copper under two conditions; as received, i.e., not annealed, and as annealed. FSW is examined under three different rotational speeds: 910 rpm, 1280 rpm, and 1700 rpm, and each rotational speed is examined at three different welding speeds 16 mm/min, 29 mm/min, and 44 mm/min. The axial and longitudinal welding force components are measured during the welding process. Tensile and hardness tests were done to evaluate the mechanical properties, and the microstructural properties were also examined by XRD, SEM, and an optical microscope. The results showed that the welding force increased and the axial force decreased as the rotational speed increased and the welding speed decreased. Voids, tunnels, and cavities are noticed in case of a low rotational speed and a high welding speed; however, almost defect-free structure obtained at the highest rotational speed examined, i.e., 1700 rpm and the lowest welding speed of 16 mm/min, in case of Al and annealed Cu joint, but in case of non-annealed copper, it was different. It can be concluded that there is an optimal combination between the rotational speed and the welding speed in order to obtain the optimum mechanical and microstructural properties of the Al–Cu-welded joints, and that speed is a function of the material conditions. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to propose a method for finding the maximum rotational speed of an inclined turntable at which the stability of the bearing oil film is maintained. Design/methodology/approach: The finite difference method was used to solve the Reynolds equation. Variation of bearing capacity of a tilted hydrostatic turret over time was determined. The combined effect of tilt and rotational speed of the turret on the oil film stability was also analyzed. Findings: When the turntable is operated at low speeds with only small angle of tilt, stability of the oil film is maintained. At lower rotational speeds, a smaller angle of tilt improves the bearing capacity and ensures stability of the oil film. Whereas, higher rotational speeds can have a considerable influence on the bearing capacity. Originality/value: The results demonstrate that the inclination or tilt of the turntable significantly affects the stability of the oil film. [ABSTRACT FROM AUTHOR]

This paper describes the MATLAB/Simulink realization of the DC motor speed control methods, namely field resistance, armature voltage and armature resistance control methods, and open-loop control system modeling for DC motor drives. [ABSTRACT FROM AUTHOR]

Rotating electrodes can effectively improve the processing performance of micro-electrical discharge machining (micro-EDM), but there is still a lack of systematic research on the specific effects of electrode rotation and rotational speed changes. In this paper, the effects of electrode rotation and rotational speed on the discharge channel, debris stress, and debris motion in micro-EDM were analyzed theoretically. An AISI304 sheet was used as the workpiece and helical tungsten carbide alloy as the electrode. The through-hole drilling experiments of micro-EDM were carried out at low and high discharge energy and different electrode rotational speeds. In terms of processing efficiency, the effects of electrode rotation and rotational speed on material removal rate (MRR), relative tool wear ratio (RTWR), and short circuit number were analyzed. The results show that MRR increases first and then decreases, RTWR and short circuit number decrease first and then increase. In the aspect of processing precision, the impacts of electrode rotation and rotational speed on taper angle and overcut were analyzed. The results show that the electrode rotational speed has little effect on the change of the taper angle. In addition, when the electrode rotational speed is small, there is no obvious change in overcut. When the speed is too high, the overcut increases obviously and shows a trend of continuous increase. Finally, by comparing the experimental results, the optimal electrode rotational speeds of micro-EDM with two kinds of discharge energy were determined. The final experimental results also verify the correctness of the previous theoretical analysis. [ABSTRACT FROM AUTHOR]

Submerged friction stir welding of magnesium alloys has not been well investigated to date. ME20M is an important lightweight magnesium (Mg) alloy with enhanced yield strength and heat resistance that merits further research. In this paper, submerged friction stir welding of the ME20M Mg alloy was carried out using different parameters for the underwater cooling. Defect-free weld joints were produced, and the macrostructure, microstructure, tensile properties, and hardness were investigated. The results show that by increasing the rotational speed, the grain size of the weld nugget increased, the tensile strength of the joint decreased, and the microhardness of the different weld zones decreased. The finest obtained grain size was about 3.5 µm in the weld nugget at a rotational speed of 1100 rpm. The highest tensile strength achieved was 183.2 MPa, which was ~ 76.32% of the base metal. The highest and lowest hardness values of the weld joint were obtained at rotational speeds of 1100 and 1600 rpm, respectively, in the weld nugget and heat-affected zones. [ABSTRACT FROM AUTHOR]

Accurate rotational speed determination for rotary machines tends to be allocated high priority in technical applications. In some cases, it is not easy to measure shaft speed directly. Vibration diagnostic tools can offer an alternative solution to the problem posed by direct rotational speed measurement. Using calculated spectra and cepstra can help to determine the rotational speed easily and accurately. This paper examines the comparison of the spectrum and cepstrum based methods in terms of their applicable ranges and rotational speed estimation accuracy. Most papers which present similar comparisons state that the speed of rotary machines can be determined better with cepstrum calculation. However, this argument does not entirely stand up to scrutiny. This paper explains how to calculate the possible speed estimation error which arises out of the resolution of the discrete output data produced by the methodologies. The novel hybrid speed estimation logic uses these equations to decide which method results in the most accurate output. Numerous vibration measurements were made to test the usability of this hybrid method. It was successfully tested on electromotive drive trains, as well as spark- and compression-ignition internal combustion engines with different cylinder numbers and arrangements. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] • Wave rotor is tried as pressure exchanger for supercritical carbon dioxide. • Unsteady pressure waves in wave rotor does not take high rim speed to do work. • Wave rotor reduce turbomachinery's rotational speed to 8 % and shaft work to 4 % • Wave rotor achieve comparable efficiency and size to turbomachinery. Supercritical carbon dioxide Brayton cycle is emerging as a solution to effective and clean power resources, and the pressure exchanger is a critical part of such cycle. While turbomachinery is the conventional technology of such pressure exchangers, it sustains high shaft work and suffers from especially high rotational speed, which is a key challenge. This work proposed a wave rotor for supercritical carbon dioxide pressure exchanger as an alternative technology of the turbomachinery. Numerical simulation results demonstrate that a wave rotor compresses and expands supercritical carbon dioxide with unsteady pressure waves, so it does not take a high rim speed to do the compression or expansion work like turbomachinery, and a low rotational speed and a low shaft work are available then. According to the design results for a practical compression ratio at 1.93 and a massflow rate at 2.30 kg/s, the wave rotor reduces the rotational speed to 8 % and the shaft work to 4 % of equivalent turbomachines, and the wave rotor has comparable efficiency and size to equivalent turbomachines. This work provides the special advantage and suitability of the wave rotor as a pressure exchanger of the supercritical carbon dioxide Brayton cycle. [ABSTRACT FROM AUTHOR]

The activity of wheel-throwing a ceramic vessel is governed by a number of physical forces. These are the rotational kinetic energy (expressed in terms of angular velocity and the moment of inertia) and manual pressures. Given the importance of the potter's wheel worldwide, and the frequently postulated socio-cultural meaning of wheel-throwing in particular, foundational research on the physics behind wheel-throwing has been under-represented, and there is a lack of understanding of the relationship between speed of wheel rotation, lifting speed and the orientation of clay pores or inclusions. The speed of rotation is highly relevant as different wheels can achieve different speeds. Thus, knowing the speed during manufacture may allow scholars to reconstruct the original device, manufacturing technique, and perhaps even the potter's level of skill. Two contrasting views can be found in the literature: a) there is a direct positive relationship between these variables, and that the angle of the inclusions/voids can therefore tell us about the wheel's speed at the time of making the pot and hence the device used; b) because pots are never thrown in one single motion, the angle of inclusions/voids is an averaging of all actions executed by the potter, and thus cannot provide meaningful inferences about speeds or device. Experiments with professional potters were devised to explore the relationship between these variables. They show that the interaction between the various physical forces, clay and potter is complex, leading to a large variance even within the work of a single potter, with finger pressure recognized as a major influencing variable. It is clear that angles of inclusions or voids cannot be used to project backwards to the wheel speed, lifting speed, skill level or device used. • Diagonal angle alignment of inclusions or voids identifies a vessel as wheel-thrown • Inclusion/void orientation does not allow retrospective deductions on wheel speed, lifting speed, the device used or a potter's skill • Inclusion or void orientation varies intra- and inter-potter • Finger pressure is most likely responsible for the steep inclusion or void orientation characteristic of wheel-throwing [ABSTRACT FROM AUTHOR]

Double groove ball-section ring is an important part of complex profiled-section rings and has been widely used in energy industries, and cold double groove ball-section ring rolling is a new plastic forming technology that can directly fracture seamless double groove ball-section rings with high-precision and high-performance. Because the speed parameters (including the rotational speed of driving roll and the feed rate of mandrel) affect the feed amount per revolution and play important roles in the stability of cold double groove ball-section ring rolling process and the quality of deformed double groove ball-section ring production, the effects of speed parameters on the variation of ring configuration and the variation of strain in cold double groove ball-section ring rolling process are investigated. The obtained results provide valuable guidelines for the selection of speed parameters in the practical cold double groove ball-section ring rolling process. [ABSTRACT FROM AUTHOR]

• Gas-liquid two-phase flows were studied in a centrifugal pump. • Effects of the rotational speed were thoroughly studied. • Hysteresis, head degradation, surging, and flow instabilities were considered. • The two-phase flow regimes were recorded and identified using a high-speed camera. • Increasing rotational speed leads to various improvements in two-phase pumping. This study presents experimental and numerical investigations on air-water flows in a centrifugal pump, extending our previous studies. The main objective of the present article is to examine the influence of rotational speed on pump performance. For that purpose, the pump performance was considered and extensively compared for two different rotational speeds, i.e., 650 rpm and 1000 rpm, covering different single and two-phase flow conditions. To allow flow visualization, the impeller and the pump body were manufactured from transparent materials, and a high-speed camera was employed for recording the two-phase flow regimes. The performance of the pump was illustrated and reported for either a constant gas volume fraction or a constant air flow rate at the pump inlet. The desired operating conditions at the inlet were achieved using various predetermined experimental procedures to study the performance hysteresis. Pump surging and breakdown conditions were also considered. Additionally, 3D URANS single-phase numerical simulations were performed to explain additional internal flow details. The moving-mesh approach combined with the k - ω SST turbulence model has been used for that purpose. The simulations agree well with the experiments in most cases. Overall, the results show that increasing the rpm enhances two-phase mixing, which leads to various and significant improvements regarding two-phase pumping performance. [ABSTRACT FROM AUTHOR]

With reductions in the pressure ratio of the fan and increases in bypass ratio of the turbofan in recent years, the engine windmilling and relight capability have attracted more and more attention in aviation safety. This paper proposes a combination of the speed model and CFD to examine the internal flow evolution of the wide-chord fan under the windmilling condition. Firstly, we establish a semi-empirical speed model for predicting the fan rotational speed of a high-bypass ratio turbofan at any flight Mach number and altitude based on the flow characteristics of a windmilling fan. The model can provide an initial windmilling airflow at the specified speed for subsequent CFD calculations to reduce the number of iterations. Then, a three-dimensional CFD model is proposed to obtain the operating boundary of the windmilling fan according to the direction of energy transfer between the fan and the airflow. The mechanisms of fan internal flow evolution and tip leakage flow when it operates at a constant speed line were analyzed. The results show that the work distribution profiles along the blade span exhibited self-similarity. The fan blade operated in both spanwise and chordwise mixed configuration. The flow moved gradually from compressor-like regions near the hub to turbine-like regions near the shroud, where the stirrer mode was the transitional stage between them during windmilling. When the rotor entered the windmilling, it operated at a significantly off-design angle of attack, that caused a large area of flow separation to occur near the pressure surface (PS) instead of on the suction surface (SS). The flow separation and loss gradually increased from the hub to the shroud. Meanwhile, the direction of tip leakage flow also changed, a streamwise vortex core was observed on the PS near the blade tip. The core mixed with the low-energy fluid on the PS, resulting in flow blockage, that changed the working profile of the rotor. As the mass flow rate increased to the turbine operating point, the intensity of interaction and influence area between the leakage flow and the main flow further increased, and the aerodynamic loss increased significantly. [ABSTRACT FROM AUTHOR]

Phase demodulation is arguably the most used technique for the estimation of the instantaneous angular speed from vibration signals measured on rotating machinery. Although phase demodulation offers a straightforward approach to determine accurately the rotation speed of a particular shaft in a rotating machine, it does have strict limitations that can hinder the estimation accuracy and its overall reliability. In general, phase demodulation relies on the presence of a single harmonic with a high signal-to-noise ratio for the full duration of the measured vibration signal. Such a precondition hinders its applicability for a generic speed estimation approach for rotating machinery. There are copious real-world scenarios where this requirement is not met, especially given the increasing complexity and dynamic operating range of rotating machines nowadays. In such complex rotating systems, the deterministic signals are not necessarily all harmonically related to a fundamental harmonic. The presence of crossing harmonic orders from non-synchronous rotating components or of lightly damped structural resonances can significantly skew the instantaneous phase demodulation. This paper proposes a novel approach towards phase demodulation by both incorporating multiple harmonics in the demodulation process and also giving the individual harmonic phases time-dependent weighting. This combination of incorporating multiple harmonics and weighting them allows for fully exploiting the information contained within the vibration signal while also promising to be more robust to changing operating regimes. The proposed multi-harmonic demodulation method is investigated thoroughly by assessing its performance on simulated data, on two benchmark experimental data sets, and on a large wind turbine vibration data set consisting of thousands of vibration measurements. • Multi-harmonic extension of standard single harmonic phase demodulation. • Maximum likelihood weighting of harmonics improves accuracy and ease-of-use. • Validation on simulated and experimental data sets. • Good performance on complex non-stationary machine vibrations. [ABSTRACT FROM AUTHOR]

This article presents a method for detecting rotational speed by LC (inductor-capacitor) wireless sensors. The sensing system consists of two identical LC resonant tanks. One is mounted on the rotating part and the other, as a readout circuit, is placed right above the rotating part. When the inductor on the rotating part is coaxially aligned with the readout inductor during rotation, the mutual coupling between them reaches the maximum, resulting in a peak amplitude induced at the readout LC tank. The period of the readout signal corresponds to the rotation speed. ADS (Advanced Design System) software was used to simulate and optimize the sensing system. A synchronous detection circuit was designed. The rotational speed of an electric was measured to validate this method experimentally, and the results indicated that the maximum error of the rotation speed from 16 rps to 41 rps was 0.279 rps. [ABSTRACT FROM AUTHOR]

The D2 wheel steel rolling wear experiment was carried out on a double-disc wear test machine. By observing the polygonisation wear of the sample surface, measuring the vibration frequency, and analyzing sample microstructure and properties, the effects of rotational speed on the polygonisation formation mechanism, microstructure and property evolution of a D2 wheel steel were studied within a certain speed range. The results indicated that polygonisation wear was the result of the coupling of vibration and wear. The dominant vibration frequency (f) was constant at the three rotational speeds studied, and was equal to the product of the rotational speed (ω) and polygonisation order (K), that is, f = 1 60 K ω. When the number of rolling cycles was the same, the sample surface became subject to more times vibration and impact as the rotational speed decreased. This increased the intensity of the wear, and the polygonisation wear began to occur faster. Conversely, the polygonisation wear caused the vibration and impact load to increase, and the coupling effect of wear and vibration increased, further aggravating the polygonisation wear. After polygonisation wear occurred, the degree of crest oxidation wear was reduced in relation to the decreasing rotational speed. The degree of trough fatigue wear was also aggravated, causing the polygonisation wear gap to become larger, while the mass wearing quantity increased significantly given the same number of rolling cycles. The thickness of the obvious plastic deformation layer, the microstructure refinement, and the change in hardness of the surface layer all increased with the intensification of polygonisation wear. • F is constant at a certain speed range, and is equal to the product of ω and K. • The polygonisation wear appears faster as the rotational speed decreases. • The crest oxidative wear increases gradually, trough fatigue wear decreases. • The polygonisation gap become larger and the mass wearing quantity increases. • Microstructure refinement and hardness change of the surface layer all increase. [ABSTRACT FROM AUTHOR]

This study aimed to explore the effects of drilling rotational speed and feed-rate on the stability of dental implants through in-vivo and ex-vivo experiments. To this end, a total of 16 identical dental implants were inserted in the mandible of four dogs. The osteotomies were made with two drilling rotational speeds, i.e., 800 and 1500 rpm, and two different feed-rates, i.e., 1 and 2 mm/s. Implant stability quotients (ISQs) were recorded immediately after inserting implants and then each week for four subsequent weeks. Then, all animals were euthanized, and a bone sample containing the implants was extracted from each hemi-mandible for the pull-out test. A two-way ANOVA was performed for ISQs, and pull-out strengths (PoS), and the significance level was set to <0.05. The effect of rotational speed and feed-rate, used in this study, on the primary stability quotients was not significant (P > 0.05). Increasing the rotational speed from 800 to 1500 rpm significantly increased both ISQ and PoS values at the end of the 4th week after the implantation (P = 0.022 and P = 0.001, respectively). Moreover, by decreasing the feed-rate from 2 to 1 mm/s, a significant increase in PoSs of the dental implants was observed four weeks after the implantation (P = 0.019). Results of this study showed that either by increasing drilling rotational speed, here from 800 to 1500 rpm, or by reducing feed-rate, here from 2 to 1 mm/s, the secondary stability would be reinforced. Further investigations are needed to see if and how the conclusions made in this study can be generalized. [ABSTRACT FROM AUTHOR]

In the process of impact-rebound, rockfalls with an initial rotational speed (RS) often undergo a violent transformation between rotational energy and translational energy, which may affect the coefficient of restitution (COR). However, owing to the complexity of experimental simulations and the influence mechanism, this issue is often neglected during research. Therefore, in this study, four representative blocks (ellipsoid, cylinder, cone with a spherical base, and disc) were selected, and impact tests of each block rotating around different axes with various RSs were conducted using a specially developed device. Based on the impact dynamics theory, the RS has no significant effect on the tangential COR (R t), while it may exhibit a positive correlation with the R t when the size of the block size is large enough. When the block rotates around the X-axis (approximately normal impact), there is no obvious relationship between the RS and the normal COR (R n). Conversely, when the block rotates around the Y-axis (often non-normal impact), the RS influences the R n , but it is difficult to determine in what manner and to what extent. Thus, to clarify the influence mechanism of RS on the R n for non-normal impacts, a comprehensive variable, the impact posture coefficient (IPC), which comprehensively considers the RS, block shape, and impact posture, was introduced, and the impact-rebound characteristics of the blocks were classified and discussed. Under the condition of bouncing after only one impact, the IPC and R n values exhibited a positive linear correlation when the block mass centre (C) is behind the contact point (CP), whereas the opposite behaviour was observed when the C is in front of the CP. Meanwhile, under the condition of bouncing after two impacts, the R n and IPC values had a positive linear correlation. These findings explain the influence mechanism of RS on the COR and provide a new idea for the accurate prediction of the impact-rebound processes of rotating irregular rockfalls. • Effect of rotational speed (RS) on coefficient of tangential restitution is not significant only for small size block. • For non-normal impact, RS does affect coefficient of normal restitution (R n) but it's hard to directly affect Rn alone. • Introducing impact posture coefficient to quantify the effect of RS on R n for non-normal impact. • Study on block's impact- rebound characteristics by classified discussion method. • Clarify the influence mechanism of RS on coefficient of restitution. [ABSTRACT FROM AUTHOR]

Copyright of Polimery is the property of Industrial Chemistry Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to predict the high-speed error motion of the porous journal air bearing, a new dynamic accuracy model is established based on the simplified nonlinear air film force considering the rotational speed. Then the effect of the speed on the accuracy is discussed by the same averaging coefficient of quasi-static condition for various shaft and bush roundness errors. It finds that the speed only affects the amplitude of the error motion but doesn't affect its frequency information. As the speed increases, the averaging coefficient increases, while its frequency information is kept the same. The accuracy decreases with the increase of the speed. The model provides a low-cost way to predict the high-speed error motion by the low-speed error motion. ● A new dynamic accuracy model of the porous journal air bearing is built based on the simplified nonlinear air film force. ● The effect of the speed on the error motion is studied by the same averaging coefficient of quasi-static condition. ● The speed only affects the amplitude of the error motion but doesn't affect its frequency information. ● As the speed increases, the value of the averaging coefficient increases, while its frequency information is kept the same. ● It provides a low-cost way to predict the high-speed error motion by the low-speed error motion. [ABSTRACT FROM AUTHOR]

The Discrete Element Method (DEM) was used to analyze the pelletization process of MgO-fluxed pellets. The effects of the charge ratio and rotational speed of the disc pelletizer on the behavior of MgO-fluxed pellets were investigated by using a simulation. The simulation results show that under the condition of a certain tilt angle of the disc pelletizer (the tilt angle is 49°), the suitable parameters of the disc pelletizer are that the charge ratio is 20% and the rotational speedis 0.7 N/NC. This simulation model proposed will be useful to research pellets behavior and for the design of disc pelletizers. [ABSTRACT FROM AUTHOR]

Samples of 6082-T6 aluminum alloy were welded by bobbin tool friction stir welding at different rotational speeds. The thermal cycles, microstructure, microhardness, and tensile properties of the specimens were investigated. The results show that the maximum temperature at the joint increases first and then decreases with increasing rotational speed, and the maximum temperature is 509 °C at 1000 r/min. The macromorphology of the cross-section of the joint is rectangular, and an ''S" line and gray-white texture can be observed. The stirred zone had much smaller equiaxed recrystallized grains. With increasing welding speed, the average grain size in the stirred zone region decreases. The microhardness distribution of the cross-section of all joints is W-shaped. When the rotational speed increases, the hardness of the heat-affected zone decreases gradually, and the hardness of the stirred zone increases. At 600 r/min, the strength is the lowest. The fracture location is between the stirred zone and the thermomechanically affected zone. When the rotational speed is increased, the fracture location is entirely located in the heat affected zone, and the fracture surface is dimple-like; the strength significantly increases and reaches a maximum at 800 r/min. [ABSTRACT FROM AUTHOR]