Input Rotational Speed Research Articles

Running Performance of a Squeeze Film Air Bearing with Flexure Pivot Tilting Pad

A novel flexure pivot tilting pad squeeze film air bearing (FPTP-SFAB) based on near-field acoustic levitation (NFAL) for a rotor is proposed in this article. The most important advantage of this structure is the suitability of the bearing for high-speed and light load conditions because the FPTP can adapt well to squeeze action during operation. The rotating orbit of the rotor can be adjusted according to the machining conditions. A theoretical model is employed to analyze the running characteristics of the rotor by using the coupled NFAL and FPTP model. Experiments were conducted to investigate the running performance of the rotor–bearing system. Moreover, the effects of input voltage, rotational speed, eccentricity ratio, radial clearance, vibration amplitude, and installation method on bearing performance were analyzed. Numerical and experimental results show that a rotor supported by the FPTP-SFAB with a reasonable input excitation magnitude can effectively adjust the rotating orbit of the rotor and inhibit the divergence of the rotor vibration amplitude, thus improving the stability of the rotor–bearing system under complicated and alternating machining conditions.

Influence of long-wave deviations on the quasi-static and dynamic excitation behavior at higher speeds

The scarcity of fossil fuels and increasing oil prices are among the factors that have led to a rising ownership of electric cars [1]. Noise reduction also plays a major role primarily in the drive train of motor vehicles. Noise and vibration excitation differ between a combustion engine and an electric motor. While the disturbing noises of auxiliaries, e.g. gear noise, have been largely masked by combustion engines, theses noises are no longer masked due to the use of electric motors [2]. Therefore, gear noise is perceived more pronounced. Considering the subjective perception and the excitation by rotational frequencies, that fall into the sensitive hearing range of high-speed gearboxes, the focus must be increasingly placed on manufacturing and assembly related long-wave deviations, such as wobble, pitch errors and eccentricities.This report investigates the effects of long-wave deviations of gears in gearboxes on the excitation and noise behavior. Quasi-static investigations were carried out to verify the influences of long-wave deviations on the long-wave excitation behavior. Therefore, the transmission error was measured, which describes the rotational fluctuation between input and output and represents the excitation.This investigation verifies according to the simulativ investigation by Brecher et al. that there is no transmission error dependency on the load [3]. In addition, this investigation proves the macro geometry-independent long-wave excitation in case of eccentricity. The reason for the invariant excitation behavior lies in the effective deviation in the gear mesh which in this case is independent of the mentioned parameters.In addition to the quasi-static tests, investigations of the structure-borne noise were carried out at higher speeds (input rotational speed up to nIn = 11,500 rpm). For these investigations, a two-stage gearbox with a test gear set was used and two different eccentricities and wobbles were manufactured. The analysis of these investigations confirm an increased excitation as a result of the deviations. Especially in natural frequency ranges, the excitation in the first rotational order is amplified by the considered long-wave deviations.The experimental results prove the importance of a function-oriented tolerance system for long-wave deviations, which lead to corresponding long-wave excitations. Furthermore, the findings constitute the first basis for the derivation of these tolerance limits.

Dynamic analysis of a helical gear reduction by experimental and numerical methods

Presented in this study is investigation of dynamic behavior of a helical gear reduction by experimental and numerical methods. A closed-loop test rig is designed to measure vibrations of the example system, and the basic principle as well as relevant signal processing method is introduced. A hybrid user-defined element model is established to predict relative vibration acceleration at the gear mesh in a direction normal to contact surfaces. The other two numerical models are also constructed by lumped mass method and contact FEM to compare with the previous model in terms of dynamic responses of the system. First, the experiment data demonstrate that the loaded transmission error calculated by LTCA method is generally acceptable and that the assumption ignoring the tooth backlash is valid under the conditions of large loads. Second, under the common operating conditions, the system vibrations obtained by the experimental and numerical methods primarily occur at the first fourth-order meshing frequencies and that the maximum vibration amplitude, for each method, appears on the fourth-order meshing frequency. Moreover, root-mean-square (RMS) value of the acceleration increases with the increasing loads. Finally, according to the comparison of the simulation results, the variation tendencies of the RMS value along with input rotational speed agree well and that the frequencies where the resonances occur keep coincident generally. With summaries of merit and demerit, application of each numerical method is suggested for dynamic analysis of cylindrical gear system, which aids designers for desirable dynamic behavior of the system and better solutions to engineering problems.

An Experimental Investigation on the Wear of Lubricated Steel Against PEEK Gears

Abstract The application of polymer gears in power transmission has been considered recently due to their advantages over metal gears, e.g., lighter weights and lower costs. Much further research work needs to be carried out to understand their wear mechanisms and to establish their design methods. This paper aims to investigate the wear and failure behavior of the poly-ether-ether-ketone (PEEK) gear against the steel gear under oil jet lubrication through the durability test with the standard FZG test rig. The service life and wear loss of PEEK gears were experimentally recorded under different moderate loading conditions ranging from the output torque of 10–20 Nm with a fixed input rotational speed of 1000 rpm. Moreover, the tooth surface morphologies and the wear loss of PEEK gears under different running stages were investigated. The experimental measurements reveal that there is a critical load magnitude for the transition of wear performance. With a load above 15 Nm, the PEEK gear wear rate increases rapidly, leading to a quick breakage failure, whereas the gear wear rate with a torque below 15 Nm is much lower. All tested PEEK gears finally failed with a pitting-induced tooth breakage mode under moderate loading conditions.

Harvesting Energy from Planetary Gear Using Piezoelectric Material

In the present study, a rotational piezoelectric (PZT) energy harvester has been designed, fabricated and tested. The design can enhance output power by frequency up-conversion and provide the desired output power range from a fixed input rotational speed by increasing the interchangeable planet cover numbers which is the novelty of this work. The prototype ability to harvest energy has been evaluated with four experiments, which determine the effect of rotational speed, interchangeable planet cover numbers, the distance between PZTs, and PZTs numbers. Increasing rotational speed shows that it can increase output power. However, increasing planet cover numbers can increase the output power without the need to increase speed or any excitation element. With the usage of one, two, and four planet cover numbers, the prototype is able to harvest output power of 0.414 mW, 0.672 mW, and 1.566 mW, respectively, at 50 kΩ with 1500 rpm, and 6.25 Hz bending frequency of the PZT. Moreover, when three cantilevers are used with 35 kΩ loads, the output power is 6.007 mW, and the power density of piezoelectric material is 9.59 mW/cm3. It was concluded that the model could work for frequency up-conversion and provide the desired output power range from a fixed input rotational speed and may result in a longer lifetime of the PZT.

Oil temperature influence on friction losses in silent chains

Evaluation of friction in chain drives is the first step in the process of reducing the friction. This paper presents the experiments on the analyses of temperature influence on friction in silent chains. A rig dedicated for friction measurements on parallel axes transmissions is used. Friction is measured as friction torque with possibility to control and measure the input rotational speed, chain tensioning, pressure and temperature of the oil for chain lubrication, pressure and temperature of the oil for bearings lubrication. Temperature depending viscosity of chain lubrication oil is measured separately. The functioning conditions of the bearings are maintained constant during the testing and only the temperature of chain oil lubrication is increased and then decreased in the range of functioning temperature of a timing chain. Oil temperature influence on friction from silent chains joints gives an image on the type of lubrication. The reduction of silent chain friction by reducing the functioning temperature may be a very simple solution and this paper shows how much power may be saved. Friction torque is measured for three distinct rotational speeds in the same tensioning parameters. Conclusions on the influence of rotational speed on friction losses with temperature are finally drawn.

Torsional Vibration and Bifurcation Characteristics of Automotive Main Reducer Based on Nonlinear Hybrid Model

In the view of integrating dynamics of systems with dynamics of structures, the pinion shaft of automobile main reducer is divided into several torsion rod elements to establish its dynamic model, while the torsional vibration dynamic model of hypoid gears is still built with lumped mass method, thus the hybrid dynamic model of automotive main reducer is obtained by the combination of two kinds of dynamic models. Considering the nonlinear factors such as time-varying mesh stiffness, backlash and static transmission error of gear pairs, Runge-Kutta method is applied to obtain the time domain spectrum, spectrum graph, phase-plane diagram, Poincaré maps, and bifurcation diagrams of the system. The dynamic response characteristics of system with different parameters such as input rotational speed and mesh stiffness are systematically investigated by numerical simulations.

Experimental evaluation of magnetic abrasive finishing process with diamond abrasive

Magnetic abrasive finishing (MAF) is one of the advanced finishing processes, in which, the work-piece is kept between two magnets and cutting force is controlled by the working gap and magnetic field. In this investigation, cylindrical surfaces of stainless steel were processed using MAF process to examine the percentage improvement in surface finish (PISF) and material removal rate (MRR). In order to complete the objective, four input process parameters (current, quantity of magnetic abrasives (MA), rotational speed, and percentage of diamond abrasives) were varied at different levels. Response surface methodology was adopted to investigate the significance of selected parameters. Further, mathematical models were proposed for response characteristics. Results exhibited that all the input parameters are significant for both the responses. The quantity of magnetic abrasives was found to have a major effect on PISF in comparison to the rotational speed. The minimum surface roughness value of Ra 17.7 nm was obtained.

Experimental evaluation of magnetic abrasive finishing process with diamond abrasive

Magnetic abrasive finishing (MAF) is one of the advanced finishing processes, in which, the work-piece is kept between two magnets and cutting force is controlled by the working gap and magnetic field. In this investigation, cylindrical surfaces of stainless steel were processed using MAF process to examine the percentage improvement in surface finish (PISF) and material removal rate (MRR). In order to complete the objective, four input process parameters (current, quantity of magnetic abrasives (MA), rotational speed, and percentage of diamond abrasives) were varied at different levels. Response surface methodology was adopted to investigate the significance of selected parameters. Further, mathematical models were proposed for response characteristics. Results exhibited that all the input parameters are significant for both the responses. The quantity of magnetic abrasives was found to have a major effect on PISF in comparison to the rotational speed. The minimum surface roughness value of Ra 17.7 nm was obtained.

Effect of two-phase flow on transmission torque of oil film at high rotational speeds

PurposeThe purpose of this paper is to study the working characteristics of hydro-viscous clutch at high rotational speeds and obtain the trend of flow field variation of oil film.Design/methodology/approachThe FLUENT simulation model of the oil film between the friction disks is built. The effect of variation of working parameters such as input rotational speed, oil flow rate and film thickness on two-phase flow regime and transmission torque is studied by using the volume of fluid model.FindingsThe results show that the higher the rotational speed, the severer the cavitation is. In addition, the two-phase flow region makes the coverage of oil film over the friction pairs’ surface reduce, which results in a decrease in transmission torque for the hydro-viscous clutch.Originality/valueThese simulation results are of interest for the study of hydro-viscous drive and its applications. This study can also provide a theoretical basis for power transmission mechanism of oil film by considering the existence of a two-phase flow regime consisting of oil and air.

Analysis of influencing factors on oil film shear torque of hydro-viscous drive

PurposeThe hydro-viscous drive (HVD) has been widely used in fan transmission in vehicles, fans, and scraper conveyors for step-less speed regulating and soft starting. It is an efficient method to save energy and reduce consumption. This study aims to analyze the influencing factors of oil film shear torque accurately.Design/methodology/approachThe shear torque calculation model of double arc oil groove friction pairs was established. The influence of groove structure parameters on shear torque was analyzed. The interaction between viscosity temperature and shear torque was considered. Meanwhile, the equivalent radius was calculated when the rupture of oil film appeared. Finally, the test rig of torque characteristics was set up. The variance of shear torque with the input rotation speed under different oil film thickness, different oil temperature, and different flow rate was seen.FindingsThe results show that the shear torque increases with the growth of rotation speed. However, the increase of torque is quite gradual because of the effect of the change of viscosity, which is caused by the rise of temperature. The shear torque increases with the decrease of thickness, the increase of inlet flow rate, and the decrease of inlet oil temperature. Meanwhile, when the feeding flow rate is less than the theoretical, the oil film gets ruptured and the shear torque decreases sharply.Originality/valueThe influence on shear torque during full film shear stage in HVD can be achieved much more accurately through both experimental research and theoretical modeling in which groove parameters, influence of temperature, and oil film rupture are considered. Therefore, the shear torque of HVD can be predicted by theoretical model and experimental research in full film shear stage.

Multibody dynamic analysis of a gear transmission system in electric vehicle using hybrid user-defined elements

Considering flexibility of the support shafts as well as bearing supports, the effect of meshing impact force and meshing stiffness on the dynamic behavior of a gear transmission system in electric vehicle is investigated in this paper using the proposed hybrid user-defined element method. First, a structured grid generation method is introduced to establish accurate mesh models of the pinion and gear teeth. Second, coupling the tooth mesh models and the flexible shafts as well as bearings, two finite element models are, respectively, constructed for the two helical gear pairs of the electric vehicle reduction unit to calculate the meshing impact force. Next, the basic mechanism of meshing impact is explained in detail according to the finite element results, and the impact force is determined as one of the main internal excitations substituted into the dynamic model established by the hybrid user-defined element method. Under 50 N m input torque and 12,010 r/min rotational speed of the input shaft, the simulation results by the hybrid user-defined element method indicate that the example system reaches a steady state and the vibrations primarily occur at the meshing frequencies. With an increment of 600 r/min of the input rotational speed, it is also concluded from the results that (1) the calculated impact force approximately presents linear growth with the increase of the input shaft rotational speed and (2) the root mean square values of the vibration acceleration generally grow with the increase of the speed.

Research on the sliding friction associated spur-face gear meshing efficiency based on the loaded tooth contact analysis.

In order to solve the problem of Meshing Efficiency of spur-face gear sliding friction, a method for calculating the Meshing Efficiency of Spur-Face gear is proposed based on Elastohydrodynamic lubrication (EHL) theory. Through the Tooth Contact Analysis (TCA) and Loaded Tooth Contact Analysis technique (LTCA) method, the meshing process of the Spur-Face gear was simulated. The calculation model of Sliding friction coefficient was established by using non Newtonian quasi steady thermal Elastohydrodynamic lubrication (TEHL) theory, and the calculation model of Meshing Efficiency of Spur-Face gear was established. The influence of input torque and rotational speed on Meshing Efficiency is analyzed. The results show that Sliding friction coefficient is an important factor affecting the Meshing Efficiency of gears. Sliding friction coefficient is not the same at different positions of the tooth surface. Sliding friction coefficient is affected by input speed and input torque. This method provides a theoretical basis for further optimization calculation of Spur-Face gear.

On the benchmarking of friction in timing chains

This paper is dealing with the evaluation of friction in timing chains. Benchmarking friction is based on the experimentally determined friction losses in basic chain drives with transmission ratio i=1. This friction is not including friction losses in bearings. These results should be used, in the simplest manner, in order to evaluate friction in timing chains (i = 2). We are presenting the theoretical approach and experimental validation that have been developed for the timing chain drives, with transmission ratio i = 2. Friction losses are presented as resistant friction torques at the input shaft, depending on input rotational speed and tensioning force in the chain drive.

Dynamic modeling and response of a spur planetary gear system with journal bearings under gravity effects

This paper focuses on the modeling method and the gravity-induced dynamic response of a spur planetary gear system with journal bearings. The lumped-parameter model of a planetary gear system with journal bearings is established. Both contact on drive-side and back-side of the tooth are considered simultaneously. Linear and nonlinear bearing force models are introduced into the system model separately to take the planet bearing oil-film forces into account. A demonstration is given to show the adopted nonlinear oil-film force model is still valid for the lubrication of support for planet gears. Equilibrium positions of the planet gear are depicted under different input rotational speeds and input torques. Under gravity effect, system responses at different rotational speeds are calculated by employing Newmark integration; tooth wedging at ring-planet meshes is examined with different backlashes. The system responses are presented as vibration spectra, planet bearing forces, orbits of members, tooth forces, and the percentage of tooth wedging in one carrier cycle. The results show that the gravity effect dominates the response at low rotational speeds. The linear bearing force model is not valid in some cases. The fluctuation of the bearing force and the enlargement of the planet orbits are induced by gravity effect. Tooth wedging is the combined effect of gravity, centrifugal force, and planet bearing clearance.

Prediction of centrifugal pump performance using energy loss analysis

In this work, a theoretical procedure has been developed to calculate the performance of a centrifugal pump using theoretical and empirical internal and external energy loss equations. These equations were implemented in the prediction program allowing the calculation of head, power and efficiency of the pump for varying input geometries, rotational speeds and fluid properties. The prediction program was tested for two centrifugal pumps of different impeller geometries handling either water or viscous fluids with different viscosities, at varying rotational speeds. Two different experimental rigs with different impeller geometries were used to generate experimental data. In the first rig, one impeller geometry was considered and data were obtained for three rotational speeds. In the second rig two different impellers of different geometries were also tested at different speeds. In both rigs, the centrifugal pump is composed of the two essential elements, namely the impeller and the casing. Good agreement was achieved when both predicted and experimental results were compared for all impeller geometries and rotational speeds considered.

Fundamental Investigation of Ultrasonic Assisted Pulsed Electrochemical Grinding of Ti-6Al-4V

Aiming at the development of a novel grinding technology for the highly efficient machining of difficult to machine materials such as Ti-6Al-4V, an ultrasonic assisted pulsed electrochemical grinding (UAECG) method was proposed. The current work is to reveal the fundamental grinding characteristics of the UAECG of Ti-6Al-4V by experimentally investigating the effect of vibration amplitude on grinding forces, actual material removal and work-surface roughness under different process parameters such as the input voltage and rotational speed. Summarizing the obtained results revealed that the grinding forces in UAECG are significantly smaller than those in conventional grinding (CG).

A method for detection and quantification of meshing characteristics of harmonic drive gears using computer vision

A lack of accurate description of the meshing characteristics and the corresponding frictional mechanism of the harmonic drive gear has limited progress toward modeling the hysteresis stiffness. This paper presents a method for detection and quantification of the meshing characteristics of the harmonic drive gear based on computer vision. First, an experimental set-up that integrates a high speed camera system with a lighting system is developed, and the image processing is adopted to extract and polish the tooth profiles of the meshed teeth pairs in each acquired video sequence. Next, a physical-mathematical model is established to determine the relative positions of the selected tooth pair in the process of the gear engagement, and the combined standard uncertainty is utilized to evaluate the accuracy of the calculated kinematics parameters. Last, the kinematics analysis of the gear engagement under the ultra-low speed condition is performed with our method and previous method, and the influence of the input rotational speed on the results is examined. The results validate the effectiveness of our method, and indicate that the conventional method is not available in the future friction analysis. It is also shown that the engaging-in phase is approximately a uniform motion process, the engaging-out phase is a variable motion process, and these characteristics remain unchanged with the variation of the input rotational speed. Our method affords the ability to understand the frictional mechanism on the meshed contact surfaces of the harmonic drive gear, and also allows for the dynamic monitoring of the meshing properties.

Tension control of wire rope in winch spooler using magneto rheological brake

While operating conventional spooler system in heavy industries such as winch reel and cranes, wire rope tangling and twisting leads wire aging with short life cycle and entangling occurs catastrophic damage to the whole system. The aim of this work is investigating a tension control system using a magneto rheological brake (MRB) to provide back tension to prevent frequent part changes and fatal malfunction. In order to achieve this aim, a basic MRB is first designed and analyzed using finite element method (FEM) with electromagnetic field and fluid analysis are performed. As second step, a prototype of the an MRB is fabricated with the optimized structural parameters and experimental apparatus is constructed. Moreover, output torque characteristics of the designed MRB with the various input current and rotational speed are evaluated. Consequently, a conventional proportional-integral-derivative (PID) controller is designed for a tension control, and the control results show the feasibility for tension control of winch spooler system.

Dynamic response of a carbon nanotube-based rotary nano device with different carbon-hydrogen bonding layout

In a nano rotational transmission system (RTS) which consists of a single walled carbon nanotube (SWCNT) as the motor and a coaxially arranged double walled carbon nanotube (DWCNT) as a bearing, the interaction between the motor and the rotor in bearing, which has great effects on the response of the RTS, is determined by their adjacent edges. Using molecular dynamics (MD) simulation, the interaction is analyzed when the adjacent edges have different carbon-hydrogen (CH) bonding layouts. In the computational models, the rotor in bearing and the motor with a specific input rotational speed are made from the same armchair SWCNT. Simulation results demonstrate that a perfect rotational transmission could happen when the motor and rotor have the same CH bonding layout on their adjacent ends. If only half or less of the carbon atoms on the adjacent ends are bonded with hydrogen atoms, the strong attraction between the lower speed (100GHz) motor and rotor leads to a synchronous rotational transmission. If only the motor or the rotor has CH bonds on their adjacent ends, no rotational transmission happens due to weak interaction between the bonded hydrogen atoms on one end with the sp1 bonded carbon atoms on the other end.