Ring Friction Research Articles

A Method for the Design of Ring Dampers for Gears in Aeronautical Applications

In order to reduce the resonant vibration of thin walled gears used for aeronautical applications, friction ring dampers may be added to the gear. In order to design the damper geometry, engineers must be able to evaluate its effect on the dynamics of the gear. In this paper a method for the calculation of the forced response of gears with friction ring dampers for aeronautical applications is proposed for the first time. The gear and the damper are modeled by means of the finite element method (FEM) and they are coupled by means of contact elements, characterized by tangential and normal contact stiffness. The periodical response of the system is computed in the frequency domain by means of the harmonic balance method. The harmonic excitation is calculated by means of the Fourier analysis of the periodic force profile acting on the gear teeth. The methodology is applied to a case of industrial interest. The effect of the principal design parameters of the ring damper is highlighted.

Analysis of the Pressure and Carrying Capacity of the Friction Pair Fluid-Film for the High Parameter Bellows Mechanical Seal

In this research, by based on the computational fluid dynamics (CFD) numerical theory, using the Standard-Turbulence model and the Standard-Wall function, the fluid-film between the clearance of the sealing ring friction pair for the bellows mechanical seal under such the high-temperature, high-pressure, high-speed as complex working conditions was numerically simulated, the pressure fluid and the relationship of the carrying-capacity of the fluid-film between the pressure inlet of seal cavity and the width of the fluid-film, and the results of the numerical analysis was compared with the theoretical value. The researching results provide the scientific basis for the optimization designing of the high parameter bellows mechanical seals.

A Study of the Effects of Biofuel Use on Piston Lubrication During Fuel Post Injection in a Direct Injection Diesel Engine

The reduction of both exhaust gases and carbon dioxide emissions is necessary to meet future emissions regulations for diesel engines. Exhaust after-treatment devices are gradually being applied to diesel engines to reduce exhaust gases. Diesel particulate filters (DPF), an after-treatment device for diesel engines, in some cases require fuel post injection for regeneration. Post injection is usually conducted at the midpoint of the expansion stroke, and therefore causes fuel adhesion to the cylinder wall. However, using biofuels in a diesel engine is an effective way of reducing carbon dioxide emissions. It is well known that biofuels are chemically unstable, but the effects of biofuels on piston lubrication condition have not been thoroughly studied. In this study, piston lubrication condition during post injection in a single cylinder DI diesel engine using biofuel was investigated. Piston and ring friction forces were measured under engine operating conditions by means of a floating liner device to investigate the lubrication condition of the piston and rings. Both light fuel oil and biofuel were used in the measurements, with rapeseed methyl ester (RME) being used as the biofuel. Lubricating oil on the cylinder wall was also sampled under engine operating conditions, and the effect of post injection on fuel adhesion to the cylinder wall was analyzed. It was found that the effect of post injection on fuel adhesion to the cylinder wall was remarkable around the top dead center (TDC), and the fuel dilution rate reached approximately 90%. The results of the measurement of the piston friction forces showed that post injection caused an increase in the friction forces at the compression TDC (CTDC) in the cases of both RME and light fuel oil, and the friction forces at CTDC increased according to the delay of the post injection timing. The increase in the piston friction forces was moderate in the case of RME. It seems that the higher viscosity and the oiliness of RME suppressed the increase in piston friction forces at TDC. The following effects were found in this study. Fuel post injection caused fuel adhesion to the cylinder wall. Such phenomena affected the lubrication condition of the piston. In the case of RME, the increase in the piston friction forces caused by post injection was smaller than that of light fuel oil, but the effects on piston lubrication condition in the case of using other biofuels needs to be investigated.

The Analysis of Stiffness Condition in Rolling Thin-Walled Ring

The thin-walled ring rolling, a new rolling process, can produce the thin-walled rings that the traditional methods are difficult to process. It has the advantages of simple equipment, low investment and high productive. According to the mechanics analysis of the multiple rollers rolling, it established a mechanical model of small deflection bending compression rod. After solved the mechanics equations, it obtained the thin-walled ring’s rolling stiffness condition. From the theoretical formula, it could find that the increase of friction coefficient, ring radius, roller radius and feed per rotation were disadvantage for the thin-walled ring rolling stiffness condition. However, the increase of the ring cross sectional inertia was advantage for the stiffness condition. The theoretical formula could provide theoretical basis and guidance for the quantity design of roller pairs in rolling machine, design of ring cross section shape and selection of ring raw material.

Applying the friction ring test on a micro and meso scale

This study analyses the friction between a micro/meso part and a tool using the friction ring test. Four different materials were analysed, SAE1020 steel, AISI304 stainless steel, AA6531 aluminium and C34000 brass. Compression tests were performed on the four materials to determine the material flow stress curves of two different test specimen sizes and look at the size effect on the compression test. Three different ring sizes in four different materials analysed were used for the friction ring tests, applying molybdenum bisulphide-based lubrication. Based on the results of the flow stress curves, the calibration curves were performed with the SIMUFATC software for each material and size of friction ring using the Amontons-Coulomb friction model. The results of the experiments indicate a reduction in friction as the part becomes smaller, and the factor material influences the reduction of friction between the part and the tool.

Enhanced tribology properties of ZnO/Al2O3 composite nanoparticles as liquid lubricating additives

Monodispersed and hydrophobic ZnO/Al2O3 composite nanoparticles are prepared by a nonhydrolytic sol–gel method. ZnCl2 and AlCl3 are dissolved in acetone and used as precursors. Oleic acid is adopted as an oxygen donor. The tribology properties of the prepared ZnO/Al2O3 composite nanoparticles are studied by the four-ball friction and thrust ring friction test. It is demonstrated that the average friction coefficient and the wear scar diameter are reduced by 37.5 and 26.2%, respectively, in comparison with pure lubricating oil. Moreover, the ZnO/Al2O3 composite nanoparticles bear the merits of ZnO and Al2O3 when used as lubricant additives, exhibiting both excellent antifriction and antiwear behaviors simultaneously. The ZnO/Al2O3 composite nanoparticles improve the lubrication effect not only by turning the sliding friction into rolling friction, but also forming a hard Al2O3 protective film onto the thrust-ring surface containing ZnO/Al2O3 nanoparticles, which have much potentiality in industrial applications.

Simulation of passenger car synchronizer ring movement during rattling

This article presents a model for the calculation of the hydrodynamic forces and vibration behaviour of a passenger car synchronizer ring during rattling, i.e. a ring which is excited by rotational speed irregularities and therefore moves within its functional clearance. The hydrodynamic forces are calculated on basis of the Reynolds equation for thin fluid films. An analytical solution and a numerical one of the Reynolds equation are presented for both dry and mixed frictions. The oil-slung-out effect in the synchronizer ring gap is also taken into account in the solution. For the simulation, a multi-body system of the gearbox inner parts and a finite element model of the gearbox housing have been developed. The simulation results show the synchronizer ring movement, oil film thickness, and oil pressure distribution at different torsional excitation levels. The influence of different oil viscosities, the maximum oil film thickness, and wear of the synchronizer ring friction lining is investigated in parameter studies. Finally, the simulation results are validated by experimental measurements on an automotive transmission rattle test bench with a single-stage gearbox. The measurement results show that the developed model is capable of representing the principal characteristics of a synchronizer ring during rattling.

Steel research int. 3/2010

Cover Photo: Sheet Cast Disc: light‐weight brake disc in composite design; its friction ring is still made of cast iron but the disc pot is an insert of a high‐strength steel sheet. This steel design ensures not only reduction in weight but also reduction in thermal distortion, which results in improved driving comfort and fuel consumption. 2009 Steel Innovation Prize by the German Steel Industry Association. Copy by courtesy of Sheet Cast Technologies GmbH, München, and Stahl‐Informations‐Zentrum, Düsseldorf.

A Study of an Earthworm Type Inspection Robot Movable in Long Pipes

This paper describes development of a three somites earthworm type mobile inspection robot which is able to move in long pipes. We have many small diameter pipes which are gas or water pipes for individual or corporate houses and boilers or hot water pipes for industries. They are settled in the ground horizontally or in the narrow spaces vertically and some of them are covered by casings or hard heat insulating matters. It is very difficult to inspect from out of the pipes. If we can insert a mobile inspection robot into the pipes from the suitable position, we are easy to inspect the pipes. Authors fabricated a three somites earthworm type mobile inspection robot in which we use three rubber bellows as pneumatic actuators. Sixteen rubber friction rings are used to get friction force between pneumatic actuators and the pipes. The electromagnetic valves and air-feeding tubes for the pneumatic actuators are carried on trolleys in order to decrease friction force between the pipes and them. The fabricated three somites earthworm type mobile inspection robot can move in a pipe which is 78 mm in inner diameter and vertical pipe carrying a load that is equivalent to the air-feeding tube of 32 m length. Consequently, the inspection robot was confirmed to move in the long pipes.

Forced Response Analysis of Integrally Bladed Disks With Friction Ring Dampers

This paper investigates a damping strategy for integrally bladed disks (blisks) based on the use of friction rings. The steady-state forced response of the blisk with friction rings is derived using the so-called dynamic Lagrangian frequency-time method adapted to cyclic structures with rotating excitations. In addition, an original approach for optimal determination of the number of Fourier harmonics is proposed. In numerical applications, a representative compressor blisk featuring several rings is considered. Each substructure is modeled using finite-elements and a reduced-order modeling technique is used for the blisk. The efficiency of this damping technology is investigated, and friction dissipation phenomena are interpreted with respect to frequency responses. It is shown that the friction damping effectiveness depends mainly on the level of dynamic coupling between blades and disk, and on whether the dynamics features significant alternating stick/slip phases. Through parameter studies, design guidelines are also proposed.

Effect of Piston Friction on the Performance of SI Engine: A New Thermodynamic Approach

Abstract This paper presents thermodynamic analysis of piston friction in spark-ignition internal combustion engines. The general effect of piston friction on engine performance was examined during cold starting and normal working conditions. Considerations were made using temperature-dependent specific heat model in order to make the analysis more realistic. A parametric study was performed covering wide range of dependent variables such as engine speed, taking into consideration piston friction combined with the variation of the specific heat with temperature, and heat loss from the cylinder. The results are presented for skirt friction only, and then for total piston friction (skirt and rings). The effect of oil viscosity is investigated over a wide range of engine speeds and oil temperatures. In general, it is found that oils with higher viscosities result in lower efficiency values. Using high viscosity oil can reduce the efficiency by more than 50% at cold oil temperatures. The efficiency maps for SAE 10, SAE 30, and SAE 50 are reported. The results of this model can be practically utilized to obtain optimized efficiency results either by selecting the optimum operating speed for a given oil type (viscosity) and temperature or by selecting the optimum oil type for a given operating speed and temperature. The effect of different piston ring configurations on the efficiency is also presented. Finally, the oil film thickness on the engine performance is studied in this paper.

Effect of La2O3 on microstructure and sliding wear properties of TiC4 ceramic coating produced by electrical discharge method

The method of electrical discharge coating with TiC4 ceramic layer in an ordinary electrical discharge machining (EDM) tool was studied. TiC4 ceramic layer was deposited on No. 45 carbon steel substrate by EDM technique. TiC4 ceramic coatings with different contents of lanthanum oxide were fabricated on No. 45 carbon steel substrate. The microstructures of the clad coatings were examined and tested for chemical composition, phase structure, friction and wear properties. Scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, hardness testing, block on ring friction and wear testing were carried out separately. Experimental results show that TiC4 ceramic coating can be deposited on a substrate of carbon steel, and the electrode doped with rare earth lanthanum oxide helps to refine coating’s microstructure and enhance the coating’s density. When the content of lanthanum oxide is increased to 0˙5%, the clad coating shows the best antiwear ability, wear resistance can be increased by three times and the friction coefficient can be decreased by 10%. If the content of lanthanum oxide exceeds that proportion, the coating’s wear resistance decreases significantly.

Hairiness of spun yarns and their reduction using air-nozzle in winding

Using ring, rotor, air-jet, and open-end friction spinning, viscose yarns of same count were spun and compared for hairiness in terms of types of hair and hair-length distributions. Hair-length distributions present on as-spun yarns, regular wound yarns, and yarns wound passing them through an air-vortex nozzle were obtained using microscope and instrument. Hairiness of Dref-II yarn is the maximum followed by ring, air-jet, and rotor yarns. Rotor and Dref yarns have higher proportion of looped hairs followed by air-jet and ring yarns. Contribution of looped hair to hairiness is predominant followed by leading or trailing hair. Smaller hair (class interval of 0–1 and 1–2 mm) are major contributors to the total number of hairs on all the yarns. Hairiness of all these yarns increases by winding without the nozzle and hairiness decreases by winding with nozzle and this is found for all types of hairs. The total number of hairs ≥ 3 mm (i.e. S3 values) for nozzle-wound yarns is about 16–30% less than that observed for the corresponding spun yarns. When many hairs are present on the yarns before feeding into the nozzle, a higher percentage reduction in hairiness is achieved by nozzle-winding. An empirical equation has been proposed based on exponential distribution to characterize the hair-length distribution present on various yarns. The number of longer hairs counted by the instrument is higher compared to that estimated by the equation and opposite is the case for the shorter hairs.

Qualitative analysis of forced response of blisks with friction ring dampers

A damping strategy for blisks (integrally bladed disks) of turbomachinery involving a friction ring is investigated. These rings, located in grooves underside the wheel of the blisks, are held in contact by centrifugal loads and the energy is dissipated when relative motions between the ring and the disk occur. A representative lumped parameter model of the system is introduced and the steady-state nonlinear response is derived using a multi-harmonic balance method combined with an AFT procedure where the friction force is calculated in the time domain. Numerical simulations are presented for several damper characteristics and several excitation configurations. From these results, the performance of this damping strategy is discussed and some design guidelines are given.

Simulated fuel dilution and friction-modifier effects on piston ring friction

Government legislation, customer requirement, and pressure from the original equipment manufacturers (OEM) continually pushes the issue of increased vehicle fuel economy to the forefront. Lubricant manufacturers responded by creating low viscosity lubricants with complex additive packages capable of reducing total engine friction while maintaining the useful life of the engine. An important component in the lubricant additive package is the friction modifier, whose job is to reduce the sliding friction of components operating in the boundary lubrication regime. It is widely agreed that 40-60 per cent of mechanical friction can be attributed to the piston/ring/cylinder wall interface, much of which is as a result of the compression ring whose lubrication is kept purposely minimal to control exhaust emissions. A logical progression to research suggests utilizing fuel to administer friction modifier directly to the top ring zone of the engine, the area where its effects are most beneficial. This article describes a series of tests conducted using a Plint TE-77 reciprocating tribometer to investigate the synergy of lubricant and fuel containing friction modifier at the top ring zone. A computational model has been modified and utilized to further investigate the potential impact of administering friction modifier at the top ring zone via the fuel.

Modeling and Fabrication of a Mobile Inspection Microrobot Driven by a Pneumatic Bellows Actuator for Long Pipes

This paper details the modeling and fabrication of an in-pipe mobile inspection microrobot able to move long distances on small diameter pipes using pneumatic and vacuum pressure switched by an electromagnetic valve for driving the microrobot. We propose that the electromagnetic valve be used near the pneumatic actuator to move the distance. A pneumatic pressure of +300kPa and vacuum pressure of -80kPa are supplied to the electromagnetic valve by two air tubes 140m long. The microrobot with four friction rings at both ends of the actuator moves 20m in 15 minutes on vinyl chloride pipe with an inner diameter of 44mm.

Analysis of Spun Yarn Failure. Part II: The Translation of Strength from Fiber Bundle to Different Spun Yarns

A generalized mathematical model has been developed for predicting the strength of spun yarns produced by ring, rotor, air-jet and open-end friction spinning systems. The model is based on the translation of fiber bundle tenacity into the yarn tenacity and it is applicable to all spun yarns. The model describes the failure behavior of spun yarns. Experimental strength results are compared with the predicted ones on the basis of theory, and a satisfactory agreement is reached. The limitations of the model are also analyzed.

Stress–strain characteristics of different spun yarns as a function of strain rate and gauge length

The influence of strain rates and gauge lengths on the characteristics of the stress–strain curves of ring, rotor, air-jet, and open-end friction spun yarns is investigated. A modified form of Vangheluwe's model is used in describing the stress–strain characteristics of spun yarns. The proposed model can fairly well replicate these characteristics.

837 空気圧とバネを用いた三体節式ミミズ型管内走行ロボット(G15-3 生物模倣型移動ロボット,G15 ロボティクス・メカトロニクス)

This paper describes a prototype of a new in-pipe mobile robot. A fabricated robot is structured by three rubber bellows, lots of friction rings, three springs and three electromagnetic valves. A robot is driven by pneumatic pressure and elastic force of spring. The pressure is switched by the electromagnetic valve. The pneumatic pressure is used to expand and the elastic force is used to contract the rubber bellows. The friction rings converts the expansion and contraction movement into the advancement drive. Consequently, the in-pipe mobile robot moves freely in the pipe and robot generates the traction force of 90N.

10405 空気圧とバネを用いた管内マイクロロボットの走行特性(メカトロニクス(2))

This paper describes a moving characteristics of in-pipe mobile microrobot driven by pneumatic pressure and elastic force of a spring. This robot consists of a bellows actuator and friction rings of robot's foot. The bellows actuator is structured by rubber bellows and spring which is inserted in the bellows. The pneumatic pressure is used to stretch and the spring is used to shrink an actuator of the microrobot. The friction ring converts the stretch motion and shrink motion into the advancement drive. We confirmed to move in 26mm inner diameter pipe and characteristics of relationship between moving speed and distance of air feeding tube.