Search

The article presents the results of a study of the influence of temperature on the coefficient of friction of radiation-modified fluoroplastic when lubricated with hydraulic fluid. A friction pair of radiation-hardened fluoroplastic with 40X steel, when lubricated with AMg-10 hydraulic fluid, has good anti-friction properties. The friction coefficient F4M when lubricated with hydraulic fluid is low. At a temperature of 90 °C and a speed of 2.5 m/s, the friction coefficient F4M at a load of 2.003 MPa is 0.04. Bushings made of F4M paired with steel 40X can be used in pumps when lubricated with AMg-10 working fluid. [ABSTRACT FROM AUTHOR]

The impact of introducing nanoparticles to lubricating oils on bearing dynamic characteristics, as well as their impact on the rotor's dynamical reaction and critical speed, has been studied. The lubrication oil pressure, reaction forces, and dynamic coefficients of journal bearings are calculated using the modified lubrication oil viscosity as a result of adding nanoparticle additions to the lubricant oil. According to the Reynolds equation's theoretical solution. The theoretical conclusions are verified using the computational fluid dynamics (CFD) fluent Ansys program. The results demonstrate that as the volume fraction of nanoparticles and aggregate fraction increases up to the angular position130, the lubrication fluid pressure increases, then decreases as both the volume fraction and aggregate fraction increase. [ABSTRACT FROM AUTHOR]

This paper presents a full elastohydrodynamic lubrication (EHL) model for the solution of involute spur gear meshing cycles using a line contact transient approach. The resulting mathematical model utilises a simultaneous solution of the Reynolds equation and the elastic film equation, both of which are highly nonlinear due to their dual dependencies on pressure and film thickness. The contact between the teeth of the spur gears was represented by a set of time varying contact parameters. These included the radius of relative curvature, the relevant surface velocities, and the load variation over the meshing cycle. The model was solved numerically based on the central finite difference method under relaxation, and different operating conditions were examined to determine their effects on both pressure distribution and film thickness, though a difference of less than 5% was observed. The results were verified against available literature, and very good agreement was obtained, suggesting that this comprehensive transient solution represents a significant model for the assessment of the behaviour of the contact problem in heavily loaded spur gears. The results also showed that the time varying parameters have a significant influence on the pressure distribution and film thickness, particularly at the change points of the load. [ABSTRACT FROM AUTHOR]

Adjustable fluid film bearings allow implementing additional functions in rotary machines and expand the range of their operating characteristics in comparison with conventional passive bearings. The effect of static reduction of viscous friction in actively lubricated bearings can be achieved by adjusting the position of the rotor in the gap. The variety of possible implementations of such bearings requires studying this effect in more detail. The article considers the influence of significant bearing parameters, such as the gap shape and the lubricant viscosity, on the implementation of the effect of static friction reduction. Water and oil are considered as the examples of the more and the less viscous lubricants that are often used in machinery, as well as circular and elliptic gap profiles are compared in the context of the studied effect. Series of computational experiments were carried out for different combinations of these factors to obtain the information about the tribological and dynamic behavior of the rotor-bearing system under such conditions. A simplified "soft" approach to the implementation of static friction reduction requiring no rotor position tracking is also proposed and analyzed. The results of the work make it possible to determine the limits of applicability of the considered approaches depending on the configuration and operational features of rotary machines in order to improve their performance by applying modern solutions in bearings. [ABSTRACT FROM AUTHOR]

Most of the bearings used in industrial machines and domestic equipment to support the rotating shafts are rolling bearings. Low friction at the contacts between the balls and the races has positive effects such as reduced temperature rises, lower vibration amplitudes, higher fatigue life and reduced premature bearing failures. This can be achieved by enhancing the availability of lubricant/grease at the contacts. Among the various available methods surface texturing of the bearing components by employing micro-tracks and micro-dimples/grooves has been extensively used. In this connection, to explore the performance behaviour of a modified/newly developed bearings a test rig has been indigenously designed and fabricated to measure tribodynamic parameters such as frictional torque, film thickness formation, temperature rise, and vibrations by implementing load cell, capacitance-based approach, thermocouple, and miniature type accelerometer respectively. The development of test rig includes selection of commercially available components (support bearings along with suitable pedestal, variable speed motor, timing belt and pulleys for power transmission), design and manufacturing of components (shaft, test bearing housing and base frame) and adopting suitable techniques for the parameters to be measured. Also, modal analysis of the test rig and bearing components have been carried out by employing FEA software to find out the natural frequencies and their corresponding modes. The developed test rig has the capability to operate up to 3,000 rpm and measure/estimate capacitance, frictional torque and temperature rise in the range of 10-1500 pF, 0-900 N.mm and 0-200 °C respectively. In addition, the vibration rms velocity of the test bearings can be measured and analysed in both time and frequency domain. [ABSTRACT FROM AUTHOR]

Wear, friction, and lubrication are all terminology used to describe the science of interacting surfaces in relative motion. Tribology is especially significant in this day and age on the grounds that such a lot of energy is lost to grinding in mechanical parts. Critical energy is lost because of grating in sliding points of interaction. Finding new techniques to decrease touch and wear through tribology developments is critical to making the world a greener and more manageable place. This article presents extensive work on tribological conduct of bio composites. [ABSTRACT FROM AUTHOR]

This paper presents, the static study of hydrodynamic short journal bearing effective under Nano lubricants. Lubricant viscosity is affected the load resonant capacity of journal bearing. The performance of the bearing is influenced by the % of Nano particles added in the base lubricants. The current work modified Reynolds equation is utilized to get the pressure of the bearing. The narrow bearing estimation method is utilized to solve the modified Reynolds equation. For different eccentricity ratios the static characteristics in terms of load capacity, attitude angle and friction evaluated. [ABSTRACT FROM AUTHOR]

Maintaining effective lubrication on the gear dynamics is essential in extending the life expectancy of a gear. Failure to protect the gear from severe friction during the gear mating will cause surface damage. Furthermore, surface damage on a gear will induce the vibration level as the operating time increases. In this study, two different lubrication conditions (dry and lubricated conditions) were employed to evaluate the effect of palm grease with nano molybdenum disulphide (MoS2) on the improvement of spur gear surface protection. The evaluated parameters were gear mass losses, surface roughness, and the vibration level at the gear mesh frequency (GMF). The lubricated condition was found to perform better in all parameters, indicating that the palm grease with nano MoS2 is suitable and effective for applications in a dynamic gear environment. [ABSTRACT FROM AUTHOR]

The impact of MHD on porous parallel stepped plate with micropolar fluid as lubricant is analyzed. The modified Reynolds equation applicable to micropolar fluid is obtained. The dimensionless expressions for pressure and work load are obtained. The results indicate that the effect of MHD in the presence of micropolar fluid increases the pressure and work load. [ABSTRACT FROM AUTHOR]

Vibrations in vibrant mechanical systems are a common problem that can cause significant damage to the system, as well as the loosening of the structure and equipment collapse, so studying vibrations in shafts of rotating bearings is critical for determining the cause of system failure and lowering system efficiency. The Dunkerley method is used to measure vibration in rotating bearing shafts. In this study, non-uniform (step shafts) with free ends or simply supported ends are investigated. Magnetic bearings are widely utilized for a variety of reasons, including the capacity to achieve exceptionally high rotation velocity without lubrication, high power density without rotor and bearing body contact, and no mechanical wear. As a result, using the COMSOL program, a typical model of active magnetic bearings was created, and the impact of adding these bearings on intensity, vibration reduction, and frequency response was explored. The intensity of vibration was considerably reduced to roughly 60% when active magnetic bearings were introduced to the revolving bearing shaft, giving them a more sturdy and robust nature. A shift in frequency values was detected when AMB was added to the rotating bearing shaft. The change in the control current generated as a result of adding active magnetic bearings, and the forces acting on AMB were studied in this paper. The addition of active magnetic bearings to the rotary bearing shaft system resulted in a high level of stability, a large reduction in vibration amplitude, and a significant performance improvement, indicating the value of using this technology in rotating machines. [ABSTRACT FROM AUTHOR]

Novel AZ91 magnesium syntactic foams are a potential choice for temporary biomedical implants. In many cases, holes of various sizes need to be machined on the biomedical temporary implants using the drilling process to facilitate placement of implants inside the human body. In this study, the drilling performance of AZ91-magnesium foam is investigated under different lubrication methods such as dry, wet (Almag® mineral Oil-wet machining), and cryogenic cooling. Drilling experiments were carried out using coated and uncoated titanium aluminium nitride (TiAlN) twist drills on varying volume fractions of AZ91 magnesium syntactic foams (5%, 10%, and 15%) reinforced with hollow alumina microspheres. A three-dimensional, thermo-mechanical finite element-based model for drilling magnesium syntactic foam using AdvantEdgeTM is presented for different lubrication conditions. The numerically predicted machining induced stress from the finite element model showed a compressive stress give a better surface integrity and quality to the machined surface in liquid nitrogen coolant when compared to dry machining. This shows cutting with cryogenic cooling as a sustainable drilling process for AZ91-magnesium syntactic foams. [ABSTRACT FROM AUTHOR]

The hypothetical examination of Rabinowitsch fluid model on the rough secant circular plates with squeeze film lubrication is investigated. By working perturbation method the altered Reynolds equation is deduced and also the outcomes for squeezing pressure, load bearing capacity & squeeze time are attained. According to the conclusions examined that, for rising integrity of roughness, curvature, upper and lower circular parameters, the pressure, loading capacity and squeezing time are significant in both radial and azimuthal patterns. [ABSTRACT FROM AUTHOR]

The influence of cavitation and surface roughness on journal bearings has been extensively researched. Even though many studies have been done on elastohydrodynamic lubrication, further research is needed. The majority of research has focused on hydrodynamic lubrication on fluid films without taking into account their interaction with the housing and shaft, or on hydrodynamic lubrication alone. The impacts of roughness on elastohydrodynamic lubrication, as represented by CFD using structural transients' module, will be discussed in this work. The 2-way FSI coupling method is the name given to this form of coupling (Fluid-Structure Interaction). For cavitation and without cavitation, as well as for many types of roughness, this study examines hydrodynamic pressure, load carrying capacity, friction force, and von Mises stress. When considering cavitation, it was established that the value of load-carrying capacity and friction force is decreasing. Furthermore, as the level of surface roughness rises, the maximum hydrodynamic pressure, load carrying capacity, friction force, and von Mises stress decrease. [ABSTRACT FROM AUTHOR]

Surface texturing is an effective approach to increase the tribological performance of lubricated mechanical components. The main concept of surface texturing is to increase the tribological performance (increasing load support and decreasing friction). In this study, it has been compared between single open pockets and multi textured surfaces to obtain the best performance by CFD (Computational Fluid Dynamic) model. In this research, surface texturing was applied on thrust bearings to improve tribology performance. Lubricant flow behavior on single open pockets and multi textured surfaces has different characteristics so as to present different distributions of pressure, temperature, load support and friction. The variation of the rotational speed of the thrust bearing is also a parameter in this study. The results showed that single open pockets are superior compared multi textured surfaces. While the increase of rotational speed will also increase the distribution of pressure, temperature, load support and friction. [ABSTRACT FROM AUTHOR]

In recent years, the high bearing performance with high external load and rotating speed are required in industrial machines. Thrust bearing can be used to resist axial forces on industrial machines. One of the methods to improve the high performance of thrust bearings is to apply an artificial slip/ hydrophobic coating on the surface of thrust bearings. In this study, an investigation was conducted on the hydrodynamic lubrication performance of thrust bearing by engineered surface texturing and artificial slip on the surface of thrust bearings. Numerical analysis was carried out using 3D Computational Fluid Dynamics (CFD) based on the hydrodynamics lubrication to obtain the hydrodynamic performance of thrust bearing. Based on the simulation, it was found that by adding artificial slip gave better performance than conventional thrust bearings. This condition has been demonstrated by increased load support and decreased friction force in thrust bearings with artificial slip. [ABSTRACT FROM AUTHOR]

Metal products with a uniform cross-section are produced by the extrusion process. The quality of extruded products depends on the type of metal, the selection of extrusion process parameters, the die geometry, and the lubrication conditions. This study aims to determine the extrusion behaviour of AA6061 as cast, AA6061-O, and AA6061-T6. Extrusion is conducted by varying the extrusion speed and lubrication conditions. The extrusion behaviour is assessed by extrusion force, microstructure, surface roughness, and hardness value after extrusion. Extrusion was carried out by direct extrusion method with a constant extrusion ratio of 1.2 and with die angle is 10°. The results show that the highest average hardness value is obtained in the 6061-T6 sample which is 79.06 HRF and the lowest average hardness value is 9.33 HRF for the AA6061-O sample. The highest extrusion force was obtained for AA6061-O without lubrication with an extrusion speed of 10 mm/minutes, which is 90.45 kN. While the lowest extrusion force was 9.15 kN obtained for AA6061-T6 with lubrication conditions at an extrusion speed of 10 mm/minutes. The lowest surface roughness value was obtained for the AA6061-T6 sample, 2.65 um at an extrusion speed of 2 mm/minutes, and the highest surface roughness was obtained in the 6061-O sample which was 4.83 um also at an extrusion speed of 2 mm/minutes. [ABSTRACT FROM AUTHOR]

This paper focus to study the couple stress effects with rotational inertia forces on ferrofluid based squeeze film between porous circular plates. Based upon Morgan –Cameron approximation, Stokes couple stress fluid model and Shliomis ferromagnetic fluid model, the squeeze film attributes for porous circular plates are achieved. From the results achieved and discussed, the impacts of rotating fluid inertia and permeability of the upper plate lead to reduce the load carrying capacity and a shorter the squeezing time as compared to the non-rotating and non-porous bearing case. The squeeze film characteristics between porous circular plates can be improved by considering rotational fluid inertia and Non-Newtonian ferrofluid as lubricant. [ABSTRACT FROM AUTHOR]

This paper provides a review on the literature on gearboxes lubrication & oil leakages in industrial gearboxes. The lubrication of gear teeth is reviewed including some key aspects of recent theoretical research and current practice. Hydrostatic, hydrodynamic lubrication & elastohydrodynamic lubrication theory carried out by several researchers is reviewed. Various techniques of gearbox lubrication including monitoring gearboxes with the use of software application, cost-effective techniques using electrical supply parameters for detecting oil degradation are reviewed. Different types of lubricants used in industries, gearbox losses and temperature behaviour of lub oils has been included. Main reasons of oil leakages & researches done on oil seals have been reviewed. [ABSTRACT FROM AUTHOR]

Machinery and equipment used in farm production is experiencing serious stress caused by both weather factors and working conditions. Their faultless operation depends on the reliability of the moving units and mechanisms. The latter may be increased through the use of lubricants. The paper proposes to use fluorinated surfactants as an additive to lubricants. Studies have shown that they form a monomolecular protective film with a thickness of 3 ... 6 nm on the surface of friction units, which does not affect the structure and hardness of the metal and, at the same time, reduces the wear rate and the friction factor. The method of applying surfactants to the metal surface affects the uniformity of oil film distribution and oil absorption. It has been found that the use of such additives increases the antifriction and wear-preventive properties of lubricants. [ABSTRACT FROM AUTHOR]

Bearing of gas turbine often works under bad lubrication conditions. Bearing under heavy load, frequent variable conditions and the instant of gas turbine start and stop will lead to interface lubrication failure and plastic deformation. Taking a typical working condition of a marine gas turbine bearing as an example, aiming at the problem of plastic deformation of gas turbine bearing, the fast Fourier transform method is used to solve the elastic-plastic deformation of bearing, and the elastohydrodynamic lubrication state of gas turbine bearing is numerically calculated. The results show that the plastic deformation will directly affect the lubrication state of gas turbine bearing. Properly increasing the rotating speed will help to form the oil film between the contact surfaces, reduce the maximum residual stress and improve the lubrication state. [ABSTRACT FROM AUTHOR]

Light weight electrically conducting materials that can be fabricated at low cost and are important for certain applications like electromagnetic shielding and field emission devices; carbon nanotubes based-composite materials are most suited for such applications. However, it is quite important to study the temperature dependent electrical behaviour. Here, we are presenting the experimental results on temperature dependent AC conductivity of few hundred micron-thick multiwall carbon nanotube-polystyrene (MWCNT-PS) composites (0.5 & 1.0 wt.%), in the temperature and frequency ranges of 154-293 K and 10 Hz-10 MHz, respectively. The free standing MWCNT-PS composite films were prepared by a simple and cost-effective solution approach, and their good quality was ascertained after characterizing by field emission scanning electron microscopy.For 0.5 wt. % composite film, the conductivity did not show any variation up to 1 MHz at all the temperatures whereas it monotonically increased from 1 MHz to 10 MHz; it followed Jonscher's law. Further, the threshold frequency shifted towards higher frequency with the temperature. The DC conductivity was observed to decrease from 34 µS/cm to 22 µS/cm with variation of temperature from 293 to 154 K, respectively; this decrease of DC conductivity is attributed to increase of activation energy of charge carriers at low temperatures. Interestingly, AC conductivity of 1.0 wt. % sampledid not exhibit any frequency dependence at any temperature; however, DC conductivity reduced to 37 µS/cm (154 K) from 70 µS/cm (293 K). [ABSTRACT FROM AUTHOR]

The primary function of a journal bearing is to hold up radial loads under different working conditions. In a journal bearing, in order to avoid metal to metal contact, the pressure is created in the thin lubricant oil film that detaches the shaft and the journal. For a Newtonian fluid, A generalized Reynolds equation has been applied to examine the geometrical analysis of Elliptical Journal Bearing. Further, the variation of film thickness and pressure profile with respect to circumferential angle has been plotted by considering the changes in parameters like eccentricity and non-circularity. The result shows that with the increase of eccentricity ratio the pressure gets increased whereas peak film thickness before and after convergence increases. With the help of a pressure profile, the load-bearing capacity of the bearing is obtained. In this study, MATLAB has been used as the programming tool and various routine of MATLAB graphics helps us to draw the results. For non-circularity of 0.7, the non-dimensional load-bearing capacity is estimated to be 2.25, 2.75, and 3.45 at journal eccentricities of 0.5, 0.7, and 0.9 respectively. [ABSTRACT FROM AUTHOR]

The paper investigates the pressure field and losses in hydrodynamically lubricated contact between axial rings of the pinion and the wheel of a high-speed gearbox under steady-state load. For that reason, a computer program was developed to numerically solve the general Reynolds and energy equations simultaneously, while considering the viscosity-temperature relationship. The Barus empirical equation was used to express a viscosity-pressure relationship as well. For the selected design parameters, dissipative heat in the lubricated contact is shown as a function of transmitted axial force. It is presented that the contact axial force and losses are affected by procedure of the filling of the gap between the rings. [ABSTRACT FROM AUTHOR]

The standard multigrid and wavelet multigrid procedure performs poorly or may break down when used to solve certain problems, such as Grease elastohydrodynamic lubrication problems with discontinuous or highly oscillatory coefficients. Objective of the proposed method is to solve this problem by using a discrete wavelet transform. In this paper, Daubechies orthogonal discrete wavelet transform with permutation matrix method is developed for the solution of Grease elastohydrodynamic lubrication problem. GEHL Numerical test problem is presented to demonstrate the versatility of the method. The analysis indicates that there is a higher accuracy obtained by Daubechies wavelets decomposition, which is in the form of a multi-resolution analysis of the function. The solution is first found on the coarse grid points, and then it is refined by obtaining higher accuracy with help of increasing the level of wavelets. The results obtained are accurate; the present method, thus, have a clear advantage over the classical numerical methods. A distinct feature of the proposed method is their simple applicability for a variety of boundary conditions. Numerical order of convergence of the proposed method is calculated. The results of numerical tests show better accuracy of the proposed method based on Daubechies wavelets for the solution of GEHL problem. [ABSTRACT FROM AUTHOR]

A fundamental component of two-stage servovalves is the flexure tube, since it both constitutes a low friction pivot for the inner flapper and allows the torque motor to be separated from the hydraulic fluid, thus avoiding contamination particles being trapped inside the torque motor. The inertia of the torque motor armature interacting with the flexure tube stiffness gives lightly damped resonances, which may lead to fatigue failure due to excessive bending under vibration, as well as limiting the position control bandwidth of the main spool. This effect is counteracted by the film of liquid interposed between the flapper and the flexure tube, which is “squeezed” during the flapper motion providing damping. However, the underlying physics of the damping mechanism caused by the squeeze film inside the flapper-flexure tube system is not well-understood, and to date the scientific literature has lacked analyses and investigations aimed at providing insights into this phenomenon. Because of this, the aim of this paper is to develop a reliable CFD model which can help to understand where and how the damping forces are generated during the flapper motion because of the squeeze film. The developed model could be used in further investigations, aimed, for example, at studying the effects of fluid properties and geometric parameters upon the damping factor, in order to achieve more effective designs which can enhance the damping factor in the flapper-flexure tube system of new generation servovalves. This work has been carried out as a collaboration between the University of Bath and the Polytechnic University of Bari, and Moog Controls ltd (Tewkesbury, UK), a world leading manufacturer of servovalves. [ABSTRACT FROM AUTHOR]

This paper presents a programming code to provide numerical solution of elastohydrodynamic lubrication problem in line contacts which is modeled through an infinite cylinder on a plane to represent the application of roller bearing. In this simulation, vegetable oils will be used as bio-based lubricants. Temperature is assumed to be constant at 40°C. The results show that the EHL pressure for all vegetable oils was increasing from inlet flow until the center, then decrease a bit and rise to the peak pressure. The shapes of EHL film thickness for all tested vegetable oils are almost flat at contact region. [ABSTRACT FROM AUTHOR]