Fluid Lubrication Research Articles

Wear Mechanism of Superhard Tetrahedral Amorphous Carbon (ta‐C) Coatings for Biomedical Applications

AbstractTetrahedral amorphous carbon (ta‐C) coatings have the potential to protect biomedical implants from wear and increase their service life. This study elucidates the biocompatibility, mechanical properties, adhesion, and wear resistance of ta‐C coatings fabricated by physical vapor deposition on cobalt‐chromium‐molybdenum (CoCr) and titanium (Ti64) alloys as well as ultrahigh molecular weight polyethylene (UHMWPE). Satisfactory cytocompatibility is verified using contact angle and surface tension measurements as well as indirect and direct cell testing. Scratch testing demonstrates excellent adhesion to the substrates and as confirmed by nanoindentation, the coatings represent an up to 13‐fold and 182‐fold increase in hardness on the hard and soft materials. In metal pin‐on‐UHMWPE disk sliding experiments under simulated body fluid lubrication, the wear rates of the disk are reduced by 48% (against CoCr) and 73% (against Ti64) while the pin wear rates are reduced by factors of 20 (CoCr) and 116 (Ti64) compared to uncoated pairings. From optical and laser scanning microscopy, Raman measurements, and particle analyses, it is shown that the underlying substrates remain well protected. Nonetheless, focused ion beam scanning electron microscopy revealed coating process‐related and thermally driven subductions as well as tribologically induced near‐surface fatigue, which can potentially constitute critical wear mechanisms.

Tribological Properties of Protic Ionic Liquid as an Additive in Aqueous Glycerol Solution for Ruby-Bearing Steel Tribo-Contact

Owing to their low cost and environmentally friendly nature, water-based lubricants have benefits over oil-based ones. However, the appropriate additive package is indispensable in improving its tribological properties. In the current study, we have investigated the friction and wear reduction ability of bis(2-hydroxyethyl) ammonium oleate protic ionic liquid (PIL) in a glycerol aqueous lubricating fluid. The tribo-tests were performed using a ruby–steel friction pair acting in reciprocation mode. The coefficient of friction and wear were the main characteristics of the evaluation. Analysis of the physical properties of the investigated lubricating samples and worn surface analysis were performed to reveal a more detailed picture. The study shows that the investigated PIL can significantly reduce friction and wear. The most suitable concentration of PIL was 0.5%, where friction and wear were reduced 2.6 and 15.8 times, respectively. Using the investigated PIL facilitates a sliding coefficient of friction as low as 0.039. It was hypothesized that the formation of the adsorption layer and metal soap was responsible for this. Further studies could be directed toward higher load and speed applications.

Simulation and experimental analysis on frictional vibration in the reversal process of a wiper-windscreen system

This paper studies the frictional vibration aspects of the automobile wiper-windscreen contact system and builds a numerical model that matches the test equipment. The reversal vibration of the contact system is examined by the dynamics part of a theoretical model with the derived analytical formulas. The fluid lubrication characteristics are investigated by the friction part of the model with solutions of the friction coefficient-negative slope formula for relative velocity and the friction coefficient formula in the time domain. The nonlinear dynamic response of the theoretical model of the wiper blade is calculated with the Runge-Kutta method and the results of the frictional vibration are well reproduced in real motions. The validity of the model is confirmed by parallel analyses of the simulated results and the experimental ones of the wiper-windscreen system. It is concluded that properly reducing the length of blade tip is an effective way to reduce vibrations of the system. The influences of the wiping speed and acceleration after reversal on the system vibrations are also analyzed through experimental investigations. The theoretical and experimental results presented in this paper can be reference to structural optimization of the wiper blade and vibration and noise control of the wiper-windscreen contact system.

СOMPARATIVE CHARACTERISTICS AND SELECTION OF SPEED BEARINGS

The characteristics of bearing supports have been considered. Improving the efficiency of mechanical processing, the quality of operation of mechanisms that use sliding bearing supports, and ensuring stable operation are always important tasks. Solving these tasks contributes to reducing labor costs, reducing operating costs, and increasing the productivity of individual operations. The following main criteria are proposed for the selection of supports: the magnitude of the loads that supports can withstand; the range of allowable shaft rotation frequencies; accuracy in maintaining the position of the axis of shaft rotation; stability of shaft rotation (possibility of autooscillations and undesirable transient processes); energy costs and economic indicators of manufacturing and operation; vibroacoustic characteristics (noise level, sound level). The study of the movement of the working body that separates the friction pairs in the bearing is based on two fundamental laws of hydrodynamic lubrication theory: the law of mass conservation and the law ofmomentumconservation.Mathematicalmodels of supports with fluid lubrication, based on the Navier-Stokes equations, were used. The requirements for bearing supports are formulated on the basis of the tasks solved by the entire mechanism. The flow parameters of the working body affect the load-bearing capacity of radial bearings, and the proposed evaluation dependencies can also be used for tapered supports. The calculation results indicate a significant influence of the flow parameters of the working body on the expansion of the areas of rarefaction and the range of their values, as well as on the reduction of the area and range of increased pressures. It has been established that with small shaft eccentricities rotating at speeds of 60–70 m/s and with a radial clearance of 80 μm, the increase in load capacity can reach 20 %. An important qualitative feature has been identified: with an increase in the Reynolds number Re*, the load capacity of the bearing increases. The greatest intensity of changes in load capacity due to the influence of flow parameters of the working body is observed at a relative eccentricity of e = 0.2–0.4. The terms in the Navier-Stokes equation that take into account the parameters of the working fluid flow can have values that are comparable to other terms, so ignoring them is not always permissible.

Study of the Wear Resistance of a Friction unit with a Non-Standard Support Profile and a Metal Coating

The theoretical calculations and the results of experiment for a friction unit consisting of a wedge-shaped support surface are presented in this research paper. The slider on the tread surface has a metal alloy. The lubricating fluid is represented by a lubricant with non-Newtonian characteristics; it has the laminar flow in this unit. The friction unit functions when the cavity between the slider and the support ring is completely filled. To solve the theoretical problem under given conditions, the equations of continuity, the rate of mechanical energy dissipation, the values of the expression for the displacement of a non-Newtonian fluid were used. In addition, equations were used to characterize the profile of a slider with a melt on the tread surface. The presented problem was solved by the self-similar variable method with asymptotic expansion in the smallest parameter. Upon calculation, it is given the equations for the first and zero pressure approximations and it is determined the velocity field are determined with and without the molten metal. Further, the friction force and load capacity were found using the non-Newtonian properties of the lubricating fluid and the above structural characteristics of non-standard surfaces for friction contact.

Experimental Study on Influence Mechanism of Electroosmotic Effect on the Penetration and Lubrication of Water-based Cutting Fluid at Tool-chip Interface

Experimental Study on Influence Mechanism of Electroosmotic Effect on the Penetration and Lubrication of Water-based Cutting Fluid at Tool-chip Interface

Influence of different oil flow directions on the friction performance of asymmetric structures in heavy load hydraulic friction pairs

Textures have obvious anti-friction and anti-wear effects, but effective textures often have complex and asymmetric characteristics. Because of the texture’s directional lubrication effect and fluid diode effect, different oil flow directions influence the friction reduction effect of asymmetric texture. Simulations and test methods are used to characterize these effects, and the friction coefficient and wear amount are used as evaluation methods to determine the optimal oil flow direction of asymmetric textures. The results show that an appropriate oil flow direction can significantly change the texture’s friction-reducing ability. The friction reduction efficiency of the texture is highest when the angle between the oil flow direction and the inflow edge of the texture is 60°–90°. When the angle between the oil flow direction and the inflow edge of the texture is 0°–30°, the texture’s anti-friction effect and efficiency are weakened.

Cytomorphological analysis of effusion fluids for detection of malignant cells in a tertiary care hospital in northern India.

All body cavities are lined by monolayered mesothelial cells and contain a minimal amount of fluid for lubrication and for protecting the underlying viscera. The peritoneal, pleural, cerebrospinal, sputum, urine, and pericardial fluids comprise the major chunk of body fluids. The study was conducted in the Department of Pathology of a tertiary care hospital in northern India, over a period of 1 year, from January 2021 to December 2021. A total of 241 samples were included in the study. Out of the 241 samples studied, 99 were peritoneal fluid, 94 were pleural fluids, 29 were CSF, and 18 were sputum samples. Maximum number of patients affected were in the age group of 41-50 years. Female preponderance was seen with male to female ratio of 1:1.7. A total of 143/241 cases (59.33%) were of transudative nature and 98/241 (27.8%) cases were exudative. Out of 241 cases, 43 (17.84%) were neoplastic, 190 (78.83%) were non-neoplastic, four (1.65%) were suspicious for malignancy, and four (1.65%) were where no opinion was possible. Peritoneal fluid was the most frequently encountered fluid accounting for 99 cases (41.07%). Adenocarcinoma was the most common malignancy accounting for 29 cases (67.44%) out of 43 malignant effusions in the present study. Cytological evaluation of body fluids is of significant utility in diagnostic medicine as it allows us to distinguish between benign and malignant etiologies and at the same time offers rapid diagnosis and staging of metastatic disease.

Effect of Cross-Sectional Profile of Circular Dimples on Hydrodynamic Lubrication Characteristics of Thrust Bearings

The effects of three types of dimples with different internal structures on the fluid lubrication characteristics of thrust bearings were investigated. The load-carrying capacity and the frictional torque were measured. The measurements were performed with a fixed constant film thickness. The behaviours of cavitation bubbles occurred within the dimple were observed through the rotating glass plate. Three types of internal structures of dimples were tested: cylindrical, sphere and conical. The measurement results were simulated by the Reynolds equation. As the results, the load-carrying capacity increased as the rotational speed increased. The cylindrical internal structure built up the largest pressure at the trailing edge, and consequently the largest load-carrying capacity. The frictional torque also increased with increasing the rotational speed. However, the effect of the internal structure on the frictional torque was not significant.

The use of platelet-rich plasma, hyaluronic acid, and botulinum toxin for the treatment of TMJ disorders

The temporomandibular joint (TMJ) is a synovial joint that connects the mandibular to the skull. Its main function is to facilitate the movement of the jaw and when it suffers any type of damage or injury, it leads to a decrease in mobility and pain in the area. This localized pain is called temporomandibular joint disorders (TMJD), and it can be caused by intraarticular or extraarticular disorders. The most common symptoms include acute pain, decreased mouth opening, tightening of the muscle, headache, and loss of joint function. Nowadays, there are treatments for temporomandibular joint dysfunction from surgical procedures up to less invasive methods, such as the use of splints. Platelet rich plasma (PRP), hyaluronic acid (HA) and botulinum toxin (BTX) injections have been categorized as a complement of primary treatment in TMJD, as well as decrease drug excess in patients. Due to their natural origin, PRP and HA can regenerate tissue in cases of cartilage degeneration, inhibit inflammation, slow down the progression of osteoarthritis and increase the production of natural lubricating fluid in the joint. Its intra-articular application reduces pain due to lubrication and nutrition to the avascular areas of the disc and condylar cartilage. Botulinum toxin (BTX) has been used for years in the medical and cosmetic field, but its use in TMJD refers to injections specifically within masseter muscle, with the objective to reduce the muscular tension TMJ overload, therefore, pain decreases, and movement increases. Over the years these less invasive methods have been increasing in the medical area due to the great pain management in the neuro-muscular and articular complex.

Метод математического моделирования гидродинамического трения плунжерных пар с учетом микрогеометрии

The fuel injection system strongly relies on a high pressure fuel pump which is essential for its overall performance. The fuel pump plunger is subject to high loads and irregular lubrication under dynamic loads, which leads to its premature wear. The industrial sector uses laser surface micro-texturing to reduce friction and improve anti-wear properties. Its positive effects are supported by both theoretical and experimental data. The paper presents a method for determining the hydromechanical characteristics of plunger pairs during hydrodynamic friction. The microgeometry of friction surfaces was taken into account due to the lubricating fluid cavitation effect described by the modified Reynolds equation. The proposed method can be applied to develop the software to analyze the contacting surfaces of plunger pairs and evaluate their tribological characteristics based on the microgeometry parameters of friction surfaces. The paper also studies the influence of microgeometry parameters on the quality criteria of the hydromechanical characteristics of plunger pairs. It gives the calculated examples of analyzing the contacting surfaces of plunger pairs separated by a lubricant layer. The technical specifications are assessed depending on the microgeometry parameters of the friction surface roughness.

Enhance the Properties of Lignosulfonate Mud by Adding Nanoparticles of Aluminum Oxide and Iron Oxide

Oil well drilling fluid rheology, lubricity, swelling, and fluid loss control are all critical factors to take into account before beginning the hole's construction. Drilling fluids can be made smoother, more cost-effective, and more efficient by investigating and evaluating the effects of various nanoparticles including aluminum oxide (Al2O3) and iron oxide (Fe2O3) on their performance. A drilling fluid's performance can be assessed by comparing its baseline characteristics to those of nanoparticle (NPs) enhanced fluids. It was found that the drilling mud contained NPs in concentrations of 0,0.25, 0. 5, 0.75 and 1 g. According to the results, when drilling fluid was used without NPs, the coefficient of fraction (CoF) was 44%, when added Al2O3 NP and Fe2O3 NP at 0.75g reduced CoF by 31% and 33% respectively. When Al2O3 and Fe2O3 NPs were used, particularly at a concentration of 1g, the amount of mud filtration decreased from 13.5ml to 9.3 ml and 8.5 ml respectively. Additional improvements rheological properties as well as swelling when Fe2O3NPs and Al2O3 NPs were added at 1g. Overall, it was found that adding NPs to the Lignosulfonate-WBM at a concentration of 1g can improve rheological, swelling, and filtration properties as well as lubrication at 0.75g.

Numerical Analysis via Mixed Inverse Hydrodynamic Lubrication Theory of Reciprocating Rubber Seal Considering the Friction Thermal Effect

This study investigates how operating conditions such as ambient temperature and sealing pressure affect sealing performance for a typical U-cup seal. The developed analysis method combines inverse fluid lubrication (IHL) theory and the Greenwood–Williamson contact model (G–W model), and the effect of increasing surface temperature due to frictional heat generated between two surfaces is considered. Commercial FE software (ABAQUS) was used to simulate the interference fit analysis of rubber seals and the pressurized process. Through this model, the film distribution, working fluid leakage, and friction force in the sealing area were discussed according to the operating parameters, such as sealed pressure, rod velocity, and ambient temperature. The simulation results demonstrate the effect of fluid viscosity on oil film formation (which varies with ambient temperature), the effect of increasing the surface temperature, and the effect of surface roughness at a very small film thickness.

Preparation, characterization and application of environment-friendly high density and low damage solid free completion fluids for completing HTHP oil and gas wells

During this study, in order to ensure the safety and efficiency of well-killing operations in the process of oil and gas development, based on the requirements of high density, low corrosion, suitable pH and density properties, solid free characteristic, low damage and biological toxicity, the high density and low damage solid free completion fluids with the density of 1.80, 1.70 and 1.60 g/cm3 were prepared. Then, the general performances, such as solid free characteristics, biological toxicity, pH and density stability of completion fluids were studied. Moreover, the thermal stability, rheological, lubrication and inhibition performances of completion fluids were investigated through qualitative and quantitative analysis. Simultaneously, the corrosion performances and mechanism of completion fluids with different density on P110 and P110S at 50–180 °C were studied by scanning electron microscope and X-ray diffraction analysis. Besides, the compatibility of completion fluids and Ca2+, Mg2+ and water-based drilling fluids was investigated. Finally, the reservoir protection performances of completion fluids were further studied by multifunctional core displacement experimental device depends on permeability recovery rate. The results indicate that the developed completion fluids with different density meet expected design and could use for well-killing operations of HTHP oil and gas wells.

Mechanical and Three Body Abrasive Wear Behaviour of Nano-Filler Filled, Chopped Glass Fiber Filled Hybrid Composites

Polymer matrix composites are developed for tribological applications due to the possibility of optimizing the properties with the addition of special filler materials as reinforcement. Filler filled polymer matrix composite systems are used in many automotive parts and components like brake pads or clutches which require high coefficient of friction coupled with low wear. However, in most cases it is the primary concern to develop polymer composites that posses low friction and low wear properties under dry sliding conditions against smooth metallic counterparts e.g., gears or bearings, chute liners and coal handling equipments in power plants, gear pumps handling industrial fluids, agricultural machine components. Polymer composites operate in applications where fluid and grease lubricants fail, and have superior tribological performance to traditional polymer composites. Particulate fillers or fibres or solid lubricants have been a part of notable reductions in the wear rate of the polymer matrix at very low loading, and there exists a wide scope on the development of polymer composites on the tribological behaviour. The incorporation of fillers in polymer could provide a synergism in terms of improving mechanical properties and wear performance, which has not been adequately explored so far. The research on nano fillers such as nano clay, Glass fiber and Titanium di-oxide (TiO2) in epoxy system is scarcely reported and further they focus on a few specific issues only. The present study was focused on investigating Mechanical - Tensile, Hardness, and three body abrasive wear characteristics of thermosetting based Epoxy composites and the effect of incorporation of nano clay, TiO2 nanoparticles and chopped glass fiber on microstructure, hardness, friction and abrasive wear are determined and analyzed. The main aim was to investigate the effect of applied load, sliding distance /abrading distance, sliding speed and percentage of filler. The surface morphology of the worn out surfaces were examined using SEM, to get a better understanding of the wear mechanisms.

Machining characterization and optimization under different cooling/lubrication conditions of Al-4Gr hybrid composites fabricated by vacuum sintering

In this study, the effects of different cooling/lubrication strategies and cutting parameters during milling hybrid composites based on Al-4Gr, a new material, were investigated. The main matrix was formed by adding Gr at a constant rate (4%) to Al. Hybrid composites were fabricated by vacuum sintering by adding WC and Al2O3 in different ratios (2-4-8 wt.%). Environmentally friendly cryogenic liquid nitrogen (cryo-LN2) and minimum quantity lubrication (MQL) fluids were used as cooling and lubricating environment in the milling process. Three different cutting speeds (150, 225, 300 m/min), three different feed rates (0.150, 0.225, 0.300 mm/rev) and a single depth of cut (0.5 mm) were selected for milling. Surface roughness, flank wear, cutting temperature, and chip morphology were evaluated for different cooling/lubrication environments. As a result, the cryo-LN2 environment reduced the surface roughness, flank wear, and cutting temperature by 34.9%, 18.5%, and 69.5%, respectively, compared to the dry medium. Adhesion wear was reduced in MQL and cryo-LN2 environments. In addition, it was determined by the analysis of variance that the most effective factor among the response parameters was cooling/lubrication. The cooling/lubrication environment has an effect of 74%, 58%, and 94% on surface roughness, flank wear, and cutting temperature, respectively.

Transient nonlinear dynamics of the rotor system supported by low viscosity lubricated bearing.

This paper clarifies the mechanism of the dynamic characteristics of the water-lubricated bearing-rotor coupling system at different operating stages. Dynamic models of the water-lubricated bearing-rotor system under fluid lubrication are developed. The influences of different operating modules on the dynamic characteristics are investigated. The effects of different speeds, different loads, and different impacts are analyzed. The time domain responses, axis orbits, and phase diagram are gained. Velocity has impacts on the vibration performance of the shaft. The external load has slight effects on the vibration characteristics. Different forms of transient impacts have different effects on the vibration characteristics. The validity of the new-built models is verified by experiments. Results provide theoretical foundations for the optimum design for such bearing-rotor systems.

A numerical strategy for predicting the interface stresses in metal strip rolling with small reduction

This paper has developed a numerical strategy for predicting the interface stresses in metal strip rolling at a small reduction. Key rolling factors such as the roll elasticity, fluid lubrication, random asperity contacts, asperity-lubricant interaction, rolling speed and reduction were comprehensively integrated into the numerical analysis. The random asperity contact at the roll-strip interface was addressed by a statistical approach with considering the elastoplastic deformations of surface asperities. A transient average Reynolds equation was utilised to deal with the fluid flow subjected to the interruptions caused by the asperity contacts. With the aid of a dynamic explicit finite element analysis, a novel modularised strategy was established to systematically accommodate the mathematical models governing the above key rolling factors, which allows the affordable computation and the effective predictions of contact characteristics in the strip rolling. It was found that both the lubrication and microscale asperity contacts disturb considerably the contact stresses at the rolling interface, and that a proper selection of rolling conditions can reasonably regulate the stresses.

Laser-Induced Heating in GdVO4: Yb3+/Er3+ Nanocrystals for Thermometry

Photoluminescent temperature sensors based on gadolinium orthovanadate (GdVO4) doped with 10% ytterbium and 2% erbium are developed and dispersed in different media (lubricant fluid, sol–gel glass, and PDMS) to evaluate the best conditions for temperature measurement. Two excitation modes are considered: (i) visible excitation by a downshifting (DS) process or (ii) NIR excitation by energy transfer upconversion (UC) between Yb and Er. The luminescence intensity ratio (LIR) of the thermally coupled Er3+ emission peaks varies linearly with temperature in the range of 25–300 °C, and this variation is reversible. The impact of the laser power density on thermometry via the UC process that has been verified with GdVO4: Yb3+/Er3+ powders and with its different dilutions (low and high concentration) shows that the LIR is highly dependent on the laser source intensity, the environmental temperature, and the dispersed medium. When GdVO4: Yb3+/Er3+ powders are dispersed at high concentration, high laser power density leads to significant laser-induced thermal heating. However, at low concentration, this laser thermal effect is no longer influenced by the laser intensity. In this paper, we propose a method to directly measure the laser-induced heating temperature and to correct the error caused by this effect on temperature measurement. According to these results, GdVO4: Yb3+/Er3+ upconversion nanoparticles can be applied for temperature sensing even if the laser-induced thermal effect occurs in the system.

How to speak and vocal hygiene.

An abnormal tongue shape, pitch difference or voice quality can lead to difficulty communicating effectively. Common among teachers are voice issues, which can be uncomfortable and make it challenging to carry out daily tasks and work-related activities. 1 Teacher who suffers from voice disorders may have trouble communicating clearly with their students. Voice disorders affect negatively a teacher's ability to communicate effectively throughout the day and their emotions, leading them to feel inadequate and frustrated at times. Voice misuse is inappropriate voice usage. It includes speaking involving hard glottal attacks and cheerleading for an extended period. 2 Vocal abuse is defined as activities having a detrimental effect on the larynx and voice. These include yelling and screaming, excessive talking or singing, excessive talking with an upper respiratory infection or allergy. It is important to identify and reduce the phono traumatic behaviours (for example loud voice use, speaking over background noise, throat clearing, cheering and screaming, and unconventional voice production), awareness about the vocal mechanism, and address high-risk situations associated with speech. In addition, it involves controlling how much you talk, monitoring your pitch and intensity (The speech of a typical adult male will have a basic frequency from 85 to 155 Hz, and a typical adult female ranges from 165 to 255 Hz.) 3 and conserving your voice by resting it. A healthy voice is dependent upon several factors, including local lubrication (About 15.5 cups (3.7 litres) of fluids per day are recommended for men. 11.5 cups (2.7 litres) of fluids per day is recommended for women)4, necessary dietary choices; as well as eliminating the effect of medications, environment, and healthy lifestyle choices (reduction of alcohol, recreational drugs, tobacco, and caffeinated beverages,). 5.Voice hygiene has two primary goals: to improve communication effectiveness and to promote vocal health. Additionally, by fostering optimal vocal habits as a precautionary measure, your voice will be maintained healthily, reducing the risk of vocal injury. Voice hygiene awareness can help all professionals, especially teachers, to maintain voice quality. We believe regular voice use is a right of every individual, and understanding is needed to make people aware of voice disorders and how to prevent them. As professionals, we can assist and help out people with voice disorders or professionals at risk of acquiring voice disorders to rule out possible causes and treatment strategies.