Low Lubricant Research Articles

Wear Behavior of TiAlN/DLC Coating on Tools in Milling Copper–Beryllium Alloy AMPCOLOY® 83

In recent years, the exponential growth of the machining industry and its needs has driven the development of new manufacturing technologies, more advanced cutting tool types, and new types of coatings to extend tool lifespan. New coating solutions have been studied and implemented for machining tools, which provide a low friction coefficient and lubrication, thus increasing tool lifespan. Following this line of reasoning, it is relevant to develop scientific work aimed at studying the behavior of cutting tools coated with thin films that promote low friction and high lubrication, as is the case with DLC (diamond-like carbon) coatings. These coatings promote good resistance to oxidation and allow high machining speeds, properties also exhibited by TiAlN (titanium aluminum nitride) coatings. In fact, there is a gap in the literature studying the performance of cemented carbide tools provided with multilayered coatings in milling operations of Cu–Be alloys, commonly used in inserts of plastic injection molds. This study’s objective was to investigate the effect of a multilayer coating (TiAlN/DLC) on end-milling tools to analyze their cutting performance when milling a Cu–Be alloy known commercially as AMPCOLOY®83. The quality of the machined surface was evaluated, and the wear of the cutting tool was studied. A comparative analysis of milling parameters with respect to their effect on the condition of the surface after machining and the resulting wear on the tools, using coated and uncoated tools and different machining parameters, allowed us to verify a better quality of the machined surface and wear quantified in approximately half when used coated tools.

A novel valve strategy for particulate matter reduction in a gasoline direct injection engine operated at cold conditions

In this study, we proposed a novel intake strategy to reduce Particulate matter (PM) emissions from gasoline direct-injection (GDI) engines during cold-start conditions emissions. This strategy is characterized by generating strong intake turbulence and low in-cylinder pressure during fuel injection through delayed intake valve opening, which theoretically promotes fuel atomization and fuel-air mixture, thereby suppressing PM formation during combustion. Experiments were conducted on a single-cylinder GDI research engine, operating at 1500 rpm, 3, 6, and 8 bar IMEP, and stoichiometric air-fuel ratio conditions with low coolant and lubricant temperatures to experimentally demonstrate the effectiveness of the proposed valve strategy in reducing PM emissions. Benchmark tests were performed using an intake camshaft with intake valve opening (IVO) at −13 °aTDC and intake valve closing (IVC) at 227 °aTDC. The novel strategy uses an intake camshaft with very late IVO at 66 °aTDC and IVC at 226 °aTDC. Two injection pressures (Pinj = 100/200 bar) were used to evaluate the pressure requirement for achieving low PM emissions with both strategies. Start of injection was swept and optimized to match the valve strategy. The results showed that the novel valve strategy leads to a 50%–90% reduction in particle number and mass emissions in cold-start conditions, and a lower injection pressure requirement to achieve comparable particle number and mass emissions compared with the normal one. For the novel valve strategy, the fuel impingement with early injection timings is largely mitigated, and thus an early injection timing shortly before the IVO is recommended.

KINETIC STUDY OF ESTERIFICATION CATALYZED WITH ALUMINUM SULFATE AIMED AT CONVERTING LEVULINIC ACID INTO METHYL LEVULINATE

Recycling lignocellulosic biomass is a sustainable alternative to the petrochemical industry since it allows the production of valuable, sustainable, and environmentally friendly chemical products, such as levulinic acid (LVA) and levulinate esters. Methyl levulinate (MLV), for example, has been assessed as a fuel additive with low toxicity, high lubricity, and flash point stability. In this respect, the present investigation details a kinetic study of methyl esterification catalyzed with aluminum sulfate aimed at converting levulinic acid into methyl levulinate. The reactions were carried out in a Parr Instruments stainless steel reactor to assess the effect of temperature (120, 140 and 160 °C) and reaction time (30, 60, 120 and 180 min) on LVA conversion into MLV, maintaining a constant LVA:methanol ratio of 1:8 and aluminum sulfate catalyst concentration of 0.04 mol.L-1. The maximum LVA-MLV conversion of 93.04 % was obtained at a temperature of 160 °C and reaction time of 60 minutes. The pseudo first-order kinetic model exhibited the best fit to the experimental data, with correlation coefficients (R²) greater than 0.96, and it was used to calculate activation energy, obtaining a value of 10.19 kcal.mol-1.

A Review on the Dynamic Performance Studies of Gas Foil Bearings

Gas foil bearings have important and wide applications in high-speed turbomachinery, generating low frictional lubricating gas film in series with underlying elastic foil structures to support the rotor system. Their dynamic performance is of vital significance in maintaining the rotor stability as well as in depressing rotor vibrations. This paper conducts a comprehensive review on dynamic performance studies conducted on gas foil bearings, including research on the dynamic stiffness and damping coefficients, bearing stability, nonlinear vibrations of the rotor–bearing system, and active methods for controlling rotor dynamic motions. This review provides clear observations towards the developments and iterations of the models, methods, and experiments of these studies.

Natural Surfactant Stabilized Aqueous MoS2 Nano-Lubricants for Reducing Friction and Wear

From the outlook of energy saving and environmental protection, the development of eco-friendly and green lubricants without compromising their lubrication performance has become a global agenda. Nevertheless, water-based lubricants suffer from low lubricity and weak load-bearing capacity, making them unsuitable for various industrial applications. Herein, using liquid-phase exfoliation, bulk MoS2 layers are delaminated into atomically thin nanosheets and stabilized in a water medium by a natural surfactant, Sapindius Mukrossi (SM). A natural SM surfactant consisting of 10 % –12 % saponin molecules has a hydrophobic tail aglycone and hydrophilic head glycone molecules that provide steric repulsive forces against the aggregation of exfoliated MoS2 nanosheets. Optimization of the surfactant concentration in water led to highly concentrated MoS2 nanosheets (∼1.23 mg/ml in a single step) with an average lateral length (<L>) and number of layers (<N>) of ∼ 150 nm and ∼ 8 layers, respectively. Owing to its high concentration and few-layers, MoS2 nanosheets based aqueous dispersion was directly tested for aqueous lubricant applications. Compared to pure water, MoS2 nanosheets (0.1 wt%) in water led to effective reductions in the coefficient of friction and wear scar diameter of ∼ 75 % and ∼ 65 %, respectively. Wear depth ∼ 15 µm on SS ball is reduced to ∼ 1 µm when 0.1 wt% of MoS2 nanosheets-SM surfactant dispersion under similar testing conditions. Post-mortem analysis suggested that the stable formation of protective tribo-film on the worn surfaces of steel surface that were tested at different intervals (1-210-400 Days) leads to an effective sliding under load. To demonstrate the practicality of this dispersion, SM surfactant stabilized MoS2 nanosheets was used as a dielectric lubricant fluid in a wire EDM for advanced metal-cutting fluid applications.

Mo2Ti2C3 and PTFE synergistically functionalized corrosion-resistant, thermally conductive, super abrasion-resistant epoxy resin composite coating

Epoxy resin (EP) matrix composites are a widely used polymer-based protective coating material. However, the low lubricity leads to frictional wear problems that make their large-scale development and application a serious challenge. Based on this, a multifunctional composite coating (MPT-EP) with low wear, high lubricity, high thermal conductivity, and corrosion resistance was prepared by introducing polytetrafluoroethylene (PTFE) and lamellar Mo2Ti2C3 as a composite lubricant into epoxy resin matrix using a simple solvent dispersion method. The results showed that the introduction of the composite lubricant resulted in enhanced hardness and mechanical properties of the composite coating. Compared with the single epoxy resin coating (0.31), the friction coefficient (COF) of the composite coating was only 0.22, and the friction surface did not show obvious abrasion marks. The surface temperature of the composite coating was up to 51.4 °C when it was placed on a hot bench at 60 °C for 60 s. In addition, the COF of the composite coating did not change significantly after being immersed in acid, alkali and salt solutions. Therefore, the Mo2Ti2C3-induced multifunctional epoxy resin matrix composites have important application potential and research value in the field of ultra-wear-resistant and high lubrication protective coatings.

Identifikasi Kenaikan Suhu Minyak Lumas Pada Motor Induk di MV. Manalagi Dasa

Lubrication is one aspect that must be paid attention to, remembering that if there is a delay in lubrication or imperfect lubrication, it will result in damage to the parts that rub together. Low lubricating oil pressure is one of the factors causing imperfect lubrication in the engine. The purpose of lubrication for the performance of the main engine is to reduce friction between other components of the main engine. This research was carried out at MV. Manalagi Dasa, the method used in this research was the Fishbone Diagram. The problem formulation of this research is what causes an increase in the temperature of the lubricating oil on the main motor and what is the impact of increasing the temperature of the lubricating oil on the main motor. Based on research that has been carried out, there are several factors that cause less than optimal lubrication of the oil cooler on the main engine, namely engine factors including damage to gaskets, human factors, namely the lack of understanding of the driver about the lo cooler, operational and maintenance method factors, namely incompatibility in implementing the PMS (Plan Maintenance System) as well as environmental factors, namely dirty sea chest filters. Efforts made include repairing or replacing gaskets on the lo cooler plate, the importance of the machinist's understanding of the lo cooler, implementing PMS (Plan Maintenance System), and cleaning the sea chest filter.

Bingham plastic fluids flow analysis in multimembranes fitted porous medium

A mathematical analysis is presented for the flow of a Bingham plastic fluid propelled by the multi-membranes pumping mechanism through porous media. Two successive membranes with different amplitude, diameter, and phase lag, are fitted at the upper wall of the channel, and the lower wall is stationary. Due to the simultaneous propagation of both membranes, the pressure is generated at the membrane's position, which helps in propelling the fluids in forward and backward directions depending upon the compression and expansion cycles of the membranes. The low Reynolds number assumption and lubrication theory are utilized to linearize the governing equations, which are further analytically derived, and then employing MATLAB codes to compute the illustrations for the interpretation of the results. The effects of key parameters like plug flow region, pore size and diameter of membranes on the velocity field, wall shear stress, pressure gradient, fanning friction factor, head loss and particle trajectories, are analysed in the microchannel. Results of the present model conclude that the geometrical properties of membranes, rheological properties of fluids and porosity of the medium significantly alter the flow and pumping characteristics which give valuable insights for the design of micro-valve less pumping actuators to be aimed at controlling microscale transport processes in various medical diagnoses and treatments.

Helical Gearbox Defect Detection with Machine Learning Using Regular Mesh Components and Sidebands.

The current paper presents helical gearbox defect detection models built from raw vibration signals measured using a triaxial accelerometer. Gear faults, such as localized pitting, localized wear on helical pinion tooth flanks, and low lubricant level, are under observation for three rotating velocities of the actuator and three load levels at the speed reducer output. The emphasis is on the strong connection between the gear faults and the fundamental meshing frequency GMF, its harmonics, and the sidebands found in the vibration spectrum as an effect of the amplitude modulation (AM) and phase modulation (PM). Several sets of features representing powers on selected frequency bands or/and associated peak amplitudes from the vibration spectrum, and also, for comparison, time-domain and frequency-domain statistical feature sets, are proposed as predictors in the defect detection task. The best performing detection model, with a testing accuracy of 99.73%, is based on SVM (Support Vector Machine) with a cubic kernel, and the features used are the band powers associated with six GMF harmonics and two sideband pairs for all three accelerometer axes, regardless of the rotation velocities and the load levels.

Effects of defect creation and passivation on graphite friction under ultra-high vacuum conditions

Graphite holds significant promise as a solid lubricating material for machine operation in ambient conditions. However, the intricacies of its mechanism remain a subject of debate at the nanoscale. In this study, atomic force microscopy (AFM) experiments conducted in ultrahigh vacuum (UHV) conditions provide direct evidence that the adsorption of water molecules significantly compromises friction performance, both on the basal plane and across step edges. This challenges the longstanding belief that the poor lubricating properties of graphite in a vacuum result from the desorption of water molecules. Moreover, the experimental findings put forth a compelling bond passivation hypothesis for graphite lubrication in ambient conditions. The process involves the introduction of defects with dangling bonds on graphite through annealing highly oriented pyrolytic graphite (HOPG) at elevated temperatures (≥773 K) in UHV conditions. Subsequently, these dangling bonds are gradually passivated by a small amount of residue atoms or molecules. Consequently, the continuously monitored friction force exhibits an exponential decrease over time following annealing. This study advances a molecular level understanding of low lubrication mechanism for graphite.

The Influence of Peripheral Components in Test Rig Creation of White Etching Cracks

White Etching Cracks (WEC) have become a subject of extensive research in material science, chemistry and lubrication, and even operational mathematics by AI learning. Initially reported in the 1960s and considered an exotic anomaly, the failures gained importance with the global rise of wind energy power and the automotive industry. Unexpectedly high failure rates in various bearing applications have led to the need for a deeper understanding and prevention of WEC. It has come a long way from materials inspection, to parametrically studying WECs on test rigs, to the understanding that WEC is a stand-alone phenomenon and sparingly related to common failures in bearing technology. It has been commonly accepted that WEC drivers have multiple dimensions, e.g., material, contact mechanics, chemistry, and electricity. The impact of these factors on WEC failures is frequently studied using test rigs at the component level, such as the FE8 test rig. The FE8 has been utilized in numerous investigations due to its ability to replicate WEC failures without requiring artificial electricity or hydrogen charging by using specific lubricant chemistry and operating conditions. However, through intensive testing, it was observed in this study that a standard material in an FE8 rig component demonstrated a profound influence on WEC formation. This paper presents the details of the testing and analysis, aiming to investigate the mechanisms of interactions between the hose material and the low reference lubricant. The results demonstrate that the chemistry of the component material plays an important role in WEC formation. This finding may have significant impact in WEC studies, especially when the FE8 rig is used.

Alcohol-diesel fuel blends and their effect in performance and exhaust emissions

The growing demand of fossil fuel and the rising of its price strengthen the incessant search for energy alternatives. The use of alcohol-diesel fuel blends in diesel engines has recently received interest as an alternative fuel for use in spark ignition (SI) engine. However, little research concerning diesel fuel has been found. Moreover, alcohols can improve the combustion phase due to an increase of the oxygen content and reduce exhaust emissions as soot and particulate matter, besides knock. The most used alcohols in blends with diesel fuel are methanol and ethanol, butanol added recently. In contrast, there are very few studies about propanol and pentanol blended with diesel fuel, although engine results are remarkable. Some of them could be even produced via biorefinery, thus being better to the environment than the petroleum-based fuels. Nevertheless, the main challenge is to overcome disadvantages of alcohols including low lubricity, difficulty of vaporization and high auto ignition temperature and definitely, their well-know immiscible problem with diesel fuel being required co-solvents or emulsifiers. Besides, these additives are used to enhance the properties of the fuel, like the increase of the cetane number or the production of a stable blend.

The significance of low and high temperature solid lubricants for brake friction applications and their tribological investigation

Solid lubricants like metal sulfides and fluorides are important ingredients in stabilizing the friction in brake pads. It is essential to consider the oxidation temperature and the compatibility of the metal sulfides. This study emphasises the importance of incorporating a variety of solid lubricants based on oxidation temperature regimes. Low-temperature solid lubricants such as molybdenum disulfide, iron sulfide, and bismuth sulfide, as well as high-temperature solid lubricants such as tin(II)sulfide, tin(IV)sulfide, and calcium fluoride were used in the preparation of brake pads. The combination of low and high-temperature solid lubricant mix was tested for tribological performance in brake pads. The results show the necessity of using both low and high-temperature solid lubricants to enhance the tribological performance of brake pads.

Bio‐inspired low wear and durable lubrication interfacial system based on thixotropic hydrogel for artificial joints

AbstractInspired by the excellent wear resistance and lubrication of articular joints, a novel bionic interfacial system was proposed by combining thixotropic hydrogel with surface porous Ultrahigh Molecular Weight Polyethylene (UHMWPE). Thixotropic hydrogel, synthesised by gelatin, alginate sodium, tannic acid and weak crosslinking by Ca2+ (Gel‐TA‐Alg@Ca2+), was used as a lubricant due to its shear‐thinning when loaded, then the recovery viscosity to be benefitted for reserving in surface pores on UHMWPE when unloaded. Surface porous UHMWPE was fabricated by using hydroxyapatite particles as porogen to control its porosity, pore size, surface roughness and surface energy (PE‐HA). Gel‐TA‐Alg@Ca2+ significantly reduced average coefficients of friction and wear factors compared to those under normal saline and calf serum solution lubricating after reciprocating tribological testing. Notably, Gel‐TA‐Alg@Ca2+ still maintained thixotropy and was stored in surface pores of UHMWPE even after tribological testing for 7200 min. Thus, durable lubrication could be realised due to the synergistic effect of surface porous structure and thixotropy. Stribeck curves showed the characterisations of mixed, elastohydrodynamic and hydrodynamic, but without boundary lubrications for PE‐30HA under three lubricants. The present results might provide the potential application to construct the durable lubrication bionic articular joint interfacial system for artificial joints.

Simulation of Air Ingestion in a Mechanical Seal With Inward Pumping Spiral Grooves

Abstract Inward pumping spiral groove seals are used in many applications, such as transmission gearboxes or electric vehicles, as they can provide zero leakage and very low operating friction. The spiral grooves are connected to the low pressure side (typically atmosphere) and pump the fluid inward that is to say toward the high pressure side (inlet). If the rotational speed is high enough, the low pressure fluid (air) completely occupies the sealing area and is used as a low friction lubricant. However, for lower operating speeds or higher fluid pressures, the seal can be lubricated by both fluids simultaneously. This occurs particularly during start-up and shutdown. In this work, a numerical simulation of the two phases in the sealing gap of an upstream pumping spiral groove seal during start-up is performed. The establishment of the film is analyzed and the effect of the rotational speed and operating pressure on the fluid composition (air and liquid) in the sealing interface is studied. For the analyzed seal, it is shown that the amount of air pumped in the sealing area is controlled by the duty parameter.

Impact of the Lubricant on a Modified Revolving Vane Expander (M-RVE) in an Organic Rankine Cycle System

The expansion device is the critical component of micro-to-small scale organic Rankine cycle (ORC) systems, substantially affecting system efficiency and cost. Low isentropic efficiency and lubrication requirements are the main issues associated with using volumetric expanders in ORC systems. Despite lubrication contributing to reducing internal leakages in an expander, it may compromise the performance of the ORC system by adversely affecting the evaporator’s thermal capacity. This study tests a recently developed and modified revolving vane expander (M-RVE) in a micro-scale ORC test rig by implementing an adjustable oil mass flow rate. The impact of the lubricant oil on the performance of the M-RVE prototype is investigated within a wide range of oil circulation rates (OCR). The results demonstrate a negligible improvement in the filling factor for OCRs higher than 1%. Moreover, the shaft power is not considerably sensitive to OCR, while the calculated isentropic efficiency of the expander improves with OCR. Furthermore, the impact of the lubricant oil on the performance of the evaporator is studied, assuming the exact OCR as the expander and measured temperature and pressure similar to the pure refrigerant for the lubricant-refrigerant mixture in the evaporator. The study shows that the evaporator capacity is penalized with OCR, especially for values higher than 1%. Hence, an OCR of about 1% is a good compromise, and it can be used as a guideline for designing revolving vane expanders for micro-scale ORC systems without a dedicated lubricant oil circuit.

Atomistic understanding of rough surface on the interfacial friction behavior during the chemical mechanical polishing process of diamond

The roughness of the contact surface exerts a vital role in rubbing. It is still a significant challenge to understand the microscopic contact of the rough surface at the atomic level. Herein, the rough surface with a special root mean square (RMS) value is constructed by multivariate Weierstrass–Mandelbrot (W–M) function and the rubbing process during that the chemical mechanical polishing (CMP) process of diamond is mimicked utilizing the reactive force field molecular dynamics (ReaxFF MD) simulation. It is found that the contact area A/A0 is positively related with the load, and the friction force F depends on the number of interfacial bridge bonds. Increasing the surface roughness will increase the friction force and friction coefficient. The model with low roughness and high lubrication has less friction force, and the presence of polishing liquid molecules can decrease the friction force and friction coefficient. The RMS value and the degree of damage show a functional relationship with the applied load and lubrication, i.e., the RMS value decreases more under larger load and higher lubrication, and the diamond substrate occurs severer damage under larger load and lower lubrication. This work will generate fresh insight into the understanding of the microscopic contact of the rough surface at the atomic level.

Experimental study on startup characteristics of R290 air conditioner with low lubricant charge

As an A3 refrigerant, the charge of the natural refrigerant R290 in the refrigeration system is limited. The use of partially miscible lubricants and a reduction of the lubricant charge can effectively decrease the refrigerant charge. These two measures affect the startup dynamic characteristics of the compressor and the air conditioner. In this paper, variations in system temperature, pressure, and oil sump parameters during the cold startup process of a 1.5P R290 split inverter room air conditioner with different charges of PAG VG40 were experimentally measured under the rated cooling and low-temperature heating condition. The experimental results showed that the viscosity of the refrigerant/lubricant mixture of low lubricant charge (LLC) was lower than that of the normal lubricant charge (NLC), and the duration of low viscosity with LLC was longer. The low viscosity during startup is mainly due to the insufficient amount of lubricant in the oil sump. Three measures were proposed to alleviate the problem of low startup viscosity. Among them, the modification of the bearing cover effectively improved the viscosity of the LLC mixture, and the minimum viscosity of the bearing cover with LLC was even higher than that of the prototype with NLC. Furthermore, the bearing cover modification allows using a lower viscosity grade of lubricant for R290 rotary compressors.

Multifunction of Biomimetic Liquid Infused Systems Derived from SLIPS Theory: A Review

AbstractSlippery liquid infused porous surface (SLIPS) inspired by the microstructure of carnivorous Nepenthes has the potential to be used in a wide range of fields, including nautical, industrial, medical, etc. Due to their excellent optical transparency, self‐healing after mechanical injury and controllable wetting properties, SLIPS has attracted extensive research interest. With appropriate lubricants, sufficient performance will be armed to the surface so as to adapt for further requirements. In this review, the first part focuses on the basic theory of the different wettable models explaining the physical phenomena of these surfaces and their wettability. Then various representative fabrication methods are listed such as lithography, layer‐by‐layer assembly, and electrochemical anodic oxidation. There are three steps including in the process of SLIPS preparation:fabrication of rough substrate, chemical modification of rough substrate and infusion of low surface energy lubricating oil. Furthermore, recent applications and researches of SLIPS are introduced, mainly about drag reduction, anticorrosion, anti‐icing, medical treatment, and droplet manipulation. Finally, make a prospection to the limitations of practical application and future development direction of the technology.

Impact of N,N-Bis(2-ethoxyethyl) Fatty Acid Amides on the Lubrication Performance of Kerosene Fuel F-34 for Use in CI Engines

In an attempt to avoid serious problems that can affect the efficiency of refueling ground-operated vehicles and aircraft during military operations, the Armed Forces of the North Atlantic Treaty Organization (NATO) are introducing the use of a unique fuel for both air and land use. The fuel that has been selected is the F-34, similar to Jet A-1, which is used in civil aviation, in order to replace diesel fuel in many applications. It has to be mentioned that tests performed with this fuel, which is kerosene type on the high frequency reciprocating rig (HFRR) have shown that such fuel is responsible for severe wear. This very high wear is related to the very low lubricity of aviation fuel. Having the idea to improve the lubricity of aviation fuel to the level of fuels used in compression ignition engines (diesel fuel), seven N,N-Bis(2-ethoxyethyl) fatty acid amides were formulated from various vegetable oils (sunflower oil, soybean oil, cottonseed oil, olive oil, tobacco seed oil, coconut oil, used frying oil), and they were evaluated as lubricity improvers of the aviation fuel. The required tribological measurements for lubricity rating were carried out by employing ISO 12156-1 test method on an HFRR instrument. The test conditions during the measurements were in the range of 55% to 58% for the relative humidity and 24 °C for the temperature. The results from the tribological measurements showed that all N,N-Bis(2-ethoxyethyl) fatty acid amides used were rated as efficient in order to provide an acceptable mean wear scar diameter (below 460 μm) at concentrations from 150 to 300 ppm. Additive concentrations below 150 ppm did not improve the lubricity at the required level. The increase of N,N-Bis(2-ethoxyethyl) fatty acid amides at concentrations over 300 ppm did not have any significant decrease in the wear scar diameter. A comparison between the N,N-Bis(2-ethoxyethyl) fatty acid amides showed that those formulated by non-polyunsaturated oils like olive oil and coconut oil seem to have better lubricity improver characteristics.