Lubricant Volume Research Articles

Functionalized porous 316 L stainless-steel with oil reservoir against ice adhesion

Slippery liquid-infused porous surfaces (SLIPSs) are used in anti-fouling, anti-icing and anti-corrosion, but lack of long-term durability is a challenge due to lubricant depletion. SLIPS with self-lubricating properties can achieve extended durability without reapplying the lubricant. Generally, lubricant is stored close to surface, thus lubricant reservoir is limited. Here bulk of porous material acts as lubricant reservoir in 316 L stainless-steel SLIPS with self-lubricating properties for lowering ice adhesion. The reservoir was fabricated by using a space holder technique in metal injection molding (MIM) with lubricant reservoir volume up to 17.3 %. Surface was activated with vinyltrimethoxysilane (VTMS) to attract lubricant. Ice adhesion strength was increased up to three times against non-porous reference in ice adhesion testing using porous surface without lubrication. The best performing SLIPS showed 6.7 times lower ice adhesion against counterpart porous surface without lubricant and 1.7 times lower than non-porous reference. This self-lubrication was achieved on mechanically durable structure having an adjustable lubricant storage capacity by temperature-driven phenomenon during de-icing.

Analysis of refrigerant/lubricant distribution and operating characteristics of a rotary booster for data center free cooling

A booster-driven loop free cooling system plays a crucial role in enhancing data center energy efficiency and reducing emissions due to the special booster with low pressure ratio as a vital driving component. And the impact of lubricant and its fraction on the booster operation are the key points under low pressure ratio, as well as lubricant distribution. In this paper, the refrigerant/lubricant two-phase mixing flow in the working chamber of a booster was investigated under low pressure ratio for data center free cooling. The volume of fluid (VOF) multiphase flow model combining the working chamber of the rotary booster and discharge valve was built up to analyze the dynamic characteristics of the booster under free cooling conditions. The effect of lubricant fraction and its working frequency on the operating indexes (exhaust temperature/pressure, mass flow rate, volumetric efficiency, indicated specific work, energy efficiency ratio) were studied. The lubricant distribution and its changes for different angles and frequencies were presented. The results indicate that it can improve the thermal performance of the booster effectively with appropriate volume fraction of lubricant. The lubricant in the two-phase flow reduces the inner temperature and pressure in the booster working chamber, which changes the exhaust pressure and volumetric efficiency as well as the cooling capacity. The exhaust pressure and the mass flow rate increase notably for the refrigerant/oil mixture with the increasing lubricant volume fraction, while other performance indexes decrease. The exhaust pressure and the mass flow rate increase by 0.51 % and 47.14 %, separately, when the lubricant volume fraction raises from 0 to 5 % at operating frequency of 50 Hz. Whereas, the exhaust temperature, refrigerant mass flow rate, volumetric efficiency, indicated specific power, cooling capacity and EER decrease by 18.11 %, 4.81 %, 47.14 %, 38.94 %, 4.81 % and 26.36 %, respectively. The investigations can support the lubrication and sealing of the booster with low pressure ratio for free cooling to reach efficient and reliable operation.

Improved Operating Behavior of Self-Lubricating Rolling-Sliding Contacts under High Load with Oil-Impregnated Porous Sinter Material

Resource and energy efficiency are of high importance in gearbox applications. To reduce friction and wear, an external lubricant supply like dip or injection lubrication is used to lubricate tribosystems in machine elements. This leads to the need for large lubricant volumes and elaborate sealing requirements. One potential method of minimizing the amount of lubricant and simplifying sealing in gearboxes is the self-lubrication of tribosystems using oil-impregnation of porous materials. Although well established in low-loaded journal bearings, self-lubrication of rolling-sliding contacts in gears is poorly understood. This study presents the self-lubrication method using oil-impregnated porous sinter material variants. For this, the tribosystem of gear contacts is transferred to model contacts, which are analyzed for friction and temperature behavior using a twin-disk tribometer. High-resolution surface images are used to record the surface changes. The test results show a significant increase in self-lubrication functionality of tribosystems by oil-impregnated porous sinter material and a tribo-performance comparable to injection-lubricated tribosystems of a sinter material with additionally solid lubricant added to the sinter material powder before sintering. Furthermore, the analyses highlight a significant influence of the surface finish, and in particular the surface porosity, on the overall tribosystem behavior through significantly improved friction and wear behavior transferable to gear applications.

Fretting Wear Behaviors of Silicone Rubber under Dry Friction and Different Lubrication Conditions.

The fretting wear behaviors of silicone rubber under dry friction and different lubrication conditions are studied experimentally. Water, engine oil, dimethyl silicone oil (DSO), and dimethyl silicone oil doped with graphene oxide (DSO/GO) are selected as lubricants. Under the liquid lubrication conditions, the silicone rubber samples are always immersed in the same volume of lubricant. The contact model of a 440C steel ball and silicone rubber sample is the sphere-on-flat contact. The reciprocating fretting wear experiments are carried out using the reciprocating friction wear tester. A scanning electron microscope and three-dimensional white-light interference profilometer are used to detect the surface wear morphology and obtain the wear volume, respectively. The influences of normal force, lubrication condition, and displacement amplitude on fretting wear behavior are discussed. The fretting wear performances of silicone rubber under different fretting states and lubrication conditions are compared. The results show that for a small normal force, silicone rubber has the best wear resistance under DSO/GO lubrication. While for a large normal force, silicone rubber has the best wear resistance under engine oil lubrication.

Exploring the Impact of Additives on Tribological Characteristics in Lubricating Oils: A Critical Review

In mechanical systems, lubricants play a crucial role in minimizing friction, dissipating heat, and preventing wear. Additives, comprising both organic and inorganic compounds and typically constituting 0.1% to 30% of lubricant volume, are introduced to enhance lubricant performance. This study investigates the influence of various additives on lubricant behaviour and performance, encompassing antifoam agents, corrosion inhibitors, antioxidants, detergents, extreme pressure additives, pour-point depressants, and viscosity index improvers. Friction coefficients were meticulously measured using a pin-on-disk tribometer to assess the Tribological and physical properties of these additives. Surface analysis via SEM provided insights into wear characteristics influenced by the additives. The comprehensive tribological assessment reveals that the incorporation of additives consistently reduces friction and wear across different base oil types. This underscores the critical role of additives in improving lubricant properties, maintaining thermal stability, and forming protective films on surfaces. Our findings advocate for the strategic use of additives to enhance lubricant performance and longevity.

Effects of Coating and Lubrication on Friction and Wear for Metal-to Metal Application

Friction and wear between sliding surfaces can lead to various issues in industrial applications, such as increased costs, reduced machine lifespan, loss of functionality, energy loss, and decreased system efficiency. To mitigate these problems, lubricants and coatings are commonly employed. This study aims to investigate the impact of coatings and lubrication on friction coefficient, wear volume loss, and lubricant temperature using the block-on-ring wear test. The effectiveness of different coatings (uncoated, DLC, CrN, and TiALN) and lubricants (anti-friction graphene oxide additive oil and strong nano engine oil additive) in reducing friction and wear is evaluated. The block-on-ring tests are conducted under varying loads (6-60 N), speeds (1450 rpm), lubricant volumes (40 ml), and durations (2-20 min). The coefficient of friction is measured using an inline load cell, wear volume loss is determined by weighing the blocks before and after the experiment, and lubricant temperature is monitored using thermocouples. The results indicate that the coefficient of friction decreases with increasing load, while the lubricant temperature rises. Coated blocks exhibit lower wear volume loss compared to uncoated blocks. Overall, the combination of CrN-coated blocks and anti-friction graphene oxide additive oil demonstrates the best tribological performance.

Machine learning-based estimation of nano-lubricants viscosity in different operating conditions

The importance of improving and optimizing the energy transfer systems has been highlighted recently due to ever-increasing demand for energy in the world, and therefore the lubrication of systems has received significant attentions. The improvement of thermophysical properties by nano-particles can be considered as an efficient approach to this end. A comprehensive study dealing with constructing myriad machine learning-based models for predicting the viscosity of nano-lubricants is lacking in the literature. This research, therefore, aims at development of eight different artificial intelligence models including, Adaptive Boosting, Random Forest (RF), Ensemble Learning, Decision Tree (DT), Support Vector Machine (SVM), K-Nearest Neighbors (KNN), Convolutional Neural Network (CNN), and Multi-Layer Perceptron Artificial Neural Network (MLP-ANN) to estimate viscosity of different nano-lubricants as a function of amount of MWCNT, nanoparticle, type of lubricant, temperature, shear rate, and solid volume fraction. These models are prepared and tested based on a databank including 1086 viscosity points. The results show that the MLP and CNN models are the most accurate methods with R-squared of 0.950131 and 0.95035, respectively, while the estimation of computational time expresses that MLP and CNN models require the most computational time for training. Moreover, sensitivity analysis reveals that temperature has the most effect on viscosity of nano-lubricants.

Measurement for Lubricant Distribution in an Angular Contact Ball Bearing and Its Influence Investigation

Oil lubrication is widely adopted in rolling bearings, the characteristics of which affect the oil film formation and friction state, and also the heat generation and dissipation characteristics. However, it is difficult to measure the internal lubrication of rolling bearings in practice, which is of great importance for lubrication and structure design. In this work, one measurement system for lubricant distribution was built and installed on a test rig to obtain original pictures of the lubricant in bearings. Grayscale images were obtained by picture processing to characterize the lubricant distribution, and the image pixels were evaluated for the characterization of lubricant volume. Finally, the measurement of the lubricant distribution in the angular ball bearing was carried out under different lubrication and cage groove conditions, and their influences were investigated. The results show that the lubricant distribution is affected by the oil jet nozzle angle, operating speed, and cage structure. The lubricant capacity among balls and the cage pocket in bearings gradually increased with the increase in the nozzle angle and the depth of the cage grooves, but decreased with the increasing operating speed. The experimental results are helpful to provide a basis for the structure and lubrication design of ball bearings.

Simulation of refrigerant-lubricant two-phase flow characteristics and performance test in space compressor

The vapor-compression heat pump allows for lightweight heat-control systems and efficient heat emissions. It is considered to be the best choice for future space thermal control systems. To solve the problem of separation and compression deterioration of conventional positive-displacement refrigeration compressors in a microgravity environment, an innovative microgravity solution, mixing refrigerant and lubricant without oil separation, is proposed. A flow model in the compression chamber was developed and simulations were performed to investigate the effects of gravity and lubricant volume fraction on the flow characteristics of the refrigerant-oil mixture in a rolling rotor compressor. A modified compressor performance test bench was built and the effect of compressor speed on parameters such as power and heat dissipation was investigated experimentally. The results showed a maximum difference between the simulated and experimental values of compressor discharge temperatures of 9.16 %. Under microgravity conditions, a lubricant-refrigerant mixture with a volume fraction of less than 5 % can serve as the system working medium. The lubricant volume fraction at the outlet of a compressor cycle in normal gravity was 4.9 %, while it was 3.34 % in microgravity. As the compressor speed increased from 1500 to 5000 rpm, the compressor power increased from 15.5 to 64.5 W and the system heat discharge rate increased from 115.2 to 164.1 W. The system refrigeration coefficient of performance (COPc) decreased from 6.4 to 1.5, while that of heat dissipation, COPh, decreased from 7.4 to 2.5.

Expanding the applicability of ASTM D3233A Pin & Vee Block method to evaluate lubricant emulsions for cutting applications

ABSTRACT ASTM Method D3233A uses a Pin&Vee Block tester to evaluate cutting fluids. However, the standard defines a steel-steel contact, uses a small volume of lubricant, and the test report is limited to the ‘ultimate failure load’. With our approach, we bring testing closer to reality, using different metallurgies and testing the oils in aqueous emulsion-form. We monitor the frictional torque throughout increasing load, so that differences between products are revealed that are not visible in failure load alone. By modifying lubrication to recirculated or misted conditions, we simulate cutting of forming operations. Consequently, this provides an additional tool for cost efficient ranking of cutting fluids, based on an industry-accepted instrument. We demonstrate same ranking of cutting fluids as well established Tapping Torque Tests, with the advantage of using a simplified and lower cost configuration. Developing a standardized test protocol involves more work on reproducibility and correlation to real machining processes.

Influence Analysis of Lubricant Recesses on the Working Capacity of the Bridge Span Spherical Bearing

The load on transport and logistics systems is increasing every year. This is due to car park growth around the world. Thus, increasing bridge structure durability is an urgent task for bridge-building companies. This study analyses the contact deformation of spherical bearing elements through an anti-friction polymer layer with different geometrical configurations of recesses for the lubricant, i.e., annular grooves and spherical holes. The material of the anti-friction layer (a modified polytetrafluoroethylene (PTFE)) is modelled within the framework of the deformation theory of plasticity. The procedure of automating the numerical model construction depends on the input parameters, including the thickness of the layer, the basic geometrical parameters of the recesses for the lubricant, and the distance between the rows of recesses, etc. The influence of the arrangement of filling sliding anti-friction layers on recesses for lubricants in the form of spherical holes on the contact deformation behaviour of bridge bearings has been considered. The reduction of lubricant volume in the sliding anti-friction layer with the geometry of recesses in the form of spherical holes ranges from 26 to 48.4%, depending on the filling scheme, has been found. In this case, structures with lubrication recesses in the form of spherical holes have several advantages, including a more uniform distribution of contact parameters in the interface areas of the steel plates with the anti-friction layer, reduction of the maximum level of the plastic deformation intensity, displacements along the normal relative to the free end of the sliding layer, and the settlement of the bearing.

Liquid-solid triboelectric nanogenerators for a wide operation window based on slippery lubricant-infused surfaces (SLIPS)

Triboelectric nanogenerators (TENG) have emerged as suitable devices that are suitable to harvest widely abundant and renewable blue energy. However, a major drawback in related deployments include the reliability of the system when operating in variable atmospheric conditions. To address this limitation, we propose the integration of slippery lubricant-infused porous surfaces (SLIPS) as key TENG component. For instance, we combine SLIPS with transistor-inspired architectures to develop a robust single-electrode triboelectric nanogenerator (SLIPS-SE-TENG) that is shown to operate effectively under extreme temperature and humidity. For this purpose, we use the energy of water droplets (as in rain) impacting a surface to generate the electrical energy output. Our theoretical calculations and atomic force microscopy measurements show that a small volume of lubricant per surface area (4 μL/ per cm2 of porous PTFE) is sufficient to produce a low water contact angle hysteresis, leading to efficient energy conversion, provided the droplet’s moving velocity on the surface surpasses a threshold (0.3 mm/s). As such, we demonstrate SLIPS-SE-TENG to generate an instantaneous short-circuit current of 3 μA (charge density 8.8 nC/cm2). Importantly, we address the limitations of TENG fabricated with traditional superhydrophobic surfaces, affording a device that works normally and stably in harsh environments, under freezing temperatures or high humidity.

Effect of the third body layer formed at different temperature on fretting wear behavior of 316 stainless steel in the composite fretting motion of slip and impact

316 SS is a commonly used material for steam generator tube. The object of this investigation is to study the influence of temperature, which is 95 °C and 250 °C, on the formation of the third body layer (TBL), and the role of TBL on the fretting wear behavior of 316 SS. Thus, the fretting wear experiment between 316 SS tube and 316 SS plate was carried out in the composite fretting motion of slip and impact in pure water environment. The experiment time was set as 24 h, 48 h, 72 h and 120 h. The results show that at 95 °C, TBL is hard and attaches closely to the surface, which can lead to uniform abrasion and result severe microploughing between the base materials. While at 250 °C, the existence of thick TBL can avoid direct contact between base materials, and it can be easily deformed by shear forces due to its ductility, which acts as a lubricant and reducing volume loss and wear coefficient. Finally, we can conclude that temperature affects the formation mechanism and properties of TBL, thus changing the fretting wear behavior.

DEFORMATION BEHAVIOR MATHEMATICAL MODELING OF A POLYMER MATERIAL LAYER WITH TECHNOLOGICAL HOLE FOR A LUBRICANT

Mathematical modeling of the flat layer of a polymeric material deformation behavior with a polished steel plate within the framework frictional contact was carried out of this work. The influence of the technological groove geometric configuration for the lubricant on the contact unit deformation is considered. The lubricant volume in the calculation scheme does not take into account that does not correspond to the favorable occasion of lack of lubrication in the recess. The parameterized model creation of a polymer layer portion with one technological recess with a different base rounding radius from 0.5 to 2 mm with a step of 0.25 mm is done. The technological recess geometrical influence on the deformation of its profile at loads from 5 to 90 MPa was established within the framework of the study. Changes in the cross-sectional area of the recess, the maximum level of the plastic deformations intensity, contact pressure, contact tangential stress and the contact interaction area from the load and the rounding radius are established. The contact zone parameters redistribution due to an increase in the contact interaction area for all rounding versions for the technological recess base for the lubricant occurs at loads of more than 40-50 MPa. The design with a rounding radius of 2 mm has a number of advantages: minimum deformation of the technological recess area, the minimum level of the maximum plastic deformations intensity, the maximum contact interaction area, etc.

Observational cohort study of the effect of a single lubricant exposure during transvaginal ultrasound on cell-shedding from the vaginal epithelium.

The outer layers of the vaginal epithelium (VE) are important because they accumulate glycogen which, under optimal conditions, Lactobacillus spp. consume to grow and acidify the vaginal microenvironment with lactic acid. We hypothesized that exposure to lubricant, for example in the conduct of a transvaginal ultrasound (TVUS), may contribute to the shedding of mature epithelial cells, exposing immature cells. Cervicovaginal fluid (CVF) was sampled at four time points by menstrual cup (Softdisc™) from 50 women referred for TVUS, during which a controlled volume of lubricant was applied to the TVUS wand. Samples were collected (1) immediately before TVUS and (2) 6-12 hours, (3) within one week, and (4) two weeks after TVUS. Clinical vaginal lubricants are similar to commercial lubricants, and often have a high osmolality or pH, and contain bactericides such as methylparaben and propylparaben. The number and maturity of epithelial cells in each CVF sample were measured by quantitative and differential fluorimetry (maturity index, MI). Comparisons of cell-counts and maturity were made by paired Wilcoxon signed-rank tests. Among women with a high pre-TVUS MI (> 3), there was a decrease in median cell-count and mean MI in the sample collected 6-12 hours after TVUS (p<0.001, n = 26 and p < 0.001, n = 26, respectively). For these women, cell-count and MI remained lower in the sample collected within the subsequent week (p<0.001, n = 29 and p<0.01, n = 29, respectively), and MI remained lower in the sample collected within two weeks of TVUS (p<0.01, n = 25), compared to the pre-TVUS sample. Among participants with a low pre-TVUS MI (< 3), cell-count was higher in the sample collected within two weeks of TVUS compared to the pre-TVUS sample (p = 0.03, n = 15), but no significant changes in MI were observed. Results were similar when restricted to reproductive-age women. This preliminary data indicates hypertonic vaginal lubricants may increase vaginal epithelial cell shedding.

Comparative Investigation of Worm Positions for Worm Gear-box Performance under No-Load Condition

The Worm Gear drive is a gear arrangement where the worm shaft meshes with a worm wheel (gear). The worm shaft plays an important role in reduction ratio &amp; efficiency. This worm shaft can be used at the top and the bottom in the gearbox. This technical research paper provides a comprehensive comparative evaluation of Input torque analysis &amp; heating rate of lubricant inside the gearbox for two positions of the worm shaft in the worm gearbox under no-load condition. Worm shaft at the top and worm shaft at the bottom were assessed at variable speed (1000-1400 rpm), the different splashed volume of lubricant (1.5-2.7 liter), and variable temperature of lubricant (30-50 ºC). Input torque was measured with the help of a direct torque measurement technique. Similarly, the heating rate of the lubricant was also measured with a temperature sensor for both orientations of the worm shaft. Full factorial experiments were performed on a specially designed and fabricated worm gear test rig. The experiments showed that the input torque requirement for the worm at the bottom position is 20 -25% higher than the worm at the top position at an average speed. The heating rate remains almost the same for both orientations. This study aimed to find the suitable orientation of the worm shaft which reduces the power losses and increases efficiency.

Investigation of the friction coefficient evolution and lubricant breakdown behaviour of AA7075 aluminium alloy forming processes at elevated temperatures

The lubricant behaviour at elevated temperatures was investigated by conducting pin-on-disc tests between P20 tool steel and AA7075 aluminium alloy. The effects of temperature, initial lubricant volume, contact pressure and sliding speed on the lubricant behaviour (i.e. evolutions of the coefficient of friction (COF) and the breakdown phenomenon) were experimentally studied. The evolutions of COF at elevated temperatures consisted of three distinct stages with different friction mechanisms. The first stage (stage I) occurred with low friction when the boundary lubrication was present. The second stage (stage II) was the transition process in which the COF rapidly increased as the lubricant film thickness decreased to a critical value. In the final plateau stage (stage III), lubricant breakdown occurred and intimate contact at the interface led to high friction values. At the low friction stage (stage I), the value of COF increased with increasing temperature. The increase in temperature, contact pressure and sliding speed as well as the decrease in initial lubricant volume accelerated the lubricant breakdown.

Multi-objective optimization of lubricant volume in an ELSD considering thermal effects

Lubricant filling into a closed fluid domain of a transmission component has always been a challenge, for it is limited by a number of factors, like structural characteristics of a transmission component, load characteristics, and oil temperature of during an operation. This paper proposes a lubricant volume optimization model that takes into account the effect of temperature and heat, with an electronically controlled limited slip differential (ELSD) for an automobile taken as the study object. In the paper, an ELSD simulation model was firstly constructed, based on a CFD numerical simulation method. After model simplification and assumption, the probes were established for fluid speed and temperature parameters during gear rotation. The influence law of lubricant volume in the ELSD on convective heat transfer was then determined by analyzing the working conditions, including different rotational speeds and different oil immersion depths. Finally, the optimization model was constructed, with the numerical values after the steady-state temperature fluctuation and the time required for the fluctuation taken as evaluation indexes. In the study, by taking specific parameters for examples and based on the proposed optimization model, quadratic response surface method was used for equation fitting of multiple results obtained from the simulation, and the lubricant volume of 37.21% of the total volume was found to be optimal, which verified the feasibility of the model. The method provides a new approach for determining the lubricant volume for a transmission component.

Towards an innovative lubricant condition monitoring strategy for maintenance of ageing multi-unit systems.

The high acquisition cost retained by replacement of ageing and deteriorating assets triggers operational life-extension for the systems. Subsequently, ageing effects like compromised performance and wear are introduced, adversely affecting system economics and performance. An integrated maintenance and spares strategy incorporating lubricant condition monitoring (LCM) under condition-based maintenance (CBM), corrective maintenance (CM) and preventive maintenance (PM) is proposed, to mitigate the ageing effect challenges. The study considers the lubricant not only as a monitored item, but as a spare like other repairable units, similarly deteriorating, and retaining different maintenance interventions. We link the lubricant degradation (iron and viscosity oil properties) and repairable units’ degradation and performance, by integrating rate-state interactions with imperfect maintenance to derive stochastic dependencies in the degradation model. The applicability of the proposed discrete event simulation model is illustrated for a geothermal drilling rig, whose performance (maintenance cost and lubricant volume) are derived. Results demonstrate system performance dependency on PM intervals and CM strategies for both the lubricant and the repairable units. The significance of LCM policy to maintenance and system performance is substantiated. The developed framework has widespread use in real-life and broader applications that include LCM in deriving maintenance decision support.

Numerical investigation of refrigerant outgassing in the screw pump of a hermetic reciprocating compressor oil supply system

This paper reports an investigation on the phenomenon of refrigerant outgassing in the screw pump of a hermetic reciprocating compressor oil supply system. The interfacial mass transfer between the refrigerant and the lubricating oil is modelled by means of a cavitation model based on the Rayleigh-Plesset equation, for cases of fixed and variable mass fractions of refrigerant dissolved in the lubricant. The influence of compressor speed and compressor crankcase pressure is evaluated by comparing the lubricant volumetric flow rate and the lubricant volume fraction field for each condition. The results reveal that significant outgassing of refrigerant may take place in the oil pump, reducing the lubricant flow rate supplied by the pump.