Lubrication Scheme Research Articles

Recent Advances in Tribology: A Review

In the last decade, there has been immense growth in research activities related to tribology. Tribology can have a big impact on the needs of industries to reduce losses and waste by developing new tribological components and materials. Hence, there is a strong connection between tribology and the fourth industrial revolution, i.e., industry 4.0. Tribology is a multidisciplinary field, and the results of research in the field of tribology are widely spread among various disciplines. This review paper briefs the recent advances in various research areas in tribology covering surface engineering, wear and lubrication. The main objective of this review is to summarize the new aspects in the field of tribology, like the numerical techniques of lubrication to model new lubrication schemes, solid superlubricity, superlubricity at the microscopic scale, superlubricity with coating and new 2D materials. The direction for future research in the field has been highlighted. The paper will be beneficial for researchers working in the field of tribology.

Experimental Study on In Situ Storage of Grease-Lubricated Ball Screws

Lubricating grease plays an important role in the rolling screw transmission of the actuation system and is particularly concerned with the performance stability of long-term storage in aerospace applications. In this article, a batch of ball screws that were lying flat in the warehouse for about eight years were selected to extract lubricating grease from the screw raceway after being stored in situ. The oxidation performance, friction performance and rheological properties of lubricating grease were tested and compared to those of fresh grease to analyze and summarize the performance changes in lubricating grease. The transmission efficiency, friction torque, and temperature rise of ball screws without removing the original grease and those filled with fresh grease after cleaning were tested and compared. The impact of grease degradation on the transmission performance of ball screws was analyzed to provide a reference for ball screw lubrication schemes and further accelerated storage experimental design.

HEAT TRANSFER APPLICATIONS IN CURVED MICRO-CHANNEL DRIVEN BY ELECTROOSMOSIS AND PERISTALTIC PUMPING

A precise model is presented to designate the curvature effects in electroosmotic flow classifications to organize flow in a curved micro-vessel. Heat transfer analysis is also considered under the viscous dissipation effect. Lubrication scheme, Debye–Hückel estimation, and suitable boundary conditions have been employed to arising nonlinear system. The coupled nonlinear PDEs are solved numerically using Mathematica software. The obtained numerical results for electric potential, stream function, pressure gradient, axial velocity, temperature and shear stress are displayed through graphical illustrations. Trapping for blood flow under the effects of physical parameter is also discussed. The annotations also demonstrate the silent features of the micro-mixer peristaltic pumps and chip devices which may additionally be exploited in hemodialysis and judgement of samples respectively.

Heat transfer analysis for EMHD peristalsis of ionic-nanofluids via curved channel with Joule dissipation and Hall effects.

The objective of this research is to study the combined influences of applied electric and magnetic fields on the two-phase peristaltic motion of nanofluid through a curved channel. A two-phase model of a nanofluid, Maxwell's model of thermal conductivity [1], and no-slip velocity and thermal boundary conditions have been used in this study. Hall effects, Joule heating (due to magnetic and electric fields), and viscous heating aspects are under consideration. Governing equations for the present flow configuration have been modeled and simplified by enforcing the lubrication scheme. Debye-Huckel approximation is used to obtain the analytical solution of the electric potential function (Poisson-Boltzmann equation). Resulting expressions are solved numerically through the NDSolve command in Mathematica and plotted in order to understand the effects of different dimensionless parameters on the temperature, stress, heat transmission rate, and fluid's velocity. Graphical results demonstrated that the thermal transmission rate is augmented by increasing the Hartmann number, Brinkman number, and Debye-Huckel parameter while decreases for zeta potential ratio, Joule dissipation parameter, and electro-osmotic velocity. A decrease in axial velocity is noted near the lower wall for higher values of [Formula: see text].

Wind Turbine Lubrication Based on Parallel Control of Multiple Factors

The lubrication needs of wind turbines vary with the operating conditions. To provide a dynamic lubrication scheme for wind turbines under variable conditions, this paper designs a dynamically adjustable lubrication scheme through parallel control of multiple influencing factors. Based on mid- and long-term loads, the proposed scheme fully considers the influence of various sudden changes in addition to slowly changing factors like load, operating hours, and speed, such as to dynamically adjust the injection flow as per the specific operating condition of the turbine. The ideal lubrication effect was tracked through the adjustment of the injection flow or injection time, and used to determine the optimal dynamic lubrication control strategy during turbine operation. The proposed control strategy overcomes the defects of the traditional fixed-time fixed-flow lubrication approach, and provides reasonable on-demand lubrication schemes for wind turbines in different operating conditions. The on-demand injection of lubricant prevents under- or over-lubrication, reduces the rate of mechanical failure, and extends the service life of wind turbines. Suffice it to say that the proposed control strategy can lower power generation cost and save energy, making wind turbines more profitable.

Chemical- and Mechanical-Induced Lubrication Mechanisms during Hot Rolling of Titanium Alloys Using a Mixed Graphene-Incorporating Lubricant.

Hot rolling of titanium alloy currently is carried out without lubrication because of the surface defects. In order to explore an effective lubrication scheme to reduce friction and wear during hot rolling of titanium alloy, a mixed graphene-incorporating lubricant has been proposed to study its lubrication performance and mechanism. The tribological experiments were carried out by ball-disk friction and wear tester under hot-rolling parameters. Scanning electron microscopy (SEM), X-ray energy spectrum analyzer (EDS), X-ray powder diffractometer (XRD) and Raman analysis were used to analyse the surface and cross-section of the wear marks on the samples after the tribological experiments. The results show that the friction coefficient decreases up to about 35% compared with tests under dry and lubricated conditions. The surface quality of the wear marks is improved significantly after applying the proposed lubricant. The graphene which is embedded in the phosphate film can be effectively applied as a lubricating material to strengthen the lubricating film with less combustion loss at high temperatures. A chemical- and mechanical-induced lubrication mechanism for the hot rolling of titanium sheets has been proposed due to the synergistic lubrication effect of the graphene, ZrO2 nano particles and phosphate. It is of great significance and potential value to apply this proposed lubricant as an effective way to reduce the wear, friction and oxidation during the hot-rolling process of titanium alloy.

Dynamic Modeling and Analysis of Involute Spur Gear Transmission System Considering Friction and Multi-State Meshing Conditions

A dynamic model for an involute spur gear system involving multi-state mesh and friction is formulated to analyze the dynamic response and meshing state property under different lubrication conditions, such as an elastohydrodynamic and mixed lubrications as well as dry friction. The dynamic equations of the system under teeth separation, drive-side and back-side tooth meshes are derived respectively based on the meshing principle of the gear transmission and the force analysis acting on teeth. The effects of the different lubrication schemes on the dynamic meshing force and motion orbit of the system are studied. Results show that the lubrication scheme greatly affects the amplitude of dynamic meshing force. However, the influence of the lubrication scheme on the motion orbit depends mainly on the meshing state. It means that the system motion orbit is largely affected by the lubrication scheme without drive-side and back-side tooth impacts, while the orbit is slightly affected by the lubrication scheme when drive-side and back-side impacts occur. Additionally, the dynamic response and meshing property are investigated with the decrease in load by defining three different Poincaré mappings. The system performs a drive-side meshing state as the load is large. The teeth separation is observed periodically with the decrease in load. While, both teeth separation and back-side mesh are observed under small load, which strengthens the impact vibration between the meshing teeth.

Tribological behaviors of fluid-lubricated DLC films under sliding and fretting conditions

To meet the ever–increasing performance requirements of mechanical equipment under various working conditions, lubrication schemes have been transformed from onefold to synergistic lubrication. Here we introduced the synergistic lubrication systems consisting of DLC film as anti–wear supporting layer and two high–performance fluids (ionic liquids (ILs) and multiply–alkylated cyclopentanes (MACs)) as lubricating layer, and their tribological properties were conducted under sliding and fretting conditions. Results show that ILs and MACs can improve the friction reduction and wear resistance of DLC film under sliding condition because a boundary lubrication film was formed by physical adsorption film and tribo–transfer film, which could minimize the shear and adhesion. Under fretting condition, the lubrication function of ILs and MACs is not superior to that under sliding condition partly because intact fluid-film has difficulty in formation on the fretting regime, and also partly because fretting conditions induce the transformation of fretting running regime from partial slip to gross slip.

Structural lubricity under ambient conditions.

Despite its fundamental importance, physical mechanisms that govern friction are poorly understood. While a state of ultra-low friction, termed structural lubricity, is expected for any clean, atomically flat interface consisting of two different materials with incommensurate structures, some associated predictions could only be quantitatively confirmed under ultra-high vacuum (UHV) conditions so far. Here, we report structurally lubric sliding under ambient conditions at mesoscopic (∼4,000–130,000 nm2) interfaces formed by gold islands on graphite. Ab initio calculations reveal that the gold–graphite interface is expected to remain largely free from contaminant molecules, leading to structurally lubric sliding. The experiments reported here demonstrate the potential for practical lubrication schemes for micro- and nano-electromechanical systems, which would mainly rely on an atomic-scale structural mismatch between the slider and substrate components, via the utilization of material systems featuring clean, atomically flat interfaces under ambient conditions.

Rheology and microstructure of non-colloidal suspensions under shear studied with Smoothed Particle Hydrodynamics

In this work a Smoothed Particle Hydrodynamics model is presented to study rheology and microstructure of a non-colloidal suspension of spherical particles in a Newtonian solvent. The scheme presented in (Bian and Ellero, 2014) is extended to three-dimensions incorporating both normal and tangential short-range interparticle lubrication forces which are solved implicitly with a refined splitting strategy. The scheme allows to bypass prohibitively small time steps generally required for handling divergent lubrication forces and allows to simulate large particle systems. Rheology of a three-dimensional hard-spheres suspension confined in a plane Couette rheometer is investigated for concentrations up to ϕ=0.5. Results for the relative suspension viscosity ηr are analyzed against sample size and numerical convergence of the splitting lubrication scheme and compared with available experimental and simulations data. Very close agreement with the experiments is obtained for ηr up to ϕ=0.35. At larger concentrations, our results are still unable to explain the significant viscosity increase observed in experiments. Modest shear-thickening is also observed which is related to anisotropy of the particle radial distribution function (RDF) and presence of reversible hydrodynamic aggregates increasing in size with increasingly applied shear rates.

Modeling and parameter optimization for cutting energy reduction in MQL milling process

Environmentally conscious manufacturing (ECM), a key concept for modern manufacturing, emphasizes the efficient and optimal use of raw materials and natural resources and minimization of the negative effects on nature and society. This study focused on achieving ECM for milling processes. Toward this end, a model predicting the specific cutting energy was developed and optimized to determine the cutting conditions that minimize the specific cutting energy. A minimum quantity lubrication scheme was employed to minimize the amount of cutting oil used, thereby minimizing the associated process cost. Four process variables or cutting conditions (cutting speed, depth of cut, feed rate, and flow rate) were selected for the specific cutting energy model, and their appropriate ranges were determined through a preliminary experiment. The specific cutting energy model was developed based on an artificial neural network, where the Levenberg-Marquardt back propagation algorithm was implemented and the number of hidden layers was determined through comparison with controlled experimental data. The cutting conditions to minimize the specific cutting energy were determined using a global optimization process-the particle swarm optimization algorithm. In this algorithm, all computations were confined within the experimental range via constraint conditions, and the resulting optimized process variables were experimentally verified.

A fictitious domain approach for the simulation of dense suspensions

Low Reynolds number concentrated suspensions do exhibit an intricate physics which can be partly unraveled by the use of numerical simulation. To this end, a Lagrange multiplier-free fictitious domain approach is described in this work. Unlike some methods recently proposed, the present approach is fully Eulerian and therefore does not need any transfer between the Eulerian background grid and some Lagrangian nodes attached to particles. Lubrication forces between particles play an important role in the suspension rheology and have been properly accounted for in the model. A robust and effective lubrication scheme is outlined which consists in transposing the classical approach used in Stokesian Dynamics to our present direct numerical simulation. This lubrication model has also been adapted to account for solid boundaries such as walls. Contact forces between particles are modeled using a classical Discrete Element Method (DEM), a widely used method in granular matter physics. Comprehensive validations are presented on various one-particle, two-particle or three-particle configurations in a linear shear flow as well as some O(103) and O(104) particle simulations.

Frictional performance of silica microspheres

We present a fundamental study of the frictional performance of silica microspheres, either 4, 2, or 0.5 μm in diameter, on a silicon substrate. The tribological properties of these rolling systems were measured with a ball-on-flat tribometer at various loads. The frictional performance of the rolling systems is found to be highly dependent on load and sphere diameter. Rolling motion was confirmed by imaging the surface of microsphere systems that have been coated with a thin layer of gold. In addition, the surface energy of the lubrication scheme was altered using coatings containing octadecyltrichlorosilane or (tridecafluoro-1,1,2,2-tetrahydrooctyl)-1-trichlorosilane precursors.

Intercalation of 3-Phenyl-1-proponal into OTS SAMs on Silica Nanoasperities to Create Self-Repairing Interfaces for MEMS Lubrication

Self-assembled monolayers (SAMs) have been widely studied as potential lubricants for microelectromechanical system (MEMS) devices. However, these single-layer films have nominally been found to be insufficient for mitigating wear in sliding contacts because of their rapid breakdown under the high pressures found within the nanoasperity junctions at such interfaces. As such, there is a critical need to explore approaches beyond simple, single-component SAMs toward films that introduce additional lubricant molecules into the system. Because alcohol vapors have previously been shown to reduce wear in MEMS devices, here we have investigated a mixed monolayer consisting of an octadecyltrichlorosilane (OTS) SAM infused with 3-phenyl-1-propanol (3P1P), assembled on silica nanoparticle films. A combination of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), and FTIR spectroscopy was employed to investigate the structural and frictional properties of the mixed monolayers and to evaluate surface wear as a function of time. The nanoparticle film/AFM tip junction provides a ready mimic for the asperity-asperity contacts found in MEMS devices. Here it was found that for a mixed monolayer of OTS with ca. 15% 3P1P, the surfaces showed dramatically reduced friction and no wear under the same load conditions as surfaces with an OTS SAM alone. Moreover, the multicomponent film also displayed no increase in friction and exhibited no wear even after 14 h of shearing contact in an AFM at loads that would break down the OTS layer. The ability of the OTS SAM to trap short-chain alcohols, such as 3P1P, and to release them under load suggests a simple MEMS lubrication scheme that could be readily integrated into MEMS device architectures.

Tailoring Silica Nanotribology for CMP Slurry Optimization: Ca2+ Cation Competition in C12TAB Mediated Lubrication

Self-assembled surfactant structures at the solid/liquid interface have been shown to act as nanoparticulate dispersants and are capable of providing a highly effective, self-healing boundary lubrication layer in aqueous environments. However, in some cases in particular, chemical mechanical planarization (CMP) applications the lubrication imparted by self-assembled surfactant dispersants can be too strong, resulting in undesirably low levels of wear or friction disabling material removal. In the present investigation, the influence of calcium cation (Ca(2+)) addition on dodecyl trimethylammonium bromide (C(12)TAB) mediated lubrication of silica surfaces is examined via normal and lateral atomic force microscopy (AFM/LFM), benchtop polishing experiments and surface adsorption characterization methods. It is demonstrated that the introduction of competitively adsorbing cations that modulate the surfactant headgroup surface affinity can be used to tune friction and wear without compromising dispersion stability. These self-healing, reversible, and tunable tribological systems are expected to lead to the development of smart surfactant-based aqueous lubrication schemes, which include designer polishing slurries and devices that take advantage of pressure-gated friction response phenomena.

Influence of process parameters on the deep drawing of stainless steel

Optimization of process parameters in sheet metal forming is an important task to reduce manufacturing cost. To determine the optimum values of the process parameters, it is essential to find their influence on the deformation behaviour of the sheet metal. The significance of three important process parameters namely, die radius, blank holder force and friction coefficient on the deep-drawing characteristics of a stainless steel axi-symmetric cup was determined. Finite element method combined with Taguchi technique form a refined predictive tool to determine the influence of forming process parameters. The Taguchi method was employed to identify the relative influence of each process parameter considered in this study. A reduced set of finite element simulations were carried out as per the Taguchi orthogonal array. Based on the predicted thickness distribution of the deep drawn circular cup and analysis of variance test, it is evident that die radius has the greatest influence on the deep drawing of stainless steel blank sheet followed by the blank holder force and the friction coefficient. Further, it is shown that a blank holder force application and local lubrication scheme improved the quality of the formed part.

Lubrication of Microelectromechanical Systems (MEMS) Using Bound and Mobile Phases of Fomblin Zdol

A lubrication scheme for MEMS electrostatic lateral output motors based on a mixture of bound and mobile lubricant was studied. Lubrication by bound monolayer alone provided some increase in operational life, but after a short time, the film wore away and the device failed in the unlubricated mode. A mobile phase was used to provide lubricant replenishment. Tribological studies were conducted on Si(100) wafers, as well as on MEMS electrostatic lateral output motors, dip-coated with a mixture of bound and mobile phases of Fomblin Zdol. Accelerated screening tests on Si(100) wafers were undertaken using a pin on disk tribometer. However, the optimum balance of bound and mobile phases was determined by studies on the device itself. The fractional surface coverage of lubricant and the ratio of bound to mobile phase was varied through selection of reaction temperature and rinse chemistry. The mobile phase on model surfaces and devices acted as a source of lubricant replenishment, and together with the bound phase provided dramatic improvement in performance. The wide variation seen in the performance of individual devices suggests that dip coating does not provide a uniform coating on the contacting surfaces of these devices.

Rolling Stock

This article discusses features of a new friction management system, which is intended to boost efficiency on the railroad. Friction Management Services LLC of West Chicago, Illinois, has developed a friction management system, called TracGlide that consists of a synthetic polymer and computerized application equipment, installed on the locomotive at the front of the train. Unlike conventional lubrication schemes, the TracGlide system applies a friction modifier, not a lubricant, to the top of the rail. Although railroads usually avoid treating the tops of rails to avoid traction problems, the TracGlide polymer tends to increase the coefficient of friction when needed. The friction modifier is applied on both rails after the last axle of the last locomotive at the front of the train passes by. The application is computer controlled, based on factors such as the train’s weight, track curvature, speed, and temperature of the lubricant, which are constantly changing.

Integration of wear-resistant titanium carbide coatings into MEMS fabrication processes

Microelectromechanical systems (MEMS) are a key technology for small-scale satellites, integrated sensors, and intelligent control systems. However, a major limitation for Si-based systems involving tribological components is their inability to withstand prolonged sliding surface contact that results in high wear and causes them to fail within minutes of operation. Our aim is to protect the Si surfaces with wear-resistant coatings. Due to practical limitations of coating fully released MEMS structures, we have addressed the integration of the coating into the MEMS processing sequence. This paper describes the direct integration of a pulsed-laser-deposited wear-resistant titanium carbide (TiC) coating into the Si MEMS fabrication process. The in situ deposited TiC layer also provides an ideal substrate to the various possible lubrication schemes proposed for moving MEMS.

99/03982 Radioactive polluting potential of coal-fired power plants from Romania

High efficiency engines that operate at high temperatures (400-1500 °F) mandate new innovative lubrication schemes to achieve success. The most significant technical obstacle is the lubrication and wear at these high temperatures. Liquid lubricants and conventional bearing designs may not be adequate to meet existing goals. Recent understanding of the nature of third body or particulate solid dynamics suggests an alternative to conventional liquid lubrication and solid (coatings) lubrication systems. It is postulated that a layered shearing of compacted triboparticulates generates velocity, pressure, density, and temperature profiles akin to those in the liquid lubricant in a fluid film bearing. Thus triboparticulates can be either injected between the mating surfaces or generated by wear so as to generate the required flows and pressures to lubricate. This paper describes a procedure used to select suitable triboparticulates and experiments that are used to develop a fundamental understanding of their behavior. The results and importance of these experiments to attaining a constitutive equation that can be used to provide design guidelines will be discussed.