Design and optimization of fluid lubricated bearings operated with extreme working performances——a comprehensive review

Fluid lubricated bearings have been widely adopted as support components for high-end equipment in metrology,semiconductor devices,aviation,strategic defense,ultraprecision manufacturing,medical treatment,and power generation.In all these applications,the equipment must deliver extreme working performances such as ultraprecise movement,ultrahigh rotation speed,ultraheavy bearing loads,ultrahigh environmental temperatures,strong radiation resistance,and high vacuum operation,which have challenged the design and optimization of reliable fluid lubricated bearings.Breakthrough of any related bottlenecks will promote the development course of high-end equipment.To promote the advancement of high-end equipment,this paper reviews the design and optimization of fluid lubricated bearings operated at typical extreme working performances,targeting the realization of extreme working performances,current challenges and solutions,underlying deficiencies,and promising developmental directions.This paper can guide the selection of suitable fluid lubricated bearings and optimize their structures to meet their required working performances.

FlowBreakdown of Hybrid Nanofluid on a Rigid Surface with Power Law Fluid as Lubricated Layers

Thiswork investigates an oblique stagnation point flowof hybrid nanofluid over a rigid surface with power lawfluidas lubricated layers. Copper (Cu) and Silver (Ag) solid particles are used as hybrid particles acting in water H2O asa base fluid. The mathematical formulation of flow configuration is presented in terms of differential systemthat isnonlinear in nature. The thermal aspects of the flow field are also investigated by assuming the surface is a heatedsurface with a constant temperature T. Numerical solutions to the governing mathematical model are calculatedby the RK45 algorithm. The results based on the numerical solution against various flow and thermal controllingparameters are presented in terms of line graphs. The specific results depict that the heat flux increases over thelubricated-indexed parameter.

MXene Lubricated Tribovoltaic Nanogenerator with High Current Output and Long Lifetime

Tribovoltaic nanogenerators(TVNGs)have the characteristics of high current density,low matched impedance and continuous output,which is expected to solve the problem of power supply for small electronic devices.However,wear occurrence in friction interface will seriously reduce the performance of TVNGs as well as lifetime.Here,we employ MXene solution as lubricate to improve output current density and lifetime of TVNG simultaneously,where a high value of 754 mA m^(-2)accompanied with a record durability of 90,000 cycles were achieved.By comparing multiple liquid lubricates with different polarity,we show that conductive polar liquid with MXene as additive plays a crucial role in enhancing the electrical output performance and durability of TVNG.Moreover,the universality of MXene solution is well demonstrated in various TVNGs with Cu and P-type Si,and Cu and N-GaAs as material pairs.This work may guide and accelerates the practical application of TVNG in future.

Cooperative effect of surface alloying and laser texturing on tribological performance of lubricated surfaces

The cooperative effect of laser surface texturing(LST) and double glow plasma surface alloying on tribological performance of lubricated sliding contacts was investigated.A Nd:YAG laser was used to generate microdimples on steel surfaces. Dimples with the diameter of 150μm and the depth of 30-35μm distributed circumferentially on the disc surface.The alloying element Cr was sputtered to the laser texturing steel surface by double glow plasma technique.A deep diffusion layer with a thickness of 30μm and a high hardness of HV900 was formed in this alloy.Tribological experiments of three types of samples(smooth,texturing and texturing+alloying) were conducted with a ring-on-disc tribometer to simulate the face seal.It is found that,in comparison with smooth steel surfaces,the laser texturing samples significantly reduce the friction coefficient.Moreover,the lower wear rate of the sample treated with the two surface techniques is observed.

Study on hydrostatic gas lubricated non-contacting mechanical seal

The principle and characteristics of hydrostatic gas lubricated non-contacting mechanical seal （HSGLNMS） are introduced. The flow field of the gas film is established by numerical analysis of end faces of HSGLNMS. The distribution of gas film pressure and seal performance parameters inclu- ding opening force and leakage are obtained. Influence of operating parameters and sealing configu- ration on the sealing performance is studied. HSGLNMS has been designed and manufactured. Its working film thickness and leakage are measured to verify the theoretical analysis. The investigation results show that HSGLNMS demonstrates good speed adaptability, which means that the seal runs successfully with both low and high speed, showing excellent performance. The seal can be regula- ted and controlled online ; the opening force will not be raised greatly with the increasing of the num- ber of throttle orifices, but the leakage of seal increases apparently ; the uniform pressure groove im- proves the sealing performance, for example, opening force and stiffness are raised obviously. While leakage is reduced. Finally, the theoretical analysis is verified by experiment.

A New Method to Calculate Water Film Stiffness and Damping for Water Lubricated Bearing with Multiple Axial Grooves

Water lubricated guide bearings for hydro turbines and pumps are conventionally designed with multiple axial grooves to provide effectively cooling and flushing away abrasives.Due to the variety of groove configuration in terms of number and size,a predication of their performance is difficult.This paper deals with an analytical procedure to investigate groove effect on load capacity,stiffness and damping for this type of bearing where it is considered as an assembly of many inclined slide bearings.The result can be applied to bearings made of hard materials combined with low bearing pressure.

Dynamic Characteristics of Ultra Thin Liquid Lubricated Head-Disk Assembly in Magnetic Hard Disk Files

The dynamic characteristics of a liquid thin film lubricated head disk system are analyzed. The shear thinning effect is taken into account by introducing modification coefficients into the lubricant rheological model. The perturbation theory is employed to set up the dynamic pressure equation. The Reynolds equation and dynamic pressure equations are solved by finite difference method. The results obtained by the difference methods agree well with that calculated by the close solutions. IBM3370 slider is employed as a physical model. The slider of the system can keep flying at 20 nm height, which promises a potential application on high density recording device.

Friction and Wear Study on Friction Pairs with a Biomimetic Non-smooth Surface of 316L Relative to CF/PEEK under a Seawater Lubricated Condition

Current studies of a seawater axial piston pump mainly solve the problems of corrosion and wear in a slipper pair by selecting materials with corrosion resistance, self-lubrication, and wear resistance. In addition, an appropriate biomimetic non-smooth surface design for the slipper pair can further improve the tribological behavior. In this paper, 316 L stainless steel and CF/PEEK were selected to process the upper and bottom specimens, and the biomimetic non-smooth surface was introduced into the interface between the friction pair. The friction and wear tests were performed on a MMD-5 A tester at a rotation speed of 1000 r/min and load of 200 N under seawater lubricated condition. The results indicate that the main friction form of the smooth surface friction pair corresponds to abrasive wear and adhesive wear and that it exhibits a friction coe cient of 0.05–0.07, a specimen temperature of 56 ℃, a high wear rate, and surface roughness. Pits on the non-smooth surface friction pairs produced hydrodynamic lubrication and reduced abrasive wear, and thus the plowing e ect is their main friction form. The non-smooth surface friction pairs exhibit a friction coe cient of 0.03–0.04, a specimen temperature of 48 ℃, a low wear rate, and surface roughness. The study has important theoretical significance for enriching the lubrication, friction, and wear theory of a seawater axial piston pump, and economic significance and military significance for promoting the marine development and the national defense military.

Tribological behaviors of spot-textured TiN coatings on M2 high-speed steel under boundary lubricated conditions

The effect of sliding duration on the tribological behaviors of spot patterned coatings was investigated. Two patterns based on physical vapor deposition （PVD） TiN coatings were used, such as, in-lined （IN） and staggered （ST） spots. The tribological behaviors were evaluated by using a Cameron-Plint wear test rig. The M2 steel discs deposited TiN coatings with IN and ST patterns slid against the ASSAB 17 tool steel pins at a speed of 0.23 m/s, in Shell Tellus T32 lubricant and were loaded with 900 N. The testing results on disc specimens with two types of PVD TiN spot patterns, all coated with a bias voltage of-180 V and slid for 4, 8 and 11 h respectively, were presented. The results revealed that the in-lined coatings possessed relatively better wear behaviors than the staggered pattern coatings. Mechanisms for such superiority and for the cause of peeling were discussed. A relevant design approach was suggested for the application of such patterned coatings.

Wear map for sliding wear behavior of Cu-15Ni-8Sn alloy against bearing steel under oil-lubricated condition

Wear behaviors of a peak-aged Cu-15Ni-8Sn alloy fabricated by powder metallurgy were investigated.The results indicated that the friction coefficients and the wear rates of Cu-15Ni-8Sn alloy within a normal load range of 50−700 N and a sliding speed range of 0.05−2.58 m/s were less than 0.14 and 2.8×10−6 mm3/mm,respectively.Stribeck-like curve and wear map were developed to describe the oil-lubrication mechanism and wear behavior.The equation of the dividing line between zones of safe and unsafe wear life was determined.Lubricating oil was squeezed into micro-cracks under severe wear conditions.In addition,the lubricating oil reacted with Cu-15Ni-8Sn alloy to generate the corresponding sulfides,which hindered the repair of micro-cracks,promoted cracks growth,and led to delamination.This work has established guidelines for the application of the Cu-15Ni-8Sn alloy under oil-lubricated conditions through developing wear map.

Performance of dynamically loaded journal bearings lubricated with couple stress fluids considering the elasticity of the liner

To take into account the couple stress effects, a modified Reynolds equation is derived for dynamically loaded journal beatings with the consideration of the elasticity of the liner. The numerical results show that the influence of couple stresses on the bearing characteristics is significant. Compared with Newtonian lubricants, lubricants with couple stresses increase the fluid film pressure, as a result enhance the load-carrying capacity and reduce the friction coefficient. However, since the elasticity of the liner weakens the couple stress effect, elastic liners yield a reduction in the load-carrying capacity and an increase in the friction coefficient. The elastic deformation of the bearing liner should be considered in an accurate performance evaluation of the journal bearing.

Comparative study on tribological properties of isostatic graphite and carbon graphite under dry sliding and water-lubricated conditions

The tribological properties of isostatic graphite and carbon graphite under dry sliding and water lubricated conditions were studied.The friction test was conducted by using a pin-on-disc tribometer.The friction coefficient and the wear rate were employed to evaluate the tribological performances of the two materials,and wear morphology was used to analyze the wear mechanism.The results show that the friction coefficient of the isostatic graphite is larger than that of the carbon graphite under the dry sliding condition,and the wear rate is lower than that of the carbon graphite.Under the water lubricated condition,the friction coefficients and the wear rates of the isostatic graphite decrease obviously.The main wear form of the isostatic graphite is abrasive wear,while the main wear form of the carbon graphite is spalling wear.Finally,the tribological mechanism of the isostatic graphite under dry sliding and water lubricated conditions were systematically analyzed.

The Friction and Wear of Sleeve-ring Pair Lubricated by Active Lubricants in the Presence of Magnetic Field

The effect of magnetic field on the tribological process of sleeve-ring pair lubricated by WRL lubricants was investigated by means of a NG-x wear tester and a PS5013 video microscope. The friction coefficient(f) and the wear weight(W) in lubricating test with WRL lubricant were decreased with the increase in the magnetic field vertical to the rubbing surface, and an almost zero wear lubricating situation was gained in a magnetic field of 1000A/m. The captured wear micro particles on the rubbing surface were observed in the testing process, and the theoretical analysis of magnetic effects was completed. It is indicated that the magnetic field has not only a capturing action of wear micro particles on the worn surface, but also a inducing polarization of magnetic anisotropy of lubricant molecular. The actions promote the absorption of WRL lubricant into the wear surface as well as wear micro-particles, so that a good tribological effect is obtained when both magnetic field and WRL present.

FINITE ELEMENTS FOR THE LUBRICATED CONTACT BETWEEN SOLIDS IN METAL FORMING REOCESSES

In this paper, the lubrication problem in nmmerical sindation of forming processes is considered.After enumerationg the difficulties encountered when trying to solve such a problem with the finite element method, a generalization of the formaulation of Liu[4-6] for the thin film hydrodynamic lubrication re- gime is presented. This method is then aplied to a strip rolling simulation,using the Arbitrary La- grangian eulerian (ALE) formalism.

Dynamic Characteristics of High-speed Water-Lubricated Spiral Groove Thrust Bearing Based on Turbulent Cavitating Flow Lubrication Model

The water-lubricated bearings are usually the state of turbulent cavitating flow under high-speed conditions. And the distribution of cavitation bubbles and the interface effect between the two phases have not been included in previous studies on high-speed water-lubricated bearings. In order to study the influence of interface effect and cavitation bubble distribution on the dynamic characteristics of high-speed water-lubricated spiral groove thrust bearings(SGTB).A turbulent cavitating flow lubrication model based on two-phase fluid and population balance equation of bubbles was established in this paper. Stiffness and the damping coefficients of the SGTB were calculated using the perturbation pressure equations. An experimental apparatus was developed to verify the theoretical model. Simulating and experimental results show that the small-sized bubbles tend to generate in the turbulent cavitating flow when at a high rotary speed, and the bubbles mainly locate at the edges of the spiral groove. The simulating results also show that the direct stiffness coefficients are increased due to cavitation effect, and cross stiffness coefficients and damping coefficients are hardly affected by the cavitation effect. Turbulent effect on the dynamic characteristics of SGTB is much stronger than the cavitating effect.

Die wall lubricated warm compaction behavior of non-lubricant admixed iron powders

The phenomena of die wall lubricated warm compaction of non-lubricant admixed iron powders were researched, and its mechanism of densification was discussed. Water atomized powder obtained from the Wuhan Iron and Steel Corporation was used. With compacting and sintering, compared with cold compaction, the density of warm compacted samples increases by 0.07 - 0. 22 g/cm^3 at the same pressed pressure. The maximum achievable green density of warm compacted samples is 7.12 g/cm^3 at 120℃, and the maximum sintered density is 7.18 g/cm^3 at 80℃. Compared with cold compaction, the ejection force of warm compaction is smaller; the maximum discrep- ancy is about 7 kN. The warm compacted mechanism of densification of iron powders can be obtained： heating the powder contributes to improving plastic deformation of powder particles, and accelerating the mutual filling and rearrangement of powder particles.

Comparison of the Wear Behavior of UHMWPE Lubricated by Human Plasma and Brine

The effect of plasma and brine lubricants on the friction and wear behavior of UHMWPE were studied by using the geometry of a Si3N4 ball sliding on a UHMWPE disc under patterns of uni-directional reciprocation and bi-directional sliding motions. The worn surface and wear particles produced in these two lubricants were analyzed. Sliding motion pattern affected the friction coefficients lubricated with plasma,while seldom affected that lubricated with brine. UHMWPE lubricated with plasma showed about half of the wear rate of that lubricated with brine. The two rates were 0.75 pg/m and 2.19 pg/m for the two motion patterns,respectively. However,wear particles generated in plasma included a greater amount of small particles,compared to that in brine. In uni-directional reciprocation,the main wear mechanism is ploughing both in plasma and in brine. In bi-directional sliding modes,the significant characteristic is ripples on the worn surface in plasma,while there are oriented fibers on the worn surface in brine.

RESEARCH OF FILM THICKNESS DURING DRAWING PROCESS LUBRICATED WITH O／W EMULSIONS~＋

Based on analysis of rheology of oil-in-water emulsions during lubrication process. we have established the mathematical model of film thickness lubricated with emulsions during drawing process, The film thickness calculated with the model under general c

Calculation of flash temperature for hybrid ceramic ball bearing lubricated with solid

The scuffing behavior of hybrid ceramic bearing lubricated with solid is greatly affected by the contact flash temperature. Formulas are dedused using Lee’s asperity flash temperature method, to calculate the flash temperature of ball bearing lubricated with solid. The maximum flash temperature is calculated for hybrid ceramic ball bearings. The results show that under given conditions, the flash temperature of inner race is higher than that of outer race, the flash temperature of the hybrid ceramic bearing is sensitive to the load, rotational speed and race curvature. The flash temperature of inner race at 20 000 r/min is 66 9% more than that that at 11 000 r/min, and with the load changing from 1.1 kN to 2 kN, the flash temperature inner race goes up to 165 7%. Very common for high speed ball bearings, when curvature coefficients of both inner and outer race change from 0 515 to 0 56, the inner race flash temperature decreases from 421 446℃ to 56 2℃.

Tribological Behaviour of GCr15 Steel to Si_3N_4 Ceramic Lubricated by Biphase Liguid Lubricants

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