Abstract The tribological behaviors of the in-situ formed TiAl-TiB2 composites were investigated from room temperature to 800 °C in low pressure oxygen and related to their hardness and partial tribo-oxidation behaviors on the frictional surface. The wear resistance of TiAl-TiB2 composites in low pressure oxygen is significantly enhanced when the TiB2 content increases from 0 to 20 Vol. %, but decreases

ABSTRACT Micropitting is a type of surface fatigue damage that occurs in rolling-sliding contacts operating under thin oil film conditions. Application of black oxide (BO) coating to steel rubbing surfaces has been suggested as a potential approach to alleviate micropitting. This paper confirms that BO coatings can prevent micropitting and identifies the predominant mechanism by which this occurs.

Abstract In this study, an experimental methodology is presented for measuring power losses of rolling element bearings under combined radial and axial loading conditions. The set-up developed for this purpose consists of a pair of test bearings and another pair of center bearings whose function is to transmit the radial load to the test bearings. The center bearings are isolated from any axial load

Abstract The present work characterizes a natural sheep wool and compares its properties to those of a range of three different, well-known organic fibers that are typically used in the friction material production: aramid, cellulose and polyacrylonitrile (PAN) fibers. The characterization work consisted of the study of the fibers alone, the non-pressed friction materials and the final railway brake

ABSTRACT Cage instability or highly dynamic cage movement can have a strong influence on the performance of rolling bearings. In addition to very loud and disturbing noises (“squealing”), bearing failure due to cage fracture can occur. This publication deals with two topics: the general classification of cage motions on the one hand and the prediction of application-dependent cage motions to prevent

ABSTRACT The tribological performances of compacted and non-compacted polydopamine (PDA)+polytetrafluoroethylene (PTFE) nanocomposite coatings on stainless steel (SS) substrates were investigated. The compaction was accomplished using a combination of heat and pressure. The non-compacted PDA + PTFE coating had an average of 11 times longer durability compared to the pure PTFE coatings. The compaction

Abstract To investigate the effects of the oil film between deformed discs on the dynamic torque behavior of hydroviscous drive (HVD), a mathematical model incorporating film lubrication, asperity contact, and translational and rotational motion from a friction system is developed based on four kinds of representative film gap cases. The main analytical solutions including squeeze velocity, angular

Abstract In rotating machines, tilting pad journal bearings (TPJBs) are widely used because of their enhanced design stability in comparison with alternative bearing configurations. In the present research, a thermohydrodynamic (THD) lubrication model for a tilting pad bearing with injection is developed. Within the THD lubrication model, the lubricant is also fed into each pad through a central injection

Abstract In the present study, a series of Ni + xCr7C3 (x is the weight fraction of the Cr7C3) clads on hydro turbine steel (CA6NM) were developed through microwave cladding. The weight fraction of Cr7C3 was 10 wt%, 20 wt%, and 30 wt% in the developed clads. These clads were developed to mitigate the erosion induced degradation of the substrate surface. The Ni + 10% Cr7C3 composite clad exhibited poor

Abstract A Cu-free brake friction material was produced with three surface scorching conditions, and the brake performance was compared using maps of the friction coefficient, maximum disc temperature, and deceleration. The tests were carried out using a subscale dynamometer to avoid any influence of hardware on the obtained brake data. The friction coefficient decreased with velocity and contact pressure

Abstract We investigated superparamagnetic nanolubricants and verified the influence of the magnetic field, particle size, and concentration on the tribological performance. The superparamagnetic nanoparticles were synthesized with two different sizes (7 and 15 nm) and dispersed in mineral oil with concentrations of 0.2 and 0.4 wt% The tribological tests were performed using a high-frequency reciprocating

Abstract To improve the tribological properties and suppress the friction-induced noise of Ti-6Al-4V alloys (TC4), TC4 with smooth surfaces (TSs), groove antifriction surfaces (GAs), Sn-Ag-Cu coating surfaces (SCs), and composite self-lubricating surfaces (CSs) with grooves and Sn-Ag-Cu coating were prepared. Experimental studies on the tribological properties and friction-induced noise were carried

To closely examine the mechanical properties of mortise and tenon woodworking joinery in outdoor environments, it is essential to obtain fundamental data regarding the influence of moisture content and wood section on the frictional properties of wood surfaces. In this study, the static and dynamic friction coefficients under varying moisture contents (5, 8.50, 11.25, 20, 30, 40, 50 and 60%) and wood

Abstract The behavior of lubricants at operational conditions, such as at high pressures, is a topic of great industrial interest. In particular, viscosity and the viscosity-pressure relation are especially important for applications and their determination by computational simulations is very desirable. In this study we evaluate methods to compute these quantities based on fully atomistic molecular

Abstract Based on functionally graded material (FGM) designed concept, the laminated-graded Ag-multilayer graphene/TC4 alloy self-lubricating composites (GTMAC) are prepared to overcome the poor friction and wear behaviors of TC4 alloy and expand its engineering application where friction is involved. Tribological experiments of GTMAC are carried out under different temperatures and loads in contrast

ABSTRACT Varnish accumulation resulting from lubricant degradation can adversely affect the efficient operation of lubricated mechanical systems. There are various chemical cleaners commercially available that claim to remove varnish, but data enabling quantitative comparisons of the performance of these cleaners is not available. Here, we used a custom test system that enables in situ imaging of varnish

Abstract The purpose of this study is to explore the transient hydrodynamic coupling mechanism for misaligned journal–thrust microgrooved coupled bearings (referred to as coupled bearings) considering the axial microvibration under water lubrication. In the present model, it is assumed that the misaligned coupled bearing performs a sinusoidal reciprocating micromotion along the axial direction. Based

Abstract To study the mechanism of brake squeal of light-rail trains, a field test and a simulation analysis of disc brake squeal were carried out. In the field test measurement, the noise and vibration characteristics of brake components under normal braking and abnormal braking were analyzed. The test results show that the peaks of the frequency spectrum of the squeal noise and brake pad vibration

Abstract The present work aims to investigate the synergetic effect of titanium dioxide (TiO2) and graphene (GnP) nanoparticle additives on the rheological and machining characteristics of biodegradable vegetable oil (rice bran). The rice bran oil has been used in turning of M2 steel using a minimum quantity lubrication (MQL) technique. The effects of varying concentrations by weight (0.5 and 1 wt%)

Abstract Five common ball bearing greases were studied using a grease-on-paper test configuration, where the bleeding dynamics of greases is described by the dynamics of a driving capillary pressure provided by the paper and its opposing counterpart in the grease matrix. The Washburn-like model for extracting the retaining capillary pressure, determined by the affinity of the oil for the grease matrix

Abstract The main purpose of the present study is to investigate the Dynamic Mixed Elastohydrodynamic Lubrication (DMEHL) behavior of the water-lubricated bearing with unbalance rotor during start-up. To achieve this, a DMEHL model that couples the rotor dynamic model considering the unbalance load with the transient mixed lubrication model is established. The validity of the calculation procedure

ABSTRACT To investigate the effects of the addition of rare earth (RE) on properties of paper-based friction materials, six samples with LaCl3•7H2O contents of 0, 1, 2, 3, 4, 5wt% were prepared. The results showed that adding a certain amount of RE can greatly improve the interfacial bonding strength, but when the content of RE exceeds 3wt%, it has a negative effect on the bonding strength. In addition

ABSTRACT In order to solve the problem that the assumption of the straight shaft is inconsistent with the actual situation of marine water-lubricated journal bearings, the journal bending curve was identified by calculating the three-dimensional mechanical model of propulsion shafting. A fluid-solid coupling model of water-lubricated journal bearing considering journal bending was proposed. The results

Abstract Solid particles mixed in the oil cause erosion of hydraulic spool valves, and these valves may fail in severe erosion. In this paper, with the help of the Euler-Lagrange solver, a numerical model of the solid-liquid two-phase flow is established for the spool valves, in which standard k-ε model is used for the turbulent flow. With a comparison of seven different erosion models, the E/CRC erosion

ABSTRACT Premature bearing failures due to White Etching Cracks (WEC) occur when the rolling contact is subjected to a so-called “additional load” such as an electrical current flow through the bearing in addition to the pure rolling load. Tests with oil-lubricated roller bearings and greased ball bearings showed that high electrical currents are a very critical WEC-trigger. The influence of the current

ABSTRACT Pour point, or the temperature below which a fluid ceases to flow, is an important lubricant property. A molecular-dynamics-based approach is developed to explore and identify the pour points of a number of fluids. Diffusion behaviors of several fluids are investigated by time-averaged mean squared displacement (MSD), and a clear trend change of the MSD data is observed as a function of temperature

Abstract This present study seeks to understand tribological properties of 13Cr martensitic stainless steel (MSS) in austenitized and tempered conditions (300, 550 and 700 °C). A ball-on-plate configuration having alumina ball as counterface was employed for dry sliding experiments. Complementary analytical techniques such as 3D-optical profilometry, optical, scanning electron microscopy/energy dispersive

ABSTRACT Reciprocating seals are essential elements for hydraulic cylinders. The status of the contact area between the seal and the counterpart directly determines the sealing performance. An optical test rig for the O ring seal was constructed in this paper to investigate the tribological characteristics among the contacting zone, where the cylinder was changed to be transparent, and a microscope

Abstract Grease life in hybrid bearings is longer than that in all-steel bearings. This will be shown in this paper by means of grease life tests with a large number of greases for both Deep Groove Ball Bearings (DGBB) and Cylindrical Roller bearings (CRB). The results show that grease life for hybrid bearings is always larger than that for equivalent all-steel bearings and that this varies between

Abstract Aiming at the phenomenon of inconsistent design standards of China railway high-speed, the effect of wheel structure on friction-induced wheel polygonal wear is studied. A finite element model is established, which consists of two rails, one wheelset, and three brake units. The motion stability of the system is studied through complex eigenvalue analysis. According to the mode analysis, the

Abstract In this paper, the tribological behaviors of Si3N4-hBN composites and PEEK materials with pre-corrosion were investigated in seawater and deionized water, respectively. Si3N4-hBN composite represented a good seawater corrosion resistance, and a low corrosion rate of 0.0037 g/(m2·h) was obtained for Si3N4-hBN composites in seawater. The seawater absorption rate of PEEK material was about 0

Abstract In this study, frictional properties of the dry gas seal rings with diamond-like carbon（DLC）film textured surface were investigated by a vertical universal friction and wear tester. The ensemble empirical mode decomposition (EEMD) method was applied to extract friction and vibration signals. In combination with the chaos theory, the analyses of friction and wear of dry gas seal rings were

ABSTRACT The critical components of mining equipment generally work in relative motion and in an abrasive environment. Under these circumstances, wear by friction represents the largest portion of the cost associated with failure and maintenance of sliding bearings. Thus, anti-wear coatings are extensively applied aimed at retrieving such equipment to its initial condition. Tamping machines are typical

Abstract Three groups of ultra-high-molecular-weight polyethylene (UHMWPE) with optimum hydrophilicity were obtained by halogenation modification. They were immersed in a 15% KBr solution for 30 h, a 10% NH4Cl solution for 60 h, or a 15% NH4Cl solution for 60 h. The mechanism of hydrophilicity enhancement by halogenation modification was investigated by combining surface morphologies and energy spectrum

ABSTRACT Friction and wear behavior of nickel base hardfacing alloys ER NiCr-A, ER NiCr-B and ER NiCr-C (ER: electrode rod, NiCr: Nickel Chromium) deposited over austenitic stainless steel was studied against silicon carbide counter body by ball-on-disc tribo testing at 25 °C (1 bar pressure, 3 × 10−5 mbar vacuum) and at 550 °C (3 × 10−5 mbar vacuum) temperature. The wear tracks were examined using

Abstract High-speed, high-load railway development has necessitated a deeper understanding of the wear behaviour and mechanism of welded steel railway joints subjected to repeated impact. Under different simulated impact loads and impact cycles, the impact damage evolution and wear mechanism of flash- and aluminothermic-welded joints in the weld and heat-affected zones and base material were compared

ABSTRACT The instability of oil film stiffness in mixed elastohydrodynamic lubrication (EHL) is a prominent cause of the fretting wear of continuously variable transmission pulley–metal sheet friction pair. In severe cases, it can induce dynamic system failure. In this study, an oil film normal stiffness model equivalent to a massless spring element is established using linear contact mixed EHL theory

Abstract In this study, a comprehensive thermoelastohydrodynamic model considering turbulence and cavitation is developed. After comparing the Reynolds-Rayleigh-Plesset and Elrod and Adams models, the EA model is adopted to consider cavitation effects. To validate the developed model, a series of novel two-phase flow or mixed bubble experiments is designed by extracting the characteristics of actual

Abstract The wear behaviors of 4145H drilling tool steel in water-based slurries were investigated under the conditions of various concentrations of SiO2, Al2O3 and SiC sands using a modified ASTM B611 rubber ring wet grinding test system. Under the identical conditions, the measured wear loss was positively correlated with the sliding distance, abrasive hardness as well as sand concentration. However

ABSTRACT Microturbomachinery implements gas bearings to produce significant power with high efficiency at high rotor speed operation. Externally pressurized porous (EPP) gas bearings allow nearly friction free operation. Presently, this paper presents rotor dynamic tests conducted with a large and heavy rotor (100 mm in outer diameter and 285 N in weight) supported on a pair of five-tilting pad EPP

ABSTRACT The effect of SrAl2O4, FeAl2O4 and FeO derived from the solid state reaction between Fe, Al and SrSO4 during the hot pressing sintering process on the tribological properties of Fe-Al-SrSO4 (FA-SrSO4) composites was investigated between room temperature and 1000 °C. The results indicated that the formation of SrAl2O4, FeAl2O4 and FeO had an impact on the friction coefficient and wear rate

Due to the unique redox characteristic of CeO2, addition of CeO2 in diesel fuel reduces diesel engine emissions; however, its influence on the friction and wear performance of the fuel injection sy...

Abstract The objective of this study is to evaluate the correlation between noise and friction variation through an analysis of data obtained from relative motion of headlining and panel. Tests were conducted using headlining and panel specimens cut from the actual vehicle. The effect of surface roughness on noise was investigated by comparing textured headlining A with non-textured headlining B. To

C/C-SiC composites with different SiC content was fabricated by reactive melt infiltration of silicon with four types of porous C/C composites, which are prepared through chemical vapor infiltratio...

The different fretting wear behaviors of alloy 690TT in air and in a flowing nitrogen environment were revealed. Moreover, the grain refinement to nanoscale caused by fretting wear in nitrogen was ...

Abstract This article presents an efficient cavitation model for fluid film bearings, considering both gaseous and vaporous cavitation. This work presents a modification of Elrod’s cavitation algorithm, where the bulk fluid is similarly considered to be a mixture of liquid and bubbles, without the need for a switch function. By solving for properties of the bulk fluid in the film, the distribution

Abstract Excessive torque on tool surfaces resulting in friction and wear in the process of well drilling remains a big challenge for the oil and gas exploration industry. In this study, two kinds of glycerides are encapsulated and serve as lubrication additives to improve the tribological properties of water-based drilling mud. It is found that encapsulation improved the thermal stability of microcapsules

Abstract In recent years, porous bearings have been increasingly used in various industrial applications because they are less noisy, have good precision, and are relatively maintenance free. In this article, the numerical analysis of a conical porous hybrid journal bearing system (CPHJBS) has been carried out. The interactive effects of permeability parameter, semi cone angle, and pseudoplastic (shear

Abstract To study the dynamic support characteristics of an auto-eliminating clearance auxiliary bearing (ACAB) after a rotor fall, this article proposes a parameter identification method based on the finite element method (FEM). First, a dynamic model of the magnetic suspension bearing–rotor system was established. Next, the support stiffness and damping matrices of the ACAB were deduced and the feasibility

Abstract An extended Reynolds equation is presented to evaluate the effects of the fluid inertia and cavitation on the performance of spiral-grooved mechanical face seals under high-speed conditions. Segregated finite element procedures are employed to solve the fluid inertia terms and the fluid film pressure distribution with the artificial viscosity stabilization strategy and streamline-upwind/Petrov-Galerkin

Wet clutches are widely used in vehicle transmission systems to start and shift. The temperature field of the wet clutch components is influenced by friction and is closely related to the vehicle p...

Abstract In previous work, a monomolecular lubricant layer was applied on coin blanks by a burnishing process. With this layer, not only was the die life increased three times but the coin surfaces were protected from tarnishing. In this work, a monomolecular octadecanethiol layer was applied on the surface of silver coins by ultrasonic bathing. After an organic accelerated sulfurization test, the

Abstract Oxygenated fuel is recognized as an effective alternative fuel for the petrochemical industry. Studies have shown that using a mixture of dimethyl carbonate (DMC) and diesel fuel can help reduce soot emissions. Due to incomplete combustion of some diesel fuel, a small amount of fuel will inevitably enter to the engine oil and cause engine oil dilution. Herein, the tribological properties of

Abstract In gas foil bearings, frictional contacts are one of the main factors that affect bearing performance, which is highly nonlinear. Using a finite element method, this article presents a nonlinear model for static performance analysis of foil bearings based on frictional contacts. The model incorporates the top foil and the interactions between bumps by modeling the foil structure with beam

Abstract The tribological performance of polymer-stabilized TiO2 particles dispersed in mineral base oil was investigated. Two polymer–TiO2 mass ratios were investigated, with a constant polymer concentration of 0.3 wt% and two nanoparticle concentrations of 0.1 and 1 wt%. Friction tests were carried out with a pin-on–reciprocating flat test configuration under boundary-lubricated sliding conditions

To explore the mechanisms of squeak generation in automotive interior, the stick-slip experiments of polypropylene verse leather were conducted under various conditions. The friction properties wer...

Abstract A test apparatus is described that evaluates the performance of static aviation seals under an environment similar to the lubrication system in gas turbine engines. The seals can be tested at operating temperatures as high as 400 °C in a static seal rig (SSR). Incorporating an air–oil mist generating system, the test facility exposes the seals to degraded oil, which can deteriorate the performance

Epoxy is a polymeric material that is widely used in various fields as an adhesive, coating, and bulk material due to its outstanding properties. Many research studies on reinforced polymers have b...

The difference in wear behavior of superelastic NiTi and conventional Ti6Al4V alloys with similar elastic limits was investigated. Reciprocating dry sliding wear tests were performed with a ball-on...

ABSTRACT In order to investigate the effects of the oil film between deformed disks on the dynamic torque behavior of hydro-viscous drive (HVD), a mathematical model incorporating film lubrication, asperity contact, translational and rotational motion from a friction system is developed based on four kinds of representative film gap cases. The main analytical solutions including squeeze velocity, angular