Showing papers in "Tribology Transactions in 2013"
TL;DR: In this article, the performance of through-hardened and carburized materials was compared from field experience from operating wind turbines that compares performance of two rotor bearings with different metallurgies.
Abstract: A critical problem for wind turbine gearboxes is failure of rolling element bearings where axial cracks form on the inner rings. Metallurgical analyses show that the failure mode is associated with microstructural alterations manifested by white etching areas (WEAs) and white etching cracks (WECs). This article presents field experience from operating wind turbines that compares performance of through-hardened and carburized materials. It shows that through-hardened bearings develop WEA/WECs and fail with axial cracks, whereas carburized bearings do not. In another comparison of two rotor bearings with different carburized metallurgies, one bearing developed WEA/WECs and failed by macropitting, whereas the other bearing did not develop WEAs or WECs and did not fail. The field experience shows that a carburized bearing that has a core with low carbon content, high nickel content, greater compressive residual stresses, and a higher amount of retained austenite provides higher fracture resistance and makes c...
89 citations
TL;DR: In this paper, a universal microtribometer with a ball-on-disk configuration was used to evaluate the friction properties between the moving mechanical components in the presence of nanofluids.
Abstract: Nanofluids have been an active area of research for almost two decades due to their enhanced thermal conductivity compared to base fluids, but the study of nanofluids for tribological purposes has been slow, with problems encountered in dispersing and stabilizing nanoparticles in lubricants. In this research, the tribological properties of nanofluids were studied through experimental investigation by dispersing ZnO nanoparticles into paraffinic mineral oil. Nanoparticles were dispersed using an ultrasonic homogenizer. Oleic acid was used as the surfactant for the improved dispersibility and stability of nanofluids. A universal microtribometer with a ball-on-disk configuration was used to evaluate the friction properties between the moving mechanical components in the presence of nanofluids. The wear track was measured using a surface profiler, and the material deposition onto the sliding interface was analyzed using X-ray photoelectron spectroscopy. The effects of the surfactant, ultrasonication time, par...
67 citations
TL;DR: In this paper, the effects of different kinds of fibers on the mechanical and tribological properties (in dry conditions) of a phenolic resin-based friction material were compared on a pin-on-disc apparatus at sliding speeds of 3.2-12.8m/s, disc temperatures of 100-350°C, and applied loads of 312.5-625n.
Abstract: The purpose of the present study is to compare the effects of different kinds of fibers on the mechanical and tribological properties (in dry conditions) of a phenolic resin–based friction material. The series of fibers used in the study include rockwool, ceramic, E-glass, and steel wool fibers. The fiber volume fraction in all composites was kept constant at 30%. Tribological studies were performed on a pin-on-disc apparatus at sliding speeds of 3.2–12.8 m/s, disc temperatures of 100–350°C, and applied loads of 312.5–625 N. Experiments showed that the friction coefficient in general decreased with increasing sliding speed and applied load but increased with increasing disc temperature up to 300°C and then decreased above this temperature. The specific wear rate was found to increase with increasing sliding speed and disc temperature. The highest friction coefficient and specific wear rate were obtained with E-glass and steel wool fiber–reinforced composites, respectively. The wear mechanism was also anal...
65 citations
TL;DR: In this article, the friction and wear properties of titanium alloys TC4, TC18, and TA19 against tungsten carbide under both dry sliding and water-lubricated conditions were investigated using a ball-on-flat sliding friction apparatus under a load of 3 n and at a sliding speed of 112 mm/s.
Abstract: The friction and wear properties of titanium alloys TC4, TC18, and TA19 against tungsten carbide under both dry sliding and water-lubricated conditions were investigated using a ball-on-flat sliding friction apparatus under a load of 3 N and at a sliding speed of 112 mm/s. These investigated titanium alloys were observed by scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). The results indicated that the kinetic friction coefficients as a function of sliding time increased at the initial friction stage under dry conditions and vary within a small range under water-lubricated conditions. Furthermore, the coefficient of friction of the TA19/WC-Co tribopair was lower than that of both TC4/WC-Co and TC18/WC-Co tribopairs. However, under water-lubricated conditions, the friction coefficients and wear volume of both TC4/WC-Co and TA19/WC-Co tribopairs decreased obviously compared to that under dry conditions, and the abrasion resistance increased. On the other hand, the effect of water...
63 citations
TL;DR: In this article, the authors compared the tribological evaluation of chemically modified rapeseed oil as a potential biodegradable automotive lubricant with and without nano-and microscale titanium dioxide (TiO2) particles, focusing on the influence of TiO2 particles to improve the friction reduction and antiwear characteristics of the chemically modified rapedeed oil.
Abstract: This study compared the tribological evaluation of chemically modified rapeseed oil as a potential biodegradable automotive lubricant with and without nano- and microscale titanium dioxide (TiO2) particles, focusing on the influence of TiO2 particles to improve the friction reduction and antiwear characteristics of chemically modified rapeseed oil. TiO2 nano- and microscale particles of anatase phase and rutile phase were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Further, the analysis of chemically modified rapeseed oil with and without TiO2 additives was carried out to determine its tribological behavior using a pin-on-disc tribometer. The experimental results showed that the addition of TiO2 nanoparticles exhibited good friction reduction and antiwear properties compared with the addition of microscale TiO2 and without TiO2 additives to chemically modified rapeseed oil. Nanoscale TiO2 is suitable as an antiwear additive in c...
60 citations
TL;DR: In this paper, a J2-based elastic-plastic finite element model coupled with a carbon diffusion model is developed that directionally predicts the directionality of white etching bands.
Abstract: Microstructural alterations in bearing steels during rolling contact cycling have been reported in the literature for more than half a century. These structural changes are primarily caused by the decay of parent martensite and have been designated as white and dark etching regions due to their preferential etching characteristics. One of the most striking features of the white etching bands is their repeatable directionality, which has puzzled investigators for decades. Despite numerous attempts, a satisfactory explanation for the orientation of these bands is still not available. In this article (Part 1), an overview of the phenomenon is presented with detailed discussion of various experimental observations from the literature. The article also examines the previous approaches adopted to explain white etching bands and address their limitations. In Part II of the article, a J2-based elastic–plastic finite element model coupled with a carbon diffusion model is developed that directionally predicts the o...
57 citations
TL;DR: In this article, two different commercially available case-carburged steels (P675, M-50 NiL) and two through-hardened steels were characterized to obtain relationships among the volume fraction of subsurface carbides, indentation hardness, elastic modulus, and yield strength as a function of depth.
Abstract: Case-hardened steels, widely used in high-performance ball and roller bearings, have high surface hardness and a gradient in material properties (hardness, yield strength, etc.) as a function of depth; therefore, they behave as functionally graded materials. Understanding the mechanical properties due to gradients in the subsurface microstructure of case-hardened steels is important for modeling the effects of cyclic damage induced by rolling contact fatigue. In the current study, two different commercially available case-carburized steels (P675, M-50 NiL) and two through-hardened steels (M-50, case P675) were characterized to obtain relationships among the volume fraction of subsurface carbides, indentation hardness, elastic modulus, and yield strength as a function of depth. A variety of methods including microindentation, nanoindentation, ultrasonic measurements, compression testing, rule of mixtures, and upper and lower bound models were used to determine the above relationships and compare the experi...
57 citations
TL;DR: In this paper, the dry sliding wear behavior of the composites in the cast conditions is examined using the pin-on-disc tribotesting machine for three different loads (20, 30, and 40 N) with three different sliding velocities (2, 3, and 4 N).
Abstract: Rice husk ash of three different particle size ranges (50–75, 75–100 and 100–150 μm) a 3, 6, 9, and 12% by weight is reinforced with an aluminum alloy (AlSi10Mg) using the liquid metallurgy method. The dry sliding wear behavior of the composites in the cast conditions is examined using the pin-on-disc tribotesting machine for three different loads (20, 30, and 40 N) with three different sliding velocities (2, 3, and 4 m/s). The results reveal that the composite reinforced with the coarse rice husk ash particles exhibits superior wear resistance compared to the fine rice husk ash particles. The wear rate of the composite decreased with an increase in the weight percentage of rice husk ash particles for all size ranges. Finally, the wear mechanism was investigated with the worn surface using a scanning electron microscope.
56 citations
TL;DR: In this paper, the CAGEDYN bearing dynamics model was used to simulate the experimental smearing test conditions, and it provided encouragement that accurate prediction of smearing risk was possible.
Abstract: Smearing damage was created on cylindrical roller bearings (CRBs) using a laboratory test protocol that required alternating the load zone direction according to a square wave function. The experimental goal was to compare the wear protection afforded by various surface treatments, including vibratory superfinishing (ES20), black oxide treatment, and special tungsten carbide–reinforced amorphous hydrocarbon roller body coatings (WC/a-C:H). The only bearing treatments that did not smear in these severe tests were the WC/a-C:H bearings. Black oxide and ES20 bearings experienced smearing with the same frequency as untreated bearings, albeit to different degrees of microscopic damage. The test rig was instrumented to measure cage slip, which provided insight about the roller–raceway slip dynamics during the tests via kinematic calculations. The CAGEDYN bearing dynamics model was used to simulate the experimental smearing test conditions, and it provided encouragement that accurate prediction of smearing risk ...
53 citations
TL;DR: In this article, an attempt was made to improve the wear resistance of short glass fiber (SGF)-reinforced epoxy composites by incorporation of microsized blast furnace slag (BFS) particles.
Abstract: Short fiber-reinforced polymer composites are used in numerous tribological applications. In the present work, an attempt was made to improve the wear resistance of short glass fiber (SGF)-reinforced epoxy composites by incorporation of microsized blast furnace slag (BFS) particles. The effect of various operational variables and material parameters on the sliding wear behavior of these composites was studied systematically. The design of experiments approach using Taguchi's orthogonal arrays was used. This systematic experimentation led to identification of significant variables that predominantly influence the wear rate. The Taguchi approach enabled us to determine optimal parameter settings that led to minimization of the wear rate. The morphology of worn surfaces was then examined by scanning electron microscopy and possible wear mechanisms are discussed. Further, in this article, the potential of using artificial neural networks (ANNs) for the prediction of sliding wear properties of polymer composit...
52 citations
TL;DR: In this paper, the effect of applied load, sliding distance, and weight percentage of reinforcement on the abrasive wear characteristics of in situ synthesized Al-12Si/TiC composites using a pin-on-disk machine was investigated.
Abstract: This study investigated the effect of applied load, sliding distance, and weight percentage of reinforcement on the abrasive wear characteristics of in situ synthesised Al-12Si/TiC composites using a pin-on-disk machine. The strength, hardness, and percentage porosity were also investigated. Scanning electron microscopy (SEM) was utilized to study the microstructure and wear surface behavior of the experimental materials. The results revealed that the strength and hardness increased with increasing weight percentage of reinforcement. However, the percentage porosity was relatively high in the higher weight percentage of reinforcement. The weight loss and coefficient of friction increased with increasing applied load and sliding distance. In contrast, the weight loss and coefficient of friction decreased when the weight percentage of TiC increased. Wear debris in the form of fine black powder and small grooves were noticed in the SEM micrograph of the abraded surfaces of all tested materials.
TL;DR: In this article, the effect of microstructural variations on solid particle erosion wear behavior of Ti-6Al-4V alloy at room temperature was described, and the results indicated that impact velocity is the most significant controlling factor influencing the erosion wear.
Abstract: The present article describes the effect of microstructural variations—that is, lamellar, bimodal, and equiaxed—on solid particle erosion wear behavior of Ti-6AL-4V alloy at room temperature. Erosion tests were carried out at various test conditions using an air jet–type test rig and Taguchi's orthogonal array experimental design. The results indicated that impact velocity is the most significant controlling factor influencing the solid particle erosion wear of Ti-6Al-4V alloy followed by impact angle, microstructural variation, and size of erodent. The lamellar microstructure of Ti-6Al-4V alloy has excellent erosion resistance, followed by bimodal and equiaxed microstructures. Ploughing or pile-up leading to platelet formation was found to be the primary mechanism of material loss in erosion of Ti-6Al-4V alloy. This mechanism of material loss is independent of its microstructural variation. These results were determined after observation of the eroded surface under a scanning electron microscope. Optical...
TL;DR: In this paper, a mass-conserving model is employed to evaluate the effects of the texture geometry, and the results reveal a strong dependence between certain parameters such as the texture cell number and dimple depth, and an increase in the texture density has beneficial effects.
Abstract: It has been proven experimentally that surface texturing represents a viable solution for increasing the load-carrying capacity of parallel fluid bearings. Along with several load-supporting mechanisms that have been identified in the literature, the texture geometry remains an important feature. With the main objective of evaluating the effects of the texture geometry, a mass-conserving model is employed. While avoiding the use of the bulk modulus β, the algorithm also deals with the cavitation phenomenon and provides rapid and accurate results. For given operating conditions (supply pressure, surface speed, or lubricant viscosity), essential geometrical features such as size, density, and shape are analyzed in detail. In terms of load support and friction, the results reveal a strong dependence between certain parameters such as the texture cell number and dimple depth, and an increase in the texture density has beneficial effects in most cases. With regard to shape, the influence of this feature proves...
TL;DR: In this article, the effectiveness of a Cr-DLC coating with ethyl-dimethyl-2-methoxyethylammonium tris(pentafluoroethyl)trifluoropho-sphate [(NEMM)MOE][FAP] and 1-butyl-1-methylpyrro-lidiniumtris (PPL) tris[BMP] [FAP]-Ionic liquids (ILs] as 1-wt% additives to a polyalphaolefin (PAO
Abstract: The lubrication of a Cr-DLC coating with ethyl-dimethyl-2-methoxyethylammonium tris(pentafluoroethyl)trifluoropho-sphate [(NEMM)MOE][FAP] and 1-butyl-1-methylpyrro-lidinium tris(pentafluoroethyl)trifluorophosphate [BMP] [FAP] ionic liquids (ILs) as 1 wt% additives to a polyalphaolefin (PAO 6) was studied. Zinc dialkyldithiophosphate (ZDDP) was also used as reference in order to evaluate the effectiveness of the ILs. Reciprocating ball-on-plate tribological tests at loads of 20 and 40 N were performed. The results showed that both ILs exhibited a friction reduction, especially at the lowest load tested. Antiwear properties were also improved; the PAO 6 + 1% [BMP][FAP] mixture was slightly better, close to the values for PAO 6 + 1% ZDDP. Scanning electron microscopy (SEM) images and X-ray photoelectron spectroscopy (XPS) analysis indicated that the additive–surface interaction was responsible for the tribological improvement.
TL;DR: In this paper, an experimental study on heavily loaded slow-speed journal bearings with various radial clearances lubricated with three different lubricants was presented, and the results of friction coefficient and total wear were reported.
Abstract: Slow-speed journal bearings subjected to heavy loads operate in a mixed/boundary lubrication regime. Clearance and lubricant play very important roles in reducing the wear and friction in these bearings. In the present article, an experimental study on heavily loaded slow-speed journal bearings with various radial clearances lubricated with three different lubricants is presented. Lubricants with varying viscosities and containing different percentages of antiwear additives have been used. Bearing surface roughness and out-of-roundness are treated as noise parameters. The results of friction coefficient and total wear have been reported. The experimental results suggest that a lubricant with high viscosity and antiwear additives significantly reduces the coefficient of friction and amount of wear under varying bearing clearances, circularity, and cylindricity. The use of such a robust lubricant may obviate the effect of manufacturing uncertainties. This results in reduction of manufacturing and measuremen...
TL;DR: In this article, an existing theoretical micropitting model, based on the competitive interaction between surface fatigue and mild polishing wear, is employed to predict the effects of different base oil/additive solutions and the relative humidity of the environment on micro-minimizing damage.
Abstract: In the present study, an existing theoretical micropitting model, based on the competitive interaction between surface fatigue and mild polishing wear, is employed to predict the effects of different base oil/additive solutions and the relative humidity of the environment on micropitting damage. These effects, though expected to be tribochemical in nature, manifest themselves mechanically; for example, by possibly affecting the fatigue strength of the surface and increasing or reducing the boundary friction and/or the mild wear rate, which altogether may cause an appreciable influence on the degree of micropitting. The present model takes into account only the last two issues (i.e., the change in boundary friction and wear) due to the presence of additives; nevertheless, it is able to predict their performance under micropitting conditions in most cases, showing good agreement with the corresponding experimental data. The results of the present work establish the basis of a blueprint for selecting oil additives for bearing applications.
TL;DR: In this article, the authors define the definition of accurate contact (collision) models, and an essential parameter within these models is the coefficient, which is defined as the ratio of the collision coefficient to the collision probability.
Abstract: Particle-based modeling approaches, such as the discrete element method, require the definition of accurate contact (collision) models. An essential parameter within these models is the coefficient...
TL;DR: In this article, the volume that is critically stressed during a rolling pass is modeled with an explicit representation of microstructure topology, and discontinuities in the subsurface stress calculation for line and circular contact loading are removed.
Abstract: Several 2D and 3D numerical models have been developed to investigate rolling contact fatigue (RCF) by employing a continuum damage mechanics approach coupled with an explicit representation of microstructure topology. However, the previous 3D models require significant computational effort compared to 2D models. This work presents a new approach wherein efficient computational strategies are implemented to accelerate the 3D RCF simulation. In order to reduce computational time, only the volume that is critically stressed during a rolling pass is modeled with an explicit representation of microstructure topology. Furthermore, discontinuities in the subsurface stress calculation in the previously developed models for line and circular contact loading are removed. Additionally, by incorporating a new integration algorithm for damage growth, the fatigue damage simulations under line contact are accelerated by a factor of nearly 13. The variation in fatigue lives and progression of simulated fatigue spalling ...
TL;DR: In this article, multiwalled carbon nanotubes were homogenously dispersed into a magnesium alloy (AZ31) using friction stir processing, and the microstructural features, mechanical behaviors including microhardness, and wear properties were investigated.
Abstract: Multiwalled carbon nanotubes were homogenously dispersed into a magnesium alloy (AZ31) using friction stir processing. The microstructural features, mechanical behaviors including microhardness, and wear properties were investigated. The results showed a significant improvement in wear resistance in the friction stir-processed AZ31 alloy containing multiwalled carbon nanotubes compared to that of the as-received alloy. This was attributed to its higher microhardness and lower coefficient of friction due to the presence of finer matrix grains and uniform dispersion of multiwalled carbon nanotubes.
TL;DR: In this article, the potential tribological properties of water-based cerium dioxide nanofluids were investigated using a pin-on-disc tester under different loading conditions.
Abstract: This article presents an investigation on the potential tribological properties of water-based cerium dioxide nanofluids. Nanofluids with different nanoparticle concentrations were prepared in a materials laboratory. A stable dispersion of nanoparticles in the fluids was achieved with an appropriate percentage of the surfactant sorbitan monostearate. The stability of particle dispersion was studied using zeta potential measurement. Additive conglomerate size in the nanofluids was measured using dynamic light scattering. It was observed that the dispersibility of nanoparticles played an important role in the frictional properties of the nanofluids. The tribological properties of the water-based nanofluids were evaluated using a pin-on-disc tester under different loading conditions. A significant improvement in the tribological properties of the water-based cerium dioxide nanofluids was observed. The worn surfaces of the contact elements were characterized using scanning electron microscopy (SEM) and a nano...
AVL1
TL;DR: In this article, the theory of the separated mathematical models and their coupling is discussed. But the authors do not consider the dynamics of the overall flexible body system in addition to the detailed properties of the contacts and the lubricant itself.
Abstract: Different types of mixed lubricated contacts are present in internal combustion engines. These are several radial slider bearings; for instance, in main bearings; big end, small end, and piston pin bearings; as well as axial slider bearings and piston–liner contacts. Phenomena such as friction power loss and wear as well as acoustic excitation and oil consumption of the overall lubrication system are mainly affected by these contacts. Therefore, the simulation-based investigation of oil film–lubricated contacts is important during the development process of internal combustion engines. Due to the highly nonlinear interactions, the applied mathematical models have to consider the dynamics of the overall flexible body system in addition to the detailed properties of the contacts and the lubricant itself. This work outlines both the theory of the separated mathematical models and their coupling. The large number of nonlinear contacts, which is possible to consider when applying the presented coupling approac...
TL;DR: In this paper, the effects of mechanical preload and bearing clearance on the rotordynamic performance of lobed gas foil bearings (GFBs) for oil-free turbochargers (TCs) were investigated.
Abstract: This article presents the results of experimental studies on the effects of mechanical preload and bearing clearance on the rotordynamic performance of lobed gas foil bearings (GFBs) for oil-free turbochargers (TCs). The lobed GFBs have a first-generation bump-type configuration within a lobe-like inner surface bearing housing. Five test GFBs were fabricated and used for experiments: three circular GFBs and two lobed GFBs. The GFB clearance was measured via GFB displacement versus static load testing. The TC housing vibrations were identified via impact tests and engine driving tests, demonstrating that the TC housing was subjected to engine-induced excitations and TC housing resonances. The second-order harmonic of the engine speed appeared to be most noticeable in the rotor motions due to the engine-induced excitations. Measurements of the rotordynamic performance of the test GFBs were conducted during a series of TC rotor speed-up and slow-down tests for an oil-free test TC driven by the diesel vehicle...
TL;DR: In this article, the effects of graphite and hexagonal boron nitride (h-BN) as solid lubricants and aluminum oxide (Al2O3) and B4C as abrasives on brake friction performance were evaluated.
Abstract: The effects of graphite and hexagonal boron nitride (h-BN) as solid lubricants and aluminum oxide (Al2O3) and boron carbide (B4C) as abrasives on brake friction performance were evaluated. Friction...
TL;DR: In this article, the effects of couple stresses were analyzed based on Stokes microcontinuum theory and the Brinkman model was utilized to model the flow in the porous region.
Abstract: This article presents an analysis of a long journal bearing with a double-layer porous lubricant film using couple stress and Newtonian fluids. The porous layer with infinite permeability analyzed in this study simulates the surface layer. The Brinkman model was utilized to model the flow in the porous region. The effects of couple stresses were analyzed based on Stokes microcontinuum theory. A double-layer porous lubricant film configuration, with a low-permeability porous layer on top of a high-permeability bearing adherent porous layer, improved the journal bearing performance characteristics. A surface porous layered lubricant film configuration increased the load-carrying capacity and reduced the coefficient of friction in a journal bearing.
TL;DR: In this paper, a thermal elastohydrod dynamic lubrication line contact model was developed to study effects of speed on the lubrication performance of a spur gear pair, and the effect of dynamic loads on film thickness, pressure distribution and temperature field were studied.
Abstract: A thermal elastohydrodynamic lubrication line contact model, which could handle ultra-thin-film conditions, was developed to study effects of speed on the lubrication performance of a spur gear pair. Dynamic loads were calculated using a classic mass-spring model. They effect of speed on lubrication performance was studied comprehensively through its direct influence on lubrication and indirect influence by affecting dynamic loads of the gear pair. The effect of dynamic loads on film thickness, pressure distribution, and temperature field were studied. It was concluded that a comprehensive model combining a lubricated contact analysis and a dynamic analysis for a gear system is required for a reasonable performance evaluation.
TL;DR: In this article, a W-aC:H coating applied to the rolling elements is shown to have significantly longer fatigue lives in debris-containing and thin-film lubrication environments and is highly resistant to wear from false brinelling and scuffing.
Abstract: Mechanical systems that operate in agricultural, construction, and mining and mineral processing applications typically operate in debris-containing and thin-film lubrication environments. Consequently, the lives of rolling element bearings in these applications are often limited by surface fatigue arising from thin-film lubrication, damage from the debris, false brinelling, and scuffing. Traditional approaches utilizing specialized heat treatments and lubricant additives can sometimes delay the onset of early raceway fatigue, but even in these cases the actual bearing life is still usually less than that for which the bearing was designed. Bearings with a highly durable W-aC:H coating applied to the rolling elements are shown to have significantly longer fatigue lives in debris-containing and thin-film lubrication environments and are highly resistant to wear from false brinelling and scuffing.
TL;DR: Schiff bases of salicylaldehyde with 1,2-phenylenediamine (H2Saloph), 1,4-phenylleniamine(H 2Salpph), and 4,4′-diaminodiphenylmethane (H 2Saldphm) have been synthesized for their application as ecofriendly, zero sulfated ash, phosphorous, and sulfur (SAPs) and ash-free antiwear additives as mentioned in this paper.
Abstract: Schiff bases of salicylaldehyde with 1,2-phenylenediamine (H2Saloph), 1,4-phenylenediamine (H2Salpph), and 4,4′-diaminodiphenylmethane (H2Saldphm) have been synthesized for their application as ecofriendly, zero sulfated ash, phosphorous, and sulfur (SAPs) and ash-free antiwear additives. Testing of the compounds was carried out in paraffin oil on a four-ball testing machine using steel balls and zinc dibutyl dithiophosphate (ZDDP) as a reference additive. Their synergistic behavior with borate ester was also studied. Testing of the compounds (1% w/v) was performed at various loads for 30-min test duration and for different times at 392 N load. On the basis of various tribological parameters, the following order is given for the activity of the compounds: When the mixtures of Schiff bases and borate ester were tested, they showed a high amount of synergy. Schiff bases follow the above order in their mixtures, too. The efficiencies of the synergistic formulations were far better than that of the standard Z...
TL;DR: In this paper, the influence of the percentages of reinforcement, load, sliding speed, and sliding distance on both the wear and friction coefficient were studied. And the wear test with an experimental plan of six loads (5-30 N) and five sliding speeds (0.5-2.5 m/s) was conducted on a pin-on-disc machine to record loss in mass due to wear for two total sliding distances of 1,000 and 2,000 m.
Abstract: The wear and sliding friction response of a hybrid copper metal matrix composite reinforced with 10 wt% of tin (Sn) and soft solid lubricant (1, 5, and 7 wt% of MoS2) fabricated by a powder metallurgy route was investigated. The influence of the percentages of reinforcement, load, sliding speed, and sliding distance on both the wear and friction coefficient were studied. The wear test with an experimental plan of six loads (5–30 N) and five sliding speeds (0.5–2.5 m/s) was conducted on a pin-on-disc machine to record loss in mass due to wear for two total sliding distances of 1,000 and 2,000 m. The results showed that the specific wear rate of the composites increased at room temperature with sliding distance and decreased with load. The wear resistance of the hybrid composite containing 7 wt% MoS2 was superior to that of the other composites. It was also observed that the specific wear rates of the composites decreased with the addition of MoS2. The 7 wt% MoS2 composites exhibited a very low coefficient ...
TL;DR: In this paper, a thermohydrodynamic (THD) model of plain journal bearings is proposed by taking mass-conserving cavitation into account, where the three-dimensional energy equation and heat conduction equations in the solids are solved simultaneously.
Abstract: The thermal boundary conditions (TBCs) play an important role in determining the temperature field of plain journal bearings. Well-chosen TBCs are beneficial in obtaining reliable results corresponding to actual operating conditions. In this article, a thermohydrodynamic (THD) model of plain journal bearings is proposed by taking mass-conserving cavitation into account. The three-dimensional energy equation and heat conduction equations in the solids are solved simultaneously. A comprehensive analysis is provided to examine the influence of the TBCs on the THD solution of plain journal bearings.
TL;DR: In this paper, the effects of different reinforcement additives on the tribological behaviors of PEEK-based composites sliding against 316 steel under seawater lubrication were investigated systematically using a ring-on-block test rig.
Abstract: Polyetheretherketone (PEEK)-based composites reinforced with lubricant additive (polytetrafluoroethylene, PTFE) and reinforcement additives including carbon fiber (CF), glass fiber (GF), and bronze powder were prepared using a hot-press molding technique. The synergetic effects of different additives on the tribological behaviors of PEEK-based composites sliding against 316 steel under seawater lubrication were investigated systematically using a ring-on-block test rig. The results showed that lubricant additive PTFE can decrease the friction coefficient and consequently improved the wear resistance of PEEK under seawater lubrication, especially when the volume fraction of PTFE was about 20%. It was also found that the incorporation of CF can further improve the wear resistance of PEEK blended with 20% PTFE, especially under high load and high sliding speed. This suggested that a synergistic effect on improving the wear resistance of PEEK existed between PTFE and CF, which originated from good lubrication...