Showing papers in "Tribology Transactions in 2012"
TL;DR: In this paper, the effect of internal clearance on radially loaded deepgroove ball and cylindrical roller bearing load distribution and fatigue life was determined for four clearance groups defined in the bearing standards.
Abstract: The effect of internal clearance on radially loaded deepgroove ball and cylindrical roller bearing load distribution and fatigue life was determined for four clearance groups defined in the bearing standards. The analysis was extended to negative clearance (interference) conditions to produce a curve of life factor versus internal clearance. Rolling-element loads can be optimized and bearing life maximized for a small negative operating clearance. Life declines gradually with positive clearance and rapidly with increasing negative clearance. Relationships were found between bearing life and internal clearance as a function of ball or roller diameter, adjusted for load. Results are presented as life factors for radially loaded bearings independent of bearing size or applied load. In addition, a modified Stribeck Equation is presented that relates the maximum rolling-element load to internal bearing clearance.
89 citations
TL;DR: In this paper, the effects of nanoparticle type, particle concentration, and surface roughness of the specimen on the friction and wear characteristics of water-based nanofluids were investigated.
Abstract: In recent years, nanofluids have been an active area of research due to their enhanced thermal conductivity over base fluids. However, the tribological properties of nanofluids have not been thoroughly studied. In this research, friction and wear characteristics of water-based nanofluids was carried out. Commercially available water-based nanofluids with 50% ZnO and 50% Al2O3 nanoparticle concentration were used as the lubricant. The 50% concentration nanofluids were diluted using deionized water and an ultrasonic bath into different volume concentrations. The effects of nanoparticle type, particle concentration, and surface roughness of the specimen on the friction and wear characteristics were investigated. The friction and wear tests were performed using a UMT-2 Micro-Tribometer with a ball-on-disk configuration. The surface roughness and wear volume were measured using a WYKO 3D optical surface profiler, and chemical characterization analysis was done using a PHI 5000 VersaProbe X-ray photoelectron sp...
81 citations
TL;DR: In this paper, a pin-on-disc wear tribometer was used to evaluate the wear and friction characteristics of a diesel engine cylinder liners and piston rings under different lubricating conditions.
Abstract: This article addresses the issue of friction and wear characteristics of diesel engine cylinder liner–piston ring combinations under different lubricating conditions using a pin-on-disc wear tribometer. The discs were made out of actual engine cylinder liner material using a casting process. Pins were made out of top compression ring material. The tests were conducted on a pin-on-disc tribometer for wear and friction characteristics of the cylinder liner and piston ring combination with diesel-contaminated rapeseed oil–based bio-lubricant, diesel-contaminated commercial synthetic lubrication oil (SAE 20W40), biodiesel-contaminated commercial synthetic lubrication oil (SAE 20W40), and used (150 h) commercial synthetic lubrication oil (SAE 20W40). Experimental results demonstrated that the rapeseed oil–based bio-lubricant and biodiesel-contaminated synthetic lubricant exhibited better performance in terms of wear, friction, and frictional force under similar operating conditions. Thus, usage of newly formul...
78 citations
TL;DR: In this article, the influence of temperature on friction and wear performance for refined, bleached, and deodorized (RBD) palm stearin and additive-free paraffinic mineral oil is presented.
Abstract: The wide use of petroleum-based oils raises concerns with regard to pollution, and the rising of awareness of greenhouse gases has created a demand for the use of environmentally friendly and biodegradable lubricants for industrial applications. Vegetable oils are one of the bio-oils that have been promoted as a replacement for petroleum products, in part due to their environmentally friendly characteristics; they are nontoxic, biodegradable, and easy to dispose of. Many researchers have performed studies on sunflower oil, corn oil, and soy oil, but few have studied palm oil as a lubricant. Palm oil produced in a high-throughput manner could fulfill the demand for biobased lubricants. In this study, the influence of temperature on friction and wear performance for refined, bleached, and deodorized (RBD) palm stearin and additive-free paraffinic mineral oil is presented. The experiments were conducted using a four-ball tribotester. Test temperatures of 55, 65, 75, and 85 ◦ C were used. The sliding speeds were set to 1,200 rpm. Experiments were run for 1 h under a 392.4 N load. The results of RBD palm stearin were compared with those of paraffinic mineral oil. The experimental results showed that the RBD palm stearin had better performance compared to paraffinic mineral oil in terms of reducing frictional constraints.
77 citations
TL;DR: In this paper, a dry sliding wear test was performed for Ti-6Al-4V alloy under loads of 50-250 N at 20-400°C and 200-200 N at 400°C.
Abstract: Tribo-oxides of titanium alloy are usually reported to provide low protection from wear. However, in this research, tribo-oxides provide a protective effect for wear. Dry sliding wear tests were performed for Ti-6Al-4V alloy under loads of 50–250 N at 20–400°C. Ti-6Al-4V alloy presented different wear behavior at 400°C than at 20–200°C. At 20°C, the wear loss increased linearly with increased load. The wear loss at 200°C marginally increased under 50–150 N loads and increased rapidly under a load of 200 N, slightly higher than at 20°C. At 400°C, the wear loss decreased under loads of 50–100 N, slightly increased and had the lowest value under loads of 100–200 N, and finally increased rapidly at loads above 200 N. The prevailing oxidative mild wear and the lowest wear loss at 400°C were attributed to the protective effect of tribo- oxides.
66 citations
TL;DR: In this article, the effectiveness of laser surface texturing in reducing wear rate was studied, with emphasis on dimple distribution angle, and experiments were performed by varying the texturing parameters to derive variational rules of the wear scar depth on laser-textured cylinder walls under starved lubrication conditions.
Abstract: The effectiveness of laser surface texturing in reducing wear rate was studied, with emphasis on dimple distribution angle. Experiments were performed by varying the texturing parameters to derive variational rulesof the wear scar depth on laser-textured cylinder walls under starved lubrication conditions, and the optimum laser texturing dimple distribution angle was obtained. It was found that the laser texturing could result in less wear rate compared to mechanical honing.
47 citations
TL;DR: The friction and wear behavior of Ag-2.5Cu-8MoS2 composite is investigated in this paper, where the MoS2 lubricating films formed on the worn surfaces and transfer layer surfaces led to a low friction coefficient.
Abstract: The friction and wear behavior of Ag-2.5Cu-8MoS2 composite is investigated in this article. Wear tests were conducted against the coin silver under a range of sliding loads from 1 to 4 N and sliding distances from 1 to 15 km. The wear loss of the composite increased linearly with increased sliding load and sliding distance. The friction coefficient reached a constant value after a short sliding distance. The MoS2 lubricating films formed on the worn surfaces and transfer layer surfaces led to a low friction coefficient. Fine MoS2 particles smeared on worn surfaces and wear debris surfaces were observed in the detailed studies. The MoS2 concentration in the worn surface of the composite was about four times higher than that in the matrix of the composite. Fine equiaxed wear debris was cut off from grooves at low sliding loads and thin sheet-like wear debris was delaminated from worn surfaces at high sliding loads. Abrasive wear and delamination wear were the dominant wear mechanisms within the studied rang...
46 citations
TL;DR: In this paper, a combined finite discrete element model (FDEM) was developed to study the effects of displacement amplitude and normal force on fretting wear, and the results indicated that the dissipated energy equation better describes wear in fretting contacts than the Archard equation.
Abstract: In this investigation, the fretting wear phenomenon was investigated experimentally and analytically. For the analytical investigation, a combined finite discrete element model (FDEM) was developed to study the effects of displacement amplitude and normal force on fretting wear. The FDEM was used to investigate the wear of a fretting Hertzian line contact calculated using the Archard and dissipated energy wear theories. Although the FDEM results from each theory were in agreement, the dissipated energy approach more accurately predicted the wear volumes obtained from experimental measurements. A fretting wear test rig (FWTR) was used to verify and corroborate the results and conclusions of the numerical investigation. The results indicated that the dissipated energy equation better describes wear in fretting contacts than the Archard equation. An energy dissipation rate map was developed from the experimental results, showing the effect of normal force and displacement amplitude on frictional energy loss....
46 citations
TL;DR: In this article, a geometric multigrid scheme for the solution of the Reynolds equation in the piston-cylinder interface of an axial piston machine is presented, which is a significant advancement in the fluid power research community.
Abstract: A geometric multigrid scheme for the solution of the Reynolds equation in the piston–cylinder interface of an axial piston machine is presented in this article. The application of this numerical method represents a significant advancement in the fluid power research community, where the solution of the fluid flow in the piston–cylinder interface has thus far been obtained using standard iterative schemes. An efficient numerical solver for the piston–cylinder interface Reynolds equation is necessary to couple the solution of the nonisothermal fluid film flow with the solid boundaries’ surface elastic deformations as part of a larger simulation procedure. The piston–cylinder interface is in fact one of the most complex tribological pairs of an axial piston machine. It operates in an elastohydrodynamic regime under oscillating load conditions, where the additional influences of heat transfer and solid boundaries’ thermal strains cannot be neglected. To consider all of the described physical phenomena and inv...
45 citations
TL;DR: In this paper, the influence of laser peening on the fretting wear behavior of Ti-6Al-4V was analyzed by transmission electron microscopy, which resulted in the formation of nanocrystallites on the surface and near surface regions, increased hardness, and compressive residual stress.
Abstract: This work deals with the influence of laser peening on the fretting wear behavior of Ti-6Al-4V. Laser peening was carried out on Ti-6Al-4V. The laser-peened surface was characterized by transmission electron microscopy. Surface roughness, nanoindentation hardness, residual stress, and tensile properties of the material in both laser-peened and unpeened conditions were determined. Fretting wear tests were conducted at different normal loads using a ball-on-flat contact geometry. Laser peening resulted in the formation of nanocrystallites on the surface and near-surface regions, increased hardness, and compressive residual stress. Laser peening did not affect the tensile properties and surface roughness significantly. There was no considerable difference between the values of the tangential force coefficient of laser-peened and unpeened samples. The fretting scar size, wear volume, and wear rate of laser-peened specimens were lower than those of unpeened samples. This may be attributed to an increase in sur...
44 citations
TL;DR: In this article, a specially designed open tribometer was used to characterize the macroscopic friction coefficient, heat partition coefficient, and adhesion in the contact versus sliding velocity and contact pressure.
Abstract: This article aims at characterizing the frictional behavior of a TiAl6V4 alloy and a carbide tool under extreme conditions corresponding to those occurring at the cutting tool–work material interface. A specially designed open tribometer was used to characterize the macroscopic friction coefficient, heat partition coefficient, and adhesion in the contact versus sliding velocity and contact pressure. It has been shown that titanium leads to intense adhesion, which seems to be even more intensive with high contact pressure and high sliding velocity, which limits the local sliding movement at the interface (stuck layer). However, the tribometer provides the evolution of an apparent friction coefficient and a macroscopic heat partition coefficient related to the shearing of titanium between the adhesive layer and the bulk material. An increase in sliding velocity or contact pressure induces a small decrease in the apparent friction coefficient as well as the heat partition coefficient. It has been shown that ...
TL;DR: A series of hydroxyl-functionalized imidazolium bis (trifluoromethylsulfonyl)imide ionic liquids (ILs) with alkyl chain lengths ranging from C1 to C10 were successfully synthesized and systematically investigated as lubricants for steel-steel contacts at room temperature and three different lubricating conditions.
Abstract: A series of hydroxyl-functionalized imidazolium bis (trifluoromethylsulfonyl)imide ionic liquids (ILs) with alkyl chain lengths ranging from C1 to C10 were successfully synthesized and systematically investigated as lubricants for steel–steel contacts at room temperature and three different lubricating conditions. The effect of either hydroxyethyl group or alkyl chain length on physicochemical and tribological properties of the ILs was discussed at length, and the optimum chemical structure was also obtained. It was found that incorporation of a hydroxyethyl group to the imidazolin cation had a great impact on thermal stability, frictional coefficient, and wear but less impact on viscosity and corrosivity. It is also found that increasing alkyl chain length in the imidazolin cation had a significant influence on corrosion, the frictional coefficient, and wear but the effect dropped rapidly from C1 to C6 and progressively recovered as it increased from C6 to C10. To a much lesser extent, a similar effect w...
TL;DR: In this paper, a mathematical model was developed to predict the wear volume and coefficient of friction of the composites and an ANOVA technique was applied to check the validity of the developed model.
Abstract: Aluminum alloy (Al/3.25Cu/8.5Si) composites reinforced with fly ash particles of three different size ranges (53–75, 75–103, and 103–150 μm) in 3, 6, 9, and 12 weight percentages were fabricated using a stir-casting technique. Pin-on-disc wear tests were conducted with 20, 30, and 40 N loads and sliding speeds of 2, 3, and 4 m/s for a constant time period of 10 min. A mathematical model was developed to predict the wear volume and coefficient of friction of the composites. An analysis of variance (ANOVA) technique was applied to check the validity of the developed model. Student's t-test was utilized to determine the significance of factors. Composites reinforced with coarse fly ash particles exhibit superior wear resistance to those reinforced with fine fly ash particles. A scanning electron microscope (SEM) study of the worn surfaces of the pins was performed to confirm the results of the model.
TL;DR: In this paper, a procedure based on ASTM standards D7214 and E2412 was defined to improve quantification of oil oxidation in used engine oils, taking into account typical problems that can be found in this type of sample, including thermal oxidation and fuel dilution.
Abstract: This article describes a procedure, based on ASTM standards D7214 and E2412, that has been defined to improve quantification of oil oxidation in used engine oils. Taking into account typical problems that can be found in this type of sample, including thermal oxidation and fuel dilution, Fourier transform infrared (FTIR) spectra were analyzed also considering the effect of the oil formulation. Two zones were considered inside the typical wavenumber range for quantification of oxidation, where those problems can be detected and assessed more easily: zone A between 1725 and 1650 cm−1, where the main oxidation products, such as aldehydes, carboxylic acids, and ketones, occur due to thermal degradation of the oil; and zone B between 1770 and 1725 cm−1, where esters due to potential biodiesel dilution problems are detected.
TL;DR: In this article, the performance of palm oil as a lubricant in a cold metal forming process was tested and evaluated by carrying out plane strain extrusion experiments and experimental analyses using a visioplasticity method.
Abstract: The performance of palm oil as a lubricant in a cold metal forming process was tested and evaluated by carrying out plane strain extrusion experiments and experimental analyses using a visioplasticity method. In the present research, two types of refined palm oil, refined, bleached, and deodorized (RBD) palm olein and RBD palm stearin, were tested as lubricants. The workpiece material was aluminum JIS-A1050. The experiments were carried out at room temperature (22°C). Paraffinic mineral oils with varying degrees of viscosity were tested for comparison. The experiment used an extrusion apparatus in which the taper dies were facing together, with zero frictional constraint at the contact plane (corresponding to the plane plate tool) conducted, and results were compared with those extruded with lubricants. Extrusion load and surface roughness of the billets were measured and compared. The distribution of the material flow velocity and effective strain in the exit zone of the billets were calculated using the...
TL;DR: In this paper, the friction reduction potential of thin Mn-phosphate coating, diamond-like carbon coating, and polishing on the bucket surface was explored using a motored valvetrain rig equipped with 3.5L V6 engine head.
Abstract: In a direct-acting mechanical bucket tappet–type valvetrain, the cam and tappet contact is responsible for about 85% of the total valvetrain frictional losses. Because this contact operates primarily in a mixed lubrication regime, it offers an opportunity for friction reduction through surface engineering. The friction reduction potential of thin Mn-phosphate coating, diamond-like carbon coating, and polishing on the bucket surface was explored using a motored valvetrain rig equipped with 3.5L V6 engine head. The durability of tappets and cam lobes was also evaluated using a different motored valvetrain rig consisting of a single lobe and a single tappet. The polished buckets demonstrated substantial friction benefit over current production buckets at all speeds investigated. The diamond-like carbon coated buckets did not show any additional friction reduction benefit. The wear data demonstrated much less wear with polished buckets and also for cam lobes when in contact with polished buckets compared to c...
TL;DR: In this paper, a series of retainer designs were made and the possibility of instability under various operating conditions of a momentum/reaction wheel used in a spacecraft was studied Various tests such as run-in test, temperature test, and overlubrication test were conducted to study the instability and select a design that is stable under all operating conditions.
Abstract: Bearing retainer instability is one of the major causes of failure in the ball bearings used in spacecraft systems These bearing failures lead to mission failure or performance degradation of the spacecraft The instability is characterized by intermittent torque fluctuations and severe audible noise in both low- and high-speed bearings It also generates severe transient forces that result in high cage wear or fracture A series of retainer designs was made and the possibility of instability under various operating conditions of a momentum/reaction wheel used in a spacecraft was studied Various tests such as run-in test, temperature test, and overlubrication test were conducted to study the instability and select a design that is stable under all operating conditions The study results showed that square pocket retainers are more stable compared to circular pocket retainers
TL;DR: In this article, three ILs with the same cation, 1-butyl-3-methylimidazolium, but different sulfate anions were tested using an ultra-high vacuum spiral orbit tribometer (SOT) and their thermal properties were determined by thermogravimetric analysis.
Abstract: Due to their low vapor pressures, low melting points, high boiling points, high radiation resistance, and high thermal stability, room-temperature ionic liquids (ILs) appear to be suitable candidates as new aerospace lubricants for the upcoming return to the Moon and eventual Mars missions and for air and rotorcraft applications. In this study, three ILs with the same cation, 1-butyl-3-methylimidazolium, but different sulfate anions were tested using an ultra-high vacuum spiral orbit tribometer (SOT) and their thermal properties were determined by thermogravimetric analysis (TGA). Specifically, 1-butyl-3-methylimidazolium methyl sulfate, 1-butyl-3-methylimidazolium ethyl sulfate, and 1-butyl-3-methylimidazolium octyl sulfate were tested. The SOT experiments revealed that the lifetimes of the three ILs decreased with increasing alkyl substituent length on the sulfate anion. Infrared and Raman spectra were taken to detect unused ILs and graphitic degradation products, respectively, on worn parts. Post-run s...
TL;DR: In this paper, the effect of cryogenic treatment on the enhancement of the wear resistance of 100Cr6 bearing steel was examined and the underlying mechanisms responsible for wear resistance by DCT at −185°C were revealed.
Abstract: The purpose of this study is to examine the effect of cryogenic treatment on the enhancement of the wear resistance of 100Cr6 bearing steel. The study also aims to reveal the underlying mechanisms responsible for the enhancement of wear resistance by deep cryogenic treatment (DCT) at −185°C. The wear behavior was assessed by a reciprocatory friction and wear monitor under varying normal loads (ASTM International, Annual Book of Standards, 1996). It was found that the wear resistance was increased by 37% due to DCT when compared with that of conventional heat treatment (CHT). A scanning electron microscopy (SEM) study was also conducted to identify the possible mechanism that augments the improvement in the wear resistance of cryogenically treated 100Cr6 bearing steels. The microstructural study suggests that the improvement in the wear resistance is attributed to the conversion of the retained austenite into martensite, along with the precipitation and distribution of the carbides brought in by the cryoge...
TL;DR: In this article, the antiwear performance of the modified nanodiamond (ND) as an additive to commercial oils was studied and the results showed that 0.01 wt% addition of ND improved the anti-wear properties of the lubricants and decreased the oil temperature.
Abstract: The antiwear performance of the modified nanodiamond (ND) as an additive to commercial oils was studied. The surface modification and ultrasonic treatment allow the introduction of ND into oils without significant agglomeration. The ND in oils displayed a high colloidal stability for prolonged times. Two fractions of ND with average particle sizes of 96 and 270 nm were used. A block-on-ring test setup was used to investigate the wear reduction capability of the additives at various load conditions and friction pairs. The results showed that 0.01 wt% addition of ND improved the antiwear properties of the lubricants and decreased the oil temperature. No significant difference in performance was found between NDs of different size. The wear reduction mechanism was attributed to the formation of a hard and porous layer between the contact surfaces.
TL;DR: Fretting fatigue is a combination of two complex mechanical phenomena, namely, fretting and fatigue as mentioned in this paper, which occurs between components that are subjected to small relative oscillatory motion.
Abstract: Fretting fatigue is a combination of two complex mechanical phenomena, namely, fretting and fatigue. Fretting appears between components that are subjected to small relative oscillatory motion. Onc...
TL;DR: In this paper, a semi-analytical method (SAM) was used to analyze three-dimensional steady-state rolling contacts, including the effects of creep, for a smooth infinite roller pressed against a half space with either a single asperity or a sinusoidal wave.
Abstract: This article presents a new rolling contact solver using a semi-analytical method (SAM) to analyze three-dimensional steady-state rolling contacts, including the effects of creep. This new solver includes both the normal and tangential contact issues for the pressure and shear tractions, respectively. The accuracy and efficiency of the present method are demonstrated by comparison to existing analytical and numerical solutions. Rolling contact problems for a smooth infinite roller pressed against a half space with either a single asperity or a sinusoidal wave are investigated. The results show the complexity of pressure and shear traction. Asperities produce higher localized pressures, which demand larger local shear tractions to produce slip in such regions. Stick regions are also observed at the trailing edge of the contact.
TL;DR: In this article, the authors experimentally and numerically investigate the oil flow in surface pocketed thrust washers and demonstrate a cavitation bubble forming on the leading edge of the pocket and a sharp transition back to liquid.
Abstract: The objectives of this study were to experimentally and numerically investigate oil flow in surface-pocketed thrust washers In order to achieve the experimental aspects of this investigation, a thrust washer test rig was designed and developed to visualize the lubricant flow at the contact interface A novel approach for creating the pockets was developed to allow optical inspection of the lubricant during thrust washer operation The thrust washers were fabricated using a glass disk with a thin layer of steel shim stock adhered to the surface The micrometer-thick shim stock was machined using an Nd:YAG laser to create the circular pocket geometries and then glued to the glass disk A mirror and camera were placed below the semitransparent washer to observe the lubricant flow in the pocket The results obtained from this configuration illustrate a cavitation bubble forming on the leading edge of the pocket followed by a sharp transition back to liquid The size of the cavitation area was found to be a f
TL;DR: In this paper, the effects of hardening laws, material properties, and residual stress on rolling contact fatigue were investigated using a two-dimensional plane-strain J2-based plasticity model.
Abstract: Preloading the rolling elements of a rolling element bearing beyond their yield limit will result in subsurface plastic strains in the deformed material. These plastic strains are manifested in the form of a three-dimensional state of residual stresses. In this analysis, a two-dimensional plane–strain J2-based plasticity model with two different hardening laws—that is, (1) linear kinematic hardening and (2) nonlinear kinematic hardening—is utilized. Using the J2 plasticity model, the effects of hardening laws, material properties, and residual stress on rolling contact fatigue are investigated. Due to the presence of initial residual stresses, the equivalent von Mises stress decreases, which consequently leads to improved rolling contact fatigue life. However, due the presence of the residual stresses, the local yield point of the material also decreases. Due to these competing mechanisms, there is an optimum level up to which beneficial effects of the residual stresses are observed. For each of the harde...
TL;DR: In this article, the effect of normal load and sliding distance on the room temperature dry sliding wear behavior of a Ti-50.3 at% Ni alloy against a bearing steel was studied.
Abstract: Effect of normal load and sliding distance on the room temperature dry sliding wear behavior of a Ti-50.3 at% Ni alloy against a bearing steel was studied. The wear tests were conducted using a pin-on-disk tribometer under normal loads of 20, 40, 50, 60 and 80 N for sliding distances up to 1000 m. The wear results showed that the wear rate of NiTi alloy decreased as the normal load increased from 40 N to 60 N. Formation of iron rich tribological oxide layers under the higher loads could be the main reason of decrease in the wear of NiTi alloy. Increasing the sliding distance decreased the wear rate of NiTi alloy under normal loads of 60 N and 80 N, which was attributed to the formation of more stable iron rich tribological oxide layers on the worn surfaces of NiTi alloy.
TL;DR: In this article, a numerical model of elastohydrodynamic contact coupled with a multiscale surface texture model was developed that allows tracking the scale effect of surface features and their interactions on friction performance and lubricant flow under hydrodynamic lubrication conditions.
Abstract: Multistage abrasive finishing processes (grinding, polishing, honing, etc.) are commonly used to produce the geometrical properties of a surface to meet its technical functionalities in the operating characteristics of contacting parts in friction, relating to their durability and reliability (running-in performance, wear resistance, load-carrying capacity, etc.). Coarse abrasive grits followed progressively finer ones are used, which leads to a multiscale stratified surface texture. In this article, a numerical model of elastohydrodynamic (EHD) contact coupled to a multiscale surface texture model was developed that allows tracking the scale effect of surface features and their interactions on friction performance and lubricant flow under hydrodynamic lubrication conditions. Because the simulation model has as an input the surface topography and to overcome the variability in surface finish formation, textured surfaces at different stages of the finishing process were simulated (virtual texturing method)...
TL;DR: In this paper, the color of wear debris was studied based on an on-line visual ferrograph (OLVF) sensor, which was converted from the initial red, green, blue (RGB) format into hue, saturation, intensity (HSI) for describing color images.
Abstract: Analytical ferrography has been proved to be one of the most popular methods for wear characterization. However, it is limited by the real-time requirement of condition-based monitoring. A new wear characterization by on-line ferrograph images is proposed. The color of wear debris was studied based on an on-line visual ferrograph (OLVF) sensor. Generally, the features of on-line ferrograph images included low resolution, high contamination, and wear debris chains. The weak color of the wear debris, especially nonferrous metal debris, in an on-line ferrograph image was unavoidably merged into the mass noises. Accordingly, the on-line images were converted from the initial red, green, blue (RGB) format into hue, saturation, intensity (HSI) for the description of color images. The transmitted image was binarized to locate all wear debris and the wear debris was extracted by their pixels from the corresponding reflected image. The distributions of two HSI components, hue and intensity, were used to characteri...
TL;DR: In this paper, the tribological performance of M50 bearing steel under extreme conditions such as those experienced by aircraft bearings was investigated to ascertain the ultimate capacity and failure regularity of the contact surfaces.
Abstract: The tribological performance of M50 bearing steel under extreme conditions such as those experienced by aircraft bearings was investigated to ascertain the ultimate capacity and failure regularity of the contact surfaces. Experiments were carried out on a two-disc test rig using synthetic aircraft engine oil No. 4050 at approximately 80°C. The testing proceeded until surface failure was detected via a sharp rise in the temperature of the tested disc and the power consumption of the motor. Heat treatment and surface finishing were applied to the tested discs in the same way as for aircraft engine ball bearings. The topography of the worn areas was observed both on the surface and in cross sections using optical microscopy and scanning electron microscopy (SEM). The maximum total contact temperature, that is, the sum of the monitored bulk temperature and the calculated flash temperature, was analyzed. The Vickers hardness and residual stress of the worn areas as a function of depth were measured. The result...
TL;DR: In this article, self-lubricating coatings of hexagonal boron nitride (hBN) particles in a deposited nickel matrix were investigated and optimized for friction and wear.
Abstract: It is often beneficial to modify surfaces to gain desirable properties such as improved wear and friction resistance. Self-lubricating coatings can improve the performance of contacting surfaces and extend component lifetimes by reducing the coefficient of friction and/or improving resistance to specific wear modes. With these goals in mind, self-lubricating coatings of hexagonal boron nitride (hBN) particles in a deposited nickel matrix were investigated and optimized for friction and wear. These self-lubricating coatings were created via high-velocity particle consolidation or cold spray using micrometer-sized hBN powder encapsulated by nickel and nickel phosphorous alloys. Relatively thick nickel encapsulation via electrolesss Ni plating was required to aid in coating bonding/formation by “tricking” the hBN into acting as monolithic Ni during deposition. Once deposited on aluminum substrates, the coatings were analyzed and found to exhibit enhanced mechanical and tribological properties such as high bo...
TL;DR: In this article, the rotordynamic coefficients of a typical compressor eye seal at different preswirl rates and eccentricities were calculated using ANSYS-CFX to investigate the exact relationship between the preswirling rate and the seal's rotord dynamic coefficients.
Abstract: Labyrinth seals are widely used in turbomachines and can have a significant influence on the stability of the rotor bearing system. The working fluid usually has a circumferential velocity component before entering the seal. The average fluid circumferential velocity in the upstream region prior to the first tooth divided by the shaft synchronous surface velocity is defined as the preswirl rate. It has been observed that the preswirl rate is an important factor affecting the rotordynamic coefficients of labyrinth seals, thus affecting the stability of the rotor. Therefore, it is of interest to investigate the exact relationship between the preswirl rate and the seal's rotordynamic coefficients. In this article, the flow in a typical compressor eye seal is simulated in 3D models with eccentricity ranging from 0.1 to 0.7 using ANSYS-CFX. The rotordynamic coefficients of the seal at different preswirl rates and eccentricities are calculated. The case with no preswirl and eccentricity of 0.1 are compared to p...