Showing papers in "Tribology Transactions in 2018"
TL;DR: In this article, the shear degradation of lithium 12-hydroxy stearate grease was measured using an in-house developed Couette aging machine, which is well defined.
Abstract: In this article, the shear degradation of lithium 12-hydroxy stearate grease will be measured using an in-house-developed Couette aging machine. In this device the shear rate is well defined. The a...
41 citations
TL;DR: In this article, the performance of a lubricant greatly depends on the additives it involves, and recently used additives produce severe pollution when they are burned and exhausted, therefore, it is n...
Abstract: The performance of a lubricant greatly depends on the additives it involves. However, recently used additives produce severe pollution when they are burned and exhausted. Therefore, it is n...
40 citations
TL;DR: In this article, an experimental study of the influence of viscosity and magnetoviscous effects on the performance of a magnetic fluid seal in a water environment is presented. And the experimental results show that the visco-temperature is a decisive factor in magnetic fluid sealing performance under water environment.
Abstract: The magnetic fluid seal is one of the most successful applications of magnetic fluids. The theory of magnetic fluid seals in liquid environments has not been developed. This work mainly presents an experimental study of the influence of viscosity and magnetoviscous effects on the performance of a magnetic fluid seal in a water environment. Three engine oil–based magnetic fluids of different viscosities and similar saturation magnetization values were prepared and a multistage magnetic seal structure was designed. The magnetoviscous effect of the magnetic fluids under different working conditions was measured with an advanced rotational rheometer. An experimental platform and a multistage magnetic seal structure were designed for the critical pressure value and durability tests. The experimental results show that the viscosity of a magnetic fluid is a decisive factor in its sealing performance under a water environment and a discussion is presented that can explain the experimental results qualitat...
38 citations
TL;DR: White etching cracking (WEC) is a subsurface bearing failure mechanism influenced by a number of factors, including lubricant composition as mentioned in this paper, which is a type of white etching.
Abstract: White etching cracking (WEC) is a subsurface bearing failure mechanism influenced by a number of factors, including lubricant composition. Certain metal-containing lubricants have been repo...
34 citations
TL;DR: In this article, the critical intersection among various lubricant-and non-lubricant-related parameters and their influence on hydrogen diffusion and white etching cracking (WEC) formation is discussed.
Abstract: White etching cracking (WEC) is a contact fatigue bearing failure commonly observed in wind turbine applications. It can lead to fatigue lifetimes more than an order of magnitude shorter than expected lifetimes. Though various mechanical and chemical factors have shown direct or indirect impacts of on WEC failure, the correlations between these factors are yet to be fully understood. The critical intersection among various lubricant- and non-lubricant-related parameters and their influence on hydrogen diffusion and WEC formation are discussed in this article. Experimental results are shown under diverse operating conditions and contact configurations using three test rigs. This study confirms that the mechanical properties of a rolling contact and lubrication parameters alone cannot predict WEC failure. The formation of a tribofilm and accumulation of atomic hydrogen below the contact surface can be essential to explain WEC events. Higher hydrogen concentration in the WEC zone depends on contact a...
32 citations
TL;DR: In this paper, the effect of wettability improvement of SiCp on the impact and sliding wear behavior of A356/20 wt% composites produced by a compocasting technique has been investigated.
Abstract: In this study, the effect of wettability improvement of SiCp on the impact and sliding wear behavior of A356/20 wt% SiCp composites produced by a compocasting technique has been investigated. The r...
29 citations
TL;DR: In this article, the effects of rocks and cutter ring properties on the wear behaviors of disc cutters for tunnel boring machines were investigated, and the effect of these properties was investigated.
Abstract: To improve the wear resistance of disc cutters for tunnel boring machines (TBMs), this study is devoted to investigating the effects of rocks and cutter ring properties on the wear behaviors of dis...
29 citations
TL;DR: In this paper, it was shown that rectangular surface pockets are effective in reducing friction in a piston-liner type contact, providing that they are oriented with their long axis transverse to the long axis.
Abstract: It has recently been shown that rectangular surface pockets are effective in reducing friction in a piston–liner type contact, providing that they are oriented with their long axis transverse to th...
29 citations
TL;DR: 60NiTi is a hard (∼60 HRC) and highly corrosion-resistant intermetallic with a relatively low elastic modulus (approximately 100 GPa) as mentioned in this paper.
Abstract: 60NiTi is a hard (∼60 HRC) and highly corrosion-resistant intermetallic with a relatively low elastic modulus (∼100 GPa). In addition, this alloy exhibits a high compressive strength (∼2,500 MPa) a...
28 citations
TL;DR: In this article, the tribological responses of palm oil and soybean oil combined with two commercial antiwear additives (zinc dialkyl dithiophosphate and boron compound), were investigated at a lubricant temperature of 100 °C and under severe contact conditions in a reciprocating sliding contact.
Abstract: The tribological responses of palm oil and soybean oil, combined with two commercial antiwear
additives (zinc dialkyl dithiophosphate and boron compound), were investigated at a lubricant
temperature of 100 °C and under severe contact conditions in a reciprocating sliding contact. The
friction coefficient of palm oil with zinc dialkyl dithiophosphate was closest to the commercial
mineral engine oil, with a 2% difference. The soybean oil with zinc dialkyl dithiophosphate
produced a 57% improvement in wear resistance compared to its pure oil state. The existence of
boron nitride in vegetable oils was only responsive in reduction of wear rather than friction. The
response of commercial antiwear additives with vegetable oils showed a potential for the future
improvement in the performance of vegetable oils.
28 citations
TL;DR: The outer circlip constraint is a typical way for a wet multidisc clutch to limit the axial displacement of friction components as mentioned in this paper, which is a common way for wet multi-disc clutches to limit friction displacement.
Abstract: The outer circlip constraint is a typical way for a wet multidisc clutch to limit the axial displacement of friction components. The pressure transmission mechanism in a clutch, excited by the conc...
TL;DR: In this article, Fatty acid ionic liquids (FAILs) were designed and synthesized by combining quaternary ammonium cations with a range of biobased fatty acid anions, which were found to be good and universal lubricants for steel-steel, steel-copper, and steel-aluminum friction pairs.
Abstract: Fatty acid ionic liquids (FAILs) were designed and synthesized by combining quaternary ammonium cations with a range of biobased fatty acid anions. They were found to be good and universal lubricants for steel–steel, steel–copper, and steel–aluminum friction pairs, which possess low corrosivities, moderate viscosity indexes, and thermal stabilities compared to commercially available synthetic oil polyalphaolefin (PAO) 10 and traditional ionic liquid (IL) L-F104. Among them, N1444Oct and N4444Oct were found to have far lower toxicity than L-F104. Investigation of the lubricating mechanism revealed that firm and effective physical adsorption and tribochemical reaction films can be easily formed on the sliding surface due to the polarity of the fatty acid anions and the aliphatic tails, which prevent metal–metal contact and further antiwear and reduce friction.
TL;DR: In this article, the statistical asperity microcontact models in combination with the acoustic spring model and the load sharing concept are utilized to study the interfacial normal contact stiffness, and a load sharing approach is proposed to study interfacial contact stiffness.
Abstract: In this work, the statistical asperity microcontact models in combination with the acoustic spring model and the load sharing concept are utilized to study the interfacial normal contact stiffness ...
TL;DR: In this paper, the tribological behavior of electroless Ni-B coating in its asplated condition at elevated operating temperatures was investigated and the worn surface of the coatings was analyzed using optical microscopy and scanning electron microscopy.
Abstract: The present work investigates the tribological behavior of electroless Ni-B coating in its as-plated condition at elevated operating temperatures. Ni-B coating is deposited using an electroless method on AISI 1040 steel specimens. Coating characterization is done using scanning electron microscopy, energy-dispersive X-ray analysis, and X-ray diffraction techniques. Vicker's microhardness and surface roughness are measured. Friction and wear tests are carried out on a pin-on-disc tribological test setup at room and elevated temperatures of 100, 300, and 500°C. The tribological behavior deteriorates at 100°C compared to room temperature. Electroless Ni-B coating shows excellent wear resistance at 300°C, which again degrades at 500°C due to severe oxidation and softening of the deposits. The worn surface of the coatings is analyzed using optical microscopy and scanning electron microscopy. Within the temperature range considered, the wear mechanism changes from adhesion to a combination of adhesion a...
TL;DR: In this paper, the glass transition viscosity of squalane at ambient pressure was determined from published visco-ity measurements and new glass transition measurements by transient hot wire and incorporated into the improved Yasutomi model and calculated glass transition temperatures as a function of pressure are comparable to those directly measured, although the hybrid model yields better agreement.
Abstract: An important part of the new quantitative approach to elastohydrodynamic lubrication (EHL) is the use of reference liquids with well-characterized thermophysical properties. New measurements are reported for the thermal and rheological properties of squalane to high pressure and of high shear rate and high-frequency viscosity of squalane thickened with polyisoprene (SQL + PIP) at ambient pressure. The glass transition viscosity of squalane at ambient pressure was found from published viscosity measurements and new glass transition measurements by transient hot wire. The glass transition viscosity so determined was incorporated into the improved Yasutomi model and the calculated glass transition temperatures as a function of pressure are comparable to those directly measured, although the hybrid model yields better agreement. The glass transition viscosity of squalane by any definition must be substantially lower than the “universal value” of 1012 Pa·s. The second Newtonian inflection cannot be cha...
TL;DR: In this article, the mechanical aging behavior of greases with a fibrous structure is studied by aging fresh samples at controlled shear rates and temperatures in an in-house-made Couet.
Abstract: In this article, the mechanical aging behavior of lubricating greases with a fibrous structure is studied by aging fresh samples at controlled shear rates and temperatures in an in-house-made Couet...
TL;DR: In this paper, the time-dependent formation process of molybdenum dithiocarbamate (MoDTC)-derived tribofilms at steel/steel contact under boundary lubrication was investigated by using an in situ R...
Abstract: In this study, the time-dependent formation process of molybdenum dithiocarbamate (MoDTC)-derived tribofilms at steel/steel contact under boundary lubrication was investigated by using an in situ R...
TL;DR: In this article, the authors study the tribological behavior of a Cu-based friction pair in different lubrication regimes, and calculate the real contact area of asperity contacts.
Abstract: When studying the tribological behaviors of a Cu-based friction pair in different lubrication regimes, calculation of the real contact area of asperity contacts is crucial but difficult. In...
TL;DR: Tilting pad journal bearing (TPJBs) have been widely used in rotating machinery such as compressors and turbines due to their superior stability compared to that of conventional fixed geometry bear as mentioned in this paper.
Abstract: Tilting pad journal bearing (TPJBs) have been widely used in rotating machinery such as compressors and turbines due to their superior stability compared to that of conventional fixed geometry bear...
TL;DR: Wang et al. as mentioned in this paper investigated wear progress of floor surfaces, investigate the mechanism of surface changes due to wear advances, and recognize their impacts on slip resistance operations. But despite the importance of flooring wear issue, their ensured operations and influences on slip resistances performance against pedestrian falls have not been systematically investigated.
Abstract: Surface conditions of pedestrian footpaths and walkways continually change throughout their services. Many causes may contribute to the variation of surface qualities, but a decline of slip resistance functioning is a critical problem for the pedestrian safety of walkway surfaces. Despite the importance of flooring wear issue, their ensured operations and influences on slip resistance performance against pedestrian falls have not been systematically investigated. The present study aims to understand wear progress of floor surfaces, investigate the mechanism of surface changes due to wear advances, and recognize their impacts on slip resistance operations. To measure traction properties and characterize wear behaviors of walkway surfaces, slip resistance tests were operated among three different types of floor specimens with a similar range of topographic characteristics and two dissimilar shoes. Wear formations and developments of the floor specimens were comprehensively assessed by a combination ...
TL;DR: In this article, the effect of varying temperature and humidity on the friction and wear properties of a silicone-based isotropic magnetorheological (MR) elastomer were examined with an applied magnetic field.
Abstract: In this study, the effect of varying temperature and humidity on the friction and wear properties of a silicone-based isotropic magnetorheological (MR) elastomer were examined with an applied magnetic field. Specifically, MR elastomer specimens were fabricated, and a temperature- and humidity-adjustable reciprocating friction tester was employed. The results indicated that the friction coefficient decreased across all tests when a magnetic field was applied. The friction coefficient increased when the temperature increased and slightly decreased following an increase in relative humidity. The wear depth results also exhibited an increasing pattern as the temperature increased and a decreasing pattern when the relative humidity increased. The surface state experienced significant changes under varying temperatures and relative humidity conditions with and without a magnetic field.
TL;DR: Calcium sulfonate complex grease is often selected for rolling bearing lubrication if there is a risk for water ingress, because it is reported throughout literature that it can absorb large quanti...
Abstract: Calcium sulfonate complex grease is often selected for rolling bearing lubrication if there is a risk for water ingress, because it is reported throughout literature that it can absorb large quanti...
TL;DR: In this article, a new stress-based life model is introduced to define dynamic stress capacity in rolling bearings for the first time, and the generalized stress capacity equations are formulated, for both point and line contacts, in terms of distinct geometrical and materials parameters while the empirical constants are now material independent.
Abstract: New stress-based life models are introduced to define “dynamic stress capacity” in rolling bearings for the first time. The generalized stress capacity equations are formulated, for both point and line contacts, in terms of distinct geometrical and materials parameters while the empirical constants are now material independent. Life equations are first developed for individual rolling element to race contacts and then statistically combined to estimate lives of both races, rolling elements, and, finally, the whole bearings for both ball and roller bearings. An estimate of the empirical constant for the ball bearing equation is derived by regression analysis of available experimental data. The applicable constant for roller bearings is then derived by relating the ball and roller bearing constants to the fundamental subsurface fatigue hypothesis applicable to both point and line contacts. For AISI 52100 bearing steel at room temperature, life predictions with the new stress-based equations are in c...
TL;DR: In this paper, the premature failures of wind turbine gearboxes are often attributed to bearing fatigue from overloading, but there is compelling evidence that wear from underloading is a significant contributory factor.
Abstract: Though the premature failures of wind turbine gearboxes are often attributed to bearing fatigue from overloading, there is compelling evidence that wear from underloading is a significant contribut...
TL;DR: In this paper, the evolution of the wear behavior of brake disc materials, such as carbon fiber, was studied. But the authors focused on the degradation of brake discs due to high thermal stress, causing thermal fatigue damage.
Abstract: In this article, brake discs are exposed to high thermal stress, causing thermal fatigue damage. The aim of this work is to study the evolution of the wear behavior of brake disc materials, such as...
TL;DR: Ionic liquids (ILs) have been demonstrated extensively to exhibit excellent tribological performance in terms of friction and wear reduction in this article, both as pure lubricants and as additive additives.
Abstract: Ionic liquids (ILs), both as pure lubricants and as lubricant additives, have been demonstrated extensively to exhibit excellent tribological performance in terms of friction and wear reduction in ...
TL;DR: In this paper, the wear and tribological performance of four ceramic tools in dry high-speed turning of a machinability criterion was evaluated. But the results were limited to the case of high speed machining.
Abstract: Tool wear is an important machinability criterion. To reduce total machining costs, this study demonstrates the wear and tribological performance of four ceramic tools in dry high-speed turning of ...
TL;DR: A mixed lubrication model based on a developed multiple-grid method to investigate the combined seal with a backup ring at different system pressures is presented, which does not require local refinement of the sealing zone.
Abstract: Nonconvergence is a frequent problem for mixed lubrication modeling of reciprocating seals, which couples a finite element analysis (FEA) commercial software with the fluid–structure interaction (F...
Abstract: In order to study the tribological properties of PTFE modified by hard nanoparticles and soft polymer under dry friction conditions, the tribological properties of polytetrafluoroethylene (PTFE) fi...
TL;DR: In this paper, a new generated axial force estimation model of tripod-type constant velocity joints was proposed, and kinematic analysis was performed to derive the reliabilities of CV joints.
Abstract: This study proposes a new generated axial force (GAF) estimation model of tripod-type constant velocity (CV) joints. For development of the model, kinematic analysis was performed to derive the rel...