Although the efficiency of a gear pair is currently high, a better understanding of surface/lubricant contribution on efficiency is critical. Electrified drivelines will, for example, impose higher speed and alternate loading, and it is expected that these new conditions will, to a greater extent, rely on the surface/lubricant characteristics. Phenomena taking place in the gear contact is often measured

The original version of this article unfortunately contained a mistake. The affiliation information was incorrect for the co-authors Shigeru Tazawa, Tsuyoshi Urano, Shinji Kobayashi.

Abstract PTFE composite wear rates are known to vary by 1000 × depending on the size and strength of their nanofiller aggregates. While these effects have been attributed to variations in subsurface reinforcement, debris regulation, transfer films, and filler abrasivity, the chain of causation has proven difficult to test. This study aimed to clarify these causal relationships by eliminating confounding

The solid particle erosion of polymers occurs in a wide variety of industries and has been extensively studied experimentally. However, numerical models capable of accurately simulating the associated material removal mechanisms and predicting erosion rate do not yet exist. In this paper, a coupled smoothed particle hydrodynamics (SPH)/finite element (FE) model was developed to simulate the erosion

Mechanical seal is installed in EVAHEART®, one of left ventricular assist device, which supports the role of original human heart. Low friction and low leakage are both required for mechanical seal for ventricular assist device to realize longer battery lifetime and less maintenance. In this study, several types of surface texture by combination of laser-induced periodic surface structure (LIPSS) and

To understand the dissipative mechanisms in soft hydrogel lubrication, polyacrylamide (PAAm) hydrogels with two distinct surface structures were examined under various contact conditions. The characteristic speed-dependent friction of the self-mated, crosslinked hydrogel surfaces could be explained by hydrodynamic shearing of a thin water layer between two rather impermeable bodies. On the other hand

Self-assembled monolayers (SAMs) can reduce friction in boundary lubricated contacts by providing a low shear strength interface for sliding. However, the nanoscale mechanisms underlying low friction on SAMs are still not fully understood, especially in liquid environments in which hydrophobility or hydrophilicity affects friction. To understand this effect, friction of SAMs in water was measured using

Soy-based fatty acid methyl ester disulfide (FAME-S2) was synthesized in good yield by oxidation of polymercaptanized soybean oil fatty acid methyl ester (PM-FAME). The chemical structure of FAME-S2 is of interest because of its potential as a biobased multi-functional additive in lubricant formulations. Neat FAME-S2 and their blends (1–10% w/w) in polyalphaolefin (PAO-6) and high oleic sunflower oil

There are a number of widely used machine components, such as rolling element bearings, gears and cams, which operate in the lubrication regime known as Elastohydrodynamics (EHD), where lubricant film thickness is governed by hydrodynamic action of convergent geometry, elastic deformation between non-conformal contacting surfaces, and the increase of lubricant viscosity with pressure. Variable loading

To investigate dry wear behavior in an aluminum-based automotive alloy, transient horizontal solidification experiments using a water-cooled directional solidification device have been performed with the Al7Si0.3Mg alloy (wt%). Samples of the as-cast ingot at positions (P) 2, 4, 6, 40, and 80 mm from the cooled interface were subjected to precipitation hardening heat treatment (T6-type). The heat treatment

Abstract Thermocapillary migration describes an interfacial phenomenon that liquids can spontaneously move from the warm to the cold regions on nonuniformly heated solids. However, it is unknown how liquids react at various interfaces subjected to a thermal gradient. In this study, migration of liquid lubricants at the free surface, the plate/plate interface, and the sphere/plate interface is investigated

The aim of this study was to evaluate the effect of dissolution of the small carbides residual from annealing and earlier processing, on the mechanical and wear properties of hot-work tool steel. Recommended as well as extreme austenitization temperatures (950 °C, 1030 °C and 1150 °C) with subsequent tempering were used aiming at same hardness level of specimens of same material. This allows correlation

Several two-dimensional (2D) materials such as graphene, molybdenum disulfide, or boron nitride are emerging as alternatives for lubrication additives to control friction and wear at the interface. On the other hand, the initiative to accelerate materials discovery through data-driven computational methods has identified numerous novel topologies and families of 2D materials that can potentially be

Indentation tips are never atomically sharp, but rounded at their end. We use atomistic simulation to study the effect of tip roundness for the particular case of a cube-corner pyramidal indenter by comparing the results of a spherical, a sharp cube-corner, and a rounded cube-corner tip during indention into bcc Fe. We find that as soon as the tip has indented so deeply that the spherical geometry

Friction is an important limitation of energy efficiency performances of MEMS/NEMS but is, in the same time, a great opportunity for harvesting energy by designing optimized tribo-electric nano-Generators (TENG). Thus, frictional behaviour can be accurately controlled in real time by using thermally sensitive periodic patterned self-assembled monolayers of n-octadecyltrichlorosilane (OTS) grafted on

Highly loaded lubricated contacts may present a friction plateau on which the friction force becomes independent from the sliding velocity. Although this phenomenon has been known for a long time, its physical origin remains poorly known. The present paper aims at giving further insight on the physical mechanisms triggering the friction plateau. The study specifically focuses on the influence of pressure

This paper investigates the tribological and related properties of naturally modified beech wood (Fagus sylvatica). The modifications were performed on steamed beech wood using a variety of treatments consisting of drying, heating in an aqueous solution, impregnation with liquefied animal glue as well as beeswax followed by compression and various combinations thereof. Results indicate that an impregnation

Oleamide and Synovene lubricant additives when mixed together show a clear co-operative effect leading to friction and wear reduction. Sum Frequency Generation vibrational spectroscopy has been used to record in situ spectra of these additives with the aim of understanding the behaviour of these molecules when adsorbed on steel immersed in a model base oil at pre-selected temperatures. The spectra

Materials providing high resistance to wear and macro-deformations or impacts are needed for many applications (material handling hoses or flexible ducting systems, snow plow cutting edges, human joint prostheses, Mars rover wheels, etc.). Production of wear-resistant materials using the promising approach of additive manufacturing (AM) is currently of great interest. Specific nature-inspired or -mimicking

Abstract In consideration of high temperature conditions, this paper focuses on the self-lubricating properties of WS2 coatings at high temperature. A low coefficient of friction (CoF) about 0.07–0.2 for WS2 coatings can be attained at temperatures of 100–400 °C. The chemical stability, mechanical and tribological properties were investigated by energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction

In this work, the relationship between rolling contact fatigue (RCF) failure and the microstructure of D2 wheel steel was studied using a GPM-30 fatigue tester under oil lubrication conditions. The microstructural evolution during the RCF process can be divided into three stages: In the first stage, the misorientation of the proeutectoid ferrite is 2°–10°, the ferrite phase in pearlite is less than

This study was designed to investigate the influence of oil temperature and contact pressure on the tribological performance of three industrial gear oils but also on the corresponding changes taking place beneath the metal surfaces in contact. The result shows that increase in the oil temperature and contact pressure increases surface–additive interaction, promoting the formation of low-friction tribofilms

Coarse-grained molecular dynamics simulations were carried out to investigate the frictional properties of lubricant molecules on nanostructured metal surfaces. The simulation cell consists of a lubricant film enclosed between two metal surfaces. The attractive potential of specific iron atoms on the surface was modified such that the lubricant molecule adsorb preferentially on these atoms. These particular

We examine the role of important alloying elements (Al, Y), on friction and wear mechanisms of Mg as a function of temperature. Friction and wear tests of Mg–5%Al and Mg–5%Y alloys performed at room temperature, 100 °C and 150 °C reveal that addition of Al and Y significantly reduces the coefficient of friction. However, despite higher hardness of Mg–5%Y alloy, its wear rate was found to be higher

Abrasive wear due to particles sliding along a surface (two-body abrasion) or in between two surfaces (three-body abrasion) often leads to early failure of machine components exposed to, e.g., slurry, sand, wear debris, and so on. The primary cause for failure due to abrasive wear is the interaction between abrasive particles and the material surface. Simulation of an entire abrasive system is complicated

Understanding the dynamics and instability of a thermal fly-height control (TFC) head slider close to and at touchdown (TD) on a magnetic recording disk is essential for developing a head slider with a clearance of ~ 0.5 nm to enhance the recording density of hard disk drives. This paper presents a theoretical simulation of a practical TD test, performed by continuously increasing the head protrusion

Abstract According to international standards, the topography and the quality of machined surfaces can be characterized simultaneously by more than 70 roughness parameters. Despite the increased accuracy of topography measurements by modern instruments, the gained information about the 3D surface is still not well understood. The fact that machined surfaces are in general of Gaussian height distribution

Abstract This works investigates the in-situ formation of MoS2 and WS2 tribofilms by the synergy between transition metal oxide nanoparticles and conventional sulphur-containing anti-wear and extreme pressure additives. The formation of these low friction tribofilms can be obtained under reciprocating sliding contact and under extreme pressure conditions, as evidenced using X-ray photoelectron spectroscopy

Abstract EHD friction curves have been measured up to very high pressure (pmean = 5 GPa, pmax = 7.5 GPa) using a newly developed, rolling-sliding, ball on disc machine, the ETM. Six base fluids have been studied, spanning the API base oil categories Group I to Group V. At high pressures, thermal effects become substantial even at quite modest slide-roll ratios, and these must be considered when analysing

Friction between two surfaces is due to nano- and micro-asperities at the interface that establish true contact and are responsible for the energy dissipation. To understand the friction mechanism, often single-asperity model experiments are conducted in atomic-force microscopes. Here, we show that the conventional interpretation of the typical results of such experiments, based on a simple mass-spring

Surface modification of an elastomer may be formed during sliding contact with a rigid counter surface. This alteration leads to a change of mechanical properties at the surface and as a result a change in frictional behavior. Therefore, investigations related to the formation of a modified surface layer on elastomers and its effect on friction are of importance. In the present study, the formation

This study examined the tribological performance of three gear oils (Oils A, B and C), in relation to surface and microstructural changes. Oil A contains molybdenum dithiophosphate friction modifier, Oil B contains amine molybdate combined with zinc dialkyl dithiophosphate antiwear additive, while Oil C contains phosphonate and a commercial gear oil package. Following sliding tests of a hardened AISI

The relative contact area of rough surface contacts is known to increase linearly with reduced pressure, with proportionality factor κ . In its common definition, the reduced pressure contains the root-mean-square gradient (RMSG) of the surface. Although easy to measure, the RMSG of the entire surface does not coincide, at small loads, with the RMSG over the actual contact area g ¯ r , which gives

The lubricant-surface system is complex in nature and can significantly affect the frictional performance of high-performance transmission systems. The complexity stems from the coupled mechanical and chemical phenomena that occur at the interfacial tooth conjunctions. A combined analytical and precision experimental approach is presented to analyse the salient parameters of the lubricant-surface system

Micropitting is a form of surface fatigue damage that happens at the surface roughness scale in lubricated contacts in commonly used machine elements, such as gears and bearings. It occurs where the specific film thickness (ratio of smooth surface film thickness to composite surface roughness) is sufficiently low for the contacts to operate in the mixed lubrication regime, where the load is in part

Casing connections in the oil and gas industry are typically coated with zinc and/or manganese phosphate for corrosion protection during storage. The presence of phosphate coatings is also known to give beneficial tribological performance. The coating allows the system to run without problems long after it is worn off. This is because of two mechanisms. Glaze layer formation on the coated surface and

The collision of two cylindrical hydrogen-free diamond-like carbon (DLC) asperities with approximately 60 % sp3 hybridization has been studied using classical molecular dynamics. The severity of the collision can be controlled by the impact parameter b that measures the width of the projected overlap of the two cylinders. For a cylinder radius of R = 23 nm, three collisions with b = 0.5 nm, b = 1 nm

Transition metal nitrides like CrN and TiN are widely used in automotive applications due to their high hardness and wear resistance. Recently, we showed that a multilayer architecture of CrN and TiN, deposited using the hybrid-high power impulse magnetron sputtering (HIPIMS) and direct current magnetron sputtering (DCMS)-HIPIMS/DCMS deposition technique, results in coatings which indicate not only

The progression of local cartilage surface damage toward early stage osteoarthritis (OA) likely depends on the severity of the damage and its impact on the local lubrication and stress distribution in the surrounding tissue. It is difficult to study the local responses using traditional methods; in-situ microtribological methods are being pursued here as a means to elucidate the mechanical aspects

Wind turbine gearbox (WTG) bearings can fail prematurely, significantly affecting wind turbine operational availability and the cost of energy production. The current most commonly accepted theory of failure mechanism is that the bearing subsurface is weakened by white etching crack (WEC) networks that eventually lead to the flaking away of material from the bearing surface. Subsurface damage due to