The adoption of vegetable oil as a basic lubricant has become increasingly prevalent due to growing environmental concerns about the harm caused by lubricants made from petroleum. As a result, many researchers are concentrating on developing new, efficient green lubricants. This current work evaluates the tribological performance of novel ficus carica (fig oil) combined with Ethylene Vinyl Acetate (EVA) viscosity modifier and Tertiary-Butyl-Hydroquinone (TBHQ) nanoparticles as an eco-friendly lubricant. The research employed a four-ball tribometer standard test (ASTM D4172-94). Field emission scanning electron microscopy (FESEM) was used for worn surface morphology examination. In the study, TBHQ was kept at 0.3 mass%, while EVA concentrations varied from 0.5, 1, 1.5, and 5 mass%. An ultrasonic homogenizer was used to combine the samples using the sonication technique. The viscometric study revealed 1 mass% EVA as optimal concentration. Thermogravimetric analysis (TGA) results showed that EVA + TBHQ inclusion resisted lubricant degradation, while oxidation time shift was at onset of 53.5 min against base oil onset of 14.1 min. The frictional results showed 100 kg of load, adding 0.9 mass% EVA + 0.3 mass% TBHQ nanoparticles gives the best reduction in wear and the coefficient of friction, although SAE-5W-30 lubricant performed better. Furthermore, the effectiveness of the added substances was determined by their ability to diffuse into the sliding contact, thereby avoiding direct contact between the sliding bodies, which, if not minimized, could result in machine damage.

The friction properties of an aluminum-silicon alloy (Al-Si) can be improved by increasing its silicon content. However, this can deteriorate the material properties necessary for engine components. Therefore, an alternative approach to reduce friction is required. This study investigated the running-in behavior, the reduction of friction from the initial to the stable phase of sliding, between Al-Si with varying silicon contents and bearing steel in fully formulated engine oil. The friction of Al-Si and the silicon-free aluminum alloy (Al) was classified into three modes: no friction reduction (mode I), friction reduction after a high-friction period (mode II), and immediate friction reduction (mode III). Al exhibited only mode I, low-silicon-content Al-Si mainly displayed mode II, and high-silicon-content Al-Si mainly exhibited mode III. Energy-dispersive X-ray spectroscopy revealed that, for mode II, zinc dithiophosphate (ZnDTP) reacted with the aluminum matrix, suppressing aluminum adhesion and forming molybdenum-dithiocarbamate-derived tribofilm. Nanoindentation and micro-Vickers tests demonstrated that the initial high hardness of the Al-Si matrix did not increase the ZnDTP reactions. However, the friction-induced hardened layer on the matrix promoted the ZnDTP reactions, suggesting that forming the hardened layer is a key factor in the low-friction interface of Al-Si without increasing silicon content.

A mechanical analysis model of angular contact ball bearings considering rotor deformation and inertial force of rolling elements is established. The research object being the rotor supported by high-speed instrument bearings as the research object, the bearing-rotor systems of cantilever support, and two-end support are analyzed. The effects of rotor structure and bearing internal parameters on bearing support force, stiffness, spin-roll ratio, and internal load distribution are examined. The results show that when the bearingrotor system is subjected to radial loads, due to the deformation of the rotor, the supporting bearings will be subjected to additional moment in addition to the radial load compared to a rigid rotor. With two-end support, the moment load on the bearing increases as the rotor length and hollowness increase. With cantilever support, the rotor hollowness has almost no effect on the radial load of the bearing, while the large rotor hollowness corresponds to large moment load on non-cantilever end bearing and small moment load on cantilever end bearing. Additionally, bearing moment load and radial load on both sides is directly proportional to rotor cantilever length. The maximum contact load of the rolling element is effectively reduced by increasing the initial contact angle and the number of rolling elements of the cantilever end bearing. The angular stiffness and the spin-roll ratio gradually decrease first and then gradually increase as the load ratio (the ratio of the radial load and the moment load) increases and are minimum when the load ratio is 0.67 and 0.61,respectively.

The relation with viscosity and pressure of lubricant has been considered in detail from the past. Barus equation that was presented in 1893 is known as the basic equation. This paper describes the new linear viscosity equation, that included dimensionless density and temperature other than pressure as functions in comparison with Barus equation. Author measured high pressure viscosity by using reciprocating-piston type test apparatus and measured high pressure density by using capacity type test apparatus in each temperature and pressure. After that, author attempted to derive the density into Barus equation and it was found that dimensionless density was preferable as density. Furthermore, author attempted to introduce temperature into Barus equation. It became able to in this way deal with the new viscosity equation as a linear equation. It found out that the logarithm of dimensionless viscosity was proportional to pressure and it was inversely proportional to temperature and dimensionless density cubed. And it was found that these slope δ of lubricants by this linear equation are intrinsic constant.

Some surface-initiated related bearing failures have their source in standstill corrosion. This can be an important issue in transportation, energy, pulp and paper and other industries where bearings run long journeys generating relatively high temperatures or being in contact with humidity and then they stop overnight were they get cold, in this way producing condensation of humidity around the contacts. This condensation can generate pitting corrosion (depending on temperatures and environment). Pitting corrosion can be very mild and without consequences but sometimes it is the source of small cracks and spalls. When the bearing runs again, these surface defects will be triggered by rolling contact fatigue and can propagate, eventually producing a large spall and a bearing failure. The present paper investigates the interaction of the phenomenon of pitting corrosion with rolling contact fatigue and proposes an engineering concept model where the main parameters are investigated giving some indication of safe and unsafe combinations for spall propagation from standstill corrosion.

This paper reports a novel method to measure the very small amount of wear that occurred at roughness peaks of the underlying base steel exposed on the surface covered with a soft material film removed by sliding. It is impossible to detect the minute wear of the exposed roughness peaks by a known method so far. Image data with three-dimensional height information obtained by a laser microscope is used to detect the position and height of roughness peaks of the underlying base steel exposed on the surface. This method makes it possible to track the minute wear progress using the mean height of all the detected roughness peaks or the wear of detected specific roughness peaks. It was also reported that this method has generality to be applied to untreated steel surfaces. It was possible to detect tiny distinctions of wear by this method. Then it was clarified that the wear of steel exposed on the MnP-treated surface is greater than that of the untreated steel, especially it was remarkable in the initial stage of sliding.

This paper focuses on the ZnDTP-derived tribofilm formation process in the early stage of sliding, mainly on the formation of a sulfide layer and a polyphosphate layer, in studying the formation process on a steel surface with roughness equivalent to that of an actual machine. Unlike the results of ZnDTP single-formulated oil using a regular mirror-finished steel test piece, the sulfur-based tribofilm was preferentially formed at the initial sliding stage on the steel test piece with relatively large roughness equivalent to the actual machine level. It was also found that it took longer to form a phosphorus-based tribofilm that exhibited wear resistance. Thus, the behavior of tribofilm formed on the test pieces with roughness equivalent to the actual machine level differed significantly from that of the mirror-finished test pieces. In particular, it was found that the sulfurization reaction in the early stage of sliding is important through the corrosive wear of the top of roughness, and played an important role in controlling the subsequent tribological behavior.

Many laboratory tribology test machines are available for evaluating the effect of different lubricants and different operating conditions on friction. For the Mini Traction Machine (MTM) there is much published data that shows how the measured friction coefficient varies with operating conditions and lubricant type. Fully formulated lubricants containing the anti-wear additive ZDDP have often been found to have a significantly higher friction coefficient, which persists to higher speeds, compared to base oils (lubricants with no additives). Recent work has found that the surface roughness of ZDDP tribo-films can evolve to become significantly higher than that of the surfaces they are deposited on. When the measured friction coefficients of lubricants tested in the MTM machine are suitably normalized and plotted against the λ ratio (which is equal to the oil film thickness separating the moving surfaces divided by the combined surface roughness) then the curves for various different lubricants lie on a “master curve” which enables reliable friction estimates to be made for lubricated contacts in the mixed lubrication regime. A simple modification to this approach also allows for the calculation method to be extended to lubricants that contain friction modifier additives.