Internal combustion engine lubrication is essential for unwanted energy and material losses. As part of the experimental work, the lubricity of both new and worn motor oils of Society of Automotive Engineers (SAE) 15W-40 and SAE 10W-40 with different American Petroleum Institute (API) performance classifications, which were taken from various motor trains during maintenance or oil change, was assessed. A total of sixteen lubricant samples were evaluated. Lubricity, i.e., the load capacity of the lubricating film, was evaluated on the basis of the Reichert test. Viscosity, as one of the most important parameters of lubricants, was evaluated by the Stabinger Viscometer. Chemical degradation of motor oils (oxidation, nitration, sulfation), contamination of oils with fuel, soot, water, and loss of antioxidant zinc dialkyldithiophosphate (ZDDP) were monitored by Fourier-transform infrared (FTIR) spectroscopy. Of the fresh motor oils, OMV 10W-40 API SL/CF motor oil had the best lubricity. URANIA LD 15W-40 API CI-4 and M7ADS V 15W-40 API CI-4 CH-4/SL oils showed similar lubricity. M7ADS III 15W-40 API CF-4/SG motor oil showed the highest wear of wear surface, i.e., the lowest lubricity, of the tested new motor oils. Correlation analysis of the experimental data confirmed that the fuel content penetrated the motor oils significantly negatively correlates with the viscosity (R = −0.87). The low water contamination in motor oil does not cause a significant negative effect on lubricity. A significant correlation between the oxidation, nitration, and sulfation products of chemical degradation of the tested oils was confirmed (R ≥ 0.90). These degradation products improve lubricity due to their polarity, i.e., they have caused better lubricity of worn oils compared to new motor oils. Even the depletion of the antioxidant ZDDP did not affect the reduction in lubricity and anti-abrasion properties of chemically degraded motor oils. The experimental results of testing of worn motor oils taken from motor trains showed that current motor oils have excellent lubricity, which they maintain throughout their life.

Study of the Effect of Physicochemical Degradation and Contamination of Motor Oils on Their Lubricity

Abstract Around 1,000 peer-reviewed papers were selected from 3,450 articles published during 2020–2021, and reviewed as the representative advances in tribology research worldwide. The survey highlights the development in lubrication, wear and surface engineering, biotribology, high temperature tribology, and computational tribology, providing a show window of the achievements of recent fundamental and application researches in the field of tribology. 

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A review of advances in tribology in 2020–2021

Performance analysis of two-dimensional section of partially textured piston ring with cavitation boundary conditions

The degradation of materials by wear is reduced by the wet chemical technique, where a thin film is coated over the surface susceptible to wear. The sol–gel coating method is one of the wet chemical techniques normally employed to improve tribological and anti-corrosive properties. This paper deals with evaluating tribological properties such as coefficient of friction, volumetric wear loss, and corrosive stability of alumina and aluminum silicate-coated aluminum alloy A356. The coating parameters affecting the tribological properties are identified and the experiments are designed using Taguchi orthogonal array and optimized using the Grey relation analysis technique. The tribological characteristics at room temperature are evaluated using a pin on disc tribometer. Among the sol–gel coating parameters chosen for minimizing the effect of wear and coefficient of friction between surfaces, the temperature for heat treatment and pH of the sol–gel are identified as the critical parameters that affect the tribological characteristics. The corrosive stability of the samples has been evaluated by corrosion current, corrosion potential, and corrosive stability methods. It is found that tribological properties and corrosive stability are improved for the coated sample compared with the uncoated sample. It is also observed that alumina coating provides better tribological properties and aluminum silicate coating provides better corrosive stability.

Parameter optimization for enhancing tribological properties of sol–gel alumina and aluminum silicate-coated aluminum alloy: Grey–Taguchi method

Research progress of surface modification and solid–liquid lubrication synergistic friction reduction and wear resistance

It is well-established that the piston ring/cylinder liner (PRCL) contact is the major contributor to friction losses in the internal combustion engine. While numerous studies have evaluated the in...

Synergistic effect of surface texturing and coating on the friction between piston ring and cylinder liner contact

For predicting the sliding wear in Pin-on-Disc (PoD) tribometer contact, a numerical wear simulation technique is presented in this paper. It is based on the Finite element method (FEM) which incorporates the Archard's wear law and the UMESHMOTION subroutine for calculating the wear depth for a 3-D PoD tribometer contact. FEM is utilized in solving the 3-D contact problem. The geometry is updated using the UMESHMOTION subroutine coupled with the Augmented Lagrangian-Eulerian (ALE) remeshing technique of ABAQUS. But, a significant disadvantage of FEM wear prediction is the enormous computational time required for performing 3-D analysis. Hence, to minimize the computational time, an approximation technique is introduced which accounts for the contact pressure evolution at the contact region. It decreased the simulation time and also preserved the accuracy of 3-D wear prediction. Finally, the results obtained from the simulations are compared with the experiments for brass-on-bearing steel PoD contact. An accuracy of 98.81% was obtained for the 10N and 83.10% for the 30N load.

3-D FEM Wear Prediction of Brass Sliding against Bearing Steel Using Constant Contact Pressure Approximation Technique

In advanced automotive engines, especially in diesel engines, consumer demand for ever increasing service intervals for vehicles has led to longer oil drain periods. Consequently this has increased contamination levels in lubricating oils that will in turn reduce engine efficiency and increase the possibility of system failure due to increases in viscosity and the potential of oil starvation leading to scuffing and catastrophic failure of the engine. Therefore it is necessary to understand the effects of contaminants in diesel engine oil on the tribological performance of tribo-contacts and also the possible interaction between the contaminants. The paper aims to investigate the influence of contaminants and their interactions on diesel engine oil using Electro sensing (ES) monitoring. Using pin-on-disc (PoD) tribometer, all tests were carried out under ambient conditions at 5 m/s sliding speed and contact stress of 1.5–2.05 GPa to simulate a valve-train in a diesel engine with fully formulated heavy-duty diesel engine oil used as lubricant. In the first phase, using a parametric study examining the effect of four contaminants (soot, oxidation, moisture, and sulphuric acid) at varying levels (four for each) on steel-on-steel sliding contact. It was observed that all contaminants and contaminant levels reduce the conductivity of the oil. Oxidation and soot contaminants produced large increases in viscosity. The wear rate was mainly influenced by acid and soot additions, while the coefficient of friction was increased by all contaminants and contaminant levels. The steady-state charge levels changed for some contaminants. The best correlation of steady-state charge with the other measured tribological parameters of wear rate, friction, and temperature is seen for the series of oxidized oils. The multi-contaminated oil (L4× 4) shows remarkably little degradation in tribological performance. Analysis of the wear mechanisms shows that soot and oxidation produced abrasion and polishing wear, respectively, while sulphuric acid and moisture produced corrosive wear. In the second phase, investigates the effects of diesel contaminants and their interaction on tribological properties for bearing steel (En31) and ceramic (Si3N4) sliding contacts using a factorial study. The contaminants are soot, sulphuric acid, moisture and oxidation, and each contaminant has three different level of concentration (low, medium and high) in the test matrix. The factorial test matrix consisted of 20 tests, constructed from a quarter fractional factorial test matrix with four points at the medium values for the contaminants. Results from this matrix required six further tests to elucidate aliased pairs of interactions using Bayesian model selection. A pin-on-disc tribometer was used to carry out all the experiments. The factorial study showed that charge was influenced by tribo-couple material; the silicon nitride discs produced higher charge than steel discs. However, it was opposite for friction; the silicon nitride disc gave lower friction and the pins showed higher friction than their steel counterparts. For wear scar and temperature, soot contaminant was found to be important. The two important interactions were found for the charge response, with the interaction between sulphuric acid and pin material being more important than sulphuric acid–oxidation interaction. Similarly to charge, an interaction between sulphuric acid and pin material interaction was found for friction. To conclude, the ES monitoring was sensitive to the presence and levels of contaminants in diesel lubricating oil, particularly diesel soot. The change in charge levels indicated the concentration of soot level present in the contact, which was directly related to wear. ES monitoring also detected interactions between the contaminants through statistical analysis. ES monitoring has shown that monitoring lubricant performance and the effects of contamination are feasible under laboratory conditions.

Ramkumar Penchaliah

Papers

Synergistic effect of surface texturing and coating on the friction between piston ring and cylinder liner contact

3-D FEM Wear Prediction of Brass Sliding against Bearing Steel Using Constant Contact Pressure Approximation Technique

Tribological Effects of Diesel Engine Oil Contamination on Steel and Hybrid Sliding Contacts