Tribological Behavior of Mild Steel under Canola Biolubricant Conditions

New lubricants based on vegetable oil were developed in this study. Different blends of canola oil mixed with fully synthetic two stock engine oils were developed (0, 20%, 40%, 60%, and 80% of synthetic oil). The viscosity of the prepared blends was determined at different temperatures (20°C–80°C). Tribological experiments were conducted to investigate the effect of the newly developed oil on the wear characteristics of mild steel material compared with stainless steel when subjected to adhesive wear loading. The weight loss (WL) and the specific wear rate (SWR) of the mild steel using each of the prepared lubricants were determined. Scanning electron microscopy was used to examine the worn surface of the mild steel. The results revealed that pure canola oil as a lubricant performed competitively against a blend of 80% synthetic and 20% canola oils. The viscosity of the canola oil and its various blends with synthetic oil are controlled by the environmental temperature since an increased temperature reduces the viscosity. Also, the experimental results revealed that operating parameters play the main role in controlling the wear behavior of mild steel since increasing the sliding distances increases the weight loss. The specific wear rate exhibited a steady state after about 5 km sliding distance, and different blends influenced the applied loads and velocity differently. The mixing ratio of canola and syntactic oil was not particularly significant since the pure canola oil exhibited competitive wear performance compared with the blends. However, an intermediate mixing ratio (40%–60% synthetic oil mixed with 60%–40% canola) can produce a slightly low specific wear rate among other things.

Tribological Behavior of Ni-Based WC-Co Coatings Deposited via Spray and Fuse Technique Varying the Oxygen Flow

The tribological behavior of Ni-based WC-Co coatings is analyzed. The coatings were deposited on gray cast iron substrates in a spray and fuse process using SuperJet Eutalloy deposition equipment, varying the oxygen flow conditions in the flame. The crystallographic structure of the coatings was characterized via the X-ray diffraction (XRD) technique. The microhardness was measured on the surface and in cross sections of the coatings by means of a Knoop microhardness tester. The topography and the morphological characteristics of the coatings and the tribo-surfaces were examined using scanning electron microscopy (SEM) and confocal microscopy, while the chemical composition was measured by means of energy-dispersive X-ray spectroscopy (EDS). The tribological behavior of the coatings was examined via a cohesion-adhesion scratch test, using cross sections of the coatings. Furthermore, two wear tests were carried out, using the pin-on-disk method under ASTM G99 standard and an ASTM standard G65 sand/rubber wheel abrasion wear test. The wear of the coatings showed a close relationship to the porosity in the metal matrix; since then, in the abrasive wear test, a high porosity is related with lower hardness in the coatings; likewise, a low hardness is related with a high wear.

Computer Simulation/Prediction of Wear in Mechanical Components

In this paper, a state of the art on computer simulation and prediction of wear in mechanical components is reviewed. Past and recent developments as well as approaches employed in the simulation and prediction of wear are reviewed. In particular, the wear models, contact analysis schemes, and wear evolution prediction procedures as well as their application to the mechanical components (including cam-follower, gears, bearings, and cylinder/piston/piston ring wear) are reviewed. Recommendations and suggestions on possible directions for further research studies are also presented.

Experimental and Numerical Investigation about Small Clearance Journal Bearings under Static Load Conditions

The aim of the present research is to characterize both experimentally and numerically journal bearings with low radial clearances for rotors in small-scale applications (e.g., microgas turbines); their diameter is in the order of ten millimetres, leading to very small dimensional clearances when the typical relative ones (order of 1/1000) are employed; investigating this particular class of journal bearings under static and dynamic loading conditions represents something unexplored. To this goal, a suitable test rig was designed and the performance of its bearings was investigated under steady load. For the sake of comparison, numerical simulations of the lubrication were also performed by means of a simplified model. The original test rig adopted is a commercial rotor kit (RK), but substantial modifications were carried out in order to allow significant measurements. Indeed, the relative radial clearance of RK4 RK bearings is about 2/100, while it is around 1/1000 in industrial bearings. Therefore, the same original RK bearings are employed in this new test rig, but a new shaft was designed to reduce their original clearance. The new custom shaft allows to study bearing behaviour for different clearances, since it is equipped with interchangeable journals. Experimental data obtained by this test rig are then compared with further results of more sophisticated simulations. They were carried out by means of an in-house developed finite element (FEM) code, suitable for thermoelasto-hydrodynamic (TEHD) analysis of journal bearings both in static and dynamic conditions. In this paper, bearing static performances are studied to assess the reliability of the experimental journal location predictions by comparing them with the ones coming from already validated numerical codes. Such comparisons are presented both for large and small clearance bearings of original and modified RKs, respectively. Good agreement is found only for the modified RK equipped with small clearance bearings (relative radial clearance 8/1000), as expected. In comparison with two-dimensional lubrication analysis, three-dimensional simulation improves prediction of journal location and correlation with experimental results.

Experimental and Molecular Level Analysis of the Tribological and Oxidative Properties of Chaulmoogra Oil

This study introduces chaulmoogra oil as a base stock for lubricant formulation. The tribological properties of chaulmoogra oil are evaluated by quantitative structure-property relation (QSPR) technique using the molecular modelling package Spartan 18. The quantum chemical calculations were performed on a typical molecule of chaulmoogra oil and its constituent fatty acids. The orbital energy gap of the constituent fatty acids in chaulmoogra oil is 7.37 eV and that of chaulmoogra oil molecule is 6.8 eV, which is less than that of the lauric acid, the main constituent of coconut oil (7.78 eV). Orbital energy gap predicts a better tribological performance for chaulmoogra oil, and the four ball test result is in agreement with this prediction. Oxidative property of chaulmoogra oil is tested by isothermal thermogravimetric/differential thermal analysis (TGA/DTA) and compared with different oils. Weight gain in oxygen is only 0.02% for chaulmoogra oil and showed better oxidative stability among all other tested oils.

Experimental Investigation of the Diagnosis of Angular Contact Ball Bearings Using Acoustic Emission Method and Empirical Mode Decomposition

Early detection of angular contact bearings, one of the important subsets of rolling element bearings (REBs), is critical for applications of high accuracy and high speed performance. In this study, acoustic emission (AE) method was applied to an experimental case with defects on angular contact bearing. AE signals were collected by AE sensors in different operating conditions. Signal to noise ratio (SNR) was calculated by kurtosis to entropy ratio (KER), then acquired signals were denoised by empirical mode decomposition (EMD) method, and optimal intrinsic mode function (IMF) was selected by the proposed method. Finally, envelope spectrum was applied to the denoised signals, and frequencies of defects were obtained in different rotating speeds, loadings, and defect sizes. For the first time, a small defect with width of 0.3 mm and loading of 475 N was detected in early stage of 0.04 KHz. Moreover, a comparison between theoretical and extracted defect frequencies suggested that our method successfully detected localized defects in both inner and outer race. Our results show promise in detecting small size defects in REBs.

Tribological Behavior of Tool Steel Substrate and Solid Films against 304 BA Austenitic Stainless Steel under Dry Sliding

The objective of this work is to study the tribological behavior of the contacting surfaces of SKD11 grade hardened cold work tool steel against grade SUS304BA austenitic stainless steel. DLC, CrN, TiN, and TiCN films were coated on the surface of the tool material to test the tribological performance. Simulation testing with a pin-on-disk was used in this study. The study was done under dry conditions with sliding velocities at 50, 100, and 150 mm/s and contact pressures of 807, 1095, and 1280 MPa. The results show that the main problem is the adhesion of the workpiece material on the tool surface. The severity of the adhesion from the workpiece material is proportional to the sliding velocity and the contact pressure between the contacting surfaces. The coefficient of friction between the contacting surfaces has a positive relationship with the adhesion occurring on the tool surface. The hardness of the film coating is useful for preventing wear of the tool material, especially under high pressure between the contacting surfaces. However, it does not prevent the adhesion of workpiece material of low sliding velocity and low contact pressure conditions. Noncoated SKD11 tool steel has better effectiveness of adhesion performance than CrN, TiN, and TiCN film coatings.

Effect of Load on the Tribological Properties of Eutectic Al-Si Reinforced n-Al2O3 under Dry Sliding Conditions

Advanced composites are the materials of the new generation. Hence, the focus of the study is to determine the tribological properties of the eutectic Al-Si alloy reinforced with (2, 4, 6, 8, and10 wt. %) of n-Al2O3 against chrome-plated steel ball under dry sliding conditions. The novelty of this work is the fabrication of the composite sample with this elemental composition, which is not done before. Spark plasma sintering (SPS) nonconventional fabrication method is used to fabricate advanced composite samples. Friction coefficient (COF) and wear rate of the composite samples were studied under high load, varying from 50 N to 300 N, using the ball-on-disc tribometer configuration, with other parameters such as stroke, frequency, sliding distance, and sliding velocity remaining constant at 2 mm, 30 Hz, 120 meter, and 0.120 m/s, respectively. Reduction in wear volume for the advanced composite was reported in the range 15.45–44.58% compared to the base alloy (eutectic Al-Si alloy). An increase in friction coefficient was reported in the range 28.80–35.65% compared to the base matrix alloy material. It was also reported that the wear rate increases and the friction coefficient of the composite sample decreases with an increase in load for the tribo-pair. It was observed that an increase in the wt. % of reinforcement influences the friction and wear behavior of the composite. Wear mechanism at high load was characterized by plastic deformation, adhesion, delamination, and abrasion wear. For pre- and postcharacterization of surface and worn tracks, scanning electron microscopy (SEM) electron dispersion spectroscopy (EDS), 3D surface profilometer, and optical microscopy were used. This work aimed to investigate the influence of load on the tribological properties of Al-Si eutectic reinforced n-Al2O3 under dry sliding conditions. Its main objective was to provide a new contribution to the tribological behavior of these composites fabricated using the nonconventional spark plasma sintering method.

Estimation of the Oxidative Deterioration of Turbine Oil Using Membrane Patch Color

Lubricating oils degrade into two main products: oxidation products and solid particles. Oxidation products, called varnish, of turbine oils for power generation have become a particularly serious problem in recent years. The first step in determining the potential to produce varnish is to determine the remaining life of the antioxidant in the oil, but even though turbine oil may have antioxidants of sufficient longevity, varnish problems still occur frequently. Accordingly, to prevent varnish, it is necessary to diagnose oil oxidation products. Thus, the authors have developed a diagnostic method using membrane patch color, but the relationship between membrane patch color and the remaining life of turbine oils has yet to be clarified. This paper investigates a new method for estimating the oxidative degradation of turbine oils that uses membrane patch color and the dry turbine oxidation stability test (dry TOST) based on oxidation products and the remaining life of the turbine oils. Sample oils were prepared and degraded by oxidation in the laboratory using a dry TOST apparatus, and the membrane patch color was measured using a colorimetric patch analyzer (CPA). The relationship between membrane patch color and the rotating pressure vessel oxidation test (RPVOT) residual rate was then investigated. The results show that the new estimation method using the CPA and dry TOST is able to monitor the decrease of the RPVOT residual rate from the early stages of oxidative deterioration.

The Performance of Squeeze Film between Parallel Triangular Plates with a Ferro-Fluid Couple Stress Lubricant

The present study aims at investigating a couple stress ferrofluid lubricant effects on the performance of the squeezed film when a uniform external magnetic field is applied. For this purpose, Shliomis ferrohydrodynamic and couple stress fluid models are employed. The considered geometry is parallel triangular plates. The effects of couple stress, volume concentration, and Langevin parameters on squeeze film characteristics including time vs. height relationship and load-carrying capacity are investigated. According to the results, employing couple stress ferrofluid lubricant in the presence of the magnetic field leads to an increased performance of the squeeze film.