Tribological study on rock-tool interaction is always challenging as the methodology for the validation of results obtained during the study is limited. The Principal Component Analysis is a machine learning algorithm that outlines and validates the modeling results of statistical distribution models with the help of a smaller set of “summary indices”, called principal components. Studying robustness is important as it evaluates the effectiveness of model parameters from the tribological study and helps to see the change in results with the change in assumptions. In this work, tools were developed by the implementation of TiAl/TiAlN film coatings on cemented carbide inserts using four-cathode reactive unbalanced direct current magnetron sputtering system. The model parameters were determined from the tribological study of coated TiAl/TiAlN pin samples in a Pin-on-Disk apparatus. The present work examines the model parameters' robustness and predicts life models using the Principal Component Analysis approach for a rock-tool interface.
The abrasive wear behaviour of A356 aluminium alloy and A356/5 wt.% SiCp composites were examined under unidirectional (USM) and reciprocating sliding modes (RSM) against 800 grit SiC abrasive medium. Wear maps developed at varying loads and velocities over a 25 metre sliding distance revealed that severe wear initiates at lower loads in RSM than USM, particularly in the base alloy. The composite exhibited enhanced wear resistance with a delayed onset of severe wear. Stereo microscopy and SEM analyses showed that RSM results in deeper, wider grooves and more surface degradation. Groove width in RSM was nearly three times greater than in USM, indicating increased wear severity. EDAX analysis revealed higher oxygen content in USM, suggesting the formation of an oxide layer which contributed to reduced friction. Overall, the findings highlight the critical role of sliding mode and SiCp (Silicon Carbide Particulates) reinforcement in influencing wear mechanisms and surface integrity in A356-based materials.
The study investigates the improvement of surface strength and reliability of fuel pump precision parts by forming wear-resistant boron–chromium diffusion layers using vacuum laser diffusion boron-chromizing with paste application. Plungers made of steels ХВГ, ЩХ15 and P18 were coated with boron–chromium paste and treated by vacuum laser diffusion metallization. The diffusion layer thickness and microhardness were measured using a PMT-3 tester, while the phase composition and microstructure were analysed by X-ray diffraction and metallography. The process produced boride-rich diffusion layers with thicknesses of about 0.17–0.35 mm and surface microhardness in the range of 18–21 GPa. The maximum microhardness reached 21.0 GPa for ХВГ, 18.6 GPa for ЩХ15 and 17.6 GPa for P18, with minimum values in the diffusion zone remaining above 8.8–11 GPa. X-ray analysis confirmed that complex iron–chromium borides with dominant low-boride (Fe,Cr)₂B phases are formed. A fine network of surface microcracks acts as a stress-relief mechanism, redistributing residual stresses in the coating. These results show that vacuum laser diffusion boron-chromizing with paste application is a promising technology for restoring and strengthening fuel pump precision parts and creates a solid basis for subsequent tribological testing under service-like conditions.
This paper is dedicated to the modeling of friction between solids with a regularized friction model. The proposed model is capable of overcoming the well-known disadvantages of Coulomb-type friction laws. The subloading-friction model, formulated based on the Mroz multi-surface type plasticity theory, is extended to introduce a smooth transition from stick to sliding contact and vice versa during the loading and unloading stages. The formulation includes a slip-memory mechanism and history-dependent effects, with frictional hysteresis, enabling accurate representation of micro-slip accumulation and cyclic energy dissipation. This extension also ensures a smooth and continuous transition between the sticking and slipping contact zones by introducing an adjustable regularization parameter, facilitating efficient implementation in a finite element code. The extended model was successfully implemented into the finite element code Abaqus/Standard using the Fric user subroutine. The extended model was successfully validated by comparison with the analytical solution proposed by Jarzeboski-Mroz for a 2D rectangular block pressed against a rigid substrate, and with the Mindlin-Deresiewicz solution for the problem of a 3D sphere in contact with a rigid plane. Furthermore, comparing the results obtained with Coulomb's law and those described by the extended model shows the significant improvement of the latter in managing the stick-slip transition and reproducing frictional hysteresis.
Laser surface hardening technology is a progressive innovation compared to traditional processing methods. The maximum hardening effect from laser surface treatment is achieved in combined technology, where the laser thermal treatment is preceded by a paste treatment or a coating application operation. With the discrete laser coating method of surface coatings, it is possible to create surfaces of certain shapes, sizes and properties on the surface, which will ensure the hardness, wear resistance and reliability of the surface during the friction process. During boronchromization, the following primary materials for powder mixtures were used: X97 ГОСТ 5905-79 chromium powder with a fraction of 0.07...0.2 mm; В4С3Н ТУ2-036-879-81 boron carbide polishing powder, ПЦ-2 ГОСТ 12601-76 zinc powder, Al2О3 GOST 3136-76 aluminum oxide. The complex diffusion metallization method chosen for the restoration of worn precision parts of fuel apparatus and pumps allows not only to restore linear dimensions, but also to harden the restored surfaces. Laser heating, which causes phase changes in the surface layer, requires a minimum density of radiation energy (103 - 104 W/cm²) and an exposure time of 10-3 - 10-2 s. It is possible to harden and restore the surface by applying paste to precision parts and then using the diffusion metallization method in vacuum with a laser.
Reliability is defined as a product's ability to perform its intended functions within specified limits (such as distance, workload, cycle count, etc.) and over a designated period of time (ISO 9000:2015). By transitioning to discrete random variables, the random number of non-failure tests (interactions) of the predicted object, along with the additional distribution function (reliability function) and the characteristic parameters of the object, can be expressed through the distribution functions of random variables that characterize the operation of machines and devices. To ensure the reliability of precision parts of fuel pump, the average value of the deformation error layer resulting from heating in laser surface hardening should be 18 μm (36 μm in diameter). This scientific work investigated precision parts of fuel pump that were subjected to laser chromium diffusion metallization in vacuum. Furthermore, to achieve the desired reliability in precision parts of fuel pump through laser surface treatment, it is recommended that the hardened layer thickness be maintained within the range of 125 μm to 130 μm. After the mechanical processing process, an 8-12 μm reinforced layer remains on the surface, which ensures the reliability of precision parts of fuel pump during operation. This study presents the reliability predicting of precision parts of fuel pump with enhanced surface hardness achieved through laser technology. The theoretical predictions were validated through experimental results, demonstrating the effectiveness of the proposed model in assessing the durability and performance of laser-hardened precision parts of fuel pump.
The laboratory scale journal bearing lubrication regimes were analysed with wide band acoustic emission (AE) measurements. Data analysis was supported by data-based clustering of AE data. The approach can be effectively used to reveal fundamental lubrication modes, i.e., hydrodynamic (HL), mixed (ML) and boundary (BL) lubrication as a function of Hersey number. Besides AE the other parameters monitored were friction torque, bearing temperature, loading, sliding velocity and oil pressure. The materials used in the experiments were case-hardened 18CrNiMo7-6 steel and nitrided 42CrMo7 steel. The tests were lubricated with synthetic extreme-pressure gear oil (SGN 320) and the bearing temperature was kept constant during the tests. The bearing pressure and sliding velocity during tests were varied in the wide range resulting in different lubrication situations. The acoustic emission signals power and frequency content was analysed, and essential features were extracted for data clustering. For lubrication regime change identification the parameters such as signal RMS and coefficient of variation (CV) proved to be important, while signal kurtosis showed to be the most sensitive in discovering anomalies. The sensitivity requires data filtering to remove erroneous peaks. It is also interesting to notice the changes in AE frequency due to different lubrication situation. In literature different clustering and classification methods has been proposed and applied for journal bearing status identification. Here the selected unsupervised clustering method was the mean-shift clustering due to fact, that the lubrication regimes in the Stribeck curve form an inseparable continuum. The algorithm does not require specifying the number of clusters in advance, i.e., the clusters are determined by the algorithm with respect to the data.
Reduced graphene oxide has Excellent frictional properties and stable dispersion in oil, which encourages its use as nano-additives for lubricants. Through this research, the use of different concentrations of reduced graphene oxide was studied in order to reach the optimum concentration and thus the high-efficiency lubricant. The base oil used was paraffin. The tribological properties of the lubricant were studied using a cross-pins test rig. The wear was assessed by measuring the scar diameter of worn surfaces of samples. More wear analysis was accomplished using Scanning Electron Microscopy (SEM). EDS mapping was performed for the worn surfaces of carbon steel (St. 60) samples lubricated with paraffin oil and solid nano-additives of RGO. The results showed that when the concentration of reduced graphene oxide was very low, the dominant effect was the oil effect only. Also, when the concentration of reduced graphene oxide nano sheets was very high, the accumulation of rGO inside the oil occurred, which disallowed the creation of a protective layer on the friction surfaces. At optimum concentration of reduced graphene oxide, rGO can easily absorbed by the friction surfaces, forming tribofilm without the need to physical deposition. This research indicates that RGO significantly enhanced the tribological properties of lubricants.
The tribological response of a laboratory prepared squeeze cast Al-Mg-Si alloy has been compared with the response of the corresponding wrought alloy. The wear resistance of the wrought alloy was found to be better than that of the cast alloy, an expected result as the wrought alloy was harder. However, Analysis of Variance revealed that the difference in wear resistance was not statistically significant. The effect of the sliding speed on the wear resistance of the alloys was not significant, but the effect of the load was significant. The friction coefficient of the wrought alloy was found to be lower than that of the cast alloy. Analysis of Variance revealed that this difference was statistically significant. The effects of the sliding speed and load on the friction coefficient were found to be significant. Scanning electron microscopy revealed the simultaneous prevalence of multiple wear mechanisms including abrasive and adhesive wear, delamination, and oxidative wear. Third body oxide particles trapped within the contact zone also influenced wear. In applications requiring a high friction coefficient, when dry sliding under load against hardened steel, the squeeze cast alloy may be employed without any significant sacrifice of wear resistance, compared with its wrought counterpart.
In this research work, testing has been conducted using a four-ball tribo-tester as per ASTM Standard 4172. The objective of this research work is to evaluate the tribological parameters of SAE-10W-30 lubricant with the addition of nano-hybrid composites as an additive. The effect of nano-composites on the tribological parameters of SAE-10W-30 lubricating engine oil has been investigated experimentally on a four-ball tribometer. The process variable levels for the four-ball tribometer are designed for concentration in the percentage of weight of nano-hybrid composites. Experimentation on a four ball tribometer is performed to determine the wear scar diameter and friction coefficient of hybrid nano-composites. It is observed that the addition of nano-composite additives in combination with SAE-10W-30 reduces the coefficient of friction by 40 %. The results of the wear scar diameter have been tested during experimental work and reported in the articles. The experimental work on hybrid nano-additives provides sustainable energy solutions and environmental conservation while simultaneously addressing current and future demands.
This study focuses on evaluating the behavior of three commercially available lithium-based lubricating greases—77 EP (from 77 Lubricants), LGMP3 (AXCL Lubes), and LHTG3 (XADO)—when applied to journal bearings operating at low (600 RPM) and high (2400 RPM) speeds. The purpose is to understand how different grease types influence the vibration performance of bearings under dynamic conditions. The analysis includes both time-domain statistical indicators and vibration characteristics in the frequency domain. Measurements such as RMS, standard deviation, skewness, kurtosis, and variance were gathered using a real-time LabVIEW setup. These metrics helped in identifying differences in system response under each lubrication condition. The outcomes revealed that higher rotational speeds significantly amplified both vibration levels and system irregularities. This behavior demonstrates the critical impact of selecting the proper lubricant, particularly in fast-moving machinery. Among the samples tested, LHTG3 achieved the most consistent results, showing lower fluctuations in vibration readings, which implies effective damping properties. LGMP3, on the other hand, showed greater variability in its data, suggesting reduced vibration stability. Although 77 EP did not score highest in time-domain statistics, it performed strongly in frequency-based analysis, reducing the effect of sudden shocks and high-frequency responses Long-term performance could benefit from LHTG3; 77 EP would be preferable for machines with varying or fast dynamic loads. These results underline the need of choosing lubricant for stability and condition of journal bearings.
In this study, an experimental bio-grease formulation composed of soybean and cottonseed oils (SBO &CSO) as base oil, lithium hydroxide thickener, and sugar cane filter cake wax (SCW) as an additive was presented. Properties such as viscosity, penetration, drop point, wear, and coefficient of friction (COF) for the formulated samples of bio-grease, were evaluated using standard methods, and the results were compared to the mineral grease. A mixture composition involving the lowest levels of relevant fatty acids in the base oils showed a good structure in the development of film formation and lubrication resulting in less wear and Friction Coefficient. The results showed that bio-grease samples with a high percentage of thickener (up to 3%) and additive at the lowest (3%) have desirable tribological characteristics that are comparable to other bio-grease samples from previous studies. Generally, all of the results indicate that a blend of vegetable oils as a base oil can be used to formulate bio-grease, and using a traditional bio-based additive can enhance the performance of that formulated grease.
Fault diagnosis of rolling element bearings is a critical aspect of machine maintenance and reliability. Bearings are extensively used in various industrial applications, and their failure can lead to costly downtime and equipment damage. Rotating machinery under continuous overload conditions can indeed significantly degrade bearing life and lead to various other issues. To identify issues in rolling element bearings (REB), several techniques and methods are employed. Diagnosing faults in ball bearings while simultaneously estimating the Remaining Useful Life (RUL) of the bearing is a crucial aspect of predictive maintenance. This can be achieved through a combination of signal processing techniques, machine learning methods, and RUL prediction models. The estimation of a bearing Remaining Useful Life (RUL) is of significant importance in predictive maintenance strategies to avoid unexpected failures, reduce downtime, and optimize maintenance costs. This literature review aims to explore the methodologies, techniques, and advancements in predicting the remaining useful life of bearings.
In recent years, there has been a growing demand for materials that are both eco-friendly and cost-effective while maintaining high performance levels. Design engineers and researchers are increasingly turning to advanced materials as substitutes for traditional metals and alloys. Journal bearings, integral components of machinery and engines, play a crucial role in their operation, significantly impacting efficiency, operational costs, system longevity, and reliability. The pursuit of eco-friendly and high-performance materials has spurred notable progress in tribological research, particularly concerning journal bearings. This study offers a comprehensive examination of lead-free composite materials for journal bearings, delving into various types such as polymers, ceramics, and metallic alloys. It meticulously evaluates their mechanical and tribological properties, as well as their microstructural characteristics. The insights gleaned from this review are invaluable for engineers and researchers seeking to enhance the design and performance of journal bearings while aligning with environmental regulations and sustainability objectives.
Additive manufacturing (AM) offers numerous advantages over traditional fabrication methods such as manufacturing complex parts. However, a significant limitation lies in the restricted surface quality, hindering its widespread use. While parts produced through conventional manufacturing techniques such as milling and grinding typically have an average roughness (Ra) value of less than 1–2 μm, those manufactured using laser powder bed fusion (LPBF) AM usually fall within the range of 10 to 30 μm. Surface roughness plays a critical role in various applications, as certain uses necessitate superior surface quality to prevent premature failure due to surface-induced cracking. Subpar surface quality not only compromises the strength, wear resistance, and corrosion resistance of parts but also impacts the precision of the fabricated components. Therefore, it is imperative to optimize the fabrication process and enhance the surface quality of metal parts. Moreover, the surface quality of each layer dictates the bonding strength between adjacent layers and process stability, as a high-quality preceding surface is essential for ensuring the integrity of subsequent layers. Consequently, surface roughness significantly influences process stability and the properties of metal parts produced through LPBF. This work aims at evaluating surface roughness of as printed 316L stainless steel parts made using LPBF AM process and their effects on tensile properties of the produced samples. Microscopic analyses are done to evaluate the roughness (including Ra, Rq, and Sa parameters) at different locations to evaluate the effects of different printing parameters on their size distributions. In addition, the macro-mechanical behaviour of the as printed samples is compared with the ones with polished surface.
The present review focuses on the progress of tribology from the prehistoric period to the contemporary interdisciplinary research trends. During the Paleolithic period, humans used sliding friction, generated inadvertently, to make fire. The Paleolithic inhabitants possessed the knowledge to wear the chloritolite blank to fabricate a bracelet using sophisticated material removal processes. Furthermore, they wore the tooth by making holes, filled them with fillings, intended as a pathologically motivated intervention. Humans wore the tooth by in vivo drilling in the Neolithic period, used as a remedial or soothing dental procedure. The Egyptians poured water on sand to ease the movement of the statue mounted on a sled, and recently, compared to the sled dragging on dry sand, the capillary water bridges easing the sled dragging on wet sand is experimentally observed. Bearings are proposed in the renaissance era, and Leonardo da Vinci initiated friction studies, which witnessed significant progress in the industrial revolution era. The industrial revolution ushered in the use of solid lubricants and lubricating oils and grease with additives. Studies in the scientific era discussed friction, wear, and lubrication problems and reported novel, proven solutions. The expansion of tribology research into different disciplines gave birth to novel interdisciplinary studies: the mimicking of biological structures to improve adhesion, use-wear patterns of ground stone tool surfaces, tribological behavior of artificial implants and medical devices, friction in oral processing, and lubricity of two-dimensional lamellar material. Green tribology is the recent focus and it promotes sustainable tribology research for the sustenance of the earth.
Wear is a significant industrial issue caused by the interaction of multiple complex factors rather than solely by material properties. CuZn37Pb2 and AISI 1060 steel are particularly susceptible to wear due to extensive industrial applications. This study developed a wear test tool, machined on a horizontal lathe, for testing under dry and lubricated conditions. A tribological comparison was conducted between the lathe test and a tribometer, examining factors like surface roughness, load, sliding speed, wear track diameter, track width, contact temperature, wear loss, and wear rate relative to the friction coefficient. Experiments were performed with torques ranging from 25 to 100 N, speeds of 0.30, 0.40, and 0.50 m/s, and wear track diameters of 4, 6, 8, and 10 mm. Worn surfaces and wear tracks were analyzed using optical microscopy and SEM-EDS. The influence of temperature (50 °C to 200 °C) on friction properties was studied, showing that sample morphology and test type greatly affect tribological response. Despite a wear rate calculation error below 8.12%, results indicated differences between laboratory and real-world tribological responses. This study enhances wear understanding by examining numerous previously unstudied characteristics and shows that, although wear cannot be entirely eliminated, it can be significantly minimized. Laboratory testing provides prototypes for industrial challenges, effectively linking academic research with industry needs.
