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First page: 011701 Abstract: AbstractThis article explores the performance of different commercial piston rings when matched with a boron-phosphorus (BP) alloy cast iron cylinder liner, specifically in high-power density diesel engines. The focus is on the friction, wear, and scuffing characteristics. An interrupted wear test was conducted under lean oil conditions to study the scuffing behavior of plated Cr-diamonds coating (GDC) and diamond-like carbon coating (DLC). The findings reveal that DLC coatings exhibit superior tribological properties, displaying low friction coefficients and wear loss at temperatures of 150 °C and 240 °C. In contrast, GDC coatings demonstrate relatively poor performance. Additionally, the DLC coating demonstrates excellent scuffing resistance, as no material transfer was observed for up to 77 min, even without lubrication. The interrupted scuffing test reveals that the scuffing process undergoes a stable wear stage, followed by a sudden drop and subsequent increase in friction force, ultimately resulting in scuffing when the BP cylinder is paired with GDC. On the other hand, although the frictional force of DLC initially increases after a brief decline, no significant adhesive wear is observed. This can be attributed to the formation of a tribo-chemical layer of carbides, which effectively prevents scuffing. In comparison to traditional methods of postwear morphology and analysis, our proposed interrupted scuffing tests offer enhanced capabilities for evaluating the wear condition of friction pairs at various time intervals during the oil depletion process. This novel approach introduces a new paradigm for investigating wear patterns in different friction pairs. PubDate: Thu, 14 Sep 2023 00:00:00 GMT DOI: 10.1115/1.4063187 Issue No:Vol. 146, No. 1 (2023)
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First page: 012101 Abstract: AbstractThe heat-treated nanoparticle heat-treated magnesium silicate hydroxide (MSHH) was obtained based on the synthesis of lamellar nanoparticle magnesium silicate hydroxide (MSH) and analysis of thermal stability, and the morphology, phase composition, and chemical groups of nanoparticles were subsequently characterized. The heat treatment process induces partial dehydroxylation of MSHH, while preserving the layered structure. Compared with MSH, the tribological performances of MSHH as a lubricant additive have been greatly improved. The mechanical properties of MSH and MSHH are analyzed by calculation of elastic constants using density functional theory (DFT). The interactions among dispersant oleic acid (OA), nanoparticles (MSH and MSHH), and Fe tribopairs were investigated by simulations of classical molecular dynamics (CMD) from the views of adsorption energy and confined shear. The tribological mechanism of MSHH as a lubricant additive is proposed based on the decreased shear strength and weakened agglomeration. PubDate: Thu, 14 Sep 2023 00:00:00 GMT DOI: 10.1115/1.4063195 Issue No:Vol. 146, No. 1 (2023)
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First page: 121703 Abstract: AbstractIn this article, solid lubricants are investigated to examine their tribological performance in a dry lubricated steel–bronze contact. The examined solid lubricants are made of polyamide (PA) and irradiated polytetrafluoroethylene (PTFE), which are chemically bonded by reactive melt extrusion. For the tribological investigations, a block-twin-disc test rig, on the one hand, and a three-disc test rig, on the other hand, were used under ambient conditions, where the solid lubricant for lubricating the steel–bronze contact was released from a block or a disc. Results from the tribological investigations are presented here, showing the friction and wear behavior in a steel–bronze contact depending on the slide-to-roll ratio in the contact between the steel disc and the compound body. Furthermore, surface analytical investigations on the steel and bronze discs were carried out. These studies showed that the chemical bonding of 20 wt% of irradiated PTFE in PA12 improves the wear and friction behavior in steel–bronze contact significantly, due to the buildup of a transfer film of PTFE on the steel surface. PubDate: Thu, 14 Sep 2023 00:00:00 GMT DOI: 10.1115/1.4063116 Issue No:Vol. 145, No. 12 (2023)
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First page: 121704 Abstract: AbstractDetermining the friction and wear behaviors of aero-engine key components under realistic conditions is important to improve their long-term reliability and service life. In this paper, the friction and wear behaviors of different bushing materials in the variable stator vane (VSV) system were investigated through the basic pin-on-disc test and actual shaft-bushing test. Different machine learning (ML) models were established based on the experimental information to predict the coefficient of friction (COF) and wear-rate. The results indicated that there is a significant temperature warning line for the wear amount of the polyimide material, while the high-temperature alloy material exhibited stable tribological performance under experimental load and temperature conditions. ML analysis indicated that the extreme gradient boosting (XGB) outperformed other ML algorithms in predicting the COF (R2 value = 0.956), while the kernel ridge regression (KRR) produced the best performance for predicting the wear-rate (R2 value = 0.997). The tribo-informatics research for bushings in the VSV system can accelerate the structural optimization and material selection and support the evaluation of new structures and materials. PubDate: Thu, 14 Sep 2023 00:00:00 GMT DOI: 10.1115/1.4063186 Issue No:Vol. 145, No. 12 (2023)
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First page: 124601 Abstract: AbstractThe present study explores the performance of novel vegetable oil–based greases containing nano-CaCO3 as an additive. A series of greases with varying nanoparticle concentrations (0–4% w/w) are evaluated on a four-ball tester machine under a standard tribological test (ASTM D2266) and simultaneously in a rolling bearing at various speeds and loads against two commercial greases as the benchmark. The vibrations and shock pulse measurements are recorded to assess the bearing performance. The tribo-dynamic investigation suggests that the eco-friendly nano-greases are at par with the commercial ones; performance varies with the nanoparticle concentration. Under the tribological test, the third-body action of nanoparticles seems to increase friction, while the interfacial deposition (physisorption) of nano-CaCO3 and nano-CaO decreases wear. Under the bearing test, the rolling effect of nanoparticles seems to influence vibrations, while their entrainment in the contact zone governs the carpet values. The nano-grease containing 4% nano-CaCO3 performs best under both assessments, displaying great prospects of a sustainable and potential alternative to existing environmentally unfriendly greases. PubDate: Thu, 14 Sep 2023 00:00:00 GMT DOI: 10.1115/1.4063138 Issue No:Vol. 145, No. 12 (2023)
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