Under high-temperature, high-speed, heavy-duty, and extreme lubrication operating conditions, such as those found in gearboxes of aviation engines and electric vehicles, gear scuffing failure has ...emerged as a critical issue and a primary technical challenge in the mechanical transmission field. As test methodologies, evaluation criteria, and load-carrying capacities related to gear scuffing are yet to reach full maturity in response to these demanding operating environments, this article examines existing literature on gear scuffing failure and its control, incorporating insights from industry practices and academic studies. The discussion encompasses the development of gear scuffing theories, experimental investigations, and practical applications, ultimately providing an overview of the most recent developments in gear anti-scuffing technologies. The ultimate goal of this work is to elucidate failure mechanisms of gear scuffing and establish effective design approaches for gear anti-scuffing.
Scuffing failure in high-speed aviation gears is a critical issue that hinders the improvement of operating performance and reliability in modern aviation equipment. The unclear failure mechanism ...limits the effective design of anti-scuffing measures. In this study, a scuffing test method was designed for high-speed aviation gears to investigate the effects of tooth profiles and surface treatment on the gear scuffing performance. The results indicate that both the pressure angle and surface treatment significantly affect gear scuffing behavior. Under different geometric treatment states, the range of the Ryder load stages at which gear scuffing initiated was between 5 and 13. The 25° pressure angle gear with barrel finishing treatment exhibited the optimal anti-scuffing performance. Compared to the ground state, barrel finishing increases gear scuffing loading capacity by 30% to 33%. Tooth profile optimization based on pressure angle changes improves gear loading capacity by 56.9%. This work provides an exploration of the anti-scuffing design of high-speed gears.
•An effective establishment of the gear temperature model is proposed.•A wireless gear temperature measuring system is developed.
A systematic investigation on gear scuffing capacity under oil jet ...lubrication was presented numerically and experimentally. A sequence coupling numerical methodology was proposed for the effective establishment of the gear temperature model. A gear scuffing test under jet lubrication was designed and conducted, in which the gear temperature was measured via a developed wireless measuring system. The proposed testing method enables a quick evaluation of gear scuffing failure without frequently dismantling the gearbox. The simulated gear bulk temperature is compared with experimental results and shows consistency, the largest deviation between which during the whole gear scuffing test is 5.4%. The simulation model provides an efficient and reliable method for the evaluation of gear scuffing capacity.
About four balls scuffing test parameters Hangan', C; Românu, I C; Muscă, I
IOP conference series. Materials Science and Engineering,
12/2020, Letnik:
997, Številka:
1
Journal Article
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The paper aims to contribute to the understanding of scuffing occurrence. The evolution of surface topography during four balls tests using two types of grease was investigated. For testing, a four ...balls experimental setup was used. The test rig allows loading the contact between balls while maintaining relative motion between surfaces. Constant velocity is maintained for 10 seconds as per the EN ISO 20623:2003 procedure. The wear scar produced during testing was investigated by means of an optical 3D profilometer and the roughness parameters were analysed. Experimental results reveal that the values of arithmetical mean height Sa and root mean square height Sq, have a significant growth and they are correlated with the occurrence of the scuffing phenomenon.
Incoloy™ 800HT and Inconel™ 617 are primary candidate structural materials for high-temperature gas-cooled reactors (HTGRs). Impurities (e.g., H2O, CH4) in the coolant induce corrosion reactions that ...affect tribological behavior. We investigate the high-temperature tribological performance of the alloys under surface conditions including: conditioned in H2O-containing helium at elevated temperatures, hardened via the carbon-diffusion Kolsterising® treatment, and conditioned after hardening. Initial friction coefficients and volume removed serve as metrics for wear performance. In this work, we find that wear mechanisms including scuffing, glaze-oxide formation, and oxide-layer wear and break-through are governed by surface hardness, chemistry, and applied load. The formation of a glaze-oxide layer is achieved with an oxide of sufficient mechanical integrity if the oxide-substrate interface is strong and the load is low.
•Spur gear bulk temperature modeling.•Non-Newtonian thermal mixed EHL modeling of gear contacts.•Coupling of bulk and flash temperature formulation to find max. temperature.•Demonstration of ...roughness and speed influences on scuffing torque.
This study proposes a scuffing model for spur gear contacts. A heat transfer formulation is devised to evaluate gear bulk temperature, with frictional heat flux yielded from thermal mixed elastohydrodynamic lubrication (EHL) analysis. In return, the bulk temperature is fed back into the EHL modeling to determine tribological behavior within contact zone, including flash temperature. After bulk temperature stabilizes, the bulk and flash components are added to arrive the total surface temperature, whose maximum is compared to a scuffing limit for failure determination. Utilizing the model, a set of simulations is performed to demonstrate the influences of surface roughness and rotational speed on scuffing load.
The purpose of this work was to investigate a new nano-additive for improved internal combustion engine oils designed for increased fuel economy and a cleaner environment. The friction and wear ...characteristics of nano-lubricants containing hybrid nano-materials of Al2O3 and TiO2 were been evaluated under reciprocating test conditions to simulate a piston ring/cylinder liner contact. Al2O3/TiO2 nanoparticles were suspended in a commercially available lubricant in various concentrations. The Al2O3 and TiO2 nanoparticles had sizes of 8–12nm and 10nm, respectively. The morphology and microstructure of the tribofilms produced during frictional contact were investigated via FE-SEM, EDS and a 3-D surface profiler. In the best case, there was a reduction of frictional power losses for the simulated piston ring assembly by 40–51% compared to a commercially available lubricant. The nano-additive composition in that case was 0.05wt% Al2O3+0.05wt% TiO2. Moreover, the wear rate of piston ring decreased by 17% after a sliding of 50km due to the delamination of Al2O3 and TiO2 nanoparticles on worn surfaces. In that case, they acted as a solid lubricant to reduce both wear and scuffing. These results present a promising and straightforward approach to automotive fuel economy and an increased life span for engine parts.
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•The frictional power losses were reduced by 40–51% using hybrid nano-lubricants.•The wear rate of the ring decreased by 17% due to the delamination mechanism.•The results showed that hybrid nano-lubricants improve the scuffing resistance.•These results present a promising approach to automotive fuel economy.
Lubrication is essential for the advancement of energy efficient modern industries. Lubricants are widely used in industry to minimize friction and wear between tools and moving components. Additives ...are utilized as common lubricants reinforcement in order to achieve overall improved tribological properties. This study presents and discusses the tribological properties of friction, wear, and extreme pressure of two synthetic lubricants: GL-4 (SAE 75W-85), a fully-formulated oil; and Poly-alpha olefin 8 (PAO 8) base oil. These lubricants were doped at various filler concentrations (0.5, 1.0, and 2.0wt%) of CuO and Al2O3 nanoparticle additives. Anti-wear tests were performed with an Optimol SRV 4 tester, according to ASTM D5707; extreme pressure tests were performed with a T-02 four-ball tribotester. Wear scar diameters (WSD) were characterized by optical microscopy, scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). Anti-wear results showed a decrease of up to 18% and 14%, on coefficient of friction (COF) and WSD with 2wt% CuO/PAO 8. The load carrying capacity (poz) of GL-4 and PAO 8 increased by ~14% and ~273%, respectively, with the addition of CuO nanoparticles. However, the incorporation of Al2O3 nanoparticles was not as effective, showing an increase of up to 18% and 12% on poz for GL-4 and PAO 8, respectively.
•GL-4 and PAO 8 nanofluids were characterized for tribological properties.•Al2O3 nanoparticles acted as an abrasive, showing a detrimental effect on both oils.•All tribological properties increased with the addition of CuO nanoparticles.•Nanoparticles may fill surface roughness decreasing friction and wear.
To explore the influence of surface quality on gear scuffing performance, an experimental investigation is performed on gears treated with different surface techniques using an FZG-type test rig. ...Scuffing loading capacity and detailed failure modes of gears with different surface technologies are discussed. Results reveal that the scuffing limiting temperature of the baseline ground gear under 50% surviving probability is 228.8 °C. The diamond-like carbon (DLC) coating greatly enhances gear scuffing performance, and the scuffing limiting temperature increases by 17.3% compared with the ground baseline. Under 99% surviving probability, the scuffing limiting temperature differences between ground, shot-peened, and superfinished gears are within 1.2%. This experimental investigation provides support for antiscuffing design of modern high-speed gear transmissions.
This study compared the tribological performance of castor oil (CO), its transesterified (TCO), and aminolyzed (ACO) forms. A limited number of research articles are available regarding the ...tribological properties of these modified forms, especially the aminolyzed. Assessments included film thickness, piezoviscosity, Stribeck curve, and scuffing resistance. The film thickness followed the same order of the dynamic viscosity, i.e.: CO > ACO > TCO. The chemical modifications reduced the piezoviscosity, which was estimated as following: CO > TCO > ACO. ACO exhibited the lowest coefficient of friction (CoF) in the mixed and boundary regimes. ACO with a strong adsorbed film and lower piezoviscosity (consequently stable viscosity and reduced heating) demonstrated superior tribological properties (higher scuffing resistance and lower CoF).
•Tribological performance of transesterified (T) and aminolyzed (A) castor oil was measured.•Film thickness followed the same order of the dynamic viscosity of the oils.•Piezoviscosity (α) was estimated, and the chemical modifications reduced α.•Biolubricant A showed the lowest friction in the mixed and boundary regimes.•Superior scuffing resistance was seen in the aminolyzed form.
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