The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Siegfried Fouvry - One of the best experts on this subject based on the ideXlab platform.
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Understanding and formalization of the fretting-wear behavior of a cobalt-based alloy at high temperature
Wear, 2020Co-Authors: Alixe Dreano, Siegfried Fouvry, Gaylord GuillonneauAbstract:The purpose of this study is to investigate the mechanisms involved in the wear of cobalt-based interfaces at high temperature. The studied contact is a cobalt-based alloy subjected to fretting against an alumina sample. At high temperature, a protective third body is spontaneously created at the interface and presents excellent tribological properties. The formation of the so-called "glaze layer" leads to an absence of wear. The investigation presents on complete description of the hightemperature tribolayer with microstructural, chemical and mechanical characterizations. The glaze layer regime is mainly related to a threshold temperature above which a thin cobalt-rich layer is formed by a tribo-sintering process. A formalization of the tribo-sintering process is proposed to predict the necessary number of fretting cycles N GL to form the glaze layer. The tribo-sintering process prevents wear debris ejection by continuously re-incorporating the wear debris particles in the glaze layer. The re-incorporation of the wear debris may be the reason for the absence of wear of the fretted interface from a macroscopic point of view. Finally, the paper presents an extended Friction Energy wear approach taking into account tribo-oxidation and tribo-sintering considerations. The formulation is able to predict wear for a large range of tribological parameters (temperature, frequency, sliding amplitude, number of cycles), when applied to the Co-based/alumina contact.
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A combined Friction Energy and tribo-oxidation formulation to describe the high temperature fretting wear response of a cobalt-based alloy
Wear, 2019Co-Authors: Alixe Dreano, Siegfried Fouvry, Gaylord GuillonneauAbstract:Abstract A cobalt-based superalloy (HS25) versus alumina contact was subjected to gross slip fretting using a cross-cylinders configuration and various tribological conditions. The present study focuses on the modelling of different wear mechanisms which mainly depend on the operating temperature. Wear below a threshold temperature (150 °C) is severe whereas a protective oxide layer is formed above the temperature transition. At low temperature, the wear process was found to be controlled by a continuous action of the oxidation of the surface and the abrasion of the latter. Wear mechanism was also showed to be strongly dependent on temperature, sliding amplitude and frequency [1] . An energetic wear law was developed to formalize the oxidative-abrasive wear mechanism displaying a good correlation with experiments. Above the threshold temperature, the oxidative-abrasive phenomenon is not operating anymore and a protective glaze layer is formed at the interface. A tribo-sintering approach is proposed to predict the glaze layer formation for various tribological parameters. Moreover, the glaze layer protective effect was taken into consideration in the wear formulation by considering that only the Friction Energy dissipated before the glaze layer creation needs to be integrated. The proposed formulation showed a very good prediction of wear volumes from ambient to high temperature (600 °C).
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prediction of the electrical contact resistance endurance of silver plated coatings subject to fretting wear using a Friction Energy density approach
Wear, 2015Co-Authors: J Laporte, O Perrinet, Siegfried FouvryAbstract:Abstract Electrical connectors need to display low and stable electrical contact resistance (ECR). However, subjected to vibrations (engines, heat, etc.), fretting wear damages promotes the formation of insulating oxide debris and a sharp ECR increase decaying the information transmission. Noble plated coatings like silver layers are usually applied to delay the ECR failure. However, to predict such ECR endurance, it appears essential to determine the fretting wear rate. In the present study, a homogeneous crossed-cylinders Ag/Ag interface was investigated under gross slip conditions imposing various loading parameters (±2 µm 4 mΩ) can be formalized, using a power law function of the mean Friction Energy density dissipated during a fretting cycle taking into account the contact area extension. Finally, a simple ECR endurance expression is derived as a function of the fretting loading parameters and the thickness of the silver plated layer. A very good correlation between experimental and predicted ECR endurances is achieved.
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An effective Friction Energy density approach to predict solid lubricant Friction endurance: Application to fretting wear
Wear, 2014Co-Authors: Siegfried Fouvry, Charleshubert PaulinAbstract:Bonded MoS2solid lubricant coatings are extensively used in tribology to reduce Friction coefficient and wear rate. This coating strategy is particularly appreciated in aeronautical applications to limit fretting wear damage. A major question, however, concerns prediction of endurance for such palliatives (Nc: μ>μc). Focusing on a MoS2-bonded solid lubricant coating fretted against a Ti-6Al-4V counter-body, an extensive fretting wear analysis coupling a large spectrum of contact pressures, sliding amplitudes, contact sizes and contact geometries was undertaken. The study showed that different Friction responses could be activated depending on contact pressure and sliding amplitude conditions. Low pressures and small sliding amplitudes induced a lubrication plateau Friction response (I) whereas high pressures and large sliding amplitudes induced continuously rising Friction combined with titanium transfer (II). The transition from Friction response (I) to Friction response (II) could be formalised using an "effective" pvefffactor. Moreover, bonded-MoS2coating endurance could be predicted by an "effective Friction" Energy density parameter expressed as the difference between the nominal Friction Energy density imputed in the interface and an Energy contribution related to the titanium transfer activation. Using this ϕ-N chart representation, all the experimental Friction endurance values followed a single endurance master curve, formalised as an inverse function of the "effective" Friction Energy density parameter. An equivalent "effective" Archard work density approach is also introduced. Based on a pressure work density parameter, this formulation is easier to apply but displays a wider scatter because Friction fluctuations are not taken into consideration.
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A Friction Energy approach to quantifying lubrication under fretting sliding
Lubrication Science, 2010Co-Authors: T. Kolodziejczyk, Siegfried Fouvry, Guillermo E. Morales-espejelAbstract:The problem of a proper lubrication under low-speed small oscillatory movement can be a decisive factor for the reliability of various components. There is a need to characterise the lubricious behaviour of the interface under oil-bath fretting wear conditions for ball bearing applications. Fast and reliable methods to quantify this behaviour for broad range of mechanical conditions are proposed and validated. Pure sliding reciprocation induces mixed lubrication mode. It was found that transient film profiles depend on the non-Newtonian response of the oils and the type of motion. Running-in period has a crucial importance for the tribofilm formation, and is a result of the interplay of the oil-sliding surfaces interface and is directly connected with the total Energy dissipated from the contact region. The stability of structured tribofilm in steady-state period relies on the balance between the competitive processes: replenishment of the oil to the contact and ejection of the oil pending the oscillatory movement. The phenomenon of starvation was observed when the system was moved away from dynamical equilibrium and the growth of the dissipated Energy was spotted. A proposed methodology provides the evaluation of the lubrication properties of the oil in a quantitative way. Copyright © 2010 John Wiley & Sons, Ltd.
Yanchao Mao - One of the best experts on this subject based on the ideXlab platform.
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single electrode triboelectric nanogenerator for scavenging Friction Energy from rolling tires
Nano Energy, 2015Co-Authors: Yanchao Mao, Dalong Geng, Erjun Liang, Xudong WangAbstract:Abstract Triboelectric nanogenerator (TENG) is a novel Energy harvesting device to convert mechanical Energy into electricity based on the universally known triboelectric principle. In this work, we demonstrated an innovative design of single-electrode TENG (S-TENG) using PDMS to simulate the tire surfaces for scavenging the wasted Friction Energy from rolling tires. By fixing the PDMS S-TENG on a rubber wheel, the performance of scavenging Friction Energy was systematically investigated. The electric output of the S-TENG-on-wheel monotonically increased with the increase of the moving speed and weight load of the wheel. The maximum instantaneous power was obtained to be 1.79 mW at a load resistance of 10 MΩ, corresponding to the highest Energy conversion efficiency of 10.4%. Multiple S-TENGs were implemented to the tires of a toy vehicle and instantaneously powered 6 commercial green light emitting diodes (LEDs) while the vehicle was moving on the ground. This successful demonstration provides a promising solution to scavenge the wasted Friction Energy from rolling tires, which may improve the fuel efficiency or the cruising ability of electric vehicles.
Jen Fin Lin - One of the best experts on this subject based on the ideXlab platform.
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Scuffing as Evaluated From the Viewpoint of Surface Roughness and Friction Energy
Journal of Tribology, 1996Co-Authors: Jeng Haur Horng, Jen Fin LinAbstract:The surface scuffing occurring in line-contact lubrication is related to the roller's roughness pattern and asperity height. For surfaces with same contact asperity height, the magnitudes ofFriction power (P f = fW V s ) relevant to various roughness patterns are found to have the same sequence as the critical local temperatures. Instead of using the nominal contact area, the real contact area (A t ) is used to obtain the true Friction power intensity (P t fi=P f /A t ). A new scuffing failure model (P tfi .σ -0.317 = C, where σ denote rms roughness) shows that the scuffing resistance of surfaces with transverse roughness pattern is higher than that of surfaces with longitudinal and oblique patterns. For certain roughness patterns, a high root mean square roughness height σ is always associated with the high P tfi value just before scuffing.
Ju Gao - One of the best experts on this subject based on the ideXlab platform.
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Strong tribo-catalysis of zinc oxide nanorods via triboelectrically-harvesting Friction Energy
Ceramics International, 2020Co-Authors: Jinhe Zhao, Lin Chen, Wenshu Luo, Yaming Zhang, Hongfang Zhang, Guoliang Yuan, Ju GaoAbstract:Abstract Friction Energy is well-known common clean Energy and can be harvested via triboelectricity. In this study, hydrothermally synthesized zinc oxide nanorods exhibit excellent tribo-catalytic dye decomposition performance via harvesting Friction Energy, which is obtained by stirring. After 60 h of stirring, tribo-catalytic dye decomposition ratio is as high as ~ 99.8%. Strong tribo-catalytic performance can be ascribed to the triboelectric effect, which originates from the Friction between zinc oxide nanorods and stirring rods. Intermediate active species hydroxyl radicals are further observed via fluorescence method, in which the number of hydroxyl radicals continuously increases with increasing stirring time. Besides, zinc oxide nanorods also exhibit good recycling utilization property after three consecutive catalytic experiments. Strong tribo-catalytic performance and good recycling utilization property of zinc oxide nanorods make it potential in utilizing Friction Energy in our environment to achieve dye wastewater purification in near future.
Xudong Wang - One of the best experts on this subject based on the ideXlab platform.
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single electrode triboelectric nanogenerator for scavenging Friction Energy from rolling tires
Nano Energy, 2015Co-Authors: Yanchao Mao, Dalong Geng, Erjun Liang, Xudong WangAbstract:Abstract Triboelectric nanogenerator (TENG) is a novel Energy harvesting device to convert mechanical Energy into electricity based on the universally known triboelectric principle. In this work, we demonstrated an innovative design of single-electrode TENG (S-TENG) using PDMS to simulate the tire surfaces for scavenging the wasted Friction Energy from rolling tires. By fixing the PDMS S-TENG on a rubber wheel, the performance of scavenging Friction Energy was systematically investigated. The electric output of the S-TENG-on-wheel monotonically increased with the increase of the moving speed and weight load of the wheel. The maximum instantaneous power was obtained to be 1.79 mW at a load resistance of 10 MΩ, corresponding to the highest Energy conversion efficiency of 10.4%. Multiple S-TENGs were implemented to the tires of a toy vehicle and instantaneously powered 6 commercial green light emitting diodes (LEDs) while the vehicle was moving on the ground. This successful demonstration provides a promising solution to scavenge the wasted Friction Energy from rolling tires, which may improve the fuel efficiency or the cruising ability of electric vehicles.
