Friction and contact temperature in dry rolling-sliding contacts with MoS2-bonded and a-C:H:Zr DLC coatings

Hofmann, Stefan; Yilmaz, M.; Maier, Enzo; Lohner, Thomas; Stahl, Karsten

doi:10.1186/s40712-021-00129-3

Cited by 12 publications

(7 citation statements)

References 38 publications

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“…The object of investigation is a contact between two disks. The contraformal reference setup refers to two disks with external raceways as considered by Hofmann et al (2021). The radii of curvature of the two convex disks are identical with R 1,2 = 40 mm.…”

Section: Methodsmentioning

confidence: 99%

Characteristics in hard conformal EHL line contacts

Schmid

Paschold

Lohner

et al. 2023

ILT

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Purpose Internal gearings are commonly used in transmissions due to their advantages like high-power density. To ensure high efficiency, load-carrying capacity and good noise behavior, a profound knowledge of the local gear mesh is essential. The tooth contact of internal gears relates to a convex and concave surface that form a conformal contact. This is in contrast to external gears, where two convex surfaces form a contraformal contact. This paper aims at a better understanding of conformal contacts under elastohydrodynamic lubrication (EHL) to improve the design of internal gearings. Design/methodology/approach An existing numerical EHL model is used for studying the characteristic properties of a hard conformal EHL line contact. A hard contraformal EHL line contact is studied as reference. Non-Newtonian fluid behavior and thermal effects are considered. By taking into account the local contact conformity and kinematics, the effects and relevance of the curvature of the lubricant gap and micro-slip are analyzed. In a parameter study, scale effects of the contact radii on film thickness, temperature rise and friction are examined. Findings The curvature of the lubricant gap and effects of micro-slip are small in hard conformal EHL line contacts. For high micro-slip, it can be neglected. Hence, the modeling of conformal contacts using an equivalent geometry of the contact problem is reasonable. The parameter study shows beneficial tribological aspects of the conformal contact compared to the contraformal contact. Higher film thickness and lower fluid coefficient of friction are observed for conformal contacts, which can be attributed to lower pressures for the case of the same external normal force, or to a higher contact temperature rise for the case of equivalent contact pressure. Originality/value Despite its widespread existence, the local geometry and kinematics in hard conformal EHL line contacts like in internal gearings have been rarely studied. The findings help for a better understanding of local contact characteristics and its relevance. The quantified scale effects help to improve the efficiency and load-carrying capacity of machine elements with hard conformal EHL contacts, like internal gearings. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2022-0366/

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Section: Methodsmentioning

confidence: 99%

Characteristics in hard conformal EHL line contacts

Schmid

Paschold

Lohner

et al. 2023

ILT

Self Cite

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“…The experiments are performed on a twin-disk tribometer, which was also used for thin-film sensor measurements in hard EHL contacts by Ebner et al [ 21 ] and in dry lubricated contacts by Hofmann et al [ 26 ]. Figure 1 shows a schematic of the mechanical layout of the twin-disk tribometer considered.…”

Section: Methodsmentioning

confidence: 99%

“…Numerical calculations of the temperature distribution in coated EHL contacts from, e.g., Ziegltrum et al [ 2 ] revealed strong temperature gradients within surface coatings. Hofmann et al [ 26 ] applied thin-film sensors to dry lubricated soft-coated rolling-sliding contacts. Beyond rolling–sliding contacts, thin-film sensors have also been investigated for temperature measurement, e.g., in cutting tools [ 27 ].…”

Section: Introductionmentioning

confidence: 99%

In Situ Contact Analysis of Polyetheretherketone under Elastohydrodynamic Lubrication

2022

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The influence of the complex material behavior of thermoplastic polymers in lubricated contacts is poorly understood. It affects the optimal design of power-transmitting thermoplastic machine elements and the exploitation of its potential, e.g., lightweight design, low-noise operation, and cost-effective manufacturing when injection-molded. This study applies the in situ thin-film sensor technology on a twin-disk tribometer in order to study the elastohydrodynamic lubrication of rolling–sliding contacts with the thermoplastic polymer polyetheretherketone. The results provide insights into the effects and relevance of its thermoplastic material properties. Pressure measurements reveal a typical hydrodynamic profile in combination with a large deformation of the contact zone. The influence of speed and slip ratio is thereby negligible. The temperature rise is low compared to elastohydrodynamically lubricated contacts with steel and is mainly influenced by the slip ratio as well as the load, whereas speed plays a subordinated role. In general, the heat generation is governed by shearing and backflow in the contact inlet zone at low slip ratios and shearing in the contact zone at high slip ratios. No effects attributed to viscoelasticity or loading frequency were observed at the operating conditions considered.

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“…They inspected from the results that the 0.2 wt.% polyether amine functionalized graphene oxide composite showed well tribological efficiency. Stefan Hofmann et al [14] investigated the impact of friction and temperature on the surface coating in the rolling-sliding contacts for application in dry lubricated gears. N. Nemati et al [15] researched a composite covering made of Polytetrafluoro Ethylene (PTFE) and graphene oxide to improve frictional behaviour in ambient and increased temperature environments considerably.…”

Section: Introductionmentioning

confidence: 99%

Effect of Temperature on Friction Behavior of Epoxy Resin Composite Coatings for Sliding Contact

Rehman

Gulzar

Shaukat

2022

PakJET

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Epoxy composite coatings are used to reduce friction in mechanical components. The epoxy composites at high temperatures cause serious frictional effects due to poor surface characteristics. Hence, there is a need to find a substitute to improve their frictional behaviour in high-temperature conditions. Adding fillers and lubrication are key solutions to improve tribological properties. In this research work, diglycidyl ether of bisphenol A (DGEBA) epoxy resin was coated on steel, and silica powder (5% by weight) was used as filler. The experiments were conducted under dry and lubricated conditions with and without filler. The coefficient of friction (COF) was examined at different temperatures. The results show that the COF increases with an increase in temperature. In addition, the minimum average COF was observed in the case of epoxy coating with the filler under lubrication conditions. For that case, up to 94.4% decrease in COF was observed as compared to epoxy coating without filler under dry conditions, a 48.33% decrease in COF to epoxy coating without filler under lubricated conditions and a 17.98% decrease in COF than epoxy coating with the filler under dry condition was perceived. Scanning Electron Microscopy (SEM) and surface roughness analyses were also conducted to examine the surface of the specimen after the experiment. A worn and rougher surface was observed in the case of epoxy without filler under dry conditions. The more coefficient of friction at high temperatures is due to the thermal degradation of the epoxy matrix at high temperatures, which results in a rougher surface.

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Friction and contact temperature in dry rolling-sliding contacts with MoS2-bonded and a-C:H:Zr DLC coatings

Cited by 12 publications

References 38 publications

Characteristics in hard conformal EHL line contacts

Characteristics in hard conformal EHL line contacts

In Situ Contact Analysis of Polyetheretherketone under Elastohydrodynamic Lubrication

Effect of Temperature on Friction Behavior of Epoxy Resin Composite Coatings for Sliding Contact

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