Laura Rosenkranz, Silvia Richter, Georg Jacobs, Adrian Mikitisin, Joachim Mayer, Andreas Stratmann and Florian König
Rolling bearing operation under mixed and boundary lubrication conditions may lead to heavy adhesive or abrasive wear, which may lead to wear-induced rolling bearing failure. The…
Abstract
Purpose
Rolling bearing operation under mixed and boundary lubrication conditions may lead to heavy adhesive or abrasive wear, which may lead to wear-induced rolling bearing failure. The purpose of this paper is to investigate the wear protection capabilities of different grease compositions at varying temperatures. It is considered that the temperature influences the lubrication conditions, the behaviour of grease components, namely, bleed oil and thickener, as well as the tribofilm formation due to tribo-chemical interactions between additives and surfaces.
Design/methodology/approach
In this study, four different greases were produced on the basis of a mineral base oil by varying the thickener and the addition of ZDDP. Various grease-lubricated rolling bearing experiments were conducted in a wide temperature range from 0°C to 120°C. Subsequently, the wear pattern, tribofilm formation and grease structures were analysed. Thereby, the influence of the different grease thickeners and the performance of ZDDP as a common antiwear and extreme pressure additive was evaluated.
Findings
The results show a strong temperature-dependency and allow a classification of temperature ranges concerning wear protection. At low temperatures, all greases provide a very good wear protection without the evidence of additive-based tribofilm formation. In the experiments at elevated temperatures, ZDDP tribofilms were formed. The formation depends on the thickener type: in comparison to lithium thickener, polyurea thickener favours more protective tribofilms at the same temperature. The experimental results show that medium temperatures in the range of 40°C–60°C are critical concerning wear due to the insufficient tribolayer formation and limited load carrying capacity of the grease.
Originality/value
Temperature is a key operating parameter for grease lubrication in roller bearings. The experimental work enables consideration of different impact pathways of temperature by combining roller bearing tests and microanalysis.
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Chia-Jui Hsu, Jenifer Barrirero, Rolf Merz, Andreas Stratmann, Hisham Aboulfadl, Georg Jacobs, Michael Kopnarski, Frank Mücklich and Carsten Gachot
To decrease wear and friction, zinc dialkyldithiophosphate (ZDDP) has been used in engine oil for several decades, but the mechanism of the tribofilm formation is still unclear…
Abstract
Purpose
To decrease wear and friction, zinc dialkyldithiophosphate (ZDDP) has been used in engine oil for several decades, but the mechanism of the tribofilm formation is still unclear. The purpose of this study is to characterize the chemical details of the tribofilm by using high-resolution approaching.
Design/methodology/approach
An ISO VG 100 mineral oil mixed with ZDDP was used in sliding tests on cylindrical roller bearings. Tribofilm formation was observed after 2 h of the sliding test. X-ray photoelectron spectroscopy (XPS) and atom probe tomography (APT) were used for chemical analysis of the tribofilm.
Findings
The results show that the ZDDP tribofilm consists of the common ZDDP elements along with iron oxides. A considerable amount of zinc and a small amount of sulfur were observed. In particular, an oxide interlayer with sulfur enrichment was revealed by APT between the tribofilm and the steel substrate. The depth profile of the chemical composition was obtained, and a tribofilm of approximately 40 nm thickness was identified by XPS.
Originality/value
A sulfur enrichment at the interface is observed by APT, which is beneath an oxygen enrichment. The clear evidence of the S interlayer confirms the hard and soft acids and bases principle.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0035/
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Organizational sociology and organization studies have a long history together, while also sharing a proclivity to self-diagnose crises. Instead of taking these assessments at…
Abstract
Organizational sociology and organization studies have a long history together, while also sharing a proclivity to self-diagnose crises. Instead of taking these assessments at face value, this paper treats them as an object of study, asking what conditions have fueled them. In the case of organizational sociology, there are indications of a connection between rising levels of discontent and community building: self-identified organizational sociologists have progressively withdrawn from general debates in the discipline and turned their attention to organization studies, which, they suspect, has seen dramatic levels of growth at their expense. Organization studies, on the other hand, are still haunted by “a Faustian bargain”: leaning heavily on the authority of the social sciences, business school faculty were able to facilitate the emergence of a scholarly field of practice dedicated to the study of organizations, which they control. However, in doing so, they also set organization studies on a path of continued dependence on knowledge produced elsewhere: notably, by university disciplines such as sociology.
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Rajesh Shah, Blerim Gashi, Vikram Mittal, Andreas Rosenkranz and Shuoran Du
Tribological research is complex and multidisciplinary, with many parameters to consider. As traditional experimentation is time-consuming and expensive due to the complexity of…
Abstract
Purpose
Tribological research is complex and multidisciplinary, with many parameters to consider. As traditional experimentation is time-consuming and expensive due to the complexity of tribological systems, researchers tend to use quantitative and qualitative analysis to monitor critical parameters and material characterization to explain observed dependencies. In this regard, numerical modeling and simulation offers a cost-effective alternative to physical experimentation but must be validated with limited testing. This paper aims to highlight advances in numerical modeling as they relate to the field of tribology.
Design/methodology/approach
This study performed an in-depth literature review for the field of modeling and simulation as it relates to tribology. The authors initially looked at the application of foundational studies (e.g. Stribeck) to understand the gaps in the current knowledge set. The authors then evaluated a number of modern developments related to contact mechanics, surface roughness, tribofilm formation and fluid-film layers. In particular, it looked at key fields driving tribology models including nanoparticle research and prosthetics. The study then sought out to understand the future trends in this research field.
Findings
The field of tribology, numerical modeling has shown to be a powerful tool, which is both time- and cost-effective when compared to standard bench testing. The characterization of tribological systems of interest fundamentally stems from the lubrication regimes designated in the Stribeck curve. The prediction of tribofilm formation, film thickness variation, fluid properties, asperity contact and surface deformation as well as the continuously changing interactions between such parameters is an essential challenge for proper modeling.
Originality/value
This paper highlights the major numerical modeling achievements in various disciplines and discusses their efficacy, assumptions and limitations in tribology research.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2023-0076/
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Andreas Ziegltrum, Stefan Emrich, Thomas Lohner, Klaus Michaelis, Alexander Brodyanski, Rolf Merz, Michael Kopnarski, Bernd-Robert Hoehn and Karsten Stahl
This paper aims to address the influence of tribofilms and running-in on failures and friction of gears. The operation regime of gears is increasingly shifted to mixed and…
Abstract
Purpose
This paper aims to address the influence of tribofilms and running-in on failures and friction of gears. The operation regime of gears is increasingly shifted to mixed and boundary lubrication, where high local pressures and temperatures occur at solid interactions in the gear contact. This results in strong tribofilm formation due to interactions of lubricant and its additives with the gear flanks and is related to changes of surface topography especially pronounced during running-in.
Design/methodology/approach
Experiments at a twin-disk and gear test rig were combined with chemical, structural and mechanical tribofilm characterization by surface analysis. Pitting lifetime, scuffing load carrying capacity and friction of ground spur gears were investigated for a mineral oil with different additives.
Findings
Experimental investigations showed a superordinate influence of tribofilms over surface roughness changes on damage and friction behavior of gears. Surface analysis of tribofilms provides explanatory approaches for friction behavior and load carrying capacity. A recommendation for the running-in of spur gears was derived.
Originality/value
Experimental methods and modern surface analysis were combined to study the influence of running-in and tribofilms on different failures and friction of spur gears.
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The purpose of this paper is to synthesize MeO‐type pigments, focusing on the oxides containing zinc and magnesium.
Abstract
Purpose
The purpose of this paper is to synthesize MeO‐type pigments, focusing on the oxides containing zinc and magnesium.
Design/methodology/approach
Oxides ZnO and MgO were synthesized, their morphology was evaluated, and their impact on the physical properties of the paint film were assessed. A pigment of ZnO/core‐shell type also was synthesized. The physical‐chemical property of the synthesized pigments and the anticorrosion efficiencies of the paint films pigmented by them were determined. The binder used in the researched coatings was epoxy‐ester resin.
Findings
The shape of the particles was identified in the synthesized pigments. X‐ray diffraction analysis revealed the degree of precipitation and lattice parameters. All of the synthesized pigments had good anticorrosion efficiency in an epoxyester coating.
Practical implications
The synthesized pigments can be used conveniently in coatings protecting metal substrates against corrosion.
Originality/value
Of benefit is the fact that the synthesized pigments do not contain any environmentally harmful substances.