| 1. |
- Kröll, Mirco, et al.
(author)
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Auswirkungen von vereinheitlichten Prozeduren auf tribologische Versuche
- 2021
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In: 62. Tribologie-Fachtagung der Gesellschaft für Tribologie.
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Conference paper (peer-reviewed)abstract
- Anerkannte Institutionen stellen ihre Kompetenzen auf dem Gebiet tribologischer Charakterisierungen Industrie und Forschung zur Verfügung (https://www.i-tribomat.eu/). Ein Aspekt hierbei ist eine tribologische Datenbank. Um die nötige Qualität der Daten sicherzustellen, sind vereinheitlichte Prozeduren erforderlich, in deren Auswirkungen dieser Vortrag einen Einblick gibt.
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| 2. |
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| 3. |
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| 4. |
- Kröll, Mirco, et al.
(author)
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On the quality of wear volume data of laboratory model tests
- 2022
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In: 63. Tribologie-Fachtagung der Gesellschaft für Tribologie.
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Conference paper (peer-reviewed)abstract
- This contribution will concentrate on wear as volume loss, which is a crucial part in quantifying the performance of a tribological system. Wear is an outcome of a tribological experiment and affected by the variables of the tribological system including the samples involved. It can be detected and assessed in various ways (e.g., via changes in volume, weight, geometry, morphology, and topography). There are several methods to measure the wear volume. Some of them are standardised, others aren’t. The comparability of these methods was analysed in two Inter-Partner Round-Robin Tests (IP-RRT) using reciprocating laboratory model tests. The evaluation of wear volumes was done on two levels for each IP-RRT. The first level focused on the comparison of wear volumes caused by different tribological experiments with the same parameters conducted by various operators at the partners with several tribometers. The second level focused on the methods used to determine the wear volume of circulated samples with wear scars produced by the tribological tests in those IP-RRTs. These considerations are especially important as within the European Tribology Centre “i-TRIBOMAT” (Grant Agreement no. 814494; call: H2020-NMBP-TO-IND-2018; https://www.i-tribomat.eu/) a shared infrastructure of more than 100 tribometers is formed. Additionally, this centre incorporates the capacities of tribological characterisation of different renowned institutions. To ensure that the wear results determined by this Open Innovative Test Bed are characteristic as well as descriptive, trustworthy, comparable, and reproducible, appropriate procedures are needed. Hence, they safeguard respective quality features, such as low standard deviations. An essential part in the development of these procedures is the continuous improvement process that was set in place within the quality management system. It contains IP-RRTs that collect data, methods used, expenses and suggestions for improvements. They also validate the procedures developed. The presentation will show that harmonised procedures and Best Practices reduce influences caused, for example, by the operators, which is necessary to reach the quality demands of the European Tribology Centre.
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| 5. |
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| 6. |
- Martin-Torres, Javier, et al.
(author)
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Brine-Induced Tribocorrosion Accelerates Wear on Stainless Steel: Implications for Mars Exploration
- 2021
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In: Advances in Astronomy. - : Hindawi Publishing Corporation. - 1687-7969 .- 1687-7977. ; 2021
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Journal article (peer-reviewed)abstract
- Tribocorrosion is a degradation phenomenon of material surfaces subjected to the combined action of mechanical loading and corrosion attack caused by the environment. Although corrosive chemical species such as materials like chloride atoms, chlorides, and perchlorates have been detected on the Martian surface, there is a lack of studies of its impact on materials for landed spacecraft and structures that will support surface operations on Mars. Here, we present a series of experiments on the stainless-steel material of the ExoMars 2020 Rosalind Franklin rover wheels. We show how tribocorrosion induced by brines accelerates wear on the materials of the wheels. Our results do not compromise the nominal ExoMars mission but have implications for future long-term surface operations in support of future human exploration or extended robotic missions on Mars.
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| 7. |
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| 8. |
- Nyberg, Erik, 1986-
(author)
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Ionic Liquid Lubricants for Space Applications
- 2021
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Doctoral thesis (other academic/artistic)abstract
- Lubrication is critical to the efficient and reliable operation of machine elements such as gears, bearings, or any other moving mechanical assembly (MMA). On Earth, machine designers are accustomed to the access of a wide range of liquid lubricants that enable predictable and reliable long-term operations of high performance MMA. In space applications on the other hand, engineers are constrained to a comparatively limited choice of lubricant candidates that can meet the stringent demands of tribosystems operating in a space environment. At the same time, repair or maintenance are seldom options that are possible in space, and consequently lubricant failures are potentially critical. As international space agencies are converging on the goal of establishing a permanently crewed lunar Gateway for human presence on the Moon and eventually onwards to Mars, there is a need for radical improvements in many aspects of space exploration technology, including space tribology and space grade lubricants. Liquid lubricants are enablers of high performance. A thin fluid film – even in the submicron scale – is often sufficient to separate opposing surface boundaries from direct contact, and thereby prevent excessive friction and wear. Liquid lubricants are therefore attractive for use in space mechanisms. Unfortunately, liquid lubricants must overcome several issues in order to be effective in the space environment. Vacuum, microgravity, and low temperatures are all factors that oppose the effective supply of liquid lubricants into the tribological contact of MMA. If the tribological contact becomes starved of oil, the surfaces enter the boundary lubrication regime where seizure is an ever-present threat. There are very few types of fluids available that meet the stringent space grade lubricant requirements. Perfluoropolyalkylethers (PFPE), or multiply alkylated cyclopentanes (MAC) are two fluids with significant heritage in space applications. These fluids are currently employed as lubricants in a wide range of space applications, as they are rare examples of fluids that meet the high demands on resistance to vacuum outgassing. Unfortunately, these compounds are susceptible to degradation under boundary lubrication conditions, and unlike conventional lubricants employed on Earth, these fluids have poor compatibility with the boundary lubrication additives that are commonly employed in conventional oils. Ionic liquids (ILs) have emerged as potential liquid lubricant candidates in space. These synthetic fluids are composed of anions and cations. The resulting ionic interaction enables the substance to have low vapor pressure with relatively low molecular weight. For this reason, ILs have been advocated as one of the candidate lubricants for space applications. When employing ILs as lubricants, the ionic charge provides Coulombic interaction with surfaces to enable the formation of a boundary lubricating film. This is an important part of the IL lubricating mechanism, but successful lubricant performance requires integrating the lubricant candidate into the tribosystem, taking into account operating conditions and environment. Therefore, the boundary film formation should be tunable to the application at hand. Ionic liquids are designable fluids, with properties dependent on the combination of anion and cation as well as incorporated functional groups. Based on this background, this work focused on evaluating the feasibility of employing ionic liquid lubricants for space applications. In this thesis, the molecular design of an IL lubricant was described Paper [1], and the resulting hydrocarbon-mimicking ionic liquid (P-SiSO) was evaluated in tribological experiments in boundary lubricated conditions. Boundary film formation by neat P-SiSO was studied in Paper [2], and in Paper [3] we describe the use of P-SiSO as a multipurpose performance ingredient in MAC. A test methodology was devised in Paper [4] in order to evaluate the lubrication performance under component scale experiments in space relevant conditions. The designed ionic liquid lubricant was evaluated in Paper [5] by the specific methodology. Advanced surface analysis was employed to understand the tribo-mechanism of P-SiSO in both the model scale experiments as well as the component scale. The lubricated surfaces were analyzed in terms of surface topography- and chemistry, and mechanisms of lubrication are discussed. A highly effective boundary film based on ionic adsorption and formation of silicate was observed by these ionic liquids. This thesis demonstrates the feasibility of employing ionic liquids for lubrication of moving mechanical assemblies in space applications.
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| 9. |
- Nyberg, Erik, 1986-, et al.
(author)
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Ionic Liquids as Performance Ingredients in Space Lubricants
- 2021
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In: Molecules. - Switzerland : MDPI. - 1431-5157 .- 1420-3049. ; 26:4
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Journal article (peer-reviewed)abstract
- Low vapor pressure and several other outstanding properties make room-temperature ionic liquids attractive candidates as lubricants for machine elements in space applications. Ensuring sufficient liquid lubricant supply under space conditions is challenging, and consequently, such tribological systems may operate in boundary lubrication conditions. Under such circumstances, effective lubrication requires the formation of adsorbed or chemically reacted boundary films to prevent excessive friction and wear. In this work, we evaluated hydrocarbon-mimicking ionic liquids, designated P-SiSO, as performance ingredients in multiply alkylated cyclopentane (MAC). The tribological properties under vacuum or various atmospheres (air, nitrogen, carbon dioxide) were measured and analyzed. Thermal vacuum outgassing and electric conductivity were meas- ured to evaluate ‘MAC & P-SiSO’ compatibility to the space environment, including the secondary effects of radiation. Heritage space lubricants—MAC and perfluoroalkyl polyethers (PFPE)—were employed as references. The results corroborate the beneficial lubricating performance of incorporating P-SiSO in MAC, under vacuum as well as under various atmospheres, and demonstrates the feasibility for use as a multifunctional additive in hydrocarbon base oils, for use in space exploration applications.
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| 10. |
- Nyberg, Erik, 1986-, et al.
(author)
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Lubrication Concept Evaluated for Geared Actuators under Starved Conditions
- 2020
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In: 45th Aerospace Mechanisms Symposium. - : National Aeronautics and Space Administration (NASA). ; , s. 255-260
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Conference paper (peer-reviewed)abstract
- Lubricant starvation leads to the risk of a shift in the lubrication regime from (elasto)hydrodynamic towards boundary conditons. Effective tribofilm formation is essential to limit surface damages in these conditions, but additive technology for space-grade lubricants is lacking. This work evaluates the feasibility of a novel type of multifunctional ionic liquid lubricant, for use with multiply alkylated cyclopentane (MAC). Actuator gearboxes are operated under starved conditions in nitrogen atmosphere to evaluate the effectiveness of the tribofilm forming lubricant (designated P-SiSO). The effectiveness of P-SiSO was evaluated from macro to micro scale in both surface and sub-surface analysis by use of microscopy (optical, interferometric, SEM) and X-ray microtomography (XMT), and mechanisms of effective lubrication are discussed.
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| 11. |
- Nyberg, Erik, 1986-, et al.
(author)
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Tribology in Space Robotic Actuators : Experimental Method for Evaluation and Analysis of Gearboxes
- 2021
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In: Aerospace. - : MDPI. - 2226-4310 .- 2226-4310. ; 8:3
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Journal article (peer-reviewed)abstract
- Liquid lubricants are critical to enable long-life operation of high-performance machinery, such as geared actuators employed in robotics. In space applications, actuator gearboxes must operate in low temperatures, where liquid lubricants face inherent problems related to low temperature rheology. Heaters are relied upon to provide acceptable gearbox temperatures. Unfortunately, heating is energy-intense and does not scale well with increasing mechanism mass and performance. Effective boundary lubrication (BL), on the other hand, can minimize problems of low temperature rheology. BL relies on tribofilm formation over conventional fluid film separation. Effective space grade boundary lubricants can potentially allow for drastically reduced amounts of oil and the accompanying rheological problems. In this work, we describe the design of a methodology to evaluate and analyze tribology of actuator gearboxes operated under cryogenic oil-starved conditions in N2 atmosphere. The devised methodology enables research pertinent to space actuator tribology by accelerated testing and advanced analysis, as demonstrated by a lubricant candidate case study. Complementary microscopy techniques are discussed, and a novel methodology devised for gear internal microstructure analysis by X-ray microtomography (XMT) is presented.
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| 12. |
- Nylander, Erik, 1986-, et al.
(author)
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Growth hormone increases dendritic spine density in primary hippocampal cell cultures
- 2020
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In: Growth Hormone & IGF Research. - : Elsevier BV. - 1096-6374 .- 1532-2238. ; 50, s. 42-47
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Journal article (peer-reviewed)abstract
- Objective: Growth hormone (GH) is widely known for its peripheral effects during growth and development. However, numerous reports also suggest that GH exert pro-cognitive, restorative, and protective properties in the brain. In in vitro studies, the detection of dendritic spines, small protrusions extending from axons, can act as a marker for cognition-related function as spine formation is considered to be associated with learning and memory. Here we show that an acute 24-hour treatment of GH can increase dendritic spine density in primary hippocampal cell cultures.Design: Primary hippocampal cells were harvested from embryonic Wistar rats and cultured for 14 days. Cells were treated with supra-physiological doses of GH (10-1000 nM) and subjected to a high-throughput screening protocol. Images were acquired and analyzed using automated image analysis and the number of spines, spines per neurite length, neurite length, and mean area of spines, was reported.Results: GH treatment increased dendritic spine density using the highest dose while the general health of the cells was unaffected.Conclusion: The results from the present study further confirms a potential role of GH in the treatment of cognitive dysfunction.
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| 13. |
- Nylander, Erik, 1986-, et al.
(author)
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The effects of morphine, methadone, and fentanyl on mitochondria : A live cell imaging study
- 2021
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In: Brain Research Bulletin. - : Elsevier. - 0361-9230 .- 1873-2747. ; 171, s. 126-134
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Journal article (peer-reviewed)abstract
- The important role of mitochondria in maintaining normal brain cell function has been demonstrated in several neurodegenerative diseases where mitochondrial dysfunction is a prominent feature. Accumulating evidence indicates that opioids may induce neuronal cell death and inhibit neurogenesis, two factors that are dependent on normal mitochondrial function. The aim of the present study was to examine the effects of morphine, methadone, and fentanyl on mitochondrial morphology. Cells from the neuroblastoma/glioma hybrid cell-line NG108-15 were seeded on 96-well cell culture plates and treated with MitoTracker™ for 30 min prior to opioid treatment. Morphine, methadone, and fentanyl were added at various concentrations and images of mitochondria were acquired every 30 min for four hours using a high-content imaging device. The morphological parameters total mitochondrial area, mitochondrial network, number of mitochondrial objects, and the mean area of mitochondrial objects were analyzed using automated image analysis. Methadone and fentanyl, but not morphine, decreased the mitochondrial network, the number of mitochondrial objects, and increased the mean area of mitochondrial objects. Both methadone and fentanyl altered mitochondrial morphology with no effects seen from morphine treatment. These data suggest that methadone and fentanyl disrupt mitochondrial morphology, which may contribute to neuronal cell death.
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| 14. |
- Pirker, Franz, et al.
(author)
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Tribological Characterisation Services for Materials – i-TRIBOMAT
- 2020
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In: Tribologie und Schmierungstechnik. - : Expert Verlag. - 0724-3472. ; 67:5-6, s. 35-50
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Journal article (peer-reviewed)abstract
- Um den Entwicklungsprozess von neuen Komponenten zu beschleunigen, ist die Vorrausage der Eigenschaften der eingesetzten Werkstoffe im Betrieb der Komponenten von enormer Bedeutung. Um neue Werkstoffe hinsichtlich Ihrer Performance (in einer Komponente) bewerten zu können, ist deshalb die Entwicklung neuer innovativer Methoden notwendig. Diese Methoden können auch unter dem Begriff „lab-to-field“ oder „materials“ – up-scaling zusammengefasst werden. D. h. Werkstoffe werden im Labor charakterisiert, und deren Eigenschaften mittels z.B. Simulation auf die Komponentenperformance hochskaliert (upscaling). i-TRIBOMAT ist ein EU gefördertes Projekt (H2020, GA Nr. 814494) mit dem Ziel ein Open Innovation Test Bed für tribologische Werkstoffcharakterisierung aufzubauen und ent-sprechende Services von der tribologischen Charakterisierung neuer Werkstoffe bis hin zu Simulationsmodellen zur Vorrausage der Perfomance von Komponenten der Industrie anzubieten. Durch die Bündelung von Knowhow und Infrastruktur zu Charakterisierung sowie den Aufbau einer digitalen Plattform, wird i-TRIBOMAT das weltgrößte Open Innovation Test Bed für tribologische Werkstoffcharakterisierung.
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| 15. |
- Tanguay, Sophie, et al.
(author)
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Reference equations for quadriceps strength, endurance and power : a multicentre study
- 2023
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In: ERJ Open Research. - : European Respiratory Society. - 2312-0541. ; 9:4
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Journal article (peer-reviewed)abstract
- Introduction: The lack of reference values of lower-limb muscle function hinders the clinical recommendations of its measurement in patients with COPD. Therefore, this study aimed to develop reference equations to predict reference values for quadriceps strength, endurance and power and evaluate their construct validity in patients with COPD.Methods: Quadriceps strength, endurance and power were assessed in 158 healthy individuals and 87 patients with COPD. In addition, patients with COPD performed a 6-min walk test (6MWT) and a 1-min sit-to-stand test (1STS). Multiple linear regressions were performed to develop reference equations. The proportion of patients with COPD with reduced quadriceps function was determined, and correlations between quadriceps strength, endurance and power expressed in percentage of predicted values and 6MWT and 1STS performance were used to document the construct validity of the reference equation.Results: Except for quadriceps isometric endurance, the proposed reference equations explained 50-70% of the variance of the quadriceps properties in healthy individuals. All quadriceps properties were systematically reduced in a large proportion of patients with COPD compared to healthy individuals. Correlation coefficients between quadriceps properties expressed in percentage of predicted values and 6MWT and 1STS performance ranged between 0.28 and 0.49 (all p<0.05).Conclusion: In healthy individuals, age, sex, height and body mass index explained 50-70% of the variance of quadriceps strength, endurance and power. When expressed in percentage of predicted values, these quadriceps properties correlated with 6MWT and 1STS performance, suggesting construct validity of the reference values in patients with COPD.
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| 16. |
- Zelleroth, Sofia, 1990-, et al.
(author)
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Structurally different anabolic androgenic steroids reduce neurite outgrowth and neuronal viability in primary rat cortical cell cultures
- 2021
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In: Journal of Steroid Biochemistry and Molecular Biology. - : Elsevier BV. - 0960-0760 .- 1879-1220. ; 210
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Journal article (peer-reviewed)abstract
- The illicit use of anabolic androgenic steroids (AAS) among adolescents and young adults is a major concern due to the unknown and unpredictable impact of AAS on the developing brain and the consequences of this on mental health, cognitive function and behaviour. The present study aimed to investigate the effects of supra-physiological doses of four structurally different AAS (testosterone, nandrolone, stanozolol and trenbolone) on neurite development and cell viability using an in vitro model of immature primary rat cortical cell cultures. A high-throughput screening image-based approach, measuring the neurite length and number of neurons, was used for the analysis of neurite outgrowth. In addition, cell viability and expression of the Tubb3 gene (encoding the protein beta-III tubulin) were investigated. Testosterone, nandrolone, and trenbolone elicited adverse effects on neurite outgrowth as deduced from an observed reduced neurite length per neuron. Trenbolone was the only AAS that reduced the cell viability as indicated by a decreased number of neurons and declined mitochondrial function. Moreover, trenbolone downregulated the Tubb3 mRNA expression. The adverse impact on neurite development was neither inhibited nor supressed by the selective androgen receptor (AR) antagonist, flutamide, suggesting that the observed effects result from another mechanism or mechanisms of action that are operating apart from AR activation. The results demonstrate a possible AAS-induced detrimental effect on neuronal development and regenerative functions. An impact on these events, that are essential mechanisms for maintaining normal brain function, could possibly contribute to behavioural alterations seen in AAS users.
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