Journal bearing lubrication status identication with acoustic emission measurements and data clustering

Les techniques de Machine Learning at de Data Analytics permettent une reconnaissance demandant de ressources informatiques peu co^uteuse en temps de calcul. Dans cette etude, c'est la methode "mean-shift clustering" qui a ete applique. L'algorithme ne necessite pas de specier le nombre de clusters a l'avance car celui-la est determine par l'algorithme en fonction des donnees. Les donnees utilisees pour l'extraction des caracteristiques ont ete mesurees a l'aide d'un systeme d'emission acoustique (AE) a large bande. Les autres parametres contr^oles ont ete le frottement, les temperatures, la charge, la vitesse de glissement et la pression de l'huile. Les materiaux utilises etaient de l'acier cemente 18CrNiMo7-6 et de l'acier nitrure 42CrMo7. Le lubriant utilise etait de l'huile synthetique EP pour engrenages. La temperature du palier a ete maintenue constante. La pression et la vitesse de glissement ont ete variees pendant les tests, ce qui a permis d'obtenir des resultats pour une large gamme en termes de nombre de Hersey. La puissance et la frequence des signaux d'emission acoustique ont ete analysees et les caracteristiques essentielles ont ete extraites pour le traitement des donnees. Le kurtosis, le RMS et le coecient de variation des signaux AE ont ete representes en fonction du nombre de Hersey. Le kurtosis a montre la plus grande sensibilite pour la detection des anomalies. Une sensibilite elevee necessite un ltrage des donnees pour eliminer les pics errones. Des observations ont egalement ete faites sur le niveau de frequence de l'AE en fonction des dierents regimes de lubrication

Micromechanical performance of high-density polyethylene:experimental and modeling approaches for HDPE and its alumina-nanocomposites

The scratch resistance of polymers is important for numerous applications, as scratching can lead to degradation of surface properties and also represents an elementary process in abrasive wear. However, scratching of polymers is a complex process involving several modes of deformation, and theoretical understanding of it is incomplete. Numerical modeling is a potentially useful means towards a clearer picture of the scratching process, but the central role of tip-substrate contact and highly localized large deformations makes finite element analysis (FEA) challenging. Here, we take further the numerical approach by investigating a highly ductile semi-crystalline polymer by FEA and taking the inherent rate dependency of polymers into account by using an elasto-viscoplastic material model. Two γ-Al2O3 and f-Al2O3 HDPE nanocomposites, which have shown themselves to be suitable for tribological applications, are studied. We discussed the effect of nanofillers on the scratch behavior and highlight the significance of recovery properties, which still pose a challenge to numerical modeling

Computer modelling and simulation approach to developing wear resistant materials

VTT researchers have been pioneers in international science with their computer modelling and simulation techniques for the development of coated surfaces with superior wear resistance and low friction properties. They have introduced a novel PPSP (Performance-Properties-Structure-Processing) multi-scale concept that is based on linking wear and friction performance by micro-FEM computer models to mechanical surface properties, surface microstructure and coating processing parameters. The modelling methods have been applied on 1–5 μm thick hard coatings, such as TiN, DLC and MoS2, on steel as well as on about 200 μm thick thermally sprayed WC-CoCr coatings developed through a Process Mapping concept. The novel approach offers completely new possibilities of systematic and focused material development of wear resistant and low friction coated surfaces with the aim to control and prolong the lifetime of machine components and industrial tools

Closing a chapter? A protocol for a longitudinal mixed methods study on retirement from elite sport.

Retirement from elite sport represents a major life transition for athletes and requires them to redefine their central life projects, identities, and perhaps even sources of meaning in life. Although an extensive body of literature has identified risk and protective factors in career termination, little is known about the more subjective processes and individual pathways of athletes as they establish their new relationship with work-life and sport. The planned longitudinal mixed methods study follows Swiss elite athletes' transition with a focus on understanding (1) the relationship between psychological resources, life situations at the end of the sports career, and the retirement process; (2) how athletes' post-retirement vocational careers interact with their subjective careers and sense of meaningful work; (3) how athletes reconstruct their identities and relationship with sport over time; and (4) how gender shapes athletes' pathways and reorientation of their life design.Using a person-oriented approach combined with narrative inquiry, we expect to identify specific types and stories which demonstrate individual differences in career and personal development throughout the transitional period, an understanding of which can be targeted towards support programmes for retiring elite athletes. As the study centralises dimensions of positive psychological functioning (meaning and purpose in life/sport/work, resilience, life satisfaction), it complements previous studies focused on psychological distress and provides much needed knowledge that can be used to foster well-being in athletic retirement. Collaborating with the Swiss Olympic Association helps to ensure that the research findings will be disseminated to relevant end-users and used towards developing socially sustainable elite sport for the future generations

Optical sensor for journal bearing oil film pressure measurements

The oil film pressure is one of the fundamental parameters influencing the operation of journal bearings. The oil film pressure is estimated by theoretical calculations, since the measurement of oil film pressure has been a demanding task in journal bearings, especially in bearings carrying dynamic loads. In this study a new approach to experimentally measure the oil film pressure has been developed and tested. The sensor design utilizes the optical fibre technique and the sensor is integrated in the sliding surface of the bearing thus providing the possibility to measure the actual oil film pressure under load without disturbing the contact conditions. The finite element method (FEM) calculations have been used for optimizing the design of the sensor and for ensuring the appropriate mechanical performance of the sensor design. The optical sensor was integrated into a hydrodynamic journal bearing made of bronze and a versatile bearing test rig was used for testing the operation of the optical sensor. The tests were carried out using both static and dynamic loading conditions with different loads and speeds. The experimental data was compared with the simulated one. The results showed that the optical sensor was capable to measure the oil film pressure in journal bearing at real operating conditions and the sensitivity of the sensor was good enough to verify the speed and load effects on the oil film pressure. According to this work, it is possible to increase the knowledge of true operating conditions of journal bearings by using the optical sensor for oil film pressure measurement. The knowledge can be utilized in the development work of safer and more efficient machines and engines with journal bearing carrying high and dynamic loads. This optical sensor configuration can be used also in other applications for measurement and control of pressure

Novel strain of Pseudoruminococcus massiliensis possesses traits important in gut adaptation and host-microbe interactions

Fecal microbiota transplantation (FMT) is an efficient treatment for recurrent Clostridioides difficile infection and currently investigated as a treatment for other intestinal and systemic diseases. Better understanding of the species potentially transferred in FMT is needed. We isolated from a healthy fecal donor a novel strain E10-96H of Pseudoruminococcus massiliensis, a recently described strictly anaerobic species currently represented only by the type strain. The whole genome sequence of E10-96H had over 98% similarity with the type strain. E10-96H carries 20 glycoside hydrolase encoding genes, degrades starch in vitro and thus may contribute to fiber degradation, cross-feeding of other species and butyrate production in the intestinal ecosystem. The strain carries pilus-like structures, harbors pilin genes in its genome and adheres to enterocytes in vitro but does not provoke a proinflammatory response. P. massiliensis seems to have commensal behavior with the host epithelium, and its role in intestinal ecology should be studied further.Peer reviewe