Search results for "Bearing"
showing 10 items of 284 documents
Rib-Roller Wear in Tapered Rolling Element Bearings: Analysis and Development of Test Rig for Condition Monitoring
2020
Rolling Element Bearings (REBs) are present in virtually all machines with moving or rotating parts, and are vital for proper performance and safe operation. Condition Monitoring (CM) of bearings often receive particular interest, as this component group rarely reach design lifetime and hence is responsible for unplanned machine downtime. Unplanned maintenance can represent a large cost which motivates development of improved CM methods for implementation of advanced maintenance regimes. Based on observations of a used bearing from an offshore drilling machine, wear on roller ends in the rib-roller contact area was identified as an area of interest for future research. A test rig for creati…
Observation and Processing of Instantaneous Frequency Variations During Bearing Tests
2020
Laboratory experiments have been performed on medium sized roller bearings with two levels of artificial damage. Recordings of long time series from accelerometers at a wide range of different radial loads and rotation speeds has been performed. Probably due to non-perfect performance of the control systems for the rotational speed or frequency, significant fluctuations were observed at all rotation speeds. The highest relative variation was observed at the lowest rotational speeds. These variations were recorded using a rotary encoder, which allows order tracking of the vibration signal. In real life condition monitoring, tachometers or rotary encoders are not always present, this can be d…
Detection of Incipient Bearing Fault in a Slowly Rotating Machine Using Spline Wavelet Packets
2018
This chapter describes a successful application of spline-based wavelet packet transforms (WPTs) described in Chap. 4 to a complicated problem of detection of incipient defects in rolling element bearings by the analysis of recorded vibration signals. The methodology presented in this chapter is applied to the analysis of vibration data recorded from large bearings working in real unfavorable operation conditions in presence of strong noise and vibrations from multiple internal and external sources. It relies on properties of discrete spline-based wavelet packets such as orthogonality, near-rectangular spectra, transient oscillating shapes of testing waveforms and fast implementation of tra…
Quantitative value of medial femoro-tibial width (FTW) with weight-bearing technique. Our experience with a modified Lyon-Schuss view.
2010
In the period between September 2008 and February 2009, we evaluated with knee radiography a group of 30 patients with known knee osteoarthritis (OA). For each patient, two weight-bearing views of the knee were acquired, the first with a standard antero-posterior (AP) technique, the latter with a posteroanterior (PA) technique with a 10° skull-caudal incidence. The radiographs obtained were evaluated blinded by two radiologist who assessed the medial femoro-tibial width (FTW). Statistical analysis of the results, carried out with the “t” Student test, showed a statistically significant difference about FTW values between the two radiographic views (t = 5.2331 for reader 1 and t=5.1970 for r…
Modelling of thermal stresses in bearing steel structure generated by electrical current impulses
2018
This work is the study of one particular candidate for white etching crack (WEC) initiation mechanism in wind turbine gearbox bearings: discharge current impulses flowing through bearing steel with associated thermal stresses and material fatigue. Using data/results from previously published works, the authors develop a series of models that are utilized to simulate these processes under various conditions/local microstructure configurations, as well as to verify the results of the previous numerical studies. Presented models show that the resulting stresses are several orders of magnitude below the fatigue limit/yield strength for the parameters used herein. Results and analysis of models …
Les formations à silex dans le Sud de la France : Élaboration en multipartenariat d’une base de données géoréférencées, premiers résultats.
2016
A georeferenced database of the main flint-bearing formations of Southern France is currently being finalised. It offers a toolto all prehistorians that is essential for the development of studies regarding raw material circulation and selection criteria. This database results from the collaborative work of various actors involved in the optimisation of flint source determination. It groups together the results of their surveys — whether these are systematic or targeted — carried out in six regions (Aquitaine, Auvergne, Languedoc-Roussillon, Midi-Pyrénées, Provence-Alpes-Côte d’Azur, Rhône-Alpes). This database also incorporates recent studies on registering the properties of palaeoenvironm…
Energy transfer between polyamine chains bearing naphthalene terminal units and k3[Co(CN)6]: An example of a molecular photoreactor
2002
Molecular photoreactors consisting of polyamine chains (receptors) bearing terminal naphthalene units (antennae) are described. The receptors are used to bind the substrate hexacyanocobaltate(III) and the antennae to transfer energy to the complex and thus promote a photoaquation reaction.
Bar-sur-Aube (Aube). 13 rue Beugnot et 2, 4, 10 rue du Prieuré [notice archéologique]
2019
Un projet immobilier de réhabilitation de l’îlot du prieuré Saint-Pierre (dépendance de l’abbaye Saint-Claude dans le Jura), accolé à l’église éponyme, au NO de la ville ancienne de Bar-sur-Aube, a entraîné la prescription d’un diagnostic archéologique sur les deux « cours » concernées par le projet et sur une analyse du potentiel archéologique conservé en élévation. Ce diagnostic a montré d’importants aménagements médiévaux encore conservés au sein du prieuré Saint-Pierre dont la création est antérieure au milieu du XIIe s., tant dans les élévations que dans les données stratigraphiques. Bien que les remaniements modernes et contemporains soient conséquents, et caractéristiques d’une opéra…
Evaluation of Load transfer in rigid pavements by Rolling wheel deflectometer and Falling weight deflectometer
2020
Abstract Rigid pavements have widespread use, e.g, in motorways and airports, due to their excellent properties such as high bearing capacity and long lifetime. However, when rigid pavements fail it is often due to bad load transfer efficiency (LTE) at its joints. Traditional methods of measuring LTE can be time consuming. Here, we study the possibility of measuring LTE using a moving load with the aim of achieving higher productivity. An experiment simulating Rolling Weight Deflectometer (RWD) measurements on a joint was carried out to gain understanding and confidence that can guide the analysis of real RWD data. Continuous data from measurements across a joint allows for determination of…
A theoretical study of the selectivity for the domino [5+2]/[4+2] cycloadditions of γ-pyrones bearing tethered alkenes with substituted 1,3-butadienes
2001
Abstract Selectivity of the domino [5+2]/[4+2] cycloaddition reactions of a β-silyloxy-γ-pyrone bearing a tethered alkene with two substituted 1,3-butadienes have been theoretically studied at the B3LYP/6-31G∗//AM1 and B3LYP/6-31G∗ computational levels. Analysis of these results allow explaining the regio, stereo and chemoselectivity observed experimentally at these domino reactions. Selectivity outcome is reproduced by these calculations.