Optimisation de l'analyse multirésolution en ondelettes des signaux de choc. Application aux signaux engendrés par des roulements défectueux

L'objectif de cet article est de proposer l'analyse multirésolution en ondelettes en tant qu'outil efficace permettant d'améliorer la sensibilité des indicateurs scalaires (kurtosis et facteur de crête) pour l'identification des défauts mécaniques induisant des forces impulsives. En effet, ces indicateurs sont très sensibles aux variations dans le signal temporel dues aux chocs périodiques causés par le défaut. Néanmoins, leur fiabilité est immédiatement limitée en présence de niveaux intenses de bruit aléatoire associés à de faibles gravités du défaut. L'analyse Multirésolution en Ondelettes (AMRO) est proposée comme solution à ce problème. Adaptée pour un tel objectif, plusieurs de ses paramètres d'analyse sont choisis, voire optimisés. Initialement la méthode proposée est appliquée sur un signal simulé. Pour la validation expérimentale, plusieurs séries d'expériences ont été réalisées sur des roulements à billes et à rouleaux cylindriques, sur lesquels différents défauts ont été provoqués. Les mesures ont été prises dans différentes configurations, 210 signaux ont été mesurés dans plusieurs fréquences d'échantillonnage et vitesses de rotation sur un banc d'essais, l'application industrielle est faite sur un groupe turbo-alternateur

Perceptual Study of Simple and Combined Gear Defects

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Experimental Study of Combined Gear and Bearing Faults by Sound Perception

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Prediction of Tool Wear in the Turning Process Using the Spectral Center of Gravity

International audienceThe recent increase in machining productivity is closely related to longer tool life and good surface quality. In the present study, an experimental technique is proposed to evaluate the performance of a cemented carbide inset during the machining of AISI D3 steel. The aim of this technique is to find a relationship between the vibratory state of the cutting tool and the corresponding wear during machining in order to detect the beginning of the transition period to excessive wear. A spectral indicator named spectral center of gravity, SCG, is proposed to highlight the three phases of tool wear using the spectra of the accelerations measured. Very promising results are obtained which can be used to underpin an industrial monitoring system capable of detecting the onset of transition to excessive wear and alerting the user of the end of the tool’s life. The purpose of this study is to review the vibration analysis techniques and to explore their contributions, advantages and drawbacks in monitoring of tool wear

Experimental study of a turbo-alternator in industrial environment using cyclostationarity analysis

International audienceThe cyclostationarity method is used in this paper for the diagnosis of a turbo-alternator working in industrial environment for the detection of the defects generated by rolling bearings, journal bearings, and gears. This study shows the advantage of using such analysis as an aid to diagnosis and decision making before a failure caused by bad vibration monitoring of rotating machinery can be produced. In fact, a cyclostationary signal has some hidden periodicities, which mean that it is not strictly periodic, but some statistical properties of the signal are periodic. This periodicity identifies the spectral correlation by integrating the modulation intensity distribution function that depends only of the cyclic frequency, which is an indicator of the presence of modulations. The method was initially applied on a theoretical signal simulating a single bearing fault. The experimental validation is then performed on the machine faults simulator (MFS) for the detection of a bearing fault, and on a turbo-alternator working in real conditions in industrial environment. The application of this method helped to highlight very clearly the presence of defects on the bearings and the gears, which has been difficult to show especially at low frequency by spectral analysis

Prediction of Optimal Lifetime of the Tool’s Wear in Turning Operation of AISI D3 Steel Based on the a New Spectral Indicator SCG

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