Comportement vibratoire de rotors operant a hautes vitesses et detection des defauts de roulements.

摘要

This thesis is aimed at bringing more insights to the dynamic behavior of high spindles when supported by ball bearings, with localized defects infecting the surface of some of their moving parts. The analysis is based on a numerical model that simulates the response of the rotor and its two supporting bearings and takes into consideration the gyroscopic effect arising at high speed and its influence on the drift of the system natural frequencies. By conducting such investigation, and integrating the non-linearity of the dynamic parameters under Coriolis Forces, we seek a fundamental understanding of high speed machining dynamics that may lead to a better adjustment of the stability conditions, and a better surface quality of the cutting process. The developed model forms the basis of a numerical simulator, capable of generating the vibration response of the entire set spindle-bearings. Several interesting features have been added to the simulator to make the results closer to reality. In particular, we can name the nonlinear behaviour of spindle shaft in high speeds and also the existence of surface localized defect on the bearings moving parts.;Moreover, this research work clearly reveals that high speed spindles cannot be considered as conventional machines. Consequently, in the decision making process, any reliable diagnosis has to consider both vibrations indicators and cutting parameters. Based on this fact, we succeeded in this thesis to develop an innovative experimental tool dedicated to CNC spindles monitoring, which is able to measure in real time the vibration parameters (and forces, sound, current) and the cutting parameters (tridimensional position XYZ, instantaneous speed, current tool, instantaneous power consumption) through a communication protocol with the machine controller.;Since several journal articles and conference papers have already been published or submitted from this research, the thesis by publication format, also known as an article thesis, is chosen here. It is a collection of research articles with introductory summary chapters and conclusions. Except for the last one, submitted recently for publication in a highly ranked journal, all previous articles were already reviewed and accepted by referees outside ETS, thus assuring international standards.;The first article, already accepted for publication in the International Journal of Condition Monitoring and Diagnostic Engineering Management (COMADEM), presents the ESD (Envelop Shock Detector) as a new automated signal processing technique for bearings defects. It allows the detection of bearings shocks, their isolation from harmonic and random components, from the time domain. ESD is applied to distinguish bearings vibration response from gears shocks. ESD could be used also as an input parameter to a Neural Network expert system to perform a proper diagnosis of bearing affected by multiple defects.;The second article, published in the Journal of engineering of industrial risk assessment (Ingenierie des Risques Industriels - IRI), presents a spindle numerical simulator based on a tridimensional model with 20-dof, including gyroscopic effect and allowing transient speed analysis -run up and coast down- with defective bearings. The simulator detects new critical speeds due to the coincidence of excitation forces (bearing fault frequencies) with shaft precession modes (forward and backward) highly harmful to the spindle components life as well as for the machining quality.;The third article, submitted for publication in the International Journal Machines, investigates the influence of high rotational speed on the spindle dynamic behaviour. New natural frequencies appear and vary according to the cutting speed. Machining stability lobes, usually established with static natural frequencies becomes inaccurate and do not describe the true dynamic behaviour of the system. The novelty in the present work is the consideration of the gyroscopic effect -induced by high rotational speeds- in the calculation of new machining stability lobes, and the study of the vibration transmissibility from a defective bearing to the spindle system including the healthy bearing.