MODELLING OF GEAR CHANGING BEHAVIOUR

This paper deals with the modelling of the gear changing behaviour. After presentation of the main synchronizer tasks, the state of the art is described. Reconsideration of the gear changing process allows better definition of synchronizer working phases. Based on this, a numerical simulation software of the synchronizer behaviour has been realized. Phenomena of angular velocity synchonization and second bump in gear changing force are modelled in details. Various mechanical behaviour influencing phenomena are taken into consideration with large number of input parameters. The software is validated with literature data. Then, it is used to investigate the effect of main parameters considered with gear changing process for a 5 speed manual car gearbox. Effects of gear changing force, synchronized inertia and initial angular velocity difference variations are shown. Visualization of parameter effects such as angle error of synchronizer cone and relative position of gear splines and sleeve splines help for better understanding of gearbox behaviour during gear changing

High frequency correction of dynamometer for cutting force observation in milling

International audienc

Tool wear detection in milling-an original approach with a non-dedicated sensor

International audienceThe aim of increasing productivity often makes optimising processes a priority and a means of anticipating defects. Metal cutting conditions are monitored to detect tool wear or breaks, so as to protect both machines and workpieces. Such monitoring relies on many different signals though two main approaches can be considered. The first consists in adding numerous sensors to the machine to obtain specific information, such as vibrations and cutting forces. The second consists in using information, often current or shaft power consumption, that can already be obtained from the machine and detected by standard sensors.This work focuses on the second approach that relies on using the sensors already installed, but optimising their capacities to the maximum for use under industrial conditions. The spindle rotary encoder signal is acquired through two systems: the first uses classical time-sampling while the second uses specific angular-sampling methodology. The differences between the two rotational frequency calculation technologies are described and discussed before focusing on the second methodology. Comparisons of cutting forces and variations in spindle rotational frequency reveal considerable similarities. Thus the occurrence of tool wear can be observed by monitoring variations in rotational frequency, and the genesis of tool tooth breaks can be established. Finally, we establish criteria for critical wear detection in both time and frequency domains

Simulation model of dispersions in turning process

9 pages.International audienceTo control and to optimise the product/process pair, manufacturing companies are more and more directed to use software tools performing virtual simulations. In this way, let us consider that one important aim of the virtual or numerical simulation of process planning is to study and take into account the machining dispersions. The global intend is to predict the intervals of tolerances of a series of manufactured parts and to compare with the specifications due to the design office. The general objective of this work is to extend the field of application and to increase the knowledge about machining dispersion simulations. This study, based on design of experiment, aims to confirm the hypothesis retained for an initial model designed to help process planning and validate chronology, sequencing, and elementary operations. In this paper, an extent of the simulation model of dispersions in turning process first exposed in [W1], is developed. This initial work is based on the characterisation and the taking into account of the geometrical default generated by the turning process. An integration of the parameters relative to the cutting conditions and to the machined and cutting materials is now proposed. The link between these parameters and the input data of the initial model is explained. An application is developed to illustrate the associated methodology. The effect of each cutting parameter on machining dispersions has been shown and quantified

Analyse et modelisation des systemes mecaniques en conception assistee par ordinateur: application a la simulation du comportement statique des boites de transmission de puissance d'helicopteres

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Hard machining of hardened bearing steel using cubic boron nitride tool

International audienc

Decision-making process, outcome, and 1-year quality of life of octogenarians referred for intensive care unit admission.

OBJECTIVE: To describe triage decisions and subsequent outcomes in octogenarians referred to an ICU. DESIGN AND SETTING: Prospective observational study in the medical ICU in a tertiary nonuniversity hospital. PARTICIPANTS: Cohort of 180 patients aged 80 years or over who were triaged for admission. MEASUREMENTS: Age, underlying diseases, admission diagnoses, Mortality Probability Model score, and mortality were recorded. Self-sufficiency (Katz Index of Activities of Daily Living) and quality of life (modified Perceived Quality of Life scale and Nottingham Health Profile) were measured 1year after triage. RESULTS: In 132 patients (73.3%) ICU admission was refused, including 79 (43.8%) considered too sick to benefit. Factors independently associated with refusal were nonsurgical status, age older than 85 years, and full unit. Greater self-sufficiency was associated with ICU admission. Hospital mortality was 30/48 (62.5%), 56/79 (70.8%), 9/51 (17.6%), and 0/2 in the admitted, too sick to benefit, too well to benefit, and family/patient refusal groups, respectively; 1-year mortality was 34/48 (70.8%), 69/79 (87.3%), 24/51 (47%), and 0/2, respectively. Self-sufficiency was unchanged by ICU stay. Quality of life (known in only 28 patients) was significantly poorer for isolation, emotional, and mobility domains compared to the French general population matched on sex and age. CONCLUSIONS: More than two-thirds of patients aged over 80 years referred to our ICU were denied admission. One year later self-sufficiency was not modified and quality of life was poorer than in the general population. These results indicate a need to discuss patient preferences before triage decisions

Analysis of surface roughness and cutting force components in hard turning with cbn tool: prediction model and cutting conditions optimization

International audienc

On the identification conditions of a constitutive model in machining of AISI 1045 steel

International audienc

On the identification conditions of a constitutive model in machining of aisi 1045 steel

International audienc