Correlation between machining direction, cutter geometry and step-over distance in 3-axis milling: Application to milling by zones.

Computer-Aided Manufacturing (CAM) occupies an increasingly important role in engineering with all it has to offer in terms of new possibilities and improving designer/manufacturer productivity. The present study addresses machining of free-form surfaces on a 3-axis NC machine tool. There have recently been a large number of studies devoted to planning tool paths on free-form surfaces with various strategies being adopted. These strategies are intended to increase efficiency by reducing the overall length of machining. Often, the choice of the cutter is arbitrary and the work focuses on planning. In order to boost productivity, the present work offers assistance in choosing the cutting tool, the machining direction and cutting by surface zones, adopting a milling strategy by parallel planes. To do so, a comparison is made between milling using a spherical end milling cutter and a torus end milling cutter with the same outer radius. This comparison relates to the radius of curvature of the trace left by the cutter at the point of contact between the tool and the workpiece in relation to the direction of feed motion

Etude du comportement dynamique des outils toriques en usinage 5 axes

Notre étude a pour but de mieux comprendre le comportement d'outils toriques de faibles diamètres lors de l'usinage de surfaces gauches. Des approches théorique et expérimentale ont été couplées. L'étude théorique s'attache à déterminer la relation entre la stratégie utilisée en terme de trajectoires outil (plans parallèles, Z constant, ...) et le comportement dynamique de l'outil en usinage. La partie expérimentale a permis d'analyser le comportement vibratoire de l'outil lors de la coupe pour différentes stratégies d'usinage. Pour cela, des analyses acoustiques, ainsi que des mesures dimensionnelles et d'états de surface ont été menées. Cela nous permet de définir des règles de construction de parcours d'usinage de surfaces complexes avec ce type d'outils. En effet, certaines stratégies s'avèrent préjudiciables à la qualité d'usinage et à la durée de vie d'outil alors que d'autres apportent une réelle amélioration sur la qualité de la pièce usinée

Numerical and experimental investigations of Ti-6Al-4V chip generation and thermo-mechanical couplings in orthogonal cutting

The chip formation mechanism of the Ti-6Al-4V remains a challenging problem in the machining process as well as its modeling and simulation. Starting from experimental observation on the titanium alloys Ti-6Al-4V machining shows that the ductile fracture in the chip formation is dominated by the shear phenomenon under high strain rate and temperature, the present work develops a new coupled behavior and damage model for better representation and understanding of the chip formation process. The behavior and damage of Ti-6Al-4V have been studied via hat-shaped specimen under temperature up to 900 °C and strain rate up to 1000 s−1. An inverse identification method based on Finite Element (FE) is established in order to determine the constitutive law’s parameters. The prediction of the segmented chip was analyzed through 3D finite element orthogonal cutting model which was validated by an in-situ and post-mortem orthogonal cutting machining observations. Finally, a particular attention is focused on the chip formation genesis which is described by three steps: Growth, Germination and Extraction

PHACTR1 genetic variability is not critical in small vessel ischemic disease patients and PcomA recruitment in C57BL/6J mice

Recently, several genome-wide association studies identified PHACTR1 as key locus for five diverse vascular disorders: coronary artery disease, migraine, fibromuscular dysplasia, cervical artery dissection and hypertension. Although these represent significant risk factors or comorbidities for ischemic stroke, PHACTR1 role in brain small vessel ischemic disease and ischemic stroke most important survival mechanism, such as the recruitment of brain collateral arteries like posterior communicating arteries (PcomAs), remains unknown. Therefore, we applied exome and genome sequencing in a multi-ethnic cohort of 180 early-onset independent familial and apparently sporadic brain small vessel ischemic disease and CADASIL-like Caucasian patients from US, Portugal, Finland, Serbia and Turkey and in 2 C57BL/6J stroke mouse models (bilateral common carotid artery stenosis [BCCAS] and middle cerebral artery occlusion [MCAO]), characterized by different degrees of PcomAs patency. We report 3 very rare coding variants in the small vessel ischemic disease-CADASIL-like cohort (p.Glu198Gln, p.Arg204Gly, p.Val251Leu) and a stop-gain mutation (p.Gln273*) in one MCAO mouse. These coding variants do not cluster in PHACTR1 known pathogenic domains and are not likely to play a critical role in small vessel ischemic disease or brain collateral circulation. We also exclude the possibility that copy number variants (CNVs) or a variant enrichment in Phactr1 may be associated with PcomA recruitment in BCCAS mice or linked to diverse vascular traits (cerebral blood flow pre-surgery, PcomA size, leptomeningeal microcollateral length and junction density during brain hypoperfusion) in C57BL/6J mice, respectively. Genetic variability in PHACTR1 is not likely to be a common susceptibility factor influencing small vessel ischemic disease in patients and PcomA recruitment in C57BL/6J mice. Nonetheless, rare variants in PHACTR1 RPEL domains may influence the stroke outcome and are worth investigating in a larger cohort of small vessel ischemic disease patients, different ischemic stroke subtypes and with functional studies

PHACTR1 genetic variability is not critical in small vessel ischemic disease patients and PcomA recruitment in C57BL/6J mice

Recently, several genome-wide association studies identified PHACTR1 as key locus for five diverse vascular disorders: coronary artery disease, migraine, fibromuscular dysplasia, cervical artery dissection and hypertension. Although these represent significant risk factors or comorbidities for ischemic stroke, PHACTR1 role in brain small vessel ischemic disease and ischemic stroke most important survival mechanism, such as the recruitment of brain collateral arteries like posterior communicating arteries (PcomAs), remains unknown. Therefore, we applied exome and genome sequencing in a multi-ethnic cohort of 180 early-onset independent familial and apparently sporadic brain small vessel ischemic disease and CADASIL-like Caucasian patients from US, Portugal, Finland, Serbia and Turkey and in 2 C57BL/6J stroke mouse models (bilateral common carotid artery stenosis [BCCAS] and middle cerebral artery occlusion [MCAO]), characterized by different degrees of PcomAs patency. We report 3 very rare coding variants in the small vessel ischemic disease-CADASIL-like cohort (p.Glu198Gln, p.Arg204Gly, p.Val251Leu) and a stop-gain mutation (p.Gln273*) in one MCAO mouse. These coding variants do not cluster in PHACTR1 known pathogenic domains and are not likely to play a critical role in small vessel ischemic disease or brain collateral circulation. We also exclude the possibility that copy number variants (CNVs) or a variant enrichment in Phactr1 may be associated with PcomA recruitment in BCCAS mice or linked to diverse vascular traits (cerebral blood flow pre-surgery, PcomA size, leptomeningeal microcollateral length and junction density during brain hypoperfusion) in C57BL/6J mice, respectively. Genetic variability in PHACTR1 is not likely to be a common susceptibility factor influencing small vessel ischemic disease in patients and PcomA recruitment in C57BL/6J mice. Nonetheless, rare variants in PHACTR1 RPEL domains may influence the stroke outcome and are worth investigating in a larger cohort of small vessel ischemic disease patients, different ischemic stroke subtypes and with functional studies.</p

PHACTR1 genetic variability is not critical in small vessel ischemic disease patients and PcomA recruitment in C57BL/6J mice

Recently, several genome-wide association studies identified PHACTR1 as key locus for five diverse vascular disorders: coronary artery disease, migraine, fibromuscular dysplasia, cervical artery dissection and hypertension. Although these represent significant risk factors or comorbidities for ischemic stroke, PHACTR1 role in brain small vessel ischemic disease and ischemic stroke most important survival mechanism, such as the recruitment of brain collateral arteries like posterior communicating arteries (PcomAs), remains unknown. Therefore, we applied exome and genome sequencing in a multi-ethnic cohort of 180 early-onset independent familial and apparently sporadic brain small vessel ischemic disease and CADASIL-like Caucasian patients from US, Portugal, Finland, Serbia and Turkey and in 2 C57BL/6J stroke mouse models (bilateral common carotid artery stenosis [BCCAS] and middle cerebral artery occlusion [MCAO]), characterized by different degrees of PcomAs patency. We report 3 very rare coding variants in the small vessel ischemic disease-CADASIL-like cohort (p.Glu198Gln, p.Arg204Gly, p.Val251Leu) and a stop-gain mutation (p.Gln273*) in one MCAO mouse. These coding variants do not cluster in PHACTR1 known pathogenic domains and are not likely to play a critical role in small vessel ischemic disease or brain collateral circulation. We also exclude the possibility that copy number variants (CNVs) or a variant enrichment in Phactr1 may be associated with PcomA recruitment in BCCAS mice or linked to diverse vascular traits (cerebral blood flow pre-surgery, PcomA size, leptomeningeal microcollateral length and junction density during brain hypoperfusion) in C57BL/6J mice, respectively. Genetic variability in PHACTR1 is not likely to be a common susceptibility factor influencing small vessel ischemic disease in patients and PcomA recruitment in C57BL/6J mice. Nonetheless, rare variants in PHACTR1 RPEL domains may influence the stroke outcome and are worth investigating in a larger cohort of small vessel ischemic disease patients, different ischemic stroke subtypes and with functional studies

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

ANALYSE QUALITATIVE DES PARAMÈTRES INFLUENTS POUR LA PLANIFICATION DES TRAJECTOIRES SUR SURFACES GAUCHES

Work done for the following PhD Thesis “Qualitative analysis of influential parameters for cutter paths planning on free-form surfaces” has two main topics.First one is about machining free-form surfaces by end-milling in 3 axis NC-Machine Tool. Lots of plannings have been yet developed, but productivity and quality are more and more important and new planning needs to be developed: solution is “iso-scallop planning”. To be sure that the developement of iso-scallop planning will be fine we first need to analyse the influential parameters: choice of the first trajectory and choice the work-piece orientation.The second goal is about side milling of ruled surfaces using milling cutter. Researches are about positioning the milling cutter to minimize the error between the milled surface and the theoretical surface.Le travail qui a été effectué lors de la thèse intitulée « Analyse qualitative des paramètres influents pour la planification des trajectoires sur surfaces gauches » suit principalement deux axes de recherche. Le premier concerne l’usinage en bout des surfaces gauches sur Machine Outil à Commande Numérique à 3 axes (MOCN 3 axes). De nombreuses stratégies d’usinage ont été développées par le passé, mais les exigences de productivité et de qualité présentes dans l’industrie nous a incité à nous intéresser à la planification de trajectoires à hauteur de crête constante. Le principe de cette nouvelle stratégie ainsi que l’analyse de ses paramètres influents (choix de la première trajectoire et du positionnement de la surface à usiner) sont étudiés. Il est nécessaire de maîtriser ces deux critères pour assurer un bon déroulement de la planification isocrête.Le second axe de recherche concerne le positionnement de l’outil pour l’usinage en roulant sur MOCN à 5 axes : plusieurs positionnements sont développés et comparés avec les positionnements existants à partir de l’erreur d’usinage générée. Une méthode de choix des dimensions de l’outil est proposée ainsi qu’une analyse de l’apparition de l’erreur d’usinage

Analyse qualitative des paramètres influents pour la planification des trajectoires sur surfaces gauches

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF