Academic literature on the topic 'Machine axiale sans fer'

AbstractTunnel construction below or adjacent to piles will affect the performance and eventually the stability of piles due to ground deformation resulting in the movement of piles and changes in the axial force distribution along the piles. A three dimensional finite element analysis using PLAXIS 3D (2013) was performed to study the behaviour of a single pile and 3 x 3 piles group during the advancement of shield tunnelling in ground. The 10-node tetrahedral elements were used to model both the soil and the tunnel lining. The Hardening Soil (HS) model was used to simulate the soil structure interaction at the tunnel-soil interface. An isotropic elastic model was used for the pile, piles cap, tunnel lining and tunnel boring machine shield (TBM). Several parametric studies were attempted including the longitudinal, lateral, and vertical tunnel location relative to pile embedded in different types of soil (clay or sand). The results showed that the pile head settlement increases during the tunnelling advancement in larger values than that for ground surface settlement. A zone of influence was determined in the range of twice the tunnel diameter in the longitudinal direction (forward and backward of the pile), and transverse direction (left and right of the tunnel centreline). If the tunnel boring is kept off this zone then there is no fear of pile collapse.

Construction des équations de fonctionnement tenant compte des discontinuités de conduction dans le système convertisseur machine. Linéarisation par les séries de Fourier. Résolution par une méthode itérative. Application à l'optimisation de l'entraînement

Les travaux présentés s'inscrivent dans le contexte de la micro-génération et de la gestion
d'énergie pour systèmes autonomes. Il s'agit du développement d'un micro générateur
discoïde, à aimants, sans fer et compatible avec des μ-turbines à gaz ou à air comprimé
opérant à haute vitesse de rotation (10 – 1 000 ktr/min). Le modèle multi-physique établi
permet d'évaluer la performance des μ-générateurs magnétiques en fonction de leurs
conditions de travail et de leurs paramètres géométriques. Un premier prototype intégré
produit une puissance de 15 mW à 60 000 tr/min, un second prototype produit 5 W à 380 000
tr/min avec ηel ≈ 57 %.
Les convertisseurs de faible puissance associés aux micro-alternateurs triphasés basse
tension sont ensuite étudiés. Un micro-redresseur triphasé, sans seuil et entièrement autonome
a été monolitiquement intégré en technologie CMOS 0,35 μm. La caractérisation a prouvé sa
pleine fonctionnalité ainsi que les bonnes performances.

The collapse strength of tubulars with recess patterns machined into their walls is an important topic for oilfield downhole tools as it applies to perforating guns, prepacked sand screens, and perforated and slotted liners. This paper presents a study of the plastic collapse behavior of thick-walled tubulars (those with an outside diameter to thickness ratio of approximately 10) having different patterns of circular recesses (blind holes partially machined into the tubing wall) that are subjected to external pressure. An empirical relationship between the reduction in collapse strength and the periodic distribution of recesses was constructed to account for the weakening effects of recess diameter, recess depth, axial spacing, angular phasing, etc. This strength reduction factor was introduced into the Tamano formula to predict collapse strength of recessed tubulars. Applicability of this empirical formula was validated with the aid of nonlinear, post-buckling Finite Element Analyses (FEA). The modeling approach was verified by full-scale physical tests. However, results of the physical testing are not presented in this paper. The strength reduction factor in combination with the Tamano formula provides a simple way of parametrically predicting the collapse strength of tubulars having circular recess patterns.

Circular saws are a common tool for cutting a variety of materials like stone, wood or alloys. Cutting results are significantly influenced by vibrations occurring during processing. Negative consequences are for example increased cutting width and noise emissions. Vibration results from impulses generated at the entrance of the tool teeth into the work piece, from axial run of the cutting tool as well as vibrations transmitted from the machines drive. Therefore, the implementation of effective and cost efficient damping measures is of significant interest. Passive damping approaches are favored because of their low costs. One approach to dampen vibrations in circular tools and tool flanges passively is the use of shape memory alloys (SMA) as damping elements. SMA and especially NiTi are able to convert large amounts of mechanical stress into heat energy by a stress induced austenite-martensite phase transformation providing the potential to dampen vibrations with more compact damping elements in contrast to other common damping materials like steel or copper used in circular saws. SMA are suitable for damping low frequencies at high amplitudes, e.g. during earthquakes and the damping of single or repetitive shocks, such as those occurring in positioning. The attenuation of higher-frequency vibrations caused by machining with fast rotating cutting tools has so far been considered inadequate but has not been sufficiently investigated in relevant frequency ranges for industrial circular saws. This paper compares the damping properties of NiTi to those of copper and steel for industrial circular saws. Therefore, the first chapter introduces different sources and types of vibrations in industrial cutting processes while the second chapter describes exemplarily the vibrations occurring in an industrial circular saw. Based on this, the third chapter illustrates common approaches to modify the static and dynamic behavior of circular saws. The fourth chapter gives a brief description of internal damping mechanism, especially the damping mechanism of SMA. The experimental methodology and evaluation of NiTi, steel and copper is in the focus of the fifth chapter. The paper concludes with a summary of findings and an outlook on following work packages.