2,124 research outputs found
Links Between Machining Parameters and Surface Integrity in Drilling Ni-Superalloy
In aerospace industry, the manufacturing of critical parts (high energy components) requires an important validation process to guarantee the quality of the produced parts, and thus their fatigue lifecycle. Globally, this validation consists in freezing the cutting conditions using metallurgical analysis or fatigue trials, and a test on the first article. This process is extremely complex and expensive. In this way establishing the correlation between the cutting conditions and the surface integrity will help us to optimize the manufacture of those parts. In this article, by the means of an experimental method, we define a domain of validation by combining the cutting conditions according to the classic criteria established by AFNOR E66-520 norm (Couple-Tool-Material) and the criteria of surface integrity for the drilling of a Nickel-base superalloy. The experimental device consists in drilling a Ă15.5 mm hole on a 3-axis milling centre instrumented by a 4 components Kistler dynamometer (Fx, Fy, Fz and Mz), a spindle power sensor âWatt-piloteâ and three accelerometers placed following the directions X, Y and Z. Scanning Electron Microscopy (SEM) observations, micro-hardness tests and topographic measurements with an optical profilometer, are carried out to characterize the metallurgical state of the holes manufactured. Finally, correlations were respectively made between the cutting conditions, the recorded signals and the metallurgical state of the holes
Identification of influent factors on surface integrity in nickel-base superalloy drilling
For the critical rotating components in aeronautical industry, the metallurgical quality achieved after machining conditions could determine their mechanical behaviour in fatigue. To guarantee this quality, the tools, materials and cutting conditions are frozen during the validation process by a cutup part following by an acceptable surface integrity. Even with the fixed parameters, perturbations can occur during the process and may have a direct impact over the metallurgical quality through the apparition of anomalies, which could reduce the calculated fatigue life. The aim of this study is to define
a Process Monitoring technique able to detect the thickness affected by the machining taking into account
the flank wear effect
A Bose-Einstein condensate bouncing off a rough mirror
We present experimental results and theoretical analysis of the diffuse
reflection of a Bose-Einstein condensate from a rough mirror. The mirror is
produced by a blue-detuned evanescent wave supported by a dielectric substrate.
The results are carefully analysed via a comparison with a numerical
simulation. The scattering is clearly anisotropic, more pronounced in the
direction of the evanescent wave surface propagation, as predicted
theoretically
Raconter sa journée : des histoires de conversations dans la conversation
La conversation prend une forme spĂ©cifique lorsque des proches « racontent leur journĂ©e », rĂ©capitulent leurs occupations rĂ©centes. Cette forme tient notamment au fait que ces occupations sont gĂ©nĂ©ralement elles-mĂȘmes des conversations. Elle est une activitĂ© conversationnelle qui a ses rĂšgles propres et mĂ©rite dâĂȘtre prise en compte. Notre recherche repose sur des donnĂ©es qui 1o font rĂ©fĂ©rence Ă des Ă©vĂ©nements passĂ©s et sont donc fondamentalement narratives; 2o font rĂ©fĂ©rence Ă des conversations et mettent ainsi en jeu des paroles rapportĂ©es; 3o font rĂ©fĂ©rence au passĂ© immĂ©diat et portent donc sur des Ă©vĂ©nements banals. Lâanalyse de ces conversations fournit lâoccasion de contribuer Ă lâĂ©laboration dâun cadre dâanalyse des diffĂ©rentes productions narratives conversationnelles, en fonction notamment de leur potentiel informatif, narratif et argumentatif.Conversation adopts a specific form when close friends "talk about their day", recount recent happenings in their lives. This particular form arises due to the fact that the happenings are generally themselves conversations. It is a conversational activity which has its own system of rules and is worthy of consideration. The data on which this study is based 1o refer to past events and are thus fundamentally narrative; 2o refer to conversations and as such bring into play instances of reported speech; 3o refer to the immediate past and thus focus on commonplace events. The analysis of these everyday conversations provides an opportunity to contribute to the elaboration of an analytical framework for different forms of conversational narratives, as a function specifically of their informative, narrative, and argumentative potential
Eolienne 2.0 du Gridlab: travail de bachelor : diplĂŽme 2016
Mettre en place un modĂšle simulant le fonctionnement dâune grande Ă©olienne en tenant compte de plusieurs paramĂštres tels que la vitesse du vent, la vitesse de rotation et le couple de la turbine, lâangle des pĂąles et le type dâĂ©olienne
Effect of picosecond strain pulses on thin layers of the ferromagnetic semiconductor (Ga,Mn)(As,P)
The effect of picosecond acoustic strain pulses (ps-ASP) on a thin layer of
(Ga,Mn)As co-doped with phosphorus was probed using magneto-optical Kerr effect
(MOKE). A transient MOKE signal followed by low amplitude oscillations was
evidenced, with a strong dependence on applied magnetic field, temperature and
ps-ASP amplitude. Careful interferometric measurement of the layer's thickness
variation induced by the ps-ASP allowed us to model very accurately the
resulting signal, and interpret it as the strain modulated reflectivity
(differing for probe polarizations), independently from dynamic
magnetization effects.Comment: 6 pages, 5 figure
Return words of linear involutions and fundamental groups
We investigate the natural codings of linear involutions. We deduce from the
geometric representation of linear involutions as Poincar\'e maps of measured
foliations a suitable definition of return words which yields that the set of
first return words to a given word is a symmetric basis of the free group on
the underlying alphabet . The set of first return words with respect to a
subgroup of finite index of the free group on is also proved to be a
symmetric basis of
Schemes for loading a Bose-Einstein condensate into a two-dimensional dipole trap
We propose two loading mechanisms of a degenerate Bose gas into a surface
trap. This trap relies on the dipole potential produced by two evanescent
optical waves far detuned from the atomic resonance, yielding a strongly
anisotropic trap with typical frequencies 40 Hz x 65 Hz x 30 kHz. We present
numerical simulations based on the time-dependent Gross-Pitaevskii equation of
the transfer process from a conventional magnetic trap into the surface trap.
We show that, despite a large discrepancy between the oscillation frequencies
along one direction in the initial and final traps, a loading time of a few
tens of milliseconds would lead to an adiabatic transfer. Preliminary
experimental results are presented
Performance of astrometric detection of a hotspot orbiting on the innermost stable circular orbit of the galactic centre black hole
The galactic central black hole Sgr A* exhibits outbursts of radiation in the
near infrared (so-called IR flares). One model of these events consists in a
hotspot orbiting on the innermost stable circular orbit (ISCO) of the hole.
These outbursts can be used as a probe of the central gravitational potential.
One main scientific goal of the second generation VLTI instrument GRAVITY is to
observe these flares astrometrically. Here, the astrometric precision of
GRAVITY is investigated in imaging mode, which consists in analysing the image
computed from the interferometric data. The capability of the instrument to put
in light the motion of a hotspot orbiting on the ISCO of our central black hole
is then discussed.
We find that GRAVITY's astrometric precision for a single star in imaging
mode is smaller than the Schwarzschild radius of Sgr A*. The instrument can
also demonstrate that a body orbiting on the last stable orbit of the black
hole is indeed moving. It yields a typical size of the orbit, if the source is
as bright as m_K=14.
These results show that GRAVITY allows one to study the close environment of
Sgr A*. Having access to the ISCO of the central massive black hole probably
allows constraining general relativity in its strong regime. Moreover, if the
hotspot model is appropriate, the black hole spin can be constrained.Comment: 13 pages, 11 figures ; accepted by MNRA
Diffraction of a Bose-Einstein Condensate in the Time Domain
We have observed the diffraction of a Bose-Einstein condensate of rubidium
atoms on a vibrating mirror potential. The matter wave packet bounces back at
normal incidence on a blue-detuned evanescent light field after a 3.6 mm free
fall. The mirror vibrates at a frequency of 500 kHz with an amplitude of 3.0
nm. The atomic carrier and sidebands are directly imaged during their ballistic
expansion. The locations and the relative weights of the diffracted atomic wave
packets are in very good agreement with the theoretical prediction of Carsten
Henkel et al. [1].Comment: submitted to Phys. Rev.
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