1,948 research outputs found
Study of the Influence of Helical Milling Parameters on the Quality of Holes in the UNS R56400 Alloy
Helical milling has been positioned as an alternative to conventional drilling, where the advantages it offers make it very attractive for use on difficult-to-machine alloys such as the titanium alloy UNS R56400. However, the correlation between the indicator of hole quality and the kinematic parameters has rarely been studied. The kinematics are what bring most advantages and that is why it is necessary to know their influence. In this aspect, there are different focuses of problems associated with the complexity of the process kinematics, which makes it necessary to undertake a deeper analysis of the process and to carry out a preliminary study. To address this problem, a DOE (Design of Experiments) is proposed to identify the sensitivity and the main trends of the properties that define the quality holes with respect to the kinematic parameters. At the same time, a nomenclature is proposed to unify and avoid misinterpretations. This study has allowed us to obtain conclusive results that offer very relevant information for future researc
Detection of a multi-shell planetary nebula around the hot subdwarf O-type star 2MASS J19310888+4324577
(Abridged) The origin of hot subdwarf O-type stars (sdOs) remains unclear
since their discovery in 1947. Among others, a post-Asymptotic Giant Branch
(post-AGB) origin is possible for a fraction of sdOs. We are involved in a
comprehensive ongoing study to search for and to analyze planetary nebulae
(PNe) around sdOs with the aim of establishing the fraction and properties of
sdOs with a post-AGB origin. We use deep Halpha and [OIII] images of sdOs to
detect nebular emission and intermediate resolution, long-slit optical
spectroscopy of the detected nebulae and their sdO central stars. These data
are complemented with other observations for further analysis of the detected
nebulae. We report the detection of an extremely faint, complex PN around 2MASS
J19310888+4324577 (2M1931+4324), a star classified as sdO in a binary system.
The PN shows a bipolar and an elliptical shell, whose major axes are oriented
perpendicular to each other, and high-excitation structures outside the two
shells. WISE archive images show faint, extended emission at 12 and 22 microns
in the inner nebular regions. The internal nebular kinematics is consistent
with a bipolar and a cylindrical/ellipsoidal shell, in both cases with the main
axis mainly perpendicular to the line of sight. The nebular spectrum only
exhibits Halpha, Hbeta and [OIII]4959,5007 emission lines, but suggests a very
low-excitation ([OIII]/Hbeta = 1.5), in strong contrast with the absence of
low-excitation emission lines. The spectrum of 2M1931+4324 presents narrow,
ionized helium absorptions that confirm the previous sdO classification and
suggest an effective temperature >= 60000 K. The binary nature of 2M1931+4324,
its association with a complex PN, and several properties of the system provide
strong support for the idea that binary central stars are a crucial ingredient
in the formation of complex PNe.Comment: 8 pages, 7 figures, accepted in Astronomy and Astrophysic
Influence of Different Machining Conditions on the Subsurface Properties of Drilled TiAl6V4
AbstractHigh thermomechanical loads in drilling of titanium alloys often cause significant alterations of the subsurface properties which are mostly connected to a degradation of the fatigue life of high dynamically loaded components. In the present study different drilling processes (conventional-, orbital- and vibration drilling), lubrication conditions (dry, MQL) and states of tool wear have been investigated regarding their influence on the subsurface properties of TiAl6V4. It was found that tensile residual stresses and increased hardness (result of severe plastic deformation) can be avoided if the process temperature and chip extraction are controlled
Five More Massive Binaries in the Cygnus OB2 Association
We present the orbital solutions for four OB spectroscopic binaries, MT145,
GSC 03161-00815, 2MASS J20294666+4105083, and Schulte 73, and the partial
orbital solution to the B spectroscopic binary, MT372, as part of an ongoing
study to determine the distribution of orbital parameters for massive binaries
in the Cygnus OB2 Association. MT145 is a new, single-lined, moderately
eccentric (e=0.291+/-0.009) spectroscopic binary with period of 25.140+/-0.008
days. GSC 03161-00815 is a slightly eccentric (e=0.10+/-0.01), eclipsing,
interacting and double-lined spectroscopic binary with a period of
4.674+/-0.004 days. 2MASS J20294666+4105083 is a moderately eccentric
(e=0.273+/-0.002) double-lined spectroscopic binary with a period of
2.884+/-0.001 days. Schulte 73 is a slightly eccentric (e=0.169+/-0.009),
double-lined spectroscopic binary with a period of 17.28+/-0.03 days and the
first "twin" in our survey with a mass ratio of q=0.99+/-0.02. MT372 is a
single-lined, eclipsing system with a period of 2.228 days and low eccentricity
(e~0). Of the now 18 known OB binaries in Cyg OB2, 14 have periods and mass
ratios. Emerging evidence also shows that the distribution of log(P) is flat
and consistent with Oepik's Law.Comment: Accepted to Astronomical Journa
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