6,901 research outputs found
Effect of frictional boundary conditions and percentage area reduction on the extrusion pressure of Aluminum AA6063 alloy using FE analysis modelling
© 2020 by the authors; licensee Growing Science, Canada. This is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).Finite Element Analysis was carried out to describe the effect of frictional boundary conditions and percentage reduction on deformation modelling (forward extrusion) of Aluminum AA6063 alloy. Curved die profiles of regular polygons (square, hexagonal, heptagonal, and octagonal) were designed using MATLAB R2009b and Autodesk Inventor 2013 to generate the coordinate and thesolid CAD model of the die profile respectively form a circular billet. The numerical analysis was performed using DeformTM-3D commercial package with frictional boundary conditions of 0.38 and 0.75 representing the wet and dry condition and varying the percentage reduction of 50%, 70%, and 90%. The results of the temperature distribution, effective stress, effective strain, andstrain rate were reported. As the percentage area reduction increases, the extrusion pressure also increases with an increasing frictional condition, and die length. Also, extrusion pressure decreases when the side of the polygon increases from square-shaped section follow by hexagonal shaped-section and least in octagonal shaped-section for both friction factors and percentage areareductions. For a given percentage reduction and cross-sectional area, there is no distinct difference between the predictive loads for the shaped-polygons. When the result of this analysis is compared with the experimental results from the literature, it is evident that DeformTM-3D is an effective tool for finite element analysis of non-isothermal deformation processes.Peer reviewedFinal Published versio
A pseudointegrable Andreev billiard
A circular Andreev billiard in a uniform magnetic field is studied. It is
demonstrated that the classical dynamics is pseudointegrable in the same sense
as for rational polygonal billiards. The relation to a specific polygon, the
asymmetric barrier billiard, is discussed. Numerical evidence is presented
indicating that the Poincare map is typically weak mixing on the invariant
sets. This link between these different classes of dynamical systems throws
some light on the proximity effect in chaotic Andreev billiards.Comment: 5 pages, 5 figures, to appear in PR
Photometric structure of the peculiar galaxy ESO 235-G58
We present the near-infrared and optical properties of the peculiar galaxy
ESO 235-G58, which resembles a late-type ringed barred spiral seen close to
face-on. However, the apparent bar of ESO 235-G58 is in reality an edge-on disk
galaxy of relatively low luminosity. We have analyzed the light and color
distributions of ESO 235-G58 in the NIR and optical bands and compared them
with the typical properties observed for other morphological galaxy types,
including polar ring galaxies. Similar properties are observed for ESO 235-G58,
polar ring galaxies, and spiral galaxies, which leads us to conclude that this
peculiar system is a polar-ring-related galaxy, characterized by a low inclined
ring/disk structure, as pointed out by Buta & Crocker in an earlier study,
rather than a barred galaxy.Comment: 16 pages, 15 figures, accepted for publication in Astronomy &
Astrophysic
A minimal statistical-mechanical model for multihyperuniform patterns in avian retina
Birds are known for their extremely acute sense of vision. The very peculiar
structural distribution of five different types of cones in the retina
underlies this exquisite ability to sample light. It was recently found that
each cone population as well as their total population display a disordered
pattern in which long wave-length density fluctuations vanish. This property,
known as hyperuniformity is also present in perfect crystals. In situations
like the avian retina in which both the global structure and that of each
component display hyperuniformity, the system is said to be multi-hyperuniform.
In this work, we aim at devising a minimal statistical-mechanical model that
can reproduce the main features of the spatial distribution of photoreceptors
in avian retina, namely the presence of disorder, multi-hyperuniformity and
local hetero-coordination. This last feature is key to avoid local clustering
of the same type of photoreceptors, an undesirable feature for the efficient
sampling of light. For this purpose we formulate a simple model that
definitively exhibits the required structural properties, namely an equimolar
three-component mixture (one component to sample each primary color, red,
green, and blue) of non-additive hard disks to which a long-range logarithmic
repulsion is added between like particles. A Voronoi analysis of our idealized
system of photoreceptors shows that the space-filling Voronoi polygons
interestingly display a rather uniform area distribution, symmetrically
centered around that of a regular lattice, a structural property also found in
human retina. Disordered multi-hyperuniformity offers an alternative to
generate photoreceptor patterns with minimal long-range concentration and
density fluctuations. This is the key to overcome the difficulties in devising
an efficient visual system in which crystal-like order is absent
Experimental and numerical prediction of extrusion load at different lubricating conditions of aluminium 6063 alloy in backward cup extrusion
In the present research work using a backward cup extrusion (BCE) die profile, different lubricating conditions on aluminum alloy AA6063 have been experimentally and numerically investigated to predict the extrusion load. It was obvious that due to an increase in applications of the extrusion process, many researchers have worked on the extrusion process using different methods to achieve their aims. This experiment was conducted with three different lubricants namely: Castor oil, Palm Oil and tropical coconut oil; as well as without lubricants. Different lubricating conditions were employed of varying strain rates ranges from 1.5×10-3s-1, 2.0×10-3s-1, 2.5×10-3s-1, and 3.0×10-3s-1; Numerical analysis and simulation for dry and lubricated conditions during extrusion load were also performed using DEFORM 3D software. The results show that prediction extrusion load increases with increasing strain rates. The maximum extrusion load was found to be higher for extrusion without lubricants. In all cases of strain rate, palm oil showed a lower extrusion load compared to the other lubricants. Castor oil indicated the highest extrusion load when the experiment was carried out using lubrication. There was a consistent agreement between the result gotten from the experiment and simulation results of the extrusion load-strike curve.Peer reviewedFinal Published versio
Edge Detecting New Physics the Voronoi Way
We point out that interesting features in high energy physics data can be
determined from properties of Voronoi tessellations of the relevant phase
space. For illustration, we focus on the detection of kinematic "edges" in two
dimensions, which may signal physics beyond the standard model. After deriving
some useful geometric results for Voronoi tessellations on perfect grids, we
propose several algorithms for tagging the Voronoi cells in the vicinity of
kinematic edges in real data. We show that the efficiency is improved by the
addition of a few Voronoi relaxation steps via Lloyd's method. By preserving
the maximum spatial resolution of the data, Voronoi methods can be a valuable
addition to the data analysis toolkit at the LHC.Comment: 6 pages, 7 figure
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