EFFECTS OF INITIAL INHOMOGENEOUS DENSITY DISTRIBUTION AND VOID SHAPE ON POWDER FORGING OF POROUS METAL

2013 ◽  
Vol 27 (19) ◽  
pp. 1341008
Author(s):  
TAIQING DENG ◽  
LIANXI HU ◽  
YU SUN ◽  
XIAOYA LIU
Keyword(s):  
Density Distribution ◽  
Initial Density ◽  
Porous Metal ◽  
Major Axis ◽  
Average Density ◽  
Semi Major Axis ◽  
Punch Force ◽  
Inhomogeneous Density ◽  
Void Shape ◽  
Initial Density Distribution

The deformation behavior during axisymmetric upsetting of sintered metals has been studied based on the finite-element method. The investigation on the effects of the initial density distribution, void shape and die friction on the density distribution and punch force during deformation have been conducted. It was found that under low-friction conditions, the initial density distribution affects the deformation geometry and the density distribution. However, the effect of the initial density distribution was found to be negligible under high-friction conditions. The initial density distribution did not affect the punch force or the average density, regardless of the friction conditions. When the force is perpendicular to semi-major axis of elliptical void, it is not only good for densification but also decrease the punch force in forging of porous metal.

IV.—Expansion of a Finite One-dimensional Gas Cloud into a Vacuum

1953 ◽  
Vol 64 (1) ◽  
pp. 57-70
Author(s):  
A. G. Mackie
Keyword(s):  
Density Distribution ◽  
Analytical Solutions ◽  
Initial Density ◽  
Initial Distribution ◽  
One Dimensional ◽  
Gas Streams ◽  
Subsequent Motion ◽  
Gas Cloud ◽  
Initial Density Distribution ◽  
Stationary Period

SynopsisAn investigation is made of the motion of a one-dimensional finite gas cloud which is initially at rest and is allowed to expand into a vacuum in both directions. The density of the gas at rest is assumed to rise steadily and continuously from zero at the boundaries to a maximum in the interior of the cloud.If the subsequent motion is continuous, it is completely specified by analytical solutions in seven different regions of the x-t plane joined together along characteristics. The motion of one of the boundaries is discussed, and conditions found for it to have (i) an initial stationary period or (ii) a final constant velocity of advance into the vacuum. The gas streams in both directions from a dividing point at zero velocity. This point ultimately tends to the mid-point of the initial distribution.The possible breakdown of the continuity of the motion is discussed, and a condition on the initial density distribution found for shock-free flow to be maintained.

The normal motion of a shock wave through a non-uniform one-dimensional medium

1955 ◽  
Vol 232 (1190) ◽  
pp. 350-370 ◽  
Keyword(s):  
Shock Wave ◽  
Density Distribution ◽  
Contact Discontinuity ◽  
Initial Density ◽  
Incident Shock ◽  
Shock Strength ◽  
Total Strength ◽  
Reflected Wave ◽  
Uniform Medium ◽  
Initial Density Distribution

The non-uniform medium is regarded as a succession of small-density discontinuities separated by uniform regions. Consideration of the interaction of a shock wave with a weak contact discontinuity gives a first-order relationship between change in shock strength and change in density across the discontinuity, which is integrated to give the shock strength as a function of the initial density of the non-uniform medium in closed form. Due to the passage of the shock, a wave is reflected back through the non-uniform medium, generating in turn a doubly reflected wave which eventually catches up the shock. A complete description of the flow as modified by the first reflected wave is obtained. The modifications to the flow caused by the doubly reflected wave are more difficult to formulate, and a complete description of the flow so modified is not given. The extra difficulty is partly due to the dependence of the doubly reflected wave on the initial density distribution, whereas the motion of the incident shock, and the flow behind it as modified only by the first reflected wave, are found to have the useful property that they are independent of the particular density-distance distribution being considered. Calculations of the total strength of the doubly reflected wave, and the strength of the incident shock when this wave has fully merged with it, have been made for a particular density distribution. A comparison of this calculated strength with the strength of the shock transmitted, after the interaction of a shock wave and a contact discontinuity, suggests that a description of the flow which takes account only of the single and double reflexions is satisfactory, even if the initial density distribution varies considerably.

scholarly journals The Ionization and Expansion of a Globule of Interstellar Gas overun by a Weak R Type Ionization Front

1977 ◽  
Vol 32 (7) ◽  
pp. 692-696
Author(s):  
J. S. Berry
Keyword(s):  
Density Distribution ◽  
Similarity Solution ◽  
Spherical Symmetry ◽  
Initial Density ◽  
Neutral Hydrogen ◽  
Ionization Front ◽  
Interstellar Gas ◽  
Ionized Gas ◽  
Initial Density Distribution

Abstract The flow of the ionized gas behind a contracting ionization front is investigated for spherical symmetry. A similarity solution is given when the initial density distribution in the neutral hydrogen is ω0/rα- where r is the distance from the centre of contraction.

scholarly journals The Evolution of Young Supernova Remnants

1983 ◽  
Vol 101 ◽  
pp. 119-124
Author(s):  
A. C. Fabian ◽  
W. Brinkmann ◽  
G. C. Stewart
Keyword(s):  
Density Distribution ◽  
Stellar Wind ◽  
Supernova Remnants ◽  
Initial Conditions ◽  
Numerical Models ◽  
Variable Mass ◽  
Initial Density ◽  
X Ray ◽  
Cassiopeia A ◽  
Initial Density Distribution

Einstein X-ray observations of the young supernova remnants Cassiopeia A (Murray et al. 1980) and Tycho (Seward, Gorenstein and Tucker 1982) indicate that the swept-up mass does not much exceed that of the observed ejecta. The initial density distribution of the ejecta and surrounding material is then important in determining the X-ray structure and evolution. Some aspects of this behaviour have been dealt with in previous numerical (e.g. Gull 1973; Itoh 1977; Jones, Smith and Straka 1981) and analytical (e.g. Chevalier 1982a,b) studies. We present here results obtained from numerical models covering a wider range of initial conditions. In particular, we consider the effect of a constant stellar wind from the progenitor star on the expansion of the remnant. We have previously suggested that variable mass loss from SN1006 may explain its warm filled interior (Fabian, Stewart and Brinkmann 1982).

Computed Dynamic Compaction of a Two-Layered Copper Powder Medium

1979 ◽  
Vol 101 (2) ◽  
pp. 122-128
Author(s):  
Yukio Sano ◽  
Kiyohiro Miyagi
Keyword(s):  
Density Distribution ◽  
Layered Medium ◽  
Initial Density ◽  
Dynamic Compaction ◽  
Volume Distribution ◽  
Green Density ◽  
Compaction Process ◽  
Density Distributions ◽  
Powder Medium ◽  
Initial Density Distribution

In the paper presented a dynamic compaction of a two-layered powder medium is analyzed. A two-layered medium is used because it is the simplest form of layered medium available. The layers are differentiated not in terms of different powdered materials but rather a difference in terms of initial-density (initial specific volume) distribution, that is a higher initial density distribution and a lower initial density distribution. Again for these initial density distributions, two forms of arrangement can be considered; for the first situation, the layer to be impacted has a lower initial density distribution, while for the second situation the arrangement is reversed. The objective of this paper, therefore, is to examine the effect that the initial density sequence has on the compaction process and on the green density of a layered powder medium, especially in terms of shock wave and elastic wave influence.

Estimation of the initial density distribution in plasma–metal liners

2016 ◽  
Vol 61 (5) ◽  
pp. 676-682 ◽  
Author(s):  
A. G. Rousskikh ◽  
A. S. Zhigalin ◽  
V. I. Oreshkin
Keyword(s):  
Density Distribution ◽  
Initial Density ◽  
Initial Density Distribution

Detection and Characterization of earth-like Planets

1997 ◽  
Vol 161 ◽  
pp. 299-311 ◽  
Author(s):  
Jean Marie Mariotti ◽  
Alain Léger ◽  
Bertrand Mennesson ◽  
Marc Ollivier
Keyword(s):  
Direct Detection ◽  
Contrast Ratio ◽  
Angular Size ◽  
Physical Nature ◽  
Major Axis ◽  
Infrared Emission ◽  
Space Technology ◽  
Semi Major Axis ◽  
Earth Like Planets ◽  
Visible Wavelengths

AbstractIndirect methods of detection of exo-planets (by radial velocity, astrometry, occultations,...) have revealed recently the first cases of exo-planets, and will in the near future expand our knowledge of these systems. They will provide statistical informations on the dynamical parameters: semi-major axis, eccentricities, inclinations,... But the physical nature of these planets will remain mostly unknown. Only for the larger ones (exo-Jupiters), an estimate of the mass will be accessible. To characterize in more details Earth-like exo-planets, direct detection (i.e., direct observation of photons from the planet) is required. This is a much more challenging observational program. The exo-planets are extremely faint with respect to their star: the contrast ratio is about 10−10at visible wavelengths. Also the angular size of the apparent orbit is small, typically 0.1 second of arc. While the first point calls for observations in the infrared (where the contrast goes up to 10−7) and with a coronograph, the latter implies using an interferometer. Several space projects combining these techniques have been recently proposed. They aim at surveying a few hundreds of nearby single solar-like stars in search for Earth-like planets, and at performing a low resolution spectroscopic analysis of their infrared emission in order to reveal the presence in the atmosphere of the planet of CO H2O and O3. The latter is a good tracer of the presence of oxygen which could be, like on our Earth, released by biological activity. Although extremely ambitious, these projects could be realized using space technology either already available or in development for others missions. They could be built and launched during the first decades on the next century.

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