Effect of Shock and Elastic Waves on Dynamic Compaction Process of Two-Layer Powder Media

1987 ◽  
Vol 109 (4) ◽  
pp. 266-271
Author(s):  
K. Miyagi ◽  
Y. Sano
Keyword(s):  
Elastic Waves ◽  
High Speed ◽  
Lower Layer ◽  
Initial Density ◽  
Dynamic Compaction ◽  
Compaction Process ◽  
Density Distributions ◽  
Layer Arrangement ◽  
Powder Medium ◽  
Compaction Processes

The dynamic compaction processes of copper powder which was filled in two layers into a die and subjected to solid punch impaction were investigated experimentally in order to assess the effect of different initial density distributions of the powder on the compaction process. The compaction experiments were performed for two situations of layer arrangement: in the first situation the upper layer had a lower uniform initial density distribution than the lower layer and in the second this order was reversed. The processes were photographed for the two situations of layer arrangement using a high speed camera in order to analyze the movement of powder medium and punch, the propagation of shock and elastic waves in the powder medium and density distributions. The pressure on the plug supporting the medium in the die was also measured so that the analysis of the photograph would be facilitated. The two compaction processes observed and analyzed differed considerably, but the green density distributions had only a slight difference. The compaction process obtained for the first situation of layer arrangement agreed well with the theoretical prediction reported previously by the authors. The compaction process for the second situation also agreed with the theoretical result, indicating that the amounts of internal energy dissipation during the two processes differ only slight.

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.

A Theoretical Derivation of the Similarity of Dynamic Compaction Processes of Powder Media in Dies

1986 ◽  
Vol 108 (2) ◽  
pp. 147-152
Author(s):  
Yukio Sano
Keyword(s):  
Cross Sections ◽  
Dynamic Compaction ◽  
Simple Type ◽  
Theoretical Derivation ◽  
Cross Sectional ◽  
Density Distributions ◽  
Powder Medium ◽  
Compaction Energy ◽  
The Mean ◽  
Compaction Processes

Multiple shock compactions of powder media within a die with a rigid punch are theoretically investigated. First, similarity of dynamic compaction processes for a powder medium of a simple type is exhibited through nondimensionalized one-dimensional equations. The similarity is established after determination of three parameters, i.e., the ratio S* of the lateral surface to the cross-sectional area of the medium, the ratio M* of the mass of the punch to that of the powder medium filled in the die, and the compaction energy per unit powder volume e. The similarity indicates that the particle velocity, specific volume and pressure have the same variation with respect to nondimensional time at all points in the medium with various cross-sections and initial lengths so long as S* is kept fixed at a certain value, i.e., at the same proportional nondimensional point in the medium. The density distributions of the green compacts are necessarily identical, and so is the mean density in all compactions. Second, it is shown in one of the nondimensionalized equations that wall frictional influence in a compaction where S* → 0 is not present, while the wall frictional influence is extremely large when S* is very large, which implies that the mean densities of the compacts are larger in compactions with smaller S*. Two types of compactions can be obtained for any powder medium because the equation used is applicable to any medium.

Multishock Compactions of a Die-Contained Copper Powder Medium Analyzed by Improved Theory

1991 ◽  
Vol 113 (4) ◽  
pp. 560-569
Author(s):  
Yukio Sano ◽  
Koji Tokushima ◽  
Tokujiro Inoue
Keyword(s):  
Copper Powder ◽  
Elastic Waves ◽  
Common Factor ◽  
Wall Friction ◽  
Compaction Process ◽  
Medium Length ◽  
Powder Medium ◽  
Compaction Processes ◽  
Initial Medium ◽  
The Waves

In the present paper, the multishock compaction process of a die-contained copper powder medium supported by an elastic plug at one end and impacted by an elastic punch at the other end, is analyzed by means of an improved theory having the effect of elasticity of the punch and plug. The compactions computed first have a constant sum of lengths of the medium and plug S0*=110, a constant ratio of punch mass to powder mass filled in the die M*=20, and an initial punch velocity ν0=50m/s. The computations of the compactions for the medium with very short lengths and the plug with long lengths confirm the existence of the medium length Scr1* corresponding to the first critical plug-length found in the previous study, and support the compaction process and the final mean density ρmean*-initial medium length S* relation of the medium shorter than the length Scr1* which were inferred in the study. Furthermore, the effect of elastic waves in the punch and plug on the process of the medium longer than Scr1* are examined. There are one common factor and one significant different factor in the processes. Explicitly, the waves in the plug exert different influence on compaction processes of the medium with different lengths, whereas the waves in the punch have similar influence on the processes. The elastic waves in the plug and die wall friction cause the medium length Scr2* corresponding to the second critical plug-length inferred in the previous study. Moreover, the waves in the plug make the form of the computed relation curve more complicated than the inferred one. The computed curve has the lengths Scr3* and Scr4* at which the density has an extreme value, respectively. Approximate similarity conditions for the compactions with various values of S0* are given by two fixed parameters M* and ν0 in region S*<Scr1*, three fixed parameters S*/S0*, M*, and ν0 in region from Scr1* to small S* where the wall friction effect can be neglected, and three fixed parameters S*, M*, and ν0 in region S*>(1/2)S0*. The computed ρmean*–S* and ρmean*–S*/S0* relations support these conditions. Furthermore, the computations of the compactions reveal that the waves in the punch, medium, and plug behave in similar manner during the processes, though they have different strengths.

Study on the Nanocrystalline WC-10Co Hard Alloys Prepared by Mixing and Explosive Compaction

2011 ◽  
Vol 233-235 ◽  
pp. 1893-1896
Author(s):  
Jin Ping Li ◽  
Song He Meng ◽  
Shi Qiang Liu ◽  
Yu Min Zhang
Keyword(s):  
Particle Size ◽  
High Speed ◽  
Initial Density ◽  
Maximum Density ◽  
Average Crystalline Size ◽  
Hard Alloys ◽  
Compaction Process ◽  
Explosive Compaction ◽  
Bulk Nanocrystalline ◽  
Secondary Explosive

The nanocrystalline WC-10Co hard alloys with high density (97.5% T.D.) have been prepared by use of mixing and explosion compaction technology and the average crystalline size is less than 100 nm. The microstructure analysis shows that, the particle size of the mixing powders is less than 200nm and that of the explosive compaction billet is even fine about 100nm. If explosive speed of any explosive is either big or small, we can not get density billets because the initial density of mixing powders is too low. If using secondary explosive compaction process (low-speed explosive Ammonium Nitrate 280g + high-speed explosive TNT 200g), we can get about 97% (maximum density of 97.58%) of the theory density of bulk nanocrystalline WC-10Co hard alloys.

Modeling of Powder Compaction: A Review

MRS Bulletin ◽  
1997 ◽  
Vol 22 (12) ◽  
pp. 45-51 ◽  
Author(s):  
I. Aydin ◽  
B.J. Briscoe ◽  
N. Ozkan
Keyword(s):  
Powder Compaction ◽  
Particle Deformation ◽  
Compaction Process ◽  
Density Distributions ◽  
Die Filling ◽  
Machine Loading ◽  
Stress Transmission ◽  
Compaction Processes ◽  
Flexible Die ◽  
Sintered Product

The compaction process involves stress transmission via rigid or flexible (die) walls and the propagation of stresses within a powder mass. The particles that comprise the powder distribute the stress by a variety of kinematic processes that involve sliding, rotation, particle deformation, and rupture. In practice the “particles” are often agglomerates of finer particles that have a range of properties. All of these factors must be considered in developing a comprehensive predictive model for compaction.The modeling of powder-compaction processes has a significant history that has been greatly advanced by the relatively recent general availability of powerful computers and their peripherals as well as by appropriate softwares. Compaction modeling may attempt to provide a basis for machine-loading specifications, or it may provide guidelines to help minimize “capping” defects where failure cracks form at the top of the green compact. It may also provide “green-body heterogeneity” through predicted stress and density distributions within a compact. Likewise compaction models may be combined with binder burnout and sintering models to predict internal microstructural features such as grain size and porosity, and the external shape of the sintered product. This article will deal only with the modeling of the compaction process; important elements such as powder flow for die filling and subsequent processing steps such as sintering and net shape predictions are not directly addressed.

Experimental Verification of the Similarity of Dynamic Compaction Processes of a Copper Powder Medium in Dies of Elementary Shapes

1987 ◽  
Vol 109 (4) ◽  
pp. 306-313
Author(s):  
Kiyohiro Miyagi ◽  
Yukio Sano ◽  
Takuo Hayashi
Keyword(s):  
Cross Section ◽  
Copper Powder ◽  
Similarity Theory ◽  
Rigid Bodies ◽  
Dynamic Compaction ◽  
Wall Friction ◽  
Simple Type ◽  
One Dimensional ◽  
Powder Medium ◽  
Compaction Processes

The similarity of dynamic compaction processes was investigated theoretically and predicted in our previous report, where powder media in a die were assumed to be of a simple type, and the punch and plug to be rigid bodies. The predictions were based on a set of one-dimensional equations and a set of nondimensionalized one-dimensional equations. The objective of this study is to examine the similarity experimentally and to present the results of compaction experiments in order to verify the existence predicted. The experiments were carried out on a copper powder medium in dies having inner cross-section in elementary shapes such as circle, square and triangle. The pressure of the medium at a point contacting the end of the plug, the density distribution and mean density of the green compacts were measured in the experiment. From the analysis of the experimental data the validity of the dynamic similarity theory was demonstrated and the similarity was verified to exist despite the differences in size and shape between the dies used, which implies that the copper powder medium in the dies of elementary shapes is of a simple type. Relations between the density and the shape coefficients showed that the density reached maximum as the coefficients decreased approaching a certain point with a decreasing influence of the die wall friction, while past that point, contrary to the prediction by the theory, it began to decrease due to an increasing influence of the elastic deformation of the punch and plug.

Finite Element Method in Powdered Metal Compaction Processes

2004 ◽  
Vol 449-452 ◽  
pp. 109-112
Author(s):  
B.D. Ko ◽  
D.H. Jang ◽  
Hyoung Jin Choi ◽  
Joong Yeon Lim ◽  
Beong Bok Hwang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Relative Density ◽  
Element Formulation ◽  
Compaction Process ◽  
Powdered Metal ◽  
Density Distributions ◽  
Multi Level ◽  
Compaction Processes ◽  
Element Method

A finite element method for the compaction process of metallic powder is introduced in the present work. Basic equations for the finite element formulation are summarized. A yield criterion, which is modified by describing asymmetric behavior of powder metal compacts, is introduced and applied to various classes of powdered metal compaction processes. Three material parameters are involved in the yield function and determined from the behavior of sintered powder compacts as a function of relative density. The FEM simulation includes single-action and double-action pressings of solid cylinders as well as cylindrical rings of relatively long parts (Class II parts). The compaction process for multi-level flanged components (Class III and Class IV parts) is also analyzed. The predicted results from simulations are summarized in terms of density distributions within the compacts and pressure distributions exerted on the die-wall interfaces, and also in terms of effectiveness with increased relative motions with in the compacts and the effect of various compaction schemes of combination of punch motions. Results obtained in the multi-level compaction process are discussed in terms of average relative density distributions at each height.

scholarly journals Measurement and analysis of gas-puff density distributions for plasma radiation source z pinches

2001 ◽  
Vol 19 (4) ◽  
pp. 579-595 ◽  
Author(s):  
D. MOSHER ◽  
B.V. WEBER ◽  
B. MOOSMAN ◽  
R.J. COMMISSO ◽  
P. COLEMAN ◽  
...  
Keyword(s):  
Radiation Source ◽  
Gas Flow ◽  
Initial Density ◽  
High Sensitivity ◽  
Plasma Radiation ◽  
Analysis Techniques ◽  
Density Distributions ◽  
Radiation Properties ◽  
Wide Range ◽  
Measurement And Analysis

High-sensitivity interferometry measurements of initial density distributions are reviewed for a wide range of gas-puff nozzles used in plasma radiation source (PRS) z-pinch experiments. Accurate gas distributions are required for determining experimental load parameters, modeling implosion dynamics, understanding the radiation properties of the stagnated pinch, and for predicting PRS performance in future experiments. For a number of these nozzles, a simple ballistic-gas-flow model (BFM) has been used to provide good physics-based analytic fits to the measured r, z density distributions. These BFM fits provide a convenient means to smoothly interpolate radial density distributions between discrete axial measurement locations for finer-zoned two-dimensional MHD calculations, and can be used to determine how changes in nozzle parameters and load geometry might alter implosion dynamics and radiation performance. These measurement and analysis techniques are demonstrated for a nested-shell nozzle used in Double Eagle and Saturn experiments. For this nozzle, the analysis suggests load modifications that may increase the K-shell yield.

INFLUENCE OF THE PYROLYTIC COMPACTION PROCESS ON THE PHYSICAL AND MECHANICAL PROPERTIES OF HIGH-DENSITY CARBON-CARBON COMPOSITE MATERIALS BASED ON PITCH MATRICES

2021 ◽  
pp. 3-9
Author(s):  
V. V. Kulakov ◽  
M. I. Pankov ◽  
V. A. Sivurova ◽  
M. S. Luchkin ◽  
A. K. Golubkov ◽  
...  
Keyword(s):  
Carbon Fibers ◽  
Initial Density ◽  
Physical And Mechanical Properties ◽  
Pyrolytic Carbon ◽  
Carbon Composite ◽  
Test Results ◽  
High Modulus ◽  
Compaction Process ◽  
Carbon Composite Materials ◽  
Density Values

The efficiency of the pyrolytic carbon compaction process by decomposing methane in samples of a carbon-carbon composite randomly reinforced with discrete high-modulus (graphitized) carbon fibers with different densities is investigated. The analysis of the test results of samples for determining the compressive strength, determining the densities of samples after compaction with pyrocarbon and after compaction by impregnation and carbonization under pressure is carried out. Scanning electron microscopy (SEM) was used to study the structure of material samples with different initial density values.

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