scholarly journals A Hot Spots Ignition Probability Model for Low-Velocity Impacted Explosive Particles Based on the Particle Size and Distribution

2017 ◽  
Vol 2017 ◽  
pp. 1-10
Author(s):  
Hong-fu Guo ◽  
Yan-qing Wu ◽  
Feng-lei Huang
Keyword(s):  
Particle Size ◽  
Probability Model ◽  
Quadratic Function ◽  
Drop Height ◽  
Low Velocity ◽  
Contact Zones ◽  
Ignition Probability ◽  
Drop Weight ◽  
Mean Size ◽  
Size Of Particles

Particle size and distribution play an important role in ignition. The size and distribution of the cyclotetramethylene tetranitramine (HMX) particles were investigated by Laser Particle Size Analyzer Malvern MS2000 before experiment and calculation. The mean size of particles is 161 μm. Minimum and maximum sizes are 80 μm and 263 μm, respectively. The distribution function is like a quadratic function. Based on the distribution of micron scale explosive particles, a microscopic model is established to describe the process of ignition of HMX particles under drop weight. Both temperature of contact zones and ignition probability of powder explosive can be predicted. The calculated results show that the temperature of the contact zones between the particles and the drop weight surface increases faster and higher than that of the contact zones between two neighboring particles. For HMX particles, with all other conditions being kept constant, if the drop height is less than 0.1 m, ignition probability will be close to 0. When the drop heights are 0.2 m and 0.3 m, the ignition probability is 0.27 and 0.64, respectively, whereas when the drop height is more than 0.4 m, ignition probability will be close to 0.82. In comparison with experimental results, the two curves are reasonably close to each other, which indicates our model has a certain degree of rationality.

Batch Precipitation of Lead Iodide

1994 ◽  
Vol 59 (6) ◽  
pp. 1301-1304
Author(s):  
Jaroslav Nývlt ◽  
Stanislav Žáček
Keyword(s):  
Aqueous Solution ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Crystal Size ◽  
Lead Nitrate ◽  
Lead Iodide ◽  
Constant Rate ◽  
Mean Size ◽  
The Mean

Lead iodide was precipitated by a procedure in which an aqueous solution of potassium iodide at a concentration of 0.03, 0.10 or 0.20 mol l-1 was stirred while an aqueous solution of lead nitrate at one-half concentration was added at a constant rate. The mean size of the PbI2 crystals was determined by evaluating the particle size distribution, which was measured sedimentometrically. The dependence of the mean crystal size on the duration of the experiment exhibited a minimum for any of the concentrations applied. The reason for this is discussed.

scholarly journals Low velocity drop weight impact behavior of Al2O3-Ni-ZrO2 and Al2O3-Ni-Cr2O3 nanocomposite systems

2021 ◽  
Author(s):  
Betül Kafkaslıoğlu Yıldız ◽  
Murat Büyük ◽  
Yahya Kemal Tür
Keyword(s):  
Network Formation ◽  
Low Energy ◽  
Impact Behavior ◽  
Precipitation Method ◽  
Low Velocity ◽  
Ballistic Performance ◽  
Crack Network ◽  
Damage Mechanisms ◽  
Drop Weight ◽  
Weight Impact

Abstract 1 vol% Ni particulate Al2O3 matrix nanocomposites prepared by the heterogeneous precipitation method with ZrO2 (5 vol%) or Cr2O3 (1 vol%) additives were subjected to the low energy drop weight impact tests to compare the behavior of the compositions under low energy impact and to investigate the damage mechanisms. The pure Al2O3, Al2O3/Ni, Al2O3/ZrO2, and Al2O3/Cr2O3 compositions with the same additive ratios were also produced to make the comparison systematically. Also, the Vickers hardness measurements were carried out and a significant increase in hardness was attained for both Al2O3/Ni + ZrO2 and Al2O3/Ni + Cr2O3. The average hardness value around 24.8 ± 1.0 GPa was measured for Al2O3/Ni + ZrO2 and Al2O3/Ni + Cr2O3 which means ∼ 15% improvement compared to the pure Al2O3. Between all the compositions, the maximum force (Fmax) value was obtained for Al2O3/Ni + ZrO2 for 12 J impact energy level (26617 N) according to the low energy drop weight impact test results. Tensile radial crack network formation, cone formation, fracture and crushing of the cone structure were observed as damage mechanisms for all the compositions. The volume of conical frustum structure was evaluated for each composition and the effect of microstructure on possible ballistic performance was also discussed.

scholarly journals The Influences of Stirring on the Recrystallization of Ammonium Perrhenate

2020 ◽  
Vol 10 (2) ◽  
pp. 656 ◽  
Author(s):  
Junjie Tang ◽  
Li Feng ◽  
Chunwei Zhang ◽  
Yuan Sun ◽  
Long Wang ◽  
...  
Keyword(s):  
Particle Size ◽  
Liquid Flow ◽  
Physical Simulation ◽  
Powder Processing ◽  
Crystal Plane ◽  
Recrystallization Process ◽  
Low Velocity ◽  
Flow Area ◽  
Ammonium Perrhenate ◽  
Turbine Impeller

Ammonium perrhenate is widely used in alloy manufacturing, powder processing, the catalytic industry, and other fields. Recrystallization can improve the specific surface area of ammonium perrhenate, reduce its particle size, and improve its particle size distribution uniformity. Therefore, recrystallized ammonium perrhenate can obtain better application benefits in the above fields. Stirring is an important factor that affects the recrystallization of ammonium perrhenate, and this paper systematically analyzes the influence of the stirring paddle types and stirring intensities on ammonium perrhenate during the homogeneous recrystallization process, ultimately revealing the relationship between the growth rate of ammonium perrhenate and the stirring process. Particle image velocimetry physical simulation results showed that the flow field in the reactor was more evenly distributed when using the disc turbine impeller, and a relatively uniform velocity liquid flow area was formed in the whole reactor, while the low-velocity liquid flow area was smaller. Therefore, this information, combined with SEM test results, suggests that under the same recrystallization time and stirring intensity, the stirring effect of a disc turbine impeller is more suitable than a propelling propeller and an Intermig impeller for the recrystallization process of ammonium perrhenate. Moreover, the XRD patterns and SEM analysis showed that if the agglomeration in the systems was too strong or too weak, the growths of the (101) crystal plane and (112) crystal plane were restrained, which caused an attenuation in the growth rates along the crystallographic directions that were orthogonal to the crystal faces. Finally, the reduction experiments show that the recrystallization of ammonium perrhenate could improve the phase parameters of rhenium powders.

Study on Process of Particle Impact on Curved Surface of Vane by Finite Element Method

2010 ◽  
Vol 139-141 ◽  
pp. 1303-1307
Author(s):  
Xiao Jing Yang ◽  
Yi Lin Chi ◽  
Guan Zhang He
Keyword(s):  
Particle Size ◽  
Energy Exchange ◽  
Surface Deformation ◽  
Plastic Property ◽  
Impact Angle ◽  
Surface Shape ◽  
Curved Surface ◽  
Particle Impact ◽  
Size Of Particles ◽  
Distribution Of Stress

The process of particle impacting and contacting curved surface of vane was studied, and the characteristics of particle size, particle initial velocity and its impacting direction affect the stress of subsurface were analyzed by using ANSYS/LS-DANY software. It is shown that the interaction between particles and surface of vane is affected by nonlinear factors such as the elastic-plastic property of material, the state of impacting and contacting and surface shape. The increment in particle size increases the stress of the surface impacted and the sphere of action is also enlarged. The influence of the size of particles is remarkable. Particle impact velocity is related to energy exchange and has influences on stress value and the area of surface deformation. Due to impact angle is related to shape of curved vane, so the distribution of stress is changed and the value of the stress in surface layer is also influenced when particles impact curved surface of vane from different directions. The research will be helpful to disclose the mechanics of the wear on the condition of particle impact.

scholarly journals Models of explosive volcanism

1995 ◽  
Vol 2 (3/4) ◽  
pp. 269-279 ◽  
Author(s):  
A. W. Woods ◽  
S. M. Bower ◽  
M. I. Bursik
Keyword(s):  
Mass Flux ◽  
Subsonic Flow ◽  
Supersonic Jet ◽  
Explosive Volcanism ◽  
Eruption Column ◽  
Flow Temperature ◽  
Mean Size ◽  
The Mean ◽  
Size Of Particles ◽  
Residual Ash

Abstract. We describe a series of models which illustrate the controls upon the evolution of an erupting mixture of ash and gas during an explosive volcanic eruption. For large eruption rates, material typically issues from a crater as a supersonic jet which may entrain and heat sufficient air to become buoyant and form a Plinian eruption column. If a buoyant eruption column is able to form, then this column may ascend to heights of order 10-30 km, depending upon the erupted mass flux. In contrast, for low eruption rates, a shock forms in the crater and the material issues as a slow subsonic flow which generates dense hot ash flows. A new model shows that as such ash flows propagate from the vent, the density of the flow decreases mainly due to sedimentation, until ultimately the residual ash flow becomes buoyant. The distance the flow travels before becoming buoyant increases with the mass flux in the current and the mean size of particles in the current, but decreases with the flow temperature. It also depends upon the mass of air entrained into the collapsing fountain. The mass fraction of solid lifted from such ash flows into the ascending cloud depends mainly upon the mass of air entrained into the collapsing fountain near the volcanic vent. We apply our models to predict run-out distances and deposition patterns produced by erupting volcanoes.

scholarly journals Al2O3 Particles on Titanium Dental Implant Systems following Sandblasting and Acid-Etching Process

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Peter Schupbach ◽  
Roland Glauser ◽  
Sebastian Bauer
Keyword(s):  
Dental Implant ◽  
Sem Analysis ◽  
Acid Etching ◽  
Mean Size ◽  
Bone Level ◽  
Titanium Dental Implant ◽  
The Mean ◽  
Particle Counts ◽  
Size Of Particles ◽  
Implant System

Dental implants with moderately rough surfaces show enhanced osseointegration and faster bone healing compared with machined surfaces. The sandblasting and acid-etching (SA) process is one technique to create moderately rough dental implant surfaces. The purpose of this study was to analyse different commercially available implant systems with a SA-modified surface and to explore the widespread notion that they have similar surface properties regarding morphology and cleanliness. SA-modified surfaces of nine implant systems manufactured by Alpha-Bio Tec Ltd, Camlog Biotechnologies AG, Dentsply Sirona Dental GmbH, Neoss Ltd, Osstem Implant Co. Ltd, Institute Straumann AG, and Thommen Medical AG were analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) and examined for surface cleanliness. Six implants from three different lots were selected per each implant system. Mean particle counts for each implant and the mean size of the particles were calculated from three different regions of interest and compared using ANOVA and Tukey’s test. SEM analysis showed presence of particles on the majority of analyzed implant surfaces, and EDX evaluations determined that the particles were made of Al2O3 and thus remnants of the blasting process. SPI®ELEMENT INICELL® and Bone Level (BL) Roxolid® SLActive® implant surfaces showed the highest mean particle counts, 46.6 and 50.3 per area, respectively. The surface of BL Roxolid® SLActive® implant also showed the highest variations in the particle counts, even in samples from the same lot. The mean size of particles was 1120±1011 μm2, measured for USIII CA Fixture implants, while the biggest particle was 5900 μm2 found on a BL Roxolid® SLActive® implant. These results suggest that not all manufacturers are able to produce implant surfaces without particle contamination and highlight that the surface modification process with the SA technique should be appropriately designed and controlled to achieve a clean and consistent final medical device.

Influence of Electrical Parameter on the Size of Superalloy Powders Prepared by Spark Plasma Discharge Process

2007 ◽  
Vol 561-565 ◽  
pp. 403-406
Author(s):  
Jun Yu ◽  
Chang Chun Ge ◽  
Guo Hua Ni ◽  
Lu Lu Meng ◽  
Wei Ping Shen ◽  
...  
Keyword(s):  
Particle Size ◽  
Pulse Duration ◽  
Electrical Parameter ◽  
Spherical Shape ◽  
Plasma Discharge ◽  
Discharge Process ◽  
Small Particle Size ◽  
Spark Plasma ◽  
Mean Size ◽  
The Mean

Superalloy powders, which have a small particle size and spherical shape, were prepared by a spark plasma discharge process. The electrical parameter, spark voltage, current and pulse duration have very important effects on the size distribution of produced superalloy powders. When current or pulse duration changed the mean size significantly changed.

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