Shock initiation of explosives: High temperature hot spots explained

2017 ◽  
Vol 111 (6) ◽  
pp. 061902 ◽  
Author(s):  
Will P. Bassett ◽  
Belinda P. Johnson ◽  
Nitin K. Neelakantan ◽  
Kenneth S. Suslick ◽  
Dana D. Dlott
Keyword(s):  
High Temperature ◽  
Hot Spots ◽  
Shock Initiation

Die-Attach Voiding Reduction in Gold Alloy Solder Preforms

2017 ◽  
Vol 2017 (HiTEN) ◽  
pp. 000099-000102
Author(s):  
Bernard Leavitt ◽  
Andy C. Mackie
Keyword(s):  
High Temperature ◽  
Eutectic Alloy ◽  
Hot Spots ◽  
Gold Alloy ◽  
High Reliability ◽  
Eutectic Alloys ◽  
Power Semiconductor ◽  
Power Semiconductor Devices ◽  
Die Attach ◽  
Alloy Solder

Abstract The need for high-temperature solders is growing as RF and power semiconductor devices continue to get smaller, with power density increasing both as a consequence of the shrink and as a result of increased power ratings. AuSn20 eutectic solder (Indalloy®182) has been the workhorse for high-temperature, high-reliability, small die-attach applications for many years; however, as junction temperatures (Tj) increase, the gold-tin eutectic is beginning to reach its limit of utility. Higher temperatures cause increased thermal fatigue, and even delamination is seen at the solder joints. The next option for RF and power semiconductor manufacturers needing these higher temperatures is either AuGe12 (Indalloy®183) or AuSi3.2 (Indalloy®184) eutectic alloy (see Table I).Table 1.Key properties of Au-based eutectic alloys. Over the years, many customers have tried AuGe12 and the feedback has been that the alloy has poor solderability, which manifests as large voids in the bond. Voids are poor conductors of heat, which create hot spots, and are the primary cause of premature failures.

scholarly journals Shock initiation and hot spots in plastic-bonded 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)

2020 ◽  
Vol 116 (12) ◽  
pp. 124102 ◽  
Author(s):  
Wei Zhang ◽  
Lawrence Salvati ◽  
Meysam Akhtar ◽  
Dana D. Dlott
Keyword(s):  
Hot Spots ◽  
Shock Initiation

Research Progress of Oil Making from Sewage Sludge

2016 ◽  
Vol 851 ◽  
pp. 232-236
Author(s):  
Jiang Long Lu ◽  
Guo Ri Dong ◽  
Fang Chen ◽  
Ji Bin Wang
Keyword(s):  
High Temperature ◽  
Sewage Sludge ◽  
Low Temperature ◽  
Hot Spots ◽  
Energy Utilization ◽  
Research Progress ◽  
Treatment And Disposal ◽  
Low Temperature Pyrolysis

the treatment and disposal of sewage sludge is one of the hot spots in recent years, and the value of its energy utilization has gradually received attention by researchers. In this paper, the concept, yield, harm as well as the conventional disposal methods of sewage sludge are described, three kinds of main technologies of oil making from sewage sludge are introduced, including high temperature pyrolysis, low-temperature pyrolysis and direct thermo chemical liquefaction, and the research progress of these three technologies is reviewed.

On Eliminating ‘Hot Streaking’ and Stratification in the VHTR Lower Plenum Using Helicoid Inserts

2008 ◽  
Author(s):  
Sal B. Rodriguez ◽  
Mohamed S. El-Genk
Keyword(s):  
High Temperature ◽  
Flow Velocity ◽  
Hot Spots ◽  
Turbulence Models ◽  
Lower Plate ◽  
Very High Temperature Reactor ◽  
High Temperature Reactor ◽  
Parallel Code ◽  
Flow Components ◽  
Very High

The helium-cooled high temperature reactor (HTR) and Very High Temperature Reactor (VHTR) designs operate at exit temperatures ranging from 873 – 923 K and 1,123 – 1,223 K, respectively. The high exit temperatures and the low heat capacity of helium require operating at a high flow velocity (> 70 m/s). The high temperature and flow velocity of the helium jets exiting the coolant channels in the prismatic reactor’s lower plate in the lower plenum (LP) cause “hot spots” (“hot streaking”) and stratification. To minimize or eliminate hot streaking and enhance mixing, this work investigated using static, quadruple helicoid inserts at the exit of the coolant channels. The helicoid inserts introduce radial and azimuthal momentum flow components, which with the extensive entrainment and mixing of the surrounding gas, significantly reduce the impingement onto the lower plate, thereby minimizing hot streaking and stratification in the LP. The present analysis was conducted using FUEGO, Sandia National Laboratories’ 3D, finite element, incompressible, reactive flow, massively-parallel code with state-of-the art turbulence models. We used helium at 1,273 K and the dynamic Smagorinsky turbulence model.

scholarly journals Microwave Heating Behavior in SiC Fiber-MO2 Mixtures (M = Ce, Zr)—Selective Heating of Micrometer-Sized Fibers Facilitated by ZrO2 Powder

Processes ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 47 ◽  
Author(s):  
Keiichiro Kashimura ◽  
Jun Fukushima ◽  
Tomoaki Namioka ◽  
Takashi Fujii ◽  
Hirotsugu Takizawa ◽  
...  
Keyword(s):  
High Temperature ◽  
Hot Spots ◽  
Weight Ratio ◽  
Temperature Gradients ◽  
Maximum Temperature ◽  
Selective Heating ◽  
Sic Fiber ◽  
Maximum Value ◽  
Rate Maximum ◽  
Heating Behavior

SiC fiber-MO2 (M = Ce, Zr) mixtures with various compositions were heated by applying an 80 W microwave electric field, to investigate their heating rate, maximum temperature, and dielectric constant. For the SiC fiber-CeO2 mixture, all three parameters continued to increase as the weight ratio of the SiC fiber increased; in contrast, for the SiC fiber-ZrO2 mixture, these parameters reached a maximum value at a certain composition. A thermal gradient of 500 °C was observed at a microlevel in the SiC fiber-ZrO2 mixture, and hot spots were located in regions with a certain composition. This result not only contributes to designing a novel good microwave absorber but also presents new aspects with regard to high-temperature microwave processing, including the mechanism behind the high-temperature gradients on the order of micrometers as well as engineering applications that utilize these high-temperature gradients.

Research on Influencing Factors of Methane/Air Combustion in the Ring Porous Medium Burner

2011 ◽  
Vol 130-134 ◽  
pp. 1734-1738 ◽  
Author(s):  
Jiang Rong Xu ◽  
Jian Ming Zhao ◽  
Shan Shan Xu ◽  
Guan Qing Wang
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
High Temperature ◽  
Temperature Distribution ◽  
Influencing Factors ◽  
Hot Spots ◽  
Theoretical Basis ◽  
Asymmetric Structure ◽  
Mixed Gas ◽  
Simulation Results

In this paper, we focuses on combustion characteristics of the mixed gas of methane/air in the ring porous medium burner using numerical simulating method. The influencing factors of combustion, such as different methane/air ratio, the velocity of flow and heat loss of internal and external wall, are discussed, and it is shown that the ring porous medium burners have some advantages different from straight or rectangular porous media burners. Due to annular asymmetric structure, the temperature distribution of ring porous media burners are more uniform, and are no unfavorable phenomena such as the local high temperature and the hot spots. The simulation results for annular porous medium provides important theoretical basis for the development of new porous medium burners.

Flow Visualization in the Scaled Up Pebble Bed of High Temperature Gas-Cooled Reactor Using Particle Image Velocimetry Method

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Jae-Young Lee ◽  
Sa-Ya Lee
Keyword(s):  
Particle Image Velocimetry ◽  
High Temperature ◽  
Flow Field ◽  
Hot Spots ◽  
Particle Image ◽  
Pebble Bed ◽  
Stagnation Points ◽  
Image Velocimetry ◽  
Particle Image Velocimetry Method ◽  
High Temperature Gas

The flow visualization in the complicated flow geometry of the pebble bed of the high temperature gas-cooled reactor is investigated to identify the stagnation points at which internal hot spots are expected. A particle image velocimetry method was employed to visualize flow for the pebble bed in the structure of the face centered cubic. The wind tunnel was designed to provide the same Reynolds number of 2.1614×104 as the pebble bed nuclear reactor. Scaling law determined the diameter of the pebble as 120 mm, which is two times bigger than the reference when we use air as a coolant rather than helium. The present scaled up design reduces the load of high speed imaged acquisition and the flow field measured by 4000 frames/s. It was found that the present method identified flow field successfully, including the stagnation points suspected to produce hot spots on the surface of the pebble bed. The present data are useful in evaluating the three-dimensional computational fluid dynamics analysis.

A novel technique to detect hot spots in high temperature boilers

2001 ◽  
Vol 95 (1) ◽  
pp. 51-54 ◽  
Author(s):  
Joseph K.L. Lai ◽  
C.H. Shek ◽  
K.W. Wong
Keyword(s):  
High Temperature ◽  
Hot Spots ◽  
Novel Technique

Investigation of local hot spots in sealing rings with different sealing materials

2021 ◽  
pp. 135065012110195
Author(s):  
Ran Gong ◽  
Xiang Li ◽  
Yi Xu ◽  
He Zhang
Keyword(s):  
High Temperature ◽  
Hot Spots ◽  
Hot Spot ◽  
Simulation Method ◽  
Test Method ◽  
Metal Composite ◽  
Quantitative Correlation ◽  
Seal Failure ◽  
Sealing Ring ◽  
Sealing Materials

The local high temperature in the sealing pair is prone to cause local wear, which easily leads to seal failure. In this paper, a numerical method based on the finite element method is proposed to investigate the local high-temperature hot spot in a sealing ring with different sealing materials. The distribution of hot spots on the sealing surface is visualized by numerical computations. The critical speeds of the hot spot for the metal, composite, and powder metallurgical sealing materials are obtained under different friction coefficients. Based on the obtained results, the quantitative correlation between the critical speed of the hot spot and elastic modulus, thermal conductivity, specific heat capacity, thermal expansion coefficient, and seal sizes is determined. Then, a test method is designed to evaluate the thermal instability of the sealing ring. Scanning electron microscopy is utilized to examine the surface morphology of the sealing rings after the hot spots appear. The results of the present study demonstrate that the proposed method is consistent with the experiment. It indicates the effectiveness of the simulation method for investigating local hot spots in the sealing ring.

High-temperature hot spots on Io as Seen by the Galileo solid state imaging (SSI) Experiment

1997 ◽  
Vol 24 (20) ◽  
pp. 2443-2446 ◽  
Author(s):  
Alfred S. McEwen ◽  
Damon P. Simonelli ◽  
David R. Senske ◽  
Kenneth P. Klaasen ◽  
Laszlo Keszthelyi ◽  
...  
Keyword(s):  
High Temperature ◽  
Solid State ◽  
Hot Spots
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