Unusual Microstructure in Shock-Compacted Graphite

1970 ◽  
Vol 28 ◽  
pp. 474-475
Author(s):  
Lucien F. Trueb
Keyword(s):  
Mechanical Characteristic ◽  
Compression Wave ◽  
Gray Zone ◽  
Flyer Plate ◽  
Compacted Graphite ◽  
The Impact

Crushed and statically compressed Madagascar graphite that was explosively shocked at 425 kb by means of a planar flyer-plate is characterized by a black zone extending for 2 to 3 nun below the impact plane of the driver. Beyond this point, the material assumes the normal gray color of graphite. The thickness of the black zone is identical with the distance taken by the relaxation wave to overtake the compression wave.The main mechanical characteristic of the black material is its great hardness; steel scalpels and razor blades are readily blunted during attempts to cut it. An average microhardness value of 95-3 DPHN was obtained with a 10 kg load. This figure is a minimum because the indentations were usually cracked; 14.8 DPHN was measured in the gray zone.

Explosive Welding of SS304 and Al6061 Using Copper as Interlayer – Development of Trial Methodology and its Optimisation

2015 ◽  
Vol 830-831 ◽  
pp. 306-309
Author(s):  
Niraj Srivastava ◽  
Abhishek Upadhyay ◽  
Sandeep Kumar ◽  
Diva ◽  
Jaspreet Singh ◽  
...  
Keyword(s):  
Explosive Welding ◽  
Welding Process ◽  
Al Alloy ◽  
Flyer Plate ◽  
Trial Methodology ◽  
Al 6061 ◽  
Velocity Of Detonation ◽  
Copper Interlayer ◽  
Weldability Window ◽  
The Impact

This paper explains the technique of explosive welding for joining SS304 and Al 6061 using Copper interlayer. The joining was done in two stages. In the first stage SS304 (thickness: 20 mm) was joined to Copper (thickness: 3mm). Second stage involved joining of SS-Cu plate to Al 6061 (thickness: 8 mm).The paper presents detailed discussion on important parameters required for explosive welded process. The most important parameter is minimum and maximum flyer plate velocity required for creating the impact. Collision angle and angle of impact are also discussed. Another important parameter is the Velocity of detonation (VOD) of explosive to be used. The explosives used have VOD of the order of 2500 m/s and 1600 m/sec. Since the explosive welding process involves formation of jet between two surface, therefore surface conditions of the base and flyer plate like its flatness, roughness and cleanliness which are very critical for proper joining have been discussed in this paper. Chisel test (which is considered to be most rugged test) was conducted on the joint. The test confirmed successful joining.The paper explains how use of trimonite expands the weldability window in comparison to NGU when used for direct SS to Al alloy welding.It also compares the results obtained by use of two different powder explosives to obtain the same tri-layered plate via two different routes. The results are particularly interesting because both the explosives have substantial difference in their properties such as Velocity of Detonation, Gurney Characteristic Velocity, density and homogeneity which can be used as advantages from different angles of views.

Numerical Investigation of Compression Wave Attenuation in Water Barriers

2015 ◽  
Vol 756 ◽  
pp. 491-494
Author(s):  
A.E. Baganina ◽  
D.Y. Paleev ◽  
Mikhail Yu. Blaschuk
Keyword(s):  
Numerical Investigation ◽  
Compression Wave ◽  
Wave Attenuation ◽  
Numerical Study ◽  
The Impact

The article presents the results of a numerical study of the compression wave attenuation (CW) in water barriers. The impact of barriers thickness, their quantity and concentration of water particles in the barrier have been analyzed in the process of CW attenuation.

Numerical Analysis of Wavy Interface Formation and Successive Temperature Change in Magnetic Pulse Welded Al/Cu Joint

2016 ◽  
Vol 877 ◽  
pp. 655-661 ◽  
Author(s):  
Junto Nishiwaki ◽  
Takashi Kambe ◽  
Yasutaka Kedo ◽  
Yohei Harada ◽  
Shinji Muraishi ◽  
...  
Keyword(s):  
Impact Velocity ◽  
Intermediate Layer ◽  
Impact Angle ◽  
Joint Interface ◽  
Dissimilar Metals ◽  
Magnetic Pulse ◽  
Flyer Plate ◽  
Interface Formation ◽  
Wavy Interface ◽  
The Impact

Magnetic pulse welding (MPW) which is one of the impact welding methods is suitable for a wide variety of combinations of similar and dissimilar metals. The flyer plate is accelerated by electromagnetic force and collided to the parent plate. A characteristic wavy interface is formed. The impact velocity and impact angle of the flyer plate during impact are important parameters which affect the interface morphology. In the case of dissimilar metals (e.g. Al/Cu, Al/Fe), the intermediate layer (such as intermetallic compound (IMC)) is formed by wavy interface formation and local temperature increase. The intermediate layer often decreases the bonding strength. Wavy interface formation mechanism and temperature increase at the joint interface should be investigated in order to obtain the dissimilar metal joint with high bonding strength. In this study, the impact velocity and impact angle of the flyer plate were obtained by using ANSYS Emag-Mechanical. Based on the obtained impact velocity and impact angle of the flyer plate in the MPW, the wavy interface formation and temperature change were reproduced by using ANSYS Autodyn for solving non-liner dynamics problems. Al sheets and Cu sheets were joined by the MPW. The joint interface was observed by OM and SEM and compared to the simulation result.

scholarly journals Ultrasonic Detection of Spall Damage Distribution Subjected to Plate Impact Test with Different Thickness

2018 ◽  
Vol 183 ◽  
pp. 02029
Author(s):  
Naoya Nishimura ◽  
Toshihiro Ito ◽  
Takeru Watanabe
Keyword(s):  
Tensile Stress ◽  
Impact Test ◽  
Plate Thickness ◽  
Flyer Plate ◽  
Plate Impact ◽  
Target Plate ◽  
Damage Distribution ◽  
Spall Damage ◽  
The Impact ◽  
Different Thickness

Plate impact test on medium carbon steel were carried out to the target plate by impacting the flyer plate with one-third and two-thirds thickness of the target plate. The spall damage within the target plate was evaluated non-destructively with a low frequency scanning acoustic microscope as well as ultrasonic velocity and backscattering intensity. We observed the spall damage distribution by the B-and Cscan images. The distribution of spall damage through the plate thickness depends on the tensile stress area within the target plate. The difference of spall damage distribution was investigated by the plate impact test by flyer plate with different thickness. In the plate impact test by the flyer plate with 1/3 target plate thickness, the spall damage was generated by tensile stress area which superposed in the back surface side. On the other hand, in the case of 2/3 target plate thickness, the spall damage was detected at the impact surface side. By generating the spall damage in the different position through the target thickness, it will be possible to evaluate the accumulation of spall damage by reflection and transmission of the stress wave at the internal damage subjected to repeated impact.

scholarly journals The Representation of Cumulus Convection in High-Resolution Simulations of the 2013 Colorado Front Range Flood

2016 ◽  
Vol 144 (11) ◽  
pp. 4265-4278 ◽  
Author(s):  
Kelly M. Mahoney
Keyword(s):  
Extreme Rainfall ◽  
Heavy Rain ◽  
Moisture Flux ◽  
Heavy Precipitation ◽  
Colorado Front Range ◽  
Convective Precipitation ◽  
Gray Zone ◽  
Front Range ◽  
Model Errors ◽  
The Impact

Abstract Model simulations of the 2013 Colorado Front Range floods are performed using 4-km horizontal grid spacing to evaluate the impact of using explicit convection (EC) versus parameterized convection (CP) in the model convective physics “gray zone.” Significant differences in heavy precipitation forecasts are found across multiple regions in which heavy rain and high-impact flooding occurred. The relative contribution of CP-generated precipitation to total precipitation suggests that greater CP scheme activity in areas upstream of the Front Range flooding may have led to significant downstream model error. Heavy convective precipitation simulated by the Kain–Fritsch CP scheme in particular led to an alteration of the low-level moisture flux and moisture transport fields that ultimately prevented the generation of heavy precipitation in downstream areas as observed. An updated, scale-aware version of the Kain–Fritsch scheme is also tested, and decreased model errors both up- and downstream suggest that scale-aware updates yield improvements in the simulation of this event. Comparisons among multiple CP schemes demonstrate that there are model convective physics gray zone considerations that significantly impact the simulation of extreme rainfall in this event.

scholarly journals Assessing the Diagnostic Accuracy of Pulse Pressure Variations for the Prediction of Fluid Responsiveness

2011 ◽  
Vol 115 (2) ◽  
pp. 231-241 ◽  
Author(s):  
Maxime Cannesson ◽  
Yannick Le Manach ◽  
Christoph K. Hofer ◽  
Jean Pierre Goarin ◽  
Jean-Jacques Lehot ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Central Venous Pressure ◽  
General Anesthesia ◽  
Fluid Responsiveness ◽  
Pulse Pressure ◽  
Predictive Value ◽  
Venous Pressure ◽  
Gray Zone ◽  
Central Venous ◽  
The Impact

Background Respiratory arterial pulse pressure variations (PPV) are the best predictors of fluid responsiveness in mechanically ventilated patients during general anesthesia. However, previous studies were performed in a small number of patients and determined a single cutoff point to make clinical discrimination. The authors sought to test the predictive value of PPV in a large, multicenter study and to express it using a gray zone approach. Methods The authors studied 413 patients during general anesthesia and mechanical ventilation in four centers. PPV, central venous pressure, and cardiac output were recorded before and after volume expansion (VE). Response to VE was defined as more than 15% increase in cardiac output after VE. The following approaches were used to determine the gray zones: resampled and two-graph receiver operator characteristic curves. The impact of changes in the benefit-risk balance of VE on the gray zone was also evaluated. Results The authors observed 209 responders (51%) and 204 nonresponders (49%) to VE. The area under receiver operating characteristic curve was 0.89 (95% CI: 0.86-0.92) for PPV, compared with 0.57 (95% CI: 0.54-0.59) for central venous pressure (P < 10). The gray zone approach identified a range of PPV values (between 9% and 13%) for which fluid responsiveness could not be predicted reliably. These PPV values were seen in 98 (24%) patients. Changes in the cost ratio of VE moderately affected the gray zone limits. Conclusion Despite a strong predictive value, PPV may be inconclusive (between 9% and 13%) in approximately 25% of patients during general anesthesia.

scholarly journals The Impact of Nanoparticles on the Immune System: A Gray Zone of Nanomedicine

2021 ◽  
Vol 5 (1) ◽  
pp. 19-33
Author(s):  
Priyanka Ray ◽  
Noor Haideri ◽  
Inamul Haque ◽  
Omar Mohammed ◽  
Saborni Chakraborty ◽  
...  
Keyword(s):  
Immune System ◽  
Genetic Disorders ◽  
Survival Rates ◽  
Adaptive Immune System ◽  
Gray Zone ◽  
Meaningful Change ◽  
Surface Receptors ◽  
Adaptive Immune ◽  
System A ◽  
The Impact

Since the early days marking the first use of nanomedicine in the early 80s, there has been a meaningful change in the scientific field involving the Fabrication, characterization, and application of nanomaterials to treat many diseases, including cancers and genetic disorders. As unique and attractive properties of this novel class of materials unraveled, significant advances and discoveries were made over time. Addressing several challenges posed by conventional therapy, which were the only available treatment option for ailing patients, nanomedicine provided enhanced benefits, including reduced dosing, improved pharmacokinetics, and superior targeting efficiency. Several such formulations have successfully made their way to clinics and have shown promise in prolonging terminally ill patient populations' survival rates. However, the complex immune system and its various components, including various proteins and surface receptors, have made nanomaterials' journey from benchtop to the bedside a treacherous one. The innate and adaptive immune system interactions with nanomaterials are still under investigation and full of mysteries. This review highlights the various aspects of therapeutic nanocarriers and their current understanding of their immune systems' interactions.

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