scholarly journals A Rapid Throughput System for Shock and Impact Characterization: Design and Examples in Compaction, Spallation, and Impact Welding

2020 ◽  
Vol 4 (4) ◽  
pp. 116
Author(s):  
K. Sajun Prasad ◽  
Yu Mao ◽  
Anupam Vivek ◽  
Stephen R. Niezgoda ◽  
Glenn S. Daehn
Keyword(s):  
Spall Strength ◽  
Impact Angle ◽  
Mechanical Shock ◽  
System A ◽  
Stress Changes ◽  
Primary Driver ◽  
Impact Welding ◽  
Strain Rate Behavior ◽  
Gas Guns ◽  
Physical Phenomena

Many important physical phenomena are governed by intense mechanical shock and impulse. These can be used in material processing and manufacturing. Examples include the compaction or shearing of materials in ballistic, meteor, or other impacts, spallation in armor and impact to induce phase and residual stress changes. The traditional methods for measuring very high strain rate behavior usually include gas-guns that accelerate flyers up to km/s speeds over a distance of meters. The throughput of such experiments is usually limited to a few experiments per day and the equipment is usually large, requiring specialized laboratories. Here, a much more compact method based on the Vaporizing Foil Actuator (VFA) is used that can accelerate flyers to over 1 km/s over a few mm of travel is proposed for high throughput testing in a compact system. A system with this primary driver coupled with Photonic Doppler Velocimetry (PDV) is demonstrated to give insightful data in powder compaction allowing measurements of shock speed, spall testing giving fast and reasonable estimates of spall strength, and impact welding providing interface microstructure as a function of impact angle and speed. The essential features of the system are outlined, and it is noted that this approach can be extended to other dynamic tests as well.

scholarly journals Anorexia Nervosa and the Immune System—A Narrative Review

2019 ◽  
Vol 8 (11) ◽  
pp. 1915 ◽  
Author(s):  
Dennis Gibson ◽  
Philip S Mehler
Keyword(s):  
Anorexia Nervosa ◽  
Immune System ◽  
Potential Role ◽  
Genetic Studies ◽  
System A ◽  
Stress Changes ◽  
Abnormal Bone Marrow ◽  
Disorder Potential ◽  
Necrosis Factor ◽  
Pro Inflammatory Cytokines

The pathogenesis of an increasing number of chronic diseases is being attributed to effects of the immune system. However, its role in the development and maintenance of anorexia nervosa is seemingly under-appreciated. Yet, in examining the available research on the immune system and genetic studies in anorexia nervosa, one becomes increasingly suspicious of the immune system’s potential role in the pathophysiology of anorexia nervosa. Specifically, research is suggestive of increased levels of various pro-inflammatory cytokines as well as the spontaneous production of tumor necrosis factor in anorexia nervosa; genetic studies further support a dysregulated immune system in this disorder. Potential contributors to this dysregulated immune system are discussed including increased oxidative stress, chronic physiological/psychological stress, changes in the intestinal microbiota, and an abnormal bone marrow microenvironment, all of which are present in anorexia nervosa.

Parameter Identification for Magnetic Pulse Welding Applications

2018 ◽  
Vol 767 ◽  
pp. 431-438 ◽  
Author(s):  
Joerg Bellmann ◽  
Joern Lueg-Althoff ◽  
Sebastian Schulze ◽  
Soeren Gies ◽  
Eckhard Beyer ◽  
...  
Keyword(s):  
Minimum Energy ◽  
Welding Process ◽  
Axial Position ◽  
Intensity Level ◽  
Magnetic Pulse ◽  
Mechanical Shock ◽  
Magnetic Pulse Welding ◽  
Impact Welding ◽  
Pulse Welding ◽  
The Impact

Magnetic pulse welding (MPW) is a promising technology to join dissimilar metals and to produce multi-material structures, e.g. to fulfill lightweight requirements. During this impact welding process, proper collision conditions between both joining partners are essential for a sound weld formation. Controlling these conditions is difficult due to a huge number of influencing and interacting factors. Many of them are related to the pulse welding setup and the material properties of the moving part, the so-called flyer. In this paper, a new measurement system is applied that takes advantage of the high velocity impact flash. The flash is a side effect of the MPW process and its intensity depends on the impact velocity of the flyer. Thus, the intensity level can be used as a welding criterion. A procedure is described that enables the user to realize a fast parameter development with only a few experiments. The minimum energy level and the optimum distance between the parts to be joined can be identified. This is of importance since a low energy input decreases the thermal and mechanical shock loading on the tool coil and thus increases its lifetime. In a second step, the axial position of the flyer in the tool coil is adjusted to ensure a proper collision angle and a circumferential weld seam.

Development and Application of Test Apparatus for Cutting Performance of Cutters of Large Excavation Equipment

2014 ◽  
Vol 670-671 ◽  
pp. 497-501
Author(s):  
Peng Lei Wang ◽  
Yi Min Xia ◽  
Tao Ouyang ◽  
Lu Tang ◽  
Ben Guo
Keyword(s):  
Test System ◽  
Test Method ◽  
Cutting Performance ◽  
Coupling Mechanism ◽  
Test Apparatus ◽  
Vertical Loading ◽  
System A ◽  
Laboratory Test Method ◽  
Loading System ◽  
Physical Phenomena

In order to study the physical phenomena and mechanical properties of cutters when cutting rock, a test apparatus for cutting performance of cutters of large excavation equipment is established. The test apparatus is composed of a vertical loading system, a rotary loading system, a control system and a test system. Tests of different cut penetrations and spacings were carried out using the test apparatus. Meanwhile, the real-time images of the cutting process and forces acting on the cutters were obtained. The result shows that the test apparatus has good practicality and reliability, and it provides a laboratory test method to study the cutter-rock coupling mechanism and cutting performance of cutters.

Thermal Management of On-Chip Hot Spot

2009 ◽  
Author(s):  
Avram Bar-Cohen ◽  
Peng Wang
Keyword(s):  
Heat Flux ◽  
Thermal Management ◽  
Hot Spot ◽  
High Heat ◽  
High Heat Flux ◽  
Switching Speed ◽  
Primary Driver ◽  
Management Approaches ◽  
On Chip ◽  
Physical Phenomena

The rapid emergence of nanoelectronics, with the consequent rise in transistor density and switching speed, has led to a steep increase in microprocessor chip heat flux and growing concern over the emergence of on-chip “hot spots”. The application of on-chip high heat flux cooling techniques is today a primary driver for innovation in the electronics industry. In this paper, the physical phenomena underpinning the most promising on-chip thermal management approaches for hot spot remediation, along with basic modeling equations and typical results are described. Attention is devoted to thermoelectric microcoolers — using mini-contcat enhancement and in-plane thermoelectric currents, orthotropic TIM’s/heat spreaders, and phase-change microgap coolers.

scholarly journals Experimental complexes for investigation of behavior of materials at a strain rate of 5·102÷105 s-1

2018 ◽  
Vol 226 ◽  
pp. 03024 ◽  
Author(s):  
Anatoly M. Bragov ◽  
Alexander Y. Konstantinov ◽  
Andrei K. Lomunov ◽  
Tatyana N. Yuzhina ◽  
Andrey R. Filippov
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
High Speed ◽  
Spall Strength ◽  
Pressure Sensors ◽  
Laser Interferometry ◽  
Strain Rate Range ◽  
Materials Testing ◽  
Dynamic Crack ◽  
Gas Guns

A description of experimental complexes, methodological and hardware means for determining the mechanical properties of materials under high-speed deformation and fracture is given in the report. Determination of mechanical properties in the strain rate range 5•102÷103 s-1 is the first direction of work in the laboratory of “Dynamic Materials Testing”. These tests are done using automated complexes based on the Kolsky method and its modifications for compression, tension and shearing. It is also possible to determine the fracture toughness, the characteristics of dynamic crack resistance, as well as to obtain stressstrain curves of low-density materials under uniaxial strain. Original gas guns with a caliber of 10, 20 and 57 mm are used for creation a dynamic load. The study of the behavior of materials at strain rates of 105 s-1 and higher is the second direction of work. In this case, the methods of a planewave shock experiment based on gas guns of 57 and 85 mm caliber are used. Manganine and dielectric pressure sensors, as well as laser interferometry are used for measuring the parameters of elastoplastic waves and for determining such important characteristics as impact compressibility, Hugoniot yield strength, spall strength.

An Experimental Research on Abrasive Water Jet Polishing of the Hard Brittle Ceramics

2013 ◽  
Vol 797 ◽  
pp. 15-20 ◽  
Author(s):  
Zhe Lv ◽  
Chuan Zhen Huang ◽  
Jun Wang ◽  
Hong Tao Zhu ◽  
Peng Yao ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Experimental Research ◽  
Traverse Speed ◽  
Impact Angle ◽  
Water Jet ◽  
Precision Machining ◽  
Abrasive Water Jet ◽  
Processing Quality ◽  
System A ◽  
Machining System

Abrasive water jet (AWJ) technology, due to its potential advantages, is a promising machining method for precision machining brittle materials. In this research, the AlN ceramics was polished using an AWJ machining system. A considerable processing quality has been achieved and a reduction up to 62% of the surface roughness has been obtained. Effects of different process parameters on the surface roughness of the polished workpiece were analyzed. Under the current conditions of the experiments, using a lower impact angle, smaller abrasives and a lower nozzle traverse speed may be appropriate for polishing AlN ceramics.

The Interpretation of Line Profiles

1977 ◽  
Vol 36 ◽  
pp. 191-215
Author(s):  
G.B. Rybicki
Keyword(s):  
Magnetic Fields ◽  
Atomic Physics ◽  
Velocity Fields ◽  
Spectral Lines ◽  
Inhomogeneous Structure ◽  
The Sun ◽  
Line Profiles ◽  
Physical Phenomena

Observations of the shapes and intensities of spectral lines provide a bounty of information about the outer layers of the sun. In order to utilize this information, however, one is faced with a seemingly monumental task. The sun’s chromosphere and corona are extremely complex, and the underlying physical phenomena are far from being understood. Velocity fields, magnetic fields, Inhomogeneous structure, hydromagnetic phenomena – these are some of the complications that must be faced. Other uncertainties involve the atomic physics upon which all of the deductions depend.

New Design for a Differentially Pumped Hydration Chamber for a Siemens IA

1971 ◽  
Vol 29 ◽  
pp. 44-45
Author(s):  
R. C. Moretz ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Electron Microscopy ◽  
Water Vapor ◽  
Electron Diffraction ◽  
Water Vapor Pressure ◽  
Biological Materials ◽  
Thin Membrane ◽  
Reliable System ◽  
System A ◽  
Water Films ◽  
Aperture Opening

Electron microscopy and diffraction of biological materials in the hydrated state requires the construction of a chamber in which the water vapor pressure can be maintained at saturation for a given specimen temperature, while minimally affecting the normal vacuum of the remainder of the microscope column. Initial studies with chambers closed by thin membrane windows showed that at the film thicknesses required for electron diffraction at 100 KV the window failure rate was too high to give a reliable system. A single stage, differentially pumped specimen hydration chamber was constructed, consisting of two apertures (70-100μ), which eliminated the necessity of thin membrane windows. This system was used to obtain electron diffraction and electron microscopy of water droplets and thin water films. However, a period of dehydration occurred during initial pumping of the microscope column. Although rehydration occurred within five minutes, biological materials were irreversibly damaged. Another limitation of this system was that the specimen grid was clamped between the apertures, thus limiting the yield of view to the aperture opening.

TEM visualization of surface replicated acid and base catalyzed sol-gel glasses

1986 ◽  
Vol 44 ◽  
pp. 448-449
Author(s):  
George C. Ruben ◽  
Merrill W. Shafer
Keyword(s):  
Elevated Temperatures ◽  
Sol Gel ◽  
Basic Medium ◽  
Glass Transition Point ◽  
Structural Space ◽  
Acid And Base ◽  
Organometallic Precursors ◽  
New Processing ◽  
Gel Glasses ◽  
Physical Phenomena

Traditionally ceramics have been shaped from powders and densified at temperatures close to their liquid point. New processing methods using various types of sols, gels, and organometallic precursors at low temperature which enable densificatlon at elevated temperatures well below their liquidus, hold the promise of producing ceramics and glasses of controlled and reproducible properties that are highly reliable for electronic, structural, space or medical applications. Ultrastructure processing of silicon alkoxides in acid medium and mixtures of Ludox HS-40 (120Å spheres from DuPont) and Kasil (38% K2O &62% SiO2) in basic medium have been aimed at producing materials with a range of well defined pore sizes (∼20-400Å) to study physical phenomena and materials behavior in well characterized confined geometries. We have studied Pt/C surface replicas of some of these porous sol-gels prepared at temperatures below their glass transition point.

High-resolution electron microscopy of Cu2O surfaces

1986 ◽  
Vol 44 ◽  
pp. 396-397
Author(s):  
V. Castano ◽  
W. Krakow
Keyword(s):  
High Resolution ◽  
Natural Extension ◽  
High Resolution Electron Microscopy ◽  
Point Of View ◽  
Initial Oxidation ◽  
System A ◽  
Resolution Electron ◽  
Surface Reconstructions ◽  
Atomic Surface ◽  
Au Thin Films

In non-UHV microscope environments atomic surface structure has been observed for flat-on for various orientations of Au thin films and edge-on for columns of atoms in small particles. The problem of oxidation of surfaces has only recently been reported from the point of view of high resolution microscopy revealing surface reconstructions for the Ag2O system. A natural extension of these initial oxidation studies is to explore other materials areas which are technologically more significant such as that of Cu2O, which will now be described.

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