Aberdeen Proving Ground, MD, United States
Aberdeen Proving Ground, MD, United States

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Champagne V.K.,U.S. Army | Helfritch D.J.,Dynamic Science Inc. | Dinavahi S.P.G.,Lockheed Martin | Leyman P.F.,Data Matrix Solutions , Inc.
Journal of Thermal Spray Technology | Year: 2011

In an effort to corroborate theoretical and experimental techniques used for cold spray particle velocity analysis, two theoretical and one experimental methods were used to analyze the operation of a nozzle accelerating aluminum particles in nitrogen gas. Two-dimensional (2D) axi-symmetric computations of the flow through the nozzle were performed using the Reynolds averaged Navier-Stokes code in a computational fluid dynamics platform. 1D, isentropic, gas-dynamic equations were solved for the same nozzle geometry and initial conditions. Finally, the velocities of particles exiting a nozzle of the same geometry and operated at the same initial conditions were measured by a dual-slit velocimeter. Exit plume particle velocities as determined by the three methods compared reasonably well, and differences could be attributed to frictional and particle distribution effects. © 2010 ASM International.


Golt M.C.,Dynamic Science Inc. | Bratcher M.S.,U.S. Army
Ceramic Engineering and Science Proceedings | Year: 2014

Periodic arrays of ceramic tiles are commonly used in ceramic-based armor applications. In these systems a minimal and consistent gapping between tiles is desired for predictable and reliable ballistic performance, often requiring high tolerance machining of the ceramic tiles. This increases the fabrication costs considerably. Alternatively, if standard tolerance tiles were dimensioned or measured and intelligently arranged as to minimize gapping, then more affordable armor could be produced. This study seeks to solve this close-packing problem through efficiently measuring hexagonal tile dimensions through a high-throughput, low-cost means and then solving for an optimal arrangement of those tiles using a genetic algorithm.


Champagne V.,U.S. Army | Helfritch D.,Dynamic Science Inc. | Wienhold E.,University of Maryland University College | Dehaven J.,Missouri University of Science and Technology
Journal of Micromechanics and Microengineering | Year: 2013

The application of fine line micro-circuitry onto ceramic substrates currently requires a multi step process including printing, baking and sintering. A new, one-step, process utilizing particle impact deposition is presented. This process directs a high velocity stream of copper particles within a helium carrier onto a ceramic substrate. Upon impact the particles deform and adhere to the substrate and to previously deposited particles. The use of a capillary tube as the flow nozzle restricts the jet and the resulting deposited copper to micron scale dimensions. The deposited copper is dense, with near zero porosity. Robot control of the jet position can yield precise conduction lines and component connections. © 2013 IOP Publishing Ltd.


Kraft R.H.,U.S. Army | Mckee P.J.,Dynamic Science Inc. | Dagro A.M.,U.S. Army | Grafton S.T.,University of California at Santa Barbara
PLoS Computational Biology | Year: 2012

This article presents the integration of brain injury biomechanics and graph theoretical analysis of neuronal connections, or connectomics, to form a neurocomputational model that captures spatiotemporal characteristics of trauma. We relate localized mechanical brain damage predicted from biofidelic finite element simulations of the human head subjected to impact with degradation in the structural connectome for a single individual. The finite element model incorporates various length scales into the full head simulations by including anisotropic constitutive laws informed by diffusion tensor imaging. Coupling between the finite element analysis and network-based tools is established through experimentally-based cellular injury thresholds for white matter regions. Once edges are degraded, graph theoretical measures are computed on the "damaged" network. For a frontal impact, the simulations predict that the temporal and occipital regions undergo the most axonal strain and strain rate at short times (less than 24 hrs), which leads to cellular death initiation, which results in damage that shows dependence on angle of impact and underlying microstructure of brain tissue. The monotonic cellular death relationships predict a spatiotemporal change of structural damage. Interestingly, at 96 hrs post-impact, computations predict no network nodes were completely disconnected from the network, despite significant damage to network edges. At early times (t<24 hrs) network measures of global and local efficiency were degraded little; however, as time increased to 96 hrs the network properties were significantly reduced. In the future, this computational framework could help inform functional networks from physics-based structural brain biomechanics to obtain not only a biomechanics-based understanding of injury, but also neurophysiological insight.


Champagne V.K.,U.S. Army | Helfritch D.J.,Dynamic Science Inc.
Journal of Biological Engineering | Year: 2013

Background: Bacterial contamination on touch surfaces results in increased risk of infection. In the last few decades, work has been done on the antimicrobial properties of copper and its alloys against a range of micro-organisms threatening public health in food processing, healthcare and air conditioning applications; however, an optimum copper method of surface deposition and mass structure has not been identified.Results: A proof-of-concept study of the disinfection effectiveness of three copper surfaces was performed. The surfaces were produced by the deposition of copper using three methods of thermal spray, namely, plasma spray, wire arc spray and cold spray The surfaces were then inoculated with meticillin-resistant Staphylococcus aureus (MRSA). After a two hour exposure to the surfaces, the surviving MRSA were assayed and the results compared.The differences in the copper depositions produced by the three thermal spray methods were examined in order to explain the mechanism that causes the observed differences in MRSA killing efficiencies. The cold spray deposition method was significantly more effective than the other methods. It was determined that work hardening caused by the high velocity particle impacts created by the cold spray technique results in a copper microstructure that enhances ionic diffusion, and copper ions are principally responsible for antimicrobial activity.Conclusions: This test showed significant microbiologic differences between coatings produced by different spray techniques and demonstrates the importance of the copper application technique. The cold spray technique shows superior anti-microbial effectiveness caused by the high impact velocity imparted to the sprayed particles which results in high dislocation density and high ionic diffusivity. © 2013 Champagne and Helfritch; licensee BioMed Central Ltd.


Casem D.T.,U.S. Army | Dwivedi A.K.,Dynamic Science Inc. | Mrozek R.A.,U.S. Army | Lenhart J.L.,U.S. Army
International Journal of Solids and Structures | Year: 2014

The mechanical response of a thermoplastic elastomer synthetic ballistic gel is studied over a range of strain-rates. Experiments were conducted at room temperature under uniaxial stress compression at rates ranging from 0.001 to 500/s. Low-rate experiments (<1/s) were conducted with a servo-hydraulic load frame. High-rate experiments (>100/s) were conducted with a polymeric Kolsky bar, along with several modifications to improve data quality. These modifications include the use of a commercial force transducer, a normal displacement interferometer, and a line laser extensometer. Because of the low shear strength and comparatively high compressibility of these materials, inertial effects are very pronounced. Specimen size is varied in an effort to study inertial effects at various loading rates. High speed photography is also used to demonstrate the presence of non-uniform deformation, due to both inertia and friction between the specimen and the loading surfaces. Finally, numerical simulation is used to verify trends observed in the experiments and further validate the data. It is concluded that this material is rate sensitive, with an almost three-fold increase in stiffness over the range of strain-rates studied. © 2014 Elsevier Ltd. All rights reserved.


Trademark
Excitement Dietetics Llc and Dynamic Science Inc. | Date: 2010-07-06

Dietary supplement for weight loss.


De Rosset W.S.,Dynamic Science Inc.
Materials and Manufacturing Processes | Year: 2012

Experiments have been conducted to see if internal grooves machined in steel cylinders will lead to higher bond strengths produced by the Gun Liner Emplacement with an Elastomeric Material (GLEEM) process. Groove depth and twist angle were varied. Both experimental and analytical studies showed that at the pressures used, there was little movement of the liner material into the machined grooves. However, the liner was seen to conform to very small machining marks in the steel cylinder inner bore, providing an increase in the coefficient of friction. Bond strengths of over 30MPa were obtained. Copyright © National Technical Systems 2012.


Miller M.D.,Benet Laboratories | Campo F.,Benet Laboratories | Troiano E.,Benet Laboratories | Smith S.,Benet Laboratories | De Rosset W.S.,Dynamic Science Inc.
Materials and Manufacturing Processes | Year: 2012

Many of the U.S. Army's gun tubes are currently electrolytically plated with chromium in order to extend their service life. In order to eliminate the hexavalent chromium used in the plating process, the development of explosively bonded refractory metal liners has been carried out. While the ultimate application of this technology is for large caliber cannons, the Bushmaster 25-mm M242 medium caliber cannon has been used as a test bed to save costs. A vendor was selected who could explosively bond refractory metals to a short section of a gun tube. The quality and strength of these bonds have been assessed in several ways. Visual observation of sectioned gun tubes showed good liner adhesion to the gun tube. Shear strength tests have been conducted on several bonded liners. Finally, hot hardness tests have been conducted on three explosively-bonded liners. These tests led to the decision to select Ta-10W as the liner material. The vendor was able to explosively bond a Ta-10W liner to a full-length M242 barrel forging. Several barrels were produced and successfully test fired. Copyright © National Technical Systems 2012.


Trademark
Nutripharm Llc and Dynamic Science Inc. | Date: 2010-06-15

Dietary supplements for weight loss.

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