Kellogg F.R.,Data Matrix Solutions , Inc. |
Klotz B.R.,Dynamic Science Inc. |
Nersisyan H.H.,Chungnam National University |
Cho K.C.,U.S. Army
Proceedings of the 8th International Conference on Tungsten, Refractory and Hardmaterials | Year: 2011
Salt-assisted combustion synthesis has been used to produce tungsten nanopowders. Tungsten trioxide, zinc, and sodium chloride were dry mixed and heated under argon to promote a combustion reaction. Reaction products were then treated with acid and subjected to hydrogen heat treatment. Samples of the tungsten powders produced were then characterized to determine particle size and purity. Nano-sized particles clustered in larger agglomerates were observed, and samples of the powder produced under different conditions were found to contain varying levels of oxygen. Plasma Pressure Compaction (P2C) was then used to consolidate the powders, and density and grain size of the resulting samples were measured. Bulk samples with nano-sized grains were able to be produced, but high density was not achieved. However, use of tungsten nano powders resulted in consolidated samples with higher density than those achieved with conventional sub-micron tungsten powders under similar processing conditions.
Swab J.J.,U.S. Army |
Pavlacka R.,U.S. Army |
Pavlacka R.,Oak Ridge Institute for Science and Education |
Gilde G.,U.S. Army |
And 5 more authors.
Journal of the American Ceramic Society | Year: 2014
The strength of two coarse-grained (grain size > 200 μm) cubic ceramics, a magnesium aluminate spinel (MgAl2O4) and an AlON, along with a fine-grained (1.5 μm) MgAl2O4, was determined by conducting a series of four-point and equibiaxial flexure tests on specimens of different sizes. Weibull strength size scaling revealed a linear relationship on a log-log plot between average flexure strength and effective specimen area for the fine-grained spinel, but a nonlinear relationship for both coarse-grained materials. Initial fractography showed that each material had a single flaw population limiting the strength over the entire specimen size range, which does not account for the nonlinear size scaling relationship in the two coarse-grained materials. However, further fractography revealed that in both materials there was an initial flaw and a critical flaw. The former appears to be machining/polishing damage that started the fracture process while the latter was a cleaved grain in AlON or a cracked grain boundary in the HP/HIP spinel that lead to fracture of the specimen. The difference between the initial and critical flaw size coupled with a detailed analysis of the strength as a function of test specimen thickness accounted for the nonlinear strength size scaling relationship. As a result, strength values obtained using thin test specimens can lead to an erroneous strength prediction for large components made of these ceramics. The implication of these findings is that strength tests must be conducted using appropriately thick specimens to obtain a representative strength value. If appropriately thick specimens cannot be tested, then fractography must be conducted to determine the flaw size. If the flaw size is sufficiently large, compared with the specimen thickness, then the strength must be adjusted according to a stress field correction factor to obtain a more accurate strength value. © Published 2013. This article is a U.S. Government work and is in the public domain in the U.S.A.
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.
Katulka G.,U.S. Army |
Condon J.,U.S. Army |
Hamaoui M.,Data Matrix Solutions , Inc.
Proceedings - 27th International Symposium on Ballistics, BALLISTICS 2013 | Year: 2013
Electromagnetic radiation from samples of explosive materials has been characterized experimentally, throughout the detonation process, with a high-speed, wideband radio-frequency (RF) data acquisition system. Samples of material, including PBXN5 and C4 having masses that ranged from 2g to as much as 500g, were experimentally characterized during the explosive event, beginning from the point just prior to ignition through cessation of detonation. Explosive samples were measured both in free space as well as buried in soil. The measured results were analyzed with Fast Fourier Transform and Wavelet Transform signal processing techniques, to determine the electric-field frequency spectral characteristics of the explosives as the detonation progressed in time. The experimental data revealed distinct signatures from the main explosive charge, where the observed electric field spectra had significant power extending to as much as 2MHz, for the explosive m aterials and the boundary conditions w hich were studied.
Silton S.,U.S. Army |
Howell B.,Data Matrix Solutions , Inc.
26th International Symposium on BALLISTICS | Year: 2011
Standard M855 tests shows yaw growth beginning at 400-m, ultimately growing to 4.5 degrees at 600-m. Stability analysis with simulated spin rates can reduce the yaw limit cycle of the M855 by approximately 0.5 degrees. Previous full range shots for M855 do not show evidence of a yaw limit cycle until 600-m. PRODAS simulations of the M855 do not show evidence of a trim angle at 600-m. Gyroscopic and dynamic stability analysis of the M193 show yaw limit cycle is present at 600-m for muzzle spin and adjusted spin cases. Matched spin experiment for the M193 is gyroscopically and dynamically stable at all Mach numbers tested.
Bratcher M.S.,U.S. Army |
Jessen T.L.,U.S. Army |
Golt M.C.,Data Matrix Solutions , Inc.
International SAMPE Technical Conference | Year: 2011
Historically, composite integral armor designs have been part of armor development programs in the U. S. Army. In general, these armor designs have two components: a) a strike face to break up incoming projectiles and b) a backing support system (BSS) that offers structural support to the strike face and absorbs residual energy and debris from the strike face and projectiles. To evaluate performance and improve designs, it is necessary to determine the degree and progression of damage in candidate BSS samples. To accomplish this, we have developed a new technique to nondestructively examine BSS materials. The method is based on measuring the dielectric properties of composite samples and is rapid enough to be inserted in multi-impact test sequences. This enables engineers to acquire novel information about the evolution of damage during the testing sequence. The output of this method is false color images that depict regions where the measured dielectric constant changes dramatically. These large changes are attributed to air now present between the layers in the BSS, such that the false color images have adopted the term 'delamination map.'.
Rogers J.,Georgia Institute of Technology |
Costello M.,Georgia Institute of Technology |
Harkins T.,U.S. Army |
Hamaoui M.,Data Matrix Solutions , Inc.
Navigation, Journal of the Institute of Navigation | Year: 2011
The use of magnetometers for orientation estimation on rapidly-spinning flight bodies is analyzed. Specifically, the effect of spin-induced magnetic field distortion is discussed, with particular attention to its implications for magnetometer-based orientation estimation. First, the nature of spin-induced field distortion is described and it is shown that, if not properly accounted for, distortion can lead to significant estimation errors in artillery projectiles. Then, an orientation estimator is constructed driven by magnetometer, gyroscope, and GPS feedback. A novel feature of this algorithm is its compensation for spin-induced distortion of the Earth's field. The algorithm also incorporates in-flight magnetometer calibration performed simultaneously with projectile orientation estimation. The comprehensive algorithm is built as a coupled set of Extended Kalman filters. Observability of the estimation problem is discussed and unobservable modes are identified. Finally, example results and Monte Carlo simulations compare estimation performance to algorithms which neglect spin-induced distortion effects or do not perform in-flight calibration. These results demonstrate that magnetometer-based systems on-board spinning projectiles should incorporate corrections for field distortion, and that overall accuracy is greatly enhanced by performing in-flight calibration.
Levine F.,Data Matrix Solutions , Inc. |
Kayea Iii R.V.,Oak Ridge Institute for Science and Education |
Wexler R.,Oak Ridge Institute for Science and Education |
Sadvary D.J.,Oak Ridge Institute for Science and Education |
And 2 more authors.
JAOCS, Journal of the American Oil Chemists' Society | Year: 2014
The military uses JP-8, a kerosene type hydrocarbon, to fuel most of its vehicles and is seeking a renewable alternative fuel that meets strict JP-8 specifications. Biodiesel is typically a mixture of different alkyl esters produced from the transesterification of triglycerides readily available in plant oils and used cooking oil. To date, no traditional biodiesel meets the requirements for heat of combustion, freezing point, viscosity and oxidative stability to be a stand-alone replacement for JP-8. This work is a fundamental survey of the heat of combustion of single fatty acid esters and a predictive model for estimating the heat of combustion given a known molecular structure. The gross heat of combustion of various C6-C18 fatty acids and the methyl, propyl and isopropyl esters of these fatty acids was measured. This study sought to relate the effect of chain length, degree of unsaturation and branching to the critical fuel property of the gross heat of combustion (H c). It was found that H c (kJ/g) increased with chain length. A nearly linear relationship was found between wt% carbon and hydrogen, and H c. Group contribution models previously published for hydrocarbons and polymers were modified to more accurately predict the heat of combustion of the fatty acids and esters. Modification of the molar heat values of carboxylic acid, methyl, and methylene groups improved correlation of the model with the experimental results. © 2013 AOCS.
Garner J.,U.S. Army |
Conroy P.,U.S. Army |
Keppinger R.,U.S. Army |
Oberlin G.,Data Matrix Solutions , Inc.
Materials and Manufacturing Processes | Year: 2012
Over the course of the past four years, advances have been made in the in-bore characterization of small arms to include 5.56mm and 7.62mm systems at the Army Research Laboratory (ARL). This involves the application of in-bore laser measurements of the gun tube surface to very high level of resolution and accuracy which was previously unobtainable using existing conventional systems. The first 5.56mm in-bore laser measuring system was manufactured for the ARL by Laser Techniques Co. (LTC) of Redmond, WA. The 5.56mm system has been applied to the following weapons: M4, M16A1, M249 as well as other 5.56mm weapons. It produces a three-dimensional (3-D) map of the bore surface to a depth resolution of 10 microns and axial resolution of 40 microns and circumferential resolution of 0.6 degrees. A color pallet is created and applied to the radial displacement from a baseline, and a picture is produced showing details of the bore surface. These characterization efforts have been augmented by visual scopes as well. One of the first applications of these systems was to analyze a series of firings in three each of M4, M16A2, and M249 weapons. This produced scans that were subsequently analyzed using Matlab to determine a history of wear life. This data is useful in enhancing predictive wear rates for barrels as well as for comparisons against recorded wear rates of fielded barrels. Copyright © National Technical Systems 2012.