Alliant Techsystems

About: Alliant Techsystems is a company organization based out in Arlington, Virginia, United States. It is known for research contribution in the topics: Propellant & Signal. The organization has 822 authors who have published 712 publications receiving 9593 citations. The organization is also known as: ATK.

Normalized smoothing functions for sph impact computations

Abstract: This paper presents a normalized smoothing function (NSF) algorithm that can improve the accuracy of smooth particle hydrodynamics (SPH) impact computations. It is presented specifically for axisymmetric geometry, but the principles also apply to plane strain and three-dimensional geometry. The approach consists of adjusting the standard smoothing functions for every node (and every cycle) such that the normal strain rates are computed exactly for conditions of constant strain rates (linear velocity distributions). This, in turn, generally improves accuracy for non-uniform strain rates. This can significantly improve the accuracy for free boundaries, for non-uniform arrangements of SPH nodes, and for small smoothing distances. A new smoothing function is also introduced. The NSF algorithm is shown to provide improved accuracy for a series of cylinder impact examples that includes two different smoothing functions and two different smoothing distances.

Influence of filament winding parameters on composite vessel quality and strength

Abstract: An experimental design investigation of manufacturing and design variables that affect composite vessel quality, strength, and stiffness was conducted. Eight 20-in. cylinders (with one additional cylinder as a replicate) were manufactured and tested for hoop strength, hoop stiffness, fiber and void volume fraction distribution through thickness, residual stress, and interlaminar shear strength. Material and processing variables were divided into five categories: (a) resin, (b) fiber, (c) fabrication process, (d) design, and (e) equipment. Five variables were selected (from a list of 12) for study using a 1 4 fractional factorial design of experiment setup. The five variables were: (a) winding tension, (b) stacking sequence, (c) winding-tension gradient, (d) winding time, and (e) cut-versus-uncut helicals. Statistical analysis of the data shows that the composite vessel strength was affected by the manufacturing and design variables. In general, it was found that composite strength was significantly affected by the laminate stacking sequence, winding tension, winding-tension gradient, winding time, and the interaction between winding-tension gradient and winding time. The mechanism that increased composite strength was related to the strong correlation between fiber volume in the composite and vessel strength. Cylinders with high fiber volume in the hoop layers tended to deliver high fiber strength.

Multi-spectral imaging system

Abstract: A multi-spectral imaging apparatus with a common collecting aperture, which combines a high performance infrared imaging system with a high performance millimeter wave transceiving system. Two mirror surfaces are combined with a refractive corrector in the infrared mode and with a single reflective parabolic antenna in the millimeter wave mode. The dual mode system functions well in a scanning as well as a staring configuration.

RF Receiving and transmitting apparatuses having a microstrip-slot log-periodic antenna

Abstract: A log-periodic antenna having a layer of dielectric media interposed between a microstrip log-periodic portion and a slot log-periodic portion where an array of two or more log-periodic antennas that may be placed about vehicles, such as air vehicles, or mounted on stationary structures, such as communication towers.