Time-resolved diagnostics for concrete target response

In order to facilitate the design of advanced penetrating weapons for defeating land targets, the interaction of concrete with high-velocity penetrators needs to be better characterized. To aid in this effort, three new types of time-resolved diagnostics are being developed and have been used in two experiments and one demonstration: fiber optic arrays to localize penetrators in space and time, Fabry-Perot velocimetry to record the concrete particle velocity, which is related to the pressure, at specific locations within concrete targets, and micropower impulse radar to provide a non-intrusive measure of the penetrator position-time history in a target. The two experiments used the fiber optic array and the Fabry-Perot velocimeter to diagnose the response of concrete to penetration by a Viper shaped charge jet. The results were analyzed using the CALE continuum mechanics simulation program, for which a preliminary model of the material properties of concrete was developed. The fiber optic arrays recorded the bow shock at locations 6.4 and 16.9 cm from the front surfaces. The Fabry-Perot velocimeter measured a free-surface velocity of 0.13 km/s at a distance of 3 cm and obliquity 70{degree} from the jet, which was moving at an interface velocity of 4.0 km/s at a depth of 29 cm. These values imply a pressure of about 6.6 kbar at that location. The demonstration used micropower impulse radar with a pulse repetition frequency of 0.25 MHz and a cell size of 30 ps to detect and record the motion of a metal penetrator simulant moving inside a cylindrical concrete target

Penetration of yawed projectiles

We used computer simulations and experiment to study the penetration of tungsten-alloy projectiles into a thick, armored steel target. These projectiles, with length-to-diameter ratios of 4, strike the target with severe yaws, up to 90{degree}(side-on-impact), such as might be induced in an originally longer projectile by a multiple-spaced plate array. In this study, we focus on the terminal ballistics of these projectiles and ignore how the yaw was induced. We found that the minimum penetration depth occurs at 90{degree}yaw. This case is well approximated by the two-dimensional plane-strain penetration of a side-on cylinder. The ratio of penetration depth to diameter, P:D, for this case is larger than that for a sphere because the plane-strain geometry lacks hoop stress, which is activated in axisymmetric geometry. A more surprising result of work is that the penetration at 60{degree} yaw is only slightly deeper than that of the side-on impact. 8 refs., 15 figs., 3 tabs

DYNAMIC YIELD STRENGTH OF A PALLADIUM ALLOY METALLIC GLASS

Des essais d'impact de Taylor en mode ballistique inverse sont effectués pour déterminer la limite élastique dynamique d'un verre métallique Pd77.5Cu6.0Si16.5. L'interface entre cible et projectile est examinée par microscopie électronique à balayage. Des simulations numériques sont effectuées pour interpréter et confirmer les résultats et les conclusions.Taylor anvil tests in the reverse ballistic mode have been carried out to determine the dynamic yield strength of a Pd77.5Cu6.0Si16.5 metallic glass. Scanning electron microscopy has been utilized to evaluate the details of the rod and anvil interface after impact. Computer simulations have also been carried out to interpret and confirm the results and conclusions

Shock hugoniot behavior of mixed phases with widely varying shock imepdances

The shock velocity dependence on shock pressure in composite explosive materials containing polymeric binders is known to exhibit marked non-linear behavior in the U{sub s} - u{sub p} plane at low pressures. This is in addition to the non-linear behavior noted in pure polymeric materials. The precise description of this behavior is important in analyzing the response of energetic materials to impact shocks. We will show that the mismatch of the shock impedances in materials such as rocket propellants composed of polymer binder, aluminum, and ammonium Perchlorate can be expected to exhibit a very large initial slope of the shock velocity, U{sub s}, dependence on the particle velocity, u{sub p}. This slope is simply a result of the equilibration of Hugoniot pressure amongst the phases. With accurate descriptions for the equations of state of the individual components, we successfully predict the extreme slope at low compression. The effect is primarily due to the very large change in compressibility of the polymeric phase at relatively low volumetric compression of the whole mixture. Examples are shown and compared with available experimental results

Dynamic Yield Strength of a Zirconium Base Metallic Glass

Taylor anvil tests in the reverse ballistic mode have been carried out to determine the dynamic yield strength of a Zr 62.6 w/o Cu 13.23, Ti 11.01, Ni 9.77, and Be 3.38 metallic glass. Scanning electron microscopy has been utilized to evaluate the details of the rod and anvil interface after impact. Computer simulations have also been carried out to interpret and confirm the results and conclusions.Le test de TAYLOR par la méthode de balistique inverse a été utilisé pour déterminer la résistance dynamique d'un verre métallique de Zr 62.6%-Cu 13.23%-Ti 11.01%-Ni 9.77% et Be 3.38%. La microscopie électronique à balayage a été utilisée pour examiner l'interface entre la cible et le barreau après impact. Des simulations numériques ont été effectuées pour interpréter et confirmer les résultats et les conclusions

Fundamental study of crack initiation and propagation. [Computer model of ductile fracture]

Objective is to determine the fracture toughness of A533B-1 steel by computer modeling Charpy V-notch tests. A computer model of ductile fracture was developed that predicts fracture initiation. The model contains a set of material-dependent parameters obtained by computer simulations of small specimen tests. The computer calculations give detailed stress and strain histories up to the time of fracture, which are used to determine the model parameter values. The calibrated fracture model, that correctly predicts fracture initiation (and initiation energy) in the Charpy specimen, may then be used to simulate tests of accepted fracture-toughness specimens and hence obtain fracture toughness. The model parameters were calibrated to predict fracture in four different test specimens: two different notched-tension specimens, a simple tension specimen, and a precracked compact-tension specimen. The model was then used in a computer simulation of the Charpy V-notch specimen to initiate and advance a flat fracture. Results were compared with interrupted Charpy tests. Calibration of the model for two additional heat treatments of A533B-1 steel is in progress