Penetration mechanics and performance of segmented rods against metal targets

Terminal ballistic experiments confirm theoretical predictions that a segmented rod will penetrate a semi-infinite metal target deeper than a continuous rod of the same material and having equal mass, diameter and velocity. For copper segmented rods impacting aluminum targets and tantalum segmented rods impacting 4340 (BHN 300) steel, penetration depths of at least 50 percent greater than that for a corresponding continuous rod are measured at impact velocities of 4 to 5 km/s. Spacing between segments of only about 2.5 segment diameters or more are required to achieve these results. Reducing the Li/D of the segments to less than 1 improves the penetration efficiency of a segmented rod. For segmented rods with segment L_i/D < 1, experiments suggest that penetration may increase with impact velocity rate greater than V^2/3.     

Penetration with instrumented rods

The response of long rods during penetration is being examined by strain measurements performed with foil resistance gages. Early experiments in this investigation employed the reverse ballistic approach in which stationary rods were impacted by armor targets launched from a light-gas gun. Although satisfactory results were obtained for both normal and oblique impacts, the reverse ballistic approach strictly limited the target diameter, and the target mass limited the impact velocity to values below the range of current ballistic interest. In order to overcome the major limitations imposed by reverse ballistics a technique for launcing instrumented rods has been developed. With this technique strain gages on the rod are connected to thin metal contacts located on the front surface of the plastic sabot. Prior to impact, the contacts are pierced by stationary probes and a low-resistance electrical path is provided during approximately 100 mm of travel by the sabot. A series of impact tests has been performed at normal incidence with steel rods impacting steel targets at a velocity of 1000 m/s. Strain-time signals from these tests were amenable to a simple wave analysis which provided relationships between stress and strain, and particle velocity and strain, to strain of 15%. Results of the analysis are discussed in the context of their relationship to the experimental technique. Details of the experimental technique and its refinement are presented and problem areas are considered.     

Penetration mechanics of yawed rods

The penetration of rod projectiles is a function of impact yaw. Armor steel targets were struck at 0° obliquity by long steel rods at ~2.15 km/s and various angles of yaw. Crater dimensions varied systematically with yaw angle. Trenching behavior was observed for yaw angles exceeding about 30°. Analysis indicates that the rods collapsed into the targets with no significant rotation, and that penetration chiefly depends on the parameters D and $\text{D}\text{sin θ}$ (where D is rod diameter and θ is yaw angle).     

Effect of alignment on the penetration of segmented rods

The purpose of this investigation is to study the effect of alignment on the performance of segmented penetrators. The Eulerian wave propagation code CTH is used for this purpose. A series of calculations using four L/D = 1 tungsten alloy segment trains at varying degrees of misalignment is performed, impacting a single finite-thickness oblique armor steel plate. Obliquity angles of 30° and 60° were considered. This study was performed primarily to investigate the effects of obliquity and is a continuation of a previous study [1] where semi-infinite armor steel plates were examined. It is shown that the obliquity of the plate can have a significant influence on the performance of the segment train. When misalignment is minimal, the performance of the segment train is not adversely affected, particularly if the misalignment positions the train in an orientation aligned with the plate normal. However, for large misalignments, degradation to the performance of the segment train is significant at all orientations.     

High velocity impact of segmented rods with an aluminum carrier tube

In this paper, we apply the method of ballistic test to investigate the history and mechanism of the tungsten alloy segmented rod with aluminium carrier tube and corresponding continuous rod penetrating into semi-infinite steel target at velocities from 1.8 to 2.0 km / s. The length to diameter ratio of the segmented rod is 1 (L/D = 1), the ratios of length of spacing between segments to diameter (s/d) are 0.5, 1.0 and 2.0 respectively. The results show that the power of penetration of the segmented rod with carrier tube is obviously higher then that of the corresponding continuous rod with carrier tube. Raising of the impact velocity, suitably increasing of the length of spacing between segments and filling the spacing with non-metallic material, etc. all can increase the penetrating power of the segmented rod. When impact velocity is 2.0 km / s, s / D=2.0, the penetrating power of the segmented rod is 10% higher than that of the corresponding continuous rod, if the spacing is filled with glass steel (non-metallic material), the power will be 20% higher. In this paper, we present a simplified model of based on hydrodynamics and penetrating mechanics. This model can properly describe the whole penetrating process of segmented rod penetrating into semi-infinite target. The shape of the crater and depth of penetration, etc. calculated are in good agreement with the results obtained by experiments.     

Penetration into ductile metal targets with rigid spherical-nose rods

We developed penetration equations for rigid spherical-nose rods that penetrate ductile metal targets. The spherical cavity-expansion approximation and incompressible and compressible elastic-perfectly plastic constitutive idealizations simplified the target analyses, so we obtained closed-form penetration equations. We compared predictions from our models with previously published penetration data and results from Lagrangian and Eulerian wavecodes.     

Hydrocode results for the penetration of continuous, segmented and hybrid rods compared with ballistic experiments

Hydrocode calculations of the penetration of various tungsten alloy and stainless steel rod penetrators into semi-infinite steel and aluminum targets are presented and compared with results from ballistic experiments. Good agreement with experimental results is seen for penetration depth, penetration with time, and crater size and profile. The rod penetrator configurations investigated in the calculations include: idealized segmented rods with various segment spacings, the corresponding hybrid rods with axial spacers, and continuous rods of various dimensions. The Eulerian hydrocode results show enhanced penetration performance for idealized segmented rods compared with the parent continuous rods. Penetration performance for the corresponding hybrid segmented rods is significantly greater, even after accounting for the added mass of axial spacers. Results for long rod penetrators of the same mass and length as the hybrid rods, provide evidence that the axial spacers contribute to penetration. Both calculations and experiment show significant differences between the crater profiles of continuous versus ideal segmented or hybrid rods. The profiles generated by continuous rods are smooth, while those by segmented and hybrid rods are scalloped. Hydrocode results show that the scalloped crater profiles arise from successive impacts of rod segments.     

Numerical investigations of nonideal explosions

This study focusses on nonideal free-field blast waves arising from the finite rate of energy addition in a distributed nonspherical source region. The behavior of the blast wave is determined in a compressible medium surrounding a centrally ignited flammable mixture during and after the propagation of a heat addition wave which models the detonative or deflagrative combustion process. Numerical integration of the nonsteady, two-dimensional Euler equations is performed by incorporating a heat addition “two-gamma” working fluid model to represent the flame or detonation wave. This study also investigated the behavior of a blast wave generated by the burst of a high-pressure ellipsoid. The effect of the heat addition waves on the near and far field blast waves was studied by determining the relevant blast parameters, peak overpressure, and positive phase impulse, as well as the detailed evolution of the gas dynamic variables with time and distance. The blast parameters which correspond to low velocity flames compare favorably with those obtained using linear acoustic monopole theory. The results indicate that pressure relief associated with the presence of a compressible inert medium surrounding the combustion products after the flame propagates to the interface of nonspherical clouds sevrely restricts the intensity of the explosion and thereby reduces the damages that can be produced by the blast wave.     

Penetration of boron carbide, aluminum, and beryllium alloys by depleted uranium rods: Modeling and experimentation

As part of the US stockpile stewardship program, it is necessary to perform experiments with various metallic components and explosives. These experiments will be conducted within specially designed blast vessels to ensure that the debris from the experiment is contained. The debris includes fragments that are launched at hypervelocities. The blast vessels are built primarily of steel, but have windows of either aluminum or beryllium alloys for diagnostic equipment requirements. To contain the hypervelocity depleted uranium fragments, ceramic armoring of the windows and steel vessel is used. To develop the necessary design tools, a program of experiments and modeling was begun. Preliminary pre-test predictions were made to design experiments. The experiments were conducted with targets representative of the armored windows in the vessel. To assist in the vessel design, two- and three-layered target analytical models were developed to predict the penetration of depleted uranium rods striking at velocities up to 2 km/s into layered targets of ceramic (boron carbide and silicon carbide) and aluminum, beryllium and steel alloys. The agreement between the pre-test predictions, the developed layered-target analytical model, and the experiments is good.     

Upset-resistance welding of aluminium to copper rods: effect of interface on performance

Upset resistance dissimilar welding of aluminium and copper narrow rods was performed. Effect of the interface characteristics was studied on the joint mechanical and electrical properties. Upset resistance welding (URW) was successful for production of joints with high strength and electrical conductivity between aluminium and copper rods. Reaction layer at the joint interface was composed of the Al₂Cu cellular phase and lamellar eutectic structure of α-Al and Al₂Cu. Enhancement of the welding current and decrease in the upset force increased the reaction layer thickness and strength of the joint. URW had no significant detrimental effect on the electrical conductivity of the weld zone. Neither the joint strength nor the joint electrical conductivity was improved by in situ post weld heat treatment.     

Basic chemical models of nonideal atomic plasma

The concept of basic chemical models is introduced, which is new from the standpoint of the physics of nonideal atomic plasma. This concept is based on the requirement of full conformity of the expression for free energy in the chemical model of plasma to exact asymptotic expansions obtained in the grand canonical ensemble within the physical model of plasma. The thermodynamic functions and equations of state and ionization equilibrium are obtained for three basic chemical models differing from one another by the choice of the atomic partition function. Comparison is made with the experimental results for nonideal plasma of cesium and inert gases. It is demonstrated that the best fit to experiment is shown by the results obtained using a basic chemical model with atomic partition function in the nearest neighbor approximation with classical determination of the size of excited atom.Translated from Teplofizika Vysokikh Temperatur, Vol. 42, No. 6, 2004, pp. 835–842.Original Russian Text Copyright © 2004 by A. L. Khomkin, I. A. Mulenko, and A. S. Shumikhin.     

Pressure fluctuations in nonideal nondegenerate plasma

Pressure fluctuations in equilibrium nonideal plasma are investigated by the method of classical molecular dynamics. Examples of plasma parameters at which the pressure-fluctuation distribution function is not normal but can be approximated by the sum of two normal distributions were found. The electron-ion interaction is described by the Coulomb potential cut-off at the depth of the potential well that is independent of the temperature and the particle density. The requirements on the choice of the interaction potential parameters and the number of particles in a calculation cell are discussed. The free and bound states are not separated in any way, which makes it possible to take into account successively the influence of density effects in the electron state spectrum on the thermodynamic properties.     

High-capacity neural networks on nonideal hardware

We present a new training-out algorithm for neural networks that permits good performance on nonideal hardware with limited analog neuron and weight accuracy. Optical neural networks are emphasized with the error sources including nonuniform beam illumination and nonlinear device characteristics. We compensate for processor nonidealities during gated learning (off-line training); thus our algorithm does not require real-time neural networks with adaptive weights. This permits use of high-accuracy nonadaptive weights and reduced hardware complexity. The specific neural network we consider is the Ho-Kashyap associative processor because it provides the largest storage capacity. Simulation results and optical laboratory data are provided. The storage measure we use is the ratio M/N of the number of vectors stored (M) to the dimensionality of the vectors stored (N). We show a storage capacity of M/N = 1.5 on our optical laboratory system with excellent recall accuracy, > 95%. The theoretical maximum storage is M/N = 2 (as N approaches infinity), and thus the storage and performance we demonstrate are impressive considering the processor nonidealities we present. Our techniques can be applied to other neural network algorithms and other nonideal processing hardware.     

Penetration dynamics of rods from direct ballistic tests of advanced armor components at 2–3 km/s

The penetration of semi-infinite steel and spaced-plate armors by continuous and segmented rods has been analyzed and measured by direct ballistic tests, hydrocode calculations, and hydrodynamic models at velocities from 2 to 4 km/s. An empirical equation of rod penetration in semi-infinite steel was formulated from hydrodynamic models of rod impact. Penetrations predicted by the equation agreed well with measured values. Increasing the spacing between segments from one to two diameters increased the penetration significantly (20%). Structures to support and align the segments can either increase or decrease the penetration, depending on their design. The relative penetrations of continuous and segmented rods depend on the parameters selected for the comparison: the segmented rod having greater penetration for equal mass and diameter and vice versa for equal mass and length. Tests of segmented rods penetrating spaced-plate armor showed that the armor is defeated by the front segment (or segments) punching a hole in the front plate (or plates) that allows the remaining segmented rod through intact to attack the main armor.     

Relaxation of concentration inhomogeneities in nonideal solutions

Numerical solutions of the nonlinear diffusion equation are obtained for non-ideal solutions satisfying an equation of state of the Van der Waals-Landau average field type. The results are compared with experiment.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 1, pp. 55–65, January 1988.     

Nonlinear phenomena in nonideal coulomb systems

The phenomenon of plasma echo under nonideal plasma conditions has been studied within the framework of a nonlinear response theory. Limitations imposed on the nonlinear response function are considered and a model for determining the quadratic response functions is presented. Conditions for the experimental realization of this temporal response are considered and it is shown that plasma echo can be induced by ultrashort field pulses.     

n-型梯度结构热电材料FeSi2/Bi2Te3的制备与性能研究*

采用热浸焊法用纯Sn作为过渡层制备了n－型FeSi2/Bi2Te3梯度结构热电材料并对其热电性能进行了测试。发现当冷热端温度在510℃以下时,梯度结构热电材料的表观See-beck系数随平均温度几乎呈线性分布在同一条带形区域内,并在相同的温度范围内,其值显著高于单种均质材料（Bi2Te3和β-FeSi2)。梯度结构热电材料的最大输出功率较单种材料高2－2．5倍以上,且当材料经190℃100h与200h的真空退火后,输出功率几乎不变。金相分析表明,在Sn层与两半导体界面处,没有明显的Sn扩散迹象,说明在所试验的条件下,用Sn作为过渡层热稳定性较好。     

壳聚糖/羟基磷灰石复合骨折内固定棒材的制备与性能研究

采用原位沉析法制备了壳聚糖/羟基磷灰石(CS/HA)复合棒材.用预先沉积的壳聚糖膜将含有Ca、P源的壳聚糖溶液与凝固液隔离,同时控制壳聚糖沉积与羟基磷灰石前驱体转化为羟基磷灰石的过程,使二者得以均匀复合.燃烧试验结果表明无机成分均匀分散于壳聚糖中,FT-IR、XRD和TEM测试证实原位生成羟基磷灰石,弯曲强度测试结果表...     

Nonlinear vibration of beams under nonideal boundary conditions

In this paper, we investigate the influence of nonideal boundary conditions on the nonlinear vibration of damped Euler?CBernoulli beams subjected to harmonic loads. These nonidealities allow for small deflections and/or moments at the supports of the beam. Using the iteration perturbation method, analytical expressions for the case of simply supported beams with immovable end conditions are provided. The results reveal that the first order of approximation obtained by the proposed method is more accurate than the perturbation solutions. Moreover, compared with the previous studies, some interesting phenomenon is predicted. We have shown that in some special combinations of the nonidealities the nonlinear frequency of vibration as well as the frequency?Cresponse curves would be unchanged.