A physically motivated Internal State Variable (ISV) constitutive model is extended to account for shear influenced void evolution for predicting damage behavior in ductile solids. The revised ISV model is calibrated for an aluminum 7085-T711 alloy using a series of microstructure and mechanical property quantification experiments. The calibrated ISV model for the aluminum alloy is implemented in an implicit finite-element code (Abaqus) to simulate the deformation of notch Bridgman tension specimens at a variety of stress states and temperatures. The model revisions and calibrated aluminum ISV model are validated through successful prediction of mechanical and microstructure evolution for structures subjected to a variety of complex stress state conditions. The extended ISV model framework is used to study shear influenced plasticity and damage mechanisms resulting from ballistic impact of metals. A Rolled Homogeneous Armor (RHA) steel alloy is selected for the impact model due to wide availability of documented penetration characteristics and ballistic performance data of RHA steel. Finite Element Analysis (FEA) simulations of ballistic impact of rolled homogeneous armor (RHA) steel projectiles against RHA steel plates are performed using a calibrated ISV constitutive model for RHA steel. An FEA simulation based parametric study is performed to assess the effect of a variety of microstructure and mechanical properties on the ballistic performance of RHA steel targets. FEA simulations are used to predict a transition in ballistic perforation mechanisms for high hardness steel alloys by accounting for variations in microstructure properties qualitatively documented in the literature.

Ballistic movements have been shown to be controlled differently by the central nervous system than slow, ramp actions. It has been suggested that the cerebellum is involved primarily with ballistic actions, while the basal ganglia primarily control slower movements. These command and control differences have been shown to manifest in unique ways at the neuromuscular level. Ballistic actions evidence high firing rates, brief contraction times, and high rates of force development. A characteristic triphasic agonistantagonist-agonist burst pattern presents itself during ballistic movement, wherein the amount and intensity of antagonist co-activation is variable. In conditions of low-grade tonic muscular activity, a premovement depression (P:MD; or silent period, PMS) can occur in both agonist and antagonist muscles prior to ballistic contraction. The agonist P:MD period may serve to potentiate the force and velocity of the following contraction A selective activation of fast twitch motor units may occur in ballistic contractions under certain movement conditions. Finally, high velocity, ballistic training induces specific neuromuscular adaptations that are representative of the underlying neurophysiological mechanisms that sub serve ballistic movement. / Thesis / Master of Science (MS)

Problem of V2 O5 nanobelts production under intensive stirring of V2 O5 powder in salted water is revisited. Method was initially proposed in 2016 but models and understanding were lacking. Here an independent attempt of the controlled V2 O5 nanobelts formation and growth under stirring with various rotation frequencies is reported, as well as some alternative mechanisms and respective mathematical models of the nanobelts growth and ripening kinetics.

This study is devoted to the development of an integrated numerical modeling enabling one to investigate the static and the dynamic behaviors and failures of 2-D textile composite as well as 3-D orthogonal woven composite structures weakened by cracks and subjected to static-, impact- and ballistic-type loads. As more complicated modeling about textile composite structures is introduced, some of homogenization schemes, geometrical modeling and crack propagations become more difficult problems to solve. To overcome these problems, this study presents effective mesh-generation schemes, homogenization modeling based on a repeating unit cell and sinusoidal functions, and also a cohesive element to study micro-crack shapes. This proposed research has two: 1) studying behavior of textile composites under static loads, 2) studying dynamic responses of these textile composite structures subjected to the transient/ballistic loading. In the first part, efficient homogenization schemes are suggested to show the influence of textile architectures on mechanical characteristics considering the micro modeling of repeating unit cell. Furthermore, the structures of multi-layered or multi-phase composites combined with different laminar such as a sub-laminate, are considered to find the mechanical characteristics. A simple progressive failure mechanism for the textile composites is also presented. In the second part, this study focuses on three main phenomena to solve the dynamic problems: micro-crack shapes, textile architectures and textile effective moduli. To obtain a good solutions of the dynamic problems, this research attempts to use four approaches: I) determination of governing equations via a three-level hierarchy: micro-mechanical unit cell analysis, layer-wise analysis accounting for transverse strains and stresses, and structural analysis based on anisotropic plate layers, II) development of an efficient computational approach enabling one to perform transient response analyses of 2-D plain woven, 2-D braided and 3-D orthogonal woven composite structures featuring matrix cracking and exposed to time-dependent ballistic loads, III) determination of the structural characteristics of the textile-layered composites and their degraded features under smeared and discrete cracks, and assessment of the implications of stiffness degradation on dynamic response to impact loads, and finally, IV) the study of the micro-crack propagation in the textile/ceramic layered plates. A number of numerical models have been carried out to investigate the mechanical behavior of 2-D plain woven, 2-D braided and 3-D orthogonal woven textile composites with several geometrical representations, and also study the dynamic responses of multi-layered or textile layered composite structures subjected to ballistic impact penetrations with a developed in-house code. / Ph. D.

The terminal guidance problem for a fixed-trim re-entry body is formulated with the objective of synthesizing a closed-loop steering law. A transformation of variables is made that reduces the order of the state system for the guidance problem, and a subsequent linearization with motion along the sight line to the target as a reference produces a further order reduction. The final, reduced-order system, although nonlinear and time-varying, is simple enough to lend itself to synthesis of a class of guidance laws. A generalization of the feedforward device of classical control theory is successfully employed for compensation of roll-autopilot lags. A comparison with existing fixed trim guidance laws is carried out computationally with a simulation model idealizing the navigation and control systems as error-free. The proposed guidance law exhibits superior miss-distance performance in the comparison. / Ph. D.

Graphite epoxy composites lack effective mechanisms for absorbing local impact energy often resulting in penetration and a structural strength reduction. The effect of adding small amounts of two types of high strain hybrid components on the impact resistance of graphite epoxy composites subjected to projectiles traveling at ballistic velocities (greater than 900 ft/sec) has been studied. The hybrid components tested include superelastic shape memory alloy (SMA), a material having an unusually high stra in to failure (15 - 20%), and a high performance extended chain polyethylene (ECPE) known as Spectra™, a polymer fiber traditionally used in soft and hard body armor applications. 1.2% volume fraction superelastic SMA fiber layer was embedded on the specimens front, middle, and backface to determine the best location for a hybrid component in the graphite composite. From visual observation and energy absorption values, it was concluded that the backface is the most suitable location for a high strain hybrid component. Unlike the front and middle locations, the hybrid component is not restricted from straining by surrounding graphite material. However, no significant increases in energy absorption were found when two perpendicular SMA layers and an SMA-aramid weave configuration were tested on the backface. In all cases, the embedded SMA fibers were pulled through the graphite without straining to their full potential. It is believed that this is due to high strain rate effects coupled with a strain mismatch between the tough SMA and the brittle epoxy resin. However, a significant increase in energy absorption was found by adding ECPE layers to the backface of the composite . With only a 12% increase in total composite mass, a 99% increase in energy absorption was observed. / Master of Science

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / The Ballistic Missile Defense Organization (BMDO) is developing new Theater Missile Defense (TMD) weapon systems to defend against the rapidly expanding ballistic missile threat. The tactical ballistic missile threats include systems with range capabilities greater than 1000 kilometers. The development and testing of systems such as the Patriot Advanced Capability 3 (PAC-3), the Theater High Altitude Area Defense (THAAD), Navy Area Defense, and the System Integration Tests (SIT) to address the interoperability of this family of systems, will require the development of the Transportable Range Augmentation and Control System for Multiple Shot Engagements (TRACS - MSE). Congress has mandated that these systems be tested in multiple simultaneous engagements. These systems will be tested at several ranges to meet all the developmental and operational testers' needs. Potential range locations include White Sands Missile Range (WSMR), Kwajalein Missile Range (KMR), the Pacific Missile Range Facility (PMRF) and the Gulf Range at Eglin Air Force Base. Due to the long distances separating the target launch site and the interceptor site, the TRACS - MSE will be required at multiple sites for each range used. To be cost effective, transportable systems should be developed to augment existing capabilities. Advances in Global Positioning System (GPS) technology and high data rate receivers make telemetry based solutions attractive. This article will address the requirements for range safety, for Time, Space, Position Information (TSPI) collection and processing requirements to support a TRACS - MSE capability.

Approved for public release, distribution is unlimited / Many potential adversaries seek, or already have theater ballistic missiles capable of threatening targets of interest to the United States. The U.S. Missile Defense Agency and armed forces are developing and fielding missile interceptors carried by many different platforms, including ships, aircraft, and ground units. Given some exigent threat, the U.S. must decide where to position defensive platforms and how they should engage potential belligerent missile attacks. To plan such defenses, the Navy uses its Area Air Defense Commander (AADC) system afloat and ashore, the Air Force has its Theater Battle Management Core Systems (TBMCS) used in air operations centers, and the Missile Defense Agency uses the Commander's Analysis and Planning Simulation (CAPS). AADC uses a server farm to exhaustively enumerate potential enemy launch points, missiles, threatened targets, and interceptor platform positions. TBMCS automates a heuristic cookie-cutter overlay of potential launch fans by defensive interceptor envelopes. Given a complete missile attack plan and a responding defense, CAPS assesses the engagement geometry and resulting coverage against manually prepared attack scenarios and defense designs. We express the enemy courses of action as a mathematical optimization to maximize expected damage, and then show how to optimize our defensive interceptor pre-positioning to minimize the maximum achievable expected damage. We can evaluate exchanges where each of our defending platform locations and interceptor commitments are hidden from, or known in advance by the attacker. Using a laptop computer we can produce a provably optimal defensive plan in minutes. / Lieutenant, United States Navy

The trajectories of ballistic targets are determined significantly by the characteristics that are specific to them. In this thesis, these characteristics are presented and a set of algorithms in order to track short-range ballistic targets are given. Firstly, motion and measurement models for the ballistic targets are formed and then four different filtering techniques are built on these models which are the extended Kalman filter, the unscented Kalman filter, the particle filter and the marginalized particle filter. The performances of these filters are evaluated by making Monte Carlo simulation. The simulations are run using target scenarios obtained according to six degrees-of-freedom trajectory for ballistic targets. Apart from the tracking errors of the filters, drag parameter estimations and the effect of drift calculation on the filter performances are investigated. The estimation results obtained by each filter are discussed in detail by making various simulations.

The effect of the chemical composition, austenitisation temperature and tempering temperature and time on the mechanical properties and on the ballistic performance of martensitic steel armour plates was studied. It was established in this study that the mechanical properties and the ballistic performance of martensitic steels can be optimised by controlling the chemical composition and the heat treatment parameters. However, it was observed that for a given chemical composition of the steel the heat treatment parameters to be applied to advanced ballistic performance armour plates were different from those required for higher mechanical properties. Such a contradiction rendered the relationship between mechanical properties and ballistic performance questionable. Systematic analysis of the microstructure and the fracture mechanism of some martensitic armour plate steels was carried out to explain the improved ballistic performance of steels whose mechanical properties were below that specificied for military and security applications. It was inferred from phase analysis and its quantification by X-ray diffraction, characterisation of the martensite using scanning electron microscopy, transmission electron microscopy and atomic force microscopy that the retained austenite located in the plate interfaces and on grain boundaries of the martensite was the main constituent resisting localised yielding during ballistic impact on thin steel plates. A part of the kinetic energy is transformed into adiabatic heat where a reaustenitisation of the plate martensite and the formation of new lath martensite was observed. Another part is used to elastically and plastically deform the ballistic impact affected region around the incidence point. Dislocation pile-ups at twinned plate interfaces suggest that the twin interfaces act as barriers to dislocation movement upon high velocity impact loading. The diameter of the affected regions, that determines the volume of the material deforming plastically upon impact, was found to vary as a function of the volume fraction of retained austenite in the martensitic steel. Upon impact, retained austenite transforms to martensite by Transformation Induced Plasticity, the “ TRIP ” effect. High volume fractions of retained austenite in the martensitic steel were found to yield low values of the ratio yield strength to ultimate tensile strength (YS/UTS) and a high resistance against localised yielding and, therefore, against ballistic perforation. A Ballistic Parameter was proposed for the prediction of ballistic performance using the volume fraction of retained austenite and the thickness of the armour plate as variables. Based on the martensite structure and the results of the ballistic testing of 13 armour plate steels a design methodology comprising new specifications was proposed for the manufacture of armour plates whose thicknesses may be thinner than 6mm. / Dissertation (MSc (Metallurgical Engineering))--University of Pretoria, 2007. / Materials Science and Metallurgical Engineering / unrestricted