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Strain-Induced Porosity Model

Advanced computer models improve the quality of titanium alloys. AFRL scientists developed advanced computer models to improve the processing and quality of titanium alloys used in manufacturing gas turbine engine parts and critical structural components for military aircraft. AFRL transferred both the models and the basic materials knowledge to titanium mill suppliers to help them eliminate strain-induced porosity (SIP)—also known as cavitation—in billet products (see Figure 1) and finished parts. The models also increase product yield by reducing the amount of scrap material, which helps lower production costs.

Posted in: Briefs, Materials

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Conductive Polymeric Nanocomposite Materials

Scientists employ carbon nanofibers to increase the conductivity of polymeric materials. AFRL scientists have developed a method for uniformly dispersing carbon nanofibers throughout polymeric materials to increase their conductivity. Engineers will be able to employ the resulting polymeric nanocomposites in conductive paints, coatings, caulks, sealants, adhesives, fibers, thin films, thick sheets, tubes, and large structural components needed for both aerospace and industry applications.

Posted in: Briefs, Materials

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Composite Material Fire Safety Training Course

Consortium develops program to train firefighters in safe and effective methods for combating composite materials fires. AFRL scientists and engineers, working cooperatively with experts from academia and the firefighting community, have developed a Composite Material Fire Safety training program designed to improve the safety and effectiveness of Air Force, Department of Defense (DoD), and civilian firefighters. The team created the program to educate firefighters on the methodologies they need to rapidly and safely extinguish composite materials fires.

Posted in: Briefs, Materials

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Automated Material Deposition Chamber

New capabilities enable researchers to deposit gradient, multilayer, solid-lubricant coatings onto aerospace components. AFRL materials scientists have acquired an automated deposition chamber (see figure on next page) that enables them to simultaneously or sequentially deposit solid-lubricant coatings onto target objectives from any of three deposition sources. The chamber also incorporates AFRLinvented technology entailing a hybrid, magnetron-assisted, pulsed-laser deposition (PLD) process. The scientists acquired the chamber to study protective solid-lubricant coatings capable of resisting wear and corrosion in (relatively) large friction components, including gears and bearings, and preventing static friction in microelectromechanical systems devices such as switches and connectors.

Posted in: Briefs, Materials

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Computational Model of a Plasma Actuator

Scientists are developing computer codes to aid designers in applying these promising devices.Controlling subsonic aerodynamic flow through the use of plasma actuators is an active area of research in both the Air Force (AF) and the general scientific community. A typical plasma actuator consists of two offset electrodes separated by a dielectric material (see Figure 1). Plasma forms as the voltage difference between the electrodes ionizes the surrounding gas. The electric field can then direct the charged particles in the plasma to transfer momentum to the surrounding, neutral (nonionized) air. Most of this momentum transfer occurs as a result of particle collisions. Experiments have demonstrated the ability of plasma actuators to reattach separated airflow at high angles of attack (see Figure 2), as well as to induce flow movement in an initially stationary air mass.1,2,3,4,5

Posted in: Briefs, Software

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AFRL Finding Ways to Decrease Unmanned Air Vehicle Costs

Testing confirms the research theory that tolerances can be relaxed on surfaces with favorable pressure gradients. In support of the Aeronautical Systems Center’s (ASC) Global Hawk Systems Group, AFRL has undertaken a program to study manufacturing tolerances for laminar flow on aircraft wings. On the drawing board, air vehicle designs have perfectly smooth aerodynamic surfaces, yet it is nearly impossible for manufacturers to fabricate those surfaces without some imperfections. Any surface imperfection, no matter how slight, can affect the properties of the boundary layer— the air flowing nearest an air vehicle’s body during flight. In turn, this airflow dramatically impacts the amount of drag an air vehicle experiences. When the boundary layer is smooth, or laminar, drag is minimal; as the boundary layer becomes more turbulent, drag increases. Nonetheless, decreasing the amount of surface imperfection is not always a practical solution, because as the manufacturing processes become more stringent, they also become increasingly expensive and time-consuming endeavors. It is therefore vitally important to determine the relationship between the height, shape, and location of surface imperfections and the resulting performance degradation.

Posted in: Briefs, Mechanical Components

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Cyberspace Security via Quantum Encryption

Quantum fluctuations at the physical layer of encryption enable ultrasecure communications with highly competitive performance metrics. Perfect information- theoretical security requires that the meaning of an encrypted message transmitted from point A to point B be statistically independent of the ciphertext in which that message is embedded. In other words, possession and analysis of the ciphertext must yield no information about the message sent. This article briefly describes cryptographic protocols exhibiting perfect, or nearperfect, security before addressing a new quantum data encryption protocol that employs quantum noise of light at the physical layer to buttress security based on mathematical complexity. This new protocol is called Keyed Communication in Quantum Noise, or KCQ. KCQ does not presently guarantee flawless informationtheoretical security; however, because of KCQ’s physical-layer encryption in the quantum noise of light, some scientists believe that it enables better security than current secure communications systems based solely on mathematical complexity.

Posted in: Briefs, Photonics

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Unified Flow Solver

The Unified Flow Solver enables accurate and efficient simulation of gas flows for the entire range of Knudsen numbers. A variety of gas flow problems are characterized by the presence of rarefied and continuum domains. In a rarefied domain, the mean free path of gas molecules is comparable to (or larger than) a characteristic scale of the system. The rarefied domains are best described by particle models such as Direct Simulation Monte Carlo (DSMC); or, they involve solution of the Boltzmann kinetic equation for the particle distribution function. The continuum flows are best described by Euler or Navier-Stokes equations in terms of average flow velocity, gas density, and temperature and are solved by computational fluid dynamics (CFD) codes. The development of hybrid solvers combining kinetic and continuum models has been an important area of research over the last decade. Potential applications of such solvers range from high-altitude flight to gas flow in microsystems.

Posted in: Briefs, Software

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A Concept for Information Extraction From Remote Wireless Sensor Networks

AFRL engineers develop advanced information management capabilities to monitor wireless sensor networks. Recent advances in the development of microsensors, microprocessors, information fusion algorithms, and ad hoc networking have led to increasingly capable wireless sensor networks. These networks, when deployed to monitor an urban area, show great promise in enhancing warfighter situational awareness. However, delivering the sensor network’s collected information back to the proper decision makers is one network capability that still requires improvement. To bridge this gap between the tactical operations center and multiple wireless sensor networks distributed across a city, engineers must create a system-of-systems architecture. This architecture must permit a warfighter to receive near-real-time sensor information from an out-of-theater operating post, whether a mile or an ocean away. Research accomplished in efforts such as the Defense Advanced Research Projects Agency’s (DARPA) Information Exploitation Officesponsored Networked Embedded Systems Technology (NEST) program has provided information gathering algorithms for wireless sensor networks that are independent of the hardware platform on which they run. Nevertheless, these networks have no means for publishing the massive amounts of information to the Global Information Grid (GIG). To address this publication requirement, AFRL engineers have begun integrating NEST technologies with the Joint Battlespace Infosphere (JBI).1, 2 They recently developed a proof-of-concept demonstration of this idea for Scientific Advisory Board (SAB) review. In this demonstration, they integrated a tracking application developed for the NEST program with the AFRLdeveloped JBI Reference Implementation and showcased the resultant capability to connect low-level information gatherers to high-level information distributors.

Posted in: Briefs, Information Sciences

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Rapid Model Fabrication for Responsive Aerodynamic Experimental Research

Researchers are exploring rapid prototyping methods and materials for wind tunnel models. Technicians machine traditional metal wind tunnel models in a process that can span months. Although these models are highly precise, the meticulously slow manufacturing process precludes a quick assessment regarding a new design’s feasibility and thus impedes the ever-increasing need to help today’s warfighter address constantly changing warfare threats. In support of the Integrated Rapid Aerodynamics Assessment program, AFRL has been exploring the impact of rapid prototyping (RP) technology in meeting this escalating need. According to AFRL’s Mr. Gary Dale, an originator of this experimental research effort, “We were looking for a way to quickly generate experimental data that we could use to verify computational fluid dynamics (CFD) results. The CFD researchers were generating solutions in a matter of days or even hours, and they wanted to verify their solutions with [wind tunnel] experimental data.” By producing a model in days—or possibly hours, depending upon model complexity—RP technology enables this concurrent study of air vehicle concepts via computer simulation and wind tunnel results.

Posted in: Briefs, Manufacturing & Prototyping

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