We present results of a sensitive 76 ksec Chandra observation of the young stellar cluster in NGC 2024, lying at a distance of ∼415 pc in the Orion B giant molecular cloud. Previous infrared observations have shown that this remarkable cluster contains several hundred embedded young stars, most of which are still surrounded by circumstellar disks. Thus, it presents a rare opportunity to study X...

Abstract. Trend of simultaneous improvement such mechanical metal properties as strength, hardness and ductility remains popular. Asymmetric accumulative roll bonding is a method severe plastic deformation that can create large shear deformations. These deformations in its turn are responsible for increase properties. Initially computer modeling was carried out to study the influence kinematic ...

Aerospace systems are expected to remain in service well beyond their designed life. Consequently, maintenance is an important issue. A novel method of implementing artificial neural networks and acoustic emission sensors to form a structural health monitoring (SHM) system for aerospace inspection routines was the focus of this research. Simple structural elements, consisting of flat aluminum p...

Surface acoustic wave (SAW) velocity spectroscopy has been long considered to be one of the leading candidates for nondestructive characterization of surface-treated metals because of its ability to probe the material properties at different penetration depths depending on the inspection frequency. We developed a high-precision laser-ultrasonic technique to study the feasibility of SAW dispersi...

The basic weldability of the alloy Al-2.2Li-2.7Cu was investigated and compared with two common aluminum alloys: 2024 and 5083. The basic weldability was characterized by the susceptibility of the alloy to hot tearing as determined by the trans-Varestraint test. The hot tearing susceptibility was characterized through plots of total crack length and maximum crack length versus augmented strain....

National Institute of Standards and Technology, Boulder, Colorado 80303 Valid comparison of impact test energies reported by various organizations and over time depends on consistent performance of impact test machines. This paper investigates the influence of various specimen and test parameters on impact energies in the 1 J to 2 J range for both Charpy V-notch and Izod procedures, leading tow...