Naval Surface Warfare Center

About: Naval Surface Warfare Center is a facility organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Radar & Sonar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

Induced Magnetic Anisotropy in Stress-Annealed Galfenol Alloys

Abstract: Values of the uniaxial anisotropy, cubic anisotropy, saturation magnetic induction, and saturation magnetostriction were obtained from measurements of the magnetization and magnetostriction of stress-annealed Galfenol (Fe100-xGax,x=12.5,18.4, and 22.0)and Fe81Al19 as a function of compressive stresses <100 MPa. The values were derived from fitting magnetization and magnetostriction curves to the energy expression Ei=-mu 0MsHalphaz+Kcubic(alpha x 4+alphay 4+alphaz 4)+Ku niaxialalphaz 2-lambdasatTalphaz 2, where Ms,lambdasat and the K's are fit parameters. The alphai's are the direction cosines of the magnetization direction with respect to the field and stress direction (z).H is the magnetic field and T is the measurement stress (compressive T<0). Data are fit with high precision by only the above four constants plus a smoothing constant. Importantly, Kuniaxial enables a prediction of the maximum usable tensile stress

Probabilistic Analysis of Roll Parametric Resonance in Head Seas

Abstract: The paper presents some background for an analysis of the risk of severe parametric roll motion for a ship operating in head seas This background includes a consideration of basic probabilistic qualities of parametric roll in head seas: ergodic qualities and distributions, since these results are necessary to establish a method of prediction of extreme values The ship motions that generate parametric excitation, heave and pitch, have also been studied in this analysis The post- Panamax C11 class container carrier was chosen for analysis, since a vessel of this type is known to have suffered significant damage in an incident attributed to severe parametric roll It was shown that despite large-amplitude of motion, pitch and heave retain their ergodic qualities and normal character of distribution, while the roll motions are clearly non-ergodic and do not have a normal distribution The analysis is built upon the numerical simulation of ship motion in head seas using Large Amplitude Motion Program (LAMP)

Flexural Creep Deformation of ZrB2/SiC Ceramics in Oxidizing Atmosphere

Abstract: Flexural creep of ZrB 2 /0-50 vol% SiC ceramics was characterized in oxidizing atmosphere as a function of temperature (1200°-1500°C), stress (30-180 MPa), and SiC particle size (2 and 10 μm). Creep behavior showed strong dependence on SiC content and particle size, temperature and stress. The rate of creep increased with increasing SiC content, temperature, and stress and with decreasing SiC particle size, especially, at temperatures above 1300°C. The activation energy of creep showed linear dependence on the SiC content increasing from about 130 to 511 kJ/mol for ceramics containing 0 and 50 vol% 2-μm SiC, respectively. The stress exponent was about 2 for ZrB 2 containing 50 vol% SiC regardless of SiC particle size, which is an indication that the leading mechanism of creep for this composition is sliding of grain boundaries. Compared with that, the stress exponent is about 1 for ZrB 2 containing 0-25vol% SiC, which is an indication that diffusional creep has a significant contribution to the mechanism of creep for these compositions. Cracking and grain shifting were observed on the tensile side of the samples containing 25 and 50 vol% SiC. Cracks propagate through the SiC phase confirming the assumption that grain-boundary sliding of the SiC grains is the controlling creep mechanism in the ceramics containing 50 vol% SiC. The presence of stress, both compressive and tensile, in the samples enhanced oxidation.