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: Sonar & Radar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

Magnetostriction and Magnetization of Common High Strength Steels

Abstract: Some common high strength steels possess enough magnetostriction to serve as the active material in sensors, e.g. torque sensors, while simultaneously performing their usual structural role. The magnetization and magnetostriction of six common high strength steels have been measured as a function of stress. Measurements were made in a hydraulic load frame at compressive stresses of -1, -50, -100, and -150 MPa with fields up to 135 kA/m (1700 Oe). With two exceptions, all of the samples displayed ldquonormalrdquo strain-field curves. The exceptions were Maraging 300 steel whose magnetostriction was continuing to increase with stress even at -150 MPa and an SAE 4130 steel that showed an ldquoinverted V rdquo shape. B-H curves of all of the samples showed some small dependencies on stress but were otherwise unremarkable. The saturation magnetostrictions (muS = 1 times 10-6) and saturation magnetization (tesla) were: AerMet 100 [30 muS, 1.68 T]; HP 9-4-20 [23 muS, 1.68 T]; SAE 4130 [10 muS, 1.81 T]; Maraging 300 [32 muS (at -150 MPa), 1.67 T]; SAE 4340 [5 muS, 1.58 T]; SAE 9310 (heat treatment I) [10 muS, 1.77 T]; and SAE 9310 (heat treatment II) [12 muS, 1.82 T]. Details of the heat treatments are given.

Thermomagnetic properties and magnetocaloric effect of FeCoNiCrAl-type high-entropy alloys

Abstract: In this work, we investigate the effects of substituting Ni/Al for Cr on the thermomagnetic and magnetocaloric properties of FeCoNiCrAl-type high entropy alloys (HEAs). Ni and Al appear to prefer the BCC phase, and increases in the Al composition appear to stabilize the BCC phase. In contrast to Al, Ni content yields an increase in the FCC phase fraction, resulting in a drop off in magnetization. The phase transformation from BCC to FCC was intensified at annealing temperatures of 800 °C and higher due to increased diffusion rates and the resulting spinodal decomposition. A magnetic phase transition around 150 K was found in the FeCoNi1.5Cr0.5Al annealed alloy potentially corresponding to the FCC phase, and a very broad magnetic phase transition was observed in the annealed FeCoNiCrAl alloy, resulting in a high refrigerant capacity of RCFWHM = 242.6 J⋅kg-1 near room temperature. A peak magnetic entropy change of −ΔSM = 0.674 J⋅kg-1⋅K-1 was also obtained at applied fields of ∼70 kOe at 290 K in the FeCoNiCrAl HEA. These magnetocaloric values are comparable to Fe-based metallic glasses such as Fe-Tm-B-Nb and Fe-Zr-B-Co alloys, with a similar transition near room temperature.

Weibull stress model for cleavage fracture under high‐rate loading

Abstract: This paper examines the effects of loading rate on the Weibull stress model for prediction of cleavage fracture in a low-strength, A515-70 pressure vessel steel. Interest focuses on low-to-moderate loading rates (K I < 2500 MPa√m s -1 ). Shallow cracked SE(B) specimens were tested at four different loading rates for comparison with previous quasi-static tests on shallow notch SE(B)s and standard C(T)s. To utilize these dynamic experimental data, we assume that the Weibull modulus (m) previously calibrated using quasi-static data remains invariant over the loading rates of interest. The effects of dynamic loading on the Weibull stress model enter through the rate-sensitive material flow properties, the scale parameter (σ u ) and the threshold Weibull stress (σ w-min ). Rate-sensitive flow properties are modelled using a viscoplastic constitutive model with uniaxial, tension stress-plastic strain curves specified at varying plastic strain rates. The analyses examine dependencies of σ w-min and σ u on K I . Present results indicate that σ w-min and σ u are weak functions of loading rate K I for this pressure vessel steel. However, the predicted cumulative probability for cleavage exhibits a strong sensitivity to σ u and, consequently, the dependency of σ u on K I is sufficient to preclude use of the static σ u value for high loading rates.

Improving the model development process: expanding our horizons in verification, validation, and accreditation research and practice

Abstract: Many different types of modeling and simulation (M&S) applications, consisting of a combination of software, hardware, and humanware, are used in dozens of disciplines under diverse objectives including acquisition, analysis, education, entertainment, research, and training. Certification of sufficient accuracy of an M&S application by conducting verification, validation, and accreditation (VV&A) requires multifaceted knowledge and experience, and poses substantial technical and managerial challenges for researchers, practitioners, and managers. The challenges can only be met by using a very broad spectrum of approaches and expanding our horizons in VV&A. This paper presents 13 strategic directions to meet those challenges. The strategic directions provide guidelines for successful VV&A research and practice.