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Friedman, B.

Publications and source records attributed to Friedman, B..

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Explosive fragmentation of additively manufactured stainless steel

Properties of fragmentation from an explosively driven 316L stainless steel spherical shell section fabricated by a laser powder bed additive manufacturing process with minimal surface finishing are investigated. This shell is driven by an insensitive high explosive, resulting in high strain rate deformation (>8 × 10 3 s –1 ) and failure of the stainless steel. Photonic Doppler velocimetry measures the expansion rate; dynamic radiography and high-speed imaging capture the fracture behavior of the stainless steel. The fracture response of the additively manufactured stainless steel shell is compared to published experimental results on additively manufactured 316L stainless steel and conventionally manufactured wrought 316L and 304 stainless steel shell fragmentation. Despite preferred crack orientation, suggesting the influence of surface grooves on fracture time, fragment size is identical to that measured in a similar experiment on wrought 304 stainless steel. Further analysis indicates that the 316L additively manufactured stainless steel shell exhibits comparable spall strength and fragmentation toughness to conventionally manufactured stainless steel yet lower failure strain due to surface stress concentrations.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Semi-empirical scaling for ion–atom single charge exchange cross sections in the intermediate velocity regime

We present a semi-empirical scaling law for non-resonant ion–atom single charge exchange cross sections for collisions with velocities from ${10}^{7}\,{\rm{t}}{\rm{o}}\,{10}^{9}\,\mathrm{cm}\,{{\rm{s}}}^{-1}$ and ions with positive charge $q\lt 8$. Non-resonant cross sections tend to have a velocity peak at collision velocities $v\lesssim 1\ {\rm{a}}{\rm{u}}$ with exponential decay around this peak. We construct a scaling formula for the location of this peak then choose a functional form for the cross section curve and scale it. The velocity at which the cross section peaks, v m , is proportional to the energy defect of the collision, ${\rm{\Delta }}E$, which we predict with the decay approximation. The value of the cross section maximum is proportional to the charge state q, inversely proportional to the target ionization energy I T , and inversely proportional to v m . For the shape of the cross section curve, we use a function that decays exponentially asymptotically at high and low velocities. We scale this function with parameters ${v}_{{\rm{m}}},{I}_{{\rm{T}}},{Z}_{{\rm{T}}},\mathrm{and}\ {Z}_{{\rm{P}}}$, where the ${Z}_{{\rm{T}},{\rm{P}}}$ are the target and projectile atomic numbers. In conclusion, for the more than 100 cross section curves that we use to find the scaling rules, the scaling law predicts cross sections within a little over a factor of 2 on average.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Comparing Photovoltaic (PV) Costs and Deployment Drivers in the Japanese and U.S. Residential and Commercial Markets

Japan has re-emerged in 2013 as one of the world's fastest-growing and largest photovoltaic (PV) markets (Renewable Energy World 2013). Year-over-year growth in Japanese installed capacity in the first half of 2013 was about 270%. Japan's PV market was on pace to triple in 2013 compared with 2012, with approximately 2.7 GW installed during the first half of 2013 (compared to about 1.6 GW in the United States). This places Japan's market among the world's largest PV markets, along with China, Germany, and the United States. This report explores details of the rapidly changing Japanese market, and similarities and differences between the Japanese and U.S. markets. We collected data from a diverse group of Japanese PV installers, and we gathered additional Japanese and U.S. data from published sources as well as internal analyses.

14 SOLAR ENERGY↗
DOE OSTI2015

A non-modal analytical method to predict turbulent properties applied to the Hasegawa-Wakatani model

Linear eigenmode analysis often fails to describe turbulence in model systems that have non-normal linear operators and thus nonorthogonal eigenmodes, which can cause fluctuations to transiently grow faster than expected from eigenmode analysis. When combined with energetically conservative nonlinear mode mixing, transient growth can lead to sustained turbulence even in the absence of eigenmode instability. Since linear operators ultimately provide the turbulent fluctuations with energy, it is useful to define a growth rate that takes into account non-modal effects, allowing for prediction of energy injection, transport levels, and possibly even turbulent onset in the subcritical regime. We define such a non-modal growth rate using a relatively simple model of the statistical effect that the nonlinearities have on cross-phases and amplitude ratios of the system state variables. In particular, we model the nonlinearities as delta-function-like, periodic forces that randomize the state variables once every eddy turnover time. Furthermore, we estimate the eddy turnover time to be the inverse of the least stable eigenmode frequency or growth rate, which allows for prediction without nonlinear numerical simulation. We test this procedure on the 2D and 3D Hasegawa-Wakatani model [A. Hasegawa and M. Wakatani, Phys. Rev. Lett. 50, 682 (1983)] and find that the non-modal growth rate is a good predictor of energy injection rates, especially in the strongly non-normal, fully developed turbulence regime.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗