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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

RidgeAlloy: A high pressure die casting alloy that captures the approaching wave of automotive body sheet scrap

Oak Ridge National Laboratory (ORNL) has recently launched an effort to economically expand the North American aluminum supply chain by designing and developing a new family of Al-Mg-Si-Fe-Mn structural die cast aluminum alloys that can be made from up to 100% mixed 5xxx and 6xxx series automotive post-consumer sheet scrap and do not require heat treatment. The goal is to develop an alloy capable of capturing the approaching scrap wave of aluminum sheet intensive vehicles (in the 2030’s) into integrated structural high pressure die castings, rather than down-cycling these high-grade sheet alloys into non-structural castings. ORNL discovered a significant gap in the commercial thermodynamic databases that were unable to predict the trends of a key primary intermetallic phase as a function of composition. Experiments were performed to correct this gap and to create a unique, corrected quaternary database for Al-Mg-Si-Fe. High throughput computational methods, including solidification simulations, were used to identify a composition volume capable of avoiding this embrittling primary intermetallic phase, even at higher Fe + Si contents. Laboratory scale castings validated the thermodynamic and solidification predictions and resulted in lab-cast alloys with little primary intermetallic, and which met or exceeded structural casting properties requirements for yield strength and ductility. An accelerated demonstration of an HPDC automotive part was conducted in collaboration with two U.S. small businesses. Ingots made from 100% recycled 5xxx and 6xxx series scrap (plus Fe) were used to die cast one variant of this new family of Al-Mg-Si-Fe-Mn alloys (with high Si + Fe content) into a mid-sized HPDC structural-type automotive component. The HPDC alloy demonstration part showed good properties (especially ductility) and good castability for a complex component.

Plotkowski, Alex [ORNL] (ORCID:0000000154718681)↗
NASA NTRS1973

Supersonic aerodynamic characteristics of hypersonic low-wave-drag elliptical body-tail combinations as affected by changes in stabilizer configuration

An investigation has been made at Mach numbers from 1.50 to 4.63 to determine systematically the effects of the addition and position of outboard stabilizers and vertical- and vee-tail configurations on the performance and stability characteristics of a low-wave-drag elliptical body. The basic body shape was a zero-lift hypersonic minimum-wave-drag body as determined for the geometric constraints of length and volume. The elliptical cross section had an axis ratio of 2 (major axis horizontal) and an equivalent fineness ratio of 6.14. Base-mounted outboard stabilizers were at various dihedral angles from 90 deg to minus 90 deg with and without a single center-line vertical tail or a vee-tail. The angle of attack was varied from about minus 6 to 27 deg at sideslip angles of 0 and 5 deg and a constant Reynolds number of 4.58 x one million (based on body length).

Spencer, B., Jr.↗
NASA NTRS1992

A method for designing blended wing-body configurations for low wave drag

A procedure for tailoring a blended wing-body configuration to reduce its computed wave drag is described. The method utilizes an iterative algorithm within the framework of first-order linear theory. Four computed examples are included. In each case, the zero-lift wave drag was reduced without an increase in the drag due to lift.

Barger, Raymond L.↗
NASA NTRS1989

Body frame close coupling wave packet approach to gas phase atom-rigid rotor inelastic collisions

The close coupling wave packet (CCWP) method is formulated in a body-fixed representation for atom-rigid rotor inelastic scattering. For J greater than j-max (where J is the total angular momentum and j is the rotational quantum number), the computational cost of propagating the coupled channel wave packets in the body frame is shown to scale approximately as N exp 3/2, where N is the total number of channels. For large numbers of channels, this will be much more efficient than the space frame CCWP method previously developed which scales approximately as N-squared under the same conditions.

Sun, Y.↗
DOE OSTI2022

Charge ordering in Ir dimers in the ground state of Ba 5 AlIr 2 O 11

It has been well established experimentally that the interplay of electronic correlations and spin-orbit interactions in Ir 4+ and Ir 5+ oxides results in insulating J eff = 1/2 and J eff = 0 ground states, respectively. However, in compounds where the structural dimerization of iridium ions is favorable, the direct Ir d-d hybridization can be significant and takes a key role. Here, in this study, we investigate the effects of direct Ir d-d hybridization in comparison with electronic correlations and spin-orbit coupling in Ba 5 AlIr 2 O 11 , a compound with Ir dimers. Using a combination of ab initio many-body wave-function quantum chemistry calculations and resonant inelastic x-ray scattering experiments, we elucidate the electronic structure of Ba 5 AlIr 2 O 11 . We find excellent agreement between the calculated and the measured spin-orbit excitations. Contrary to expectations, the analysis of the many-body wave function shows that the two Ir (Ir 4+ and Ir 5+ ) ions in the Ir 2 O 9 dimer unit in this compound preserve their local J eff character close to 1/2 and 0, respectively. The local point group symmetry at each of the Ir ions plays an important role, significantly limiting the direct d-d hybridization. Our results emphasize that minute details in the local crystal field environment can lead to dramatic differences in the electronic states in iridates and 5d oxides in general.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1986

Radiation of plasma waves by a conducting body moving through a magnetized plasma

A theory is presented describing energy loss due to radiation of plasma waves by a conducting body moving through a magnetized plasma, which makes it possible to estimate the total power radiated at all frequencies. Using energy conservation and a source current deduced by physical reasoning, numerical predictions were made for the power radiated. It was found that radiation is produced at all frequencies for which one of the plasma modes has zero phase velocity in some direction.

Barnett, Alan↗
NASA NTRS1960

Some Examples of the Applications of the Transonic and Supersonic Area Rules to the Prediction of Wave Drag

The experimental wave drags of bodies and wing-body combinations over a wide range of Mach numbers are compared with the computed drags utilizing a 24-term Fourier series application of the supersonic area rule and with the results of equivalent-body tests. The results indicate that the equivalent-body technique provides a good method for predicting the wave drag of certain wing-body combinations at and below a Mach number of 1. At Mach numbers greater than 1, the equivalent-body wave drags can be misleading. The wave drags computed using the supersonic area rule are shown to be in best agreement with the experimental results for configurations employing the thinnest wings. The wave drags for the bodies of revolution presented in this report are predicted to a greater degree of accuracy by using the frontal projections of oblique areas than by using normal areas. A rapid method of computing wing area distributions and area-distribution slopes is given in an appendix.

Nelson, Robert L.↗
DOE OSTI2021

High-Quality Revision of the Israeli Seismic Bulletin

Seismic bulletins, with trustworthy phase picks, origin times, and source locations are key for regional seismic studies, such as travel-time (TT) tomography, attenuation tomography, and anisotropy studies. To lay the groundwork for such studies in Israel, we revised the seismic bulletin of Israel and the surrounding area and obtained a trustworthy TT data set. From the earthquake and explosion bulletins of the Geophysical Institute of Israel, we compiled a starting data set of about 123,000 earthquakes and explosions that occurred during the past 40 yr. After screening out the poorly recorded events, we were left with a data set of ~38,000 well-recorded events. We then revised the remaining data set in two consecutive steps. In the first, we reviewed and updated station metadata, including changes in station metadata parameters over time. In the second step, we jointly relocated a list of selected seismic events, using the Bayesian hierarchical location software package (BayesLoc) of Myers et al. (2007) that performs joint relocation of multiple events. We observed striking dissimilarities between the spatial distributions of the newly relocated catalog and the initial locations. Although the depth distribution of the starting catalog is trimodal with peaks at 0, 5, and 10 km, the distribution in this study is unimodal, with a broad peak between 7.5 and 12.5 km. By differencing the observed arrival times and the origin times obtained through relocation with BayesLoc, we obtained a revised TT database that consists of 261,336 Pg, 132,876 Pn, 114,816 Sg, and 60,394 Sn arrivals, from a set of 30,458 jointly relocated seismic sources. In this work, we compared prerevision and postrevision TTs as a function of epicentral distance and concluded that the revised data set contains far fewer outliers and inconsistencies than the original data set. The revised TT data set may be used for seismic studies, such as TT tomography, attenuation tomography, and anisotropy studies.

58 GEOSCIENCES↗
DOE OSTI2021

Exploring the Effects of Emplacement Conditions on Explosion P/S Ratios across Local to Regional Distances

High-frequency (~> 2 Hz) seismic P/S amplitude ratios are well-established as a discriminant to distinguish between natural earthquakes and underground explosions at regional distances (~200–1500 km). As research shifts toward identifying lower-yield events, work has begun to investigate the potential of this discriminant for use at local distances (<200 km), in which initial results raise questions about its effectiveness. Here, we utilize data from several chemical explosion experiment series at the Nevada National Security Site in southern Nevada in the United States to study explosion Pg/Lg ratios across the range of local to regional distances. Additionall, the experiments are conducted over differing emplacement conditions, with contrasting geologies and a variety of yields and depths of burial, including surface explosions. We first establish the similarities of Pg/Lg ratios from chemical explosions to those from historic nuclear tests and conclude that, as previous data have suggested, chemical explosion ratios are good proxies for nuclear tests. We then examine Pg/Lg ratios from the new experiment series as functions of distance, yield, depth of burial, and scaled depth of burial (SDOB). At far-local and regional distances, we observe consistently higher ratios from hard-rock explosions compared to ones in a weaker dry alluvium medium, consistent with prior regional distance results. No other trends with yield, depth of burial, or SDOB are strongly evident. Scatter in the observed ratios is very high, particularly at the shortest event-to-station distances, suggesting that small-scale path effects play a significant role. On average, the local distance explosion Pg/Lg ratios show remarkable consistency across all the variations in emplacement. Explosion source models will need to reproduce these results.

58 GEOSCIENCES↗
DOE OSTI2022

Estimating Explosion Yields Using Moment Tensor Solutions and Seismic Moment

We report seismic moment, a measurable and well-understood quantity of seismic sources, is used to estimate the yield of explosions. Application of such a method in the past, as in the manner of m b -derived yields, has been complicated by the effect of variations in the explosion working point, depth, and secondary source effects (such as spalling and tectonic release) on the observed moment. We start using the full (six-element) moment tensor solution, which can capture the relevant source physics and, at least in theory, better isolate the primary explosion source. The moment-to-yield ratio is then estimated using an explosion source model which, provided with emplacement conditions, can relate the two parameters. We discuss the major sources of uncertainty associated with the method, and calibrate it with chemical and nuclear explosions at the Nevada National Security Site. We then apply the method to published moment tensor solutions for the six declared North Korean nuclear explosions that occurred between 2006 and 2017. The results are mostly consistent with other yield estimates made using a variety of high-frequency methods. This technique is a new approach to estimating explosive yield and simple to implement, as much of the complexity is captured by the source models.

58 GEOSCIENCES↗
NASA NTRS1983

An experimental investigation of the impingement of a planar shock wave on an axisymmetric body at Mach 3

An experimental study of the flow caused by a planar shock wave impinging obliquely on a cylinder is presented. The complex three dimensional shock wave and boundary layer interaction occurring in practical problems, such as the shock wave impingement from the shuttle nose on an external fuel tank, and store carriage interference on a supersonic tactical aircraft were investigated. A data base for numerical computations of complex flows was also investigated. The experimental techniques included pressure measurements and oil flow patterns on the surface of the cylinder, and shadowgraphs and total and static pressure surveys on the leeward and windward planes of symmetry. The complete data is presented in tabular form. The results reveal a highly complex flow field with two separation zones, regions of high crossflow, and multiple reflected shocks and expansion fans.

Brosh, A.↗