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Dagel, Daryl

Publications and source records attributed to Dagel, Daryl.

35 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Characterization of the Fe-Co-1.5V soft ferromagnetic alloy processed by Laser Engineered Net Shaping (LENS)

Processing of the low workability Fe-Co-1.5V (Hiperco® equivalent) alloy is demonstrated using the Laser Engineered Net Shaping (LENS) metals additive manufacturing technique. As an innovative and highly localized solidification process, LENS is shown to overcome workability issues that arise during conventional thermomechanical processing, enabling the production of bulk, near net-shape forms of the Fe-Co alloy. Bulk LENS structures appeared to be ductile with no significant macroscopic defects. Atomic ordering was evaluated and significantly reduced in as-built LENS specimens relative to an annealed condition, tailorable through selection of processing parameters. Fine equiaxed grain structures were observed in as-built specimens following solidification, which then evolved toward a highly heterogeneous bimodal grain structure after annealing. The microstructure evolution in Fe-Co is discussed in the context of classical solidification theory and selective grain boundary pinning processes. In conclusion, magnetic properties were also assessed and shown to fall within the extremes of conventionally processed Hiperco® alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Carrier dynamics model for laser-solid interactions

This report describes a model for the time development of carrier distributions within a metallic or semiconductor target after the onset of an incident laser pulse. The dynamics of electron and hole populations in momentum-resolved conduction- and valence-band states are treated at the level of carrier-carrier and carrier-phonon scattering. These scattering events result in plasma and lattice heating, which in turn lead to electron thermionic emission and tunneling, and target material ablation. A fairly phenomenological approach is taken to mitigate numerical computation demands, in order to facilitate parametric studies. Two examples of application are presented. One involve s the incident of an intense near-infrared laser pulse on a solid aluminum target, where the goal is to connect excited species emission to physics at a band-structure level. The second involves modeling the trigger mechanism in laser-triggered high-voltage switches, where the results are used as input to highly intensive particle-in-cell (PIC) plasma simulations of switch operation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Measurement of Laser Weld Temperatures for 3D Model Input

Laser welding is a key joining process used extensively in the manufacture and assembly of critical components for several weapons systems. Sandia National Laboratories advances the understanding of the laser welding process through coupled experimentation and modeling. This report summarizes the experimental portion of the research program, which focused on measuring temperatures and thermal history of laser welds on steel plates. To increase confidence in measurement accuracy, researchers utilized multiple complementary techniques to acquire temperatures during laser welding. This data serves as input to and validation of 3D laser welding models aimed at predicting microstructure and the formation of defects and their impact on weld-joint reliability, a crucial step in rapid prototyping of weapons components.

47 OTHER INSTRUMENTATION↗