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Mahaffey, Jacob Thomas

Publications and source records attributed to Mahaffey, Jacob Thomas.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Thermographic phosphor digital image correlation

The invention advances the ratio method of phosphor thermography using two machine vision cameras for full-field temperature measurements of a solid surface. As an example, algorithms from digital image correlation (DIC) can be used to determine the stereoscopic imaging system intrinsic and extrinsic parameters, and accurately register material points on the sample to subpixel locations in each image with 0.07 px or better accuracy. A phosphor calibration sample fabricated using aerosol deposition can be used for in situ determination of the temperature-versus-intensity ratio relationship. The full calibration methodology and several improvements on two-color phosphor thermography open the door for full-field temperature measurements in dynamic tests with deforming test specimens. In particular, thermographic phosphors can be combined with stereo digital image correlation in a novel diagnostic, TP+DIC, to measure time-resolved full-field surface strains and temperatures simultaneously, thereby enabling testing in combined thermo-mechanical environments.

Winters, Caroline↗
DOE OSTI2021

Mechanical and Corrosion Response of 316SS in Supercritical CO 2

The supercritical carbon dioxide (s-CO 2 ) Brayton cycle is currently being explored as a replacement for the steam Rankine cycle due to its potential for higher efficiency and lower cycle cost. 316 stainless steel is a candidate alloy for use in s-CO 2 up to roughly 600 °C, but the mechanical effects of prolonged exposure of base and welded material in s-CO 2 have not been analyzed. The potential for carburization makes this an important concern for the implementation of 316 and similar austenitic stainless steels in the s-CO 2 environment. In this study, welded and base material of two types of 316–316L and 316H–were exposed in either s-CO 2 or argon at 550 °C or 750 °C for 1000 h. 550 °C s-CO 2 exposure yielded a thin (< 1 µm) Cr oxide with occasional nodules of duplex Fe oxide and Fe–Cr spinel that were up to 5 microns thick. However, tensile results from s-CO –2 exposure matched those of 550 °C thermal aging in Ar, indicating that no mechanically detrimental carburization occurred in either 316 variant after 1000 h exposure. Conversely, 750 °C s-CO 2 exposure produced roughly 10 × the oxide thickness, with a more substantial Fe oxide (3–5 µm) on the majority of the surface and nodules of up to 40 µm thick. In comparison to aged samples, tensile testing of 750 °C CO 2 -exposed samples revealed ductility loss attributed to carburization. As a result, projections of 316L performance in s-CO 2 indicate that mechanically detrimental carburization—equal to that shown here for 750 °C, 1000 h—will likely be present after 7–14 years of service at 550 °C.

316 stainless steel↗
DOE OSTI2020

Additive Manufacturing of MITL's and Convolutes

Stockpile stewardship requires accurate and predictive models relying on the generation of extreme environments which is both incredibly difficult and profoundly necessary. Next generation pulsed power facilities (NGPPF), where these environments are created, may require a paradigm shift in equipment engineering/manufacture to fulfill this need. Therefore, this research aims to investigate the limitations, capabilities and efficacy of leveraging advancements in the field of additive manufacturing (AM) in order to produce novel power flow components for NGPPFs. This work focused on commercial 3D metal AM equipment producing several prototypes addressing prescient needs/shortcomings, and a technique wherein a lightweight polymer core is metalized. Ultimately, commercial 3D metal AM is considered a viable path forward but would require a sizeable investment and does not currently support the scale and complexity necessary for NGPPFs. Moreover, initial results from our composite technique are promising and is considered a realizable path forward given further investigation.

42 ENGINEERING↗
DOE OSTI2020

Carburization resistance of cu-coated stainless steel in supercritical carbon dioxide environments

This study investigates the effectiveness of Cu as a corrosion barrier in supercritical carbon dioxide (s-CO 2 ) by coating 316 stainless steel (316) with various thicknesses of Cu. In this work, 316 exposed to s-CO 2 with 50 ppm CO showed a reduction in oxidation corresponding to the thickness of its Cu barrier coating. Additionally, a continuous Cu layer between the environment and the alloy was found to correlate to an elimination of carburization and corrosion-related mechanical degradation. This Cu coating technique could be applied over a variety of temperatures to improve the corrosion resistance of alloys that are susceptible to carburization.

36 MATERIALS SCIENCE↗