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Search Publications by: Nik Hrabe (Fed)

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Displaying 51 - 75 of 92

Effects of laser-energy density and build orientation on the defect structure, microstructure and tensile properties of Inconel 718 parts manufactured with laser powder bed fusion

June 30, 2020
Author(s)
Dillon Watring, Jake Benzing, Nik Hrabe, Ashley Spear
This study investigates the processing-structure-property relationships of Inconel 718 manufactured by laser powder bed fusion. Three di erent build conditions were selected for the Inconel 718 specimens: 0 build orientation and 38 J/mm3, 0 build

Development and Validation of Small Punch Testing at NIST

April 16, 2020
Author(s)
Enrico Lucon, Jake T. Benzing, Nikolas W. Hrabe
Small Punch (SP) testing is a methodology that uses tiny disks (generally 8 mm in diameter and 0.5 mm thick) to estimate mechanical properties of metallic materials, such as tensile properties, fracture toughness, and ductile-to-brittle transition

Multiple Changepoint Analysis of Noisy Nonlinear Data with an Application to Modeling Crack Growth in Additively Manufactured Titanium

December 5, 2019
Author(s)
Lucas N. Koepke, Jolene D. Splett, Timothy P. Quinn, Nikolas W. Hrabe, Jake T. Benzing, Michael R. Frey
Noisy measurement data pose a challenge for changepoint analysis, especially in the presence of multiple changepoints and when the model is nonlinear. We explore various approaches to estimating changepoints and their standard errors under these conditions

Hot isostatic pressing (HIP) to achieve isotropic microstructure and retain as-built strength in additive manufacturing titanium alloy (Ti-6Al-4V)

September 23, 2019
Author(s)
Jake T. Benzing, Nikolas W. Hrabe, Timothy P. Quinn, Ryan M. White, Ross A. Rentz, Magnus Ahlfors
Hot isostatic pressing (HIP) treatments are used to seal internal porosity because defects exist in as-built Ti-6Al-4V parts produced by electron beam melting powder bed fusion. Standard HIP treatment of Ti-6Al-4V parts reduces internal porosity but

Resonant acoustic nonlinearity and loss in additively manufactured stainless steel

May 8, 2019
Author(s)
Ward L. Johnson, Justin G. Whiting, Felix H. Kim, Paul R. Heyliger, Nikolas W. Hrabe
Resonant acoustic nonlinearity and loss in additively manufactured stainless steel were measured with the aim of assessing the potential of such measurements for nondestructively sensing defects that degrade mechanical performance. The material was

Instrumented impact testing of miniaturized Charpy specimens of AM Ti-6Al-4V

April 11, 2018
Author(s)
Enrico Lucon, Nikolas W. Hrabe
An investigation on the impact toughness properties of wrought and additively-manufactured (AM) Ti 6Al 4V was conducted at NIST Boulder, by means of instrumented impact tests on miniaturized Charpy specimens. Full transition curves for absorbed energy and

Fatigue measurement of pipeline steels for application of gaseous hydrogen transport

February 5, 2018
Author(s)
Andrew J. Slifka, Elizabeth S. Drexler, Robert L. Amaro, Louis E. Hayden, Damian S. Lauria, Nikolas W. Hrabe, Douglas G. Stalheim
A comprehensive testing program to determine the fatigue crack growth rate of pipeline steels in pressurized hydrogen gas was completed; the project was sponsored by the Department of Transportation, and was conducted in close collaboration with the ASME