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Search Publications by: Nik Hrabe (Fed)

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Displaying 26 - 50 of 58

Assessment of intra-build variations in tensile strength in electron beam powder-bed fusion Ti-6Al-4V part 2: Effects of powder mixing

May 31, 2022
Author(s)
Nicholas Derimow, Jake Benzing, Orion Kafka, Newell Moser, Priya Pathare, Michael Walker, Frank DelRio, Nik Hrabe
In Part 2 of this paper series, high-throughput tensile testing and characterization of porosity, microstructure, and oxygen content was carried out on Ti-6Al-4V samples that were fabricated via electron beam powder-bed fusion (PBF-EB) to test our

In situ absorption synchrotron measurements, predictive modeling, microstructural analysis, and scanning probe measurements of laser melted Ti-6Al-4V single tracks for additive manufacturing applications

December 29, 2021
Author(s)
Nicholas Derimow, Edwin Schwalbach, Jake Benzing, Jason Killgore, Aly Artusio-Glimpse, Nik Hrabe, Brian Simonds
In this work, the fundamental processing-structure-property (PSP) relationships that govern laser-based additive manufacturing were investigated with the Ti-6Al-4V alloy. X-ray synchrotron imaging carried out in conjunction with in-situ integrating sphere

Sintered powder oxidation variation as a function of build height for titanium alloy produced by electron beam powder-bed fusion

November 26, 2021
Author(s)
Nicholas Derimow, Alejandro Romero, Aldo Rubio, Cesar Terrazas, Francisco Medina, Ryan Wicker, Nik Hrabe
It is well-established that titanium alloy (Ti-6Al-4V) powder oxidizes during electron beam powder-bed fusion (PBF-EB) due to the high background temperatures resulting from layer preheating and sintering of the powder bed before melting. However, it is

Evaluation of a Modified Void Descriptor Function to Uniquely Characterize Pore Networks and Predict Fracture Location in Additively Manufactured Metals

November 15, 2021
Author(s)
Dillon Watring, Jake Benzing, Orion Kafka, Li-Anne Liew, Newell Moser, John Erickson, Nik Hrabe, Ashley Spear
Variations in additive manufacturing (AM) processing parameters can lead to variations in porosity, making it challenging to predict pore- or void-sensitive mechanical response in AM metals. A recently developed pore metric, the void descriptor function

Damage tolerant design of additively manufactured metallic components subjected to cyclic loading: State of the art and challenges

March 18, 2021
Author(s)
Uwe Zerbst, Giovanni Bruno, Jean-Yves Buffiere, Thomas Wegener, Tao Wu, Xiang Zhang, Nikolai Kashaev, Giovanni Meneghetti, Nik Hrabe, Mauro Madia, Tiago Werner, Kai Hildgenburg, Radek Proch?zka, Martina Koukol?kov?, Jan D?ugan, Benjamin M?ller, Stefano Beretta, Alexander Evans
Undoubtedly, a better understanding and the further development of approaches for damage tolerant component design of AM parts are among the most significant challenges currently facing the use of these new technologies. This article presents a thorough

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
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