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Search Publications by: Ward L. Johnson (Fed)

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Displaying 1 - 25 of 54

Evidence for contributions of lack-of-fusion defects and dislocations to acoustic nonlinearity and loss in additively manufactured aluminum

February 2, 2024
Author(s)
Ward L. Johnson, Paul R. Heyliger, Jake Benzing, Orion Kafka, Newell Moser, Derek Harris, Jeremy Iten, Nik Hrabe
Resonant acoustic nonlinearity and loss have previously been found to be correlated with porosity in additively manufactured (AM) commercially pure aluminum and stainless steel, and this effect offers a potential basis for rapid nondestructive

Novel or Improved NDE Inspection Capabilities for Additively Manufactured Parts

February 26, 2022
Author(s)
Ward L. Johnson, Anne-Francoise Obaton, Alex Van den Bossch, Bryan Butsch, Imane Zouggarh, Olivier Burnet, Florent Soulard
Additive manufacturing (AM) enables the production of parts with extremely complex shapes, such as lattice structures and internal structures (cavities, channels). As a result of this geometric complexity, the applicability of most conventional

Mechanisms of Anelastic Loss in Langasite at Temperatures from 113 K to 1324 K

May 4, 2021
Author(s)
Ward L. Johnson, Yuriy Suhak, Holger Fritze
Synthetic piezoelectric crystals with the structure of langasite (LGS) are being pursued for resonant acoustic sensors that can operate at temperatures exceeding the range of conventional piezoelectric materials. The optimization of these crystals is

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

Phase noise generated by vibration of bacteria adhered to a quartz resonator

September 22, 2017
Author(s)
Ward L. Johnson, Danielle C. France, F L. Walls, William T. Cordell, Nikki S. Rentz
An approach is presented for sensing mechanical fluctuations of bacteria, with potential application in monitoring microbial responses to changes in chemical environment, such as antimicrobial intervention. Bacteria are tethered to a quartz crystal

Resonant Acoustic Frequency Shifts Associated with Cracks in Multilayer Ceramic Capacitors

June 6, 2017
Author(s)
Ward L. Johnson, Jaemi Herzberger, Sudook A. Kim, Kirsten L. Peterson, Paul R. Heyliger, Grady S. White
Resonant ultrasound spectroscopy (RUS) was used in this study to measure shifts in resonant frequency that arise from the presence of cracks in barium-titanate-based multi-layer ceramic capacitors (MLCCs). This work was motivated by an industrial need for

Vibrational Modes of Multilayered Ceramic Capacitors

April 28, 2016
Author(s)
Kirsten L. Peterson, Ward L. Johnson, Sudook A. Kim, Paul R. Heyliger
Micron-scale spacing of interleaved electrodes and high-dielectric ceramics in multilayer ceramic capacitors (MLCCs) provide exceptionally high capacitances in small volumes. This has led to MLCCs being the preferred type of capacitor in a wide range of

Nonlinear resonant acoustic detection of cracks in multilayer ceramic capacitors

September 3, 2014
Author(s)
Ward L. Johnson, Sudook A. Kim, Grady S. White, Jaemi Herzberger
Abstract—Measurements of resonant ultrasonic frequencies of multilayer ceramic capacitors (MLCC) were performed as a function of excitation amplitude to assess the potential of nonlinear acoustic methods for sensing the presence of cracks. The ultimate

High-Temperature Electromechanical Properties of CTGS

December 1, 2013
Author(s)
Ward L. Johnson, Michal Schulz, Holger Fritze
CTGS (Ca3TaGa3Si2O14) is a commercially available, Czochralski-grown piezoelectric material from the langasite family that has an ordered crystal structure. It can be excited piezoelectrically up to at least 1285 °C, which is very close to the melting

Continuum-based free vibration of circular trigonal and isotropic plates

May 28, 2013
Author(s)
Ward L. Johnson, Paul R. Heyliger
The free vibration behavior of completely unrestrained elastic circular plates with trig- onal and isotropic material symmetry is studied using approximate solutions to the three- dimensional theory of linear elasticity. Of primary interest are 1) the

Nonlinear acoustic effects in multilayer ceramic capacitors

January 25, 2013
Author(s)
Ward L. Johnson, Sudook A. Kim, Timothy P. Quinn, Grady S. White
Nonlinear resonant acoustics was explored as an approach for nondestructively evaluating the susceptibility of BaTiO3-based multilayer ceramic capacitors to electrical failure during service. The acoustic nonlinearity was characterized through measurements