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Displaying 101 - 125 of 1316

Microscale Mapping of Structure and Stress in Barium Titanate

April 19, 2020
Author(s)
Jane A. Howell, Mark D. Vaudin, Lawrence Henry Friedman, Robert F. Cook
Cross-correlation of electron backscatter diffraction (EBSD) patterns was used to generate rotation, strain, and stress maps of single-crystal tetragonal barium titanate (BaTiO3) containing isolated, small, sub-micrometer a domains separated from a c-

Dynamic Compression Tests of Alumina Dumbbells Using a Spherical Joint

December 19, 2019
Author(s)
Richard Rhorer, George D. Quinn, Steven Mates
The dynamic compressive strength of ceramic armor materials is difficult to obtain experimentally due to the sensitivity of fracture strength to even small bending stresses. In this work we introduce a spherical joint into a compression Kolsky bar to

A critical evaluation of indentation crack lengths in air

November 13, 2019
Author(s)
Robert F. Cook
A extensive overview is presented of Vickers indentation crack lengths in ceramics in air. Measurement of such crack lengths is one of the most common and powerful assessments of the fracture properties of ceramics and the overview provides a critical

Stress measurements in alumina by optical fluorescence: revisited

August 27, 2019
Author(s)
Robert F. Cook, Chris A. Michaels
Stress measurements in single crystal and polycrystalline alumina are revisited using a recently-developed optical fluorescence energy shift method. The method simultaneously utilizes the R1 and R2 Cr-related ruby line shifts in alumina to determine two

DESIGN OF AN INTELLIGENT PYTHON CODE FOR VALIDATING CRACK GROWTH EXPONENT BY MONITORING A CRACK OF ZIG-ZAG SHAPE IN A CRACKED PIPE

July 27, 2019
Author(s)
Jeffrey T. Fong, Pedro V. Marcal, Robert B. Rainsberger, Nathanael A. Heckert, James J. Filliben
When a small crack is detected in a pressure vessel or piping, we can estimate the fatigue life of the vessel or piping by applying the classical law of fracture mechanics for crack growth if we are certain that the crack growth exponent is correct and the

Disordered Heterogeneous Materials

July 1, 2019
Author(s)
Andrew J. Allen
This chapter describes the use of diffraction-based methods to characterize amorphous or disordered heterogeneous materials. Quantitative materials microstructure characterization using small-angle scattering methods is emphasized. While these techniques

Fracture Sequences During Elastic-Plastic Indentation of Brittle Materials

April 12, 2019
Author(s)
Robert F. Cook
A fracture analysis is developed for crack initiation sequences occurring during sharp indentation of brittle materials. Such indentations, generated by pyramidal or conical loading, generate elastic and plastic deformation. The analysis uses a non-linear

An Inter-Laboratory Comparative High Throughput Experimental Materials Study of Zn-Sn-Ti-O Thin Films

March 19, 2019
Author(s)
Jason R. Hattrick-Simpers, Zachary T. Trautt, Kamal Choudhary, Aaron G. Kusne, Feng Yi, Martin L. Green, Sara Barron, Andriy Zakutayev, Nam Nguyen, Caleb Phillips, John Perkins, Ichiro Takeuchi, Apurva Mehta
High throughput experimental (HTE) techniques are an increasingly important way to accelerate the rate of materials research and development for many possible applications. However, there are very few publications on the reproducibility of the HTE results

Exposure Study on the Aging of PTFE and Ceramic Diffusers

February 6, 2019
Author(s)
Benjamin K. Tsai, Catherine C. Cooksey, David W. Allen, Christopher C. White, Walter E. Byrd, Deborah S. Jacobs
This paper describes efforts to quantify the effects of aging in the ultraviolet (UV) on polytetrafluoroethylene (PTFE) and ceramic samples. Long term UV aging may significantly alter the reflectance factor and cause an error in the calibration of

Uncertainty Quantification of Failure Probability and a Dynamic Risk Analysis of Decision Making for Maintenance of Ageing Infrastructure

January 2, 2019
Author(s)
Jeffrey T. Fong, James J. Filliben, Nathanael A. Heckert, Dennis D. Leber, Paul A. Berkman, Robert E. Chapman
Risk, as the product of failure probability and failure consequence, has been estimated and applied by engineers and managers to help make critical decisions on (a) maintenance of ageing plants, and (b) planning of new infrastructure. For ageing plants

Lamellar and bundled domain rotations in barium titanate

August 27, 2018
Author(s)
Jane A. Howell, Mark D. Vaudin, Lawrence Henry Friedman, Robert F. Cook
Cross-correlation of electron backscatter diffraction patterns has been used to generate rotation maps of single crystals of tetragonal barium titanate (BaTiO3) containing multiple lamellae and bundles of  90 domains. Rotation measurement angular

UNCERTAINTY IN MULTI-SCALE CREEP RUPTURE LIFE MODELING AND A NEW APPROACH TO ESTIMATING FREQUENCY OF IN-SERVICE INSPECTION OF COMPONENTS AT ELEVATED TEMPERATURES (*)

April 3, 2018
Author(s)
Jeffrey T. Fong, Nathanael A. Heckert, James J. Filliben, Marvin J. Cohn
Uncertainty in modeling the creep rupture life of a full-scale component using experimental data at microscopic (Level 1), specimen (Level 2), and full-size (Level 3) scales, is addressed by applying statistical theory of prediction intervals, and that of

Experimental scattering matrix for lunar regolith simulant JSC-1A at visible wavelengths

March 8, 2018
Author(s)
Edward J. Garboczi, Ann C. Chiaramonti Debay, Thomas V. Lafarge, O Munoz, J Escobar-Cerezo, D Guirado, JC Gomez-Martin, Jay Goguen, F Moreno
We present the experimental scattering matrix as a function of the scattering angle of the lunar soil simulant JSC-1A. The measurements were performed at 488 nm, 520 nm and 647 nm, covering the range of scattering angles from 3o to 177o. The size
Displaying 101 - 125 of 1316