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Portune A.R.,Oak Ridge Institute for Science and Engineering ORISE | Hilton C.D.,Oak Ridge Institute for Science and Engineering ORISE
International Journal of Applied Ceramic Technology | Year: 2013

The uncertainty of transition velocity estimates made for five armor ceramic materials was quantified by applying Bayesian hypothesis testing to the McCauley Wilantewicz method. Likelihood functions of the ceramic plasticity parameter and estimated transition velocity for each material were determined through analysis of load-hardness probability spaces. Parameters of these functions were analyzed to quantify variability in expected material performance. The applied statistical methodology enabled formation of probability of penetration curves that indicated how the certainty of interface defeat varied as a function of impact velocity. Qualitative and quantitative analysis of results increases the utility of the McCauley Wilantewicz method as a screening tool for ceramic materials by providing additional information regarding the variability of expected material performance. Information revealed by this statistical approach could potentially be harnessed to drive future material development by indicating microstructural states more likely to result in desirable material behavior. © 2012 The American Ceramic Society. Source

Portune A.R.,Oak Ridge Institute for Science and Engineering ORISE | Hilton C.D.,Oak Ridge Institute for Science and Engineering ORISE
Journal of Materials Science | Year: 2012

This article presents methodology for constructing a probability space that quantifies the load-hardness relationship in ceramics. Aspects of this space are indicative of uncertainties introduced by variations in material microstructure, instrument repeatability, and technician skill. The developed method is general in nature, and can be made specific to particular types of hardness measurements or equations used to describe the load- hardness relationship such as Meyer's law, the modified proportional specimen resistance model, and others. Construction of the probability space is accomplished by applying Bayesian hypothesis testing to determine the likelihood function of critical parameters of the chosen load-hardness equation. A demonstration of this methodology is presented for Vickers hardness measurements made at four applied loads on tungsten carbide. The utility of the technique in quantifying microstructural uncertainty is shown using Knoop hardness datasets for aluminum oxynitride and two types of silicon carbide. Analysis of the normality of hardness values was shown to provide an objective criterion for determining when enough measurements have been made to adequately describe material behavior. The probability spaces constructed for each material were used to quantify uncertainty in the load- hardness curve that would extend to predictions regarding microstructural features or performance based on this relationship. © 2012 Springer Science+Business Media, LLC. Source

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