SYMPOSIA PAPER Published: 17 April 2019
STP160720170221

Error and Uncertainty in Metallographic Measurement

Source

Technical standards are increasingly moving toward a requirement to understand and account for uncertainties in measurement. The need to quantify uncertainty, and to express it together with the measurement result, has been a focus for international standards for some time. In practice, this has led to a great deal of difficulty in some applications as to how uncertainty is assessed and how much uncertainty there really is from any part of the apparatus and process. Simultaneously, the competitive nature of business is driving a need for tighter manufacturing tolerances in order to improve technical performance or efficiencies. The consequences of errors in measurement are potentially more severe, and there is an associated need to measure with greater accuracy. New technologies can accommodate this need in many circumstances, but for a wide cross section of established businesses, it may not be financially viable to reinvent the process, and refining measurement accuracy is a preferable approach. Mathematical analysis can quantify uncertainty but does not always address how it may be improved. Understanding potential sources of error, and as importantly their relative contribution, can be essential to addressing the need to improve both reliability and reproducibility of results. The objective of this paper is to separate and examine individual sources of error in a number of typical measurements. We will focus on measurements of real microstructural features using optical microscopy and digital imaging. Areas examined will include metallographic preparation, microscope components and settings, camera selection and settings, software considerations, and some human factors. For each potential source of error, the relative contribution to total error will be assessed. Where possible, specific recommendations for best practice will be outlined.

Author Information

Keeble, Michael, E.
Buehler, A Division of ITW, Lake Bluff, IL, US
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Details
Developed by Committee: E04
Pages: 53–65
DOI: 10.1520/STP160720170221
ISBN-EB: 978-0-8031-7660-7
ISBN-13: 978-0-8031-7659-1