Investigations on SI-Traceable Dynamic Calibration of Instrumented Charpy Strikers Activities performed at NIST in FY2019
Nicholas A. Vlajic, Akobuije D. Chijioke, Enrico Lucon, Lance Einfeld
In recent years, investigations have been conducted at NIST (as a collaboration between the Fatigue and Fracture Group in Boulder, CO and the Force and Mass Group in Gaithersburg, MD) toward an SI-traceable dynamic calibration of instrumented Charpy strikers. Although Charpy tests are few-millisecond-duration events in which dynamic phenomena are often clearly present, the force measurements from instrumented Charpy tests are predominantly obtained using static calibrations, which has long been recognized as a potential source of significant errors. Several approaches to dynamic calibration have been considered for this work, including methods that have previously been implemented at NIST and elsewhere, and methods that are new in the sense that they are not commonly used or incorporated into standards. A key objective of these investigations is that the calibration be traceable to the International System of Units. A summary of the activities conducted between January and December 2017 was published as NIST TN 1991, issued in May 2018 with the title Investigations on SI-Traceable Dynamic Calibration of Instrumented Charpy Strikers, authors: A. Chijoke, N. Vlaijc, E. Mulhern, and E. Lucon. A paper on investigations aimed at optimizing the design of an instrumented Charpy striker were summarized in a paper titled Design Considerations to Optimize Charpy Instrumented Strikers (authors: N. Vlaijc, A. Chijoke, and E. Lucon). The paper was submitted in 2018 but has not yet been published at the time of writing, being still in review after initial rejections. The activities and accomplishments of this project during FY2019 are described in this Technical Note.