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Analyzing the NIST Charpy Program Database: Influence of Impact Hammer Type (C vs. U) on Test Results



Enrico Lucon, Raymond L. Santoyo


The NIST Charpy Machine Verification Program supplies ASTM E23 certified Charpy reference specimens to customers all over the world since 1989, when the program was transferred from the US Army at Watertown Arsenal, Massachusetts. Starting in 1993, customer test results have been recorded in the form of absorbed energy values in an electronic database, which currently contains more than 70,000 records. In this study, data from the period 2000-2021 have been analyzed to investigate the influence of machine type/hammer configuration (C-type vs. U-type) on Charpy test results at three absorbed energy levels. The significance of the trends observed has been assessed statistically, and compared to the trends observed for the three NIST reference machines used for the certification of Charpy reference specimens. The current line-up of NIST machines (one C-type and two U-type) has been found to provide the highest percentage of successful verifications with respect to other combinations of reference machines.
ASTM Journal of Testing and Evaluation


ASTM E23, Charpy reference specimens, C-type Charpy hammer, NIST Charpy Program, NIST Charpy reference machines, U-type Charpy hammer.


Lucon, E. and Santoyo, R. (2022), Analyzing the NIST Charpy Program Database: Influence of Impact Hammer Type (C vs. U) on Test Results, ASTM Journal of Testing and Evaluation, [online], (Accessed June 25, 2024)


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Created July 20, 2022, Updated November 29, 2022