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Test Temperature Range for NIST Certified Charpy Specimens for Testing at "Room Temperature"



Enrico Lucon


The NIST Charpy Machine Verification Program is ready to introduce low-energy and high energy certified specimens that can be tested at room temperature instead of -40 °C, thus accommodating the requests of many customers during the past 35 years. An investigation aimed at providing a practical and technically sound definition of "room temperature" (barycentric value and tolerance) was conducted, by examining previously obtained Charpy energy transition curves for different energy levels, as well as by testing certified low energy specimens at 21 °C (ambient temperature of the NIST Charpy Lab in Boulder, Colorado) and additional temperatures in the range 21 °C ± 5 °C. Results have shown that for low-energy specimens, even within a relatively small 10 °C range, the influence of test temperature on Charpy absorbed energy can be significant enough to cause "good" machines to fail the requirements of the ASTM E23 standard. Therefore, at this energy level, the allowable test temperature range must be restricted to 21 °C ± 1 °C. For the other two energy levels (high and super-high), the influence of test temperature is small enough that the allowable temperature range can be expanded to 21 °C ± 3 °C.
NIST Interagency/Internal Report (NISTIR) - 8470
Report Number


Charpy Machine Verification Program, Charpy transition curves, NIST certified Charpy specimens, room temperature


Lucon, E. (2023), Test Temperature Range for NIST Certified Charpy Specimens for Testing at "Room Temperature", NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed May 24, 2024)


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Created June 20, 2023