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

摘要

The NIST Charpy Machine Verification Program has been supplying ASTM E23-18, Standard Test Methods for Notched Bar Impact Testing of Metallic Materials certified Charpy reference spec-imens 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 versus 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.