Estimation of Uncertainty in Charpy Pendulum Impact Test Using the Reference Material

Abstract

An urgent task for accredited testing laboratories is to estimate the uncertainty of test results. In Charpy pendulum impact test the sources of the main contributions from the measuring instrument to the uncertainty of the result are: the angle of rise and the angle of fall of the pendulum, force exerted by the pendulum, and the distance from the axis of rotation to the center of strike. The aim of the work is to describe the method for estimating the uncertainty of the results of Charpy pendulum impact test based on information about the calibration of the impact testing machine and traceability to the reference material of impact energy (absorbed energy) of steel grade 45 GSO 11934–2022. The uncertainty estimation method is based on the statistical model from ISO 21748–2017. Uncertainty estimation was carried out for a pendulum impact tester TE JBW-300 using GSO 11934–2022 type 11 samples according to GOST 9454–78 with a type V-notch concentrator at room temperature. The study found that the greatest contribution to the uncertainty of test results is made by a systematic error associated with traceability to CRM GSO 11934–2022 and a random component of measurements. Accounting of traceability to the CRM GSO 11934–2022 increases the estimate of the uncertainty of the result, but makes it possible to correctly compare the results of two different laboratories, which is of fundamental importance in arbitration tests.