Avaliação da incerteza associada à tenacidade à fratura obtida via integral-J

Abstract

This work aims to evaluate the uncertainty associated with the fracture toughness obtained via conventional tests (J integral) in accordance with the determinations of the ASTM E1820 (ASTM, 2020) Standard. For that, a detailed study of the test method was carried out, as well as the instrumentation used. Then, all measurands and input variables were identified, as well as the mathematical models for calculating the measurement uncertainty. The GUM and Monte Carlo methods were applied. A methodology was developed and documented using Microsoft Excel® 2019. The results obtained showed that the expanded uncertainty associated with fracture toughness obtained via J Integral test, considering three specimens manufactured in AISI 4340 (28 HRC) steel, is 12.91 kJ/mm², representing 8.5 % of the average value of J (152.18 J/mm²) with coverage probability of 95. 45 %. The greatest contribution in this case is associated with the variability of J values obtained considering three tests performed under repeatability conditions. Analyzing data from the literature, it was possible to observe that this variability can generate an expanded uncertainty of up to 14.5 % of the average value of J.