Avaliação da incerteza associada à tenacidade à fratura obtida via indentação instrumentada

Abstract

This work aims to evaluate the uncertainty associated with the fracture toughness of 4130 M steel obtained from instrumented indentation tests. Three different methodologies for obtaining fracture toughness were considered: Lee et al. (2006), Zhang, Wang, and Wang (2019), and Yu et al. (2023). In this study, uncertainties were calculated using the Guide to the Expression of Uncertainty in Measurement (GUM) method and the Monte Carlo method. For uncertainty assessment, all measurands and input variables were identified based on the equations proposed by these authors. Then, the standard uncertainty associated with each input variable was calculated using the GUM method. To quantify the uncertainties of variables with complex equations, the Monte Carlo method was used. The expanded uncertainties related to fracture toughness were 4.94, 7.52, and 19.97 MPa∙m0.5 considering the methodologies of Lee et al. (2006), Zhang, Wang and Wang (2019a) and Yu et al. (2023), respectively, for a coverage level of 95.45 % and k factor = 2.00. Although the uncertainty of the Yu et al. (2023) methodology was the largest among the three evaluated, the fracture toughness value for this methodology was the closest to the reference value estimated by Melo (2019), with less than 2 % difference. The Lee et al. (2006) methodology presented a difference in the toughness value of approximately 23 % in relation to the reference value. The Mann-Whitney statistical test indicated that only the methodology of Yu et al. (2023) provides values statistically equal to those obtained by Melo (2019), for a coverage level of 95 %.