Avaliação da incerteza associada ao módulo de elasticidade no ensaio de tração

Abstract

Knowledge of the elasticity modulus of steels and alloys is important in many professional sectors, from material producers and consumers to research organizations and government agencies, with different needs and applications. This study evaluated the uncertainty associated with the modulus of elasticity provided by a tensile test performed by the Instron® model 8801 universal testing machine using the GUM method. A cylindrical cross-section specimen made of 4340 steel and a rectangular cross-section specimen made of 304 steel were considered. The uncertainty calculation routines were implemented using Matlab®R2018b to avoid calculation errors and perform the direct reading of the Excel® file generated by the testing machine. For the 95 % coverage probability and coverage factor of 12.71, the measurement result for cylindrical specimen is 214.55 ± 2.97 GPa, while for rectangular specimen it is 163.66 ± 2.53 GPa. The expanded uncertainty associated with the modulus of elasticity of cylindrical specimen represents 1.38 % of the mean value, whereas for rectangular specimen is 1.55 %. These results can be considered adequate since they are similar to those found in the literature.