Avaliação do Método SPB utilizado na determinação do crescimento estável de trinca em testes de fratura

Abstract

Since its proposal for the evaluation of stable crack growth, the Spb method has been successfully applied in the evaluation of fracture toughness of metallic and polymeric materials. However, some points of the methodology have not been studied indepth, such as the applicability in standardized geometries in which ηpl depends on the a/W ratio, as well as the choice of the a/W ratio for the specimen used as a reference. To discuss this and other aspects, theoretical analyzes of the Spb method and experimental tests were carried out. The theoretical analysis revealed that considerable differences can be achieved in the C(T) and SE(T) geometries when the same ηpl factor is used in the specimens with blunt and pre-cracked notches. To minimize these differences, it was proposed to use a more general expression of the Spb method, together with the ηpl factors provided by the standards for geometries, where ηpl changes with a/W. As well as some a/W ratios are recommended for the reference specimen, which were determined according to the useful plastic displacements that each specimen can achieve. The proposed experimental methodology, based on the load separation and the ηpl factors provided by the standards, proved to be adequate for the C(T) geometry, while for the SE(T) geometry the results indicate that further research is needed.Também disponível on-line