Aplicação da metodologia da curva mestra à avaliação da temperatura de referência em um aço martensítico.

Abstract

This work addresses an experimental investigation concerning the brittle fracture behavior of a martensitic steel using SE(B) specimens in a standardized configuration according to the ASTM E1921 standard. The purpose of this work is to assess Master Curve Methodology (MCM) applicability on evaluation reference temperature ( 0 ) derived from fracture toughness data measured in the ductile-to-brittle transition region (DBT) of a quenched martensitic steel USI AR 450 which according to ASTM E1921 is not applicable to martensitic steels only quenching. The work also presents a relatively straightforward procedure for the determination of new coefficients of the master curve for the sake of a better description of median fracture toughness change (expressed in terms of the elastic-plastic stress intensity factor ) according to the temperature in the DBT region and, hence, a more accurate 0 estimate. Fracture toughness tests, conducted at different temperatures in the DBT region using SE(B) specimens extracted in the TL orientation of a quenched martensitic steel plate, provide the fracture toughness data in terms of the J-integral at instability point, .Importantly, fracture toughness data of high strength martensitic steels tests described here provide a fracture toughness database for a material small explored in Master Curve methodology, which highlights its relevance in contributing to bank expansion and enrichment. Fracture toughness experimental data present a relatively significant dispersion and are well described by the Weibull probability distribution in its triparametric form. Notwithstanding that the Master Curve uses in its standard formulation provides a good description of fracture toughness dependence with temperature for the tested material ( vs. ), it is possible to afford a more accurate correlation from new coefficients proposed for the martensitic steel used in this study. Furthermore, a new value for the median fracture toughness closely related to the reference temperature is proposed.