The role of the testing rate on Small Punch tests for the estimation of fracture toughness in hydrogen embrittlement

ABSTRACT: In this paper, different techniques to test notched Small Punch (SPT) samples in fracture conditions in aggressive environments are studied, based on the comparison of the micromechanisms at different rates. Pre-embrittled samples subsequently tested in air at rates conventionally employed (0.01 and 0.002 mm/s) are compared to embrittled ones tested in environment at the same rates (0.01 and 0.002 mm/s) and at a very slow rate (5E-5 mm/s). A set of samples tested in environment under a set of constant loads that produce very slow rates completes the experimental results. As a conclusion, it is recommended to test SPT notched specimens in environment at very slow rates, of around E-6 mm/s, when characterizing in Hydrogen Embrittlement (HE) scenarios, in order to allow the interaction material-environment to govern the process