Study of the energy for embrittlement damage initiation by SPT means. Estimation of KEAC in aggressive environments and rate considerations

A Proposal for the Application of Failure Assessment Diagrams to Subcritical Hydrogen Induced Cracking Propagation Processes

“…The method consists in their superposition to the P-COD curve from the test, and their intersection at the point where the crack length, a, has the same value as the iso-a curve crossing, as is explained in refernece [4] in detail. Hydrogen diffusion inside the material is promoted by exposure to the environment, normally during a certain amount of time prior to the mechanical solicitation [10][11][12] as well as during the test. A subsequent SEM fractographic study is often used to reveal the mechanisms behind the cracking process [10][11][12].…”

“…However, it is well known that the fracture toughness in aggressive environments such as HIC, K IHIC , is usually lower than its equivalent in air. Hence, a more brittle condition takes place [4,5,10,11], which will lead to higher K r values in the FAD representation of the subcritical crack path propagation [6].…”

Rate effects on the estimation of fracture toughness by small punch tests in hydrogen embrittlement scenarios

“…The SPT, that is in a pre-standard state, has been successfully employed in the evaluation of tensile [20] and fracture [21] properties of different materials. Because of its reduced dimensions and simplicity, this technique has been applied to characterize embrittlement situation on steels, such as the evolution of materials properties with neutron irradiation [22], the brittle-ductile transition temperature of metallic materials [23], or environmental embrittlement [5][6][7][8][9][10][11][12]. A schematic of the device used in this work for the performance of these tests is represented in Figure 3; during the test the force and the punch displacement were registered continuously.…”

“…• Embrittled samples tested in continuous exposition to the environment at a very slow rate, 500 times lower than the conventional rate, of 5E-5 mm/s that has been previously employed by some authors [5,6,9,10].…”

“…The SPT, based on punching a reduced dimensions plane specimen, allows the estimation of parameters such as the yield stress, ultimate tensile strength and fracture toughness of metallic materials with high reliability. Over the last years, some authors have proved the validity of the SPT when used in HE and SCC characterization [5][6][7][8][9][10][11][12]. In order to reproduce accurately the micromechanisms taking place in HE failures, as it is imposed by standardised environmental characterizations, the test rates should be very slow, or even quasi-static [5,11].…”