Small punch test methodologies for the analysis of the hydrogen embrittlement of structural steels

Abstract

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

“…It consists of the interconnection, via an acid electrolyte, of a noble material (platinum in this case) and the steel, which will be protected due to the fixed current interposed [1,17,18]. In this study, for the cathodic charge situations, an environmental condition in accordance [7,10,11,17,18,19] was proposed, consisting of an 1N H2SO4 solution in distilled water containing 10 drops of CS2 and 10mg of As2O3 dissolved per liter of dissolution. The solution of As2O3 was prepared using Pessouyre's method [17,19].…”

“…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].…”

The development of a novel small ring specimen tensile testing technique

“…In general there are two main types of small specimens used for tensile testingsmall punch specimen and miniaturized standard specimen. Small punch specimens are suitable for identifying yield strength and UTS [5], while miniaturized standard specimens are suitable for identifying the whole stress/strain curve including Young's modulus [1]. Small punch specimens are rather standard, with most being either square 10mm x 10mm x 0.5mm [5] or circular with a diameter between 3mm [6] and 10mm [7] and similar thickness to square specimens.…”