The Small punch test, whose European standard will be published soon, is a technique to be taken into account for the estimation of mechanical properties when there is shortage of material. In recent works it has been applied to tensile and fracture properties estimation of steels in hydrogen embrittlement scenarios.

In the aforementioned situations test rate is one of the most relevant variables; some standards recommend tests under a constant load, for the threshold determination, but this requires a large amount of time and presents inaccuracies. To solve this issue there have been published standards like ASTM F1624-12, which consists on applying steps under constant incremental loads one after the other up to the specimen’s rupture governed by the material-environment interaction, that allows to estimate the threshold by testing at least 3 specimens. In a previous work, a modification of this technique had been applied for the estimation of tensile threshold of two medium and high strength steels in hydrogen embrittlement scenarios with good results. In order to adapt the aforementioned standard to small punch testing, the duration of the loading steps was modified, proposing much shorter ones according to the Small Punch specimens dimensions and the punch rate taking place in these scenarios. This proposal allows to obtain a threshold load by using at least 3 specimens in a total time of around a week.

As a continuation of the previous results, in this work, the incremental step loading technique from ASTM F1624 standard is applied to the Small Punch test in order to estimate tensile threshold in a wider range of metallic materials and aggressive environments, in order to generalize its validity. For the experimental program, a medium and a high strength steels are employed in hydrogen embrittlement environments by cathodic polarization of 5 mA/cm^2^ in 1N H~2~SO~4~ acid electrolyte. The study is completed with an Mg-Al alloy exposed simulated human fluid, in orde to cover a wider material-environment combination range.

Regular standard tests on cylindrical tensile specimens were carried out under the same material-environment combination following the ASTM F1624 standard, in order to validate the methodology proposed.


Validation of the Incremental Step Loading Technique Application to Small Punch Tests in Aggressive Environments

Division / Sponsors: 
Pressure Vessels & Piping (PVP)


Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2020/volume/83815

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