| To investigate the reason which controlls the depth of origin of the hydrogen induced blistering in steel, Fe-1.7% Mn steel is selected. For this study, using Tresca`s yield criterion, a model is proposed and the feasibility of the model is exercised experimentally. It is assumed that the hydrogen induced blistering is taking place due to a modified triaxial stress state around a void in which hydrogen gas generates high hydrostatic pressure. Triaxial stress state around the void can be modified by the external or residual stress to give biaxial stress. This modified biaxial stress induces the shear stress component which is in responsible for the plastic deformation. For the verification of this hypothesis, specimens are cold rolled and pulled in tension to give compressive and tensile residual stress states in the specimens, respectively. It is observed that as the amount of the cold rolling increases the compressive residual stress raises and the depth of hydrogen induced crack is also deepened. However, those specimens which are tensioned is believed to have almost same residual tensile stress regardless the amount of the tensile strain and it is observed that the depth of the crack origin did not change with deformation except for the first small strain. These observed experimental results give a strong confirmation of the proposed hypothesis which is based on the pressure theory of hydrogen embrittlement. |
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