Shielding or anti-shielding effects of solute hydrogen near a finite length crack: A new possible mechanism of hydrogen embrittlement

摘要

A two-dimensional elastic solution for the stress field of a dilatation line near an elliptical void in an infinite matrix is obtained. The dilatation line is used to represent a row of equally spaced solute atoms. This elastic solution is employed to study the shielding or anti-shielding effect of solute atoms near a finite length crack. The stress intensity factor of stress field induced by a dilatation line is analytically obtained. It is shown that whether solute atoms have a shielding or anti-shielding effect on the crack tips depends on the position of solute atoms. An equaling zero curve is defined, on which the solute dilatation line induces zero Mode I stress intensity factor at the crack-tip. It is found that the shape of equaling zero curve is independent of any model parameters. The shielding and anti-shielding effects of a lot of solute hydrogen (hydrogen atmospheres) are studied through an integral scheme. The hydrogen concentration field is assumed to equilibrate with external or internal stress fields. We consider two cases. One case is that an externally uniaxial load in the direction vertical to crack is applied. Another case is that there exists an edge dislocation near crack. Based on these studies, a new possible mechanism of hydrogen embrittlement is proposed, which can be referred to as hydrogen induced anti-shielding crack mechanism.