Influence of Surface Tension on Mixed-Mode Cracks

Surface tension inherently exists on free surface, and its effect becomes quite important at sharp crack tip. In the present paper, we investigate the influence of surface tension on mixed-mode cracks by finite element method. It is found that surface tension significantly alters the stress fields and J-integral around crack tip, depending on the profile of crack tip. Generally, surface tension decreases the J-integral and thus enhances material toughness, especially for sharp crack. Based on the criteria of energy release rate, the critical stress intensity factor (SIF) for brittle materials is also determined. Surface tension yields an enhanced critical SIF for mixed-mode cracks, and more significant strengthening effect is obtained for Mode-I crack than for Mode-II crack. Moreover, an analytical expression is advanced to characterize the influence of surface tension on fracture, which shows a good agreement with numerical calculations.