Damage assessment in fretting fatigue specimens with micro-voids using critical plane approach

In this work, the influence of micro-voids on damage severity under fretting fatigue conditions is analysed for a regular and a random distribution of micro-voids. The finite element method is employed to obtain the stress field during a loading cycle. The well-known Smith-Watson-Topper and McDiarmid multiaxial fatigue criteria are assessed by means of critical plane analysis. Additionally, averaging methods are employed in order to consider the length scale for damage initiation. Furthermore, a direct comparison with the homogeneous case is presented. Different size and distribution of micro-voids are analysed. The numerical results show that the heterogeneity has a noticeable influence on the damage severity. In addition, the numerical model suggests that damage may firstly initiate at the upper edge of the micro-voids located close to the contact edge, generally leading to a mean increase of the damage severity. However, in some cases, the introduction of micro-voids reduces the stress intensity at the contact edge, and therefore, decreases the damage severity in the vicinity of the contact edges