The nucleation of a mode-I Zener crack from a wedge disclination dipole in the presence of a circular inhomogeneity was investigated. It was assumed that the disclination dipole and the nucleated Zener crack lay along the radial direction of the inhomogeneity. Two cases were considered, with the positive or negative wedge disclination of the dipole located nearer to the inhomogeneity. In order to investigate how various factors, such as elastic mismatch between inhomogeneity and matrix, influenced nucleation of the Zener crack, the stress intensity factor at the sharp tip of the Zener crack was determined for various sets of geometrical and material parameters, using the distributed-dislocation technique. The resultant singular integral equations were then solved numerically. The results indicated that a nearby so-called hard inhomogeneity (having a higher shear modulus than that of the matrix) was beneficial to crack nucleation in the first case (positive disclination located nearer to the inhomogeneity) but retarded crack nucleation in the second case (negative disclination located nearer to the inhomogeneity). A nearby soft inhomogeneity was helpful to crack nucleation in the second case, but had an inverse effect upon crack nucleation in the first case. The results could be explained by the concept of material force. The characteristics of crack nucleation, and the effects of disclination strength, distance between inhomogeneity and dipole, disclination dipole arm length and inhomogeneity size upon crack nucleation were systematically studied.

On the Nucleation of a Zener Crack from a Wedge Disclination Dipole in the Presence of a Circular Inhomogeneity. T.Wang, J.Luo, Z.Xiao, J.Chen: European Journal of Mechanics A, 2009, 28[4], 688-96