Investigation On The Interaction Between Screw Dislocation Dipole And Interfacial Defects

The interaction of dislocation, inhomogeneity and interfacial defects is a greatly significant subject in the fields of solid mechanics and materials science. The elastic interactions between screw dislocation dipole and interfacial line defects and circular line defects are investigated firstly in this paper. The problems of screw dislocation dipole interacting with interfacial cracks and rigid lines are solved.Using Riemann-Schwarz's symmetry principle of complex functions, the above problems are transformed into Riemann-Hilbert boundary problems. By combining the analysis of singularity of complex functions, generalized Liouville's theorem, Cauchy model integral and residue theory, the general solutions of above problems are provided. For special example, the closed form solutions to complex potentials are derived explicitly when interface contains a single crack or rigid line, and the appropriate expressions of the stress intensity factors at the tip of crack or rigid line are examined. Applying perturbation technique, the image force and image torque acting the center of dislocation dipole are obtained. The dependence of stress intensity factors, image force and image torque on materials'properties, the length of interfacial crack or rigid line are discussed.As a result, analysis and discussion show that the influence of interfacial crack or rigid line inclusion on the interaction between screw dislocation dipole and inhomogeneity is significant. When the radian of crack reaches extensive magnitude, the presence of interfacial crack can change the interaction mechanism between screw dislocation dipole and soft inclusion. When the radian of rigid line reaches extensive magnitude, the presence of interfacial rigid line inclusion can change not only attraction force on dislocation dipole arisen by soft inhomogeneity into repulsion force, but also the interaction effects between screw dislocation and soft matrix. The screw dislocation dipole has strong shielding or anti-shielding effects on the stress intensity factor at the tip of interfacial defect. The hard inhomogeneity repels dislocation dipole but the interface crack attracts it; under some conditions the combination of them will result in the appearing of free dislocation zone near the crack. When the length of interfacial defects and shear modulus ratio of materials reach critical values, the interaction mechanism between dislocation dipole and interface may be changed. The anisotropies of materials will enhance the attracting force arising from interface crack on dipole, and weaken the repulsing force arising from interfacial rigid line. The present solutions contain a number of previously known results which can be shown to be special cases.