The Interaction Of Inclusion, Dislocation And Interface Effect

In recent years, with the rapid development of nano-science and nano-technology,the nano-materials, such as crystal materials, nano-porous materials, nanoscalecore-shell materials, nanoscale mechanical structures are more widely used. Nanoscalematerials and structure devices have higher ratio of surface area, as the atomicity of thesurface/interface increases, surface/interface atoms and internal atoms show differentperformance, and surface/interface present more signicant propertites on nanoscalematerial, the nano-scale material and structure components show some completelydifferent performance from the macro-scale material and structure devices.This work was supported by the NSFC (11062004) and Doctoral Fund of LanzhouUniversity of Technology. In this thesis, the size-dependence of the nano-scaleinclusions are discussed in detail, the main contents and innovations are listed asfollows:1. The interaction between a screw dislocation inside a coated nano-inhomogeneityand the matrix incorporating interface stresses is investigated. The analyticalexpressions of the complex potentials for the three material regions, the stress fields inheterogeneous materials and the image force acting on the screw dislocation areobtained by means of the complex variable function method and Peach-Koehlerformulations. The results indicate that the influence of the interface stress on themovement and equilibrium positions of the screw dislocation becomes remarkable whenthe radius of the coated inhomogeneity is reduced to nanometers. An additionalrepulsive force or attractive force acting on the screw dislocation is produced forconsidering the interface stresses, which causes the image force to decrease or increaseand the normalized image force acting on the screw dislocation depends on the size ofthe inhomogeneity. The present result is completely differernt from the classical elasticresults.2. The interaction of two circular cylinder nano-inhomogeneities embedded in theinfinite matrix with interface stress is investigated. The Gurtin–Murdoch model isapplied to taking into account the surface/interface stress effects. The closed-formsolution of the elastic field of the infinite solid is obtained by applying the complexpotential approach in conjunction with the techniques of conformal mappling, Laurent’s series expansion, etc. Numerical results show that when the size of the inhomogeneityreduces to nanometers, the contribution from interface stress becomes important, andthe elastic felds of inhomogeneous materials depend on the radius of the inhomogeneity,surface elastic constants and surface residual stress.