Boundary Element Method For Elastoplastic Bimaterial Interface Crack Problems

The boundary element method for elastoplastic bimaterial interface crack problems is researched further in the dissertation. The boundary element numerical analyses are carried out for some elastoplastic bimaterial interface crack problems that are of significance theoretically and practically.The main contents of the present dissertation can be abstracted as follows:A subregion approach of elastoplastic boundary element method is presented, and the intrinsic method of elastoplastic boundary element analysis for a body composed of some kinds of materials is studied further. The method has many applications and is suitable for the analysis of local yielding of multi-material body and interface crack problems. The work consummates the two—dimensional elastoplastic boundary element method.The elastoplastic boundary element method with bimaterial fundamental solution was first proposed by the author and is developed in the dissertation. The complete formulations of the free terms relevant to the plastic strains in the stress rate formulations of interior point are obtained after complicated derivations. The difficulties, which occurs in the case when the plastic zone develops onto the interface and when using the constant plastic strain field approach to solve the Cauchy principal values of singular cell connecting on the interface as singular point lies on interface, are overcome by use of partially discontinuous boundary elements and interior cells. The present method is specially suitable for the numerical analysis of elastoplastic bimaterial interface crack problems.The stress intensity factors of bimaterial interface crack are analyzed using the boundary element method with bimaterial fundamental solutions. The complex stress intensity factors are gained by the modified method which using the traction singular quarter-point elements as crack tip elements and using thenumerical extrapolation method of determining the stress intensity factors to avoid the oscillation singularity of asymptotic fields of elastic interface crack. In the analysis the interface needs not to be discretized, which is advantageous to improve the accuracy and efficiency of computation.The small—scale yielding problem of bimaterial interface crack is analyzed by the elastoplastic boundary element subregion method proposed in the dissertation. The full field boundary element solutions are solved for the small—scall yielding problem of boundary layer formulation. It is proved by comparing the obtained results with the present results of theory and finite element method that the method of the dissertation is feasible for such problem.