SINGULAR THIN-LAYER ELEMENT AND ITS APPLICATION IN BI-MATERIAL INTERFACE FRACTURE ANALYSIS

A stress singular thin-layer element was developed and its -1/2 singularity was proved. Then the element was adopted to study the effects of interface stiffness on the crack tip field of a bi-material interface crack. The results demonstrate that for mode I interface fracture, the decreasing of normal interface stiffness will introduce more significant variations of stress intensity factors K_Ⅰ and K_Ⅱ than the decreasing of shear interface stiffness. It also causes notable changes of both normal and shear stress components at a crack tip. However, decreasing shear stiffness only affects the shear stress component notably. In this fracture model, effects of reducing either normal or shear stiffness on K_Ⅱ are more marked than on K_Ⅰ. On the contrary, for model II interface fracture, shear stiffness becomes the dominator on the two stress intensity factors and both normal and shear stress components vary greatly with its decreasing. Reducing normal interface stiffness just remarkably affects normal stress component other than all the stress components. In this case, K_Ⅰ is more sensitive to the two interface stiffness parameters than K_Ⅱ. For any fracture model, stress intensity factors and stress concentrations at a crack tip approach to those of no thickness perfect interface when interface stiffness of bi-material increase.